JP2943206B2 - Method for producing copolymer latex - Google Patents

Description

The present invention relates to a method for producing a copolymer latex having excellent properties such as adhesive strength and blister resistance and low odor when used in an adhesive or the like. .

[Prior art] A copolymer latex obtained by emulsion polymerization of a monomer comprising a conjugated diene monomer, an ethylenically unsaturated monomer, an ethylenically unsaturated carboxylic acid, etc., has excellent adhesiveness. Widely used as various adhesives.

In the production of these copolymer latexes, mercaptan compounds and disulfide compounds are effective as polymerization chain transfer agents and are widely used.

However, mercaptan compounds and disulfide compounds generally have an unpleasant odor, and this odor can be a problem not only during polymerization but also during product processing.
Reduction of this odor has been desired.

For this reason, for example, JP-A-53-121890 proposes the use of a non-sulfur type chain transfer agent having a low odor. However, these chain transfer agents are expensive and
There was a problem in practicality.

[Problems to be Solved by the Invention] The present invention provides a method for producing a copolymer latex that is excellent in properties such as adhesive strength and blister resistance when used in an adhesive or the like and is substantially free of odor. The purpose is to do so.

[Means for Solving the Problems] As a result of intensive studies, the present inventors have achieved the above object by using a copolymer latex obtained by emulsion polymerization of a monomer in the presence of a specific organic solvent. The inventors have found that the present invention has been achieved, and have completed the present invention based on this finding.

That is, the present invention relates to a method for emulsion polymerization of 100 parts by weight of a monomer containing (a) 10 to 80 parts by weight of a conjugated diene monomer and (b) 20 to 90 parts by weight of an ethylenically unsaturated monomer. The emulsion polymerization comprises: 0.1 to 10 parts by weight of a polymerization chain transfer agent, and 0.5 to 20 parts by weight of a non-polymerizable organic solvent having a boiling point in the range of 30 to 250 ° C. and a solubility parameter of 7 to 11,
The emulsion polymerization is carried out by a two-stage polymerization. In the first stage, 10 to 50 parts by weight of the monomer is polymerized.
It is intended to provide a method for producing a copolymer latex, wherein 90 parts by weight are polymerized.

 Hereinafter, the present invention will be described in detail.

The monomer used in the present invention contains the following monomer components (a) and (b).

(A) Conjugated diene monomer Specific examples of the conjugated diene monomer include butadiene,
Examples thereof include isoprene, 2-chloro-1,3-butadiene, and 2-ethyl-1,3-butadiene. These can be used alone or in combination of two or more. Of these, butadiene is particularly preferred.

The amount of the conjugated diene-based monomer to be used is selected from the range of 10 to 80 parts by weight, preferably 10 to 70 parts by weight, particularly preferably 20 to 65 parts by weight based on 100 parts by weight of the total monomers. If the amount is less than 10 parts by weight, sufficient adhesive strength cannot be obtained, while if it exceeds 80 parts by weight, water resistance and adhesive strength are undesirably reduced.

(B) Ethylenically unsaturated monomer Specific examples of the ethylenically unsaturated monomer include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, and (meth) acrylic acid. Alkyl or methacrylic acid alkyl ester compounds such as methyl, ethyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and glycidyl methacrylate Acrylamide or methacrylamide compounds of ethylenically unsaturated carboxylic acids such as acrylamide, methacrylamide, N, N-dimethylacrylamide, N-methyl acrylamide, carboxylic acid vinyl esters such as vinyl acetate, 2-cyanoethyl (meth) Acrylate, acrylonitrile , Vinyl cyanide compounds such as methacrylonitrile and α-chloroacrylonitrile; basic monomers such as dimethyloxyethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine and 4-vinylpyridine; Monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, dicarboxylic acids such as itaconic acid, and further, methyl maleate,
Unsaturated carboxylic acids such as half esters such as methyl itaconate and β-methacryloxyethyl acid hexahydrophthalate can be mentioned. Also, anhydrides of dicarboxylic acids can be used. These can be used alone or in combination of two or more. Of these, styrene and the like are particularly preferable as the aromatic vinyl compound, methyl methacrylate and the like as the alkyl ester compound, acrylonitrile and the like as the cyanide vinyl compound, and acrylic acid and itaconic acid as the unsaturated carboxylic acid. It is preferably used.

