ES2464573T3 - Composition containing aqueous silica and paper production process - Google Patents

Abstract

The process for making paper from a suspension containing cellulosic fibers, and optionally fillers, which comprises adding at least one organic cationic polymer and an aqueous composition containing silica, comprising an anionic condensate of formaldehyde. naphthalene sulfonate, which has a conductivity of less than 20 mS / cm and silica-based anionic particles, comprising particles based on silica in the form of aggregate or microgel, the composition having a weight ratio of anionic condensate of naphthalene formaldehyde sulphonate to silica-based particles, calculated as SiO2, in the range of 0.2: 1 to 90.1 and containing an anionic condensate of naphthalene formaldehyde-sulphonate and silica-based particles, calculated as SiO2, in an amount of at minus 0.01% by weight, based on the total weight of the aqueous composition containing silica and where the composition contains and equal to or less than 10% by weight of gluing agent reactive with cellulose.

Description

Composition containing aqueous silica and paper production process

Technical field

The present invention relates to a process for the production of paper from a suspension containing cellulosic fibers, which comprises adding at least one cationic organic polymer and a composition containing aqueous silica, comprising an anionic formaldehyde sulphonate condensate. of naphthalene and silica-based anionic particles. The invention further relates to a composition containing aqueous silica and methods for the preparation of the composition containing aqueous silica and uses of the composition containing aqueous silica.

Background of the invention

In the papermaking technique, an aqueous suspension containing cellulosic fibers, and optionally fillers and additives, cited as paper pulp, is fed to a machine head that expels the suspension on a metal forming mesh. Water is extracted from the pulp by means of the metal forming mesh, so that a continuous wet web of paper is formed and drained on the metal mesh. Next, this paper web is dried in the drying section of the paper machine. Drainage and retention aids are conventionally introduced into the pulp in order to facilitate drainage and to increase the adsorption of the fine particles on the cellulosic fibers such that the fine particles are retained with the fibers on the metal mesh.

U.S. Pat. No. 4,388,150 describes a binder in papermaking comprising a complex of cationic starch and colloidal silicic acid, to produce a paper having increased strength and improved retention levels of added and fine minerals for papermaking.

U.S. Pat. 4,750,974 describes a coacervated binder for use in papermaking comprising a tertiary combination of a cationic starch, a high molecular weight anionic polymer and a dispersed silica.

U.S. Pat. 5,368,833 describes silica soles containing silica particles modified with aluminum, with a high specific surface area and a high microgel content.

U.S. Pat. 6,083,997 describes nanocomposites, which are prepared by adding a polyelectrolyte to a silicate solution and then combining them with silicic acid. The nanocomposites have drainage and retention yields in papermaking.

European patent application EP 0418015 A1 describes an active sizing composition, which contains an aqueous emulsion in combination with an anionic dispersant or emulsifier. By using anionic polyacrylamide, anionic starch or colloidal silica, the anionic charge density in the sizing composition can be extended.

U.S. Pat. 4,443,496 refers to a method for modifying a hardened cement surface layer or substrates using the agent comprising, in a specific relationship, an alkali metal silicate solution and a sodium naphthalene sulfonate formaldehyde condensate.

U.S. Pat. 4,559,241 refers to an aqueous solution of alkali metal silicate and nitrite. The solution may also contain additives, such as formaldehyde condensate with naphthalene sulfonate.

U.S. Pat. 5,595,629 refers to a papermaking process comprising adding an anionic polymer and a cationic polymer to the suspension, in order to increase retention and / or drainage. The anionic polymer comprises a formaldehyde condensate of a salt of naphthalene sulfonic acid with a molecular weight in the range of 500 to 120,000.

U.S. Pat. 6,033,524 describes a method for increasing the retention and drainage of the loading components in the raw material for papermaking in a papermaking process, which comprises adding to the raw material a suspension of loading components, which contains also a phenolic improver.

U.S. Pat. 4,772,332 refers to a thermostable suspension of a mass kaolin pigment, which is prepared by mixing a water-soluble cationic material with a kaolin clay pigment in the presence of water.

U.S. Pat. 5,733,414 refers to a process for making paper from a cellulosic suspension, which comprises adding a water-soluble cationic polymer and a water-soluble formaldehyde condensate resin.

U.S. Pat. 5,110,414 describes a process for manufacturing lignocellulosic material products and improving their water resistance and impermeability characteristics, adding high lignin derivatives

mass in moles to the material.

It would be advantageous to be able to provide adjuvant drainage and retention agents with improved performance. Also, it would be advantageous to be able to provide adjuvant retention and drainage agents with good storage stability. It would also be advantageous to be able to provide a papermaking process with improved drainage and / or retention performance.

