JPH02210094A - Copolymer latex and composition for coating paper - Google Patents

Abstract

PURPOSE:To provide the subject latex giving coated paper having excellent adhesive strength, water-resistant strength, etc., by emulsion-copolymerizing a dienic monomer, an aromatic vinyl monomer, an ethylenic unsaturated carboxylic acid monomer, an alkenylpyrrolidone, etc., in a specific ratio. CONSTITUTION:100 pts.wt. of a monomer mixture comprising (A) 20-60 pts.wt., preferably 25-60 pts.wt., of a conjugated dienic monomer (preferably butadiene), (B) 10-79.4 pts.wt., preferably 15-70 pts.wt., of an aromatic vinyl monomer (preferably styrene), (C) 0.5-10 pts.wt., preferably 1-7 pts.wt., of an ethylenic unsaturated carboxylic acid monomer [e.g. (meth)acrylic acid], (D) 0.1-10 pts.wt., preferably 0.5-5 pts.wt., of an alkenylpyrrolidone (preferably N-vinyl-2-pyrrolidone) and (E) 0-50 pts.wt., preferably 5-40 pts.wt., of any other copolymerizable vinylic monomer [e.g. alkyl (meth)acrylate ester] is emulsion-copolymerized to provide the objective latex.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a copolymer latex for coating paper and a composition for coating paper using the same. Strength 9 This relates to a copolymer latex for paper coating that has excellent properties such as ink receptivity and blister resistance, and is also excellent in workability. It is extremely useful for obtaining not only paper but also coated paperboard with excellent workability and printability during water gloss treatment, and coated paper for gravure printing with excellent calendar roll stain resistance and gravure printing suitability.

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

Coated paper obtained by applying a paper coating composition containing this carboxyl group-modified copolymer latex as a binder has good adhesive strength, water resistance, gloss, etc., and is used for various purposes. .

In recent years, there has been a significant demand for printed matter using coated paper, and as a result, there has been an increasingly strong trend toward faster printing and diversification of printing methods. For this reason, it is necessary to improve various physical properties of coated paper and, in turn, binders for paper coating, more than ever before, and in particular, to improve all or several of these properties at the same time: adhesive strength, water resistance, ink adhesion, and blister resistance. This is becoming a requirement.

In order to meet these demands, various improvements have been made to copolymer latexes used as paper coating binders. For example, JP-A-57-153012, JP-A No. 81-
No. 8!1794 and No. 81-207894 disclose that adhesive strength or blister resistance can be improved by modifying the method of adding monomers and polymer chain transfer agents.

Furthermore, JP-A-54-80910 and JP-A-54-587
No. 89.

Publication No. 60-215895 discloses that adhesive strength, water resistance, and ink receptivity can be improved by modifying the surface charge state of copolymer latex.

Alternatively, proposals have been made to improve various physical properties by imparting a different layer structure to copolymer latex.

However, none of these techniques has been improved enough to meet the above-mentioned requirements.

Furthermore, in order to increase production capacity in line with the growth in coated paper,
In order to further advance high-speed coating and further reduce production costs, efforts are being made to increase the concentration of color solids and reduce the amount of binder.

As for increasing the concentration of color solids, the viscosity of the paper coating composition is too high, resulting in poor fluidity, resulting in a problem with operability. A method was adopted to increase the usage ratio of finely divided heavy calcium carbonate, and to reduce the amount of natural water-soluble binders such as casein and starch, which have strong thickening effects, to make the binder relatively latex-rich. The method is becoming commonly used (Ref', TAPPI Coating Conf.
erence' 79).

However, when such a method is adopted, in terms of operation, backup rolls, calender rolls, etc. become dirty and crumble, and improvements in this respect are strongly desired.

In addition, in coated paper for gravure, from the viewpoint of suitability for gravure printing, the use of sole binders that do not use natural binders but only synthetic binders is already progressing, but even with this method, problems such as roll stains still remain. Not resolved.

Furthermore, in the field of paperboard, a switch is being made from casein, whose price is soaring, to synthetic binders.

When manufacturing paperboard - for boat fishing, the coated surface is treated with zinc sulfate water to increase gloss, smoothness and water resistance (
If casein is not used in water gloss treatment, there is a problem in that roll stains occur, and an improvement is desired.

However, conventional paper coating compositions have not been able to satisfactorily solve problems during operation such as roll stains as described above.

[Problems to be Solved by the Invention] As mentioned above, the conventional paper coating binder has poor adhesive strength and water resistance in the coated paper obtained using it.

There has been a problem in that it is not possible to simultaneously satisfactorily meet the requirements for coated paper physical properties such as ink receptivity, blister resistance, gravure printing suitability, and operability.

The present invention aims to achieve a high level of both operability during water gloss treatment and coated paperboard quality in paperboard coating, and to achieve a high level of operability during water gloss treatment and the quality of coated paperboard, and in gravure printing paper coating, particularly in terms of resistance to calendar roll staining during operation and suitability for gravure printing. The purpose of this invention is to obtain a coated paper that is excellent in resistance to back-up roll staining during operation, water resistance strength, and ink receptivity in offset printing paper coating.

[Means for Solving the Problems] In order to solve the above problems, the first invention provides (a) a conjugated diene monomer, 20 to 80 parts by weight, and (b) an aromatic vinyl monomer, 10 to 80 parts by weight. 79.4 parts by weight (c)
Ethylenically unsaturated carboxylic acid monomer 0.5 to 10 parts by weight (d) Alkenylpyrrolidone 0.1 to 10 parts by weight (e) Other copolymerizable vinyl monomers 0 to 50 parts by weight The present invention relates to a copolymer latex for coating paper, which is obtained by emulsion polymerization of 100 parts by weight of a copolymer latex.

