JP3115837B2 - Method for producing 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 novel method for producing a copolymer latex which is used as a binder in the production of a coated paper having good blister resistance and surface strength.

[0002]

2. Description of the Related Art In recent years, coated paper has been widely used for printing due to its excellent printing effect.
Its demand is ever-increasing. Against the background of such an increase in demand, coated papers have been required to have higher performance.

[0003] Of the various performances required, blister resistance and surface strength, which determine printing speed, are particularly important.

[0004] In the production of coated paper, it is known that the copolymer latex used as a binder has a great effect on these properties, and therefore, by changing the composition or structure of the copolymer latex. Improvements in blister resistance and surface strength are generally made.

In particular, it is known that the gel content of the copolymer latex is an important controlling factor for these physical properties. Further, the gel content is generally adjusted by the amount of the chain transfer agent used. However, the blister resistance of the coated paper improves as the gel content decreases, and the surface strength of the coated paper improves as the gel content increases. That is, the blister resistance and surface strength of the coated paper were contradictory physical properties. Therefore, various studies have been made to simultaneously satisfy the blister resistance and the surface strength of the coated paper. For example, Japanese Patent Application Laid-Open Nos. 3-109451 and 3-200802 propose a use of a specific compound.

[0006]

However, none of the techniques satisfy the currently required performance. Therefore, an object of the present invention is to provide a good copolymer latex that simultaneously satisfies the blister resistance and surface strength of coated paper.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a copolymer latex is a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring. In the emulsion polymerization in the presence of the ethylenically unsaturated carboxylic acid monomer was added by a specific addition method, a specific gel content, a copolymer latex having a specific amount of the acid content of the aqueous phase part The present inventors have found that a coated paper excellent in blister resistance and surface strength can be obtained by using the same, and reached the present invention.

That is, the present invention is as follows.
From 10 to 80 parts by weight of an aliphatic conjugated diene monomer, 0.6 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer and 10 to 89.4 parts by weight of other monomers copolymerizable therewith. The total amount of the ethylenically unsaturated carboxylic acid monomer used in the emulsion polymerization of a monomer mixture (total 100 parts by weight) in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring Polymerization is started by allowing Y parts by weight of the X parts by weight to be present in the polymerization system, wherein X and Y satisfy the following conditions 1 and 2, the gel content is 20% by weight or less, and the aqueous phase It is intended to provide a method for producing a copolymer latex, which is characterized in that polymerization is carried out so that the amount of acid in a part becomes 0.01 to 0.4 meq / 1 g (solid content). Condition 1: 0.2 ≦ Y ≦ 1 Condition 2: 0.1 ≦ Y / (XY) ≦ 0.5

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the aliphatic conjugated diene monomer in the present invention,
1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated Hexadienes and the like can be used, and one kind or two or more kinds can be used. Especially 1,
3-Butadiene is preferred.

Examples of the ethylenically unsaturated carboxylic acid monomer in the present invention include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid. Species or two or more can be used.

Other monomers copolymerizable with the aliphatic conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include an aromatic vinyl monomer and an unsaturated carboxylic acid alkyl ester monomer. And unsaturated monomers containing a hydroxyalkyl group, vinyl cyanide monomers, unsaturated carboxylic acid amide monomers, and the like, and one or more kinds can be used.

The aromatic vinyl monomers include styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyl toluene and divinyl benzene, and the like,
One or more kinds can be used. Particularly, styrene is preferred.

The unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl dimethyl Examples include itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate, and the like, and one or more kinds can be used. Particularly, methyl methacrylate is preferred.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate,
Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl)
Maleate, 2-hydroxyethyl methyl fumarate and the like can be mentioned, and one kind or two or more kinds can be used. Particularly, β-hydroxyethyl acrylate is preferable.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like.
One or more kinds can be used. Acrylonitrile is particularly preferred.

The unsaturated carboxylic acid amide monomers include:
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Acrylamide is particularly preferred.

Further, in addition to the above monomers, fatty acid vinyl esters such as vinyl acetate and vinyl propionate,
Basic monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine, and 4-vinylpyridine, vinyl chloride, and vinylidene chloride can be used. it can.

