JPS62236810A - Production of latex of excellent water resistance - Google Patents

Abstract

PURPOSE:To make it possible to improve the water resistance and adhesion of a film prepared from the obtained latex, by polymerizing a (meth)acrylate- based monomer mixture in the presence of a specified seed latex. CONSTITUTION:The polymerization is performed according to the following first and second stages. First stage: a monomer mixture comprising 0.5-50wt% carboxyl group-containing ethylenically unsaturated monomer (a), 20-99.5wt% (meth)acrylate (b), 0-79.5wt% other ethylenically unsaturated monomers (c) is emulsion-polymerized in an aqueous medium containing 0.5-7pts.wt., per 100pts.wt. monomer mixture, nonionic and/or anionic surfactants to obtain a seed latex. Second stage: a monomer mixture comprising 20-100wt% (meth) acrylate (d), 0-7wt% carboxyl group-containing ethylenically unsaturated monomer (e) and 0-80wt% other ethylenically unsaturated monomers (f) is allowed to flow into the system and polymerized in the presence of the seed latex.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a polymer latex that can form a coating with excellent water resistance.

[Conventional technology and its problems]

Polymer latex is effectively used as it is or with the addition of various additives in industrial fields such as paints, adhesives, paper processing agents, fiber processing agents, etc., but it is generally used as aqueous polymer latex containing surfactants. It is produced by the well-known emulsion polymerization method in which monomers are emulsified and dispersed in a medium and polymerized using a polymerization catalyst that generates radicals.The polymer in latex is generally in a concentration of 40 to 65% by weight and in particles. It has a diameter of 0.01 to 1 micron and exists in a stable dispersed state.

The surfactant is generally used in an amount of 1 per 100 parts by weight of monomer.
It is used in an amount of ~7 parts by weight and plays an important role in providing a polymerization site for monomers in an aqueous medium and keeping the emulsion and dispersion state stable over a long period of time. Since they lack compatibility with polymers, their presence greatly impairs the water resistance of the polymer coating formed by drying the latex.

Due to these drawbacks, latex, which is advantageous in terms of ease of handling and safety and hygiene, cannot be used in applications where high water resistance is required for the coating, and organic solvent solutions of polymers, which are inferior in these aspects, cannot be used. The most important problem to be solved was improving water resistance, which is an essential drawback of latex.

In order to improve the water resistance of latex coatings, it is sufficient to reduce the amount of surfactant. However, when the amount of surfactant is reduced, emulsion polymerization cannot be carried out at polymer concentrations of 40% by weight or more, which are usually practiced industrially, and an unacceptably large amount of aggregates is generated. .

On the other hand, water resistance can be achieved by blending crosslinking agents such as melamine resins, urea resins, epoxy resins, isocyanate compounds, and aziridine compounds, or by introducing various functional groups into the polymer and then subjecting it to high heat treatment to cause a crosslinking reaction. Although there are techniques to improve this, it has been difficult to use them for general purposes because they require high heat treatment at 150° C. or higher, and are two-component and have a limited usable time.

[Means for solving problems]

The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems, and have found that even with a small amount of surfactant used, high-concentration latex can be stably produced without causing the formation of aggregates, and it has water resistance. The present inventors have discovered a method for producing latex that can provide an excellent coating, and have completed the present invention.

That is, the present invention comprises f8) 0.5 to 50% by weight of an ethylenically unsaturated monomer having a carboxyl group, (b) 20 to 99.5% by weight of an acrylic ester or a methacrylic ester.
, (C) Other ethylenically unsaturated monomers 0 to 79.5
% by weight, the monomer mixture consists of 10% by weight.
A first step of obtaining a seed latex by emulsion polymerization in an aqueous medium containing 0.5 to 7 parts by weight of a nonionic and/or anionic surfactant, the seed latex prepared in the first step. In the presence of (
d) Acrylic ester or methacrylic ester 20
~100% by weight, (e) 0 to 7% by weight of ethylenically unsaturated monomers having carboxyl groups, and (f) 0 to 80% by weight of other ethylenically unsaturated monomers. a second stage of polymerization, wherein the amount of ethylenically unsaturated monomers having carboxyl groups is in the range of 0.5 to 7% by weight of the total monomers, and the amount of surfactant is in the range of 0.5 to 7% by weight of the total monomers; The present invention relates to a method for producing latex with excellent water resistance, characterized in that the amount is 1 part by weight or less per 100 parts by weight of total monomers.

