FI71570C - BINDEMEDELSBLANDNING FOER PAPPERSBESTRYKNINGSMASSOR. - Google Patents

Abstract

1. Binder mixture for paper-coating compositions based on aqueous dispersions of from 95 to 70 parts by weight of an emulsion polymer A, which contains acrylate and ethylenically unsaturated carboxylic acids as copolymerised units, and from 5 to 30 parts by weight of a copolymer B of from 15 to 55% by weight of acrylic acid and/or methacrylic acid, where appropriate up to 10% by weight of acrylamide and/or methacrylamide and from 85 to 45% by weight of other monomers which form water-insoluble homopolymers, at least 20% by weight of these hydrophobic monomers being esters of acrylic acid or methacrylic acid with alcohols which contain from 1 to 4 carbon atoms, wherein copolymer A contains, as copolymerised units, (a) from 80 to 96% by weight of esters of acrylic acid and monohydric C2 -C8 -alcohols, (b) up to 19.5% by weight of styrene, acrylonitrile and/or methylmethacrylate, and (c) from 0.5 to 10% by weight of other monomers which form water-soluble homopolymers.

Description

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National Board of Patents and Registration Date of publication and publication. - 10.10.86

Patent and registration authorities '' Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed — Begärd priority 17-05-79

German Federal Republic of Germany (DE) P 2919937-9 (71) BASF Aktiengesel1schaft, Ludwigshafen, Federal Republic of Germany Federal Republic of Germany (DE) (72) Kurt Wendel, Ludwigshafen, Ludwigshafen, Gunther

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (74) Oy Koister Ab (54) Binder mixture for paper-making pulps -

Bindemedelsb1andning för pappersbestrykningsmassor

It has long been known to use aqueous dispersions of acrylic ester copolymers as synthetic binders, alone or in combination with naturally occurring binders such as starch, casein or soy protein. However, in high-speed coating machines, they often have insufficient shear stability and unsatisfactory compatibility with certain pigments, such as satin white. It is known from U.S. Pat. No. 3,081,198 to use mixtures of acrylic ester and vinyl ester copolymers with acrylic acid-acrylic ester copolymers as synthetic binders for paper coating compositions. The pigment coatings thus prepared show insufficient printability in gravure printing, which is manifested in the fact that the gravure ink, especially in the half-shades, does not transfer to the coating sufficiently evenly, whereby defects appear in the printing ice, so-called "missing dots".

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DE-PS 12 58 721 discloses binder mixtures for neutral or alkali-bonded paper-coating rays on the basis of aqueous dispersions. These are emulsion polymers A which contain 40 to 70 parts by weight of styrene, 30 to 60 parts by weight of acrylic acid or containing 2 to 12 carbon atoms in the chain, and optionally up to 10 parts by weight of ethylenically unsaturated copolymerizable compounds, and emulsion copolymer B comprising 15 to 55% by weight of acrylic and / or methacrylic acid, optionally up to 10% by weight of acrylic and / or methacrylamide and 85 to 45% by weight of other water-insoluble homopolymer-forming monomers, of which at least 20% by weight, based on the weight of these hydrophobic monomers, are esters of acrylic acid or methacrylic acid with alcohols containing 1 to 4 carbon atoms. The binder mixture contains 5 to 40 parts by weight of at least one copolymer B and 95 to 60 parts by weight of at least one copolymer A. The paper coating inks produced during the use of these binder blends do meet the manufacturing requirements, but are no longer suitable for the increased printability requirements of such coated papers. magazine printing.

It is an object of the invention to provide a binder which, compared with known binders, can be used in smaller quantities for the production of paper coating compositions and which provides coated papers which give a better printing result, above all in magazine printing.

The object is achieved according to the invention by a binder mixture for paper coating compositions based on aqueous dispersions comprising 95 to 70 parts by weight of emulsion copolymer A containing acrylic acid ester and ethylenically unsaturated carboxylic acids in the form of copolymerized copolymer, and 5 to 30 parts by weight of copolymer 15 to 55% by weight of acrylic and / or methacrylic acid, optionally up to 10% by weight of acrylic and / or methacrylamide and 85 to 45% by weight of other monomers forming water-insoluble homopolymers, of which at least 20% by weight, based on these hydrophobic monomers, there are esters of acrylic acid or methacrylic acid with alcohols containing 1 to 4 carbon atoms, 71570 atoms, the copolymer A containing 80 to 96% by weight of an ester of acrylic acid with monohydric C 1 -C 6 alcohols, 3 to 19.5% by weight. % styrene, acrylonitrile and / or methacrylic acid methyl ester, and 0.5-10% by weight of other water-soluble homopolymers monomers copolymerized.

