JP2745634B2 - Copolymer latex for paper coating and composition for paper coating - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a copolymer latex for paper coating and a composition for paper coating using the same, and more particularly, to the adhesive strength and water resistance of coated paper. The present invention relates to a copolymer latex for paper coating which is excellent in properties such as strength, inking property, blister resistance and the like, and furthermore excellent in operability. It is extremely useful for obtaining not only paper but also coated paperboard excellent in operability and printability during water gloss treatment, and coated paper for gravure printing excellent in calender roll stain resistance and gravure printability.

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

Coated papers obtained by applying the coating composition containing the carboxyl group-modified copolymer latex as a binder have good adhesive strength, water resistance, gloss, etc., and are therefore used in various applications. .

In recent years, there has been a remarkable demand for printed materials using coated paper, and accordingly, there has been an increasing tendency to increase printing speed and diversify printing methods. For this reason, coated paper, and thus paper coating binders, should have improved physical properties more than ever, especially, all or more of the adhesive strength, water resistance, inking property and blister resistance, or a plurality of them at the same time. Is required.

To meet such demands, various improvements have been made to copolymer latex used as a binder for paper coating. For example, JP-A-57-153012 and JP-A-61-63794.
JP-A-61-207694 discloses that the adhesive strength or blister resistance is improved by devising a method of adding a monomer or a polymerization chain transfer agent.

Further, JP-A-54-30910, JP-A-54-58789, and JP-A-60-58789
No. 215895 discloses an adhesive strength, a water resistance strength, and a surface tension state of a copolymer latex.
It is disclosed that ink receptivity is improved.

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

However, none of these techniques has been improved sufficiently to meet the aforementioned requirements.

Furthermore, high-speed coating has been further promoted in order to increase production capacity with the growth of coated paper, and in order to reduce production costs, higher concentration of color solids and reduction of binder amount have been promoted. .

As for the high concentration of the color solids, the operability becomes a problem as a result of the deterioration of fluidity due to the viscosity of the paper coating composition being too high. A method of increasing the use ratio of fine particulate heavy calcium carbonate is used, and the amount of a natural water-soluble binder such as casein and starch having a large thickening action is reduced as a binder to make the binder latex-rich relatively. Methods are becoming more common (Ref. TAPPI Coating Conference '79). However, when such a method is employed, in operation, a backup roll, a calendar roll, and the like are liable to be stained, and improvement in this point is strongly desired.

In addition, in the coated paper for gravure, from the viewpoint of gravure printing suitability, the use of a sole binder using only a synthetic binder without using a natural binder is already in progress,
Even with this method, problems such as roll contamination have not been solved yet.

In the field of paperboard as well, the switch from casein, which is rising in price, to synthetic binders is being promoted. At the time of paperboard production, generally, the coated surface is treated with zinc sulfate water (water gloss treatment) in order to increase white paper gloss, smoothness and water resistance. However, if casein is not used, roll contamination occurs at this time. There is a problem, and improvement is desired.

However, conventional paper coating compositions have not been able to sufficiently address the above-mentioned problems during operation such as roll contamination and the like.

[Problems to be Solved by the Invention] As described above, in the conventional paper coating binder, the coated paper obtained by using the binder has adhesive strength, water resistance, inking property, blister resistance, suitability for gravure printing. However, there has been a problem that requirements for physical properties and operability of coated paper cannot be sufficiently satisfied at the same time.

The present invention, in the paperboard coating, to achieve a high level of compatibility between the operability and the quality of the coated paperboard at the time of the water gloss treatment, especially in the gravure printing paper coating in the calender roll stain resistance during operation and gravure printing aptitude. It is an object of the present invention to obtain a coated paper excellent in resistance to contamination of a backup roll during operation, water resistance, and inking property in offset printing paper coating.

[Means for Solving the Problems] In order to solve the above problems, the first invention is directed to (a) 20 to 60 parts by weight of a conjugated diene monomer and (b) an aromatic vinyl monomer 10 to 79.4 parts by weight (c) 0.5 to 10 parts by weight of ethylenically unsaturated carboxylic acid monomer (d) 0.1 to 10 parts by weight of alkenylpyrrolidone (e) Other copolymerizable vinyl monomers 0 to 50 parts by weight The present invention relates to a copolymer latex for paper coating, which is obtained by emulsion polymerization of 100 parts by weight of a monomer.

The second invention comprises: (a) 20 to 60 parts by weight of a conjugated diene monomer (b) 10 to 79.4 parts by weight of an aromatic vinyl monomer (c) 0.5 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer 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; Using 100 parts by weight of a monomer composed of 0 to 50 parts by weight of a vinyl monomer, (a), (b) and (c)
Emulsion polymerization of 10 to 95 parts by weight of a monomer composed of at least one selected from (d) and (e) is carried out. In the second stage, in the presence of the obtained polymer latex, 10 The present invention relates to a copolymer latex for paper coating, which is obtained by polymerizing not less than% by weight and the remaining monomer containing at least (a) and (b).