If these requirements are not met, it will not be possible to prevent the formation of large amounts of agglomerates during emulsion polymerization, and it will not be possible to improve the water resistance of the coating formed from the latex. Note that the second step of the present invention can also be performed in two or more steps.

Examples of the ethylenically unsaturated monomer having a carboxyl group in the present invention include acrylic acid, methacrylic acid,
Itaconic acid, fumaric acid, maleic acid, maleic anhydride, etc., and their amount must be in the range of 0.5 to 7% by weight based on the total monomer, and if it is less than 0.5% by weight, it will be unstable. It is difficult to carry out proper emulsion polymerization, and if the amount exceeds 7% by weight, the water resistance of the coating will decrease. The preferred range is 1-4% by weight.

Acrylic ester or methacrylic ester (hereinafter simply referred to as (meth)acrylic ester). ], for example, methyl (meth)acrylate, (
meth)ethyl acrylate, butyl (meth)acrylate,
Examples include cyclohexyl (meth)acrylate, dodecyl (meth)acrylate, and 2-ethylhexyl acrylate.

Examples of other ethylenically unsaturated monomers include aromatic monomers such as styrene and vinyltoluene, vinyl esters such as vinyl acetate, vinyl propionate, and vinyl versatate, and vinyl cyanides such as (meth)acrylonitrile. and vinyl halides such as vinyl chloride and vinylidene chloride, and various functional monomers such as (meth)acrylamide, diaseptone acrylamide, glycidyl (meth)acrylate, and 2-(meth)acrylic acid. Hydroxyethyl, N-methylolacrylamide, N-butoxymethylacrylamide, methacrylic acid phosphooxyethyl, 3-chloro-2-acid phosphooxypropyl methacrylate, methylpropanesulfonic acid acrylamide, divinylbenzene, allyl (meth)acrylate, (Poly)oxydiethylene di(meth)acrylate, trimethylolpropane triacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.

Examples of nonionic or anionic surfactants include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, oxyethylene oxypropylene block copolymer, fatty acid soap, and alkyl sulfone. Examples include anionic surfactants such as acid salts, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkylaryl sulfates. In addition to these ordinary surfactants, so-called reactive surfactants, which have both a polymerizable vinyl or allyl group and a hydrophilic group such as a sulfonic acid group, hydroxyl group, or polyoxyethylene group, can also be used effectively. can. These reactive surfactants are disclosed in, for example, Japanese Patent Publication No. 49-46291, Japanese Patent Publication No. 51-44157, Japanese Patent Publication No. 56-29658, Japanese Patent Application Laid-open No. 30284-1984, Japanese Patent Application Publication No. 144317-1987, Japanese Patent Publication No. It is disclosed in the publication No. 58-203960. The amount of these nonionic, anionic or reactive surfactants must be 1 part by weight or less per 100 parts by weight of the total monomers; if it is more than this, the water resistance of the coating will decrease. I end up.

