JPH0912647A - Production of copolymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a copolymer latex which, when used as a binder for paper coating, gives a coated paper improved in ink set properties, adhesive strength, and blister resistance. SOLUTION: A monomer mixture comprising 10-80wt.% aliph. diene monomer, 0.5-10wt.% ethylenically unsatd. carboxylic acid monomer, and 10-89.5wt.% other copolymerizable monomer is subjected to emulsion polymn. at 60-100 deg.C in the presence of an α-methylstyrene dimer in an amt. of 0.2-2 pts.wt. (based on 100 pts.wt. monomer mixture) in such a manner that the final conversion of the monomer mixture is 80-95%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for producing a copolymer latex.

[0002]

2. Description of the Related Art The so-called 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. When the copolymer latex is used for these applications, the copolymer latex is required to have high adhesive strength and excellent blister resistance during drying and heating. The performance required for the binder is diverse including these purposes, and it is common to change the composition and structure of the butadiene-based copolymer latex in accordance with it. In recent years, the production of coated paper has increased remarkably as the demand for multicolor printed magazines, pamphlets, and advertisements has expanded. In addition, as the printing speed in offset printing increases, the performance required for coated paper and binder is also becoming more sophisticated. Therefore, in addition to the adhesive strength and the blister resistance, there is a demand for a coated paper that has a fast ink fixing property, that is, a fast ink setting property, and particularly a binder that provides such a coated paper. JP-A-3-109451 proposes the use of α-methylstyrene dimer as a polymerization chain transfer agent for the purpose of improving adhesive strength and blister resistance. Also, in Japanese Patent Laid-Open No. 4-41501, a proposal is made to define the polymerization conversion rate of the monomer for the purpose of improving the adhesive strength and the blister resistance. However, none of the techniques was sufficiently satisfactory to simultaneously improve the ink setting property, and further the adhesive strength and the blister resistance to high levels.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a copolymer latex used as a binder for paper coating, which can provide a coated paper having an excellent balance of ink setting property, adhesive strength and blister resistance. The purpose is to get.

[0004]

That is, the first aspect of the present invention
The invention comprises 10 to 80% by weight of an aliphatic conjugated diene monomer,
0.5 to 10% by weight of ethylenically unsaturated carboxylic acid monomer
And 10 to 89.5% by weight of other copolymerizable monomer
In emulsion-polymerizing a monomer consisting of 100 to 100 ° C., 0.2 to 2 parts by weight of α-methylstyrene dimer is used per 100 parts by weight of all the monomers, and The present invention provides a method for producing a copolymer latex, which comprises polymerizing so that the final polymerization conversion rate is 80 to 95%. The second invention of the present invention provides the method for producing a copolymer latex according to the first invention, wherein a part or the whole amount of α-methylstyrene dimer is added at the initial stage of the polymerization. Hereinafter, the present invention will be described in detail.

Examples of the aliphatic conjugated diene-based monomer in the present invention include 1,3-butadiene and 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 mentioned, and one kind or two 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 above-mentioned aliphatic conjugated diene monomer and ethylenically unsaturated carboxylic acid monomer include aromatic vinyl monomers and unsaturated carboxylic acid alkyl ester monomers. Examples thereof include a monomer, a hydroxyalkyl group-containing unsaturated monomer, a vinyl cyanide monomer, and an unsaturated carboxylic acid amide monomer.

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

Examples of the unsaturated monomer 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 and α-ethylacrylonitrile.
One or more kinds can be used. Acrylonitrile is particularly preferred.

As the unsaturated carboxylic acid amide monomer,
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 above monomer composition has 10 to 80% by weight of the aliphatic conjugated diene-based monomer, 0.5 to 10% by weight of the ethylenically unsaturated carboxylic acid monomer, and other copolymerizable with these. The amount of the monomer is 10 to 89.5% by weight. If the amount of the aliphatic conjugated diene monomer is less than 10% by weight, the adhesive strength is 8
If it exceeds 0% by weight, the water resistance tends to be poor, which is not preferable. 0.5% by weight of ethylenically unsaturated carboxylic acid monomer
If it is less than 10% by weight, the mechanical stability is poor, and if it exceeds 10% by weight, the viscosity of the latex tends to increase, which is not preferable. If the amount of the other copolymerizable monomer is less than 10% by weight, the water resistance tends to be inferior.

