JPH0356588B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved thermoplastic acrylic resin composition, and more specifically to an acrylic resin composition with excellent heat resistance and impact resistance. Acrylic resin has the advantages of excellent transparency, weather resistance, moldability, and beautiful appearance.
Widely used both indoors and outdoors. However, this acrylic resin does not necessarily have sufficient impact strength, and when it comes into contact with certain solvents, it tends to craze or crack, especially when internal stress or external stress is applied. Improvements were desired. To improve the impact resistance of acrylic resin, a method is generally used to blend rubber into the hard resin layer. For example, blending a polymer with a multilayer structure of three or more layers with a hard thermoplastic polymer is used. Methods have been proposed to improve impact resistance without compromising transparency. The present inventors also discovered an acrylic resin composition with excellent impact resistance, good transparency, weather resistance, and moldability, and filed a patent application. (Patent Application No. 56-84307). However, the acrylic resin compositions obtained by these methods have a low heat deformation temperature, which significantly narrows the range of their use, which is a practical problem. The present inventors conducted intensive studies to develop an acrylic resin composition with high impact resistance while maintaining a high heat deformation temperature, and found that a specific heat resistant acrylic copolymer (A) and a specific The present inventors have discovered that the objective can be achieved by blending the acrylic polymer (B) with a multilayer structure, and have completed the present invention. That is, the present invention includes [I] 41 to 97.5 mol% of methyl methacrylate, 0 to 5 mol% of alkyl acrylate having 1 to 4 carbon atoms, 1 to 26 mol% of maleic anhydride, and styrene.
an acrylic copolymer (A) having a molar ratio of 1.5 to 60 mol% and styrene to maleic anhydride of 1:1.5 to 1:5; A hard first layer consisting of a methyl methacrylate polymer or a copolymer mainly composed of methyl methacrylate with a point of 25°C or higher;
0.1 to 5% by weight of a polyfunctional grafting agent based on the total weight of the mixture, which forms a copolymer at 25°C or lower and is mainly composed of alkyl acrylate and further includes at least one of a copolymerizable monomer and a polyfunctional crosslinking agent. A soft second layer obtained by emulsion polymerization of a mixture containing
forming a polymer or copolymer at 25°C or higher;
A hard third layer having a molecular weight that gradually decreases from the inside to the outside, obtained by emulsion polymerization of methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate in the presence of the second layer. Multilayer structure acrylic polymer (B) consisting of
The blend ratio of (A):(B) is 3:1.
The present invention relates to an acrylic resin composition with excellent heat resistance and impact resistance with a ratio of ~1:1.5. (Method for producing acrylic copolymer (A)) Acrylic copolymer (A) contains 41 to 97.5 mol% of methyl methacrylate, preferably 41 to 70 mol%, and methyl as an alkyl alkylate having 1 to 4 carbon atoms. Acrylate ethyl acrylate, butyl acrylate 0-5 mol%, maleic anhydride 1-26
mol%, preferably 12-22 mol% and styrene
It is a copolymer consisting of 1.5 to 60 mol%, preferably 18 to 40 mol% of the constituent components. If the amount of the component deviates from this range, the effects of the present invention cannot be obtained. Also,
In the above structure, it is extremely important that the molar ratio of maleic anhydride to styrene is in the range of 1:1.5 to 1:5, and even if it deviates from this range, the object of the present invention will not be achieved. If the ratio of styrene to maleic anhydride is less than the above range, the effect of improving heat deformation resistance will be insufficient, and if it exceeds the ratio, physical properties, particularly mechanical strength such as tensile strength, will deteriorate, which is not preferred. A particularly preferred ratio of styrene to maleic anhydride is 2 to 3 moles. Under these conditions of introduction of maleic anhydride and styrene, if the methyl methacrylate content is less than 40 mol%, the mechanical strength will be low, and if the methyl methacrylate content exceeds 97.5 mol%, satisfactory heat resistance will not be obtained. Furthermore, if maleic anhydride is less than 1 mol% or styrene is less than 1.5 mol%, the effect of improving heat deformation resistance will be small, and if maleic anhydride exceeds 26 mol%, mechanical strength will decrease, and if styrene is 60 mol%.