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, and one or both of R ₂ and R ₃ are Carbon number 1
4 alkyl group.

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 (II) as a pigment binder. A weight ratio of the latex (I) to the latex (II) of 99.8: 0.2 to 85:15.

Alkali-insoluble copolymer latex (I): (a) 20 to 60 parts by weight of a conjugated diene monomer (b) 10 to 79.4 parts by weight of an aromatic vinyl monomer (c) Monomer of an ethylenically unsaturated carboxylic acid 0.5 to 10 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 structural formula (I) and alkenylpyrrolidone; Using 100 parts by weight of a monomer composed of 0 to 50 parts by weight of a polymerizable vinyl monomer, (a), (b) and (c) as the first stage,
Emulsion polymerization of 10 to 95 parts by weight of a monomer composed of at least one selected from (d) and (e) is carried out. In the second stage, in the presence of the obtained polymer latex, 10 A copolymer latex obtained by polymerizing at least% by weight and the remaining monomer containing at least (a) and (b).

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

 Hereinafter, the present invention will be described in detail.

Among the monomers used for producing the copolymer latex of the present invention, specific examples of (a) the conjugated diene-based monomer 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. Of these, butadiene is particularly preferred.

The conjugated diene-based monomer is used in an amount of 2 parts per 100 parts by weight of the total monomer in order to impart appropriate elasticity and film hardness to the copolymer.
It is used in a proportion of 0 to 60 parts by weight, preferably 25 to 60 parts by weight. If the use ratio is less than 20 parts by weight, the adhesive strength on the coated paper cannot be sufficiently obtained. On the other hand, when the use ratio exceeds 60 parts by weight, the water resistance of the coated paper decreases.

(B) As the aromatic vinyl monomer, styrene, α
-Methylstyrene, vinyltoluene, p-methylstyrene and the like. The proportion of the aromatic vinyl monomer used is 10 to 79.4 parts by weight, preferably 15 to 70 parts by weight, based on 100 parts by weight of the total monomers. If the use ratio is less than 10 parts by weight, the water resistance and roll stain resistance of the coated paper are inferior. On the other hand, if the use ratio exceeds 79.4 parts by weight, the adhesive strength on the coated paper is inferior, which is not preferable.

(C) As the ethylenically unsaturated carboxylic acid monomer,
For example, mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid can be mentioned, and further, dicarboxylic acid anhydrides can 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 100 parts by weight, based on 100 parts by weight of all monomers.
7 parts by weight. If this use ratio is less than 0.5 parts by weight,
In addition to the adhesive strength in the coated paper, the mechanical stability of the copolymer latex decreases. On the other hand, when the use ratio exceeds 10 parts by weight, the viscosity of the copolymer latex becomes high, and the handling (handling) becomes difficult, and the operability decreases.

(D) Among the amide group-containing ethylenically unsaturated monomers,
As the compound represented by the structural formula (I), N-
Methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N
N-monoalkyl (meth) such as tert-butylacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N-butylmethacrylamide, N-trt-butylmethacrylamide
Acrylamide; and N, N-dimethylacrylamide,
N, N-diethyl acrylamide, N, N-dimethyl methacrylamide, N, N-
Examples thereof include dialkyl (meth) acrylamide.

Further, among the components (d), examples of the alkenylpyrrolidone include N-vinyl-3-methyl-2-pyrrolidone, 3-vinyl-2-pyrrolidone, and N-vinyl-5-methyl-2-pyrrolidone. .

As the component (d), N, N-dimethylacrylamide and N-vinyl-2-pyrrolidone are particularly preferred.

These components (d) are used to improve coated paper properties such as adhesive strength, water resistance, inking property, blister resistance and suitability for gravure printing, and operability. The amount is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight based on parts by weight. The usage rate is
If the amount is less than 0.1 part by weight, the object of the present invention cannot be achieved. On the other hand, if the amount exceeds 10 parts by weight, the viscosity of the copolymer latex becomes high, and the handling (handling)
And the operability decreases, and the flowability of the paper coating composition deteriorates, making the coating substantially difficult.

(E) Other copolymerizable monomers are not particularly limited, but include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, methacrylic acid 2
Alkyl esters of acrylic acid or methacrylic acid such as hydroxyethyl and glycidyl methacrylate;
Amide group-containing ethylenically unsaturated monomers other than the above-mentioned component (d) such as acrylamide, methacrylamide and N-methylolacrylamide; carboxylic acid vinyl esters such as vinyl acetate, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, etc. And vinyl cyanide monomers. These can be used alone or in combination of two or more.

