JPH06248031A - Copolymer latex - Google Patents

Abstract

PURPOSE:To obtain a copolymer latex, excellent in chemical and mechanical stability and suitable as a composition for coating paper, especially excellent in adhesive strength, etc. CONSTITUTION:This copolymer latex is obtained by carrying out the emulsion copolymerization of (A) 100 pts.wt. monomers composed of (a) 10-65wt.% conjugated diene-based compound, (b) 0-70wt.% aromatic vinyl compound, (c) 0-10wt.% ethylenically unsaturated carboxylic acid and (d) 0-70wt.% other copolymerizable monomers in the presence of >=0.001 to <10 pts.wt. starch. The copolymer latex has >=300 to <2,000Angstrom average particle diameter of the copolymer particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copolymer latex obtained by emulsion polymerization of a specific monomer in the presence of a specific amount of starch. Excellent in chemical and mechanical stability and adhesive strength,
The present invention relates to a copolymer latex useful as a binder for a paper coating composition for paperboard or gate roll coating.

[0002]

BACKGROUND OF THE INVENTION Starch is widely used as a water-soluble binder for a paper coating composition together with a synthetic binder because it is inexpensive and imparts high rigidity to a coating layer. Since it was inferior and non-thermoplastic, there was a problem that it was inferior in smoothness in calendering and in developing glossiness of white paper (Soichi Muroi, "Paper coating", application of polymer latex, P64-78, 1886, high) Published by Molecular Publishing Association).

Starch is used as a protective colloid in emulsion polymerization, and a monomer that can be polymerized by using a general polymerization catalyst such as ceric ammonium nitrate, persulfate and hydrogen peroxide as a catalyst is used. It is a known fact that a grafted starch is produced when polymerized in the presence of
However, these techniques can be achieved only with a specific starch and a specific monomer composition, and further, they do not cause precipitation or separation of particles, which is required for, for example, a paper coating composition, and the chemical composition is No latex which is physically and mechanically stable has been obtained.

On the other hand, in recent years, with the rapid increase in printed matter, the tendency toward high-speed printing, especially in offset printing, has been strengthened, and plain printing,
In both offset printing, there is an increasing demand for a stable latex that is excellent in adhesive strength and has a good quality balance and is free from coagulation.

In general, emulsion polymerization of copolymer latex is
It is carried out using a surfactant such as rosin acid soap as an emulsifier, but the surfactant remains in the copolymer latex, which adversely affects the physical properties.

For example, when a copolymer latex is used as a binder for a paper coating composition, a low molecular weight compound such as a surfactant is deposited on the surface of the coating layer after migration, resulting in the coated paper. To lower the physical properties,
Foaming occurs during coating. Further, if the amount of the surfactant used is limited to improve these problems, there is a problem that the stability of the latex decreases.

[0007]

The present invention has been made against the background of the above-mentioned problems of the prior art, and is a composition for paper coating which is excellent in chemical and mechanical stability, and particularly in adhesive strength. The purpose of the present invention is to provide a copolymer latex suitable for.

[0008]

Means for Solving the Problems To solve the above problems, the copolymer latex of the present invention comprises: (a) a conjugated diene compound of 10 to 65% by weight (b) an aromatic vinyl compound of 0 to 70% by weight ( c) Ethylenically unsaturated carboxylic acid 0 to 10 wt% (d) Other copolymerizable monomer 0 to 70 wt% Monomer (A) 100 parts by weight 0.001 parts by weight or more 10 parts by weight It is obtained by emulsion polymerization in the presence of less than part of starch, and is characterized in that the average particle size of the copolymer particles is 300 angstroms or more and less than 2,000 angstroms.

The emulsion polymerization is preferably carried out in the presence of 0.01 to 20 parts by weight of a chain transfer agent having no mercapto group and / or halogen atom as a substituent.

(Structure) The present invention will be described in detail below.

