JPH0768318B2 - Multi-layered acrylic polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-layered acrylic polymer, and more specifically, it is blended with a thermoplastic acrylic resin to provide transparency, impact resistance and The present invention relates to a multi-layered acrylic polymer used for obtaining a thermoplastic acrylic resin composition having excellent haze temperature dependence.

[Prior Art] Generally, a so-called elastomer component is introduced as a means for improving the impact resistance of the thermoplastic acrylic resin. Here, the introduction of a diene-based eratomer is not suitable as a method for outdoor use because it has poor weather resistance.

Various introductions of acrylic elastomers have been studied in order to impart impact resistance without lowering weather resistance. In particular, many examples using an acrylic polymer having a multilayer structure as an acrylic elastomer have been proposed.

For example, the impact resistance is improved without impairing the transparency by blending a three-layer or four-layer or more multi-layer structure granular composite and a thermoplastic polymer (Japanese Patent Publication No. 55-27576). And having an intermediate layer having a concentration gradient that changes at a substantially constant rate between these layers (Japanese Patent Publication No. 58-1
694, JP-B-59-36645) Basically a three-layer structure with one or more intermediate layers between the central soft layer and the outermost layer (JP-B-59-36646, JP-B-63-8983) , A soft-hard-soft-hard four-layer structure (Japanese Patent Publication No. 62-41241) and the like have been proposed. However, although these methods are certainly effective in improving the stress whitening resistance, they have a problem that transparency and / or haze temperature dependency is poor, or impact resistance is insufficient.

Also, during polymerization of the second layer (soft layer), addition and polymerization of the monomer mixture of the third layer (hard layer) was started at a polymerization rate of 60 to 90% by weight (JP-A-59-202213). ), The monomer mixture forming the second layer (soft layer) is left unreacted in an amount of 15 to 30% by weight, and the third layer monomer mixture is polymerized to form a layer having a gradual change in composition (Japanese Patent Application Laid-Open No. 2004-242242). 63-27516) has been proposed. However, although these methods improve impact resistance and weather resistance, they are inferior in transparency.

[Problems to be Solved by the Invention] As described above, an acrylic polymer having a multilayer structure for the purpose of improving impact resistance while maintaining desirable properties of acrylic resins such as transparency and weather resistance. Have been proposed as a thermoplastic acrylic resin composition by blending as a modifier. However, in the proposals so far, although the impact resistance and the stress whitening resistance are considerably improved, the transparency and the temperature dependence of the haze are still not sufficiently satisfactory.

The object of the present invention is to improve the drawbacks of such a conventional multi-layered acrylic polymer, excellent transparency of the acrylic resin, excellent flow resistance and excellent impact resistance, temperature dependence of haze. An object of the present invention is to provide an acrylic resin composition having reduced properties.

[Means for Solving the Problems] The present inventors have made the transparency of the impact-resistant acrylic resin composition,
As a result of extensive studies to improve impact resistance, it was found that the above object can be achieved by using a multi-layered acrylic polymer having a specific structure, and the present invention was completed based on this finding. Came to do.

That is, the present invention comprises: (a) 90 to 99% by weight of methyl methacrylate and 1 to 10% by weight of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms.
And a monomer mixture consisting of 0.01 to 0.3% by weight of a graft-bonding monomer consisting of at least one kind of allyl, methallyl or crotyl ester of an α, β-unsaturated carboxylic acid copolymerizable therewith. 25-45% by weight of the innermost hard layer polymer obtained by (b) 70-90% by weight of n-butyl acrylate, 10-30% by weight of styrene, and An allyl of a polymerizable α, β-unsaturated carboxylic acid,
35 to 45% by weight of a soft layer polymer obtained by polymerizing a monomer mixture of 1.5 to 3.0% by weight of a graft-bonding monomer of at least one selected from methallyl or crotyl ester, (c) the above In the presence of a polymer composed of an innermost hard layer and a soft layer, 90 to 99% by weight of methyl methacrylate, an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 1 to 10
20 to 30% by weight of the outermost hard layer polymer obtained by polymerizing a monomer mixture consisting of 1% by weight, (d) soft layer polymer / (innermost hard layer polymer + soft layer polymer) (E) a multilayer structure acrylic polymer having an average particle diameter of 0.2 to 0.3 μm and further fractionating the multilayer structure acrylic polymer with acetone, f) a graft ratio of 20 to 40% by weight, and (g) a multilayered acrylic polymer characterized in that the acetone insoluble portion has a tensile elastic modulus of 1000 to 4000 Kg / cm ² . .

