HK1104330A

HK1104330A - Filler or figment or mineral for paper, method for making same, compositions containing them and uses

Info

Publication number: HK1104330A
Application number: HK07109049.5A
Authority: HK
Inventors: P．A．C．甘恩; M.布里; R．V．布拉姆; B.卡斯
Original assignee: Omya发展股份公司
Priority date: 1998-12-24
Filing date: 2007-08-20
Publication date: 2008-01-11

Description

Paper filler or pigment or mineral, process for its manufacture, composition and use thereof

This application is a divisional application filed on 24.12.1999 under application No. 99816351.1 entitled "treated novel paper fillers or pigments or minerals, particularly pigments containing natural calcium carbonate, methods of making the same, compositions and uses thereof".

The present invention relates to the technical field of inorganic fillers particularly suitable for papermaking applications, and their improvement by appropriate treatments with the aim of improving the paper manufacturing process or the paper properties.

Such fillers are known to the person skilled in the art and include, for example, natural calcium carbonate, synthetic calcium carbonate, i.e. "precipitated" calcium carbonate (PCC), and also various fillers such as dolomite, mixed fillers based on different metals, such as, in particular, calcium carbonate in combination with magnesium, and the like, various fillers such as talc, and mixtures of these fillers, such as talc-calcium carbonate mixtures, calcium carbonate-kaolin mixtures, or mixtures of natural calcium carbonate with aluminium hydroxide, mica, or with synthetic or natural fibres.

It is not advantageous to describe the manufacturing process of paper or the like in detail. The person skilled in the art knows how to manufacture a pulp mainly comprising fibres (cellulose fibres of natural origin-such as resiniferous wood or broad-leaved wood-or synthetic cellulose fibres or mixtures thereof), a filler as defined above and a suitable amount of water.

Typically to make a thick pulp that can be diluted with water to a thin pulp. Various additives such as various polymers are added to this pulp to improve the flocculation conditions, thus "forming" the paper, retaining the filler and draining the water under the filter cloth. The aqueous medium which is discharged below and which contains part of the initial filler under pressure is referred to as "white water". The sheet is then subjected to various treatments including an important operation known as gumming. During this gluing operation, it is known that there is a loss of glue and of glued paper. This sized paper is recovered as a bulk filler and is referred to as "crash size".

The invention particularly relates to the use of one or more strong to strong H₃O⁺The combination of an ion donor and an active gaseous medium treats an aqueous suspension of a pigment containing a natural carbonate, such as natural calcium carbonate, a filler or a mineral, and a pigment containing natural calcium carbonate in combination with other minerals. In fact, natural calcium carbonate can be compared to the medium to strong H well known to the paper industry₃O⁺The mixture of minerals whose ion donors are inert isIt is inevitable.

The use of the invention is particularly in the paper industry, in particular to obtain a performance comparable or better than that of paper of the same thickness, in particular in terms of opacity or whiteness, and with a reduced weight. The phenomenon of reducing the weight of the paper at a constant thickness and maintaining or improving the properties of the paper is referred to hereinafter as "bulk" properties.

A particular and interesting use of the invention relates in a non-limiting manner to the improvement of the properties when digital printing is carried out, for example by ink-jet printing on a sheet which is not gummed but contains the filler treated according to the invention or on a sheet which is surface-treated or gummed with the pigment according to the invention.

In this particular, but not limiting, field of ink-jet printing, the invention relates to compositions in which the filler has at the same time a high particle size distribution, a rougher texture and a high specific surface.

Another particular application of the invention is in the field of paints.

It is therefore a primary object of the present invention to reduce the weight of a given size sheet while maintaining the same, or even improving, properties of the sheet.

Another important object of the invention relates to the treatment and gumming of paper or broadside paper comprising or similar, in particular the treatment of the coloured surface of the paper, with the composition according to the invention.

For transport reasons, in particular mailing costs, and environmental reasons, i.e. in particular saving of natural materials and energy, it is of interest to reduce the weight of a given thickness of paper.

Thus, the patent WO 92/06038, which aims at improving the opacity and whiteness of the paper containing therein the "bulk" agent or the glue to which it is applied, proposes a solution which, however, does not allow energy savings.

Opacity and better whiteness are obtained by the very complex processes involved in forming the paper. As is known, paper is formed on felts by flocculation or coagulation or interlacing of different components in the pulp, particularly at the fibre or fibril stage thereof. This "coagulation" process is facilitated by drawing drainage under the carpet. Some of these physico-chemical phenomena may have developed, or at least some transformations or interactions there, especially in the vicinity of the head box, which will contribute to certain properties being exhibited on or further from the carpet.

While not wishing to be bound by any theory, applicants believe that the filler will interact differently with the fibrils or fibers depending on the treatment to which the filler is or is not subjected. The invention is based on a specific treatment which, in this context, will lead to "bulky" properties, i.e. a good interaction with the web. As also indicated in WO 92/06038, "bulk" manifests itself in that the paper produces better light dispersion effects.

However, as the machine speed tends to increase more and more, this entails increasing the volume of the voids inside the paper (WO96/32449, page 2, line 15 and beyond), slowing down the drainage rate and thus slowing down the paper making process, complicating the problem of "bulk" solutions.

The invention also greatly improves the final abrasion performance of the pigment in the paper making process, that is, the abrasion of the metal screen or the polymer used can be reduced, and the abrasion performance of the pigment in the paper coating process, that is, the abrasion of the flakes used can be reduced. The importance of this property is emphasized in patent WO96/32449, which points out the pigmentary TiO₂Is a good "bulk" agent, but is too abrasive (page 1, line 35 and beyond) and is expensive.

Finally, the present invention also enables paper stiffness to be reduced for special applications such as the manufacture of envelopes.

As mentioned above, and as demonstrated in particular in patents WO 96/32448 and WO96/32449, we know that there are mainly two calcium carbonates, one natural and the other synthetic.

Synthetic calcium carbonate, i.e., PCC, is produced by adding calcium oxide (or hydrated lime) to CO₂The intermediate reaction is obtained in a known manner, in which case synthetic calcium carbonate having different shapes, such as needle-like or other crystal shapes, is obtained depending on the reaction conditions. There are many patents relating to the synthesis of PPC.

Completely as a reference, patent USP-5,364,610 describes a process for the production of calcium carbonate to obtain scalenohedral PCC. As a prior art process, this patent describes the use of CO₂The preparation method is completed by carbonation. This PPC is used to impart better properties, in particular whiteness, to the paper. We also cite the patent USP-5,075,093.

It is also known that PCC can impart "bulk" properties, which include weakening the web interactions. In addition, the patent WO 93/06038 cited above describes a process in which lime is carbonated to obtain PCC having "bulk" properties.

In contrast, natural calcium carbonate does not provide this property, and it is therefore clearly of particular interest to obtain this property without being forced by the paper industry to use synthetic carbonates.

Thus, there is an urgent need to obtain "bulk" properties or interactions that are favorable to surface properties from natural carbonates. Furthermore, it is particularly surprising that the novel pigments of the invention not only give the same properties as PCC, but also retain the advantageous properties of natural calcium carbonate, since PCC has a disadvantageous interaction with the forces of the fibrous web.

Very surprisingly, pigments having desirable synergistic properties have been developed.

Various treatments have been proposed by the industry concerned.

Patent WO 96/32448 describes the treatment of calcium carbonate dispersions (referred to in the relevant industry as "slurries") containing low concentrations of carbonate (1-30% solids) using polydiMDAC, a low molecular weight 10,000-500,000 cationic aggregating agent capable of achieving "bulk" properties. This patent uses, in addition to PCC, ground natural carbonates, denoted by the word g (n) CC (i.e. ground natural calcium carbonate), or mixtures thereof. The method is mainly flocculation, i.e. aggregation of small particles with the coarsest particles, and the properties of interaction with fibres are mainly obtained by the pure coarse particle size of the particles. When the weight thereof is reduced, the physical properties of the paper are adversely affected.

Patent WO96/32449 describes essentially the same information. The aim is to obtain selective aggregation of fine and ultrafine particles by means of an aggregating agent having a charge opposite to the overall charge of the filler.

The patent USP-4,367,207 cited in WO 92/06038 describes the use of CO in the presence of an anionic polyorganophosphonate-based electrolyte₂Treatment of CaCO₃The object of the invention is only to obtain a slurry of finely divided carbonate.

EP0406662 describes a process for the manufacture of synthetic carbonates, according to which an aragonitic CaCO is prepared₃Premixing with lime, adding a "phosphoric acid derivative", such as phosphoric acid or its salt, or various phosphates, to the slurry, see page 4, line 17 and following, and introducing CO₂Conventional carbonation is performed. The aim of this patent is to obtain directionally PCC of large particle size and special crystalline form (needle shape) which has not been commercially available. This patent cites as prior art other processes involving the manufacture of PCC by carbonation, as an improvement involving the introduction of CO via successive stages₂Or a nucleation center corresponding to the desired crystalline form is added prior to the reaction.

In this patent EP0406662, phosphoric acid (page 4, line 46 and the following) is used to form aragonite form directionally via a compound different from "calcium phosphate", which acts as a novel nucleation center to form the desired crystalline form (line 52, line 55).

Page 5, line 2 and the following indicate the use of the obtained carbonate. Particularly in the field of thermal insulation and the like, such carbonates are used in the paper industry in order to be able to incorporate large amounts of inorganic substances in the paper, rendering the interior of the paper non-flammable. There is no mention in this patent of any properties such as opacity, brightness or "bulk" of the paper, which is clearly not the object of this patent. In addition, the only application example relates to the carbonate/resin composition.

Methods for imparting specific properties to carbonates are also known.

We will particularly cite the method of obtaining acid resistance as one of the conventional papermaking methods applicable when carbonates are used as fillers in the acid papermaking process, for example, us patent 5,043,017 describes the stabilization of calcium carbonate, particularly PCC, by the action of a calcium chelating agent (such as calcium hexametaphosphate) and a conjugate base (which may be an alkali metal salt of a weak acid, such as phosphate, citrate, borate, acetate, etc.) (column 1, line 27). This document cites the prior art in which sodium hexametaphosphate is used as a dispersant, according to which, in the manufacture of PCC, the salt of this weak acid is used after the "primary" carbonation or, conversely, after the first stage of manufacture. This document also cites patent USP-4,219,590 which describes a method for improving dry calcium carbonate by treatment with "anhydrous, fully dry acid gas". In this document, it is actually concerned with improving the treatment of known surfaces, i.e. processes carried out with acidic gases or acidic resins and the like (column 1, line 17). This document treats carbonates with phosphoric acid, hydrochloric acid, nitric acid, capric acid, acrylic acid vapour or aluminium chloride or fluoride, or fumaric acid, etc. The purpose is to decrepitate the carbonate particles into fine particles (column 2, line 65). This document claims the use of HF, SO₂Or phosphoric anhydride, the only example being the use of HF or titanium tetrachloride, which improves the opacity of the paper (see column 3, line 12 and the following).

Also known is the patent USP-5,230,734, which uses CO₂The carbonate of Ca-Mg is produced.

Patent WO 97/08247 describes a process for the manufacture of carbonates for paper obtained by the weak acid process. The carbonate is treated with a mixture of a weak base and a weak acid, the phosphoric acid being one of the first two reagents, originating from an organic acid.

Patent WO 97/14847 also describes acid-resistant carbonates for paper which are treated with a mixture of two weak acids to passivate the surface of the carbonate.

Patent WO 98/20079 also describes a method for making carbonates, in particular PCC acid resistant by adding calcium silicate and a weak acid or alum. This document cites the transfer of CO₂Treatment to obtain resistance to acidic media patent USP-5,164,006 is known as prior art. However, the addition of compounds such as zinc chloride is necessary at this time, but this does not comply with environmental regulations. In addition, the pigments of the invention are acid-intolerant, have an unexpectedly high activity and are capable of very good interaction with the fibers.

