DE2632350A1 - PROCESS FOR MANUFACTURING PAPER AND FILLER CONGLOMERATE TO BE USED IN IT - Google Patents

Description

Dipl.-Ing. H. MITSCHERLICH D-B MUNICH 22

_, ... i ^. * »» iKx & ik.im.1 Steinsdorfstrasse 10

DiPL-In ₉ -K-GUNSCHMANN. ^ ₆₆₈₄

Dr. r.r. not. W. KÖRBER Dipf.-Ing. J. SCHMIDT-EVERS

PATENT LAWYERS

MART IN CLARK RIDDELL 2632350

Nurseries Road

Kidlington , Oxfordshire,.

England

Patent application

Process for producing paper and the filler conglomerate to be used in this process

The invention relates to the manufacture of paper and in particular relates to a method for enlarging the Mineral filler content of paper,

When producing paper webs, it is customary to use the aqueous Paper stock before its transfer to the endless paper machine screen in the wet end of the paper machine a mineral To add filler, which primarily serves to improve the surface of the paper so that it can look makes the paper easier to print, as well as the manufacturing costs to belittle. However, in practice the amount of filler which can be used in this way is limited by the fact that the tensile strength of the paper web decreases with increasing filler content. This is due to the fact that the filler particle the hydrogen bond between the pulp fibers interfere, and that with increased filler content in the paper web, a smaller amount of fiber is present that you could give the required strength.

It is known, usually just before the wire of the paper machine small amounts of polymeric materials in the dilute aqueous suspensions of paper stock and filler material introduce the retention of filler material on the

609880/1055

To improve the screen during sheet formation and thereby the efficiency of the papermaking process increase that the losses of filler material are reduced, which can be attributed to the leakage of filler material in the sewage are. For example, in GB-PS 883 973 the use of a restraint aid is described in which it are only trace amounts of a water-soluble, non-cationic, linear polymer that has a molecular weight of at least 5 χ 10 and at least mainly consists of carbamoylalkylene bonds, which are not contain more than 4 carbon atoms, the polymer of the filler-containing aqueous suspension of the cellulose fibers is added before the leaves form on the sieve.

In GB-PS 1 353 015 a method for reducing the chemical reactivity of a calcium carbonate filler in a papermaking process in which sizing takes place under acidic conditions, e.g. usual sizing with resin soap and papermaker's alum, and with the calcium carbonate particles protected by a coating which is produced by the fact that a certain gellable water-attracting organic material an aqueous Suspension of calcium carbonate particles is added, whereupon the material with the help of a suitable gelling agent is caused to gel, so that accumulations of gelled hydrophilic material and calcium carbonate particles are formed. Under certain conditions, accumulations of a fiber-like nature arise. In such thread-like collections, several filler particles are assigned to one another and gelled linearly to provide a protective coating on the particles. It is stated that the use of the calcium carbonate filler thus protected leads to a somewhat better retention of the filler without the Reduced strength of the paper.

DT-OS 2 516 097 proposes increased amounts of a calcium carbonate filler in the manufacture of paper without a reduction in the strength of the paper in such a way that

886 / 1ÖSI

-3- 253235Q

apply that the paper pulp calcium carbonate in the form of a mixture of calcium carbonate with an aqueous latex one film-forming polymeric binder, e.g. a styrene-butadiene latex, is attached.

Because mineral fillers are considerably cheaper than new derived pulp fibers, a significant economic benefit would be obtained by considering the filler content a paper web considerably beyond what has been achieved up to now If it were possible at the same time, the tensile strength and other physical properties could be increased to the maximum Leave the properties of the paper unchanged.

Filler particles contained in a solution or suspension usually have an electrostatic charge. In general, the filler particles will be negatively charged, but can in some cases they have a positive charge, depending on the hardness of the water, because there is an excess of positive ions present when the water is hard.

