Graft copolymer and thermoplastic resin composition

Abstract

A graft copolymer obtained by carrying out graft polymerization of monomers including a vinyl cyanide-based monomer and an aromatic vinyl-based monomer on a propylene-based polymer, wherein the propylene-based polymer is a random copolymer, and the melt flow rate of the propylene-based polymer at 230°C and 2.16 kg is greater than or equal to 1.5 g / 10 minutes but less than 8 g / 10 minutes.

Description

Graft copolymer and thermoplastic resin composition

[0001] The present invention relates to a graft copolymer and a thermoplastic resin composition.

[0002] Rubber-reinforced thermoplastic resin compositions containing rubber-based graft copolymers and the like are excellent in moldability, impact resistance, mechanical strength, etc., and are widely used in industrial parts, household electrical appliances, automobile interiors and exteriors, etc. By changing the components contained in the rubber-reinforced thermoplastic resin composition, it is possible to adjust the properties to suit various applications, and it is known, for example, that adding a graft copolymer of a propylene-based polymer to a rubber-reinforced thermoplastic resin composition improves the paintability of molded articles.

[0003] As a graft copolymer of a propylene polymer to be added to a rubber-reinforced thermoplastic resin composition, for example, Patent Document 1 proposes a multiphase structure thermoplastic resin consisting of 5 to 99% by weight of a propylene polymer segment and 95 to 1% by weight of a vinyl (co)polymer segment formed from a vinyl monomer containing 50% by weight or more of styrene, while Patent Document 2 proposes a graft polymer obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another copolymerizable vinyl compound in the presence of polypropylene or the like.

[0004] JP 2003-176391 JP 02-097550

[0005] However, as a result of investigations by the present inventors, it has become clear that there is a problem in that mold contamination is likely to occur when a rubber-reinforced thermoplastic resin composition containing a graft copolymer of a propylene-based polymer is continuously molded.

[0006] Therefore, an object of the present invention is to provide a graft copolymer of a propylene polymer which, when added to a rubber-reinforced thermoplastic resin composition, can improve the coatability of the molded article and prevent mold contamination during continuous molding, and a thermoplastic resin composition containing the same.

[0007] In view of the above circumstances, the present invention provides the following [1] to [4]. [1] A graft copolymer obtained by graft polymerizing a propylene polymer with a monomer including a vinyl cyanide monomer and an aromatic vinyl monomer, wherein the propylene polymer is a random copolymer, and the propylene polymer has a melt flow rate (MFR) of 1.5 g / 10 min or more and less than 8 g / 10 min at 230°C and 2.16 kg. [2] The graft copolymer according to [1], wherein the propylene polymer is a propylene-ethylene random copolymer. [3] The graft copolymer according to [1] or [2], wherein the graft ratio is 25% or more. [4] A thermoplastic resin composition comprising the graft copolymer according to any one of [1] to [3] and a rubber-reinforced styrene resin, wherein the content of the graft copolymer is 1 to 10 parts by mass per 100 parts by mass of the total amount of the thermoplastic resin composition excluding the graft copolymer.

[0008] According to the present invention, it is possible to provide a propylene-based polymer graft copolymer that, when added to a rubber-reinforced thermoplastic resin composition, can improve the coatability of the molded article and prevent mold contamination during continuous molding, and a thermoplastic resin composition containing the same.

[0009] Hereinafter, preferred embodiments of the present invention will be described. In this specification, the term "(meth)acrylic acid ester" refers to an acrylic acid ester or a methacrylic acid ester, and the same applies to similar expressions such as "(meth)acrylate."

[0010] <Graft Copolymer> The graft copolymer of the present embodiment is obtained by graft polymerizing a propylene polymer with monomers including a vinyl cyanide monomer and an aromatic vinyl monomer.

[0011] A propylene-based polymer is a polymer mainly composed of monomer units derived from propylene. The propylene-based polymer is a random copolymer obtained by random copolymerization of propylene and a copolymerizable monomer. The propylene-based polymer is preferably a propylene-ethylene random copolymer.

[0012] The content of the propylene-derived monomer units in the propylene polymer may be 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, based on the mass of the propylene polymer. The content of the propylene-derived monomer units may be 98% by mass or less, 97% by mass or less, 96% by mass or less, or 95% by mass or less, based on the mass of the propylene polymer.

[0013] The copolymerizable monomer constituting the propylene-based polymer may be, for example, ethylene or an α-olefin, and the α-olefin may be an α-olefin having 4 to 20 carbon atoms. The copolymerizable monomer may be any combination selected from ethylene and α-olefins.

