JP5688975B2 - Rubber-modified thermoplastic resin composition, injection-molded body thereof, and lid of washing machine using the same - Google Patents

Description

  The present invention relates to a rubber-modified thermoplastic resin composition, an injection molded body thereof, and a lid of a washing machine using the same.

  In general, ABS resin is widely used in home appliances, electrical / electronic equipment parts, OA equipment, pachinko parts, etc. because of its excellent impact resistance, mechanical properties, and molding processability. For applications that require transparency, transparent ABS resin is used (Patent Document 1). However, such transparent ABS resin is not sufficiently resistant to organic solvents such as alcohol, detergents, etc., and there is a problem that cracks and cracks may occur depending on the application and use environment, which impairs commercial value. There is a need to improve sex. In addition, there is a problem of deformation due to exposure to hot air with a dryer or the like, and contact with hot water or steam around the kitchen or sanitary, and improvement in heat resistance is also demanded.

  As means for improving the chemical resistance of these transparent ABS resins, it is generally known to increase the content of vinyl cyanide, and various so-called high nitrile-containing thermoplastic resin compositions have been proposed.

  For example, Patent Documents 2 to 4 propose resin compositions comprising a styrene-acrylonitrile-methyl methacrylate copolymer and a graft copolymer. Patent Document 5 proposes a resin composition comprising a copolymer of alkyl acrylate having 1 to 4 carbon atoms and methyl methacrylate, a styrene-acrylonitrile copolymer, and a graft copolymer. Furthermore, Patent Document 6 proposes a resin composition comprising an acrylic resin, an ABS resin, and a copolymer of vinyl cyanide and aromatic vinyl.

JP 2001-226547 A JP 2002-179873 A JP 2002-212369 A JP 2005-317093 A JP-A-2-274747 JP 2006-2038 A

However, the prior art described in the above document has room for improvement as follows, for example.
First, in Patent Documents 2 to 4, a resin composition comprising a copolymer of styrene-acrylonitrile-methyl methacrylate and a graft copolymer has a problem that the hue deteriorates as it becomes a high nitrile. It was.

  Second, in Patent Document 5, a resin composition comprising a copolymer of alkyl acrylate having 1 to 4 carbon atoms and methyl methacrylate, a styrene-acrylonitrile copolymer, and a graft copolymer has poor transparency, Further, since alkyl acrylate is copolymerized to improve thermal stability, there is a problem that heat resistance is low.

  Thirdly, in Patent Document 6, a resin composition comprising an acrylic resin, an ABS resin, and a copolymer of vinyl cyanide and aromatic vinyl has a problem in transparency as in Patent Document 5.

  As a result of intensive studies, the present inventors have determined that a specific styrene-methacrylic acid ester copolymer, a specific styrene-vinyl cyanide copolymer, and a specific graft copolymer have specific conditions. In addition, the rubber-modified thermoplastic resin composition contained in a specific composition is generally in a trade-off relationship with each other, and it is difficult to satisfy at the same time, chemical resistance, transparency, hue It was found that heat resistance and impact resistance are excellent in a well-balanced manner.

  That is, according to the present invention, a rubber containing a styrene-methacrylic acid ester copolymer (A), a styrene-vinyl cyanide copolymer (B), and a graft copolymer (C). A modified thermoplastic resin composition is provided. And this (A) component is 1-15 mass% of styrene-type monomer units, when the total mass of a styrene-type monomer unit and a methacrylic ester-type monomer unit is 100 mass%, methacryl It is a styrene-methacrylic acid ester copolymer in which an acid ester monomer unit is contained within a range of 85 to 99% by mass. In addition, the component (B) is composed of 80 to 90% by mass of styrene monomer units and cyan when the total mass of the styrene monomer units and the vinyl cyanide monomer unit is 100% by mass. It is a styrene-vinyl cyanide copolymer containing vinyl halide monomer units in the range of 10 to 20% by mass. Further, the component (C) is formed by copolymerizing a rubbery elastic body with a styrene monomer, a methacrylic acid ester monomer, and a vinyl cyanide monomer. In this case, the molded product having a thickness of 2 mm is a graft copolymer in which the total light transmittance is 85% or more.

  And when the total mass of these (A) component, (B) component, and (C) component is 100 mass%, this (A) component is 15-54 mass%, (B) component is 20- 63 mass%, this (C) component is contained within the range of 10-50 mass%. The difference between the refractive index of the mixture of the component (A) and the component (B) and the refractive index of the component (C) is 0.005 or less. Furthermore, the vinyl cyanide monomer unit in the mixture of these (A) component and (B) component is 6-15 when the total mass of (A) component and (B) component is 100 mass%. It is in the range of mass%.

  According to these conditions and blending composition, a specific styrene-methacrylic acid ester copolymer, a specific styrene-vinyl cyanide copolymer, and a specific graft copolymer are Because it is contained in a specific composition, it is generally considered that it is difficult to satisfy at the same time because it is in a trade-off relationship with each other, in terms of chemical resistance, transparency, hue, heat resistance, and impact resistance. A rubber-modified thermoplastic resin composition excellent in balance can be obtained.

  Moreover, according to this invention, the injection molded object formed by injection-molding said rubber-modified thermoplastic resin composition is provided. Since the rubber-modified thermoplastic resin composition having a good balance of chemical resistance, transparency, hue, heat resistance, and impact resistance is used, injection molding is performed by injection molding the rubber-modified thermoplastic resin composition. Similarly, the body is well balanced in chemical resistance, transparency, hue, heat resistance and impact resistance.

  Furthermore, according to this invention, the lid | cover of a washing machine using said injection molded object as a member is provided. Since the above-mentioned injection molded article having excellent balance in chemical resistance, transparency, hue, heat resistance and impact resistance is used, the lid of a washing machine using the injection molded article as a member is also chemically resistant, Excellent balance in transparency, hue, heat resistance and impact resistance.

It is a perspective view for demonstrating the chemical-resistance test method using the test piece (350x20x2mmt) press-molded to the Bergen type 1/4 elliptical jig in an Example and a comparative example.

