KR20030040696A - Methods for manufacturing acrylic impact modifiers and PVC compound with improved thermal stability containing them - Google Patents

Abstract

PURPOSE: A method for preparing an acryl-based impact reinforcing agent and a PVC composition containing the impact reinforcing agent prepared by the method are provided, to improve the heat stability and the dynamic stability of PVC. CONSTITUTION: The method comprises the steps of polymerizing a seed, a core rubber layer and a shell, respectively and three times; mixing the polymerized latex with an emulsifier such as a saturated or unsaturated fatty acid salt and agglomerating the mixture by using a water-soluble salt having a two or three valent cation to prepare dry powdered acryl-based impact reinforcing agent. The seed and the core rubber layer comprise 70-95 wt% of an alkyl acrylate. The PVC composition comprises 80-99 wt% of a poly(vinyl chloride) resin; and 1-20 wt% of the impact reinforcing agent prepared by the method.

Description

Method for manufacturing acrylic impact modifiers and PVC compound with improved thermal stability containing them

The present invention relates to a method capable of improving the thermal and dynamic stability of a vinyl chloride resin (polyvinylchloride, hereinafter abbreviated as "PVC") by an acrylic impact modifier produced by emulsion polymerization.

Polymers or copolymers containing chlorine, such as PVC, generally require stabilizers because they are thermally and kinematically unstable and susceptible to degradation during processing. The most widely used stabilizers are basic lead salts, cadmium, barium compounds or organotin compounds.

Pyrolysis of PVC resin in processing equipment is generally as follows. When the PVC is put into the processing equipment and starts processing, first of all, the melting of the PVC is caused by friction and mechanical shear between the PVC particles and the PVC particles and various additive particles. At this time, the decomposition of PVC begins to occur due to frictional heat and mechanical shear. In this process, some of the hydrogen chloride in PVC is removed, causing the PVC chain to break. The radicals thus generated promote the crosslinking reaction of PVC, and the progress of this process is indicated by discoloration, carbonization, and viscosity increase of the resin. In fact, the decomposition of PVC starts to occur between 80 ° C and 100 ° C.

In general, the impact modifier used to improve the impact strength of PVC is known to play a role in improving the processability of PVC in addition to the impact strength improvement effect. That is, it acts as one of the additives that facilitate the decomposition of the PVC particles in the process. The fact that it promotes processing also means that the decomposition of PVC is also easy, and thus a role of a stabilizer to compensate for this is necessary.

Impact modifiers used to improve the impact resistance of vinyl chloride resins include methyl methacrylate butadiene styrene (MBS) resins, ethylene chloride (CPE) resins, and acrylic resins. Among these, acrylic resins have excellent weather resistance and are widely used as impact modifiers for outdoor plastic products having a lot of daylight exposure time. For example, a product obtained by grafting a methacryl-based polymer having excellent compatibility with vinyl chloride resin in a rubber material composed of alkyl acrylate is mainly used for a product requiring both impact resistance and weather resistance, such as a window frame.

Therefore, the present invention has been proposed to solve the problems of the prior art as described above, and an object of the present invention is to prepare an acrylic impact modifier added to improve the impact resistance of PVC, saturated or unsaturated fatty acid in the polymerized latex The present invention provides a method of obtaining drypowder by adding an emulsifier such as potassium and then blending it with a metal salt, and improving the thermal and dynamic stability of PVC by the impact modifier prepared by the above method. In addition, the preparation of the impact modifier to improve the storage stability of the polymerized latex by blending by adding an emulsifier to the polymerized latex.

Looking at the monomers used in the present invention in detail. First, the rubber component is an alkyl acrylate having 2 to 8 carbon atoms of an alkyl group, that is, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate or 2- Ethyl hexyl acrylate and the like are used, and one kind or two or more kinds can be used.

Alkyl methacrylates having 1 to 4 carbon atoms of the alkyl group are used as the shell-forming monomer. Specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, and butyl methacrylate. Etc. In addition, ethyl acrylate, methyl acrylate, butyl acrylate, and the like may be added to control the glass transition temperature of the shell component, and acrylonitrile, methacrylonitrile, etc. may be added to increase compatibility with the matrix. It may be.

