JP2002212205A - Copolymer latex, and composition for paper coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolymer latex which gives a coating paper excellent in the pick-up strength, wet picking strength, blister resistance, and blistering resistance and which is excellent in the roll staining resistance when coating. SOLUTION: The copolymer latex is obtained by the two-step copolymerization in the presence of a specific reactive emulsifier, of (a) a conjugated diene monomer, (b) an ethylenically unsaturated carboxylic acid monomer, and (c) the other monomer copolymerizable with (a) the conjugated diene monomer and (b) the ethylenically unsaturated carboxilic acid monomer, each of a specified amount, by using each monomer of the same kind at the each step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diene copolymer latex used for a carpet backing agent, an adhesive, a pressure-sensitive adhesive, a fiber binder, a water-based developable photosensitive resin for flexographic printing and a paint. Regarding paper coating latex, more specifically, high performance diene copolymer latex suitable as a binder for paper coating used for coated paper or coated paperboard used for offset printing, gravure printing, etc. And a paper coating composition using the same.

[0002]

2. Description of the Related Art Conventionally, synthetic copolymer latex has been widely used as, for example, a binder for paper coating, a binder for carpet backsizing, a binder for bonding fibers such as nonwoven fabric and artificial leather, or an adhesive for various materials. Used. When the copolymer latex is used for such applications, the copolymer latex is required to have high adhesive strength, excellent water resistance, and excellent resistance to blistering by drying and heating. Coated paper, for the purpose of improving the printability of paper and optical properties such as gloss, on the surface of the base paper made, pigments such as kaolin clay, calcium carbonate, satin white, talc, titanium oxide,
Starch as a copolymer latex and a viscosity modifier or an auxiliary binder as those binders,
The paper coating composition containing a water-soluble polymer such as polyvinyl alcohol and carboxymethyl cellulose as a main component is coated.

Here, as a copolymer latex as a binder, a styrene-butadiene copolymer latex emulsion-polymerized with styrene and butadiene as main monomer components, a so-called SB latex, has been widely used. . In recent years, the demand for color printed magazines, brochures, and advertisements has been increasing, and the printing speed has been increased. The demands for coated papers and pigment binders have been increasingly sophisticated. Among them, particularly, improvement in ink pick resistance, so-called pick strength, and ink pick resistance after a dampening solution is applied, so-called wet pick strength, are strongly required. Not only is the pick strength performance itself negatively correlated, but it is also negatively correlated with other print properties, such as blister resistance and anti-backing roll stain properties in paper coating, so these properties There is a need for further improvements to balance to a high level. Since these contradictory physical properties strongly depend on the performance of the diene-based copolymer latex used as a pigment binder, various studies have been made on the diene-based copolymer latex.

For example, with the aim of achieving a high balance of these various physical properties, an improvement of latex using a method of polymerizing with a specific monomer composition in a two-stage or multi-stage polymerization method has been proposed (Japanese Patent No. 1427990, Japanese Patent Laid-Open No. 62-1
17897, JP-A-6-240559, JP-A-7-258308, JP-A-7-324112
JP, JP-A-7-324113, JP-A-9-3
1141, JP-A-9-31895). However, in this technical field in recent years, it has been required to achieve a higher level of balance of physical properties, and any of these methods is required to apply coated paper properties such as pick strength, wet pick strength, and blister resistance in coated paper and paper coating. However, it was difficult to say that this method was sufficient as a method for improving the backing roll stain resistance in the above.

On the other hand, in recent years, high-speed coating has been promoted in order to improve the production capacity of coated paper, and in the case of coating liquids, it is necessary to cope with a decrease in drying capacity and to increase production efficiency due to high-speed coating. For the purpose, high solid differentiation of the coating liquid has been promoted. In order to differentiate the coating liquid into high solids, improve the fluidity from the pigment surface, such as increasing the mixing ratio of heavy calcium carbonate, and reduce the amount of latex by increasing the amount of latex by reducing the water-soluble binder with a large viscosity such as starch. Improvements have been made from the surface. However, improving the fluidity from the pigment side to increase the calcium carbonate ratio is not preferable because the gloss of white paper is reduced. In addition, improving the fluidity from the binder surface, which increases the amount of latex, is undesirable because it increases the stickiness of the coated paper surface and causes problems such as backing roll stains and supercalender stains. In order to solve these problems, in polymerizing a copolymer latex, it has been proposed to polymerize a vinyl cyanide monomer and an amide group-containing ethylenically unsaturated monomer in the second stage in a two-stage polymerization. (JP-A-4-240297, JP-A-5-240297)
However, these methods can improve the printability of coated paper and the tackiness of the copolymer latex, but cannot be said to be sufficient, and coating under high solid content conditions for high-speed coating is difficult. The fluidity of the working liquid was not satisfactory. Further, when polymerizing the copolymer latex, 2
In the second stage, methacrylonitrile is continuously added and polymerized at a certain addition speed in the second stage, thereby improving the printability of coated paper and the fluidity of a high solids coating liquid for high-speed coating. It is proposed to be superior (Japanese Patent Laid-Open No. 10-18270).
9) However, even with this method, the printability of the coated paper and the backing roll stain resistance in paper coating could not be satisfied. As described above, the conventional technology cannot cope with a further increase in the speed of printing and production of coated paper, and as a binder as a binder which increases productivity and enables production of high quality coated paper. At present, latex is strongly required.

