Resin composition, molded body, and multicolor injection molded body

Abstract

A resin composition includes a polyacetal resin and a core-shell elastomer. The resin composition is molded into a multipurpose test piece (ISO test piece) having a thickness of 4 mm, the flexural modulus measured in accordance with ISO 178 is 50-1000 MPa, and the resin composition is a resin composition for multicolor injection molding.

Description

Technical Field

[0001] The present invention relates to a resin composition, a molded body, and a multi-color injection molded body, and particularly to a resin composition containing a polyacetal resin as a main component. Background Art

[0002] Polyacetal (POM) resin, a type of engineering plastic, has excellent properties in terms of mechanical properties, thermal properties, electrical properties, sliding properties, moldability, etc., and is widely used as structural materials and mechanism parts in electrical / electronic equipment, automobile parts, commercial equipment parts, daily sundry goods parts, etc. In addition, elastomers are blended to impart softness to polyacetal resin.

[0003] On the other hand, due to when the polyacetal resin composition comprising polyacetal resin and elastomer is molded, even the molded body with complicated shape can also be molded, and is suitable for mass production, therefore, in many cases, injection molding is applied.In addition, in recent years, the requirement of high performance / high functionality of resin parts and components becomes strict, wherein, polyacetal resin and the composite of the resin composition comprising polyacetal resin and elastomer also attract attention.Here, for composite, it is most effective to make the two mutually thermally welded (also referred to as welding) by the injection molding as the molding method common to both.As an example, in patent documentation 1, record to some extent.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-048252 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Here, the molded body formed by the polyacetal resin composition with a large proportion of elastomer has a tendency to be highly flexible. On the other hand, the molded body formed by the polyacetal resin composition with a low proportion of elastomer or without elastomer has a tendency to be hard. If such a hard component and a component with high flexibility can be molded and composited by multi-color injection molding, it is beneficial. In addition, depending on the application, quietness is required.

[0009] The present invention aims to solve the above problems and to provide a polyacetal resin composition having high softness, a molded body and a multi-color injection molded body. The polyacetal resin composition can be multi-color injection molded with a hard polyacetal component and has excellent quietness.

[0010] Solutions to the problem

[0011] The present inventors have conducted studies based on the above problems and have found that the above problems can be solved by blending a core-shell elastomer into a polyacetal resin.

[0012] Specifically, the above problems can be solved by the following methods.

[0013] <1> A resin composition comprising a polyacetal resin and a core-shell elastomer,

[0014] The resin composition was molded into a multi-purpose test piece (ISO test piece) with a thickness of 4 mm. The bending elastic modulus measured according to ISO178 was 50 to 1000 MPa. The resin composition was a resin composition for multi-color injection molding.

[0015] <2> The resin composition according to <1>, wherein

[0016] The above-mentioned bending modulus is 800 MPa or less.

[0017] <3> The resin composition according to <1> or <2>, wherein

[0018] The ratio of the polyacetal resin is 10 to 50% by volume relative to the total volume of the resin components in the resin composition.

[0019] <4> The resin composition according to any one of <1> to <3>, wherein

[0020] The core-shell elastomer accounts for 30 to 90% by volume of the total volume of the resin components in the resin composition.

[0021] <5> The resin composition according to any one of <1> to <4>, wherein

[0022] The shell of the core-shell elastomer contains an acrylic resin.

[0023] <6> The resin composition according to any one of <1> to <5>, wherein

[0024] The resin composition contains 0.01 to 1 part by mass of a compound capable of capturing ions, based on 100 parts by mass of the total of the resin components in the resin composition.

[0025] <7> The resin composition according to <6>, wherein

[0026] The compound capable of capturing ions includes at least one selected from the group consisting of a triazine skeleton-containing compound, a hindered amine, an alkaline earth metal hydroxide, a hydrotalcite, and a fatty acid metal salt.

[0027] <8> The resin composition according to any one of <1> to <7>, which is a resin composition for multi-color injection molding, wherein the ratio of the resin composition (B) to the polyacetal resin is 50 to 100% by volume.