Emulsifiers used in the present invention include ionic emulsifiers, such as saturated or unsaturated fatty acid potassium salts, OLK (potassium oleate), SLS (sodium laurylsulfate), SDBS (sodium dodecylbenzenesulfonate), and the total weight of the polymerization monomers. Preference is given to the use of 0.1 to 4.0% by weight. Examples of the polymerization initiator include ammonium persulfate, potassium persulfate, benzoyl peroxide, azobisbutylonitrile, butyl hydroperoxide, cumin hydroperoxide, and the like. Among these, a polymerization initiator by thermal decomposition or oxidation / reduction reaction is preferable. .

Hereinafter, the present invention will be described in detail.

The present invention is to prepare an acrylic impact modifier rubber particles to improve the thermal stability of PVC, using a water-soluble salt having a divalent or trivalent cation after blending by adding an emulsifier such as saturated or unsaturated fatty acid potassium to the polymerized latex The present invention provides a method of obtaining dry powder by agglomeration, and a method of improving thermal and dynamic stability of PVC by an impact modifier manufactured by the above method. In another aspect, the present invention provides a method for improving the storage stability of the polymerized latex by blending by adding an emulsifier to the polymerized latex during the preparation of the impact modifier.

Thermal stability improvement effect of the PVC resin by the impact modifier prepared by the method described in the present invention is as follows.

Impact modifiers Dry powder particles are made up of hundreds of millions to billions of latex particles. When the polymerized impact modifier latex is blended with an emulsifier such as potassium potassium, and then agglomerated using a metal salt such as calcium chloride, these compounds are added to the corresponding metal salt of fatty acid (eg , Calcium stearate, magnesium stearate, and the like). These salts are widely known as lubricants added when processing PVC resins. In the processing of the PVC composition added with the impact modifier prepared in this way, the impact modifier particles are finely dispersed into the original latex size particles in the processing machine and are well dispersed between the PVC particles. The dispersed impact modifier particles transfer mechanical shear from the processing machine to the PVC particles to promote the decomposition and melting of the PVC. In addition, lubricants such as calcium stearate contained in the impact modifier reduce the melt viscosity to inhibit excessive frictional heat rise to delay the pyrolysis time of PVC.

The present invention provides a method that can improve the storage stability of the polymerized latex in addition to improving the thermal stability of the PVC by the impact modifier. That is, in the case of manufacturing the impact modifier in the above manner, the storage stability of the latex is improved by the emulsifier added to the latex after the completion of the polymerization.

The acrylic impact modifier of the present invention polymerizes the seed and the core component monomer is added to grow the rubber particles, and finally the shell component monomer is added to wrap the core surface to prepare a latex having a particle size of 120nm to 300nm. .

Rubber particles of the impact modifier prepared according to the present invention are i) 9 to 99.95% by weight of the alkyl acrylate having 2 to 8 carbon atoms and 0.05 to 5.0% by weight of the crosslinking agent. Done; ii) It is preferable that the core rubber layer which occupies 55 to 90 weight% with respect to the whole polymer contains 95.0 to 99.95 weight% of alkyl acrylates of 2 to 8 carbon atoms, and 0.05 to 5.0 weight% of a crosslinking agent.

The alkyl acrylates in iii) and ii) are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate One or more monomers selected from or homopolymers and copolymers of these monomers can be used.

In addition, the crosslinking agent in i) and ii) 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, allyl One or more monomers selected from the group consisting of acrylate, allyl methacrylate, trimethylolpropane triacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate and divinylbenzene can be used. The crosslinking agent is preferably used 0.05 to 5.0% by weight of the total weight of the monomers in each of the latex of the present invention.

The shell of the impact modifier prepared by the present invention occupies 5 to 30% by weight based on the total polymer, and the monomers constituting the shell include 90 to 100% by weight of alkyl methacrylate having 1 to 4 carbon atoms of the alkyl group. Nitrile components, such as ethyl acrylate, methyl acrylate, butyl acrylate, acrylonitrile, and methacrylonitrile, can also be added at 10 weight% or less.

In the preparation of the impact modifier described in the present invention, an emulsifier may be used a saturated or unsaturated fatty acid potassium salt, potassium oleate salt, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, and the like.

In addition, the sheath and the core rubber layer of the acrylic impact modifier of the present invention contains 70% to 95% by weight of the rubber component monomer of the total monomer.

