JP2009197154A - Method for producing vinyl chloride polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride polymer, by which scales in a polymerization vessel are prevented upon suspension polymerization of vinyl chloride or a mixture monomer of vinyl chloride and monomers copolymerizable therewith. <P>SOLUTION: The method comprises suspension polymerization of a single monomer of vinyl chloride or a mixture monomer of vinyl chloride and monomers copolymerizable with vinyl chloride in an aqueous medium, wherein polymerization is carried out while intermittently or continuously adding a water-soluble polymerization inhibitor from the initial stage of polymerization to the middle of polymerization. The polymerization inhibitor is preferably at least one selected from sodium nitrite and hydroquinone. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a vinyl chloride polymer.

  Since vinyl chloride resin is inexpensive and excellent in quality balance, it is used in various fields such as soft field and hard field. For example, pipes, films, industrial plates, window frames and the like are used in the hard field, and electric wire coatings, wrap films, sheets and the like are used in the soft field. On the other hand, vinyl chloride resin as a material is a general-purpose resin whose essential requirement is that it is inexpensive, and various means for improving polymerization productivity have been conventionally attempted in order to reduce manufacturing costs. Further, in order to prevent the vinyl chloride monomer from being released into the air or waste water, the polymerization system is closed. In order to improve polymerization productivity and reduce the release of vinyl chloride monomer, which leads to a reduction in manufacturing costs, it is important to improve the number of batches charged continuously without opening the manhole of the polymerization reactor.

 However, in the suspension polymerization of vinyl chloride, scales are formed and adhered in the polymerization reactor, and therefore it is necessary to periodically open a manhole and clean it. Various efforts have been made to prevent this scale, and although certain effects have been achieved, they are insufficient.

 For example, Patent Document 1 proposes a method of spraying an aqueous solution of a substance having a polymerization inhibiting effect on the incidental equipment as a scale prevention of the auxiliary equipment of the polymerization reaction can, but it is merely a scale prevention of the incidental equipment.

 In Patent Document 2, a polymerization inhibitor is added to prevent polymerization in the can, but the scale is reduced by suppressing the initial polymerization rate, but scale suppression is insufficient even in batch polymerization. In addition, when vinyl chloride or a monomer copolymerizable therewith is added continuously or intermittently, the effect is not sufficient.

There are a method of forming a coating film for preventing scale adhesion on the inner wall of the polymerization can as in Patent Documents 3 and 4, and a method for preventing scale adhesion by applying electrolytic polishing treatment to the inner wall surface, but the effect is insufficient. In addition, in the case of copolymerization with a highly water-soluble vinyl chloride copolymerizable monomer, the effect is further reduced.
Japanese Patent Publication No.58-043407 Japanese Patent No. 2549294 Japanese Patent No. 2702232 Japanese Patent No. 2735292

  The present invention has been made in view of such a current situation, and prevents the scale in the polymerization reaction vessel when suspension polymerization of vinyl chloride or a mixed monomer of vinyl chloride and a monomer copolymerizable therewith is prevented. It provides a way to

  The present inventor, when polymerizing a single monomer of vinyl chloride or a mixed monomer of a monomer copolymerizable with vinyl chloride, a water-soluble polymerization inhibitor is intermittently or from the beginning of polymerization and during polymerization. It discovered that the said subject could be solved by superposing | polymerizing, adding continuously.

That is, the present invention relates to a method for suspension polymerization of a vinyl chloride single monomer or a mixed monomer of a monomer copolymerizable with vinyl chloride in an aqueous medium, wherein a water-soluble polymerization inhibitor is polymerized. It is a method for producing a vinyl chloride polymer, characterized in that polymerization is carried out intermittently or continuously from the beginning and during polymerization.
The polymerization inhibitor is preferably one or more selected from sodium nitrite and hydroquinone.

  According to the present invention, it is possible to prevent scale formation and adhesion in the polymerization reaction can, open the manhole of the polymerization reaction can and extend the cleaning cycle, and improve productivity and manufacture. It is possible to reduce costs and prevent the outflow of vinyl chloride monomer.

  Examples of the monomer that can be copolymerized with vinyl chloride in the mixed monomer of the vinyl chloride single monomer or the monomer copolymerizable with vinyl chloride in the present invention include vinyl such as vinyl acetate and vinyl propionate. Esters, vinyl ethers such as isobutyl vinyl ether, acrylic esters such as ethyl acrylate, alkyl acrylate derivatives such as hydroxyethyl acrylate, alkyl methacrylates, maleic anhydride, alkyl maleates, acrylonitrile, styrene And olefins such as ethylene. These may be used singly or in combination of two or more.

  Vinyl chloride or these copolymerizable monomers may be batch polymerization charged in the initial stage of polymerization, or semi-batch polymerization that is added continuously or intermittently during the initial stage and during the polymerization. But well. In semi-batch polymerization, a higher scale prevention effect than before can be obtained.