The ethylenically unsaturated monomer is used for imparting appropriate hardness, elasticity and water resistance to the obtained copolymer, but the amount used is 20 to 100 parts by weight of all monomers. 90
Parts by weight, preferably in the range of 20 to 80 parts by weight.
If this amount is less than 20 parts by weight, water resistance is poor, while 90
If the amount is more than 10 parts by weight, the copolymer becomes too hard, and the adhesion strength is undesirably reduced.

In the present invention, as part of the component (b), an unsaturated carboxylic acid monomer is usually used in an amount of from 0.5 to 10
Parts by weight, preferably 1 to 7 parts by weight,
The adhesive strength and mechanical stability of the obtained copolymer latex can be further improved.

Next, a non-polymerizable organic solvent (hereinafter referred to as "organic solvent") used in the method for producing a copolymer latex of the present invention.
Has a boiling point (bp) at normal pressure of 30 to 250 ° C., preferably
In the range of 50-200 ° C and the solubility parameter (δ)
Is from 7 to 11, preferably from 7.2 to 10.5, and must be sparingly soluble in water.

Here, poorly soluble in water means that the solubility in water at 20 ° C. is 1% by weight or less.

Specific examples of such an organic solvent include, for example, n-hexane (bp = 68.7 ° C., δ = 7.3), n-octane (bp
= 125.7 ° C, δ = 7.5), cycloalkanes such as cyclopentane (bp = 49.3 ° C, δ = 8.1), cyclohexane (bp = 80.7 ° C, δ = 8.2), benzene (bp = 80.1 ° C, δ = 9.2), toluene (bp = 11)
0.6. ° C, δ = 8.), m-xylene (bp = 139.1 ° C, δ = 8.
Aromatic hydrocarbons such as 8), chloroform (bp = 61.2
° C, δ = 9.1), 1,2-dichloroethane (bp = 83.5 ° C,
δ = 9.7), isopropyl bromide (bp = 59.4 ° C., δ = 8.
5), halogenated hydrocarbons such as chlorobenzene (bp = 131.7 ° C, δ = 9.6), 1-octanol (bp = 195 ° C,
δ = 9.0).

If the boiling point (bp) of the organic solvent is less than 30 ° C., ordinary handling becomes difficult. If it exceeds 250 ° C., it becomes difficult to recover the solvent by stripping or distillation under reduced pressure, and the solvent is contained in the copolymer latex. It is not preferable because it remains.

If the solubility parameter (δ) is less than 7 or exceeds 11, the compatibility between the produced copolymer and the organic solvent is poor,
The amount of mercaptans or disulfides used as a polymerization chain transfer agent cannot be reduced, and the object of the present invention cannot be achieved. The solubility parameter δ is calculated by the following equation. (Δh _vap : molar evaporation heat, v _o : molar volume).

The amount of these specific organic solvents to be used is 0.5 to 20 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of all monomers.

If the amount is less than 0.5 part by weight, the reduction in the amount of the polymerization chain transfer agent, which is the object of the present invention, cannot be achieved, and the odor of the obtained copolymer latex cannot be substantially eliminated. On the other hand, if the amount exceeds 20 parts by weight, a large amount of coagulated material is generated during the polymerization, which is not preferable.

In the present invention, by using a polymerization chain transfer agent and an organic solvent in combination, it is possible to relatively reduce the amount of the polymerization chain transfer agent, and as a result, unpleasant odor due to a mercaptan compound or a disulfide compound is substantially reduced. Can be considerably eliminated.

Thus, the reason that the amount of the polymerization chain transfer agent can be reduced by the presence of the organic solvent in the polymerization system is that the organic solvent is absorbed by the produced copolymer and reduces the viscosity of the copolymer. It is considered that the absorption efficiency and activity of the polymerization chain transfer agent are increased.

The method for producing a copolymer latex in the present invention can be carried out by a conventionally known emulsion polymerization method, except that the above-mentioned monomer and organic solvent are used. That is, emulsion polymerization is performed by adding a monomer, an organic solvent, a polymerization initiator, an emulsifier, a polymerization chain transfer agent and the like to an aqueous medium (usually water).

There is no particular limitation on the polymerization initiator used in the emulsion polymerization in the present invention, for example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, hydroperoxides such as paramenthane hydroperoxide, benzoyl peroxide, lauroyl peroxide and the like Use organic polymerization initiators such as peroxides and azo compounds such as azobisisobutyronitrile, and inorganic polymerization initiators such as persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate. be able to.