Even if it exceeds this, the strength of the resin tends to decrease, which is not preferable. Further, it is preferable to use 0 to 5 mol% of the alkyl acrylate, and by using the alkyl acrylate, the heat decomposition resistance can be improved. If it is used in an amount exceeding 5 mol%, the heat deformation resistance temperature decreases, which is not preferable. Furthermore, in the present invention, it is important that the monomer remaining in such a copolymer resin is 1.5% by weight or less, and preferably 1.0% by weight or less. If this amount exceeds 1.5% by weight, it is not preferable because its plasticizing effect lowers heat deformation resistance and causes problems such as significant deterioration of appearance due to foaming caused by volatile matter during heat processing. In particular, the amount of residual maleic anhydride must be 0.1% by weight or less, and since a polymer with a large amount of residual maleic anhydride exhibits a yellow color, it is desirable to reduce this amount as much as possible. The apparent molecular weight of the copolymer that is the acrylic copolymer (A) of the present invention needs to be from 80,000 to 250,000 as measured by GPC. When the molecular weight is less than 80,000, mechanical properties such as tensile strength are significantly reduced, which is not preferable. Moreover, if it exceeds 250,000, the viscosity during melting becomes high and injection molding is not possible, which is not preferable. Thermal decomposition index α of the acrylic copolymer (A) of the present invention
must be 7 or less; if it exceeds 7, silver etc. will be generated during injection molding, which is undesirable. The amount of residual maleic anhydride in the copolymer is
If it exceeds 0.1%, the thermal decomposition index α exceeds 7,
Furthermore, it is difficult to reduce the thermal decomposition index α to 7 or less unless the blended molar ratio of maleic anhydride and styrene is specified, the type and amount of the initiator, and the type of chain transfer agent. Bulk polymerization using a radical color initiator is suitable for the polymerization of the acrylic polymer (A) of the present invention, and liquid polymerization can also be employed. In copolymerization, for example, azobisisobutyronitrile, 2,
Azo initiators such as 2'-azobis(2,4-dimethylvaleronitrile) and peroxides such as benzoyl peroxide and t-butylperoxy 2-ethylhexanoate can be used. When lauryl peroxide or decanoyl peroxide is used, it is particularly preferable because it has excellent transparency, hot water whitening resistance, and the like. As the chain transfer agent, alkyl mercaptans such as butyl mercaptan and octyl mercaptan can be used. It is extremely important that the residual amount of maleic anhydride in the acrylic copolymer (A) of the present invention is 0.1% by weight or less. However, according to conventional methods, it has been difficult to reduce the residual amount of maleic anhydride. For example, according to the method of Example 1 disclosed in French Patent No. 1,476,215, the remaining amount of maleic anhydride in the copolymer obtained is 0.2% by weight, and the object of the present invention cannot be achieved. A particularly preferred method for producing the acrylic copolymer (A) of the present invention includes two endless belts made of surface-treated stainless steel that run opposite each other, and a pair of endless belts that run at the same speed on both sides of the belt. A molding space is formed with a continuous soft vinyl chloride gasket, the thickness of the resulting cast polymer is kept constant, and a degassed partial polymer of the above constituent monomers is continuously injected and heated at 40°C. After passing through the first polymerization zone at ~80°C, it passes through the second polymerization zone and slow cooling zone at 110~130°C to obtain a colorless and transparent plate. Also, if necessary, crush the board,
Pellets can also be obtained while removing volatile components using a vented extruder. In order to obtain a copolymer with a small residual amount of maleic anhydride in this production method, it is very important that the molar ratio of styrene to maleic anhydride is in the range of 1:1.5 to 1:5. is 1:
If it is lower than 1.5, it is not possible to obtain a transparent plate with a low residual amount of maleic anhydride. It is also possible to crush the plate and remove the volatile matter using a vented extruder, but if the amount of maleic anhydride remaining in the transparent plate is 0.1% by weight or more, the resulting pellets It cannot be used for practical purposes because it is colored yellow. Another preferred method of production is continuous bulk polymerization. 30% by weight or more in the first reactor, which carries out a homogeneous polymerization reaction at a constant temperature in the range of 50°C to 150°C.