The multi-layered acrylic polymer in the present invention is a multi-layered acrylic polymer composed of methyl methacrylate, an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, an aromatic vinyl monomer, and a polyfunctional crosslinking agent. .

The multilayer structure acrylic polymer in the present invention is the innermost hard layer polymer 25 to 45% by weight, preferably 30 to 37% by weight, the soft layer polymer 35 to 45% by weight and the outermost hard layer polymer 20 to 30. It is composed of a three-layer structure of weight%. When it deviates from these ranges, the impact resistance and / or the temperature dependence of haze are poor.

Furthermore, the weight ratio of soft layer polymer / (innermost hard layer polymer + soft layer polymer) is 0.45 to 0.57, preferably 0.50 to 0.
It is characterized by being 55. Here, when the weight ratio of soft layer polymer / (innermost hard layer polymer + soft layer polymer) is less than 0.45, the resulting thermoplastic acrylic resin composition is inferior in impact resistance, and when it exceeds 0.57. Has poor temperature dependence of haze.

Further, the graft ratio measured by fractionating the multi-layer structure acrylic polymer in the present invention with acetone is 20 to 40%, preferably 20 to 30%. If the graft ratio is less than 20%, the resulting thermoplastic acrylic resin composition is inferior in impact resistance and temperature dependency of haze, and if it exceeds 30%, the impact resistance is inferior.

The multilayer structure acrylic polymer of the present invention is blended with an acrylic resin by setting a specific range in the above-mentioned soft layer polymer / (innermost hard layer polymer + soft layer polymer) weight ratio and graft ratio. When a thermoplastic acrylic resin composition is obtained in this way, it is considered that both impact resistance and temperature dependence of haze can attain high levels.

The multi-layered acrylic polymer in the present invention is produced by sequential multi-stage polymerization, and it is preferable to use an emulsion polymerization method as a polymerization method. However, the method is not particularly limited to this, and the emulsion can also be produced by an emulsion suspension polymerization method in which after the emulsion polymerization up to the soft layer, it is converted into a suspension system during the outermost hard layer polymerization.

Here, examples of the alkyl acrylate having an alkyl group having 1 to 8 carbon atoms include methyl acrylate, ethyl acrylate, and n-butyl acrylate 2-ethylhexyl acrylate, and n-butyl acrylate is preferably used.

Examples of aromatic vinyl compounds include styrene and substituted styrene derivatives, with styrene being preferred.

The graft-linking monomer used in forming the innermost hard layer and soft layer polymer of the multi-layer structure acrylic polymer in the present invention is a polyfunctional monomer having different functional groups, for example, acrylic acid. , Methacrylic acid, maleic acid, allyl ester of fumaric acid, etc., and allyl methacrylate is preferably used.

Further, in forming the soft layer polymer, a polyfunctional crosslinking monomer may be used in combination with the above graft-bonding monomer. As the polyfunctional crosslinking monomer, a generally known crosslinking agent such as a divinyl compound, a diallyl compound, a diacrylic compound or a dimethacrylic compound can be used, but a diallyl compound is preferably used. Such a polyfunctional crosslinkable monomer is mixed in a monomer mixture for forming the soft layer in an amount of 3% by weight or less and then subjected to polymerization. Here, the amount of the polyfunctional crosslinkable monomer used is 3% by weight.
If it exceeds, the effect of imparting impact strength to the acrylic resin of the multi-layered acrylic polymer decreases, which is not preferable.

In addition, when forming the outermost hard layer, it is preferable to adjust the molecular weight by using a suitable chain transfer agent in order to improve the compatibility of the multilayer structure acrylic polymer with the thermoplastic acrylic resin. Examples of the chain transfer agent include compounds containing one or two or more mercapto groups. Alkyl mercaptans are generally used, and n-octyl mercaptan is preferable.

The average particle diameter of the multilayer structure acrylic polymer of the present invention is 0.
2 to 0.3 μm, preferably 0.23 to 0.27 μm. When the average particle size is less than 0.2 μm, the resulting thermoplastic acrylic resin composition is inferior in impact resistance, and when it exceeds 0.3 μm, inferior in transparency.

