JPS61235401A - Polymerization of vinyl monomer - Google Patents

Abstract

PURPOSE:To polymerize a vinyl monomer without deposition of polymer scale on the inside surface of a polymerizer, by previously coating the inside surface of the polymerizer with a specified reaction product and polymerizing the monomer in an aqueous medium in the polymerizer. CONSTITUTION:In polymerizing a vinyl monomer in an aqueous medium, the inside surface of the polymerizer is previously coated with a reaction product between a high-molecular alcohol having hydroxyl groups in the molecule and a phenolic aldehyde. Examples of the vinyl monomers which can be applied include vinyl chloride and a mixture thereof with a monomer copolymerizable therewith. Examples of the high-molecular alcohols having hydroxyl groups in the molecule include polyvinyl alcohol prepared by saponifying polyvinyl acetate, etc. Examples of the phenolic aldehydes include hydroxybenzaldehyde, resorcylaldehyde and gentisaldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improved method for polymerizing vinyl monomers, and more particularly, to a method for polymerizing vinyl monomers using an aqueous medium. The present invention relates to a polymerization method for preventing polymer schools from adhering to the inner surface of a polymerization reactor during polymerization or emulsion polymerization.

[Conventional technology]

When vinyl monomers are polymerized in the presence of a dispersant or emulsifier and a polymerization initiator, there is a problem in which solid polymers called scale adhere to the inside surface of the polymerization reactor, that is, its inner walls, stirring blades, baffle plates, condensers, etc. There is.

This scale causes a decrease in heat transfer efficiency, a decrease in product yield, a decrease in quality due to the contamination of the product with exfoliated scale, a decrease in productivity due to the labor and time required for scale removal, and labor safety. It causes many disadvantages because it causes hygiene problems.

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

For example, there are methods in which dyes, pigments, other polar organic compounds, radios and their salts, polyvalent metal salts, etc. are applied to the inner surface of the polymerization vessel or added to the aqueous medium, but these methods do not affect their effectiveness. It has drawbacks such as difficulty in sustainability and deterioration of product properties. As a method for improving these methods, a method has also been proposed in which a polymer compound having a functional group that prevents scale formation is coated on the inner surface of the polymerization vessel. Phenolic compounds have conventionally been used as polymerization inhibitors, and many methods using them have been proposed.

For example, JP-A No. 55-16004 describes a product prepared by reacting a phenol-aldehyde initial condensate with yanitrophenols, and US Pat. No. 173 describes a self-condensed polyhydric phenol and Worth 7 Thor, special! ! Showa 55-54!
No. 517 discloses that a condensate of a phenolic compound and an aromatic aldehyde, a reaction product of JP-A-55-102610 oil or a semi-drying oil, a 7-ethanol compound, and if necessary an aldehyde is applied to the inner surface of a polymerization vessel. A method is disclosed.

However, when these methods are used, for example, the polymerization rate decreases or the durability of the coating film is insufficient, so that the descaling effect does not last long. There are many points that need improvement, such as the occurrence of problems.

[Problem that the invention seeks to solve]

As a result of intensive research in order to eliminate these drawbacks, the present inventors have discovered that certain polymeric compounds, especially vinyl monomers, can be applied to the inner surface of the polymerization vessel during polymerization. They discovered that school adhesion can be significantly prevented and completed the present invention.

[Means for solving problems]

That is, in the present invention, when a vinyl monomer is polymerized in an aqueous medium, a reaction product of a polymeric alcohol having a hydroxyl group in the molecule and a phenolic aldehyde is applied to the inner surface of the polymerization vessel in advance. The present invention relates to a method for polymerizing vinyl monomers.

Examples of the polymeric alcohol having a hydroxyl group in the molecule used in the present invention include polyvinyl alcohol obtained by completely or partially pycnicizing polyvinyl acetate, saponified products of copolymers of ethylene and vinyl chloride and vinyl acetate, Polymers of acrylic esters of polyhydric alcohols, polyglycerin and cellulose and their derivatives, or polymeric compounds with epoxy groups in their molecules such as novolak epoxy resins or epoxy-modified liquid polybutadiene. Examples include compounds obtained by ring opening.