According to the invention it has been shown that certain long-chain, relatively high molecular weight polymers have the ability to attract several filler particles and thereby one Form filler-polymer conglomerate in which the numerous filler particles are created by an electrostatic attraction be retained between the filler particles and the polymer and by bridging effects of the polymer, and that it is possible to use such conglomerates in the manufacture of a paper web in order to increase the filler content of the paper to increase without affecting the strength properties of the paper are significantly impaired because the filler-polymer conglomerates reduce the deleterious effect of the filler on the hydrogen bonding of the fibers. Furthermore, according to the Invention found that such filler-polymer conglomerates to a considerable extent the various shear forces withstand that normally occur in a papermaking plant of known type.

- * - 2132350

The invention provides a method for producing a paper web with the aid of a paper machine an aqueous paper stock containing a mineral filler has been created, which is characterized is that the mineral filler is added to the paper stock in the form of a filler-polymer conglomerate, which thereby is generated by bringing a particulate mineral filler into contact with a polymer whose Zeta potential in the range from -40 to +40 electron volts (eV) and which has a molecular weight of at least 2 χ 10.

The invention also provides a novel composition of matter or mass in the form of a filler-polymer conglomerate which is obtained by bringing a particulate mineral filler into contact with a polymer which has a zeta potential in the range of -40 to +40 eV and a molecular weight of at least 2 χ 10 ⁶ .

The long chain polymers of relatively high molecular weight that are capable of making such filler-polymer conglomerates form, have a zeta potential (ZP) in the range of -40 to +40 eV and a molecular weight of at least 2 χ 10 and

Ct Ct

preferably between 2 χ 10 and 20 χ 10 and in particular in the range from 4 χ 10 to 12 χ 10. This is convenient Zeta potential near zero, or it is slightly negative, i.e. it is in the range of +5 to -20 eV, and that Molecular weight is in the range from about 5 to 10 χ 10.

The zeta potential, also known as the electrokinetic potential is defined as the electrical potential at the diffuse part of a double ion layer, which is a charged Surrounds particles in an ionic liquid, e.g. water. For example, if an electronegatively charged polymer is dissolved in water becomes, the polymer attracts a large number of electropositive Ions form a thin, concentrated layer adjacent to the polymer form. Outside this thin layer there is a thicker and more diffuse layer, in which electropositive

charged ions in the water differ from the electronegatively charged one Polymer particles are only moderately attracted. This electric Potential at the said diffuse layer is called denotes the zeta potential.

One can measure the zeta potential by adding a 0.1 weight percent of the polymer containing solution in deionized water and an electrophoretic device, e.g. a "Zeta-Meter" or a "Laser Zee Meter" is used.

The polymers used in accordance with the invention may vary depending on the charge assigned to the filler be positively or negatively charged. As examples of polymers that are particularly Polyacrylamides of high molecular weight, which are honey polymers, may be mentioned which can achieve good results or copolymers of acrylamide. The molecular Weights of these polymers can be determined in a known manner determine by looking at their intrinsic viscosity in normal saline solutions certainly.. .

The homopolymers of acrylamide, which are normally essentially nonionic, contain repeating units of the following form:

■ CH, - C

C-

Herein, R denotes a hydrogen polyacrylamide or a Methyl polymethacrylamide.

The copolymers of acrylamide can be anionic in nature since they _{contain several anionic groups (Y) instead of some of the CONH o} groups, or they can be cationic if there are several cationic groups (X) _{instead of some of the CONH 3 "groups} Thus, the copolymers can contain repeating units of the following types:

09881/1 0.1

-O-

—CH "- CH-

or

COiNH,

- CH-

CONH,

CH. L.

Ιο

1,-

-C

Here, Y can denote, for example, a carboxylic acid group (COOH) or an ammonium salt, an alkali metal salt, an amine salt or a substituted amine salt of the group mentioned or an analogous sulfonate salt; For example, X can be a substituted Denote amide group or a corresponding cation of a quaternary ammonium salt; m and y can vary so that a weight percentage ratio between 100: 0 and 50:50 that is, up to 50 percent of anionic or cationic groups can be present in the polymer. Alternatively the copolymers can be nonionic if the copolymerizing Monosier a nonionic finyl monomer, see 3. Is acrylonitrile or ethyl acrylate. Such. Copolymers of acrylamide can have molecular weights in the range from 2 to 20 χ 10 °.

