JP2002114828A - Method for producing vinyl chloride graft copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride graft copolymer enabling stable polymerization free from adverse effect of styrene monomer in the case of graft-polymerizing vinyl chloride to an acrylic copolymer. SOLUTION: The vinyl chloride graft copolymer is produced by the graft- copolymerization of (a) 50-99 wt.% vinyl monomer composed mainly of vinyl chloride to (b) 1-50 wt.% acrylic copolymer using an aqueous emulsion solution having a styrene monomer concentration (concentration reduced to the aqueous emulsion solution having an acrylic copolymer concentration of 30 wt.%) of <=1,000 ppm in the aqueous emulsion solution containing the acrylic copolymer composed of at least one kind of (meth)acrylate giving a homopolymer having a glass-transition temperature of >=-140 deg.C and <0 deg.C, 100 pts.wt. of styrene monomer and 0.1-10 pts.wt. of a polyfunctional monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a vinyl chloride-based graft copolymer.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride resins have been used in many applications as materials having excellent mechanical strength, weather resistance and chemical resistance. However, when used for hard materials, they have a disadvantage of poor impact resistance, and various improvement methods have been proposed. Particularly, for applications requiring impact resistance and weather resistance, a vinyl chloride resin obtained by graft copolymerizing vinyl chloride with a rubber component composed of an acrylic copolymer (Japanese Patent Application Laid-Open No. 60-25813) has been proposed. ing.

However, when the above rubber component is mixed into the vinyl chloride resin, the impact resistance is improved with an increase in the amount of the rubber component, but on the other hand, the transparency, the tensile strength and the bending strength are increased. Mechanical strength such as elasticity tends to decrease, and there is an industrial demand for improving transparency and mechanical strength while maintaining impact resistance.

As a method for improving the transparency and the bending elasticity, Japanese Patent Application Laid-Open No. 61-195106 discloses a method in which styrene is copolymerized with an acrylic copolymer. Further, we also describe in JP-A-10-265533 and JP-A-10-218948,
We have proposed a transparent impact-resistant vinyl chloride graft copolymer with transparency.

In these production methods, when an acrylic copolymer is prepared, a styrene monomer is often used as a high Tg high refractive index monomer for the purpose of adjusting the refractive index and controlling the mechanical strength. However, the styrene monomer itself becomes a strong polymerization inhibitor when polymerizing the vinyl chloride monomer. Therefore, when graft polymerization of vinyl chloride to the acrylic copolymer, the residual styrene monomer in the acrylic copolymer or in the emulsion aqueous solution containing the acrylic copolymer adversely affects the graft polymerization of vinyl chloride, Delayed polymerization time, increased amount of required initiator,
Problems such as an increase in the particle size of the graft polymer occur.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, the present invention reduces the residual styrene monomer concentration in an acrylic copolymer or an emulsion aqueous solution containing an acrylic copolymer to reduce the concentration of the acrylic copolymer. An object of the present invention is to provide a method for producing a vinyl chloride-based graft copolymer capable of performing stable polymerization without adverse effects of a styrene monomer when graft-polymerizing vinyl chloride.

[0007]

The process for producing a vinyl chloride graft copolymer according to the present invention comprises the steps of:
This is a method for producing a vinyl chloride-based graft copolymer in which 50% by weight and 50 to 99% by weight of vinyl chloride are graft-polymerized. The acrylic copolymer has at least one type of (meth) acrylate monomer having a glass transition temperature of a homopolymer of −140 or more and less than 0 ° C., and 100 parts by weight of a styrene monomer; It is an acrylic copolymer (a) consisting of 10 parts by weight. In the present invention, the concentration of the residual styrene monomer in the aqueous emulsion solution containing the acrylic copolymer (converted concentration when the acrylic copolymer (a) in the emulsion aqueous solution contains 30% by weight) is 1000 ppm or less. By
It is characterized in that stable polymerization can be achieved without adverse effects such as a delay in polymerization time of vinyl chloride graft polymerization, an increase in the amount of required initiator, and an increase in particle size of the graft polymer.