The second invention is as follows: (a) Conjugated diene monomer 20 to 60 parts by weight (b) Aromatic vinyl monomer 10 to 79.4 parts by weight (e) Ethylenically unsaturated carboxylic acid monomer 0 .5~
Part by weight of IO (d) 0.1 to 10 parts by weight of at least one amide group-containing ethylenically unsaturated monomer selected from the compound represented by the following structural formula (I) and alkenylpyrrolidone (e) Other co-products Using 100 parts by weight of a monomer consisting of 0 to 50 parts by weight of a polymerizable vinyl monomer, the first stage is selected from (a), (b), (c), (d) and (e). at least one monomer containing 5 to 99.
5 parts by weight is emulsion polymerized, and in the second stage, 10% by weight or more of (d) and the remaining monomer are polymerized in the lower left of the obtained polymer latex. This invention relates to copolymer latex for paper coating.

Structural Formula (I) In Structural Formula (1), R1 is a hydrogen atom or a methyl group, R,, R, is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and any of R,, R, One or both are alkyl groups having 1 to 4 carbon atoms.

A third invention is a paper coating composition comprising a pigment as a main component and the following alkali-insoluble copolymer latex (I) and alkali-soluble copolymer latex (n) as a pigment binder. The weight ratio of the latex (I) and latex i) is 99.8:0.2 to 85:15.
A paper coating composition characterized in that the present invention relates to a composition for coating paper.

Alkali-insoluble copolymer latex (I) = (g) Conjugated diene monomer 20 to 80 parts by weight (b) Aromatic vinyl monomer 10 to 79.4 parts by weight (e) Ethylenically unsaturated carboxylic acid 0.5 to 10 parts by weight of monomer (d) 0.1 to 10 parts by weight of at least one amide group-containing ethylenically unsaturated monomer selected from the compound represented by the above structural formula CI) and alkenylpyrrolidone ( e) A copolymer latex obtained by copolymerizing 100 parts by weight of a monomer consisting of 0 to 50 parts by weight of other copolymerizable vinyl monomers.

Alkali-soluble copolymer latex (■): 10 to 60 parts by weight of ethylenically unsaturated carboxylic acid monomer, 10 to 90 parts by weight of ethylenically unsaturated carboxylic acid ester monomer
A copolymer latex obtained by copolymerizing 100 parts by weight of a monomer consisting of 0 to 80 parts by weight of other copolymerizable vinyl monomers.

The present invention will be explained in detail below.

Among the monomers used in the production of the copolymer latex of the present invention, specific examples of the conjugated diene monomer (a) include butadiene, isoprene, 2-chloro-1,3-butadiene, 2-methyl -1,3-butadiene and the like can be mentioned. These can be used alone or in combination of two or more. Among these, butadiene is particularly preferred.

The conjugated diene monomer is used in an amount of 20 to 60 parts by weight, preferably 25 to 60 parts by weight, based on 100 parts by weight of the total monomer, in order to impart appropriate elasticity and hardness to the copolymer. use. If the proportion used is less than 20 parts by weight, sufficient adhesive strength in coated paper cannot be obtained. On the other hand, if the proportion used exceeds 60 parts by weight, the water resistance of the coated paper will decrease.

(b) Examples of aromatic vinyl monomers include styrene, α-
Examples include methylstyrene, vinyltoluene, p-methylstyrene, and the like. The proportion of the aromatic vinyl monomer used is 10 to 79.4 parts by weight based on 100 parts by weight of the total monomers,
Preferably it is 15 to 70 parts by weight. The usage rate is 1
If it is less than 0 parts by weight, the coated paper will have poor water resistance and roll stain resistance. On the other hand, if the proportion used exceeds 79.4 parts by weight, the adhesive strength on coated paper will be poor, which is not preferable.

(c) Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid; Anhydrous forms of can also be used. These can be used alone or in combination of two or more.

The proportion of the ethylenically unsaturated carboxylic acid monomer used is 0.5 to 10 parts by weight, preferably 1 to 7 parts by weight, based on 100 parts by weight of the total monomers. If the proportion used is less than 0.5 parts by weight, not only the adhesive strength in coated paper but also the mechanical stability of the copolymer latex will decrease. On the other hand, the usage rate is 1
If it exceeds 0 parts by weight, the viscosity of the copolymer latex becomes high, making it difficult to handle and reducing operability.

(d) Among the amide group-containing ethylenically unsaturated monomers, the compounds represented by the above structural formula (1) include N-methylacrylamide, N-ethylacrylamide, N-
Isopropylacrylamide, N-butylacrylamide, N-tert-butylacrylamide, N-methylmethacrylamide.

N-ethyl methacrylamide, N-isopropyl methacrylamide, N-butyl methacrylamide.

N-monoalkyl (meth)acrylamide, such as N-tert-butylmethacrylamide; and N.

N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylmethacrylamide, N,N
-N,N-dialkyl (meth)acrylamide such as diethylmethacrylamide, and the like.

Furthermore, among component (d), alkenylpyrrolidone includes N-vinyl-2-pyrrolidone, 3-vinyl-2-pyrrolidone,
Examples include pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, and the like.

Particularly preferred as component (d) are N,N-dimethylacrylamide and N-vinyl-2-pyrrolidone.

These components (d) are used to improve coated paper properties such as adhesive strength, water resistance, 9 inking properties, blister resistance, and suitability for gravure printing, as well as workability. The amount is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. If the proportion used is less than 0.1 parts by weight, the purpose of the present invention cannot be achieved, while if the proportion used exceeds 10 parts by weight, the viscosity of the copolymer latex becomes high and its handling ()\
In addition, the paper coating composition has poor fluidity, making coating substantially difficult.

