JPS58126396A - Paint for paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paper coating mainly consisting of an aqueous phase in which pigments are dispersed and a binder. The present invention relates in particular to new binders for paper coatings.

BACKGROUND OF THE INVENTION In multicolor printing at high printing speeds, where coated offset papers are becoming more and more important as offset printing becomes more and more widespread, ever higher demands are made regarding the quality of the paper coatings. As the printing cylinder rotates away from the paper surface, high tensile forces act on the paper surface due to the tackiness of the printing ink. Efforts are therefore being made to provide high structural strength perpendicular to the paper surface through suitable application. Because the printing process transfers moisture onto the paper,
High structural strength must be maintained even in wet conditions. This property is related to wet paper peel resistance (Naeqrupff
Also called estigkelt.

During the production of multicolor prints during the working process, moisture transferred to the non-printed surface must be quickly removed. This is because, if not removed, the printing ink will be repelled by the remaining water film on the surface during the next printing process.

Originally, paper coatings contain natural substances, such as starch or casein, as fillers. However, the coating produced using this method does not have sufficient paper peel resistance when wet, and its quality is also uneven.

The combination of these natural products with dispersed synthetic binders has the same drawbacks. European Patent Publication No. 14904 proposes a combination of two synthetic resins as a binder for paper paints; 10,000 of these synthetic resins are soft and sticky, and the other 10,000 are acrylic. acid or methacrylic acid and units of hydroxyalkyl esters of unsaturated acids to form a co-binding agent (Oob'1n-de
r)' is extremely hydrophilic.

The subject of European Patent Publication No. 15517 is also the combination of a binder-spinning mixture consisting of a soft dispersion resin consisting of a natural or synthetic polymer and a hydrophilic binder. This hydrophilic binder is first emulsified in oil and added in this form to the paint.

German Patent Publication No. 2933765 also refers to the principles of binders and spinning mixtures, where the hydrophilic spinning mixture is partly water-soluble and partly chemically bonded to the binder. .

DE 30 35 179° describes dispersed synthetic resins which can be used as sole binders in paper coatings. This resin is an emulsion polymer made in two steps from dienes, styrene, acrylic esters, unsaturated acids, and optionally limited amounts of hydroxyalkyl esters. However, they are relatively hydrophobic, so that in practice good results can only be obtained when used as a spinning mixture in combination with hydrophilic natural products, such as starch or casein.

,lii! It can be produced with certain properties as an adhesive, can be used as a sole binder, and can be mixed into synthetic resin whole paper coatings to produce paper coatings with high wet paper peel resistance and high water absorption. is good.

In order to solve this problem, the paper paint described in claim 1 is proposed.

This new paint contains as an essentially new component (5) filler B, preferably in an amount of about 5 to 25% by weight, based on the weight of filler C. The other ingredients are conventional in paper coatings. The paints always contain water as the liquid vehicle and chalk, kaolin, barite, titanium dioxide or other white or colored pigments as a full-filling substance. The amount of filler relative to the solids content of the paint is generally 80-95% by weight.
It is. Other additives which can optionally be used together are wetting agents, defoamers, thickeners or stabilizers. Additional binders are basically not necessary, although it is of course possible, if not advantageous, to add other binders.

The dispersant (D) is a common and necessary component of the binder dispersion, but in the paint according to the invention it also has the function of completely dispersing the filler.

Advantages of the invention 2. By completely avoiding the use of natural products as binders or spinning mixtures, the properties of the paper paints of the invention and of the paper coatings produced therefrom are always combined with the use of organic natural products. There is no fluctuation.

(6) Therefore, the paper coating can always be processed in a uniform manner, and a paper coating film of uniform quality can always be obtained. Another advantage is that these objectives can be achieved with a single binder. This reduces costs for paper coating manufacturers both in storage of raw materials and in production by eliminating metering and mixing steps. For the user, all problems that would arise in conventional multicomponent binders due to inaccuracies in adjusting the mixing ratio of binder and spinning mixture are eliminated.

The new binder provides paper coatings with excellent water absorption and rapid migration properties, as well as excellent wet peel resistance.

Binder (B): Binder B is a latex produced by emulsion polymerization from the monomer components described in (1) to (5) of Claim 1.

The main components are preferably alkyl esters of acrylic acid and/or methacrylic acid in which the alkyl group has 1 to 12 carbon atoms, optionally in a mixture with styrene. However, compositions without styrene are advantageous. It is advantageous if part of the ester alkyl groups has 4 or more carbon atoms and if a certain amount of methyl or ethyl ester is also present. Furthermore, it is advantageous if the ester is at least partially derived from acrylic acid.

A preferred composition of the ester component (1) consists of methyl methacrylate as the curable component and ethyl acrylate or especially butyl acrylate as the softening component.