The tensile modulus of the insoluble portion when the multi-layered acrylic polymer is fractionated with acetone in the present invention is 1000 to 4000 Kg / cm ² .
When the elastic modulus is less than 1000 Kg / cm ² , the resulting thermoplastic acrylic resin composition is inferior in temperature dependence of haze 4000 Kg
If it exceeds / cm ² , the impact resistance is poor.

Although it is advantageous to use an emulsion polymerization method as described above for the production of the multilayer structure acrylic polymer of the present invention, a suitable polymerization temperature for forming the polymer or copolymer of each layer is Each layer is selected in the range of 30 to 120 ° C, preferably 50 to 100 ° C. Further, in order to form such a multilayer structure polymer, it is possible to form the polymer by sequentially adding and reacting each monomer or a mixture of monomers, a so-called seed polymerization method. It is advantageous to use At this time, when carrying out the polymerization of the second and subsequent layers, it is necessary to select the conditions such that new particles are not formed, but this can be realized by making the amount of the emulsifier used below the critical micelle concentration. it can. Whether or not new particles are generated can be confirmed by observation with an electron microscope.

The emulsifier used in emulsion polymerization is not particularly limited, and any one can be selected from those conventionally used. Examples thereof include long-chain alkylcarboxylic acid salts, sulfosuccinic acid alkyl ester salts, and alkylbenzene sulfonic acid salts.

The polymerization initiator used at this time is not particularly limited, and a commonly used inorganic initiator such as water-soluble persulfate or perborate alone or sulfite or thiosulfate can be used. Can also be used in combination as a redox initiator system. Furthermore, oil-soluble organic peroxide / ferrous iron salt,
Redox initiator systems such as organic peroxide / sodium sulfoxylate can also be used.

The multi-layered acrylic polymer obtained by such a polymerization method is obtained as a particulate solid by subjecting the state of the polymer latex to a treatment such as salting out, washing and drying by a known method.

A thermoplastic acrylic resin composition can be produced by melt-kneading the multi-layered acrylic polymer of the present invention with a thermoplastic acrylic resin. The thermoplastic acrylic resin used here is a known polymerization method, for example, a block. polymerization,
Those obtained by any method such as solution polymerization and suspension polymerization may be used.

The ratio of the multi-layered acrylic polymer in the composition is 5
The amount is preferably up to 40 parts by weight, and when it is less than 5 parts by weight, the impact resistance is insufficient, and when it exceeds 40 parts by weight, the color tone is poor.

When kneading to produce the acrylic resin composition, stabilizers, lubricants, dyes, pigments and the like can be added as necessary.

By injection-molding or extrusion-molding the acrylic resin composition thus obtained, it is possible to obtain a molded article which is excellent in transparency and impact resistance and has reduced haze temperature dependency.

Furthermore, the multi-layered acrylic polymer of the present invention is a homo- or copolymer of alkyl methacrylate other than methyl methacrylate, styrene, styrene derivative, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, etc., and further polycarbonate, polyamide, polyester. It can also be used by blending with the above.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited by this. The measurements in Examples and Comparative Examples were performed using the following methods or measuring instruments. Izod impact strength; ASTM D256 haze; 3mm thickness using integrating sphere haze meter
The haze of the test piece at 70 ° C. was measured. The results are shown in the ranks below.

A haze less than 5% B 〃 less than 10% C 〃 less than 15% D 〃 more than 15% Average particle size; Multilayer acrylic polymer latex is sampled, diluted with water to a solid content of 50 ppm, and spectroscopically measured. Absorbance at a wavelength of 550 nm was measured using a photometer. From this value, the average particle size was determined using a calibration curve prepared by similarly measuring the absorbance of a sample in which the latex particle size was measured from a transmission electron micrograph.

Graft ratio: About 1.00 g of a dry powdery multi-layered acrylic polymer was precisely weighed (W ₁ ), 30 ml of acetone was added, and the mixture was left standing overnight at room temperature and shaken for 2 hours. Centrifuge at 20000 rpm for 30 minutes at 5 ° C. After shaking, the supernatant was decanted off, 30 ml of acetone was newly added, and the mixture was shaken at room temperature for 1 hour. After shaking, 30 at 5 ° C, 20000 rpm
Centrifuge for minutes. The supernatant is decanted off and air dried overnight. After vacuum drying at 100 ° C. for 4 hours and cooling to room temperature in a desiccator, the weight of the residue is weighed (W ₂ ). The acetone insoluble portion (wt%) is calculated by the following formula (X).