Therefore, the industry has been working for decades to improve the properties of natural carbonates and/or to produce synthetic carbonate PCC exhibiting specific properties. In these studies, some trials involving "bulk" were envisaged, but we noted that nothing was involved in the use of CO₂. Such gases are used to impart acid resistance properties unrelated to "bulk" properties, or treatments intended to make PCC by carbonation. Phosphoric acid and CO have also been used₂In connection with, but only improving the manufacture of PCC.

Indeed, the industry has specifically sought to produce synthetic carbonates with improved properties, in view of the better properties conferred by PCC. The advantage of the present invention is that it has been studied on the basis of natural carbonates.

The present invention therefore relates to the development of novel aqueous dispersions of one or more pigments, fillers or minerals, optionally containing polymeric dispersants as rheology stabilizers for suspensions, these said pigments being capable of reducing the weight of the paper at a constant surface area.

The novel aqueous suspensions are characterized in that:

a) it contains natural carbonate and one or more of said carbonate and gas CO₂The products of the reaction, and one or more of said carbonates with one or more of the strong to strong ions H₃O⁺The product of the donor reaction, and

b) it has a pH value of greater than 7.5 measured at 20 ℃.

The pigment, the filler or the mineral is characterized in that the BET specific surface area of the pigment, the filler or the mineral is 5-200 m measured according to standard ISO 9277²Preferably 20 to 80 m/g²A more preferable range is 30 to 60 m/g²/g。

In a particular way, the aqueous suspension according to the invention is characterized in that the pigments, fillers or minerals have the following characteristics:

at the device Sedigraph5100^TMThe average particle diameter of the particles measured by the sedimentation method is 50-0.1 mu m

-a BET specific surface, measured according to standard ISO 9277, of 15 to 200m²/g。

In a more particular way, the pigments, fillers or minerals are characterized by the following features:

at the device Sedigraph5100^TMThe average particle diameter as measured by sedimentation is 25 to 0.5 μm, more specifically 7 to 0.7 μm;

-a BET specific surface, measured according to standard ISO 9277, of 20 to 80m²A specific value is 30 to 60m²/g。

The invention also relates to pigments or fillers in the dry state, such as natural calcium carbonate or various pigments containing natural calcium carbonate, which are obtained by drying the aqueous suspensions according to the invention by carrying out drying processes known to those skilled in the art.

The invention also relates to a method for treating pigments or fillers in the form of an aqueous suspension, such as natural calcium carbonate or various pigments containing natural calcium carbonate, or mixtures thereof (including other fillers and pigments which do not contain carbonate ions), to compositions containing them and to their use in paper manufacture, in particular for obtaining better bulk properties, and to papers so loaded or so sized.

More precisely, the invention relates to an aqueous suspension capable of containing a polymeric dispersant as a rheological stabilizer of the suspension and containing a pigment, filler or mineral of a natural carbonate, such as natural calcium carbonate or dolomite, the suspension being passed through one or more H of strong to strong nature₃O⁺Ion donor and CO₂Combined treatment of gases.

As examples of different natural carbonates obtained from chalk, in particular chalk, calcite or marble in the Champagne area, mixtures thereof with talc, kaolin and/or dolomite, and/or aluminium hydroxide, and/or titanium oxide, magnesium oxide, and similar oxides and hydroxides well known in the relevant industry can be cited.

For convenience, in this application, these various fillers and mixtures of fillers, or mixed fillers, are generally ascribed the generic term "filler" unless it is necessary to refer more precisely to the filler or filler class.

The acid used is one which generates H under the treatment conditions₃O⁺A strong to strong acid of various kinds of ions or any mixture of such acids.

According to a preferred embodiment, the strong acid will be chosen from acids having a pKa value at 22 ℃ of less than or equal to 0, more particularly from sulfuric acid, hydrochloric acid or mixtures thereof.

According to a preferred embodiment, the moderately strong acid will be chosen from acids having a pKa value of between 0 and 2.5 at 22 ℃, more particularly from H₂SO₃、HSO₄ ^-、H₃PO₄Oxalic acid or mixtures thereof. Specific examples thereof include pKa₁H equal to 2.161₃PO₄(Römpp Chemie，Edition Thieme)。

According to a preferred embodiment, one or several moderately strong acids can be mixed with one or several moderately strong acids.

According to the invention, with respect to CaCO₃Moderate to strong H in mole number₃O⁺The total number of moles of the ion donors is 0.1 to 2, preferably 0.25 to 1.

The method for treating an aqueous suspension of pigments, fillers or minerals containing natural carbonates according to the invention is characterised in that the pigment is one or more H of strong to strong H₃O⁺Ion donor and CO₂And (4) carrying out gas combined treatment.

Preferably, the process of the invention for treating pigments, fillers or minerals in aqueous suspension containing natural carbonates, capable of reducing the weight of paper with a constant surface, is characterized in that it comprises the following 3 steps:

a) using one or more kinds of H with strength to strength₃O⁺Ion donor treatment

b) With gaseous CO₂Treatment which is either a constituent of step a), is carried out in parallel with step a), or is carried out after step a)

c) The pH value, measured at 20 ℃, is adjusted to above 7.5 by adding alkali within the interval of 1 to 10 hours, preferably 1 to 5 hours after the end of steps a) and b) or immediately after the end of steps a) and b), this step c) being the last step of the process.

Preferably, CO₂Gas from external CO₂Source or recycle CO₂Or the same medium to strong H as used in process step a) added continuously₃O⁺Ion donor or another medium to strongH₃O⁺Ion donor or overpressure of CO₂CO preferably at an overpressure of 0.05 to 5bar₂. It should be noted here that the height of the treatment tank filled with a filling material having a specific gravity of about 1-2 may reach, for example, 20m, which results in CO that can reach several bars₂The overpressure can reach, in particular, approximately 5bar at the bottom of the tank or in a closed tank.

According to a preferred embodiment, steps a) and b) can be repeated several times.

Also according to a preferred embodiment, the pH value measured at 20 ℃ during steps a) and b) of the treatment is between 3 and 7.5 and the treatment temperature is between 5 and 90 ℃, preferably between 45 and 60 ℃.

According to a preferred embodiment, the pH is higher than 7.5 at ambient temperature without any addition of base for 1 to 10 hours, more particularly 1 to 5 hours, after the end of the treatment. If any base is added, the pH rises immediately at this point. Again, it should be noted that after a few days, no acid resistance was observed.

The process according to the invention for treating an aqueous suspension of pigments, fillers or minerals containing natural carbonates, capable of reducing the weight of paper of constant surface area, is characterised in that the CO content of the suspension is measured by volume₂The gas concentration is such that the volume of the suspension is related to the CO₂The volume ratio of the gas is 1: 0.05-1: 20, the ratio in the step a) is 1: 1-1: 20, and the ratio in the step b) is 1: 0.05-1: 1.

Particularly preferably, the CO in the suspension is measured by volume₂The gas concentration is such that the volume of the suspension is related to the CO₂The volume ratio of the gas is 1: 0.05-1: 5, the ratio in the step a) is 1: 0.5-1: 10, and the ratio in the step b) is 1: 0.05-1: 1.

CO₂The gas can be metered in liquid form or anhydrous form.

Preferably, the time of the treatment step b) is 0 to 10 hours, preferably 2 to 6 hours.

The treatment process of the invention is carried out in an aqueous phase (slurry) at low, medium or high dry matter content, but can also be carried out with slurry mixtures of these different concentration compositions. Preferably, the dry matter content is 1 to 80 wt%.

Without wishing to be bound by any theory, the applicant believes that CO₂The gas acts in particular as a pH regulator and as an adsorption/desorption regulator.

According to one mode of the invention, the method for the production of an aqueous suspension according to the invention is characterized in that, after the three steps of the treatment method according to the invention, the treated product is suspended with the aid of a dispersing agent and optionally re-concentrated.

The aqueous filler suspension obtained according to the invention can be added to the process for the preparation of paper, or the like, at the time of the preparation of the thick stock or thin stock, or at both these sites, depending on the papermaking process. In practice, the filler is added in one or more portions as recommended by the paper industry practice.

The fillers treated according to the invention are also of great significance in connection with the formation of paper, and in particular the fillers according to the invention can be added to recycled white water or to "gummed particles" which are also recycled.

Alternatively, the treatment of the invention can be applied to circulating white water or "glued chaff", when the circulating medium is treated according to the steps of the invention, as described earlier.

The invention applies to the manufacture of paper based on cellulose fibres of wood origin, such as paper based on hardwood or resin-containing wood.

The invention also applies to paper obtained from non-wood-derived, but on the contrary synthetic fibres.

The invention therefore also relates to a process for the production of paper, or the like, thus improved for the introduction of the process according to the invention.

The invention also relates to a novel product obtained by the method.

Drawings

FIG. 1 is a graph of the imprint of inventive sample (A) and prior art sample (B).

FIG. 2 is a graph of thickness versus weight plotted for different weight calculations.

The following examples are intended to illustrate the invention without limiting its scope.

A series of tests was carried out on low dry matter content slurries, i.e. up to about 30% slurries, and another series of tests was carried out on high dry matter content slurries, i.e. up to about 80% slurries.

High contents are of great interest in the industry concerned, but have particular problems with viscosity. Therefore, the dispersants should be added in a frequent but random manner, which may cause defects in the process (the dispersants interfere with the surface of carbonates or other types of fillers due to competing reactions in terms of adsorption phenomena).

Example 1

This example illustrates the invention and relates to the treatment of a slurry with a low dry matter content.

For this purpose, in each test of example 1 involving an aqueous suspension of low dry matter content, a suspension (slurry) or a filter cake or a dry powdery calcium carbonate or an inorganic mixture containing calcium carbonate in which the solids, i.e. the dry matter content, is 5 to 30% by weight is prepared in a suitable reactor, if necessary diluted with desalted or tap water to the desired solids content.

For tests involving aqueous suspensions of medium dry matter content, calcium carbonate was prepared in the form of a suspension (slurry) in which the solid matter, i.e. the dry matter content, was about 45% by weight.

For all tests, 1-liter or 10-liter glass reactors or 100-liter plastic containers or 40m were used³Equipped with a rotor/stator type stirrer, high-speed stirrers comprising a 50mm diameter rotating disc for 1-liter and 10-liter reactors, and 200mm diameter rotating discs for 100-liter plastic containers, for 40m³The diameter of the rotating disc is 1500 mm.

For some tests, which will be described in more detail in the examples which follow, a fluidized bed mixer of the type 6 liter or 600 liter L ö dige was used.

After uniform mixing, the suspension or slurry was adjusted to a temperature corresponding to the test.

Then adding a solution preferably selected from H with the concentration of 1-85 wt% in a specified time interval₂SO₃、HSO₄ ^-、H₃PO₄Medium to strong H of oxalic acid or mixtures thereof₃O⁺An ion donor. The deviations are described below.

Carbon dioxide is added or passed through the bottom of the vessel or by means of a tube extending through the vessel from top to bottom for the time indicated below.

The control group was treated in the same manner with the same untreated 75g/m²Fillers and paper made in parallel with the same batch of cellulose.

Test 1：

5kg of Norwegian marble-type natural calcium carbonate having a particle size distribution of 75% by weight of particles with a diameter of less than 1 μm, measured by means of a Sedigraph5100 from Micromeritics, calculated on the dry pigment content, were diluted with distilled water in a 100 litre container until a slurry with a dry matter content of 10% by weight was obtained. Then at 20 ℃ with the aid of a catalyst containing 0.20mol of H per mol of calcium carbonate₃The slurry thus formed was treated with a 10 wt% sulfuric acid solution of O while stirring at 500rpm for 2 minutes. After 15 minutes, two are placed under an overpressure of 50mbarCarbon oxide is bubbled through the calcium carbonate suspension for 5 hours such that the volume ratio of the suspension to carbon dioxide gas is about 1 to 0.15.

