JPS5927762B2 - Emulsion polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of emulsion polymerization, more specifically, using a fatty acid soap containing (meth)acrylic ester (meaning acrylic ester or methacrylic ester, hereinafter the same). The present invention relates to a method for emulsion polymerization of monomers in an aqueous dispersion medium.

Conventionally, aqueous emulsion polymerization of monomers containing (meth)acrylic acid esters has been widely adopted in applied fields such as acrylic rubber and paints, but acrylic acid esters and higher esters of methacrylic acid have a glass transition point. Due to its low viscosity and stickiness, the polymer tends to adhere to the inner walls of the reactor, the stirrer, etc., inhibiting a smooth polymerization reaction, and requires a great deal of effort and time to remove the adhered polymer, making it difficult to use on an industrial scale. Yanghe's production was presenting a big problem.

Various methods have been studied to prevent the polymer from adhering to the walls of the reactor, for example, methods have been proposed such as lining the inner surface of the reactor with glass or changing the emulsifier. However, the method of lining the inner surface of the reactor with glass makes the inner surface of the reactor smoother due to the glass lining of the inner wall of the reactor.
Although polymer adhesion is reduced to some extent compared to conventional reactors made of stainless steel, etc., the manufacturing cost of the reactor is high;
It has the disadvantage that it is easily damaged by impact during operation or cleaning such as removing attached polymer. On the other hand, the method of changing the emulsifier can reduce the adhesion of the polymer to some extent by adjusting the conditions of use, but it is not sufficient. In addition, the emulsifiers currently used in aqueous emulsion polymerization, such as alkylaryl sulfonates, alkyl sulfate ester salts, and dialkyl sulfosuccinates, are expensive and have poor biodegradability, resulting in contamination by wastewater. It has the disadvantage of being prone to problems. As a result of various studies in view of these circumstances, the present inventors have found a method that can solve these problems at once by using a special aqueous dispersion medium, and have completed the present invention.

That is, the gist of the present invention is that when a monomer containing an acrylic ester and/or a methacrylic ester is polymerized in an aqueous medium using an emulsifier containing a fatty acid soap as a main component, in the aqueous dispersion, Boric acid ion (BO3
- 0.01 to 0.5y ions/l) and coexistence of an alkali metal salt or ammonium salt of boric acid so that the pH is within the range of 5.5 to 9.5. It is an emulsion polymerization method.

In the present invention, the alkali metal salts or ammonium salts of boric acid (hereinafter simply referred to as borates) used together in the aqueous dispersion medium are hydroxides, carbonates, and carbonates of boric acid and alkali metals or ammonium. It is a salt produced by neutralization in coexistence with bicarbonate.

As a method for coexisting borate in an aqueous dispersion medium,
For example, but not limited to, a method of dissolving a calculated amount of boric acid and at least one of an alkali metal or ammonium hydroxide, carbonate, and bicarbonate, or a method of dissolving boric acid and a completely neutralized alkali metal of boric acid. Alternatively, a method such as dissolving the ammonium salt in an aqueous dispersion medium can be used.

Specific examples of alkali metal or ammonium hydroxides, carbonates and bicarbonates that can be used to obtain borates include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate. , potassium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, ammonium hydroxide, ammonium carbonate, and the like. In the present invention, the metal salts used to generate the borate are preferably alkali metal salts, such as alkaline earth metal salts such as magnesium, calcium, barium, aluminum, tin, chromium, etc.
Metal salts having high valences such as manganese, iron, nickel, and cobalt are not preferred because they react with borate ions to form water-insoluble precipitates, reducing or eliminating the effective amount of borate ions.

The amount of borate to be dissolved and coexisting in the aqueous dispersion medium is not particularly limited as long as it does not cause a large amount of adhering polymer in the reactor and has good dispersion, but borate ion (BO3--1)
It is preferable to coexist so that the concentration of ions is in the range of 0.01 to 0.57 ions/l.