Representative examples of the conjugated diene compound which is the component (a) used in the production of the copolymer latex of the present invention include butadiene, isoprene, sulfonated isoprene and 2-chloro-1,3-butadiene. Can be mentioned. The proportion of the component (a) used should be in the range of 10 to 65% by weight based on the total amount of the monomers, in order to impart appropriate elasticity and hardness of the film to the copolymer. 20-55% by weight, more preferably 25-50
% By weight. When the proportion of component (a) used is less than 10% by weight, the copolymer obtained is hard and brittle, while 65% by weight
If it exceeds the range, it becomes too soft and the water resistance is lowered, and the tackiness is increased, so that the drum of the dryer is contaminated and the operability is lowered.

Typical examples of the aromatic vinyl compound as the component (b) include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, 2-vinylpyridine,
4-vinyl pyridine etc. can be mentioned. The proportion of component (b) used is 0 to 70% by weight, preferably 0.
-60% by weight. If the proportion of the component (b) used exceeds 70% by weight, the polymerization stability is lowered and the coating workability is lowered.

In the present invention, the use of the ethylenically unsaturated carboxylic acid as the component (c) in the production of the copolymer latex makes it possible to obtain a copolymer having excellent adhesive strength and mechanical stability. Examples of the ethylenically unsaturated carboxylic acid include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid. Furthermore, dicarboxylic acid anhydrides can also be used. The proportion of component (c) used is 0
It is 10% by weight, preferably 0.1 to 10% by weight, particularly preferably 1 to 7% by weight. Use ratio of component (c) is 1
If it exceeds 0% by weight, the viscosity of the latex becomes too high and handling becomes difficult.

Other copolymerizable monomers which are the component (d) used in the production of the copolymer latex of the present invention include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate and butyl methacrylate. Ethylenically unsaturated carboxylic acid esters such as alkyl acrylates and alkyl methacrylates; Vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; Acrylamide, methacrylamide, N-methylol acrylamide, diacetone acrylamide, crotonamide, itaconamide, methyl Itacone amide, maleic acid monoamide, methylene diacrylamide, dimethyl acrylamide, diethyl acrylamide, dimethyl methacrylamide, diethyl meth Amide vinyl compounds such as dialkyl (meth) acrylamides such as acrylamide; 2-
Hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2,3,3
4,5,6-pentahydroxyhexyl acrylate,
Vinyl compounds containing hydroxyl groups such as 2,3,4,5,6-pentahydroxyhexyl methacrylate, 2,3,4,5-tetrahydroxypentyl acrylate and 2,3,4,5-tetrahydroxypentyl methacrylate; Chlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxyethyltrimethoxysilane, γ- Examples thereof include copolymerizable silicon-containing compounds such as (meth) acryloxyethyltriethoxysilane. Furthermore, (d)
Divinylbenzene, diallylbenzene, divinylsulfone, N, N'-methylenebisacrylamide, 2,2-bisacrylamidoacetic acid, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate as components , 1,3-divinyltetramethyldisiloxane, bis (2-methylallyl) carbonate, ethylene oxide-modified bisphenol A di (meth) acrylate, and other bifunctional monomers.
The components (d) may be used alone or in combination of two or more. The use ratio of the component (d) is 0 to 7
It is 0% by weight, preferably 1 to 50% by weight. When the proportion of the component (d) used exceeds 70% by weight, the viscosity of the composition becomes too high and the operability is lowered, which is not preferable.

The starch used in the present invention includes, for example, starch from potato, tapioca, wheat, rice, corn, sweet potato and the like, and starch of potato, tapioca and corn is particularly preferable. Starch is decomposed by acid hydrolysis, enzymatic decomposition or oxidative hydrolysis into processed starch. The starch used in the present invention also includes modified starch. Examples of such processed starch include roasted dextrin, enzyme-modified dextrin, acid-decomposed starch, oxidized starch, pregelatinized starch, esterified starch, etherified starch, crosslinked starch, and cationized starch. Of these, particularly preferred are oxidized starch and cationized starch.