[0028] <9> The resin composition according to any one of <1> to <8>, wherein

[0029] The core-shell elastomer accounts for 30 to 90% by volume of the total volume of the resin components in the resin composition, and the ion-capturing compound accounts for 0.01 to 1 part by mass of the compound based on 100 parts by mass of the total resin components in the resin composition.

[0030] <10> The resin composition according to any one of <1> to <8>, wherein

[0031] With respect to the total volume of the resin components in the resin composition, 35 to 50 volume % is the polyacetal resin, and 35 to 50 volume % is the core-shell elastomer.

[0032] <11> Pellets comprising the resin composition according to any one of <1> to <10>.

[0033] <12> A molded article formed from the resin composition according to any one of <1> to <10>.

[0034] <13> A molded body formed from the particles according to <11>.

[0035] <14> A multi-color injection-molded article, comprising a resin composition (B) according to any one of <1> to <10>, wherein the ratio of the resin composition to the polyacetal resin is 50 to 100% by volume.

[0036] Effects of the Invention

[0037] According to the present invention, a polyacetal resin composition having high softness, a molded product, and a multi-color injection molded product can be provided. The polyacetal resin composition can be multi-color injection molded with a hard polyacetal member and has excellent quietness. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a cross-sectional schematic diagram showing an example of a two-color injection-molded body according to the present embodiment.

[0039] Explanation of symbols

[0040] 1Dual color injection molding

[0041] 2. Hard member (molded body formed from resin composition (B))

[0042] 3. Soft member (molded article formed from resin composition (A)) DETAILED DESCRIPTION

[0043] Hereinafter, a mode for implementing the present invention (hereinafter, simply referred to as "this embodiment") will be described in detail. It should be noted that the following this embodiment is an example for describing the present invention, and the present invention is not limited to this embodiment.

[0044] In addition, in this specification, "to" is used to mean that the numerical values ​​described before and after it are included as a lower limit and an upper limit.

[0045] In this specification, various physical property values ​​and characteristic values ​​are values ​​at 23°C unless otherwise specified.

[0046] The measurement methods and the like described in the standards shown in this specification may differ depending on the year, but unless otherwise specified, they are based on the standards as of January 1, 2022.

[0047] In the present specification, the total volume of the resin components in the resin composition means the total volume of the polyacetal resin, the elastomer, the stress relaxation agent and other resin components.

[0048] The resin composition of the present embodiment (hereinafter, sometimes referred to as resin composition (A)) comprises a polyacetal resin and a core-shell elastomer, and the resin composition is molded into a multi-purpose test piece (ISO test piece) with a thickness of 4 mm, and the bending elastic modulus measured according to ISO178 is 50 to 1000 MPa, and the resin composition is a resin composition for multi-color injection molding. By setting such a structure, a polyacetal resin composition with high softness can be provided, the resin composition can be multi-color injection molded with a hard polyacetal component, and has excellent quietness.

[0049] That is, in order to obtain a component with high softness, it is considered to reduce the bending modulus by adding an elastomer to the polyacetal resin. Moreover, for such a polyacetal resin composition containing a large amount of elastomer, the present inventors have studied two-color injection molding with a hard polyacetal resin composition, for example, a resin composition (B) in which the ratio of the polyacetal resin is 50 to 100 volume %. However, for a soft polyacetal resin composition containing a large amount of elastomer, it is known that sometimes the composition itself cannot be manufactured, or even if the composition can be manufactured, two-color injection molding cannot be performed. Moreover, the present inventors have conducted more specific research and speculated that the reason why the soft polyacetal resin composition containing a large amount of elastomer and the hard resin composition (B) cannot be two-color injection molded is that layer peeling occurs in the elastomer part. In addition, the present inventors have conducted research and speculated that the problem is that if a general elastomer such as polyurethane is added to the resin composition in large quantities, the elastomer will not be dispersed in the polyacetal resin, and the polyacetal resin cannot be dispersed in the elastomer.

