JPH049801B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improved polymerization method for vinyl chloride monomers, and particularly aims to provide a polymerization method with less scale adhesion on the inner wall of a polymerization vessel, the surface of an agitator, etc. (Prior art) As a conventional method for polymerizing vinyl chloride monomers, suspension polymerization using an oil-soluble radical polymerization initiator in an aqueous medium has been widely practiced. Polymer scale adheres to the inner walls, the surface of the stirring device, etc., which reduces the cooling capacity of the polymerization vessel, and also causes the disadvantage that the scale mixes into the produced polymer, degrading the quality of the product. On the other hand, removing scale that has adhered to the inner walls of the polymerization vessel, stirrer, etc. not only requires excessive labor and time, but also poses a risk to the safety and health of workers since unreacted monomers are adsorbed in the scale. There is a problem above. As a method to prevent polymer scale from adhering to the inner walls of the polymerization vessel, etc., there is a method of coating the inner walls of the polymerization vessel and the stirrer with polar organic compounds such as amine compounds, quinone compounds, aldehyde compounds, dyes, pigments, etc. Known methods include coating a compound or dye treated with a metal salt, coating a mixture of an electron-donating compound and an electron-accepting compound, and coating an inorganic salt or an inorganic complex. In addition to the above-mentioned coating method as a measure to prevent polymer scale, attempts have also been made to suppress scale adhesion to the inner walls of the polymerization vessel as much as possible by improving the formulation itself for charging the polymerization vessel. For example, published patent publication No. 57-500614,
-500650, in polymerizing vinyl chloride in an aqueous medium, a water-insoluble crosslinked polymer obtained by crosslinking and copolymerizing a crosslinkable monomer such as allylpentaerythritol or allylsucrose with acrylic acid in an aqueous medium. A polymerization recipe has been disclosed in which is added as a dispersant, and this has the effect of reducing the amount of scale deposited on the inner wall of the polymerization vessel. However, this effect of reducing scale adhesion is small and not satisfactory. (Structure of the Invention) The present inventors have conducted extensive research in order to more effectively suppress scale adhesion to the inner walls of the polymerization vessel by improving the polymerization recipe. The present invention was completed by confirming that an excellent effect of inhibiting scale adhesion can be obtained by allowing the presence in That is, the present invention provides for suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium using a polymerization initiator. To 100 parts by weight of the monomer mixture, (a) 0.005 to 1 part by weight of a nonionic surfactant and (b) an olefinic unsaturated carboxylic acid containing at least two CH ₂ =C groups in one molecule. 0.01 to 2 parts by weight of a partially crosslinked copolymer obtained by copolymerizing an organic phosphorus compound with Scale adhesion on the inner walls of the vessel can be significantly reduced. In addition to the use of the above partially crosslinked copolymer, the adhesion of polymer scale can be more reliably prevented by applying a technique of applying a scale adhesion preventive agent to the inner wall of the polymerization vessel, etc. Although the reason why the method of the present invention provides a remarkable scale adhesion prevention effect is not clear, when the partially crosslinked copolymer is dissolved in an aqueous medium, it exhibits an excellent dispersing agent effect on monomer droplets. This is presumed to be due to the fact that the monomer droplets are prevented from coming into contact with the wall surface of the polymerization vessel in order to stabilize them, and even if they come into contact, they do not become unstable. The present invention will be explained in detail below. (a) Nonionic surfactants used to carry out the method of the present invention include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polystyrylphenyl ether, polyoxyethylene Polyoxypropylene block copolymer, glycerin fatty acid partial ester, sorbitan fatty acid partial ester, pentaerythritol fatty acid partial ester, propylene glycol monofatty acid ester, sucrose fatty acid partial ester, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester , polyoxyethylene glycerin fatty acid partial ester,
Polyethylene glycol fatty acid ester, polyglycerin fatty acid partial ester, polyoxyethylated castor oil, fatty acid diethanolamide, N,
Examples include N-bis-2-hydroxyalkylamine, polyoxyethylenealkylamine, triethanolamine fatty acid ester, and trialkylamine oxide, which may be used singly or as a mixture of two or more. Next, (b) the partially crosslinked copolymer is obtained by copolymerizing an olefinic unsaturated carboxylic acid and an organic phosphorus compound having at least two CH ₂ =C groups in one molecule; Examples of unsaturated carboxylic acids include alluric acid, methacrylic acid,
Examples include itaconic acid, chloroacrylic acid, cyanoacrylic acid, α-phenylacrylic acid, α-benzylacrylic acid, crotonic acid, maleic acid, fumaric acid, sorbic acid, and other olefinic unsaturated carboxylic acids. These are not limited to one type, and two or more types may be used in combination at the same time. On the other hand, examples of the organic phosphorus compound having an unsaturated group include those described below. However, Me in each chemical formula represents a methyl group. 2-Acryloyloxyethyl acid phosphate 2-methacryloyloxyethyl acid phosphate Diallyldibutylphosphonosuccinate These organic phosphorus compounds are not limited to one type, but two
You may use more than one species in combination. The proportion of the organic phosphorus compound to be copolymerized with the olefinic unsaturated carboxylic acid is 0.1 to 30% by weight (particularly 0.1 to 10% by weight) per 100 parts by weight of the olefinic unsaturated carboxylic acid. It is desirable to set the range. If this amount is too small, no crosslinking effect will be obtained, and if it is too large, crosslinking will be excessive and the copolymer will no longer exhibit the effect of a dispersant. The crosslinking copolymerization reaction is carried out using an azo-based, peroxide-based, redox-based catalyst, etc. as a polymerization initiator, such as azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile). ), benzoyl peroxide, cumene hydroperoxide, tertiary butyl hydroperoxide, persulfates, combinations of persulfates and percarbonates,
This is carried out by using a combination of persulfate and sulfite and reacting in a solvent such as benzene, toluene, n-hexane, or ethyl acetate. Components (a) and (b) are added to the aqueous medium in amounts per 100 parts by weight of monomer to be added.