After 24 hours of storage, a paper containing the calcium carbonate suspension to be tested as filler was formed.

For this purpose, paper was made from SR23 grade cellulose pulp containing kraft pulp of wood and fibers consisting of 80% birch and 20% pine. At this point, 45g (dry basis) of the pulp was diluted in 10 liters of water in the presence of about 15g of the dry filler composition to be tested, and the filler content was found to be about 20 to 0.5% by experiment. After stirring for 15 minutes, 0.06% of a retention agent of polyacrylamide type, relative to the dry weight of the paper, is added, the grammage of the paper formed being equal to 75 g/m.m²The filler content is 20 +/-0.5 percent. The apparatus used to form the paper was a Rapid-K ö the system, model 20.12MC, from Haage.

The paper thus formed was dried at 92 ℃ and 940mbar vacuum for 400 seconds. Filler content was controlled by analyzing ash.

The thickness of the paper thus formed was measured.

The thickness of a sheet or cardboard is the perpendicular distance between two parallel surfaces.

The samples were conditioned for 48 hours (German standard DIN EN 20187).

This standard specifies that paper is a hygroscopic substance and is therefore characterized by the fact that its moisture content can be adjusted to a suitable degree with respect to the moisture content of the ambient air. When the humidity of the ambient air increases, moisture is absorbed, and conversely when the humidity of the ambient air decreases, moisture is discharged.

If the temperature is not kept constant within certain limits, the moisture content of the paper is not necessarily the same even if the relative humidity is at a constant level. As the moisture content increases or decreases, the physical properties of the paper change.

Therefore, the sample should be conditioned for a period of at least 48 hours until equilibrium is reached. The test specimens were also tested under the same climatic conditions.

The climatic conditions of the paper test were determined as data corresponding to:

relative humidity 50% (+ -3)

Temperature 23 ℃ (± 1)

The thickness was determined according to German standard DIN EN 20534 using a micrometer, the test trace being up to 10n/cm². The test results were determined by calculating the average of 10 measurements. The unit of the results is μm.

The control group was the same amount but untreated 75g/m²Filler and paper made in parallel from the same batch of cellulose.

The results were:

a) for pigments:

the pH of the slurry was 7.6 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

for the raw material samples, i.e. the control group: at 75g/m²Is 112 μm in diameter

For the test specimens: at 75g/m²When it is 120 μm, the number of grams given is 70g/m when converted to a thickness of 112 μm²。

We see that in this test, if the sheet thickness is converted to a common value of 112 μm, 5g/m is omitted²I.e. 6.6% of the weight of the paper, which is a significant saving in terms of the environment.

Test 2

In a 10 l glass reactor and with stirring at a temperature of 20 ℃Next, the amount of the catalyst is adjusted to 0.15mol of H per mol of calcium carbonate₃O⁺3kg of Norwegian marble type presscake in the form of a slurry with a dry matter concentration of 10% by weight, measured with a Sedigraph5100 from Micromeritics, having a particle size distribution such that 75% by weight of the particles have a diameter of less than 1 μm, calculated as dry pigment. Then, carbon dioxide was bubbled through the slurry with an overpressure of about 100mbar for 5 hours, so that the volume ratio of suspension to carbon dioxide gas was equal to about 1: 0.1. The pH was measured immediately after manufacture, after 1 hour, 2 hours, 3 hours, 4 hours and 5 hours. Paper is formed from pulp having a low dry matter content. The dry matter concentration can be increased to a value of 47% by weight using 0.53% by weight, relative to the dry weight of the pigment, of a sodium polyacrylate type dispersant having a specific viscosity of 0.75.

In these examples, the specific viscosity of the anionic dispersant, indicated by the greek letter η, is determined by the following method: the measurement was carried out by dissolving 50g of the dry polymer in 1 liter of distilled water containing 60g of NaCl to prepare a solution of the polymer, and neutralizing it to 100% with a sodium hydroxide solution (pH 9). The time required for a precisely defined volume of the basic polymer solution to flow through the capillary was then measured in a heated bath thermostated to 25 ℃ using a capillary viscometer with a Baume constant of 0.000105 and compared with the time required for the same volume of solution containing 60g/l of sodium chloride to pass through the capillary.

The specific viscosity η can be determined in the following manner:

η ═ passing time of polymer solution-passing time of NaCl solution)/passing time of NaCl solution

Better results are obtained if the diameter of the capillary is chosen such that the time required for the polymer solution minus the time required for the solution containing only NaCl is between 90 and 100 seconds.

After 24 hours of storage, 75g/m in the same operating mode as in test 1²The sheet was formed, and the thickness was measured in the same manner as in test 1.

The results were:

a) for pigments:

the pH of the slurry 3 hours after the end of the natural calcium carbonate treatment in this test was 7.5, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

for the raw material samples, i.e. the control (untreated filler): at 75g/m²At the time, it is 113 μm

For the test specimens: at 75g/m²123 μm in terms of thickness, and 68.9g/m in terms of thickness of 113 μm²。

We have seen that in this test, if the sheet thickness is converted to a value of 113 μm, 6.1g/m is omitted²I.e. 8.8% of the weight of the paper, which is a significant saving in terms of the environment.

Opacity and whiteness measurements were also made on the previously formed paper.

Opacity is measured by measuring the translucency index of the paper using a Data Color Elrepho model 2000 spectrophotometer according to standard DIN 53146.

The whiteness of the paper is measured with a Data Color Elrepho 2000 type spectrophotometer using ultraviolet light on a Tappi filter according to the ISO standard named brightness R457. Measurements were made on a stack of 10 sheets to avoid the effects of translucency.

The result obtained by the above-described operating mode is:

whiteness of inventive samples: 89.6

Opacity of the inventive specimens: 89.4

Whiteness of control sample (untreated): 88.4

Opacity of control samples (untreated): 86.4.

test 3

In a glass reactor at a temperature of 20 ℃ with a reaction solution corresponding to 0.25mol H per mol calcium carbonate₃O⁺75g, calculated as pigment, of a Norwegian marble type presscake in the form of a slurry having a dry matter concentration of 10% by weight, the particle size distribution of which, determined using a Sedigraph5100 from Micromeritics, is such that 75% by weight of the particles have a diameter of less than 1 μm, are treated with a 10% by weight phosphoric acid solution. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to carbon dioxide gas was equal to about 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry was 7.7 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²When measured, the thickness was 119 μm, and when converted to a thickness of 113 μm, the thickness was 71.1g/m²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 3.9g/m is omitted²I.e. 5.2% of the weight of the paper, which is a significant saving in terms of the environment.

Test 4

At a temperature of 20 ℃ with a quantity of H corresponding to 0.15mol per mol of calcium carbonate₃O⁺1kg of calcium carbonate of the Finnish marble type calculated as dry pigment, wet-ground to a dry matter concentration of 75 wt% using 0.55 wt% sodium polyacrylate with a specific viscosity of 0.54, and diluted to a slurry with a dry matter content of 45%, the particle size distribution of which, measured with a Sedigraph5100 from Micromeritics, is such that 63 wt% of the particles have a diameter of less than 1 μm. Then, carbon dioxide was bubbled through the slurry with an overpressure of about 100mbar for 5 hours, so that the volume ratio of suspension to carbon dioxide gas was equal to 1: 0.1.

The product was sieved and, after 24 hours of storage, at 75g/m in the same operating mode as in test 1²A paper sheet was formed and the thickness was measured in the same manner as in test 1, and the results were compared with those obtained using an untreated calcium carbonate product having a particle size distribution such that 63% by weight of the particles had a diameter of less than 1 μm as determined by a Sedigraph5100 of Micromeritics.

The results were:

a) for pigments:

the pH of the slurry 2 hours after the end of the natural calcium carbonate treatment in this test was 7.6, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²When the thickness was 116 μm, it gave 72.9g/m in terms of the thickness of 113 μm²。

We have seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 2.1g/m is omitted²I.e. 2.8% of the weight of the paper, which is a significant saving in terms of the environment.

Test 5

In a glass reactor at a temperature of 35 ℃ with 0.15mol of H per mol of calcium carbonate₃O⁺Treatment with a 10% by weight phosphoric acid solution 75g of calcium carbonate, norwegian marble type, in the form of a slurry with a dry matter concentration of 10% by weight, calculated as dry pigment, have a particle distribution such that 75% by weight of the particles have a diameter of less than 1 μm, measured with a Sedigraph5100 from Micromeritics. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to the carbon dioxide gas was equal to 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry was 7.8 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²118 μm in terms of thickness of 113 μm, and 71.8g/m in terms of thickness²。

We have seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 3.2g/m is omitted²I.e. 4.2% of the weight of the paper, which is a significant saving in terms of the environment.

Test 6

In a glass reactor at a temperature of 45 ℃ with a quantity of H corresponding to 0.30mol per mol of calcium carbonate₃O⁺Treatment with a 10% by weight phosphoric acid solution of 75g, calculated on the dry pigment, in the dry matter concentration10% by weight of slurry Norwegian marble type calcium carbonate, the particle size distribution, determined using a Sedigraph5100 from Micromeritics, Inc., is such that 75% by weight of the particles have a diameter of less than 1 μm. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to carbon dioxide gas was equal to about 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry was 7.9 4 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

Test 7

In a glass reactor, at a temperature of 35 ℃ with a quantity of H corresponding to 0.32mol per mol of calcium carbonate₃O⁺36g of calcium carbonate of the Finnish marble type in the form of a slurry with a dry matter concentration of 4.8 wt.% (i.e. more dilute) calculated on dry pigment, the particle size distribution of which, measured at 21.6 wt.% using a Sedigraph5100 from Micromeritics, Inc., is such that 65 wt.% of the particles have a diameter of less than 1 μm.Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to the carbon dioxide gas was equal to 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry was 7.5 6 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²121 μm in terms of thickness, and gives 70.0g/m in terms of thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 5g/m is omitted²I.e. 6.6% of the weight of the paper, which is a significant saving in terms of the environment.

Test 8

In a glass reactor at a temperature of 60 ℃ with a quantity of H corresponding to 0.5mol per mol of calcium carbonate₃O⁺3750g of calcium carbonate of Finnish marble type in the form of a slurry with a dry matter concentration of 20% by weight, calculated as dry pigment, at 75.0% by weight, the particle size distribution, measured with a Sedigraph5100 from Micromeritics, is such that 65% by weight of the particles have a diameter of less than 1 μm. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 2 hours so that the volume ratio of the suspension to the carbon dioxide gas was equal to 1: 0.1.

The results were:

a) for pigments:

the pH of the slurry was 7.8 at 6 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²It was 132 μm and it was converted to a thickness of 113 μm to give 64.2g/m²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 10.8g/m is omitted²I.e. 14.4% of the weight of the paper, which is a significant saving in terms of the environment.

Test 9

In a glass reactor at a temperature of 45 ℃ with 0.32mol of H per mol of calcium carbonate₃O⁺36g of calcium carbonate of Finnish marble type in the form of a slurry with a dry matter concentration of 4.8% by weight, calculated as dry pigment, at 21.6% by weight, the particle size distribution, measured with a Sedigraph5100 from Micromeritics, is such that 65% by weight of the particles have a diameter of less than 1 μm. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to the carbon dioxide gas was equal to 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry was 8.1 at 8 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²126 μm in the case of the thickness, and gives 67.1g/m in terms of the thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 7.9g/m is omitted²I.e. 10.5% of the weight of the paper, which is a significant saving in terms of the environment.

The abrasion measurement result was 1.7mg, and the abrasion value of the control group was 4.5 mg.

Test 10

In a glass reactor, this time at a temperature of 90 ℃ with a quantity of H corresponding to 0.32mol per mol of calcium carbonate₃O⁺36g of calcium carbonate of Finnish marble type in the form of a slurry with a dry matter concentration of 4.8% by weight, calculated as dry pigment, at 21.6% by weight, the particle size distribution, measured with a Sedigraph5100 from Micromeritics, is such that 65% by weight of the particles have a diameter of less than 1 μm. Then, carbon dioxide at atmospheric pressure was bubbled through the slurry for 5 hours so that the volume ratio of the suspension to carbon dioxide gas was equal to about 1: 0.05.