The invention

According to the present invention, it has been unexpectedly found that an improved drainage and / or retention effect of a cellulosic suspension on a metal mesh can be obtained using an aqueous composition containing silica, comprising an anionic condensate of naphthalene formaldehyde-sulphonate and silica based particles. The present invention makes it possible to increase the speed of the paper machine and use a lower dose of additives to provide a corresponding drainage and / or retention effect, thereby leading to an improved papermaking process and economic benefits.

The term "drainage and retention adjuvant", as used herein, refers to one or more components, which when added to an aqueous cellulosic suspension, provide better drainage and / or retention than is obtained when not said one or more components are added. All types of paper pulp, in particular paper pulps having high salts (high conductivity) and colloidal substances, will obtain better drainage and retention yields by adding the composition according to the present invention. Better drainage and retention yields are important, in papermaking processes with a high degree of white water closure, that is, extensive recycling of white water and limited supply of fresh water.

According to the present invention, there is provided a process for the manufacture of paper from a suspension containing cellulosic fibers, and optionally fillers, comprising adding to the suspension at least one organic cationic polymer and an aqueous composition containing silica, which comprises an anionic formaldehyde-naphthalene sulfonate condensate, which has a conductivity of less than 20 mS / cm and anionic silica-based particles, comprising silica-based particles in the form of aggregate or microgel, the composition having a weight ratio of one anionic condensate of naphthalene formaldehyde-sulphonate to silica-based particles, calculated as SiO2, in the range of 0.2: 1 to 90.1 and containing an anionic condensate of naphthalene-formaldehyde-sulphonate and silica-based particles, calculated as SiO2, in an amount of at least 0.01% by weight, based on the total weight of the aqueous composition that c It contains silica and wherein the composition contains equal to or less than 10% by weight of the cellulose reactive sizing agent.

A method is also provided for the preparation of an aqueous composition containing silica, comprising mixing in the presence of equal or less than 10% by weight of cellulose reactive sizing agent, an anionic condensate of naphthalene formaldehyde sulphonate with a sol based on alkali metal stabilized aqueous silica having an S value in the range of about 5 to about 50%, which contains silica-based particles in the form of an anionic aggregate or microgel to provide an aqueous composition containing silica, which has a ratio by weight of anionic condensate of naphthalene formaldehyde sulphonate to silica-based particles in the range of 0.2: 1 to 90.1, and containing anionic condensate of naphthalene formaldehyde sulphonate and silica-based particles, calculated as SiO2, in an amount of at least 0.01% by weight.

The process for the production of paper according to the present invention comprises adding at least one cationic organic polymer and an aqueous composition containing silica to the suspension, comprising anionic condensate of naphthalene formaldehyde sulphonate and silica-based particles. The term "anionic formaldehyde-naphthalene sulfonate condensate" as used herein, represents a group of polymers obtained by condensation polymerization of formaldehyde with one or more naphthalene sulfonic acids

or salts thereof.

The anionic formaldehyde sulphonate condensate of naphthalene can be reacted with a base, such as alkali metal and alkaline earth metal hydroxides, for example, sodium hydroxide, ammonia or an amine, for example, triethylamine, thereby forming a metal counterion alkaline, alkaline earth or ammonium.

The anionic formaldehyde sulphonate condensate of naphthalene has a molecular weight of at least about 500, suitably of about 1,000. The upper limit is not critical, it can be up to 1,000,000, usually up to 300,000, suitably up to 150,000 and preferably up to

60,000

The aqueous silica-containing composition used in the process according to the invention further comprises silica-based anionic particles, that is, SiO2-based particles, preferably formed by polymerizing silicic acid, encompassing both homopolymers and copolymers. Optionally, the silica-based particles may be modified and may contain other elements, for example, amine, aluminum and / or boron, which may be present in the aqueous phase and / or in the silica-based particles.

Examples of suitable silica-based particles include colloidal silica, colloidal silica modified with aluminum or aluminum silicate, and different types of poly (silicic acid) and mixtures thereof, alone or in combination with other types of silica-based anionic particles . In the art, poly (silicic acid) is also referred to as polymeric silicic acid, poly (silicic acid) microgel, polysilicate and polysilicate microgel, which are all included in the term poly (silicic acid) used herein. Compounds containing aluminum of this type are commonly referred to as poly (aluminum silicate) and microgel of poly (aluminum silicate) which includes colloidal silica modified with aluminum and aluminum silicate.

It is preferable that the silica-based anionic particles are in the colloidal range of particle size, that is, particles based on colloidal silica. This colloidal state comprises particles small enough not to be affected by gravitational forces, but large enough not to show a marked deviation from the properties of typical solutions, that is, an average particle size significantly less than 1 μm. The anionic silica-based particles have an average particle size suitably less than 50 nm, preferably less than about 20 nm and more preferably in the range of about 1 to about 50 nm, most preferably about 1 nm to about 10 nm. As is conventional in silica chemistry, particle size refers to the average size of the primary particles, which may be aggregated or not aggregated. Suitably, the silica-based particles present in the aqueous silica-containing composition of the invention comprise silica-based particles in the form of aggregate or microgel, optionally and usually in combination with non-aggregated or monodispersed silica-based particles.