<Explanation of terms>
In this specification, the symbol “to” means “above” and “below” and includes an upper limit value and a lower limit value indicated by “to”, respectively. For example, the description “A to B” means A or more and B or less. “Contains” includes “consisting essentially of” and “consisting of”.

  Hereinafter, embodiments of the present invention will be described in detail.

<Rubber-modified thermoplastic resin composition>
According to this embodiment, the rubber modification containing a styrene-methacrylic acid ester copolymer (A), a styrene-vinyl cyanide copolymer (B), and a graft copolymer (C). A thermoplastic resin composition is provided. Since the rubber-modified thermoplastic resin composition of the present embodiment contains these component (A), component (B), and component (C) so as to satisfy the specific conditions and compounding composition described later, Have a good balance of chemical resistance, transparency, hue, heat resistance and impact resistance, which are said to be in a trade-off relationship and difficult to satisfy at the same time.

(I) Component (A): Styrene-methacrylic acid ester copolymer The above component (A) is a styrene-methacrylic acid ester copolymer containing a styrene monomer unit and a methacrylic acid ester monomer unit. It is a coalescence. The structure of the styrene-methacrylic ester copolymer is not particularly limited, and a copolymer having an arbitrary structure including a styrene monomer unit and a methacrylic ester monomer unit can be used. That is, the copolymers are roughly classified into four types of structures: random copolymers, alternating copolymers, periodic copolymers, and block copolymers. One type of block copolymer is a graft system. Although there is a copolymer (a copolymer having a branched structure in which different types of branched polymer chains are bonded to a main polymer chain), a copolymer having any structure may be used.

  Examples of the styrene monomer unit used in the component (A) include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, and pt-butylstyrene. Chlorostyrene, bromostyrene and the like can be mentioned, but from the viewpoint of kneadability and stability against thermal decomposition, styrene and α-methylstyrene are preferable, and styrene is particularly preferable. These styrenic monomers may be used alone or in combination of two or more. About these styrene-type monomer units, it can manufacture using the raw material which consists of a corresponding monomer or contains, for example.

  Examples of the methacrylic acid ester monomer units used in the component (A) include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. From the viewpoint of imparting heat resistance to the resin, It is preferable to use methyl methacrylate. These methacrylic acid ester monomers may be used alone or in combination of two or more. These methacrylic acid ester-based monomer units can be produced using, for example, a raw material comprising or including a corresponding monomer.

  In this styrene-methacrylic acid ester copolymer, when the total mass of the styrene monomer unit and the methacrylic acid ester monomer unit is 100% by mass, the styrene monomer unit is 1 It is preferable that -15 mass% and a methacrylic acid ester monomer unit are contained in the range of 85-99 mass%. Similarly, it is more preferable that the styrene monomer unit is contained within the range of 2 to 13% by mass and the methacrylic acid ester monomer unit within the range of 87 to 98% by mass. This is because if the styrene monomer unit is 15% by mass or less, the smaller the styrene monomer unit, the more transparent the rubber-modified thermoplastic resin composition containing this styrene-methacrylic acid ester copolymer. This is because the property is improved. Further, if the styrene monomer unit is 1% by mass or more, the more styrene monomer units, the more heat of the rubber-modified thermoplastic resin composition containing the styrene-methacrylic acid ester copolymer. This is because stability is excellent and transparency and hue are improved.

  The weight average molecular weight (Mw) of the styrene-methacrylic acid ester copolymer as the component (A) is preferably 70,000 to 100,000, and preferably 80,000 to 90,000. Is particularly preferred. When the weight average molecular weight is 70,000 or 80,000 or more, the chemical resistance of the rubber-modified thermoplastic resin composition containing the styrene-methacrylic acid ester copolymer is improved. In addition, if the weight average molecular weight is 100,000 or 90,000 or less, the melt mass flow rate (MFR) of the rubber-modified thermoplastic resin composition containing the styrene-methacrylic acid ester copolymer can be maintained high. In addition, the moldability can be maintained well. In addition, the weight average molecular weight here was measured by the following gel permeation chromatography (GPC) method.

Device name: SYSTEM-21 Shodex (manufactured by Showa Denko)
Column: PL Gel MIXED-B in series 3 Temperature: 40 ° C
Detection: Differential refractometer Solvent: THF (tetrahydrofuran)
Concentration: 2% by mass
Calibration curve: prepared using standard polystyrene (PS) (manufactured by PL), and the weight average molecular weight (Mw) was expressed in terms of PS.

(Ii) Component (B): Styrene-vinyl cyanide copolymer The above component (B) is a styrene-vinyl cyanide copolymer comprising a styrene monomer unit and a vinyl cyanide monomer unit. It is a coalescence. The structure of the styrene-vinyl cyanide copolymer is not particularly limited, and a copolymer having an arbitrary structure including a styrene monomer unit and a vinyl cyanide monomer unit can be used. That is, the copolymers are roughly classified into four types of structures: random copolymers, alternating copolymers, periodic copolymers, and block copolymers. One type of block copolymer is a graft system. Although there is a copolymer (a copolymer having a branched structure in which different types of branched polymer chains are bonded to a main polymer chain), a copolymer having any structure may be used.

  Examples of the styrene monomer unit used in the component (B) include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, and pt-butylstyrene. Chlorostyrene, bromostyrene and the like can be mentioned, but from the viewpoint of kneadability and stability against thermal decomposition, styrene and α-methylstyrene are preferable, and styrene is particularly preferable. These styrenic monomers may be used alone or in combination of two or more. These styrenic monomer monomer units can be produced using, for example, a raw material comprising or including a corresponding monomer.

  Examples of the vinyl cyanide monomer unit used in the component (B) include acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, and the like, and imparts chemical resistance and a styrene-methacrylate copolymer. From the viewpoint of compatibility with acrylonitrile, acrylonitrile is preferred. These vinyl cyanide monomers may be used alone or in combination of two or more. These vinyl cyanide monomer units can be produced using, for example, a raw material comprising or including a corresponding monomer.

