JPH11293594A - Production of copolymer latex, and composition for coating paper containing the copolymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a copolymer latex excellent in stability when carrying out the polymerization and having excellent adhesive strength and blistering resistance when used as a binder for coated paper. SOLUTION: When the emulsion copolymerization of monomers comprising 15-75 pts.wt. of butadiene, 1-10 pts.wt. of itaconic acid and 15-84 pts.wt. of other copolymerizable monomers (100 pts.wt. total amount thereof) is carried out in the presence of 2-40 pts.wt. of cyclohexene, at least >50 wt.% of the cyclohexene is continuously added to a polymerization reactor after the amount of a produced polymer attains at least 5 pts.wt. to thereby produce a copolymer latex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel method for producing a copolymer latex and a paper coating composition using the copolymer latex obtained by the method.

[0002]

BACKGROUND OF THE INVENTION It is well known that carboxy-modified butadiene-based copolymer latex is widely used as a binder in the field of paper processing and carpet backsizing. The performance required of the binder in each application is diverse, and the required performance is generally met by changing the composition and structure of the butadiene copolymer latex accordingly. In recent years, in the field of paper processing, the speed of paper coating and printing has been remarkably increased, and quality that can withstand these speed increases has been demanded. At the same time, rationalization by reducing the amount of copolymer latex used as a binder is being pursued. That is, coated papers having excellent blister resistance are required, and at the same time, those having the same adhesive strength as before even if the copolymer latex as a binder is reduced.

[0003]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that only one ring is provided in the ring.
At least one type of hydrocarbon (A) 2 selected from unsaturated cyclic hydrocarbons having 5 to 8 carbon atoms having two unsaturated bonds
In the emulsion copolymerization in the presence of 40 parts by weight, after the amount of the produced polymer reaches at least 5 parts by weight, continuously or in an amount exceeding at least 50% by weight of the total amount of the hydrocarbon (A) used By discontinuously adding to the polymerization reactor,
The present inventors have found that it is possible to obtain a copolymer latex for paper coating which gives a coated paper having excellent blister resistance and adhesive strength, and reached the present invention.

That is, the present invention relates to an aliphatic conjugated diene monomer of 15 to 75 parts by weight, an ethylenically unsaturated carboxylic acid monomer of 1 to 10 parts by weight, and other copolymerizable monomers of 15 to 84 parts. A monomer consisting of 100 parts by weight (total 100 parts by weight) was converted into a monomer having 5 carbon atoms having one unsaturated bond only in the ring.
When the emulsion copolymerization was carried out in the presence of 2 to 40 parts by weight of at least one type of hydrocarbon (A) selected from unsaturated cyclic hydrocarbons of from 8 to 8, the amount of polymer produced reached at least 5 parts by weight. Thereafter, at least 50% of the total amount of the hydrocarbon (A) used
An object of the present invention is to provide a method for producing a copolymer latex, which comprises continuously or discontinuously adding an amount of more than% by weight to a polymerization reactor. Hereinafter, the present invention will be described in detail.

The aliphatic conjugated diene monomer in the present invention includes 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene,
Examples thereof include 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and one or more kinds can be used. In particular, 1,3-butadiene is preferred.

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.

Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid.

Other monomers which can be combined with the aliphatic conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include unsaturated carboxylic acid alkyl ester monomers,
Examples include an unsaturated monomer containing a hydroxyalkyl group, a vinyl cyanide monomer, and an unsaturated carboxylic acid amide monomer.

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 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.

As unsaturated monomers containing a hydroxyalkyl group, β-hydroxyethyl acrylate, β
-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.

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.

Furthermore, in addition to the above-mentioned 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 unsaturated cyclic hydrocarbon having 5 to 8 carbon atoms having one unsaturated bond only in the ring (A) includes cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like. And one or more kinds can be used. Particularly, cyclohexene is preferred. Some of these are added continuously or discontinuously, but there is no particular limitation on the rate and number of additions, and they may be changed during the course. Further, it may be added after all the monomers have been added.

The above monomer composition (100 parts by weight in total)
Are 15 to 75 parts by weight of an aliphatic conjugated diene monomer, 1 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and 15 to 84 parts by weight of another copolymerizable monomer. In the present invention, if the amount of the above-mentioned monomer is outside the scope of the present invention, the adhesive strength is undesirably reduced.

In the emulsion polymerization of the above monomers,
Emulsion copolymerization is carried out in the presence of 2 to 40 parts by weight of at least one hydrocarbon (A) selected from the unsaturated cyclic hydrocarbons mentioned in the present invention, and the amount of polymer produced is at least 5 parts by weight. Parts, it is necessary that more than at least 50% by weight of the total amount of the hydrocarbon (A) used be added continuously or discontinuously. If the total amount of the hydrocarbon (A) is less than the range of the present invention, the adhesive strength and the blister resistance are inferior, and if it exceeds the range of the present invention, the stability during polymerization is undesirably reduced. If the amount of the polymer produced is less than 5 parts by weight and more than 50% by weight of the hydrocarbon is added, the stability at the time of polymerization decreases, which is not preferable.