Suitably, the silica-based particles have a specific surface area greater than 50 m2 / g, preferably greater than 100 m2 / g. The specific surface area may be up to 1,700 m2 / g, preferably up to 1,300 m2 / g and usually in the range of 300 to 1,300 m2 / g, preferably 500 to 1,050 m2 / g. The specific surface area can be measured by titration with NaOH according to the method described by Sears, in Analytical Chemistry 28 (1956), 12, 1981-1983 or in US Pat. No. 5,176,891. The area thus obtained represents the specific average surface area of the particles.

The aqueous silica-containing composition used in the process according to the invention has a weight ratio of anionic condensate of naphthalene formaldehyde-sulphonate to silica-based anionic particles, calculated as SiO2, in the range of 0.2: 1 to 90 , 1, preferably from 0.25: 1 to 85.1. The total weight of the anionic condensate of naphthalene formaldehyde-sulphonate and the silica-based anionic particles, calculated as SiO2, present in the aqueous composition containing silica is at least 0.01% by weight, calculated on the total weight of the aqueous silica-containing composition, suitably the concentration of anionic condensate of naphthalene formaldehyde sulphonate to anionic silica-based particles, calculated as SiO2, is in the range of 1 to 45% by weight, preferably in the range of 2 to 35% in weight, most preferably 5 to 30% by weight.

The silica-containing aqueous composition may have an anionic charge density of at least 0.1 meq / g, usually the charge is within the range of 0.1 to 6 meq / g, suitably within the range of 0.1 to 5 meq / g, preferably within the range of 0.2 to 4 meq / g, and most preferably 0.2 to 3.5 meq / g.

The aqueous silica-containing composition according to the invention contains equal to or less than 10%, suitably less than 5%, preferably less than 1% by weight of cellulose reactive sizing agent. Most preferably, there is no cellulose reactive sizing agent in the aqueous silica-containing composition.

According to a preferred embodiment of the present invention, the silica-containing aqueous composition does not contain substantially nitrites. The term "does not contain substantially" means that equal to or less than 10%, suitably less than 5%, preferably less than 1% by weight of nitrites is present in the aqueous composition containing silica. Most preferably, there is no cellulose reactive sizing agent in the aqueous silica-containing composition, that is, the composition is free of nitrites. The term "nitrites" encompasses all nitrites, such as ammonium, lithium, sodium, calcium, magnesium, sodium and potassium nitrites.

The present invention further relates to a method for the preparation of an aqueous composition containing silica. The two components are preferably agitated together. The anionic condensate of naphthalene formaldehyde sulphonate can be added to an aqueous sol containing silica-based particles or silica-based particles can be added to an aqueous solution of anionic condensate of naphthalene formaldehyde sulfonate. Before mixing the anionic condensate of naphthalene formaldehyde-sulphonate with the silica-based particles, the aqueous solution of anionic condensate of naphthalene formaldehyde-sulphonate may be desalinated or deionized. Desalination or deionization can be carried out with dialysis, membrane filtration, ultrafiltration, reverse osmosis or ion exchange or the like. It is preferred that desalination or deionization be carried out through the use of ultrafiltration or dialysis.

The anionic condensate of naphthalene formaldehyde sulphonate to be mixed with the silica-based particles has the properties mentioned above and has a conductivity of less than 20 mS / cm, and most preferably less than 15 mS / cm, measured at an anionic condensate content of naphthalene formaldehyde sulphonate of 10%.

The silica-based particles, preferably anionic, which are to be mixed with the anionic formaldehyde sulphonate condensate of naphthalene have the properties mentioned previously. Suitably, silica-based particles are present in a sol, preferably stabilized with alkali metal, before mixing with the anionic formaldehyde-naphthalene sulfonate condensate. The sun can have an S value in the range of 5 to 50%, preferably 8 to 45%, and most preferably 10 to 30%. The calculation and measurement of the S value can be performed as described by Iler & Dalton in J. Phys. Chem. Vol. 60 (1956), pp. 955-957. The S value indicates the degree of aggregate or microgel formation, so a lower S value is indicative of a higher degree of aggregation. Suitably, silica-based particles comprise silica-based particles in the form of aggregate or microgel, optionally and usually in combination with non-aggregated or monodisperse silica-based particles.

Suitably, silica-based particles have a mole ratio of Si2O: Na2O of less than 60, usually within the range of 5 to 60, and preferably within the range of 8 to 55.

The anionic formaldehyde sulphonate condensate of naphthalene is usually mixed with the silica-based particles, in a weight ratio in the range of 0.2: 1 to 99.1, suitably 0.2: 1 to 90.1, preferably from 0.25: 1 to 85.1.

Products prepared by any of these methods show improved storage stability and, therefore, better performance of drainage and retention aids when stored.