  The styrene-vinyl cyanide-based copolymer that is the component (B) is styrene when the total mass of the styrene monomer unit and the vinyl cyanide monomer unit is 100% by mass. It is preferable that the monomer unit is contained in the range of 80 to 90% by mass and the vinyl cyanide monomer unit in the range of 10 to 20% by mass. Similarly, it is more preferable that the styrene monomer unit is contained in the range of 80 to 88% by mass and the vinyl cyanide monomer unit is contained in the range of 12 to 20% by mass. And it is especially preferable that the styrene monomer unit is contained in the range of 80 to 84% by mass and the vinyl cyanide monomer unit in the range of 16 to 20% by mass. This is because if the vinyl cyanide monomer unit is 20% by mass or less, the smaller the vinyl cyanide monomer unit, the smaller the rubber-modified thermoplastic resin composition containing this styrene-vinyl cyanide copolymer. This is because the transparency of the material is improved. Further, if the vinyl cyanide monomer unit is 10% by mass or more, the more vinyl cyanide monomer units, the more the rubber-modified thermoplastic resin composition containing this styrene-vinyl cyanide copolymer. This is because the chemical resistance is improved.

  The weight average molecular weight (Mw) of the styrene-vinyl cyanide copolymer as the component (B) is preferably 100,000 to 190,000, and 160,000 to 180,000. It is particularly preferred. If the weight average molecular weight of the styrene-vinyl cyanide copolymer is 100,000 or 160,000 or more, the impact resistance of the rubber-modified thermoplastic resin composition containing the styrene-vinyl cyanide copolymer If the weight average molecular weight of the styrene-vinyl cyanide copolymer is 190,000 or 180,000 or less, the rubber modification containing the styrene-vinyl cyanide copolymer can be maintained. The moldability of the thermoplastic resin composition can be maintained well.

(Iii) Component (C): Graft copolymer The component (C) includes a rubber-like elastic body, a styrene monomer, a methacrylic acid ester monomer, and a vinyl cyanide monomer. Is a graft copolymer. The structure of the graft copolymer is not particularly limited, and a rubber-like elastic body is copolymerized with a styrene monomer, a methacrylate ester monomer, and a vinyl cyanide monomer. Any graft copolymer can be used. That is, it may be a graft copolymer having a branched structure in which different types of branched polymer chains are bonded to a general polymer chain serving as a trunk.

  As the rubber-like elastic body used in the above component (C), even if a slight external force, which is the definition of a general rubber-like elastic body, is added, it shows a large elongation. However, if the external force is removed, it will return instantly. Any polymer compound may be used. For example, polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene-acrylic copolymer, styrene-butadiene-styrene block copolymer, polyisoprene, styrene-isoprene copolymer. Conjugated diene rubbers such as polymers, and hydrogenated products thereof, acrylic rubbers such as ethyl acrylate and butyl acrylate, ethylene-α-olefin-polyene copolymers, ethylene-α-olefin copolymers, silicones Examples include rubber, silicone-acrylic rubber copolymer, and the like. These may be used alone or in combination of two or more. Can be used in combination. Among these, from the viewpoint of imparting hue and impact resistance, a rubber-like elastic body containing a styrene-butadiene copolymer as a main component is particularly preferable.

  In addition, although there is no restriction | limiting in particular in the ratio of styrene and a butadiene in the case of using a styrene-butadiene copolymer as a rubber-like elastic body used by said (C) component, The total mass of styrene and a butadiene is 100 mass%. In this case, the styrene content is preferably 15 to 50% by mass, the butadiene content is preferably 50 to 85% by mass, the styrene content is 20 to 45% by mass, and the butadiene content is 55 to 80% by mass. -More preferred are butadiene copolymers. When the difference between the refractive index of the mixture of the component (A) and the component (B) and the refractive index of the component (C) is 0.005 or less, the styrene-butadiene copolymer used in the component (C) When the styrene content in the polymer is 20% by mass or more, the refractive index of the rubber-like elastic material containing a styrene-butadiene copolymer as a main component becomes high, so that the rubber-modified thermoplastic resin composition The blending ratio of the styrene-vinyl cyanide copolymer (B) can be increased, and the chemical resistance is improved. Further, when the styrene content is 45% by mass or less, the properties as an elastic body are further improved, so that the impact strength of the rubber-modified thermoplastic resin composition is improved.

  Examples of the styrene monomer used in the component (C) include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, pt-butylstyrene, Chlorostyrene, bromostyrene and the like can be mentioned, and from the viewpoints of compatibility and kneadability between the component (A) and the component (B), styrene and α-methylstyrene are preferable. Styrene is preferred. These styrenic monomers may be used alone or in combination of two or more.

  Examples of the methacrylic acid ester monomer used in the component (C) include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. The component (A) and the component (B) From the viewpoint of compatibility and heat resistance, it is preferable to use methyl methacrylate. These methacrylic acid ester monomers may be used alone or in combination of two or more.

  Examples of the vinyl cyanide monomer used in the component (C) include acrylonitrile, methacrylonitrile, etaacrylonitrile, fumaronitrile, and the like. The phase of the component (A) and the component (B) From the viewpoint of imparting solubility and chemical resistance, acrylonitrile is preferred. These vinyl cyanide monomers may be used alone or in combination of two or more.

  Here, the graft copolymer as the component (C) preferably has a total light transmittance of 85% or more of a 2 mm-thick molded product obtained by press molding the graft copolymer, in particular 88. More preferably, it is% or less. If the total light transmittance of this press-molded body is 85% or 88% or more, the transparency of the resin composition as a material for molding the press-molded body is also improved.

  In order to obtain a graft copolymer having a total light transmittance of 85% or 88% or more in the press-molded product, no complicated preparation is required. The refractive index of the rubber-like elastic material and the styrene-based copolymer are not required. It is easily obtained by adjusting the graft branch composition so that the difference from the refractive index of the graft branch formed by copolymerizing the monomer, methacrylate ester-based monomer and vinyl cyanide-based monomer is as small as possible. be able to.