[0006]

As described above, conventional paper coating binders are used to improve the coated paper properties such as pick strength, wet pick strength, blister resistance, etc., and operability of coated paper using the binder. The request could not be satisfied at the same time. Under such circumstances, the present invention has excellent coated paper properties such as pick strength, wet pick strength, and blister resistance in coated paper, and has excellent backing roll stain resistance (stickiness and stickiness) in paper coating. An object of the present invention is to provide a high-performance copolymer latex having excellent redispersibility.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems of the prior art, and as a result, have obtained a specific polymer obtained by emulsion polymerization in the presence of a reactive emulsifier. It has been found that the diene-based copolymer latex achieves the object, and the present invention has been completed. That is, a first aspect of the present invention is a conjugated diene copolymer latex obtained by emulsion polymerization by a multistage polymerization method in the presence of one or more reactive emulsifiers, wherein the first step is a conjugated diene copolymer latex. Based monomer (a) 10 to 50% by weight, ethylenically unsaturated carboxylic acid monomer (b) 0.5 to 30% by weight, conjugated diene monomer (a) and ethylenically unsaturated carboxylic acid 20-89.5% by weight of other monomer (c) copolymerizable with monomer (b) (provided that (a) + (b) +
(C) = 100% by weight), and in the second step, 30 to 80% by weight of the conjugated diene monomer (a), 0 to 20% by weight of the ethylenically unsaturated carboxylic acid monomer (b), and Other monomers (c) copolymerizable with the diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b)
It is a conjugated diene copolymer latex consisting of 70% by weight ((a) + (b) + (c) = 100% by weight). A second aspect of the present invention is that the reactive emulsifier has the following general formula (I):
The diene-based copolymer latex according to claim 1, wherein

[0008]

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Wherein R ¹ is hydrogen or a methyl group, R ² is a hydrocarbon group or an acyl group having 8 to 24 carbon atoms, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 0 to 50, n is 0
And M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms. A third aspect of the present invention is the diene-based copolymer latex according to claim 1, wherein the reactive emulsifier has the following general formula (II).

[0010]

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Wherein A is an alkylene group having 2 to 4 carbon atoms, k is an integer of 1 or 2, l is an integer of 1 to 50, m is an integer of 0 to 50, n is an integer of 1 or 2, X is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or a hydroxyalkylammonium having 1 to 4 carbon atoms.) In a fourth aspect of the invention, the reactive emulsifier has the following general formula (III):
The diene-based copolymer latex according to claim 1, wherein

[0012]

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(Wherein, R ¹ is an alkyl group, alkenyl group or aralkyl group having 6 to 18 carbon atoms, R ² is hydrogen or an alkyl group, alkenyl group or aralkyl group having 6 to 18 carbon atoms, R ³ is hydrogen or A propenyl group, A is an alkylene group having 2 to 4 carbon atoms, n is an integer of 1 to 200, M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or a hydroxyalkyl ammonium having 1 to 4 carbon atoms. A fifth aspect of the present invention is the diene copolymer latex according to claim 1, wherein the reactive emulsifier has the following general formula (IV).

[0014]

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Wherein A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 0 to 100, n is an integer of 0 to 100,
Is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms. In a sixth aspect of the present invention, the reactive emulsifier is represented by the following general formula (V):
2. The method according to claim 1, wherein (VI), (VII), and (VIII).
It is a diene copolymer latex of the description.

[0016]

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(In the above formula, R ¹ is hydrogen or a methyl group, R ² is a hydrocarbon or a hydrocarbon group having a substituent or an organic group containing an oxyalkylene group;
4 alkylene groups or substituted alkylene groups, n represents 0 or an integer. M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms. A seventh aspect of the present invention is a paper coating composition containing the diene-based copolymer latex according to any one of the first to sixth aspects of the invention.

The present invention will be described in more detail below. The diene-based copolymer latex of the present invention is produced by emulsion polymerization using a multi-stage polymerization method of two or more stages. The reactive emulsifier used in the present invention means an emulsifier having a radical polymerizable double bond in a molecule, and may be anionic, nonionic or cationic, and examples thereof include the following. be able to.

