JP2011225631A - Copolymer latex composition, paper-enameling composition, and enamel paper - Google Patents

Abstract

Copolymer radex composition which improves pick strength and wet pick strength of coated paper when used for coated paper and has excellent disintegration in the process of reusing coated paper Offer things.
SOLUTION: (a) (a) Conjugated diene monomer 30 to 60% by mass, (b) Ethylene unsaturated carboxylic acid monomer 0.5 to 7% by mass, (c) Other copolymerizable Copolymer obtained by emulsion polymerization of a monomer mixture comprising 33 to 69.5% by mass of a monomer (provided that the total amount of (a), (b), and (c) is 100% by mass). Including 100 parts by weight of polymer latex (in terms of solid content), (b) 0.003 to 0.1 parts by weight of a halocyanoacetamide compound, and (c) 0.01 to 0.8 parts by weight of an alcohol compound. A copolymer latex composition.
[Selection figure] None

Description

  The present invention relates to a copolymer latex used for pigment binders for coated paper, carpet backing agents, adhesives, pressure-sensitive adhesives, fiber binders, paints, and the like. Of these, it particularly relates to a copolymer latex suitably used as a pigment binder for coated paper. More specifically, the present invention relates to a copolymer latex excellent in adhesive strength (pick strength and wet pick strength) and disaggregation property of coated paper.

  Copolymer latexes are used in a wide range of applications such as pigment binders for paper coating, various adhesives and pressure-sensitive adhesives, fiber-binding binders such as nonwoven fabrics and artificial leather, and paints. Copolymer latex used for these applications is required to have excellent adhesion to substrates and pigments to be blended.

  Coated paper, for example, for the purpose of improving the printability of paper and improving the optical properties such as gloss, pigments such as kaolin clay, calcium carbonate, satin white, talc, titanium oxide, etc. A paper coating composition (paper coating agent) comprising a copolymer latex as a binder and a water-soluble polymer (starch, polyvinyl alcohol, carboxymethyl cellulose, etc.) as a viscosity modifier or an auxiliary binder as preferred main constituents ) Is formed by coating. It is known that the properties of the copolymer latex used as a pigment binder have a great influence on the surface strength and print quality of coated paper using this, and the disintegration of the coated paper.

  Here, as the copolymer latex as the binder, a styrene-butadiene copolymer latex formed by emulsion polymerization using styrene and butadiene as main monomer components, so-called SB latex has been conventionally used.

  In recent years, printing speeds and sophistication have progressed, and the required level for coated paper and pigment binders has become increasingly sophisticated. In particular, resistance to destruction of the paper surface due to ink tack, so-called dry pick strength improvement, and wet pick that is ink pick resistance when water is applied, which is important when printing in the presence of dampening water. There is a need for improved strength. Furthermore, in order to reduce the production cost of the coated paper, an improvement in the adhesive strength of the latex is also desired in order to reduce the usage rate of the latex, which is a relatively expensive raw material.

  In addition, it is required to reuse the coated paper for the purpose of dealing with environmental problems and suppressing production costs. For this reason, there is an increasing demand for disaggregation property that the coating component of the coated paper is easy to be detached and dispersed from the pulp of the base paper. Furthermore, it is known that the resistance to soiling of the roll for drying in the paper making process correlates with the disaggregation property, and the improvement of the disaggregation property is desired from the viewpoint of operability.

  Under such circumstances, Patent Document 1 (Japanese Patent Laid-Open No. 10-007706) describes a copolymer having an alkylbenzene sulfonate and an alkyl diphenyl ether disulfonate as emulsifiers, and having a number average particle diameter of 100 nm or less. A method of obtaining high pick strength by obtaining latex has been proposed.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 07-316212) describes the amount of water used in the first and second stages in the emulsion polymerization of a monomer having a specific composition in the presence of α-methylstyrene dimer. Has been proposed to improve the pick strength and the wet pick strength by setting the number average particle size within a range of 60 to 160 nm by setting the value to a certain range.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-144058) proposes a method of improving pick strength by emulsion polymerization of a monomer having a specific composition in the presence of α-methylstyrene dimer.