  Moreover, in said (C) component, in the range which does not impair the effect of the rubber-modified thermoplastic resin composition of this embodiment, ethyl acrylate, methacrylate, propyl methacrylate, butyl methacrylate, stearyl methacrylate, etc. It is also possible to graft a rubber-like elastic body using other copolymerizable vinyl monomers such as acrylic acid esters and methacrylic acid esters.

  In the above component (C), the rubber-modified thermoplastic resin composition containing the graft copolymer has a volume average particle size of the graft copolymer of 0.25 to 0.80 μm. In order to obtain good transparency and impact resistance, it is particularly preferably 0.30 to 0.70 μm. If the volume average particle diameter is 0.25 μm or 0.30 μm or more, the impact resistance is excellent, and if it is 0.80 μm or less, the transparency can be maintained well, which is preferable. Here, the volume average particle diameter is a volume-based median diameter measured by a light scattering type particle size distribution measuring device in which a vinyl copolymer is dispersed in N, N-dimethylformamide (DMF).

(Iv) Compounding composition of rubber-modified thermoplastic resin composition In the rubber-modified thermoplastic resin composition of the present embodiment, the total mass of the component (A), the component (B) and the component (C) is 100% by mass. In this case, in order to obtain a rubber-modified thermoplastic resin composition having excellent chemical resistance, transparency, heat resistance, and impact resistance, the component (A) (styrene-methacrylate copolymer) is 15 to 54% by mass, 20% to 63% by mass of the component (B) (styrene-vinyl cyanide copolymer), and 10% to 50% by mass of the component (C) (graft copolymer). It is preferable that

  Similarly, in order to obtain a rubber-modified thermoplastic resin composition that is further excellent in chemical resistance, transparency, heat resistance, and impact resistance, the above component (A) (styrene-methacrylate copolymer) Is 20 to 40% by mass, the component (B) (styrene-vinyl cyanide copolymer) is 20 to 40% by mass, and the component (C) (graft copolymer) is 15 to 45% by mass. It is preferable that it is contained within.

  In the rubber-modified thermoplastic resin composition of the present embodiment, a mixture of the component (A) (styrene-methacrylic acid ester copolymer) and the component (B) (styrene-vinyl cyanide copolymer). And the difference between the refractive index of the component (C) (graft copolymer) is preferably 0.005 or less, particularly preferably 0.003 or less. When this refractive index difference is 0.005 or 0.003 or less, the transparency of the resulting rubber-modified thermoplastic resin composition can be maintained well. The refractive index referred to here is a molded product having a thickness of 2 mm by press molding from a mixture of the component (A) and the component (B) or a resin composition containing the component (C) as a main component. Measured using an Abbe refractometer.

  Furthermore, in the rubber-modified thermoplastic resin composition of the present embodiment, a mixture of the component (A) (styrene-methacrylic acid ester copolymer) and the component (B) (styrene-vinyl cyanide copolymer). The content of the vinyl cyanide monomer unit in the inside is preferably in the range of 6 to 15% by mass when the total mass of the component (A) and the component (B) is 100% by mass. If the content of the vinyl cyanide monomer unit is 6% by mass or more, the chemical resistance of the resulting rubber-modified thermoplastic resin composition can be maintained satisfactorily. If the content of is 15% by mass or less, the yellowness can be suppressed from becoming strong, so that the hue can be maintained well.

(V) Method for Producing Rubber-Modified Thermoplastic Resin Composition The above styrene-methacrylic acid ester copolymer (A) and styrene-vinyl cyanide copolymer constituting the rubber-modified thermoplastic resin composition of the present embodiment The method for producing the combination (B) is not particularly limited, and any known polymerization method such as a bulk polymerization method, a suspension polymerization method, a bulk-suspension polymerization method, a solution polymerization method, and an emulsion polymerization method can be used. However, in order to obtain heat resistance, better hue, and transparency, it is preferable that the copolymers of the above components (A) and (B) are polymerized by continuous bulk polymerization.

  On the other hand, the production method of the graft copolymer (C) constituting the rubber-modified thermoplastic resin composition of the present embodiment is not particularly limited as well, and is an emulsion polymerization method, a bulk polymerization method, a bulk-suspension. Any known polymerization method such as a polymerization method or a solution polymerization method can be used, and among these, an emulsion polymerization method can be suitably employed from the viewpoint of transparency and appearance of an injection-molded product. In any of the production methods, a part of the styrene-methacrylic acid ester copolymer (A) constituting the continuous phase may be produced simultaneously with the production of the graft copolymer (C). In addition, any of a batch polymerization method and a continuous polymerization method can be used.

  These styrene-methacrylic acid ester copolymers (A), styrene-vinyl cyanide copolymers (B), and graft copolymers (C) are polymerized by using azobis as a polymerization initiator. Azo compounds such as butyronitrile, azobiscyclohexanecarbonitrile, benzoyl peroxide, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, di-t-butylperoxide, dicumylper Organic peroxides such as oxide and ethyl-3,3-di- (t-butylperoxy) butyrate can be used. Further, t-dodecyl mercaptan, n-dodecyl mercaptan, 4-methyl-2,4-diphenylpentene-1 may be added as a molecular weight adjusting agent, and diisobutyl adipate, butylbenzyl phthalate, or the like may be added as a plasticizer. .

  In the production of the rubber-modified thermoplastic resin composition of the present embodiment, a styrene-methacrylic acid ester copolymer (A), a styrene-vinyl cyanide copolymer (B), and a graft copolymer (C). The mixing method is not particularly limited. For example, after premixing with a known mixing apparatus such as a Henschel mixer or a tumbler mixer, the mixture is melt-kneaded using an extruder such as a single screw extruder or a twin screw extruder. By performing the above, uniform mixing can be performed.

  The rubber-modified thermoplastic resin composition of the present embodiment includes a styrene-methacrylic acid ester copolymer (A), a styrene-vinyl cyanide copolymer (B), and a graft copolymer (C). Moreover, arbitrary well-known additives can be mix | blended as needed. For example, plasticizers, lubricants, silicone oils and the like can be blended in order to improve fluidity and releasability. Moreover, in order to provide a weather resistance, a light stabilizer and a ultraviolet absorber can be mix | blended. Other examples include antioxidants, antistatic agents, colorants, pigments, dyes, lubricants, antiblocking agents, foaming agents, foaming aids, crosslinking agents, and crosslinking aids.