  The aqueous solvent used in the present invention is water or a medium containing water as a main component, particularly deionized water, further heated deionized degassed water, and further heated and degassed and then cooled degassed. This is preferably ionic water. The temperature of the aqueous solvent is preferably in the range of 10 ° C to 95 ° C, and more preferably in the range of 50 ° C to 95 ° C in order to shorten the heating time. The initial ratio of the aqueous solvent to the vinyl chloride monomer and the comonomer is preferably 0.9 to 10, and the ratio during the polymerization period is preferably controlled to the range of 0.8 to 2.5. .

  The polymerization reactor in the present invention may be any pressure-resistant polymerization reactor, and there is no particular limitation on the shape of a stirrer used in the polymerization reactor, such as a stirrer and baffle used as desired. Known stirring devices generally employed in the suspension polymerization method of vinyl monomers can be used, and examples of such stirring blades include paddle blades, blue margin blades, fiddler blades, turbine blades, A propeller blade, a pitch paddle blade, etc. are mentioned, These stirring blades may be used by one kind, may be combined with many stirring blades, and may be used in several steps. Examples of the baffle include a plate type, a cylindrical type, a D type, a loop type, and a finger type. In addition, a heating / cooling jacket or an external slurry circulation type heat exchanger may be used for the polymerization reaction can. Examples of such a heating / cooling jacket include an external jacket and an internal jacket. Examples of the circulation heat exchanger include a shell and tube type, a multi-tube type, a coil type, a spiral type, and the like, and a circulation pump may be generally used. Further, a reflux condenser attached to the polymerization apparatus may be used, and the installation type may be either direct or indirect by gas / condensate piping. The condenser type is preferably a shell and tube type that can be easily washed. However, any of a multi-tube type, a coil type, a spiral type, and the like may be used.

The capacity of the polymerization reaction can in the present invention is not particularly limited, but it is 25 m ³ or more, more preferably 35 m ³ or more, because it is possible to produce a vinyl chloride polymer with good production efficiency. It is preferable to use a polymerization reaction vessel of 60 m ³ or more.
Further, the scale inhibitor may be applied to the polymerization reaction can and incidental equipment, and further, washing with high-pressure water may be used in combination.

Examples of the polymerization inhibitor used in the present invention include nitrites such as sodium nitrite, thiocyanates such as potassium thiocyanate, metal salts such as sulfur derivatives of carbonic acid such as sodium diethyldithiocarbamate, Organic substances may be used. Organic substances include hydroquinone, dialkylhydroxylamines such as diethylhydroxylamine, hydroxyl-substituted mercaptans such as methyl mercaptoethanol, hydroxyl-substituted divalent mercaptans such as 1,2-dithioglycerol, Mercaptocarboxylic acids such as hydroacrylic acid, nitro-substituted mercaptans such as β-nitroethyl mercaptan, amino-substituted mercaptans such as thioethanolamine, sulfide carboxylic acids such as thiodiglycolic acid, dithio Although disulfides such as glycolic acid and sulfur-containing organic compounds such as ammonium sulfamate can be raised, the better the water-solubility and the less the transition to the vinyl chloride liquid phase is. In particular, it is good also from the aspect of initiator efficiency and the scale prevention effect. Preferably, sodium nitrite and hydroquinone are preferable.
It is necessary to set the total amount of the polymerization inhibitor initially and additionally in consideration of the color tone, transparency, and thermal stability. For example, in the case of sodium nitrite, at least 1 ppm, preferably 2 ppm or more, and the upper limit is 10 pppm or less, preferably 5 ppm or less with respect to the amount of vinyl chloride or mixed monomer, but in the case of hydroquinone, 5 ppm or more. The upper limit is desirably 10 ppm or more, and the upper limit is 50 ppm or less, preferably 30 ppm or less. These can also be used in combination.
The amount of polymerization inhibitor added during the polymerization is preferably 25% or more, more preferably 40% or more of the total amount. The addition of a polymerization inhibitor during polymerization is preferably continuously added from the start of polymerization to the end of polymerization. However, when the monomer is charged before the start of polymerization, 70% of the polymerization time until the end of polymerization is reached. In the case of the semi-batch polymerization mode in which the monomer is added, it may be added until the time exceeding 70% of the time from the completion of the monomer charging to the completion of the polymerization. . Further, it may be added in two or more times, preferably in three or more times without adding continuously.