The quantitative ratio of the curable and softening monomer components is (component (2)
(5) With all efforts, it is determined that the minimum film-forming temperature (MFT according to DIN 53787) of the binder latex does not exceed 50°C, preferably below 40°C. In general, this depends on the composition of component (1), which in most cases consists of lower methacrylic esters and/or styrene having 1 to 4 carbon atoms in the ester alkyl group, on the other hand, higher methacrylic esters and/or styrene. Alternatively, it can be achieved by composition of component (1) from acrylic ester.

As hydroxyalkyl esters (2) of acrylic or methacrylic acid, those having 2 to 5 carbon atoms in the hydroxyalkyl group are preferably used. Advantageously hydroxyethyl ester, 2-hydroxypropyl ester and 4-hydroxybutyl ester,
Particular preference is given to the aforementioned esters of acrylic acid. Although the absorbency of the paper coating increases with increasing amount of hydroxyester, the wet peel resistance is maximum at about 10-15 inches, so it is advantageous for the amount of hydroxyester to exceed 20%. isn't it.

Acrylamide or/and methacrylamide (3) is a secondary compound along with hydroxy ester in the emulsion polymer.
It is contained as a hydrophilic component. Both hydrophilic components alone cannot achieve the advantageous combination of high wet peel resistance and high absorbency of the paper coatings produced. Methacrylamide is particularly effective.

(9) Unsubstituted amides are preferred, but optionally the corresponding N
It is also possible to use -alkyl-substituted amides (for example with the cl-0°-alkyl group).

As the polyunsaturated carboxylic acid (4), it is advantageous for acrylic acid or methacrylic acid to participate in the composition of the emulsion polymer. Advantageous amounts are 1 to 3% by weight. The carboxyl groups can optionally also be neutralized with suitable bases such as ammonia, organic amines or alkali metal hydroxides before, during or after polymerization. The advantageous pH value of the paint is from 7.5 to 11.Other components (5) are not necessary to achieve the object of the invention, but are different from components (1 to (4)). Limited amounts of radically polymerizable monomers are often incorporated into emulsion polymers without disadvantage. Examples of such comonomers that often work advantageously are acrylonitrile and methacrylnitrile; is often avoided due to the difficult-to-avoid residual upper zummer content.

(10) Other monoethylenically unsaturated comonomers that can be used are vinylpyrrolidone, vinyl chloride, vinylidene chloride, vinyl acetate or other vinyl esters or monoolefins. Monomers with a large number of unsaturations, such as glycol diacrylate, are preferably used sparingly.

This is because it acts on crosslinking which reduces water absorption and prevents film formation. If this is contained as an impurity in the hydroxy ester used,
Its weight relative to the total polymer should be so low that it has no adverse effects. Thus, it is generally advantageous to have it as low as 0.5% by weight, in particular as low as 0.055% by weight.

Emulsion polymers are prepared in a conventional emulsion-type process using water-soluble radical formers such as beroxysulfate, hydrogen peroxide or water-soluble redox systems and emulsifiers (preferably anionic and/or nonionic) in the aqueous phase. It can be manufactured by The particle size of the latex particles is advantageously 30 Qn
m (weighted average value). The emulsification type @ is carried out discontinuously by a monomer or emulsion supply method, and the amount of emulsifier is adjusted at the critical micelle formation concentration. When used in an aqueous charge or carried out batchwise by the latex seed process,
The particle size can be controlled most precisely. This method is known to the expert.

Dispersant (D): Dispersant (D) consists of a number of components. Generally, these are anionic and/or nonionic emulsifiers already used in the production and stabilization of binder latices. Other dispersants are required for pigment dispersion. For example ld
Polyacrylic acid or its water-soluble salt or polyphosphate having a K value of 10 to 35 can be mentioned. Furthermore, cellulose or starch derivatives may be present. They are primarily used for thickening, adjusting the desired viscosity of the paint.

Example 1 A reaction product consisting of 0.51 ammonium d-oxydisulfate, triisobutylphenol and 7 mol of ethylene oxide was prepared in a Witt's topf (2t) vessel equipped with a reflux condenser, a stirrer and a feeder. Industrial emulsifier sulfated and converted to IJium salt 0.4fl't 40ml of distilled water at 80°C
Dissolve in 0f. Methyl methacrylate 430f was added to this solution in advance.

