THERMOPLASTIC RESIN COMPOSITION

Abstract: A thermoplastic resin composition substantially constituted of (A) 25 to 70 % by weight of a polyamide, (B) 25 to 70 % by weight of a polyphenylene ether and (C) 2 to 25 % by weight of a block copolymer having at least one polymer block mainly comprised of a vinyl aromatic compound and at least one polymer block mainly comprised of a conjugated diene compound having the content of the vinyl aromatic compound in the range of 25 to 85 % by weight; wherein said polyamide forms a continuous phase, and, in said continuous phase, said polyphenylene ether is dispersed to form a dispersed phase having its average particle diameter ranging from 0.5 to 10 µm, and further, substantially all of said block copolymer is micro-­ dispersed in the dispersed phase of the polyphenylene ether. The composition is widely used as outerplate materials or wheel caps of automobiles, electrical or electronical parts, especially various connectors used for automobiles, etc.

Description: TECHNICAL FIELD The present invention relates to an improvement of a thermoplastic resin composition mainly constituted of components comprising polyamide, polyphenylene ether and a rubber-like substance. More specifically, it relates to a thermoplastic resin composition in which the above three components constitute a blend system in a specified dispersion form, and which is excellently balanced in heat distortion resistance, impact resistance, oil resistance, stiffness, molding flow properties and so on. BACKGROUND ART Polyamide resins have excellent mechanical strength, oil resistance, abrasion resistance, thermal resistance, etc. and have been hitherto utilized in a great quantity as one of the most typical engineering plastics. However, the polyamides have disadvantages that they are poor in the properties such as dimensional stability, moisture absorption, heat distortion resistance under high load, and impact resistance in a dry state, as compared with other plastics. In contrast thereto, polyphenylene ether resins are resins having excellent dimensional stability, electrical properties, heat distortion resistance under high load, water resistance, etc., and have been industrially widely used in the form of a blend with polystyrene resins. The polyphenylene ether resins, however, have serious disadvantages that they have poor oil resistance and molding flow properties. Thus, attempts have been made to blend both of these resins for the purpose of making the most of the advantages inherent respectively in both of the resins and compensating the disadvantages in both of the resins with each other, and a great number of such resins have been also proposed hithertofore. Such resins include those obtained by simply blending both of the resins, in particular, by melt blending them (as disclosed in U.S. Patent No. 3,379,792 and U.S. Patent No. 4,338,421). Since, however, polyphenylene ethers and polyamides are hardly compatible with each other in nature, it is impossible to obtain a molded product having excellent mechanical strength from such a simple blend. Also known is a composition obtained by compounding as a compatibility-improving agent a copolymer of a styrene compound with an α, β-unsaturated dicarboxylic acid anhydride, together with polyphenylene ether and polyamide, and further adding a rubber-like substance as an impact resistance-reinforcing agent (as disclosed in U.S. Patent No. 4,339,376). Although in this composition the mechanical performance or oil resistance can be enhanced by virtue of the improvement in the compatibility, the attachment (presumably by graft polymerization) between both of the resins through the compatibility-improving agent becomes excessive to make so extremely fine the dispersion between both of resins that there may be accompanied with disadvantages such that the molding flow properties may be extremely lowered and the heat distortion resistance under high load cannot be sufficiently enhanced. There have been further proposed a process for producing a modified polymer by adding to a polyamide and a polyphenylene ether, a compound having (a) a carbon-carbon double bond or a carbon-carbon triple bond and (b) a functional group such as a carboxyl group and an acid anhydride group in the molecule thereof, followed by melt kneading (as disclosed in U.S. Patent No. 4,315,086), and a composition to which a rubber-like substance is further added (as disclosed in Japanese Unexamined Patent Publication No. 49753/1981). In these, however, there are disadvantages that sufficient impact resistance cannot be achieved and that molding flow properties are inferior. In other words, there has been found in conventional arts no process for obtaining a resin composition excellent and well balanced in any of the impact resistance, heat distortion resistance, stiffness and molding flow properties. In such circumstances, the present invention aims to meet the need for a thermoplastic resin composition excellently balance in heat distortion resistance, impact resistance, oil resistance, stiffness, molding flow properties, etc. in a blend system comprising polyamide and polyphenylene ether. The present inventors have made intensive studies to achieve the above purpose, and, as a result, found that the purpose can be achieved by controlling