JP3437018B2 - Method for producing vinyl chloride polymer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer. In particular, it has a high porosity particle structure, has high plasticizer absorbency, can produce a vinyl chloride polymer with less fisheye when molded, and has high adhesion due to less polymer scale during polymerization. It relates to a method with productivity. [0002] Hitherto, many methods for producing a vinyl chloride polymer having high porosity and excellent processability have been proposed. For example, JP-A-52-5886, JP-A-52-15890, JP-A-55-1
Nos. 12210, 53-6392 and JP-B-61-18562 disclose that a porosity is increased by using a so-called oil-soluble polyvinyl alcohol having a saponification degree of 55 mol% or less and an average polymerization degree of 600 or less as a dispersion stabilizer. , Fish eye, and a method for improving plasticizer absorbency and the like. [0003] According to these production methods, the porosity of the obtained polymer is certainly increased to some extent. However, the apparent viscosity of the slurry increases at the end of polymerization, and the fluidity of the slurry decreases. For this reason,
The heat of polymerization reaction generated in the reaction mixture cannot be sufficiently removed. Therefore, the degree of polymerization, plasticizer absorbency, and quality of fish eyes and the like when molded are likely to be adversely affected. Therefore, the obtained polymer is not satisfactory in terms of improving fish eye and plasticizer absorption. [0004] Further, there are problems that the obtained polymer has a small particle size, the particle size distribution becomes broad, and that the polymer scale adheres to the polymerization vessel during the polymerization. Therefore, an object of the present invention is to provide a vinyl chloride polymer having a narrow particle size distribution, a small fish eye and a high plasticizer absorbability while effectively suppressing the adhesion of the polymer scale. An object of the present invention is to provide a method for stably manufacturing with high productivity. The present inventors have made intensive studies and found that vinyl chloride or a mixture of vinyl monomers mainly composed of vinyl chloride is subjected to suspension polymerization in an aqueous medium. At this time, they have found that the above problems can be solved by using a specific dispersion stabilizer. That is, as a means for solving the above-mentioned problems, the present invention provides a method of suspending a vinyl chloride monomer or a mixture of vinyl monomers mainly comprising vinyl chloride in an aqueous medium in the presence of a dispersion stabilizer. In the method for producing a vinyl chloride polymer comprising polymerizing, the dispersion stabilizer (A) has an average degree of polymerization of 300 to 2,000, a degree of saponification of 70 to 98 mol%, and is provided at at least one terminal of a molecular chain. A partially saponified polyvinyl alcohol having a mercapto group, and (B) a hydroxypropoxy substitution degree of 40 to 67% by weight, and 20% of a 2% by weight aqueous solution.
It is intended to provide a method for producing a vinyl chloride-based polymer, characterized by containing hydroxypropylcellulose having a viscosity at 5 ° C. of 5 to 20,000 cP. Hereinafter, the present invention will be described in detail. Component (A) Partially saponified polyvinyl alcohol
The dispersion stabilizer used in the production method of the present invention has an average degree of polymerization of 300 to 2000, preferably 500 to 1500, and a degree of saponification of 70 to 98 mol%, preferably 75 to 98 mol%. It is necessary to contain a partially saponified polyvinyl alcohol having a mercapto group at at least one terminal of the molecular chain (hereinafter, referred to as dispersion stabilizer (A)). Average degree of polymerization is less than 300 or degree of saponification is 70 mol%
When it is less than 1, the particle size of the obtained vinyl chloride polymer becomes too fine or the particle size distribution becomes broad. Adhesion of polymer scale during polymerization is also likely to increase. Conversely, if the average degree of polymerization exceeds 2,000 or the degree of saponification
If it exceeds 98 mol%, the porosity of the obtained polymer will decrease, or the amount of fish eyes in molding the polymer will increase. The partially saponified polyvinyl alcohol has the general formula: ## STR1 ## Wherein Z may be the same or different;
A mercapto group or a hydrogen atom (at least one of which is a mercapto group), and x and y are [Expression 2] is a positive integer satisfying 300 ≦ x + y ≦ 2000]. Component (B) Hydroxypropylcellulose Another component of the dispersion stabilizer used in the production method of the present invention is hydroxypropylcellulose [hereinafter referred to as a dispersant.