The method of adding the various components in the present invention is not particularly limited, and any of a divided addition method and a continuous addition method can be employed. Also, there is no particular limitation on the emulsion polymerization method, and any one of single-stage polymerization, two-stage polymerization, and multi-stage polymerization can be employed.
Further, in emulsion polymerization, a conventional chain transfer agent, an emulsifier,
A polymerization initiator, an electrolyte, a polymerization accelerator, a chelating agent 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 Styrene dimer, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide,
Thiuram compounds such as tetramethylthiuram monosulfide, phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane, carbon tetrachloride , Halogenated hydrocarbon compounds such as carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, and thioglycolic acid Thiomalic acid, 2-ethylhexyl thioglycolate, etc .;
More than one species 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, but is preferably 0.1 to 100% by weight of the monomer mixture. 05 to 10% by weight.

Examples of the emulsifier include anionic surfactants such as sulfates of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, aliphatic carboxylates, sulfates of nonionic surfactants, and polyethylene glycol. Nonionic surfactants such as alkyl ester type, alkyl phenyl ether type and alkyl ether type are used alone or in combination of two or more.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate, and sodium persulfate, a redox-based initiator, or an oil-soluble initiator such as benzoyl peroxide can be used.

The paper coating composition of the present invention comprising the copolymer latex and the pigment obtained by the above-mentioned production method is excellent in blister resistance and adhesive strength. Further, the copolymer can be used not only as a paper coating composition, but also as an adhesive composition for carpet backing, an adhesive composition for rock fiber, an adhesive composition for leather, and the like.

The paper coating composition of the present invention is prepared as an aqueous dispersion of the copolymer latex, together with a pigment and, if necessary, other binders.

At this time, the copolymer latex of the present invention is preferably used in an amount of 2 to 1 based on 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, as the pigment, kaolin clay,
Talc, barium sulfate, titanium oxide, calcium carbonate,
Examples thereof include inorganic pigments such as aluminum hydroxide, zinc oxide and satin white, and organic pigments such as polystyrene latex, and these are used alone or in combination.

If necessary, modified starches such as starch, oxidized starch and esterified starch, natural binders such as soybean protein and casein, and synthetic latexes such as polyvinyl alcohol, polyvinyl acetate latex and acrylic latex are used. May be.

To prepare the paper coating composition of the present invention,
Furthermore, other auxiliaries, such as dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), defoamers (polyglycols, fatty acid esters, phosphate esters, silicone oils, etc.), leveling agents (funnel oil, Dicyandiamide, urea, etc.),
Preservatives, waterproofing agents, release agents (calcium stearate,
Paraffin emulsion), a fluorescent dye, and a color water retention enhancer (such as carboxymethyl cellulose and sodium alginate) are added as necessary.

Further, a method for applying the paper coating composition to coated paper may be a known technique, for example, an air knife coater,
It is performed by a coating machine such as a blade coater, a roll coater, and a bar coater. After the application, the surface is dried and finished with a calender ring or the like.

[0029]

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.

The amount of polymer produced The copolymer latex during polymerization is sampled, and the solid content is measured. From the obtained solid content (%), the amount of polymer produced is determined by the following formula. Polymer production amount (parts by weight) = solid content (%) × total amount added to polymerization tank (parts by weight) / 100

Aggregate Amount 1 kg of the copolymerized latex having been polymerized is filtered through a 200 mesh wire netting. The dry weight of the filtration residue is measured, and the weight% based on the copolymer latex is determined.

Gel content The copolymer latex was dried at 80 ° C. and had a thickness of about 0.5 m.
m is prepared. About 1 g of the film is precisely weighed and
It is immersed in 00 cc of toluene for 48 hours, filtered through a 300-mesh wire gauze, dried, and the toluene-insoluble matter (gel) is weighed to calculate the gel content.

Adhesive force RI Dry Pick The degree of picking when printing with a RI printing machine without using fountain solution is visually judged, and the degree of picking is determined to be 1st (best) to 5th.
It was evaluated on a five-point scale (the worst). The average value of 6 times is shown.

The degree of picking when printing with a fountain solution on a RI Wet Pick RI printing machine is visually judged, and five grades from first grade (best) to fifth grade (worst). It was evaluated by the method. The average value of 6 times is shown.

