JPH08217806A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE: To provide a process for stably producing a vinyl chloride polymer having excellent plasticizer absorbability and high bulk specific gravity. CONSTITUTION: A vinyl chloride polymer is produced by the suspension polymerization of a vinyl chloride monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer. In the above process, a water-soluble polymerization inhibitor is added in an amount of 0.001-0.02 pts.wt. based on 100 pts.wt. of the vinyl chloride monomer when the polymerization conversion of the vinyl chloride monomer reaches 5-70%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer having a high bulk density and excellent plasticizer absorbency.

[0002]

2. Description of the Related Art As a technique for increasing the bulk density of a vinyl chloride polymer, JP-A-4-311708 discloses a method of changing the number of revolutions during polymerization, and JP-A-4-32320.
Japanese Patent Publication No. 2 describes a method using polyvinyl alcohol having a high degree of saponification (hereinafter referred to as PVA) and the like.

[0003]

However, in the above method of changing the number of revolutions during the polymerization, the obtained vinyl chloride polymer has excellent plasticizer absorbability and high bulk specific gravity. However, since the number of rotations is changed during the polymerization, there are problems that the polymerization reaction device becomes complicated and the quality of each batch is not stable. Further, in the method using PVA having a high degree of saponification, the obtained vinyl chloride-based polymer had a high bulk specific gravity, but had a problem that the plasticizer absorption amount was reduced.

Therefore, an object of the present invention is to provide a method for stably producing a vinyl chloride polymer having excellent plasticizer absorption and high bulk density without using a complicated polymerization reaction apparatus.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that in a method for producing a vinyl chloride polymer by suspension polymerization in an aqueous medium, In order to complete the present invention, it was found that a vinyl chloride polymer having a high bulk specific gravity excellent in plasticizer absorbability can be stably produced by adding a specific addition amount of a polymerizable polymerization inhibitor at a specific addition time. I arrived.

That is, the present invention provides a method for producing a vinyl chloride polymer by suspension polymerizing a vinyl chloride monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer. The polymerization inhibitor is added in an amount of 0.001 to 0.02 parts by weight with respect to 100 parts by weight of the vinyl chloride monomer in a range of 5 to 70% in the conversion rate of the vinyl chloride monomer. The subject is a method for producing a vinyl chloride polymer.

The present invention will be described in detail below.

Examples of the vinyl chloride-based monomer used in the method of the present invention include a vinyl chloride monomer and a mixture of a vinyl chloride monomer and a vinyl chloride monomer-copolymerizable monomer. To be

Here, as the monomer copolymerizable with the vinyl chloride monomer, any monomer can be used so long as it is copolymerizable with the vinyl chloride monomer. For example, olefins such as ethylene and propylene. , Vinyl acetates such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, acrylic acid esters such as methyl acrylate and ethyl acrylate,
Examples thereof include esters or anhydrides such as maleic acid and fumaric acid, aromatic vinyl compounds such as styrene, and acrylonitrile. The copolymerizable monomer is
It is usually preferable to use it in a proportion of 20% by weight or less based on the vinyl chloride monomer.

The oil-soluble polymerization initiator used in the method of the present invention is not particularly limited and may be one generally used as an oil-soluble polymerization initiator, such as diisopropyl peroxydicarbonate or di-2- Peroxycarbonate compounds such as ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; Peroxy ester compounds such as t-butyl peroxyneodecanate and α-cumylperoxyneodecanate; Acetylcyclohexylsulfonyl peroxide and the like Peroxides: azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4-dimethylvaleronitrile); further potassium persulfate, ammonium persulfate , Hydrogen peroxide, etc. Gerare, it can be used either individually or in combinations of two or more.

The dispersant used in the method of the present invention is not particularly limited and may be one generally used as a dispersant for suspension polymerization. For example, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose. Examples thereof include cellulose derivatives such as PVA, partially saponified PVA, acrylic acid polymers, water-soluble polymers such as gelatin, nonionic surfactants, anionic surfactants, etc. These may be used alone or in combination of two or more. It is possible. And, since the vinyl chloride polymer having excellent plasticizer absorbability and high bulk density is easily obtained, the saponification degree is 70 to 95.
It is preferable to use PVA having a mol% and an average degree of polymerization of 600 to 3000.

As the water-soluble polymerization inhibitor used in the method of the present invention, any water-soluble polymerization inhibitor may be used, and examples thereof include thiocyanates, nitrites and water-soluble sulfur-containing organic compounds.

Examples of thiocyanates include ammonium thiocyanate, zinc thiocyanate, sodium thiocyanate, potassium thiocyanate and aluminum thiocyanate.

As the nitrite, sodium nitrite, potassium nitrite, ammonium nitrite, calcium nitrite, silver nitrite, strontium nitrite, cesium nitrite, barium nitrite, magnesium nitrite, lithium nitrite, dicyclohexylammonium nitrite, etc. Can be mentioned.