(e) Other copolymerizable monomers include, but are not particularly limited to, methyl acrylate, ethyl acrylate, and butyl acrylate.

Methyl methacrylate, 2-hydroxy acrylate.

Alkyl esters of acrylic acid or methacrylic acid such as ethyl, 2-hydroxymotyl methacrylate, and glycidyl methacrylate; acrylamide;

Ethylenically unsaturated monomers containing amide groups other than component (d) such as methacrylamide and N-methylolacrylamide; carboxylic acid vinyl esters such as vinyl acetate; cyanogens such as acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile; Examples include vinyl monomers. These can be used alone or in combination of two or more.

The proportion of component (e) used is 0 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the total monomers. If the proportion used exceeds 50 parts by weight, the adhesive strength and water resistance of the coated paper will decrease, which is not preferable.

When an alkyl ester of acrylic acid or methacrylic acid is used as component (e), the ink receptivity to coated paper is excellent, and an even more excellent effect can be obtained in reducing coagulum during production. In order to obtain this effect, the preferred proportion of the alkyl ester used is 5 to 30% of the total monomers.
Weight%.

When a vinyl cyanide monomer is used as the component (e), even better effects can be obtained in terms of printing gloss. In order to obtain this effect, the preferred proportion of vinyl cyanide monomer used is 3 to 20% by weight of the total monomers.

When emulsion polymerizing these monomers (a) to (e) components, the following polymerization chain transfer agents, polymerization initiators, and emulsifiers can be used.

As a polymerization chain transfer agent, octyl mercaptan, n-
Dodecyl mercaptan, tert-dodecyl mercaptan, n-hexadecyl mercaptan.

Mercaptans such as n-tetradecylmecabutane and tert-tetradecylmercaptan; xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, and diisopropylxanthogen disulfide; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, etc. Thiuram disulfides; hydrocarbons or halogenated hydrocarbons such as carbon tetrachloride, ethylene bromide, and pentaphenylethane; or acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, and the like. These polymer chain transfer agents can be used alone or in combination of two or more. How to use it: - Addition.

Either divisional addition or continuous addition may be used.

As the polymerization initiator, inorganic initiators and organic initiators can be used.

Inorganic initiators include potassium persulfate, sodium persulfate, ammonium persulfate, etc.; organic initiators include cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, benzoyl hydroperoxide, etc. Organic peroxide; azo compounds such as azobisisobutyronitrile can be used. These catalysts can be used alone or in combination with a reducing agent as a so-called redox catalyst.

When organic initiators are used alone, the mechanical stability of the system is poor and the amount of coagulation in the latex increases.
It is preferable to use it together with an inorganic initiator.

The usage ratio of the polymerization initiator is 0.1 to 5% of the total monomers.
% by weight, preferably 0.5-2% by weight.

As the emulsifier, anionic surfactants, nonionic surfactants and amphoteric surfactants can be used.

Examples of the anionic surfactant include sulfate ester salts of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, and the like.

Nonionic surfactants include ordinary polyethylene glycol alkyl ester type, alkyl ether type,
Alkylphenyl ether type etc. are used.

Amphoteric surfactants include carboxylates, sulfate esters, and sulfonates as anionic moieties.

Examples include phosphoric acid ester salts having amine salts and quaternary ammonium salts as cation moieties. Specifically, the alkyl betaine salts include lauryl betaine,
Stearyl betaine, cocoamidopropyl betaine, 2
-Undecyl-hydroxyethylimidazolium betaine salts are mentioned, and examples of the amino acid type include lauryl-β-alanine and stearyl-β-alanine.

Lauryl di(aminoethyl)glycine, octyldi(aminoethyl)glycine, dioctyldi(aminoethyl)
Each salt of glycine is mentioned.

These can be used alone or in combination, but
Anionic surfactants such as sulfuric ester salts of higher alcohols, alkylbenzene sulfonates, and aliphatic sulfonate salts are preferably used as main agents, and alkylbenzene sulfonate salts are particularly preferred. The proportion of the emulsifier used is preferably 0.1 to 2% by weight of the total monomers from the viewpoint of water resistance.

The copolymer latex for paper coating of the present invention can be suitably produced by two-stage emulsion polymerization. That is, (a) and (b) as the first stage of polymerization.

At least one selected from (c), (d) and (e)
5 to 99.5 parts by weight, preferably 10 to 9 parts by weight of monomers
5 parts by weight are subjected to emulsion polymerization as a second stage, and in the presence of the polymer latex obtained in the first stage, the remaining units containing 10% by weight or more, preferably 20% by weight or more of (d) are added. Polymerize the polymer. In the second stage of this polymerization, the amount of the amide group-containing ethylenically unsaturated monomer (d) used was 10
If it is less than % by weight, it is difficult to obtain the improvement effect of the present invention.

The copolymer latex for paper coating of the present invention can be used alone as a binder in a composition for coating paper, but when used in combination with the alkali-soluble copolymer latex described in detail below, it can be used for paperboard. It can exhibit even more excellent properties as a coating composition for gravure printing paper.

The alkali-insoluble copolymer latex of the present invention (hereinafter referred to as “
Alkali-soluble copolymer latex (hereinafter referred to as latex (II)) used in combination with latex (I)j)
The ethylenically unsaturated carboxylic acid monomer used in the production of the latex (1) of the present invention is the same as that used in the latex (1) of the present invention, and acrylic acid and/or methacrylic acid are particularly preferably used. . The amount of the ethylenically unsaturated carboxylic acid monomer is 10 to 60 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the monomer for producing latex Cm). This is 10
If less than one part by weight is used, a paper coating composition with high water retention cannot be obtained.