The binder mixture copolymer A contains an essential part of an acrylic acid ester with monohydric alcohols having 2 to 8 carbon atoms. These are, for example, acrylic acid ethyl ester, acrylic acid n-propyl ester, acrylic acid isopropyl ester, acrylic acid n-, iso- and / or tert. butyl ester and acrylic acid 2-ethylhexyl ester. Preferably, those acrylic acid esters derived from isobutanol and n-butanol are used to form copolymer A. In copolymer A, up to 50% by weight of the esters of acrylic acid and monohydric C0-C0 alcohols can be replaced by acrylic acid methyl

/ - O

ester and / or esters of methacrylic acid and monohydric C2-C8 alcohols. The proportion of acrylic acid ester in the formation of emulsion copolymer A is 80-96% by weight, preferably 80-90% by weight.

Copolymers A may otherwise contain a group of styrene, methacrylic acid methyl ester or acrylonitrile monomers. The proportion of these monomers in the formation of copolymer A is 3 to 19.5%, preferably 3 to 15% by weight.

An essential additive in copolymers A are monomers that form water-soluble homopolymers. These are, for example, ethylenically unsaturated C8-C8 carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid or crotonic acid, the corresponding acid amides of the ethylene-unsaturated carboxylic acids, such as, for example, acrylamide and methacrylamide, compounds such as vinylsulfonic acid, styrene p-sulfonic acid, acrylamidopropanesulfonic acid and sodium vinyl sulfonate. This group of monomers accounts for 0.5-10% by weight in the formation of copolymers. Preferably, the copolymer A contains 1.0 to 5% of monomers forming water-soluble homopolymers, of which acrylic acid, acrylamide and methacrylamide or mixtures thereof can be preferably used.

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The glass temperature of copolymer A can be between -20 and + 10 ° C. (Glass temperature is defined in P.J. Flory, Principles of Polymer Chemistry, Cornell University Press, Ithaca, New York, 1953, page 56).

Emulsion copolymers B are known from German patent publication DE-PS 12 58 728. These copolymers contain 15-55% by weight of acrylic acid or methacrylic acid, 0-10% by weight, in particular 2-6% by weight of acrylamide or methacrylamide and 85-45% by weight. hydrophobic, water-insoluble homopolymerate-forming monomers, of which at least 20% by weight are esters of acrylic acid or methacrylic acid with aliphatic C1-C4 alcohols. Suitable hydrophobic monomers which form water-insoluble homopolymers are, for example, acrylic acid or methacrylic acid esters of the highest aliphatic, cycloaliphatic or aromatic hydroxyl compounds, preferably vinyl acetate, vinyl acetate, vinyl propionate, acrylic propionate, acrylic Copolymers B preferably contain acrylic acid and / or methacrylic acid and finally or predominantly acrylic acid or methacrylic acid esters of monohydric alcohols having 1 to 4 carbon atoms. In addition, terpolymers which also contain acrylonitrile, vinyl acetate or acrylamide or methacrylamide copolymerized are preferably suitable.

Copolymers A and B can be prepared by polymerizing monomers in an aqueous emulsion according to a method known per se, using customary anionic or nonionic emulsifiers in the presence of polymerization initiators. Suitable emulsifiers are, for example, the potassium salts of the potassium or sodium, sodium or sulfuric acid half-esters of n-dodecylsulfonic acid, sodium or sulfuric acid half-esters, starting from long-chain alcohols having an even number of carbon atoms, or the corresponding ethoxylated (e.g. 2-25 moles) ethylene salts. and p-isooctylphenol and sodium lauryl sulfate reacted with 5 to 5 moles of ethylene oxide. Emulsifiers are regularly added in amounts of 0.5 to 5% by weight, based on the amount of monomers to be polymerized.

