JPH04161403A - Production of copolymer latex - Google Patents

Abstract

PURPOSE:To obtain the subject latex excellent in bond strength, blister resistance, etc., low in odor and useful as an adhesive, etc., by carrying out emulsion polymerization of monomers containing a conjugated diene-based monomer and an ethylene-based unsaturated monomer in the presence of a polymerization chain transfer agent, a water soluble ether, etc. CONSTITUTION:In the presence of 0.5-20 pts.wt., preferably 1-10 pts.wt. water soluble ether (preferably having 30-200 deg.C boiling point, e.g. THF) and/or monoalcohol (preferably having 30-230 deg.C boiling point and 7.5-13 solubility parameter, e.g. methanol) and 0.1-10 pts.wt. polymerization chain transfer agent, 100 pts.wt. monomers containing (A) 10-80 pts.wt., preferably 20-65 pts.wt. conjugated diene-based monomer (e.g. butadiene) and (B) 20-90 pts.wt., preferably 20-80 pts.wt. ethylene-based unsaturated monomer [e.g. styrene or methyl (meth) acrylate] is subjected to emulsion polymerization, thus obtaining the objective latex.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a copolymer latex that has excellent properties such as adhesive strength and blister resistance and has little odor when used in adhesives and the like. .

[Conventional technology] Conjugated diene monomer, ethylenically unsaturated monomer.

Copolymer latex obtained by emulsion polymerization of monomers such as ethylenically unsaturated carboxylic acids is widely used as various adhesives because of its excellent adhesive properties.

When producing 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 may pose a problem not only during polymerization but also during product processing, and it has been desired to reduce this odor.

For this reason, for example, JP-A-53-121890 proposes the use of a non-sulfur chain transfer agent with less odor. However, these chain transfer agents are expensive and have problems in practical use.

[Problems to be Solved by the Invention] The present invention provides a method for producing a copolymer latex that has excellent properties such as adhesive strength and blister resistance when used in adhesives, etc., and is substantially odorless. The purpose is to

[Means for Solving the Problem] As a result of intensive studies, the present inventors have achieved the above object by using a copolymer latex obtained by emulsion polymerization of monomers in the presence of a specific organic solvent. The present invention was completed based on this finding.

That is, the present invention includes (a) 10 to 80 parts by weight of a conjugated diene monomer (b)
When emulsion polymerizing 100 parts by weight of monomers containing 20 to 90 parts by weight of ethylenically unsaturated monomers, 0.1 to 10 parts by weight of a polymerization chain transfer agent and water-soluble ethers and/or monoalcohols are added. The present invention provides a method for producing a copolymer latex, characterized in that emulsion polymerization is carried out in the presence of 0.5 to 20 parts by weight (hereinafter collectively referred to as "organic solvent").

The present invention will be explained in detail below.

The monomers used in the present invention include monomer components (a) and (b) shown below.

(a) Conjugated diene monomer Specific examples of the conjugated diene monomer include butadiene, isoprene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, etc. . These can be used alone or in combination of two or more.

Among these, butadiene is particularly preferred.

The amount of the conjugated diene 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 used 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 will decrease, which is not preferred.

(b) Ethylenically unsaturated monomer Specific examples of this ethylenically unsaturated monomer include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-methylstyrene; (meth)acrylic acid Alkyl ester compounds of acrylic acid or methacrylic acid 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, and N-methylolacrylamide; carboxylic acid vinyl esters such as vinyl acetate; 2-cyanoethyl (meth)acrylate; Vinyl cyanide compounds such as acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile; basic monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-vinylpyridine, and 4-vinylpyridine; Monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; and methyl maleate,
Mention may be made of unsaturated carboxylic acids such as half esters such as methyl itaconate and β-methacryloxyethyl acid hexahydrophthalate. Anhydrides of dicarboxylic acids can also be used.

These can be used alone or in combination of two or more. Among these, aromatic vinyl compounds include styrene, alkyl ester compounds include methyl methacrylate, vinyl cyanide compounds include acrylonitrile, and unsaturated carboxylic acids include acrylic acid and itaconic acid. Preferably used.

The ethylenically unsaturated monomer is used to impart appropriate hardness, elasticity, and water resistance to the resulting copolymer.
The amount used is 20 to 9 parts by weight per 100 parts by weight of the total monomers.
0 parts by weight, preferably from 20 to 80 parts by weight. If the amount used is less than 20 parts by weight, the water resistance will be poor, while if it exceeds 90 parts by weight, the copolymer will become too hard.
This is not preferable because the adhesive strength decreases.