If more than 60 parts by weight of the ethylenically unsaturated carboxylic acid monomer is used, not only will a large amount of coagulum be generated during emulsion polymerization, but also a paper coating composition with high water retention cannot be obtained.

Further, as the ethylenically unsaturated carboxylic acid ester monomer for polymerizing the latex (II), for example, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms or a carbon number 2 to 4 and A (meth)acrylic acid hydroxyalkyl ester having an alkyl group having a hydroxyl group is preferably used. Specific examples of the latter include 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate. One or more of these compounds may be used. The proportion of the ethylenically unsaturated carboxylic acid ester used is 10 to 90 parts by weight, preferably 20 to 80 parts by weight, per 100 parts by weight of the monomer. If the amount is less than 10 parts by weight, polymerization stability during polymerization will decrease, while if it exceeds 90 parts by weight, a paper coating composition with high water retention cannot be obtained.

Other vinyl monomers that are copolymerizable with the monomer for polymerizing latex (n) include:
Styrene, α-methylstyrene.

Aromatic vinyl compounds such as vinyltoluene and paramethylstyrene; acrylamide, methacrylamide, N-
Copolymerizable unsaturated compounds having an amide bond such as methylol acrylamide, N-butoxyacrylamide, and diaseptone acrylamide; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; vinyl acetate, vinyl formate, allyl acetate, methalyl acetate, etc. Monoolefins; methylene bis(meth)acrylamide, divinylbenzene, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, vinyl(meth)acrylate, trivinylbenzene, pentaerythritol tetramethacrylate,
Examples include polyfunctional monomers such as pentaerythritol triacrylate and pentaerythritol pentaacrylate.

These monomers may be used alone or in combination of two or more in order to appropriately adjust the water retention, viscosity and fluidity of the paper coating composition.

These monomers are used in an amount of 0 to 80 parts by weight, preferably 1 to 40 parts by weight, and more preferably 1 to 20 parts by weight, based on 100 parts by weight of the monomer. If more than 80 parts by weight is used, a paper coating composition with sufficiently high water retention cannot be obtained.

When copolymerizing the above monomer mixture, methyl cellulose,
Cellulose derivatives represented by semi-synthetic cellulose derivatives such as ethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose; alkali metal salts of polyacrylic acid are used. Semi-synthetic products such as hydroxyethyl cellulose, carboxymethyl cellulose, and alkali metal salts of polyacrylic acid, and synthetic products such as polyacrylic acid, are preferred from the viewpoint of less variation between lofts and ease of handling, and carboxymethyl cellulose is more preferred.

By using these cellulose derivatives and/or alkali metal salts of polyacrylic acid during copolymerization of the above monomer mixture, it is possible to maintain a suitable viscosity without reducing the physical properties of the coated paper.
It imparts appropriate fluidity and water retention, and furthermore, remarkable stability can be obtained in blending the alkali-soluble copolymer latex (n) with the alkali-insoluble copolymer latex (I) of the present invention.

The preferred amount of the cellulose derivative and/or alkali metal salt of polyacrylate used to achieve the desired effect is 0.5 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the monomer mixture. It is. This usage amount is 0.5
If the amount is less than 5 parts by weight, the above-mentioned effects cannot be obtained, whereas if it exceeds 5 parts by weight, a large amount of coagulated material is likely to be generated during polymerization, which is not preferable.

When emulsion polymerizing the alkali-soluble copolymer latex (n), the above-mentioned alkali-insoluble copolymer latex (n)
The known emulsifier, 9 polymerization initiators, 1 polymerization chain transfer agent, and polymerization method described in 1) are used.

The alkali-soluble copolymer latex (n) acts as a thickener when some or all of the carboxyl groups are neutralized with an alkali, increasing the viscosity of the paper coating composition and providing high water retention. However, the weight ratio of latex (1) and latex (n) is 99.8:
It is necessary to use it in a range of 0.2 to 85:15, preferably 99:1 to 90:10. If the amount of latex (1) exceeds the above range, the viscosity and water retention of the resulting coating solution will be low, and the solid content will increase during coating operation.
A stable and good coated surface cannot be obtained. On the other hand, latex (
If (ii) exceeds the above range, the thickening effect of the coating liquid becomes significant, impeding operability.

In the paper coating composition of the present invention, the latex (
1) and latex (II) or latex (1)
) A single pigment binder is preferably used in an amount of 5 to 25 parts by weight, more preferably 6 to 23 parts by weight, based on 100 parts by weight of the pigment. If the amount used is less than 5 parts by weight, the paper surface strength will be low and the operability will be reduced, which is not preferable. If the amount used exceeds 25 parts by weight, the ink receptivity during printing of the resulting coated paper and coated paperboard will not only be poor and the ink setting will be slow, but also the suitability for gravure printing will be impaired. This is not preferable because it tends to be inferior.

As the pigment constituting the paper coating composition together with the copolymer latex of the present invention, an inorganic pigment or an organic pigment, preferably an inorganic pigment, is used. The paper coating composition is prepared as an aqueous dispersion further containing other binders as required.

Here, the pigments include inorganic pigments such as kaolin clay talc, barium sulfate, titanium oxide (rutile anatase), calcium carbonate, aluminum hydroxide, zinc oxide, and satin white, or polystyrene latex,
Organic pigments such as hollow latexes may be mentioned, which may be used alone or in mixtures.

Further, as other binders, natural binders such as starch, oxidized starch, soybean protein, and casein, or synthetic latexes such as polyvinyl alcohol, polyvinyl acetate latex, and acrylic latex are used. These binders are used in an amount of 0 to 10 parts by weight, preferably 1 to 8 parts by weight, per 100 parts by weight of the pigment.