As represented by the following general formula (I):
For example, Adecaria Soap (trademark) S manufactured by Asahi Denka Kogyo Co., Ltd.
E-1025N and the like. Alternatively, as a phosphate ester-based compound represented by the following general formula (II), Asahi Denka Kogyo Co., Ltd. SDX-1055 or the like. Alternatively, an alkylphenol ether represented by the following general formula (III):
For example, Aqualon (trademark) HS- manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
10 mag.

Alternatively, a compound represented by the following general formula (IV), for example, Aqualon (trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
KH-10 and the like. Alternatively, the following general formulas (V) and (V
Allylsulfosuccinates represented by I), (VII) and (VIII), for example, Latemul (trademark) S-120, S-180A, S-180 manufactured by Kao Corporation, Eleminor manufactured by Sanyo Chemical Industries, Ltd. (Trademark) JS-2 and the like. Other, p
Styrene sulfonate, methylpropanesulfonic acid acrylamide salt, acrylic acid sulfoalkyl ester salt, methacrylic acid sulfoalkyl ester salt, and the like, but are not limited thereto.

One or two or more of these reactive emulsifiers can be used, and the amount thereof is 0.01 to 10% by weight, preferably 0.1 to 10% by weight, based on the weight of all monomers.
02 to 7% by weight, more preferably 0.03 to 5% by weight
Range. If the amount is less than 0.01% by weight, the copolymer latex redispersibility, which is one of the indicators of the backing roll stain resistance in paper coating, is low, and the polymerization stability is poor. The wet pick strength of the coated paper is undesirably reduced.

The monomer in the first step of the present invention comprises a conjugated diene monomer (a), an ethylenically unsaturated carboxylic acid monomer (b), a conjugated diene monomer (a) and ethylene. It comprises the unsaturated unsaturated carboxylic acid monomer (b) and another copolymerizable monomer (c). The (a) conjugated diene monomer used in the first step of the present invention includes, for example, 1,
3-butadiene, isoprene, 2,3-dimethyl 1,3
-Butadiene, 2-ethyl-1,3-butadiene, 2-
Methyl-1,3-butadiene, 1,3-pentadiene,
Chloroprene, 2-chloro-1,3-butadiene, cyclopentadiene and the like can be mentioned, and 1,3-butadiene is preferable. These conjugated diene monomers are used alone or in combination of two or more.

The preferred amount of the conjugated diene monomer (a) used is 10 to 50% by weight of the monomer in the first step,
Preferably 15 to 45% by weight, more preferably 20 to 45% by weight.
40% by weight. If the amount of the component (a) is less than 10% by weight, the obtained polymer becomes brittle, and the effect of improving the pick strength of the coated paper cannot be sufficiently obtained. On the other hand, if it exceeds 50% by weight, the effect of improving the tackiness of the copolymer latex and the effect of improving the wet pick strength of the coated paper, which are indicators of the backing roll stain resistance in paper coating, are not sufficiently exhibited. However, the object of the present invention cannot be sufficiently achieved.

The ethylenically unsaturated carboxylic acid monomer (b) used in the first step includes, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. These ethylenically unsaturated carboxylic acid monomers may be used alone or in combination of two or more. The preferred amount of use is 0.5 to 30% by weight, more preferably 0.1 to 30% by weight of the monomers in the first step. It is selected in the range of 7 to 25% by weight, most preferably 1 to 20% by weight. When this amount is less than 0.5% by weight, the dispersion stability of the latex is not sufficient, and various problems occur in the preparation of the coating liquid and during coating, and the pick strength is low. If the amount exceeds 10 parts by weight, the viscosity of the latex or the coating liquid becomes too high, and the wet pick strength tends to decrease.

The conjugated diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b) used in the first step
Other monomers (c) that can be copolymerized with: vinyl aromatic monomers, vinyl cyanide monomers, alkyl (meth) acrylate monomers, (meth) acrylamide monomers Carboxylic acid vinyl esters such as vinyl acetate, vinyl halides such as vinyl chloride, amino group-containing ethylenic monomers such as aminoethyl acrylate and dimethylaminoethyl acrylate, and sodium styrene sulfonate. it can. These copolymerizable monomers are used alone or in combination of two or more.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, vinylxylene, bromostyrene, vinylbenzyl Chloride, pt-butylstyrene, chlorostyrene, alkylstyrene, divinylbenzene, trivinylbenzene and the like can be mentioned, but styrene is particularly preferred. Examples of the alkyl (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, and isobutyl (meth) acrylate. (Meth) acrylate, n-amyl (meth) acrylate, isoamylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (Meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, diethylene glycol ethoxy acrylate, triethylene glycol di (meth) acrylate , Tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate,
Polypropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, allyl (meth) acrylate, bis (4-acryloxypolyethoxyphenyl) Propane, methoxypolyethylene glycol (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, 2,2-bis [4-((meth) acryloxyethoxy) phenyl] propane 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane,
Examples thereof include 2,2-bis [4-((meth) acryloxypolyethoxy) phenyl] propane and isobornyl (meth) acrylate.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like, and acrylonitrile is particularly preferable. These vinyl cyanide monomers may be used alone or in combination of two or more.
The preferred amount of the component (b) is at most 60 parts by weight, preferably at most 50 parts by weight, based on the weight of all monomers.
If the amount is more than 60 parts by weight, the polymerization stability of the latex is poor, which is not preferable.

