JP2792166B2 - Method for producing copolymer latex - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a copolymer latex, and in particular, generates less fine coagulated material and has excellent mechanical stability.
The present invention also relates to a method for producing a copolymer latex having excellent physical properties such as adhesive strength and blister resistance when used as an adhesive or the like.

(Prior art) A carboxyl group-modified copolymer latex obtained by emulsion polymerization of a monomer mixture composed of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid, etc. is excellent in adhesiveness. It is widely used as an adhesive, especially as a binder for paper coating alone or with a natural or synthetic binder such as casein, starch, protein, cellulose, polyvinyl alcohol and the like.

Coated paper obtained by coating 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 therefore suitable for various uses. It is used.

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.

For this reason, a 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 express various properties of the above.

Carboxyl group-modified polymer latex, which is a component of paper coating composition and is used as a binder, is important because it greatly affects the mechanical stability of paper coating composition and the performance of coated paper. Have been watched.

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

This fine coagulate is mainly generated during the production of the polymer latex. If this fine coagulated material is large, a streak trouble during coating and a problem of roll dusting travel occur,
The adhesive strength and water resistance of the coated paper are reduced, and problems such as blanket contamination during printing occur.

As a method for removing fine coagulated material, a method for filtering a polymer 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 propose a method of using a polymerization chain transfer agent. However, the effects of these techniques are not always satisfactory. These problems are common in the field of adhesives other than the binder for paper coating.

(Problems to be Solved by the Invention) The present invention is directed to a copolymer in which the generation of fine coagulated material is small, the mechanical stability is excellent, and the adhesive strength and blister resistance when used in an adhesive or the like are further improved. It is an object of the present invention to provide a method for producing latex.

(Means for Solving the Problems) As a result of intensive studies, the present inventors have found that the above-mentioned copolymer latex is obtained by using a copolymer latex obtained by emulsion polymerization of a monomer in the presence of a specific polymerization chain transfer agent. The inventors have found that the object has been achieved, and have completed the present invention based on this finding.

That is, the first invention of the present invention comprises: (a) 10 to 69.5% by weight of a conjugated diene monomer; (b) 30 to 89.5% by weight of an ethylenically unsaturated monomer other than (c); A monomer containing 0.5 to 10% by weight of an unsaturated carboxylic acid monomer is emulsion-polymerized in the presence of α-methylstyrene dimer, and has a gel content of 10% or more. It relates to a manufacturing method.

The second invention of the present invention comprises: (a) 10 to 70% by weight of a conjugated diene monomer; (b) 30 to 89.5% by weight of an ethylenically unsaturated monomer other than (c); A monomer containing 1 to 10% by weight of a carboxylic acid monomer, (A) 10 to 90% by weight of at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene; Emulsion polymerization in the presence of a polymerization chain transfer agent comprising 10 to 90% by weight of at least one compound selected from mercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides It relates to a latex production method.

The third invention of the present invention comprises: (a) 10 to 79.4% by weight of a conjugated diene monomer (b) an ethylenically unsaturated monomer other than (c) and (d)
20 to 89.4% by weight (c) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer (d) A monomer containing 0.1 to 10% by weight of an ethylenically unsaturated amine monomer is converted to α-methylstyrene dimer. The present invention relates to a method for producing a copolymer latex, which is subjected to emulsion polymerization in the presence of (i) and having a gel content of 10% or more.

The fourth invention of the present invention comprises: (a) 10 to 79.4% by weight of a conjugated diene-based monomer (b) 20 to 89.4% by weight of an ethylenically unsaturated monomer other than (c) and (d) A monomer containing 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer (d) and 0.1 to 10% by weight of an ethylenically unsaturated amino monomer is converted into (A) terpinolene, α-terpinene, γ-terpinene and It comprises 10 to 90% by weight of at least one compound selected from dipentene, and 10 to 90% by weight of (B) at least one compound selected from alkylmercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides. The present invention relates to a method for producing a copolymer latex, which is characterized by performing emulsion polymerization in the presence of a polymerization chain transfer agent.

Furthermore, in the present invention, in at least a part of the polymerization step, polymerization is performed while continuously adding a monomer and a polymerization chain transfer agent, and a monomer and a polymerization chain transfer agent that are continuously added are added. It is preferable to continuously change the weight ratio per unit time.

 Hereinafter, the present invention will be described in detail.

