JP2646770B2 - Method for producing copolymer latex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for preparing a monomer containing a diene monomer, an ethylenically unsaturated monomer and an ethylenically unsaturated carboxylic acid monomer by using a seed latex. And a method for producing a copolymer latex that polymerizes in the presence of a specific chain transfer agent, and more specifically, avoids agglomeration and coalescence of copolymer particles, has high productivity, and is, for example, a composition for paper coating. The present invention relates to a method for producing a copolymer latex which imparts excellent adhesive strength and blister resistance when used as a binder for a product.

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

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

In recent years, demand for coated paper has been remarkable, and with this, paper coating technology and printing technology have been remarkably advanced, and higher coating speed and printing speed have been promoted from the viewpoint of productivity improvement, labor saving and rationalization. ing.

Therefore, the composition for paper coating is required to have stability against mechanical shearing force in high-speed coating, and the coated paper has excellent adhesive strength, water resistance or blister resistance during printing. It is necessary to exhibit various properties.

Particularly, coated paper for web offset printing is increasingly required to have improved adhesive strength and blister resistance.

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, JP-A-61-6379
Patent Document 4 discloses that the adhesive strength or the blister resistance is improved by devising a method of adding a polymerization chain transfer agent.

On the other hand, the carboxyl group-modified copolymer latex, which is a component of the paper coating composition and is used as a binder, greatly contributes to the mechanical stability of the paper coating composition and the performance of coated paper. Because it is important.

As a cause of impairing the mechanical stability of the paper coating composition, there is a fine coagulated product of a copolymer latex.

This fine coagulate is mainly generated during the production of the copolymer latex. If the amount of the fine coagulated material is large, problems such as streak trouble and roll dusting trouble at the time of coating occur, the adhesive strength and water resistance of the coated paper are reduced, and problems such as blanket contamination at the time of printing occur.

As a method of removing fine coagulated material, a method of filtering a copolymer latex is known, but it is not preferable because the operation is complicated and costs are increased.

As means for solving such a problem, Japanese Patent Application Laid-Open No. 55-90
Nos. 697 and 58-91707 provide a method for using a polymerization chain transfer agent. However, the effects of these techniques are not always satisfactory.

[Problems to be Solved by the Invention] As described above, the conventional copolymer latex generates a fine coagulated product during polymerization. For example, when used in a paper coating composition, it is difficult to form a high-speed coating. At the same time, it has not been possible to fully satisfy the requirements for the operation and the physical properties of the coated paper such as adhesive strength and blister resistance at the same time. There is a similar problem.

An object of the present invention is to produce a copolymer latex useful as a paper coating binder with reduced coagulation during polymerization, particularly excellent in mechanical stability, and having improved adhesive strength and blister resistance. It is in.

[Means for Solving the Problems] The first invention of the present invention comprises: (a) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and (b) an ethylenically unsaturated crosslinkable monomer. (C) 50 to 100% by weight of a conjugated diene monomer and / or an ethylenically unsaturated monomer other than the components (a) and (b). Seed latex and α-
(D) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (e) 0 to 40% by weight of an ethylenically unsaturated crosslinking monomer, (f) a conjugated diene monomer And 50 to 100% by weight of an ethylenically unsaturated monomer other than the components (d) and (e), and a monomer having a composition different from that of the seed latex is emulsion-polymerized. And a method for producing a copolymer latex.

The second invention of the present invention comprises (a) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, and (c) a conjugated diene. Monomer and / or ethylenically unsaturated monomer other than the components (a) and (b) 50 to 100
(D) an ethylenically unsaturated carboxylic acid monomer in the presence of a seed latex obtained by copolymerizing a monomer containing, by weight, at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene; 0 to 10% by weight, (e) an ethylenically unsaturated crosslinkable monomer 0 to 40% by weight, (f) a conjugated diene monomer and / or an ethylenically unsaturated monomer other than the components (d) and (e). And 50 to 100% by weight of a saturated monomer, and the seed latex relates to a method for producing a copolymer latex, wherein monomers having different compositions are emulsion-polymerized.

