JPS63235593A - Paper coating composition - 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 (Industrial Application Field) The present invention provides a paper coating composition, specifically a copolymer latex obtained by emulsion polymerization in an aqueous medium in which a water-soluble organic solvent is dissolved, as a pigment binder. The present invention relates to a paper coating composition used as a paper coating composition.

(Prior art) A carboxyl group-modified copolymer latex obtained by emulsion polymerization of a monomer mixture consisting of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid, etc. can be used alone or with casein, starch, protein, etc. It is well known that it is used as a paper coating binder together with natural or synthetic binders such as cellulose, polyvinyl alcohol, and the like.

Coated paper (hereinafter sometimes referred to as !Nie8 paper) obtained by applying a paper coating composition containing the carboxyl group-modified copolymer latex as a pigment binder has various properties such as adhesive strength and gloss. Due to its excellent properties, it is used for various purposes.

Here, adhesive strength refers to a property that resists the mechanical force applied to the coated paper surface during printing, prevents the coating from peeling off, and enables beautiful printing on the coated paper.

In recent years, the number of printed materials using coated paper has increased significantly, and as a result, there has been a growing trend toward faster printing and diversification of printing methods. Therefore, coated paper and, in turn, binders for paper coating are required to have improved physical properties more than ever before.

That is, it has become necessary to improve all or a plurality of items such as adhesion, gloss, blister resistance, and ink transferability at the same time.

The damage to the paper surface becomes more severe as the printing speed increases and the number of overprints increases, and coated paper that can withstand this is required. To achieve this, a paper coating binder with excellent adhesive strength is required. Is required.

In addition, in order to further exhibit the effect of a beautiful print finish, it is necessary that the coated paper has excellent gloss and printing gloss. For this purpose, a binder for coating paper that provides coated paper with such excellent gloss is required.

In addition, especially in the case of rotary offset printing, due to the nature of the printing method, high-speed printing and high-temperature and high-speed drying are required.
Blisters are likely to occur, and when these blisters occur, the commercial value of the printing paper is greatly impaired.

Since the binder for coating on paper is a major factor in the occurrence of blisters, a binder for coating on paper with excellent blister resistance is required.

In order to meet the above requirements, various improvements have been made to copolymer latexes used as pigment binders. For example, JP-A-54-30910° JP-A-60-21
No. 5895 discloses that by adding a device to the surface charge state of copolymer latex, Japanese Patent Application Laid-Open No. 61-194
Publication No. 296 discloses that adhesive strength and ink transferability can be improved by using a special emulsifier, but gloss and blister resistance have not been improved at the same time. Japanese Patent Application Publication No. 61-207694, No. 61-6379
Publication No. 4 discloses that gloss and blister resistance can be improved by adding innovations to the method of adding monomers and polymerization degree regulators, but adhesive strength and ink transfer properties are also improved at the same time. This has not yet been achieved. Also, JP-A-50-9
4034 by using a vinyl cyanide monomer, JP-A-54-64116 by imparting a different layer structure to a copolymer latex, and JP-A-56-30418 by imparting a different layer structure to a copolymer latex. discloses that various physical properties can be improved by imparting alkali functionality to a copolymer latex, but improvements have not yet been made to the extent that the above-mentioned demands can be met.

(Problems to be improved by the invention) The present invention solves the above-mentioned drawbacks of the prior art and provides a copolymer with sufficiently improved adhesive strength, gloss, blister resistance, and ink transfer properties. The purpose is to provide latex.

As a result of extensive studies, the present inventors found that the above object could be achieved by carrying out the copolymerization reaction in an aqueous medium in which a water-soluble organic solvent was dissolved.Based on this knowledge, the present inventors completed the present invention. Ta.

(Means for solving the problem) That is, the present invention provides an aliphatic conjugated diene monomer of 15 to 80
Weight% ethylenically unsaturated carboxylic acid monomer 0.5-10
Weight % and other copolymerizable monomers 10-84.
A monomer mixture consisting of 5% by weight is added to a stone-active water-soluble organic solvent for the polymerization reaction in all or part of the process.
The present invention relates to a paper coating composition characterized in that a copolymer latex obtained by polymerization in an aqueous medium in which 50% by weight is dissolved is used as a pigment binder.