[0050] Based on the above situation, the inventor has studied and found that the core-shell elastomer is used as a part or all of the elastomer matched in polyacetal resin. When using the core-shell elastomer, it is dispersed in the polyacetal resin in the state of particles. Therefore, in the molded body formed by the resin composition comprising the above-mentioned core-shell elastomer, the polyacetal resin of the outermost layer becomes more. In addition, the outermost layer becomes the state that the polyacetal resin is coated with the core-shell elastomer (particle). Therefore, it can be inferred that the double-color injection molding with the resin composition (B) of hardness can be carried out.

[0051] <Polyacetal resin>

[0052] The resin composition (A) of the present embodiment contains a polyacetal resin.

[0053] The polyacetal resin is not particularly limited and may be a homopolymer containing only a divalent oxymethylene group as a structural unit, or a copolymer containing a divalent oxymethylene group and a divalent oxyalkylene group having 2 to 6 carbon atoms as structural units.

[0054] Examples of the oxyalkylene group having 2 to 6 carbon atoms include oxyethylene, oxypropylene, and oxybutylene.

[0055] In the polyacetal resin, the ratio of the oxyalkylene group having 2 to 6 carbon atoms to the total molar number of the oxymethylene group and the oxyalkylene group having 2 to 6 carbon atoms is not particularly limited and may be 0.5 to 10 mol %.

[0056] In order to produce the above-mentioned polyacetal resin, three In order to introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin, a cyclic formal or a cyclic ether can be used. Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxolane, Examples of the cyclic ethers include 1,3-dioxolane, 1,3-dioxolane, 1,3,5-trioxolane, 1,3,6-trioxolane, etc. Specific examples of the cyclic ethers include ethylene oxide, propylene oxide, and butylene oxide. To introduce ethylene oxide into the polyacetal resin, 1,3-dioxolane can be used as the main raw material. To introduce propylene oxide, 1,3-dioxolane can be used as the main raw material. In order to introduce oxybutylene groups, 1,3-dioxepane can be used as the main raw material. It should be noted that in the polyacetal resin, it is preferred that the amount of hemiformal terminal groups, formyl terminal groups, and terminal groups unstable to heat, acid, and alkali are small. Here, the hemiformal terminal group refers to a group represented by -OCH2OH, and the formyl terminal group refers to a group represented by -CHO.

[0057] The polyacetal resin (A) used in the present embodiment preferably has a melt volume flow rate (MVR) of 0.5 cm / s as measured under the conditions of a temperature of 190° C. and a load of 2.16 kg according to ISO 1133. 3 / 10 minutes or more, more preferably 0.6 cm 3 / 10 minutes or more, more preferably 0.8 cm 3 / 10 minutes or more, more preferably 1 cm 3 / 10 minutes or more, more preferably 5cm 3 / 10 minutes or more. By setting it to be above the above lower limit, there is a tendency for the fluidity and productivity of the resin composition to be further improved. In addition, the MVR of the above polyacetal resin is preferably 100 cm 3 / 10 minutes or less, more preferably 80cm 3 / 10 minutes or less, more preferably 70cm 3 / 10 minutes or less, more preferably 50cm 3 / 10 minutes or less, and more preferably 20 cm 3 By setting it to the above upper limit value or less, there exists a tendency for the dispersibility of the core-shell elastomer (B) to improve.

[0058] As the polyacetal resin, in addition to the above, the polyacetal resins described in paragraphs 0018 to 0043 of JP-A-2015-074724 may be used, and the contents thereof are incorporated herein.

[0059] Relative to the total volume of the resin components in the resin composition (A) of the present embodiment, it is preferred that the polyacetal resin contains 10% by volume or more, more preferably 15% by volume or more, further preferably 20% by volume or more, and may contain 30% by volume or more, may contain 35% by volume or more, and may contain 40% by volume or more. Relative to the total volume of the resin components in the resin composition (A), the upper limit is further preferably 50% by volume or less, further preferably 47% by volume or less, and further preferably 45% by volume or less.

