JP3230322B2 - Copolymer latex - Google Patents

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-polymerizing a specific monomer in the presence of a specific amount of starch. Excellent in chemical and mechanical stability, opacity, glossiness of white paper, inking property and workability during coating, excellent in energy saving, useful as binder for paper coating composition for fine coating or gravure printing A copolymer latex.

[0002]

2. Description of the Related Art Copolymer latexes containing a conjugated diene compound as an essential component are widely used as binders for various applications including binders for paper coating compositions.

[0003] Paper coating compositions provide opacity, glossiness of white paper and inking property of printing ink by coating paper coating composition on base paper. There is a limit to the improvement of the composition for paper coating using as a binder, and there is a demand for a composition for paper coating with further excellent opacity, glossiness of white paper and inking property. In addition, in order to improve coating workability in the production of coated paper and to save energy during drying, a paper coating composition having low viscosity, excellent chemical and mechanical stability, and a high solid content is used. It has been demanded.

When a copolymer latex having a large average particle size of the copolymer particles is used as a binder component of a paper coating composition, a paper coating composition having low viscosity and capable of high solid differentiation can be obtained. However, in the conventional technology, it is difficult to produce a copolymer latex having a large particle size by emulsion polymerization of a monomer comprising a conjugated diene, an aromatic vinyl, and an unsaturated carboxylic acid using an emulsifier such as soap. Furthermore, it was extremely difficult to produce a copolymer latex having excellent chemical and mechanical stability and a large particle size.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and provides a copolymer latex having excellent chemical and mechanical stability and a large average particle size. The purpose is to do so.

[0006]

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

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) Hereinafter, the present invention will be described in detail.

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

Representative examples of the aromatic vinyl compound as the component (b) include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, 2-vinylpyridine,
4-vinylpyridine and the like can be mentioned. The component (b) is used in an amount of 0 to 70% by weight, preferably 0 to 70% by weight.
６０60% by weight. When the use ratio of the component (b) exceeds 70% by weight, the polymerization stability decreases, and the coating workability decreases.

In the present invention, when an ethylenically unsaturated carboxylic acid as the component (c) is used in the production of a copolymer latex, a copolymer having more excellent adhesive strength and mechanical stability can be obtained. 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 anhydrides can be used. (C) The use ratio of the component is 0 to
It is 10% by weight, preferably 0.1 to 10% by weight, particularly preferably 1 to 7% by weight. (C) Component usage ratio 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 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. Ethylenic unsaturated carboxylic acid esters such as alkyl acrylates and alkyl methacrylates; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, N-methylolacrylamide, diacetone acrylamide, crotonamide, itaconamide, methyl Itaconamide, maleic monoamide, methylenediacrylamide, dimethylacrylamide, diethylacrylamide, dimethylmethacrylamide, diethylmethamide 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
4,5,6-pentahydroxyhexyl acrylate,
Hydroxyl-containing vinyl compounds 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- Copolymerizable silicon-containing compounds such as (meth) acryloxyethyltriethoxysilane are exemplified. Further, (d)
Ingredients: 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 And 1,3-divinyltetramethyldisiloxane, bis (2-methylallyl) carbonate, and ethylene oxide-modified bisphenol A di (meth) acrylate.
The component (d) may be used alone or in combination of two or more. The use ratio of the component (d) is from 0 to 7
0% by weight, preferably 1 to 50% by weight. When the use ratio of the component (d) exceeds 70% by weight, the viscosity of the composition becomes too high, and the operability is undesirably lowered.

The starch used in the present invention includes, for example, starch from potato, tapioca, wheat, rice, corn, sweet potato, and the like. Particularly preferred is potato, tapioca, and corn starch. Starch is broken down by acid, enzymatic or oxidative hydrolysis into processed starch. The starch used in the present invention also includes modified starch. Examples of such modified 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 in the present invention is emulsion-polymerized using a necessary amount of starch so that the latex has excellent stability and the average particle size of the produced latex is in a specific range. The amount of the starch to be used is 0.001 to 10 parts by weight, preferably 0.005 to 9 parts by weight, more preferably 0.05 to 100 parts by weight based on 100 parts by weight of the monomer (A).
To 8 parts by weight, particularly preferably 0.05 to 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, production conditions are limited and difficult to obtain a stable latex.