The aliphatic conjugated diene monomer used in the present invention includes:
1,3-butadiene, 2-methyl-1°3-butadiene, 2,3-dimethyl-1,3-butadiene, pentadiene and other hydrocarbon analogs of 1,3-butadiene, as well as 2-chloro-1, Examples include substituted 1,3-butadienes such as 3-butadiene and 2-cyano-1,3-butadiene. In particular, 1,3-butadiene is preferred from the viewpoints of price, easy availability, and excellent properties of the resulting copolymer.

The proportion of the aliphatic conjugated diene monomer used is 15 to 80% by weight, preferably 20 to 70% by weight of the monomer mixture.
It is. If it is less than 15% by weight, the resulting copolymer will have low adhesive strength and will be hard and brittle. On the other hand, if it exceeds 80% by weight, the resulting copolymer will have poor printing gloss and will be too soft.

Examples of the ethylenically unsaturated carboxylic acid monomer used in the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, etc. Alkyl esters of carboxylic acids;
Acrylamide.

Alkylamides of ethylenically unsaturated carboxylic acids such as methacrylamide and N-methylolacrylamide; carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc. and ethylenically unsaturated carboxylic acids.

The usage ratio of the above ethylenically unsaturated carboxylic acid monomer is:
0.5 to 10 weight percent of the monomer mixture or 0.5
~6% by weight. If it is less than 0.5% by weight, the effect of improving adhesive strength is not sufficient.

On the other hand, if it exceeds 10% by weight, the viscosity of the copolymer latex becomes too high.

Other copolymerizable monomers used in the present invention include aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene; vinyl cyanide monomers such as acrylonitrile, methachronitrile, and α-chloroacrylonitrile. mer; unsaturated fatty acid glycidyl esters such as glycidyl acrylate and glycidyl methacrylate; monoamides; aminoalkyl esters of ethylenically unsaturated carboxylic acids such as aminoethyl acrylate, dimethylaminoethyl methacrylate, butylaminoethyl acrylate; aminoethyl acrylamide, dimethyl Examples include aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethyl methacrylamide and methylaminopropyl methacrylamide.

As the aromatic vinyl compound, styrene is preferred because of its price and availability. The use of vinyl cyanide monomers is
Effective for improving print gloss. The amount of vinyl cyanide monomer used is preferably 3 to 60% by weight, more preferably 5 to 50% by weight. If it is less than 3% by weight,
The effect of improving printing gloss is low, and on the other hand, if it exceeds 60% by weight,
The resulting copolymers have low adhesive strength and are too hard and brittle.

The copolymer latex used in the present invention contains the above-mentioned monomer mixture, which is water-soluble and inert to the polymerization reaction. It is prepared by emulsion polymerization in an aqueous medium in which 5 to 50% by weight of a solvent is dissolved.

The above-mentioned water-soluble organic solvent inert to the polymerization reaction means an organic solvent that is inert to the emulsion polymerization of the monomer mixture and has a solubility in water of at least 5% by weight, a typical example of which is methanol. , ethanol, propatool, isoproptool, butanol, amyl alcohol, ethylene glycol, propylene glycol, butanediol, alcohols such as glycerol, dioxane, acetone, ketones such as methyl ethyl ketone, cyclic ethers such as tetrahydrofuran, cellosolve, methyl cellosolve,
Examples include cellosolves such as butyl cellosolve, nitriles such as acetonitrile, and amides such as N,N-dimethylformamide. In particular, methanol, ethanol, and isopropanol have a carbon number of 1, because of their price, ease of availability, and ease of separation and recovery after emulsion polymerization.
-3 alcohols are preferred. These organic solvents can be used alone or in combination of two or more.

In the present invention, emulsion polymerization is carried out in an aqueous medium in which a water-soluble organic solvent inert to the polymerization reaction is dissolved in water in an amount of 5 to 50% by weight. Less than % by weight, the above adhesive strength, gloss, blister resistance,
Ink transferability is not sufficiently improved, and on the other hand, if it exceeds 50% by weight, a large amount of aggregates will be produced during polymerization, which is not preferable.