Butyl acrylate 4009, 2-hydroxyethyl acrylate tooy, Methacrylic acid amide 50f,
An emulsion prepared from 202 grams of methacrylic acid, 9.35 grams of the emulsifier, 1.59 grams of the initiator, and 615 tons of distilled water was added dropwise at 80.degree. C. over 4 hours with stirring. After the end of the feed, the dosage is kept at 80 DEG C. for a further 2 hours, cooled to 50 DEG C. and adjusted to pH 7.5 with NH3 solution. Reaction product 15f of 1 mol of isononylphenol and 7 mol of ethylene oxide and 42.9 35% reaction product of 1 mol of isononylphenol and 7 mol of ethylene oxide (7)
Add more of the mixture consisting of 9. After cooling to room temperature, it is filtered through a fine mesh width sieve made of stainless steel (13).

This dispersion has a solids content of about 50% by weight and an average particle size of 154H. MFT: 19°C.

Example 2 (Repeat the comparative experiment Example 10 method, but with methyl methacrylate) 4BO
f (instead of 4309) and no methacrylic acid amide.

A dispersion with a solids content of approximately 50% by weight and an average particle size of 154 nm is obtained. MFT2 21℃.

Example 3 (Comparative Example) Repeat the method of Example 1 but with butyl acrylate 500y (
400f) and no 2-hydroxyethyl acrylate.

The average particle size is 136 nm and the solids content is approximately 50! A dispersion of Fuchi is obtained. MFT: 24°C.

Example 4 The procedure is as in Example 1, but the feed consists of an emulsion with the following composition: Methyl methacrylate 4309 Butyl acrylate 300f(14) 4-Hydroxybutyl acrylate) 200f Methacrylic acid amide 502 Methacrylic acid 20° Triisobutylphenol and 7 moles of ethylene oxide, sulfated,
Reaction product converted to Na salt 9.35
.

Ammonium peroxydisulfate 1.52 Distilled water
6152 This dispersion is solid gold! 49.9 inches and has an average particle size of 136 parts mK. Midfielder
T: 24°C.

Manufacture of Paper Coating In order to produce the paper coating for offset paper, 200 parts of Chaika clay and 200 parts of paint chalk are mixed in a dispersion device with a conventional dispersant based on low molecular weight polyacrylic acid (for example, ROH&GIT). 5L252) (solid) are used to disperse in 250 parts of water.

To this is added 120 fBe of the binder described in the previous example with stirring, and the pH of the paint is adjusted to 8.5 with NaOH. The wet peel resistance of papers coated with these coatings was pre-wetted and tested using a test device - a multi-purpose sample printing device.

In this method, the IJ tube of the test paper is moistened with a mixture of water and isopropanol (80/20) using a rubber roll and subsequently printed flat with a pick-resistant ink.

Test conditions: Ink 2 Paper peeling resistance ink Inko 14.8 (H
Uber, Munich Amount: 200 ■ Pre-moistening: Rubber roll 2 crn Printing plate: Rubber roll 4 cfn Printing pressure: 300 N/crn Printing speed: 2 m/sha Result: Paper peeling in the area that was not moistened (paper peeling when dry)
was not recognized at all. Similarly, no repulsion phenomenon of printing ink due to pre-wetting was observed. The obvious difference is in the determination of the build-up of the coating on the printing plate (m-layers occur when the coating melts due to prewetting and transfers onto the printing plate during subsequent printing). The evaluation of the printing results is listed in the table.

(17) Continued from page 1 0 Inventor: Winfried Hetzterich, Federal Republic of Germany, Griesheim, Schienvaibergasse 5 0 Inventor: Zubert Rauch, 1 Odenwaldstrasse, Federal Republic of Germany, 1 Odenwaldstrasse 6

Claims (1)

[Claims] 1. A binder in the form of latex particles, A) a binder in the form of latex particles, a conventional filler D) a dispersant, E) optionally other conventional additives, B is 1) an alkyl ester of acrylic acid or/and methacrylic acid that may be mixed with styrene, 45 to 94.5% by weight, 2) a hydroxyalkyl ester of acrylic acid or methacrylic acid, 3 to 20% by weight, 3) acrylamide and/or methacrylamide or N-alkyl derivative thereof 2 to 10% by weight, 4) 0.5 to 5% by weight of polymerizable unsaturated carboxylic acid, 5) Optionally, other monomers based on the weight of the mixed polymer, respectively. A paper coating comprising an emulsion polymer comprising up to 20% by weight of an olefinically unsaturated monomer, characterized in that the aqueous dispersion of the emulsion polymer has a minimum film-forming temperature not exceeding 50°C. 2. Paper coating according to claim 1, wherein the alkyl ester (1) participating in the composition of the emulsion polymer at least partially has an alkyl group having at least 4 carbon atoms. 3. Paper paint according to claim 1 or 2, wherein the alkyl ester (1) participating in the composition of the emulsion polymer is at least partially derived from acrylic acid. 4. The paper paint according to any one of claims 1 to 3, wherein the average particle size of the binder (B) is at most 30 Qnm.