in a particular state the dispersion form of the three components in a composition comprising in a specified proportion a polyamide, a polyphenylene ether and, as a reinforcing agent, a rubber-like substance having a specified structured. The present invention has thus been accomplished based on such a finding. DISCLOSURE According to the present invention, there is provided a thermoplastic resin composition substantially constituted of (A) 25 to 70 % by weight of a polyamide, (B) 25 to 70 % by weight of a polyphenylene ether and (C) 2 to 25 % by weight of a block copolymer having at least one polymer block mainly comprised of a vinyl aromatic compound and at least one polymer block mainly comprised of a conjugated diene compound having the content of the vinyl aromatic compound in the range of 25 to 85 % by weight; wherein said polyamide forms a continuous phase, and, in said continuous phase, said polyphenylene ether is dispersed to form a dispersed phase having its average particle diameter ranging from 0.5 to 10 µm, and further, substantially all of said block copolymer is micro-dispersed in the dispersed phase of the polyphenylene ether. The resin composition of the present invention has excellent thermal resistance, stiffness, molding flow properties and oil resistance, since it has the structure such that the block copolymer has been micro-dispersed in the dispersed phase, the polyphenylene ether phase, without dispersing solely in the continuous phase of the polyamide. It is further considered that the impact resistance can be enhanced without impairing the above properties, since the resin composition has the structure such that the polyphenylene ether phase in which the block copolymer is microdispersed is finely dispersed in the polyamide phase. The polyphenylene ether used in the composition of the present invention comprises a repeating unit or units of the formula (I) and/or (II) shown below: wherein R₁, R₂, R₃, R₄, R₅ and R₆ may be the same or different and each represent a monovalent radical such as an alkyl group having 1 to 4 carbon atoms excluding tert-butyl group, an aryl group, a halogen atom and a hydrogen atom; provided that R₁ and R₂, as well as R₃ and R₄, each are not hydrogen at the same time, including a homopolymer comprising the constituent unit of Formula (I) or a copolymer comprising the constituent units of Formulae (I) and (II), and a graft copolymer obtained by graft polymerizing said copolymer with styrene. Typical examples of the homopolymer of polyphenylene ether may include homopolymers such as poly (2,6-dimethyl-1,4-phenylene) ether, poly(2-methyl-6-ethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene) ether, poly(2-ethyl-6-n-propyl-1,4-phenylene) ether, poly(2,6-di-n-propyl-1,4-phenylene) ether, poly(2-methyl-6-n-butyl-1,4-phenylene) ether, poly(2-ethyl-6-isopropyl-1,4-phenylene) ether, poly(2-methyl-6-chloro-1,4-phenylene) ether, poly(2-methyl-6-hydroxyethyl-1,4-phenylene) ether and poly(2-methyl-6-chloroethyl-1,4-phenylene) ether. The polyphenylene ether copolymer may include polyphenylene ether copolymers mainly comprised of a polyphenylene ether structure obtained by copolymerization with alkyl substituted phenols such as o-cresol and a 2,3,6-trimethylphenol represented by the formula: wherein R₃, R₄, R₅ and R₆ each represent a monovalent radical such as an alkyl group having 1 to 4 carbon atoms excluding tert-butyl group, an aryl group, a halogen atom and a hydrogen atom; provided that R₃ and R₄ each are not a hydrogen at the same time. The polyamide used in the composition of the present invention may be any of those having a bond in the main chain of the polymer and capable of being melted with heating. Typical examples thereof may include nylon 4, nylon 6, nylon 6,6, nylon 12, nylon 6,10, a polyamide from terephthalic acid and trimethylhexamethylenediamine, a polyamide from adipic acid and methaxylilenediamine, a polyamide from adipic acid, azelaic acid and 2,2-bis(p-aminocyclohexyl)-propane, a polyamide from terephthalic acid and 4,4′-diaminodicylcohexylmethane, a polyamide comprising combination of two or more of these, etc. Of these, particularly preferred is nylon 6, nylon 6,6, nylon 6,10 or a nylon 6-, 6,6- copolymer. In the block copolymer used in the composition of the present invention, it is required that substantially all of the copolymer is micro-dispersed in the polyphenylene ether phase present as a dispersed phase, and for such a purpose, the copolymer is required to be a rubber-like substance having stronger affinity for polyphenylene ether rather than polyamide. The block copolymer usable in the composition of the present invention is limited to a block copolymer having at least one polymer block mainly comprised of a vinyl aromatic compound and at least one polymer block mainly comprised of a conjugated diene compound having the content of the vinyl aromatic compound in the range of 25 to 85 % by weight. The content of the vinyl aromatic compound is preferably in the range of 30 to 70 % by weight, more preferably of 35 to 60 % by weight. When the content of the vinyl aromatic compound is less than 25 % by weight, none of the rubber-like substance can substantially be present in any blending conditions in the polyphenylene ether phase which is present as a dispersed phase. The