Resin composition

Abstract

The present invention addresses the problem of providing a resin composition which is excellent in terms of colorability and demoldability in injection molding. This resin composition comprises a copolymer (A) comprising a styrene-based monomer unit and a monomer based on vinyl cyanide and at least one release agent (B) selected from among aliphatic alcohols having 16 or more carbon atoms and fatty acids, wherein the content of the release agent (B) is 200-800 ppm. The resin composition has a transmittance, as determined at an optical path length of 115 mm and a wavelength of 450 nm, of 40% or greater.

Description

[Technical field]

[0001] The present invention relates to a resin composition of a copolymer containing a styrene monomer unit and a vinyl cyanide monomer. [Background technology]

[0002] Copolymers mainly composed of styrene monomer units and vinyl cyanide monomers have excellent properties such as transparency, chemical resistance, rigidity, moldability, etc., and are therefore used in a wide range of fields. They can also be easily colored with dyes, and are used in cosmetic containers, water coolers, etc. (Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 04-503083 [Patent Document 2] Japanese Patent Application Publication No. 08-301913 [Patent Document 3] Japanese Patent Application Publication No. 10-139965 [Patent Document 4] JP 2002-114822 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a resin composition which is excellent in colorability and mold releasability during injection molding. [Means for solving the problem]

[0005] (1) A resin composition containing (A) a copolymer having a styrene-based monomer unit and a vinyl cyanide-based monomer, and (B) at least one type of release agent selected from an aliphatic alcohol having 16 or more carbon atoms and a fatty acid, wherein the content of the release agent (B) is 200 to 800 ppm, and the transmittance at a wavelength of 450 nm and an optical path length of 115 mm is 40% or more. (2) The resin composition according to (1), wherein the content of the styrene-based monomer unit in 100 mass% of the copolymer (A) is 79 to 85 mass% and the content of the vinyl cyanide-based monomer is 15 to 21 mass%. (3) The resin composition according to (1) or (2), further comprising an antioxidant (C). (4) The resin composition according to any one of (1) to (3), which is colored with a dye. (5) An injection-molded article of the resin composition according to any one of (1) to (4). Effect of the Invention

[0006] The resin composition of the present invention is very little discolored due to deterioration caused by high temperature treatment during molding. Therefore, because it has excellent colorability, molded articles with clear colors can be obtained by coloring with dyes. In addition, molded articles are often produced by injection molding for applications such as cosmetic containers and water coolers, and the resin composition has excellent mold releasability during injection molding. Therefore, cracks are unlikely to occur when the mold is released, and stable continuous molding can be achieved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] <Terminology explanation> In the present specification, for example, the description "A to B" means A or more and B or less.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention are described in detail below. The embodiments described below can be combined with each other.

[0009] The resin composition of the present invention contains (A) a copolymer having a styrene-based monomer unit and a vinyl cyanide-based monomer, and (B) at least one type of release agent selected from aliphatic alcohols and fatty acids having 16 or more carbon atoms.

[0010] The copolymer (A) is a copolymer having a styrene-based monomer unit and a vinyl cyanide-based monomer unit, and is, for example, a styrene-acrylonitrile copolymer.

[0011] The styrene monomer unit is styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, etc. Among these, styrene is preferred. The styrene monomer unit may be used alone or in combination of two or more kinds. The copolymer (A) preferably contains 79 to 85 mass% of the styrene monomer unit in 100 mass% of the copolymer (A), more preferably 80 to 82 mass%. The content of the styrene monomer unit is specifically, for example, 79, 80, 81, 82, 83, 84, or 85 mass%, and may be within a range between any two of the numerical values ​​exemplified here. If the content of the styrene monomer unit is within the above range, the balance between the chemical resistance and color tone of the obtained resin composition is excellent. The styrene monomer unit is a value measured by 13C-NMR.

[0012] The vinyl cyanide monomer unit is acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, etc. Among these, acrylonitrile is preferable. The vinyl cyanide monomer unit may be used alone or in combination of two or more kinds.

[0013] Other copolymerizable monomers for the copolymer (A) include (meth)acrylic acid ester monomers such as methyl methacrylate, acrylic acid ester monomers such as butyl acrylate and ethyl acrylate, (meth)acrylic acid monomers such as methacrylic acid, acrylic acid monomers such as acrylic acid, and N-substituted maleimide monomers such as N-phenylmaleimide. The copolymer (A) preferably contains 15 to 21 mass% of vinyl cyanide monomer units, more preferably 18 to 20 mass%, based on 100 mass% of the copolymer (A). The content of the vinyl cyanide monomer units is specifically, for example, 15, 16, 17, 18, 19, 20, or 21 mass%, and may be within any two of the numerical values ​​exemplified here. If the content of the vinyl cyanide monomer units is within the above range, the balance between chemical resistance and color tone of the resulting resin composition is excellent. The amount of vinyl cyanide monomer units was measured by 13C-NMR.