[0060] For the resin composition (A) of the present embodiment, the resin composition (A) preferably contains 10% by mass or more of the polyacetal resin, more preferably 15% by mass or more, further preferably 25% by mass or more, and further preferably 35% by mass or more. The upper limit is preferably 70% by mass or less, more preferably 65% ​​by mass or less, further preferably 60% by mass or less, and further preferably 55% by mass or less.

[0061] The resin composition of the present embodiment may contain only one polyacetal resin or two or more polyacetal resins. When containing two or more polyacetal resins, the total amount is preferably within the above range.

[0062] <Core-shell elastomer>

[0063] The resin composition (A) of the present embodiment contains a core-shell elastomer. By containing the core-shell elastomer, a molded product having excellent flexibility can be obtained, and multi-color injection molding can be performed.

[0064] The core-shell elastomer is a polymer having a multilayer structure having a core and a shell layer covering part or all of the core, and known ones include Kane Ace series from Kaneka Corporation and Metablen series from Mitsubishi Chemical Corporation.

[0065] The type of core-shell elastomer used in the present embodiment is not particularly limited, and the core is preferably a rubber polymer. As the rubber polymer, it is preferably selected from at least one of butadiene-containing rubber, butyl acrylate-containing rubber, 2-ethylhexyl acrylate-containing rubber, and silicone rubber, and more preferably includes butadiene-containing rubber. The shell is preferably a polymer of one or more monomers selected from (meth)acrylate, aromatic vinyl compound, etc., and more preferably a polymer (acrylic resin) in which the unit from (meth)acrylate occupies more than 50% by mass of the whole.

[0066] In the core-shell elastomer used in the present embodiment, it is preferred that the core contains a rubber-based polymer and the shell contains an acrylic resin. If such a core-shell elastomer is used, there is a tendency that the effects of the present invention can be more effectively exerted.

[0067] The specific gravity of the core-shell elastomer used in the present embodiment is preferably 0.9 or more, and preferably 1.3 or less.

[0068] <Elastomers other than core-shell elastomers (non-core-shell elastomers)>

[0069] The resin composition (A) of the present embodiment may contain an elastomer other than the core-shell elastomer (non-core-shell elastomer). By containing the non-core-shell elastomer, a molded product having excellent softness can be obtained.

[0070] Examples of the non-core-shell elastomer include polyolefin elastomers, polystyrene elastomers, polyurethane elastomers, polyester elastomers, copolyester / ether elastomers, acrylic elastomers, and vinyl chloride / nitrile elastomers, and polyurethane elastomers are preferred.

[0071] <Content of elastomer>

[0072] The resin composition (A) of the present embodiment preferably contains 30% by volume or more of the elastomer, more preferably 40% by volume or more, preferably 50% by volume or more, more preferably 52% by volume or more, and further preferably 55% by volume or more, relative to the total volume of the resin components in the resin composition (A). The upper limit is preferably 90% by volume or less, more preferably 85% by volume or less, further preferably 80% by volume or less, and may be 70% by volume or less, relative to the total volume of the resin components in the resin composition (A).

[0073] In particular, the ratio of the core-shell elastomer in the resin composition (A) to the total volume of the resin components is preferably 30% by volume, more preferably 35% by volume or more, and may be 40% by volume or more. In addition, it is preferably 90% by volume or less, more preferably 85% by volume or less, and may further be 70% by volume or less, 66% by volume or less, 60% by volume or less, 50% by volume or less, or 47% by volume or less.

[0074] The resin composition (A) of the present embodiment preferably contains 30% by mass or more of the elastomer in the resin composition (A), more preferably 35% by mass or more, further preferably 40% by mass or more, and further preferably 45% by mass or more. The upper limit is preferably 90% by mass or less, more preferably 85% by mass or less, further preferably 75% by mass or less, and further preferably 65% ​​by mass or less.

[0075] The resin composition of the present embodiment may contain only one type of elastomer (particularly, each of a core-shell elastomer and a non-core-shell elastomer) or two or more types. When containing two or more types, the total amount is preferably within the above range.