The average particle size of the copolymer latex is 2,000.
0 Å or more, preferably 2,000 to 2
0,000 angstroms, more preferably 2,1
It is preferably from 00 to 10,000 angstroms, particularly preferably from 2,300 to 8,000 angstroms. If the average particle size is less than 2,000 angstroms, opacity, gloss of white paper, and inking property are poor, and an appropriate viscosity cannot be obtained.

Generally, in order to control the average particle size, the amounts of water and emulsifier are adjusted. Usually, a large amount of water and an emulsifier are used to reduce the particle size, and small amounts 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 produced polymer, but the present invention can also be used if necessary.

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

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 preferred composition for the α-methylstyrene dimer is that the component (A) is 40% by weight.
As described above, the component (B) and / or the component (C) are at most 60% by weight, more preferably the component (A) is at least 50% by weight, and the component (B) and / or the component (C) are at 50% by weight.
Hereinafter, particularly preferably, the component (a) is 70% by weight or more,
Component (b) and / or 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 such as unreacted α-methylstyrene, α-methyl other than the components (a), (b) and (c) as long as the object of the present invention is not impaired. It may contain a styrene oligomer or an α-methylstyrene polymer.

It is preferred that one or more chain transfer agents are used. The preferred chain transfer agent is a chain transfer agent (T) having no mercapto group and / or halogen atom as a substituent, and among the chain transfer agents (T), α-methylstyrene dimer is particularly preferred. When these preferred chain transfer agents are used, the effects aimed at by the present invention are further improved, and a copolymer latex having low odor and good environmental health 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). The chain transfer agent other than the chain transfer agent (T) is preferably a mercaptan. When used in combination, a preferable ratio is that the chain transfer agent other than (T) / (T) is 2%.
/ 98 to 100/0% by weight, more preferably 10/9
0 to 90/10% by weight. By using a chain transfer agent in combination, a copolymer latex having further excellent chemical and mechanical stability can be obtained.

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

The copolymer latex in 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.

Examples of the polymerization initiator used in the present invention include organic and inorganic peroxide compounds, persulfate compounds such as sodium persulfate, potassium persulfate, and ammonium persulfate; azobisisobutyronitrile; -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'-azobisisobutylamide dihydrate, ceric ammonium nitrate or a redox initiator may be used. As the reducing agent used in the redox-based initiator, ammonium monosulfate,
Ascorbic acid, sodium thiosulfate, sodium bisulfite, sodium metabisulfite and the like. Of these initiators, particularly preferred are potassium persulfate and ceric ammonium nitrate. Further, these initiators may be used at a time in the required amount at the beginning of the 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, a sulfate, a sulfonate, and a phosphate as an anion portion, and an amine salt and a quaternary ammonium salt as a cation portion,
Specifically, the salts of alkyl betaines include lauryl betaine, stearyl betaine, cocoamidopropyl betaine, and salts of 2-undecyl-hydroxyethyl imidazolinium betaine, and those of the amino acid type include lauryl-β-alanine and stearyl. -Β-alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine. Examples of the anionic surfactant include a sulfate of a higher alcohol, an alkylbenzene sulfonate, and an aliphatic sulfonate. Further, as the nonionic surfactant, an alkyl ester type, an alkyl ether type, an alkyl phenyl ether type and the like of ordinary polyethylene glycol are used.

The temperature of the emulsion polymerization of the present invention is selected depending on the polymerization initiator to be used and the like.
° C, preferably 0 ° C to 100 ° C.