The size of the filler-polymer conglomerates is determined depending on the polymer used, but can be changed by setting the weight ratio between the polymer and the filler can be changed. For example, the conglomerate 0.01 to 0.5 percent by weight of the dry polymer based on the dry weight of the filler. Preferably the conglomerate has an average diameter in the range from 50 to 100 micrometers. It is beneficial when the conglomerates are of such a size that when they are subjected to shear forces such as those on a paper machine occur, at least the greater part of the conglomerates assumes a thread-like shape, whereby the hydrogen binding of the cellulose fibers and the retention of the filler

can be improved without affecting the appearance of the paper web.

Calcium carbonate, for example, can be used as the mineral filler in the production of the filler-polymer conglomerate, specifically in any commercially available form, for example in the form of natural whipped chalk. Alternatively, the filler, for example, from china clay, talc, or titanium dioxide can consist _»o = overall optionally one can use a mixture of different fillers.

One can use the filler-polymer conglomerates according to the invention by adding the polymer, preferably in the form of a solution in water, to an aqueous suspension of the filler containing, for example, 20 to 35 percent by weight of the filler contains, and by subjecting the mixture thus produced, if necessary, to a slight force of gravity, for example by Passing the mixture through a stationary mixer to avoid any fluctuations in the particle size of the conglomerates to reduce. The generation of the conglomerates can be carried out batchwise or continuously, and the size of the Conglomerate particles can be controlled by changing the rate of addition of the polymer. The ones obtained in this way Conglomerates can then be used in a papermaking system of the otherwise known type instead of the normal Filler particles are used. In other words, the conglomerate particles can be added to the paper stock, before this is fed to the wet end of the paper machine in a known manner. If necessary, one can use the conglomerates pass through one or more other devices for applying shear forces, e.g. through fabric cleaners, mechanical sieves or vane pumps, by means of which an adjustable shear force can be brought into effect before the stock is fed to the paper machine.

The conglomerates are conveniently generated by going continuously an aqueous solution of the high molecular weight polymer, e.g., a solution of substantially nonionic High molecular weight polyacrylamide, a flowing

the aqueous suspension of a mineral filler, e.g. calcium carbonate, added, whereupon the resultant v / aqueous suspension of filler-polymer conglomerates through a stationary mixer is passed, from which the low gravity conglomerate is a component the suspension can be fed to an aqueous paper stock stream which is passed to the wet end of a paper machine will. If the conglomerates are produced continuously in the manner just described, it is expedient to use the conglomerate suspension to be fed to the paper machine via a pipeline, at least a part of which is transparent, see above that one can observe the particle size and structure of the conglomerates and change them if necessary.

If necessary, resins of a known type or a starch, e.g., an oxidized starch, to increase wet or dry strength during the formation of the filler-polymer conglomerates be present, because it has been shown that the presence of such resins or starch contributes to to further improve the mechanical stability which the conglomerates normally have to a considerable extent. Examples of such resins are polyamide-spichlorohydrin or polyamide-polyamine-epichlorohydrin resins to increase the wet strength and melamine-formaldehyde resins for Called increase in dry strength. The latter can be sulfited so that they are alkaline and anionically charged. These resins or the starch can either be added to the polymer or add to the aqueous filler suspension before the contact between the filler and the former is brought about. Resins to increase wet and dry strength are usually available in the trade in the form of aqueous solutions and may for example be added in an amount of from 0.02 to 0.8 percent by weight of the aqueous solution based on the weight of the polymer will.

The papermaking process according to the invention can be carried out using a paper stock of a known type, partly made of hardwood and partly made of V / calibrated

wood and optionally contains an internal sizing agent, e.g. an aqueous ketene dimer emulsion, for example the product sold under the trademark "Aquapel" in England by Hercules Powder Company Ltd. is put on the market.