The above (meth) acrylate monomer forms an acrylic copolymer and is blended to improve the impact resistance of the produced vinyl chloride graft copolymer resin. Therefore, the homopolymer has a glass transition temperature of −140 ° C. or more and less than 0 ° C. In order to impart sufficient flexibility to the vinyl chloride-based graft copolymer resin, the type is not particularly limited as long as it is less than 0 ° C, but in view of the glass transition temperature of a polymer generally used industrially, is -140 ° C or more. Is appropriate.

As the above (meth) acrylate monomer, the homopolymer has a glass transition temperature of −140 ° C. or more and 0 ° C.
It is not particularly limited as long as it is less than, for example, n-butyl acrylate (Tg = −54 ° C., only the temperature is indicated in parentheses below), n-hexyl acrylate (−57
C), 2-ethylhexyl acrylate (-85C),
n-octyl acrylate (-85 ° C), isononyl acrylate (-85 ° C), n-decyl acrylate (-
70 ° C), lauryl methacrylate (-65 ° C), ethyl acrylate (-24 ° C), n-propyl acrylate (-37 ° C), n-butyl acrylate (-54
° C), isobutyl acrylate (-24 ° C), sec-
Butyl acrylate (−21 ° C.), n-hexyl acrylate (−57 ° C.), n-octyl methacrylate (−
25 ° C.), isooctyl acrylate (−45 ° C.), n
-Nonyl methacrylate (-35 ° C), n-decyl methacrylate (-45 ° C) and the like. These can be used alone or in combination of two or more. The glass transition temperature of the homopolymer of the (meth) acrylate monomer having a glass transition temperature of −140 ° C. or more and less than 0 ° C. is described in “Polymer Data Handbook (Basic Edition)” edited by the Society of Polymer Science, Japan. (1986, Baifukansha)
According to

The styrene monomer is copolymerized at the time of polymerization of the acrylic copolymer to adjust the refractive index of the acrylic copolymer and to improve the mechanical strength of the vinyl chloride graft copolymer. Is added to control the amount of

The ratio between the (meth) acrylate monomer and the styrene monomer is adjusted so that the transparency and mechanical strength of the subsequent vinyl chloride-based graft copolymer and the molded product thereof are adjusted to exhibit desired performance. Although not particularly limited, it is usually preferable that the (meth) acrylate monomer is blended in an amount of 20 to 80% by weight in consideration of exhibiting impact resistance.

The above-mentioned polyfunctional monomer crosslinks the above-mentioned acrylic copolymer, makes it difficult for resin particles made of the above-mentioned acrylic copolymer to coalesce, and further reduces the impact resistance of the obtained vinyl chloride resin. It is added for the purpose of improving.

The above-mentioned polyfunctional monomers include, for example,
Examples of the di (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate.
Examples include acrylate, 1,6-hexanediol di (meth) acrylate, and trimethylolpropane di (meth) acrylate. Examples of tri (meth) acrylate include trimethylolpropane tri (meth) acrylate and ethylene oxide-modified trimethylolpropane. Tri (meth) acrylate, pentaerythritol tri (meth) acrylate and the like. Other polyfunctional monomers include dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, diallyl phthalate, diallyl maleate, diallyl fumarate, diallyl succinate, triallyl isocyanurate and the like. Alternatively, a triallyl compound, a divinyl compound such as divinylbenzene, butadiene and the like can be mentioned, and these can be used alone or in combination of two or more.

The compounding amount of the polyfunctional monomer in the acrylic copolymer is such that the homopolymer has a glass transition temperature of -140 or more and less than 0 ° C. to form an acrylic copolymer. , Styrene monomer 1
0.1 to 10 parts by weight with respect to 00 parts by weight. If the amount of the polyfunctional monomer is less than 0.1 part by weight,
Since the acrylic copolymer cannot maintain an independent particle shape in the vinyl chloride-based graft copolymer resin, the impact resistance of the vinyl chloride-based graft copolymer resin is reduced. on the other hand,
If it exceeds 10 parts by weight, the crosslink density of the acrylic copolymer increases, and effective impact resistance cannot be obtained, so that the content is limited to the above range.

