JPH0714985B2 - Method for manufacturing latex with excellent water resistance - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polymer latex capable of forming a coating film having excellent water resistance.

[Conventional technology and its problems]

The polymer latex is effectively used in the industrial field such as paints, adhesives, paper processing agents, fiber processing agents as it is or by adding various compounding agents, but it is generally an aqueous solution containing a surfactant. Emulsified and dispersed monomer in a medium, produced by a well-known emulsion polymerization method in which polymerization is carried out by a polymerization catalyst that generates radicals, the polymer in the latex is generally 40-65 wt% concentration, particles It has a diameter of 0.01 to 1 micron and exists in a stable dispersed state.

Surfactants are generally 1 to 100 parts by weight of the monomer.
It is used in an amount of 7 parts by weight and provides an important place for polymerization of the monomer in an aqueous medium and keeps the emulsion-dispersed state stable for a long period of time. Due to its lack of compatibility with the polymer, its presence greatly impairs the water resistance of the polymer coating formed by drying the latex.

Due to such drawbacks, in an application field where high water resistance is required for the coating, it is not possible to use a latex advantageous in terms of handleability and safety and hygiene, and an organic solvent solution of a polymer inferior in these aspects cannot be used. In some cases, it was necessary to use, and the improvement of water resistance, which is an essential drawback of the latex, was the most important problem to be solved.

In order to improve the water resistance of the latex coating, the amount of surfactant should be reduced. However, when the amount of surfactant is reduced, it is usually 40% by weight which is industrially practiced.
At the above polymer concentrations, emulsion polymerization cannot be carried out and unacceptably large amounts of aggregates are generated.

On the other hand, by adding a cross-linking agent such as melamine resin, urea resin, epoxy resin, isocyanate compound, aziridine compound, etc., or introducing various functional groups into the polymer, a high heat treatment is used to cause a cross-linking reaction to obtain water resistance. However, it was difficult to use it for general purpose because it requires high heat treatment at 150 ° C or higher, and it is a two-liquid type and its usable time is limited.

[Means for solving problems]

The present inventors have made extensive studies in order to solve the above-mentioned problems, and even with a small amount of the surfactant used, stable formation of a high-concentration latex without the formation of agglomerates and water resistance The present invention has been completed by finding a method for producing a latex capable of giving an excellent coating film of

That is, the present invention includes (a) 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 acid ester, and (c) other ethylenically unsaturated monomers. A monomer mixture comprising 0 to 79.5% by weight of the monomer is added to the nonionic and / or anionic surfactant in an amount of 0.5 to 7 with respect to 100 parts by weight of the monomer mixture.
First step of obtaining a seed latex by emulsion polymerization in an aqueous medium containing parts by weight, in the presence of the seed latex prepared in the first step,
(D) Acrylic acid ester or methacrylic acid ester 20
-100% by weight, (e) 0 to 7% by weight of ethylenically unsaturated monomer having a carboxyl group, (f) 0 to 80% by weight of other ethylenically unsaturated monomer inflowing monomer mixture The second step is to polymerize, and the amount of the ethylenically unsaturated monomer having a carboxyl group is in the range of 0.5 to 7% by weight based on the total amount of the monomer, and the amount of the surfactant is equal to the total amount of the monomer. The present invention relates to a method for producing a latex having excellent water resistance, which is 1 part by weight or less based on 100 parts by weight of a monomer.

If these requirements are not satisfied, it is not possible to prevent a large amount of aggregates from being generated during emulsion polymerization and improve the water resistance of the coating film formed from the latex. The second step of the present invention can 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,
There are itaconic acid, fumaric acid, maleic acid, maleic anhydride, etc., and the amount thereof should be in the range of 0.5 to 7% by weight in the total monomers. It is difficult to carry out, and if the amount exceeds 7% by weight, the water resistance of the coating film decreases. The preferred range is 1
~ 4% by weight.

