JPH10101737A - Production of vinyl chloride polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vinyl chloride polymer being porous and excellent in plasticizer absorption, processing ability to calendering acid heat stability by polymerizing the polymerization in the presence of a specified dispersant and a specified nonionic surfactant in suspension-polymerizing a vinyl chloride mono mer in the presence of an oil-soluble polymerization initiator in an aqueous medium. SOLUTION: In suspension-polymerizing a vinyl chloride monomer in the presence of an oil-soluble polymerization initiator in an aqueous medium, the polymerization is carried out in the presence of a partially saponified polyvinyl alcohol used as the dispersant and comprising one (A) having an average degree of polymerization of 1,000-3,000 and a degree of saponification of 70-90mol%, one (B) having an average degree of polymerization of 500-900 and a degree of saponification of 70-80mol% and one (C) having an average degree of polymerization of 200-600 and a degree of saponification of 20-55mol% and a nonionic surfactant having an HLB of 10-18. The amount of the dispersant used is such that the A/B weight ratio is 9/1-1/9, desirably 7/3-3/7 and that 0.04-0.2 pt.wt., in total, A and B and 0.005-0.03 pt.wt. C are used per 100 pts.wt. monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer. More specifically, the present invention relates to a method for producing a vinyl chloride-based polymer which is porous, has excellent plasticizer absorption, has little roll stickiness during calendering, and has excellent heat stability.

[0002]

2. Description of the Related Art Vinyl chloride polymers are used in a wide range of fields from hard to soft because they are well-balanced polymer materials in processability, physical properties and price. Among them, in the field of softness, since a relatively large amount of a plasticizer is blended, it is desirable that the plasticizer absorbs the plastic at a high rate and that the obtained molded article has less fish eyes. In order to improve the plasticizer absorption, the particles of the vinyl chloride polymer must be made more porous, and in order to meet these requirements, for example, JP-A-53-13689 discloses:
Partially saponified polyvinyl alcohol used as a main dispersant (degree of saponification 70 to 90 mol%, average degree of polymerization 700 to
2600), a degree of saponification of 60 mol% or less and an average degree of polymerization of 5
A method has been proposed in which partially saponified polyvinyl alcohol having a low degree of saponification and a low degree of polymerization of 00 or less is used in combination as a secondary dispersant.

However, when a large amount of the secondary dispersant is used, the plasticizer absorbability of the obtained vinyl chloride polymer is improved, but when the vinyl chloride polymer is subjected to calendering, the molten resin is reduced. There is a problem that sticking to the roll or plate-out is likely to occur, and calenderability is deteriorated.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have developed a method for producing a vinyl chloride polymer which is porous, has excellent plasticizer absorption, has low roll adhesion during calendering, and has excellent heat stability. Diligently studied. As a result, three types of partially saponified polyvinyl alcohol having a specific average degree of polymerization and a specific degree of saponification are used as dispersants,
When a vinyl chloride-based monomer is subjected to suspension polymerization in the presence of a nonionic surfactant having a BL value of 10 to 18, the resulting polymer is porous and excellent in the absorbability of a plasticizer. The present inventors have found that a vinyl chloride-based polymer having low heat resistance and excellent heat stability can be obtained, and the present invention has been completed based on this finding. As is clear from the above description,
An object of the present invention is to provide a method for producing a vinyl chloride-based polymer which is porous, has excellent plasticizer absorption, has low roll adhesion during calendering, and has excellent heat stability.

[0005]

Means for Solving the Problems The present invention provides a method for solving the above-mentioned problems, in which a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator. As a dispersant used for suspending and dispersing the vinyl monomer, (A) a partially saponified polyvinyl alcohol having an average degree of polymerization of 1000 to 3000 and a degree of saponification of 70 to 90 mol%, (B) an average degree of polymerization 500 to 900, and a partially saponified polyvinyl alcohol having a saponification degree of 70 to 80 mol%, and (C) a partially saponified polyvinyl alcohol having an average polymerization degree of 200 to 600 and a saponification degree of 20 to 55 mol%. It is characterized by being used and being polymerized in the presence of a nonionic surfactant having an HLB value of 10 to 18.

