JP3619926B2 - Method for producing vinyl chloride polymer - Google Patents

Description

【００２５】
【発明の効果】
本発明の製造方法によれば、短時間の混練時間でも、成形体におけるフィッシュアイが極めて少ない塩化ビニル系重合体を得ることができ、得られた塩化ビニル系重合体は軟質塩化ビニル樹脂用に極めて好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a vinyl chloride polymer with less generation of fish eyes in a molded product.
[0002]
[Prior art]
Vinyl chloride polymers have been used in a wide range of fields due to their excellent physical and mechanical properties. Recently, in the soft molding, the molding temperature is lowered to improve the weather resistance of the molded body. It is requested.
[0003]
As the vinyl chloride polymer for softness, a polymer obtained by a suspension polymerization method is usually used, and in the polymer, hardly fusible polymer particles that cause fish eyes in a molded product are used. (Hereinafter referred to as “hardly fusible particles”), the generation of fish eyes in the molded body is suppressed by using the temperature condition at which the hardly fusible particles melt.
For this reason, when a vinyl chloride polymer having a high content of hardly fusible particles is used, the molding temperature becomes high. As a result, there arises a problem that the weather resistance of the molded body is inferior. Therefore, a vinyl chloride polymer having a low content of hardly fusible particles that can be molded at a low molding temperature is demanded as a material for a soft vinyl chloride resin.
[0004]
As a method for producing the vinyl chloride polymer having a low content of hardly fusible particles, a highly partially saponified polyvinyl alcohol having a saponification degree of 65 to 75 mol% and a low partially saponification having a saponification degree of 35 to 45 mol% are used. Of using three types of dispersants, chloropolyvinyl alcohol and hydroxypropyl methylcellulose having a methoxy group content of 28-30 mol% and a hydroxy group content of 7-12 mol% (Japanese Patent Laid-Open No. 61-152703) However, in order to eliminate the generation of fish eyes, improvement of fish eyes in a molded article is not sufficient, for example, a kneading time of about 5 minutes is required.
In addition, for the purpose of removing unreacted monomers, there is a method (JP-A-53-43792) using an oil-soluble specially saponified polyvinyl alcohol having a saponification degree of 60 mol% or less as a polymerization aid. Although it has been proposed, as a result of confirmation by the present inventors, only using one kind of partially saponified polyvinyl alcohol having a saponification degree of 60 mol% or less has a sufficient effect for suppressing fish eyes in a molded article. I couldn't see it.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a vinyl chloride polymer that has a very low content of hardly fusible particles, and therefore, has a short kneading time and extremely little fish eye in a molded product.
[0006]
[Means for Solving the Problems]
As a result of intensive research, the present inventors have used the above-mentioned problems by using two types of low partially saponified polyvinyl alcohols having different saponification degrees as dispersants in an aqueous suspension polymerization method of a vinyl chloride polymer. As a result, the present invention has been completed.
[0007]
That is, the present invention
In a method for producing a vinyl chloride polymer, a suspension comprising a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith in an aqueous medium in the presence of a dispersant,
As a dispersant
(A) The viscosity at a temperature of 20 ° C. of a solution in which a saponification degree is 20 to 50 mol% and water: methyl alcohol is dissolved in an amount of 4 % by weight in a mixed solvent having a volume ratio of 1: 1 is 2 Partially saponified polyvinyl alcohol which is ˜7 cps;
(B) A method for producing a vinyl chloride polymer characterized by using a partially saponified polyvinyl alcohol having a saponification degree of 10 to 20 mol% higher than that of (A) and 60 mol% or less. It is.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. The saponification degree and the viscosity in the present invention are both measured by the method described in JIS K 6726 (Test method for polyvinyl alcohol).
[0009]
