JP2879121B2 - Method for producing copolymer latex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a novel method for producing a copolymer latex.

[0002]

2. Description of the Related Art Butadiene-based copolymer latex containing butadiene as a main component is used in the paper processing field or
It is well known that it is widely used as a binder in back sizing of carpets and the like.

[0003] The performance required of the binder in each application varies widely, and the composition and structure of the butadiene-based copolymer latex are generally changed accordingly.

[0004] These copolymer latexes are generally produced by emulsion polymerization. At this time, slight differences are observed depending on the composition of the monomer mixture constituting the copolymer latex and the types and amounts of various additives. However, there is a problem that a fine coagulated product is generated in the copolymer latex.

In recent years, speeding up of paper coating and printing has been promoted in terms of labor saving and rationalization, and a coating color that can withstand high-speed coating and a coated paper that can withstand high-speed printing have been demanded. Have been.

That is, the coating color is required to have stability against mechanical shearing as a performance during coating, and the coated paper is required to have excellent adhesive strength, water resistance, blister resistance, and the like.

It is known that a copolymer latex, which is a component of the coating color, has a great influence on these properties. Fine coagulation in the copolymer latex is known as a factor that impairs the mechanical stability of the coating color.If such coagulation is large, streak trouble during blade coating, applicator contamination, and contamination during calendering This causes problems such as blanket piling during printing.

[0008] Further, these copolymer latexes
Adhesives for carpet backing such as tufted carpets and needle punch carpets and car cushion materials,
It is also used as an adhesive for rock fiber substrates used in applications such as civil engineering mats and industrial filters, but even in this case, fine coagulated material in the copolymer latex adversely affects the adhesive strength and water resistance. Has been exerted.

[0009]

As described above, the fine coagulated material in the copolymer latex causes contamination of the reactor and causes various adverse effects in each end use.
Usually, it is removed by a filtration step or the like.

However, this filtration step is also complicated, and the amount of the fine coagulated material to be removed is limited. Therefore, it is difficult to completely remove the fine coagulated material, and the productivity must be reduced. I was

Further, these copolymer latexes include:
Odors, often due to alkyl mercaptans, particularly used as chain transfer agents, can be problematic. This odor reduces the commercial value of the final product,
There is a need for a copolymer latex that produces less odor.

[0012]

Means for Solving the Problems The present inventors have conducted intensive studies on the above problems, and as a result, a copolymer latex obtained by emulsion polymerization in the presence of a specific compound has all of these problems. And found that a paper coating composition using the copolymer latex had excellent performance, and completed the present invention.

That is, the present invention relates to an aliphatic conjugated diene monomer of 10 to 80% by weight, an ethylenically unsaturated carboxylic acid monomer of 0.5 to 10% by weight and other monomers copolymerizable therewith. An object of the present invention is to provide a method for producing a copolymer latex, which comprises subjecting 10 to 89.5% by weight to emulsion polymerization in the presence of a chain unsaturated hydrocarbon having one unsaturated bond.

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.

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 copolymerizable with the aliphatic conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include alkenyl aromatic monomers and unsaturated carboxylic acid alkyl ester monomers. And unsaturated monomers containing a hydroxyalkyl group, vinyl cyanide monomers, unsaturated carboxylic acid amide monomers and the like.

Alkenyl aromatic 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 malate, 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.

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. 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.

The above monomer composition is composed of 10 to 80% by weight of an aliphatic conjugated diene monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith. It is 10 to 89.5% by weight of the body.

When the amount of the aliphatic conjugated diene monomer is less than 10% by weight, the adhesiveness is low. When the amount is more than 80% by weight, the water resistance tends to be inferior. If the amount of the ethylenically unsaturated carboxylic acid monomer is less than 0.5% by weight, mechanical stability is poor, and if it exceeds 10% by weight, the viscosity of the latex tends to increase, which is not preferable. 10 other copolymerizable monomers
If the amount is less than 8% by weight, the water resistance tends to be poor.