Using the copolymer latex of the present invention1. In order to prepare a paper coating composition, other auxiliary agents such as dispersants (sodium pyrophosphate, sodium hexametaphosphate, sodium polyacrylate, etc.), antifoaming agents (fatty acid esters, phosphate esters, silicone oil, etc.), leveling agents (funnel oil, dicyandiamide, urea, etc.)
,Preservative.

Water resistance agents (melamine resin, polyamide resin, urea resin, glyoxal, etc.), M type agent (calcium stearate, paraffin emulsion, etc.), fluorescent dye, color water retention improver (carboxymethyl cellulose, sodium alginate, etc.) are required. Added accordingly.

The paper coating composition using the copolymer latex of the present invention can be applied to coated paper using a known technique, such as a coating machine such as an air knife coater, a blade coater roll coater, or an applicator. After application, the surface is dried and finished by calendering, etc.

[Examples] The present invention will be described in detail below with reference to Examples, but the present invention is not limited to the Examples in any way. Note that "%" and "parts" used in the examples mean "% by weight" and "parts by weight."

Example 1 Capacity 100! 3 parts of itaconic acid, 0.5 parts of acrylic acid, 5 parts of butadiene, 7 parts of styrene, and 5 parts of methyl methacrylate were placed in a pressure-resistant reaction vessel, followed by 150 parts of water, 1.5 parts of carbon tetrachloride, and dodecylbenzenesulfonic acid. Add 0.2 parts of sodium and 1.0 parts of potassium persulfate,
Polymerization was carried out at a temperature of 70° C. for 2 hours in a nitrogen atmosphere (first stage polymerization). Next, 23 parts of butadiene, 48 parts of styrene
．． 5 parts of methyl methacrylate, 3 parts of acrylonitrile and 1 part of N,N-dimethylacrylamide were added continuously over a period of 8 hours,
Polymerization was carried out by adding 0.2 parts of sodium dodecylbenzenesulfonate at once at the 5th hour (second stage polymerization).

Thereafter, in order to complete the polymerization, the reaction (aging) was continued for 3 hours, and the polymerization was completed at a polymerization rate of 98%.

Next, the pH of the obtained latex was adjusted to 7 using sodium hydroxide, and then unreacted monomers were removed by blowing in water vapor, and the solid content concentration of the latex was made 50% by heating and vacuum distillation. The latex (1) thus obtained is referred to as "latex A".

Examples 2-12. Comparative Examples 1 to 10 Polymerization was carried out in the same manner as latex A except that the polymerization conditions for polymer component 1 shown in Tables 1 and 2 were used to obtain copolymer latex C-■. In addition, copolymer latex B is N
, was obtained by polymerization in the same manner as Latex A, except that 2 parts of N-dimethylacrylamide was added in bulk at 10 hours after the start of the first stage polymerization (polymerization conversion rate 90%).

Note that copolymer latex A-G and LP are copolymer latexes of Examples, while copolymer latex H-
, Q-V is a copolymer latex of a comparative example. The gel contents of these copolymer latexes are shown in Tables 1 and 2.
It is also shown in the table.

The gel content is determined by adjusting the resulting copolymer latex at pH 8.
, After adjusting to 0, coagulate with isoproper tool, wash and dry, then set! (approximately 0.3g) of sample! (1,0
After immersing the sample in 0 ml of toluene for 20 hours, the toluene-insoluble content was measured, and the toluene-insoluble content was expressed as weight % of the sample.

Next, various coated papers were prepared using the copolymer latexes obtained in Examples and Comparative Examples, and various properties shown below were evaluated.

(Evaluation Method) 1) R1 Dry Vic: Indicator of Adhesive Strength The degree of picking when printed with the R1 printing machine was visually judged and evaluated using a 5-step method. The higher the score, the better. The judgment value was expressed as the average value of 6 measurements.

2) Index of R1 Wet Bickening Water Resistance The degree of picking when printing was performed using a Morton roll with an RI printing machine and applying dampening water was visually judged and evaluated using a 5-step method. The higher the score, the better. The judgment value was expressed as the average value of 6 measurements.

3) C. Z-7 Wet Rub: Indicator for water resistance and roll stain resistance The sample was sampled on an Adams tester for 15 seconds, and the transmittance of the cloudy water obtained at that time was measured using a spectrophotometer. The larger the number, the better.

4) Ink receptivity When printing was carried out using a Morton roll with an RI printing machine, applying dampening water and under conditions where no picking occurred, the ink density was determined visually and evaluated using a 5-step method. The higher the score, the better.

5) Mechanical stability The paper coating composition liquid is kneaded between rubber rolls using a gum-up tester, and the time required for coagulation to form on the rubber roll is measured under mechanical shearing.

Evaluation criteria O: 20 minutes or more Δ: 10-20 minutes ×: 10 minutes or less The longer the time until the formation of coagulum, the better.

B) Blister resistance Coated paper coated on both sides (coating amount on one side: 15g/rrr) was adjusted to humidity (approximately 6%) and thrown into a heated oil bath.
Indicates the lowest temperature at which blistering occurs.

(Blending formulation of paper coating composition) A paper coating composition having the following formulation was obtained using copolymer latex A-V.

Mixed recipe clay: 80 parts Calcium carbonate 20 parts (contains 0.5 parts of sodium pyrophosphate as a dispersant) Copolymer latex (solid content equivalent) 12 parts Oxidized starch
Add 4 parts water in a sufficient amount so that the total solids content is 60%. The obtained paper coating composition liquid was coated on 72 g/rrr of coated base paper using a coating blade to give a coating amount of 15%.
Coated paper was obtained by coating on one side so that g/rrf was achieved.

(Evaluation Results) Using the copolymer latex shown in Application Examples 1 to 7 and Comparative Application Examples 1 to 4.9.10 Table 1 and a part of Table 2, the results of evaluation using the evaluation method described above are shown in Table 1. It is shown in Table 3.