  When the rubber-modified styrenic resin composition of the present embodiment is processed into various shapes such as pellets as raw materials, there is no particular limitation on compounding and melt extrusion, and a known method can be employed. For example, each raw material such as styrene-methacrylic acid ester copolymer (A), styrene-vinyl cyanide copolymer (B), and graft copolymer (C) is previously uniform using a tumbler or Henschel mixer. There is a method in which the mixture is fed to a single-screw extruder or a twin-screw extruder, melt-kneaded, and adjusted as pellets. The rubber-modified styrenic resin composition of the present embodiment thus obtained can be processed into various molded bodies and put to practical use by methods such as injection molding, compression molding and extrusion molding. The rubber-modified styrenic resin composition of the form is injection molded by injection-molding this rubber-modified styrenic resin composition in order to satisfy the chemical resistance, transparency, hue, heat resistance, and impact resistance properties in a well-balanced manner. The body is extremely excellent in practice.

<Injection molded body>
The injection-molded product of the present embodiment can be obtained by molding the rubber-modified thermoplastic resin composition into a predetermined shape by injection molding. The injection-molded product of this embodiment is particularly effective when applied to containers and container lids that are required to satisfy chemical resistance, transparency, hue, heat resistance, and impact resistance in a well-balanced manner. .

  The raw material for obtaining this injection-molded body may be made of the above-mentioned rubber-modified thermoplastic resin composition, and the shape and the like are not particularly limited, but the handling property and moldability during injection molding are good. In order to do so, it is preferable to have a pellet shape.

  The temperature of injection molding of the rubber-modified thermoplastic resin composition is preferably in the range of 180 to 280 ° C., for example, from the viewpoint of moldability and hue. If this injection temperature is 180 ° C. or higher, the fluidity of the rubber-modified thermoplastic resin composition is increased and the mold can be filled well, so that the moldability is improved. Moreover, if this injection temperature is 280 ° C. or lower, it is possible to suppress the occurrence of burns in the injection-molded product.

<Washing machine lid>
The lid of the washing machine of the present embodiment is a lid of a washing machine using the above injection molded body as a member. The washing machine here generally means a machine that performs washing semi-automatically or fully automatically. However, it is not intended to exclude a manual washing machine that manually rotates the washing tub. Conventionally, opaque parts have generally been used for lids of washing machines. However, due to the recent increase in demand for design, a material having transparency and excellent hue is required for the lid. Also, the lid of the washing machine is frequently exposed to the chemical solution due to the splashing of the detergent solution from the inside of the washing tub, so that it is easily affected by the rotation of the washing tub and the opening / closing of the lid by the user. Heat generated from the machine drive and when the user is washing with hot water may be exposed to the high temperature of the detergent solution. Therefore, the lid of the washing machine is required to satisfy the chemical resistance, transparency, hue, heat resistance, and impact resistance characteristics in a well-balanced manner. On the other hand, the injection-molded product satisfies the chemical resistance, transparency, hue, heat resistance, and impact resistance properties in a well-balanced manner, and thus is suitable as a member for such a transparent lid.

  Note that the lid of the washing machine of the present embodiment does not need to be made of the above-described injection-molded body as a whole, for example, a transparent viewing window provided so that a user can look inside the washing tub of the washing machine. It may be used as a member. In this way, an injection-molded body that satisfies the above-mentioned properties of chemical resistance, transparency, hue, heat resistance, and impact resistance can be used only in a necessary range. Manufacturing costs can be reduced.

  The rubber-modified thermoplastic resin composition and the like described by the above aspects and embodiments are not intended to limit the present invention but are disclosed for the purpose of illustration. The technical scope of the present invention is defined by the description of the claims, and those skilled in the art can make various design changes within the technical scope of the invention described in the claims.

  For example, in the above embodiment, the rubber-modified thermoplastic resin composition includes a styrene-methacrylic acid ester copolymer (A), a styrene-vinyl cyanide copolymer (B), and a graft copolymer. (C) is included, but it is not intended to exclude the inclusion of other types of resins or copolymers. For example, depending on the use of the rubber-modified thermoplastic resin composition, polystyrene, MS resin, AS resin, ABS resin, acrylic resin, polycarbonate, and the like can be used as long as the object of the present invention is not impaired. It may be included as a polymer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these. Note that the parts and ratios described in the examples are all based on mass unless otherwise specified.

<Measurement method>
Various measured values and various physical properties constituting the styrene-methacrylic acid ester copolymer, styrene-vinyl cyanide copolymer, graft copolymer and rubber-modified thermoplastic resin composition used in this example. A method for measuring the value will be described below.

(1) Resin composition of styrene copolymer, vinyl cyanide content: FT-NMR (FX-90Q manufactured by JEOL Ltd.) was prepared as a measurement material by dissolving the copolymer in deuterated chloroform to prepare a 2% solution. ¹³ C was used and calculated from the peak areas of styrene, methyl methacrylate and acrylonitrile.

  (2) Graft branch composition of the graft copolymer: The graft copolymer was stirred in methyl ethyl ketone at a temperature of 23 ° C. for 24 hours and centrifuged at a temperature of −9 ° C. and a rotational speed of 20000 rpm for 60 minutes. The insoluble matter was separated and then allowed to stand for 30 minutes. The supernatant of the centrifuged solution was collected, methanol was added, and an ungrafted styrene-methacrylate copolymer was precipitated. The precipitate was collected, dissolved in deuterated chloroform, and the composition was determined using FT-NMR (FX-90Q type manufactured by JEOL Ltd.). In these graft copolymers, the composition of the styrene-methacrylic acid ester copolymer grafted on the rubber-like elastic body is the same as that of the ungrafted styrene-methacrylic acid ester copolymer. Therefore, this measured value was set as the composition of the styrene-methacrylic ester copolymer grafted on the rubber-like polymer.

  (3) Refractive index of copolymer: A molded product having a thickness of 2 mm was prepared by press molding, and measured using an Abbe refractometer (DR-M2) manufactured by Atago Co., Ltd.