The acrylic impact modifier of the present invention is to agglomerate latex with an electrolyte, an organic acid, or an inorganic acid, and then filtered and dried to obtain an impact modifier. The electrolyte may be a water-soluble magnesium salt such as calcium chloride or magnesium sulfate.

Referring to the process of producing an acrylic impact modifier of the present invention in more detail as follows. It demonstrates centering on a superposition | polymerization process and agglomeration process here.

1) One Step Reaction-Preparation of Seeds

Seed is

95.0 to 99.95% by weight of alkyl acrylate having 2 to 8 carbon atoms of the alkyl group;

0.05 to 5.0 wt% crosslinking agent;

0.1 to 3.0 wt% of a polymerization initiator;

0.1 to 4.0 wt% emulsifier; And

1000 wt% of ion-exchanged water

It is prepared by crosslinking a composition mixture comprising a temperature of 60 ℃ to 80 ℃.

2) two-step reaction-preparation of the core rubber layer

Core rubber layer

95.0 to 99.95% by weight of alkyl acrylate having 2 to 8 carbon atoms of the alkyl group;

0.05 to 5.0 wt% crosslinking agent;

0.1 to 4.0 wt% emulsifier; And

80% by weight of ion-exchanged water

After preparing a composition mixture comprising a in a pre-emulsion state, the emulsion was continuously added to the seed prepared in step 1) while simultaneously adding 0.1 to 3.0% by weight of a polymerization initiator and polymerized.

3) 3-step reaction-preparation of the shell

The shell comprises 90 to 100% by weight of alkyl methacrylate having 1 to 4 carbon atoms of the alkyl group;

Up to 10% by weight of alkyl acrylate selected from the group consisting of ethyl acrylate, methyl acrylate and butyl acrylate;

0.1 to 4.0 wt% emulsifier; And

150% by weight of ion exchange water

After preparing a composition mixture comprising a in a pre-emulsion state, the emulsion is continuously added to the secondary polymer prepared in step 2) while simultaneously adding 0.1 to 3.0% by weight of a polymerization initiator is prepared by polymerization.

The polymerization initiator used in the preparation of the seed, the core rubber layer and the shell may use any compound that may cause a crosslinking reaction, specifically, ammonium persulfate, potassium persulfate, benzoyl peroxide, azobisbutylonitrile, butyl Hydroperoxides, cumene hydroperoxides and the like can be used.

In addition, the emulsifier used in the production of the seed, the core rubber layer and the shell is an ionic type such as saturated or unsaturated fatty acid potassium salt, potassium oleate (OLK), sodium lauryl sulfate (SLS), sodium dodecylbenzenesulfonate (SDBS), etc. Emulsifiers can be used.

4) Manufacture of acrylic impact modifier (agglomeration process)

Into the latex prepared from the polymerization process of 1) to 3), ion-exchanged water was added to lower the solid content to 10% by weight, and then 10% by weight calcium chloride solution was added to aggregate. The aggregated mixture is heated to 90 ° C., aged, cooled, washed with ion exchanged water and filtered to obtain agglomerated impact modifiers.

The present invention also provides a vinyl chloride resin composition with improved thermal stability prepared by adding 1 to 20% by weight of the acrylic impact modifier to 80 to 99% by weight of vinyl chloride resin.

The present invention will be described in more detail with reference to the following examples. However, the Examples are provided to illustrate the present invention and the present invention is not limited thereto.

Example 1

1) One step reaction

In the step of polymerizing the seed, 339.8 g of ion-exchanged water was introduced into the reactor and the temperature was raised to 70 ° C. When the temperature of the ion-exchanged water reaches 70 ° C, 49.85 g of butyl acrylate, 0.05 g of allyl methacrylate, 0.10 g of 1,3-butanediol dimethacrylate, 16.59 g of sodium lauryl sulfate (SLS) (3 wt% solution) ) Was added at the same time. The seed was polymerized by adding 26.77 g (1 wt%) of potassium persulfate while maintaining the temperature in the reactor at 70 ° C. The particle size of the polymerized latex was measured using NICOMP, a laser light scattering device, and the particle size was 85 nm.