The copolymer latex obtained according to the present invention is suitably 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, is further added to such a 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 the other binder is 100 parts by weight of the pigment in terms of solid content.
Usually, 0 to 30 parts by weight, preferably 2 to 10 parts by weight is used. When the amount of the copolymer latex is less than 3 parts by weight, sufficient adhesive strength cannot be obtained, and on the other hand, the viscosity of the coating composition exceeding 40 parts by weight increases and the fluidity decreases, so that the coating workability decreases. .

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

Examples of other binders include natural binders such as starch, oxidized starch, soybean protein, and casein; or 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, other auxiliaries such as dispersants (sodium pyrophosphate, sodium hexametaphosphate), defoamers (polyglycol, fatty acid ester, phosphate ester, silicone) Oils), leveling agents (funnel oil, dicyandiamide, urea, etc.), preservatives, waterproofing agents (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), mold release agents (calcium stearate, paraffin emulsion, etc.), fluorescence Dyes and color water retention improvers (such as carboxymethyl cellulose and sodium alginate) are added as necessary.

After coating the paper coating composition, the surface is dried,
Finished with a calender ring.

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 increases, and the operability decreases.
If the temperature is higher than 0 ° C., the adhesive strength is undesirably reduced.

The copolymer latex of the present invention is useful as a binder for gravure printing or a finely coated paper coating composition, or as a modifier for resins, rubbers, thermoplastic elastomers and the like. Note that the fine-coating shows the coated amount of degree less usual per coated paper 1 m ² 10 g applications Kaminuri the composition.

[0037]

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 Examples, "parts" and "%" indicating percentages 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 the obtained copolymer latex was adjusted to pH 8.0, the copolymer in the latex was coagulated with isopropanol, washed and dried, and a predetermined amount (about 0.3 g) was obtained. After the sample was immersed in a predetermined amount (100 ml) of toluene for about 20 hours, the remaining solid content obtained by filtration through a 120-mesh wire net was measured, and the result was shown in terms of% by weight based on the sample. 1 kg of a finely coagulated copolymer latex was sampled, filtered through a 400-mesh wire gauze, the amount of coagulation remaining on the wire gauze was measured, and the ratio to the sample (in terms of solid content) was determined.
The stability was evaluated by the following three stages, and the stability of the produced latex was evaluated based on the amount of the fine coagulated product.

：: 0.05% or less: good stability Δ: more than 0.05% and less than 0.1%: slightly poor stability ×: 0.1% or more: poor stability Examples 1 to 9 ( Production of copolymer latex) In a 100-liter pressure-resistant reaction vessel, the monomers of the components shown in Table 1 and water (the required amount of water excluding starch, a surfactant, and water used for adding a polymerization initiator) were added. Etherified starch (30% strength aqueous solution), chain transfer agent, surfactant (10% strength) dissolved at 80 to 90 ° C.
% Aqueous solution), polymerization initiator (3-15% aqueous solution)
After that, in a nitrogen atmosphere at a temperature of 70 ° C. for 12 hours.
Polymerization was carried out for a period of time, and the polymerization was completed at a polymerization conversion of 98 to 100%.

After adjusting the pH of the obtained copolymer latex to 7.5 using sodium hydroxide, steam is blown in to remove unreacted monomers, and the copolymer having a solid content of 50% is distilled by heating under reduced pressure. A polymer latex was obtained.

Table 1 shows the composition of the copolymer latex, the stability of the obtained latex, the insoluble matter in toluene, and the particle size of the latex. In each of the examples, the copolymer latex obtained in the present invention shows little generation of fine coagulated products and shows that the stability is very excellent. The particle size of the obtained latex is 2,000 angstroms or more in each case.

[Table 1] Comparative Examples 1 to 6 (Production of copolymer latex) In a 100-liter pressure-resistant container, a monomer having the components shown in Table 2, water, a polymerization chain transfer agent,
After sequentially charging an aqueous solution of a surfactant having a concentration of 10% and an aqueous solution of a polymerization initiator having a concentration of 3 to 15%, polymerization was performed in a nitrogen atmosphere at a temperature of 70 ° C. for 12 hours in the same manner as in the above-described example. The polymerization was completed at a conversion of 98 to 100%.