The results were:

a) for pigments:

the pH of the slurry 2 hours after the end of the natural calcium carbonate treatment in this test was 7.5, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²125 μm, giving 67.7g/m in terms of thickness of 113 μm²。

We have seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 7.3g/m is omitted²I.e. 9.7% of the weight of the paper, which is a significant saving in terms of the environment.

The abrasion performance was measured by means of an Einlehner 2000 apparatus to give a data of 2.0mg, compared with a control group having an abrasion value of 4.5 mg.

The tests described above show that the advantages of the invention are a reduction in weight for paper of the same thickness, a reduction in abrasion, a better smoothness for better whiteness and a better retention of filler.

Test 11

At a height of 12m of 40m³In a reactor, at a temperature of 55 ℃, with a catalyst containing 0.30mol of H per mol of calcium carbonate₃O⁺3600kg of calcium carbonate of the Carrare marble type in the form of a slurry with a dry matter content of 24.8% by weight, calculated on dry pigment, were treated with a 10% by weight phosphoric acid solution, the particle size distribution at 28.6% by weight being determined with a Sedigraph5100 from Micromeritics such that 65% by weight of the particles have a diameter of less than 1 μm. Simultaneously with this reaction and then, with internally circulated carbon dioxide and injected at a pressure of 1.2bar at the bottom of the reactorIs bubbled through the slurry for 5 hours so that the volume ratio of suspension to carbon dioxide gas is equal to about 1: 5.

The results were:

a) for pigments:

BET specific surface area was 35.5m²/g。

The BET specific surface is measured according to the BET method of ISO standard 9277, i.e.under liquid nitrogen cooling and under nitrogen flow, with a sample dried to constant weight and thermostatted at 250 ℃ for 1 hour under nitrogen. These conditions are in the claims the conditions of the standard specifically referred to as ISO standard 9277.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²126 μm in the case of the thickness, and gives 67.3g/m in terms of the thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 7.7g/m is omitted²I.e. 10.3% of the weight of the paper, which is a significant saving in terms of the environment.

Test 12

This test illustrates the invention and relates to gumming examples with different grammage on a plastic support, using on the one hand a low-concentration slurry of untreated filler and on the other hand a low-concentration slurry of filler treated according to the invention.

According to the general mode of operation of test 11, a slurry containing 17.2% dry content of ground calcium carbonate and 0.5% by weight of a dispersant of the polyacrylate type is treated until the particle size distribution, measured with a Sedigraph5100 from Micromeritics, is such that 65% by weight of the particles have a diameter of less than 1 μm.

The procedure for the gumming test consists in using an Erichsen Bechcoat^TMA model gummer gummed on a semi-matte plastic foil sold by the company Mulhlebach, Switzerland.

Two coating slips used had a slip containing 100 parts of the pigment to be tested and 12 parts of the pigment available from BASF under the trade name Acronal S360D^TMCompositions of styrene/acrylate based latexes are marketed.

For the first, the pigment slurry to be tested corresponds to an untreated calcium carbonate slurry with a dry content of ground calcium carbonate of 17.2% containing 0.5% by weight of a polyacrylate type dispersant until the particle size distribution determined with a Sedigraph5100 from Micromeritics corporation is such that 65% by weight of the particles have a diameter of less than 1 μm.

For the second, the pigment slurry to be tested corresponds to a slurry with a dry calcium carbonate content of 17.2% of the same calcium carbonate treated according to the previous mode of operation.

The results of the thickness measurements of three tests, one on the plastic carrier, are summarized in the following table and in FIG. 2; once on a support coated with an untreated precipitated calcium carbonate slurry; the last time is for the support coated with the treated precipitated calcium carbonate slurry:

	thickness of uncoated Carrier (μm)	Thickness (. mu.m) of the coating with untreated calcium carbonate	Coating the adhesive in gram number of g/m²	Thickness (. mu.m) of the coating with calcium carbonate treated according to the invention	Coating the adhesive in gram number of g/m²
	thickness of uncoated Carrier (μm)		Coating the adhesive in gram number of g/m²		Coating the adhesive in gram number of g/m²		79.59
Scraper 3		81.19	4.78	95.19	4.28		79.59
Scraper 3		81.19	4.78	95.19	4.28	Scraper 4		83.19	8.44	104.1	7.09
Scraper 5		85.19	11.09	109.59	8.78	Scraper 4		83.19	8.44	104.1	7.09

A study of the above table shows:

the thickness of the paper, when not gummed, is 79.59

4.78g/m by conventional gumming²The thickness of the weight paper sheet is increased to 81.19

Gumming with the composition of the invention, at 4.28g/m²The thickness of the paper increases significantly to 95.19.

The thickness of the glue layer is, of course, obtained from the difference in thickness between the glued and the unglued paper.

Thus, the paper thickness was 7.95 for a weight of 4.28g/m²Is coated with the product of the invention and untreated paperThe increase in the thickness of the glue applied between sheets (95.19 and 79.59) was 15.6 μm and 4.78g/m for weight²There was only a 1.6 increase between gumming with the conventional composition and untreated paper (81.19 vs 79.59).

Thus, the increase in thickness (expressed as so-called "bulk") resulting from the use of the composition of the invention is 10 times greater for almost the same weight.

The same calculation for different weights can be plotted for thickness (. mu.m) and weight (g/m) in FIG. 2²) The relationship between them.

The explanation of FIG. 2 makes it clear that in the control, i.e. the untreated test, the slope of the paste thickness is 0.5 μm g^-1·m^-2In the test of the present invention, however, the slope of the paste thickness was 3.5. mu. m.g^-1·m^-2。

Thus, we see that, thanks to the use of the product of the invention, a paper with better paper hiding, better calendering and greater porosity is obtained.

Test 13:

this test illustrates the invention, using 150g (dry basis) of a calcium carbonate cake of the Norwegian marble type, the particle size distribution of the Sedigraph5100 being such that 65% by weight of the particles, containing 0.5% by weight (dry basis) of sodium polyacrylate with a specific viscosity of 0.75, have a diameter of less than 1 μm, diluted to 20% with water. At this point 1 liter of product was prepared in a glass reactor and heated to 70 ℃. An amount of hydrochloric acid in the form of a 10% aqueous solution corresponding to 0.507mol of H per mol of calcium carbonate was added dropwise over a period of 1 hour₃O⁺. The product obtained is then re-reacted for 30 minutes by internally circulating carbon dioxide and carbon dioxide injected from the bottom of the reactor, and then stored in horizontal position on two rotating cylinders at a pH of 7.6.

The results were:

a) for pigments:

b) For paper:

the thickness measurements were:

for the raw material samples, i.e. the control group: at 75g/m²At the time, it is 114 μm

For the test specimens: at 75g/m²120 μm in the case of the composition, and gives 71.2g/m in terms of a thickness of 114 μm²。

We have seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 3.8g/m is omitted²I.e. 5% of the weight of the paper, which is a significant saving in terms of the environment.

Test 14:

this test illustrates the invention, using 150g (dry basis) of a calcium carbonate cake of the Norwegian marble type, the particle size distribution of the Sedigraph5100 being such that 65% by weight of the particles, containing 0.5% by weight (dry basis) of sodium polyacrylate with a specific viscosity of 0.75, have a diameter of less than 1 μm, diluted to 20% with water. At this point 1 liter of product was prepared in a glass reactor and heated to 70 ℃. Oxalic acid containing 2mol of water of crystallization in the form of a 10% aqueous solution is added dropwise in the course of 1 hour, in an amount corresponding to 0.335 mol 1H mol per mol of calcium carbonate₃O⁺。

The product was then reacted for 30 minutes with internally circulated carbon dioxide and carbon dioxide injected from the bottom of the reactor, and then stored in a horizontal position on two rotating cylinders at a pH of 7.7.

The results were:

a) for pigments:

the pH of the slurry was 8.0 at 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²121 μm in the case of the resin composition, and gives 70.4g/m in terms of a thickness of 114 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 4.6g/m is omitted²I.e. 6.1% of the weight of the paper, which is a significant saving in terms of the environment.

Example 2:

this example relates to the treatment of a slurry with a high dry matter content.

For this purpose, in all the tests of example 2, minerals in suspension (slurry) or filter cake or dry powder form, whose solid or dry matter content can be up to 80% by weight, are prepared in suitable reactors, if necessary diluted with demineralized water or tap water until the desired solid content is reached.

Test 15:

for this test, which illustrates the prior art, an aqueous composition was prepared by introducing the following ingredients into a mixer with stirring:

750g (dry basis) of Norwegian marble, the particle size distribution of the Sedigraph5100 being such that 75% by weight of the particles have a diameter of less than 1 μm,

250g (dry basis) of talc from Finland, the particle size distribution, measured in Sedigraph5100, being such that 45% by weight of the particles have a diameter of less than 2 μm,

5g (dry basis) of an acrylic adhesive comprising 90% by weight of acrylic acid and 10% by weight of tristyrylphenol methacrylate containing 25mol of ethylene oxide,

-the amount of water required to form an aqueous composition having a dry matter concentration of 65%.

After stirring for 30 minutes and the formation of co-structures between the marble or talc particles by means of a binder, 5.2g of a polyacrylate salt partially neutralized with sodium hydroxide and having a specific viscosity equal to 0.5, and the make-up of water and sodium hydroxide, are added to give an aqueous suspension having a dry matter content of 59.4% by weight.

75g/m was formed using the same operating mode as in test 1²And the thickness was measured in the same manner as in test 1. For 75g/m²The measured thickness was 116 μm.

Test 16:

to carry out this test, which illustrates the prior art, a Norwegian marble aqueous suspension with a dry matter concentration of 77.5% was used to make a gram number of 75g/m, using the same operating mode as test 1²The particle size distribution of (2) is such that 63% by weight of the particles have a diameter of less than 1 μm, as measured by Sedigraph 5100.

For 75g/m²The measured thickness was 115 μm.

The opacity measured according to the same operating mode as test 2 and according to standard DIN 53146 was 86.4.

The whiteness measured in the same operating mode as in test 2 and in accordance with the standard ISO Brightness R457 filter Tappi is 88.4.

Test 17:

to perform this test, which illustrates the prior art, the same operating die as in test 1 was usedFormula (I) A number of grams of 75g/m was made from an aqueous suspension of a Norwegian marble-type filter cake having a dry matter concentration of 67.2%²The paper of (4) having a particle size distribution, measured in Sedigraph5100, such that 75% by weight of the particles have a diameter of less than 1 μm and also containing 0.5% by weight (dry basis) of sodium polyacrylate having a specific viscosity equal to 0.75.

For 75g/m²The measured thickness was 114 μm.

Test 18:

for the tests which illustrate the invention, 4000g of the composition of test 12 in the form of a suspension having a dry matter content of 59.4%, a mixture of 25% by weight (dry basis) talc and 75% by weight (dry basis) calcium carbonate from Norwegian marble was prepared in a fluidized bed mixer (L ö dige apparatus), and phosphoric acid in the form of a 20% aqueous solution was added dropwise in the course of 45 minutes in an amount corresponding to 0.15mol H per mol calcium carbonate₃O⁺。

After treatment, L ö dige continued to rotate for 1 hour. This continuously rotating fluidized bed apparatus exchanges air with the carbon dioxide gas produced by the reaction, which results in the presence of carbon dioxide gas in the atmosphere of the apparatus.

The product obtained is then stored in a horizontal position on two rotating cylinders at a pH of 7.6.