In the present invention, as part of component (b), an unsaturated carboxylic acid monomer is usually added in an amount of 0.5 parts per 100 parts by weight of the total monomers.
By using up to 10 parts by weight, preferably 1 to 7 parts by weight, the adhesive strength and mechanical stability of the resulting copolymer latex can be further improved.

Next, the organic solvent used in the method for producing the copolymer latex of the present invention has a boiling point (b) at normal pressure.

p) is usually 250°C or less, preferably 30 to 200°C, and is water-soluble.

If the boiling point (b, p) of the organic solvent exceeds 250° C., it will be difficult to recover the solvent by stripping or vacuum distillation, and the solvent will remain in the copolymer latex, which is not preferable.

Furthermore, in the present invention, water-soluble means that the solubility in water at 20° C. exceeds 1% by weight.

Further, the organic solvent used in the method for producing a copolymer latex of the present invention preferably has a solubility parameter of 7 to 14. The solubility parameter 6 can be determined from the following formula % (Δh5.: molar heat of vaporization + vO: molar volume).

Examples of ethers among organic solvents include tetrahydrofuran (b, p-66°C, δ-9,1), dioxane (b, p-101,3°C, δ-9,8), and the like.

In such ethers, the boiling point is preferably 3
4 to 200°C, and the solubility parameter is preferably 7.
-11, more preferably 7.2-10.5.

In addition, examples of monoalcohols include methanol (
b, p-64,5, δ-12,9), ethanol (b, p-78,3℃, δ-11,5), 2
-Proper tool (b, p -82,4, δ-11
,5), tert-butyral:7-l (b,
Examples include those having 5 or less carbon atoms, such as p-82,5,6-Lo, 7).

In such alcohols, the boiling point is preferably 30 to 230°C, and the solubility parameter is preferably 7.5 to 13.

The amount of these specific organic solvents used is 05 to 20 parts by weight, preferably 0.5 to 15 parts by weight, and more preferably 1 to 10 parts by weight, based on 100 parts by weight of the total monomers.

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

In the present invention, by using a polymer chain transfer agent and an organic solvent together, the amount of the polymer chain transfer agent used can be relatively reduced, and as a result, unpleasant odors caused by mercaptan compounds, disulfide compounds, etc. can be substantially reduced. can be eliminated considerably.

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

There are no particular limitations on the polymerization initiator used in the emulsion polymerization in the present invention, such as cumene hydroperoxide, diisopropylbenzene hydroperoxide,
Hydroperoxides such as paramenthane hydroperoxide, peroxides such as benzoyl peroxide and lauroyl peroxide, and organic polymerization initiators such as azo compounds such as azobisisobutyronitrile, as well as potassium persulfate and peroxide. Inorganic polymerization initiators such as persulfates such as sodium sulfate and ammonium persulfate can be used.

In the present invention, when an organic polymerization initiator is used alone, the mechanical stability of the copolymer latex obtained is poor;
Furthermore, since a large amount of coagulated material is generated during polymerization, it is preferable to use an inorganic polymerization initiator alone or in combination with an organic polymerization initiator.

The above polymerization initiator can also be used as a so-called redox polymerization initiator in combination with a reducing agent such as sodium bisulfite.

Among these polymerization initiators, persulfates such as potassium persulfate and ammonium persulfate, combinations thereof with azobisisobutyronitrile or benzoyl peroxide, and combinations thereof with reducing agents are preferred. used.

The amount of polymerization initiator used in the present invention is 100% of the total monomer.
It is usually 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight. When an inorganic polymerization initiator and an organic polymerization initiator are used together, the proportion of the organic polymerization initiator is preferably 70% by weight or less, more preferably 50% by weight or less of the total polymerization initiator. If the proportion of the organic polymerization initiator exceeds 70% by weight, problems similar to those caused when the organic polymerization initiator is used alone are undesirable.

The emulsifier used in 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 ester salts of higher alcohols such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, sulfonates of aliphatic carboxylic acid esters such as sodium dioctyl sulfosuccinate, polyethylene Nonionic surfactants such as glycol alkyl ester type, alkylphenyl ether type, and alkyl ether type can be used. In addition, as amphoteric surfactants, carboxylates, sulfate ester salts, sulfonates, phosphates, phosphate ester salts are used as anionic moieties, and amine salts, phosphate ester salts are used as cationic moieties.
Examples include those having quaternary ammonium salts. Specifically, alkyl betaine salts include lauryl betaine, stearyl betaine, cocoamidopropyl betaine, and 2-undecylhydroxyethylimidazolium betaine salts, and amino acid types include lauryl-β-alanine and stearyl-β. - Mention may be made of the salts of alanine, lauryl di(aminoethyl)glycine, octyldi(aminoethyl)glycine, dioctyldi(aminoethyl)glycine.