The vinyl chloride polymer in the present invention is a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith (hereinafter referred to as “vinyl chloride monomer”) in an aqueous medium. Monomers that can be copolymerized with vinyl chloride monomer include ethylene, propylene, vinyl acetate, alkyl vinyl ether, acrylic acid or methacrylic acid and esters thereof, maleic Examples thereof include acid or fumaric acid and esters thereof, and these monomers are preferably used in an amount not exceeding 20 parts by weight with respect to 100 parts by weight of the vinyl chloride monomer.
[0010]
The production method according to the present invention is as follows: (A) The temperature of a solution in which a saponification degree is 20 to 50 mol% and dissolved in an amount of 4 % by weight in a mixed solvent in which water: methyl alcohol has a volume ratio of 1: 1 is 20 Partially saponified polyvinyl alcohol (hereinafter simply referred to as “PVA”) having a viscosity at 2 ° C. of 2 to 7 cps, and (B) the saponification degree is 10 to 20 mol% higher than (A) and 60 mol% or less. Two types of PVA are used as a dispersant.
[0011]
In the production method of the present invention, the total amount of PVA to be used is preferably 0.02 to 0.50 parts by weight, more preferably 0.05 to 0 parts per 100 parts by weight of the vinyl chloride monomer. 40 parts by weight. If the total amount of PVA is less than 0.02 parts by weight, the generation of fish eyes tends to increase, whereas if it exceeds 0.50 parts by weight, the resulting polymer particles tend to be fine.
[0012]
Furthermore, in the production method of the present invention, a dispersant other than the above may be used in combination. Examples of the dispersant that can be used in combination include polyvinyl alcohol having a saponification degree of 60% or more, water-soluble cellulose ethers such as methyl cellulose, hydroxypropyl cellulose, and methylhydroxypropyl cellulose, acrylic acid copolymers, maleic anhydride copolymers, Protective colloidal drugs such as gelatin and den powder, natural polymer compounds, esters of higher fatty acids and polyhydric alcohols, nonionic surfactants such as polyoxyethylene derivatives, metal salts of higher fatty acids and higher alcohol sulfates Examples thereof include an anionic surfactant such as an alkali salt, and the other dispersant is preferably 80% by weight or less of the total amount of the dispersant.
[0013]
In the production method of the present invention, the amount of the total dispersant used is preferably 0.03 to 0.5 parts by weight with respect to 100 parts by weight of the vinyl chloride monomer. When the amount of the dispersant used is less than 0.03 parts by weight, the polymer particles are coarsened, and fish eyes are easily generated in the molded body. When the amount exceeds 0.5 parts by weight, the polymer particles obtained are fine, Particle handling may be difficult.
[0014]
Furthermore, in the production method of the present invention, water is used as a medium, but the ratio of water to the vinyl chloride monomer is, by weight, water / vinyl chloride monomer = 0.8-4. A range of 0.0 is preferable.
[0015]
In the present invention, various radical polymerization catalysts can be used as the polymerization initiator. For example, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, tertiary butyl peroxyneodecanoate, di (2-ethoxyethyl) peroxydicarbonate, tertiary hexyl peroxyneohexanoate, isobutyryl per Use organic peroxides such as oxide and cumylperoxyneodecanoate, azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis-dimethylvaleronitrile, or combinations thereof. Is also possible.
The amount of the polymerization initiator used is preferably 0.02 to 0.20 parts by weight, more preferably 0.03 to 0.15 parts by weight, per 100 parts by weight of the vinyl chloride monomer.
[0016]
In the production method of the present invention, the polymerization reaction temperature is preferably in the range of 30 to 90 ° C., and the polymerization time is suitably 2 to 15 hours.
[0017]
Moreover, in the manufacturing method in this invention, in the range which does not impair the objective of this invention, another additive can be used together arbitrarily.
Examples of these additives include alcohols, fatty acid salts, esters, buffering agents, hydrogen chloride scavengers such as hydrotalcite and zeolite, and the like. Moreover, it does not specifically limit about the addition method of the said additive.