The filler-polymer conglomerates produced according to the invention can be used in an alkaline papermaking system, ie. a system in which the paper stock is maintained at an alkaline pH; alternatively, one can use the filler-polymer conglomerates in an acidic papermaking system at which the paper stock has an acidic pH, either in conjunction with a chemically neutral filler such as china clay or, surprisingly, even in combination with a filler, which is normally reactive in an acidic system, e.g. with calcium carbonate, which is relatively cheap and easy to use Beschaffen.ist, because it has been shown that according to the invention Conglomerates produced using calcium carbonate surprisingly have considerable resistance to acid attack own.

It was also found that when using the invention Filler-polymer conglomerates is possible Filler content of the finished paper compared to one Increase paper with a normal filler by an amount that is 25 to 60% higher, while still maintaining the strength and other physical properties desired in the finished paper are retained. Thus made possible the invention is to replace relatively expensive new pulp fibers with a relatively cheap filler.

The invention and advantageous details of the invention are explained in more detail below with the aid of exemplary embodiments explained.

09806 / iQSS

example 1

This example illustrates the application of the invention to an alkaline papermaking system in which Whipping chalk is used as a filler.

The paper stock was made from fully bleached chemical pulps and reclaimed residues in the usual manner of the same fabric made to be 34 weight percent hardwood, 36 weight percent softwood and 30 weight percent consisted of recovered fines. An alkaline interior glue was added to the fabric, and the product "Fibran", which is sold in England by the company Laing-National is launched; the finished paper stock had a pH of 7.2.

A commercially available homopolymer of acrylamide with a zeta potential of -14 eV, which with a solution of 0.1 percent by weight in distilled water with a "Laser Zee Meter" had been measured, the homopolymer having a molecular weight of about 8 χ 10 and a viscosity accordingly 92 centipoise at 15 ° C (measured on a 0.5 weight percent solution at 50 rpm with an RVT Brookfield viscometer), was dissolved in tap water with a total hardness of about 300 ppm so that a polyacrylamide solution obtained with 0.5 weight percent solids. The viscose solution produced in this way was fed at a flow rate from about 180 ltr / h by means of a positive displacement pump into a feed line promoted by an aqueous slurry of natural slurry circles (calcium carbonate) as a filler with 25 Percent by weight was flowed through; this mud circles will in England under the trademark "Snowcal 8.SW" by The Cement Marketing Company Limited brought to the market} the throughput rate of this slurry was 30 ltr / min, so that the wet filler flow about 10% of the polymer solution was added. The polyacrylamide solution became the filler line immediately after the supply of the dilution water and shortly before a mixer at rest

60 9 886/1 ÖS p

fed. The dilution water became the filler line fed at such a rate that a dilution factor of about 3: 1 resulted.

The stream given off by the mixer at rest, the whiting-chalk-polyacrylamide conglomerates suspended in water, the conglomerates had a mean diameter in The thin material flow was passed through a transparent plastic pipe fed shortly before the feed box. A water solution of one Polyamine retention aid from the commercial product "Natron 88" made in England by the company Laing-National is put on the market, was added immediately in front of the feed box to hold back the fines and to bring the retention of the glue to a maximum value.

Then, cream wove paper was made on a paper machine using a slightly alkaline system generated at which the zeta potential was approximately zero. This was done with a production speed of 400 kg / h worked at the exit end of the paper machine and a running speed of 242 m / min.

In the table below are the physical values which were obtained with the paper which was produced according to the invention according to the preceding example, and these results are compared with the results for paper produced in a similar manner was, apart from the fact that instead of the filler-polymer conglomerates an untreated calcium carbonate filler was used in the usual manner.

Basic Total Basic Burst Tear

Paper ash fiber stiffness length

Weight content based on the weight

g / m ² % g / m ² 100 g fiber web

Conglomerate 80 29 56.8 396 6210

Filler.

CaCO ₃ 75 18 61.5 S90 6170

60 9886 / 1Ö5S

The above results show that it is in use the invention is possible, the filler content of the paper web can be increased considerably without any impairment of strength "

Example 2

This example illustrates the application of the invention to using an alkaline papermaking system of china clay as a filler.