  (4) Refractive index of copolymer: A molded product having a thickness of 2 mm was produced by press molding, and measured using an Abbe refractometer (DR-M2) manufactured by Atago Co., Ltd.

  (5) Total light transmittance / HAZE: Measured according to ASTM D-1003 using a Nippon Denshoku Industries HAZE meter (NDH-2000). If the total light transmittance is 88% or more and HAZE is 7% or less, it can be judged that the transparency is good.

  (6) Hue: The b value was measured by a transmission method using a color difference meter (Σ-80) manufactured by Nippon Denshoku. If the b value is 5 or less, it can be determined that the hue is excellent.

  (7) MFR: Measured under the conditions of a temperature of 220 ° C. and a load of 10 kg according to JIS K6874 using a sample pellet.

  (8) Charpy impact strength: A test piece having dimensions of 12.7 × 64 × 6.4 mm was formed at a cylinder temperature of 220 ° C. using Toshiba Machine Co., Ltd. (IS-80CNV). It measured based on ISO 179-2 using this test piece. If the Charpy impact strength is 5 kJ / m 2 or more, it can be determined that the impact resistance is good.

  (9) Vicat softening point: A test piece having a size of 12.7 × 64 × 6.4 mm was molded at a cylinder temperature of 220 ° C. using an injection molding machine (IS-80CNV) manufactured by Toshiba Machine Co., Ltd. Using this test piece, measurement was performed under the condition of a load of 49.0 N in accordance with JIS K7206. If the Vicat softening point is 100 ° C. or higher, it can be determined that the heat resistance is good.

(10) Volume average rubber particle diameter of the graft copolymer: measured using a Beckman Coulter Coalter Multisizer (LS230).
The volume average particle size referred to here is measured with a light scattering particle size distribution analyzer by dissolving the graft copolymer (C) and the rubber-modified thermoplastic resin composition in N, N-dimethylformamide (DMF). The volume-based median diameter.

  (11) Chemical resistance: A test piece (350 × 20 × 2 mmt) press-molded on the Bergen-type 1/4 elliptical jig shown in FIG. 1 is fixed along the curvature, and 20 g of the target chemical is uniformly applied. After standing for 48 hours at ℃ and humidity 55% RH, check the occurrence of crazes and cracks, calculate critical strain ε (%) from the following formula, and if the value is less than 0.3%, .3 to 0.6% is △, 0.6 to 0.9% is ○, 0.9% or more is ◎, and ○ and ◎ are excellent in chemical resistance. did. As chemicals, attack (weak alkaline laundry detergent, Kao) and magic phosphorus (alkaline residential detergent, Kao) were used.

Where ε: critical strain (%)
a: Long axis of 1/4 ellipse method jig (mm)
b: minor axis (mm) of 1/4 ellipse method jig
t: Test piece thickness (mm)
X: Crack occurrence point (mm)
It is.

<Example of copolymer production>
(A) Method for producing styrene-methacrylic acid ester copolymer Styrene-methacrylic acid ester copolymer (a-1)
A complete mixing type continuous reaction tank having a volume of about 20 L equipped with a stirring blade, a column type plug flow type continuous reaction tank having a volume of about 11 L, and a flash type devolatilization tank equipped with a preheater were connected in series. 0.0073 parts by mass of t-butylperoxyisopropyl monocarbonate and 0.32 of n-dodecyl mercaptan with respect to a solution composed of 79.2% by mass of methyl methacrylate, 8.8% by mass of styrene, and 12.0% by mass of ethylbenzene Mass parts were mixed to obtain a raw material solution. This raw material solution was supplied to a complete mixing type continuous reaction vessel maintained at a temperature of 125 ° C. at 3.9 kg / h for polymerization. The conversion rate at the outlet of the complete mixing type continuous reaction vessel was controlled to 55 to 58%. Further, this polymerization solution was supplied to a tower type plug flow type continuous reaction vessel adjusted so as to have a gradient of 125 ° C. to 144 ° C. in the flow direction, and polymerized. The conversion rate at the outlet of the column type plug flow type continuous reaction vessel was controlled to 75 to 78%. While this polymerization solution was heated to 230 ° C. with a preheater, it was introduced into a flash-type devolatilization tank depressurized to 1.3 kPa, and unreacted monomers were removed at a tank temperature of 235 ° C. The resin at 232 ° C. was extracted with a gear pump, and extruded and cut into a strand shape to obtain a pellet-shaped styrene-methacrylic acid ester copolymer (a-1).

Styrene-methacrylic acid ester copolymer (a-2)
Styrene-methacrylic acid was carried out in the same manner as in (a-1) except that a monomer solution consisting of 79.8% by weight of methyl methacrylate, 2.2% by weight of styrene and 18.0% by weight of ethylbenzene was used. An ester copolymer (a-2) was obtained.

Styrene-methacrylate copolymer (a-3)
Styrene-methacrylic acid was carried out in the same manner as in (a-1) except that a monomer solution composed of methyl methacrylate 70.0% by mass, styrene 18.0% by mass, and ethylbenzene 12.0% by mass was used. An ester copolymer (a-3) was obtained.

Styrene-methacrylic acid ester copolymer (a-4)
Except having made the quantity of n-dodecyl mercaptan 0.45 mass part, it implemented similarly to (a-1) and obtained the styrene-methacrylic acid ester type copolymer (a-4).

Styrene-methacrylate copolymer (a-5)
Except having made the amount of n-dodecyl mercaptan into 0.20 mass part, it implemented similarly to (a-1) and obtained the styrene-methacrylic acid ester type copolymer (a-5).

Polymethyl methacrylate (a-6)
As polymethyl methacrylate, Kuraray Parapet G was used.

Styrene-methacrylic acid ester copolymer (a-7)
A monomer mixture of 52 kg of styrene, 38 kg of methyl methacrylate and 10 kg of acrylonitrile, 80 g of benzoyl peroxide as a polymerization initiator, and 300 g of t-dodecyl mercaptan as a chain transfer agent were added to a 200 L autoclave at a temperature of 95 ° C. while stirring. After heating for 2 hours at a temperature of 130 ° C., the suspension polymerization was stopped by cooling. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene-methacrylic acid ester copolymer (a-7).