The results were:

a) for pigments:

b) For paper:

the thickness measurements were:

for the starting sample, i.e. the control (run 10): at 75g/m²At the time, it is 116 μm

For the test specimens: at 75g/m²118 μm in terms of thickness of 116 μm, and 73.9g/m in terms of thickness²。

We have seen that in this test, if the sheet thickness is converted to a common value of 116 μm, 1.1g/m is omitted²I.e. 1.5% of the weight of the paper, which is a significant saving in terms of the environment.

Test 19:

for the test which illustrates the invention, 3290g of the composition of test 15, which is calcium carbonate of Norway marble origin with a dry matter content of 75.8%, was prepared in the form of a slurry in a fluidized bed mixer (L ö dige device) and phosphoric acid in the form of a 20% aqueous solution was added dropwise in an amount corresponding to 0.5mol H/mol calcium carbonate over 2 hours₃O⁺。

Then, at a pH of 7.6, the product will be stored in a horizontal position on two rotating cylinders.

The results were:

a) for pigments:

the pH of the slurry was 7.6 7 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

for the starting sample, i.e. the control (run 11): at 75g/m²At the time, it is 115 μm

For the test specimens: at 75g/m²130 μm in the case of the resin composition, and gives 66.5g/m in terms of a thickness of 115 μm²。

We have seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 8.5g/m is omitted²I.e. 11.3% of the weight of the paper, which is a significant saving in terms of the environment.

Test 20:

for the test which illustrates the invention, 1600g of Norwegian marble-type calcium carbonate having a particle size distribution determined in Sedigraph5100 such that 75% by weight of the particles have a diameter of less than 1 μm, the calcium carbonate being in the non-dispersed state in the form of a filter cake having certain properties, are sheared within 30 minutes in a fluidized bed apparatus (L ö dige device) having a dry matter concentration of 52.8% (see above) and 400g of another mixture of different carbonates obtained according to test 18 above, dispersed with 0.5% by weight (dry basis) of a sodium polyacrylate dispersant having a specific viscosity equal to 0.75 and then adjusted to a concentration of 60%. The product was then stored in a horizontal position on two rotating cylinders at a pH of 8.5.

The results were:

a) for pigments:

the pH of the slurry was 8.5 at 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

for the starting material sample, i.e. the control group (run 12): at 75g/m²At the time, it is 114 μm

For the test specimens: at 75g/m²118 μm in terms of thickness of 114 μm, and gives 72.2g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 2.8g/m is omitted²I.e. 3.7% of the weight of the paper, which is a significant saving in terms of the environment.

Test 21:

for the test which illustrates the invention, 1200g of calcium carbonate of the Norwegian marble type having a dry matter concentration of 52.8% and a particle size distribution, measured by Sedigraph5100, such that 65% by weight of the particles have a diameter of less than 1 μm, and 300g of another mixture of different carbonates treated according to the above test 18, the calcium carbonate being in the form of a filter cake in the non-dispersed state, are sheared in the presence of water, thus giving a concentration of 60%. This shearing was carried out in a fluid-bed mixer (L ö dige apparatus) for 30 minutes, with the addition of 500g of talc of Finnish origin and water, the particle size distribution of the Sedigraph5100 being such that 35% by weight of the particles have a diameter of less than 1 μm, the talc having been treated beforehand with 1.2% of an acrylic copolymer-based binder, so as to obtain a concentration of 60%. The mixture was sheared again for 30 minutes with the injection of carbon dioxide at a flow rate of 100 ml/min and then dispersed with a 0.5% by weight (dry basis) sodium polyacrylate having a viscosity equal to 0.75. The product was then stored in a horizontal position on two rotating cylinders at a pH of 8.4.

The results were:

a) for pigments:

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²When the thickness was 116 μm, it was converted to a thickness of 114 μm, giving 73.5g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 1.5g/m is omitted²I.e. 2% of the weight of the paper, which is a significant saving in terms of the environment.

Test 22:

to carry out this test, which illustrates the invention, the slurry obtained in the preceding test was aerated with carbon dioxide at a flow weight of 100 ml/min over a period of 5 hours, and the product obtained was then stored in a horizontal position on two rotating cylinders at a pH of 8.1.

The results were:

a) for pigments:

the pH of the slurry was 8.1 at 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

For the test specimens: at 75g/m²When the thickness was 117 μm, it was converted to a thickness of 114. mu.m, giving 73.1g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 1.9g/m is omitted²I.e. 2.5% of the weight of the paper, which is a significant saving in terms of the environment.

Test 23:

for this test to illustrate the invention, 6000g of calcium carbonate of norwegian marble origin in the form of a dispersion or slurry having a dry matter concentration equal to 77.8% by weight were prepared in a fluidized bed mixer (L ö dige device), the particle size distribution determined by Sedigraph5100 being such that 65% by weight of the particles had a diameter of less than 1 μm and were then diluted with water to a concentration of 75.7% by weight. 0.15mol of H per mol of calcium carbonate are added dropwise within 45 minutes via phosphoric acid in the form of a 20% aqueous solution₃O⁺。

Carbon dioxide was then bubbled through the product at a rate of 100 ml/min over a period of 5 hours, then a portion of the resulting product was stored on two rotating cylinders in a horizontal position for 1 week and another portion for 4 weeks.

The results were:

a) for pigments:

the pH of the slurry was 7.6 at 3 hours after the end of the natural calcium carbonate treatment of this test, and 7.8 after one and 4 weeks, indicating some degree of stability to acid.

b) For paper:

and (3) thickness measurement:

after one week of storage, 75g/m in the same operating mode as in test 1²The sheet was formed, and the thickness was measured in the same manner as in test 1.

The results of the thickness measurements are:

for the raw material samples, i.e. the control group: at 75g/m²At the time, it is 115 μm

For the testThe sample (2): at 75g/m²When measured, the thickness was 119 μm, and when converted to a thickness of 115 μm, it gave 72.2g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 2.8g/m is omitted²I.e. 3.7% of the weight of the paper, which is a significant saving in terms of the environment.

After 4 weeks of storage, 75g/m in the same operating mode as in test 1²The sheet was formed, and the thickness was measured in the same manner as in test 1.

The results of the thickness measurements are:

For the test specimens: at 75g/m²When measured, the thickness was 119 μm, and when converted to a thickness of 115 μm, it gave 72.2g/m²。

Test 24:

this test illustrates the invention, illustrating the recycling of carbon dioxide gas by means of a rotor/stator mixer of the Silverson type.

At a height of 1m of 2m³In a pilot plant, 284 litres of a slurry of natural calcium carbonate of source of Carrare marble with a dry matter concentration of 27%, measured as the particle size distribution in Sedigraph5100, were initially charged at 62 ℃ in a reactor equipped with a Silverson stirrer, so that 65% by weight of the particles had a diameter of less than 1 μm, and then diluted with the necessary amount of water to give a suspension with a dry matter concentration of 23.1%, then mixed with the corresponding 0.26mol H/mol calcium carbonate₃O⁺Mixed with 50% phosphoric acid solution. The addition time was 1 hour 45 minutes and the temperature at the start of the acid addition was 52 ℃. This was added manually using a beaker. With the acids usedThe amount of water added together resulted in the formation of a slurry with a dry matter concentration of 15.8%.

The slurry was then treated with 60kg of recycled carbon dioxide over 4 hours in a stirred tank of a Silverson containing approximately 50 litres of the contents.

The results were:

a) for pigments:

b) For paper:

the thickness measurements were:

for the raw material samples, i.e. the control group: at 75g/m²Is 117 μm in time

For the test specimens: at 75g/m²126 μm in the case of the thickness, and 69.6g/m in the case of conversion to the thickness of 117. mu.m²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 117 μm, 5.4g/m is omitted²I.e. 7.2% of the weight of the paper, which is a significant saving in terms of the environment.

Test 25:

this test illustrates the invention and the "size-breaking" treatment.

For this purpose, in order to obtain a "crash size" concentration of 10% by weight, dispersion was carried out in water with a mass of 800g of 100g/m, with stirring and within 30 minutes²The "size-reduced coating composition" of (1), having a filler content of about 15% by weight, corresponds to a particle size distribution determined on a dry basis of 120g of a Sedigraph5100 such that 35% by weight of natural calcium carbonate of the Finnish marble type having a particle diameter of less than 1 μm (coating rate per side of 25 g/m)²) Also dispersed in water is 400g (dry basis) of a natural carbon of the Finnish marble type having a particle size distribution measured in Sedigraph5100 such that 80 wt% of the particles have a diameter of less than 1 μmCalcium carbonate, the marble was ground by using 0.8 wt% (dry basis) sodium polyacrylate as a dispersant and an abrasive, and styrene-butadiene latex as a sizing binder.

At the end of the dispersion, the slurry having a dry matter concentration of 10% by weight was treated at 55 ℃ in a 10 liter glass reactor equipped with a stirrer, the amount of 50% by weight phosphoric acid solution used corresponding to 0.4mol H per mol calcium carbonate₃O⁺. Then, bubbling was carried out in the slurry and the fibers at atmospheric pressure and over 5 hours, so that the volume ratio of the suspension to the carbon dioxide gas was equal to 1: 0.1.

Paper was made in the same mode of operation as in the previous tests, with mixing of the "size coat" treated with fresh fibres, to give a final paper with a filler content of 20% by weight.

The results were:

a) for pigments:

the pH of the "size broken" slurry was 7.6 at 5 hours after the end of the natural calcium carbonate treatment in this test, indicating some degree of stability to acid.

b) For paper:

the thickness measurements were:

for the starting material samples, i.e. the control (samples prepared without acid and carbon dioxide gas treatment): at 75g/m²At the time, it is 115 μm

For the test specimens: at 75g/m²123 μm in the case of the thickness, and gives 70.1g/m in terms of the thickness of 115. mu.m²。

It is observed that in this test, if the sheet thickness is converted to a common value of 115 μm, 4.9g/m is omitted²I.e. 6.5% of the weight of the paper, which is a significant saving in terms of the environment.

Test 26:

for the purpose of illustrating the inventionFor this test, 447kg of the composition of test 15, which is a Norwegian marble-derived calcium carbonate in the form of a slurry with a dry matter concentration of 75.8% was prepared in a fluidized-bed mixer (L ö dige device), and the amount of calcium carbonate corresponding to 0.3mol of H per mol of calcium carbonate was added dropwise over a period of 2 hours₃O⁺20% phosphoric acid aqueous solution.

After completion of the phosphoric acid treatment, the product was stored for 3 hours, during which time carbon dioxide treatment was carried out by internally circulating carbon dioxide gas.

The product was then stored in a horizontal position in two rotating cylinders, the pH after 5 hours being 7.8.

After 24 hours of storage, a paper sheet was produced with a grammage of 75g/m in the same operating mode as in test 1²But with 25% pigment filler, the thickness was also measured in the same way as in test 1.

The BET specific surface area measured in the same manner as in test 11 was 11.5m²/g。

The results of the thickness measurements are:

for the raw material sample, i.e. the control (25% pigment-containing filler of test 13): at 75g/m²At the time, it is 114 μm

For the test specimens: at 75g/m²When measured, the thickness was 119 μm, and when converted to a thickness of 114 μm, it gave 71.8g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 3.2g/m is omitted²I.e. 4.3% of the weight of the paper, which is a significant saving in terms of the environment.

The breaking length measured according to the standard DIN EN ISO 1924-2, including the standard DIN 53112-1, is:

for the raw material sample, i.e. the control (25% pigment filler for test 13): 2.22km

For test specimens containing 25% of pigment filler: 2.54km, this ratioAt 75g/m²The breaking length of the untreated product was increased by 14.4%.

In addition, for a product with a size of 15mm, the tensile strength measured according to the standard DIN EN ISO 1924-2 is 28N in this test, whereas the control group has only 24.5N.

The opacity measured according to the same operating mode as test 2 and according to standard DIN 53146 was 86.6.

The whiteness measured in the same operating mode as in test 2 and according to a standard ISO Brightness R457 filter Tappi is 89.0.