Telegraph paper was made in a manner similar to Example 1 except that instead of natural whiting chalk as filler china clay of the type Lee I4oor grade B lump (English Clays Lovering Pochin & Co. Limited) was used.

The following table shows the physical properties compared to the usual use of untreated China clay were obtained.

Basic burst rupture

Fiber stiffness length

Weight based on the

2 100 g fiber web

Base- total paper Ash- weight salary g / m <- % Konglo merat 73.0 20th porcelain Earth 70.5 14th

g / m '

58.4

60.7

275

231

6520

5500

These results indicate that the application of the invention makes it possible to increase the filler content considerably, without affecting the physical strength properties of the paper web in any way.

Example 3

This example illustrates the application of the invention using an acidic papermaking system of whipped chalk as filler, with a resin to increase during the formation of the filler-polymer conglomerates the wet strength is present.

S09886 / 10S

A fully bleached paper stock was made in the usual way chemical pulp and recycled fines, the was from a similar stock made to be about 45 weight percent hardwood, 40 weight percent softwood and contained 15 weight percent of recycled fines. A resin-alum glue was added to this paper stock, and the stock then had a pH of about 6.3.

A commercially available nonionic homopolymer of acrylamide

with a molecular weight of about 5 χ 10 and a viscosity corresponding to 82 centipoise at 15 C (measured on a solution of 0.5 percent by weight at 50 rpm with an RVT Brookfield viscometer) and 0.05 percent by weight (based on the weight of the polyacrylamide) of a commercially available one aqueous solution of a polyamide-epichlorohydrin resin to increase wet strength (in England under the name "Kymene 557" from Hercules Powder Company Limited to the Market) were dissolved in tap water to make a polyacrylamide solution containing 0.3 percent by weight solids with a zeta potential of -2 eV. The on this Way obtained viscose solution was with a throughput rate of about 80 ltr / h by means of an inevitable Displacement working pump in a feed line fed by an aqueous slurry of natural Mud chalk (calcium carbonate) as a filler with a content of 35 percent by weight was flowed through, namely with a Throughput rate of 900 ltr / h, so that the polymer solution is added to the wet filler flow in an amount of about 8.8% was added; said whitewash chalk is sold in England under the name "Snowcal 4MB" by The Cement Marketing Company Limited launched. The polyacrylamide solution was fed to the filler line, and the one so formed Mixture was passed through a stationary mixer to ensure thorough mixing.

The stream given off by the mixer at rest, the whiting-chalk-acrylamide conglomerates suspended in water, the conglomerates having a mean diameter in the range

609886/1055

from 60 to 65 micrometers was fed into the second cleaning stage through a transparent plastic pipe introduced for the paper stock. A water solution of a polyacrylamide retention aid, namely the product sold under the name "Percol" in England by the company Allied Colloids being launched was added just before the feed box to hold back the fines and to ensure maximum retention of the glue.

A high quality paperboard was then made on a paper machine using a mildly acidic system in which the zeta potential was approximately zero. The cardboard was produced at a production speed of 1850 kg / h End of delivery of the paper machine and generated at a running speed of 95 m / min.

The following table gives the physical results that apply to the paperboard made according to the invention after previous example was generated; these results are compared with the results that apply to paperboard, which was generated in a similar manner, except that an * * -. replace filler-polymer conglomerates with an untreated calcium carbonate filler in the usual way became.

conglomerate

filler
CaCO ₀

Base-

paper

weight

g / m ²

146 150

Total-

Ash-

salary

egg

10

Basic burst rupture

Fiber stiffness length

Weight based on the

₂ 100 g fiber web

g / m m

18.7
13.7

118
136.5

284
260

6525 6480

The above results indicate that by application the invention is possible to considerably increase the filler content of the cardboard or paper web without becoming the strength of the web somehow deteriorates. The pro-

6Ö98d6 /

■ -.-. 263235

percent increase in ash content was 36%, while the percent increases in burst strength and tear length, i.e. tensile strength, were 9.2 and 0.6%, respectively.