[0014] Specific examples of the α-olefin having 4 to 20 carbon atoms include butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, and decene-1. The propylene polymer may be a copolymer of propylene and one or more copolymerizable monomers selected from ethylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, and decene-1, and specific examples thereof include a propylene-ethylene copolymer, a propylene-butene-1 copolymer, a propylene-ethylene-butene-1 copolymer, a propylene-hexene-1 copolymer, and a propylene-ethylene-hexene-1 copolymer. Of these, a propylene-ethylene copolymer is preferred.

[0015] The content of the monomer units derived from a copolymerization monomer (e.g., ethylene) in the propylene-based polymer may be 0.1% by mass or more, or 2.0% by mass or more, and may be 15% by mass or less, 10% by mass or less, 7.0% by mass or less, 6.0% by mass or less, or 5.0% by mass or less, based on the mass of the propylene-based polymer.

[0016] The melt flow rate (MFR) of the propylene polymer at 230°C and 2.16 kg is 1.5 g / 10 min or more and less than 8 g / 10 min, preferably 1.5 g / 10 min or more and less than 7 g / 10 min, and more preferably 1.5 g / 10 min or more and 6 g / 10 min or less, thereby improving the coatability of molded articles and preventing mold contamination during continuous molding.

[0017] Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, etc. These may be used alone or in combination of two or more.

[0018] Examples of aromatic vinyl monomers include styrene, α-methylstyrene, paramethylstyrene, bromostyrene, etc. These may be used alone or in combination of two or more.

[0019] The content of the aromatic vinyl monomer used in the graft polymerization can be, for example, 55 to 75 mass%, preferably 50 to 70 mass%, and more preferably 55 to 65 mass%, based on the total amount of monomers. The content of the vinyl cyanide monomer used in the graft polymerization can be, for example, 25 to 45 mass%, preferably 30 to 50 mass%, and more preferably 35 to 45 mass%, based on the total amount of monomers.

[0020] The graft copolymer of the present embodiment preferably contains the propylene polymer in an amount of 35 to 90% by mass, more preferably 45 to 80% by mass, and even more preferably 55 to 75% by mass.

[0021] The graft ratio of the graft copolymer of this embodiment is preferably 15% or more, more preferably 20% or more, and even more preferably 25% or more. The upper limit of the graft ratio is not particularly limited, but can be, for example, 60% or less, 50% or less, or 40% or less.

[0022] The graft copolymer of the present embodiment can be obtained by graft polymerizing the propylene polymer with a monomer containing a vinyl cyanide monomer and an aromatic vinyl monomer. The graft polymerization can be carried out by a conventionally known method, such as emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, or a combination thereof, but suspension polymerization is preferred.

[0023] The graft copolymer of the present embodiment, when added to a rubber-reinforced thermoplastic resin composition, can improve the coatability of molded articles and prevent mold contamination during continuous molding.

[0024] <Thermoplastic Resin Composition> The thermoplastic resin composition of the present embodiment contains the above-described graft copolymer and a rubber-reinforced styrene-based resin.

[0025] The content of the graft copolymer in the thermoplastic resin composition of the present embodiment is preferably 1 to 10 parts by mass, more preferably 1.5 to 6 parts by mass, and even more preferably 2 to 4 parts by mass, relative to 100 parts by mass of the total amount of the thermoplastic resin composition excluding the graft copolymer.

[0026] Specific examples of rubber-reinforced styrene resins include rubber-reinforced polystyrene resin (HIPS resin), acrylonitrile-butadiene rubber-styrene polymer (ABS resin), acrylonitrile-acrylic rubber-styrene polymer (AAS resin), methyl methacrylate-butadiene rubber-styrene resin (MBS resin), and acrylonitrile-ethylene-propylene rubber-styrene polymer (AES resin).

[0027] The content of the rubber-reinforced styrene-based resin in the thermoplastic resin composition of this embodiment is preferably 10 to 50 parts by mass per 100 parts by mass of the thermoplastic resin composition excluding the graft copolymer.

[0028] The thermoplastic resin composition of this embodiment may contain other thermoplastic resins. Examples thereof include non-rubber-reinforced styrene-based resins; acrylic-based resins such as polymethyl methacrylate resins; polycarbonate-based resins; polyester-based resins such as polybutylene terephthalate resins, polyethylene terephthalate resins, and polylactic acid resins; polyamide-based resins; and engineering plastics such as (modified) polyphenylene ether-based resins, polyoxymethylene-based resins, polysulfone-based resins, polyarylate-based resins, polyphenylene-based resins, and thermoplastic polyurethane-based resins. These may be used alone or in combination of two or more.