In the present invention, examples of the method of copolymerizing the acrylic monomer and styrene monomer with the polyfunctional monomer include an emulsion polymerization method and a suspension polymerization method. Among them, the emulsion polymerization method is preferable because it has good impact resistance and easily controls the particle size of the acrylic copolymer. In addition, the said copolymerization means all copolymerizations, such as a random copolymerization, a block copolymerization, a graft copolymerization.

The above-mentioned emulsion polymerization method can be carried out by a conventionally known method. For example, if necessary, an emulsifying dispersant, a polymerization initiator, a pH adjuster, an antioxidant and the like may be added.

The emulsifying and dispersing agent is an acrylic monomer,
It is used for improving the dispersion stability of a mixture of a styrene monomer and a polyfunctional monomer in an emulsion and efficiently performing polymerization. The emulsifying dispersant is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, partially saponified polyvinyl acetate, cellulose dispersants, and gelatin. Among these,
Anionic surfactants are preferable, and specific examples of the anionic surfactant include polyoxyethylene nonyl phenyl ether sulfate (“Hitenol N-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

The polymerization initiator is not particularly limited.
For example, water-soluble polymerization initiators such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, organic peroxides such as benzoyl peroxide and lauroyl peroxide, and azo initiators such as azobisisobutyronitrile. No.

The type of the emulsion polymerization method is not particularly limited.
For example, a batch polymerization method, a monomer dropping method, an emulsion dropping method and the like can be mentioned.

In the above batch polymerization method, pure water, an emulsifying dispersant, and a monomer are added all at once to a jacketed polymerization reactor, and the mixture is stirred under a nitrogen stream under pressure to sufficiently emulsify. This is a method in which the temperature is raised to a predetermined temperature in a jacket, and then polymerization is performed.

In the monomer dropping method, pure water, an emulsifying dispersant, and a polymerization initiator are charged into a polymerization reactor equipped with a jacket, oxygen is removed under a stream of nitrogen, and pressurization is performed. After raising the temperature to the above, a certain amount of the monomer is added dropwise to carry out polymerization.

In the emulsion dropping method, an emulsion monomer is prepared in advance by stirring a monomer, an emulsifying dispersant, and pure water, and then pure water and a polymerization initiator are charged into a jacketed polymerization reactor. This is a method in which oxygen is removed under a nitrogen stream and pressurization is performed, the inside of the reactor is heated to a predetermined temperature by a jacket, and then the above-mentioned emulsified monomer is dropped in a predetermined amount for polymerization.

In the above-mentioned emulsion dropping method, if a method is used in which a part of the above-mentioned emulsifying monomer is added all at once (hereinafter referred to as a seed monomer) at the beginning of polymerization and the remaining emulsifying monomer is dropped, the amount of the seed monomer is reduced. By changing the particle size, the particle size of the produced acrylic copolymer can be easily controlled. Further, by sequentially changing and distinguishing the types and compositions of the seed monomer and the emulsified monomer to be dropped, a multilayer structure such as a core-shell can be formed.

In the above-mentioned polymerization method, after the dropping of the monomers is completed, the mixture is further cured at the polymerization temperature for 1 hour (stirred for 1 hour) so that all the monomers are subjected to the polymerization reaction.
I do. In this way, most of the monomer is consumed, but a small amount of unreacted monomer remains. When the styrene monomer is used as described above, although it varies depending on the polymerization conditions, usually, about 1000 ppm to about 10000 ppm of the styrene monomer remains in the aqueous emulsion solution after polymerization containing 30% by weight of the acrylic copolymer. Various problems occur during the graft polymerization of vinyl chloride monomers.

The styrene monomer concentration in the aqueous acrylic copolymer emulsion solution of the present invention (converted concentration when the acrylic copolymer (a) in the aqueous emulsion solution contains 30% by weight) is 1000 ppm or less. 1000
If it exceeds ppm, problems such as a delay in polymerization time, an increase in the amount of a required initiator, and an increase in the particle size of the graft polymer occur when graft polymerization of vinyl chloride is carried out.