In the present invention, the mechanical stability of the copolymer latex obtained by using an organic polymerization initiator alone is inferior,
Further, since a large amount of coagulated product is generated during the polymerization, it is preferable to use the inorganic polymerization initiator alone or in combination with the organic polymerization initiator.

In addition, the said polymerization initiator can also be used as what is called a redox-type polymerization initiator combined with reducing agents, such as sodium bisulfite.

Among these polymerization initiators, persulfates such as potassium persulfate and ammonium persulfate, or a combination thereof with azobisisobutyronitrile or benzoyl peroxide, and a combination of these with a reducing agent are preferably used. Is done.

The amount of the polymerization initiator used in the present invention is 100
It is usually 0.1 to 5 parts by weight, preferably 0.5 to 5 parts by weight.
~ 2 parts by weight. When an inorganic polymerization initiator and a mucopolymerization polymerization initiator are used in combination, the ratio of the organic polymerization initiator is preferably 70% by weight or less of the total polymerization initiator, more preferably 50% by weight or less. is there. If the proportion of the organic polymerization initiator exceeds 70% by weight, problems such as those occurring when the organic polymerization initiator is used alone are not preferred.

The emulsifier used for the emulsion polymerization in the present invention is not particularly limited, and any of anionic, nonionic and amphoteric surfactants can be used. These can be used alone or in combination of two or more. For example, anionic surfactants such as sulfate salts of higher alcohols such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and sulfonates of aliphatic carboxylic acid esters such as sodium dioctylsulfosuccinate; polyethylene Nonionic surfactants such as an alkyl ester type, an alkyl phenyl ether type, and an alkyl ether type of glycol can be used. As the amphoteric surfactant, a carboxylate, a sulfate, a sulfonate, a phosphate,
Phosphoric acid ester salts and those having an amine salt or a quaternary ammonium salt as a cation moiety can be mentioned. Specifically, lauryl betaine, stearyl betaine, cocoamidopropyl betaine, 2-undecylhydroxyethyl imidazolium betaine salts as alkyl betaine salts, and lauryl-β-alanine, stearyl-β as amino acid type salts -Salts of alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, dioctyldi (amnoethyl) glycine.

Among these emulsifiers, an alkylbenzene sulfonate is particularly preferably used. More specifically, sodium dodecylbenzenesulfonate and the like are particularly preferably used. The alkyl benzene sulfonate may be used in combination with other surfactants such as sulfates of higher alcohols.
It may be used in combination with an anionic surfactant such as a sulfonate of an aliphatic carboxylic acid ester or a nonionic surfactant such as an alkyl ester type, an alkyl ether type or an alkylphenyl ether type of polyethylene glycol.

The amount of the emulsifier used is usually 0.0
It is 5 to 2 parts by weight, preferably 0.05 to 1 part by weight. If the amount of the emulsifier exceeds 2 parts by weight, the water resistance is poor and the foaming of the paper coating composition becomes remarkable, causing a problem during coating. When the alkylbenzene sulfonate is used in combination with another anionic or nonionic surfactant, the proportion of the alkylbenzene sulfonate is preferably 50% by weight or more of the total emulsion.

As the polymerization chain transfer agent used for the emulsion polymerization in the present invention, for example, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan,
Meltaptans such as t-tetradecyl mercaptan;
Xanthogen disulfides such as dimethyl xanthogen disulfide, diethylxandogen disulfide, diisopropylxanthogen disulfide; dithiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiurame disulfide and tetrabutylthiuram disulfide; halogens such as carbon tetrachloride and ethylene bromide Hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terpinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer (2- 4
-Diphenyl-4-methyl-1-pentene is preferably 50 parts by weight or more), and unsaturated cyclic carbonization such as 9,10-dihydroanthracene, 1,4-dihydronaphthalene, indene and 1,4-cyclohexadiene. Hydrogen compounds; examples include unsaturated heterocyclic compounds such as xanthene and 2,5-dihydrofuran.

These can be used alone or in combination of two or more.

Of these, mercaptans, xanthogen disulfides, thiuram disulfides, α-methylstyrene dimers, unsaturated cyclic hydrocarbon compounds, and unsaturated heterocyclic compounds can be preferably used.

