JP2002121235A - Method for producing vinyl chloride resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride resin having uniform particle size distribution and excellent impact resistance and weather resistance in high polymerization efficiency. SOLUTION: The method for the production of a vinyl chloride resin comprises the 1st step to perform the emulsion polymerization of 100 pts.wt. of an alkyl (meth)acrylate giving a homopolymer having a second order transition temperature of <0 deg.C and 0.1-30 pts.wt. of a polyfunctional monomer in a 1st reactor, the 2nd step to add 0.1-3 pts.wt. of a partially saponified polyvinyl acetate to 100 pts.wt. of the obtained copolymer after the emulsion polymerization, the 3rd step to transport the mixed liquid to a 2nd reactor and the 4th step to perform the graft-polymerization of vinyl chloride monomer in the 2nd reactor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a vinyl chloride resin.

[0002]

2. Description of the Related Art Vinyl chloride resins have excellent chemical properties,
Because of its physical and mechanical properties, it is widely used as a general-purpose resin.However, when a homopolymer is used for a hard molded product, there is a drawback that the impact resistance and weather resistance are poor. .

In order to solve these drawbacks, vinyl chloride resins obtained by graft-polymerizing vinyl chloride to an alkyl acrylate (co) polymer have been proposed. (For example, JP-B-39-17067, JP-A-60-2
No. 55813)

[0004] The production of the vinyl chloride resin is generally carried out by
After the alkyl acrylate is polymerized by emulsion polymerization, vinyl chloride is subjected to suspension polymerization by suspension polymerization. In this case, there are differences between the emulsion polymerization and the suspension polymerization, such as the size of the tank, the stirring blade, the pressure resistance, and the device for adding and removing the vinyl chloride monomer. Prepared, mechanically transport the emulsion polymerization solution obtained by emulsion polymerization in the emulsion polymerization tank to the suspension polymerization tank, and perform suspension polymerization in the suspension polymerization tank to obtain a vinyl chloride resin. Have been.

However, the emulsion polymerization liquid of alkyl acrylate has low mechanical stability, and when the emulsion polymerization liquid is forcibly transported from the emulsion polymerization tank to the suspension polymerization tank by a transportation pump or the like,
In some cases, the emulsion polymerization liquid was subjected to pressure or shear stress to break the emulsification, causing the particles to aggregate and coalesce. As a result, even when the emulsion polymerization solution is transported, the piping becomes clogged or transported, but the suspension polymerization becomes unstable, and the particle size distribution of the obtained vinyl chloride resin is widened.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned disadvantages, an object of the present invention is to provide a method for producing a vinyl chloride resin having a uniform particle size distribution and excellent impact resistance and weather resistance with high polymerization efficiency. Is to provide.

[0007]

According to the method for producing a vinyl chloride resin of the present invention, 100 parts by weight of an alkyl (meth) acrylate having a secondary transition temperature of a homopolymer of less than 0 ° C. in a first reaction vessel. And a first step of emulsion-polymerizing 0.1 to 30 parts by weight of a polyfunctional monomer and 0.1 to 3 parts by weight of partially saponified polyvinyl acetate with respect to 100 parts by weight of the obtained copolymer after emulsion polymerization. , A third step of transporting the mixture to the second reaction tank, and a fourth step of graft-polymerizing a vinyl chloride-based monomer in the second reaction tank.

In the first step of the present invention, 100 parts by weight of an alkyl (meth) acrylate having a secondary transition temperature of a homopolymer of less than 0 ° C. and 0.1 to 30 of a polyfunctional monomer are placed in a first reaction vessel. This is a step of emulsion polymerization of parts by weight.

As the above alkyl (meth) acrylate, when the secondary transition temperature of the homopolymer increases, the particles become hard and brittle, and the impact resistance decreases. Examples of such an alkyl (meth) acrylate include, for example, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and sec- Butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate,
Isononyl (meth) acrylate, n-decyl (meth)
Examples thereof include acrylate, lauryl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate, which may be used alone or in combination of two or more.