  As the polymerization initiator used in the present invention, those generally known as polymerization initiators can be used, such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, etc. Peroxycarbonate compound, t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-hexylperoxybivalate, t-amylperoxyneodecanoate, 1,1-dimethyl- Peroxyester compounds such as 3-hydroxybutylperoxyneodecanoate, t-hexylperoxydiglycolate, α-cumylperoxyneodecanate, peroxides such as acetylcyclohexylsulfonyl peroxide, azobis (2, 4-Dimethyl bar Azo compounds such as relonitrile) and azobis (4-methoxy-2,4-dimethylvaleronitrile), and hydrogen peroxide. These may be used singly or in combination of two or more. Moreover, it is preferable to use this polymerization initiator in 0.001-1 weight part with respect to 100 parts of vinyl chloride or a mixed monomer. The addition method to this polymerization machine may be a commonly used method, and it is added directly into the aqueous medium during the preparation of the aqueous medium or as an emulsion aqueous solution using an emulsifier, surfactant or suspending agent. Or during the charging of the vinyl chloride monomer, add it directly into the monomer or as an emulsion aqueous solution using an emulsifier, surfactant or suspending agent, or during the polymerization reaction after the charging is completed It is not particularly limited, for example, it can be used alone or in the form of an aqueous emulsion solution, and a part of the initiator is charged.

  The dispersion stabilizer used in the present invention is not particularly limited and may be generally used as a dispersion stabilizer for suspension polymerization. For example, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl ethyl cellulose, etc. Cellulose derivatives, partially saponified polyvinyl alcohol (PVA), acrylic acid polymers, water-soluble polymers such as gelatin, nonionic surfactants, anionic surfactants, and the like. These may be used alone or in combination of two or more. It is also possible to use the dispersant, and the dispersant is preferably used in an amount of 0.01 to 1 part by weight with respect to 100 parts by weight of vinyl chloride or a mixed monomer.

  Furthermore, for the polymerization system, if necessary, a thickener, a polymerization regulator, a chain transfer agent, a pH regulator, a gelation improver, an antistatic agent, a crosslinking agent, which are appropriately used for the polymerization of the vinyl chloride monomer. It is also optional to add agents, stabilizers, fillers, antioxidants, buffers, scale inhibitors and the like.

Example 1
To 100 parts of vinyl chloride, 200 parts of ion-exchanged water, 0.06 part of PVA, 0.02 part of t-butyl peroxyneodecanate and 0.0002 part of sodium nitrite are used in the polymerization reactor. First, the temperature was raised with a jacket, and polymerization was started at 63 ° C. When the temperature inside the polymerization reactor reached 63 ° C., 0.0001 part of 0.5% aqueous sodium nitrite was added from the polymerization reactor header, and was added in 300 minutes. The polymerization was completed after a polymerization time of 420 minutes. The amount of scale adhering to the inside of the polymerization machine after the completion of the polymerization discharge was equivalent to about 0.07 part of vinyl chloride.

(Example 2)
40 parts vinyl chloride, 20 parts vinyl acetate, 200 parts ion-exchanged water, 0.14 parts PVA, 0.026 parts t-butylperoxyneodecanate, 0.0002 parts sodium nitrite, polymerized The reactor was charged, the temperature was raised with a jacket, and polymerization was started at 63 ° C. Thirty minutes after the polymerization temperature reached 63 ° C., 40 parts of vinyl chloride was added over 300 minutes. Moreover, from the time when the temperature inside the polymerization machine reached 63 ° C., 0.002 part of 1% aqueous hydroquinone was added from the bottom nozzle of the polymerization machine and added over 430 minutes. The polymerization was completed at a polymerization time of 460 minutes. The amount of scale adhering to the inside of the polymerization machine after the completion of the polymerization discharge was equivalent to about 0.5 part of the mixed monomer.

(Comparative Example 1)
To 100 parts of vinyl chloride, 200 parts of ion-exchanged water, 0.06 part of PVA, 0.02 part of t-butylperoxyneodecanate, and 0.0002 part of sodium nitrite are charged into the polymerization reactor. The temperature was raised with a jacket, and polymerization was started at 63 ° C. The polymerization was completed in 420 minutes after the polymerization temperature reached 63 ° C. The amount of scale adhering to the inside of the polymerization machine after the completion of the polymerization discharge was equivalent to about 0.11 part of vinyl chloride.

(Comparative Example 2)
40 parts vinyl chloride, 20 parts vinyl acetate, 200 parts ion-exchanged water, 0.14 parts PVA, 0.026 parts t-butylperoxyneodecanate, 0.0002 parts sodium nitrite, polymerized The reactor was charged, the temperature was raised with a jacket, and polymerization was started at 63 ° C. Thirty minutes after the polymerization temperature reached 63 ° C., 40 parts of vinyl chloride was added over 300 minutes. Further, from the time when the temperature inside the polymerization machine reached 63 ° C., the polymerization was completed in a polymerization time of 460 minutes. The amount of scale adhering to the inside of the polymerization machine after the completion of the polymerization discharge was equivalent to about 1.1 parts of the mixed monomer.

Claims (2)

  A method for suspension polymerization of a vinyl chloride single monomer or a mixed monomer of a monomer copolymerizable with vinyl chloride in an aqueous medium, wherein a water-soluble polymerization inhibitor is added at an initial stage of polymerization or during polymerization. , A method for producing a vinyl chloride polymer, characterized by being polymerized while being added intermittently or continuously   The method for producing a vinyl chloride polymer according to claim 1, wherein the polymerization inhibitor is one or more selected from sodium nitrite and hydroquinone.