JPH0651761B2 - Method for producing cationic emulsion - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a cationic emulsion which has a low viscosity even at a high resin concentration and is excellent in polymerization stability.

Conventional technology and its problems Conventionally, as a method for producing a cationic emulsion, emulsion polymerization using a cationic surfactant, emulsion polymerization using a cationic water-soluble polymer as a protective colloid, cationic There is known a method of emulsion polymerization in which a surfactant and a cationic water-soluble polymer are used in combination. However, such a method has drawbacks such that as the concentration of emulsion is increased, the polymerization stability is lowered, coarse particles are generated, and the viscosity of emulsion is increased. Therefore, the emulsion having a good polymerization stability and a low viscosity has an emulsion concentration of about 50% by weight. Therefore, when it is put into practical use, it causes various problems. For example, when it is mixed with paint, cement, etc., it has drawbacks such as slow curing rate and large volume shrinkage due to a large amount of water. The range of application as is limited. Furthermore, when a cationic surfactant is used, (i) the surfactant is highly toxic,
(Ii) There are drawbacks such that bubbles easily occur in the emulsion and are hard to disappear, so that various harmful effects are caused, and (iii) the emulsion and the cured resin easily turn yellow.

There is also known a method in which emulsion polymerization is carried out in the presence of a nonionic surfactant, and various cationic surfactants are added to the emulsion obtained to produce a cationic emulsion. It is well known that when emulsion-polymerizing an acrylic acid alkyl ester or a methacrylic acid alkyl ester by this method, HLB of the nonionic surfactant greatly affects the polymerization stability,
With surfactants having an HLB of less than 15, the polymerization stability is significantly reduced, and therefore surfactants with HLB of 15 or higher are used. However, even in the method for producing emulsion using such a high HLB surfactant, if the concentration of emulsion is high, the polymerization stability of emulsion decreases, coarse particles are generated, or the viscosity of emulsion increases. It is difficult to obtain a cationic emulsion having a high concentration and a low viscosity. Further, in such emulsion, there is a defect that the bond between the cationic substance and the emulsion particles is weak, and the emulsion substance is easily desorbed by the cationic substance, and the emulsion particle is likely to become unstable. It is inferior in stability.

Further, there is also known a method of producing a cationic emulsion by emulsion-polymerizing an ethylenically unsaturated monomer in the presence of a cationic monomer (Japanese Patent Publication No. 43-28110). However, this method has drawbacks such that the viscosity increases and the polymerization stability decreases as the resin concentration of emulsion is increased. In addition, in such a cationic emulsion, it is possible to improve the polymerization stability by increasing the addition amount of the cationic monomer, but if the addition amount of the cationic monomer is increased, the water resistance of the resin dry film is increased. The property becomes extremely inferior, and there is a problem that it is easily re-emulsified.

Means for Solving the Problems In view of the problems of the prior art as described above, the present inventor has a high concentration, low viscosity, and excellent polymerization stability and mechanical and chemical stability. We have conducted extensive research to find a method for producing a cationic emulsion. As a result, when emulsion polymerization of an alkyl acrylate and / or an alkyl methacrylate is carried out in the presence of an amino group-containing acrylic monomer as a cationic monomer, it has not been conventionally used for emulsion polymerization of an acrylic monomer. By using a polyethylene oxide nonionic surfactant having an HLB value of 14 or less, surprisingly, a cationic emulsion excellent in polymerization stability can be obtained, and this emulsion has a high concentration and a low viscosity. It has been found that it can be used in a wide range of applications. The present invention is based on such knowledge.

That is, in the present invention, when emulsion-polymerizing an alkyl acrylate and / or an alkyl methacrylate in the presence of 1 to 5% by weight of an amino group-containing acrylic monomer based on all monomers, an HLB value of 14 or less is obtained. The present invention relates to a method for producing a cationic emulsion, which is characterized by including a polyethylene oxide nonionic surfactant.