content more than 85 % by weight may result in drastic decrease in the reinforcing effect as a rubber-like substance and cannot bring about sufficient impact resistance. When the content of the vinyl aromatic compound ranges from 25 to 30 % by weight, the block copolymer can be present in the polyphenylene ether phase, but the diameter of dispersed particles tends to be enlarged to lower the impact resistance. When the content of the vinyl aromatic compound ranges from 30 to 35 % by weight, the block copolymer can be present in the polyphenylene ether phase and also the diameter of dispersed particles of polyphenylene ether can be small, whereby the impact resistance is enhanced. When the content of the vinyl aromatic compound ranges from 35 to 60 % by weight, the block copolymer can be very homogeneously dispersed in the polyphenylene ether phase and, at the same time, the dispersed particles of polyphenylene ether can be also homogeneously dispersed in the polyamide phase, whereby a composition most excellently balanced in the respective properties can be obtained. When the content of the vinyl aromatic compound ranges from 70 to 85 % by weight, the dispersed phase can be finely dispersed, but it may sometimes occur that the reinforcing effect by the rubber-like substance or the heat distortion resistance is slightly lowered. The above vinyl aromatic compound constituting the block copolymer is selected from one or two or more of, for example, styrene, α-methylstyrene, vinyltoluene, etc., and styrene is particularly preferred. The conjugated diene compound is selected from one or two or more of, for example, butadiene, isoprene, 1,3-pentadiene, and butadiene is particularly preferred. Molecular structure of the rubber-like substance may be straight chain, branched or radial, or any of these may be freely combined. When an average value of the content of the vinyl aromatic compound is in the above range, two or more of block copolymers having different content of the vinyl aromatic compound may be used (provided, however, that the vinyl content in the respective block copolymer is required to be in the range of 20 to 90 % by weight). The block copolymer may also be more or less modified by an organic compound or an inorganic compound so far as the properties thereof are not impaired. Blending proportion of polyamide, polyphenylene ether and rubber-like substance in the composition of the present invention may be 25 to 70 % by weight, preferably 30 to 60 % by weight, of polyamide; 25 to 70 % by weight, preferably 30 to 60 % by weight, of polyphenylene ether; and 2 to 25 % by weight, preferably 5 to 20 % by weight, of the block copolymer, based on the total amount of these three components. As for the dispersion form of the respective components, it is required that the polyamide forms a continuous phase, and, in the continuous phase, the polyphenylene ether is dispersed having its average particle diameter ranging from 0.5 to 10 µm, preferably from 0.8 to 7 µm, to form a dispersed phase, and further, substantially all of the block copolymer is micro-dispersed in the dispersed phase of the polyphenylene ether. When the content of polyamide is less than 25 % by weight or that of the polyphenylene ether is more than 70 % by weight based on the total amount of the above three components, it is impossible for the polyamide to form a continuous phase and for the polyphenylene ether to form a dispersed phase, under any blending conditions. On the other hand, when he content of polyamide is more than 70 % by weight or that of polyphenylene ether is less than 25 % by weight, the heat distortion resistance of the composition under high load may become undesirably poor. The block copolymer is necessary for enhancing the impact resistance, and the content thereof less than 2 % by weight may result in no improvement effect in the impact resistance, and, on the other hand, the content more than 25 % by weight may result in decrease in the mechanical strength. The dispersion form of the respective components has been defined as above for the reasons as follows: When the dispersed phase is formed by polyamide or the continuous phase is formed by both of polyamide and polyphenylene ether, the oil resistance, the heat resistance and the stiffness may be lowered. When the average particle size of the dispersed phase of polyphenylene ether is less than 0.5 µm, the impact resistance and the molding flow properties may be lowered, and, when it is more than 10 µm, it then becomes difficult to form the dispersed phase in a stable state even under a severe molding condition. Further, when the block copolymer is independently present in the polyamide layer in a large amount, the heat distortion temperature and the stiffness may be lowered. General process for producing the composition of the present invention will be described below, but any other production process may be employed if the above respective conditions are satisfied. The composition of the present invention can be obtained by melt kneading the polyamide, the polyphenylene ether and the block copolymer used in the proportion of 25 to 70 % by weight, 25 to 70 % by weight and 2 to 25 % by weight, respectively, based on the total amount of these. In this occasion, it is preferable to use as a regulator for dispersed