(B). The dispersant (B) has a hydroxypropoxy substitution degree of 40 to 67% by weight and a 2% by weight aqueous solution of 20%.
It is necessary that the viscosity at 5 ° C. is 5 to 20,000 cP. When the hydroxypropoxy substitution degree of the dispersant (B) is less than 40% by weight, the porosity of the obtained polymer is low. Conversely, if the content exceeds 67% by weight, the particle size distribution becomes broad, which hinders handling. The ratio of the charged amounts of the dispersant (A) and the dispersant (B) is preferably such that the weight ratio (A) / (B) is 95/5 to 3/7,
The range of / 1-1 / 1 is more preferable. Also, dispersant (A)
, (B) is preferably 0.02 to 0.5 part by weight, preferably 0.03 to 0.2 part by weight per 100 parts by weight of the vinyl chloride monomer.
Parts by weight are more preferred. Other Polymerization Conditions Other polymerization conditions in the production method of the present invention include ordinary polymerization conditions used for suspension polymerization of vinyl chloride or a vinyl monomer mixture mainly composed of vinyl chloride in an aqueous medium. May be the same as It is described below. The monomer monomer is vinyl chloride alone or a mixture of vinyl chloride and a vinyl monomer copolymerizable with vinyl chloride (usually, vinyl chloride is a main component and is contained in an amount of 50% by weight or more). ) Is used. Examples of vinyl monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; and (meth) acrylates such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Olefins such as ethylene and propylene; maleic anhydride; acrylonitrile; styrene; and vinylidene chloride. Polymerization initiator Examples of the polymerization initiator include t-butyl peroxy neodecanoate, t-butyl peroxy pivalate, and t-butyl peroxy neodecanoate.
Hexyl peroxypivalate, α-cumyl peroxy neodecanoate, t-hexyl neohexanoate,
2,4,4-trimethylpentyl-2-peroxy-2
A perester compound such as neodecanoate; a percarbonate compound such as diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, di-2-ethoxyethylperoxydicarbonate, dimethoxyisopropylperoxydicarbonate; decanoylper; Oxide, lauroyl peroxide, benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide, p-menthane hydroperoxide, 3,5,5-trimethylhexanoyl peroxide, isobutyryl peroxide Oxides, peroxide compounds such as acetylcyclohexylsulfonyl peroxide; α, α'-azobisisobutyronitrile, α, α '
-Azobis (2,4-dimethylvaleronitrile), α,
azo compounds such as α'-azobis (4-methoxy-2,4-dimethylvaleronitrile); persulfates such as potassium persulfate and ammonium persulfate; and hydrogen peroxide. These can be used alone or in combination of two or more. The amount of the polymerization initiator is based on 100 parts by weight of the monomer.
It is preferably 0.01 to 0.5 part by weight, more preferably 0.03 to 0.2 part by weight. Aqueous Medium As the aqueous medium, deionized water and the like can be mentioned, and the addition amount thereof is usually 90 to 200 parts by weight, preferably 90 to 130 parts by weight, per 100 parts by weight of the monomer. The aqueous medium may be added as needed during the polymerization. Other Additives The additives used as needed include, for example, polymerization regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, polymer scale inhibitors, and the like. Also, a small amount of a surfactant can be added. Polymerization The method for charging the above-mentioned monomer, aqueous medium and other materials, and polymerization conditions such as polymerization temperature may be in accordance with a known suspension polymerization method for a vinyl chloride polymer. According to a representative embodiment, for example, this is done as follows. First, the dispersant (A), the dispersant (B) and the aqueous medium are charged into a polymerization vessel. Next, the inside of the polymerization vessel is evacuated to a reduced pressure state, and then a monomer is charged. Next, an aqueous suspension is prepared by charging a polymerization initiator. The temperature is raised while stirring the aqueous suspension, and the polymerization is usually carried out at a reaction temperature of 30 to 80 ° C. During the polymerization, one or more of the above-mentioned aqueous medium, suspending agent, polymerization initiator and other additives may be added as necessary. After the completion of the polymerization reaction, unreacted monomers are recovered, and the polymer slurry is dehydrated and dried to obtain a polymer. The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In each of Examples 1 and 2 and Comparative Examples 1 to 4 , an autoclave (polymerizer) having an internal volume of 2 m ³ was placed in an autoclave.