2) two-step reaction

A step of polymerizing the core rubber layer. A preemulsion was prepared by mixing 208.4 g of ion-exchanged water, 448.66 g of butyl acrylate, 0.450 g of allyl methacrylate, 0.90 g of 1,3-butanediol dimethacrylate, and 74.68 g (3 wt% solution) of SLS. After the stabilized pre-emulsion was made, the seed latex produced in the one-step reaction was continuously added at a constant flow rate for 1 hour 30 minutes. At the same time, 149.34 g (1% by weight) of potassium persulfate was continuously added for 1 hour and 30 minutes to proceed with the polymerization. And the core part was completed by aging at 70 ^° C. for 1 hour.

3) 3-step reaction

The step of polymerizing the shell portion to the core portion made up to step 2, first made a pre-emulsion of 197.5 g of ion-exchanged water, 117.75 g of methyl methacrylate, 9.25 g of ethyl acrylate, and 13.8 g (3 wt% solution) of SLS. The pre-emulsion and potassium persulfate 69.2 g (1 wt% solution) were added to the latex up to two stages simultaneously for 1 hour to proceed with the reaction of the shell portion. Likewise, the polymerization was completed by aging for 1 hour while maintaining a constant temperature in the reactor at 70 ^° C. The size of the final polymerized particles was 190 nm.

4) Preparation of acrylic impact modifier (agglomeration process)

2.0 phr of potassium stearate (F / S) and ion-exchanged water were added to the polymerized latex to lower the solids content of the polymerized latex to 10% by weight, followed by stirring for about 30 minutes, followed by 4% by weight of calcium chloride (10 Wt% solution) was added at once to aggregate. The aggregated mixture was raised to 90 ° C., aged for 10 minutes and then cooled. By-products were washed through two to three washes with ion-exchanged water, and then agglomerated impact modifiers were obtained through filtration. In order to dry the impact modifier, FBD (Fluidized Bed Dryer) was used to dry at 85 ° C. for 2 hours to obtain a final impact modifier in powder form.

Example 2

F / S was used instead of SLS for the emulsifier used for the polymerization, and the input amount was 8.0g (8% solution) in the one-step reaction, 37.0g in the two-step reaction, and 7.0g in the three-step reaction. Other polymerization formulations, dosing methods and aggregation methods are the same as in Example 1.

Example 3

Potassium oleic acid salt (OLK) was used for the emulsifier used in the polymerization instead of SLS, and other polymerization formulations, dosing methods and agglomeration methods were the same as in Example 2.

Example 4

Sodium dodecylbenzene sulfonate (SDBS) was used in place of SLS instead of SLS, and the amount was 6.0 g (8% solution) in one step reaction, 27.75 g in two step reaction and 5.25 g in three step reaction. Other polymerization formulations, dosing methods and aggregation methods were the same as in Example 1.

Example 5

The polymerization formulation and the method of addition were the same as in Example 3, except that the emulsifier to be added to the polymerized latex was used by latex blending potassium oleate salt (OLK) instead of F / S.

Comparative Examples 1 to 4

Comparative Examples 1 to 4 were each polymerized in the same manner as in Examples 1 to 4, but were polymerized in the same manner as in Examples 1 to 4, but in Examples 1 to 4, they were aggregated without adding an emulsifier to the polymerized latex.

Comparative Examples 5-6

In Comparative Examples 5 and 6, the polymerization was carried out in the same manner as in Examples 2 and 3, but in Examples 2 and 3, an emulsifier to be added to the polymerized latex was added at the time of polymerization in Comparative Examples 5 to 6.

Experimental Example 1 Measurement of Pyrolysis Time (Thermal Stability Evaluation)

The thermal decomposition time of the PVC composition prepared by adding each of the impact modifiers obtained in Examples 1 to 5 and Comparative Examples 1 to 6 was measured and shown in Table 1 below.

100% by weight of polyvinyl chloride resin (PVC; LS-100 manufactured by LG Chemical, polymerization degree = 1000), 4.0% by weight of heat stabilizer, 0.9% by weight of calcium stearate (Ca-St), polyethylene A master batch was prepared by mixing 1.36 wt% of wax (PE Wax), 1.0 wt% of processing aid (PA-821 manufactured by LG Chemical), 5.0 wt% of CaCO ₃ , and 4.0 wt% of TiO ₂ .

6 wt% of the desired impact modifier powders obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were added to the master batch, followed by mixing, 56 g of which was measured, and dynamic thermal stability was measured using a Brabender Rheomixer.