Among these emulsifiers, alkylbenzene sulfonates are particularly preferably used. More specifically, sodium dodecylbenzenesulfonate and the like are particularly preferably used. This alkylbenzene sulfonate can be used with other surfactants, such as anionic surfactants such as higher alcohol sulfate ester salts, aliphatic carboxylic acid ester sulfonates, or polyethylene glycol alkyl ester, alkyl ether, and alkyl esters. It may be used in combination with a nonionic surfactant such as a phenyl ether type surfactant.

The amount of emulsifier used is usually 0 per 100 parts by weight of total monomers.
．． 0.05 to 2 parts by weight, preferably 0.05 to 1 part by weight. If the amount of emulsifier used exceeds 2 parts by weight, the water resistance will be poor and the paper coating composition will foam significantly, causing problems during coating. In addition, when an alkylbenzene sulfonate is used in combination with another anionic or nonionic surfactant, the proportion of the alkylbenzene sulfonate used is preferably 50% by weight or more of the total emulsifier.

Examples of the polymerization chain transfer agent used in the emulsion polymerization in the present invention include octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, and t-dodecyl mercaptan.
-Mercaptans such as tetradecyl mercaptan; halogenated hydrocarbons such as ethylene; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terpinolene, α-terpinene, γ-terpinene, dipentene, α - Methylstyrene dimer (preferably 50 parts by weight or more of 2-4-diphenyl-4-methyl-1-pentene), furthermore 9゜10-dihydroanthracene, 1,4-dihydronaphthalene, indene, 1.4-
Examples include unsaturated cyclic hydrocarbon compounds such as cyclohexadiene; unsaturated heterocyclic compounds such as xanthine and 2.5-dihydrofuran.

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

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

The amount of polymerization chain transfer agent used in the present invention is based on the total monomer 1
The amount is 0.1 to 10 parts by weight, more preferably 0.2 to 7 parts by weight per 00 parts by weight. If the amount of the polymerization chain transfer agent used is less than 0.1 parts by weight, the blister resistance will be poor, while if it exceeds 10 parts by weight, a large amount of coagulation will occur during emulsion polymerization, making it difficult to produce copolymer latex. It becomes practically difficult.

There are no particular limitations on the emulsion polymerization method and conditions in the present invention, and the emulsion polymerization can be carried out under conventionally known methods and conditions.

For example, the method of adding the polymer chain transfer agent may be a batch addition method, a divided addition method, a continuous addition method, or a combination thereof.

The monomer addition method may be a batch addition method, a divided addition method, a continuous addition method, or a combination thereof. Among these methods, the divided addition method or the continuous addition method is preferable from the viewpoint of reducing the formation of coagulum and removing the heat of reaction. Furthermore, 10 to 100% of the monomer containing the whole or a part of the ethylenically unsaturated carboxylic acid monomer
According to a two-stage polymerization method in which 50 parts by weight of the monomer is polymerized in the first stage, and the remaining 50 to 90 parts by weight of the monomer is continuously added in the second stage for emulsion polymerization, the formation of a coagulated product in the polymerization process is It is preferable to carry out the emulsion polymerization of the present invention by this two-stage polymerization method, since this can further reduce the amount of paper coating composition intended by the present invention.

In addition, when adopting a two-stage polymerization method in the production method of the present invention, the organic solvent may be added at either the first stage or the second stage, or it may be added at both stages. Good too.

Alternatively, a so-called seed polymerization method may be employed in which the monomers described above are polymerized in the presence of seed latex and the organic solvent of the present invention. The monomer composition of the seed latex preferably includes 01 to 10% by weight of ethylenically unsaturated carboxylic acid monomer, and the monomer component (a
) and/or (b) 50 to 99.9% by weight, 0 to 40% by weight of ethylenically unsaturated crosslinkable monomer, preferably 0
．． It is 1 to 40% by weight. The amount of seed latex used is 10% of the total monomers polymerized in the presence of the seed latex.
0 parts by weight, preferably 0.05 to 20 parts by weight (
solid content).

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 preferably removed by steam stripping, vacuum distillation, or the like after the polymerization is completed.

At this time, the amount of residual organic solvent is 10
The amount 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.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Note that "%" and "part" in the examples are based on weight.

<Examples 1 to 7. Comparative Examples 1 to 4> (Production of copolymer latex A-G, ad) 100!
After charging 150 parts of water into a pressure-resistant reactor, and further charging the first stage components shown in Table 1 (monomer 1 polymerization chain transfer agent 1 polymerization initiator, emulsifier, organic solvent), the reactor was heated at a temperature of 7 in a nitrogen atmosphere.
Polymerization was carried out at 0°C for 2 hours.

Next, the second-stage component monomer and polymerization chain transfer agent were continuously added over 8 hours to perform polymerization.