  In Patent Document 4 (Japanese Patent Application Laid-Open No. 11-012979), excellent pick strength and disaggregation properties are obtained by using cationized starch whose viscosity has been lowered to a specific viscosity by enzyme modification as a paper strength enhancer. A method for improving the above has been proposed.

  However, in the method described in Patent Document 1, since the amount of alkylbenzene sulfonate used is relatively large, the water resistance decreases, and good wet pick strength may not be obtained.

  In the method described in Patent Document 2, there is still room for improvement from the viewpoint of disaggregation.

  Further, the method described in Patent Document 3 still has room for improvement from the viewpoint of wet pick strength or disaggregation.

  In the method described in Patent Document 4, there is still room for improvement from the viewpoint of wet pick strength.

Japanese Patent Laid-Open No. 10-007706 JP 07-316212 A JP 2008-144058 A Japanese Patent Laid-Open No. 11-012979

  The present invention can improve the pick strength and wet pick strength of coated paper from the above situation, and is a copolymer latex excellent in disintegration in the process of reusing waste paper of coated paper. It is an issue to provide.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that a copolymer latex composition comprising a copolymer latex having a specific composition and a specific amount of a halocyanoacetamide compound and an alcohol compound. Has found that the above-mentioned problems can be solved, and further research has been made to complete the present invention.

That is, the present invention is as follows.
[1] (A) (a) 30-60% by mass of conjugated diene monomer, (b) 0.5-7% by mass of ethylenically unsaturated carboxylic acid monomer, and (c) other copolymerizable Obtained by emulsion polymerization of a monomer mixture comprising 33 to 69.5% by mass of a monomer (provided that the total amount of (a), (b), and (c) is 100% by mass). 100 parts by mass of copolymer latex (in terms of solid content), (b) halocyanoacetamide compound: 0.003 to 0.1 part by mass, and (c) 0.01 to 0.8 part by mass of alcohol compound. A copolymer latex composition comprising.
[2] The copolymer latex composition according to the above [1], wherein the component (b) is 2,2-dibromo-3-nitrilopropionamide.
[3] The copolymer latex composition according to the above [1] or [2], wherein the component (c) is one or more compounds selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol. object.
[4] The copolymer latex composition according to any one of [1] to [3], wherein the emulsion polymerization is performed during the emulsion polymerization.
[5] A paper coating composition comprising the copolymer latex composition according to any one of [1] to [4].
[6] A coated paper produced using the paper coating composition described in [5] above.

  According to the copolymer latex composition of the present invention, it is possible to provide a copolymer latex that improves the pick strength, wet pick strength and disaggregation properties of coated paper.

  That is, when the copolymer latex is produced, the composition of the raw material monomer is limited to a specific range, and the copolymer latex and a copolymer comprising a specific amount of a halocyanoacetamide compound and an alcohol compound are included. It is the essence of the present invention that it is a polymer latex composition.

  Moreover, according to the paper coating composition and the coated paper of the present invention, the pick strength, wet pick strength and disaggregation property of the coated paper can be remarkably improved.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described. However, the present invention is not limited to the following embodiments, and is based on ordinary knowledge of a person skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

The copolymer latex composition of the present invention comprises (a) (a) 30 to 60% by mass of a conjugated diene monomer, (b) 0.5 to 7% by mass of an ethylenically unsaturated carboxylic acid monomer, and (C) Emulsion polymerization of a monomer mixture composed of 33 to 69.5% by mass of other copolymerizable monomers (however, the total amount of (a), (b), and (c) is 100% by mass) Copolymer latex 100 parts by mass (in terms of solid content), (b) halocyanoacetamide compound: 0.003 to 0.1 part by mass, and (c) alcohol compound 0.01 to 0.8. It is a copolymer latex composition comprising parts by weight. Hereinafter, these will be sequentially described.
Copolymer latex (I)

The copolymer latex (a) constituting the copolymer latex composition of the present invention comprises (a) 30 to 60% by mass of a conjugated diene monomer and (b) an ethylenically unsaturated carboxylic acid monomer. 5 to 7% by mass, and other copolymerizable monomers 33 to 69.5% by mass (however, the total amount of (a), (b), and (c) is 100 parts by mass) Obtained by emulsion polymerization of the body mixture.
Conjugated diene monomer (a)