Examples of (meth) acrylamide monomers include N-monoalkyl (meth) acrylamide such as (meth) acrylamide, N-methylol (meth) acrylamide, N-methyl (meth) acrylamide, and N, N- N, N-dialkyl (meth) acrylamide such as dimethyl (meth) acrylamide, glycidyl methacrylamide, N-alkoxy (meth) acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and the like are used. 10 parts by weight or less, more preferably 7 parts by weight or less based on the weight of the monomer.
Not more than parts by weight. If it is used in excess of 10 parts by weight, the low shear viscosity of the latex and the paper coating composition is increased, and the workability is undesirably deteriorated.

The monomer in the second step of the present invention comprises a conjugated diene monomer (a), an ethylenically unsaturated carboxylic acid monomer (b), a conjugated diene monomer (a) and ethylene. It comprises the unsaturated unsaturated carboxylic acid monomer (b) and another copolymerizable monomer (c). The conjugated diene monomer (a) used in the second step of the present invention is the same as the example of the conjugated diene monomer used in the first step.
Butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, chloroprene, 2-chloro-1,3 -Butadiene, cyclopentadiene, etc., and preferably 1,
3-butadiene. These conjugated diene monomers are used alone or in combination of two or more.

The preferred amount of the conjugated diene monomer (a) used is 30 to 80% by weight of the monomer in the second step,
Preferably 35 to 75% by weight, more preferably 40 to 75% by weight.
70% by weight. If the amount is less than 30% by weight, the resulting polymer becomes too brittle, and it is difficult to obtain a sufficiently high pick strength. On the other hand, if it exceeds 80% by weight, it is difficult to achieve the required stickiness resistance, and the object of the present invention cannot be sufficiently achieved. Examples of the ethylenically unsaturated carboxylic acid monomer (b) used in the second step include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. These ethylenically unsaturated carboxylic acid monomers may be used alone or in combination of two or more, and the preferred amount thereof is 0 to 20% by weight, more preferably 0 to 18% by weight of the monomer in the second step. %, Most preferably in the range of 0 to 15% by weight.
If the amount exceeds 20 parts by weight, the wet pick strength is deteriorated and the viscosity of the coating liquid is too high, which is not preferable.

The conjugated diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b) used in the second step
Examples of the other monomer (c) copolymerizable with the conjugated diene-based monomer (a) used in the first step are the same as the examples of the other monomer copolymerizable with the conjugated diene-based monomer (a). Monomers, vinyl cyanide monomers, alkyl (meth) acrylate monomers, (meth) acrylamide monomers, vinyl carboxylate esters such as vinyl acetate, and vinyl halides such as vinyl chloride And aminoethyl-containing ethylenic monomers such as aminoethyl acrylate and dimethylaminoethyl acrylate, and sodium styrenesulfonate. These copolymerizable monomers are used alone or in combination of two or more.

In the present invention, in order to exhibit the effects of the present invention, the gel obtained at the time when the polymerization of the copolymer obtained by emulsion polymerization from the monomer added in the first step is started in the second step is started. The content is preferably from 20 to 90% by weight, and more preferably from 30 to 80% by weight. If the gel content at the start of the polymerization in the second step is less than 20% by weight, improvement in stickiness resistance, which is an index of the backing roll stain resistance in paper coating, is not sufficiently recognized, and exceeds 90% by weight. And the pick strength is not sufficiently improved.
In the present invention, the gel content is defined as the toluene insoluble content.

The polymerization conversion at the time when the polymerization of the monomer added in the first step is started in the second step is 50 to 90.
%, More preferably 60 to 80% by weight. When the polymerization conversion is less than 50% by weight, the wet pick strength and the backing roll stain resistance in paper coating are not sufficiently improved, and 90% by weight.
If it exceeds, no improvement in pick strength is sufficiently recognized. The weight ratio of the monomer added in the first step and the monomer added in the second step of the present invention depends on the composition of the monomer used, the polymerization conversion, and the copolymer derived from each monomer. Although it cannot be unconditionally determined by the compatibility between the polymers, it is usually selected from 1/9 to 9/1, and preferably from 3/7 to 7/3.
When the weight ratio is less than 1/9, the effect of improving wet pick strength and stickiness resistance is not sufficient, and when the ratio is more than 9/1, the effect of improving pick strength is not particularly sufficient. It is not preferable because the balance of coated paper properties such as a certain pick strength, wet pick strength, and blister resistance is not sufficiently improved.