The third invention of the present invention comprises: (a) 0.1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, (c) a) a seed latex copolymerized with a monomer containing 50 to 99.9% by weight of an ethylenically unsaturated monomer other than a) and (b);
(G) 10 to 60% by weight of a conjugated diene-based monomer, (h) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (i) the above (g) and (h) ), A monomer containing 30 to 89.5% by weight of an ethylenically unsaturated monomer other than the above) is emulsion-polymerized.

The fourth invention of the present invention comprises: (a) 0.1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, (c) a seed latex obtained by copolymerizing a monomer containing 50 to 99.9% by weight of an ethylenically unsaturated monomer other than a) and (b), and at least one selected from terpinolene, α-terpinene, γ-terpinene and dipentene (G) 10 to 60% by weight of a conjugated diene monomer, (h) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (i) the above (g) and (h) A monomer containing 30 to 89.5% by weight of an ethylenically unsaturated monomer other than the above, which is emulsion-polymerized.

 Hereinafter, the present invention will be described in detail.

The monomers (a), (b) and (c) used for producing the seed latex used in the present invention are described below.

(A) 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. Acids and methacrylic acid are preferred. Furthermore, anhydrides of dicarboxylic acids can also be used. These can be used alone or in combination of two or more.

The proportion of the monomer (a) used is 0 to 10% by weight, preferably 0.1 to 10% by weight, particularly preferably 0.1 to 5% by weight, based on the whole monomer of the seed latex. When the proportion of the monomer (a) exceeds 10% by weight, the generation of coagulated products in the subsequent polymerization increases, and the object of the present invention cannot be achieved.

(B) Examples of the ethylenically unsaturated crosslinking monomer include divinylbenzene, ethylene glycol dimetallate, 1,3-butylene glycol dimethacrylate,
Examples thereof include divinyl monomers such as trimethylolpropane trimethacrylate and allyl methacrylate, and trivinyl monomers, preferably divinylbenzene, ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate, more preferably divinylbenzene. It is.

These monomers (b) are used for imparting appropriate crosslinking to the copolymer used as a seed, and for limiting the swelling capacity of the seed particles by the monomer and the monomer absorption rate.

The proportion of the monomer (b) used is from 0 to 40% by weight, and preferably from 0 to 40% by weight, based on the whole monomers used for the seed latex.
It is 1 to 40% by weight, more preferably 1 to 35% by weight, particularly preferably 5 to 35% by weight. If the proportion of the monomer (b) is more than 40% by weight, coagulated products are liable to be generated during the production of the seed latex, which is not suitable for use as seed particles.

(C) Examples of the ethylenically unsaturated monomer other than the components (a) and (b) include, for example, styrene, α-methylstyrene, vinyltoluene, ethylvinylbenzene, p-
Aromatic vinyl monomers such as methylstyrene and sodium p-styrenesulfonate; methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methacrylic acid Alkyl esters of acrylic acid or methacrylic acid such as glycidyl; acrylamides of ethylenically unsaturated carboxylic acids such as acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide; vinyl esters of carboxylic acids such as vinyl acetate Vinyl cyanides such as acrylonitrile, methacrylonitrile and α-chloroacrylonitrile; and conjugated diene-based monomers such as butadiene, isoprene and 2-chloro-1,3-butadiene. To It can gel. Of these, styrene and methyl methacrylate are particularly preferred.

These monomers can be used alone or in combination of two or more.

The proportion of the monomer (c) used is 50 to 100% by weight, preferably 50 to 99.9% by weight, particularly preferably 55 to 99.5% by weight, based on the whole monomer of the seed latex. When the use ratio of the monomer (c) is less than 50% by weight, coagulated matter is easily generated during the production of the seed latex, which is not preferable.

As an emulsifier used for emulsion polymerization of the seed latex, any of an anionic type and a nonionic type can be used. These can be used alone or in combination of two or more.

Examples of the emulsifier include sulfates of higher alcohols such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, sulfonates of aliphatic esters such as sodium dioctylsulfosuccinate, and alkyldiaryl ether sulfonates. And anionic surfactants such as alkylnaphthalene sulfonate, and nonionic surfactants such as polyethylene glycol alkyl ester type, alkyl phenyl ether type and alkyl ether type.