Examples of the phenolic aldehydes include hydroxybenzaldehyde, resorcyl aldehyde, gentisic aldehyde, protocatenic aldehyde, and galloaldehyde.

A polymeric alcohol having a hydroxyl group in the molecule of the present invention,
To produce a reaction product with phenolic aldehydes, a polymeric alcohol having a hydroxyl group in its molecule and a phenolic aldehyde are mixed in an appropriate solvent with an acid catalyst such as salt and vinegar or sulfuric acid. for 5 minutes to 10 hours at 10 to 150°C, preferably 40 to 100°C, preferably for 1 hour.
It is produced by reacting for ~5 hours.

The mixing ratio of the polymeric alcohol having a hydroxyl group in the molecule and the phenolic aldehyde is in the range of 11 to 2 moles, preferably a, S to 1 mole of hydroxyl group. It is used in a range of 1 mol.

Methanol is used as a solvent in the reaction system.

Alcohols such as ethanol, or chlorine-based solvents such as ethylene chloride and chloroform are suitable, but a mixture of these solvents may be used.

The appropriate amount of hydrochloric acid and sulfuric acid used as catalysts is 1 to 15 parts, preferably 5 to 10 parts, per 100 parts of the polymeric alcohol.

The descaling agent produced in this manner is used after being dissolved in a hydrocarbon polar solvent or an alkaline solution.

This solution is used by being applied to the surface of the polymerization vessel by a method such as a spraying method or a rinsing method so that the descaling agent is α019/d to 109/− per square meter of the surface of the polymerization vessel.

Polymerization of vinyl monomers using the present invention includes suspension polymerization,
Emulsion polymerization is employed, but there are no particular restrictions on the dispersant, emulsifier, initiator, etc. used in this polymerization, and commonly used ones can be used.

For example, as dispersants and emulsifiers, protective colloidal compounds such as partially nanized polyvinyl acetate, acrylic cut copolymers, cellulose derivatives, gelatin, starch, etc., esters of higher fatty acids and polyhydric alcohols, Anionic surfactants such as oxyethylene derivatives, metal salts of higher fatty acids, and metal salts of alkylbenzenesulfonic acids are used.

Benzoyl peroxide is used as a polymerization initiator.

Organic peroxides such as lauroyl peroxide and dioctyl peroxydicarbonate, azo compounds such as azobisisodimethylvaleronitrile, and persulfates such as potassium persulfate and ammonium persulfate are used.

The vinyl monomer referred to here is a monomer having a vinyl group, such as 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 esters such as permethyl methacrylate, metal salts or esters such as maleic acid and hexamaric acid, aromatic vinyls such as styrene, ζ.

Examples include diene monomers such as butadiene, cloprene, and isoprene, acrylonitrile, etc., and vinyl monomers that can be copolymerized with these monomers.

Moreover, the polymerization temperature is carried out within the commonly used range of 30 to 80°C.

Although the present invention can be used for the polymerization of the above-mentioned vinyl monomers alone or a mixture of two or more vinyl monomers, it is particularly effective in polymerizing monomers mainly composed of vinyl chloride. .

〔Effect of the invention〕

As described above, scale adhesion can be significantly improved.

〔Example〕

The present invention will be explained below with reference to examples, but the scope of the present invention is not limited by these examples.

[Reference Example 1] In a four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 100 parts of polyvinyl alcohol prepared by saponifying 96 to 97 mol% of polyvinyl acetate, 200 parts of hydroxybenzaldehyde, and 500 parts of ethanol were added. and stir to completely dissolve, then heat to 70℃,
A solution prepared by dissolving 10 parts of concentrated sulfuric acid in 20 parts of ethanol was added dropwise thereto, and the mixture was reacted at 70°C for 4 hours. After the reaction was completed, water was added to the reaction solution while stirring to precipitate the product, which was washed with water and dried.