  The conjugated diene monomer (a), which is an essential component of the copolymer latex (a), is an effective component for imparting flexibility to the copolymer and providing pick strength and impact absorption. When all the monomers constituting the coalescence (that is, the total of the monomers (a), (b) and (c)) are 100% by mass, 30 to 60% by mass, preferably 35 to 55% by mass, More preferably, it is used in a proportion of 38 to 53% by mass. When used in a proportion within this range, the copolymer latex exhibits excellent pick strength and excellent wet-stickiness resistance. Preferable examples of the conjugated diene monomer (a) to be used include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene and the like, and these are one kind alone or two kinds. The above is used in combination.

Ethylenically unsaturated carboxylic acid monomer (b)
The ethylenically unsaturated carboxylic acid monomer (b) is an essential component for improving the pick strength of the coated paper and ensuring the dispersion stability of the copolymer latex. When the total amount of the constituent monomers (that is, the sum of the monomers (a), (b), and (c)) is 100% by mass, 0.5 to 7% by mass, preferably 1 to 5% by mass Most preferably, it is used in a proportion of 1.5 to 4.5% by mass. By using the ethylenically unsaturated carboxylic acid monomer in this ratio, the required dispersion stability was imparted to the copolymer latex, and the viscosity of the copolymer latex was optimized, which hindered handling. Not. Preferable examples of the ethylenically unsaturated carboxylic acid monomer (b) include monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Two or more types are used in combination.

Other copolymerizable monomers (c)
Moreover, the other monomer (c) copolymerizable with the said (a)-(b) monomer is included as another raw material. Various properties can be imparted to the copolymer latex by appropriately selecting the monomer (c). Preferred examples of the other copolymerizable monomer (c) include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and p-methylstyrene, methyl acrylate, ethyl acrylate, and acrylic. Alkyl acrylates such as butyl acid and 2-ethylhexyl acrylate, alkyl methacrylates such as methyl methacrylate and butyl methacrylate, and hydroxyalkyl esters such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate Aminoalkyl esters such as aminoethyl acrylate, dimethylaminoethyl acrylate and diethylaminoethyl acrylate, pyridines such as 2-vinylpyridine and 4-vinylpyridine, glycidyl acrylate and glycidyl methacrylate. Gills, acrylamide, methacrylamide, N-methylolacrylamide, N-methylacrylamide, N-methylmethacrylamide, glycidylmethacrylamide, amides such as N, N-butoxymethylacrylamide, vinyl acetates such as vinyl acetate , Vinyl halides such as vinyl chloride, p-styrenesulfonic acid and its sodium salt, and the like. These may be used alone or in combination of two or more.

  In emulsion polymerization of the copolymer latex (a), it is preferable that the polymerization temperature includes a step of lowering the polymerization temperature during the polymerization. The temperature decrease referred to here indicates that the polymerization temperature has dropped by 0.1 ° C. or more in an arbitrary 20 minutes. Preferably, in the present invention, the rate of temperature decrease during the temperature decrease is in the range of 1 to 10 ° C./hr. More preferably, the rate of descent is in the range of 2-5 ° C./hr, most preferably in the range of 2.5-4 ° C./hr. By setting the rate of decrease in the polymerization temperature within this range, a copolymer latex with better pick strength and mechanical stability can be obtained, and temperature control may be difficult even in large-scale actual equipment considering mass production. Absent.

In the emulsion polymerization of the copolymer latex (i), an emulsifier, a radical initiator, a chain transfer agent, various polymerization regulators and the like can be appropriately blended in addition to the above components.
As such an emulsifier, an anionic, cationic, amphoteric or nonionic surfactant, or a reactive emulsifier can be used.
These can be used alone or in combination of two or more.

  Examples of preferable surfactants include, for example, anionic surfactants such as aliphatic soaps, rosin acid soaps, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates; polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers And nonionic surfactants such as polyoxyethyleneoxypropylene block copolymers.