[0014] The copolymer (A) is a copolymer mainly composed of a styrene monomer and a vinyl cyanide monomer. Preferably, the copolymer (A) is a copolymer substantially composed of only a styrene monomer and a vinyl cyanide monomer. The constituent units of the copolymer (A) are preferably 79 to 85 mass% of styrene monomer units and 15 to 21 mass% of vinyl cyanide monomer units, more preferably 80 to 82 mass% of styrene monomer units and 18 to 20 mass% of vinyl cyanide monomer units. If the constituent units are within the above ranges, the resulting resin composition has an excellent balance between chemical resistance and color tone.

[0015] The copolymer (A) can be produced by a known method. For example, it can be produced by bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. The reactor can be operated in a continuous, batch (batch) or semi-batch manner. In terms of quality such as color tone and productivity, bulk polymerization or solution polymerization is preferred, and continuous polymerization is preferable. Examples of the solvent for bulk polymerization or solution polymerization include alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane.

[0016] In the bulk polymerization or solution polymerization of the copolymer (A), a polymerization initiator and a chain transfer agent can be used, and the polymerization temperature is preferably in the range of 120 to 170° C. Examples of the polymerization initiator include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide, alkyl peroxides such as t-butyl peroxyacetate and t-amyl peroxyisononanoate, dialkyl peroxides such as t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide, and the like. peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxycarbonates such as t-butylperoxyisopropyl carbonate and polyethertetrakis(t-butylperoxycarbonate); N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]; and these may be used alone or in combination of two or more. Examples of chain transfer agents include n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer, ethyl thioglycolate, limonene, and terpinolene.

[0017] A known method can be used for removing volatile components such as unreacted monomers and the solvent used in the solution polymerization from the solution after the polymerization of the copolymer (A). For example, a vacuum volatilization tank with a preheater or a vented volatilization extruder can be used. The resin temperature during volatilization is preferably 240°C or lower, and when a vacuum volatilization tank with a preheater is used, the outside temperature of the preheater is preferably 280°C or lower. The volatilized molten copolymer (A) is transferred to a granulation process, extruded into strands through a multi-hole die, and processed into pellets by a cold cut method, an air hot cut method, or an underwater hot cut method.

[0018] From the viewpoint of strength and moldability of the resin composition, the weight average molecular weight of the copolymer (A) is preferably 50,000 to 250,000, more preferably 150,000 to 200,000. The weight average molecular weight of the copolymer (A) is a polystyrene-equivalent value measured in THF solvent using gel permeation chromatography (GPC) under the following conditions. Device name: SYSTEM-21 Shodex (Showa Denko Co., Ltd.) Column: 3 PL gel MIXED-B in series Temperature: 40℃ Detection: Differential refractive index Solvent: Tetrahydrofuran Concentration: 2% by mass Calibration curve: Prepared using standard polystyrene (PS) (PL Corporation).

[0019] The release agent (B) is at least one selected from aliphatic alcohols and fatty acids. The aliphatic alcohols and fatty acids have a carbon number of 16 or more, preferably 16 to 22, and more preferably 16 to 18. Specifically, for example, the carbon number is 16, 17, 18, 19, 20, 21, or 22, and may be within a range between any two of the numerical values ​​exemplified here. The release agent (B) is preferably an aliphatic alcohol, and has excellent retention heat stability during injection molding.

[0020] The fatty alcohol having 16 or more carbon atoms is cetyl alcohol, heptadecyl alcohol, stearyl alcohol, etc., and among these, stearyl alcohol is preferable. If the number of carbon atoms is less than 16, mold contamination may occur during injection molding. From the viewpoint of industrial availability, the number of carbon atoms is preferably 22 or less, and more preferably 20 or less.

[0021] The fatty acid having 16 or more carbon atoms is palmitic acid, stearic acid, behenic acid, etc., and among these, stearic acid is preferable. If the number of carbon atoms is less than 16, mold contamination may occur during injection molding. From the viewpoint of industrial availability, the number of carbon atoms is preferably 22 or less, and more preferably 20 or less.