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

The monomer (a) is used for imparting appropriate elasticity and film hardness to the obtained copolymer. In the first and second inventions, the amount of the monomer (a) used is 10 to 80% by weight, preferably 20 to 60% by weight,
And in the fourth invention, the content is 10 to 60% by weight, preferably 20 to 60% by weight. If the amount is less than the above range, the adhesive strength cannot be obtained. On the other hand, if the amount is more than the above range, the water resistance and the adhesive strength are undesirably reduced.

(B) Specific examples of the ethylenically unsaturated monomer include:
And in the second invention, aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, methacrylic acid Alkyl or methacrylic acid alkyl ester compounds such as 2-hydroxyethyl and glycidyl methacrylate; acrylamide or methacrylamide compounds of ethylenically unsaturated carboxylic acids such as acrylamide, methacrylamide, N, N-dimethylacrylamide and N-methylolacrylamide Carboxylic acid vinyl esters such as vinyl acetate, vinyl cyanide compounds such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, methylaminoethyl (meth) acrylate, Tylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, 2-vinyl Pyridine, 4-
Examples thereof include ethylenically unsaturated monomers other than the component (c) described below, such as ethylenically unsaturated amine compounds such as vinylpyridine. These can be used alone or in combination of two or more. Of these, styrene is particularly preferably used as the aromatic vinyl compound, methyl methacrylate is preferably used as the alkyl ester compound, and acrylonitrile is preferably used as the vinyl ianide compound.

As a preferred monomer (b), the aromatic vinyl compound and / or the alkyl (meth) acrylate are at least 10% by weight, more preferably at least 10% by weight, based on all the monomers (b).
It is contained at a content of 20% by weight or more.

In the third and fourth inventions, examples of the monomer (b) include those obtained by removing the (d) ethylenically unsaturated amine compound described below from the monomer (b), and are preferred. The same monomer as described above can be used as the monomer (b).

The monomer (b) is used for imparting appropriate hardness, elasticity and water resistance to the obtained copolymer. In the first and second inventions, the amount of the monomer (b) used is from 20 to 89.5% by weight, preferably from 30 to 79.5%, based on the total amount of the monomers.
% By weight, in the third and fourth inventions, 20 to 89.4
%, Preferably 30 to 79.4% by weight. If the amount is less than the above range, the water resistance is inferior. On the other hand, if it is more than the above range, the copolymer becomes too hard and the adhesive strength is undesirably reduced.

(C) Specific examples of the ethylenically unsaturated carboxylic acid monomer include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; Half esters such as methyl itaconate and β-methacryloxyethyl acid hexahydrophthalate can be exemplified. Also, anhydrides of dicarboxylic acids can be used. These can be used alone or in combination of two or more.

As the monomer (c), it is preferable that at least one selected from dicarboxylic acids, half esters thereof and dicarboxylic anhydrides is essential, and it is particularly preferable to use dicarboxylic acids. The weight ratio (α) / (β) of at least one (α) selected from dicarboxylic acids, half esters and dicarboxylic anhydrides to monocarboxylic acid (β) is 5/95 to 100/0, More preferably, it is 10/90 to 95/5. When used in this ratio range, the adhesive strength, the latex, and the mechanical stability of the coating composition are excellent.

The amount of the monomer (c) used is 0 to 10% by weight, preferably 0.1% by weight in the first and second inventions, based on all monomers.
5 to 10% by weight, in the third and fourth inventions, 0.5 to 10% by weight
It is 10% by weight, preferably 1 to 7% by weight. If this amount is less than the above range, in addition to adhesive strength, the mechanical stability of the copolymer latex decreases, while if it is more than the above range, the viscosity of the copolymer latex increases,
Handling becomes difficult, and operability is undesirably reduced.

Examples of the (d) ethylenically unsaturated amine monomer which is an essential component in the third and fourth inventions are the same as the ethylenically unsaturated amine compound in the monomer (b). Can be. When such an ethylenically unsaturated amine monomer is used, a copolymer latex having more excellent water resistance can be obtained.

The amount of the monomer (d) used is 0.1 to 10
%, Preferably 0.5 to 7% by weight. If the amount is less than the above range, further excellent water resistance cannot be obtained, while if it is more than the above range, fine coagulated products may be produced during the production of the copolymer latex.

In the polymerization of the monomer (d), the pH of the polymerization system
Is usually 7 or more, preferably 7.5 or more.