Incidentally, the emulsifier as the second stage component was added at once to the mouth 5 hours after the start of addition. Thereafter, in order to complete the polymerization, the reaction was continued for an additional 3 hours, and the polymerization was completed at a polymerization conversion rate of 98%.

The obtained copolymer latex was adjusted to pn 7.5 using sodium hydroxide, then steam was blown in to remove unreacted monomers and organic solvents, and the solid content concentration was reduced to 50% by heating and vacuum distillation. Seven types of copolymer latexes A to G according to examples of the present invention and four types of copolymer latexes ad according to comparative examples were obtained.

Each of the obtained copolymer latexes was examined for gel content, residual amount of organic solvent, and odor generation by the following methods, and the results are shown in Table 2. In addition, the boiling point of ethylene glycol used as the organic solvent in Comparative Example 4 is 197° C., and the solubility parameter is 14.7.

After adjusting the gel content of the copolymer latex to pt+g,o, it was coagulated with isopropanol, washed, and dried.

Next, about 0.3 g of sample was taken and immersed in 100 ml of toluene for 20 hours, and the toluene insoluble content was measured.
The gel content was determined by calculating the ratio (%) to the sample.

Amount of residual organic solvent The amount (%) of organic solvent in the copolymer latex was measured by gas chromatography.

Odor The odor copolymer latex was clear-coated on a polyester film at a coating weight of 10 g/g using a coating rod and dried at 120°C for 30 seconds.The odor was judged by the sense of smell and evaluated on the following 3 scales. did.

O: Almost no odor △: Slight odor x: Strong odor (adjustment of paper coating composition) Using the above copolymer latex A-H, a-d A paper coating composition (paint) was prepared according to the following formulation.

Mixed recipe Clay 80 parts Calcium carbonate 20 parts Copolymer latex 10 parts Oxidized starch 5 parts Sodium birophosphate 0.5 parts Water
The paint obtained in an amount with a total solids content of 60% 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 the paint to a base paper with a basis weight of 64 g#+f using a coating blade at a coating amount of 20 g/rrr.

■Dry Vic (adhesive strength index) The degree of picking when printed with the R1 printing machine was visually judged and evaluated using a 5-step method. The higher the score, the better. The score was expressed as the average value of 6 measurements.

(2) RI Wet Vic (indicator of water resistance) The degree of picking when printed using a Morton roll with an RI printing machine and applying dampening water was visually judged and evaluated using a five-point scale.

The higher the score, the better. The score was expressed as the average value of 6 measurements.

■ Blister resistance After double-sided printing coated paper was adjusted to fj (approximately 6%), it was thrown into a heated oil bath, and the lowest temperature at which blistering occurred was determined.

Examples 1 to 7 are examples using copolymer latexes produced using organic solvents within the scope of the present invention, and Comparative Examples 1 to 3 are copolymer latexes produced without using organic solvents. Comparative Example 4 is an example in which a copolymer latex produced using an organic solvent outside the scope of the present invention was used.

Note that Comparative Examples 1 and 2 correspond to Examples 1 and 2 in terms of monomer composition and type of polymerization chain transfer agent, respectively.

Compared to Comparative Examples 1 to 4, Examples 1 to 7 have the same or similar monomer composition and the amount of polymerization chain transfer agent used is smaller or the same, but the gel content is lower, and the polymerization It can be seen that the efficiency of the chain transfer agent has increased.

Furthermore, the odor during drying of the coating film of the obtained copolymer latex was considerably improved in the examples because the amount of polymer chain transfer agent used was relatively reduced compared to the comparative examples.

Furthermore, regarding the physical properties of the coated paper, it can be seen that 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 during polymerization, it is possible to relatively reduce the amount of the polymerization chain transfer agent used. As a result, problems caused by polymer chain transfer agents can be improved, for example, the odor of the obtained copolymer latex can be reduced, and physical properties of the coating film such as adhesive strength, water resistance, and blister resistance can be improved. It is useful as various adhesives.

The copolymer latex obtained by the present invention can be particularly suitably used as a binder for paper coating compositions for coated paper and coated paperboard, as well as carpet backing agents, paints, industrial and household adhesives, etc. Can be used for various adhesive applications.

Claims (1)

[Claims] (1) When emulsion polymerizing 100 parts by weight of monomers containing (a) 10 to 80 parts by weight of a conjugated diene monomer (b) 20 to 90 parts by weight of an ethylenically unsaturated monomer, a polymerization chain transfer agent is used. 0.1 to 10 parts by weight and 0 water-soluble ethers and/or monoalcohols
．． A method for producing a copolymer latex, comprising emulsion polymerization in the presence of 5 to 20 parts by weight.