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

Other ethylenically unsaturated monomers include aromatic monomers such as styrene and vinyltoluene, vinyl acetates such as vinyl acetate, vinyl propionate and vinyl versatate, vinyl cyanides such as (meth) acrylonitrile, Vinyl halides such as vinyl chloride and vinylidene chloride, (meth)
Acrylamide, diacetone acrylamide, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, methylpropanesulfonic acid acrylamide, divinyl Benzene, allyl (meth) acrylate,
It is selected from the group consisting of (poly) oxyethylene di (meth) acrylate, trimethylolpropane triacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

Examples of the nonionic or anionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitan fatty acid esters, oxyethyleneoxypropylene block copolymers and other nonionic surfactants, fatty acid soaps, alkyl sulfones. Examples thereof include anionic surfactants such as acid salts, dialkylaryl sulfonates, alkylsulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylaryl sulfates, and the like. In addition to these ordinary surfactants, so-called reactive surfactants are also effectively used with compounds having a polymerizable group of vinyl group or allyl group and hydrophilic groups such as sulfonate group, hydroxyl group and polyoxyethylene group. it can. These reactive surfactants include, for example, JP-B-49-46291 and JP-B-51-4.
No. 4157, Japanese Patent Publication No. 56-29658, Japanese Patent Publication No. 51-30284, Japanese Unexamined Patent Publication No. 54-144317, and Japanese Unexamined Patent Publication No. 58-203960. The amount of these nonionic, anionic or reactive surfactants needs to be 1 part by weight or less based on 100 parts by weight of the total monomers, and if the amount is larger than this, the water resistance of the coating decreases. Will end up.

In the practice of the present invention, a usual emulsion polymerization method can be adopted. The polymerization catalyst is one that causes radical addition decomposition of a monomer by heat or a reducing substance to cause addition polymerization of a monomer, and a water-soluble or oil-soluble persulfate, a peroxide, an azobis compound or the like can be used. Specific examples thereof include potassium persulfate,
Ammonium persulfate, sodium persulfate, hydrogen peroxide,
t-Butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, 2,2-azobis (2-amidinopropane) hydrochloride, 2,2-
Azobis (2,4-dimethylvaleronitrile) etc.
Particularly, a water-soluble substance is preferably used, and its amount is usually 0.1 to 1% by weight based on the monomer. In addition,
When it is desired to accelerate the polymerization rate or to carry out the polymerization at a lower temperature, a reducing agent such as sodium bisulfite, ferrous chloride, ascorbic acid and Rongalit is used in combination with the polymerization catalyst.

Further, if desired, various polymerization regulators are often added, for example, pH adjustment of sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, etc. The agent is a chelating agent such as ethylenediaminetetraacetic acid and its salt, or a chain transfer agent for adjusting the molecular weight of the polymer.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a latex that forms a water-resistant coating film of a higher degree than ever before, and as it is or by adding various compounding agents, paints, adhesives, paper processing that are resistant to water. Agents, fiber processing agents and the like can be prepared.

〔Example〕

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples. Parts and% in the examples are by weight.

Example 1 In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer, 15 parts of methacrylic acid, 30 parts of methyl methacrylate,
Styrene 15 parts, 2-ethylhexyl acrylate 40 parts, water
238.5 parts, 25% aqueous solution of polyoxyethylene nonyl phenyl ether (Emulgen 920, Kao Soap Co., Ltd.) 8
Parts, 4 parts of a 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate (Rebenol WZ, manufactured by Kao Soap Co., Ltd.) and 300 parts of water are added as an emulsion of a monomer. Raise the temperature to 80 ° C and then add 2 of ammonium persulfate.
% Aqueous solution and add for 1 hour. This prepares the first stage seed latex.

Next, 117 parts of ethyl methacrylate, 90 parts of ethylene, 190 parts of 2-ethylhexyl acrylate and 3 parts of methacrylic acid, and an aqueous solution of 1.2 parts of ammonium persulfate and 184 parts of water were placed in a reaction vessel. 3 from separate dripping tanks
Inflow over time. After the flow ends, the temperature is set to 83 ℃.
And keep it for 2 hours. After cooling, the pH was adjusted to 8.5 by adding a 25% aqueous ammonium solution, and then filtered with a 200-mesh filter cloth. The dry weight of the filtered agglomerates was very small, 0.03% based on the total monomers.