As a method of reducing the residual styrene monomer concentration, for example, after the above-mentioned curing for one hour, under an atmosphere of nitrogen and open to the atmosphere, for another one to three hours,
There is a method of stirring and holding. At this time, the temperature in the polymerization machine is preferably high, specifically, the polymerization temperature or higher. In addition, this operation may be performed under reduced pressure under conditions that do not cause boiling. By such an operation, the concentration of the residual styrene monomer in the aqueous emulsion solution after polymerization can be reduced to 1000 ppm or less.

In the polymerization method as described above, the solid content ratio of the acrylic copolymer obtained after completion of the reaction is 10 to 60% by weight from the viewpoint of the productivity of the acrylic copolymer and the stability of the polymerization reaction. preferable. In the above-mentioned polymerization method, a protective colloid or the like may be added for the purpose of improving the mechanical stability of the acrylic copolymer after the completion of the reaction.

In the method for producing a vinyl chloride-based graft copolymer according to the present invention, the acrylic copolymers 1 to 50 are used.
Graft polymerization of vinyl chloride and 50 to 99% by weight of vinyl chloride

When the amount of the acrylic copolymer is less than 1% by weight, the produced vinyl chloride-based graft copolymer cannot obtain sufficient impact resistance. Since the mechanical strength such as the bending strength and the tensile strength of the vinyl chloride-based graft copolymer to be used is low, the mechanical strength is limited to the above range. The preferred blending amount of the acrylic copolymer is 4 to 20% by weight.

The polymerization degree of polyvinyl chloride in the vinyl chloride graft copolymer resin is preferably from 300 to 2,000, more preferably from 400 to 1600. Degree of polymerization is 30
If it is less than 0 or more than 1600, the moldability at the time of molding the vinyl chloride graft copolymer produced by the production method of the present invention may be deteriorated.

The method for graft copolymerizing vinyl chloride with the acrylic copolymer is not particularly limited.
Examples thereof include a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, and a bulk polymerization method. Among these, the suspension polymerization method is preferred.

In carrying out the polymerization by the above suspension polymerization method,
You may use a dispersing agent, a polymerization initiator, etc.

The dispersant is not particularly limited, but improves the dispersion stability of the acrylic copolymer,
It is added for the purpose of efficiently performing the graft polymerization of vinyl chloride. For example, poly (meth) acrylate, (meth) acrylate-alkyl acrylate copolymer, methylcellulose, ethylcellulose, hydroxypropylmethylcellulose, polyethylene glycol, polyvinyl acetate and its partially saponified substance, gelatin, polyvinylpyrrolidone, starch, Maleic anhydride-styrene copolymers and the like can be mentioned, and these can be used alone or in combination of two or more.

The polymerization initiator is not particularly limited, but is preferably used because a radical polymerization initiator is advantageous for graft copolymerization. For example, lauroyl peroxide, t-butyl peroxypivalate,
Organic peroxides such as diisopropyl peroxy dicarbonate, dioctyl peroxy dicarbonate, t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, 2,2-azobisisobutyronitrile, And azo compounds such as 2-azobis-2,4-dimethylvaleronitrile.

When graft copolymerizing vinyl chloride,
A coagulant may be added to the dispersion of the acrylic copolymer for the purpose of reducing the scale adhering in the polymerization tank during the polymerization. Further, if necessary, a pH adjuster, an antioxidant, and the like may be added.

As the above suspension polymerization method, for example, the following method can be used. That is, in a reaction vessel equipped with a temperature controller and a stirrer, pure water, the acrylic copolymer dispersion solution, a dispersant, a polymerization initiator, and, if necessary, a water-soluble thickener, Add the regulator. After that, the air in the polymerization vessel was discharged by a vacuum pump, and vinyl chloride and, if necessary, other vinyl monomers were added under stirring conditions. Perform polymerization. At this time, the polymerization temperature is preferably 30 to 90 ° C., and the polymerization time is preferably 2 to 20 hours.