As the polymerization initiators, ordinary 5,71570 radical-generating compounds such as peroxides, persulfates, or azo compounds can be used. Suitable are, for example, potassium persulphate, cumene hydroperoxide or hydrogen peroxide. It is also possible to initiate the polymerization with redox catalysts or activated initiator systems, e.g. a system consisting of potassium persulphate and ascorbic acid, the sodium salt of oxymethanesulphonic acid or triethanolamine. Temperatures in the polymerization are in the usual range, e.g. between 70-95 ° C, they may be lower if redox catalysts are used. It is also possible to polymerize at higher temperatures and under pressure. To control the molecular weight of the polymers, chain modifiers such as dodecyl mercaptan and halogenated hydrocarbons such as chloroform, carbon tetrachloride and tetrachlorethylene can be used in the polymerization.

The binder mixture according to the invention contains 95 to 70 parts by weight of emulsion copolymer A and 5 to 30 parts by weight of copolymer B.

Outside this range, there are binder mixtures with less favorable properties.

The paper coating compositions contain from 3 to 7 parts by weight of finely divided pigment, preferably from 4.5 to 5.5 parts by weight, of the binder mixture according to the invention. They may additionally contain customary additives, e.g. 0.05-3% by weight of dispersants based on low molecular weight polymers of acrylic acid (polymer k-value between 10-25), optical brighteners and customary auxiliaries such as stearates, colorants, antifoams, etc.

In order to achieve the desired technical effects, it does not matter whether the aqueous dispersions of copolymers A and B are mixed before or during the preparation of the coating paints.

The order in which the individual components are added in the production of the coating ink is also irrelevant to the properties of the coating composition or the paper coated with it. However, in order to simplify the preparation of coating dyes, it is advantageous to mix the aqueous dispersions of copolymers A and B in the respective amounts before preparing the coating dyes. The mixture of copolymers A and B is characterized by an unusually high storage stability, which exceeds the corresponding values of known binder mixtures. The solids content of the dispersions of copolymers Λ and B can be varied over a wide range. Preferably, dispersions with a very high solids content, e.g. 45-50% by weight, are used. High-concentration aqueous polymer dispersions are also easy to handle, they can be pumped, for example. When neutralizing copolymer B or a mixture of copolymers A and B, the addition of a base such as ammonia, sodium carbonate, amine or caustic soda increases the viscosity. Depending on the solids content of the dispersion, a flowable paste can be obtained with difficulty in neutralization.

The finished paper coating compositions can be applied to the raw paper by any known method. Due to their high shear stability, paper coating compositions can be used in high speed roller or rough coating machines. They are used primarily in the manufacture of papers printed in magazine gravure printing. These papers give a better print result than papers made with known paper coating compositions. Better print quality in gravure printing is determined by missing dots. In the use of the binder compositions according to the invention, less binder is required, per pigment, than in the case of known binder compositions, for the production of paper coating compositions. Despite the reduced binder content in the paper coating composition obtained by using the binder composition according to the invention, the papers coated with these paper coating compositions do not show dusting of the pigment coating.

The parts mentioned in the following examples are by weight. K values were determined according to H. Fikentscher, Cellulose-Chemie, 13, 58-64 and 71-74 (1932), in 0.5% dimethylformamide solution at 20 ° C; then means K = k.10 ^.

Preparation of an aqueous dispersion of copolymer A.

Copolymer A 1

First, two different feed mixtures are prepared. Feed mixture 1 comprises 460 parts of water, 32 parts of a 20% solution of the sodium salt of the sulfated 7,71570 reaction product, 738 parts (82%) of isobutyl acrylate, 126 parts (14%) of the reaction product which has been reacted with 3 moles of ethylene oxide. %) methyl methacrylate, 18 parts (2%) methacrylamide. Feed mixture 2 comprises 200 parts of water and 4.5 parts of potassium peroxide sulfate.

A mixing vessel equipped with a stirrer, a reflux condenser, a thermometer and two feed vessels, which can be heated, is charged with 230 parts of water, 56 parts of feed mixture 1 and 40 parts of feed mixture 2, and heated to 85 ° C. After 15 minutes, using the polymerization allowed to flow into one of the feed mixture within two hours and the feed mixture 2 and the two flow within half an hour at a temperature of 85 ° C to a mixing vessel. After the feed mixture 2 has been completely metered into the mixing vessel, the temperature is maintained at 85 [deg.] C. for a further two hours, cooled to 20 [deg.] C., the pH is adjusted to 5 by adding ammonia and filtered. No coagulation was formed during polymerization. In this way a 50% aqueous dispersion is obtained.