Graft ratio (wt%) is calculated by the following formula, where A and B are the weight% of the innermost hard layer polymer and the soft layer polymer in the multilayer structure acrylic polymer, respectively.

Tensile elastic modulus; Insoluble part obtained by acetone fractionation is compression molded at 150 ° C to make a film, from which width 15 ± 0.5m
A test piece having a thickness of 0.50 ± 0.05 mm and a length of 100 ± 1 mm was prepared. Distance between chucks is 50 mm and tensile speed is measured using a tensile tester.
It was measured at 50 mm / min.

The abbreviations used in Examples and Comparative Examples represent the following compounds.

MMA; methyl methacrylate BA; n-butyl acrylate St; styrene MA; methyl acrylate ALMA; allyl methacrylate PEGDA; polyethylene glycol diacrylate (molecular weight
200 or 600) n-OM; n-octyl mercaptan HMBT; 2- (2'-hydroxy-5'-methylphenyl)
Benzotriazole Example 1 Ion-exchanged water 6860 m was placed in a reactor with a reflux condenser having an internal volume of 10 l.
l, 13.7 g of sodium dihexyl sulfosuccinate was added, and the mixture was stirred at a rotation speed of 250 rpm while stirring at 75 ° C under a nitrogen atmosphere.
The temperature was raised to 0, and there was virtually no effect of oxygen.

222 g of the mixture (I-1) consisting of MMA907g, BA33g, HMBT0.28g and ALMA0.93g were added all at once, and after 5 minutes, 0.22g of ammonium persulfate was added. 40 minutes later (I-
The remaining 719 g of 1) was continuously added over 20 minutes, and after the addition was completed, it was held for another 60 minutes. Then, after adding 1.01 g of ammonium persulfate, BA1067 g,
A mixture of St219g, HMBT0.39g ALMA27.3g (I-
2) was continuously added over 140 minutes, and after the addition was completed, it was kept for 180 minutes.

Next, after adding 0.30 g of ammonium persulfate, 730 g of MMA,
BA26.5g, HMBT0.22g n-OM0.76g6 mixture (I-
3) was continuously added over 40 minutes, and after the addition was completed, the temperature was raised to 95 ° C. and kept for 30 minutes.

A small amount of the latex thus obtained was sampled, and the average particle size was determined by absorptiometry.

The remaining latex was poured into a 3% by weight aqueous solution of sodium sulfate to salt out and coagulate, and then dehydration and washing were repeated, followed by drying to obtain a multilayer structure acrylic polymer (I).
Got

The multi-layered acrylic polymer (I) was fractionated with acetone and the graft ratio was measured to be 23%. Also, the acetone insoluble portion was subjected to compression molding and the tensile elastic modulus was measured, and it was found to be 2500 Kg / cm ² .

30 parts by weight of this multi-layered acrylic polymer (I) and MMA / MA
Copolymer (II) [MMA / MA = 94/6 weight ratio, η _sp /C=0.70dl
/ g (0.30 g / dl chloroform solution, 25 ° C)] 70 parts by weight were mixed with a Henschel mixer for 20 minutes, and then a 30 mm vented twin-screw extruder (type A manufactured by Nakatani Machinery Co., Ltd.) was used.
Pelletized at 260 ° C. In-line screw injection molding machine (TOSHIBA MACHINE CO., LTD. IS-75S)
Using a mold, predetermined test pieces were prepared under the conditions of a molding temperature of 250 ° C., an injection pressure of 900 kgf / cm ² and a mold temperature of 50 ° C., and physical properties were measured.

The obtained resin composition was excellent in transparency and haze temperature dependency, and also had good impact resistance. The results are shown in Table-1.

Example 2 In Example 1, the mixture constituting (I-1) was added to MM
A1075g, BA39g, HMBT0.33g, ALMA1.11g, and the mixture constituting (I-2) is BA1173g, St241
g, HMBT0.43 g, ALMA30.0 g, and the mixture constituting (I-3) was MMA608 g, BA22 g, HMBT0.
The same procedure as in Example 1 was carried out except that 18 g and n-OM 0.63 g were used. The results are shown in Table-1.

