JPH07109302A - Suspension polymerization of vinyl chloride resin - Google Patents

Abstract

PURPOSE:To provide a suspension polymerization process which can provide vinyl chloride resins having primary particle sizes controlled, sharp particle size distribution and excellent gelation properties. CONSTITUTION:In the suspension polymerization of vinyl chloride monomer, the power needed for stirring is set to 4 to 6kW/m<3> while the monomer conversion is in the range of from 5 to 10%, and set to 0.1 to 0.5kW/m<3> in the range of from 30 to 35%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suspension-polymerizing vinyl chloride monomer in producing vinyl chloride resin.

[0002]

2. Description of the Related Art Vinyl chloride resin has impact resistance, weather resistance,
Although it is used in many applications as a material having excellent properties such as chemical resistance, it has been attempted to be improved because it has defects in thermal stability or processability.

In Japanese Patent Laid-Open No. 3-287603, a shear rate is changed during polymerization, a constant high-speed shearing stirring is performed, and then a constant low-speed shearing stirring is performed to have a sharp particle size distribution and a fish eye. There is disclosed a technique for obtaining a vinyl chloride resin having a low content. JP-A-4-31170
Japanese Unexamined Patent Publication No. 8 discloses a technique of obtaining a vinyl chloride resin having a high bulk specific gravity, a small fish eye and an excellent plasticizer absorbability by selecting a dispersant and limiting stirring conditions.

However, although the above method can improve the workability to some extent, it has not been fully satisfactory. Further, it is not sufficient in terms of improving the particle size distribution, which causes troubles during the production and molding of vinyl chloride resin.

In order to improve the processability of the vinyl chloride resin, especially the gelation property, it is necessary that the particle structure of the vinyl chloride resin, especially the primary particle diameter, is sufficiently small. In the above-mentioned known method, the primary particle size cannot be reduced sufficiently,
A vinyl chloride resin with a sufficiently sharp particle size distribution could not be obtained.

[0006]

In view of the above, the present invention controls the primary particle size of the obtained vinyl chloride resin, has a sufficiently sharp particle size distribution, and is a suspension of the vinyl chloride resin excellent in gelling property. It is intended to provide a polymerization method.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is that when a vinyl chloride resin is produced by suspension polymerization of a vinyl chloride monomer, first, the conversion rate of the monomer to the polymer is 5 to 5. In the range of 10%, the power required for stirring required for the polymerization was set in the range of ⁴ to 6 kW / m ³ , and then the conversion rate of the monomer into the polymer was 30 to 3
Between 5%, the power required for stirring is 0.1 to 0.5 kW / m.
^It is limited to the range of ³ .

In the suspension polymerization method of the present invention, the power required for stirring is limited by the degree of progress of the conversion rate of the monomer into the polymer as described above. In the suspension polymerization method of the present invention, conventional methods can be used for deionized water, suspension dispersant, monomer charging method, deaeration method and the like.

Examples of the suspension dispersant used in the present invention include partially saponified polyvinyl alcohol; methyl cellulose, ethyl cellulose, hydroxyethyl cellulose,
Water-soluble cellulose ethers such as hydroxypropyl cellulose, hydroxypropylmethyl cellulose and carboxymethyl cellulose; water-soluble polymers such as gelatin and polyacrylic acid; oil-soluble emulsifiers such as sorbitan monolaurate and sorbitan monostearate; polyoxyethylene, polyoxyethylene Sorbitan monolaurate,
Water-soluble emulsifiers such as sodium laurate; calcium carbonate, sodium dodecylbenzene sulfonate, and the like. These can be used alone or in combination of two or more. Of these, partially saponified polyvinyl alcohol is preferred, with a saponification degree of 60 to 90 mol% and an average degree of polymerization of 50 to 2 in particular.
500 is preferable, and the addition amount thereof is preferably 400 to 2000 ppm with respect to the vinyl chloride monomer.

As the polymerization initiator, those generally used for the polymerization of vinyl chloride resins can be used. For example, organic peroxides such as benzoyl peroxide, lauroyl peroxide and 2-ethylhexyl peroxydicarbonate. Compounds, azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, and water-soluble polymerization initiators such as potassium persulfate and ammonium persulfate. These can be used alone or in combination of two or more. Organic peroxides are more preferred.

In the present invention, a vinyl chloride monomer is charged and suspension polymerization is carried out with stirring. The power required for stirring at the start of stirring is not particularly limited, and the power required for stirring is not particularly limited when the polymerization conversion rate is less than 5%.

From the time when the polymerization conversion rate reaches 5 to 10%, the power required for stirring is limited to the range of ⁴ to 6 kW / m ³ . When a stirring power requirement of more than 6 kW / m ³ is applied, the particle size distribution becomes too wide, and at a stirring power requirement of less than 4 kW / m ^{3, the} primary particles are too large, and the gelation properties of the resulting vinyl chloride resin deteriorate. .