The emulsion polymerization of the monomer used in the present invention is not particularly limited, and the emulsifier other than the monomer, the chain transfer agent and the reactive emulsifier in an aqueous medium may be used by a conventionally known method. An aqueous dispersion of copolymer particles, that is, a diene-based copolymer latex, is obtained by polymerizing a monomer in a dispersion system having a radical polymerization initiator and other additive components used as necessary as basic constituent components. Is used. The concentration of the copolymer in the diene-based copolymer latex is selected in the range of 40 to 60% by weight.
The average particle size is preferably in the range of 0.04 to 0.4 μm, and more preferably in the range of 0.05 to 0.2 μm. The average particle size can be adjusted by the use ratio of the seed latex or the emulsifier, and generally, the higher the use ratio, the smaller the average particle size of the produced copolymer latex tends to be. The polymerization of the seed latex may be performed in the same reaction vessel prior to the polymerization of the latex of the present invention, or a seed latex polymerized in a different reaction vessel may be used.

As the method of adding the monomer composition, in each polymerization step, a method of adding the monomer composition all at once, intermittently or continuously according to the progress of polymerization after a part of the monomer composition is added. Or a method of continuously adding the monomer composition. In addition, there is no particular limitation on the addition rate when the monomer composition is continuously added.

The diene copolymer latex of the present invention comprises
Known chain transfer agents used in general emulsion polymerization can be used. For example, dimers of nuclear-substituted α-methylstyrene such as α-methylstyrene dimer, n-
Butyl mercaptan, n-octyl mercaptan, n-
Lauryl mercaptan, n-dodecyl mercaptan, t
-Mercaptans such as dodecyl mercaptan, tetramethylthiuram disulfide, disulfides such as tetraethylthiuram disulfide, carbon tetrachloride, halogenated derivatives such as carbon tetrabromide, 2-ethylhexyl thioglycolate, terpinolene and the like. One or more are used. As the chain transfer agent, α-methylstyrene dimer and t-dodecyl mercaptan are particularly preferred. It is preferable to use the chain transfer agent in the range of 0.2 to 10 parts by weight per 100 parts by weight of the monomer. Outside of this range, the balance between pick strength, wet pick strength, and blister resistance is reduced, making it difficult to achieve the effects of the present invention. α-Methylstyrene dimer has 2,4-diphenyl-4- as an isomer
Methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene and 1,1,3-trimethyl-3-
Although there is phenylindane, the α-methylstyrene dimer used in the present invention includes 2,4-diphenyl-
The proportion of 4-methyl-1-pentene is preferably at least 60% by weight, particularly preferably the proportion of 2,4-diphenyl-4-methyl-1-pentene is at least 80% by weight.

As the emulsifier other than the reactive emulsifier, known emulsifiers used in general emulsion polymerization can be used. For example, anionic emulsifiers such as aliphatic soap, rosin acid soap, alkyl sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl aryl sulfate, polyoxyethylene alkyl Nonionic emulsifiers such as ethers, polyoxyethylene alkylaryl ethers, polyoxyethyleneoxypropylene block copolymers, and, if necessary, amphoteric emulsifiers such as betaine-type emulsifiers. One or more of these are used. . The emulsifier is usually used in the form of an anionic emulsifier alone, a reactive emulsifier alone, or an anionic / reactive or anionic / nonionic mixed system. The amount of the emulsifier is usually from 0 to 3 based on the weight of all monomers. It is selected in the range of weight%.

The radical polymerization initiator initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing substance, and either an inorganic initiator or an organic initiator can be used. Such include, for example, water-soluble or oil-soluble peroxodisulfates, peroxides,
Azobis compounds and the like, specifically, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide And POLYMER HANDBOOK (3rd ed
ition), J. et al. Brandrup and E.C. H. I
Merrygut, John Willy & Son
s (1989). Also, a so-called redox polymerization method in which a reducing agent such as sodium acid sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof, or Rongalit is used in combination with a polymerization initiator can be employed. In the first step, it is particularly preferable to use an inorganic radical polymerization initiator, and it is more preferable to use an inorganic radical polymerization initiator in all the polymerization steps. Of these, peroxodisulfate is particularly suitable as a polymerization initiator. The amount of the polymerization initiator used is usually in the range of 0.1 to 5.0% by weight based on the weight of all monomers, preferably 0.2 to 5.0% by weight.
To 3.0% by weight.