Further, the obtained copolymer latex was adjusted to pH 7.5 using an aqueous sodium hydroxide solution, steam was blown in to remove unreacted monomers, and the solid content was reduced to 50% by heating under reduced pressure. % Copolymer latex was obtained.

Table 2 shows the composition of the copolymer latex, the stability of the obtained latex, the insoluble matter in toluene, and the particle size of the latex.

[Table 2] Comparative Examples 1 and 2 are examples in which polymerization was carried out in the same monomer composition as in Examples 1 to 5 and in the absence of starch. The copolymer latexes obtained in these comparative examples show poor stability and a particle size of less than 2,000 angstroms.

Comparative Example 3 is an example in which polymerization was carried out in the same monomer composition as in Example 6 and in the absence of starch. The obtained copolymer latex was inferior in stability and had a particle size of 2 2,000 angstroms.

In Comparative Example 4, 1,3-butadiene contained 10%
And less than 70% styrene, indicating that the resulting copolymer latex has poor stability and a particle size of less than 2,000 angstroms.

In Comparative Example 5, 1,3-butadiene contained 65%
The results show that the obtained copolymer latex has inferior stability and a particle size of less than 2,000 angstroms.

Comparative Example 6 shows that the particle size of the resulting copolymer latex is less than 2,000 angstroms. Application Examples 1 to 10 (Preparation of Paper Coating Composition) Using the thus obtained copolymer latex, a composition for paper coating according to the following formulation (A) and formulation (B): Was prepared. Formulation (A) Australia Clayco Marco (Komarco, "Komarco") 25 parts Second grade clay (EM & C, "HT") 25 parts Calcium carbonate (Fuji Kaolin Co., Ltd., "Carbital-90") 50 parts Dispersant (Toa Gosei Co., Ltd., "Aron T-40") 0.28 parts Waterproofing agent (Sumitomo Chemical Co., Ltd., "Smiletz 633" 0.30 parts Lubricant (San Nopco Co., Ltd., "Nopcoat C-104") 0.50 parts Preservatives (Katayama Chemical Co., Ltd., "Mornon 900") 0.05 parts Synthetic latex 14 parts 25% aqueous ammonia solution 0.10 parts Water Required amount to give a solid concentration of 64% Formulation (B) Kaolinite clay (J 30 parts Ultra White Clay (manufactured by EMC, "Ultra White-90") 40 parts Calcium carbonate (manufactured by Fuji Kaolin) Tal-90 ") 30 parts Dispersant (Toa Gosei Co., Ltd.," Aron T-40 ") 0.20 part Waterproofing agent (Sumitomo Chemical Co., Ltd.," Smileets 633 ") 0.30 part Lubricant (San Nopco Co., Ltd.) , "Nopcoat C-104") 1.00 part Preservative (Katayama Chemical Co., Ltd., "Mornon 900") 0.05 part Synthetic latex 14 part 25% ammonia aqueous solution 0.10 part Water The required amount to make the solid concentration 64% After dispersing the dispersant in water, the preservative and calcium carbonate are added, and then clay, a 25% aqueous ammonia solution, a waterproofing agent, a lubricant and a synthetic latex are gradually added and dispersed in this order while stirring with a Coreth disperser. In the preparation of the composition for paper coating, if starch is required, it is heated and melted at a temperature of 80 to 90 ° C., and is previously mixed with the dispersion and used to adjust the final solid concentration to 64%. The ratio of starch to synthetic latex is 3 parts of starch with respect to 10 parts of synthetic latex, and the starch is represented by the total amount including starch contained in the synthetic latex. In the case where the amount of starch in the synthetic latex was higher than this ratio, the obtained composition for paper coating was used by rod coating (Matsuo Sangyo, rod coating # 8). Coated paper (Oji Paper Co., Ltd.)
High quality paper OK64, basis weight 64.5 g / m ² ), the coating amount is 30 to 35 ± 1 g / m ² , then dried at 150 ° C. for 10 seconds, and further at 50 ° C., pressure 1
Calendering was performed twice under the condition of 50 kg / cm ² .