The amount of the aliphatic conjugated diene monomer is 10 to 80 parts by weight. Outside this range, the surface strength of the coated paper is poor. Preferably 15 to 65 parts by weight, more preferably 2 parts by weight
0 to 50 parts by weight. The amount of the ethylenically unsaturated carboxylic acid monomer is 0.6 to 10 parts by weight. If the amount is less than 0.6 parts by weight, the polymerization stability will decrease. If the amount exceeds 10 parts by weight, the viscosity of the copolymer latex is undesirably high. The other copolymerizable monomer is 10 to 89.4 parts by weight. Outside this range, the surface strength of the coated paper is poor.

Most of the cyclic unsaturated hydrocarbon having one unsaturated bond in the ring used in the present invention remains unreacted after the polymerization, and it is necessary to recover the unreacted product. Therefore, those having a boiling point of 140 ° C. or less are preferable.
Specific examples include cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like.

In the present invention, one unsaturated bond is contained in the ring.
The amount of the cyclic unsaturated hydrocarbon used is preferably 0.1 to 30 parts by weight based on 100 parts by weight of the monomer mixture. When the amount is less than 0.1 part by weight, the effect of the present invention is insufficient, and when the amount exceeds 30 parts by weight, the amount of the compound remaining as an unreacted substance relatively increases, and the energy required for the recovery is greatly increased. Is not preferred. Preferably it is 0.5 to 15 parts by weight.

The gel content of the copolymer latex of the present invention is not more than 20% by weight. If the gel content exceeds 20% by weight, the blister resistance of the coated paper is inferior.

The gel content in the present invention refers to the ratio of an insoluble portion to toluene in a copolymer latex film. Specifically, the copolymer latex is dried to obtain a copolymer having a known weight. The latex film is immersed in toluene, filtered, weighed dry weight, and calculated by calculating the ratio of the dry weight of the organic solvent insoluble portion of the copolymer latex film to the dry weight of the copolymer latex film.

In order to achieve the object of the present invention, it is important to limit the method of using the ethylenically unsaturated carboxylic acid monomer. It is necessary that the amount be substantially present in the polymerization system before the polymerization starts.

The amount of acid in the aqueous phase of the copolymer latex in the present invention is measured by conducting the copolymer latex with conductivity. In the present invention, the acid amount in the aqueous phase of the copolymer latex needs to be 0.01 to 0.4 meq per 1 g of the solid content of the copolymer latex. The acid content of the aqueous phase of the copolymer latex is 0.01 m
If it is less than eq / 1 g (solid content), the amount of fine coagulated material in the copolymer latex increases, and if it exceeds 0.4 meq / 1 g (solid content), the blister resistance is poor.

The amount of acid in the aqueous phase of the copolymer latex can be adjusted by selecting the amount and type of the ethylenically unsaturated carboxylic acid used, but the object of the present invention is achieved. To achieve this, the total amount of the ethylenically unsaturated carboxylic acid used, X parts by weight, and the ethylenically unsaturated carboxylic acid, Y parts by weight, present in the polymerization system before the start of the polymerization,
It is necessary to satisfy the following conditions: 0.2 ≦ Y ≦ 1, 0.1 ≦ Y / (XY) ≦ 0.5.

With respect to the copolymer latex prepared by a method other than the above method, a coated paper having good blister resistance and surface strength cannot be obtained when the copolymer latex is used, or There is a problem that the production cost is high because the polymer latex contains many fine coagulated products and the yield is reduced.

The method of adding various monomer components other than the ethylenically unsaturated carboxylic acid monomer in the present invention is not particularly limited, and any of a batch addition method, a split addition method, and a continuous addition method is employed. Can be
Polymerization is started in a part of a monomer mixture composed of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith, and then the remaining monomer A so-called multi-stage addition method of adding the body mixture into the polymerization system is preferred.

In order to prevent the formation of fine coagulates in the copolymer latex during the emulsion polymerization, the amount of the monomer mixture present in the polymerization system at the beginning of the polymerization should be 100 parts by weight of the total monomer mixture. Preferably, the amount is 8 to 30 parts by weight.

Regarding the kind of the ethylenically unsaturated carboxylic acid monomer existing in the polymerization system before the start of the polymerization, it is particularly preferable to include fumaric acid in terms of polymerization stability.