As the emulsifier, preferably an anionic surfactant,
More preferred are alkyl benzene sulfonate, alkyl diaryl ether sulfonate and alkyl naphthalene sulfonate. The proportion of the emulsifier used is determined based on the total amount of the monomers (a), (b), and (c) in order to prevent the generation of coagulated products during the polymerization of the seed latex and to obtain seed particles having a particle diameter suitable for seed polymerization. 0.5 ~ 40
% By weight is preferred.

The polymerization initiator used for the emulsion polymerization of the monomers (a) to (c) includes cumene hydroperoxide, diisopropylbenzene hydroperioside,
Organic polymerization initiators such as hydroperoxides such as paramenthane hydroperoxide; peroxides such as benzoyl peroxide and lauroyl peroxide; azo compounds such as azobisisobutyronitrile;
And inorganic polymerization initiators such as persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate.

These polymerization initiators can also be used as a so-called redox polymerization initiator in combination with a reducing agent such as sodium bisulfite.

As the polymerization initiator, inorganic polymerization initiators such as potassium persulfate and sodium persulfate are preferable. The proportion of the polymerization initiator used is usually 0.1 to 2% by weight based on the total of the monomers (a), (b) and (c).

The seed latex of the present invention can be produced by ordinary emulsion polymerization using the above-mentioned ones. That is, a monomer mixture and a polymerization aid such as a polymerization initiator and an emulsifier are added to water, and the mixture is polymerized at a temperature of 40 to 95 ° C. with stirring. The method of adding monomers and other polymerization aids is batch addition,
Either split addition or continuous addition may be used.

When the seed latex is subjected to subsequent polymerization, the copolymer preferably has an average particle size of 1000 ° or less, more preferably 500 to 100 °, and a gel content of 70% by weight or more, more preferably 80% by weight or more. When polymerization is performed using a seed latex having these conditions, a copolymer latex is produced which is more excellent in terms of coagulation, mechanical stability, adhesive strength and the like.

The seed latex may be used after adjusting the pH with sodium hydroxide, potassium hydroxide, aqueous ammonia or the like in advance.

The copolymer latex in the present invention is obtained by emulsion polymerization in an aqueous medium.A feature of the present invention is that this emulsion polymerization is carried out in the presence of the aforementioned seed latex and the following specific polymerization chain transfer agent. It is in.

That is, in the first and third inventions of the present invention, preferably, 2 to 100% by weight of α-methylstyrene dimer and 98 to 0% by weight of another polymerization chain transfer agent in the presence of α-methylstyrene dimer. And in the second and fourth inventions of the present invention, in the presence of at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene, preferably ( A) 2 to 100% by weight of at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene, and if necessary, (B) selected from alkyl mercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides Emulsification in the presence of a polymerization chain transfer agent comprising at least 98% by weight of at least one compound Perform polymerization.

The first to fourth inventions will be described in detail below.

The polymerization chain transfer agent (hereinafter referred to as polymerization chain transfer agent (I)) used in the first and third inventions comprises an α-methylstyrene dimer and another polymerization chain transfer agent used as required. .

As α-methylstyrene dimer, as isomers, (a) 2-4-diphenyl-4-methyl-1-pentene, (b) 2-4-diphenyl-4-methyl-2-pentene, and (c) There is 1-1-3-trimethyl-3-phenylindane. The preferred composition of the α-methylstyrene dimer is as follows: (a) component is 40% by weight or more, (b) component and / or
Or (C) component is 60% by weight or less, more preferably,
The component (A) is at least 50% by weight, the component (B) and / or the component (C) is at most 50% by weight, particularly preferably the component (A) is at least 70% by weight, the component (B) and / or (C) ) The component is 30% by weight or less. The higher the composition ratio of the component (a), the more excellent the chain transfer effect.

The α-methylstyrene dimer may be any impurities, for example, unreacted α-methylstyrene, α-methylstyrene oligomers other than the above-mentioned components (a), (b) and (c), as long as the object of the present invention is not impaired. -It may contain a methylstyrene polymer.

When α-methylstyrene dimer is used, it can be used in an unpurified state after synthesis of α-methylstyrene dimer as long as the purpose is not impaired.