Component (e) is used in an amount of 0 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of all monomers. If the use ratio exceeds 50 parts by weight, the adhesive strength and water resistance of the coated paper are undesirably reduced.

When an alkyl ester of acrylic acid or methacrylic acid is used as the component (e), the inking property of the coated paper is excellent, and the effect of further reducing coagulated material during production can be obtained. In order to obtain this effect, a preferable use ratio of the alkyl ester is 5 to 30 of the total monomers.
% By weight.

When a vinyl cyanide monomer is used as the component (e),
Greater effects can be obtained in terms of print gloss. In order to obtain this effect, a preferable usage ratio of the vinyl cyanide monomer is 3 to 20% by weight of all the monomers.

When emulsion-polymerizing these monomers (a) to (e), the following polymerization chain transfer agent, polymerization initiator and emulsifier can be used.

Octyl mercaptan, n- as a polymerization chain transfer agent
Dodecyl mercaptan, tert-dodecyl mercaptan, n
Mercaptans such as hexadecyl mercaptan, n-tetradecyl mecaptan, tert-tetradecyl mercaptan; xanthogen disulfides such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl Thiuram disulfides such as thiuram disulfide; hydrocarbons or halogenated hydrocarbons such as carbon tetrachloride, ethylene bromide and pentaphenylethane; or acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate and the like. . These polymerization chain transfer agents can be used alone or in combination of two or more. The method of use may be any of batch addition, divided addition or continuous addition.

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

Examples of inorganic initiators include potassium persulfate, sodium persulfate, and ammonium persulfate, and examples of organic initiators include cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, and benzoyl hydroperoxide. Organic peroxides; azo compounds such as azobisisobutyronitrile can be used. These can be used alone or as a so-called redox catalyst combined with a reducing agent.

When the organic initiator is used alone, the mechanical stability of the system is inferior and the amount of coagulated material in the latex increases, so it is preferable to use the organic initiator together with the inorganic initiator.

The ratio of the polymerization initiator used is 0.1 to 5 relative to all monomers.
%, Preferably 0.5 to 2% by weight.

As the emulsifier, an anionic surfactant, a nonionic surfactant and an amphoteric surfactant can be used.

Examples of the anionic surfactant include sulfates of higher alcohols, alkylbenzene sulfonates,
And aliphatic sulfonic acid salts.

As the nonionic surfactant, an alkyl ester type, an alkyl ether type, an alkyl phenyl ether type or the like of ordinary polyethylene glycol is used.

Examples of the amphoteric surfactant include those having a carboxylate, a sulfate, a sulfonate, or a phosphate as an anion portion, and an amine salt or a quaternary ammonium salt as a cation portion. Specifically, as salts of alkyl betaines, lauryl betaine, stearyl betaine, cocoamidopropyl betaine, 2-undecyl-
Each salt of hydroxyethyl imidazolium betaine is mentioned, and the amino acid type is lauryl-β
-Alanine, stearyl-β-alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine.

These can be used alone or in combination, but anionic surfactants such as sulfates of higher alcohols, alkylbenzenesulfonates, and aliphatic sulfonates are preferred, and alkylbenzenesulfonates are more preferred. Is particularly preferred. The use ratio of the emulsifier is preferably from 0.1 to 2% by weight of all monomers from the viewpoint of water resistance.

Incidentally, the copolymer latex for paper coating of the present invention can be suitably produced by two-stage emulsion polymerization. That is, as the first stage of the polymerization, at least one kind of monomer 5 to 9 selected from (a), (b), (c), (d) and (e) is used.
Emulsion polymerization of 9.5 parts by weight, preferably 10 to 95 parts by weight, as a second stage, in the presence of the polymer latex obtained in the first stage, at least 10% by weight of (d), preferably 20% by weight
The remaining monomers including the above are polymerized. In the second stage of this polymerization, if the amount of the amide group-containing ethylenically unsaturated monomer (d) used is less than 10% by weight, the improvement effect of the present invention is hardly obtained.

The paper coating copolymer latex of the present invention can be used alone as a binder for the paper coating composition, but by using in combination with an alkali-soluble copolymer latex described in detail below, paperboard And 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)”
As the ethylenically unsaturated carboxylic acid monomer used in the production of the latex (I) of the present invention, and in particular, acrylic acid and / or methacrylic acid are preferably used. . The ethylenically unsaturated carboxylic acid monomer is used in an amount of 10 to 60 parts by weight, based on 100 parts by weight of the monomer for producing the latex (II),
Preferably it is 20 to 40 parts by weight. If this is used in an amount of less than 10 parts by weight, a paper coating composition having high water retention cannot be obtained. In addition, an ethylenically unsaturated carboxylic acid monomer
If it is used in an amount exceeding 60 parts by weight, not only a large amount of coagulated product is generated during the emulsion polymerization, but also a paper coating composition having high water retention cannot be obtained.