The copolymer latex of the present invention is emulsion polymerized by using a necessary amount of starch so that the stability of the latex is excellent and the average particle size of the latex produced is within a specific range. The amount of starch used is 0.001 part by weight or more and less than 10 parts by weight, preferably 0.005 to 9 parts by weight, and more preferably 0.05 based on 100 parts by weight of the monomer (A).
-8 parts by weight, particularly preferably 0.05 parts by weight or more and less than 5 parts by weight. If the amount of starch used is less than 0.001 part by weight, it is difficult to obtain a stable latex, and if it exceeds 10 parts by weight, the production conditions are limited to obtain a stable latex, which is difficult.

The average particle size of the copolymer latex is 300 angstroms or more and less than 2,000 angstroms.
It is preferably 500 angstroms or more and less than 2,000 angstroms, and more preferably 800 to 1,90.
It is 0 angstrom. If the average particle size is less than 300 Å, the viscosity is high and the tackiness is high, which is not preferable. On the other hand, the average particle size is 2,000
If it is at least angstrom, the adhesive strength will decrease.

Generally, the amounts of water and emulsifier are adjusted to control the average particle size. Usually, a large amount of water and an emulsifier are used to reduce the particle size, and a small amount of water and an emulsifier are used to increase the particle size.

Generally, in emulsion polymerization, a chain transfer agent is used to adjust the molecular weight of the resulting polymer, but the present invention can also be used as necessary.

Examples of the chain transfer agent include n-dodecyl mercaptan, t-dodecyl mercaptan, bromoform, α-methylstyrene dimer, terpinolene and α.
-Terpinene, γ-terpinene, dipentene, 1,4-
Hexadiene, 3-phenyl-1-pentene, 1-phenyl-2-pentene, 1-phenyl-2-hexene, 2
-Phenyl-3-hexene and the like can be mentioned.

As the α-methylstyrene dimer, (I) 2,4-diphenyl-4-methyl-
There are 1-pentene, (b) 2,4-diphenyl-4-methyl-2-pentene, and (c) 1,1,3-trimethyl-3-phenylindane. A preferable composition for the α-methylstyrene dimer is 40% by weight of the component (a).
As described above, the content of the component (b) and / or the component (c) is 60% by weight or less, more preferably 50% by weight or more of the component (b) and 50% by weight of the component (b) and / or (c).
In the following, particularly preferably, the component (a) is 70% by weight or more,
The amount of the component (b) and / or the component (c) 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 is an impurity, for example, unreacted α-methylstyrene, and α-methylstyrene other than the above-mentioned components (a), (b) and (c) within a range not impairing the object of the present invention. It may contain a styrene oligomer or an α-methylstyrene polymer.

The chain transfer agent is preferably used alone or in combination of two or more. A preferable chain transfer agent is a chain transfer agent (T) having no mercapto group and / or a halogen atom as a substituent, and α-methylstyrene dimer is particularly preferable among the chain transfer agents (T). When these preferred chain transfer agents are used, the effect of the present invention is further improved, and a copolymer latex having a weak odor and good environmental hygiene can be obtained.

The chain transfer agent (T) is preferably used alone or in combination with a chain transfer agent other than the chain transfer agent (T). Chain transfer agents other than the chain transfer agent (T) are preferably mercaptans. When used in combination, a preferable ratio is (T) / (T) other than 2 chain transfer agents.
/ 98 to 100/0% by weight, more preferably 10/9
It is 0 to 90/10% by weight. By using a chain transfer agent in combination, a copolymer latex having excellent chemical and mechanical stability can be obtained.

The chain transfer agent is preferably used in an amount of 0.01 to 2 with respect to 100 parts by weight of the monomer (A).
The amount is 0 parts by weight, more preferably 0.1 to 5 parts by weight.
When the chain transfer agent is in this range, it gives excellent mechanical strength when the copolymer latex is used as various binders.