The polymerization temperature in this emulsion polymerization is usually 6
The temperature is selected in the range of 0 to 100 ° C., but the polymerization may be performed at a lower temperature by the redox polymerization method or the like. Further, the polymerization temperature in each polymerization step may be the same or different. The polymerization time is usually 5 to 30 hours. Further, after the second step of the present invention, a monomer may be further added and the polymerization step may be repeated. In the present invention, various polymerization regulators can be added as needed. For example, as a pH adjuster, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, sodium carbonate,
A pH adjuster such as disodium hydrogen phosphate can be added. Among them, potassium hydroxide is particularly preferred in terms of enhancing the balance between pick strength and wet pick strength, and is suitable as a pH adjuster after polymerization. Various chelating agents such as sodium ethylenediaminetetraacetate can also be added as a polymerization regulator. If necessary, an alkali-sensitive latex may be added to the copolymer latex of the present invention.

When the diene-based copolymer latex of the present invention is used as a binder for a paper coating composition, it can be carried out in an ordinary mode. That is, in water in which a dispersant is dissolved, kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, inorganic pigments such as talc, organic pigments known as plastic pigments and binder pigments, starch,
Water-soluble polymers such as casein, polyvinyl alcohol and carboxymethylcellulose, thickeners, dyes, defoamers, preservatives, water-proofing agents, lubricants, printability improvers, water-retaining agents, and other additives are used as diene copolymers. In this embodiment, a combined dispersion is added and mixed to form a uniform dispersion. The proportion of the pigment and the diene-based copolymer latex of the present invention can be appropriately determined depending on the purpose of use of the composition, but is preferably 3 to 30 parts by weight of the latex per 100 parts by weight of the pigment. The paper coating liquid can be applied to the base paper by an ordinary method using various blade coaters, roll coaters, air knife coaters, bar coaters and the like.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by these examples. In addition, each characteristic was calculated | required as follows. (1) Properties of copolymer latex (i) Particle size Light scattering particle size analyzer (Model 600 manufactured by C-Nwood Inc.)
According to 0), the average diameter of the copolymer latex particles was measured. (R) Gel Content (Toluene-Insoluble Content) A copolymer latex sample was adjusted to pH 8 and dried at 100 ° C. for 30 minutes to produce a film. Toluene (30
This dried film (0.5 g) was shaken for 3 hours, filtered through a 325-mesh wire gauze, and the solid content remaining on the wire gauze was dried to determine the weight% of the total solid content. .

(A) Stickiness resistance After applying a latex to a Mylar film using a No. 13 wire bar, the film is dried at 130 ° C. for 60 seconds. It is superimposed on black rasha paper and passed through a super calender at a temperature of 70 ° C. and a linear pressure of 20 kg / cm. The black rasha paper was peeled off from the Mylar film, and the transfer of the rasha paper fibers onto the latex film was visually observed. Evaluation is performed by a 10-point evaluation method.
The lower the metastasis, the higher the score. (2) Redispersibility After applying the latex to the Mylar film with a No. 18 wire bar, the film is dried at 90 ° C for 30 seconds. The obtained latex film was immersed in water at 30 ° C. for 30 seconds, taken out of the water, rubbed with a finger, and visually evaluated for the degree of redispersion. The evaluation was performed by a five-point evaluation method, and the higher the degree of re-dispersion, the higher the score.

(2) Evaluation of Paper Coating Performance (i) Pick Strength Using a RI printing tester (Meiji Seisakusho), a base paper (30 cm) was prepared by laying coated paper (1.5 cm × 20 cm) on the center part.
cm × 25.5 cm), printing ink (manufactured by
Product Name: SD Super Deluxe 50 Beni B (Tack 18
0.4 cc) was printed on a mount with a printing area of 25 cm × 21 cm, and overprinted on coated paper. The picking state that appeared on the rubber roll was backed by another mount, and the state was observed. The evaluation was performed by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

(B) Wet pick strength Using a RI printing tester (Akira Seisakusho Co., Ltd.), a backing paper (30 c
m × 25.5 cm) and water was supplied to the surface of the coated paper with a Molton roll. Immediately thereafter, 0.4 cc of printing ink (trade name: SD Super Deluxe 50 red B (manufactured by Toka Pigment Co., Ltd., Tack 15)) of 25 cm was added. Printing was performed once with a printing area of × 21 cm, and the picking condition that appeared on the rubber roll was backed up on another backing paper, and the condition was observed, and the condition was evaluated by a 10-point evaluation method. And

(A) Blister resistance Using a RI printing tester (Meiji Seisakusho), mount (30 cm)
X 25.5cm) coated paper (20cm x 20c)
m) and printing ink (Dainippon Ink Co., Ltd., trade name:
Webb Zett yellow) 0.3cc is 25cm x 21
The whole mount was printed with a printing area of cm. The coated paper printed on both sides under these conditions was cut into an appropriate size, and the test piece was immersed in a silicone oil thermostat adjusted to a predetermined temperature to observe whether blisters were generated. This test was performed by changing the temperature of the thermostat. The higher the blister generation temperature, the better the blister resistance.