The concentration of borate ions in the aqueous dispersion medium is O, 017 ions/
If the concentration of borate ions is below 0.57 ions/l, the stability of emulsion polymerization becomes worse, and the polymer coagulum floating in the resulting latex is degraded. This is not preferable since the amount produced tends to increase. Furthermore, the degree of neutralization of boric acid cannot be determined unambiguously because it depends on the type of alkali and the concentration of borate, but when the concentration of borate ions is between 0.01 and 0.57 ions/l, It is desirable to adjust the pH to within the range of 5.5 to 9.5. If the pH is outside this range, the stability of emulsion polymerization will be poor and the latex may be destroyed during polymerization, which is not preferred. The monomer containing acrylic ester and/or methacrylic ester used in carrying out the present invention has 1 to 12 carbon atoms.
acrylic or methacrylic esters of aliphatic, alicyclic, aromatic alcohols and phenols, singly or as a mixture, or as a mixture with other copolymerizable monomers containing these.

Specific examples of acrylic or methacrylic esters of aliphatic, alicyclic, aromatic alcohols and phenols having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. , alkyl (meth)acrylates such as butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, Hydroxyethyl (meth)acrylate, hydroxypropyl (
hydroxyalkyl (meth)acrylates such as meth)acrylates, aminoalkyl (meth)acrylates such as N-N-dimethylaminoethyl (meth)acrylates,
Examples include epoxyalkyl (meth)acrylates such as glycidyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

Among these, methyl (meth)acrylate, (
meth)ethyl acrylate, butylene (meth)acrylate,
Monomers selected from 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, etc. are preferred. Examples of other comonomers that can be used in combination with the above-mentioned acrylic esters and methacrylic esters include α/β monounsaturated acids such as acrylic acid, methacrylic acid, and itaconic acid; Acid esters, α and β monounsaturated acid amides such as acrylamide and methacrylamide, and derivatives thereof, α and β monounsaturated nitrites such as acrylonitrile and methacrylonitrile, aromatics such as styrene, vinyltoluene, and α-methylstyrene. Vinyl compounds, vinyl esters such as vinyl acetate and vinyl propionate, allyl compounds such as allyl acetate and allyl maleate, vinyl halides such as vinyl chloride and vinylidene chloride, dienes such as butadiene and 2-cucarobutadiene, and single molecule Compounds having two or more copolymerizable unsaturated bonds therein, such as (poly)ethylene glycol di(meth)acrylate, allyl(meth)acrylate, triallyl(iso)cyanurate, and divinylbenzene, can be mentioned.

Further, fatty acid soaps used as emulsifiers in the present invention include, for example, sodium laurate, sodium myristate, potassium palmitate, potassium stearate, potassium oleate, ammonium laurate,
Examples include alkali metal salts or ammonium salts of higher carboxylic acids having 12 to 18 carbon atoms such as ammonium myristate, and the amount used is 0 parts per 100 parts of water.
．． It ranges from 5 to 10 parts.

In the present invention, some of these fatty acid soaps may be replaced with higher alcohol sulfate ester salts, phosphate ester salts, dialkyl sulfosuccinates, alkylaryl sulfonates, α-olefin sulfonates, etc. Can be implemented. Polymerization initiators used in the practice of the present invention include water-soluble peroxides such as persulfates, perborates, percarbonates, hydrogen peroxide and ferrous salts, hydroperoxides and sodium fluoride, etc. Examples include redox initiators typified by combinations of aldehyde sulfoxylates, etc.
The amount used is generally 0 to 100 parts by weight of the monomer.
．． About 0.001 to 1 part by weight is used.

The monomer/water ratio when carrying out aqueous emulsion polymerization is not particularly limited and is carried out in the range of about 1/1 to 1/5, and the monomers may be added all at once before carrying out the polymerization, but Depending on the purpose, it may be added in portions or continuously during polymerization.