The copolymer latex of the present invention can be produced by a conventionally known emulsion polymerization method using the above-mentioned monomer component and starch. That is, it can be obtained by adding a monomer mixture, starch, a polymerization initiator, an emulsifier and the like to an aqueous medium (usually water) and carrying out emulsion polymerization.

As the polymerization initiator used in the present invention, organic and inorganic peroxide compounds, persulfate compounds such as sodium persulfate, potassium persulfate and ammonium persulfate, azobisisobutyronitrile, 2,2 '. -Azobis (2-aminodipropane) dihydrochloride, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 4,4'-azobis (4-cyanovaleric acid), 2,
2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2-methyl-N- [1,1
-Bis [hydroxymethyl) -2-hydroxyethyl]
Propionamide], an oil-soluble or water-soluble azo compound such as 2,2'-azobisisobutyramide dihydrate, cerium ammonium nitrate or a redox initiator may be used. As the reducing agent used in the redox type initiator, primary ammonium sulfate,
Examples thereof include ascorbic acid, sodium thiosulfate, sodium bisulfite, sodium metabisulfite and the like. Among these initiators, potassium persulfate and ceric ammonium nitrate are particularly preferable. In addition, these initiators may be used in a required amount at a time at the beginning of polymerization, or may be divided and added at an arbitrary time.

In the present invention, an emulsifier can be used if necessary.

Here, as the emulsifier, for example, an amphoteric surfactant, an anionic surfactant, or a nonionic surfactant can be used. Examples of the amphoteric surfactant include those having a carboxylate salt, a sulfuric acid ester salt, a sulfonate salt, and a phosphoric acid ester salt as the anion portion, and an amine salt and a quaternary ammonium salt as the cation portion.
Specifically, as salts of alkyl betaines, lauryl betaine, stearyl betaine, cocoamido propyl betaine, 2-undecyl-hydroxyethyl imidazolinium betaine salts, respectively, amino acid type of lauryl-β-alanine, stearyl Examples include respective salts of -β-alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine. Examples of the anionic surfactant include sulfuric acid ester of higher alcohol, alkylbenzene sulfonate, and aliphatic sulfonate. Further, as the nonionic surfactant, an ordinary polyethylene glycol alkyl ester type, alkyl ether type, alkyl phenyl ether type or the like is used.

The temperature of the emulsion polymerization of the present invention is selected depending on the polymerization initiator used and the like, but it is usually from -5 ° C to 150 ° C.
C., preferably 0.degree. C. to 100.degree.

The copolymer latex obtained by the present invention is preferably used as a binder for a paper coating composition. The copolymer latex in this case may be used as it is depending on the purpose, and if necessary, an inorganic pigment or an organic pigment, preferably an inorganic pigment, may be further added to the copolymer latex, if necessary. It is prepared as an aqueous dispersant by adding other binders.

At this time, the copolymer latex of the present invention is usually 3 to 40 parts by weight, preferably 5 to 30 parts by weight, and other binders are added to 100 parts by weight of the pigment in terms of solid content.
It is usually used in an amount of 0 to 30 parts by weight, preferably 2 to 10 parts by weight. If the amount of the copolymer latex is less than 3 parts by weight, sufficient adhesive strength cannot be obtained, while if it exceeds 40 parts by weight, the viscosity of the coating composition increases and the fluidity decreases, so that the coating workability decreases. .

Examples of the pigments include inorganic pigments such as kaolin clay, talc, barium sulfate, titanium oxide (rutile anatase), calcium carbonate, aluminum hydroxide, zinc oxide and satin white, or organic pigments such as polystyrene latex. These may be used alone or in combination.