The amount of the polymerization chain transfer agent used in the present invention is
0.1 to 10 parts by weight, more preferably 0.2 to 100 parts by weight
７7 parts by weight. The amount of the polymerization chain transfer agent used is 0.1
When the amount is less than 10 parts by weight, the blister resistance is inferior. On the other hand, when the amount is more than 10 parts by weight, a large amount of coagulated product is generated during the emulsion polymerization, and the production of the copolymer latex becomes substantially difficult.

The emulsion polymerization method and its conditions in the present invention are not particularly limited, and can be carried out under conventionally known methods and conditions.

For example, the addition method of the polymerization chain transfer agent may be any of a batch addition method, a division addition method, a continuous addition method, or a combination thereof.

As for the method of adding the monomer, a batch addition method,
Any of a split addition method, a continuous addition method, or a combination thereof may be used. Among these methods, the split addition method or the continuous addition method is preferred from the viewpoints of reduction in the formation of coagulated material and removal of reaction heat. Further, 10 to 10 of the monomer containing the whole or a part of the ethylenically unsaturated carboxylic acid monomer
50 parts by weight are polymerized in the first stage, and the remaining 50
According to the two-stage polymerization method in which the emulsion polymerization is carried out by continuously adding ~ 90 parts by weight, the formation of coagulated product in the polymerization step can be further reduced, and the paper coating composition aimed at by the present invention can be effectively used. It is preferable to carry out the emulsion polymerization of the present invention by this two-stage polymerization method because it can be obtained.

In the case where the two-stage polymerization method is employed in the production method of the present invention, the organic solvent may be added in one of the first and second stages, or may be added in both stages. Is also good.

Further, a so-called seed polymerization method in which the above-mentioned monomer is polymerized in the presence of the seed latex and the organic solvent of the present invention may be employed. The monomer composition of the seed latex is preferably 0.1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, 50 to 99.9% by weight of the monomer component (a) and / or (b), 0 to 40% by weight, preferably 0.1 to 4% by weight of ethylenically unsaturated crosslinking monomer
0% by weight. The amount of the seed latex to be used is preferably 0.05 to 20 parts by weight (solid content) based on 100 parts by weight of all monomers polymerized in the presence of the seed latex.

The ethylenically unsaturated crosslinkable monomer is preferably divinylbenzene, ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate, more preferably divinylbenzene.

In the present invention, the organic solvent used in the polymerization step is
After completion of the polymerization, it is preferably removed by a method such as steam stripping or distillation under reduced pressure. At this time, the residual amount of the organic solvent is based on 100 parts by weight of the obtained copolymer.
It is preferably less than 1 part by weight, more preferably less than 0.5 part by weight, particularly preferably less than 0.2 part by weight.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “%” and “parts” are based on weight.

<Examples 1 to 5, Comparative Examples 1 to 4> (Production of copolymer latexes A to E, a to d) 150 parts of water were charged into a 100 pressure-resistant reactor, and the first-stage components shown in Table 1 ( After charging monomers, a polymerization chain transfer agent, a polymerization initiator, an emulsifier, and an organic solvent), polymerization was performed at 70 ° C. for 2 hours in a nitrogen atmosphere.

Next, the monomer of the second stage component and the polymerization chain transfer agent were added in 8 parts.
Polymerization was carried out by continuous addition over time. In addition, the emulsifier of the second stage component was added all at once 5 hours after the start of the addition.
Thereafter, in order to complete the polymerization, the reaction was further continued for 3 hours, and the polymerization was completed at a polymerization conversion of 98%.

After adjusting the pH of the obtained copolymer latex to 7.5 using sodium hydroxide, steam is blown to remove unreacted monomers and organic solvents, and the solid content is adjusted to 50% by heating and distillation under reduced pressure. Then, five types of copolymer latexes A to E according to examples of the present invention and four types of copolymer latexes a to d according to comparative examples were obtained.

For each of the obtained copolymer latexes, the gel content, the residual amount of the organic solvent, and the state of generation of odor were examined by the following methods. The results are shown in Table 2. Comparative Example 4
The boiling point of acetonitrile used as an organic solvent in
1.6 ° C., dissolution parameters 11.8.

Gel content The copolymer latex was adjusted to pH 8.0, coagulated with isopropanol, washed, and dried. Then, about 0.3g
Sample was collected and immersed in 100 ml of toluene for 20 hours, and the toluene-insoluble content was measured.
Was determined as the gel content.