The mixing process of the previously mentioned methods is suitably carried out, in the presence of substantially no cellulose reactive sizing agent. The term "substantially nothing" means that it is present at least 10% by weight, suitably less than 5%, preferably less than 1% by weight of cellulose reactive sizing agent. Most preferably, the cellulose reactive sizing agent is not present.

The present invention further relates to a process for the production of paper from an aqueous suspension containing cellulosic fibers. The process comprises adding a cationic organic polymer and the silica-containing aqueous composition of the invention to the suspension. The cationic organic polymer according to the invention can be linear, branched or crosslinked. Preferably, the cationic polymer is water soluble or water dispersible.

Examples of suitable cationic polymers include synthetic organic polymers, for example, step growth polymers and chain growth polymers, and polymers derived from natural sources, for example, polysaccharides.

Examples of suitable cationic synthetic organic polymers include vinyl addition polymers, such as acrylate and acrylamide based polymers, as well as cationic poly (diallyldimethylammonium chloride), cationic polyethyleneimines, cationic polyamines, polyamidoamines and vinyl amide based polymers, melanin resins -formaldehyde and urea-formaldehyde.

Examples of suitable polysaccharides include starches, guar gums, cellulose derivatives, chitins, chitosans, glycans, galactans, glucans, xanthan gums, pectins, mannanos, dextrins, preferably starches and guar gums. Examples of suitable starches include potato, corn, wheat, tapioca, rice, waxy corn, barley, etc.

Cationic starches and acrylamide-based cationic polymers are the preferred polymers according to the invention, and can be used individually, mixed together or in conjunction with other polymers, with cationic starches and acrylamide-based cationic polymers having at least less an aromatic group.

The cationic organic polymers can have one or more hydrophobic groups attached to them. Hydrophobic groups may be aromatic groups, groups comprising aromatic groups or non-aromatic groups, preferably hydrophobic groups comprise aromatic groups. The hydrophobic group may be attached to a heteroatom, for example, nitrogen or oxygen, the nitrogen being optionally charged, which heteroatom in turn may be attached to the polymer backbone, for example, through a chain of atoms. The hydrophobic group may have at least 2 and usually at least 3 carbon atoms, suitably from 3 to 12 and preferably from 4 to 8 carbon atoms. The hydrophobic group is suitably a hydrocarbon chain.

The appropriate doses counted as dry substance based on dry pulp and optional charge, of the cationic polymer in the system is 0.01 to 50 kg / t (kg / ton, "metric ton") of, preferably 0.1 to 30 kg / t and most preferably 1 to 15 kg / t.

Suitable doses counted as dry substances based on dry pulp and optional filler of the aqueous composition containing silica previously defined in the system are 0.01 to 15 kg / t, preferably 0.01 to 10 kg / t calculated as an anionic condensate of naphthalene formaldehyde sulphonate and silica-based anionic particles, and most preferably 0.05 to 5 kg / t.

Suitable mineral fillers of conventional type can be added to the aqueous cellulosic suspension according to the invention. Examples of suitable fillers include kaolin, kaolinitic clay, titanium dioxide, gypsum, talc and natural or synthetic calcium carbonates such as chalk, ground marble and precipitated calcium carbonate (CCP).

Naturally, additional additives that are conventional in papermaking can be used in combination with the chemical compounds according to the invention, for example, anionic waste collectors 20 (CDA), moisture resistance agents, dry strength agents, optical illuminating agents, dyes, aluminum compounds, etc. Examples of suitable aluminum compounds include alumina, aluminates, aluminum chloride, aluminum nitrate and polyaluminium compounds, such as aluminum polychlorides, aluminum polysulfates, polyaluminium compounds containing chloride and / or sulfate ions, polysilicates and polysulfates of aluminum, and mixtures thereof. The polyaluminium compounds may also contain other anions other than chloride, for example, sulfuric acid anions, phosphoric acid, or organic acids such as citric acid and oxalic acid. When an aluminum compound is used in the present process, it is usually preferable to add it to the pulp prior to the polymer component and micro- or nano-particle material. Suitable levels of addition of compounds containing aluminum are at least 0.001 kg / t, preferably 0.01 to 5 kg / t and more preferably 0.05 to 1 kg / t, calculated as Al2O3 based on dry paper pulp. and optional charge.

Examples of suitable anionic waste collectors include cationic polyamines, quaternary amine polymers or copolymers, or compounds containing aluminum.

The process of this invention is used for paper production. The term "paper", as used herein, does not only include paper and its production, but also other products of the continuous web type, such as for example board and cardboard, and their production. The invention is particularly useful in the manufacture of paper having grammages below 150 g / m2, preferably below 100 g / m2, for example, thin paper, newspaper, light coated paper, supercalendered paper and tissue .