Application Examples 1 to 7 are examples in which a copolymer latex within the scope of the present invention was used, and the object of the present invention was obtained.

Comparative Application Examples 1 and 2.4 are examples in which the amount of the amide group-containing ethylenically unsaturated monomer of the present invention is less than the range of the present invention, and the results are as follows: adhesive strength, water resistance, roll stain resistance, ink receptivity, And the physical property balance of mechanical stability is inferior to Application Examples 1 to 7.

Comparative Application Example 3 is an example in which only acrylamide, which is outside the scope of the present invention, is used as the amide group-containing monomer, and the physical property balance of adhesive strength, water resistance, and ink receptivity is inferior to Application Examples 1 to 7.

Comparative Application Example 9 is an example in which the butadiene content is less than the range of the present invention, and is inferior in adhesive strength, water resistance, and roll stain resistance.

Comparative Application Example 10 is an example in which the styrene content is less than the range of the present invention, and the water resistance and roll stain resistance are poor.

Application examples 8 to 12. Comparative Application Examples 5 to 8 Table 4 shows the results of evaluation using the above-mentioned evaluation method using the copolymer latex shown in part of Table 2.

Application Examples 8 to 12 are examples in which copolymer latexes within the scope of the present invention were used, and the objects targeted by the present invention were obtained. Further, since the gel content of the copolymer latex LP in these application examples is all 70% or less, the blister resistance is also good.

Comparative Application Examples 5 and 6 are examples in which the amount of the amide group-containing ethylenically unsaturated monomer of the present invention is less than the range of the present invention, and the results are shown in Table 1. The physical property balance of stability is inferior to Application Examples 8 to 12.

Comparative Application Example 7 is an example in which only acrylamide, which is outside the scope of the present invention, is used as the amide group-containing monomer, and adhesive strength,
Water Resistance 1 The physical property balance of ink adhesion, blister resistance, and mechanical stability is inferior to Application Examples 8 to 12.

Comparative Application Example 8 is an example in which the amount of N,N-dimethylacrylamide used exceeds the range of the present invention, and the viscosity of the copolymer latex is high, resulting in a high viscosity of the paper coating composition liquid. Coating was not possible.

[Evaluation of paperboard and gravure paper] (Evaluation method) The evaluation method used in the following examples is as follows.

(1) Concerning the paper coating composition ■) Viscosity The initial viscosity was measured using a BM type viscometer (60 rpm, Na4 spindle).

2) High shear viscosity Vercules ψ high shear viscometer (4400r
Lung size was determined by p rin, e bob).

3) Water retention Measured by permeation color method. Specifically, a dye that develops color with water is sprinkled on one side of a filter paper, and the filter paper is placed on the surface of the paper coating composition with that side facing up. When water in this composition reaches the upper surface of the filter paper through capillary osmosis and comes in contact with the dye, the dye develops color. The time from placing a filter paper on the surface of the coating composition until color development is measured. The larger the number, the better the water retention.

(2) Regarding coated paper ■) White paper gloss The surface of the coated paper was measured using a Murakami gloss meter at a measurement angle of 75°. As for the white paper gloss value, the larger the numerical value, the better.

2) Printing Gloss Using an RI type printing machine, perform one solid print using 0.4 cc of commercially available red ink for offset printing, leave it at room temperature for one day and night, and measure the surface of this test paper with a Murakami gloss meter. The measurement was carried out using a measuring angle of 75@. The larger the printing gloss value, the better.

3) Misdot rate (indicator of suitability for gravure printing) A test piece is printed using a gravure printing tester typed by the Printing Bureau of the Ministry of Finance.

Use halftone gravure as an illustration. The number of misdots that occurred was defined as a percentage of the number of wire mesh points, and expressed as a percentage. The smaller the value, the better.

Note that the evaluation of IR Dry Vic and IR Wet Vic is based on the method described above.

(3) Regarding the operability of coated paper and coated paperboard l) Apply a 3% zinc sulfate aqueous solution to coated paperboard suitable for water gloss treatment using a plate, and immediately apply the conditions at a temperature of 60°C and a linear pressure of 75 kg/ca+. The degree of contamination on the surface of the metal roll is evaluated in the following four stages through a super calender.

◎ ... No stains O ... Slight stains Δ ... Stains × ... Severe stains 2) Super calendar roll stain resistant double-sided coated paper is humidity controlled (approximately 70%) and layered with an aluminum sheet. The mixture is then passed through a high-pressure super calender at a temperature of 60°C and a linear pressure of 200 kg/cm. The aluminum sheet was peeled off from the coated paper and the degree of dirt on the aluminum surface was evaluated on the following four scales.

◎ ... No stain 0 ... Slight stain △ ... Stain × ... Severe stain and scratches (manufacture of coated paper) (1) Manufacture of alkali-insoluble copolymer latex (1) of the present invention Using the polymerization conditions for polymerization component 1 shown in Table 5, polymerization was carried out in the same manner as in Example 1, except that the pH of the obtained latex was adjusted to 5.7 using sodium hydroxide, and copolymer latex a - f I got it.

Incidentally, copolymer latex a ''-' c is the copolymer latex of the example, while copolymer latex d ~
[ is a copolymer latex of a comparative example. The gel contents of these copolymer latexes a to f are also shown in Table 5.

(2) Production of alkali-soluble copolymer latex (n) In an autoclave, 250 parts of water, 2 parts of sodium dodecylbenzenesulfonate, 100 parts of the monomer mixture shown in Table 6, and a cellulose derivative and/or An aqueous solution was prepared by adding water to an alkali metal acrylic acid salt to make 50 parts. Thereafter, the autoclave was heated to 60° C., 0.5 part of sodium persulfate was dissolved in water, and the reaction was started.