[0029] Specific examples of non-rubber-reinforced styrene-based resins include styrene polymer (PS resin), styrene-acrylonitrile copolymer (AS resin), α-methylstyrene-acrylonitrile copolymer (αMS-ACN resin), methyl methacrylate-styrene copolymer (MS resin), methyl methacrylate-acrylonitrile-styrene copolymer (MAS resin), styrene-N-phenylmaleimide copolymer (S-NPMI resin), and styrene-N-phenylmaleimide-acrylonitrile copolymer (S-A-NPMI resin).

[0030] The content of the other thermoplastic resin in the thermoplastic resin composition of this embodiment can be, for example, 30 to 80 parts by mass per 100 parts by mass of the thermoplastic resin composition excluding the graft copolymer.

[0031] To the thermoplastic resin composition of the present embodiment, known additives such as pigments, dyes, reinforcing agents (talc, mica, clay, glass fiber, carbon fiber, etc.), ultraviolet absorbers, antioxidants, lubricants, mold release agents, plasticizers, flame retardants, antistatic agents, inorganic and organic antibacterial agents, etc. may be blended during mixing of the resin, molding, etc., depending on the purpose, as long as the purpose of the present invention is not impaired.

[0032] The thermoplastic resin composition of the present embodiment can improve the coatability of molded articles and prevent mold contamination during continuous molding, and therefore can be suitably used as a resin composition for graining.

[0033] The thermoplastic resin composition of the present embodiment can be molded by injection molding, extrusion molding, compression molding, injection compression molding, blow molding, or the like using a mold or roll having a textured surface, to obtain a molded article having the textured surface of the mold or roll transferred to its surface.

[0034] The thermoplastic resin composition of the present embodiment can be suitably used in the interior and exterior applications of automobiles.

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "%" and "parts" are all by mass.

[0036] <Propylene Polymers> Propylene polymer (a-1): propylene-ethylene random copolymer, MFR = 1.5 g / 10 min Propylene polymer (a-2): propylene-ethylene random copolymer, MFR = 6 g / 10 min Propylene polymer (a-3): homopropylene polymer, MFR = 8 g / 10 min Propylene polymer (a-4): propylene-ethylene block copolymer, MFR = 9 g / 10 min Propylene polymer (a-5): propylene-ethylene-1-butene random copolymer, MFR = 9 g / 10 min

[0037] <Fluidity (Melt Flow Rate: MFR) of Polypropylene-Based Polymer> The melt flow rate (230°C, 2.16 kg) was measured and evaluated in accordance with ISO 1133 (unit: g / 10 min).

[0038] <Production of Graft Copolymer (A)> [Example 1: Production of Graft Copolymer (A-1)] A 100 L pressure vessel was charged with 270 parts of deionized water, 0.12 parts of polyoxyethylene polyoxypropylene glycol (manufactured by ADEKA Corporation; Pluronic (registered trademark) F-68), 0.6 parts of magnesium sulfate, and 60 parts of propylene polymer (a-1), and the atmosphere in the vessel was purged with nitrogen while stirring. Thereafter, a monomer mixture consisting of 24.5 parts of styrene, 15.5 parts of acrylonitrile, 0.45 parts of tert-butylperoxy-2-ethylhexanoate (manufactured by Kayaku Nouryon Co., Ltd.; Trigonox 21S), and 0.045 parts of 1,4-benzoquinone and 30 parts of deionized water was charged, and the atmosphere in the vessel was purged with nitrogen. The temperature in the vessel was raised to 85°C, and the reaction was continued for 1 hour after reaching 85°C. After the reaction was completed, the temperature inside the tank was cooled to 40° C., and the reaction mixture was recovered, washed, and dried to obtain a graft copolymer (A-1).

[0039] Example 2 Production of Graft Copolymer (A-2) Graft copolymer (A-2) was produced in the same manner as in the production of graft copolymer (A-1), except that propylene polymer (a-1) was changed to propylene polymer (a-2).

[0040] Comparative Example 1: Production of Graft Copolymer (A-3) Production of graft copolymer (A-3) was attempted in the same manner as for graft copolymer (A-1), except that the propylene polymer (a-1) was changed to propylene polymer (a-3). However, the propylene polymers stuck together in the vessel, and graft polymerization did not proceed. Therefore, this was not included in the subsequent evaluations.

[0041] Comparative Example 2: Production of Graft Copolymer (A-4) Production of graft copolymer (A-4) was attempted in the same manner as for graft copolymer (A-1), except that the propylene polymer (a-1) was changed to propylene polymer (a-4). However, the propylene polymers stuck together in the vessel, and graft polymerization did not proceed. Therefore, this was not included in the subsequent evaluations.