The procedure can be used in the production of paper of all types of paper pulps, both those containing wood and wood-free ones. The different types of cellulose-containing fiber suspensions and suspensions should suitably contain at least 25% by weight and preferably at least 50% by weight of said fibers, based on dry substance. The suspensions comprise fibers from chemical pulp, such as sulfate pulp, sulphite and organosolv containing wood or mechanical pulp, such as thermomechanical pulp, chemo-thermomechanical pulp, refined pulp and ground pulp, both hardwood and softwood, and can also be based on recycled fibers, optionally for paper pulp, and mixtures thereof. Preferably, the pulp is a pulp containing wood, which has a high salt content and, therefore, high conductivity.

The chemical compounds according to the present invention can be added to the aqueous cellulosic suspension, or pulp, in a conventional manner and in any order. It is usually preferable to add the cationic polymer to the pulp before adding the aqueous composition containing silica, even if the opposite order of addition can be used. It is further preferable to add the cationic polymer before a shear stage, which can be selected from pumping, mixing, cleaning, etc., and adding the aqueous silica-containing composition after that shear stage.

The aqueous silica-containing composition can be used as a flocculating agent in the treatment of water for the production of drinking water or as an environmental treatment of water, for example, in lakes. The composition can also be used as a flocculating agent in the treatment of wastewater or sewage sludge.

The invention is further illustrated by means of the following examples, not intended to limit its scope. Parts and percentages refer to parts by weight and weight percentages, respectively, and all solutions are aqueous, unless otherwise indicated. The units are metric.

Example 1

Test samples of aqueous compositions containing silica according to the invention were prepared by mixing an aqueous solution of formaldehyde-naphthalene sulfonate condensate (FSN) with a silica sol containing silica-based particles in different doses under moderate agitation. Also, reference samples were prepared under the same conditions as the test samples. A sample of FSN was ultrafiltered and the product obtained (FSN I) had a concentration of 12% by weight and the samples were diluted to a concentration of 5% by weight and had a conductivity of 12 mS / cm. Another sample of FSN was dialyzed and the product obtained (FSN II) had a concentration of 12% by weight and the samples were diluted to a concentration of 5% by weight and had a conductivity of 12 mS / cm. Samples of untreated FSN (FSN III) were diluted to a concentration of 5% by weight and had a conductivity of 25 mS / cm. All conductivities in the examples were measured at a concentration of 10% by weight of FSN. The silicas used in the following examples are all defined, then in Table 1.

Table 1

Silica I Silica sol of the type described in US Pat. 5,447,604 having a mole ratio SiO2: Na2O of 10, specific surface area of 870 m2 / g, S value of 35% and silica content of 10.0% by weight.

Silica II Silica sol of the type described in US Pat. 5,603,805 having a mole ratio SiO2: Na2O of 45, specific surface area of 850 m2 / g, aluminum modified with sodium aluminate up to an Al2O3 grade of 0.25%, S value of 20% and silica content of 8.0% by weight.

Silica III Silica sol of the type described in US Pat. 6,083,997 having a mole ratio SiO2: Na2O of 17 obtained by mixing sodium silicate having a mole ratio SiO2: Na2O of 3.4, a silica content of 15% by weight with poly (silicic acid) (PAS ), which has a silica content of 6.0% by weight.

Example 2

In the following examples, test samples of naphthalene sulfide formaldehyde-sulphonate condensate and silica-based particles in different doses were added to a test pulp to evaluate the performance of the composition as a drainage agent. The drainage performance was assessed by means of a dynamic drainage analyzer (ADD), available from Akribi, Sweden. The ADD measures the drainage time of a given volume of pulp through a metal mesh when a plug is removed and vacuum is applied to the face of the mechanical mesh opposite the face on which the pulp is present.

In the examples a cationic polymer was added to the pulp before the aqueous compositions containing silica according to the invention or the anionic reference.

Test samples were prepared from the mixtures of FSN II and Silica I at different ratios, which were tested in a test pulp containing wood with a pH of 7.6, a conductivity of 5.0 mS / cm, and a consistency of 1.43 g / l. The pulp was stirred in a vat with baffles at a speed of 1,500 rpm throughout the test.

In the test, 20 kg / t (20 kg / ton) of cationic starch (C1) was added, which was a cationic potato starch with a nitrogen content of 0.5%, obtained by quaternizing native potato starch with 3-Chloro-2-hydroxypropyl-dimethyl-benzyl ammonium chloride, after 30 seconds of stirring the anionic mixture was added, followed by 15 seconds of stirring before draining.

Silica I was used as a reference. All samples were diluted to 0.5% solids before testing. The relationships and results are summarized in Table 2.

Table 2

Sample

Relationship Drainage time (sec) at the dose of

1 kg / t

2 kg / t 3 kg / t

Silica I

26.0 23.9 20.0

FSN II + Silica I

0.25: 1 25.5 19.1 15.3

FSN II + Silica I

0.67: 1 21.6 15.5 12.5

FSN II + Silica I

1: 1 20.4 14.9 12.7

FSN II + Silica I

1.5: 1 19.3 13.8 12.3

FSN II + Silica I

4: 1 17.0 12.3 13.3

Example 3

Test samples were prepared from FSN II and Silica II. Silica II was used as a reference. All samples were diluted to 0.5% solids before drainage evaluation, which was performed as in Example 2, with the same paper pulp and with 20 kg / t of C1. The relationships and results are summarized in Table 3.