The reaction was continued as it was, and the reaction was completed in 3 hours.
A seed alkali-soluble copolymer latex g~1 was obtained.

Incidentally, copolymer latexes g-j belong to Examples, while copolymer latexes and l belong to Comparative Examples.

As the cellulose derivative necessary for producing this copolymer latex, carboxymethylcellulose (Cerodan-5A; manufactured by Dai-Kogyo Seiyaku Co., Ltd.) is used, and as the alkali metal salt of polyacrylate, sodium polyacrylate (Aron AIO3L; (manufactured by Toagosei Chemical Industry Co., Ltd.) was used.

(3) Blend preparation of alkali-soluble copolymer latex (I) and alkali-insoluble copolymer latex (If) Copolymer latex (1) obtained in (1) and (2) above
) and (II) in the proportions shown in Table 7 to obtain blended binders 1llIIL1 to N11L15. Using this, the following physical properties of the paper coating composition, coated paper properties, and operability were evaluated.

(4) Preparation of paper coating composition (a) Paperboard coating composition (Examples 16 to 21. Comparative Examples 14 to 21) The copolymer latex blended in the above (3) is shown in Table 8. A paperboard coating composition having a pH of about 11 was prepared according to the following formulation.

Combination prescription (part)
-
55 Light calcium carbonate 15 Titanium dioxide
10 Di-Cryte 15 Sachin White 5 Copolymer latex (solid content equivalent) 20 Dispersant
0.2 Sodium hydroxide 0.25 Water (
Note that in Comparative Example 21, casein (dissolved in aqueous ammonia, solid content equivalent) was added to the pigment formulation instead of the polymer latex as a binder. amount)
6-part copolymer latex (Japan Synthetic Rubber Seikan 0692) 1
A paperboard coating composition having a total solids content of 40% was prepared using 4 parts.

(b) Gravure printing paper coating composition (Examples 22 to 24. Comparative Examples 22 to 24) Using the copolymer latex blended in (3) above as shown in Table 9, the following formulation was applied. A composition for coating gravure printing paper was prepared.

Mixed prescription (part) Clay 100 Dispersant
0.2 Copolymer latex (solid content equivalent jl) 7.0 Water (added to give a solid content of 60%) Then, these coating compositions were adjusted to pH approximately 9.5 with an aqueous sodium hydroxide solution. I made it.

(5) Preparation of coated paperboard and coated paper The coating amount of each composition was 15 ± 0.5 g per side on the base paper.
It was coated with an electric blade coater (manufactured by Kumagai Riki Co., Ltd.) so that the coating film had a coating film of rrr, and was dried in a gear oven at 140° C. for 20 seconds.

Each base paper is 270 g/rrr paperboard base paper, 5
A medium-quality base paper of 4 g/rrr was used for gravure printing.

The obtained coated paperboard was coated with 3% zinc sulfate water, passed through a super calender at a temperature of 40°C and a linear pressure of 40 kg/cm, and then subjected to water gloss treatment at a temperature of 100°C.

Passed through a gloss calendar with a linear pressure of 50 kg/cm,
A gloss was applied and a prescribed test was conducted.

The obtained coated paper was tested under the conditions of 40°C and 200 kg/cm of linear pressure for coated paper for gravure printing, and 60°C and 160 kg/am of linear pressure for coated paper for offset printing. It was passed through a super calender to give it a gloss and a prescribed test was conducted.

In addition, the coated paperboard and coated paper for evaluation of operability were evaluated using samples immediately after coating and drying.

(Paper coating composition, coated paper physical property evaluation) Tables 8 and 9 show the evaluation results of the paper coating composition, coated paperboard, and coated paper of Example 2 Comparative Example.

The evaluation results of each example and comparative example will be explained below.

(1)' Paperboard Coating Composition Examples 16 to 18 These examples are alkali-insoluble copolymer latex (1)
The monomer composition of Comparative Example 2 was changed according to the scope of the present invention.
It shows the same suitability for water gloss treatment as the casein-containing water gloss treatment shown in 1. Also, in terms of coated paper quality, it exhibits better ink receptivity and gloss than Comparative Example 21.

Examples 19-20 These examples are alkali-soluble copolymer latex (n)
When the monomer composition of the paper is varied within the scope of the present invention, excellent suitability for water gloss treatment and coated paper quality are exhibited in all cases.

These examples in Comparative Examples 14 to 1 are cases where the amount and type of the amide group-containing ethylenically unsaturated monomer in the alkali-insoluble copolymer latex (1) are not included in the scope of the present invention, and the amount used is In Comparative Example 14, in which the coating composition was less than the range of the present invention, the aptitude for water gloss treatment was significantly poor, and the quality of the coated paper was also poor in terms of adhesive strength, water resistance, and gloss.

Comparative Example 16, on the other hand, is an example in which the amount used exceeds the range of the present invention, and the latex viscosity and coating liquid viscosity were too high, making it unsuitable for air knife coating, so subsequent tests were not conducted. There wasn't.

Comparative Example 15 is an example in which only acrylamide, which is different from the amide group-containing ethylenically unsaturated monomer of the present invention, is used, and water gloss treatment suitability 1 inking property is poor.

Comparative Example 17.18 Comparative Example 17 contains too little methacrylic acid and has insufficient viscosity and water retention.

Comparative Example 18 contains too much methacrylic acid and has high viscosity.

Comparative Example 19.20 The mixing ratio of copolymer latex (I) and (II) was outside the range of the present invention, and Comparative Example 19 was a case where the latex (El) was too large, and the viscosity of the coating liquid was is too expensive.