[0076] In the resin composition (A) of the present embodiment, when the total amount of the elastomer is 100 parts by mass, the ratio of the core-shell elastomer is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, further preferably 75 parts by mass or more, and may be 85 parts by mass or more, or 90 parts by mass or more. The upper limit is when the core-shell elastomer is 100 parts by mass.

[0077] In the resin composition (A) of the present embodiment, the total amount of the polyacetal resin and the elastomer preferably accounts for 85% by mass or more of the resin composition, more preferably 90% by mass or more, and may be 94% by mass or more.

[0078] In the resin composition (A) of the present embodiment, the total amount of the polyacetal resin, the elastomer and the stress relaxation agent preferably accounts for 90% by mass or more of the resin composition, more preferably 95% by mass or more, and may be 97% by mass or more.

[0079] <Compounds that can capture ions>

[0080] The resin composition (A) of the present embodiment preferably contains 0.01 to 1 parts by mass of a compound capable of capturing ions relative to 100 parts by mass of the resin composition (A). By containing such a compound capable of capturing ions, even if the content of the elastomer, especially the non-core-shell elastomer, is increased, extrusion can be performed, and excellent multi-color injection molding properties can be achieved.

[0081] The compound capable of capturing ions preferably contains at least one selected from the group consisting of a triazine skeleton-containing compound, a hindered amine, an alkaline earth metal hydroxide, a hydrotalcite, and a fatty acid metal salt.

[0082] As the triazine skeleton-containing compound, the description in paragraphs 0095 to 0097 of JP-A-2014-005385 can be referred to, and the contents are incorporated into the present specification.

[0083] For hindered amines, reference can be made to the description in paragraphs 0030 to 0031 of JP-A-2019-038990, the contents of which are incorporated into this specification.

[0084] As the hydroxide salt of the alkaline earth metal, the description in paragraph 0044 of JP-A-2014-234511 can be referred to, and the content thereof is incorporated into the present specification.

[0085] As hydrotalcite, the description in paragraphs 0042 and 0043 of JP-A-2019-065221 can be referred to, and the contents thereof are incorporated into the present specification.

[0086] As the fatty acid metal salt, reference can be made to the description in paragraphs 0028 and 0029 of JP-A-2021-080443, the contents of which are incorporated herein by reference.

[0087] In the case where the resin composition (A) of the present embodiment includes a compound that can capture ions, relative to a total of 100 parts by mass of the resin component in the resin composition (A), its content is preferably more than 0.01 parts by mass, more preferably more than 0.03 parts by mass, further preferably more than 0.05 parts by mass, more preferably more than 0.07 parts by mass, and further preferably more than 0.09 parts by mass. By being set to more than the above-mentioned lower limit, there is a tendency that the extrudability of the acid ions in the polyacetal resin and the resin composition (A) are further improved. In addition, relative to a total of 100 parts by mass of the resin component in the resin composition (A), the upper limit of the content of the compound that can capture ions is preferably less than 1 part by mass, more preferably less than 0.8 parts by mass, further preferably less than 0.6 parts by mass, further preferably less than 0.4 parts by mass, and further preferably less than 0.2 parts by mass. By being set to less than the above-mentioned upper limit, there is a tendency that mold contamination during continuous injection molding can be more effectively suppressed.

[0088] The resin composition (A) of the present embodiment may contain only one type of compound capable of capturing ions, or may contain two or more types. When containing two or more types, the total amount is preferably within the above range.

[0089] <Stress Relaxants>

[0090] The resin composition (A) of the present embodiment may further contain a stress relaxant. By containing a stress relaxant, the elastic modulus of the resin composition can be further reduced, and the residual strain generated during molding can be effectively removed.

[0091] The stress relaxer used in this embodiment is preferably at least one selected from polyether ester amide block copolymers, polyolefin / polyether copolymers, polyamide / polyalkylene glycol block copolymers, polyethylene glycol with a number average molecular weight of 20,000 or more, and polyethylene oxide with a number average molecular weight of 20,000 or more, and more preferably polyethylene oxide with a number average molecular weight of 20,000 or more.