Other binders include natural binders such as starch, oxidized starch, soybean protein and casein, polyvinyl alcohol, polyvinyl acetate latex, acrylic latex, carboxy-modified SB latex, butadiene-methyl methacrylate and the like. Synthetic latex is used.

To prepare the paper coating composition, further other auxiliaries such as dispersants (sodium pyrophosphate, sodium hexametaphosphate, etc.), antifoaming agents (polyglycols, fatty acid esters, phosphate esters, silicones) are used. Oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), preservative, water resistance agent (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), mold release agent (calcium stearate, paraffin emulsion, etc.), fluorescent Dyes and color water retention agents (carboxymethyl cellulose, sodium alginate, etc.) are added as necessary.

After the composition for paper coating is applied, the surface is dried,
Finished with a calendar ring.

The copolymer latex of the present invention comprises a coating agent other than the binder of the paper coating composition as described above,
It is also useful as a resin improver, a binder for paints, and a binder for various other uses.

The glass transition temperature of the copolymer latex of the present invention is preferably in the range of -50 ° C to + 40 ° C.
When the glass transition temperature is lower than −50 ° C., the tackiness of the copolymer latex becomes high, and the operability is lowered, while +40.
If the temperature is higher than ° C, the adhesive strength will be decreased, which is not preferable.

[0039]

EXAMPLES Next, the present invention will be described with reference to examples.
The present invention is not limited to the following examples unless it exceeds the gist. In the examples, "parts" and "%" indicating proportions mean parts by weight and% by weight, respectively.

Various test methods for the copolymer latex used in the examples are shown below. Average particle size The average particle size of the copolymer was measured using a particle size analyzer LPA3100 manufactured by Otsuka Electronics Co., Ltd. Toluene insoluble matter (gel content) After adjusting the obtained copolymer latex to pH 8.0, the copolymer in the latex was coagulated with isopropanol, washed and dried, and then a predetermined amount (about 0.3 g) of The sample was dipped in a predetermined amount (100 ml) of toluene for about 20 hours and then filtered through a 120-mesh wire net to measure the residual solid content, which was shown in% by weight based on the sample. Fine coagulated product 1 kg of the copolymer latex was taken as a sample, this was filtered through a 400-mesh wire net, the amount of coagulated material remaining on the wire net was measured, and the ratio to the sample (solid content conversion) was determined,
The stability was evaluated by the following three stages, and the stability of the produced latex was evaluated from the production amount of this fine coagulated product.

◯: 0.05% or less: Good stability Δ: Greater than 0.05% and less than 0.1%: Slightly inferior ×: 0.1% or more: Poor stability Examples 1 to 6 ( Manufacture of copolymer latex) In a 100 liter pressure resistant reactor, monomers of the components shown in Table 1, water (a necessary amount of water excluding water used for adding starch, a surfactant, and a polymerization initiator), Etherified starch dissolved at 80 to 90 ° C (30% concentration aqueous solution), chain transfer agent, surfactant (concentration 10%
% Aqueous solution), polymerization initiator (concentration 3-15% aqueous solution)
, And then in a nitrogen atmosphere at a temperature of 70 ° C for 12
Polymerization was carried out for a time, and the polymerization was completed at a polymerization conversion rate of 98 to 100%.

The obtained copolymer latex was adjusted to pH 7.5 with sodium hydroxide, and then unreacted monomers were removed by blowing steam, and the copolymer having a solid content of 50% was distilled by heating under reduced pressure. A polymer latex was obtained.

The composition of the copolymer latex, the stability of the obtained latex, the insoluble matter in toluene and the particle size of the latex are shown in Table 1. Each of the examples shows that the copolymer latex obtained in the present invention has little generation of fine coagulation and is very excellent in stability. Further, the particle size of the obtained latex is 300 to 2, in any case.
It is in the range of 000 angstroms.