The method of adding various monomers in the present invention is not particularly limited, and any of a batch addition method, a divided addition method and a continuous addition method can be adopted. Also, the emulsion polymerization method is not particularly limited, and any one-step polymerization, two-step polymerization, multi-step polymerization or the like can be adopted, but the emulsion polymerization is preferably carried out by the following method. That is, in the first stage, 3 to 40% by weight is polymerized with respect to all the monomers, and the remaining monomers are added when the polymerization conversion in the first stage reaches 40% or more.

The final polymerization conversion rate of the mixture of the above monomers must be 80 to 95%. When it exceeds 95%, the effect of the present invention is not sufficiently exhibited. Also, 80%
If it is less than the above range, the water resistance of the copolymer latex decreases, which is not preferable. The method of stopping the polymerization at the above-mentioned polymerization conversion rate is not particularly limited, and it can be achieved by adding a polymerization inhibitor, reducing the polymerization temperature, or the like so that the radical is not generated.

The polymerization temperature in the emulsion polymerization of the present invention is set in the range of 60 to 100 ° C.

In the present invention, α-methylstyrene dimer is used as a chain transfer agent. It is also possible to use other chain transfer agents with the α-methylstyrene dimer. Other chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, dimethylxanthogen sulfide, diisopropylxanthogen disulfide. Compounds such as xanthogen compounds, terpinolene, and thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide, phenol compounds such as 2,6-di-t-butyl-4-methylphenol, and styrenated phenol. Compounds, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, carbon tetrachloride, carbon tetrabromide, α-ben Oxy styrene,
Examples include vinyl ethers such as α-benzyloxyacrylonitrile and α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, and 2-ethylhexylthioglycolate. More than one species can be used.

The amount of α-methylstyrene dimer used is
0.2 to 2 parts by weight based on 100 parts by weight of all monomers,
If it is less than 0.2 parts by weight, the effect of the present invention is not sufficiently exhibited, and if it exceeds 2 parts by weight, the water resistance is lowered, which is not preferable. It is preferably 0.5 to 1.5 parts by weight. Also,
The amount of the other chain transfer agent used is not particularly limited and can be appropriately adjusted according to the performance required for the copolymer latex, but is preferably 0.05 to 100 parts by weight of all the monomers. 5 parts by weight.

Regarding the method of adding α-methylstyrene dimer, it is preferable to add a part or the whole amount thereof at the initial stage of polymerization, and if any other adding method is adopted, the effect of the present invention tends to be insufficient. is there. Particularly, 50 to 100% by weight of α-methylstyrene dimer, and further 7
It is preferable to add 0 to 100% by weight at the initial stage of polymerization. The term "initial stage of polymerization" means that the polymerization conversion rate of all monomers is 3%. Further, there is no particular limitation on the method of adding the other chain transfer agent.

Further, in the emulsion polymerization, an emulsifier, a polymerization initiator, an electrolyte, a polymerization accelerator, a chelating agent and the like which are commonly used can be used.

As the emulsifier, anionic surfactant such as sulfuric acid ester salt of higher alcohol, alkylbenzene sulfonate, aliphatic sulfonate, aliphatic carboxylate, sulfuric acid ester salt of nonionic surfactant or polyethylene glycol. One or more nonionic surfactants such as alkyl ester type, alkyl phenyl ether type, and alkyl ether type are used.

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

In the emulsion polymerization, cyclopentene, cyclohexene, cycloheptene, 4-
Cyclic unsaturated hydrocarbon having one unsaturated bond in the ring such as methylcyclohexene and 1-methylcyclohexene,
You may add benzene, toluene, cyclohexane, etc. The amount of such a compound used is 0.1 to 30 parts by weight based on 100 parts by weight of all the monomers.

The copolymer latex obtained by the above-mentioned production method is not only a composition for paper coating, but also an adhesive composition for carpet backing, an adhesive composition for rock fiber, an adhesive composition for leather, etc. Can also be used as

For example, a paper coating composition is prepared as an aqueous dispersion of the copolymer latex, together with a pigment and, if necessary, other binder.

At this time, the copolymer latex of the present invention is preferably 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 include inorganic pigments such as aluminum hydroxide, zinc oxide, and satin white, and organic pigments such as polystyrene latex, which may be used alone or in combination.