In the above suspension polymerization method, the temperature in the reaction vessel, that is, the polymerization temperature can be controlled by changing the jacket temperature. After the completion of the reaction, unreacted vinyl chloride and the like are removed to form a slurry, which is then dehydrated and dried to produce a vinyl chloride graft copolymer.

The vinyl chloride graft copolymer obtained by the above-mentioned production method has excellent impact resistance and mechanical strength and mechanical strength because a part of polyvinyl chloride is directly bonded to the acrylic copolymer. Excellent fatigue strength (durability).

Since such a vinyl chloride-based graft copolymer has the above-mentioned properties, it is suitably used for molded articles requiring impact resistance, mechanical strength and fatigue strength.

When a molded article is obtained by molding the above-mentioned vinyl chloride graft copolymer, a heat stabilizer, a stabilizing aid, a lubricant, a processing aid, an antioxidant,
Light stabilizers, pigments, fillers and the like may be added.

The heat stabilizer is not particularly limited.
For example, dimethyltin mercapto, dibutyltin mercapto, dioctyltin mercapto, dibutyltin malate, dibutyltin malate polymer, dioctyltin malate, dioctyltin malate polymer, dibutyltin laurate,
Organic tin stabilizers such as dibutyltin laurate polymer, lead stabilizers such as lead stearate, dibasic lead phosphite, and tribasic lead sulfate, calcium-zinc stabilizer, barium-
Zinc-based stabilizers and barium-cadmium-based stabilizers are exemplified. These may be used alone or in combination of two or more.

The stabilizing aid is not particularly limited, and includes, for example, epoxidized soybean oil, epoxidized linseed oil, epoxidized tetrahydrophthalate, epoxidized polybutadiene, phosphate ester and the like. These may be used alone or in combination of two or more.

Examples of the lubricant include an internal lubricant and an external lubricant. The internal lubricant is used for the purpose of lowering the flow viscosity of the molten resin at the time of molding and preventing frictional heating. The internal lubricant is not particularly limited and includes, for example, butyl stearate, lauryl alcohol, stearyl stearate, epoxidized soybean oil, glycerin monostearate, stearic acid, bisamide and the like. These may be used alone or in combination of two or more. The external lubricant is used for the purpose of enhancing the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and includes, for example, montanic acid wax, paraffin wax, polyolefin wax, ester wax and the like. These may be used alone or in combination of two or more.

The processing aid is not particularly limited.
For example, an acrylic processing aid which is an alkyl acrylate-alkyl methacrylate copolymer having a weight-average molecular weight of 100,000 to 2,000,000 is mentioned, and specific examples thereof include n-butyl acrylate-methyl methacrylate copolymer,
-Ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymer. These may be used alone or in combination of two or more.

The antioxidant is not particularly restricted but includes, for example, phenolic antioxidants. These may be used alone or in combination of two or more.

The light stabilizer is not particularly limited.
For example, a salicylic acid ester type, benzophenone type, benzotriazole type, cyanoacrylate type or the like ultraviolet absorber, or a hindered amine type light stabilizer may be used. These may be used alone or in combination of two or more.

The above-mentioned pigments are not particularly restricted but include, for example, organic pigments such as azo, phthalocyanine, sulene and dye lakes, oxides, molybdenum chromate, sulfide / selenide, ferrocyanide. And inorganic pigments such as oxides. These may be used alone or in combination of two or more.

When the above-mentioned molded article is obtained, a plasticizer may be added to the above-mentioned vinyl chloride-based graft copolymer for the purpose of improving the processability during molding. The plasticizer is not particularly limited and includes, for example, dibutyl phthalate, di-2-ethylhexyl phthalate, di-2-ethylhexyl adipate and the like. These may be used alone or in combination of two or more.