The copolymer latex in the present invention is obtained by emulsion polymerization of the above monomer in an aqueous medium, and the feature of the present invention is that this emulsion polymerization is performed in the presence of a specific polymerization chain transfer agent. . That is, in the first and third inventions of the present invention, α-methylstyrene dimer is preferably used in the presence of α-methylstyrene dimer.
In the presence of a polymerization chain transfer agent consisting of 0% by weight and 98 to 0% by weight of another polymerization chain transfer agent, and in the second and fourth inventions of the present invention, terpinolene, α-terpinene, γ-terpinene And in the presence of at least one compound selected from dipentene and dipentene, preferably (A) at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene;
Emulsion polymerization is carried out in the presence of a polymerization chain transfer agent comprising 98% by weight of (B) at least one compound selected from (B) alkyl mercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides. .

The first, third and second and 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 and diisopropyl xanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethyltium disulfide, tetrabutylthiuram disulfide; carbon tetrachloride; Halogenated hydrocarbons such as ethylene; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terpinolene, α-terpinene, γ-terpinene, dipentene, 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 2 to 100% by weight, preferably 3 to 100% by weight,
More preferably, it is 5 to 95% by weight.

If the proportion of the α-methylstyrene dimer is less than 2% by weight, a copolymer latex having excellent adhesive strength and blister resistance cannot be obtained. In addition, the reactivity at the time of polymerization can be increased by using α-methylstyrene dimer in combination with another polymerization chain transfer agent.

The amount of the polymerization chain transfer agent (I) to be used is generally 0.05 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight, per 100 parts by weight of the total monomers. When the amount of the polymerization chain transfer agent (I) is less than 0.05 part by weight, the blister resistance is inferior. On the other hand, when the amount exceeds 20 parts by weight, the adhesive strength is undesirably lowered.

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 polymerization chain transfer agent used as needed. And preferably 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-mentioned mercaptans. Of these, t-dodecyl mercaptan is preferably used.

Specific examples of the xanthogen disulfide and the thiuram disulfide include the same compounds as the xanthogen disulfide and the thiuram disulfide.

The ratio of the component (A) in the polymerization chain transfer agent (II) is 2 to 10
0% by weight, preferably 10-90% by weight. If the proportion of the component (A) in the polymerization chain transfer agent is less than 2% by weight, it is not possible to obtain a paper coating composition which is the object of the present invention and has both excellent adhesive strength and blister resistance.

The amount of the polymerization chain transfer agent (II) to be used is generally 0.05 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7 parts by weight, based on 100 parts by weight of all monomers. If the amount of the polymerization chain transfer agent (II) is less than 0.05 part by weight, the blister resistance is poor, and if it exceeds 20 parts by weight, the adhesive strength is undesirably reduced.

The amount of the component (A) used was 100% for all monomers.
It is preferably used in the range of 0.1 to 5 parts by weight with respect to parts by weight.

The copolymer latex in the present invention can be produced by a conventionally known emulsion polymerization method except that the above-mentioned monomer and polymerization chain transfer agent are used. That is, it can be obtained by adding a monomer, a polymerization initiator, an emulsifier, a polymerization chain transfer agent and the like to an aqueous medium (usually water) and performing emulsion polymerization.

There is no particular limitation on the polymerization initiator used in the emulsion polymerization in the present invention, for example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, hydroperoxides such as paramenthane hydroperoxide, benzoyl peroxide, lauroyl peroxide and the like Use organic polymerization initiators such as peroxides and azo compounds such as azobisisobutyronitrile, and inorganic polymerization initiators such as persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate. be able to.

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 polymerization. , Or in combination with an organic polymerization initiator.

In addition, the said polymerization initiator can also be used as what is called a redox-type polymerization initiator combined with reducing agents, such as sodium bisulfite.

Among these polymerization initiators, 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. Is done.

The amount of the polymerization initiator used in the present invention is 100
It is usually 0.1 to 5 parts by weight, preferably 0.5 to 5 parts by weight.
~ 2 parts by weight. When using an inorganic polymerization initiator and an organic polymerization initiator together, the ratio of the organic polymerization initiator is as follows:
It is preferably at most 70% by weight of the total polymerization initiator, more preferably at most 50% by weight. 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.