Hereinafter, the present invention will be described in detail. The weight ratio (A) / (B) of the amounts of the dispersants (A) and (B) used in the present invention is 9/1 to 1/9, preferably 7/3.
3/7, and the total amount of (A) and (B) charged was 0.04 to 0.4% per 100 parts by weight of charged monomer.
Used in proportions of 2 parts by weight. If the weight ratio of (A) / (B) exceeds 9/1, the resulting polymer will have poor plasticizer absorption, and if it is less than 1/9, the resulting polymer particles will be too fine to handle powder. It becomes difficult. If the total of the charged amounts of (A) and (B) is less than 0.04 parts by weight, the dispersion of the charged monomers becomes unstable, and as a result, a particulate polymer is not obtained. Even if it is obtained, the polymer particles tend to be coarse, and if it exceeds 0.2 parts by weight, the obtained polymer particles become fine and powder handling becomes difficult.

In the method for producing a vinyl chloride polymer according to the present invention, in addition to the dispersants (A) and (B), the dispersant (C) is further charged, and
Used in the range of 0.005 to 0.03 parts by weight. When the degree of saponification of the dispersant (C) is lower than 20 mol%, the obtained polymer may be coarsened, scale may be attached in the polymerization vessel, or the degree of saponification may be higher than 55 mol% or the polymerization may be carried out. If the degree exceeds 600, the resulting polymer will have poor plasticizer absorbency. On the other hand, if the amount exceeds 0.03 parts by weight, the obtained polymer particles may be fine and handling of the powder may be difficult. Further, the method of adding the partially saponified polyvinyl alcohol (C) is not particularly limited, but for example, it may be added directly as it is,
Solvent such as acetone, methyl acetate, ethyl acetate or water /
It may be used by dissolving it using a mixed solvent such as an organic solvent, or it may be added as an aqueous emulsion.

The nonionic surfactant used in the present invention must have an HLB value in the range of 10 to 18 which is usually used as an index of the balance between hydrophilicity and lipophilicity. The HLB value is less than 10 or 18
When a nonionic surfactant exceeding the above is used, a vinyl chloride polymer having excellent effects of the present invention cannot be obtained.

Specific examples of the nonionic surfactant include alkyl esters of polyoxyethylene, alkyl ethers and alkylphenyl ethers of polyoxyethylene, allyl ethers of polyoxyethylene, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene. Examples thereof include sorbitol fatty acid esters, block copolymers of polyoxyethylene and polyoxypropylene, and polyoxyethylene glycerin fatty acid esters. These may be used alone or in combination of two or more. The preferred amount of these additives is 0.1 to 100 parts by weight of the charged monomer.
When the amount is from 0.01 to 0.1 part by weight and less than 0.01 part, the roll adhesion of the obtained polymer is not sufficiently improved. The transparency of a molded article using the polymer deteriorates.

When the above-mentioned surfactants are added to the polymerization system, it is preferable to add them all at once before the start of the polymerization.
The plasticizer absorption of the obtained polymer is not improved, and the transparency of the molded article using the obtained polymer is lowered and the fish eye is increased.

The vinyl chloride monomer used in the production method of the present invention includes, in addition to the vinyl chloride monomer, a polymerizable compound having a vinyl group at one end capable of copolymerizing with the vinyl chloride monomer. And a mixture of the vinyl chloride monomer,
The polymerizable compound is not particularly limited as long as it can be copolymerized with a vinyl chloride monomer, and specific examples thereof include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, ethylene and propylene. Α-monoolefin monomers, alkyl acrylates such as methyl acrylate, and alkyl methacrylates such as methyl methacrylate.

The oil-soluble polymerization initiator used in the present invention includes tertiary butyl peroxy neodecanoate,
Tertiary butyl peroxypivalate, perester compounds such as α-cumylperoxy neodecanoate,
Diisopropylperoxydicarbonate, dicyclohexylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate,
Di-3-methoxybutylperoxydicarbonate, di-3-methoxy-3-methylbutylperoxydicarbonate, percarbonate compounds such as disi-butylbutylperoxydicarbonate, peroxides such as acetylcyclohexylsulfonyl peroxide, and α,
Azo compounds such as α'-azobis-4-methoxy-2-, 4-dimethylvaleronitrile can be mentioned, and these can be used alone or in combination of two or more.