Styrene-methacrylic acid ester copolymer (a-8)
Styrene-methacrylic acid was carried out in the same manner as in (a-1) except that a monomer solution composed of methyl methacrylate 43.0% by mass, styrene 45.0% by mass, and ethylbenzene 12.0% by mass was used. An ester copolymer (a-8) was obtained.

  The compositions of the styrene-methacrylic acid ester copolymers (a-1) to (a-8) described so far are summarized in Table 1 below.

(B) Method for producing styrene-vinyl cyanide copolymer Styrene-vinyl cyanide copolymer (b-1)
A complete mixing type continuous reaction tank having a volume of about 20 liters equipped with a stirrer, a column type plug flow type continuous reaction tank having a volume of about 40 L, and a flash type devolatilization tank having a preheater were connected in series. A solution composed of 81 parts by mass of styrene, 19 parts by mass of acrylonitrile, and 10 parts by mass of ethylbenzene is mixed with 0.02 parts by mass of t-butylperoxyisopropyl monocarbonate and 0.02 parts by mass of n-dodecyl mercaptan, did. This raw material solution was supplied to a complete mixing type continuous reaction vessel controlled at a temperature of 130 ° C. at 6.0 kg / h and polymerized. In addition, the stirring number of the complete mixing type reactor was 180 rpm. Further, the reaction liquid was continuously withdrawn from the complete mixing type reactor, supplied to a tower type plug flow type continuous reaction tank adjusted so as to have a gradient of 130 ° C. to 160 ° C. in the flow direction, and polymerized. While this polymerization solution was heated to 230 ° C. with a preheater, it was introduced into a flash-type devolatilization tank depressurized to 1.0 kPa, and unreacted monomers were removed at a tank temperature of 235 ° C. This resin was extracted with a gear pump and extruded and cut into a strand to obtain a pellet-shaped styrene-vinyl cyanide copolymer (b-1).

Styrene-vinyl cyanide copolymer (b-2)
A styrene-acrylonitrile copolymer (b-2) was obtained in the same manner as (b-1) except that 70 parts by mass of styrene and 30 parts by mass of acrylonitrile were used.

Styrene-vinyl cyanide copolymer (b-3)
A styrene-acrylonitrile copolymer (b-3) was obtained in the same manner as (b-1) except that 88 parts by mass of styrene and 12 parts by mass of acrylonitrile were used.

Styrene-vinyl cyanide copolymer (b-4)
A styrene-acrylonitrile copolymer (b-4) was obtained in the same manner as in (b-1) except that 92 parts by mass of styrene and 8 parts by mass of acrylonitrile were used.

Styrene-vinyl cyanide copolymer (b-5)
Except that n-dodecyl mercaptan was changed to 0.035 parts by mass, the same procedure as in (b-1) was carried out.
A styrene-acrylonitrile copolymer (b-5) was obtained.

Styrene-vinyl cyanide copolymer (b-6)
Except that n-dodecyl mercaptan was changed to 0.04 parts by mass, the same procedure as in (b-1) was carried out.
A styrene-acrylonitrile copolymer (b-6) was obtained.

Styrene-vinyl cyanide copolymer (b-7)
Except that n-dodecyl mercaptan was changed to 0.015 part by mass, the same procedure as in (b-1) was carried out.
A styrene-acrylonitrile copolymer (b-7) was obtained.

  The compositions of the styrene-vinyl cyanide copolymers (b-1) to (b-7) described so far are summarized in Table 2 below.

(C) Method for producing graft copolymer Graft copolymer (c-1)
Styrene-butadiene latex (styrene content 40% by mass, rubber particle diameter 0.3 μm) 36 kg in terms of solid content is weighed and transferred to a 200 L autoclave equipped with a stirrer, and the water content is combined with the water content in the polybutadiene latex. Pure water was added to 100 kg, and the temperature was raised to 50 ° C. in a nitrogen atmosphere while stirring. To this, 1.8 g of ferrous sulfate, 3.6 g of sodium ethylenediaminetetraacetate and 108 g of Rongalite dissolved in 2 kg of pure water were added, and a mixture consisting of 13.2 kg of styrene, 10.8 kg of methyl methacrylate and 240 g of t-dodecyl mercaptan. And 48 g of diisopropylbenzene hydroperoxide and 450 g of potassium oleate dispersed in 8 kg of pure water were continuously added separately over 6 hours. After completion of the addition, the temperature was raised to 70 ° C., 24 g of diisopropylbenzene hydroperoxide was further added, and the mixture was allowed to stand for 2 hours to complete the polymerization. Antioxidant is added to the obtained emulsion, the solid content is diluted to 15% by mass with pure water, the temperature is raised to 70 ° C., dilute sulfuric acid is added with vigorous stirring, and salting out is performed. The mixture was heated to 95 ° C. and solidified, then dehydrated, washed with water and dried to obtain a powdered graft copolymer (c-1).
The obtained graft copolymer had a volume average particle size of 0.35 μm.

Graft copolymer (c-2)
A graft copolymer (c-2) was obtained in the same manner as (c-1) except that 1.2 kg of acrylonitrile, 12.7 kg of styrene, and 10.1 kg of methyl methacrylate were added to 36 kg of styrene-butadiene latex. .
The obtained graft copolymer had a volume average particle size of 0.35 μm.

Graft copolymer (c-3)
The same procedure as in (c-1) was conducted except that 2.8 kg of acrylonitrile, 11.6 kg of styrene, and 9.6 kg of methyl methacrylate were added to 36 kg of styrene-butadiene latex to obtain a graft copolymer (c-3). .
The obtained graft copolymer had a volume average particle size of 0.35 μm.

Graft copolymer (c-4)
A graft copolymer (c-4) was obtained in the same manner as (c-1) except that 9.6 kg of styrene and 14.4 kg of methyl methacrylate were added to 30 kg of styrene-butadiene latex.
The obtained graft copolymer had a volume average particle size of 0.35 μm.