The emulsifier used for the emulsion polymerization in the present invention is not particularly limited, and any of anionic, nonionic and amphoteric surfactants can be used. These can be used alone or in combination of two or more. For example, anionic surfactants such as sulfate salts of higher alcohols such as sodium lauryl sulfate, alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate, and sulfonates of aliphatic carboxylic acid esters such as sodium dioctyl sulfosuccinate; polyethylene Nonionic surfactants such as an alkyl ester type, an alkyl phenyl ether type, and an alkyl ether type of glycol can be used. As the amphoteric surfactant, a carboxylate, a sulfate, a sulfonate, a phosphate,
Phosphoric acid ester salts and those having an amine salt or a quaternary ammonium salt as a cation moiety can be mentioned. Specifically, lauryl betaine, stearyl betaine, cocoamidopropyl betaine, 2-undecylhydroxyethyl imidazolium betaine salts as alkyl betaine salts, and lauryl-β-alanine, stearyl-β as amino acid type salts -Salts of alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, dioctyldi (aminoethyl) glycine.

Among these emulsifiers, an alkylbenzene sulfonate is particularly preferably used. More specifically, sodium dodecylbenzenesulfonate and the like are particularly preferably used. The alkyl benzene sulfonate may be an anionic surfactant such as a sulfate of a higher alcohol or a sulfonate of an aliphatic carboxylic acid ester, or an alkyl ester type, an alkyl ether type or an alkyl ether type of polyethylene glycol. You may use together with nonionic surfactants, such as a phenyl ether type.

The amount of the emulsifier used is usually 0.0
It is 5 to 2 parts by weight, preferably 0.05 to 1 part by weight. If the amount of the emulsifier exceeds 2 parts by weight, the water resistance is poor and the foaming of the paper coating composition becomes remarkable, causing a problem during coating. When the alkylbenzene sulfonate is used in combination with another anionic or nonionic surfactant, the proportion of the alkylbenzene sulfonate is preferably 50% by weight or more of the total emulsifier.

The emulsion polymerization method and its conditions in the present invention are not particularly limited, and can be carried out under conventionally known methods and conditions.

For example, the addition method of the polymerization chain transfer agent may be any of a batch addition method, a division addition method, a continuous addition method, or a combination thereof.

As for the method of adding the monomer, a batch addition method,
Any of a split addition method, a continuous addition method, or a combination thereof may be used. Among these methods, the split addition method or the continuous addition method is preferred from the viewpoints of reduction in the formation of coagulated material and removal of reaction heat. Furthermore, 10 to 10% of all monomers including all or part of the ethylenically unsaturated carboxylic acid monomer
50% by weight is polymerized in the first stage, and the remaining 50
According to the two-stage polymerization method in which the emulsion polymerization is carried out by continuously adding up to 90% by weight, the formation of coagulated product in the polymerization step can be further reduced. Therefore, the emulsion polymerization of the present invention is carried out by this two-stage polymerization method. Is preferred. In this method, the polymerization chain transfer agent may be added to one of the first and second stages, or may be added to both.
When the polymerization chain transfer agent is used in the second stage, it is preferably added continuously.

Further, in the present invention, in the first stage and / or the second stage, preferably 10% by weight or more of the monomer and preferably 5% by weight or more of the polymerization chain transfer agent are continuously added. In addition, it is preferable to carry out emulsion polymerization while continuously changing the weight ratio of the monomer and the polymerization chain transfer agent continuously added per unit time as described above.

That is, in the first step, the second step, or both the first and second steps, for example, it is preferable to adopt an addition method as shown in FIGS. 1 (1) to (4). .

In FIGS. 1 (1) to (4), the horizontal axis represents the elapsed time from the start of each polymerization step, and the vertical axis represents the weight ratio of the amount of the polymerization chain transfer agent to the monomer per unit time ( γ)
Represents

In the embodiment shown in FIG. 1 (1), in the initial stage (B) of the process, γ is added at a constant value, that is, the polymerization chain transfer agent and the monomer are added in a state where the weight ratio is constant,
In the middle stage (A), γ increases linearly, that is, the polymerization chain transfer agent is increased at a fixed ratio to the monomer, and in the second stage (C), γ is again increased as in the initial state. Is constant.

In the embodiment shown in FIG. 1 (2), γ is kept constant in the initial stage (B) and late stage (C), and γ is decreased linearly in the middle stage (A). It is added in a state where it is reduced at a fixed rate with respect to the monomer.

Similarly, in the embodiment shown in FIG. 1 (3), an example is shown in which the addition amount of the polymerization chain transfer agent is changed so that γ linearly increases and then linearly decreases in the middle stage (A) of the process. In the embodiment shown in FIG. 1 (4),
In the middle stage (A) of the process, an example is shown in which the amount of the polymerization chain transfer agent is changed so that γ decreases linearly and then increases linearly.