Residual amount of organic solvent The amount (%) of organic solvent in the copolymer latex was measured by a gas chromatography method.

The odor copolymer latex, using a coating rod to clear coated onto a polyester film at a coverage 10 g / m ^2, as judged by olfactory odor when dried for 30 seconds at 120 ° C., in the following three stages evaluated.

：: Almost no odor Δ: Slight odor X: Strong odor (Preparation of paper coating composition) Using the above copolymer latexes A to E, ad to paper coating according to the following formulation A composition (paint) was prepared.

Formulation Clay 80 parts Calcium carbonate 20 parts Copolymer latex 10 parts Oxidized starch 5 parts Sodium pyrophosphate 0.5 parts Water Amount that total solid valve becomes 60% The obtained paint was evaluated by the following test method. The results are shown in Table 2. The coated paper used in the test was obtained by applying a coating material to a base paper having a basis weight of 64 g / m ² using a coating blade at a coating amount of 20 g / m ² .

Dry Pick (Indicator of Adhesive Strength) The degree of picking when printed with an RI printing machine was judged with the naked eye, and evaluated by a five-step method. The higher the score, the better. The score was indicated by an average value of six measurements.

RI Wet Pick (Indicator of Water Resistance) The degree of picking when printing was performed by applying dampening water using a Molton roll with an RI printing machine was visually judged, and evaluated by a five-point method. The higher the score, the better. The score was indicated by an average value of six measurements.

Blister resistance After the double-sided printing coated paper was humidified (about 6%), it was thrown into a heating oil bath, and the lowest temperature at which blisters were generated was indicated.

Examples 1 to 5 are examples using a copolymer latex manufactured using an organic solvent within the scope of the present invention, and Comparative Examples 1 to 3 are copolymer latexes manufactured without using an organic solvent. Comparative Example 4 is an example using a copolymer latex produced using an organic solvent outside the scope of the present invention.

Note that Comparative Examples 1, 2, 3, and 4 correspond to Examples 1, 2, 5, and 3, respectively, in terms of monomer composition.

In Examples 1 to 5, the gel content was low in comparison with Comparative Examples 1 to 4 even though the amount of the polymerization chain transfer agent was smaller in the same monomer composition, and the efficiency of the polymerization chain transfer agent was lower. It can be seen that is increasing.

Further, the odor of the obtained copolymer latex during drying of the coating film is considerably improved in the examples since the amount of the polymerization chain transfer agent used is relatively reduced as compared with the comparative example.

Further, it can be seen that, in the physical properties of the coated paper, the examples are generally superior to the comparative examples in terms of adhesive strength, water resistance, and blister resistance.

[Effects of the Invention] According to the present invention, by using a specific organic solvent at the time of polymerization, it is possible to relatively reduce the amount of the polymerization chain transfer agent, and as a result, the amount of the polymerization chain transfer agent is reduced. Problems can be improved, for example, the odor of the obtained copolymer latex can be reduced, and further, the coating properties such as adhesive strength, water resistance and blister resistance can be improved, and various types of adhesion can be achieved. Useful as an agent.

The copolymer latex obtained by the present invention is, in particular,
It can be suitably used as a binder for a paper coating composition of coated paper and coated paperboard, and further can be used for various adhesive applications such as carpet backing agents, paints, industrial and household adhesives.

Claims (3)

(57) [Claims] (1) (a) 10 to 80 parts by weight of a conjugated diene monomer,
And (b) when 100 parts by weight of a monomer containing 20 to 90 parts by weight of an ethylenically unsaturated monomer is emulsion-polymerized, the emulsion polymerization comprises 0.1 to 10 parts by weight of a polymerization chain transfer agent and a boiling point of 30. 0.5 to 20 parts by weight of a non-polymerizable organic solvent having a solubility parameter of 7 to 11,
The emulsion polymerization is carried out by two-stage polymerization, and the first-stage
10 to 50 parts by weight are polymerized, and the remaining monomer 50 to 90 in the second stage
A method for producing a copolymer latex, wherein parts by weight are polymerized. 2. The method for producing a copolymer latex according to claim 1, wherein the non-polymerizable organic solvent is added in at least one of a first stage and a second stage. 3. The method for producing a copolymer latex according to claim 1, wherein the first-stage monomer contains all or a part of an ethylenically unsaturated carboxylic acid monomer. .