JP3601156B2 - Method for producing vinyl chloride polymer - Google Patents

Description

【００４６】
【発明の効果】
本発明によれば、混練時にゲル化しやすく、かつ、かさ比重も高いＰＶＣが得られ、その工業的価値は非常に高いものである。
【００４７】[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a vinyl chloride-based polymer, and more particularly, to a method for producing an improved vinyl chloride-based polymer which is easily gelled during kneading and has a high bulk specific gravity.
[0002]
[Prior art]
BACKGROUND ART A vinyl chloride polymer (hereinafter, referred to as PVC) has excellent physical and mechanical properties and is used in various fields. As a trend in the market, in the case of extrusion molding as a hard compound, development of PVC having a high bulk specific gravity has been demanded in order to increase the extrusion amount of a molding machine. However, the conventionally known suspension polymerization method can only provide PVC which is excellent in only one of bulk specific gravity and gelling property, and all of them are insufficient for use in extrusion processing.
[0003]
JP-A-62-504 proposes a method of performing polymerization in the presence of a specific alkylhydroxycellulose.
[0004]
JP-A-57-14607 discloses that polymerization is initiated in the presence of polyvinyl alcohol having a degree of polymerization of 500 or less and a degree of saponification of 60 mol% or less, and when the degree of polymerization reaches 5 to 40%. A method of adding a water-soluble cellulose derivative has been proposed.
[0005]
Japanese Patent Application Laid-Open No. 61-111307 proposes a method for lowering the initial water / monomer ratio.
[0006]
[Problems to be solved by the invention]
However, PVC obtained by the method proposed in JP-A-62-504 was spherical and had a high specific gravity, but was non-porous and had insufficient gelling properties.
[0007]
PVC obtained by the method proposed in JP-A-57-14607 is porous and excellent in gelling property, but has a low bulk specific gravity and is insufficient for extrusion. .
[0008]
In addition, PVC obtained by the method proposed in JP-A-61-111307 could not obtain a sufficient bulk specific gravity.
[0009]
Therefore, an object of the present invention is to provide a method capable of producing PVC having a high bulk specific gravity and being easily gelled during kneading.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, it is easy to gel at the time of kneading by performing polymerization under specific conditions using a specific polymerization apparatus, and a PVC having a high bulk specific gravity can be obtained. It has been found that the present invention has been completed.
[0011]
That is, in a method for producing PVC by performing suspension polymerization of a vinyl chloride-based monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator in a reactor provided with a reflux condenser,
B) As the reflux condenser, a reflux condenser having a jacket in the upper, lower, and connecting portions to the reactor and having a structure in which a portion in contact with the vinyl chloride monomer can be entirely jacket-cooled is used. The condenser is heated before the temperature is raised to start the polymerization of the vinyl chloride monomer, and is maintained at the polymerization temperature or higher until the conversion of the vinyl chloride monomer reaches 5% or more.
B) The aqueous medium used in the suspension polymerization is an aqueous medium in which the temperature of the aqueous medium is 30 ° C. or higher and the concentration of dissolved oxygen in the aqueous medium is 2 ppm or higher;
D) PVC, wherein during the suspension polymerization, the ratio of the vinyl chloride monomer (B) in the aqueous medium (A) is set to A / B = 0.9 to 1.2 to initiate the polymerization. And a method for producing the same.
[0012]
Hereinafter, the present invention will be described in detail.
[0013]
The reflux condenser used in the present invention is a reflux condenser having a jacket at the upper, lower, and a connection portion with the reactor, and having a structure capable of entirely cooling the contact portion with the vinyl chloride monomer. .
[0014]
In the present invention, the reflux condenser is heated before the temperature starts to start the polymerization of the vinyl chloride monomer, and is kept at the polymerization temperature or higher until the conversion of the vinyl chloride monomer reaches 5% or more. Will be kept. The time for keeping the reflux condenser at the polymerization temperature or higher is such that the conversion rate of the vinyl chloride-based monomer is 5 because it is easy to gel at the time of kneading and it is possible to efficiently produce PVC having a high bulk specific gravity. It is more preferable that the content is not less than 20% and not more than 20%. In the present invention, this operation suppresses the destruction of particles in the initial stage of the reaction accompanying the evaporation of the condensable vinyl chloride-based monomer gas, and as a result, a PVC having a high specific gravity is obtained. If the temperature of the reflux condenser becomes lower than the polymerization temperature before the conversion of the vinyl chloride monomer reaches 5%, only PVC having a low bulk specific gravity can be obtained due to the destruction of the particles.