As the other polymerization chain transfer agent used in combination with the α-methylstyrene dimer, a known polymerization chain transfer agent used in general emulsion polymerization can be used. Specifically, for example, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-
Mercaptans such as tetradecyl mercaptan; xanthogen disulfides such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide; Halogenated hydrocarbons such as ethylene; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terpinolene, α-terpinene, γ-terpinene, dipuntene, and the like. it can. These can be used alone or in combination of two or more. Of these, mercaptans, xanthogen disulfides, thiuram disulfides, carbon tetrachloride and the like are preferably used.

The proportion of the α-methylstyrene dimer in the polymerization chain transfer agent (I) is preferably 2 to 100% by weight, more preferably 3 to 100% by weight, and particularly preferably 5 to 95% by weight. The ratio of the α-methylstyrene dimer is 2% by weight.
If it is less than 3, a copolymer latex excellent in adhesive strength and blister resistance cannot be obtained.

The amount of the polymerization chain transfer agent (I) used may be the total amount of the monomers ((d) + (e) + (f) or (g) + (h) +
(I) It is usually 0.05 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight, particularly preferably 0.5 to 7 parts by weight, per 100 parts by weight. When the amount of the polymerization chain transfer agent (I) is less than 0.05 part by weight, the blister resistance is poor. On the other hand, when the amount exceeds 20 parts by weight, the adhesive strength is undesirably reduced.

The amount of the α-methylstyrene dimer used is preferably 0.1 to 5 parts by weight based on 100 parts by weight of all monomers.

Next, the polymerization chain transfer agent (hereinafter referred to as polymerization chain transfer agent (II)) used in the second and fourth inventions is:
(A) at least one compound selected from terpinolene, α-terpinene, γ-terpinene, and dipentene (hereinafter, referred to as “component (A)”), and (B) another chain transfer agent used as needed; It is preferably composed of at least one compound selected from alkyl mercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides (hereinafter, referred to as “component (B)”).

Specific examples of the alkyl mercaptans of the component (B) include the same compounds as the above-described alkyl mercaptans, and among them, t-dodecyl mercaptan is preferably used.

Further, specific examples of the xanthogen disulfides and the thiuram disulfides include the same compounds as the above-described xanthogen disulfides and the thiuram disulfides.

The proportion of the component (A) in the polymerization chain transfer agent (II) is preferably 2 to 100% by weight, more preferably 3 to 100% by weight, particularly preferably 5 to 95% by weight. When the component (A) and the component (B) are used in combination, a paper coating composition having more excellent adhesive strength and blister resistance as intended by the present invention can be obtained.

The amount of the polymerization chain transfer agent (II) to be used is usually 0.05 per 100 parts by weight of all monomers ((d) + (e) + (f)) described later.
To 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight. If the amount of the polymerization chain transfer agent (II) is less than 0.05 part by weight, the blister resistance is poor, and
Exceeding the parts by weight is not preferred because the adhesive strength decreases.

The amount of the component (A) used was 100% for all monomers.
It is preferable to use 0.1 to 5 parts by weight based on parts by weight.

Next, the polymerization of the monomer performed in the presence of the seed latex and the above-described specific chain transfer agent will be described.

The monomers used for the polymerization in the first and second inventions are a monomer (d) an ethylenically unsaturated carboxylic acid monomer, (e) an ethylenically unsaturated crosslinkable monomer and (f)
It is composed of a conjugated diene monomer and / or an ethylenically unsaturated monomer other than the components (d) and (e). Here, the monomer (d) is the same as the monomer (a), and the monomer (e) is the same as the monomer (b). )) May be the same as the above-mentioned monomer (c), and the proportions used are also the same.

The monomers used for the polymerization in the third and fourth inventions are monomers (g), (h) and (i) described below.
It is composed of

(G) As the conjugated diene monomer, the monomer (c)
And the same as the conjugated diene-based monomer exemplified in (1).

The usage ratio of the monomer (g) is the total monomer ((g) +
(H) + (i)) 10 to 60% by weight, preferably 20 to 60% by weight
60% by weight. If the use ratio is less than 10% by weight, a sufficient adhesive strength cannot be obtained. On the other hand, if it exceeds 60% by weight, water resistance decreases, which is not preferable.