Table 3

Sample

Relationship Drainage time (sec) at the dose of

1 kg / t

2 kg / t 3 kg / t

Silica II

25.5 22.0 18.7

FSN II + Silica II

0.25: 1 - 17.1 -

FSN II + Silica II

0.67: 1 - 14.6 -

FSN II + Silica II

1: 1 20.4 13.0 11.1

FSN II + Silica II

1.5: 1 18.6 13.2 12.1

FSN II + Silica II

4: 1 16.1 12.7 12.1

Example 4

Test samples were prepared from FSN I and Silica I. Silica I was used as reference. Samples were diluted to 0.5% solids and drainage tests were performed as in Example 1. 20 kg / t of C1 to pulp. The pulp was a pulp containing wood that had a conductivity of 5.0 mS / cm, a consistency of 1.52 g / l and a pH of 7.8. The ratios and drainage times are summarized in Table 4.

Table 4

Sample

Relationship Drainage time (sec) at the dose of

1 kg / t

2 kg / t 3 kg / t 4 kg / t

Silica I

34.0 29.2 25.8 24.0

FSN I + Silica I

0.25: 1 30.1 22.4 17.6 14.0

FSN I + Silica I

0.67: 1 26.9 17.7 13.3 12.2

FSN I + Silica I

1: 1 25.0 16.1 12.0 12.1

FSN I + Silica I

1.5: 1 22.1 14.6 12.5 13.0

FSN I + Silica I

4: 1 18.9 13.5 12.7 14.0

Example 5

Test samples were prepared from FSN I and Silica I. Silica I was used as reference. The preparation procedure was the same as in the previous examples. The conductivity of the pulp containing wood was only 0.5 mS / cm. The amount of C1 was 30 kg / t in all trials. The drainage time for starch

15 cationic added was only 22 seconds. The ratios and drainage times are summarized in Table 5.

Table 5

Sample

Relationship Drainage time (sec) at the dose of

1 kg / t

2 kg / t 3 kg / t 4 kg / t

Silica I

19.1 16.0 13.2 9.7

FSN I + Silica I

0.25: 1 14.3 11.6 9.4 8.5

FSN I + Silica I

0.67: 1 14.3 10.0 9.2 8.2

FSN I + Silica I

1: 1 13.7 9.9 8.5 8.5

FSN I + Silica I

1.5: 1 12.2 9.9 8.7 8.6

FSN I + Silica I

4: 1 12.0 10.4 9.7 9.7

Example 6

Test samples were prepared from FSN I and Silica I. Silica I was used as reference. The pulp

5 containing wood had a conductivity of 5.0 mS / cm, a consistency of 1.52 g / l and a pH of 7.8. At the start of the test, 3 kg / t of a cationic polyacrylamide (PAM-C) was added to the pulp, which was prepared by the polymerization of acrylamide (90 mol%) and acryloxy-ethyl dimethyl benzyl chloride -ammonium (10 mol%), and has a molecular weight of approximately 6,000,000. After 30 seconds of stirring the compositions of FSN I and Silica I were added, followed by 15 seconds of stirring before draining. The compositions of

10 FSN I and Silica I were diluted to 0.5% solids and PAM-C to 0.1% solids, before adding to the pulp. The ratios and drainage times are summarized in Table 6.

Table 6

Sample

Relationship Drainage time (sec) at the dose of

0.5 kg / t

1.0 kg / t

Silica I

14.4 10.3

FSN I + Silica I

0.25: 1 11.2 8.9

FSN I + Silica I

0.67: 1 10.3 9.1

FSN I + Silica I

1: 1 10.0 9.5

FSN I + Silica I

1.5: 1 10.4 9.7

Example 7

15 Test samples were prepared from FSN III and Silica I, and FSN III and Silica III. An evaluation of the drainage of the samples was carried out as in the previous examples, in a high conductivity pulp with a conductivity of 5.0 mS / cm. C1 was added in an amount of 20 kg / t to the pulp. The ratios and drainage times are summarized in Table 7.

Table 7

Sample

Relationship Drainage time (sec) at the dose of

1 kg / t

3 kg / t

FSN III + Silica III

0.077: 1 34.2 21.2

FSN III + Silica III

0.15: 1 31.0 18.0

FSN III + Silica I

0.2: 1 29.9 17.7

FSN III + Silica III

0.2: 1 29.2 16.4

FSN III + Silica I

0.3: 1 27.9 16.2

FSN III + Silica III

0.3: 1 28.0 14.6

The results show that the aqueous silica-containing composition according to the invention has improved drainage properties.