[Reference Example 2] Similarly to Reference Example 1, 100 parts of the same polyvinyl alcohol used in Reference Example 1 and 250 parts of β-resorcyl aldehyde were added in a four-necked 7-rasf equipped with a stirrer, a thermometer, and a reflux condenser. The reaction and post-treatment were carried out in the same manner as in Reference Example 1, and the product was washed with water and dried.

[Comparative Example 1] 250 parts of pure water, 25 parts of partially saponified polyvinyl acetate α, and 05 parts of 2,21-azobis-2,4 dimethylvaleronitrile α were charged into a polymerization vessel with an internal volume of 1, and then chlorinated under reduced pressure. 100 parts of vinyl monomer were injected.

Next, the temperature was heated to 57°C while stirring, and the pressure inside the polymerization vessel was reduced from the steady state pressure of the polymerization reaction to 29/cI/!
When the temperature decreased, recovery of unreacted monomers was started. The polymerization time at this time was 10 hours. After collecting unreacted monomers, the polymerization suspension was taken out from the polymerization vessel, and the inner surface was washed with low-pressure water.

Thereafter, the amount of scale adhering to the inner surface of the polymerization vessel was measured and found to be 1209/m'.

[Example 1.2] Each of the products obtained by the method of Reference Example 1.2 was made into a 5% ethanol solution, sprayed onto the inner surface of the polymerization vessel used in Comparative Example 1, and dried. The amount of coating at this time is α59/
-It was.

Using this polymerization vessel, polymerization reactions were carried out in the same manner as in Comparative Example 1. The polymerization time was 10 hours in both cases, and the scale adhesion amounts were 69/d and 49/d, respectively.
It was /n/.

[Comparative Example 2] After charging 250 parts of pure water, 5 parts of vinyl acetate, 25 parts of partially saponified polyvinyl acetate α, and 105 parts of 2,27-azobis-2,4 dimethylvaleronitrile into a polymerization vessel with an internal volume of 1-. , injecting 100 parts of vinyl chloride monomer under reduced pressure,
Next, the temperature was heated to 60'CK while stirring, and the pressure inside the polymerization vessel was reduced from the pressure in the steady state of the polymerization reaction to 2 to 9/cl/
When the temperature decreased, recovery of unreacted monomers was started. The polymerization time at this time was 85 hours. After collecting unreacted monomers, the polymerization suspension was taken out from the polymerization vessel, and the inner surface was washed with water.

Thereafter, the amount of scale adhering to the inner surface of the polymerization vessel was measured and found to be 1909/-.

[Example 4] The products obtained by the methods of Reference Examples 1 and 2 were each made into a 5% ethanol solution, sprayed onto the inner surface of the polymerization vessel used in Comparative Example 2, and dried. The coating amount at this time is 0.59
/nf.

Using this polymerization vessel, polymerization reactions were carried out in the same manner as in Comparative Example 2. The polymerization time was 85 hours in both cases, and the amount of school attached was 99/- and 59/-, respectively.
/I was.

Claims (4)

[Claims] (1) When polymerizing vinyl monomers in an aqueous medium,
A method for polymerizing vinyl monomers that is characterized by applying the reaction product of a polymeric alcohol with a hydroxyl group in its molecule and a phenolic aldehyde to the inner surface of a polymerization vessel in advance. (2) The polymerization method according to claim 1, wherein the vinyl monomer is vinyl chloride alone or a mixture of vinyl chloride and a monomer copolymerizable therewith. (3) The polymerization method according to claim 1, wherein the polymeric alcohol having a hydroxyl group in the molecule is polyvinyl alcohol obtained by saponifying polyvinyl acetate. (4) The polymerization method (2) according to claim 1, wherein the phenolic aldehyde is hydroxybenzaldehyde, resorcyl aldehyde, gentisic aldehyde, protocatechualdehyde, and galloaldehyde.