[0042] Comparative Example 3: Production of Graft Copolymer (A-5) Graft copolymer (A-5) was produced in the same manner as in the production of graft copolymer (A-1), except that propylene polymer (a-1) was changed to propylene polymer (a-5).

[0043] <Production of ABS Resin> [ABS Resin (B-1) Powder] A glass reactor was charged with 60 parts (solids equivalent) of styrene-butadiene rubber latex (5% styrene, 95% butadiene, mass average particle size 440 nm), stirring was initiated, and nitrogen substitution was performed. After nitrogen substitution, the temperature inside the reactor was raised to 65°C. When it reached 65°C, an aqueous solution prepared by dissolving 0.06 parts of glucose, 0.03 parts of anhydrous sodium pyrophosphate, and 0.001 parts of ferrous sulfate in 10 parts of deionized water was added, and the temperature was then raised to 70°C. Thereafter, a mixture of 10 parts of acrylonitrile, 30 parts of styrene, 0.3 parts of t-dodecyl mercaptan, and 0.1 parts of t-butyl hydroperoxide, and an emulsifier aqueous solution prepared by dissolving 1.0 parts of potassium oleate (solids equivalent) in 20 parts of deionized water were continuously added dropwise over 4 hours. After the dropwise addition, the mixture was maintained for 3 hours to obtain an ABS resin (B-1) latex. The resulting ABS resin (B-1) latex was then added to an aqueous solution containing magnesium sulfate, followed by coagulation, dehydration, and drying to obtain ABS resin (B-1) powder. The mass average particle diameter of the styrene-butadiene rubber latex was determined as follows. ４ The area of ​​800 rubber particles was measured using an image analysis processing device (device name: IP-1000PC manufactured by Asahi Kasei Corporation), and their circle-equivalent diameters (diameters) were determined to calculate the mass-average particle diameter.

[0044] [AS Resin (C-1) Pellets] AS Resin (C-1) pellets consisting of 75 parts of styrene and 25 parts of acrylonitrile were obtained by a known bulk polymerization method. The reduced viscosity of the obtained AS Resin (C-1) pellets was 0.45 dl / g. In the examples, the reduced viscosity was determined as follows.

[0045] <Reduced Viscosity> The measurement subject was dissolved in N,N-dimethylformamide to prepare a solution with a concentration of 0.4 g / 100 ml, and the reduced viscosity was determined from the flow time measured at 30° C. using a Cannon-Fenske viscometer. The reduced concentration of the acetone soluble portion was measured by drying the acetone soluble portion.

[0046] [AS Resin (C-2) Powder] 120 parts of deionized water was added to a glass reactor, followed by nitrogen substitution. The reactor was then heated to 60°C, and a 3% aqueous solution containing 0.3 parts of potassium persulfate as a polymerization initiator was added. A mixed solution consisting of 75 parts of styrene, 25 parts of acrylonitrile, and 0.07 parts of t-dodecyl mercaptan and a 5% aqueous solution containing 1.5 parts of potassium oleate (solids equivalent) were then continuously added dropwise at 60°C over 4 hours. After the dropwise addition, the mixture was held for 3 hours to obtain an AS Resin (C-2) latex. The resulting AS Resin (C-2) latex was then added to an aqueous solution containing magnesium sulfate, followed by coagulation, dehydration, and drying to obtain an AS Resin (C-2) powder. The reduced viscosity of the acetone-soluble portion was 1.2 dl / g.

[0047] [AMS Resin (C-3) Powder] A glass reactor was charged with 150 parts of deionized water and 0.7 parts of sodium rosinate (solids equivalent), and stirring was initiated. Nitrogen substitution was then performed. After nitrogen substitution, 4.2 parts of acrylonitrile, 10.8 parts of α-methylstyrene, and 0.08 parts of t-dodecyl mercaptan were added, and the temperature inside the reactor was raised to 65°C. When the temperature inside the reactor reached 70°C over 1 hour, an aqueous solution of 0.2 parts of potassium persulfate dissolved in 10 parts of deionized water was added dropwise over 4.5 hours. After the dropwise addition, the mixture was maintained for 4.5 hours to obtain an AMS Resin (C-3) latex. The resulting AMS resin (C-3) latex was then added to an aqueous solution containing magnesium sulfate, followed by coagulation, dehydration, and drying to obtain AMS resin (C-3) powder. The reduced viscosity of the acetone-soluble portion was 0.47 dL / g.