5 Example 8

Test samples of compositions of FSN I and Silica I, and FSN III and Silica III were prepared. Silica I and Silica III were used as reference. An evaluation of the drainage of the samples was carried out as in the previous examples, in a high conductivity pulp with a conductivity of 5.0 mS / cm. C1 was added in an amount of 20 kg / t to the pulp. The ratios and drainage times are summarized in Table 8.

10 Table 8

Sample

Relationship Drainage time (sec) at the dose of

2 kg / t

3 kg / t

Silica I

27.2 24.3

Silica III

26.8 20.9

FSN III + Silica III

0.077: 1 27.3 21.2

FSN III + Silica III

0.15: 1 23.1 18.0

FSN I + Silica I

0.2: 1 21.4 15.8

FSN I + Silica I

0.3: 1 20.7 15.1

FSN III + Silica III

0.2: 1 20.7 16.4

FSN III + Silica III

0.3: 1 20.2 14.6

The results show that the aqueous compositions containing silica according to the invention have improved drainage properties. Example 9 A high molecular weight anionic polyacrylamide (PAM-A), with molecular weight of about 10 to 20 million, containing about 30 mol% of anionic groups, was prepared in the form of an emulsion of 10

water in inverted oil and diluted with water to a concentration of 0.1%. PAM-A was mixed with 0.1% Silica I in three different ratios of PAM-A to Silica I of 2: 1, 1: 1 and 0.5: 1. Compositions of FSN III and Silica III (a) were prepared by adding a dilute sodium silicate (15% SiO2 and SiO2 ratio: Na2O 3.4) to FSN III (as a 30% aqueous solution) with stirring. To this mixture was added poly (silicic acid), with a concentration of

5 6.0% SiO2 at a pH of 2.5, with stirring for 20 minutes. The poly (silicic acid) was prepared from dilute sodium silicate, which was circulated through a column filled with strong ionization resin, strong cationic, saturated with hydrogen.

The mixture of FSN III and Silica III (b) was prepared by mixing FSN III with poly (silicic acid) with stirring for 5 minutes and then this mixture was added to the sodium silicate with stirring for 20 minutes.

10 An evaluation of the drainage of the samples of this example was performed on a high conductivity pulp (5.0 mS / cm). Before the anionic mixtures, a cationic starch (C2) was added to the pulp, which was a cationic potato starch with a nitrogen content of 0.7%, obtained by quaternization of native potato starch with 3 -chloro-2-hydroxypropyl dimethyl benzyl ammonium. C2 was added in an amount of 12 kg / t. The following drainage times were obtained:

15 Table 9

Sample

Relationship Drainage time (sec) at the dose of

2.0 kg / t

PAM-A

33.0

Silica I

16.9

PAM-A / Silica I

0.5: 1 28.7

PAM-A / Silica I

1: 1 25.5

PAM-A / Silica I

2: 1 29.4

FSN III / Silica III a

0.38: 1 22.0

FSN III / Silica III a

1.9: 1 21.0

FSN III / Silica III a

9: 1 17.7

FSN III / Silica III b

0.5: 1 23.0

FSN III / Silica III b

9: 1 16.8

Example 10 The storage stability of the different mixtures of FSN and silica was determined. The FSN samples were desalinated by the use of ultrafiltration (FSN I) with a conductivity of 12 mS / cm measured at 10% by weight 20 solids, before mixing with the silica to form the aqueous compositions. Untreated FSN III was mixed with silica for comparison purposes. All aqueous compositions obtained and reference samples are

stored according to the following procedure: in a refrigerator for 9 weeks; then in an oven at a temperature of 40 ° C for 3 weeks;

25 in an oven at a temperature of 60 ° C for 1 week; and in an oven at a temperature of 80 ° C for 6 weeks.

The total storage time was 20 weeks. Storage times are summarized in Table 10. Table 10

Sample

Relationship Active substance (SiO2 + FSN) Gel formation time

FSN III + Silica III

0.15: 1 7.2% gel after 14 weeks

FSN I + Silica III

0.15: 1 7.2% without gel after 20 weeks

FSN I + Silica III

0.2: 1 7.3% without gel after 20 weeks

Samples without gel formation showed better stability than samples with gel formation, and not even 5 showed an increase in viscosity.

Example 11

Test samples of mixtures of FSN III and Silica I, and mixtures of FSN III and Silica III were prepared. Silica III was used as a reference. An ADD evaluation of the samples was performed on a high conductivity pulp with a conductivity of 5.0 mS / cm. C1 was added in an amount of 20 kg / t to the pulp.

10 Drainage times are summarized in Table 11.

Table 11

Sample

Drainage times (seconds) 1 kg / t

Silica sun III

32.1

Silica III sol with 7.7% FSN III

34.2

Silica III sol with 7.7% FSN III

29.4

Silica III sol with 15% FSN III

31.0

Silica III sol with 15% FSN III

30.7

The results show that mixtures containing Silica I have received improved drainage time compared to Silica III. Silica I was a silica sol stabilized with alkali metal.