Add 900 kg of pure water and dispersants (A) and (B) shown in Table 1 to Table 1.
It was prepared under the conditions shown in FIG. Next, the inside of the autoclave was evacuated with a vacuum pump until the pressure became -700 mmHg (8 kPa). Thereafter, 700 kg of a vinyl chloride monomer was charged, and further, 420 g of t-butyl peroxyneodecanoate, which is a polymerization initiator, was charged.Then, the internal temperature was raised to 57.0 ° C., and the temperature was maintained. . Internal pressure 6.0kg / cm ² G (690 kP
The polymerization was stopped when a) was reached. Then, the unreacted monomer was recovered, the slurry was extracted from the autoclave, and the obtained slurry was dehydrated and dried to obtain a polymer. [Table 1] The bulk specific gravity, particle size distribution, amount of plasticizer absorbed, fish eye, and the state of adhesion of the polymer scale in the polymerization vessel of the polymer obtained in each example were measured as follows. Table 2 shows the results. Bulk specific gravity Measured according to JIS K-6721. Particle size distribution Measured according to JIS Z-8801. Amount of plasticizer absorbed A glass fiber was packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of a sample resin was put into the glass fiber. Further, 15 cc of DOP (dioctyl phthalate) was added, and left for 30 minutes to allow the DOP to penetrate into the resin. afterwards,
Excess DOP was centrifuged at an acceleration of 1,500 G. The amount of DOP absorbed by the resin was determined and expressed as a value per 100 parts by weight of the resin. Fish eye 100 parts by weight of a sample resin, 1 part by weight of tribasic lead sulfate, 1.5 parts by weight of lead stearate, 0.2 parts by weight of titanium dioxide, 0.1 parts by weight of carbon black and 50 parts by weight of DOP were mixed. 25 g of the obtained compound was collected, and rolled at 145 ° C for 3 g.
Kneaded for a minute and then made into a sheet 0.2 mm thick. The number of transparent particles in 100 cm ^{2 of} this sheet was measured and defined as the number of fish eyes. [0033] - polymer scale deposition polymerization After completion, extracted polymer from the polymerization vessel was washed with water in the polymerization vessel. Then, on the inner wall of the polymerization vessel, the state of the adhesion of the polymer scale was visually observed in the vicinity of the gas-liquid interface and in the portion corresponding to the liquid phase when the polymer was contained. [Table 2] According to the production method of the present invention, a polymer having a narrow particle size distribution and high porosity can be produced. In addition, when this polymer is molded, a molded article with less fish eyes can be obtained. Further, since the polymer scale is less adhered in the polymerization vessel after the polymerization, the polymerization vessel can be used repeatedly without removing the polymer scale. For this reason, a polymerization vessel can be used efficiently and productivity is high.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-127604 (JP, A) JP-A-8-109206 (JP, A) JP-A-7-76603 (JP, A) 191806 (JP, A) JP-A-60-197229 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 2/00-2/60, 14/06

Claims (1)

(57) [Claim 1] Suspension polymerization of a vinyl chloride monomer or a mixture of vinyl monomers based on vinyl chloride in an aqueous medium in the presence of a dispersion stabilizer. Wherein the dispersion stabilizer comprises: (A) an average degree of polymerization of 300 to 2,000, a degree of saponification of 70 to 98 mol%, and a mercapto group at at least one terminal of a molecular chain. Having partially saponified polyvinyl alcohol, and (B) a hydroxypropoxy substitution degree of 40 to 67% by weight, and 2% by weight.
A method for producing a vinyl chloride polymer, comprising a hydroxypropylcellulose having a viscosity of an aqueous solution of 5 to 20,000 cP at 20 ° C.