Examples of the emulsifying dispersant for emulsifying and dispersing include water-soluble polymers such as polyvinyl alcohol, nonionic surfactants, anionic surfactants, cationic surfactants, other surfactants, and amphoteric surfactants. Is mentioned.
Such various dispersions that can be emulsified and dispersed can be used singly or in combination.

  A radical initiator is one that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing agent. In the present invention, either an inorganic initiator or an organic initiator may be used. Is possible. Preferable examples include peroxodisulfate, peroxide, azobis compound, etc., specifically potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide 2,2-azobisbutyronitrile, cumene hydroperoxide, and the like. These may be used alone or in combination of two or more. A so-called redox polymerization method using a reducing agent such as acidic sodium sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof, or Rongalite in combination with a polymerization initiator can also be used.

  In producing the copolymer latex (a), it is possible to use a known chain transfer agent or polymerization retarder usually used in radical polymerization. Preferred examples of chain transfer agents and polymerization retarders include α-methylstyrene dimer, n-butyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, and n-lauryl mercaptan, which are dimers of nucleus-substituted α-methylstyrene. And mercaptans such as t-dodecyl mercaptan, disulfides such as tetramethylthuradium disulfide and tetraethylthuradium disulfide, halogenated derivatives such as carbon tetrachloride and carbon tetrabromide, and 2-ethylhexylthioglycolate. These can be used alone or in combination of two or more.

  The polymerization temperature for producing the copolymer latex (a) is usually in the range of 40 to 100 ° C., but the production efficiency and quality such as pick strength of the coated paper using the resulting copolymer latex. From the above viewpoint, the polymerization temperature at the start of the polymerization is preferably in the range of 55 to 85 ° C, more preferably 60 to 80 ° C, still more preferably in the range of 70 to 80 ° C.

  The polymerization solid content concentration in the case of producing the copolymer latex (i) is preferably 35 to 60% by mass, more preferably 40 to 50% from the viewpoints of production efficiency and particle size control during emulsion polymerization. % By mass. The solid content concentration here refers to the ratio of the solid mass obtained by drying the copolymer latex to the mass of the copolymer latex before drying.

  In the production of the copolymer latex (a), a known seed polymerization method can be used to adjust the particle diameter, and after the seed is prepared, the copolymer latex is polymerized in the same reaction system. A method such as a seed method or an external seed method using a separately prepared seed can be appropriately selected and used.

  The toluene-insoluble content of the copolymer latex (a) is preferably in the range of 80 to 96% by mass, more preferably in the range of 85 to 95% by mass, and most preferably in the range of 89 to 93% by mass. It is in. By making the amount of the toluene insolubles within these ranges, the wet-sticking resistance of the copolymer latex is further improved, and it is possible to avoid problems of roll dirt such as backing roll dirt, and excellent pick strength and wet pick strength. Thus, it becomes possible to achieve the printing gloss more remarkably. The toluene-insoluble content of the copolymer latex can be adjusted by adjusting the amount of chain transfer agent used during the polymerization reaction. As a method for adding the chain transfer agent into the polymerization system, any of batch addition, batch addition, and continuous addition may be used, or these may be combined.

  Moreover, it is preferable that the particle diameter of the said copolymer latex (I) is 60-130 nm. The particle diameter is more preferably 70 to 110 nm, and most preferably 80 to 100 nm. By setting the particle diameter within this range, the viscosity of the copolymer latex can be adjusted to a suitable range, and the workability can be prevented from being lowered. By setting the particle diameter within this range, it is possible to achieve further excellent pick strength and wet pick strength.

  For the copolymer latex (a), various known polymerization regulators can be used as necessary. These are, for example, pH adjusters and chelating agents, and preferred examples of pH adjusting agents include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate and disodium hydrogen phosphate. Preferable examples include sodium ethylenediaminetetraacetate.

  There is no restriction | limiting in particular also about solid content concentration as final product of copolymer latex (i), This solid content concentration is normally prepared by diluting or concentrating in the range of 30-60 mass%.