In the present invention, as the surfactant, a polyethylene oxide nonionic surfactant having an HLB value of 14 or less is used, and preferably a polyethylene oxide nonionic surfactant having an HLB value of 4 to 14 is used. In the present invention, the HLB value is a numerical value calculated by HLB = E / 5 based on the weight percentage E of ethylene oxide in the molecule. In the present invention, in emulsion polymerization of an acrylic monomer, a polyethylene oxide nonionic surfactant having an HLB value of 14 or less, which has not been used as a poor polymerization stability, is used in combination with an amino group-containing acrylic monomy. By doing so, it is possible to use a nonionic surfactant having an HLB of 14 or less without lowering the polymerization stability, and, surprisingly, when using such a combination, the polymerization stability is high even at a high resin concentration. It was clarified that the emulsion can be stably produced with little deterioration of the sex. Further, the emulsion obtained in this manner has a low viscosity even when the resin concentration is about 60%, and is excellent in mechanical stability and chemical stability, and is suitable for use in various applications. It turned out to be a reward.

Polyethylene oxide nonionic surfactants that can be used in the present invention include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene nonyl ether, and polyoxyethylene nonyl ether. Examples thereof include phenyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, oxyethylene oxypropylene block polymer and the like.

The amount of the nonionic surfactant used may vary depending on the properties required for the emulsion, but generally, the purpose is to improve the polymerization stability and suppress the generation of coarse particles, and the mechanical and chemical properties of the emulsion. A large amount of surfactant is preferably used for the purpose of improving stability, and a small amount is preferable for improving the water resistance of the dry film, usually 1 to 10% by weight based on all monomers. The amount to be used may be determined within the range of the degree according to the purpose.

In the present invention, various ones can be used as acrylic acid alkyl ester and methacrylic acid alkyl ester. For example, specific examples of acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxypropyl acrylate, Examples include β-ethoxyethyl acrylate and glycidyl acrylate.
Further, specific examples of the methacrylic acid alkyl ester include
Methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Examples thereof include hydroxypropyl methacrylate, β-ethoxyethyl methacrylate, glycidyl methacrylate and the like. These monomers can be used alone or in appropriate combination. In the present invention,
If necessary, another monomer copolymerizable with the acrylic acid alkyl ester or the methacrylic acid alkyl ester may be added for copolymerization. Such monomers include vinyl acetate, styrene, acrylonitrile,
Examples of vinyl monomers such as vinyl chloride can be added up to about 1/1 (weight ratio) with respect to alkyl acrylate and alkyl methacrylate.

In the present invention, the polymerization reaction is carried out in the presence of an amino group-containing acrylic monomer, which is a cationic monomer, in order to impart cationic properties to the emulsion. The amino group-containing acrylic monomer has a general formula (In the formula, R ₁ represents hydrogen or a methyl group, R ₂ represents a C _{1 to} C ₈ alkylene group, and R ₃ and R ₄ represent hydrogen or a C _{1 to} C ₆ alkyl group). )
Acrylate and / or general formula (Wherein R ₁ represents hydrogen or a methyl group, R ₂ represents a C _{1 to} C ₈ alkylene group, R ₃ and R ₄ represent hydrogen or a C _{1 to} C ₆ alkyl group). (Meth) acrylamide can be used. The amount of the amino group-containing acrylic monomer used may be in the range of 1 to 5% by weight based on the total monomers, and may be determined according to the desired properties of the emulsion. If the amount of the amino group-containing acrylic monomer used is too large, the water resistance of the resin dry film will decrease and the viscosity of the emulsion will increase, while if the amount of the amino group-containing acrylic monomer used is small, the polymerization stability of the emulsion will be high. However, in the present invention, by using the amino group-containing acrylic monomer and the above-mentioned nonionic surfactant in combination, by appropriately combining the amounts, a high concentration and a low viscosity can be obtained. It has become possible to produce emulsions with excellent polymerization stability and excellent dry film water resistance.

Specific examples of the amino group-containing acrylic monomer include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, and t as aminoalkyl (meth) acrylate of the general formula (I).
-Butylaminoethyl acrylate, t-butylaminoethyl methacrylate, monomethylaminoethyl acrylate, monomethylaminoethyl methacrylate and the like can be mentioned. Examples of the N-aminoalkyl (meth) acrylamide of the general formula (II) include dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide and the like.