[Table 1] Comparative Examples 1 to 6 (Production of Copolymer Latex) In a 100 liter pressure resistant container, monomers of components shown in Table 2, water, a polymerization chain transfer agent,
After a surfactant aqueous solution having a concentration of 10% and a polymerization initiator aqueous solution having a concentration of 3 to 15% were charged in this order, polymerization was carried out at a temperature of 70 ° C. for 12 hours in a nitrogen atmosphere in the same manner as in the above-mentioned Examples to carry out polymerization. Polymerization was completed at a conversion of 98 to 100%.

Further, the obtained copolymer latex was adjusted to pH 7.5 with an aqueous sodium hydroxide solution, and then steam was blown thereinto to remove unreacted monomers. % Copolymer latex was obtained.

The composition of the copolymer latex, the stability of the obtained latex, the toluene insoluble content and the particle size of the latex are shown in Table 2.

[Table 2] Comparative Examples 1 and 2 are examples in which the same monomer composition as in Examples 1 to 4 was used and polymerization was performed in the absence of starch. It shows that the stability of the copolymer latexes obtained in these comparative examples is poor.

Comparative Example 3 is an example in which the monomer composition was the same as in Example 5 and the polymerization was carried out in the absence of starch, and it shows that the copolymer latex obtained is inferior in stability.

In Comparative Example 4, 1,3-butadiene is 10%.
And less than 70% of styrene, indicating that the obtained copolymer latex is inferior in stability.

In Comparative Example 5, 1,3-butadiene was 65%.
The above shows that the stability of the obtained copolymer latex is poor.

Comparative Example 6 shows that the particle size of the copolymer latex obtained exceeds 2,000 angstroms. Application Examples 1 to 8 (Preparation of composition for paper coating) Using the copolymer latex thus obtained, a composition for paper coating according to the following formulation (A) and formulation (B) Was prepared. Formulation (A) Australian clay Comarco (manufactured by Comalco, “Comarco”) 25 parts Grade 2 clay (manufactured by EM & C, “HT”) 25 parts Calcium carbonate (manufactured by Fuji Kaolin, “Carbital-90”) 50 parts Dispersant (Toa Gosei Co., Ltd., "Aron T-40") 0.28 part Water resistant agent (Sumitomo Chemical Co., Ltd., "Smilet 633") 0.30 part Lubricant (San Nopco, "Nopcoat C-104") ) 0.50 parts Preservative (Katayama Chemical Co., Ltd., "Mornon 900") 0.05 parts Synthetic latex 14 parts 25% Aqueous ammonia solution 0.10 parts Water Required amount for solid concentration of 64% Compounding recipe (B) Kaolinite clay ( JM Huber, "Hydro Sparse") 30 parts Ultra White Clay (EMC, "Ultra White-90") 40 parts Calcium Carbonate (Fuji Kaolin, "Ca Vital-90 ") 30 parts Dispersant (Toa Gosei Co., Ltd.," Aron T-40 ") 0.20 part Water resistant agent (Sumitomo Chemical Co., Ltd.," Smilets 633 ") 0.30 part Lubricant (San Nopco Corp.) , "Nopcoat C-104") 1.00 part Preservative (Katayama Chemical Co., Ltd., "Mornon 900") 0.05 part Synthetic latex 14 parts 25% Aqueous ammonia solution 0.10 part Water Required amount that the solid content concentration becomes 64%, that is, After the dispersant is dissolved in water, the preservative and calcium carbonate are added, and then clay, 25% aqueous ammonia solution, water-proofing agent, lubricant and synthetic latex are gradually added and dispersed in this order while stirring with a Choles disperser. It was In the preparation of the composition for paper coating, when starch was necessary, it was dissolved by heating at a temperature of 80 to 90 ° C. and premixed with the above dispersion liquid to prepare a final solid content concentration of 64%. The ratio of starch to synthetic latex is 3 parts of starch to 10 parts of synthetic latex, and the starch is shown as the total amount including the starch contained in the synthetic latex. When the amount of starch was less than this ratio, the starch was added by the above method, and when the amount of starch in the synthetic latex was more than this ratio, it was used as it was.