In the copolymer chain obtained in the method of polymerizing to a polymerization rate of 70% by weight, and then increasing the polymerization rate by 10% to 30% by weight in a second reactor consisting of a flow reactor, By controlling the molar ratio of styrene to maleic anhydride in the range of 1:1.5 to 1:5, monomers, solvents, etc. remaining in the polymer mixture exiting the second reactor are eliminated. After reacting so that the concentration ratio of maleic anhydride in the volatile components is 2.5% by weight or less,
By sending the polymer to a devolatilization step, a polymer having a maleic anhydride concentration of 0.1% by weight or less can be obtained.
If the molar ratio of styrene to maleic anhydride is less than 1:1.5, the proportion of maleic anhydride in the polymerization mixture sent to the devolatilization step should be
It is difficult to reduce the content to 2.5% by weight or less. (Production method of multilayer structure acrylic polymer (B)) Multilayer structure acrylic polymer (B) is obtained by () emulsion polymerization and has a glass transition point of
A hard first layer consisting of a methyl methacrylate polymer or a copolymer mainly composed of methyl methacrylate at a temperature of 25°C or higher, () a glass transition point of 25 when polymerized alone.
℃ or less, mainly composed of alkyl acrylate, and further containing 0.1 to 5% by weight of a polyfunctional grafting agent based on the total weight of the mixture with at least one of a copolymerizable monomer and a polyfunctional crosslinking agent. A soft second layer obtained by emulsion polymerization of a mixture containing the mixture in the presence of the first layer and () having a glass transition point of 25 when polymerized alone.
℃ or higher to form a polymer or copolymer, obtained by emulsion polymerization of methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate in the presence of a second layer, gradually decreasing from the inside to the outside. It is a multilayer structure acrylic polymer consisting of a hard third layer with a molecular weight of As described above, the multilayer structure acrylic polymer of the present invention is formed from three layers (), (), and (), but the material for the first layer () is a homopolymer of methyl methacrylate or A copolymer mainly composed of methyl methacrylate is used. A copolymer mainly composed of methyl methacrylate is a copolymer containing 80% by weight or more of methyl methacrylate and 20% by weight or less of other copolymerizable monomers, and a copolymer with a smaller amount of methyl methacrylate than this. is undesirable because it deteriorates the characteristics of acrylic resin, such as transparency, weather resistance, beauty of appearance, and moldability. Examples of monomers copolymerizable with methyl methacrylate include ethyl methacrylate,
Vinyl compounds such as propyl methacrylate, butyl methacrylate, allyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methacrylic acid, acrylic acid, acrylonitrile, vinyl acetate, vinyl chloride, and styrene are used. The polymer or copolymer of this first layer needs to have a glass transition point (Tg) of 25°C or higher, preferably 50°C or higher. If a glass transition point of less than 25° C. is used, a molded article with poor stress whitening resistance will be obtained. Next, the material for the second layer () is a copolymer mainly composed of alkyl acrylate, which has a glass transition point when polymerized in the absence of the first layer.