Examples of the ethylenically unsaturated carboxylic acid ester monomer for polymerizing the latex (II) include, for example, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms or a hydroxyl group having 2 to 4 carbon atoms and a hydroxyl group. A hydroxyalkyl (meth) acrylate having an alkyl group having a 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, based on 100 parts by weight of the monomer. If this is less than 10 parts by weight, polymerization stability during polymerization is reduced,
On the other hand, if it exceeds 90 parts by weight, a paper coating composition having high water retention cannot be obtained.

A monomer for polymerizing latex (II),
Other vinyl monomers copolymerizable with the monomer include styrene, α-methylstyrene, vinyltoluene,
Aromatic vinyl compounds such as paramethylstyrene; copolymerizable unsaturated compounds having an amide bond such as acrylamide, methacrylamide, N-methylolacrylamide, N-butoxyacrylamide and diacetoneacrylamide; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile Monoolefins such as vinyl acetate, vinyl formate, allyl acetate, and methallyl acetate; methylene bis (meth) acrylamide, divinylbenzene, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, vinyl (meth) acrylate, trivinylbenzene, and pentane Multifunctionality such as erythritol tetramethacrylate, pentaerythritol triacrylate, pentaerythritol pentaacrylate Monomers.

These monomers are 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, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the monomers. If this is used in excess of 80 parts by weight, a paper coating composition having a sufficiently high water retention cannot be obtained.

During the copolymerization of the monomer mixture, methylcellulose, ethylcellulose, hydroxyethylcellulose,
Cellulose derivatives typified by semi-synthetic cellulose derivatives such as carboxymethylcellulose; alkali metal salts of polyacrylic acid are used. Semi-synthetic products and synthetic products such as hydroxyethylcellulose, carboxymethylcellulose, and alkali metal salts of polyacrylic acid are preferable because of low lot-to-lot variation and easy handling.
More preferred is carboxymethyl cellulose.

By using these cellulose derivatives and / or alkali metal polyacrylates at the time of copolymerization of the above monomer mixture, appropriate viscosity, appropriate fluidity, and water retention can be imparted without deteriorating the physical properties of coated paper. Furthermore, remarkable stability can be obtained in the blending of the alkali-soluble copolymer latex (II) and the alkali-insoluble copolymer latex (I) of the present invention.

The preferred amount of the cellulose derivative and / or the alkali metal polyacrylate to obtain the effect of use is 0.5 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, per 100 parts by weight of the monomer mixture. If the amount is less than 0.5 part by weight, it is difficult to obtain the above-mentioned effects, while if it exceeds 5 parts by weight, a large amount of coagulated material is apt to be generated during polymerization, which is not preferable.

When emulsion-polymerizing the alkali-soluble copolymer latex (II), the known emulsifier, polymerization initiator, polymerization chain transfer agent, and polymerization method described in the aforementioned alkali-insoluble copolymer latex (I) are used. Is used.

The alkali-soluble copolymer latex (II) acts as a thickener when part or all of the carboxyl groups are neutralized with alkali, increases the viscosity of the paper coating composition and provides high water retention. However, the weight ratio of latex (I) to latex (II) is 99.8: 0.2 to 8
It is necessary to use in the range of 5:15, preferably 9
9: 1 to 99:10. When the latex (I) is more than the above range, the resulting coating liquid has low viscosity and low water retention,
The solid content increases during the coating operation, and a stable and good coated surface cannot be obtained. On the other hand, when the amount of the latex (II) is more than the above range, the effect of increasing the viscosity of the coating liquid becomes remarkable, which impairs the operability.

In the paper coating composition of the present invention, the latex (I) and the latex (II) or the pigment binder comprising the latex (I) alone are preferably used in an amount of 5 to 25 parts by weight, more preferably 5 to 25 parts by weight, based on 100 parts by weight of the pigment. Preferably, 6 to 23 parts by weight are used. If the amount is less than 5 parts by weight, the paper surface strength is low and the operability is undesirably reduced. Further, when the amount used exceeds 25 parts by weight, the ink-coating property at the time of printing the obtained coated paper and coated paperboard is inferior, not only the ink setting is delayed, but also the gravure printing suitability at the time of gravure printing. It 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 necessary.

Here, examples of the pigment include inorganic pigments such as kaolin clay, talc, barium sulfate, titanium oxide (rutile anatase), calcium carbonate, aluminum hydroxide, zinc oxide, and satin white; and organic pigments such as polystyrene latex and hollow latex. And these may be used alone or as a mixture.