It should also be noted that this process does not involve any Difficulties arose from using whiting chalk as a filler in an acidic system, as they normally do occur when working according to the known method.

Example 4

This example illustrates the application of the invention in an acidic papermaking system using china clay as a filler, with during formation a resin is present in the filler-polymer conglomerates to increase hate resistance.

A paper stock was fully bleached in the usual manner chemical pulps and recycled fines derived from a similar paper stock, manufactured in such a way that he 55 weight percent hardwood, 35 weight percent softwood and contained 10% by weight of returned fines. An amount of a resin-alum size was added to this paper stock to give a pH of 5.5.

A commercial homopolymer of acrylamide with a molecular

Ct

Cell weight of about 5 χ 10 and a viscosity accordingly 82 centipoise at 15 C (measured on a solution of 0.5 percent by weight at 50 rpm with an RVT Brookfield-> Viscometer) and 0.05 percent by weight (based on the weight of the polyacrylamide) of a commercially available aqueous solution a polyamide-epichlorohydrin resin to increase the wet strength, which in England under the name "Kymene 557 "launched by Hercules Powder Company Limited were mixed with tap water to form a polyacrylamide solution containing 0.3% by weight of solids with a zeta potential of + IeV. The viscose solution prepared in this way was

609866 / 1ÖSS

speed of about. 220 Itr / h by means of an inevitable Displacement working pump fed into a feed line by a 25 percent strength by weight aqueous slurry a china clay usable as a filler was flowed through at a throughput rate of 2450 ltr / h, so that the polymer solution was added to the wet filler stream in an amount of about 9.0%. The polyacrylamide solution was fed to the filler line, and the resulting mixture was passed through a stationary mixer to ensure thorough mixing.

The current given off by the stationary mixer, the china clay-polyacrylamide conglomerates suspended in water containing a mean diameter in the range of 50 to 55 micrometers, was made via clear tubing Plastic is fed into the papermaking system at a point prior to the mechanical stock screens. One Water solution of a polyamide retention aid, namely the commercially available one, made in England by the Bayer company under the name "Retaminol" Introduced into the paper stock immediately in front of the feed box in order to hold back the fines and achieve maximum retention of the glue.

A wood-free continuous writing paper web was then made on a paper machine using an acidic system generated with a slightly positive zeta potential. The production speed was 4200 kg / h at a running speed of 600 m / min.

The following table illustrates the physical results obtained in the paper produced according to the invention according to the preceding example, compared to the Results which apply to paper produced in a similar manner, except that instead of the filler-polymer conglomerates in the usual way untreated porcelain earth was used as filler.

609886/1 05S

conglomerate

Base-

paper

weight

g / m ²

53.1

Total-

Ash-

salary

China clay 52.0

14 9

Base = bursting rupture

Fiber stiffness length

Weight based on the

2 100 g fibers web g / m m

4850 4450

45.66
47.3

199
197

The above results show that by applying the invention it is possible to reduce the filler content of the paper web without to significantly increase any deterioration in strength. The increase in ash content was 55.5%, while the Burst strength increased by 1.0% and the tear length or tensile strength increased by 8.9%.

Example 5

This example illustrates the application of the invention in an acidic papermaking system using china clay as a filler.

A paper stock was completely bleached in the usual way Chemical pulps and recycled fines derived from a similar paper stock, manufactured so that it Contained 55 weight percent hardwood, 35 weight percent softwood and 10 weight percent of the recycled fines. This paper stock was given a resin-alum sizing agent in one added in such an amount as to give a pH of 5.5.

A commercial homopolymer of acrylamide with a molecular weight of about 5 χ 10 and a viscosity accordingly 82 centipoise at 15 ° C (measured on a 0.5 weight percent solution at 50 rpm using an RVT Brookfield viscometer) was dissolved in tap water so that a polyacrylamide solution with a solids content of 0.3 percent by weight and a zeta potential of +1 eV. The viscose solution was at a rate of about ltr / h by means of a working with inevitable displacement

609866/10 55

Pump fed to a feed line by a 25 percent by weight aqueous slurry of a china clay suitable as a filler at a throughput rate of 2450 ltr / h was flowed through, so that the polymer solution was added to the wet filler flow in an amount of about 9.0% was attached. The polyacrylamide solution became the filler line and the mixture thus obtained was passed through a stationary mixer to ensure thorough mixing to guarantee.

