CA2032964C

CA2032964C - Method for preparing vinyl chloride resin

Info

Publication number: CA2032964C
Application number: CA 2032964
Authority: CA
Inventors: Yoshihiro Umeda; Seiichi Masuko; Tomonari Ryu
Original assignee: Mitsui Toatsu Chemicals Inc
Current assignee: Mitsui Chemicals Inc
Priority date: 1989-12-28
Filing date: 1990-12-21
Publication date: 1997-03-18
Anticipated expiration: 2010-12-21
Also published as: JPH03200817A; CA2032964A1; JP2910774B2

Abstract

A method for preparing a vinyl chloride resin comprises the steps of copolymerizing 80 to 99.9% by weight of an alkyl acrylate and/or an alkyl methacrylate whose homopolymer has a second-order transition temperature of not more than -10°C , 20 to 0.1% by weight of allyl methacrylate and/or triallyl isocyanurate and 0 to 20% by weight of a monomer copolymerizable with these monomers to form an acrylic rubbery copolymer having an average particle size ranging from 0.01 to 0.5 µ m and then graft-copolymerizing vinyl chloride monomer to the acrylic rubbery copolymer. The graft copolymerized resins obtained according to the foregoing method can be mixed with a variety of additives such as heat stabilizers, lubricants, processing aids, antioxidant, fillers, ultraviolet absorbers, pigments or the like which are commonly employed in the fabrication of vinyl chloride resins and can be processed and/or molded according to the usual manner. The graft copolymerized resins are excellent in not only impact resistance but also tensile properties and, therefore, these resins can be used for manufacturing construction materials, high impact pipes or the like in which well-balanced impact resistance and tensile properties are required and can provide products which can be used in the open air.

Description

Method for Preparing Vinyl Chloride Resin BACKGRO~D OF TEIE INV~;N 110 (Field of the In~ention) The present invention relates to a method for preparing a ~inyl chloride resin and more specifically to a method for preparing a vinyl ch~oride resin excellent in impact resistance and tensile properties.

(Description of the Prior Art) Vinyl chloride resins have excel~ent physical and mechanical properties. Therefore, these resins have widely been used in various fields,i.e. rigid, semirigid and flexible uses. However, vinyl chloride homopolymers ha~e low impact resistance when applied in rigid uses.
Many attempts have been directed to the development of methods for eliminating these drawbacks. For instance, Japanese Patent Publication ~ox Opposition Purpose (hereunder referred to as "J.P. KOKOKU") No. Sho 39-170~7 discloses a vinyl chloride-grafted copolymer obtained by graft-copolymerizing vinyl chloride to an alkyl acrylate polymer.
However, the physical properties such as impact resistance of this resin were still insuf~icient. On the other hand, the vinyl chloride resins obtained according to the method whi~h was previous developed by the inventors of this invention ~see, for instan~e, Japanese Patent Unexamined Publication (hereunder referred to as "J.P. KOKAI") No. Sho 60-255813) make it possible to achieve any desired impact resistance if the content of a rubbery copolymer in the vinyl chloride resin is properly controlled. Furthermore, these resins are easily processed and excellent in weatherability and, therefore, they are practically applicable as materials used in the open air such as construction materials.
This method makes it possible to form a vinyl chloride resin having very excellent impact resistance if the content of such rubbery copolymer therein are increased, but the resulting vinyl chloride resins exhibit insufficient tensile properties such as tensile strength and the resulting vinyl chloride resins are limited in the use application such as, for example, high impact pipe which require excellent impact resistance and also tensile strength. ~nder such circumstances, there has long been desired for the development of a method which makes it possible to simultaneously fulfill these two requirements which are contrary to one another.