The temperature of the Brabender Rheomixer was maintained at 190 ^° C. and the screw rotation speed was set at 60 rpm. The mixture (56 g) was added to a mixer and the change in melt torque over time was observed for 25-30 minutes. The time from the start of the dosing until the torque started to increase again beyond the equilibrium torque range was measured as the pyrolysis time.

Experimental Example 2: Evaluation of the physical properties of the impact modifier (Izod impact strength evaluation)

In order to evaluate the properties of the impact modifier, 100% by weight of polyvinyl chloride resin (PVC; LS-100 manufactured by LG Chemical, polymerization degree = 1000), 4.0% by weight of heat stabilizer (DLP), 0.9% by weight of calcium stearate (Ca-St) , Polyethylene wax (PE Wax) 1.36% by weight, processing aid (Pa-821 manufactured by LG Chemical) 1.0% by weight, CaCO ₃ 5.0% by weight, TiO ₂ 4.0% by weight into a mixer at room temperature and then at 1000rpm Mixing was carried out while the temperature was raised to 115 ° C. After reaching 115 ° C., the temperature was lowered to 400 rpm and cooled to 40 ° C. to complete the master batch butyl acrylate.

7 wt% of each desired impact modifier was added to the master batch and then milled at 190 ° C. for 7 minutes using a 2-roll mill to form a 0.6 mm sheet. The sheet was cut to a size of 150 mm x 200 mm and then laminated to a mold of 3 mm x 170 mm x 220 mm with a constant milling direction. A 3 mm thick specimen was prepared by preheating (0.5 Kg) for 8 minutes, compressing (10 Kg) for 4 minutes, and cooling (10 Kg) for 3 minutes using a 190 ° C. hot press.

The specimens made as described above were exquisitely cut according to ASTM D-256 standard to make impact specimens and then measured the Izod impact strength. Table 1 summarizes the results of measuring the impact strength of the impact modifiers obtained in Examples 1 to 5 and Comparative Examples 1 to 6.

Experimental Example 3 Latex Stability Evaluation

In order to evaluate the stability of the latex, 200 g of the polymerized latex was placed in a beaker and stirred using Robomixer, and then the weight of the coagulum obtained was measured. The stirring speed was 8000 rpm and the mixture was stirred for 10 minutes, and the coagulum was obtained by filtration with 200 µm sieve. The value which shows the ratio of the weight of the coagulated | cured material obtained in this way and the weight of solid content in used latex as a percentage is a numerical value which shows stability. Table 1 summarizes the latex stability evaluation results of Examples 1 to 5 and Comparative Examples 1 to 6.

Emulsifier (wt%) added to the polymerized latex Pyrolysis Time (min) Latex Stability (%) Izod impact strength (kgcm / cm) F / S OLK Example 1 Example 2 Example 3 Example 4 Example 5 2.02.02.02.0- ---- 2.0 1920212218 0.050.070.060.100.05 27.528.828.328.527.0 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 ------ 912131499 * 2.11.81.00.070.06 27.428.627.427.925.025.6

F / S: Potassium Stearate

OLK: Potassium Oleate

*: Latex stability is destroyed after 2 minutes.

As shown in Examples 1 to 4 and Comparative Examples 1 to 4 of Table 1, the agglomeration with F / S addition to the polymerized latex showed better thermal stability than the agglomeration without addition of an emulsifier. . As in Example 5, even when OLK was added instead of F / S, excellent thermal stability was shown compared to the case where no emulsifier was added. Latex stability was greatly improved by the emulsifier added after the polymerization was completed, but the Izod impact strength was relatively unaffected.

As shown in Comparative Examples 5 and 6, when the emulsifier was added in the polymerization process, the latex stability was improved, but the thermal stability was rather decreased, and the Izod impact strength was slightly decreased. This is a result of the presence of excess emulsifier in the polymerization process which inhibits the graft reaction and thus is not effectively dispersed in the PVC composition.

Examples 6-9

In Examples 6 to 9, F / S and SLS (or SLS only) were mixed and used as various emulsifiers to be added to the polymerized latex. The other polymerization prescription | coating and the input method were the same as that of Example 1.

Examples 10-13

In Examples 10 to 13, F / S and SLS (or only SLS) were mixed and used in various ratios as an emulsifier to be added to the polymerized latex. The other polymerization prescription and the input method were the same as in Example 2.