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

To prepare a paper coating composition using the copolymer latex of the present invention, other auxiliaries such as dispersion (sodium pyrophosphate, sodium hexametaphosphate, sodium polyacrylate, etc.), defoamer (Fatty acid ester, phosphate ester, silicone oil, etc.),
Leveling agents (funnel oil, dicyandiamide, urea, etc.), preservatives, waterproofing agents (melamine resin, polyamide resin, urea resin, glyoxal, etc.), release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color Water retention agents (such as carboxymethyl cellulose and sodium alginate) are added as needed.

The method for applying a paper coating composition using the copolymer latex of the present invention to a coating paper is performed by a known technique, for example, a coating machine such as an air knife coater, a blade coater, a roll coater, or an applicator. After the application, the surface is dried and finished with a calender ring or the like.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples. “%” And “parts” used in the examples mean “% by weight” and “parts by weight”.

Example 1 A pressure-resistant reaction vessel having a capacity of 100 was charged with 3 parts of itaconic acid, 0.5 part of acrylic acid, 5 parts of butadiene, 7 parts of styrene and 5 parts of methyl methacrylate, and further 150 parts of water, 1.5 parts of carbon tetrachloride, dodecylbenzene sulfone. 0.2 part of sodium acid and 1.0 part of potassium persulfate were charged and polymerized at 70 ° C. for 2 hours in a nitrogen atmosphere (first stage polymerization).
Next, the remaining monomer consisting of 23 parts of butadiene, 48.5 parts of styrene, 5 parts of methyl methacrylate, 3 parts of acrylonitrile and 1 part of N, N-dimethylallylamide was added continuously over 8 hours to give dodecylbenzenesulfonic acid. At the 5th hour, 0.2 part of sodium was added all at once to perform polymerization (second stage polymerization).

Thereafter, in order to complete the polymerization, the reaction (aging) was continued for 3 hours, and the polymerization was terminated at a polymerization rate of 98%.
The resulting latex is then treated with sodium hydroxide
After adjusting the pH to 7, unreacted monomers were removed by blowing steam, and the solid content of the latex was reduced to 50% by heating under reduced pressure. The latex (I) thus obtained is referred to as “latex A”.

Examples 2 to 12, Comparative Examples 1 to 10 Polymerization was carried out in the same manner as for Latex A except that the polymerization components and polymerization conditions shown in Tables 1 and 2 were used, to obtain copolymer latexes C to V. . The copolymer latex B is
It was obtained by performing polymerization in the same manner as for latex A, except that 2 parts of N, N-dimethylacrylamide were added all at once at 10 hours (polymerization conversion rate: 90%) from the start of the first stage polymerization.

Incidentally, the copolymer latexes A to G and LP are the copolymer latexes of the examples, while the copolymer latexes H to
K, Q to V are copolymer latexes of Comparative Examples. The gel contents of these copolymer latexes are shown in Tables 1 and 2.

The gel content of the obtained copolymer latex was adjusted to pH 8.
After adjusting to 0, coagulated with isopropanol, washed and dried, a predetermined amount (about 0.3 g) of the sample was immersed in a predetermined amount (100 ml) of toluene for 20 hours, and the toluene-insoluble content was measured. % By weight.

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

(Evaluation method) 1) RI dry pick: index of adhesive strength The degree of picking when printed with an RI printing machine was judged with the naked eye, and evaluated by a five-step method. The higher the score, the better. The judgment value was indicated by an average value of six measurements.

2) RI Wet Topic: Index of Water Resistance The degree of picking when printing was performed by applying dampening water with a Molton roll using an RI printing machine was visually judged, and evaluated by a five-point method. The higher the score, the better. The judgment value was indicated by an average value of six measurements.

3) Wet Rub: Index of Water Resistance and Roll Soil Resistance A test was performed on an Adam tester for 15 seconds, and the transmittance of the cloudy water obtained at that time was measured by a spectrophotometer. The larger the value, the better.

4) Meatability The ink density when printing was performed under conditions where picking did not occur by applying a dampening solution using a Molton roll in an RI printing machine was visually evaluated, and evaluated by a five-step method. The higher the score, the better.

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

 Evaluation criteria ○: 20 minutes or more Δ: 10 to 20 minutes ×: 10 minutes or less The longer the time until the coagulated product is generated, the better.

6) Blister resistance Humidity control (about 6%) of coated paper coated on both sides (coating amount on one side is 15g / m ² ) and thrown into a heated oil bath to indicate the minimum temperature at which blisters are generated .

(Blending formulation of composition for paper coating) A composition for paper coating with the following formulation was obtained using the copolymer latexes A to V.