[0048] [Other additives] Ethylene bisstearamide (EBS): manufactured by Kao Corporation; Kaowax EB-FF

[0049] [Production of Rubber-Reinforced Thermoplastic Resin Composition] The components were melt-kneaded in the following proportions to obtain a rubber-reinforced thermoplastic resin composition. (Rubber-reinforced styrene-based resin) ABS resin (B-1): 28 parts (Other thermoplastic resins) AS resin (C-1): 47 parts AS resin (C-2): 4 parts AMS resin (C-3): 21 parts (Other additives) EBS: 0.5 parts

[0050] <Polymerization Evaluation> In the production of graft copolymer (A), when the propylene polymers stuck to each other in the vessel and the graft polymerization did not proceed, it was evaluated as "×", and when the propylene polymers did not stick to each other and the polymerization proceeded, it was evaluated as "◯". The results are shown in Table 1.

[0051] <Mold Contamination Evaluation> 9.5 parts of graft copolymers (A-1), (A-2), and (A-5) were added to 100 parts of the rubber-reinforced thermoplastic resin composition, mixed, and then melt-kneaded in a φ26 mm twin-screw extruder set at a cylinder temperature of 250°C, a main screw rotation speed of 400 rpm, and a discharge rate of 20 kg / hr, followed by pelletization. The resulting pellets were injection-molded using an injection molding machine (Sumitomo Heavy Industries, Ltd. "SE75EV"). Continuous molding was performed using a two-plate mold measuring 55 mm long x 90 mm wide x 3 mm thick, with a textured design surface, under molding conditions of a cylinder temperature of 230°C, a mold temperature of 30°C, and an injection speed of 50 mm / s. The number of shots required to visually confirm the accumulation of contaminants in the texture was confirmed. The results are shown in Table 1. ○: No white haze was observed on the mold surface even after 5,000 shots. x: White mist is observed on the mold surface after 5,000 shots or less.

[0052] <Paintability (Absorption Evaluation)> Three parts of graft copolymers (A-1), (A-2), and (A-5) were added to 100 parts of the rubber-reinforced thermoplastic resin composition, and the resulting pellets were pelletized in the same manner as in the mold contamination evaluation described above. Each pellet was injection-molded using an injection molding machine ("J-180ADS" manufactured by The Japan Steel Works, Ltd.). A mold for paint evaluation (150 mm length x 90 mm width x 2 mm thickness) was used, and molding was performed under molding conditions of a cylinder temperature of 200°C, a mold temperature of 15°C, and an injection speed of 50 mm / s. The resulting test pieces were painted with an acrylic resin paint, and the paint absorption phenomenon appearing on the molded product was visually observed. The paintability (absorption) was evaluated according to the following criteria. The results are shown in Table 1. ∘: No irregularities were observed on the surface of the molded product, making it extremely excellent. ×: Irregularities were observed on the entire surface of the molded product, making it unsuitable for practical use.

[0053] <Measurement of Graft Ratio of Graft Copolymer (A)> The graft ratio of graft copolymer (A) was measured by the following method. The propylene polymer content in graft copolymer (A) was calculated by the following formula (1), assuming that 99% of the charged amount of propylene polymer was contained in the graft copolymer. Propylene polymer content (%) = [{charged amount of propylene polymer (parts) × 0.99} / mass of graft copolymer (parts)] × 100 (1) Next, graft copolymer (A) was fractionated into a soluble portion and an insoluble portion using dichloromethane. The mass ratio of the dichloromethane-insoluble portion to the total amount of graft copolymer (A) was calculated. Since the propylene polymer was present in the dichloromethane-insoluble portion, the graft ratio was calculated by the following formula (2). Graft ratio (%)=[{mass ratio (%) of dichloromethane insoluble portion−propylene polymer content (%)} / propylene polymer content (%)]×100 (2)

[0054]

Claims

1. A graft copolymer obtained by graft polymerizing a propylene polymer with a monomer including a vinyl cyanide monomer and an aromatic vinyl monomer, wherein the propylene polymer is a random copolymer, and the melt flow rate of the propylene polymer at 230°C and 2.16 kg is 1.5 g / 10 min or more and less than 8 g / 10 min.

2. The graft copolymer according to claim 1, wherein the propylene polymer is a propylene-ethylene random copolymer.

3. The graft copolymer according to claim 1 or 2, having a graft ratio of 25% or more.

4. A thermoplastic resin composition comprising the graft copolymer according to claim 1 or 2 and a rubber-reinforced styrene-based resin, wherein the content of the graft copolymer is 1 to 10 parts by mass per 100 parts by mass of the total amount of the thermoplastic resin composition excluding the graft copolymer.

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