[0022] The content of the release agent (B) in the resin composition is 200 to 800 ppm, preferably 300 to 700 ppm. Specifically, for example, it is 200, 300, 400, 500, 600, 700, or 800 ppm, and may be within a range between any two of the numerical values ​​exemplified here. If the content of the release agent (B) is less than 200 ppm, the mold releasability during injection molding is poor, and if it exceeds 800 ppm, it becomes difficult to disperse the release agent in the resin composition.

[0023] The resin composition preferably contains an antioxidant (C), which provides a more excellent color tone. The antioxidant is preferably a combination of a hindered phenol-based antioxidant and a phosphorus-based antioxidant. The content of the antioxidant (C) in 100% by mass of the resin composition is preferably 0.05 to 0.5% by mass, more preferably 0.05 to 0.4% by mass, from the viewpoint of optimizing the color tone. Specifically, for example, it is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.45, or 0.5% by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0024] Hindered phenol antioxidants are antioxidants that have a phenolic hydroxyl group in the basic skeleton. Examples of hindered phenol antioxidants include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, pentane, etc. pentane erythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis[(dodecylthio)methyl]-o-cresol, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 4,4'-thiobis(6-t-butyl-3-methylphenol) ), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), bis-[3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)-butanoic acid]-glycol ester, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 2,6-di-tert-butyl-4-[ Examples of the tertiary ester include 4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, 2'3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]propionohydrazide, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate.Preferred are pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,6-bis[(dodecylthio)methyl]-o-cresol, 2,6-di-tert-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, and 2'3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]propionohydrazide. More preferred are pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane. The hindered phenol-based antioxidants may be used alone or in combination of two or more kinds.

[0025] Phosphorus-based antioxidants are phosphorous esters, which are trivalent phosphorus compounds. Examples of phosphorus-based antioxidants include 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butylbenz[d,f][1,3,2]dioxaphosphepine, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, and tris(2,4-di-tert-butylphenyl)phosphite. , bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, cyclic neopentanetetraylbis(octadecyl phosphite), bis(nonylphenyl)pentaerythritol diphosphite, 4,4'-biphenylene diphosphinic acid tetrakis(2,4-di-tert-butylphenyl), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylene diphosphonite, and the like. Preferred are tris(2,4-di-tert-butylphenyl)phosphite, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butylbenz[d,f][1,3,2]dioxaphosphepine, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite. More preferred is tris(2,4-di-tert-butylphenyl)phosphite. The phosphorus-based antioxidant may be used alone or in combination of two or more kinds.

[0026] The resin composition can be produced from the copolymer (A), the release agent (B), and the antioxidant (C) by a known method, but it is preferable to add and mix the copolymer (A) during the production process, since this can minimize the thermal history of the copolymer. The release agent (B) is preferably added between the time when the copolymer (A) is devolatilized and the time when the copolymer (A) is granulated, and it is preferable to mix the release agent (B) using a static mixer or an extruder. The antioxidant (C) has the effect of preventing discoloration due to deterioration of the copolymer (A) caused by the thermal history during devolatilization, so it is preferable to add the antioxidant (C) to the solution containing the copolymer (A) before devolatilization.

[0027] The resin composition may contain a plasticizer, an ultraviolet absorber, a hindered amine stabilizer, an antistatic agent, or an external lubricant such as ethylene bisstearyl amide, within the range that does not impair transparency.

[0028] The transmittance of the resin composition at a wavelength of 450 nm measured with an optical path length of 115 mm is 40% or more, preferably 50% or more. Specifically, for example, it is 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 60, 65, or 70%, and may be within a range between any two of the numerical values ​​exemplified here. The measurement is a value obtained by using a spectrophotometer for a plate-shaped molded product after end face polishing. If the transmittance at a wavelength of 450 nm is lower than 40%, the resin composition will have a dull color even if it is colored with a dye. The transmittance at a wavelength of 450 nm can be made 40% or more by appropriately combining the vinyl cyanide monomer unit of the copolymer (A) in an appropriate range, the resin temperature adjustment during devolatilization, and the addition of an antioxidant (C).

[0029] The resin composition is preferably colored with a dye, which is given a color index number based on its chemical structure, such as Disperse Violet 28, Solvent Blue 35, 83, 94, 97, 104, 105, Solvent Green 3, Solvent Red 52, Solvent Violet 13, 31, 33, 34, 36, etc.

[0030] Coloring with a dye can be carried out by a known method, and coloring in an extruder or by adding a dye during the production process of the copolymer (A) is also possible.

[0031] The resin composition can be molded into a molded article by a known molding method, but since it has excellent mold releasability, it is preferably used for injection molding. In addition, since it has excellent colorability, it can be used for molded articles that require a high-quality appearance, such as cosmetic containers. EXAMPLES

[0032] The following detailed description will be given using examples, but the present invention is not limited to the following examples.