particle diameter of polyphenylene ether, a maleic acid compound, a copolymer of styrene compound with α,β-unsaturated dicarboxylic derivative, or a silane compound. The maleic acid compound may include, for example, maleic acid, maleic anhydride, a half alkyl ester of maleic acid, an amide of maleic acid, an imide of maleic acid. Of these, preferred are maleic acid and maleic anhydride. The copolymer of styrene compound with α,β-unsaturated dicarboxylic derivative may include a copolymer of styrene with maleic anhydride, a copolymer of styrene with a half alkyl ester of maleic acid, a copolymer of styrene with an imide of maleic acid, etc. Of these, preferred is a copolymer of styrene with maleic anhydride. The silane compound refers to a compound simultaneously having a) carbon-silicon bond, b) a halogen atom or an alkoxy group and c) an alkyl group, a vinyl group, an amino group, an epoxy group or a mercapto group. Of these, preferred are vinyl methoxysilane and γ-aminopropylmethoxysilane. The maleic acid compound, the copolymer of styrene compound with α,β-unsaturated dicarboxylic derivative, or the silane compound may be selected in the range of 0.05 to 10 % by weight, preferably of 0.1 to 5% by weight, based on the total amount of the abovementioned three components. The amount less than 0.05 % by weight for the addition of the maleic acid compound, the copolymer of styrene compound with α,β-unsaturated dicarboxylic derivative, or the silane compound, may result in more than 10 µm of the average particle diameter of the dispersed phase. It is unnecessary, from an economical view-point, to add it in an amount of more than 10 % by weight. As a dispersion form-controlling agent for readily and homogeneously dispersing the rubber-like substance in the dispersed phase of polyphenylene ether, there may be used a particular amine compound in combination with the maleic acid compound, the copolymer of styrene compound with α,β-unsaturated dicarboxylic derivative, or the silane compound. Such an amine compound is a compound having in the molecule at least one nitrogen atom and sulfur atom, which may include, for example, phenothiazine, and phenothiazine derivatives having a substituent such as an alkyl group or an alkenyl group having 1 to 30 carbon atoms, an aryl group, an amide group and an acyl group. When these amine compounds are added, the amount therefor may be selected from the range of 0.05 to 2 % by weight, preferably of 0.1 to 1 % by weight, based on the total amount of the above-mentioned three components. The amount less than 0.05 % by weight may result in substantially no effect being shown. Even if it is more than 2 % by weight, it may not necessarily follow that the effect is further improved. Temperature and time for melt kneading may vary depending on the kind of polyamide to be used or the compositional proportion between polyamide and polyphenylene ether, but usually used are a temperature ranging from 240°C to 350°C, preferably from 260°C to 320°C, and a kneading time of about 0.2 minute to 10 minutes, preferably about 0.5 minute to 5 minutes. Usable melt kneading machine may including an extruder, a kneader, a roll, etc. Particularly preferable is an extruder. To the composition of the present invention, other polymers, plasticizers, flame retarding agents or fillers such as glass fiber, carbon fiber, carbon black, silica and clay, and so forth may be optionally added so far as the purpose of the present in invention may not be damaged. Said other polymers are preferably polymers substantially compatible with the polyphenylene ether phase, and may include, for example, polystyrenes, rubber modified polystyrenes, etc. The dispersion form and the diameter of dispersed particles can be determined by an electron microscope photography. The diameter of dispersed particles can be calculated in the manner shown below: That is, a transmission type electron microscope photograph (photograph magnification: 4,000) of an ultra-thin strip cut out of a molded product is taken, from which a dispersed particle diameter d i and a particle number n i is determined to calculate the average particle diameter of the dispersed phase according to the following formula: Here, when the shape of particles can not be regarded as being round, the minor axis and the major axis thereof are measured to regard a half of the sum of both as the particle diameter. In calculating the average particle diameter, diameters for at least 2,000 particles are measured. The thermoplastic resin composition of the present invention, which is mainly constituted of the components comprising the polyamide, the polyphenylene ether and the block copolymer, shows properties well balanced in heat distortion resistance, impact resistance, oil resistance, stiffness, molding flow properties, etc. as compared with conventional products, since the three components have specified dispersion forms. EXAMPLES The present invention will be described in greater detail by the following Examples. Commercially available products were used as the block copolymer when commercially available. Names of manufacturers thereof are noted at the foot of the respective table. When not commercially available, copolymers were copolymerized following the process shown below, and used. Copolymerization of the block copolymer: Using a butylithium catalyst and in cyclohexane, 12.5 parts by weight of styrene were polymerized and thereafter 75 parts by weight of butadiene were polymerized, followed by further polymerization by adding 12.5 parts by weight of styrene to obtain a 20 wt.