Conventional emulsion polymerization methods can be employed to carry out the present invention. The polymerization catalyst is one that causes addition polymerization of monomers by radical decomposition using heat or a reducing substance, and water-soluble or oil-soluble persulfates, peroxides, azobis compounds, etc. can be used. Specific examples include potassium persulfate,
ammonium persulfate, sodium persulfate, hydrogen peroxide,
t-Butyl hydroperoxide, benzoyl peroxide, 2.2=azobisisobutyronitrile, 2.2-azobis(2-amidinopropane) hydrochloride, 2
Examples include 2-azobis(2,4-dimethylvaleronitrile), and water-soluble ones are particularly preferably used, and the amount thereof is usually 0.1 to 1% by weight based on the monomer. In addition, when acceleration of the polymerization rate or polymerization at a lower temperature is desired, a reducing agent such as sodium bisulfite, ferrous chloride, ascorbic acid, or Rongalit is used in combination with a polymerization catalyst.

In addition, various polymerization regulators are often added as desired, such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, phosphoric acid, etc.
These include pH adjusting agents such as sodium hydrogen and sodium dihydrogen phosphate, chelating agents such as ethylenediaminetetraacetic acid and its salts, and chain transfer agents for adjusting the molecular weight of the polymer.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a latex that forms an unprecedentedly highly water-resistant film, and can be used as it is or by adding various additives to water-resistant paints, adhesives, and paper processing. It is possible to prepare agents, fiber processing agents, etc.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited only to these Examples.

Note that parts and percentages in the examples are by weight.

Example 1 15 parts of methacrylic acid and 3 parts of methyl methacrylate were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a temperature needle.
0 parts, 15 parts of styrene, 40 parts of 2-ethylhexyl acrylate, 238.5 parts of water, polyoxyethylene tunylphenyl ether (manufactured by Emulken 92o1 Kao Soap@)
j1 consisting of 8 parts of a 25% aqueous solution of , 4 parts of a 25% aqueous solution of sodium polyoxyethylene nonyl phenyl ether sulfate (Levenol WZ, manufactured by Kao Soap Examples), and 300 parts of water.
Add 1 part of emulsion.

Raise the temperature to 80 °C, then add 2% of ammonium persulfate
Add 15 parts of aqueous solution and hold for 1 hour. As a result, the first stage seed latex is manufactured.

Next, 117 parts of methyl methacrylate, 90 parts of styrene, 190 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid,
1.2 parts of mixed monomers and an aqueous solution of 1.2 parts of ammonium persulfate and 184 parts of water were flowed into the reaction vessel from separate dropping tanks over a period of 3 hours.

After the inflow is finished, the temperature is brought to 83° C. and maintained for 2 hours.

After cooling, a 25% ammonia aqueous solution was added to adjust the pH to 8.
5 and filtered through a 200 mesh filter cloth.

The dry N amount of the filtered aggregate is 0.0 based on the total monomer.
The percentage was very small at 3%.

Next, 10 parts of 50% butyl cellosolve water and 5 parts of 2-ethylhexyl cellosolve were added as film-forming aids to 100 parts of the obtained latex, and then an asbestos slate plate was coated with 150% water.
g/n? It was coated uniformly at a ratio of 20° C. and dried at 20° C. for 24 hours. After soaking this in water at 20'C for 24 hours,
When the condition was observed, no abnormalities such as whitening, swelling, blistering, or peeling of the film were observed.

Example 2 200 parts of water and 0.1 part of ammonium persulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, and the temperature was raised to 80°C.
parts, 100 parts of methyl methacrylate, 8 parts of butyl acrylate
9 parts, acrylamide 1 part, lauryl mercaptan 0.
1 part, 100 parts of water, 25% of polyoxyethylene nonylphenyl ether (Emulgen 920, manufactured by Kao Soap ■)
4 parts of aqueous solution, 2 parts of polyoxyethylene nonyl phenyl ether sodium sulfate (Levanol, manufactured by Kao Soap@)
A monomer emulsion consisting of 4 parts of a 5% aqueous solution and 0.5 part of ammonium persulfate is run in over a period of 1.5 hours. This prepares the first stage seed latex.