[0092] Preferably, the melting point of the polyetheresteramide block copolymer is equal to the melting point of the polyacetal (e.g., the difference in melting point is within 10°C) or equal to the actual temperature at which the polyacetal is processed (e.g., 200°C) (e.g., the difference between the melting point of the copolymer and the processing temperature is within 10°C).

[0093] The polyolefin constituting the polyolefin / polyether copolymer is preferably polyethylene or polypropylene. In addition, the polyether is preferably polyethylene glycol, and preferably has a melting point equal to that of polyacetal (e.g., the difference in melting point is within 10° C.) or equal to the actual temperature (e.g., 200° C.) during processing of polyacetal (e.g., the difference between the melting point of the copolymer and the temperature during processing is within 10° C.).

[0094] As the polyethylene glycol having a number average molecular weight of 20,000 or more, the number average molecular weight is preferably 20,000 to 100,000, more preferably 20,000 to 50,000.

[0095] The number average molecular weight of the polyethylene oxide having a number average molecular weight of 20,000 or more is preferably 20,000 to 500,000, more preferably 80,000 to 30,000, and even more preferably 100,000 to 200,000.

[0096] The melting point and number average molecular weight of the stress relaxation agent used in the present embodiment can adopt the catalog values ​​in the case of commercially available products.

[0097] In the case where the resin composition (A) of the present embodiment includes a stress relaxant, relative to a total of 100 parts by mass of the resin component in the resin composition (A), its content is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, further preferably 0.7 parts by mass or more, further preferably 1.0 parts by mass or more, and further preferably 1.2 parts by mass or more. By being set to above the above lower limit, there is a tendency that the softness of the obtained molded article is further improved. In addition, relative to a total of 100 parts by mass of the resin component in the resin composition (A), the upper limit of the content of the above stress relaxant is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less. By being set to below the above upper limit, it is possible to effectively suppress the reduction of toughness.

[0098] The resin composition (A) of the present embodiment may contain only one type of stress relaxation agent, or may contain two or more types. When containing two or more types, the total amount is preferably within the above range.

[0099] <Other ingredients>

[0100] The resin composition (A) of the present embodiment may contain any known additives and fillers within the scope of not damaging the purpose of the present invention. As additives and fillers used in the present embodiment, for example, thermoplastic resins other than polyacetal resins, ultraviolet absorbers, antioxidants, antistatic agents, carbon fibers, glass fibers, glass flakes, potassium titanate whiskers, etc. can be cited. Their details can be referred to the records of paragraphs 0113 to 0124 of Japanese Patent Publication No. 2017-025257, and their contents are introduced into this specification.

[0101] <Physical properties of resin composition>

[0102] For the resin composition (A) of the present embodiment, the above-mentioned resin composition (A) is molded into a multi-purpose test piece (ISO test piece) with a thickness of 4 mm, and the bending modulus measured according to ISO178 is 50 to 1000 MPa. By setting it below the above-mentioned upper limit, a molded body with excellent softness can be obtained. In addition, when the bending modulus is reduced, the resonant frequency (Hz) is reduced, and there is a tendency to obtain a material with high quietness, so it is preferred.

[0103] The above-mentioned bending elastic modulus is preferably below 900MPa, more preferably below 800MPa, further preferably below 750MPa, and can be below 500MPa, below 400MPa, depending on the purpose. In addition, the lower limit of the above-mentioned bending elastic modulus is determined according to the purpose, and can usually be more than 100MPa, more than 350MPa, or more than 500MPa.

[0104] The above bending modulus is mainly achieved by combining an elastomer. The elastomer used to adjust the elastic modulus can be a core-shell elastomer or other elastomers. In addition, it can also be adjusted by combining a stress relaxant.

[0105] <Multi-color injection molding>

[0106] The resin composition (A) of the present embodiment is a resin composition for multi-color injection molding. The resin composition for multi-color injection molding refers to, for example, a resin composition for multi-color injection molding in which the ratio of the resin composition (B) to the polyacetal resin is 50 to 100 volume %, and more specifically, the resin composition for multi-color injection molding refers to, in the examples described later, the resin composition (A) of the present embodiment can be molded into a two-color injection molded body with polyacetal resin particles (B) (Mitsubishi Engineering-Plastics Co., Ltd., F20-03, polyacetal resin), and the components (A) and (B) constituting the two-color injection molded body are bonded together with a bonding strength that reaches the destruction of the base material when peeled off.