The cationic monomer is used after being neutralized with an acid. The degree of neutralization (acid / amino group-containing acrylic monomer (molar ratio)) is about 0.2 or more, and can be more than 1 depending on the application of emulsion. Specifically, when the degree of neutralization becomes high, the hydrophilicity becomes strong, and when the degree of neutralization becomes low, the emulsifying power becomes weak and the polymerization stability tends to decrease. The degree of neutralization may be determined according to the properties, the amount used, the intended use of the product emulsion, and the like.

As the acid used for neutralization, various inorganic acids or organic acids can be used, and as the inorganic acid, for example, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, etc. can be used, and as the organic acid, for example, formic acid. , Acetic acid, propionic acid, succinic acid, citric acid,
Malic acid etc. can be used.

The polymerization method in the present invention may be carried out according to a usual emulsion polymerization method, for example, a method of charging and polymerizing a main monomer, an amino group-containing acrylic monomer and a nonionic surfactant all at once, while continuously supplying each component. Various methods such as a method of polymerizing are possible, and any method can obtain a cationic emulsion which achieves the intended purpose. In the case of continuous supply, each component may be added alone, or any component may be mixed in advance and added. The polymerization reaction is carried out under heating, usually 50 to 85
It may be performed at a temperature of about ℃.

In the present invention, as the catalyst for the polymerization reaction, both a general nonionic catalyst and a cationic catalyst can be used, but a water-soluble salt of a known cationic catalyst 2,2′-azobis (2-amidinopropane), For example, it is preferable to use hydrochloride or the like.

In the present invention, if necessary, other nonionic surfactants, water-soluble polymers and the like may be used in combination within a range that does not cause adverse effects such as decrease in stability and increase in viscosity. Further, chain transfer agents such as various alcohols, aldehydes and mercaptans can be used within a range that does not cause various harmful effects.

EFFECTS OF THE INVENTION The cationic emulsion obtained according to the present invention is excellent in polymerization stability even in a high-concentration state, has few coarse particles, and can be continuously and stably produced. Further, even at a high concentration of about 60% by weight of the resin, it has a low viscosity and good mechanical stability and chemical stability, so it has excellent workability and can be applied to various applications. Further, since no cationic surfactant is used, the generation of bubbles is small, and the problem of toxicity due to the surfactant does not occur. Furthermore, by using a combination of a nonionic surfactant and an amino group-containing acrylic monomer, without lowering the polymerization stability,
It is possible to reduce the amount of the amino group-containing acrylic monomer used, and the dry film has excellent water resistance.

The cationic emulsion obtained by the present invention has excellent properties as described above and can be used in various applications as the cationic emulsion, and has the following excellent effects.

Being cationic, it has excellent adsorption and adhesion to anionic substances (normal wood, paper, fiber, concrete, metal, etc.), and cationic substances (eg, certain antistatic agents, polyamines, polyvalents) Good mixing stability with metal ions, etc.).

Since the concentration is high, it is possible to obtain a blended product which has a high drying rate, has a large degree of freedom of blending when blended into a paint or the like, and has a high concentration and a small volume shrinkage. Further, since the concentration is high, the transportation cost can be reduced.

It is possible to control the mechanical stability and chemical stability of emulsion by selecting the type and amount of the amino group-containing acrylic monomer, the degree of neutralization and the type and amount of the nonionic surfactant. Moreover, it is possible to control the viscosity of the emulsion formulation.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

Examples 1 to 7 and Comparative Examples 1 to 6 To a separable flask equipped with a stirring blade, a condenser and a thermometer, 65 parts by weight of nitrogen-exchanged deionized water was added,
Then, the surfactants shown in Table 1 were added and dissolved.

Next, this surfactant solution was kept at 75 ° C., and 2 parts by weight of dimethylaminoethyl methacrylate (2 parts by weight of dimethylaminoethyl acrylate in Example 7) was added as an amino group-containing acrylic monomer. 1.6 parts by weight of hydrochloric acid diluted with ion exchanged water to a concentration of 18% (1.5 parts by weight in Example 7) was added and mixed sufficiently to neutralize the amino group-containing acrylic monomer, and then 2,2 ' A 14% aqueous solution of azobis (2-amidinopropane) dihydrochloride
0.7 parts by weight was added. Then, continuous dropwise addition of 98 parts by weight of a 1/1 (weight ratio) mixed solution of methyl methacrylate and 2-ethyl-hexyl-acrylate was started. The inside of the flask was kept at 78 ° C. ± 2 ° C. with a water bath, and the dropping of the monomer mixture solution was completed in 4 hours.