[0013] In addition, as long as the effects of the present invention are not impaired,
Other additives usually used in suspension polymerization, for example, a stabilizer capable of preventing scale adhesion to the inner wall of the polymerization vessel, an antioxidant, a chain transfer agent for adjusting the average degree of polymerization,
It does not matter at all if an antifoaming agent or a pH adjusting agent for adjusting the pH of the aqueous polymerization medium is added.

In the method for producing a vinyl chloride polymer according to the present invention, for example, the amount of an aqueous medium used per charged monomer, a polymerization initiator and a vinyl chloride monomer, and if necessary, other comonomer, etc. The amount used, the method of charging them, the polymerization temperature and the like may be determined under conventionally known conditions.

As the metal stabilizer to be incorporated in the vinyl chloride polymer obtained in the present invention, a composite metal soap stabilizer in addition to an organotin stabilizer can exhibit sufficiently excellent thermal stability, but an organic tin stabilizer can be used. The effect of the present invention is greater when a tin-based stabilizer is used.

The organic tin-based stabilizer used as a stabilizer in the present invention is not particularly limited, and is usually an organic tin-based stabilizer for PVC. As the composite metal soap stabilizer, an organic acid salt of zinc, an alkali metal and / or
Or in combination with alkaline earth metal organic acid salts,
Examples of the kind of the alkali metal and / or the alkaline earth metal include lithium, sodium, potassium, magnesium, calcium and the like, and among them, a combination of calcium and zinc is preferable. Examples of the organic acid include, but are not limited to, carboxylic acids such as formic acid, acetic acid, propionic acid, caprylic acid, lauric acid, palmitic acid, and stearyl acid.

[0017]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the evaluation method implemented in the Example and the comparative example was based on the following method.

(1) Evaluation of Roll Adhesion Roll adhesion temperature: 100 parts by weight of vinyl chloride polymer, 1.2 parts by weight of dibutyltin maleate stabilizer, 2.5 parts by weight of epoxidized soybean oil, 0.2 parts of stearic acid After weighing out the parts by weight, they are mixed using a Henschel mixer (stirring at 1000 rpm for 10 minutes). 100 g of the resulting mixture is
Using an inch electric roll, wrap it around the roll at a temperature of 170 ° C, and heat it up at a rate of 1 ° C / min.
The mixture was kneaded while the temperature was raised to 0 ° C., and the temperature at which the sheet having a thickness of 0.5 mm adhered to the roll surface and could not be removed was measured.
It means that the higher the temperature is, the harder it is to stick to the roll.

Roll adhesion: 100 g of the above composition was kneaded with an 8-inch roll at a roll temperature of 180 ° C. for 5 minutes, and a sheet was taken out. Next, the composition was newly kneaded for 5 minutes and the sheet was taken out. This operation was repeated until the sheet was stuck to the 8-inch roll and the sheet was cut and could not be taken out, and the number of times at that time was judged. The criteria for judgment are as follows. Judgment ○: 6 times or more △: 3 to 5 times ×: 2 times or less

(2) Thermal Stability of Molded Article The above composition was kneaded with an 8-inch roll at 160 ° C. for 5 minutes to form a sheet having a thickness of about 0.5 mm, which was placed in an oven at 185 ° C. Remove every 10 minutes until carbonization occurs. The longer the blackening time of these sheets, the better the thermal stability.

(3) Transparency of molded article (haze value) The above-mentioned sheets were overlaid and pressed under the conditions of 160 ° C and 100 kg / cm ² to prepare a pressed plate having a thickness of 5 mm. The transparency (haze value) of this press plate was measured using a color computer manufactured by Suga Test Instruments Co., Ltd. The lower the haze value, the higher the transparency.

(4) Plasticizer Absorption A glass fiber is filled in the bottom of a glass container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of a sample of a vinyl chloride polymer is sampled and charged. To this, 20 g of dioctyl phthalate (DOP) is added and left for 60 minutes to allow the DOP to sufficiently penetrate into the polymer. After that, 3 at 3000 rpm
Excess DOP is centrifuged by rotation for 0 minute, and the amount (% by weight) of DOP absorbed by the polymer is determined by weight per 100 parts by weight of the polymer.