SUMMARY OF THE lNV~NllON
Accordingly, an object of the present inventlon is generally to prov}de a method for preparing a vinyl chloride resin and more specifically to ptovide a method for improving tensi7e properties of vinyl chloride resins which are obtained by graft-copolymerizing vinyl chloride to acrylic rubbery polymers.
Other objects of the present invention wil~ become more apparent from the following description.
The inventors of this invention have conducted intensive studies to achieve the faregoing ob~ects, have unexpectedly found out that a graft copolymer having high impact resistance and e~cellent tensile properties can be obtained through a graft-copolymerizat~on of vinyl chloride to an acrylic rubbery copolymer by making use of an acrylic rubbery copolymer which has a speci~ic average particle s~ze and which is obtained by copolymerizing a specific alkyl acrylate and/or alkyl methacrylate and a specific crosslinking agent through an emulsion polymerization and thus have completed the present invention.
According to the present invention, the foregoing ob~ects can sffective~y be achieved by providing a method for preparing vinyl chloride resin which comprises the steps of emulsion-polymerizing 80 to 99.9% by weight of an alkyl acrylate and/or an al~yl methacrylate whose homopolymer has a second-order transition temperature of not more than -lO'C , 20 to 0.1% by weight of allyl methacrylate and/or triallyl isocyanurate and 0 to 20% by weight of a monomer copolymerizable with the foregoing monomers to form an acrylic rubbery copolymer having an average particle size ranging from 0.01 to 0.5 ~ m and then graft-copolymerizing 99 to 70~ by weight of vinyl chloride monomer to 1 to 30%
by weight of the acrylic rubbery copolymer.

DESCRIPTION OF TEIE PE~;~ ED E~3ODIMENTS
The method of the present invention will hereinafter be explained in more d~tail.
As alkyl acrylates and alkyl methacrylates used in the present invention, there may be mentioned, for instance, alkyl acrylates such as ethyl acrylate, n-propyl acrylate, iso-butyl acrylate, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acry~ate, n-octyl acrylate, n-decyl acrylate and n-dodecyl acrylate; and alkyl methacrylates such as 2-ethylhexyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, n-lauryl methacrylate and n-tetradecyl methacry~ate. ~hese alkyl acrylates and alkyl methacrylates may be used alone or in any combination of two or more of these monomers. Among these, particularly preferred are ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate. When these alkyl acrylates and/or alkyl methacrylates are copolymerized with allyl methacrylate and/or triallyl isocyanu~ate to prepare an acrylic rubbery copolymer and vinyl chloride monomer is graft-polymerized to the acrylic rubbery copolymer, there is obtained a graft copoly~er having good impact resistance and also tensile properties.
In the method of the present invention, allyl methacrylate and/or triallyl isocyanurate are preferably used in an amount ranging from 0.1 to 20% by weight, more preferably 0.2 to 1~% ~y weight and most preferably 0.3 to 6% by weight. This is because, if the amount thereof is less than 0.1~ by weight, the resulting graft copolymer has insufficient impact resistance, while if it exceeds 20% by weight, the tensile properties of the resulting graft copolymer are markedly improved, but on the contrary the impact resistance thereof is greatly lowered.