Halocyanoacetamide compounds (b)
The halocyanoacetamide-based compound (b) is an essential component for ensuring improved disintegration of the coated paper, and is 0.003 to 100 parts by mass (in terms of solid content) of the copolymer latex (i). It is used in a proportion of 0.1 parts by mass, preferably 0.005 to 0.08 parts by mass, and most preferably 0.01 to 0.06 parts by mass. By using the halocyanoacetamide-based compound (b) at this ratio, the copolymer latex exhibits excellent disaggregation and also exhibits excellent wet tack resistance. The halocyanoacetamide compound (b) is preferably a carboxylic acid amide compound having at least one halogeno group and at least one cyano group, and preferred examples thereof include 2,2-dibromo-3-nitrilopropion. Amide, 2-chloro-3-nitrilopropionamide, 2-bromo-3-nitrilopropionamide, 2,2-dichloro-3-nitrilopropionamide, N-methyl-2,2-dibromo-3-nitrilopropionamide Among them, 2,2-dibromo-3-nitrilopropionamide is most preferable.

Alcohol compounds (C)
The alcohol-based compound (C) is an essential component for ensuring improvement in pick strength of the coated paper, and is 0.01 to 0.00% relative to 100 parts by mass (in terms of solid content) of the copolymer latex (I). 8 parts by mass, preferably 0.03 to 0.6 parts by mass, most preferably 0.05 to 0.4 parts by mass. By using the alcohol compound (c) at this ratio, the copolymer latex exhibits excellent pick strength and excellent wet stickiness resistance. The alcohol compound (c) is preferably a hydrocarbon compound having at least one hydroxy group, and preferred examples thereof include alcohols such as isopropyl alcohol and benzyl alcohol, ethylene glycol, propylene glycol, diethylene glycol and dipropylene. Examples include glycols such as glycol, tetramethylene glycol, and polypropylene glycol. Among them, ethylene glycol, propylene glycol, and diethylene glycol are most preferable. Each of these may be used alone or in combination of two or more.

Copolymer Latex Composition The copolymer latex composition of the present invention comprises the above-described copolymer latex (i), halocyanoacetamide compound (b), and alcohol compound (c) in the above-mentioned proportions. It is a thing. Therefore, the said composition may be comprised only by said (I), (B), and (C), and may contain the other component.

  In the copolymer latex composition of the present invention, various additives can be added as necessary, or other latexes can be mixed and used as long as the effect is not greatly impaired. It is possible to add antifoaming agents, anti-aging agents, water-proofing agents, bactericides, printing suitability improvers, lubricants, and the like, and alkali-sensitive latex or organic pigments can also be mixed and used.

Next, a method using the copolymer latex composition of the present invention will be described.
First, the case where the copolymer latex composition of the present invention is used as a binder for coated paper will be described. In such a case, a paper coating composition is first prepared. The composition for paper coating can be produced in a conventional manner. That is, for example, pigments selected from inorganic pigments such as kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white and talc, and organic pigments known as plastic pigments and binder pigments in water in which a dispersant is dissolved. , Starch, casein, polyvinyl alcohol, carboxymethylcellulose, and the like, and thickeners, dyes, antifoaming agents, preservatives, water resistance agents, lubricants, printability improvers, pH adjusters, and water retention agents A copolymer latex composition is added and mixed together with various additives selected from the above to obtain a uniform dispersion (composition for paper coating).

  The use ratio of the pigment and the copolymer latex composition can be appropriately determined depending on the purpose of use of the paper coating composition, but the copolymer latex composition is 3 to 30 parts by mass with respect to 100 parts by mass of the pigment. It is preferable to use (in terms of solid content). The composition for paper coating can be applied to the base paper by a usual method using various blade coaters, roll coaters, air knife coaters, bar coaters, etc. In such coating, a blade coater is used. It is preferable. The coating form can also be applied to one side or both front and back sides of the base paper, and the number of times of coating per side is one, and the coating process is performed twice. It can also be used for so-called double coating. In this case, the copolymer latex composition of the present invention can be used for both the undercoat paper coating composition and the topcoat paper coating composition.