An acrylic rubber whose temperature is below 25°C, preferably below 0°C is used. If the glass transition point of this material is higher than 25°C, sufficient impact resistance cannot be obtained. As the above alkyl acrylate, those having an alkyl group having 1 to 8 carbon atoms are preferred, and particularly preferred are n-butyl acrylate, 2-
It is ethylhexyl acrylate. Since these alkyl acrylate copolymers have a refractive index different from that of methyl methacrylate polymers, the resulting resin will become cloudy when molded as it is. Therefore, when transparency is required, transparency can be improved by copolymerizing the alkyl acrylate with other monomers to match the refractive index of the rubber layer to that of the methyl methacrylate polymer. It is necessary to do so. Further, a polyfunctional crosslinking agent may be copolymerized in order to impart appropriate elasticity to the rubber layer. As the polyfunctional crosslinking agent, commonly used crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, and dimethacrylic compounds can be used. Furthermore, a polyfunctional grafting agent is used to effect chemical bonding with the third layer (). Examples of the polyfunctional grafting agent include polyfunctional monomers having different functional groups, such as allyl esters such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid, with allyl acrylate and allyl methacrylate being particularly preferred. The third layer () is a hard layer of a polymer or copolymer with a glass transition point of 25°C or higher when polymerized alone, and is a hard layer of methyl methacrylate homopolymer or 80% by weight or more of methyl methacrylate, alkyl acrylate. 20% by weight or less of at least one type and, if desired, other copolymerizable monofunctional monomers
% by weight or less. The above alkyl acrylate and copolymerizable monomer include:
The same ones as shown for the second layer () and the first layer () can be used, respectively. This third layer (2) must consist of multi-layered layers in which the inner layer has a higher molecular weight and the molecular weight gradually decreases toward the outer layer. Such a multi-layered structure is achieved by dividing the polymerization into two or more times to form the third layer, and each time the molecular weight is gradually decreased by, for example, increasing the amount of chain transfer agent. brought about by lowering. The molecular weight of each step formed at this time is determined by polymerizing the monomer mixture used each time individually under the same conditions and measuring the molecular weight of the resulting polymer. If the molecular weight is gradually decreased from the inside to the outside in this way, stress whitening resistance in particular can be significantly improved, but if the molecular weight of the third layer () is kept constant throughout the layer, Depending on their molecular weight, they have poor fluidity and stress whitening resistance. The molecular weight of this third layer () is 300,000 to 5,000,000 at the innermost molecular weight part, preferably
It is best to set it in the range of 500000 to 2000000. If the molecular weight of this part is less than 300,000, good stress whitening resistance cannot be obtained, and the molecular weight
Setting it to more than 5,000,000 is not practical because it requires special reaction conditions. On the other hand, the molecular weight of the smallest outer molecular weight part of the third layer () is preferably 60,000 to 200,000.
It is best to set it in the range of 80000 to 150000. If the molecular weight of this part is larger than 200,000, fluidity will decrease, and if it is smaller than 60,000, solvent resistance will decrease.
Strength decreases. In addition, in the present invention, the first layer (A) and the second layer (B)
There is no particular restriction on the structure, and any structure can be used as long as the glass transition point and composition satisfy the above-mentioned conditions. For example, a structure with a so-called intermediate layer between the first layer and the second layer with a gradient composition, a structure with a so-called graft layer in which a large amount of polyfunctional grafting agent is added to the intermediate layer, and a structure with a so-called graft layer in which a large amount of polyfunctional grafting agent is added to the intermediate layer; It is possible to have a structure in which more than one stage of pseudolayers are provided, and the concentration of a polyfunctional crosslinking agent or a polyfunctional grafting agent is varied for each pseudolayer. The multilayered acrylic polymer of the present invention is obtained by emulsion polymerization. In this case, it is necessary to select conditions that will not generate new particles when polymerizing the second layer () and third layer (), and for this purpose it is recommended to use the so-called seed polymerization method. It's advantageous. Then, when polymerizing the