Formulation Clay 80 parts Calcium carbonate 20 parts (containing 0.5 parts of sodium pyrophosphate as dispersant) Copolymer latex (solid content conversion) 12 parts Oxidized starch 4 parts Water Equivalent amount so that total solid content is 60% Addition The obtained paper coating composition liquid was coated on one side of a coated base paper of 72 g / m ² using a coating blade so that the coating amount was 15 g / m ² to obtain a coated paper. .

(Evaluation Results) Application Examples 1 to 7 and Comparative Application Examples 1 to 4, 9, and 10 Using the copolymer latexes shown in Tables 1 and 2 as part of Table 2, the results evaluated by the above-described evaluation methods were used. The results are shown in Table 3.

Application Examples 1 to 7 are examples using the copolymer latex within the scope of the present invention, and the objective of the present invention has been obtained.

Comparative Application Examples 1, 2, and 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,
The physical balance of adhesive strength, water resistance, roll stain resistance, inking property, and mechanical stability is inferior to Application Examples 1 to 7.

Comparative Application Example 3 is an example in which only acrylamide outside the scope of the present invention was used as the amide group-containing monomer.
Inferior to.

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 is inferior in water resistance and roll stain resistance.

Application Examples 8 to 12 and Comparative Application Examples 5 to 8 Table 4 shows the results of evaluation using the copolymer latexes shown in part of Table 2 by the evaluation method described above.

Application Examples 8 to 12 are examples using the copolymer latex within the scope of the present invention, and the objective of the present invention has been obtained. In addition, the gel content of the copolymer latexes L to P in these application examples is 70% or less, so that 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 adhesive strength, water resistance, inking property, blister resistance, and mechanical The balance of physical properties of stability is inferior to those of Application Examples 8 to 12.

Comparative application example 7 is an example in which only acrylamide outside the scope of the present invention was used as the amide group-containing monomer, and the balance of physical properties of adhesive strength, water resistance, inking property, prister resistance and mechanical stability was applied. Inferior to Examples 8-12.

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, and as a result, the viscosity of the paper coating composition liquid increases, Coating failed.

[Evaluation of Paperboard and Gravure Paper] (Evaluation Method) The evaluation methods used in the following examples are as follows.

(1) Composition for paper coating 1) Viscosity The initial viscosity was measured with a BM type viscometer (60 rpm, No. 4 spindle).

2) High shear viscosity Hercules high shear viscometer (4400rp
m, E Bob).

3) Water retention Measured by a permeation coloring method. Specifically, apply a dye that develops color with water to one side of the filter paper, with that side up,
Leave on the surface of the paper coating composition. The moisture of this composition reaches the upper surface of the filter paper by capillary penetration, and when the dye comes into contact with the dye, the dye is colored. The time from placing the filter paper on the surface of the coating composition to developing the color is measured. The higher the number, the better the water retention.

(2) Coated paper 1) Blank gloss The coated paper surface was measured at a measuring angle of 75 ° using a Murakami gloss meter. The larger the blank paper gloss value, the better.

2) Printing gloss Using a RI printer, 0.4 cc of commercially available red ink for offset printing was used to perform solid printing once, and allowed to stand at room temperature for 24 hours. The surface of this test paper was measured using a Murakami gloss meter. Use 75
It was measured at a measurement angle of ゜. The larger the numerical value, the better the print gloss value.

3) Misdot ratio (index of gravure printing suitability) A test piece is printed using a gravure printing tester of the Ministry of Finance, Ministry of Finance. Use dot gravure as an illustration. Define the number of missed dots as a percentage of the total number of halftone dots,
%. The smaller the value, the better.

The evaluation of the IR dry pick and the IR wet pick is based on the method described above.

(3) Operability of coated paper and coated paperboard 1) Suitability for water gloss treatment A 3% aqueous solution of zinc sulfate is applied to the coated paperboard using a plate, and immediately at a temperature of 60 ° C and a linear pressure of 75 kg / cm. Of the surface of the metal roll is evaluated through the following four stages through a super calendar.

◎… No dirt ○… Slight dirt △… Dirt ×… Dirt is terrible 2) Super calendar roll dirt resistance Humidity control (about 70%) on both sides coated paper, superimpose with aluminum sheet, temperature 60 ℃, linear pressure Pass through a high pressure spar calendar of 200 kg / cm. The aluminum sheet is peeled from the coated paper, and the degree of dirt on the aluminum surface is evaluated according to the following four grades.

◎… No stain ○… Slightly stain △… Stain × × Severe stain (Production of coated paper) (1) Production of alkali-insoluble copolymer latex (I) of the present invention Polymerization components and polymerization shown in Table 5 Polymerization was carried out in the same manner as in Example 1 except that the obtained latex was adjusted to pH 5.7 using sodium hydroxide under the conditions, and copolymer latexes a to f were obtained.