Comparative Example 20 is a case where latex (If) is too small,
The viscosity and water retention of the coating fluid are poor.

(2) Coating liquid composition Examples 22 to 24 for gravure printing paper These examples are based on alkali-insoluble copolymer latex (I)
The monomer composition of is changed within the scope of the present invention, and exhibits excellent gravure printability and calendar roll stain resistance.

Comparative Example 22 In this example, the amount of amide group-containing ethylenically unsaturated monomer in the alkali-insoluble copolymer latex (1) was less than the range of the present invention, and the calender roll stain resistance was poor.

Comparative example 23.24 Examples of these are copolymer latex (I).

This is a case where the mixing ratio of (II) is outside the scope of the present invention. Comparative Example 23 is a case in which the amount of latex (n) is too high, the viscosity of the coating liquid is too high, the quality of the coated paper is poor in adhesive strength, and the resistance to calendar roll staining is also poor. Comparative Example 24 is a case where the amount of latex (n) is too small, and the viscosity and water retention of the coating liquid are poor.

[Effects of the Invention] As mentioned above, by using the copolymer latex for paper coating and its composition of the present invention, excellent adhesive strength, water resistance, inking property, blister resistance, and gravure suitability can be obtained. Furthermore, the copolymer latex for paper coating and its composition of the present invention have excellent workability and are extremely useful for producing various coated papers.

Furthermore, when the paper coating composition of the present invention is used for paperboard coating, it has excellent operability during water gloss treatment, and when used for gravure printing paper coating, it has excellent operability due to calendar roll stains. It has excellent resistance, and when used in coatings for offset printing paper, it has excellent water resistance and roll stain resistance, and is also excellent in coated paper quality.

Patent applicant: Japan Synthetic Rubber Co., Ltd. Agent Patent attorney: Michie Fuse (2 others) 2゜3゜4゜Procedural amendment (voluntary) January 18, 1990 Patent application No. 22999 of 1999 Invention Name: Copolymer latex for paper coating and composition for paper coating.Relationship with the case concerning the person correcting the paper coating composition.Patent applicant address: 2-11-24 Tsukiji, Chuo-ku, Tokyo.Name (
417) Japan Synthetic Rubber Co., Ltd. Representative Tatsuo Asakura 7 Contents of amendment (1) “3” from line 3 to line 4 of page 16 of the specification
-vinyl-2-pyrrolidone" is corrected to "N-vinyl-3-methyl-2-pyrrolidone."

(2) Same as above, page 17, lines 5 to 6 A: “2-hydrodiethyl methacrylate, glycidyl methacrylate”
is corrected to "2-hydroxyethyl methacrylate, glycidyl methacrylate".

(3) Same as above, page 49, line 16, “Gravure aptitude J”
Corrected to ``Gravure printing suitability.''

that's all 5゜ Date of amendment order Self Departure

Claims (3)

[Claims] (1) (a) Conjugated diene monomer 20 to 60 parts by weight (b) Aromatic vinyl monomer 10 to 79.4 parts by weight (c) Ethylenically unsaturated carboxylic acid monomer 0.5 to 60 parts by weight 1
0 parts by weight (d) Alkenylpyrrolidone 0.1 to 10 parts by weight (e) Other copolymerizable vinyl monomers 0 to 50
A copolymer latex for paper coating, characterized in that it is obtained by emulsion polymerization of 100 parts by weight of monomers. (2) (a) Conjugated diene monomer: 20 to 80 parts by weight (b) Aromatic vinyl monomer: 10 to 79.4 parts by weight (c) Ethylenically unsaturated carboxylic acid monomer: 0.5 to 80 parts by weight 1
0 parts by weight (d) 0.1 to 10 parts by weight of at least one amide group-containing ethylenically unsaturated monomer selected from the compound represented by the following structural formula (I) and alkenylpyrrolidone (e) Other components Polymerizable vinyl monomer 0-50
Using 100 parts by weight of a monomer consisting of 5 to 99 parts by weight, at least one monomer selected from (a), (b), (c), (d) and (e) is used as the first stage. ．．
5 parts by weight is emulsion polymerized, and in the second stage, 10% by weight or more of (d) and the remaining monomer are polymerized in the presence of the obtained polymer latex. Copolymer latex for paper coating. Structural formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the structural formula (I), R_1 is a hydrogen atom or a methyl group, R_2 and R_3 are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, Either or both of R_2 and R_3 is an alkyl group having 1 to 4 carbon atoms. (3) A paper coating composition comprising a pigment as a main component and the following alkali-insoluble copolymer latex (I) and alkali-soluble copolymer latex (II) as a pigment binder, comprising: The weight ratio of latex (I) and latex (II) is 99.8:0.2-8
A paper coating composition characterized in that the ratio is 5:15. Alkali-insoluble copolymer latex (I): (a) Conjugated diene monomer 20 to 80 parts by weight (b) Aromatic vinyl monomer 10 to 79.4 parts by weight (c) Ethylenically unsaturated carboxylic acid Monomer 0.5-1
0 parts by weight (d) At least one amide group-containing ethylenically unsaturated monomer selected from the compound represented by the structural formula (I) and alkenylpyrrolidone 0.1 to 10 parts by weight (e) Other copolymers Possible vinyl monomers 0-50
A copolymer latex obtained by copolymerizing 100 parts by weight of monomers. Alkali-soluble copolymer latex (II): Ethylenically unsaturated carboxylic acid monomer 10 to 80 parts by weight Ethylenically unsaturated carboxylic acid ester monomer 10 to 9
A copolymer latex obtained by copolymerizing 100 parts by weight of a monomer consisting of 0 parts by weight and 0 to 80 parts by weight of other copolymerizable vinyl monomers.