-203Z96a~

In the preparation of the acrylic rubbery elastomer used in the present invention, other monomers copolymerizable with the foregoing monomeric co~pounds can be copolymerized with these monomers in an amount ranging from 0 to 20% by weight, depending on the applications o~ the resulting copolymers and/or for the purposes of changing gloss, of improving the stability of acrylic rub~ery copolymer latexes and of reducing the cost.
Specific examples of such optional monomers copolymerizable with the essential monomer components are monofunctional monomers, for instance, olefins such as ethylene, propylene and hexene; aromatic vinyl monomers such as styrene, a -methylstyrene and vinyltoluene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate; and vinyl ethers such as butyl vinyl ether and lauryl vinyl eher; and polyfunctional monomers, for instance, acrylates and methacrylates of mono- or polyalkylene glycols such as ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene gly~ol dimethacrylate, triethylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol dimsthacrylate and 1,4-butylene glycol dimethacrylate; and divinyl compo~nds such as divinylbenzene and butadiene.
~ hese optional monomers may be used, in the copolymerization, alone or in combination of two or more of these monomers depending on the applications. In this 203~964 respect, these optional monomers frequently elevate the second-order transition temperature of the resulting acrylic rubbery copolymer and often adversely affect the impact resistance of the graft copolymer. Therefore, it is preferred that the amount thereof to be used be limited to not more than 20~ ~y weight.
The acrylic rubbery copolymer used in the present invention is one obtained through an emulsion polymerization and the average particle size thereof which is in a latex state preferably ranges from 0.01 to 0.5 ~ m, more preferably ~.03 to 0.3~ m and most preferably 0.05 to 0.2~
m. This is because, if the average particle size thereof exceeds 0.5~ m, the tensile properties of the resulting acrylic vinyl chloride resin is greatly lowered, while it is quite difficult to form an acrylic rubbery copolymer having an average particle size (in the form of a latex) of less than 0.01 ~ m. The average particle size of the acrylic rubbery copolymer can be determined by, for instance, observing the latexes through a transmission electron microscope.
If the acrylic rubbery copolymer is prepared according to the usual emulsion polymerization, for instance, pure water, an emulsifying agent and a polymerization initiator are introduced into a polymerizer equipped with a jacket, the air present in the polymerizer is evacuated, then an alkyl acrylate and/or alkyl mithacrylate and allyl methacrylate and/or triallyl isocyanurate and optionally monomers copolymerizable with these monomers are introduced -- 2~329~4 into the polymerizer and emulsified therein, followed by the application of heat to the polymerizer through the jacket for initiating the polymerization reaction. The reaction is exothermic and thus, the temperature of the reaction system is, if necessary, contro~led by cooling with the ~acket.
After comp~etion of the polymerization reaction, the unreacted monomers are, if necessary, removed out of the polymerizer to thus give a latex of an acrylic rubbery copolymer. The entire charge may be introd~ced into the polymerizer at a time from the commencement of the polymerization reaction or alternatively a part or the whole thereof can be introduced into the polymerizer continuously or in several portions.
The emulsifying agents used in this emulsion polymerization may be any known ones which may ~e used alone or in any combination of two or more of them. Specific examples thereof include anionic surfactants such as fatty acid salts, alkylsulfuric acid salts, alkylbenzenesu~fonic acid salts, alkylnaphthalenesulfonic acid salts, alkylsulfosuccinic acid salts, alkyldiphenyl ether disulfonic acid salts and alkylphosphoric acid salts; non-ionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylallyl ethers; and cationic surfactants such as quaternary ammonium salts. These emulsifying agents may be used in an amount ranging from 0.1 to 3% by weight on the basis of the total weight of the mixture of water and monomers.
Examples of the polymerization initiators usable in the ~2964 emulsion po~ymerization include water-soluble peroxides such as hydrogen peroxide, potassium persulfate and ammonium persulfate; oil-solu~le azo compounds such as azobisisobutyronitrile; and organic peroxides such as lauroyl peroxide and cumene hydroperoxide. Alternatively, it is also possible to use these polymerization initiators in the form of a redox catalyst obtained by combining them with a reducing agent such as sulfurous acid salts, salts of divalent iron or sodium formaldehyde sulfoxylate.
These polymerization initiators may be used in an amount ranging from 0.02 to 3~ by weight on the basis of the total weight of the monomer mixture.
The foregoing method makes it possible to prepare a latex of the acrylic rubbery copolymer having a concentration of up to about 50% by weight, but the latex preferably has a concentration ranging from 10 to 30% by weight from the viewpoint of the preparation and handling thereof.
The graft copolymerization of vinyl chloride monomer to the acrylic rubbery copolymer can be performed according to any known manner such as suspension polymerization, emulsion polymerization, solution polymerization and bulk polymerization, but suspension polymerization is most prefera~ly adopted.
When the graft copolymerization is performed according to an aqueous suspension polymerization, the amount of water to ~e used ranges from 0.8 to 5 times and preferably 0.9 to 3 times the total amount of the acrylic rubbery copolymer and vinyl ch~oride monomer.