FIGS. 1 (1) to 1 (4) illustrate an embodiment of a method of adding a monomer and a polymerization chain transfer agent, and the method of addition is not limited thereto, and the following cases may be considered.

(1) γ need not necessarily change linearly, but may change in a curve.

(2) The initial stage (B) and / or the late stage (C) of the process include:
The addition need not always be continuous, and can be arbitrarily selected from batch addition or divided addition.

(3) For the initial stage (B) and the late stage (C) of the process,
Either one or both steps may not be performed.

(4) In the middle of the step in which γ changes, a step in which γ becomes a constant value, such as the initial stage (B) or the late stage (C), may be included.

As described above, by continuously changing the weight ratio γ of the polymerization chain transfer agent to the monomer per unit time, the adhesive strength and the blister resistance can be further improved. In particular, according to the addition method shown in FIG. 1 (1), the adhesive strength is further improved, and according to the addition method shown in FIG. 1 (2), the blister resistance is further improved.

The gel content of the obtained copolymer latex is preferably 5% or more, more preferably 10 to 98%. If the gel content is less than 5%, the adhesive strength and mechanical stability are greatly reduced, and further, problems such as backing roll stains occur with the increase in the tackiness of the latex film. On the other hand, if the gel content exceeds 98%, the adhesive strength tends to decrease, which is not preferable.

When the copolymer latex of the present invention is used as a binder for an offset rotary printing paper paper coating composition, a preferred monomer component of the copolymer latex is (a) a conjugated diene monomer in an amount of 20 to 50% by weight. %, Preferably 25 to 45% by weight, (b) 40 to 79.5% by weight, preferably 40 to 74.5% by weight, and (c) 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer. %, Preferably 1 to 7% by weight
It is. In this case, the gel content of the copolymer latex is
Preferably it is 65% by weight or less, more preferably 60 to 5% by weight.

The polymerization conversion in the production of the copolymer latex of the present invention is preferably 90% by weight or more, more preferably 93% by weight or more, and particularly preferably 95% by weight or more.

A paper coating composition can be obtained by blending the copolymer latex of the present invention with an inorganic pigment or an organic pigment, preferably an inorganic pigment or, if necessary, with another binder. The blending amount of the copolymer latex in the paper coating composition is usually 5 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the pigment in terms of solid content. The amount of the other binder added as necessary is usually 10 parts by weight or less, preferably 2 to 5 parts by weight, based on 100 parts by weight of the pigment in terms of solid content.

As the inorganic pigment, kaolin clay, talc, barium sulfate, titanium oxide (rutile anatase), calcium carbonate, aluminum hydroxide, zinc oxide, satin white and the like can be used. As the organic pigment, polystyrene latex and the like can be used. These can be used alone or in combination of two or more.

Other binders include starch, oxidized starch,
Examples include natural binders such as soybean protein and casein, and synthetic latexes such as polyvinyl alcohol, polyvinyl acetate latex, and acrylic terrax.

In the paper coating composition containing the copolymer latex of the present invention, various commonly used auxiliaries such as a dispersant (sodium pyrophosphate, sodium hexametaphosphate), an antifoaming agent (polyglycol, Fatty acid esters, phosphate esters, silicone oils, etc.), leveling agents (funnel oil, dicyandiamide, urea, etc.), preservatives, water resistant agents (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), mold release agents (stearin) Potassium silicate, paraffin emulsion, etc.), a fluorescent dye, a color retention improver (carboxymethyl cellulose, sodium alginate, etc.) and the like can be blended as required.

The paper coating composition containing the copolymer latex of the present invention can be applied by a conventionally known method, for example, using an air knife coater, a blade coater, a roll coater, an applicator, or the like.

Further, the copolymer latex of the present invention can be used in various adhesive applications such as carpet backing agents, paints, industrial and household adhesives.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “%” and “parts” are based on weight.