next layer, it is necessary not to add a new emulsifier, or even if it is necessary to add it, it is necessary to keep it within a range that does not generate new particles. The presence or absence of new particle generation can be easily detected using an electron microscope. To suitably prepare the multilayer structure acrylic polymer of the present invention, the monomer or monomers necessary for forming the first layer (2) are added to water containing additives necessary for emulsion polymerization such as an emulsifier. The mixture and a polymerization initiator such as a peroxide catalyst or a redox catalyst are added, and polymerization is carried out while stirring. Once this polymerization is complete, a mixture of the monomers, polyfunctional grafting agent, and optionally added polyfunctional crosslinking agent necessary for forming the second layer (2) is added and reacted. At this time, if necessary, a polymerization initiator can be added. When the formation of the second layer (2) is completed, the raw material mixtures necessary to form the polymers at each stage of the third layer (2) described above are added and reacted. At this time, in order to form a layer in which the inner layer has the largest molecular weight and the molecular weight gradually decreases toward the outer layer, a chain transfer agent such as alkyl mercaptan is used, and the amount of the chain transfer agent is increased or decreased to form a layer. Adjust the molecular weight of the polymer to be used. The multilayered acrylic polymer thus obtained is then subjected to a suitable aggregation treatment and separated and recovered. Acrylic copolymer obtained as above
The most preferred method for blending (A) and the multilayered acrylic polymer (B) is a method in which (A) and (B) are mixed in a preliminary mixing tank and then melt-kneaded in an extruder. Alternatively, it can also be obtained by dissolving the multi-vessel structure acrylic polymer (B) in an MMA monomer or the like and polymerizing the acrylic copolymer (A). The blending ratio of (A) and (B) is particularly important for obtaining the composition of the invention. (A):(B) is 3:1~1:1.5
The ratio is particularly preferably 1:1. If the ratio (A):(B) is greater than 3:1, the Izot impact value will be low, which is undesirable. If the ratio (A):(B) is less than 1:1.5, the HDT decreases and the object of the present invention cannot be satisfied. The composition of the present invention can improve transparency by making the refractive index of copolymer (A) and polymer (B) constant. (a) Measurement of Molecular Weight of GPC The molecular weight of GPC is generally measured as described in, for example, the literature "Gel Chromatography (Basic Edition)" (written by Takeda et al., published by Kodansha, pp. 97-122). For example, the apparent molecular weight of the copolymer of the present invention was measured as follows. HSG-20, 50 (Shimadzu Corporation) as a column
A calibration curve was created using standard polystyrene manufactured by Pressure Chemical Company. The elution curve obtained using a sample solution in which 75 mg of the copolymer was dissolved in 30 ml of methyl ethyl ketone was divided into equal parts, the height of the curve at the dividing points was measured, and the weight average molecular weight Mw was determined using the following formula. The carrier used methyl ethyl ketone as the solvent and the flow rate was 1.
Measurements are carried out at ~1.5 ml/min and 30°C. However, Hi is the height of the elution curve at split point i, Mi(p) is the molecular weight of standard polystyrene at split point i, and Q _M and Q _P are the Q factors of the copolymer and polystyrene, which are 40 and 41, respectively. . (b) Measurement of thermal decomposition index α Using pyrolysis gas chromatography (DY-IA, G (6A) manufactured by Shimadzu Corporation), the copolymer was decomposed at 450°C in an N ₂ atmosphere, and the total amount of decomposition occurring in 60 minutes was measured. Detect and integrate the decomposed gas and let this be x,
The gas decomposed and generated in 30 minutes at 290°C was detected and integrated, and this was set as y, and α was calculated as the thermal decomposition index α=y/x. (c) Pyrolysis weight loss measurement method Measurement was performed using a simultaneous differential thermogravimetric measurement device (SSC/560GH) manufactured by Daini Seikosha. sample
Using 40 to 45 mg, measurements at the experimental temperature were started after preheating at 150 °C for 10 minutes under a _N2 atmosphere. The details of the invention will be specifically explained below with reference to Examples. The heat deformation resistance was evaluated by measuring the HDT specified in ASTM-D648 (no heat treatment). The residual monomer was measured by the GO method. It was measured according to a conventional method. The melt index was measured according to ASTM-D1238 (I conditions), and the bending strength was measured according to ASTM-D1238 (I conditions).