(H) As the ethylenically unsaturated carboxylic acid monomer, those similar to the above-mentioned monomer (a) can be mentioned.

The ratio of the monomer (h) used is the total monomer ((g) +
(H) + (i)) 0.5 to 10% by weight, preferably 1%
~ 7% by weight. If the use ratio is less than 0.5% by weight, the mechanical stability of the copolymer latex will decrease in addition to the adhesive strength, while if it exceeds 10% by weight, the viscosity of the copolymer latex will increase and the handling (handling) Becomes difficult, and the operability decreases, which is not preferable.

(I) Examples of the ethylenically unsaturated monomer include those similar to the ethylenically unsaturated monomer exemplified in the monomer (c).

The ratio of the monomer (i) used is the total monomer ((g) +
(H) + (i)) 30 to 89.5% by weight, preferably 30
~ 79.5% by weight. When the proportion of the monomer (i) is less than 30% by weight, the water resistance is lowered. On the other hand, when it exceeds 89.5% by weight, the adhesive strength is undesirably lowered.

Emulsifiers used for emulsion polymerization of monomers containing these monomers (d), (e), (f) or (g), (h), (i) include anionic type, nonionic type and nonionic type. Any of the amphoteric surfactants can be used. These can be used alone or in combination of two or more.

As the emulsifier, for example, a nonionic surfactant similar to that used for the copolymerization of the seed latex can be 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, lauryl betaine, stearin betaine, cocoamidopropyl betaine, and 2-undecylhydroxyethyl imidazolium betaine salts as alkyl betaine salts,
Examples of the amino acid type include salts of lauryl-β-alanine, stearin-β-alanine, lauryldi (aminoethyl) glycine, acryldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine.

As the emulsifier, an anionic surfactant is particularly preferred. The use ratio of the emulsifier is preferably from 0.01 to 2% by weight based on all monomers.

Examples of the polymerization initiator used for the emulsion polymerization of the monomer include the same ones as in the case of the copolymerization of the seed latex. However, in the present invention, when the organic polymerization initiator is used alone, the obtained copolymer latex has poor mechanical stability, and a large amount of coagulated product is generated during the polymerization. It is preferable to use the agent alone or in combination with an organic polymerization initiator. These polymerization initiators can also be used as so-called redox-based polymerization initiators in combination with a reducing agent such as sodium bisulfite. Of these, persulfates such as potassium persulfate and ammonium persulfate, or a combination thereof with azobisisobutyronitrile or benzoyl peroxide, and a combination of these with a reducing agent are preferably used.

The amount of the polymerization initiator used is 0.1 to 5 based on all monomers.
%, Preferably 0.5 to 2% by weight. When the inorganic polymerization initiator and the organic polymerization initiator are used in combination, the ratio of the organic polymerization initiator is 70% by weight or less, preferably 50% by weight or less of the whole polymerization initiator. The ratio of organic polymerization initiator is 70
If the amount is more than 10% by weight, problems such as the case where the organic polymerization initiator is used alone are not preferred.

In the present invention, in the presence of the seed latex and the specific polymerization chain transfer agent described above, the monomer (d),
The target copolymer latex is obtained by polymerizing a monomer containing (e), (f) or (g), (h), (i). In any of the first to fourth inventions, all monomers ((d) + (e) +
(F) or (g) + (h) + (i)) 100 to 100 parts by weight of solid content, preferably 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, particularly preferably 0.2 to 5 parts by weight. Department. If the amount of the seed latex used is less than 0.05 part by weight, the generation of fine coagulates during the polymerization increases, and the stability of the copolymer latex is not sufficient, which is not preferable.
On the other hand, if the amount of the seed latex exceeds 20 parts by weight, the resulting copolymer latex has insufficient adhesive strength, which is not preferable.

In the present invention, except for performing polymerization in the presence of a seed latex and a specific polymerization chain transfer agent, the conditions for emulsion polymerization are not particularly limited, and can be carried out under conventionally known methods and conditions. . For example, the method of adding the monomer and the polymerization initiator, emulsifier, polymerization chain transfer agent and the like may be batch addition, divisional addition, continuous addition, or a combination thereof.