Example 1 (Production of copolymer latex) As shown in Table 1, 2 parts of itaconic acid, 1 part of acrylic acid, 10 parts of butadiene, and 18 parts of styrene were placed in a 100 pressure vessel as shown in Table 1. , 10 parts of methyl methacrylate and 5 parts of acrylonitrile, and
Part, α-methylstyrene dimer 1.5 part, sodium dodecylbenzenesulfonate 0.3 part and potassium acetate sulfate
After charging 1.0 part, polymerization was carried out at 70 ° C. for 2 hours in a nitrogen atmosphere. Next, as a second-stage monomer mixture, 15 parts of butadiene, 31 parts of styrene, 3 parts of acrylonitrile and 5 parts of methyl methacrylate, and 1.5 parts of α-methylstyrene dimer were continuously added over 8 hours. To perform polymerization. Thereafter, in order to complete the polymerization, the reaction was further continued for 3 hours, and the polymerization was completed at a polymerization conversion of 98%.

After adjusting the pH of the obtained copolymer latex to 7.5 using sodium hydroxide, steam is blown to remove unreacted monomers, and the solid content concentration is further reduced by heating under reduced pressure.
50% of a copolymer latex (I-1) was obtained.

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

Brand name: NOFMER MSD (manufactured by NOF CORPORATION) Composition Composition Composition (wt%) 2-4-diphenyl-4-methyl-1-pentene 92.0% or more 2-4-diphenyl-4-methyl-2- Penten 5.0% or less 1-1-3-trimethyl-3-7-phenylindane 1.5% or less α-methylstyrene 1.0% or less The gel content of this copolymer latex (II) was measured by the following method.

After adjusting the copolymer latex to pH 8.0, it was coagulated with isopropanol, washed, and dried. Then, about 0.
A sample of 3 g was collected, immersed in 100 ml of toluene for 20 hours, and the toluene-insoluble content was measured, and the ratio (%) to the sample was determined to be the gel content.

Further, the amount of coagulated product generated during the polymerization of the copolymer latex 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 the evaluation was made according to the following three grades.

○: less than 0.05 (small) △: 0.05% to 0.1% (slightly large) ×: more than 0.1% (very large) (Preparation of paper coating composition) Using the above copolymer latex (I-1) A paper coating composition (color) was prepared according to the following formulation.

Clay 80 parts Calcium carbonate 20 parts Copolymer latex 10 parts Oxidized starch 5 parts Sodium pyrophosphate 0.5 part Water The amount that the total solid content becomes 60 The color obtained was evaluated by the following test method. In addition,
The coated paper used in the test was obtained by applying a color to a base paper having a basis weight of 64 g / m ² using a coating blade at a coating amount of 20 g / m ² .

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

Blister resistance After the double-sided printing coated paper was humidified (about 6%), it was thrown into a heating oil bath, and the lowest temperature at which blisters were generated was indicated.

Mechanical Stability The color is adjusted to a solid concentration of 20% by weight, kneaded between the rubber rolls at a pressure of 10 kg, 100 rpm and 60 ° C using a gum-up tester, and subjected to mechanical shear until coagulated material is generated on the rubber rolls. (Min) was measured and evaluated in the following three stages.

 : 30: 30 minutes or more Δ: 20 minutes or more and less than 30 minutes ×: less than 20 minutes The results are shown in Table 2.

Examples 2 to 10, Comparative Example 1 In Example 1, a monomer mixture, a polymerization chain transfer agent,
Except that the polymerization initiator and the emulsifier were changed as shown in Table 1, a copolymer latex (I-
2) to (I-10) and the comparative copolymer latex (I
−11). The copolymer latex (I-10) differs from Example 1 in that the first-stage polymerization was performed for 6 hours and the second-stage polymerization was performed for 2 hours. The polymerization was terminated at a polymerization addition rate of 98% for all copolymer latexes.

Using these copolymer latexes, a paper coating composition was prepared in the same manner as in Example 1, and its performance was evaluated.

 Table 2 shows the results.

Example 11 In a pressure vessel of 100, as shown in Table 3, 2 parts of itaconic acid, 1 part of acrylic acid, 10 parts of butadiene, 11 parts of styrene, 5 parts of methyl methacrylate and 5 parts of acrylonitrile Charge 3 parts and add water 150
Parts, terpinolene 0.1 parts, t-dodecyl mercaptan 0.1
Parts, 0.2 parts of sodium dodecylbenzenesulfonate and 1.0 part of potassium persulfate, and then polymerized at 70 ° C. for 2 hours in a nitrogen stream. Next, 15 parts of butadiene, 44 parts of styrene, 5 parts of methyl methacrylate and 3 parts of acrylonitrile, 0.1 part of terpinolene and 0.1 part of t-dodecyl mercaptan were continuously added as the second-stage monomer mixture over 8 hours. To carry out polymerization. afterwards,
In order to complete the polymerization, the reaction was further continued for 3 hours, and the polymerization was completed at a polymerization conversion of 98%.