Test 27:

for this test to illustrate the invention, 447kg of a test 15 composition in the form of a slurry of Norwegian marble-derived calcium carbonate having a dry matter concentration of 75.8% was prepared in a fluidized bed mixer (L ö dige apparatus), but with a particle size distribution determined with Sedigraph5100 such that 40% by weight of the particles had a diameter of less than 1 μm, 0.3mol H per mol of calcium carbonate being added dropwise over 2 hours with the aid of phosphoric acid in the form of a 20% aqueous solution₃O⁺。

The product was then stored in a horizontal position in two rotating cylinders at a pH of 7.6.

The BET specific surface area measured in the same manner as in test 11 was 9.8m²/g。

The results of the thickness measurements are:

for the raw material sample, i.e. the control (25% pigment filler for test 11): at 75g/m²At the time, it is 114 μm

For the test specimens: at 75g/m²121 μm in the case of the thickness, and to 114 μm in the case of the thicknessYield 70.7g/m²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 114 μm, 4.3g/m is omitted²I.e. 5.7% of the weight of the paper, which is a significant saving in terms of the environment.

for the raw material sample, i.e. the control (25% pigment filler for test 11): 2.30km

For test specimens containing 25% of pigment filler: 2.48km, the ratio being 75g/m²The breaking length of the untreated product was increased by 8.7%.

In addition, for a product with a size of 15mm, the tensile strength measured according to the standard DIN EN ISO 1924-2 is 27.3N in this test, whereas the control group has only 24.5N.

The opacity measured according to the same operating mode as test 2 and according to standard DIN 53146 was 87.7.

This same test specimen was subsequently gummed on a low wood content paper by means of a laboratory coater (Dixon spiral coater) to a thickness of 53 μm, the grams being 32.9g/m²±0.39％。

A short "dwell" head with a wiper angle of 45 ° was used. The speed of the glue application was 800 m/sec.

The coating slip used had a composition of 100pph of the pigment to be tested, 12pph of latex (styrene-butadiene latex type DL 966) and 0.5pph of carboxymethylcellulose (Finnfix FF5), the dry matter content being 56.6%.

The results obtained were:

thickness of the non-gummed paper: 53 μm

For the control group of test 13, coated with 7g/m²The thickness of the paper of (a): 56 μm

For this test according to the invention, a coating of 7g/m is applied²The thickness of the paper of (a): 59 μm

For the control group of test 13, coated with 7g/m²Coating thickness of (a): 3 μm

For this test, a coating of 7g/m²Coating thickness of (a): 6 μm

These results can indicate that the coating thickness can be increased by 1-fold relative to the control.

Example 3

This example relates to the use of treated or untreated calcium carbonate as a paper filler in ink jet printing.

In a 10 l vessel, 0.5kg (calculated as dry pigment) of Norwegian marble-type natural calcium carbonate in the form of a presscake, in Micromeritics, are diluted with distilled water^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 75 wt% of the particles had a particle diameter of less than 1 μm until a slurry with a dry matter concentration of 15 wt% was obtained. The slurry thus formed was then treated with 10% phosphoric acid as a 10 wt% solution over a period of 20 minutes at 65 ℃ and with stirring at 500 rpm. After 15 minutes, carbon dioxide was bubbled through the calcium carbonate suspension over a period of 1 hour.

After the bubbling was stopped, a paper containing a suspension called the calcium carbonate slurry to be tested as filler was produced.

For this purpose, paper was made from SR23 grade cellulose pulp containing kraft pulp and fibers consisting of 80% birch and 20% pine. 45g (dry basis) of this pulp was diluted in 10 l of water in the presence of about 15g of the filler composition to be tested, giving a filler content of about 20 to 0.5% as determined by the test. After stirring for 15 minutes, 0.06% by weight (dry basis relative to the dry weight of the paper) of a polyacrylamide retention agent is added, forming a gram number of 75g/m²The paper of (3), having a filler content of 20. + -. 0.5%. The equipment used for making paper is model 20 from hage corporation. 12MC Rapid-K ö the system.

The paper thus formed was dried at 92 ℃ and a vacuum of 940mbar for 400 seconds.

The filler content was controlled by analyzing the ash.

The thickness of the paper thus formed was measured. The thickness of a sheet or board is the perpendicular distance between its two parallel surfaces.

The samples were conditioned for 48 hours (according to German standard DIN EN 20187).

This standard specifies in detail that paper is a water-absorbing substance, and in this case has the property of being able to adjust its moisture content to the moisture content of the air environment. Moisture is absorbed when the moisture content of the ambient air increases, and conversely, moisture is released when the humidity of the air environment decreases.

Even if the relative humidity is kept constant, the moisture content of the paper is not necessarily the same if the temperature cannot be kept constant within certain limits. As the moisture content increases or decreases, the physical properties of the paper change.

For this reason, the samples should be conditioned for at least 48 hours until equilibrium is reached. The test specimens were also tested under the same climatic conditions.

The climatic conditions of the paper test were determined to meet the following data:

relative humidity 50% (+ -3)

Temperature 23 ℃ (± 1)

The thickness is determined using a micrometer according to German standard DIN EN 20534, the test indentation of which is up to 10n/cm². The results of the test were determined by calculating the average of 10 tests. The unit of the results is μm. The control group used the same amount (75 g/m)²) But untreated filler and the same batch of cellulose were used with the sameIn parallel to the paper produced.

As a result:

a) pigment:

as in this example, the pH of the slurry was 7.2 after 12 hours of treatment of the natural calcium carbonate, indicating acid stability.

b) Paper sheet

The results of the thickness measurements are:

For the test specimens: at 75g/m²120 μm in the case of the resin composition, and gives 70g/m in terms of a thickness of 112 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 112 μm, 5g/m is omitted²I.e. 6.6% of the weight of the paper, which is a significant saving in terms of the environment.

Characteristics of the impression:

if an EPSON for ink jet comprising a product of the prior art (FIG. 1, B) and tested according to the invention (FIG. 1, A) is used^TM Stylus COLOR 500^TMThe printing by the ink jet printer will see a much clearer impression of the present invention. The above figures are seen in the appendix.

Example 4:

this example relates to the use of treated or untreated calcium carbonate for ink-jet printing as a sizing and filler for paper.

In a 10 l vessel, 0.5kg (calculated as dry pigment) of Norwegian marble-type natural calcium carbonate in the form of a presscake, in Micromeritics, are diluted with distilled water^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 75 wt% of the particles had a diameter of less than 1 μm until a slurry with a dry matter concentration of 15 wt% was obtained. Then at 65 ℃ andthe slurry thus formed was treated with 10% phosphoric acid as a 10 wt% solution over a 20 minute period with stirring at 500 rpm. After 15 minutes, carbon dioxide was bubbled through the calcium carbonate suspension over a period of 1 hour.

Gluing operation procedure:

the same procedure as described above for test 26 was used, namely with the aid of a laboratory gumming machine (Dixon)^TMHelicoater of^TM) The test specimens were coated on low wood content paper having a thickness of 53 μm and a grammage equal to 32.9g/m²±0.39％。

The coating slip used had a composition containing 100pph of the pigment to be tested, 12pph of latex (DL 966 type styrene-butadiene latex) and 0.5pph of carboxymethylcellulose (Finnfix FF5)^TM) The dry matter content of (2) was 56.6%.

The samples were conditioned for 48 hours (according to German standard DIN EN 20187). This standard specifies in detail that paper is a water-absorbing substance, and in this case has the property of being able to adjust its moisture content to the moisture content of the air environment. Moisture is absorbed when the moisture content of the ambient air increases, and conversely, moisture is released when the humidity of the air environment decreases.

Even if the relative humidity is kept constant, the moisture content of the paper is not necessarily the same if the temperature cannot be kept constant within certain limits. As the moisture content increases or decreases, the physical properties of the paper change. For this reason, the samples should be conditioned for at least 48 hours until equilibrium is reached. The test specimens were also tested under the same climatic conditions.

Determining that the climate conditions of the paper test meet the following data:

relative humidity 50% (+ -3)

Temperature 23 ℃ (± 1)

The thickness was determined using a micrometer according to German standard DIN EN 20534 with a test indentation of 10n/cm². The results of the test were determined by calculating the average of 10 tests. The unit of the results is μm. The control group used the same amount (75 g/m)²) But untreated filler and the same batch of cellulose were made in parallel in the same manner.

As a result:

a)

pigment:

b) Paper sheet

The results of the thickness measurements are:

Print density was measured according to the following mode of operation and the results are summarized in table 1 below.

Optical density is a measure of the reflection density of an image. According to the manufacturer Hewlett-Packard company (HP)^TMIn the established mode of operation, special patterns are printed on the paper by means of a reflection densitometer (Macbeth RD 918)^TM) It was measured for optical density of pure black, composite black, and cyan, magenta, and yellow.

For all the examples that were tested, this procedure was valid if not stated to the contrary.

The experiments of Table 1 were carried out on a cellulose paper support or on a special paper consisting of 100 parts of the pigment to be tested, 15 parts of PVA (polyvinyl alcohol), 5 parts of the additive PK-130 of Stockhausen, the specific surface of the filler being 70m²A coarse filler characterized by a high specific surface.

Desk coater with the aid of an Erichsen apparatus^TMGlue was applied to the paper as defined in table 1.

The first two experiments of table 1 correspond to pigmented paper (coated with starch on the surface of the machine paper) without glue applied.

The following two correspond to papers treated with synthetic silicates. We see that in order to obtain good optical density, special paper must be used.

The last two experiments correspond to papers gummed with the composition of the invention. We see that the present invention enables the use of normal inkjet printed paper at comparable print densities without the use of more expensive specialty paper.

It has been shown in practice that the invention shows significant advantages (1.40 to 1.20 and 1.39 to 1.30) compared to the uncoated sheets, the value of 1.40 obtained on normal sheets according to the invention corresponding absolutely to the value of 1.40 obtained on special sheets according to the prior art.

TABLE 1

Density measurement for inkjet printing

The experimental results are as follows: average of 15 times

Paper sheet	Printing	Adjustment of	Black printing Density B	Cyan-blue print Density C	Magenta print Density M	Yellow print density Y
Paper sheet	Printing	Adjustment of	Black printing Density B	Cyan-blue print Density C	Magenta print Density M	Yellow print density Y	MühlebachMultiline Top	HP deskjet895Cxi	Normal paper	1.92	1.38	1.40	1.30
MühebachMultiline Top	Epson StylusColor 500	Normal paper	1.74	1.50	1.28	1.20	MühlebachMultiline Top	HP deskjet895Cxi	Normal paper	1.92	1.38	1.40	1.30
MühebachMultiline Top	Epson StylusColor 500	Normal paper	1.74	1.50	1.28	1.20	Epson inkjet paper 720dpi	HP deskjet895Cxi	High brightness (whiteness) HP ink-jet paper	1.95	1.38	1.23	1.08
Epson inkjet paper 720dpi	Epson StylusColor 500	Special adhesive coated paper 720dpi	1.94	1.80	1.55	1.44	Epson inkjet paper 720dpi	HP deskjet895Cxi	High brightness (whiteness) HP ink-jet paper	1.95	1.38	1.23	1.08
Epson inkjet paper 720dpi	Epson StylusColor 500	Special adhesive coated paper 720dpi	1.94	1.80	1.55	1.44	According to the invention	HP deskjet895Cxi	Normal paper	1.94	1.57	1.59	1.39
According to the invention	Epson StylusColor 500	Normal paper	1.80	1.70	1.46	1.40	According to the invention	HP deskjet895Cxi	Normal paper	1.94	1.57	1.59	1.39

Example 5

This example relates to the use of coarse-grained but high specific surface treated or untreated calcium carbonate as a paper filler.