Example 3 In Example 1, the mixture constituting (I-1) was added to MM
A1047g, BA67g, HMBT0.33g, ALMA1.11g, and the mixture constituting (I-2) is BA1058g, St228
g, HMBT0.39g, ALMA27.3g and PEGDA (molecular weight 200) 2.5g
Was carried out in the same manner as in Example 1, except that the mixture constituting (I-3) was composed of MMA711g, BA45g, HMBT0.22g, and n-OM0.76g. The results are shown in Table-1.

Example 4 In Example 1, the mixture constituting (I-1) was added to MM
The same procedure as in Example 1 was carried out except that A1075 g, BA39 g, HMBT0.33 g and ALMA1.11 g were used. The results are shown in Table-1.

Example 5 In Example 4, the mixture constituting (I-3) was added to MM
The same procedure as in Example 4 was performed, except that A854g, BA31g, HMBT0.26g, and n-OM0.89g were used. Table of results
Shown in 1.

Example 6 In Example 5, the mixture constituting (I-1) was added to MM
The same procedure as in Example 5 was performed except that A1161g, BA42g, HMBT0.36g and ALMA0.35g were used. The results are shown in Table-1.

Example 7 The procedure of Example 3 was repeated except that the amount of sodium dihexylsulfosuccinate used was 20.6 g. The results are shown in Table-1.

Comparative Example 1 A reactor with a reflux condenser having an internal volume of 10 l was charged with 6000 m of ion-exchanged water.
l, 12g of sodium dihexyl sulfosuccinate was added,
While stirring at a rotation speed of 250 rpm, the temperature was raised to 70 ° C. under a nitrogen atmosphere to virtually eliminate the influence of oxygen. After adding ammonium persulfate 1.6g, MMA928g, BA56g, HMBT0.24
A mixture (I-1) consisting of g and 2.4 g of ALMA was continuously added over 60 minutes, and the mixture was kept for 30 minutes after the addition was completed.
The polymer latex thus produced was cooled to 40 ° C., St 28 g was added, and the mixture was stirred for 60 minutes. Next BA112g, HMB
A mixture (I-2) consisting of T0.08 g, ALMA 1.2 g and PEGDA (molecular weight 600) 1.2 g was added, and the mixture was further stirred for 60 minutes.

Next, this latex was heated to 70 ° C., and after adding 1.6 g of ammonium persulfate, BA236g, St56g, HMBT0.16g, AL
A mixture of 2.8 g MA and 2.8 g PEGDA (molecular weight 600) (I
-3) was continuously added over 100 minutes, and the addition was continued for another 60 minutes.

Finally, a mixture (I-4) consisting of MMA916g, BA68g, n-OM2.8g and HMBT0.32g was continuously added over 20 minutes,
After the addition was completed, the temperature was maintained for another 30 minutes, then the temperature was raised to 95 ° C. and the temperature was maintained for 1 hour.

The subsequent steps were performed in the same manner as in Example 1.

Comparative Example 2 A reactor similar to that of Example 1 was charged with 6860 ml of ion-exchanged water and 13.72 g of sodium dihexylsulfosuccinate, and 250 r
While stirring at a rotation speed of pm, the temperature was raised to 70 ° C. under a nitrogen atmosphere.

0.74 g of ammonium persulfate was added. 10 minutes later, MMA
Mixture (I-1) consisting of 238 g, BA 16.3 g and ALMA 0.64 g
Was continuously added over 10 minutes, and after addition was completed, it was held for 30 minutes.

Then 2.85 g of ammonium persulfate was added. After 10 minutes, a mixture consisting of BA1443g, St338g and ALMA18.9g (I
-2) was continuously added over 140 minutes, and it was held for 150 minutes after the addition was completed.

Next, 1.22 g of ammonium persulfate was added. After 10 minutes, a mixture (I-3) consisting of MMA718g, BA45.8g and n-OM2.29g was continuously added over 50 minutes, and after the addition was completed, the mixture was kept for 70 minutes.

The latex thus obtained was treated in the same manner as in Example 1, and kneaded, molded and evaluated.