The copolymer latexes a to c are the copolymer latexes of the examples, while the copolymer latexes d to f are the copolymer latexes of the comparative examples. Table 5 also shows the gel contents of these copolymer latexes a to f.

(2) Production of alkali-soluble copolymer latex (II) In an autoclave, 250 parts of water, 2 parts of sodium dodecylbenzenesulfonate, and a monomer mixture shown in Table 6
An aqueous solution was prepared by adding 100 parts and 50 parts by adding water to a cellulose derivative and / or an alkali metal polyacrylate. Thereafter, the autoclave was heated to 60 ° C., and 0.5 part of sodium persulfate was dissolved in water to start the reaction. The reaction was continued as it was, and the reaction was completed in 3 hours to obtain six kinds of alkali-soluble copolymer latexes g to l. Incidentally, the copolymer latexes g to j belong to the examples, while the copolymer latexes k and 1 belong to the comparative examples.

Carboxymethyl cellulose (Cellogen-5A; manufactured by Daiichi Kogyo Seiyaku) is used as the cellulose derivative required for the production of this copolymer latex, and sodium polyacrylate (Alone) is used as the alkali metal polyacrylate. A10SL; manufactured by Toa Gosei Chemical Industry Co., Ltd.).

(3) Blend preparation of alkali-soluble copolymer latex (I) and alkali-insoluble copolymer latex (II) The copolymer latexes (I) and (II) obtained in the above (1) and (2) are Blends were prepared at the ratios shown in Table 7 to obtain blended binder Nos. 1 to 15. Using this, the following paper coating composition physical properties, coated paper physical properties and operability were evaluated.

(4) Preparation of Composition for Coating Paper (a) Composition for Coating Paperboard (Examples 16 to 21, Comparative Examples 14 to 21)
Using the composition shown in the table, a paperboard coating composition having a pH of about 11 was prepared according to the following formulation. Formulation (part) Clay 55 Light calcium carbonate 15 Titanium dioxide 10 Ziglite 15 Satin white 5 Copolymer latex (solid content conversion amount) 20 Dispersant 0.2 Sodium hydroxide 0.25 Water (Total solid content is 45% In Comparative Example 21, in place of the polymer latex as a binder in the pigment formulation, casein (dissolved in aqueous ammonia, converted to solid content) 6 parts copolymer latex (Japan A synthetic paperboard coating composition adjusted to a total solids content of 40% was prepared using 14 parts of synthetic rubber (# 0692).

(B) Gravure printing paper coating composition (Examples 22 to 24, Comparative Examples 22 to 24)
Using the composition shown in the table, a composition for coating gravure printing paper was prepared according to the following formulation. Formulation (parts) Clay 100 Dispersant 0.2 Copolymer latex (solid content equivalent) 7.0 Water (added to 60% solid content) Then, these coating compositions were pH adjusted with aqueous sodium hydroxide solution. To about 9.5.

(5) coated board, coated with motorized blade coater so coating amount is one-sided 15 ± 0.5g / m ² of coated paper created each composition on coated base paper (manufactured by Kumagai rickshaw) It was dried in a gear oven at 140 ° C. for 20 seconds.

The base paper used was 270 g / m ² of paperboard base paper and 54 g / m ² of medium base paper for gravure printing.

The coated paperboard obtained is 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 a water gloss treatment. Then, at a temperature of 100 ° C and a linear pressure of 50 kg / cm. Through a gloss calender to impart gloss and perform a predetermined test.

The obtained coated paper was coated at a temperature of 40 ° C and a linear pressure of 200kg / cm for gravure printing coated paper, and at a temperature of 60 ° C and a linear pressure of 160kg / cm for offset printing coated paper. Through a super calendar, gloss was imparted and a predetermined test was performed.

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

(Evaluation of Paper Coating Composition and Coated Paper Properties) Tables 8 and 9 show the evaluation results of the paper coating compositions, coated paperboard, and coated paper of Examples and Comparative Examples. Hereinafter, the evaluation results of the respective examples and comparative examples will be described.

(1) Composition for coating paperboard Examples 16 to 18 In these examples, the monomer composition of the alkali-insoluble copolymer latex (I) was changed within the scope of the present invention, and the casein shown in Comparative Example 21 was used. It shows suitability for water gloss treatment equivalent to the water gloss treatment of the formulation. Comparative example 21 also shows the quality of the coated paper.
Shows better inking properties and gloss.

Examples 19 to 20 These examples are based on the alkali-soluble copolymer latex (I
When the monomer composition of I) is varied within the scope of the present invention,
In each case, excellent water gloss treatment suitability and coated paper quality are exhibited.

