JPH02292310A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To prevent foaming in the production of a vinyl chloride polymer and to improve the initial color of the polymer by adding a polyoxyalkylene glycol to water containing a dispersant, feeding a vinyl chloride monomer to the system after evacuating the system, and polymerizing the monomer. CONSTITUTION:A polyoxyalkylene glycol of any one of formulas I to V (wherein (p), (t), (x), (y) and (z) are each >=2 and (q), (r), (s), (u), (v) and (w) are each >=1) in an amount of 0.000001 to 0.01 pt.wt. per 100 pts.wt. vinyl chloride monomer and a catalyst (e.g. azobis-alpha,alpha-dimethylvaleronitrile) are added to an aqueous medium containing dispersant, and the system is evacuated. A vinyl chloride monomer or a mixture thereof with a vinyl monomer (e.g. vinyl acetate) is added to this aqueous medium and (co)polymerized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a vinyl chloride polymer, which is useful as various molding materials and is free from initial coloring and consists of particles of uniform and suitable size. This paper relates to a method for producing vinyl chloride polymers that prevents the initial coloring of the resulting polymer and improves its particle shape by suppressing the generation of bubbles during the polymerization process. (Conventional technology and its problems) Conventionally, in the production of vinyl chloride polymers. Generally, water in which a dispersing agent such as a suspending agent is dissolved is charged into a polymerization vessel, the upper gas phase is evacuated, and vinyl chloride monomer is charged. However, during this vacuum operation, a large amount of bubbles are generated, making it difficult to draw the vacuum, and as a result, a large amount of oxygen remains in the polymerization reactor, resulting in very fine particles of polyvinyl chloride obtained by the polymerization. There was a problem that the initial coloration was worsened. Therefore, a method of mechanically breaking the bubbles using a defoaming blade etc. was proposed, but
This method did not completely eliminate bubbles, the degree of vacuum was not constant, the particle size of the resulting polyvinyl chloride products varied, and the initial coloration was not sufficiently improved. (Means for solving the problem) Therefore, as a result of intensive research in order to solve this problem, the present inventors have found that vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride, When polymerizing in an aqueous medium, adding polyoxyalkylene glycols to the polymerization system before vacuum operation makes the particles of the resulting polyvinyl chloride product uniform and of a suitable size, and also improves its initial coloration. The present invention was achieved based on the discovery that

To explain this, in the present invention, polyoxyalkylene glycols are added at the same time or after adding water in which a dispersing agent such as a suspending agent is dissolved into the polymerization system, and then vacuum operation is performed to remove vinyl chloride monomers. When performing operations such as charging the polymer, the foaming phenomenon during vacuum operation is effectively suppressed, ensuring the desired degree of vacuum and maintaining and adjusting the ultimate vacuum degree, so the difference in particle size between polymerization batches is small. This method has an extremely large industrial effect, as it provides a polyvinyl chloride product that has a uniform particle shape of a constant size and has improved initial coloring.

The polyoxyalkylene glycols used in the present invention may be homopolymers of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, or random or block copolymers of these alkylene oxides, and these may be used alone or Two or more types can be used in combination.

If these are shown as structural formulas, the following are examples. i: HO+C, H4-0-C, H, -0+-C, H. -OH
P (here p is an integer of 2 or more) ii: HO+C, H4-0}-{-C, H, -08-C, H.
-0-}-Hq r
S (where each q.r.s is an integer of 1 or more) City: HO%C2H4-0-C4Ha-0-+-tC2H4-
OH (here, t is an integer of 2 or more) iV: HO÷C, H 4-0 +-+C 4H . −0←→C
,H,−0←Hu v
v (where u.v.w are each integers of 1 or more) HO-E{C, H4-0+-+
C, H, -0←±C, H. -OHx
y z (where x, y, and z are each an integer of 2 or more) These polyoxyalkylene glycols can be added to the polymerization system as they are or by dissolving or dispersing them in water or a solvent. This is done at the same time as charging water in which a dispersing agent such as a turbidity agent is dissolved, or before vacuum operation after charging, and before operations such as charging vinyl chloride monomer, but especially at the same time as suspending agent. It is preferable to do so.

This addition is 0.0 parts by weight per 100 parts by weight of vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride.
00001 to 0.01 parts, preferably 0.0005
A foaming suppressing effect can be provided by using a proportion of 0.008 parts by weight. This is o. If it is less than oooooot part by weight, there is no effect, and if it exceeds 0.01 part by weight, no further improvement in the foaming suppressing effect can be expected, so it is not economical, and the polymer particles obtained by affecting the polymerization system. This is not desirable because it makes it difficult to control the diameter. The method of the present invention can be applied to, for example, suspension polymerization, emulsion polymerization, etc. when vinyl chloride monomers are polymerized in an aqueous medium, but particularly great effects are brought about when the suspension polymerization method is used.

This polymerization is not limited to vinyl chloride monomer alone, but also vinyl monomers that are copolymerizable with vinyl chloride (mainly vinyl chloride) (
comonomers) (vinyl chloride is 50% by weight or more); examples of the comonomers include vinyl esters such as vinyl acetate and vinyl propionate; acrylic esters such as methyl acrylate and ethyl acrylate; Acrylic acid esters; olefins such as ethylene and propylene; vinyl ethers such as lauryl vinyl ether and inbutyl vinyl ether; maleic anhydride; acrylonitrile amount styrene; vinylidene chloride; and other monomers copolymerizable with vinyl chloride.