[0046]

Example 1 3.0 parts by weight of an aqueous dispersion of seed particles having an average diameter of 0.035 μm (seed solid concentration: 35% by weight) were placed in a pressure-resistant reaction vessel equipped with a stirrer and a jacket for temperature control, and further added with water. 70 parts by weight, reactive emulsifier A
(Adecaria Soap (trademark) SE-1025N, manufactured by Asahi Denka Co., Ltd.) 1 part, the addition ratio of the first step to the composition (parts by weight) of itaconic acid in the first step monomers shown in Table 1 (% By weight), and the internal temperature was raised to 80 ° C.
Then, the number of parts obtained by multiplying the composition (parts by weight) of the monomer excluding itaconic acid and the chain transfer agent among the monomers for the first step polymerization shown in Table 1 by the addition ratio (% by weight) of the first step was mixed. The obtained monomer composition and an initiator-based aqueous solution comprising 15 parts by weight of water, 1 part by weight of sodium peroxodisulfate, 0.1 part by weight of sodium lauryl sulfate, and 0.2 part by weight of sodium hydroxide,
The addition was performed at a constant flow rate over 2 and 3 hours, respectively. One hour after the end of the addition of the monomer mixture for the first step, the composition (parts by weight) of the monomer for the second step shown in Table 1 is multiplied by the addition ratio (% by weight) of the second step. Was continuously added over 3 hours.
Then, the temperature was kept at 80 ° C. for 4 hours and then cooled. Then, sodium hydroxide was added to the resulting diene copolymer latex to adjust the pH to 8. Next, unreacted monomers were removed by steam stripping,
The mixture was filtered through a 0 mesh wire mesh. The diene-based copolymer latex was adjusted so that the solid content concentration finally became 50% by weight. The diene-based copolymer latex thus obtained is referred to as latex (a).

[0047]

Examples 2 to 7 Reactive emulsifiers shown in Table 1 (B: phosphate ester type reactive emulsifier, SDX-1055, manufactured by Asahi Denka Co., Ltd., C: Aqualon (trademark) HS-10, Daiichi Kogyo Pharmaceutical Co., Ltd., D: Aqualon (trademark) KH-10,
E: Eleminor (trademark) JS, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
-2, manufactured by Sanyo Chemical Co., Ltd.), a monomer component, and a chain transfer agent, and the same method as in Example 1 except that the addition time of the monomer composition was increased or decreased according to the addition ratio of each step. To obtain latexes (b) to (g).

[0048]

Comparative Examples 1 to 3 The same procedures as in Example 1 were carried out except that the addition time of the monomer composition was increased or decreased in accordance with the addition ratio of each step by using the emulsifier, monomer component and chain transfer agent shown in Table 1. Latexes (h) to (nu) were obtained in the same manner.

[0049]

[Table 1]

[0050]

Examples 8 to 14 Using the latexes (a) to (g), compositions for paper coating were prepared in the following proportions. (Blending formulation) Kaolin clay 70 parts by weight Calcium carbonate 30 parts by weight Sodium polyacrylate 0.2 parts by weight 0.1 parts by weight sodium hydroxide 2.5 parts by weight Phosphated starch 2.5 parts by weight Copolymer latex 12 parts by weight Water ( (Added so that the total solid content is 64%)

The kaolin clay is Ultra White 90 (manufactured by ENGELHARD), the calcium carbonate is Carbital 90 (manufactured by ECC), the sodium polyacrylate is Alon T-40 (manufactured by Toa Gosei), MS-46 is a phosphorylated starch.
00 (manufactured by Nippon Shokuhin Kako) was used. The obtained paper coating composition was coated on a base paper having a basis weight of 75 g / m ^{2 with} a double-sided blade so that the coating amount was 14 g / m ² on one side, to obtain a coated paper. Table 2 shows the results of the evaluation performed using this coated paper.

[0052]

Comparative Examples 4 to 6 Coated papers were obtained in the same manner as in Examples 8 to 14, except that (h) to (nu) were used as the latex. Table 2 shows the results of the evaluation performed using this coated paper.