Blister resistance The minimum temperature at which blisters are formed when a double-sided coated paper is humidified (about 6%) and thrown into a heated oil bath.

Example 1 Preparation of Copolymer Latex 100 parts by weight of water, 0.4 part of sodium dodecylbenzenesulfonate, 0.3 part of sodium hydrogen carbonate, 0.8 part of potassium persulfate were placed in a 20-liter autoclave. And a part of the monomer mixture and the chain transfer agent shown in Table 1 and an unsaturated cyclic hydrocarbon were charged and heated to 70 ° C. When the reaction temperature was reached, the remaining monomer mixture and chain transfer agent were added continuously over 7 hours. When the amount of the unsaturated cyclic hydrocarbon reached the amount of polymer production (parts) shown in Table 1, a predetermined amount was continuously added to the reaction tank for a predetermined time. Final polymerization addition rate of 9
The polymerization was continued until the concentration reached 7% or more. The obtained copolymer latex was adjusted to pH 8 using sodium hydroxide, and then unreacted monomers and residual unsaturated cyclic hydrocarbons were distilled off by steam distillation. Removed, copolymer latexes A-D,
ab were obtained. The gel amount and the aggregate amount of the obtained copolymer latex were measured. The results are shown in Table 1.

Preparation of Paper Coating Composition Copolymer latexes A to D and a to b were each adjusted with pure water so as to have a solid content of 58% based on the following formulation. A composition for use was obtained.

(Formulation) Kaolin clay 80 parts Calcium carbonate 20 parts Modified starch 8 parts Copolymer latex 12 parts (solid content)

Further, after coating and drying a commercially available high-quality paper (84 g / m 2) using a coating bar so that the coating amount of the above composition is 10 g / m 2 on one side, the roll temperature is 5 ° C.
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 adhesive strength and blister resistance were measured. The results are shown in Table 1.

[0040]

[Table 1]

(Example 2) Preparation of copolymer latex In a 20-liter autoclave, 120 parts by weight of water, 0.7 part of sodium dodecylbenzenesulfonate, 0.2 part of sodium hydrogencarbonate, 1.0 part of potassium persulfate were placed. A part of the monomer mixture and the chain transfer agent shown in Table 1 and an unsaturated cyclic hydrocarbon were charged and the temperature was raised to 72 ° C. When the reaction temperature was reached, the remaining monomer mixture and chain transfer agent were added continuously over 7 hours. When the amount of the unsaturated cyclic hydrocarbon reached the amount (parts) of the polymer shown in Table 2, a predetermined amount was continuously added to the reaction tank for a predetermined time. Final polymerization addition rate of 9
The polymerization was continued until the concentration reached 8% or more, and the obtained copolymer latex was adjusted to PH8 using sodium hydroxide. Then, unreacted monomers and residual unsaturated cyclic hydrocarbons were removed by steam distillation. The copolymer latexes E to J and c to e were obtained in the same manner as in Example 1. The gel amount and the aggregate amount of the obtained copolymer latex were measured. Table 2 shows the results.

Preparation of Paper Coating Composition Each of the copolymer latexes E to J and c to e was adjusted to have a solid content of 62% based on the following formulation, using pure water. In the same manner as in Example 1, a paper coating composition was obtained.

(Formulation) Kaolin clay 60 parts Calcium carbonate 40 parts Modified starch 4 parts Copolymer latex 10 parts (solid content)

Further, after coating and drying a commercially available high-quality paper (64 g / m 2) using a coating bar so that the coating amount of the above composition is 8 g / m 2 on one side, the roll temperature is set at 50 g / m 2.
A super calender treatment was performed at a temperature of 50 ° C. and a linear pressure of 50 to 60 kg / cm to obtain a coated paper. The adhesive strength and blister resistance were measured. Table 2 shows the results.

[0045]

[Table 2]

[0046]

The copolymer latex obtained by the production method of the present invention has excellent stability during polymerization, and has excellent adhesive strength and blister resistance as a binder for coated paper.

Claims (2)

[Claims] 1. It comprises 15 to 75 parts by weight of an aliphatic conjugated diene monomer, 1 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer and 15 to 84 parts by weight of another copolymerizable monomer. Monomer (100 parts by weight in total)
At least one type of hydrocarbon (A) 2 selected from unsaturated cyclic hydrocarbons having 5 to 8 carbon atoms having two unsaturated bonds
In the emulsion copolymerization in the presence of 40 parts by weight, after the amount of the produced polymer reaches at least 5 parts by weight, continuously or in an amount exceeding at least 50% by weight of the total amount of the hydrocarbon (A) used A method for producing a copolymer latex, which is added discontinuously to a polymerization reactor. 2. A paper coating composition comprising a pigment and a copolymer latex obtained by the production method according to claim 1.