For this purpose, 0.5kg (calculated as dry pigment) of Norwegian marble-type natural calcium carbonate, calculated as Micromeritics, was diluted in a 10 l container^TMCompany Sedigraph5100^TMMeasured particlesThe degree distribution is such that 65% by weight of the particles have a diameter of less than 1 μm and a BET specific surface area of up to 15.5m²In the form of a dispersion or slurry with a dry matter concentration of 75%, and also containing a dispersant of the sodium polyacrylate type, diluted until a slurry with a dry matter concentration of 20% by weight is obtained (test according to BET method of ISO standard 9277). The slurry thus formed was then treated with 20%, 30% or 40% phosphoric acid as a 10% by weight solution at a flow rate of 30 l/min at atmospheric pressure at the bottom of the vessel at 65 ℃ under gentle stirring over a period of 2 hours. After 2 hours, carbon dioxide was bubbled through the calcium carbonate suspension over a period of 1 hour.

The filler has the following characteristics:

example 5A, 20% phosphoric acid

a) For pigments

-analysis of the mean diameter of the particles by visual means under an electron microscope: 7 μm

BET specific surface (BET method test according to ISO standard 9277): 38.5m²/g

b) For paper

And (3) thickness measurement:

for a sample control of the starting material (untreated filler): at 75g/m²At the time of 113 μm

For the test specimens: at 75g/m²133 μm in terms of thickness of 113 μm, and 63.7g/m in terms of thickness²。

We have seen that in this test, 11.3g/m is omitted if the sheet thickness is converted to a common value of 113 μm²I.e. 15.0% of the weight of the paper, which is a significant saving in terms of the environment.

Example 5B, 30% phosphoric acid

a) For pigments

-analysis of the mean diameter of the particles by visual means under an electron microscope: 9 μm

BET specific surface (BET method test according to ISO standard 9277): 44.2m²/g

b) For paper

And (3) thickness measurement:

control (untreated filler) for a sample of raw material: at 75g/m²At the time of 113 μm

For the test specimens: at 75g/m²139 μm in the case, and gives 61.0g/m in terms of a thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 14.0g/m is omitted²I.e. 18.7% of the weight of the paper, which is a significant saving in terms of the environment.

Example 5C, 40% phosphoric acid

a) For pigments

-analysis of the mean diameter of the particles by visual means under an electron microscope: 13 μm

BET specific surface (BET method test according to ISO standard 9277): 58.4m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²When the thickness was 152 μm, it gave 55.7g/m in terms of the thickness of 113 μm²。

It can be seen that in this test, 19.3g/m was omitted if the sheet thickness was converted to a common value of 113 μm²I.e. 25.7% of the weight of the paper, which is a significant saving in terms of the environment.

Example 6:

this example relates to a process for the continuous production of the product according to the invention and to the use of coarse-grained but high BET surface area treated or untreated calcium carbonate as a paper filler.

For this purpose, 100kg (calculated as dry pigment) of natural calcium carbonate of the Norwegian marble type, which is available as Micromeritics, are diluted with water in a 3000 l vessel^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 65% by weight of the particles had a diameter of less than 1 μm and a BET specific surface area of 15.5m²In the form of a dispersion or slurry with a dry matter concentration of 75%, and also containing a sodium polyacrylate dispersant, diluted until a slurry with a dry matter concentration of 10% by weight is obtained (test according to BET method of ISO standard 9277). The slurry thus formed was then treated with 10%, 20% or 30% phosphoric acid in about 15% by weight solution at a dosage of 1/4 phosphoric acid at a flow rate of 50 liters/minute at the bottom of each chamber at atmospheric pressure in 4 25 liter chambers in succession at 65 ℃. The product remained in each chamber for 15 minutes.

The filler has the following characteristics:

example 6A, 10.0% phosphoric acid

a) For pigments

Slurry concentration: 7.8 percent

Using Micromeritics^TMCompany Sedigraph5100^TMAverage diameter of the particles measured, 1.7 μm

BET specific surface (test according to BET method of standard ISO 9277): 36.0m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²It is 123 μm, converted to 113 μmm, gives 68.9g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 6.1g/m is omitted²I.e. 8.1% of the weight of the paper, which is a significant saving in terms of the environment.

Example 6B, 19.1% phosphoric acid

a) For pigments

Slurry concentration: 7.8 percent

Average diameter of the particles analyzed by visual means under an electron microscope: 12 μm

BET specific surface (test according to BET method of standard ISO 9277): 49.9m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²It was 135 μm and gave 62.8g/m in terms of the thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 12.2g/m is omitted²I.e. 16.6% of the weight of the paper, which is a significant saving in terms of the environment.

Example 6C, 30% phosphoric acid

a) For pigments

Slurry concentration: 17.9 percent

Average particle diameter, 12 μm, visualized under an electron microscope

BET specific surface (test according to BET method of standard ISO 9277): 45.7m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²158 μm in terms of thickness of 113 μm, and 53.6g/m in terms of thickness²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 21.4g/m is omitted²I.e. 28.5% of the weight of the paper, which is a significant saving in terms of the environment.

Example 6D:

For this purpose, 100kg (calculated as dry pigment) of natural calcium carbonate of the Norwegian marble type, which is available as Micromeritics, are diluted with water in a 3000 l vessel^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 65% by weight of the particles had a diameter of less than 1 μm and a BET specific surface area of 15.5m²In the form of a dispersion or slurry with a dry matter concentration of 75%, according to the BET method of standard ISO 9277, and also containing a dispersant of the sodium polyaspartate type, diluted so as to obtain a slurry with a dry matter concentration of 10% by weight. The slurry thus formed was then treated with 10%, 20% or 30% phosphoric acid in about 15% by weight solution at a dosage of 1/4 phosphoric acid at a flow rate of 50 liters/minute at the bottom of each chamber at atmospheric pressure in 4 25 liter chambers in succession at 65 ℃. The product remained in each chamber for 15 minutes.

The filler has the following characteristics:

a) for pigments

Slurry concentration: 8.9 percent

Using Micromeritics^TMCompany Sedigraph5100^TMMeasured average particle diameter, 1.9 μm

BET specific surface (test according to BET method of standard ISO 9277): 39.1m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²123 μm in terms of thickness, and 68.8g/m in terms of thickness of 113 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 113 μm, 6.2g/m is omitted²I.e. 8.1% of the weight of the paper, which is a significant saving in terms of the environment.

Example 7:

this example relates to the use of a treated/untreated calcium carbonate mixture as a paper filler.

a) Preparation of the treated pigment:

0.6kg (calculated as dry pigment) of Norwegian marble-type natural calcium carbonate, in Micromeritics, was diluted in a 1 l container^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 65% by weight of the particles had a diameter of less than 1 μm and a BET specific surface area of 8.4m²In the form of a dispersion or slurry having a dry matter concentration of 20%, measured according to the BET method of standard ISO 9277, and subsequently diluted with water to give a slurry having a dry matter concentration of 10.2% by weight. The slurry thus obtained was then treated with 70% phosphoric acid in a 10% by weight solution at 60 ℃ with stirring over a period of 1 hour. After 1 hour, carbon dioxide was bubbled through the calcium carbonate suspension for 0.5 hour.

b) Preparation of a mixture of treated and untreated pigments: mix for 15 minutes with stirring.

The filler has the following characteristics:

example 7A, 100% treated pigment:

a) for pigments

By Micromeritics^TMCompany Sedigraph5100^TMThe particle size distribution was measured such that 21 wt% of the particles had a diameter of less than 1 μm,

BET specific surface (test according to BET method of standard ISO 9277): 44.5m²/g

b) For paper

And (3) thickness measurement:

control (untreated filler) for a sample of raw material: at 75g/m²At the time of 115 μm

For the test specimens: at 75g/m²162 μm in the case of the resin composition, and gives 52.2g/m in terms of a thickness of 115 μm²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 22.7g/m is omitted²I.e. 30.3% of the weight of the paper, which is a significant saving in terms of the environment.

Example 7B, 21.5% example 7A treated pigment and 78.5% untreated pigment:

as a result:

a) for pigments

By Micromeritics^TMCompany Sedigraph5100^TMThe particle size distribution was measured such that 63 wt% of the particles had a diameter of less than 1 μm,

BET specific surface (test according to BET method of standard ISO 9277): 15.5m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²124 μm in terms of thickness of 115 μm, and 69.5g/m in terms of thickness²。

It can be seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 5.5g/m is omitted²I.e. 7.3% of the weight of the paper, which is a significant saving in terms of the environment.

Example 7C, 35.5% example 7A treated pigment and 64.5% untreated pigment:

a) for pigment mixtures

By Micromeritics^TMCompany Sedigraph5100^TMThe particle size distribution was measured such that 60 wt% of the particles had a diameter of less than 1 μm,

BET specific surface (test according to BET method of standard ISO 9277): 20.0m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²130 μm in the case of the thickness, and gives 66.3g/m in terms of the thickness of 115. mu.m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 8.7g/m is omitted²I.e. 11.6% of the weight of the paper, which is a significant saving in terms of the environment.

Example 7D, 50.0% example 7A treated pigment and 50.0% untreated pigment:

a) in the case of a mixture of pigments,

by Micromeritics^TMCompany Sedigraph5100^TMThe particle size distribution was measured such that 42.0 wt% of the particles had a diameter of less than 1 μm,

BET specific surface (test according to BET method of standard ISO 9277): 28.0m²/g

b) For paper

And (3) thickness measurement:

For the test specimens: at 75g/m²It was 137 μm, and when converted to a thickness of 115 μm, it gave 62.9g/m²。

We have seen that in this test, if the sheet thickness is converted to a common value of 115 μm, 12.1g/m is omitted²I.e. 16.0% of the weight of the paper, which is a significant saving in terms of the environment.

Example 8:

this example relates to the use of treated or untreated calcium carbonate in coatings.

For this purpose, at a distance of 45m³In a vessel of (a) 5 tons (calculated on dry pigment) of norwegian marble type natural calcium carbonate in the form of a presscake, in Micromeritics, are diluted with distilled water^TMCompany Sedigraph5100^TMThe particle size distribution was measured so that 70.0 wt% of the particles had a diameter of less than 1 μm until a slurry with a dry matter concentration of 25% was obtained. Then stirred at 60 ℃ and 200rpm for 2 hours with a solution of 0.20mol H per mol calcium carbonate₃O⁺The slurry thus obtained was treated with a 10% phosphoric acid solution.

After 2 hours, carbon dioxide was bubbled through the calcium carbonate suspension for 5 hours at an overpressure of 50mbar so that the volume ratio of suspension to carbon dioxide gas was about 1: 0.15.

After 24 hours of storage, the slurry was dried using a spray dryer to form an emulsion coating containing the dry calcium carbonate to be tested as part of the filler.

The operation procedure for preparing the coating is as follows:

at one 1m³The coating is prepared by dispersing the additives and pigments in water over 10 minutes with stirring at 3000rpm, then the speed is reduced to 1000rpm and the latex is added. And then redispersed for 10 minutes.