The current given off by the mixer at rest, in the porcelain earth-polyacrylamide conglomerates were suspended in water having a mean diameter ranging from 25 to 35 microns was attached to a papermaking system via clear plastic tubing Point fed in front of the mechanical sieves for the paper stock. A water solution of a retention aid, and Although the product marketed in England by Bayer under the name "Hetaminol C", was immediately before fed to the feed box to hold back the fines and to ensure maximum retention of the glue.

Then, an endless wood-free writing paper sheet was made on a paper machine using an acidic system with a slightly positive zeta potential generated. This was done with a production speed of 4200 kg / h and a running speed worked from 600 m / min.

The table below illustrates the physical results obtained with the invention according to the above Example produced paper compared to the results obtained which apply to paper that is based on in the same way, but using untreated china clay as a filler instead of that according to the invention Filler-polymer conglomerates had been produced.

60988S / 1Ö5S

Base- Total- Base- Bursting Tear paper Asehe- Fas he - sturdiness length weight salary weight based on the O 100 g fibers train g / m " ⁵ Oil
ίο g / nT m conglomerate 52.2 12th 46.2 197 4500 porcelain Earth 52.0 9 47.3 197 4450

The above results show that the application of the invention makes it possible to reduce the filler content of the paper web without to significantly increase any impairment of strength. The increase in ash content was 33.3% while the burst strength increased by 1% and the tear length increased by 5%.

Example 6

This example illustrates the application of the invention in an acid papermaking system using china clay as a filler in the presence of a die Dry strength enhancing resin during the formation of the filler-polymer conglomerates.

Ss became a paper stock from fully bleached chemical pulps and from a similar paper stock in the usual manner originating, returned fines or fragments so that they contain 10 percent by weight hardwood, 80 percent by weight softwood and contained 10 percent by weight of recycled fines. A fortified resin-alum sizing agent was added to the paper stock added in such an amount that the pH was about 5.8.

A commercial homopolymer of acrylic amide of molecular weight of about 5 χ 10 and a viscosity accordingly 82 centipoise at 15 C (measured on a 0.5 weight percent solution at 50 rpm with an RVT Brookfield viscometer) so / ie a 0.5 percent strength by weight aqueous solution (based on the weight of the polyacrylamide) of a commercially available one sulphited melamine-formaldehyde resin for increasing the dry strength, which is produced in England by the British Industrial Plastics Limited have been supplied with

60988 <6 / 10SS

water mixed so that a polyacrylamide solution with a solids content of 0.4 percent by weight and a zeta potential received from -20 eV. The viscose solution prepared in this way was at a throughput rate of about 186 ltr / h conveyed to a feed line by means of a pump working with positive displacement, which is fed by a 20 percent strength by weight aqueous slurry of china clay with a throughput rate of 1550 liters / h was flowed through, so that the polymer solution to the wet filler current was added in an amount of about 20%. The polyacrylamide solution was fed to the filler line, and the mixture obtained in this way was passed through a stationary mixer in order to ensure thorough mixing.

The current given off by the stationary mixer, the china clay-polyacrylamide conglomerates suspended in water containing a mean diameter in the range of 85 to 95 micrometers, was made via clear tubing Plastic fed to the feed box distributor of a paper machine. No retention means1 was added to the paper stock.

Then paper was made on the paper machine using an acidic system with a slightly positive zeta potential Used as a lining for sugar sacks. This was done with a production speed of 2000 kg / h and a running speed of 100 m / min at the end of the machine.

The table below illustrates the physical results obtained in accordance with the invention after the above Example compared to the results obtained for paper made in the same way, but below Using untreated china clay as a filler instead of the filler-polymer conglomerates had been made.