(a) 0.005 to 1 part by weight of nonionic surfactant (preferably 0.01 to 0.5 part by weight), (b) Partially crosslinked copolymer
It is necessary to adjust the amount to 0.01 to 2 parts by weight (preferably 0.02 to 0.5 parts by weight). As a result, the monomer exists as stable fine droplets in the aqueous medium, and polymerization is carried out without scale adhesion. In the method of the present invention, the adhesion of polymer scale can be more completely prevented by applying a scale adhesion preventive agent to the surfaces of the inner wall of the polymerization vessel, the stirring device, etc. in advance. Conventionally known scale adhesion inhibitors are used, including those disclosed in Japanese Patent Publication No. 45-30343, Japanese Patent Publication No. 45-30835, Japanese Patent Publication No. 56-5442, Japanese Patent Publication No. 56-5443, Japanese Patent Publication No. 56-56.
- Various dyes such as direct dyes, acid dyes, basic dyes, mordant dyes, sulfur dyes, vat dyes, disperse dyes, oil-soluble dyes, and reactive dyes, and other amine compounds described in Publication No. 5444, etc. Examples include acidic organic compounds such as , quinone compounds, and aldehyde compounds. Among these, dyes having an azine ring are particularly preferred. The oil-soluble polymerization initiators used in carrying out the method of the present invention include diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, acetylcyclohexylsulfonyl peroxide, and t-butyl peroxydicarbonate. barreto, benzoyl peroxide,
organic peroxides such as lauroyl peroxide,
Azobisisobutyronitrile, azobis-2,4
Examples include azo compounds such as -dimethylvaleronitrile and azobis-4-methoxy-2,4-dimethylvaleronitrile. The method of the present invention is particularly suitably applied to suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride, but when the purpose is to obtain a copolymer, acetic acid is Vinyl esters such as vinyl, vinyl ethers, acrylic acid or methacrylic acid and their esters, maleic acid or fumaric acid or their esters, maleic anhydride, aromatic vinyl compounds, unsaturated nitrile compounds such as acrylonitrile, vinylidene fluoride, chloride Examples include vinylidene halides such as vinylidene, and olefins such as ethylene and propylene. When carrying out the method of the present invention, the effect of preventing scale adhesion is further improved by adding a water-soluble basic substance to the polymerization system (aqueous medium) in an amount of 0.1% by weight or less based on the monomer charged. can be done. Note that the amount of polymerization initiator added, polymerization temperature, polymerization time, etc. may be determined according to the conditions conventionally adopted when vinyl chloride is polymerized in an aqueous medium, and these are not particularly limited. . Next, examples of the present invention will be given. In a stainless steel polymerization vessel with an internal volume of 100, 60 kg of deionized water, 20 g of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator, the following [partially crosslinked copolymers (a) to (e)], and nonionic Pour 30g each of surfactants [(1) to (3)] into the polymerization vessel.
After degassing to 50 mmHg, 30 kg of vinyl chloride monomer was charged, and the temperature was raised to 57°C while stirring to initiate polymerization. 6 hours after the start of polymerization, the internal pressure of the polymerization vessel was 6.0Kg/cm ² G.
At this point, the polymerization was stopped, unreacted vinyl chloride was collected, the contents were taken out of the polymerization vessel, and the inside of the polymerization vessel was observed. The above polymerization operation was repeated as one batch until scale adhesion was observed on the inner wall of the polymerization vessel. The results were as shown in Table 1. Partially crosslinked copolymer (a): Crosslinked copolymer of 100 parts by weight of acrylic acid and 0.5 part by weight of the above organic phosphorus compound [2] Partially crosslinked copolymer (b): 100 parts by weight of acrylic acid and 0.5 part by weight of the above organophosphorus compound [] ] Partially crosslinked copolymer with 0.7 parts by weight Partially crosslinked copolymer (c): Crosslinked copolymer with 100 parts by weight of acrylic acid and 0.4 part by weight of the organic phosphorus compound Partially crosslinked copolymer (d): Acrylic Crosslinked copolymer of 100 parts by weight of acid and 0.2 parts by weight of allylpentaerythritol Partially crosslinked copolymer (E): Crosslinked copolymer of 100 parts by weight of acrylic acid and 1.3 parts by weight of allyl sutucarose Nonionic surfactant ( 1): Sorbitan monolaurate nonionic surfactant (2): polyoxyethylene sorbitan monolaurate nonionic surfactant (3): polyoxyethylene sorbitan monooleate

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Claims (1)

[Scope of Claims] 1. When carrying out suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium using a polymerization initiator, the above-mentioned vinyl chloride or this monomer mixture is added to the aqueous medium. (a) 0.005 to 1 part by weight of a nonionic surfactant and (b) an olefinic unsaturated carboxylic acid in one molecule, per 100 parts by weight of a monomer mixture mainly consisting of
A method for polymerizing vinyl chloride monomers, which comprises adding 0.01 to 2 parts by weight of a partially crosslinked copolymer obtained by copolymerizing an organic phosphorus compound having at least two CH ₂ =C< groups. .