As the water-soluble sulfur-containing organic compound, mercaptoethanol, monothiopropylene glycol,
Hydroxyl-substituted mercaptans such as thioglycerol; mercaptocarboxylic acids such as thioglycolic acid, thiohydroacrylic acid, thiolactic acid and thiomalic acid; amino-substituted mercaptans such as thioethanolamine; nitro-substituted mercaptans such as β-nitroethylmercaptan; Hydroxyl-substituted divalent mercaptans such as 2-dithioglycerol and 1,3-dithioglycerol, dimercaptoketones such as 1,3-dimercaptoacetone; dimercaptocarboxylic acids such as β, β-dithioisobutyric acid; and thiodiglycol. Hydroxyl-substituted sulfides; sulfide-carboxylic acids such as thiodiglycolic acid, β, β'-thiodipropionic acid, and thiodilactic acid; aldehyde-substituted sulfides such as β-methylthiopropionaldehyde; amino-substituted sulfides such as β-aminoethyl sulfide; β − It can be mentioned mercapto-substituted sulfides of β--mercaptoethyl sulfide and the like; nitro-substituted sulfides such as Toro ethyl sulfide.

The water-soluble polymerization inhibitor used in the method of the present invention is preferably added in the range of 0.001 to 0.02 parts by weight with respect to 100 parts by weight of the vinyl chloride monomer. If the amount of the water-soluble polymerization inhibitor added is less than 0.001 part by weight, a vinyl chloride polymer having a high bulk specific gravity cannot be obtained, which is not preferable. Further, when the amount of the water-soluble polymerization inhibitor added exceeds 0.02 part by weight, a vinyl chloride polymer having a high bulk specific gravity cannot be obtained, and the polymerization rate of the polymerization system is remarkably reduced, resulting in production. It is not preferable because the property deteriorates.

In the method of the present invention, the water-soluble polymerization inhibitor is added at a polymerization conversion ratio of vinyl chloride monomer of 5 to 70.
It is preferably in the range of%. If the polymerization conversion rate is less than 5%, the polymerization system becomes poorly dispersed, and the resulting vinyl chloride polymer becomes coarse particles, and as a result, high bulk specific gravity is not obtained. Also, when the addition is carried out after the polymerization conversion exceeds 70%, the obtained vinyl chloride polymer does not have a high bulk specific gravity, which is not preferable.

Although the mechanism by which the effect of adding the water-soluble polymerization inhibitor to the high bulk specific gravity is excellent in the present invention, which is excellent in plasticizer absorbability, is not clear, the usual production method does not produce a vinyl chloride polymer in the aqueous phase. It is considered that fine particles are generated and the fine particles adversely affect the plasticizer absorbability and the bulk specific gravity.
However, in the present invention, by adding a specific addition amount of the water-soluble polymerization inhibitor at a specific addition timing, the generation of the fine particles is suppressed, and the plasticizer absorbability is excellent and the vinyl chloride-based vinyl chloride has a high bulk density. It is believed that a polymer is obtained.

In the method of the present invention, the water-soluble inhibitor is added in the range of 5 to 70% in conversion of vinyl chloride monomer polymerization.
0.001 to 100 parts by weight of vinyl chloride monomer
~ 0.02 parts by weight, except for the addition of other polymerization conditions such as an aqueous medium, vinyl chloride monomer, a polymerization initiator, a dispersant, etc., a charging method, a charging ratio and a polymerization temperature condition to the polymerization vessel. The above may be performed in the same manner as the conventional method, and is not particularly limited. Also, if necessary, pH
A regulator, a polymerization degree regulator, etc. may be used as long as they do not affect the object of the present invention.

[0020]

EXAMPLES The present invention will be described below based on examples.
The present invention is not limited to these.

The polymers obtained in Examples and Comparative Examples were evaluated by the following methods.

-Absorption amount of plasticizer- At room temperature, an excess amount of a plasticizer (dioctyl phthalate; DOP) is added to the obtained polymer, and the mixture is allowed to stand for 10 minutes and 3000 rp
After centrifuging at m 2, the DOP amount retained in the polymer was measured, and the ratio of DOP to the polymer was expressed as a percentage, which was taken as the plasticizer absorption amount.

-Bulk Specific Gravity-Measured according to the method specified in JIS K-6721.

-Average particle size of polymer- Size of sieve through which 50% of polymer particles pass (μ
It is represented by m).