The method of mixing the above various additives and plasticizers with the vinyl chloride graft copolymer is not particularly limited, and examples thereof include a method using hot blending and a method using cold blending. The method for molding the vinyl chloride-based graft copolymer is not particularly limited, and examples thereof include an extrusion molding method, an injection molding method, a calendar molding method, and a press molding method.

[0050]

EXAMPLES The effects of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

[Polymerization of Acrylic Copolymer] An acrylic copolymer was obtained according to the polymerization procedure shown in Table 1 by the following procedure. Monomers for forming the core layer, the intermediate layer, and the outermost layer shown in Table 1 (hereinafter, referred to as a core layer-forming monomer, an intermediate layer-forming monomer, and an outermost layer-forming monomer) are each in a predetermined amount. Pure water (monomer 1)
(60 parts by weight with respect to 00 parts by weight), a polyfunctional monomer, and polyoxyethylene nonylphenyl ether ammonium sulfate (an emulsifying dispersant), followed by stirring to prepare each emulsifying monomer.

Next, 150 kg of pure water is placed in a 400 L reactor equipped with a stirrer and a reflux condenser (preferably 160 parts by weight with respect to 100 parts by weight of all monomers), and oxygen in the vessel is replaced with nitrogen. After that, the reaction temperature was raised to 70 ° C. under stirring. After the completion of the temperature increase, the initiator and the proportion corresponding to 30% by weight of the total amount of the monomers for forming the core layer among the monomers for forming the core layer were charged all at once to initiate the polymerization. Subsequently, the remainder of the core layer forming monomer was dropped.
As soon as the dropping of the monomer for forming the core layer was completed, the monomer for forming the intermediate layer and the monomer for forming the outermost layer were sequentially dropped. The dropping of all the emulsified monomers was completed in 3 hours, and after an aging period of 1 hour, the above-mentioned styrene-free monomer treatment was performed for 3 hours. An emulsion solution of an acrylic copolymer having a concentration of not more than 1000 ppm was obtained. In the case of the comparative example, only this step of removing the styrene monomer was not performed. The average particle size and refractive index of the obtained acrylic copolymer particles and the concentration of residual styrene monomer in the emulsion solution were measured by the following evaluation methods, and the results are shown in Table 1.

[Evaluation Method] (Average particle diameter) Particles of the acrylic copolymer were measured with a light scattering particle size meter (DLS-7000: Otsuka Electronics Co., Ltd.).
Manufactured). (Refractive index of acrylic copolymer) The refractive index of the acrylic copolymer is determined by measuring the refractive index of the dispersion solution of the acrylic copolymer obtained after the polymerization reaction is completed in the production of the acrylic copolymer. Measured with a refractometer, the following formula (1)
Was calculated. Refractive index of particles = [(refractive index of dispersion solution of acrylic copolymer−refractive index of water) / solid content ratio of acrylic copolymer] + refractive index of water (1) (residual styrene monomer concentration) The styrene monomer concentration was determined by gas chromatography (HP-5890 SERIES II: HEWLETT).
PACKARD). Column is SIMAD
ZU CB P-1-W12-500 was used.

[Production of vinyl chloride graft copolymer]
Then the internal volume 2200 with stirrer and jacket
In an L polymerization vessel, 1100 kg (280 parts by weight) of pure water, 190 kg (50 parts by weight) of the above-mentioned acrylic copolymer latex liquid (15 parts by weight of an acrylic copolymer solid content), partially saponified polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) , Kuraray Povar L-8), 5 parts by weight of a 3% aqueous solution, hydroxypropyl methylcellulose (Shin-Etsu Chemical Co., Ltd .;
2.5 parts by weight of a 3% aqueous solution of H50), 0.04 parts by weight of di-sec-butylperoxydicarbonate, 0.03 parts by weight of α-cumylperoxy neodecanoate, and an aluminum-based acrylic copolymer Aluminum ions were added all at once so that the solid content became 15 ppm by weight with respect to 15 parts by weight. Thereafter, the air in the polymerization reactor was discharged by a vacuum pump, and 125 parts by weight of vinyl chloride was further added under stirring conditions. Thereafter, the polymerization temperature was controlled to 61.5 ° C. by controlling the jacket temperature.
To start graft polymerization.