  In addition, the above-mentioned composition for paper coating can be coated on the surface of the coating base paper to obtain a coated paper for printing or a coated paper board for printing. This printing coated paper or printing coated paperboard includes various types of printing paper such as offset sheet-fed printing paper, offset rotary printing paper, gravure printing paper, flexographic printing paper and letterpress printing paper, and various printing paperboards. Is preferably used.

  The copolymer latex composition of the present invention can be used for adhesives and various paints in addition to paper coating agents and carpet backing agents.

Next, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.
Each physical property was evaluated by the following method.
Evaluation (1) Physical properties of coated paper (pick strength)
Using an RI printing tester (Meiji Seisakusho), 0.4 cc of printing ink (SD Super Deluxe 50 Red B; Tack 18) manufactured by T & K Toka Co., Ltd. was overprinted on the coated paper sample, and picking appeared on the rubber roll. The state was backed on another mount and the state was observed.

The evaluation was a relative 10-point evaluation method, and the higher the score, the smaller the picking phenomenon.
Evaluation (2) Physical properties of coated paper (wet pick strength)
Water was applied to the coated paper surface with a sleeve roll using an RI printing tester (Meiji Seisakusho), and immediately after that printing ink (SD Super Deluxe 50 Crimson B; Tack 15 manufactured by T & K Toka Co., Ltd.) 0.4 cc was printed once. Then, the picking state appearing on the rubber roll was backed on another mount and the state was observed.

The evaluation was a relative 10-point evaluation method, and the higher the score, the smaller the picking phenomenon.
Evaluation (3) Physical properties of coated paper (disaggregation)
20 g of coated paper piece split into 3 cm ² was placed in 980 g of water and stirred at 3000 rpm using a stirrer (ROBOMICS manufactured by Primics Co.), and the time until the paper piece completely disaggregated was measured.

The evaluation was a relative 10-point evaluation method, and the shorter the time until disaggregation, the higher the score.
From the description in Tables 1 to 4, when the copolymer latex of the present embodiment was used, the pick strength, wet pick strength, and disaggregation property of the coated paper were all at high levels.

[Example 1]
Preparation of copolymer latex composition 15% by mass of the initial raw material for polymerization shown in Table 1 and the mixture of the monomer and chain transfer agent described in the first step was pressure-resistant with a stirrer and a temperature control jacket attached. The reaction vessel was placed and the internal temperature was adjusted to 78 ° C.
Thereafter, 0.8 part by mass of sodium peroxodisulfate was added to initiate polymerization. 15 minutes later, the remaining 85% by mass of the monomer and chain transfer agent mixture described in the first step was added to the reactor over 3 hours, and after 30 minutes from the addition of sodium peroxodisulfate, Table 1 Was added at a constant rate until the end of the first step.

  Simultaneously with the completion of the first step, the monomer and chain transfer agent described in the second step shown in Table 1 were continuously added over 2 hours.

From the start of continuous addition of the monomer and chain transfer agent mixture for the second polymerization step, the polymerization temperature, that is, the internal temperature of the pressure-resistant reactor is started at a rate of 2.9 ° C / hr, and the polymerization temperature is 70 ° C. When it became, temperature reduction was finished. Moreover, 15 mass% aqueous solution using itaconic acid shown in Table 1 was continuously added at a constant rate over 1 hour after 30 minutes from the start of the second step.
The temperature was raised to 95 ° C. over 1 hour after the addition of the monomer was completed, and then maintained at 95 ° C. for 40 minutes to obtain a copolymer latex.
The obtained latex was filtered through a 200-mesh wire mesh, and the pH was adjusted to 7.5 by adding an aqueous sodium hydroxide solution to the copolymer latex.

Unreacted monomer was removed by a steam stripping method, and after further concentration, an aqueous sodium hydroxide solution was added. The amount of 2,2-dibromo-3-nitrilopropionamide and ethylene listed in Table 1 was added to this copolymer latex. After the addition of glycol, the solid content was finally adjusted to 50% and pH 8.
The obtained copolymer latex composition was designated as latex composition A. From this, the coated paper was prepared by the method described in the preparation of coated paper described below, and the physical properties of the coated paper were evaluated.