The copolymer latex obtained by the method of the present invention,
Although it can be used for various applications, the copolymer (latex) according to the third and fourth inventions, that is, 0.1 to 10% by weight, preferably 0.1 to 5% by weight of the monomer (a) as a seed latex, Monomer (b) 0 to 40% by weight,
Preferably 1 to 40% by weight, and monomer (c) 50 to 99.9
%, Preferably 55 to 99.9% by weight, and in the presence of this seed latex, 10 to 60% by weight of monomer (g), preferably 20 to 60% by weight. Monomer (h) 0.5 to 10% by weight, preferably 1 to 7% by weight, and monomer (i) 30 to 89.5% by weight, preferably 30
A copolymer latex obtained by polymerizing a monomer comprising up to 79.5% by weight is suitably used as a binder for a paper coating composition.

The gel content of the copolymer latex obtained by the present invention is preferably 5% or more, more preferably 10 to 98%, and the particle size is usually 700 to 3000 °, preferably 700 to 25%.
00Å.

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

(1) Production of seed latex (seed latex A) In a pressure-resistant reaction vessel having a capacity of 100, 4 parts of acrylic acid, 76 parts of styrene, 20 parts of divinylbenzene, 30 parts of sodium dodecylbenzenesulfonate, and 1.5 parts of potassium persulfate were charged. Polymerization was performed at a temperature of 80 ° C. for 2 hours in a nitrogen atmosphere.
As a result, a seed latex having a polymerization conversion rate of 99% or more and belonging to the range of the present invention was obtained. This is referred to as “seed latex A”.

(Seed latex B to E, and a) Polymerization was performed in the same manner as seed latex A except that the polymerization components and polymerization conditions shown in Table 1 were used, and four types of seed latex B, C, D, E and one kind of seed latex a not belonging to the scope of the present invention were obtained.

(2) Production of copolymer latex by seed polymerization (Example 1) Seed latex A1 was placed in a pressure-resistant reaction vessel having a capacity of 100.
Part, itaconic acid 3 parts, acrylic acid 1 part, butadiene 22
Part, styrene 48 parts, methyl methacrylate 10 parts, acrylonitrile 5 parts, α-methylstyrene dimer 1.5 parts,
0.1 parts of sodium dodecylbenzenesulfonate, water 200
And 0.8 part of potassium persulfate were charged and polymerized at 60 ° C. for 5 hours in a nitrogen atmosphere (first stage polymerization). Further, during the continuation of the polymerization, 0.15 part of sodium dodecylbenzenesulfonate was added in two portions at 2 hours and 4 hours after the start of the polymerization.

Next, 6 parts of butadiene, 2 parts of styrene, and 3 parts of methyl methacrylate were continuously added over 2 hours to carry out polymerization (second stage polymerization). Thereafter, in order to complete the polymerization, the reaction (aging) was continued for 4 hours, and the polymerization was terminated at a polymerization conversion of 99%.

Then, after adjusting the pH of the obtained copolymer latex to 7 using sodium hydroxide, steam was blown to remove unreacted monomers, and the solid content concentration of the copolymer latex was reduced by distillation under heating and reduced pressure to 50. %. Thus, the copolymer latex of the example was obtained.

The α-methylstyrene dimer used here,
The α-methylstyrene dimer used in the following Examples and Comparative Examples is as follows.

Trade name: NOFMER MSD (manufactured by NOF CORPORATION) Composition Composition name Composition (% by weight) 2-4-diphenyl-4-methyl-1-pentene 92.0%
2-4-diphenyl-4-methyl-2-pentene 5.0%
Below: 1-1-3-trimethyl-3-phenylindane 1.5
% Or less α-methylstyrene 1.0% or less (Examples 2,4 to 6,8,10, Comparative Examples 1 to 3) The same procedures as in Example 1 were carried out except that the polymerization components and polymerization conditions shown in Table 2 were used. Polymerization was carried out in the same manner as the polymer latex to obtain six types of copolymer latex according to the examples. These are Examples 2,4 to 6,8,10. Similarly, three types of copolymer latexes according to comparative examples were obtained. These were compared with Comparative Examples 1 to
3 is assumed.

