JPH0660210B2 - Polymerization method of vinyl monomer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improved method for polymerizing vinyl monomers, and more specifically, suspension of vinyl monomers using an aqueous medium. The present invention relates to a polymerization method for preventing adhesion of polymer scale generated on the inner surface of a polymerization reactor during polymerization or emulsion polymerization.

[Conventional technology]

When polymerizing a vinyl monomer in the presence of a dispersant or emulsifier and a polymerization initiator, a problem that a solid polymer called scale adheres to the inner surface of the polymerization reactor, that is, its inner wall, stirring blades, baffle plates, condensers, etc. There is.

Due to this scale, heat transfer efficiency is reduced, product yield is reduced, quality is deteriorated due to incorporation of peeling scale into the product, productivity is reduced due to the time and labor required for scale removal, and occupational health and safety. The above problems cause many disadvantages.

In order to solve these problems, many methods for preventing scale formation and their adhesion to the polymerization vessel have been proposed.

For example, dyes, pigments, other polar organic compounds, inorganic acids and their salts, polyvalent metal salts, etc. may be applied to the inner surface of the polymerization vessel or added to an aqueous medium. However, there are drawbacks such as poor sustainability and deterioration of various product characteristics. As a method for improving these, a method of applying a polymer compound having a functional group that prevents scale formation to the inner surface of the polymerization vessel has been proposed.

Conventionally, phenolic compounds have been used as polymerization inhibitors, and many methods utilizing them have been proposed.

For example, JP-A-55-16004 discloses a reaction product of a phenol / aldehyde initial condensation product with nitrophenols, and US Pat. No. 4,080,173 discloses a self-condensed polyphenol and polynaphthol. Sho 5
No. 5-54317 discloses a condensate of a phenolic compound and an aromatic aldehyde, JP-A No. 55-102610 discloses propylene glycol alginate, and JP-A No. 55-11209 discloses a nitrile-containing polymer. 58-204006 discloses a method of applying a reaction product or the like of a drying oil or a semi-drying oil and a phenol compound and, if necessary, an aldehyde, to the inner surface of the polymerization vessel.

However, when these methods are used, there are many points to be improved, for example, the polymerization rate is lowered, and the durability of the coating film is insufficient, which causes a problem in the sustainability of the descaling effect.

[Problems to be solved by the invention]

The present inventors, as a result of earnest research to eliminate these drawbacks, when a certain polymer compound is polymerized particularly vinyl monomers, when this is applied to the inner surface of the polymerization vessel for polymerization, The present invention has been completed by finding that scale adhesion can be greatly prevented.

[Means for solving problems]

That is, in the present invention, when polymerizing a vinyl-based monomer in an aqueous medium, a reaction product of polyvinyl acetate or a partially saponified product thereof and a phenolic carboxylic acid is applied to the inner surface of the polymerization vessel in advance. And a method for polymerizing a vinyl monomer.

Examples of the phenolic carboxylic acids used in the present invention include hydroxybenzoic acid, resorcinic acid, gentisic acid, protocatechuic acid and gallic acid.

Polyvinyl acetate of the present invention or a partially saponified product thereof,
As a method for producing a reaction product with a phenolic carboxylic acid, polyvinyl acetate or a partially saponified product thereof, and a phenolic carboxylic acid in a suitable solvent,
Using an acid catalyst such as p-toluenesulfonic acid or sulfuric acid, the temperature is 10 to 150 ° C, preferably 40 to 100 ° C for 5 minutes to
It is produced by reacting for 10 hours, preferably for 1 to 5 hours.

The mixing ratio of polyvinyl acetate or its partially saponified product and phenolic carboxylic acid is in the range of 0.1 to 5 mol, preferably 0.3 to 2 mol, of phenolic carboxylic acid compound per 1 mol of acetic acid group. Used in a range.

As the solvent used in the reaction system, an inert solvent such as acetone, dioxane, methyl ethyl ketone, or methyl isobutyl ketone is suitable.

The amount of p-toluenesulfonic acid or sulfuric acid used as a catalyst is 0.1 to 5 per 1 mol of acetic acid group.
A molar range is suitable, preferably 0.3 to 2 mol.

The descaling agent thus produced is used by dissolving it in a hydrocarbon-based polar solvent or an alkaline solution.

The solution spray method so that the proportion of 0.01g / m ² ~10g / m ² as a descaling agent per square meter of the polymerization vessel surfaces of interest, deposited on methods polymerization vessel surface, such as rinsing method To use.

The polymerization of the vinyl-based monomer using the present invention includes suspension polymerization,
Emulsion polymerization is adopted, but the dispersant, initiator, etc. used in this polymerization are not particularly limited, and commonly used ones can be used.

For example, as the dispersant and the emulsifier, a partially saponified product of polyvinyl acetate, an acrylic acid copolymer, a cellulose derivative, gelatin, a protective colloidal compound such as starch, or an ester of a higher fatty acid and a polyhydric alcohol,
Anionic surfactant such as polyoxyethylene derivative,
Anionic surfactants such as metal salts of higher fatty acids and metal salts of alkylbenzene sulfonic acid are used.

As the polymerization initiator, organic peroxides such as benzoyl peroxide, lauroyl peroxide, dioctyl peroxydicarbonate, azo compounds such as azobisisodimethylvaleronitrile, and persulfates such as potassium persulfate and ammonium persulfate are used. To be done.