[0033] The release agents (B) and antioxidants (C) used in the examples and comparative examples are as follows: <Release agent (B)> (B-1) Stearyl alcohol (Kao Corporation, Kalcol 8098) (B-2) Stearic acid (Lunac S-90, manufactured by Kao Corporation) (B-3) Docosanol (1-Docosanol, manufactured by Tokyo Chemical Industry Co., Ltd.) (B-4) Ethylene bis-stearyl amide (Kao Wax EB-P, manufactured by Kao Corporation) (B-5) Myristyl alcohol (Kao Corporation, Kalcol 4098) <Antioxidants (C)> (C-1) Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox1010 manufactured by BASF Japan Ltd.) (C-2) C-1: Tris(2,4-di-tert-butylphenyl)phosphite (ADEKA Corporation, Adeka STAB 2112)

[0034] <Example 1> The feed liquid to be supplied to a 50L reactor was prepared to be 70 parts by mass of styrene, 15 parts by mass of acrylonitrile, 15 parts by mass of ethylbenzene, 0.02 parts by mass of t-butylperoxyisopropyl carbonate as a polymerization initiator, and 0.01 parts by mass of n-dodecyl mercaptan as a chain transfer agent. After bubbling this feed liquid with nitrogen gas, it was continuously supplied to the reactor at a rate of 10.8L / hour, and the polymerization temperature was kept at 145°C and the filling rate of the reaction liquid in the reactor was kept at 70vol%, and the same amount of polymer solution as the amount of the feed liquid was continuously extracted. To the polymer solution continuously extracted from the reactor, 0.5ppm of Solvent Violet 13 was added as a dye to the polymer, and antioxidants C-1 and C-2 were added to the contents in Table 1, and then the solution was supplied to a vacuum devolatilizer tank equipped with a preheater, and unreacted styrene, acrylonitrile, ethylbenzene, etc. were separated. The temperature of the preheater was adjusted so that the polymer temperature in the devolatilizer tank was 235°C, and the pressure in the devolatilizer tank was 1 kPa. The molten polymer was extracted from the vacuum devolatilizer tank by a gear pump, mixed with the release agent B-1 in a static mixer so as to obtain the content in Table 1, extruded into a strand shape, cooled with cooling water, and cut to obtain a pellet-shaped resin composition. The weight-average molecular weight of the copolymer was 182,000.

[0035] <Example 2> A resin composition was obtained in the same manner as in Example 1, except that the content of B-1 was changed.

[0036] <Example 3> A resin composition was obtained in the same manner as in Example 1, except that the addition of C-1 and C-2 was stopped.

[0037] <Example 4> A resin composition was obtained in the same manner as in Example 1, except that B-1 was changed to B-2.

[0038] <Example 5> A resin composition was obtained in the same manner as in Example 1, except that B-1 was changed to B-3.

[0039] <Example 6> A resin composition was obtained in the same manner as in Example 1, except that the content of C-1 was changed.

[0040] <Example 7> A resin composition was obtained in the same manner as in Example 1, except that the content of C-2 was changed.

[0041] <Example 8> Except for changing the amount of styrene to 65 parts by mass and acrylonitrile to 20 parts by mass in the feed liquid supplied to the reaction vessel, a resin composition was obtained in the same manner as in Example 1. The weight average molecular weight of the copolymer was 176,000.

[0042] <Comparative Example 1> A resin composition was obtained in the same manner as in Example 1, except that the addition of B-1, C-1, and C-2 was stopped.

[0043] <Comparative Example 2> A resin composition was obtained in the same manner as in Example 1, except that B-1 was changed to B-4 and the content was changed.

[0044] <Comparative Example 3> A resin composition was obtained in the same manner as in Example 1, except that the content of B-1 was changed.

[0045] <Comparative Example 4> As a result of changing the content of B-1, the dispersibility of B-1 deteriorated, the strands became disordered, and it was impossible to produce a resin composition.

[0046] <Comparative Example 5> A resin composition was obtained in the same manner as in Example 1, except that B-1 was changed to B-5.

[0047] <Comparative Example 6> A resin composition was obtained in the same manner as in Example 8, except that the addition of C-1 and C-2 was stopped.

[0048] (Melt Mass Flow Rate) The melt mass flow rate was measured at 220°C and a load of 98N based on JIS K7210.