Note that the water-soluble organic solvent used is removed by vacuum or the like.

In emulsion polymerizing the above monomer mixture, an emulsifier,
As the polymerization initiator, polymerization chain transfer agent 1, etc., the same ones used in known emulsion polymerization can be used. As the polymerization method, any of batch polymerization, semi-patch polymerization, and continuous polymerization may be employed.

So-called anionic surfactants are preferably used as emulsifiers, such as higher alcohol sulfate ester salts, alkylaryl sulfonates, alkali salts of sulfurides of higher alcohol (poly)ethylene oxide esters, alkyl sulfonates, and alkyl sulfonates. Examples include succinate sulfonates, alkali salts of phosphoric acid mono(or di)esters of (poly)ethylene oxide of higher alcohols, sulfuric acid esters and phosphoric acid ester salts of nonionic surfactants.

Also polyoxyethylene alkylphenol ether in combination with anionic surfactant.

It is also possible to use nonionic surfactants, such as fatty acid esters of polyethylene glycol.

Polymerization initiators include inorganic peroxides such as persulfates and hydrogen peroxide, organic peroxides such as cumene hydroperoxide, lauroyl peroxide, and diisobutylbenzoyl peroxide, and azo compounds such as azobisisobutyronitrile. Further examples include so-called redox catalysts which are used in combination with the oxidation catalyst and a reducing agent such as sodium hyposulfite or sodium salt of ethylenediaminetetraacetic acid.

Examples of chain transfer agents include halogenated hydrocarbons such as chloroform, bromoform, carbon tetrachloride, and carbon tetrabromide, n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t- Mercaptans such as dodecyl mercaptan,
All xanthogens that can be used in ordinary emulsion polymerization can be used, such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide.

These can be used alone or in combination of two or more. The addition method may be one-time addition, multi-part addition, or continuous addition.

The paper coating composition of the present invention contains mineral pigments commonly used for paper coating such as clay, barium sulfate, titanium oxide, calcium carbonate, satin white, and talc, and organic pigments such as polystyrene and phenolic resin. The copolymer latex of the present invention is added as a pigment binder to the pigment selected from the above, and if necessary, natural or synthetic binders and thickeners such as casein, starch, cellulose, polyvinyl alcohol, and alkali thickening emulsion are blended. You can get it. The amount of copolymer latex used is preferably 5 to 30 parts by weight per 100 parts by weight of the pigment.

Furthermore, various commonly used compounding agents such as water resistance improvers, water resistance reaction accelerators, pigment dispersants, viscosity modifiers, coloring pigments, fluorescent dyes and pH adjusters may be added as necessary. can.

(Examples) Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Note that parts and % in Examples mean parts by weight and % by weight, respectively.

Example 1 A mixture of the following formulation 1 was charged into an autoclave equipped with a stirrer, and the mixture was heated to 60° C. to initiate a reaction.

笈f yo water 250.
0 parts Methanol 150.0 parts Sodium dodecylbenzenesulfonate 2.0 parts Butadiene 45.0 parts Styrene
23.0 parts Methyl methacrylate 15.0 parts Acrylic acid
2.0 parts acrylonitrile
15.0 parts t-dodecyl mercaptan
1.0 part carbon tetrachloride 4
．． 0 parts Potassium persulfate 1.0 parts When the polymerization conversion rate of the above monomer composition reached 97%, an aqueous sodium hydroxide solution was added to adjust the pH of the latex to 8.
．． Adjusted to 5. Next, the alcohol, unreacted monomers, and a portion of the water were removed under reduced pressure to obtain a copolymer latex (2). Its solid content was 40.0%.

A monomer composition as shown in Table 1 was polymerized under the same conditions as for copolymer latex ■, and copolymer latex ■~(10)
I got it.