The polyfunctional monomer may have a plurality of functional groups that can be copolymerized with the alkyl (meth) acrylate. Examples thereof include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, modified ethylene oxide trimethylolpropane tri (meth) acrylate (Meth) acrylates such as pentaerythritol tri (meth) acrylate, pentaerythol tetra (meth) acrylate, dipentaerythol hexa (meth) acrylate; diallyl phthalate, diallyl maleate Di- or triallyl compounds such as diallyl fumarate, diallyl succinate and triallyl isocyanurate; divinyl compounds such as divinylbenzene and butadiene; and the like, which may be used alone or in combination of two or more. .

The polymerization ratio of the polyfunctional monomer with respect to the alkyl (meth) acrylate is such that when the polymerization ratio of the polyfunctional monomer is low, the crosslinking density is low, the impact resistance of the molded article is low, and conversely, it is too high. And the crosslink density becomes too high, and the impact resistance and tensile strength of the molded article decrease, so that 0.1 to 30 parts by weight of the polyfunctional monomer is copolymerized with respect to 100 parts by weight of the alkyl (meth) acrylate. Preferably it is 0.2 to 10 parts by weight.

In the polymerization of the alkyl (meth) acrylate and the polyfunctional monomer, a copolymerizable vinyl monomer may be copolymerized. Such vinyl monomers include, for example, polar group-containing vinyl monomers such as (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-acryloyloxyethyl phthalic acid; styrene ,
aromatic vinyl monomers such as α-methylstyrene and vinyltoluene; unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate; and may be used alone or in combination of two or more. May be used in combination.

If the amount of the vinyl monomer increases, the impact resistance of the molded article decreases. Therefore, the amount is preferably 25 parts by weight or less based on 100 parts by weight of the alkyl (meth) acrylate.

The above alkyl (meth) acrylate and the polyfunctional monomer are emulsion-polymerized, and any known emulsion polymerization method may be adopted as the emulsion polymerization method.
For example, water, an alkyl (meth) acrylate, a polyfunctional monomer, an emulsifier, and a polymerization initiator are supplied to a first reaction tank, and the mixture is stirred while heating.

The emulsifier may be any one generally used in emulsion polymerization. Examples thereof include fatty acid salts, alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkyl phenyl ethers. Anionic surfactants such as sulfates; and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, and polyoxyethylene polyoxypropylene alkyl ether. And polyoxyethylene nonylphenyl sulfate (trade name: Hytenol N-08, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are preferably used.

The polymerization initiator may be any of those generally used in emulsion polymerization, and includes, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide and the like. Further, at the time of polymerization, a pH adjuster, a chain transfer agent, an antioxidant, and the like may be added as necessary.

In the second step of the present invention, after the emulsion polymerization is completed, 0.01 to 0.5 part by weight of partially saponified polyvinyl acetate is added to 100 parts by weight of the obtained copolymer and mixed. This is the step of obtaining

As the above partially saponified polyvinyl acetate, those commercially available as partially saponified polyvinyl alcohol for polymerization can be generally used. However, from the viewpoint of protective colloid power and water solubility, the degree of polymerization is 500 to 2,000. And a saponification degree of 70 to 85%.

If the amount of the partially saponified polyvinyl acetate is too small, the mechanical stability of the emulsion polymerization solution is not improved, and if it is too large, the particle size after graft polymerization becomes small. The amount is 0.1 to 3 parts by weight, preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the copolymer.

The method of mixing the partially saponified polyvinyl acetate is not particularly limited. However, the partially saponified polyvinyl acetate can be mixed and dispersed uniformly in the emulsion polymerization solution.
It is preferred that the partially saponified polyvinyl acetate is dissolved in water (concentration: 1 to 5% by weight), and the emulsion polymerization liquid at 50 to 70 ° C is added with stirring.

In the third step of the present invention, the mixed solution is subjected to the second step.
This is the step of transporting to the reaction tank. The transportation is generally carried out by a pump from a first reaction tank through a pipe arranged in a second reaction tank. A general-purpose pump can be used as the pump, for example, a monoflow pump, a gear pump,
A centrifugal pump and the like can be mentioned, and a low shearing force monoflow pump can be suitably used. The transport speed may be appropriately determined within a range in which the emulsification of the mixture is not destroyed, but is generally preferably 100 to 500 kg / min.

The fourth step in the present invention is a step of graft-polymerizing a vinyl chloride monomer in the second reaction tank.

The vinyl chloride monomer is mainly composed of a vinyl chloride monomer. That is, it is a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a copolymerizable vinyl monomer mainly containing the vinyl chloride monomer (including 50% by weight or more).