Comparative Examples 14 to 16 These examples are cases in which the amount and type of the amide group-containing ethylenically unsaturated monomer of the alkali-insoluble copolymer latex (I) are not included in the scope of the present invention. In Comparative Example 14, which is less than the scope of the present invention, the suitability for water gloss treatment is extremely poor, and the quality of coated paper is also poor in adhesive strength, water resistance, and glossiness.

Comparative Example 16 is an example in which the amount used was more than the amount used in the range of the present invention, and the latex viscosity and the coating solution viscosity were too high and were not suitable for air knife coating. Did not.

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

Comparative Examples 17 and 18 In Comparative row 17, the amount of methacrylic acid was too small, and the viscosity and water retention were insufficient.

Comparative Example 18 is excessive in methacrylic acid and has a high viscosity.

Comparative Examples 19 and 20 The mixing ratio of the copolymer latexes (I) and (II) was out of the range of the present invention.
The case of I) is excessive, and the viscosity of the coating liquid is too high.

In Comparative Example 20, the amount of latex (II) was too small, and the viscosity and water retention of the coating liquid were inferior.

(2) Coating liquid composition for gravure printing paper Examples 22 to 24 These examples were obtained by changing the monomer composition of the alkali-insoluble copolymer latex (I) within the scope of the present invention.
Shows excellent gravure printability and calendar roll stain resistance.

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

Comparative Examples 23 and 24 These examples are cases where the mixing ratio of the copolymer latexes (I) and (II) is out of the range of the present invention. Comparative example
No. 23 is a case where the latex (II) is excessive, the viscosity of the coating liquid is too high, the adhesive strength is poor in the coated paper quality, and the calender roll stain resistance is also poor. In Comparative Example 24, the amount of latex (II) was too small, and the viscosity and water retention of the coating liquid were inferior.

[Effects of the Invention] As described above, by using the copolymer latex for paper coating of the present invention and its composition, adhesive strength, water resistance, inking property, blister resistance, and gravure printing suitability are improved. An excellent coated paper is obtained, and the copolymer latex for paper coating of the present invention and the composition thereof have excellent operability and are extremely useful for production of various coated papers. .

Furthermore, the paper coating composition of the present invention has excellent operability during water gloss treatment when used for paperboard coating, and calender roll stain when used for gravure printing paper coating. It has excellent resistance, and when used for offset printing paper coating, has excellent water resistance and roll stain resistance, and also has excellent coated paper quality.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor ▲ Yoshi ▼ Hiroshi Tadashi 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-61-225395 (JP, A) JP-A-57-153015 (JP, A) JP-A-63-303196 (JP, A)

Claims (2)

(57) [Claims] (1) 20 to 60 parts by weight of a conjugated diene monomer (b) 10 to 79.4 parts by weight of an aromatic vinyl monomer (c) 0.5 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer Part (d) 0.1 to 10 parts by weight of an amide group-containing ethylenically unsaturated monomer represented by the following structural formula (I) (e) Other copolymerizable vinyl monomer 0 to 50 parts by weight Using 100 parts by weight of monomer, (a), (b) and (c), and (d)
And 10-95 parts by weight of a monomer comprising at least one selected from (e) and (e), and as a second step, in the presence of the obtained polymer latex, at least 10% by weight of (d). And a copolymer latex for paper coating obtained by polymerizing the remaining monomer containing at least (a) and (b). 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, and one or both of R ₂ and R ₃ are C 1-4
Is an alkyl group. 2. 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. , The latex (I)
And a weight ratio of latex (II) of 99.8: 0.2 to 85:15. Alkali-insoluble copolymer latex (I): (a) 20 to 60 parts by weight of a conjugated diene monomer (b) 10 to 79.4 parts by weight of an aromatic vinyl monomer (c) Monomer of an ethylenically unsaturated carboxylic acid 0.5 to 10 parts by weight (d) Amide group-containing ethylenically unsaturated monomer represented by the following structural formula (I) 0.1 to 10 parts by weight (e) Other copolymerizable vinyl monomers 0 Using 100 parts by weight of a monomer consisting of 50 parts by weight, (a), (b) and (c), and (d)
And 10-95 parts by weight of a monomer comprising at least one selected from (e) and (e), and as a second step, in the presence of the obtained polymer latex, at least 10% by weight of (d). And a copolymer latex obtained by polymerizing the remaining monomer containing at least (a) and (b). 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, and one or both of R ₂ and R ₃ are C 1-4
Is an alkyl group. Alkali-soluble copolymer latex (II): 10-60 parts by weight of ethylenically unsaturated carboxylic acid monomer 10-90 parts by weight of ethylenically unsaturated carboxylic acid ester monomer Other copolymerizable vinyl monomers A copolymer latex obtained by copolymerizing 100 parts by weight of a monomer consisting of 0 to 80 parts by weight.