-;~3Z964 In the present invention, 99 to 70% ~y weight, prefera~ly 98 to 75% by weight, and more preferably 97 to 82~ ~y weight of vinyl chloride monomer is graft copolymerized to 1 to 3~% by weight, pre~erably 2 to 25~ by weight, and more preferably 3 to 18% by weight of the acrylic rubbery copolymer.
When a graft-copolymerized resin is prepared by suspension polymerization, for instance, pure water, a radical polymerization initiator a stabilizer for suspension and an agent for coagulating an acrylic rubbery copolymer latex and an optional polymerization degree regulator are introduced into a polymerizer provided with a jacket, an acrylic rub~ery copolymer latex is introduced into the polymerizer to coagulate the same with stirring, then the air in the polymerizer is evacuated and vinyl chloride monomer and optional other vinyl compounds are added. Thereafter, the contents of the polymerizer are heated through the jacket to thus initiate the graft copolymerization. The graft copolymerization is an exothermic reaction. The temperature of the contents of the polymerizer is, if necessary, controlled by the jacket dllring the graft copolymerization. After completion of the graft copolymerization reaction, the unreacted monomers such as vinyl chloride are discharged outside the reaction system to thus give a slurry-like graft copolymer resin. The slurry is dehydrated and dried in the usual manner to recover the graft copolymer.
In the present invention, the acrylic rubbery copolymer ~- 1 o 203;~964 is charged in the polymerizer in the form of a latex and the graft copolymerization of the rub~ery copolymer with vinyl chloride is carried out in the form of the latexes, or alternatively it is also possible to perform the graft copolymerization with vinyl chloride after the rubbery copolymer is coagulated in the polymerizer by the addition of, for instance, inorganic salts. Further, the acrylic rub~ery copolymer could be coagulated outside the potymerizer prior to the graft copolymerization with vinyl chloride and then introduced into the polymerizer to perform graft copolymerization with vinyl chloride. Either of these methods makes it possible to provide a graft copolymer in which the particles of the acrylic rubbery copolymer are uniformly dispersed throughout the copolymer through the graft copolymerization reaction.
In practicing the graft copolymerization, other monomers may be added to the polymerization system in an amount at which they do not adversely affect the impact resistance, weatherability and tensile properties of the resulting graft copolymer. Specific examples thereof include ~lefins such as ethylene, propylene and hexene; aromatic vinyl monomers such as styrene and vinyl toluene; unsaturated nitriles such as acrylonitrile and methacrylonitrile;
vinyl esters such as vinyl acetate and vinyl propionate;
and vinyl ethers such as butyl vinyl ether and lauryl vinyl ether.
Upon practicing the method of the present invention, the graft copolymerization is preferably performed according 203Z9~i4 to a radical polymerization method. In this case, there may ~e used, for instance, oil-soluble polymerization initiators such as organic peroxides, e.g., lauroyl peroxide, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate and dioctyl peroxydicarbonate, azo compounds, e.g., 2,2'-azobisisobutylonitrile and 2,2'-azobis-2,4-dimethylvaleronitrile; and water-soluble polymerization initiators such as potassium persulfate and ammonium persulfate, as a radical polymerization initiator. These radical polymerization initiators may be used alone or in any combination o~ two or more of these. The amount of these polymerization initiators preferably ranges from ~.005 to 1.0 part by weight per 100 parts by weight of vinyl chloride.
Examples of dispersants preferably employed in the graft copolymerization are organic substances such as methyl cellulose, ethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohols and partially saponified products thereof, gela~in, polyvinyl pyrrolidone, starches and maleic anhydride/styrene copolymers; and inorganic substances such as magnesium carbonate, calcium carbonate and calcium phosphate. These dispersants may be used alone or in any combination of two or more of these.
The amount of these dispersants suitably ranges from 0.01 to 1.0 part by weight per 100 parts by weight of vinyl chloride.
Moreover, a chain transfer agent which has been conventionally used in methods for polymerizing vinyl chloride can be added to the graft copolymerization system of the present invention in an amount ranging from 0.001 to 10 X~)32964 parts ~y weight per 100 parts by weight of vinyl chloride.
The graft copolymerized resins obtained according to the method o~ this invention ~an ~e mixed with a variety of additives such as heat sta~ilizers, lubricants, processing aids, antioxidants, fillers, ultraviolet absorbers, pigments or the like which are commonly e~ployed in the fabrication of v~nyl chloride resins and can be processed and/or molded according to the usual manner. Further, the graft copolymerized resins of the present invention are excellent in not only impact resistance but also tensile properties and, therefore, these resins can be used ~or manufacturing construction materials, high impact pipes or the like in which well-balanced impact resistance and tensile properties are required and can provide products which can be used in the open air.
The method of the present invention will hereinafter be described in more detail with reference to the following non-limitative working Examples and the effects practically achieved by the present invention will also be discussed in c~mparison with ~mr~rative Examples.

Examples 1 to 10:
Preparation of Acrylic Rub~ery Copolymer To a 5 mJ internal volume polymerizer equipped with a stirring blade, there were added 2000 kg of deionized water, 7.0 kg of an anionic emulsifying agent, 0.7 kg of ammonium persulfate and 725 kg of a monomer mixture comprising an alkyl acrylate and/or an alkyl methacrylate, allyl 2~)32964 methacrylate and/or triallylisocyanurate and an optional polyfunctional monomer whose composition is detailed in the following Table 1 ~in terms of "g by weight"), the air in the polymerizer was replaced with nitrogen gas and the polymerization was performed at 60C for 20 hours with stirring. The concentration of each resulting acrylic ru~bery copolymer latex was found to be 26~ by weight. The average particle size o~ each acrylic rubbery copolymer was determined and summarized in Table 1.