Examples of the vinyl monomer include vinyl esters such as vinyl acetate and vinyl propionate; alkyl (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate; olefins such as ethylene and propylene; ) Acrylic acid, maleic anhydride, acrylonitrile, styrene, vinylidene chloride and the like.

As the above graft polymerization method, any known polymerization method may be employed, but suspension polymerization is preferred. Suspension polymerization is a polymerization method generally employed in the polymerization of vinyl chloride, and may be carried out in the same manner as in the polymerization of vinyl chloride. In this case, the second reaction tank is used when polymerizing vinyl chloride. A reaction vessel comprising a pressure vessel equipped with a stirring device, a heating device, a cooling device and a decompression device is used.

In the case of suspension polymerization, in the present invention, since the mixed solution transported to the second reaction tank is an emulsion polymer, a coagulant is first added to cause coagulation. The coagulant is not particularly limited as long as it can coagulate the polymer in the emulsion polymerization liquid, and examples thereof include sodium chloride, calcium chloride, potassium chloride, magnesium chloride, and aluminum chloride.

Next, an oil-soluble polymerization initiator is added, the air in the reaction tank is removed by a decompression device, a vinyl chloride monomer is supplied while stirring, and the temperature is raised to start polymerization.
When the temperature inside the reaction tank rises due to the reaction heat, the temperature is adjusted by cooling with a cooling device. After the completion of the reaction, the unreacted vinyl chloride-based monomer is removed from the reaction tank, and the reaction product in a slurry state is dehydrated and dried to obtain a vinyl chloride-based resin.

In the present invention, since the partially saponified polyvinyl acetate is added in the second step, it is not necessary to add a dispersant at the time of suspension polymerization. Good. However, as the amount of the dispersant added increases, the particle size of the obtained vinyl chloride resin decreases, so it is preferable that the amount is as appropriate as possible.

As the above dispersant, dispersants generally used in suspension polymerization of a vinyl chloride resin can be used. For example, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropylmethyl cellulose, polyvinyl alcohol, partially saponified poly (vinyl alcohol), Examples include vinyl acetate, gelatin, polyvinylpyrrolidone, starch, and maleic anhydride-styrene copolymer.

As the oil-soluble polymerization initiator, a polymerization initiator generally used in suspension polymerization of a vinyl chloride monomer may be used. For example, diisopropyl peroxycarbonate, di-2-ethylhexyl par Peroxycarbonate compounds such as oxycarbonate and diethoxyethylperoxycarbonate; α-cumyl peroxyneodecanate, t-butylperoxyneodecanate, t-butylperoxypivalate, t-hexylperoxyneodecanate Peroxides such as acetylcyclohexylsulfonyl peroxide and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; azobis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4 −Jimme Le valeronitrile) azo compounds and the like such as may be used alone, or two or more kinds may be used in combination.

In addition, polymerization regulators, chain transfer agents, and pH modifiers conventionally used in the suspension polymerization of vinyl chloride monomers.
A regulator, a gelling improver, an antistatic agent, a polymer scale adhesion inhibitor, and the like may be added.

The vinyl chloride resin obtained by the production method of the present invention does not improve the impact resistance when the amount of the copolymer obtained by the emulsion polymerization decreases, and when the amount increases, the tensile strength, bending strength, etc., increase. Since the mechanical strength decreases, the ratio of the copolymer obtained by emulsion polymerization in the vinyl chloride resin is 1 to 30% by weight.
And more preferably 4 to 20% by weight.

[0033]

EXAMPLES (Examples 1 to 3, Comparative Examples 1 to 3) Pure water 3 was added to a first reaction tank equipped with an emulsion polymerization stirrer and a reflux condenser.
30 parts by weight, 100 parts by weight of n-butyl acrylate, 0.5 part by weight of trimethylolpropane triacrylate,
1 part by weight of polyoxyethylene nonylphenyl sulfate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Hytenol N-08) and 0.1 part by weight of ammonium persulfate were supplied, and the reaction system was replaced with nitrogen. The mixture was heated and reacted for 5 hours to obtain an emulsion polymerization solution having a copolymer concentration of 30% by weight.