% solution of a block polymer having a styrene content of 25 % by weight. This block copolymer had a melt index of 6.0 (under Condition G). Block copolymers having different sytrene content were also synthesized to give products having substantially the same melt index as above. Examples 1 to 3 and Comparative Examples 1 to 3 50 parts by weight of poly(2,6-dimethyl-1,4-phenylene)ether having an intrinsic viscosity of 0.62 (25°C, in chloroform), 40 parts by weight of nylon 6,6 (produced by Asahi Chemical Industry Co., Ltd.; trade name: LEONA 1300S), 10 parts by weight of a block copolymer (having the structure and the styrene content as shown in Table 1 were used), and 0.5 part by weight of maleic anhydride were fed into a twin screw extruder of 30 mm diameter, and extrusion kneaded at 300°C and at a shear rate of 5 cm/sec to form pellets. Subsequently, test pieces were prepared using an injection molding machine to evaluate the properties according to the following test methods. Results obtained are shown in Table 1. Heat distortion temperature: JIS K-7207; load: 18.6 kg/cm² Izod impact strength, notched: JIS K-7110, 1/4″ thick Flexural modulus: ASTM-D 790 Flow: Short shot molding pressure at the molding of dumbbell test pieces at 290°C Oil resistance: State of appearance of molded products after exposure to steam of 1,1,1-trichloroethane for 5 minutes As shown in Table 1, Examples 1 to 3 show excellent heat distortion resistance, impact resistance, stiffness and oil resistance. Contrary thereto, in Comparative Examples 1 and 2 wherein the block copolymer had no polystyrene block portion, most part of the rubber-like substance does not disperse in polyphenylene ether, but disperse in the polyamide phase to lower the heat distortion resistance, the stiffness and the flow properties. Also, in Comparative Example 3 wherein Example 1 was repeated except that the extrusion was carried out at a shear rate of 2 cm/sec., the average particle diameter of PPE (polyphenylene ether) results in 10 µm or more to extremely lower the impact resistance or strength. Examples 4 to 7 and Comparative Example 4, 5 Example 1 was repeated except for varied bound styrene content in block SBR (styrene-butadiene rubber). Results obtained are shown in Table 2. Examples 4 to 7 which are within the scope of the present invention are seen to be excellently balanced in the heat distortion, the impact resistance, the stiffness and the flow properties. On the other hand, in Comparative Example 4 which is outside the present invention, using a block copolymer having 20 % by weight of bound styrene content, the block copolymer does not disperse in polyphenylene ether to become poor in the impact resistance, the heat distortion resistance, the stiffness and the flow properties. Also, in Comparative Example 5 wherein the copolymer has styrene block portion but the bound styrene content is 90 % by weight, the impact resistance is poor. Examples 8 to 12 and Comparative Examples 6,7 These Examples were carried out by varying the formulation of the polyphenylene ether, the polyamide and the block copolymer. Results obtained are shown in Table 3. Any of Examples 8 to 12 which are within the scope of the formulation according to the present invention are seen to be very excellently balanced in the heat distortion resistance, the impact resistance, the stiffness, the flow properties and the oil resistance. Contrary thereto, in Comparative Example 6, the polyphenylene ether also forms a continuous layer to extremely worsen the oil resistance, the heat distortion resistance, the impact resistance and the flow properties. In Comparative Example 7, the content of polyphenylene ether is small to lower the heat distortion resistance and the stiffness. Example 13 Example 1 was repeated by replacing nylon 6,6 with nylon 6 (trade name: AMILAN 1017; produced by Toray Industries, Inc.). Results obtained are shown in Table 4. Example 14 Example 1 was repeated by replacing maleic anhydride as the dispersed particle diameter regulator with vinyl methoxysilane. Results obtained are shown in Table 4. Example 15 Example 2 was repeated except for addition of 0.2 % by weight of phenothiazin as the dispersion form-controlling agent used in Example 2. Results obtained are shown in Table 5. Addition of phenothiazin has made small the dispersion diameter of PPE, and also made homogeneous the dispersion of the rubber-like substance in the PPE phase. The heat distortion resistance and the impact resistance have also enhanced. Example 16 This Example was carried out by using in combination, two kinds of block copolymers having different styrene content. Namely, Example 1 was repeated except for using in combination 7 parts by weight of a block copolymer having a styrene content of 20 % by weight and 3 parts by weight of a block copolymer having a styrene content of 70 % by weight (Average content: 35 % by weight). Results obtained are shown in Table 6. It is seen that excellent properties are attained when the average content is in the specified range.