After completion of the monomer mixture droplets, 0.7 parts by weight of a 14% aqueous solution of 2,2'-azobis (2-amidinopropane) dihydrochloride was added, and the temperature inside the flask was adjusted to 82 ± 2 ° C and left for 2 hours. Then, it was cooled to obtain a cationic emulsion.

As a result of measuring the resin concentration of the obtained emulsion by the method shown below, all were about 60%. The results of measuring the physical properties of this emulsion are shown in Table 1. The measuring method is as shown below.

Resin concentration (according to JIS K 6833) Accurately weigh 1 g of sample in a plate made of aluminum with a diameter of 4 cm, put it in a dryer kept at 105 to 110 ° C for 3 hours, let it cool in a desiccator, then sample The weight of the dried product was precisely weighed.

Viscosity (according to JIS K 6833) Approximately 250 g of a sample is placed in a polybeaker, immersed in a water tank at 25 ± 1 ° C for 1 hour, then thoroughly stirred with a glass rod and a B-type viscometer 12
The rpm viscosity was measured.

The dry weight of the filtration residue produced by passing the filtration residue emulsion through 100 mesh stainless steel was weighed to determine the ratio of the filtration residue weight to the emulsion weight.

As is clear from Table 1, the emulsions obtained in Examples 1 to 7 had a resin concentration of about 60% and a viscosity of 20%.
It was as low as 000 cps or less, and the filtration residue was 0.1 or less, and stable production was possible. On the other hand, in Comparative Example 6 in which no surfactant is used, the emulsion gels and HLB
However, in Comparative Examples 1 to 5 in which the nonionic surfactant outside the scope of the present invention was used, problems such as increase in viscosity and increase in filtration residue occurred.

Comparative Example 7 Ion-exchanged water without using a nonionic surfactant
116 parts by weight, 8 parts of dimethylaminoethyl methacrylate
Part by weight, 1/1 (weight ratio) mixed solution of methyl methacrylate and 2-ethyl-hexyl acrylate 94 parts by weight, 18%
A cationic emulsion having a resin content of 45% was obtained in the same manner as in Example 1 except that 4.8 parts by weight of hydrochloric acid was used. The emulsion had a viscosity of 500 cps and a filtration residue of 0.1 and had good physical properties, but the dry film had very poor water resistance when it was immersed in water, just before re-emulsification.

Comparative Example 8 As a surfactant, the nonionic surfactant has an HLB value of
Except using 3.5 parts by weight of 8.6 sorbitan laurate,
A cationic emulsion was obtained in the same manner as in Example 1.

The obtained emulsion had a high viscosity of 50,000 cps and a filtration residue of 5% or more, and was inferior in polymerization stability.

Comparative Example 9 A cationic emulsion was obtained in the same manner as in Example 1 except that 2.0 parts by weight of alkyltrimethylammonium chloride, which is a cationic surfactant, was used as the surfactant.

The obtained emulsion had a filtration residue of 0.1%, but had a high viscosity of 60,000 cps, and contained a lot of bubbles, which was not practical.

Comparative Example 10 A cationic emulsion was obtained in the same manner as in Example 1 except that 8 parts by weight of dimethylaminoethyl methacrylate was used as the amino group-containing acrylic monomer.

The obtained emulsion had a filtration residue of 0.1%, but had a high viscosity of 50,000 cps, and the dry film had a very poor water resistance when it was immersed in water and was about to be re-emulsified.

Claims (1)

[Claims] 1. A polyethylene having an HLB value of 14 or less when emulsion-polymerizing an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester in the presence of 1 to 5 wt% of an amino group-containing acrylic monomer based on all monomers. A method for producing a cationic emulsion, which comprises the presence of an oxide nonionic surfactant.