In the emulsion polymerization of the present invention, conventional chain transfer agents, polymerization initiators, emulsifiers, electrolytes, polymerization accelerators, chelating agents and the like can be used.

The chain transfer agent used in the present invention includes:
n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan and other alkyl mercaptans, xanthogen compounds such as dimethyl xanthogen disulfide, diisopropyl xanthogen disulfide, α-methyl Compounds such as styrene dimer and terpinolene; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide and tetramethylthiuram monosulfide; phenols such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol System compounds, allyl compounds such as allyl alcohol, halogenated hydrocarbons such as dichloromethane, dibromomethane, carbon tetrachloride, and carbon tetrabromide Compounds, alpha-benzyloxy styrene, alpha-benzyloxy acrylonitrile, alpha-benzyloxy ethers such as acrylamide, triphenyl ethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalate, 2
-Ethylhexyl thioglycolate and the like, and one or more kinds can be used.

The use amount of these chain transfer agents is not limited at all, and can be appropriately adjusted according to the performance required for the copolymer latex. Preferably, the amount is 0.1 to 100 parts by weight of the monomer mixture. 05 to 10 parts by weight.

Examples of the initiator include a water-soluble initiator such as potassium persulfate, ammonium persulfate and sodium persulfate, a redox initiator, and an oil-soluble initiator such as benzoyl peroxide. It is preferable to use 0.05 to 10 parts by weight based on parts by weight.

Examples of the emulsifier include anionic surfactants such as sulfates of higher alcohols, alkyl benzene sulfonates, alkyl diphenyl ether sulfonates, sulfates of nonionic surfactants, and alkyl ester types of polyethylene glycol, alkyl phenyl. One or more nonionic surfactants such as ether type and alkyl ether type are used.

The amount of water used in the emulsion polymerization is 80 to 400 parts by weight based on 100 parts by weight of the monomer mixture.

The copolymer latex obtained by the above-described production method is used not only as a paper coating composition for producing coated paper, but also as an adhesive composition for carpet backing and an adhesive for rock fiber. It can also be used as a composition, an adhesive composition for leather and the like.

When the copolymer latex produced by the present invention is used as one component of a paper coating composition for paper coating, for example, a pigment, a water-soluble polymer, A method can be employed in which the copolymer latex is added and mixed with various additives and used as a homogeneous dispersion. Then, the composition for paper coating is applied to base paper by an ordinary method using various blade coaters, roll coaters, air knife coaters, and the like, and after drying, calendering and the like are performed as necessary. Can be obtained.

In this case, preferably, the copolymer latex of the present invention is used in an amount of 2 to 1 with respect to 100 parts by weight of the pigment in terms of solid content.
00 parts by weight, more preferably 5 to 30 parts by weight, and other binders of 0 to 30 parts by weight can be used.

Here, examples of the dispersant include sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate and the like.

Examples of the pigment include inorganic pigments such as kaolin clay, talc, barium sulfate, titanium oxide, calcium carbonate, aluminum hydroxide, zinc oxide, and satin white; and organic pigments such as polystyrene latex. Are used alone or as a mixture.

Examples of the water-soluble polymer include modified starches such as starch, oxidized starch and esterified starch, natural binders such as soybean protein and casein, polyvinyl alcohol, carboxymethyl cellulose and the like.

Examples of various additives include antifoaming agents (polyglycol, fatty acid ester, phosphate ester,
Silicone oil, etc.), leveling agents (funnel oil, dicyandiamide, urea, etc.), preservatives, waterproofing agents, mold release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, etc., and are added as necessary. .

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. In the examples, parts and percentages indicating percentages are based on weight. The measurement of various physical properties in the examples was based on the following methods.