[Examples 2-7] Polymerization was carried out in the same manner as in Example 1 with the blending amounts described in Table 1, and latex composition B by adding halocyanoacetamide compounds and alcohol compounds described in Table 1; C, D, E, F, G were obtained. In Example 4, the polymerization temperature was not lowered.
The coated paper physical properties were evaluated and listed in Table 3.

[Comparative Examples 1-7] Polymerization was carried out in the same manner as in Example 1 except for the matters described in Table 2 (blending amount and rate of decrease in polymerization temperature), and latex compositions H, I, J, K, L , M, N were obtained.
The physical properties of the coated paper were evaluated and listed in Table 4.

Preparation of coated paper First, a master color was prepared with the following constituent materials excluding copolymer latex.

Fine kaolin clay: 50 parts by weight Coarse grain kaolin clay: 10 parts by weight Heavy calcium carbonate (fine particles): 30 parts by weight Heavy calcium carbonate (coarse particles): 10 parts by weight Sodium polyacrylate: 0.2 parts by weight Hydroxylation Sodium: 0.1 parts by mass Phosphate esterified starch: 2.5 parts by mass Water (added so that the total solid content of the coating liquid is 68% by mass)
The fine kaolin clay is Hydra Gloss 90 (US, manufactured by JM HUBER; the ratio of particle diameter is 2 μm or less = 96 mass% or more), and the coarse kaolin clay is Hydra Sparse (US, JM). Manufactured by HUBER; ratio of particle size of 2 μm or less = 80 to 82% by mass), as fine heavy calcium carbonate, Carbital 97 (manufactured by Imeris Minerals Japan; ratio of particle size of 2 μm or less = 97% by mass or more), The coarse heavy calcium carbonate is Carbital 75 (Imeris Minerals Japan Co., Ltd .; the ratio of particle size 2 μm or less = 75 mass%), and the sodium polyacrylate is Aron T-40 (Toagosei Co., Ltd.) and phosphoric acid. MS-4600 (manufactured by Nippon Food Processing Co., Ltd.) was used as the esterified starch.

The master color was filtered through a metal mesh having an opening of 50 μm, and then subdivided, and each master color was prepared in the preparation of the copolymer latex composition at a ratio of 10 parts by mass per 100 parts by mass of the pigment. One of the copolymer latexes A to N (selected according to Table 3 or 4) and water were added and mixed so that the final solid content was 64% by mass to obtain a coating color.
Next, the coating color was coated on a coated base paper having a basis weight of 74 g / m ^{2 with} a blade coater so that the coating amount was 13 g / m ² on one side, and dried.
Thereafter, super calendering was performed at a roll temperature of 50 ° C. and a linear pressure of 147000 N / m to obtain coated paper.
The obtained coated paper was used for a printing test (the above evaluations (1) to (3)).

  The copolymer latex obtained by the present invention is preferably used for pigment binders, carpet backing agents, adhesives, fiber binders and paints in paper coating.

  Furthermore, since the copolymer latex obtained in the present invention can provide a coated paper having high pick strength, wet pick strength, and disaggregation property, it is preferably used in the field of coated paper for printing.

Claims (6)

(A) (a) 30-60% by mass of conjugated diene monomer, (b) 0.5-7% by mass of ethylenically unsaturated carboxylic acid monomer, and (c) other copolymerizable monomers Copolymer latex obtained by emulsion polymerization of a monomer mixture comprising 33 to 69.5% by mass of the product (provided that the total amount of (a), (b) and (c) is 100% by mass) 100 parts by mass (in terms of solid content)
(B) 0.003 to 0.1 parts by mass of a halocyanoacetamide compound, and (c) 0.01 to 0.8 parts by mass of an alcohol compound,
A copolymer latex composition comprising:   The copolymer latex composition according to claim 1, wherein the component (b) is 2,2-dibromo-3-nitrilopropionamide.   The copolymer latex composition according to claim 1 or 2, wherein the component (c) is one or more compounds selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.   The copolymer latex composition according to any one of claims 1 to 3, wherein the emulsion polymerization is performed at a temperature lowering during the emulsion polymerization.   A paper coating composition comprising the copolymer latex composition according to any one of claims 1 to 4.   Coated paper produced using the paper coating composition according to claim 5.