When the polymerization proceeds and the polymerization conversion rate reaches 30 to 35%, the power required for stirring is 0.1 to 0.5 k.
It is limited to the range of W / m ³ . When the required stirring power of more than 0.5 kW / m ³ is applied, the particle size distribution becomes too wide, and the required stirring power of less than 0.1 kW / m ³ causes the resin in the polymerization vessel to coalesce, Neither can obtain the intended vinyl chloride resin.

The shape and structure of the polymerization vessel (pressure autoclave) used in the present invention are not particularly limited, and those commonly used can be appropriately used. Also the stirring blade,
Baffles can be used as appropriate for commonly used ones such as fowlers, paddles, turbines, etc.
There is no particular limitation on the combination with.

As the monomer used in the present invention, in addition to vinyl chloride monomers, vinyl-based monomers copolymerizable with vinyl chloride can be used. Examples thereof include vinyl acetate and vinyl propionate. Vinyl esters; α-olefins such as ethylene, propylene and isobutyl vinyl ether; maleic anhydride, acrylonitrile and styrene. These can be used alone or in combination of two or more.

In the present invention, as a method of charging ion-exchanged water, monomers and the like into the reaction system, a usual method can be appropriately used. Polymerization regulator used depending on the polymerization conditions,
Addition of a chain transfer agent, an antistatic agent, a cross-linking agent, a stabilizer, a filler, an anti-scale agent, etc. can be appropriately performed.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples of the present invention, but the present invention is not limited thereto.

Example 1 50 kg of deionized water and partially saponified polyvinyl alcohol (saponification degree 72%, average degree of polymerization 600) were added to a reaction vessel set in a pressure-resistant autoclave having an internal volume of 100 l in an amount of 500 ppm with respect to a vinyl chloride monomer. t-Butylperoxy neodecanoate was added to vinyl chloride monomer at 500
ppm was added. After degassing the reaction vessel to 50 mmHg, 33 kg of vinyl chloride monomer was charged. The power required for stirring was adjusted to the value shown as the first step in Table 1, and the polymerization was started while the temperature was raised. The polymerization temperature was 57 ° C., and this temperature was maintained until the completion of the polymerization. For the power required for stirring, the energy applied to the reaction system was measured with a torque meter. Table 1
In the range of the polymerization conversion rate of the second stage and the third stage shown in
Polymerization was continued by stirring under the power required for stirring in the relevant column of each table. The power required for stirring in each stage was continuously changed. The reaction was terminated when the polymerization conversion rate reached 90%. After recovering the unreacted monomer in the reaction vessel, the polymer was taken out of the system in a slurry form and dehydrated and dried.

The vinyl chloride resin produced above was evaluated for quality as follows. Particle size distribution: Measured according to JIS Z-8801. 6
It was carried out by sieving using a sieve of 0, 100 and 200 mesh and calculating the passing amount (% by weight). Primary particle diameter: The internal structure of the resin was photographed using a transmission electron microscope, about 100 primary particle diameters were measured from the photograph, and the average value was taken as the primary particle diameter (μm). Gelability: Using Plastomill (manufactured by Toyo Seiki Co., Ltd.),
Gel time and maximum torque were measured. As a pretreatment of the resin to be put into the plastomill, montanic acid ester (manufactured by Hoechst Co .; WA
0.5 parts by weight of XOP and 2 parts by weight of dibutyltin mercapto (manufactured by Sansha Machine Synthetic Co., Ltd .; JF-10B) as a stabilizer are added, and the mixture is heated to 120 ° C. with a super mixer (manufactured by Mitsui Miike Co., Ltd.). did. After mixing, the mixture was cooled to 40 ° C. and taken out, and put into a plastomill. The amount of resin charged into the plastomill was 60 g, the temperature of the plastomill was 170 ° C., and the rotation speed of the plastomill was 30 revolutions. A resin having a short gelling time and a low maximum torque was determined to have a good gelling property. The above test results are shown in Table 1.

Examples 2 and 3, Comparative Examples 1 to 7 Polymerization was carried out in the same manner as in Example 1 except that the values of the polymerization conversion rate and the power required for stirring were changed as shown in Table 1. The quality was evaluated. The results are shown in Table 1.

[0021]

[Table 1]

[0022]

Industrial Applicability According to the method of the present invention, a vinyl chloride resin having a primary particle size controlled, a sharp particle size distribution and an excellent gelling property can be efficiently produced.

Claims (1)

[Claims] 1. For suspension polymerization of vinyl chloride monomer
Therefore, while the conversion rate of the monomer to the polymer is 5 to 10%,
Power required for stirring is 4 to 6 kW / m³And to the monomer polymer
The power required for stirring is 0.1 to 30% while the conversion rate of 30 to 35%.
0.5 kW / m ³Characterized by carrying out polymerization as a salt
Method of suspension polymerization of vinyl chloride resin.