Measured according to ASTM-D790. Izot impact strength was measured using the ASTM-D256 method. Next, the present invention will be explained in more detail with reference to Examples. Example 1 (Production of acrylic copolymer (A)) A first reactor consisting of a homogeneous stirring tank with a reaction volume of 10, followed by a reaction volume consisting of L/D = 20
A polymer was obtained using an apparatus consisting of a 1.5 plug flow second reactor and a three-stage vented extruder as a devolatilization device. Methyl methacrylate 72, styrene as raw materials
18, a mixture consisting of a monomer consisting of 9 maleic anhydride and 1 methyl acrylate, a catalyst consisting of 0.45 of lauryl peroxide, 0.11 of octyl mercaptan, and 42.9 parts by weight of methyl ethyl ketone was heated countercurrently with nitrogen gas in a deoxidizing tower. Contact with oxygen concentration 1/20
A reaction stock solution reduced in concentration to below was obtained and continuously supplied to the first reactor. The first reactor is operated at 78°C with a residence time of 4 hours. Inside is nitrogen gas 6
It is pressurized to Kg/cm ² G to prevent air from entering.
Subsequently, the residence time was increased in the second plug flow reactor, where the temperature was gradually increased to 78°C at the inlet and 110°C at the outlet.
The reaction was carried out in 0.6 hours. After 20 hours of reaction, the reaction mixture was sampled from the outlet of the first reactor and the second reactor, and composition analysis was performed. As a result, the polymerization reaction rate was 55% and 80%. The composition ratio of the polymer was determined by infrared absorption spectroscopy, acid drop method, and pyrolysis gas chromatography.In the first reactor, 64.7% of methyl methacrylate and 64.7% of styrene were used.
22.0, maleic anhydride 12.1, methyl acrylate
1.0 mol%, at the outlet of the second reactor: 67.5 methyl methacrylate, 20.5 styrene, maleic anhydride
10.9, methyl acrylate 1.0 mol%. On the other hand, the volatile components in the first reactor were 41.3% by weight of methyl methacrylate, 6.5% by weight of styrene, 2.9% by weight of maleic anhydride, 0.5% by weight of methyl acrylate, and 48.8% by weight of methyl ethyl ketone. At the outlet of the second reactor, methyl methacrylate 28.7, styrene
1.9, maleic anhydride 0.9, methyl acrylate
0.3, and 68.2% by weight of methyl ethyl ketone.
These polymerization reaction materials at the outlet of the second reactor are devolatilized by reducing the pressure to 150℃ under atmospheric pressure at the first vent, 20Tow at 220℃ at the second vent, and 4Tow at 220℃ at the third vent. Summer. The obtained polymer is
Methyl methacrylate 67.5, styrene 20.5, maleic anhydride 10.9, methyl acrylate 1.0 mol%
In the copolymer, residual monomers were detected at 300 ppm of methyl methacrylate, and styrene and maleic anhydride were below the detection limit of 100 ppm. The apparent molecular weight of the obtained pellets measured by GPO was 140,000, and the thermal decomposition index α was 3.0.
The thermal decomposition loss was 0.8% at 275°C for 10 minutes. Pressure mold the pellets in a press at 270℃ for 10 minutes,
A specimen of 100 x 4 mm was obtained. No air bubbles were detected anywhere in this specimen, and almost no coloring was observed. The HDT value of this specimen was 100°C and MI = 1.4. (Manufacture of multilayered acrylic polymer (B)) Add 5.7 g of distilled water, 20 g of dioctyl sodium sulfosuccinate as an emulsifier, and 1.2 g of Rongarit as a reducing agent to a 10-beaker equipped with a stirrer and a condenser, and dissolve uniformly. 220g of methyl methacrylate (hereinafter abbreviated as MMA) as the first layer;
n-butyl acrylate (hereinafter abbreviated as BA) 3.0
g. Allyl methacrylate (hereinafter abbreviated as ALMA)
Add a homogeneous solution of 0.8 g and 0.2 g of diisopropylbenzene hydroperoxide (hereinafter abbreviated as PBP).
Polymerization was carried out at 80°C. The reaction was completed in about 15 minutes. The Tg of the obtained polymer was 108°C. Next, as the second layer, BA1270g, styrene (hereinafter abbreviated as ST) 320g
g, diethylene glycol diacrylate (hereinafter
A homogeneous solution of 20 g of DEGA (abbreviated as DEGA), 13.0 g of MMA, and 1.6 g of PBP was added dropwise over 1 hour. The reaction was completed approximately 40 minutes after the completion of the dropwise addition. The Tg of the polymer obtained by polymerizing this product alone was -38°C.