If necessary, modified starch such as starch, oxidized starch, esterified starch, natural binder such as soybean protein and casein, or synthetic latex such as polyvinyl alcohol, polyvinyl acetate latex and acrylic latex is used. You may.

In order to adjust the composition for paper coating, other auxiliary agents such as dispersant (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), defoaming agent (polyglycol, fatty acid ester, Phosphoric acid ester, silicone oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), preservative,
A water resistance agent, a release agent (calcium stearate, paraffin emulsion, etc.), a fluorescent dye, a color water retention improver (carboxymethyl cellulose, sodium alginate, etc.) are added as necessary.

Further, the method for applying the paper coating composition to the coated paper is known in the art, 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 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. 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.

Measurement of Polymerization Conversion of All Monomers About 1.0 g of a latex sample was accurately weighed to obtain 150
After drying for 60 minutes in an oven at ℃, the residual amount is measured, and the polymerization conversion rate is calculated by the following calculation. Solid content ratio = weight after drying (g) / weight before drying (g)

Preparation of copolymer latex In a 10 liter autoclave, 100 parts by weight of water, 0.4 part of sodium dodecylbenzene sulfonate, 0.3 part of sodium hydrogen carbonate, 0.9 part of potassium persulfate and Table 1 or Table. The first-stage monomer mixture and the chain transfer agent shown in 2 are charged, and the first-stage polymerization is carried out at 65 ° C. When the polymerization conversion rate becomes 50% or more, the second-stage monomer is added. The body mixture and the chain transfer agent were continuously added for 7 hours to carry out the second stage polymerization. Then, the polymerization was continued until the polymerization conversion rate shown in Table 1 was reached, and then cooled to complete the polymerization. The obtained copolymer latex was adjusted to pH 8 with sodium hydroxide, and then unreacted monomers and the like were removed by steam distillation to obtain copolymer latexes 1-8. In addition, in the table, the amount of addition in the first stage is shown on the left side and the amount of addition in the second stage is shown on the right side across "/".

Preparation of Paper Coating Composition Copolymer latices 1 to 8 were prepared according to the following prescriptions so as to have a solid content concentration of 62% with pure water. I got a thing.

(Formulation) Kaolin clay 80 parts Calcium carbonate 20 parts Modified starch 6 parts Copolymer latex 10 parts (solid content)

A commercially available high-quality paper (64 g / m ² ) was coated and dried using a coating bar so that the coating amount of the above composition would be 10 g / m ^{2 on} one side, and then the roll temperature was 5
Super calendering was performed under the conditions of 0 ° C. and linear pressure of 70 to 80 kg / cm to obtain coated paper. About the obtained coated paper, ink setting property, RI Dry Pick, RI
Wet Pick and blister resistance were evaluated. The evaluation method is as follows.

Ink setting property An ink for sheet offset was printed on the surface of coated paper with an RI printer, and then white paper was overlaid and pressed with a constant pressure, and the density of the ink transferred to the white paper was visually evaluated. The case where there was no transfer to the white paper was 1 point, and the case where the ink was transferred to the white paper was 5 points, and between 1 point and 5 points, the state of transfer of the ink was observed to judge. The smaller the number, the better the ink setting property.

RI Dry Pick The degree of picking when printed by the RI printing machine is judged with the naked eye, the best one is 1 point, the worst is 5 points, and 1 point and 5 points are relative. It was evaluated. The average of 6 times is shown.

Evaluation was performed using RI Wet Pick dampening water in the same manner as in the above RI Dry Pick.

Blister-resistant double-sided coated paper is humidity-controlled (about 6%) and thrown into a heated oil bath to indicate the minimum temperature at which blister occurs. The higher the minimum temperature, the better the blister resistance.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

EFFECT OF THE INVENTION By using the copolymer latex according to the present invention as a binder for paper coating, it is possible to provide a coated paper having improved ink setting property, adhesive strength and blister resistance.

Claims (2)

[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 copolymerizable monomers 10 to 89.5
When emulsion-polymerizing a monomer composed of 10% by weight at a polymerization temperature of 60 to 100 ° C., 0.2 is added to 100 parts by weight of all the monomers.
~ 2 parts by weight of α-methylstyrene dimer is used, and the polymerization is performed such that the final polymerization conversion rate of all monomers is 80 to 95%. 2. The method for producing a copolymer latex according to claim 1, wherein a part or the whole amount of α-methylstyrene dimer is added at the initial stage of the polymerization.