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, and α- Methylstyrene dimer, terpinolene, thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, and phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol ,
Allyl compounds such as allyl alcohol, dichloromethane,
Halogenated hydrocarbon compounds such as dibromomethane, carbon tetrachloride, carbon tetrabromide, α-benzyloxystyrene, α-
Vinyl ethers such as benzyloxyacrylonitrile and α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrylolein, thioglycolic acid, 2-ethylhexylthioglycolate, and the like, and one or more kinds may be used. it can.

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 0.05 to 100 parts by weight based on 100 parts by weight of the monomer mixture. 10 parts by weight.

The chain-like unsaturated hydrocarbon having one unsaturated bond used in the present invention preferably has a boiling point of 140 ° C. or less, since it is necessary to recover an unreacted product after the polymerization. Specifically, 1-butene, 2-butene, 1-
Pentene, 2-pentene, 2-methyl-1-butene,
2,3-dimethyl-2-butene, 4-methyl-2-pentene, 2-methyl-1-pentene, 1-hexene, 2-
Hexene, 1-heptene, 3-methyl-2-pentene,
2,4,4-trimethyl-1-pentene, 2,4,4-
Trimethyl-2-pentene, 2,3,4-trimethyl-
Examples thereof include 2-pentene, 3,4,4-trimethyl-2-pentene, 1-octene, and the like, and one or more kinds can be used.

The amount of the compound used in the present invention is 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 energy required for recovering these compounds becomes undesirably large. Preferably it is 0.5 to 15 parts by weight.

The method of adding the various components in the present invention is not particularly limited, and any of a batch addition method, a division addition method, and a continuous addition method can be employed. Further, in the emulsion polymerization, a commonly used emulsifier, polymerization initiator, electrolyte, polymerization accelerator, chelating agent and the like can be used.

In the present invention, any one of single-stage polymerization, two-stage polymerization and multi-stage polymerization can be employed, but it is particularly preferable to carry out emulsion polymerization by the following method.

That is, in the first stage, 3 to 40% by weight, preferably 5 to 30% by weight of the monomer is polymerized with respect to all the monomers, and the polymerization conversion in the first stage is 50% or more. Preferably, the remaining monomer is polymerized when it becomes 70% or more, and the polymerization is substantially completed. In the above-mentioned production method, it is particularly preferable to use the ethylenically unsaturated carboxylic acid monomer in the first stage in total amount.

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, or a redox initiator or an oil-soluble initiator such as benzoyl peroxide can be used.

By adopting the above-mentioned production method, it is possible to suppress the generation of fine coagulated products and to obtain a copolymer latex having good polymerization stability. Since a chain unsaturated hydrocarbon having one bond is not preferable in terms of working environment hygiene in the final use, in the present invention, after polymerizing a copolymer latex according to the production method, the compound is substantially converted to an unsaturated hydrocarbon. (Per 100 parts by weight of copolymer latex (solid content)
0.5 parts by weight or less).

Known methods for removing the compound include:
For example, it can be removed by steam distillation, vacuum distillation, or blowing of an inert gas.

The paper coating composition comprising the copolymer latex and pigment obtained by the above-described production method is excellent in adhesive strength, blister resistance and odor. further,
The copolymer is not only a paper coating composition, but also an adhesive composition for carpet backing, an adhesive composition for a rock fiber base, an adhesive composition for a tire cord, an adhesive composition for wood, and leather. Can be used as an adhesive composition or the like.

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

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, 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.

Other binders include 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. Is used.

Further, in order to prepare the paper coating composition, other auxiliaries such as dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.) and defoamers (polyglycol, fatty acid ester, etc.) , Phosphate esters, silicone oils, etc.), 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), a fluorescent dye, and a color water retention enhancer (such as carboxymethyl cellulose and sodium alginate) are added as necessary.

Further, the method for applying the paper coating composition to the 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.

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.