The physical properties of the coated paper thus obtained were evaluated according to the following evaluation methods. Table 3 shows the results of the evaluation.

[Table 3] The evaluation method of the coated paper is shown below. Blank paper gloss Measured using a Murakami gloss meter (75 ° -75 °)
The evaluation was made in three stages.

：: Excellent Δ: Slightly poor ×: Poor print gloss Solid printing of the ink for web offset using an RI printer and measurement using a Murakami gloss meter (75 ° -7)
(5 °)).

：: Excellent △: Slightly poor ×: Poor inferiority The degree of ink transfer when dampening water was applied using a Molton roll with an RI printing machine was measured, and evaluated in three steps.

：: Excellent Δ: Slightly poor ×: Poor opacity Measured according to JIS P 8138, and evaluated in three steps.

：: Excellent Δ: Slightly poor ×: Poor In all of the application examples 1 to 10, the stability of the composition for paper coating was extremely excellent in any of the compounding formulations (A) and (B). Shows that the coated paper has excellent physical properties.

When the composition for paper coating is used as a binder for a paper composition for gravure printing, excellent opacity and gloss of white paper are required as coated paper properties, and the composition for fine coating is further required. When used as a binder, it is required to reduce the coating amount in addition to the above physical properties.

The use of the paper coating composition prepared by using the copolymer latex of the present invention having a large particle size can reduce the amount of coating, and is excellent as shown in the above application examples. The copolymer latex of the present invention is useful as a binder for a composition for gravure printing or for coating a lightly coated paper because of having a coated paper physical property such as opacity and glossiness of white paper. Comparative Application Examples 1 to 6 Preparation of a paper coating composition and evaluation of physical properties of coated paper were performed in the same manner as shown in Application Examples 1 to 10. Table 4 shows the results.

[Table 4] Comparative application examples 1 to 3 are all cases in which a copolymer latex polymerized in the absence of starch is used. In all cases, the stability of the obtained paper coating composition is poor, and the physical properties of the coated paper are also low. Indicates that the inking property and the opacity are inferior.

In Comparative Application Examples 4 and 5, the monomer component ratio of the copolymer latex used exceeded the range of the present invention, and the stability of the obtained paper coating composition was inferior. This shows that the physical properties of the coated paper are inferior.

In Comparative Examples 1 to 6, the particle size was 2,0.
When a copolymer latex of less than 00 angstroms is used, the obtained paper coating composition shows poor opacity among the coated paper properties.

[0057]

According to the present invention, it is possible to obtain a copolymer latex with less generation of fine coagulates, excellent chemical and mechanical stability, and a large average particle size.

The copolymer latex of the present invention is useful as a binder for a paper coating composition for paper coating or gravure printing, and as a binder for coating agents and paints.

The paper coating composition using the copolymer latex of the present invention as a binder is excellent in white paper gloss, print gloss, inking property, and opacity, and further excellent in workability during coating and energy saving.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Matsui 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-5-209024 (JP, A) 3-503908 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 251/00 D21H 19/54

Claims (1)

(57) [Claims] (1) a conjugated diene compound
65% by weight (b) Aromatic vinyl compound 0 to 70% by weight (c) Ethylene unsaturated carboxylic acid 0 to 10% by weight (d) Other copolymerizable monomer 0 to 70% by weight The copolymer (A) is obtained by emulsion polymerization of 100 parts by weight of starch in the presence of 0.001 to less than 10 parts by weight of starch, and the copolymer particles have an average particle size of 2,000 angstroms or more. Copolymer latex.