[0107] Such a multi-color injection molding resin composition can be prepared by adjusting the amounts of the polyacetal resin and the core-shell elastomer, adding a compound capable of capturing ions, a stress relaxant, etc. in addition to the core-shell elastomer.

[0108] Figure 1 An example of a multi-color injection molded body using the resin composition (A) and the resin composition (B) according to this embodiment is shown. Figure 1In the figure, 1 represents a two-color injection molded body, 2 represents a hard member (a molded body formed from the resin composition (B)), and 3 represents a soft member (a molded body formed from the resin composition (A)).

[0109] exist Figure 1 In the process, first, the resin composition (B) is injection molded into a mold. Then, after the resin composition (B) is solidified, the resin composition (A) is injection molded into the mold. Then, by cooling in the mold, a two-color injection molded body can be obtained. In addition, the order of the resin composition (B) and the resin composition (A) can be opposite. In addition, it can also be a multi-color injection molded body using more than 3 kinds of resin composition (A), resin composition (B) or other resin compositions.

[0110] The polyacetal resin contained in the resin composition (B) has the same meaning as the polyacetal resin contained in the resin composition (A). The content of the polyacetal resin contained in the resin composition (B) is 50 to 100% by volume, preferably 60% by volume or more, more preferably 70% by volume or more, further preferably 80% by volume or more, further preferably 90% by volume or more, and may be 95% by volume or more.

[0111] The resin composition (B) may contain other components within the scope of the present invention. Examples of other components include the compounds capable of capturing ions and other components described in the above section on the resin composition (A).

[0112] In addition, the resin composition (B) preferably contains substantially no elastomer. Substantially containing no elastomer means that the content of the elastomer is 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less of the resin composition (B).

[0113] The resin composition (B) is molded into a 4 mm thick multipurpose test piece (ISO test piece), and the flexural modulus measured according to ISO178 is preferably greater than 1000 MPa, and is usually about 2000 to 3000 MPa.

[0114] In addition, for details of multi-color injection molding, reference can be made to the description in Japanese Patent Application Publication No. 2022-021882, the description in paragraphs 0067 to 0087 of International Publication No. 2014 / 021413, and the description in paragraphs 0045 to 0056 of International Publication No. 2020 / 045467, and their contents are incorporated into this specification.

[0115] The resin composition (A) according to the present embodiment is excellent in multi-color injection moldability particularly when it has the following composition.

[0116] (1) A resin composition, wherein 30 to 90% by volume (preferably 35% to 85% by volume) of the total volume of the resin components in the resin composition is a core-shell elastomer, and 0.01 to 1 part by mass of a compound capable of capturing ions is contained per 100 parts by mass of the total resin components in the resin composition. In addition, within the above range, an elastomer other than the core-shell elastomer may be contained at a ratio of, for example, 15% by volume or less.

[0117] (2) In the above resin composition, 35 to 50% by volume (preferably 40% to 47% by volume) of the total volume of the resin components in the resin composition is the polyacetal resin, and 35 to 50% by volume (preferably 40% to 47% by volume) of the core-shell elastomer is contained. In addition, within the above range, an elastomer other than the core-shell elastomer and / or a stress relaxant may be contained at a ratio of, for example, 15% by volume or less.

[0118] <Method for producing resin composition (A)>

[0119] The resin composition (A) of the present embodiment contains the above-mentioned essential components and the above-mentioned optional components used as needed. The production method thereof is arbitrary, and these raw materials may be mixed and kneaded using any conventionally known production method for a resin composition.