[0015]
In the present invention, when the reflux condenser is operated after the conversion of the vinyl chloride monomer exceeds 5%, the jacket of the reflux condenser is controlled so that the jacket temperature of the reactor at the time of operation becomes constant. It is preferred to control the temperature.
[0016]
The aqueous medium used in the present invention is an aqueous medium in which the temperature of the aqueous medium is 30 ° C. or higher and the concentration of dissolved oxygen is 2 ppm or higher, more preferably 6 ppm or higher. When the temperature of the aqueous medium is lower than 30 ° C., only PVC having a low bulk specific gravity can be obtained. When the concentration of dissolved oxygen in the aqueous medium is lower than 2 ppm, only a PVC having a low bulk specific gravity can be obtained. Further, the aqueous medium used in the present invention is water or a medium containing water as a main component, and there is no problem even if it includes any medium without departing from the object of the present invention.
[0017]
At the start of the polymerization of the present invention, the ratio of the aqueous medium (A) used for the polymerization to the vinyl chloride monomer (B) is A / B = 0.9 to 1.2. When A / B> 1.2, the bulk specific gravity of the obtained PVC is low. On the other hand, when A / B <0.9, there is a problem that the obtained PVC particles are coarsened. And, in the present invention, the fluidized state of the suspension at the time of polymerization is kept constant, and it is easy to gel at the time of kneading stably. Preferably, an equal volume of water is added.
[0018]
The vinyl chloride monomer used in the present invention is a vinyl chloride monomer or a mixture of a vinyl monomer and a vinyl monomer copolymerizable with the vinyl chloride monomer. Examples of the vinyl monomer copolymerizable with the monomer include olefin compounds such as ethylene and propylene; vinyl esters such as vinyl acetate and vinyl propionate; and unsaturated monocarboxylic acids such as acrylic acid and α-alkylacrylic acid. Acids, alkyl esters or amides thereof; unsaturated nitriles such as acrylonitrile; unsaturated dicarboxylic acids such as maleic acid and fumaric acid; alkyl esters or anhydrides thereof; N-substituted maleimides; vinyl methyl ether; Examples include vinyl alkyl ethers such as vinyl ethyl ether; various vinylidene compounds.
[0019]
Examples of the oil-soluble polymerization initiator used in the present invention include, for example, acetylcyclohexylsulfonyl peroxide, isobutyryl peroxide, (α, α-bisneodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, and diisopropylperoxide. Oxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxy Organic peroxides such as pivalate and lauryl peroxide; azo compounds such as azobis-2,4-dimethylvaleronitrile, azobis- (4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile); And It can be used alone or in combination of several kinds including other known ones.
[0020]
In the present invention, if necessary, a dispersion stabilizer can be used. As the dispersion stabilizer, a general dispersion stabilizer is used, for example, partially saponified polyvinyl acetate, a cellulose derivative, polyvinyl pyrrolidone, and vinyl acetate-. Water-soluble polymers such as a maleic anhydride copolymer, starch, gelatin, a nonionic surfactant, and an anionic surfactant can be used, and these can be used alone or in combination.
[0021]
If necessary, a pH adjuster, an antistatic agent, an antioxidant, and the like may be added to the polymerization system before and / or after the polymerization. May be added.
[0022]
【Example】
Hereinafter, the production method of the present invention will be described based on examples, but the present invention is not limited to these examples.
[0023]
The polymers obtained in the examples were evaluated by the following methods.
[0024]
~ Bulk specific gravity ~
The measurement was performed according to JIS K6721.
[0025]
~ Gel time ~
To 100 parts by weight of the obtained polymer, 3 parts of tribasic lead sulfate and 1 part of lead stearate were added and mixed well, and then 64 g of this mixture was placed in a Plastograph tester manufactured by Brabender Co., Ltd. Kneading was performed under the conditions of several 60 rpm and a chamber temperature of 190 ° C., and the time from when the mixture was charged to when the maximum torque was reached was measured as the gel time.
[0026]
Example 1