(Examples 3, 7, 9) Using the polymerization components and polymerization conditions shown in Table 2, 0.2 part of sodium dodecylbenzenesulfonate was added in two portions at 4 hours and 6 hours after the start of polymerization. Polymerization was carried out in the same manner as in the copolymer latex of Example 1 except for performing the above, to obtain three types of copolymer latex according to the example. These are Examples 3, 7, and 9.

(Example 11) Polymerization was performed in the same manner as in the copolymer latex of Example 1 except that the polymerization components shown in Table 2 were used, to obtain a copolymer latex.

(3) Physical properties of copolymer latex Gel content The gel content of the seed latex and the copolymer latex obtained in the above (1) and (2) was determined by the following method.

After adjusting the pH of the latexes (1) and (2) to pH 8.0, the latex was coagulated with isopropanol, washed, and dried. Next, a sample of about 0.3 g was taken, and 2
After immersion for 0 hours, the triene-insoluble content was measured, and the ratio (%) to the sample was determined to be the gel content.

 The results are shown in Tables 1 and 2.

Coagulation amount About the copolymer latex obtained in the above (2),
The amount of coagulated material generated during the polymerization was measured by the following method.

A sample of 1 kg of copolymer latex was collected and
The mixture was filtered through a 00 mesh wire mesh, the amount of coagulated material remaining on the wire mesh was measured, the ratio to the sample (in terms of solid content) was determined, and evaluated by the following three steps.

:: 0.05% or less (small) Δ: 0.05 to 0.1% (slightly large) ×: 0.1% or more (very large) The results are shown in Table 3.

Contamination of the reactor Regarding the copolymer latex obtained in the above (2),
Dirt (coagulated product) attached to the reactor during polymerization was visually observed and evaluated according to the following three grades.

：: very little △: little ×: many The results are shown in Table 3.

(4) Preparation of composition for paper coating Of the copolymer latexes obtained in the above (2),
Using the copolymer latexes obtained in Examples 1 to 10 and Comparative Examples 1 to 3, a paper coating composition (color) was prepared according to the following formulation.

Formulation Clay 80 parts (containing 0.5 parts of sodium pyrophosphate as dispersant) Calcium carbonate 20 parts Copolymer latex 12 parts Starch oxide 5 parts Water Amount that total solid content is 60% The obtained color is evaluated by the following test method did. The coated paper used in the test was obtained by applying a color to base paper having a basis weight of 64 g / m ² using a coating blade at a coating amount of 15 g / m ² .

(5) Evaluation method of paper coating composition and coated paper Mechanical stability of coating color The paper coating composition liquid was kneaded between rubber rolls using a gum-up tester, and the rubber rolls were subjected to mechanical shearing. The time until the formation of coagulated material 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.

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 results were indicated by an average value of six measurements.

RI wet pick: index of water resistance Using a Molton roll with an RI printing machine, the degree of picking when printing with dampening water was visually determined, and evaluated by a five-point method. The higher the score, the better. The results were indicated by an average value of six measurements.

Wet Rub: Index of water resistance and roll stain resistance A test was conducted on an Adam tester for 15 seconds, and the transmittance of the cloudy water obtained at that time was measured with a spectrophotometer. Larger numbers are better.

Calender roll stain resistance Place the coated surface of the coated paper before supercalendering on a rasha paper and pass it through a supercalender 10 times at 50 ° C and 250 kg / cm. At this time, the picking state of the coated paper is determined based on dirt on the lash paper. Those with less stains have better calendar roll stain resistance.

Evaluation criteria ◎: No stain ○: Slight stain is observed △: Slightly stained ×: Slightly stained Blister resistance After conditioning the double-sided printing coated paper (about 6%), throw it into a heated oil bath and remove the blister. The lowest temperature (° C.) at which generation occurs is shown.

(6) Evaluation results In Examples 1 to 11, the copolymer latex can be produced without the contamination of the reactor and the precipitation of fine coagulated products, and the copolymers obtained in Examples 1 to 10 were used. Good results were obtained for each property of the coated paper.