The vinyl-based monomer referred to here is a monomer having a vinyl group, for example, olefins such as ethylene and propylene, vinyl halides such as vinyl chloride and vinylidene chloride, vinyl esters such as vinyl acetate, Vinyl ethers such as ethyl vinyl ether, acrylic acid esters such as methyl methacrylate, metal salts or esters such as maleic acid and fumaric acid, aromatic vinyls such as styrene, and diene-based monoamines such as butadiene, chloroprene and isoprene And vinyl monomers that are copolymerizable with these monomers.

The polymerization temperature is usually in the range of 30 to 80 ° C.

INDUSTRIAL APPLICABILITY The present invention can be used for the polymerization of the above vinyl-based monomers alone or a mixture of two or more vinyl-based monomers, and particularly shows a remarkable effect on the polymerization of vinyl chloride-based monomers. .

〔The invention's effect〕

As described above, scale adhesion can be significantly improved.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples.
This does not limit the scope of the invention.

Reference Example 1 Polyvinyl acetate 100 having a degree of polymerization of 500 was placed in a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser.
Parts, gallic acid 250 parts, and 800 parts acetone were charged, stirred and completely dissolved, and then heated to 60 ° C.,
A solution prepared by previously dissolving 220 parts of p-toluenesulfonic acid in 220 parts of acetone was added dropwise thereto and reacted at 60 ° C. for 4 hours.

As the reaction proceeded, the reaction product was precipitated, so the reaction solution was cooled after completion of the reaction, and then the reaction product was separated by suction filtration.

Further, it was washed with acetone and dried under reduced pressure to obtain a product.

[Reference Example 2] As in Reference Example 1, in a four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 100 parts of the same polyvinyl acetate used in Reference Example 1 and p-hydroxybenzoic acid 2 were used.
The reaction and post-treatment were carried out in the same manner as in Reference Example 1 using 50 parts, and the product was purified and dried.

Comparative Example 1 After charging 250 parts of pure water, 0.25 part of partially saponified polyvinyl acetate and 0.05 part of 2,2'-azobis-2,4 dimethylvaleronitrile into a polymerization vessel having an internal volume of 1 m ³ . Then, 100 parts of vinyl chloride monomer was injected under reduced pressure.

Then, the mixture was heated to 57 ° C. with stirring, and when the pressure in the polymerization reactor dropped 2 kg / cm ³ from the pressure in the steady state of the polymerization reaction, the recovery of unreacted monomers was started.

The polymerization time at this time was 10 hours.

Then, after recovering the unreacted monomer, the polymerization suspension was taken out from the polymerization vessel, and the inner surface was washed with low pressure water. After that, when the amount of scale attached to the inner surface of the polymerization vessel was measured, it was found to be 130
It was g / m ² .

[Examples 1 and 2] The products obtained by the methods of Reference Examples 1 and 2 were each added to 5
% Ethanol solution was spray-coated on the inner surface of the polymerization vessel used in Comparative Row 1 and dried. The coating amount at this time was 0.5 g / m ² .

By using this polymerization vessel was subjected to each polymerization reaction in the same manner as in Comparative Example 1, a polymerization time both 10 hours, respectively scale deposition amount 4g / m ² and 7 g / m ²
Met.

Comparative Example 2 250 parts of pure water and 5 parts of vinyl acetate were placed in a polymerization vessel having an internal volume of 1 m ^3.
Parts, partially saponified polyvinyl acetate 0.25 parts, and 2,2'-azobis-2,4 dimethylvaleronitrile 0.05 parts were charged, and then 100 parts of vinyl chloride monomer was injected under reduced pressure, followed by stirring. While stirring, heat to 60 ° C, and the pressure inside the polymerization reactor is 2 kg / cm from the pressure in the steady state of the polymerization reaction.
^{When the} temperature dropped to ³ , the recovery of unreacted monomer was started.

The polymerization time at this time was 8.5 hours.

Then, after recovering the unreacted monomer, the polymerization suspension was taken out from the polymerization vessel, and the inner surface was washed with water.

Then, the amount of scale attached to the inner surface of the polymerization vessel was measured and found to be 190 g / m ² .

[Examples 3 and 4] The products obtained by the methods of Reference Examples 1 and 2 were each added to 5
% Ethanol solution, and spray-coated on the inner surface of the polymerization vessel used in Comparative Row 2 and dried.

The coating amount at this time was 0.5 g / m ² .

Using this polymerization vessel, a polymerization reaction was carried out in the same manner as in Comparative Example 2. The polymerization times were both 8.5 hours, and the scale deposits were 6 g / m ² and 8 g / m ^2, respectively.
It was m ² .

Claims (3)

[Claims] 1. When polymerizing a vinyl-based monomer in an aqueous medium, a reaction product of polyvinyl acetate or a partially saponified product thereof and a phenolic carboxylic acid is applied to the inner surface of the polymerization vessel in advance. A characteristic method of polymerizing vinyl monomers. 2. The vinyl monomer is vinyl chloride alone, or
The polymerization method according to claim 1, which is a mixture of vinyl chloride and a monomer copolymerizable therewith. 3. The polymerization method according to claim 1, wherein the phenolic carboxylic acids are hydroxybenzoic acid, resorcinic acid, gentisic acid, protocatechuic acid and gallic acid.