The polymerization initiator may be an oil-soluble catalyst or a water-soluble catalyst conventionally used in vinyl chloride polymerization.

Examples of the oil-soluble catalyst include azo compounds such as azobis-α,α'-dimethylvaleronitrile, 2,2'-azobis-2,4'dimethyl-4-methoxyvaleronitrile; diisopropylperoxydicarbonate, di-2-ethyl Percarbonate compounds such as hexyl oxydicarbonate, di(β-ethoxyethyl) peroxydicarbonate; t-butyl peroxy neodecanate, t-butyl peroxy piperate, t-hex silver oxy piperate, Perester compounds such as α-cumyl peroxyneodecanate; acetyl hexyl sulfonyl peroxide, 2,4.4-trimethylpentyl-2-peroxyphenoxy acetate, 3,5.
5-peroxides such as trimethylhexanoyl peroxide and lauroyl peroxide; examples of water-soluble catalysts include potassium persulfate, ammonium persulfate, hydrogen peroxide, and cumene hydroperoxide; They can be used alone or in combination of two or more.

Dispersion aids for a single basin in an aqueous medium may be conventionally known ones, such as styrene-maleic acid copolymer; partially saponified polyvinyl alcohol; methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, Water-soluble cellulose ethers such as hydroxypropyl methylcellulose; water-soluble polymers such as acrylic acid polymers and gelatin; oils such as sorbitan monolaurate, triolate, sorbitan monostearate, glycerin tristearate, and ethylene oxide propylene oxide block copolymers Soluble emulsifiers: Water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, sodium lauryl sulfate; Examples include calcium carbonate, calcium phosphate, sodium dodecylbenzenesulfonate, and these may be used alone or in combination of two or more. used in combination.

The other conditions for this polymerization, the method of charging the aqueous medium, vinyl chloride monomer, other comonomers, suspending agent, etc. Polymerization conditions such as polymerization temperature may also be the same. Furthermore, if necessary, polymerization regulators, polymerization degree regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, crosslinking agents, stabilizers, and fillers used as appropriate for vinyl chloride polymerization. It is also optional to add antioxidants, buffers, scale inhibitors, etc.

(Examples) Specific aspects of the present invention will be explained below using Examples and Comparative Examples, but the present invention is not limited thereto. Example 1. Add 900 kg of deionized water to a stainless steel autoclave with internal volume of 2000 Q and a stirrer and jacket.
, 420 g of partially saponified polyvinyl alcohol, 260 g of 2-ethylhexyl oxydicarbonate, and polyoxyalkylene glycols of the type and amount shown in Table 1 were charged, and the inside of the container was degassed with a vacuum pump. The degree of vacuum was measured after 8 minutes. This was repeated 10 times for each, and the highest and lowest values are also listed in Table 1. Thereafter, 600 kg of vinyl chloride monomer was charged into the vessel, and the temperature was raised to 57°C by passing hot water through the jacket while stirring, and polymerization was continued while maintaining that temperature. When the internal pressure of the polymerization vessel decreased to 6.0 kg/cwfG, unreacted monomers were collected, and the polymer slurry was taken out of the vessel.
After dehydration and drying, a vinyl chloride polymer was obtained. The obtained polymer powder was '60,' according to JIS Z-8801.
The material was sieved using #200 and #200 sieves, and the amount that passed through each was measured. This was repeated 10 times, and the highest and lowest values are also listed in Table 1 to represent the state of the particle size distribution.

The polyoxyalkylene glycols in the table are as follows.

i: In formula i, p = 30...: In formula i, q = 15, r = 80, s = 5 V: In formula V, u = 10. v = 30, w = 40
Later examples 2. Experiment No. in the previous example. Among the samples 1, 4, 6, and 7, the initial coloring of the batches that reached the degree of vacuum shown in Table 2 was measured by the method below, and the results are shown in Table 2.
Also listed in 2.

・Initial coloring method: Vinyl chloride resin 100 parts by weight Impact modifier B-22 (manufactured by Kaneka) 8 Eboxidized soybean oil 6II Calcium stearate
0.1 zinc stearate
0.3 Lubricant (Hoechstwax PE-190)
5 at L80℃ using a test roll with a blend of 0.2 Jl.
Knead for minutes and press (185℃, 10 minutes) to a thickness of 5
A +nm test piece was prepared, and the b value was measured using a color meter (manufactured by Nippon Denshoku Kogyo ■).

Table 0) OAG: polyoxyalkylene glycol, the amount added is the same as in Table 1) (Effects of the invention) According to the present invention, foaming during the production of vinyl chloride polymers can be effectively suppressed, and the desired degree of vacuum can be achieved. As the final vacuum level is completely maintained and adjusted, the resulting polyvinyl chloride product has small particle size differences between polymerization batches, and has a uniform particle shape of a constant size. The initial coloring is improved, and its industrial value is extremely large.

procedure correction calligraphy (spontaneous) July 1999 6th

Claims (1)

[Claims] 1. When polymerizing vinyl chloride monomer or a mixture of vinyl monomers mainly consisting of vinyl chloride in an aqueous medium,
A method for producing a vinyl chloride polymer, which comprises adding polyoxyalkylene glycols before vacuum operation.