Example 1 30 kg of deionized water was charged into a stainless steel polymerization vessel having an internal volume of 50 liter and equipped with a stirrer, and then PVA having a saponification degree of 80 mol% and an average polymerization degree of 2600 (clouding point of 0.1% by weight aqueous solution: 12.5 g of (48 ° C.) was charged. Then, it was deaerated with a vacuum pump until the internal pressure of the polymerization container reached 60 mmHg. After deaeration, 25 kg of vinyl chloride monomer was charged, then 12.5 g of t-butylperoxyneodecanoate was charged, and the temperature was raised to 58 ° C with stirring to carry out polymerization. It took 40 minutes to raise the temperature to the predetermined polymerization temperature. Also,
The internal pressure of the polymerization container at that time was 9.0 kg / cm ² G (pressure gauge pressure). Thereafter, when the polymerization conversion rate of the vinyl chloride monomer reached 8%, 2.5 g of ammonium thiocyanate (0.01 part by weight based on 100 parts by weight of the vinyl chloride monomer) was charged. Then, the reaction was stopped when the internal pressure of the polymerization container dropped to 6.0 kg / cm ² G (pressure gauge pressure), then unreacted vinyl chloride monomer was recovered, and the system was replaced with nitrogen. The vinyl chloride polymer slurry was taken out and dehydrated and dried to obtain a vinyl chloride polymer.

The evaluation results of the obtained vinyl chloride polymer are shown in Table 1.

The obtained vinyl chloride polymer was excellent in plasticizer absorbability and had a high bulk specific gravity.

Example 2 The same procedure as in Example 1 was carried out except that the addition timing of ammonium thiocyanate was changed to a polymerization addition rate of vinyl chloride monomer of 40%.

Table 1 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer was excellent in plasticizer absorption and had a high bulk specific gravity.

Example 3 The same procedure as in Example 1 was carried out except that the addition timing of ammonium thiocyanate was changed to a polymerization addition rate of the vinyl chloride monomer of 60%.

The evaluation results of the obtained vinyl chloride polymer are shown in Table 1.

The obtained vinyl chloride polymer was excellent in plasticizer absorption and had a high bulk specific gravity.

Example 4 Ammonium thiocyanate was added in an amount of 0.005 parts by weight, and the addition timing was 40% for the polymerization of vinyl chloride monomer.
The same procedure as in Example 1 was performed except that the time was changed.

Table 1 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer was excellent in plasticizer absorbability and had a high bulk specific gravity.

Comparative Example 1 The procedure of Example 1 was repeated except that ammonium thiocyanate was not added. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity.

Comparative Example 2 Instead of PVA having a saponification degree of 80 mol% and an average polymerization degree of 2600 as a dispersant without adding ammonium thiocyanate, a PV having a saponification degree of 88 mol% and an average polymerization degree of 2600 was used.
The same method as in Example 1 was performed except that A was added.

The evaluation results of the obtained vinyl chloride polymer are shown in Table 2.

The vinyl chloride polymer obtained had a low plasticizer absorbability.

Comparative Example 3 The same procedure as in Example 1 was carried out except that ammonium thiocyanate was added before the start of polymerization.

The evaluation results of the obtained vinyl chloride polymer are shown in Table 2.

The obtained vinyl chloride polymer had a low bulk specific gravity.

Comparative Example 4 The same procedure as in Example 1 was carried out except that the timing of adding ammonium thiocyanate was changed to a polymerization addition rate of the vinyl chloride monomer of 75%.

The evaluation results of the obtained vinyl chloride polymer are shown in Table 2.

The obtained vinyl chloride polymer had a low bulk specific gravity.

Comparative Example 5 Ammonium thiocyanate was added in an amount of 0.0005 parts by weight, and the addition timing was 40% for the polymerization of vinyl chloride monomer.
The same procedure as in Example 1 was carried out except that the percentage was changed.

Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity.

Comparative Example 6 The same procedure as in Example 1 was repeated except that the amount of ammonium thiocyanate added was 0.03 part by weight, and the addition timing was changed to a polymerization addition rate of the vinyl chloride monomer of 70%. It was

Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity. Also, the polymerization time required a long time.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

According to the method of the present invention, it is possible to obtain a vinyl chloride polymer having an excellent plasticizer absorption and a high bulk density.
The industrial value of the present invention is enormous.

Claims (1)

[Claims] 1. A vinyl chloride monomer or a mixture of a vinyl chloride monomer and a vinyl chloride monomer-copolymerizable monomer (hereinafter referred to as a vinyl chloride-based monomer) is oil-soluble. In a method for producing a vinyl chloride polymer by carrying out suspension polymerization in an aqueous medium in the presence of a polymerization initiator and a dispersion stabilizer, a water-soluble polymerization inhibitor is added to a vinyl chloride monomer at a polymerization conversion ratio of 5 to 5.
A method for producing a vinyl chloride polymer, comprising adding 0.001 to 0.02 part by weight to 100 parts by weight of a vinyl chloride monomer in a range of 70%.