Furthermore, in the above formulation 1, 250.0 parts of water and 1 part of methanol were added.
50.0 parts, (a) 350.0 parts of water, 5 methanol
0.0 part, (b) 350.0 parts of water, 50.0 parts of ethanol
(c) 350.0 parts of water, 50.0 parts of isopropanol
(d) 300.0 parts of water, 100.0 parts of methanol,
(a) 300.0 parts of water, 80.0 parts of methanol, 20.0 parts of n-butanol, (f) 250.0 parts of water, too, o parts of methanol, 50.0 parts of ethanol, (g) 20 parts of water
0.0 part, methanol 200.0 parts, (h) water 150.
Copolymer latexes (11) to (19) were obtained in the same manner as in the production of copolymer latex (1), except that (i) 0 parts of methanol, 250.0 parts of methanol, and 400.0 parts of water (i) were used. However, copolymer latex (18), (19
), the addition of an aqueous sodium hydroxide solution was followed by 300% of water.
0 parts were added, and then the solution was subjected to dropless treatment under reduced pressure.

The following formulation 2 using copolymer latex ω~(lO)
A paper coating composition was prepared.

Kaolinite clay 1 ■ 60.0 parts Calcium carbonate ■ 30.0 parts Polystyrene pigment ■ 10.0 parts Dispersant
) 0.2 parts sodium hydroxide
0.1 part starch ■
4.0 parts copolymer latex (as solid content) 10.0 parts water Add appropriate amount so that the total solid content is 60% by weight ■ High Truss Birds manufactured by J, M, Huber ■ Rubitar manufactured by Fuji Kaolin Co., Ltd. 9
0■ Manufactured by Japan Synthetic Rubber Co., Ltd. #0640 (A)
Aron T-40 manufactured by Toagosei Co., Ltd. Tamago Ace C coating method manufactured by Tamago Cornstarch Co., Ltd. Coating amount of each composition on the base paper was 14.0 ± 0.5 on one side.
Coat with an electric blade coater (manufactured by Kumagai Rensho Co., Ltd.) so that
Dry for 5 seconds. The obtained coated paper was heated at 23°C, 50% R,
H, left for a day and night under indoor conditions, then linear pressure 100k
Super calender treatment was performed four times under the conditions of g/cm and a roll temperature of 50°C.

The following tests were conducted using the obtained coated paper.

The results are shown in Table 2.

Test Method 1) RI Dry Pick: Indicator of Adhesive Strength The degree of picking when printing with an RI printing machine (manufactured by Akashi Seisakusho) was visually determined and evaluated on a five-point scale. The higher the score, the better.

2) Print gloss Print the web offset ink using an RI printing machine and measure it using a Murakami gloss meter (60°-60
°) did.

3) Blister resistance The moisture content of the double-sided coated paper was adjusted to 6%.

The lowest temperature at which blisters occur when placed in a heated oil bath is shown.

4) RI inking: index of ink transferability Ink density was determined visually when printing was performed using a Morton roll with an RI printing machine and dampening water was applied, and evaluated using a 5-step method. The higher the score, the better.

A paper coating composition was prepared using the copolymer latexes (1) and (11) to (19) according to the above formulation 2, and coated paper was produced using the above coating method. The above test was conducted using these coated papers. The results are shown in Table 3.

In Table 3, the amount of aggregates produced during the synthesis of each copolymer latex is also listed in weight % based on the solid content of the latex.

(The following is a blank space) [Effects of the Invention] As is clear from the results in Tables 2 and 3, the coated paper obtained using the paper coating composition of the present invention has excellent adhesive strength, gloss, Excellent blister resistance and ink transfer properties.

Therefore, the present invention provides an extremely excellent composition for coating paper, and has great industrial significance.

Claims (2)

[Claims] (1) 15-80% by weight of aliphatic conjugated diene monomer, 0.5-10% by weight of ethylenically unsaturated carboxylic acid monomer, and 10-84.5% by weight of other copolymerizable monomers
A copolymer latex obtained by emulsion polymerizing a monomer mixture consisting of the A paper coating composition characterized in that it is used as a binder. (2) The paper coating composition according to claim 1, wherein the water-soluble organic solvent is an alcohol having 1 to 3 carbon atoms.