Next, 130 parts of methyl methacrylate, 161 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid, 6 parts of glycidyl methacrylate, 0.7 parts of ammonium persulfate, and 20 parts of water.
A monomer emulsion consisting of 0 parts of ammonium persulfate, 0.75 parts of ammonium persulfate, and 1 part of a 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate (Levanol, manufactured by Kao Soap ■) was introduced over 2 hours. After the inflow is over, the temperature is increased to 83°C and maintained for 2 hours. Then, after cooling 2
The pH was adjusted to 8.5 by adding a 5% aqueous ammonia solution, and the mixture was filtered through a 200 mS filter cloth. The dry weight of the filtered aggregate was very small at 0.04% based on the total monomers. Next, 100 parts of the latex obtained in the same manner as in Example 1 was added to 10 parts of 50% water of butyl cellosolve.
After blending 1 part and 5 parts of 2-ethylhexyl cellosolve as a film-forming aid, the mixture was coated uniformly on an asbestos slate plate at a rate of 150 g/fff, and dried at 20°C for 24 hours. After immersing this in water at 20°C for 24 hours, its condition was observed, and no abnormalities such as whitening, swelling, blistering, or peeling of the film were observed.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that methacrylic acid was not used in the stage of preparing seed latex.
The amount of aggregates filtered through the 0-mesh filter cloth was 2.5%, making it impossible to stably produce latex.

Comparative Example 2 200 parts of water and 0.1 part of ammonium persulfate were put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a temperature needle, the temperature was raised to 80°C, and then 15 parts of methacrylic acid was added.
150 parts of methyl methacrylate, 75 parts of styrene, 260 parts of 2-ethylhexyl acrylate, 238.5 parts of water, 1.5 parts of ammonium persulfate, polyoxyethylene nonylphenyl ether (Emulgen 920, Kao Stone th)
An emulsion of a monomer mixture consisting of 40 parts of a 25% aqueous solution of a (manufactured by I11) and 20 parts of a 25% aqueous solution of sodium polyoxyethylene nonyl phenyl ether sulfate (Levenol-2, manufactured by Kao Soap ■) was poured over a period of 3 hours. do.

After the inflow is finished, the temperature is brought to 83° C. and maintained for 2 hours. After cooling, 25% 7 ammonia aqueous solution was added to pn
was adjusted to 8.5, and then filtered through a 200 MSO filter cloth. The dry weight of the filtered aggregate is 0 based on the total monomer.
．． It was very small at 0.05%. Next, 10 parts of 50% butyl cellosolve water and 5 parts of 2-ethylhexyl cellosolve were added as film-forming aids to 100 parts of the latex obtained in the same manner as in Example 1, and then an asbestos slate plate was coated with 150 parts of water.
It was applied uniformly at a ratio of g/rd and dried at 20° C. for 24 hours. After immersing this in water at 20°C for 24 hours, we observed the condition and found that the base had become so white that it could no longer be seen.
In addition, many blisters with a diameter of about 1 mm were observed.

Example 3 5 parts of acrylic acid, 53 parts of styrene, 40 parts of 2-ethylhexyl acrylate, 2 parts of N-butoxymethylacrylamide, and polyoxyethylene nonyl were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a temperature needle. 9 parts of a 25% aqueous solution of phenyl ether (Emulgen 950, manufactured by Kao Soap ■), 4 parts of a 25% aqueous solution of polyoxyethylene nonyl phenyl ether sodium sulfate (Ko1 ζ Mar NC1 manufactured by Kao Soap ■), 0 parts of disodium hydrogen phosphate An emulsion of a monomer mixture consisting of .5 parts and 246 parts of water is added.Then, the temperature is lowered to 80°C.
15 parts of a 2% aqueous solution of ammonium persulfate is added and held for 1 hour. This prepares the first stage seed latex.