[0053]

[Table 2]

As is clear from Table 2, the coated papers using the copolymer latexes (a) to (e) of the present invention as binders (Examples 8 to 12) all had a pick strength in the coated paper. It can be seen that the coated paper has excellent physical properties such as wet pick strength, and has excellent stickiness resistance and redispersibility which are indicators of the backing roll stain resistance in paper coating. In the case of the latex (f) in which the addition ratio in the first step was 30% by weight, the wet pick strength and the stickiness resistance were slightly inferior (Example 13).

In the case of the latex (g) in which the addition ratio in the first step is 70% by weight, the sticking resistance is slightly superior, but the pick strength is slightly inferior (Example 14). On the other hand, latexes (h) to (h) not using a reactive emulsifier are particularly inferior in wet pick strength, stickiness resistance and redispersibility, and slightly inferior in polymerization stability (Comparative Examples 4 to 6). .

[0056]

According to the present invention, coated paper properties such as pick strength, wet pick strength, and blister resistance of coated paper can be improved in a well-balanced manner. In addition, stickiness resistance and redispersibility, which are indicators of the backing roll stain resistance in paper coating, can be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 KA04 KA05 KA06 KA09 KA14 KA21 KB13 4J100 AB02R AB03R AB04R AB08R AB09R AB15R AB16R AJ01Q AJ02Q AJ08Q AJ09Q AL03R AL04R AL08R AL09R AL11R17P02 AS03A03 AS02A FA34 FA37 HA61 HC13 HC34 HD13 JA01 JA13 4L055 AG11 AG12 AG27 AG34 AG48 AG63 AG70 AG71 AG74 AG76 AG89 AH02 AH37 AH50 AJ04 BE07 BE08 EA30 EA32 FA11 FA13 FA19 GA19

Claims (7)

[Claims] 1. The method according to claim 1, wherein the first step is carried out in the presence of one or more reactive emulsifiers.
0% by weight, ethylenically unsaturated carboxylic acid monomer (b)
0.5 to 30% by weight, and a conjugated diene monomer (a)
And 20 to 89.5% by weight of another monomer (c) copolymerizable with the ethylenically unsaturated carboxylic acid monomer (b)
(However, (a) + (b) + (c) = 100% by weight), and the second step is a conjugated diene monomer (a) 30 to 80
Wt%, ethylenically unsaturated carboxylic acid monomer (b) 0
20% by weight, and 0 to 70% by weight of another monomer (c) copolymerizable with the conjugated diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b) (where (a) +
(B) + (c) = 100% by weight). A diene-based copolymer latex obtained by emulsion polymerization by a two-stage polymerization method. 2. The diene copolymer latex according to claim 1, wherein the reactive emulsifier has the following general formula (I). Embedded image (Wherein, R ¹ is hydrogen or a methyl group, and R ² is C ⁸ -C 5)
0 is a hydrocarbon group or an acyl group, A is an alkylene group having 2 to 4 carbon atoms, m is an integer of 0 to 50, n is an integer of 0 to 50, M is a hydrogen atom, an alkali metal, an alkaline earth metal,
Ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms. ) 3. The diene copolymer latex according to claim 1, wherein the reactive emulsifier has the following general formula (II). Embedded image Wherein A is an alkylene group having 2 to 4 carbon atoms, k is an integer of 1 or 2, l is an integer of 1 to 50, m is an integer of 0 to 50, n is an integer of 1 or 2, X is hydrogen Atom, alkali metal, alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms.) 4. The reactive emulsifier according to the following general formula (III)
The diene copolymer latex according to claim 1, wherein Embedded image (Wherein, R ¹ represents an alkyl group, an alkenyl group, or an aralkyl group having 6 to 18 carbon atoms, and R ² represents hydrogen or 6 to 18 carbon atoms.
18 alkyl groups, alkenyl groups or aralkyl groups,
R ³ is hydrogen or a propenyl group, A is an alkylene group having 2 to 4 carbon atoms, n is an integer of 1 to 200, M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxy having 1 to 4 carbon atoms. Alkylammonium. ) 5. The diene copolymer latex according to claim 1, wherein the reactive emulsifier has the following general formula (IV). Embedded image (Wherein, A is an alkylene group having 2 to 4 carbon atoms, and m is 0 to 1)
An integer of 00, n is an integer of 0 to 100, and M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms. ) 6. The reactive emulsifier according to the following general formula (V):
2. The method according to claim 1, wherein (VI), (VII), and (VIII).
The diene copolymer latex according to the above. Embedded image (In the above formula, R ¹ is hydrogen or a methyl group, R ² is a hydrocarbon or a hydrocarbon group having a substituent or an organic group containing an oxyalkylene group, A is an alkylene group having 2 to 4 carbon atoms or a substituted alkylene. A group, n represents 0 or an integer, and M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or hydroxyalkylammonium having 1 to 4 carbon atoms.) 7. A paper coating composition comprising the diene copolymer latex according to claim 1.