Next, 100 parts of the obtained latex was mixed with 5 parts of butyl cellosolve.
After mixing 10 parts of 0% water and 5 parts of 2-ethylhexyl cellosolve as a film forming aid, the mixture was uniformly applied to an asbestos slate board at a rate of 150 g / m ² and dried at 20 ° C. for 24 hours. 20 ° C
After immersing it in water for 24 hours and then observing the state, no abnormalities such as whitening, swelling, swelling, and peeling of the film were observed.

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 thermometer, the temperature was raised to 80 ° C., and then 10 parts of methacrylic acid and methacrylic acid were added. Methyl acid 100 parts, butyl acrylate 89 parts, acrylamide 1 part, lauryl mercaptan 0.1 part, water 100 parts,
4 parts of 25% aqueous solution of polyoxyethylene nonylphenyl ether (Emulgen 920, manufactured by Kao Soap Co., Ltd.), 4 parts of 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate (Lebenol WZ, manufactured by Kao Soap Co., Ltd.) and A monomer emulsion consisting of 0.5 parts of ammonium persulfate is flowed in over 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, 200 parts of water, 0.75 parts of ammonium persulfate, sodium polyoxyethylene nonylphenyl ether sulfate (Rebenol WZ, Kao soap) 25% aqueous solution 1)
The monomer emulsion consisting of parts is allowed to flow in for 2 hours.
After the inflow is complete, bring the temperature to 83 ° C and hold for 2 hours. Then, after cooling, a 25% aqueous ammonia solution was added to adjust the pH to 8.5, and then filtered with a 200-mesh filter cloth. The dry weight of the filtered agglomerates was 0.04%, which was very small with respect to the total amount of the monomers. Next, 100 parts of the latex obtained in the same manner as in Example 1 was mixed with 10 parts of 50% butyl cellosolve water and 2-
After 5 parts of ethylhexyl cellosolve was mixed as a film forming aid, it was uniformly applied to an asbestos slate board at a rate of 150 g / m ² , and dried at 20 ° C. for 24 hours. After immersing this in water at 20 ℃ for 24 hours, when observing the state, whitening of the coating,
No abnormalities such as swelling, blistering, or peeling were observed.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that methacrylic acid was not used at the stage of seed latex preparation.
The amount of agglomerates filtered with a mesh filter cloth was 2.5%, and latex could not be stably produced.

Comparative Example 2 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer was charged with 200 parts of water and 0.1 part of ammonium persulfate, the temperature was raised to 80 ° C., and then 15 parts of methacrylic acid and methacrylic acid were added. Methyl acid 150 parts, styrene 75 parts, acrylic acid 2-
260 parts ethylhexyl, 238.5 parts water, ammonium persulfate
1.5 parts, 25% aqueous solution of polyoxyethylene nonylphenyl ether (Emulgen 920, Kao Soap Co., Ltd.) 40
Part, an emulsion of a monomer mixture consisting of 20 parts of a 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate (Rebenol WZ, manufactured by Kao Soap Co., Ltd.) over 3 hours. After the inflow is completed, set the temperature to 83 ° C 2
Keep time Then, after cooling, a 25% aqueous ammonia solution was added to adjust the pH to 8.5 and then filtered with a 200-mesh filter cloth. The dry weight of the filtered agglomerates is based on all monomers
It was very small at 0.05%. Next, 100 parts of the latex obtained in the same manner as in Example 1 was mixed with 50 parts of butyl cellosolve.
% 10 parts of water and 5 parts of 2-ethylhexyl cellosolve were mixed as a film forming aid, and then uniformly coated on an asbestos slate board at a rate of 150 g / m ² , and dried at 20 ° C. for 24 hours. After immersing this in water at 20 ° C for 24 hours, observing its state,
It was so white that the base could not be seen, and many blisters with a diameter of about 1 mm were observed.

Comparative Example 3 15 parts of methacrylic acid and 30 parts of methyl methacrylate were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer.
Parts, styrene 15 parts, 2-ethylhexyl acrylate 40
Part, water 238.5 parts, sodium polyoxyethylene nonylphenyl ether sulfate (Lebenol WZ, manufactured by Kao Corporation)
An emulsion of a monomer consisting of 32 parts of 25% aqueous solution and 300 parts of water is charged. After raising the temperature to 80 ° C., add 15 parts of a 2% aqueous solution of ammonium persulfate and hold for 1 hour. This prepares the first stage seed latex.