[0049] (Vicat softening temperature) The Vicat softening point was measured using a test piece of 10 mm x 10 mm and 4 mm thick, according to the JIS K7206 50 method (load 50N, heating rate 50℃ / hour). The measuring machine used was a HDT&VSPT tester manufactured by Toyo Seiki Seisakusho Co., Ltd.

[0050] (Optical path length 115mm, transmittance at wavelength 450nm) Using an injection molding machine (Japan Steel Works, Ltd., J140AD-180H), a plate-shaped molded product with a length of 127 mm, width of 127 mm, and thickness of 3 mm was molded under molding conditions of a cylinder temperature of 240°C and a mold temperature of 70°C. The plate-shaped molded product was cut and the end faces were polished to prepare a test piece with an optical path length of 115 mm. Using a JASCO Corporation UV-Visible Spectrophotometer V-670, the transmittance was measured at an optical path length of 115 mm and a wavelength of 450 nm for incident light with a size of 20 x 1.6 mm and a spread angle of 0°.

[0051] (Haze, Hue) A mirror plate 90 mm long, 55 mm wide, and 2 mm thick molded using an injection molding machine (Toshiba Machine IS-50EP) under molding conditions of a cylinder temperature of 240°C and a mold temperature of 60°C was measured for haze using a haze meter (Nippon Denshoku Industries NDH-1001DP) in accordance with ASTM D1003. The b value was measured using an ultraviolet-visible spectrophotometer (JASCO V-670) in accordance with JIS K7105.

[0052] (retention thermal stability) Using an injection molding machine (Toshiba Machine IS-50EP), a mirror-finished plate measuring 90 mm in length, 55 mm in width, and 2 mm in thickness was molded under molding conditions of a cylinder temperature of 240°C and a mold temperature of 60°C. After obtaining a good product, 10 shots were molded, and then the resin was allowed to remain in the cylinder for 10 minutes, after which 10 shots were molded. Δb was calculated by subtracting the maximum b value of the hue before retention from the maximum b value of the hue after retention. The larger Δb, the greater the discoloration due to retention during molding.

[0053] (Mold release resistance) A mold release resistance mold (box molded product dimensions: length 60mm, width 130mm, depth 45mm, thickness 2mm) with a load cell attached to the ejector pin was attached to a 100t injection molding machine (J100E-P) manufactured by Nippon Steel Corporation, and continuous molding was performed with a cylinder temperature of 230℃ and a mold temperature of 40℃, and the ejection force of the ejector pin was measured when the molded product was released from the mold when the mold was opened. The mold release property was evaluated by the maximum mold release resistance value (N), and the smaller the value, the better the mold release property.

[0054] (Mold dirt) Using an injection molding machine (Toshiba Machine IS-50EP), 50 shots were continuously molded under molding conditions of a cylinder temperature of 280°C and a mold temperature of 60°C. After that, the surface of the mold and the appearance of the molded product were observed, and those without contamination were marked with an ◯, and those with contamination were marked with an ×.

[0055] (color tone) The injection molded products were visually observed, and a clear, vivid blue color was marked with an ⊚, a slightly grayish blue color was marked with an ◯, and a dull grayish blue color was marked with an ×.

[0056] [Table 1]

[0057] As can be seen from the results in Table 1, the resin compositions of the examples have low mold release resistance and excellent mold releasability. In addition, the molded products obtained have excellent color tone and a clear, vivid blue color. [Industrial Applicability]

[0058] The resin composition of the present invention has excellent colorability, and therefore can be colored with a dye to obtain a molded product with a clear color tone. In addition, the resin composition has excellent mold releasability during injection molding, so that cracks are unlikely to occur when the resin composition is released from the mold, and stable continuous molding can be achieved.

Claims

1. A resin composition comprising (A) a copolymer having a styrene-based monomer unit and a vinyl cyanide-based monomer unit, (B) at least one type of release agent selected from the group consisting of an aliphatic alcohol having 16 or more carbon atoms and a fatty acid, and (C) an antioxidant, the content of the styrene-based monomer unit is 79 to 85 mass% and the content of the vinyl cyanide-based monomer unit is 15 to 21 mass% in 100 mass% of the copolymer (A); A resin composition having a content of the release agent (B) of 300 to 700 ppm, a content of the antioxidant (C) of 0.05 to 0.5 mass% in 100 mass% of the resin composition, and a transmittance of 40% or more at an optical path length of 115 mm and a wavelength of 450 nm (excluding those containing 65 mass% or more of PETG resin in 100 mass% of the resin component).

2. The resin composition according to claim 1, which is colored with a dye.

3. An injection molded article of the resin composition according to claim 1 or 2.

Images