Thereafter, a copolymer latex (II-1) was obtained in the same manner as in Example 1.

Next, using this copolymer latex, a paper coating composition was prepared in the same manner as in Example 1.

The gel content of the copolymer latex was measured and the characteristics of the paper coating composition were evaluated in the same manner as in Example 1. Table 4 shows the results.

Examples 12 to 16, Comparative Example 2 In Example 10, the monomer mixture, the polymerization chain transfer agent,
Except that the polymerization initiator and the emulsifier were changed as shown in Table 3, the copolymer latex (II-
2) to (II-6) and a copolymer latex for comparison (II
-7) was obtained. The copolymer latex (II-6) differs from Example 11 in that the first-stage polymerization took 6 hours and the second-stage polymerization took 2 hours.

Using these copolymer latexes, a paper coating composition was prepared in the same manner as in Example 11, and the performance was evaluated.

 Table 4 shows the results.

Example 17 In Example 1, the amount of the polymerization chain transfer agent and the weight ratio γ of the monomer in the second stage were changed from γ ₀ = 0.05 at the start of addition to γ at the end of addition.
Copolymer latex (I-1) was prepared in the same manner as in Example 1 except that the addition polymerization was carried out while continuously reducing _F 2 to 0.0056.
2) got. The polymerization was completed at a polymerization conversion of 98%.

Example 18 In Example 10, the weight ratio γ per unit time between the amount of the polymerization chain transfer agent and the amount of the monomer in the first stage was γ ₀ = 0.01 at the start of the addition.
From the end of addition, a copolymer latex (I-13) was obtained in the same manner as in Example 10, except that addition polymerization was carried out for 6 hours while continuously increasing γ _F = 0.0522. The polymerization was completed at a polymerization conversion of 98%.

Next, the gel content of these copolymer latexes (I-12, 13) was measured and the properties of the paper coating composition were evaluated in the same manner as in Example 1. Table 2 shows the results.

Example 19 In Example 13, the weight ratio γ between the amount of the polymerization chain transfer agent and the monomer in the second stage was continuously reduced from γ ₀ = 0.06 at the start of the addition to γ _F = 0.0127 at the end of the addition. Except for polymerizing, a copolymer latex (II-
8) was obtained. The polymerization was completed at a polymerization conversion of 98%.

Example 20 In Example 16, the weight ratio γ per unit time between the amount of the polymerization chain transfer agent in the first stage and the amount of the monomer at the start of addition γ ₀ = 0.01
A copolymer latex (II-9) was obtained in the same manner as in Example 13, except that the addition polymerization was continuously increased from 5 to γ _F = 0.0409 at the end of the addition. The polymerization was completed at a polymerization conversion of 98%.

Next, these copolymer latexes (II-8, II-9)
Was measured for the gel content and the characteristics of the paper coating composition were evaluated in the same manner as in Example 1. Table 4 shows the results.

Examples 21 and 22 and Comparative Examples 3 and 4 150 parts of water, a monomer mixture of the first-stage components shown in Table 5, a polymerization chain transfer agent, an emulsifier, and a polymerization initiator were charged into the pressure-resistant containers of 100, and then nitrogen atmosphere was added. Polymerization was carried out at a temperature of 70 ° C. for 2 hours. Next, a monomer mixture excluding the ethylenically unsaturated amine monomer of the second stage component in Table 5 was continuously added over 8 hours to carry out polymerization at a polymerization temperature of 70 ° C. Then, the pH of the polymerization system was adjusted to 7.5 with aqueous ammonia, and an ethylenically unsaturated amine monomer was added. The polymerization was continued for 3 hours, and the polymerization was completed at a polymerization conversion of 98%. Then, two types of copolymer latex were obtained for the example and two types of copolymer latex were obtained for the comparative example. These are referred to as copolymer latexes III-1 to III4.

For these copolymer latexes, a paper coating composition was prepared in the same manner as in Example 1 and evaluated by the same evaluation method as in Example 1 and the following water resistance evaluation method. The evaluation results are shown in Table 6. .

Evaluation Method of Water Resistance RI Wet Pick: Index of Water Resistance The degree of picking when printing was performed by applying dampening water using a Molton roll with an RI printing machine was visually judged, and evaluated by a five-step method. The higher the score, the better. Number of measurements 6
Displayed as the average value of times.