Next, as the third layer, MMA340g, BA2.0g,
PBP0.3gn-octyl mercaptan (hereinafter OM
0.1 g of homogeneous solution was added. The molecular weight of the polymer obtained by polymerizing this substance alone is
1220000, Tg was 109℃. This stage of the reaction was completed in approximately 15 minutes. Next, OM as the third layer 2nd stage
A solution having the same composition as the first stage of the third layer was added, except that the amount of was changed to 1.0 g. A polymer obtained by polymerizing this product alone had a molecular weight of 117,000 and a Tg of 108°C. The reaction was completed in about 15 minutes at this stage. The temperature was then raised to 95°C and held for 1 hour. The obtained emulsion was poured into a 0.5% aluminum chloride aqueous solution to coagulate the polymer, which was washed five times with warm water and dried to obtain a white flocculent polymer. The acrylic copolymer (A) obtained as described above and the multilayer structure acrylic polymer (B) were pre-blended at a ratio of 1:1 using a 30 mmφ twin-screw extruder (manufactured by Nakatani Kikai).
The mixture was melted and kneaded. The obtained pellets were injection molded using an ounce injection molding machine (manufactured by Toshiba Machinery). Table 1 shows the physical property evaluation results. Comparative Examples 1-2 The acrylic copolymer (A) obtained in Example 1 was injection molded alone, and the results shown in Table 1 were obtained. (Comparative example 1)
Further, the multilayer structure acrylic polymer (B) obtained in Example 1 was mixed with a commercially available acrylic resin molding material (Delpet 80N, manufactured by Asahi Kasei Industries, Ltd.) at a ratio of 1:1, pelletized through an extruder, and then injection molded. The results shown in Table 1 were obtained. (Comparative Example 2) In the same manner as in Example 2 and Example 1, an acrylic copolymer (A) shown in Table 2 was obtained. Further, polymerization was carried out using the same equipment and under the same conditions as in Example 1, except that the monomer composition of the second layer was changed as shown in Table 2, to obtain a multilayered acrylic polymer (B). Example 1 The copolymer (A) and polymer (B) obtained as above were mixed at the blend ratio shown in Table 2.
Melt kneading and injection molding were carried out in the same manner as above to obtain the results shown in Table 2.

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Claims (1)

[Claims] 1. 41 to 97.5 mol% of methyl metatarylate, 0 to 5 mol% of alkyl acrylate having 1 to 4 carbon atoms, 1 to 26% of maleic anhydride, and 1.5 mol% of styrene.
~60 mol%, and a copolymer having a molar ratio of styrene to maleic anhydride of 1:1.5 to 1:5, wherein (a) the amount of residual maleic anhydride in the copolymer is 0.1;
% by weight or less, and the total amount of residual monomer is
1.5% by weight or less; (a) an acrylic material with an apparent molecular weight of 80,000 to 250,000 as measured by gel permeation chromatography (GPC); (c) a thermal decomposition index α of 7 or less. Copolymer (A) and 2() have a glass transition obtained by emulsion polymerization.
A hard first layer consisting of a methyl tacrylate polymer or a copolymer mainly composed of methacrylate at a temperature of 25°C or higher;
0.1 to 5% by weight of a polyfunctional grafting agent based on the total weight of the mixture, which forms a copolymer at 25°C or lower and is mainly composed of alkyl acrylate and further includes at least one of a copolymerizable monomer and a polyfunctional crosslinking agent. A soft second layer obtained by emulsion polymerization of a mixture containing
forming a polymer or copolymer at 25°C or higher;
A multilayer consisting of a hard third layer with a molecular weight that gradually decreases from the inside to the outside, obtained by emulsion polymerization of methyl methacrylate or a monomer mixture mainly composed of methyl methacrylate in the presence of a second layer. An acrylic resin composition having excellent heat resistance and impact resistance, comprising a structural acrylic polymer (B) and having a blend ratio of (A):(B) of 3:1 to 1:1.5.