JP2002012619A - Method for purifying latex for paper coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently removing fine coagulated matters included in a copolymer latex. SOLUTION: This method for purifying a latex for paper coating is characterized in that a copolymer latex obtained by subjecting a conjugate dienic monomer, an ethylenically unsaturated carboxylic acid monomer and another copolymerizable monomer to an emulsion polymerization is filtered by using 0.2-5 wt.% diatomaceous earth comprising >=80 wt.% particles having 10-40 μm particle diameters based on 100 pts.wt. copolymer latex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying latex for paper coating. More specifically, the present invention relates to a purification method for removing fine coagulated material contained in a copolymer latex using a specific diatomaceous earth.

[0002]

2. Description of the Related Art Latexes for paper coating are usually obtained by emulsion polymerization, and include fine coagulated products formed during polymerization. When used as a paper coating latex, when this fine coagulated material is present, at the time of coating,
It causes roll contamination and lowers productivity. In addition, in the case of coated paper as a product, the uniformity of the surface is reduced. For this reason, studies have been made to prevent the formation of fine solids during emulsion polymerization and to remove the formed fine solids. As a method for purifying latex for paper coating, JP-B-46-32058 and JP-B-3-6582
0, a method of removing fine coagulated material using diatomaceous earth is introduced. In Japanese Patent Publication No. 46-32058, diatomaceous earth is used in an amount of 1 to 10% by weight with respect to the polymer emulsion. The diatomaceous earth has a large particle diameter, preferably 20 to 50 μm. In Japanese Patent Publication No. 3-65820, diatomaceous earth is used in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the polymer emulsion, and the weight% to be added to the precoat and the polymer emulsion is specified. However, since diatomaceous earth is natural and has a wide particle size distribution, selection of the average particle size alone is not sufficient, and also includes those indicated elsewhere, and is not necessarily in terms of filtration rate. Nothing was satisfactory.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently removing fine coagulated substances contained in a copolymer latex.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by using diatomaceous earth having a specific particle size distribution, the fine particles in the latex for paper coating can be obtained. The present inventors have found that the coagulated material can be removed very efficiently with a high filtration rate, and have completed the present invention. That is, the present invention, 100 parts by weight of a copolymer latex obtained by emulsion polymerization of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and other copolymerizable monomers, What is provided is a method for purifying a latex for paper coating, characterized by filtering using 0.2 to 5 parts by weight of diatomaceous earth having a particle diameter in the range of 10 μm to 40 μm but having a weight fraction of 80% or more. It is.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

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

The ethylenically unsaturated carboxylic acid monomer used in the present invention includes mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid. Alternatively, two or more kinds can be used.

Other copolymerizable monomers usable in the present invention include aromatic vinyl monomers, vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, and hydroxyalkyl groups. And unsaturated carboxylic acid amide-based monomers.

As the aromatic vinyl monomers, 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.

As the vinyl cyanide monomer used in the present invention, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like can be mentioned, and one or more kinds can be used. Particularly, acrylonitrile and methacrylonitrile are preferred. As unsaturated carboxylic acid alkyl ester monomers, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate,
Butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate, and one or more kinds thereof 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.

The unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide,
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 can also be used.

The copolymer latex of the present invention is obtained by emulsion polymerization of the above-mentioned conjugated diene monomer, ethylenically unsaturated carboxylic acid monomer and other copolymerizable monomers. The composition of these monomers is not particularly limited, but 10 to 90% by weight of a conjugated diene monomer,
It is preferable that the content of the ethylenically unsaturated carboxylic acid monomer is 0.1 to 20% by weight and the other copolymerizable monomer is 10 to 89.9% by weight.

As the method for producing the copolymer latex in the present invention, known emulsion polymerization methods such as continuous emulsion polymerization, batch emulsion polymerization, two-stage emulsion polymerization, and division addition emulsion polymerization can be employed. In the emulsion polymerization, additives and auxiliaries used in general emulsion polymerization such as known chain transfer agents, emulsifiers, polymerization initiators, electrolytes and chelating agents can be used.

Examples of such a chain transfer agent include n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, and t-octyl mercaptan.
Dodecyl mercaptan, alkyl mercaptans such as n-stearyl mercaptan, xanthogen compounds such as dimethyl xanthogen disulfide, diisopropyl xanthogen disulfide, terpinolene and α-methylstyrene dimer, tetramethylthiuram disulfide,
Thiuram compounds such as tetraethylthiuram disulfide and tetramethylthiuram monosulfide, phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane and dibromomethane , Halogenated hydrocarbon compounds such as carbon tetrabromide, α-benzyloxystyrene, α-benzyloxyacrylonitrile,
Vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, and the like, and one or more of these are used. be able to.

Examples of the emulsifier include higher alcohol sulfates, alkylbenzene sulfonates, alkyldiphenyl ether sulfonates, aliphatic sulfonates,
Aliphatic carboxylate, anionic surfactants such as sulfate salts of nonionic surfactants or alkyl ester type of polyethylene glycol, alkyl phenyl ether type, nonionic surfactants such as alkyl ether type, and the like. One or more of these can be used.