Claims (17)

one.

 The process for making paper from a suspension containing cellulosic fibers, and optionally fillers, which comprises adding at least one organic cationic polymer and an aqueous composition containing silica, comprising an anionic condensate of formaldehyde. naphthalene sulphonate, which has a conductivity of less than 20 mS / cm and silica-based anionic particles, comprising particles based on silica in the form of aggregate or microgel, the composition having a weight ratio of anionic condensate of naphthalene formaldehyde sulphonate to silica-based particles, calculated as SiO2, in the range of 0.2: 1 to 90.1 and containing an anionic condensate of naphthalene formaldehyde-sulphonate and silica-based particles, calculated as SiO2, in an amount of at minus 0.01% by weight, based on the total weight of the aqueous composition containing silica and where the composition contains and equal to or less than 10% by weight of gluing agent reactive with cellulose.

2.

 The process according to claim 1, wherein the anionic formaldehyde sulphonate naphthalene condensate has a conductivity of less than 15 mS / cm.

3.

 The process according to any one of claims 1 and 2, wherein the aqueous composition containing silica has a weight ratio of anionic condensate of naphthalene formaldehyde sulphonate to silica-based particles, calculated as SiO2, in the range of 0, 2: 1 to 85.1.

Four.

 The process according to any one of claims 1-3, wherein the silica-based anionic particles have a specific surface area in the range of 300 to 1,300 m2 / g.

5.

The process according to any one of claims 1-4, wherein the organic cationic polymer is cationic starch or cationic polyacrylamide.

6.

 The process according to any one of claims 1-5, wherein the organic cationic polymer has at least one aromatic group.

7.

 The aqueous composition containing silica for use as a flocculating agent in pulp and paper production and water purification, which comprises an anionic condensate of naphthalene formaldehyde sulphonate, which has a conductivity of less than 20 mS / cm and anionic particles based on silica, comprising silica-based particles in the form of aggregate or microgel, the composition having a weight ratio of anionic condensate of naphthalene formaldehyde-sulphonate to silica-based particles, calculated as SiO2, in the range of 0.2 : 1 to 90.1 and containing an anionic condensate of naphthalene formaldehyde-sulphonate and silica-based particles, calculated as SiO2, in an amount of at least 0.01% by weight, based on the total weight of the aqueous composition containing silica and wherein the composition contains equal to or less than 10% by weight of cellulose reactive sizing agent.

8.

 The composition according to claim 7, wherein the anionic formaldehyde sulphonate naphthalene condensate has a conductivity of less than 15 mS / cm.

9.

 The composition according to any one of claims 7 and 8, wherein the aqueous composition containing silica has a weight ratio of anionic condensate of naphthalene formaldehyde-sulphonate to silica-based particles, calculated as SiO2, in the range of 0, 2: 1 to 85.1.

10.

 The composition according to any one of claims 7-9, wherein the silica-based anionic particles have a specific surface in the range of 300 to 1,300 m2 / g.

eleven.

 A method for the preparation of an aqueous composition containing silica, comprising mixing in the presence of equal or less than 10% by weight of cellulose reactive sizing agent, an anionic condensate of naphthalene formaldehyde sulphonate having a conductivity of less than 20 mS / cm with an alkali metal stabilized aqueous silica based sol having an S value in the range of about 5 to about 50%, containing silica-based particles in the form of an anionic aggregate or microgel, to provide an aqueous composition containing silica having a weight ratio of anionic condensate of formaldehyde-naphthalene sulfonate to silica-based particles, calculated as SiO2, in the range of 0.2: 1 to 90.1, and containing anionic condensate of formaldehyde- Naphthalene sulfonate and silica-based particles, calculated as SiO2, in an amount of at least 0.01% by weight.

12.

 The method according to claim 11, wherein the anionic formaldehyde sulphonate naphthalene condensate has a conductivity of less than 15 mS / cm.

13.

 The method according to any one of claims 11 and 12, which comprises desalinating the aqueous solution of anionic formaldehyde sulphonate naphthalene condensate.

14.

 The method according to any one of claims 11-13, wherein the aqueous composition containing silica has a weight ratio of anionic condensate of naphthalene formaldehyde sulphonate to silica-based particles, calculated as SiO2, in the range of 0, 2: 1 to 85.1.

fifteen.

 The method according to any one of claims 11-14, wherein the silica-based anionic particles have a specific surface area in the range of 300 to 1,300 m2 / g.

16.

 The method according to any one of claims 11-15, wherein the sol has an S value in the range of 5 to 50% before mixing with the anionic condensate of naphthalene sulfide.

17.

 The method according to any one of claims 11-16, wherein the sol has an S value in the range of 8 to 45% before mixing with the anionic condensate of naphthalene formaldehyde sulphonate.