Preparation of Graft Copolymer To a 7 mJ internal volume polymerizer equipped with a stirring blade, there were added 2700 kg of deionized water, 2.05 kg of a partially saponified polyvinyl alcohol, 2.05 kg o methyl cellulose, 0.075 kg of 2,2'-azobisisobutyronitrile and 0.24 kg of ~ azobis-2,~-dimethylvaleronitrile. As an acrylic ru~bery copolymer, each acrylic rubbery copolymer latex obtained according to the foregoing method was diluted with water to a concentration of 15~ by weight to obtain each diluted latexes. The acrylic rubbery copolymer as the latex as such was added to the polymerizer in an amount (% by weight) listed in Table 1 and the air in the polymerizer was evacuated. Then vinyl chlorlde monomer was added in an amount (% by weight) listed in T~le 1, provided that the total amount of the acrylic rubbery copolymer and vinyl chloride was equal to 15~0 kg. Thereafter, ~he polymerization was carried out at ~7 C with stirring. The polymerization was interrupted at a time when the inner pressure of the ~03'Z964 polymerizer was reduced down to 6.5 kg/cm2, followed by the recovery of unreacted monomers, dehydration of the resulting slurry and drying to give white powder.
To 100 parts by weight of the resultant graft copolymer, there were added 2 parts by weight of tribasic lead sulfate, 1 part by weight of dibasic lead stearate and 1.5 part by weight of lead stearate and the mixture was uniformly admixed, The mixture was further kneaded at 180 C
for ~ minutes with heated rolls and then pressed at 180C
for 5 minutes to give a sheet. The sheet was cut into small pieces which was used as a sample for determining Chaxpy impact strength and weatherability as well as tensile strength and elongation at break as the indices for tensile properties which were determined according to the following methods. The results thus obtained are also listed in Table 1.

Charpy Impact Strength: JIS K-674~.
Tensile Strength and Elongation at Break: JIS K-6745.
Weatherability: Each sample was irradiated w ith light rays for 200 hours with Carbon Arc Sunshine Weatherometer (spray 12/60 min.; Temp. of black panel = 63C ) and the degree of discoloration was evaluated by comparison.

Comparative Examples 1 to 5 The same procedures used in Examples 1 to 5 were repeated except that the ingredients listed in Table 1 were used to obtain graft copolymers and the properties thereof 26)3Z964 were likewise determined. In Comparative Example 5, the amount of the anionic emulsifying agent was changed to 3.0 kg. The results thus obtAine~ are summarized in Table 1.
The results listed in Table 1 clearly indicate that the graft copolymers obtained according to the method of this invention exhibit excellent impact resistance, tensile properties and weatherability.

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Claims

1. A method for preparing a vinyl chloride resin which comprises the steps of emulsion-polymerizing 80 to 99.9% by weight of an alkyl acrylate and/or an alkyl methacrylate whose homopolymer has a second-order transition temperature of not more than -10 °C , 20 to 0.1% by weight of allyl methacrylate and/or triallyl lsocyanurate and 0 to 20% by weight of a monomer copolymerizable with the foregoing monomers to form an acrylic rubbery copolymer having an average particle size ranging from 0.01 to 0.5 µ m and then graft-copolymerizing 99 to 70% by weight of vinyl chloride monomer to 1 to 30% by weight of the acrylic rubbery copolymer.

2. The method for preparing a vinyl chloride resin of claim 1 wherein the alkyl acrylate and/or the alkyl methacrylate are at least one member selected from the group consisting of ethyl acrylate, n-propyl acrylate, iso-butyl acrylate, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, n-lauryl methacrylate and n-tetradecyl methacrylate.

3. The method for preparing a vinyl chloride resin of claim 2 wherein the alkyl acrylate and/or the alkyl methacrylate are selected from the group consisting of ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate.

4. The method for preparing a vinyl chloride resin of claim 1 wherein the amount of allyl methacrylate and/or triallyl isocyanurate ranges from 0.2 to 10% by weight.