Claims: A thermoplastic resin composition substantially constituted of (A) 25 to 70 % by weight of a polyamide, (B) 25 to 70 % by weight of a polyphenylene ether and (C) 2 to 25 % by weight of a block copolymer having at least one polymer block mainly comprised of a vinyl aromatic compound and at least one polymer block mainly comprised of a conjugated diene compound having the content of the vinyl aromatic compound in the range of 25 to 85 % by weight (the percentage of components (A), (B) and (C) are based on the total amount of those three components); wherein said polyamide forms a continuous phase, and, in said continuous phase, said polyphenylene ether is dispersed to form a dispersed phase having its average particle diameter ranging from 0.5 to 10 µm, and further, substantially all of said block copolymer is micro-dispersed in the dispersed phase of the polyphenylene ether. The composition according to Claim 1, wherein the component (C) is a block copolymer having the contents of the vinyl aromatic compound in the range of 30 to 70 % by weight. The composition according to Claim 1, wherein the component (C) is a block copolymer having the content of the vinyl aromatic compound in the range of 35 to 60 % by weight. The composition according to Claim 1, wherein the component (C) is a block copolymer comprising styrene and butadiene and having the styrene content in the range of 35 to 60 % by weight. The composition according to Claim 1, wherein the component (A) is at least one selected from the group consisting of nylon 6, nylon 6,6 and a nylon 6-, 6,6-copolymer. The composition according to anyone of Claims 1 to 5, wherein the component (B) is a polyphenylene ether comprising a structure unit of the formula (I) shown below: wherein R₁ and R₂ may be the same or different and each represent a monovalent radical selected from the group consisting of an alkyl group having 1 to 4 carbon atoms excluding tert-butyl group, an aryl group, a halogen atom and a hydrogen atom, and R₁ and R₂ are not a hydrogen atom at the same time. The composition according to anyone of Claims 1 to 5, wherein the component (B) is poly(2,6-dimethyl-1,4-phenylene) ether. The composition according to anyone of Claims 1 to 5, wherein the component (B) is a copolymer comprising structure units of the formulae (I) and (II) shown below: wherein R₁, R₂, R₃, R₄, R₅ and R₆ may be the same or different and each represent a monovalent radical selected from the group consisting of an alkyl group having 1 to 4 carbon atoms excluding tert-butyl group, an aryl group, a halogen atom and a hydrogen atom; provided that R₁ and R₂, as well as R₃ and R₄, each are not a hydrogen at the same time. The composition according to Claim 4, wherein the component (A) is at least one selected from the group consisting of nylon 6, nylon 6,6 and a nylon 6-,6,6-copolymer and the component (B) is poly(2,6-dimethyl-1,4-phenylene) ether. The composition according to any one of Claims 1 to 9, wherein the dispersed phase formed by dispersing polyphenylene ether in the continuous phase has an average particle diameter of 0.8 to 7 µm. The composition according to Claim 10, wherein the composition further comprises 0.05 to 2 % by weight of a dispersion form-controlling agent. The composition according to Claim 11, wherein said dispersion form-controlling agent is phenothiazine.

Inventors: HARADA, HIROSHI, KASAI, KOJI, UEDA, SUMIO, YOSHIDA, KAZUO
Applicants: ASAHI KASEI KOGYO KABUSHIKI KAISHA
Application year: 1986
Main classification: C08L71
IPC codes: C08L77, C08L71