On the other hand, Comparative Example 1 is an example using a seed latex out of the range of the present invention, and compared with Examples 1 to 10, in terms of soiling of the reactor, generation of fine coagulates, and mechanical stability of the coating color. It is clearly inferior, and further inferior in adhesive strength, water resistance, and stain resistance to calender rolls.

Comparative Example 2 is an example in which only a polymerization chain transfer agent other than the present invention was used, and the reactor was poor in mechanical stability of stains, fine coagulated products, and coating colors, and also had poor adhesive strength and stain resistance to calendar rolls. Inferior.

Comparative Example 3 is an example in which the amount of the ethylenically unsaturated carboxylic acid monomer used is less than the range of the present invention, and the mechanical stability of the reactor stain, the fine coagulated product, and the coating color is remarkably inferior.

[Effects of the Invention] The copolymer latex obtained by the method for producing a copolymer latex of the present invention has an extremely small amount of fine coagulated material, excellent stability, various adhesives including paper coating,
It can be used for carpet backing agents, cement modifiers, foam rubbers, modifiers such as rubber, resins, fibers, etc., pharmaceuticals, etc. If this is used as a binder for a paper coating composition, for example, mechanical stability , Adhesive strength, water resistance,
It has excellent properties such as calender roll stain resistance and blister resistance in a well-balanced manner, and is extremely useful in the production of various coated papers.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication (C08F 279/02 236: 04) (C08F 291/00 236: 04) (72) Inventor Shozo Nishida Central Tokyo 2-11-24 Tsukiji-ku, Japan Synthetic Rubber Co., Ltd. (56) References JP-A-3-182559 (JP, A) JP-A-3-182558 (JP, A) JP-A-60-168710 (JP, A) A) JP-A-57-185307 (JP, A) JP-A-53-121891 (JP, A)

Claims (4)

(57) [Claims] (1) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, (c) a conjugated diene monomer And / or a seed latex copolymerized with a monomer containing 50 to 100% by weight of an ethylenically unsaturated monomer other than the components (a) and (b).
(D) ethylenically unsaturated carboxylic acid monomer 0 to 10% by weight, (e) ethylenically unsaturated crosslinking monomer 0 to 40% by weight, (f) conjugated diene monomer Monomer and / or ethylenically unsaturated monomer other than the components (d) and (e).
%, And emulsion-polymerizing a monomer having a composition different from that of the seed latex. (2) 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinking monomer, (c) a conjugated diene monomer. And / or 50 to 100 ethylenically unsaturated monomers other than the components (a) and (b).
(D) an ethylenically unsaturated carboxylic acid monomer in the presence of a seed latex obtained by copolymerizing a monomer containing at least one compound selected from the group consisting of: 0 to 10% by weight, (e) an ethylenically unsaturated crosslinkable monomer 0 to 40% by weight, (f) a conjugated diene monomer and / or an ethylenically unsaturated monomer other than the components (d) and (e). Saturated monomer 50-100
%, And wherein the seed latex is emulsion-polymerized with monomers of different compositions. (A) an ethylenically unsaturated carboxylic acid monomer
0.1 to 10% by weight, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, (c) 50 to 99.9% by weight of an ethylenically unsaturated monomer other than the above (a) and (b), Seed latex obtained by copolymerizing a monomer containing
(G) 10 to 60% by weight of a conjugated diene-based monomer, (h) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (i) the above (g) and (h) A method for producing a copolymer latex, which comprises emulsion-polymerizing a monomer containing 30 to 89.5% by weight of an ethylenically unsaturated monomer other than the above). (4) (a) an ethylenically unsaturated carboxylic acid monomer
0.1 to 10% by weight, (b) 0 to 40% by weight of an ethylenically unsaturated crosslinkable monomer, (c) 50 to 99.9% by weight of an ethylenically unsaturated monomer other than the above (a) and (b), (G) a conjugated diene-based monomer in the presence of 10 to 60% by weight of a seed latex copolymerized with a monomer containing (H) a monomer containing 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, (i) 30 to 89.5% by weight of an ethylenically unsaturated monomer other than the above (g) and (h). A method for producing a copolymer latex, which is characterized by emulsion polymerization.