[0018]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. The particle size distribution and fish eye of the polymer were measured by the following methods.
1) Particle size distribution: measured by a sieve shaking method.
2) Fisheye: After mixing 100 parts by weight of vinyl chloride polymer, 50 parts by weight of trimellitic plasticizer, 5 parts by weight of basic lead and 1 part by weight of lead stearate, the diameter is 8 inches and the rotational speed is 19/21 rpm. The two rolls were heated to a temperature of 170 ° C. and kneaded for 4 minutes with a roll gap of 0.3 mm to prepare a sheet, and the number of fish eyes found in an area of 10 cm × 10 cm was counted.
[0019]
Example 1
The content volume of 5 liter autoclave, deionized water 2700 g, (A) a saponification degree 34 mol% as a dispersing agent, and a volume ratio of 1: 1 water - solution amount dissolved as a 4% by weight in a mixed solvent of methanol 0.3 g of polyvinyl alcohol having a viscosity of 5 cps at a temperature of 20 ° C.
(B) Polyvinyl alcohol 0.3 g having a viscosity of 5 cps at a temperature of 20 ° C. of a solution dissolved in an amount of 4% by weight in a water-methanol mixed solvent having a saponification degree of 52 mol% and a volume ratio of 1: 1,
(C) a saponification degree 80 mol%, and 4 wt% Temperature 20 viscosity at ℃ is 34cps polyvinyl alcohol 1.2g of an aqueous solution, cumyl peroxyneodecanoate 0.3g and di (2-ethoxyethyl) peroxy 1.0 g of dicarbonate was charged, and the air in the autoclave was removed with a vacuum pump.
Thereafter, 1900 g of vinyl chloride monomer was inserted, and polymerization was carried out for 8 hours under stirring at a temperature of 57 ° C.
[0020]
Example 2
Instead of (A), a polyvinyl alcohol having a viscosity of 3 cps at a temperature of 20 ° C. in a solution of 4 mol% in a water-methanol mixed solvent having a saponification degree of 40 mol% and a volume ratio of 1: 1 was obtained. Polymerization was carried out in the same manner as in Example 1 except that 3 g was used.
[0021]
Example 3
Instead of (A), 1 in saponification degree 40 mol%, and volume ratio: 1 water - Polyvinyl alcohol 0 viscosity of 3cps at mixing temperature 20 ° C. of the solvent to 4% by weight and comprising an amount dissolved solution of methanol .4 g, instead of (B), a viscosity of 3 cps at a temperature of 20 ° C. of a solution dissolved in an amount of 4% by weight in a water-methanol mixed solvent having a saponification degree of 52 mol% and a volume ratio of 1: 1 Polymerization was performed in the same manner as in Example 1 except that 0.2 g of polyvinyl alcohol was used.
[0022]
Comparative Example 1
Instead of (A), a polyvinyl alcohol having a viscosity of 3 cps at a temperature of 20 ° C. in a solution of 4 mol% in a water-methanol mixed solvent having a saponification degree of 40 mol% and a volume ratio of 1: 1 was obtained. Polymerization was carried out in the same manner as in Example 1 except that .6 g was added and (B) was not used.
[0023]
Evaluation of Examples 1 to 3 and Comparative Examples For the polymerization products obtained in Examples 1 to 3 and Comparative Examples, the particle size distribution and the number of fish eyes were measured by the methods described above. The results are shown in Table 1 below.
[0024]
[Table 1]

[0025]
【The invention's effect】
According to the production method of the present invention, it is possible to obtain a vinyl chloride polymer having very little fish eye in a molded product even in a short kneading time, and the obtained vinyl chloride polymer is used for a soft vinyl chloride resin. Very suitable.

Claims (1)

In a method for producing a vinyl chloride polymer, a suspension comprising a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith in an aqueous medium in the presence of a dispersant,
As a dispersant
(A) The viscosity at a temperature of 20 ° C. of a solution in which a saponification degree is 20 to 50 mol% and water: methyl alcohol is dissolved in an amount of 4 % by weight in a mixed solvent having a volume ratio of 1: 1 is 2 Partially saponified polyvinyl alcohol which is ˜7 cps;
(B) a degree of saponification of the (A) 10 to 20 mol% higher than that, and is partially saponified be used together polyvinyl alcohol you wherein the vinyl chloride polymer is 60 mol% or less Production method.