Dirt of the reactor After polymerization, deposits on the inner wall of the reactor were visually observed. ：: Very small Δ: Little ×: Many Evaluation was made in these three steps.

The amount of the fine coagulated material of several μm to 50 μm is observed with a microcoagulated product microscope. ：: very small Δ: small ×: large The evaluation is performed in these three stages.

Gel content A latex film is prepared by drying at room temperature. Thereafter, about 1.0 g of the latex film was accurately weighed, placed in 400 cc of toluene, left to dissolve for 48 hours, filtered through a 300-mesh wire gauze, dried, and the toluene insoluble content (gel) on the wire gauze was measured to calculate the gel content. I do.

Preparation of Copolymer Latex In a 10 liter autoclave, 100 parts by weight of water, 0.3 part of sodium dodecylbenzenesulfonate, 0.2 part of sodium hydrogen carbonate, 1.0 part of potassium persulfate and Table 1 or Table 1 The first-stage polymerization was carried out at 65 ° C. by charging a first-stage monomer mixture, a chain transfer agent, and a chain-like unsaturated hydrocarbon having one unsaturated bond shown in FIG. When the conversion of the first-stage emulsion polymerization reached 70%, the second-stage polymerization was performed by continuously adding the monomer mixture, the chain transfer agent, and the unsaturated hydrocarbon in the second-stage for 7 hours. . Thereafter, in order to complete the polymerization, the reaction was further continued for 3 hours, and the polymerization was terminated at a polymerization conversion of 98%. After adjusting the pH of the obtained copolymer latex to 8 using sodium hydroxide, the unreacted monomer and the unsaturated unsaturated residue remaining as unreacted by steam distillation.
The chain unsaturated hydrocarbon having one bond was removed to obtain copolymer latexes 1 to 14.

In the table, the left side indicates the weight of the first row and the right side indicates the weight of the second row with "/" therebetween.

Preparation of Paper Coating Composition Each of the copolymer latexes 1 to 14 was adjusted with pure water to a solids concentration of 60% based on the following formulation to obtain a paper coating composition. Was.

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

Further, the composition was coated on a commercially available high-quality paper (64 g / m ² ) using a coating bar so that the coating amount of one side of the composition was 10 g / m ^2, and dried.
A super calender treatment was performed at 70 ° C. and a linear pressure of 70 to 80 kg / cm 2 to obtain a coated paper. The obtained coated paper was measured for RI Wet Pick, RI Dry Pick, and blister resistance.

Mechanical Stability The above paper coating composition was kneaded between a metal roll and a rubber roll using a patter -stable tester, subjected to mechanical shearing, and measured for the time (minutes) until a coagulated product was formed on the rubber roll. Measure. ：: 30 minutes or more △: 20 minutes or more and less than 30 minutes ×: less than 20 minutes

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

The evaluation was performed in the same manner as in the above-mentioned RI Wet Pick except that the RI Dry Pick fountain solution was not used.

Blister resistance Indicates the minimum temperature at which a double-sided printing coated paper is humidified (about 6%) and thrown into a heated oil bath to generate blisters.

A coated paper was obtained in the same manner as the above-mentioned coating method, except that the coating amount of the odor paper coating composition was 20 g / m ^{2 on} one side. A test piece of 10 cm × 10 cm was prepared from the obtained coated paper, and three test pieces were placed in a glass bottle capable of being sealed. After leaving at 50 ° C. for 1 hour, the stopper was removed to determine the degree of odor. did. ：: Smell △: Slightly smell ×: Almost no smell

Table 3 shows the results.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

Claims (1)

(57) [Claims] 1. An aliphatic conjugated diene monomer in an amount of 10 to 80% by weight and an ethylenically unsaturated carboxylic acid monomer in an amount of 0.5 to 10%.
% By weight and other monomers copolymerizable therewith.
A process for producing a copolymer latex, wherein 9.5% by weight is subjected to emulsion polymerization in the presence of a chain unsaturated hydrocarbon having one unsaturated bond.