Comparative Example 3 Comparative Example 3 was carried out in the same manner as Comparative Example 3 except that the addition time of (I-1) was changed to 20 minutes, and finally the temperature was raised to 95 ° C. and maintained for 60 minutes.

Comparative Example 4 The same reactor as in Example 1 was charged with 6860 ml of ion-exchanged water and 13.7 g of sodium dihexyl sulfosuccinate, and 250 rpm
While stirring at a rotation speed of m, the temperature was raised to 75 ° C. under a nitrogen atmosphere, and the effect of oxygen was virtually eliminated.

After adding ammonium persulfate 0.22g, MMA746g, BA1
0, HMBT 0.23 g, and ALMA 0.38 g (I-
1) was continuously added over 60 minutes, and after the addition was completed, it was kept for 60 minutes.

Next, after adding 0.96 g of ammonium persulfate, BA990 g, S
t232g, HMBT0.37g, ALMA13.0g and PEDGA (molecular weight 200)
The mixture (I-2) consisting of 1.59 g was continuously added over 130 minutes, and the mixture was kept for 180 minutes after the addition was completed.

Next, after adding 0.29 g of ammonium persulfate, MMA711 g,
A mixture consisting of BA9g, HMBT0.22g and n-OM1.44g (I-
3) is continuously added over 40 minutes, and after the addition is completed,
Hold for 60 minutes. Then, the temperature was raised to 95 ° C. and held for a minute.

The latex thus obtained was treated in the same manner as in Example 1, and kneaded, molded and evaluated.

Comparative Example 5 The procedure of Example 3 was repeated, except that the amount of ALMA in the mixture constituting (I-2) was changed to 6.8 g.

Comparative Example 6 The procedure of Example 3 was repeated, except that ALMA in the mixture constituting (I-2) was changed to 41.7 g. The results are shown in Table-1.

Comparative Example 7 The same procedure as in Example 1 was carried out except that 27.4 g of sodium dioctylsulfosuccinate was used in Example 1 and (I-1) was continuously added over 20 minutes without division.

Table 1 shows the physical property evaluation results of the test pieces in these comparative examples.
Shown in.

As described above, when the content deviates from the range of the present invention, a composition excellent in impact resistance and haze temperature dependence cannot be obtained.

[Advantages of the Invention] According to the present invention, the drawbacks of the conventional multi-layered acrylic polymer are improved, and the acrylic resin has excellent transparency and molding processability, and also has impact resistance and haze. An acrylic resin composition having excellent temperature dependence can be provided.

Claims (2)

[Claims] (A) 90 to 99% by weight of methyl methacrylate, 1 to 10% by weight of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and allyl of an α, β-unsaturated carboxylic acid copolymerizable therewith. 25 to 45% by weight of the innermost hard layer polymer obtained by polymerizing a monomer mixture consisting of 0.01 to 0.3% by weight of a graft-bonding monomer consisting of at least one selected from the group consisting of methallyl, and crotyl ester. b) 70 to 90% by weight of n-butyl acrylate, 10 to 30% by weight of styrene, and allyl of an α, β-unsaturated carboxylic acid copolymerizable therewith, in the presence of the innermost hard layer polymer.
35 to 45% by weight of a soft layer polymer obtained by polymerizing a monomer mixture of 1.5 to 3.0% by weight of a graft-bonding monomer of at least one selected from methallyl or crotyl ester, (c) the above The outermost hard layer weight obtained by polymerizing a monomer mixture having 90 to 99% by weight of methyl methacrylate and an alkyl group having 1 to 8 carbon atoms in the presence of a polymer composed of an innermost hard layer and a soft layer. And (d) the soft layer polymer / (innermost hard layer polymer + soft layer polymer) has a weight ratio of 0.45 to 0.57, and (e) an average particle diameter of 0.2 to A multi-layered acrylic polymer having a thickness of 0.3 μm, and when the multi-layered acrylic polymer is further fractionated with acetone, (f) the graft ratio is 20 to 40% by weight, and (g) the acetone Tensile elastic modulus of insoluble part is 1000-40
A multi-layered acrylic polymer characterized in that it is 00 kg / cm ² . 2. The multi-layered acrylic polymer according to claim 1, wherein the graft-bonding monomer is at least one selected from allyl esters of acrylic acid, methacrylic acid, maleic acid and fumaric acid. .