The obtained paper coating composition was coated with rod coating (Matsuo Sangyo, Rod coating # 8) (Oji Paper Co., Ltd.)
Fine quality paper OK64, basis weight 64.5 g / m ² ) is coated at a coating amount of 30 to 35 ± 1 g / m ² and then dried at a temperature of 150 ° C. for 10 seconds, and further at a temperature of 50 ° C. and a pressure. 1
It was calendered twice under the condition of 50 kg / cm ² . The coated paper thus obtained was evaluated according to the following evaluation methods. The evaluation results are shown in Table 3.

[Table 3] The evaluation method of coated paper is shown below. RI dry pick: index of adhesive strength The degree of picking when printed by an RI printing machine was judged with the naked eye, and 5 points without picking were evaluated by 5 points.

◯: 4.0 or more Δ: 2.5 or more and less than 4.0 x: less than 2.5 RI wet pick: index of water resistance Picking when dampening water was applied using a Molton roll in a RI printing machine The grade was evaluated with the naked eye, and no picking was scored as 5 points, and evaluation was made on a scale of 5 points.

◯: 4.0 or more Δ: 2.5 or more and less than 4.0 x: less than 2.5 Ink transferability By using a RI printing tester, a blank sheet is pressed against the printing surface after printing, and ink is applied to the blank sheet. The metastatic property was judged with the naked eye and evaluated in three levels.

◯: Excellent Δ: Slightly inferior ×: Inferior printing gloss The ink for web offset was solidly printed using an RI printer and measured using a Murakami gloss meter (75). ° -7
5 °) and evaluated in 3 stages.

◯: Excellent Δ: Slightly inferior ×: Inferior Application Examples 1 to 8 show that the coated paper has excellent physical properties in both cases of the compounding formulations (A) and (B). Show. The stability of the paper coating composition was also excellent. Comparative Application Examples 1 to 6 Preparation of a paper coating composition and evaluation of coated paper physical properties were carried out in the same manner as shown in Application Examples 1 to 8. The results are shown in Table 3.

Comparative Application Examples 1 to 3 all use a copolymer latex polymerized in the absence of starch, and all have poor ink transfer properties, and Comparative Application Example 3 has poor wet adhesion strength. Indicates that.

Comparative Application Examples 4 and 5 show that when the ratio of the monomer components of the copolymer latex used exceeds the range of the present invention, the physical properties of all coated papers are inferior.

Comparative Application Example 6 shows that the adhesive strength is inferior when a copolymer latex having a particle size of more than 2,000 Å is used.

In each of Comparative Application Examples 1 to 6, the stability of the obtained paper coating composition was poor.

[0059]

EFFECT OF THE INVENTION The copolymer latex of the present invention has less generation of fine coagulation, excellent mechanical and chemical stability,
It also has excellent adhesive strength.

The copolymer latex of the present invention is a binder for a paper coating composition, a coating agent, a resin improving agent,
It is useful as a binder for paints and as a binder for various other applications.

The composition for paper coating using the copolymer latex of the present invention as a binder is excellent in adhesive strength and further excellent in stability, so that high speed coating is possible, and It has excellent operability during production, and is particularly useful as a binder for paper coating compositions such as paperboard and gate roll coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Matsui 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd.

Claims (1)

[Claims] 1. (a) Conjugated diene compound 10-
65 wt% (b) Aromatic vinyl compound 0-70 wt% (c) Ethylenically unsaturated carboxylic acid 0-10 wt% (d) Other copolymerizable monomer 0-70 wt% Obtained by emulsion polymerization of 100 parts by weight of the body (A) in the presence of 0.001 part by weight or more and less than 10 parts by weight of starch, and the average particle size of the copolymer particles is 300 angstroms or more and less than 2,000 angstroms. A copolymer latex characterized by the following.