Examples 21 and 22 are copolymer latexes belonging to the third aspect of the present invention. Since ethylenic unsaturated amine monomer is used as a monomer, the water resistance of Examples 21 and 22 is lower than that of Example 1 not using this. It is even better.

On the other hand, Comparative Examples 3 and 4 are examples using a polymerization chain transfer agent outside the range of the present invention, and are inferior in water resistance as compared with Examples 21 and 22.

From the above results, it can be seen that when the polymerization chain transfer agent of the present invention is used in combination with the ethylenically unsaturated amine monomer, a more excellent water resistance can be obtained.

(Effects of the Invention) The copolymer latex produced by the method of the present invention has a small amount of fine coagulated material, has excellent mechanical stability, and has excellent adhesive strength and blister resistance. Useful as Among them, the copolymer latex of the present invention can be preferably used as a binder for a paper coating composition of a coated paper, particularly a coated paper for offset rotary printing. It can be used for various adhesives such as adhesives for home use and home use.

[Brief description of the drawings]

FIGS. 1 (1) to 1 (4) are explanatory diagrams showing the state of addition of a polymerization chain transfer agent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 236: 04 220: 04 220: 34) (72) Inventor Masaaki Yada 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber (72) Inventor Masafumi Wakamori 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-61-268709 (JP, A) JP-A-57-108104 ( JP, A) JP-A-53-118489 (JP, A) JP-A-53-121891 (JP, A) JP-A-60-84315 (JP, A) US Patent 2,292,781 (US, A) Introduction to polymer latex 1980 Published by Kobunsha Co., Ltd., written by Soichi Muroi) P156-P159 (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 9/00-21/02 C08L 25/08-25/14 C08F 2/38

Claims (5)

(57) [Claims] (1) 10 to 69.5% by weight of a conjugated diene monomer (b) 30 to 89.5% by weight of an ethylenically unsaturated monomer other than (c) (c) Monomer of an ethylenically unsaturated carboxylic acid A method for producing a copolymer latex, which comprises subjecting a monomer containing 0.5 to 10% by weight of a monomer to emulsion polymerization in the presence of α-methylstyrene dimer, and having a gel content of 10% or more. 2. (a) 10 to 70% by weight of a conjugated diene monomer (b) 30 to 89.5% by weight of an ethylenically unsaturated monomer other than (c) (c) Monomeric amount of an ethylenically unsaturated carboxylic acid A monomer containing 0 to 10% by weight of a monomer, (A) 10 to 90% by weight of at least one compound selected from terpinolene, α-terpinene, γ-terpinene and dipentene; (B) an alkyl mercaptan; A process for producing a copolymer latex, which comprises carrying out emulsion polymerization in the presence of a polymerization chain transfer agent comprising 10 to 90% by weight of at least one compound selected from carbon chloride, xanthogen disulfides and thiuram disulfides. (3) 10 to 79.4% by weight of a conjugated diene monomer (b) 20 to 89.4% by weight of an ethylenically unsaturated monomer other than (c) and (d) (c) Ethylene unsaturated Carboxylic acid monomer 0.5 to 10% by weight (d) A monomer containing 0.1 to 10% by weight of an ethylenically unsaturated amino monomer is emulsion-polymerized in the presence of α-methylstyrene dimer to reduce the gel content. A method for producing a copolymer latex, which is at least 10%. 4. (a) 10 to 79.4% by weight of a conjugated diene monomer (b) 20 to 89.4% by weight of an ethylenically unsaturated monomer other than (c) and (d) (c) Ethylene unsaturated Carboxylic acid monomer 0.5 to 10% by weight (d) Monomer containing 0.1 to 10% by weight of ethylenically unsaturated amine monomer is selected from (A) terpinolene, α-terpinene, γ-terpinene and dipentene A polymerization chain transfer agent comprising 10 to 90% by weight of at least one compound and 10 to 90% by weight of (B) at least one compound selected from alkyl mercaptans, carbon tetrachloride, xanthogen disulfides and thiuram disulfides. A process for producing a copolymer latex, which is carried out by emulsion polymerization in the presence of (a). 5. The method according to claim 1, wherein in at least a part of the polymerization step, the polymerization is carried out while continuously adding the monomer and the polymerization chain transfer agent. A method for producing a copolymer latex, wherein a weight ratio of a monomer to be added and a polymerization chain transfer agent per unit time is continuously changed.