Although the polymerization temperature can vary depending on the type and composition of the monomers used, it is usually carried out at 20 to 100°C.

The present invention is suitable for producing latex by emulsion polymerization of monomers containing (meth)acrylic acid esters, but it is also suitable for producing latexes by adding other monomers to the latexes or diene rubber latexes. It can also be applied to an aqueous emulsion polymerization method in which graft polymerization is carried out.

The invention will now be explained in more detail by way of example.

In the examples, parts represent parts by weight, and % represents weight %. Example 1 A mixture consisting of the following monomer composition and the dispersion medium composition area shown in Table 1 was charged into a stainless steel reactor with an internal volume of 21 mm equipped with a stirrer, a thermometer, and a nitrogen blowing tube, and the contents were After nitrogen gas was blown into the system at room temperature for 15 minutes while stirring to drive out oxygen from the system, the internal temperature was heated to 60°C using a jacket.

After 3 hours, the latex produced was sampled and analyzed for residual monomer using a gas chromatograph.
It had a polymerization rate of 9.5% or more.

After the contents of the reactor were cooled, the coagulated polymer floating in the latex was separated using a 100-mesh stainless wire gauze, dried at 50° C. for 48 hours, and weighed. In addition, the polymer adhering to the reactor wall was also collected, dried in the same manner, and weighed. The results are shown in Table-2. Monomer composition example 2 Methyl methacrylate 4007 (80 parts), acrylic acid 2
- A monomer mixture consisting of ethylhexyl 1007 (20 parts) was prepared in the stainless steel reactor shown in Example 1 using a dispersion medium consisting of boric acid and sodium carbonate at various concentrations as shown in Table 3. Polymerization was carried out at 60°C for 3 hours.

The results are shown in Table 4. Example 3 A monomer mixture of benzyl acrylate 1507 (30 parts), butyl acrylate 3457 (70 parts), and triallylsilylsil*K annulate 57 (1.0 parts) was prepared in various dispersion media as shown in Table 15. Polymerization was carried out according to column 1, and the results shown in Table 6 were obtained.

Example 4 Polybutadiene latex 10 with a polymer content of 50% by weight
A dispersion medium consisting of 100 parts of deionized water, 1.5 parts of boric acid, 0.3 parts of sodium carbonate, 0.3 parts of potassium persulfate, and 1 part of potassium oleate, and 70 parts of methyl methacrylate per 0 parts.
%, 50 parts of a monomer consisting of 30% styrene was added to the reactor shown in Example 1, nitrogen gas was passed through it for 15 minutes while stirring at room temperature, and then polymerization was carried out by heating to 70°C from the outside. The polymerization rate was 99.3%, and a graft-polymerized latex material was obtained.

The floating polymer and attached polymer in this polymerization were 0.19% and 0.14%, respectively. On the other hand, when this polymerization was carried out without boric acid and sodium carbonate in the dispersion medium, the emulsified state was destroyed during the polymerization.
Latex was not available. Example 5 Using the dispersion medium shown in Table 7 below, the same monomer composition as in Example 1 was polymerized, and the results shown in Table 8 were obtained.

Claims (1)

[Scope of Claims] 1. When emulsion polymerizing monomers containing acrylic esters and/or methacrylic esters in an aqueous dispersion medium using an emulsifier containing a fatty acid soap as a main component, boron is added to the aqueous dispersion medium. Acid ion (BO_3^-^-^-) 0.0
Contains 1 to 0.5 g ions/l and has a pH of 5.5 to 9.
5. An emulsion polymerization method characterized in that an alkali metal salt or ammonium salt of boric acid is present in the range of 5. 2. A patent characterized in that the alkali metal salt or ammonium salt of boric acid is an alkali metal salt or ammonium salt of boric acid produced from boric acid and a hydroxide, carbonate, or bicarbonate of an alkali metal or ammonium. The emulsion polymerization method according to claim 1.