When the pressure in the polymerization vessel dropped to a pressure of 0.72 MPa, the conversion of the vinyl chloride monomer was reduced to 80.
%, The completion of the reaction was confirmed, and the reaction was stopped after adding an antifoaming agent (manufactured by Toray Industries, Inc., Toray Silicon SH5510) under pressure. Thereafter, unreacted vinyl chloride monomer was removed, and further dehydration drying was performed to obtain a vinyl chloride resin. The acrylic copolymer weight ratio, polymerization degree, and particle size of the obtained vinyl chloride copolymer were measured by the following evaluation methods, and the results are shown in Table 1.

[Evaluation Method] (Acrylic Copolymer Weight Ratio) The chlorine weight content (Cl%) of the vinyl chloride copolymer was measured in accordance with JIS K7229, and the acrylic weight was calculated from the chlorine weight content according to the following formula. The polymer weight ratio was calculated. Acrylic copolymer weight ratio (% by weight) = (1-1.76)
2 × C) × 100 where C = Cl% / 100 in the above equation. (Degree of polymerization) 5 g of the above vinyl chloride graft copolymer resin
Was dissolved in 100 g of tetrahydrofuran, only the soluble portion was precipitated with methanol, filtered and dried. After the drying was completed, the degree of polymerization of the insoluble components was measured according to JIS K6721.

(Particle Size of Vinyl Chloride-Based Graft Copolymer) The particle size of the vinyl chloride-based graft copolymer was measured with a light scattering particle size analyzer (particle size analyzer LA-910: manufactured by Horiba, Ltd.).

[Production of Roll Sheet] 2 parts by weight of an organic tin-based stabilizer (trade name: ONZ-7F, manufactured by Sankyoki Gosei Co., Ltd.) was added to 100 parts by weight of the obtained vinyl chloride copolymer resin, and a lubricant ( 0.5 part by weight of trade name: WAX-OP, manufactured by Hoechst Japan Co., Ltd. was stirred and mixed with a super mixer (100 L, manufactured by Kawata) to obtain a vinyl chloride resin composition. The obtained vinyl chloride resin composition was roll-kneaded at 190 ° C. for 3 minutes, and cooled on a flat ground to obtain a roll sheet.

[Evaluation of Thermal Stability of Static Aging of Roll Sheet]
The above-mentioned roll sheet was cut into a square of about 5 cm × 5 cm, and ten sheets were held at a high temperature in a 200 ° C. gear oven. A sample was taken every 10 minutes, and the time when it completely darkened was defined as the aging time. Table 1 shows the results.

[0060]

[Table 1]

[0061]

According to the method for producing a vinyl chloride copolymer of the present invention, the residual styrene monomer concentration of the emulsion solution containing the acrylic copolymer subjected to the vinyl chloride graft polymerization is 1000 ppm or less. The polymerization time during graft polymerization is short, the particle size distribution is stable, and a resin having excellent thermal stability can be supplied.

Continued on the front page F term (reference) 4J011 KA02 KA10 KB29 4J026 AA17 AA45 BA10 BB01 DA04 DB04 FA04 GA02

Claims (1)

[Claims] The glass transition temperature of the homopolymer is -140.
Emulsion aqueous solution containing acrylic copolymer (a) consisting of at least one type of (meth) acrylate having a temperature of not lower than 0 ° C and lower than 0 ° C, and 100 parts by weight of a styrene monomer and 0.1 to 10 parts by weight of a polyfunctional monomer. Styrene monomer concentration (converted concentration when the acrylic copolymer (a) in the aqueous emulsion solution contains 30% by weight) is 10
Using an aqueous emulsion solution of 00 ppm or less and graft copolymerizing 50 to 99% by weight of a vinyl monomer (b) containing vinyl chloride as a main component with 1 to 50% by weight of an acrylic copolymer (a). A method for producing a vinyl chloride-based graft copolymer, which is characterized by the following.