Copolymer A 2 This copolymer is prepared analogously to copolymer A 1, except that it consists of 85% isobutyl acrylate, 12% acrylonitrile, 1.5% acrylic acid and 1.5% methacrylamide.

Preparation of an aqueous dispersion of copolymer B.

According to the formula described in Example 1 of German patent publication DE-PS 12 58 721, copolymer B is prepared which comprises 75% ethyl acrylate, 5% acrylamide and 20% acrylic acid.

Example 1

An aqueous solution of 0.3 parts of sodium polyacrylate with a k-value of 12 is introduced with 100 parts of a commercially available coating clay by means of a high-speed mixer. As a binder, 9.6 parts of a mixture comprising 80 parts of a 50% aqueous dispersion of copolymer A 3 and 20 parts of a 45% aqueous dispersion of copolymer B 1 are added and the coating color is adjusted to pH 8.5 by adding sodium hydroxide solution. At a solids content of 58%, the coating mass has a viscosity of 1400 mPas (measured with a Brookfield viscometer at 100 rpm).

8 71570 The paper coating pulp thus prepared is applied with a granular coating machine at a speed of 800 m / min to paper comprising 55% wood chips, 45% bleached sulphate cellulose, 2 with an ash content of 6% and a basis weight of 38 g / m · Paper 2 is coated on both sides. The amount of coating is 10 g / m on each side. In the supercalender, satin paper with a speed of 300 m / min and a line pressure of 2000 N / cm has good gloss and good smoothness and excellent printability. Printing performed with a Haindl laboratory gravure press has less than 10 missing dots in an area of 30 cm in a half-2 shade. Missing dots were determined so that error points were calculated visually.

Example 2

According to the instructions given in Example 1, a paper coating composition is prepared, however, 10.2 parts of a binder mixture comprising 75 parts of a 50% aqueous dispersion of copolymer A 1 and 25 parts of a 45% aqueous dispersion of copolymer B 1 are used per 100 parts of commercially available coating clay. The viscosity of the coating paint is 56% at a solids content of 1300 mPas (Brookfield viscometer, 100 rpm). Experimenting with the imprint according to Example 1 results in less than 10 missing dots. Comparative Example

However, the paper coating pulp is prepared as indicated in Example 1, using as a binder, calculated per 100 parts of coating clay, 10.2 parts of a mixture of 80 parts of a 50% aqueous dispersion of a copolymer comprising 55% isobutyl acrylate, 42% styrene, 1.5% acrylic acid and 1.5% methacrylamide, and 20 parts of a 45% dispersion of copolymer 3 L. The coating paint has a viscosity of 1200 mPas (Brookfield viscometer, 100 rpm) with a solids content of 56%. According to the instruction given in Example 1, this coated paper and the satin-coated paper 2 have a gravure printing in half shade of more than 20 missing dots in an area of 30 cm.

Claims (2)

9 71570 A binder mixture for paper coating compositions based on aqueous dispersions comprising 95 to 70 parts by weight of emulsion copolymer A containing acrylic acid ester and ethylenically unsaturated carboxylic acids copolymerized, and 5 to 30 parts by weight of copolymer B, comprising 15% by weight of copolymer B, and / or methacrylic acid, optionally up to 10% by weight of acrylic and / or methacrylamide and 85 to 45% by weight of other monomers forming water-insoluble homopolymers, of which at least 20% by weight, based on the weight of these hydrophobic monomers, is esters of acrylic acid or methacrylic acid with alcohols containing 1 to 4 carbon atoms, characterized in that the copolymer A contains (a) 80 to 96% by weight of an ester of acrylic acid with monohydric C 1 -C 0 alcohols, Δ O (b) 3 to 3 19.5% by weight of styrene, acrylonitrile and / or methacrylic acid methyl ester, and (c) 0.5-10% by weight of other water-soluble homopolymers and forming monomers co-polymerized Tuina. Binder mixture according to Claim 1, characterized in that the copolymer A contains (a) 80 to 90% by weight of esters of acrylic acid with monohydric C0-C0 alcohols, Δ O (b) 3 to 15% by weight of styrene, acrylonitrile and / or methacrylic acid methyl ester, and (c) 1-5% by weight of acrylic acid, acrylamide and / or methacrylamide copolymerized.