Next, 224 parts of styrene, 160 parts of 2-ethylhexyl acrylate, 8 parts of methacrylic acid, 8 parts of N-butoxymethylacrylamide, and sodium polyoxyethylene nonyl phenyl ether sulfate (Levenol Yami, manufactured by Kao Soap Example)
An emulsion of a monomer mixture consisting of 4 parts of a 25% aqueous solution of , 1 part of disodium hydrogen phosphate, 1.2 parts of ammonium persulfate, and 145 parts of water is flowed into the reaction vessel over a period of 3 hours. After the inflow is finished, the temperature is brought to 83° C. and maintained for 2 hours. After cooling, a 25% aqueous ammonia solution was added to adjust the pH to 7.5, and the mixture was filtered through a 200 mesofilter cloth.

The dry weight of the filtered aggregate is 0.0 based on the total monomer.
It was very small at 5%.

Next, 5 parts of dibutyl phthalate was added to 100 parts of the obtained latex to make a homogeneous mixture, and this mixture was evenly coated on aluminum foil (thickness: 17 microns) to a thickness of 25 microns. I worked on it. Then, cardboard (basis weight 200 g/%) was immediately laminated and passed through a heated roll at 110°C. After immersing this aluminum foil laminated paper in water at 40°C for 24 hours, the beer adhesive strength was measured.
Cohesive failure of the paper occurred at 165 g/25 mm. In addition,
The normal adhesive strength before immersion in water was 350 g/25 mm, indicating cohesive failure of the paper.

Comparative Example 3 200 parts of water and 0.1 part of ammonium persulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a temperature needle, the temperature was raised to 80°C, and then 10 parts of methacrylic acid was added.
parts, 280 parts of styrene, 200 parts of 2-ethylhexyl acrylate, 10 parts of N-butoxymethylacrylamide,
30 parts of a 25% aqueous solution of polyoxyethylene nonylphenyl ether (Emulgen 950, manufactured by Kao Soap ■), 20 parts of a 25% aqueous solution of polyoxyethylene nonylphenyl ether sodium sulfate (Emar NC, manufactured by Kao Soap ■), dihydrogen phosphate An emulsion of the monomer mixture consisting of 200 parts of natrirum water is run in over a period of 3 hours. After the inflow is finished, the temperature is brought to 83° C. and maintained for 2 hours. After cooling, a 25% ammonia aqueous solution was added to adjust the pH to 7.5, and the mixture was filtered through a 200-mesh filter cloth. The dry weight of the filtered aggregate was as small as 0.03% based on the total monomers.

Next, latex 100 obtained in the same manner as in Example 3
After adding 5 parts of dibutyl phthalate to the mixture to form a uniform mixture, this mixture was uniformly coated onto aluminum foil (thickness: 17 microns) to a thickness of 25 microns. Then, cardboard (basis weight 200 g/rrr) was immediately laminated thereon and passed through a heated roll at 110°C. When this aluminum foil laminated paper was immersed in water at 40° C. for 24 hours, it peeled off naturally. The normal adhesive strength before immersion in water was 33.
At 0g/25mm, there was cohesive failure of the paper.

Claims (1)

[Claims] (1) (a) 0.5 to 50% by weight of ethylenically unsaturated monomer having a carboxyl group, (b) 20 to 99.5% by weight of acrylic ester or methacrylic ester, (c)
0 to 79.5% by weight of other ethylenically unsaturated monomers,
Seed latex is obtained by emulsion polymerizing a monomer mixture consisting of: First step, in the presence of the seed latex prepared in the first step, (
d) Acrylic ester or methacrylic ester 20
~100% by weight, (e) 0 to 7% by weight of ethylenically unsaturated monomers having carboxyl groups, and (f) 0 to 80% by weight of other ethylenically unsaturated monomers. a second stage of polymerization, in which the amount of ethylenically unsaturated monomers having carboxyl groups is
Excellent water resistance, characterized in that the amount of surfactant is in the range of 0.5 to 7% by weight of the total monomers, and the amount of surfactant is 1 part by weight or less per 100 parts by weight of the total monomers. A method of manufacturing latex.