Next, a mixed monomer consisting of 117 parts of methyl methacrylate, 90 parts of styrene, 190 parts of 2-ethylhexyl acrylate and 3 parts of methacrylic acid, and an aqueous solution consisting of 1.2 parts of ammonium persulfate and 184 parts of water were separately charged into a reaction vessel. It is allowed to flow from the dropping tank for 3 hours. After the inflow is complete, bring the temperature to 83 ° C and hold for 2 hours. After cooling, the pH was adjusted to 8.5 by adding a 25% aqueous ammonia solution, and then filtered with an 80-mesh filter cloth. The dry weight of the filtered agglomerates is 3.
It was 2%. Next, 100 parts of the latex obtained in the same manner as in Example 1 was mixed with 10 parts of 50% butyl cellosolve water and 2-
Aggregates were generated when 5 parts of ethylhexyl cellosolve was mixed as a film-forming aid, so after filtration with an 80-mesh filter cloth, it was uniformly coated on an asbestos slate plate at a rate of 150 g / m ² , and then at 24 ° C at 20 ° C. After immersing for a period of time, the state was observed, and the coating was whitened, swelling and swelling were observed on the whole,
The water resistance was poor.

Comparative Example 4 200 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 thermometer, the temperature was raised to 80 ° C., and then 10 parts of methacrylic acid and methacrylic acid were added. Methyl acid 100 parts, butyl acrylate 89 parts, acrylamide 1 part, lauryl mercaptan 0.1 part, water 92 parts,
A monomer emulsion consisting of 16 parts of a 25% aqueous solution of sodium polyoxyethylene nonylphenyl ether sulfate (Rebenol WZ, manufactured by Kao Corporation) and 0.5 part of ammonium persulfate is flowed in for 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, 177 parts of water, 0.75 parts of ammonium persulfate, sodium polyoxyethylene nonylphenyl ether sulfate (Novenol WZ, Kao ( (Manufactured by K.K. Co., Ltd.) and a monomer emulsion consisting of 24 parts of a 25% aqueous solution is allowed to flow in for 2 hours. After the inflow is complete, bring the temperature to 83 ° C and hold for 2 hours. Then
After cooling, the pH was adjusted to 8.5 by adding a 25% aqueous ammonium solution, and then filtered with a 200-mesh filter cloth. The dry weight of the filtered agglomerates was 0.25% based on the total monomers. Next, latex 10 obtained in the same manner as in Example 1 was used.
After adding 10 parts of 50% water of butyl cellosolve and 5 parts of 2-ethylhexyl cellosolve to 0 part as a film forming aid, it is evenly coated on an asbestos slate board at a rate of 150 g / m ² , and at 24 ° C at 20 ° C.
After immersing for a time, when the state was observed, the coating film was whitened, swelling and swelling were observed throughout, and the water resistance was poor.

Claims (1)

[Claims] (1) 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 acid ester or a methacrylic acid ester, (c) other ethylenic unsaturated Emulsifying a monomer mixture consisting of 0 to 79.5% by weight of a monomer in an aqueous medium containing 0.5 to 7 parts by weight of a nonionic and / or anionic surfactant with respect to 100 parts by weight of the monomer mixture. First step of polymerizing to obtain a seed latex, in the presence of the seed latex prepared in the first step,
(D) Acrylic acid ester or methacrylic acid ester 20
~ 100% by weight, (e) 0-7% by weight of ethylenically unsaturated monomer having a carboxyl group, (f) 0-80% by weight of other ethylenically unsaturated monomer flowed in monomer mixture The second step is to polymerize, and the amount of the ethylenically unsaturated monomer having a carboxyl group is
Latex having excellent water resistance, which is in the range of 0.5 to 7% by weight based on the total amount of the monomers, and the amount of the surfactant is 1 part by weight or less based on 100 parts by weight of the total monomers. Manufacturing method.