Examples 14-17

In Examples 14 to 17, F / S and SLS (or only SLS) were mixed and used in various ratios as an emulsifier to be added to the polymerized latex. The other polymerization prescription | coating and the input method were the same as Example 3.

Examples 18-21

In Examples 18 to 21, F / S and SLS (or only SLS) were mixed and used in various ratios as an emulsifier to be added to the polymerized latex. The other polymerization prescription and the dosing method were the same as in Example 4.

Emulsifier (weight%) added to the polymerized latex Pyrolysis Time (min) F / S SLS Example 6 Example 7 Example 8 Example 9 1.51.00.50.0 0.51.01.52.0 18.917.616.816.5 Example 10 Example 11 Example 12 Example 13 1.51.00.50.0 0.51.01.52.0 19.618.617.817.3 Example 14 Example 15 Example 16 Example 17 1.51.00.50.0 0.51.01.52.0 20.619.818.518.4 Example 18 Example 19 Example 20 Example 21 1.51.00.50.0 0.51.01.52.0 16.515.815.214.5

F / S: Potassium Stearate

SLS: Sodium Lauryl Sulfate

As shown in Examples 6 to 21, the emulsifier added to the polymerized latex showed a greater thermal stability as the F / S content increased compared to SLS.

As described above, the present invention, in the manufacture of an acrylic impact modifier added to improve the impact resistance of PVC, by blending with emulsifiers such as saturated or unsaturated fatty acid potassium to the polymerized latex and then blended by using a metal salt It provides a way to get dry powder. Including the impact modifier prepared in the above method in the vinyl chloride resin has the effect of improving the thermal and dynamic stability of PVC. In addition, when the impact modifier is prepared, an emulsifier is added and blended to the polymerized latex to improve storage stability of the polymerized latex.

Claims (10)

Iii) the sheath and the core rubber layer comprise 70 to 95% by weight of alkyl acrylate, Ii) by a three-step polymerization process of the sheath, core rubber layer, shell, Iii) acrylic impact, characterized in that the polymerized latex is blended by adding an emulsifier such as saturated or unsaturated fatty acid salt, and then agglomerated using a water-soluble salt having a divalent or trivalent cation as a coagulant to prepare a dry powder. Method of Making Reinforcing Agent 2. The alkyl acrylate constituting the sheath and core rubber layer of claim 1 is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate and A method for producing an acrylic impact modifier, characterized in that it is at least one monomer selected from the group consisting of 2-ethylhexyl acrylate or homopolymers and copolymers of these monomers. The crosslinking agent used in the polymerization process of ii) is a monomer having 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4- At least one monomer selected from the group consisting of butanediol dimethacrylate, allyl acrylate, allyl methacrylate, trimethylolpropane triacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate and divinylbenzene Method for producing an acrylic impact modifier, characterized in that The acrylic impact modifier according to claim 1, wherein the emulsifier used in the polymerization process of ii) is one selected from saturated or unsaturated fatty acid potassium salts, potassium oleate salts, sodium lauryl sulfate, sodium dodecylbenzenesulfonate. Manufacturing method. The polymerization initiator according to claim 1, wherein the polymerization initiator used in the polymerization process of ii) is selected from the group consisting of ammonium persulfate, potassium persulfate, benzoyl peroxide, azo bis butyronitrile, butyl hydroperoxide and cumene hydroperoxide Method of producing an acrylic impact modifier, characterized in that one species. The alkyl methacrylate constituting the shell of ii) is 1 selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate. A method of producing an acrylic impact modifier, characterized in that the monomer of the species. The acrylic impact modifier according to claim 1, wherein the emulsifier to be added after completion of the polymerization of i) is one selected from saturated or unsaturated fatty acid potassium salts, potassium oleate salts, sodium lauryl sulfate, and sodium dodecylbenzenesulfonate. Manufacturing method. The method for producing an acrylic impact modifier according to claim 4 or 7, wherein the emulsifier used is 0.1 to 4.0% by weight of the total weight of the polymerization monomers. The method for producing an acrylic impact modifier according to claim 1, wherein the flocculant used in the flocculation step of i) is a water-soluble magnesium salt such as calcium chloride or magnesium sulfate. A vinyl chloride resin composition having improved thermal stability, comprising 80 to 99% by weight of vinyl chloride resin and 1 to 20% by weight of an acrylic impact modifier prepared by the method of claim 1.