Coating formulation

Based on 18% TiO₂The formula (1)	kg	Base material	-15％ TiO₂	-30％ TiO₂
Based on 18% TiO₂The formula (1)	kg	Base material	-15％ TiO₂	-30％ TiO₂	Mowilith LDM 1871 about 53%	kg	147.0	147.0	147.0
Tiona RCL-535	kg	180.0	153.0	126.0	Mowilith LDM 1871 about 53%	kg	147.0	147.0	147.0
Tiona RCL-535	kg	180.0	153.0	126.0	Filler material	kg	0.0	27.0	54.0
Omyacarb 2-Gu	kg	107.0	107.0	107.0	Filler material	kg	0.0	27.0	54.0
Omyacarb 2-Gu	kg	107.0	107.0	107.0	Finnatalc M50	kg	50.0	50.0	50.0
Omyacarb 10-Gu	kg	108.0	108.0	108.0	Finnatalc M50	kg	50.0	50.0	50.0
Omyacarb 10-Gu	kg	108.0	108.0	108.0	Calcimatt	kg	70.0	70.0	70.0
Coatex BR 910G，10％	kg	48.5	48.5	48.5	Calcimatt	kg	70.0	70.0	70.0
Coatex BR 910G，10％	kg	48.5	48.5	48.5	Coatex P50	kg	3.0	3.0	3.0
Mergal K15	kg	2.0	2.0	2.0	Coatex P50	kg	3.0	3.0	3.0
Mergal K15	kg	2.0	2.0	2.0	Calgon N	kg	1.0	1.0	1.0
NaOH，10％	kg	2.0	2.0	2.0	Calgon N	kg	1.0	1.0	1.0
NaOH，10％	kg	2.0	2.0	2.0	Byk 032	kg	3.0	3.0	3.0
Tylose MH 30 000 YGB	kg	3.0	3.0	3.0	Byk 032	kg	3.0	3.0	3.0
Tylose MH 30 000 YGB	kg	3.0	3.0	3.0	Deionized water	kg	275.5	275.5	275.5
Total of		1000.0	1000.0	1000.0	Deionized water	kg	275.5	275.5	275.5
Total of		1000.0	1000.0	1000.0	Data of the recipe
					Data of the recipe
					PVC	％	71.0	71.5	71.9
Density of solid	g/cm³	2.48	2.44	2.41	PVC	％	71.0	71.5	71.9
Density of solid	g/cm³	2.48	2.44	2.41	Density of liquid	g/cm³	1.56	1.55	1.55
Volume of solids per liter	ml/l	369	372	375	Density of liquid	g/cm³	1.56	1.55	1.55
Volume of solids per liter	ml/l	369	372	375	Volume per kg solids	ml/kg	236	239	243
Solids content	％	60.3	60.3	60.3	Volume per kg solids	ml/kg	236	239	243
Solids content	％	60.3	60.3	60.3	Pigment/binder: ratio of solids		6.61∶1	6.61∶1	6.61∶1

The results are shown below, with the control group containing 18% Ti₂Aqueous emulsion coating of O:

whiteness (DIN 53140) (control)

18％ TiO₂ 15.3％ TiO₂ 12.6％ TiO₂

(liquid thickness 300 μm)

For white Ry 90.8% 91.1% 91.2%

89.2% for black Ry 89.6% 89.7%

Opacity (ISO2814) 98.3% 98.4%

Ry black/Ry white 100

The whiteness and opacity of the control samples were the same as for the two inventive experiments containing-15% and-30% titanium dioxide pigment.

The dry film thickness was 104 μm 113 μm 112 μm

Dry film weight 177g/m² 166g/m² 163g/m²

In this experiment we see that the weight of the sample is 177g/m for a control sample having a thickness of 104 μm²The weight of the film containing the calcium carbonate of the invention is only 153g/m, respectively²And 151g/m²If the thickness of the coating is converted to a common value of 104 μm, 24g/m is omitted²And 26g/m²Corresponding to 13.5% and 14.7% of the coating weight, respectively, which is a great saving in the environmental field.

Claims

1. An aqueous suspension of one or more pigments, fillers or minerals capable of reducing the weight of a paper of constant surface area, optionally containing polymeric dispersants as rheology stabilizers for the suspension, characterized in that:

a) it contains natural carbonate, one or more of the reaction products of said carbonate and carbon dioxide gas, one or more of said carbonate and one or more of moderate-to-strong H₃O⁺The product of the ion donor reaction, and

b) which has a pH value, measured at 20 ℃, of more than 7.5,

wherein the natural carbonate is a mixture of the natural carbonate and talc, kaolin and/or titanium dioxide TiO thereof₂Magnesium oxide and other strong to medium H₃O⁺The ion donor is a mixture of inert minerals.

2. The aqueous suspension of claim 1 characterized in that said one or more strong H's are₃O⁺The ion donor is hydrochloric acid, sulfuric acid or their mixture, and the intermediate strength H₃O⁺The ion donor being H₂SO₃、HSO₄ ^-、H₃PO₄Oxalic acid or mixtures thereof.

3. Aqueous suspension according to claim 1, characterised in that the H is of moderate to strong strength in mol number relative to the carbonate₃O⁺The number of moles of the ion donor is 0.1 to 2 in total.

4. Aqueous suspension according to claim 3, characterised in that the H is of moderate to strong strength in mol number relative to the carbonate₃O⁺The number of moles of the ion donor is 0.25 to 1 in total.

5. The aqueous suspension of claim 1, characterized in that the BET specific surface area of the pigment, filler or mineral, measured according to standard ISO 9277, is between 5 and 200m²/g。

6. The aqueous suspension of claim 5, characterized in that the BET specific surface area of the pigment, filler or mineral, measured according to standard ISO 9277, is between 20 and 80m²/g。

7. The aqueous suspension of claim 5, characterized in that the BET specific surface area of the pigment, filler or mineral, measured according to standard ISO 9277, is between 30 and 60m²/g。

8. The aqueous suspension of claim 1, characterized in that the pigments, fillers or minerals have the following characteristics:

using Sedigraph5100^TMThe average particle diameter of the particles measured by a sedimentation method is 50-0.1 mu m

A BET specific surface, measured according to standard ISO 9277, of 15 to 200m²/g。

9. The aqueous suspension of claim 8, characterized in that the pigments, fillers or minerals have the following characteristics:

using Sedigraph5100^TMThe average particle diameter of the particles measured by a sedimentation method is 25-0.5 mu m

A BET specific surface, measured according to standard ISO 9277, of 20 to 80m²/g。

10. The aqueous suspension of claim 8, characterized in that the pigments, fillers or minerals have the following characteristics:

using Sedigraph5100^TMThe average particle diameter of the particles measured by a sedimentation method is 7-0.7 mu m

-a BET specific surface, measured according to standard ISO 9277, of 30 to 60m²/g。

11. Pigment, filler or mineral in dry state, characterized in that it is obtained by drying an aqueous suspension according to any one of claims 1 to 10.

12. Process for the preparation of an aqueous suspension according to any one of claims 1 to 10, characterized in that one or more medium to strong H is/are used₃O⁺The ion donor and carbon dioxide gas together treat the pigment, filler or mineral to adjust the pH to above 7.5.

13. The method of claim 12, characterized in that the carbon dioxide gas is derived from externally supplied carbon dioxideRecycled carbon dioxide or continuously added medium to strong H of the same type as used for the treatment₃O⁺Ion donor or another medium to strong H₃O⁺An ion donor.

14. The method according to claim 12, characterized in that the carbon dioxide gas comes from carbon dioxide at an overpressure of 0.05 to 5 bar.

15. A method according to claim 12, 13 or 14, characterized in that the method comprises the following 3 steps:

a) with one or more kinds of H from medium to strong₃O⁺Treating the ion donor;

b) treatment with carbon dioxide gas, either as a constituent of step a), or in parallel with step a), or after step a);

c) within the interval of 1-10 hours after the steps a) and b) are finished, adding no alkali or immediately after the steps a) and b) are finished, adjusting the pH value measured at 20 ℃ to be more than 7.5 by adding alkali, wherein the step c) is the last step of the method.

16. The method of claim 15, characterized in that it comprises the following 3 steps:

c) within the interval of 1-5 hours after the steps a) and b) are finished, adding no alkali or immediately after the steps a) and b) are finished, adjusting the pH value measured at 20 ℃ to be more than 7.5 by adding alkali, wherein the step c) is the last step of the method.

17. The method of claim 15, characterized in that steps a) and b) are repeated several times.

18. The process according to claim 15, characterized in that the pH value measured at 20 ℃ during the treatment steps a) and b) is 3 to 7.5 and the treatment temperature is 5 to 90 ℃.

19. The process according to claim 18, characterized in that the pH value measured at 20 ℃ during the treatment steps a) and b) is 3 to 7.5 and the treatment temperature is 45 to 60 ℃.

20. The process according to claim 15, characterized in that the concentration by volume of carbon dioxide gas in the suspension is such that the ratio by volume of suspension to carbon dioxide gas is from 1: 0.05 to 1: 20, and in step a) the ratio is from 1: 1 to 1: 20 and in step b) the ratio is from 1: 0.05 to 1: 1.

21. The process as claimed in claim 20, characterized in that the concentration by volume of carbon dioxide gas in the suspension is such that the ratio by volume of suspension to carbon dioxide gas is from 1: 0.05 to 1: 10, and in step a) the ratio is from 1: 0.5 to 1: 10 and in step b) the ratio is from 1: 0.05 to 1: 1.

22. The process according to claim 15, characterized in that the time of treatment step b) is from more than 0 to 10 hours.

23. The process according to claim 22, characterized in that the time of the treatment step b) is 2 to 6 hours.

24. A process according to claim 12, characterised in that the natural carbonate-containing pigment, filler or mineral is selected from natural calcium carbonate or carbonate-containing dolomite and their mixtures with talc, kaolin and/or titanium dioxide TiO₂Manganese oxide MnO and others known in the art of papermaking from medium to strong H₃O⁺The ion donor is a mixture of inert minerals.

25. Process according to claim 24, characterized in that the natural calcium carbonate is marble, calcite or chalk.

26. The method of claim 12, characterized in that said one or more strong H s₃O⁺The ion donor is selected from the group consisting of hydrochloric acid and sulfuric acid, said medium-strength H₃O⁺The ion donor being selected from the group consisting of H₂SO₃、HSO₄ ^-、H₃PO₄And oxalic acid.

27. The process according to claim 15, characterized in that said 3 treatment steps are followed by a dispersion with a dispersant and an optional re-concentration step.

28. An aqueous suspension, characterized in that it consists at least of the suspension obtained by the process according to any one of claims 12 to 27.

29. The aqueous suspension according to claim 28, characterized in that the pigment, filler or mineral containing natural carbonate is selected from natural calcium carbonate or dolomite containing carbonate and their mixtures with talc, kaolin and/or titanium dioxide TiO₂Manganese oxide MnO and other moderately strong to strong H known in the papermaking art₃O⁺The ion donor is a mixture of inert minerals.

30. Pigments, fillers or minerals in the dry state, characterized in that they are obtained by drying the aqueous suspensions according to claim 28 or 29.

31. Composition for the manufacture of paper, characterized in that it comprises at least one aqueous suspension according to any one of claims 1 to 10, 28 or 29.

32. Use of an aqueous suspension according to any one of claims 1 to 10, 28 or 29 for gumming paper.

33. Use of the aqueous suspension according to any one of claims 1 to 10, 28 or 29 as a filler for paper.

34. Use of the aqueous suspension according to any of claims 1 to 10, 28 or 29 both as a filler and as a size for paper and/or for the surface colouration of paper.

35. Use according to claim 33, characterized in that the paper produced is reduced in weight by 3-15% at a constant surface area.

36. Use of the aqueous suspension according to any one of claims 1 to 10, 28 or 29 in the field of coatings.

37. A method for the manufacture of paper or board, characterized in that the suspension according to any of claims 1-10, 28 or 29 or the composition according to claim 32 is added in one or several times during the paper making process, when making thick pulp or when making thin pulp, or in both stages according to the paper making process.

38. A method according to claim 37, characterized in that the suspension according to any one of claims 1-10, 28 or 29 or the composition according to claim 31 is added to circulating white water or circulating "size".

39. A method according to claim 38, characterized in that the method according to any of claims 12-27 is applied to the white water or circulating "size stock".

40. A method according to any one of claims 37 to 39, characterised in that the paper or board is derived from cellulose fibres based on a wood source.

41. The method of claim 40, characterized in that the paper or paperboard is derived from cellulose fibers of hardwood or resin-containing wood sources.

42. A method according to any one of claims 37 to 39, characterised in that the paper or board is obtained from fibres not originating from wood but from synthetic fibres.

43. Paper or board, characterized in that it is manufactured by a method according to any one of claims 37 to 42.

44. Use of the paper or paperboard of claim 43 in digital printing.

45. Use of the paper or paperboard of claim 43 in ink jet printing.