Preparation of Mixed Liquid A predetermined amount of partially saponified polyvinyl acetate (Kuraray Co., trade name Kuraray Povar L-8, trade name: 550, degree of polymerization: 550, degree of saponification: 72) was added to the obtained emulsion polymerization liquid. %) Was added and mixed to obtain a mixed solution. The partially saponified polyvinyl acetate was added as a 3% by weight aqueous solution.

The resulting mixture was transported by a monoflow pump to a second reaction tank equipped with a graft polymerization stirrer and a cooling device. Next, the results are shown in Table 2 with respect to 100 parts by weight of the copolymer. A predetermined amount of partially saponified polyvinyl acetate (Kuraray Co., Ltd., trade name Kuraray Povar L)
−8, polymerization degree 550, saponification degree 72%), hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metrolose 60SH50) and pure water. Partially saponified polyvinyl acetate and hydroxypropyl methylcellulose were each added in a 3% by weight aqueous solution to make the total supply of pure water 3030 parts by weight.

Then, with stirring, the calcium chloride 0.1.
After adding 3 parts by weight and coagulating, 0.8 parts by weight of t-butyl peroxyneodecanate was added, the air in the reaction vessel was removed by a vacuum pump, and 2170 parts by weight of vinyl chloride was added. Stir for 1 minute, mix evenly, heat to 57 ° C
To initiate polymerization.

After the start of the polymerization, the internal pressure of the reaction vessel is 0.69MP.
After the polymerization was stopped at the stage when the temperature decreased to a, unreacted vinyl chloride was removed, and the obtained slurry polymer was centrifugally dehydrated and dried to obtain a vinyl chloride resin. All polymerization times were 5.5 hours except that Example 3 was 6 hours.

Measurement of physical properties The coagulation rate of the obtained mixture was measured and shown in Table 1, and the particle size distribution, viscosity average polymerization degree, impact resistance and tensile strength of the vinyl chloride resin were measured and shown in Table 2. . In addition, the measuring method is as follows.

(1) Coagulation rate An aqueous sodium hydroxide solution was added to the obtained mixture to adjust the pH to 6.0, and then pure water was added to adjust the copolymer concentration to 20% by weight. According to JIS K 6392, 23 ° C, load 10
The coagulation rate was determined under the conditions of Kg and a shear time of 10 minutes, and was used as a measure of the mechanical stability of the mixed solution.

(2) Particle size distribution The obtained vinyl chloride resin is # 60, # 100 in accordance with JIS Z8801.
And using a # 200 sieve, and the amount of pass (% by weight) was measured.

(3) Viscosity average polymerization degree The obtained vinyl chloride resin was measured according to JIS K6721. (4) Impact resistance and tensile strength A composition comprising 100 parts by weight of the obtained vinyl chloride-based resin, 0.5 part by weight of an organotin-based stabilizer and 1 part by weight of a montanic acid-based lubricant was mixed at 200 ° C. with 3 parts.
After roll kneading for 3 minutes, press molding was performed at 200 ° C. for 3 minutes to obtain a sample having a thickness of 3 mm. Using the obtained sample, JI
A Charpy impact test was performed at 23 ° C. according to SK7111, and a tensile strength was measured at 23 ° C. according to JIS K7113.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

The method for producing a vinyl chloride resin according to the present invention is as described above. Therefore, the emulsion polymerization solution of the alkyl (meth) acrylate is stabilized in the second reaction vessel for graft-polymerizing the vinyl chloride monomer. It can be transported efficiently, and the emulsion does not break down during transportation, and the particles do not aggregate and coalesce. Therefore, a vinyl chloride resin having a uniform particle size distribution and excellent impact resistance and weather resistance can be produced with high polymerization efficiency.

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Claims (1)

[Claims] In a first reaction vessel, 100 parts by weight of an alkyl (meth) acrylate having a homopolymer having a secondary transition temperature of less than 0 ° C. and 0.1 to 30 parts by weight of a polyfunctional monomer are emulsion-polymerized. First step, after completion of emulsion polymerization, second step of adding 0.1 to 3 parts by weight of partially saponified polyvinyl acetate to 100 parts by weight of the obtained copolymer, and mixing the mixed solution in a second reaction tank And a fourth step of graft-polymerizing a vinyl chloride-based monomer in a second reaction vessel for transporting the vinyl chloride-based monomer to a vinyl chloride-based resin.