5. The method for preparing a vinyl chloride resin of claim 4 wherein the amount of allyl methacrylate and/or triallyl isocyanurate ranges from 0.3 to 6% by weight.

6. The method of preparing a vinyl chloride resin of claim 1 wherein the copolymerizable monomer is at least one member selected from the group consisting of ethylene, propylene, hexene, styrene, .alpha.-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, butyl vinyl ether, lauryl vinyl ether, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3 butylene glycol dimethacrylate, 1,4-butylene glycol dimethyacrylate, divinylbenzene and butadiene.

7. The method of preparing a vinyl chloride resin of claim 1 wherein the average particle size of the acrylic rubbery copolymer which is in a latex state ranges from 0.03 to 0.3 µm.

8. The method for preparing a vinyl chloride resin of claim 7 wherein the average particle size of the acrylic rubbery copolymer which is in a latex state ranges from 0.05 to 0.2 µm.

9. The method for preparing a vinyl chloride resin of claim 1 wherein the emulsion-polymerization is performed in the presence of an emulsifying agent and a polymerization initiator.

10. The method for preparing a vinyl chloride resin of claim 9 wherein the emulsifying agent is at least one member selected from the group consisting of fatty acid salts, alkylsulfuric acid salts, alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acid salts, alkylsulfosuccinic acid salts, alkyldiphenyl ether disulfonic acid salts, alkylphosphoric acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkylallyl ethers and quaternary ammonium salts and the amount thereof used ranges from 0.1 to 3% by weight on the basis of the total weight of the mixture of water and monomers.

11. The method for preparing a vinyl chloride resin of claim 9 wherein the polymerization initiator is at least one member selected from the group consisting of hydrogen peroxide, potassium persulfate, ammonium persulfate, azobisisobutyronitrile, lauroyl peroxide and cumene hydroperoxide and these polymerization initiators in the form of a redox catalyst obtained by combining them with a reducing agent selected from the group consisting of sulfurous acid salts, salts of divalent iron or sodium formaldehyde sulfoxylate and the amount thereof used ranges from 0.02 to 3% by weight on the basis of the total weight of the monomer mixture.

12. The method for preparing a vinyl chloride resin of claim 1 wherein the concentration of the resulting latex of the acrylic rubbery copolymer ranges from 10 to 30% by weight.

13. The method for preparing a vinyl chloride resin of claim 1 wherein the graft copolymerization of vinyl chloride monomer to the acrylic rubbery copolymer is performed by an aqueous suspension polymerization and the amount of water to be used ranges from 0.8 to 5 times the total amount of the acrylic rubbery copolymer and vinyl chloride monomer.

14. The method for preparing a vinyl chloride resin of claim 13 wherein the amount of water to be used ranges from 0.9 to 3 times the total amount of the acrylic rubbery copolymer and vinyl chloride monomer.

15. The method for preparing a vinyl chloride resin of claim 1 wherein the graft copolymerization of vinyl chloride monomer to the acrylic rubbery copolymer is performed in the presence of at least one monomer selected from the group consisting of ethylene, propylene, hexene, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, butyl vinyl ether and lauryl vinyl ether.

16. The method for preparing a vinyl chloride resin of claim 1 wherein the graft copolymerization is performed by a radical polymerization method in the presence of at least one radical polymerization initiator selected from the group consisting of lauroyl peroxide, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, dioctyl peroxydicarbonate, 2,2'-azobisisobutylonitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, potassium persulfate and ammonium persulfate in an amount ranging from 0.005 to 1.0 part by weight per 100 parts by weight of vinyl chloride.

17. The method for preparing a vinyl chloride resin of claim 1 wherein the graft copolymerization is performed in the presence of at least one dispersant selected from the group consisting of methyl cellulose, ethyl cellulose, hydroxypropylmethyl cellutose, hydroxyethyl cellulose, polyvinyl alcohols and partially saponified products thereof, gelatin, polyvinyl pyrrolidone, starches, maleic anhydride/styrene copolymers, magnesium carbonate, calcium carbonate and calcium phosphate and the amount thereof used ranges from 0.01 to 1.0 part by weight per 100 parts by weight of vinyl chloride.

18. The method for preparing a vinyl chloride resin of claim 1 wherein the graft copolymerization is performed in the presence of a chain transfer agent in an amount ranging from 0.001 to 10 parts by weight per 100 parts by weight of vinyl chloride.