609886 / 10SS

Base-
Pap i er -
weight
g / m ² -21- Base-
Fiber-
weight
g / m ² 2632350 Tear
length
the
train
m 67.2 Total-
Ash-
salary
% 59.1 Bursting
sturdiness
based on
100 g fibers 7820 conglomerate 64.6 12.3 59.0 440 6330 porcelain
Earth 8.7 424

The above results show that through the application the invention is possible, the filler content of the paper web without significantly increasing any impairment of strength. The increase in ash content was 34.5%, the increase in burst strength was 3.7% and the improvement in tear length or the tensile strength 23.5%.

Patent claims:

609886/1055

Claims (19)

PATENT CLAIMS \1. Method for producing paper by means of a paper machine using an aqueous paper stock containing a mineral filler, characterized in that the mineral filler is the paper stock added in the form of a filler-polymer conglomerate formed by bringing a particulate mineral filler into contact with a polymer which has a zeta potential in the range from -40 to +40 eV and a molecular weight of at least 2 χ 10. 2. The method according to claim 1, characterized in that the polymer has a molecular weight in the range of 4 χ 10 to 12 χ 10 has. 3. The method according to claim 1, characterized in that the polymer has a zeta potential in the range of +5 to -20 eV and has a molecular weight in the range of 5 10 to 10 χ 10. 4. The method according to claim 3, characterized in that the polymer is an acrylamide polymer. 5. The method according to claim 4, characterized in ^that: the polymer is a substantially non-ionic homopolymer of acrylamide. 6. The method according to any one of claims 1 to 5, characterized in that that the conglomerate is 0.01 to 0.5 percent by weight of dry polymer based on the dry weight of the filler contains. 7. The method according to any one of claims I to 6, characterized in that that the particles of the filler-polymer conglomerate have an average diameter in the range from 50 to 100 Have micrometers. 6,9886 / 1 OBS ■ -23- 8. The method according to any one of claims 1 to 7, characterized in that that the mineral filler is calcium carbonate, china clay, talc or titanium dioxide. delt. 9. The method according to any one of claims 1 to 8, characterized in that the filler-polymer conglomerates be obtained that an aqueous solution of the polymer is added to an aqueous suspension of the filler, and that the mixture obtained in this way then optionally a small one Shear force is exposed. 10. The method according to any one of claims 1 to 9, characterized in, that the filler and the polymer in the presence of one increase the wet strength or the dry strength Resin or a starch are brought into contact. 11. The method according to claim 10, characterized in that the resin used to increase wet strength is a polyamide-epichlorohydrin or a polyamide-polyamine-epichlorohydrin resin. 12. The method according to claim 10, characterized in that the resin serving to increase the dry strength is a melamine-formaldehyde resin is, which is optionally sulfited so that it is alkaline and anionically charged. 13. filler-polymer conglomerate, characterized in that it has been formed in that a particulate mineral filler has been brought into contact with a polymer that has a zeta potential im Range from -40 to +40 eV and a molecular weight of min- ß
has at least 2 χ 10. 14. Conglomerate according to claim 13, characterized in that that the polymer has a zeta potential in the range from +5 to 6 -20 eV and a molecular weight in the range from 5 χ 10 to 10 χ 10 ⁶ has. - 609886/1055 15. Conglomerate according to claim 14, characterized in that the polymer is an acrylamide polymer. 16. Conglomerate according to claim 15, characterized in that the polymer is an essentially nonionic homopolymer of acrylamide is. 17. Conglomerate according to one of claims ¹ . 13 to 16, characterized in that it contains 0.01 to 0.5 percent by weight of dry polymer based on the dry weight of the filler material. 18. Conglomerate according to one of claims 13 to 17, characterized characterized in that its particles have an average diameter in the range of 50 to 100 micrometers. 19. Conglomerate according to one of claims 13 to 18, characterized in that it is the mineral filler calcium carbonate, china clay, talc or titanium dioxide. Dei / patent attorney: 609886/1055