Fine Coagulated Material The amount of coagulated material having a size of 50 μm or less in the copolymer latex is observed with a microscope, and the evaluation is performed in the following three stages. The smaller the coagulated material, the better the polymerization stability. ：: very little △: little ×: many

Gel content The obtained copolymer latex was spread on a glass plate at 85 ° C.
And dry for 4 hours. About 0.3 grams of this film (A)
Is precisely weighed and immersed in 100 ml of toluene for 48 hours.
Thereafter, the mixture is filtered through a 300-mesh wire gauze, dried, and the toluene-insoluble content on the wire gauze is weighed (B). The gel content is calculated according to the following equation. Gel content = B / A × 100

Amount of Acid in Aqueous Phase 5 g of a copolymer latex solid content was diluted with distilled water to obtain 400 parts.
g. A 0.1N HCl aqueous solution was added until pH 3 was reached, and after standing for 12 hours, a 0.1N NaOH aqueous solution was added at 0.05 ml per second, and conductivity titration was performed to determine the acid content of the aqueous phase. It is the acid amount per 1 g of the solid content of the copolymer latex.

Surface Strength The degree of picking when simultaneously printing each coated paper sample with an RI printing machine was visually judged and relatively evaluated from 5 to 1 point. The higher the score, the better.

Blister resistance The minimum temperature at which blisters are generated by throwing a double-sided printing coated paper into a heated oil bath after moisture conditioning (water content: 6%). The higher the minimum temperature, the better the blister resistance.

Preparation of Copolymer Latex In a 100 liter autoclave, 100 parts by weight of water were added.
0.3 parts by weight of sodium hydrogen carbonate, potassium persulfate
After adding 0 parts by weight and the monomer mixture, emulsifier, chain transfer agent, etc. of the left part with the “/” in the tables shown in Tables 1 and 2 charged, polymerization was started, and 1 hour at 70 ° C. Polymerization was carried out for hours. Then, as shown in Tables 1 and 2, 6 parts of the monomer mixture, emulsifier, chain transfer agent, etc., on the right side of the
It was added continuously over time. After the polymerization was continued until the polymerization conversion rate reached 97%, the polymerization was terminated. After the obtained copolymer latex was adjusted to PH8 using sodium hydroxide, unreacted monomers and the like were removed by steam distillation to obtain copolymer latexes 1 to 10.

The obtained copolymer latexes 1 to 10 were evaluated for fine coagulated products, and the results are shown in Tables 1 and 2.

Each of the copolymer latexes 1 to 10 was 300
The mixture was filtered through a mesh wire mesh, and the gel content and the acid content in the aqueous phase were measured. The results are shown in Tables 1 and 2.

Preparation of Paper Coating Composition Copolymer latex 1 filtered through a 300 mesh wire mesh
Using No. 10, each was adjusted with pure water so that the solid content concentration was 58% based on the following prescription, to obtain a paper coating paint.

[0053]

The composition was coated on a commercially available high-quality paper (64 g / m 2) using a coating bar so that the coating amount on one side was 10 g / m 2 and dried.
Super calendering was performed under the conditions of 0 ° C. and a linear pressure of 70 to 80 kg / cm to obtain a coated paper. The surface strength and blister resistance of the obtained coated paper were measured.
2 is shown.

Table 1

Table 2

[0057]

As described above, according to the production method of the present invention, a copolymer latex having a small amount of fine coagulated product can be obtained.
Coated paper using the copolymer latex of the present invention as a binder has excellent surface strength and blister resistance.

Continued on the front page (72) Inventor Wataru Fujiwara 2-10-2 Kikumotocho, Niihama-shi, Ehime Pref. (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (2)

(57) [Claims] 1 to 10 parts by weight of an aliphatic conjugated diene monomer and 0.6 to 10 parts of an ethylenically unsaturated carboxylic acid monomer.
Parts by weight and other monomers copolymerizable therewith
When emulsion polymerization of a monomer mixture consisting of 89.4 parts by weight (total 100 parts by weight) in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring, an ethylenically unsaturated carboxylic acid Polymerization is started by allowing Y parts by weight of the total amount of the monomer to be used in the polymerization system, and the X and Y satisfy the following conditions 1 and 2 and the gel content is 20 parts by weight.
Weight% or less and the amount of acid in the aqueous phase is 0.01 to 0.4 me.
A method for producing a copolymer latex, wherein polymerization is performed so as to be q / 1 g (solid content). Condition 1: 0.2 ≦ Y ≦ 1 Condition 2: 0.1 ≦ Y / (XY) ≦ 0.5 2. The process for producing a copolymer latex according to claim 1, wherein fumaric acid is present in the polymerization system as an ethylenically unsaturated carboxylic acid monomer to initiate polymerization.