As the polymerization initiator, a water-soluble polymerization initiator such as potassium persulfate, sodium persulfate and ammonium persulfate, a redox polymerization initiator, and an oil-soluble polymerization initiator such as benzoyl peroxide can be appropriately used. In particular, use of a water-soluble polymerization initiator is preferred.

In the polymerization of the copolymer latex of the present invention, saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane and cycloheptane, unsaturated hydrocarbons such as pentene, hexene and heptene, cyclopentene and cyclohexene, Use of hydrocarbon compounds such as cycloheptene, 4-methylcyclohexene, cyclic unsaturated hydrocarbon having one unsaturated bond in the ring such as 1-methylcyclohexene, and aromatic hydrocarbons such as benzene, toluene and xylene. Can be. In particular, the emulsion polymerization is preferably performed in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring.

In the present invention, the copolymer latex obtained above is filtered using diatomaceous earth. The diatomaceous earth used in the present invention has a particle diameter in the range of 10 μm to 40 μm, but has a weight fraction of 80%.
%. If it is in the range of 10 μm to 40 μm but the weight fraction is less than 80%, the filtration rate is reduced, and it is not preferable because the fine coagulated material cannot be removed efficiently. Preferably, the weight fraction in the range of 10 μm to 40 μm is 85% or more, more preferably 90% or more. The amount of diatomaceous earth used in the present invention is 0.2 to 5 per 100 parts by weight of the copolymer latex.
Parts by weight. In addition, when filtering, it is usually preferable to use a part of the diatomaceous earth for precoating, add the remainder to the copolymer latex, and filter.

[0020]

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.

[0021]Diatomaceous earth adjustment  By classifying or mixing commercially available diatomaceous earth
The particle size was adjusted.

[0022]Measurement of particle size of diatomaceous earth  Particle size distribution by centrifugal sedimentation using Shimadzu SA-CP3
It was measured.

[0023]Preparation of copolymer latex  100 liters of water, charcoal in a 10 liter autoclave
0.4 parts of sodium hydrogen oxyate, 1.0 part of potassium persulfate,
0.5 parts of sodium dodecylbenzenesulfonate, itacone
2.5 parts of acid, 35 parts of butadiene, 57.5 parts of styrene,
5 parts of methyl methacrylate, t-dodecyl mercaptan
0.5 part was added and the temperature was raised to 70 ° C. to perform polymerization. Polymerization conversion
The polymerization was continued until the rate reached 97%, and the polymerization was terminated. Profit
Use sodium hydroxide for the copolymer latex
After adjusting the pH to 7, the unreacted monomer is removed by steam distillation.
Removed and further reduced the solid content of the copolymer latex to 50%
It was adjusted. Evaluation of filterability using this copolymer latex
Value.

[0024]Evaluation method of filterability  Buchner of 9.6cm inside diameter in 500cc suction filtration bottle
No. with a diameter of 9 cm was attached. One filter paper is installed
I do. The suction filter bottle is evacuated with a circulation aspirator.
2 g of each diatomaceous earth was dispersed in 100 g of water and suction-filtered,
Create a precoat layer. Next, a copolymer having a solid content of 50%
2 g of diatomaceous earth was added to 200 g of latex,
Stir well. It is suction filtered. Copolymer latek
From the time when the filtrate of
Measure the time until the surface of the diatomaceous earth can be seen, and
Evaluate the degree. The shorter this time, the faster the filtration rate. Conclusion
The results are shown in Table 1. In addition, the copolymer latex after filtration
Then, it was spread on a glass plate and fine coagulated material was visually observed.
However, no microcoagulated product was observed in any of the examples.

[0025]

[Table 1]

[0026]

By employing the purification method of the present invention, fine coagulated products in the copolymer latex can be efficiently removed. In addition, by using the copolymer latex obtained by this method as a latex for paper coating, it is possible to obtain a coated paper that is less likely to cause roll contamination during coating and has high surface uniformity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 19/20 D21H 19/20 A F-term (Reference) 4J011 KA03 KA04 KA10 KA23 KB29 4J038 CA051 CC011 CG141 CG161 CG171 CH121 GA06 KA08 KA20 LA05 MA08 MA10 PC10 4J100 AB02R AB03R AB04R AB16R AG02R AG04R AJ01Q AJ02Q AJ08Q AJ09Q AL03R AL04R AL08R AL09R AL10R AL34R AL36R AL39R AM02R AM03R AM15R AM21R AS02P01 AG03 AG03 AG01

Claims (1)

[Claims] 1. Particles are prepared based on 100 parts by weight of a copolymer latex obtained by emulsion polymerization of a conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and other copolymerizable monomers. A method for purifying a latex for paper coating, characterized by filtering using 0.2 to 5 parts by weight of diatomaceous earth having a diameter in the range of 10 μm to 40 μm and a weight fraction of 80% or more.