Example 1 100 k of pure water was placed in a stainless steel polymerization vessel having an inner volume of 0.2 m ^3.
g, and as a dispersant therein, a saponification degree of 7
18.75 g of partially saponified polyvinyl alcohol (0.025 parts by weight per 100 parts by weight of charged monomer) having 2 mol% and an average degree of polymerization of 760 and partially saponified polyvinyl alcohol having an degree of saponification of 80 mol% and an average degree of polymerization of 2600 30.
Of water (0.04 parts by weight per 100 parts by weight of charged monomer) and a saponification degree of 3
15.00 g (0.02 parts by weight per 100 parts by weight of the charged monomer) of 5 mol%, partially saponified polyvinyl alcohol having an average degree of polymerization of 250 was dissolved in a mixed solvent of methyl alcohol and water (weight ratio: 1: 1). Each solution,
Further, 37.50 g of hexaglycerin monolaurate (HLB value: 12) was charged as a nonionic surfactant (0.05 part by weight per 100 parts by weight of charged monomer), and t-butyl neodeca was used as an initiator. 35 g of noate
Was added. In addition, 75 kg of vinyl chloride monomer is charged,
The temperature inside the polymerization vessel was raised to 67 ° C. with stirring to carry out a polymerization reaction of vinyl chloride. When the pressure inside the polymerization vessel dropped to 9 kg / cm ² , the reaction was stopped, and then unreacted monomers were recovered. The reaction product in the polymerization vessel was washed with water, dehydrated and dried to obtain a vinyl chloride polymer. The above-mentioned evaluation tests were carried out using the obtained polymers, and the results are shown in Table 1.

Example 2, Comparative Examples 1 to 3 The procedure of Example 1 was repeated, except that the types and amounts of the partially saponified polyvinyl alcohol and the nonionic surfactant were changed to the conditions shown in Table 1. To perform a polymerization reaction,
Polymer particles were obtained. The above-mentioned evaluation test was performed using the obtained polymer particles, and the results are shown in Table 1.

Examples 3-5, Comparative Examples 4-5 Example 1 except that the types and combination amounts of the partially saponified polyvinyl alcohol and the nonionic surfactant were changed to the conditions shown in Table 2. Perform a polymerization reaction according to
Polymer particles were obtained. The above-mentioned evaluation test was performed using the obtained polymer particles, and the results are shown in Table 2.

Comparative Examples 6 to 10 The polymerization reaction was carried out in the same manner as in Example 1 except that the kind and the amount of the partially saponified polyvinyl alcohol and the nonionic surfactant were changed to the conditions shown in Table 3. Do
Polymer particles were obtained. The above-mentioned evaluation tests were performed using the obtained polymer particles, and the results are shown in Table 3.

[0027]

According to the production method of the present invention, compared with the vinyl chloride polymer obtained by the conventional vinyl chloride suspension polymerization method (Comparative Example 1), the plasticizer-absorbing property is higher and there is a concern. Polymer particles having low roll adhesion during calendering and good thermal stability can be obtained.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

Claims (2)

[Claims] When a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator, the dispersant (A) has an average degree of polymerization of 1,000 to 3,000 and a degree of saponification. 70-90 mol% of partially saponified polyvinyl alcohol, (B) partially saponified polyvinyl alcohol having an average degree of polymerization of 500-900, and 70-80 mol%, and (C) average degree of polymerization of 200-600, The partially saponified polyvinyl alcohol having a degree of saponification of 20 to 55 mol% was added to the above components A and B per 100 parts by weight of the monomer.
(A) / (B) = 1 / 9-9 / 1 (weight ratio), and (C)
Is in the range of 0.005 to 100 parts by weight of the monomer.
A method for producing a vinyl chloride polymer, characterized in that the polymerization is carried out in the presence of a nonionic surfactant having an HLB value of 10 to 18 in an amount of 0.03 parts by weight. 2. The process for producing a vinyl chloride polymer according to claim 1, wherein the average degree of polymerization of the obtained vinyl chloride polymer is in the range of 400 to 1500.