The upper part, the lower part, and the connection part with the reactor also have a jacket structure. The reflux condenser of a reactor having a heat transfer area of 6 m ² having a heat transfer area of 70 ° C. is passed through the reflux condenser. 100 parts of deionized water having a concentration of 9.8 ppm, 0.1 part of partially saponified polyvinyl acetate, 0.048 part of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator, 100 parts of vinyl chloride monomer ( 515 Kg) was charged into the reactor, stirring was started, and the temperature was raised to 57 ° C.
[0027]
When the conversion of the vinyl chloride monomer reaches 5%, the jacket temperature of the reflux condenser is lowered, and the polymerization is continued while controlling the jacket temperature of the reflux condenser so that the jacket temperature of the reactor becomes constant. did. Then, water was continuously injected at a rate of 22 liters / hour during the polymerization. After completion of the polymerization, the unreacted monomer was recovered, and then the polymer slurry was taken out and dehydrated and dried to obtain a vinyl chloride polymer.
[0028]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0029]
Example 2
Polymerization was carried out under the same conditions as in Example 1 except that the concentration of dissolved oxygen in the charged deionized water was changed to 3.2 ppm to obtain a vinyl chloride polymer.
[0030]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0031]
Comparative Example 1
Polymerization was carried out under the same conditions as in Example 1 except that the dissolved oxygen concentration of the charged deionized water was 0.9 ppm to obtain a vinyl chloride polymer.
[0032]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0033]
Comparative Example 2
Polymerization was performed under the same conditions as in Example 1 except that heating was not performed on the upper and lower portions of the reflux condenser and the connection portion with the reactor, thereby obtaining a vinyl chloride polymer.
[0034]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0035]
Comparative Example 3
Polymerization was carried out under the same conditions as in Example 1 except that the connection between the reflux condenser and the reactor was not heated to obtain a vinyl chloride polymer.
[0036]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0037]
Comparative Example 4
Polymerization was carried out under the same conditions as in Example 1 except that the temperature of the charged deionized water was changed to 10 ° C. to obtain a vinyl chloride polymer.
[0038]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0039]
Comparative Example 5
Polymerization was carried out under the same conditions as in Example 1 except that the charging ratio of water and the vinyl chloride monomer (419 kg) was changed without changing the charging ratio in Example 1 to obtain a vinyl chloride polymer.
[0040]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0041]
Comparative Example 6
Polymerization was carried out under the same conditions as in Example 1 except that the charging ratio of water and the vinyl chloride monomer (597 kg) was changed without changing the charging ratio in Example 1, to obtain a vinyl chloride polymer.
[0042]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0043]
Comparative Example 7
Polymerization was carried out under the same conditions as in Example 1 except that the reflux condenser was shut off from the reactor and the polymerization initiator di-2-ethylhexyl peroxydicarbonate was changed to 0.034 parts to obtain a vinyl chloride polymer. .
[0044]
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.
[0045]
[Table 1]

[0046]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it is easy to gelatinize at the time of kneading, and a high bulk specific gravity is obtained, and its industrial value is very high.
[0047]

Claims (1)

In a reactor provided with a reflux condenser, a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer (hereinafter, referred to as a vinyl chloride monomer). ) Is carried out suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator to produce a vinyl chloride polymer,
B) As the reflux condenser, a reflux condenser having a structure in which jackets are provided at the upper, lower and connecting portions with the reactor so that the entire area in contact with the vinyl chloride monomer can be jacket-cooled is used. The condenser is heated before the temperature is raised to start the polymerization of the vinyl chloride monomer, and is kept at the polymerization temperature or higher until the conversion of the vinyl chloride monomer reaches 5% or more.
B) The aqueous medium used for the suspension polymerization is an aqueous medium in which the temperature of the aqueous medium is 30 ° C. or higher and the concentration of dissolved oxygen in the aqueous medium is 2 ppm or higher;
D) In the suspension polymerization, the polymerization is started by setting the ratio of the aqueous medium (A) and the vinyl chloride monomer (B) to A / B = 0.9 to 1.2. A method for producing a vinyl polymer.