Graft copolymer (c-5)
A graft copolymer (c-5) was obtained in the same manner as in (c-1) except that a styrene-butadiene latex having a rubber particle diameter of 0.2 μm was used.
The obtained graft copolymer had a volume average particle size of 0.23 μm.

Graft copolymer (c-6)
A graft copolymer (c-6) was obtained in the same manner as in (c-1) except that a styrene-butadiene latex having a rubber particle diameter of 0.6 μm was used.
The obtained graft copolymer had a volume average particle size of 0.65 μm.

Graft copolymer (c-7)
A graft copolymer (c-7) was obtained in the same manner as in (c-1) except that a styrene-butadiene latex having a rubber particle diameter of 0.8 μm was used.
The obtained graft copolymer had a volume average particle size of 0.82 μm.

Graft copolymer (c-8)
A styrene-butadiene latex having a styrene content of 25% by mass was used, and the same procedure as (c-1) was carried out except that 9.6 kg of styrene and 14.4 kg of methyl methacrylate were added to 36 kg of the styrene-butadiene latex. A graft copolymer (c-8) was obtained.
The obtained graft copolymer had a volume average particle size of 0.35 μm.

Graft copolymer (c-9)
The graft copolymer (c-9) was prepared in the same manner as (c-1) except that 30 kg of styrene-butadiene latex was added with 13.4 kg of styrene, 9.4 kg of methyl methacrylate, and 1.2 kg of n-butyl acrylate. )
The obtained graft copolymer had a volume average particle size of 0.35 μm.

  The compositions of the graft copolymers (c-1) to (c-7) described so far are summarized in Table 3 below.

<Examples 1 to 15 and Comparative Examples 1 to 13>
Styrene-methacrylic acid ester copolymers (a-1) to (a-7), styrene-vinyl cyanide copolymers (b-1) to (b-7), grafts obtained by the above method After mixing the system copolymers (c-1) to (c-11) with a Henschel mixer at the blending ratios shown in Tables 4 to 6, a twin-screw extruder (TEM35B manufactured by Toshiba Machine Co., Ltd., cylinder temperature 220 ° C.) was used. The resulting mixture was melt-kneaded to produce pellets to obtain a rubber-modified thermoplastic resin composition. The pellet was then injection molded to obtain a molded body. The transparency and hue of the resulting molded product were evaluated and are shown in Tables 4-6.

<Consideration of evaluation results>
As shown in the above Tables 4 to 6, it is clear that all of the rubber-modified thermoplastic resin compositions of Examples 1 to 17 are excellent in chemical resistance, transparency, hue, heat resistance, and impact resistance in a well-balanced manner. It is. On the other hand, since at least one characteristic of the rubber-modified thermoplastic resin compositions of Comparative Examples 1 to 10 is inferior to that of Examples 1 to 17, chemical resistance, transparency, hue, and heat resistance The impact resistance could not be achieved in a well-balanced manner.

  In the above, this invention was demonstrated based on the Example. It is to be understood by those skilled in the art that this embodiment is merely an example, and that various modifications are possible and that such modifications are within the scope of the present invention.

a Long axis of 1/4 elliptical jig b Short axis of 1/4 elliptical jig X Crack occurrence point

Claims (7)

When the total mass of the styrene monomer unit and the methacrylate ester monomer unit is 100% by mass, the styrene monomer unit is 1 to 15% by mass and the methacrylate ester monomer unit is 85%. A styrene-methacrylic acid ester copolymer (A) contained in a range of ˜99% by mass,
When the total mass of the styrene monomer unit and the vinyl cyanide monomer unit is 100% by mass, the styrene monomer unit is 80 to 90% by mass and the vinyl cyanide monomer unit is 10%. A styrene-vinyl cyanide copolymer (B) contained in a range of ˜20% by mass;
A rubber-like elastic body is formed by copolymerizing a styrene monomer, a methacrylic acid ester monomer, and a vinyl cyanide monomer, and the entire molded body having a thickness of 2 mm when press-molded. Containing a graft copolymer (C) having a light transmittance of 85% or more,
When the total mass of the styrene-methacrylic acid ester copolymer (A), the styrene-vinyl cyanide copolymer (B) and the graft copolymer (C) component is 100% by mass, The acid ester copolymer (A) is 15 to 54% by mass, the styrene-vinyl cyanide copolymer (B) is 20 to 63% by mass, and the graft copolymer (C) is 10 to 50% by mass. Contained within the range,
The difference between the refractive index of the mixture of the styrene-methacrylic acid ester copolymer (A) and the styrene-vinyl cyanide copolymer (B) and the refractive index of the graft copolymer (C) is 0.005. And
When the total mass of the styrene-methacrylic acid ester copolymer (A) and the styrene-vinyl cyanide copolymer (B) component is 100% by mass, the styrene-methacrylic acid ester copolymer (A). And the vinyl cyanide monomer unit in the mixture of styrene-vinyl cyanide copolymer (B) is in the range of 6 to 15% by mass.
A rubber-modified thermoplastic resin composition.   The weight average molecular weight of the styrene-methacrylic acid ester copolymer (A) is in the range of 70,000 to 100,000, and the molecular weight of the styrene-vinyl cyanide copolymer (B) is 100,000 to 190. The rubber-modified thermoplastic resin composition according to claim 1, which is within a range of 1,000.   The rubber-modified thermoplastic resin composition according to claim 1 or 2, wherein the graft copolymer (C) has a volume average particle diameter in the range of 0.25 to 0.80 µm.   The rubber-modified thermoplastic resin composition according to any one of claims 1 to 3, wherein the method for producing the styrene-methacrylic acid ester copolymer (A) is continuous bulk polymerization.   The rubber-modified thermoplastic resin composition according to any one of claims 1 to 4, wherein the method for producing the styrene-vinyl cyanide copolymer (B) is continuous bulk polymerization.   An injection-molded article obtained by injection-molding the rubber-modified thermoplastic resin composition according to any one of claims 1 to 5.   A lid for a washing machine using the injection-molded body according to claim 6 as a member.

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