[0120] As one of the methods for making the average secondary particle size within the above range, there can be cited a method in which a polyacetal resin and a core-shell elastomer are mixed with a roller, extruded through a melt-kneading machine, and cut into strands to form particles. At this time, as a melt-kneading machine, a twin-screw extruder is preferably used from the aspect that secondary coagulation is easy to occur in the case of a single-screw extruder. Among them, the ratio of the length L (mm) of the screw to the diameter D (mm) of the screw, i.e., L / D, is preferably 20 or more, more preferably 30 or more, and preferably 100 or less, more preferably 70 or less. By setting the above L / D to 20 or more, the core-shell elastomer is easily micro-dispersed, and the secondary coagulation of the core-shell elastomer can be effectively suppressed. In addition, by setting the above L / D to 100 or less, there is a tendency to effectively suppress the discoloration of the resin composition caused by thermal degradation.

[0121] The shape of the die nozzle is not particularly limited. From the perspective of particle shape, a circular nozzle with a diameter of 1 mm or more is preferred, and a circular nozzle with a diameter of 2 mm or more is more preferred. A circular nozzle with a diameter of 10 mm or less is also preferred, and a circular nozzle with a diameter of 7 mm or less is more preferred.

[0122] In addition, the melting temperature of the resin composition during melt kneading is preferably 170° C. or higher, more preferably 190° C. or higher, and preferably 250° C. or lower, more preferably 230° C. or lower. By setting the melting temperature to 170° C. or higher, there is a tendency that melting becomes sufficient and production volume is improved. In addition, by setting it to 250° C. or lower, there is a tendency that discoloration of the resin composition caused by thermal degradation can be effectively suppressed.

[0123] The screw structure of the twin-screw extruder is not particularly limited, and one of the preferred embodiments is to have at least two kneading sections. The kneading section has a kneading disk, which mainly contributes to the melting of the resin and the dispersion of the elastomer.

[0124] The screw speed during melt kneading is preferably 50 rpm or more, more preferably 70 rpm or more, and preferably 500 rpm or less, more preferably 350 rpm or less. By setting the screw speed to 50 rpm or less, the core-shell elastomer is easily micro-dispersed, and there is a tendency to more effectively suppress the occurrence of secondary agglomeration. In addition, by setting it to 500 rpm or less, the heat generated during melt kneading can be suppressed, and there is a tendency to effectively suppress the discoloration of the resin composition caused by thermal degradation. In addition, the ejection amount is preferably 5 kg / hr or more, more preferably 7 kg / hr or more, preferably 1000 kg / hr or less, and more preferably 800 kg / hr or less. By setting it to 5 kg / hr or more, the core-shell elastomer is more easily micro-dispersed, and the occurrence of secondary agglomeration can be effectively suppressed. In addition, by setting it to 1000 kg / hr or less, the heat generated during melt kneading can be effectively suppressed, and there is a tendency to effectively suppress the discoloration of the resin composition caused by thermal degradation.

[0125] The ratio (Q / Ns) of the screw speed (Ns) to the discharge amount (Q) during melt kneading also depends on the screw diameter and screw structure of the extruder, and is, for example, preferably 0.5 or more, more preferably 0.7 or more, particularly preferably 0.9 or more, and preferably 1.5 or less, more preferably 1.3 or less, particularly preferably 1.2 or less. The above Q / Ns is particularly preferred in an embodiment in which the screw diameter is 18 to 75 mm (further 58 mm) and has two kneading sections as the screw structure.

[0126] Examples of the mixer include a kneader, a Banbury mixer, an extruder, etc. There are no particular restrictions on the various conditions and devices for mixing / kneading, and they can be appropriately selected and determined from any known conditions. Kneading is preferably carried out at a temperature above the melting temperature of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally above 180° C.).

[0127] <Molding body>

[0128] The molded body of the present embodiment is formed by the resin composition (A) of the present embodiment. There is no particular limitation on the shape of the molded body, and it can be appropriately selected according to the use and purpose of the molded body, and for example, it can be exemplified by the shapes of plate, disk, rod, sheet, film, cylinder, ring, circle, ellipse, gear, polygon, special-shaped product, hollow product, frame, box, panel, cap, etc. The molded body of the present invention can be a component or a finished product.

[0129] In this embodiment, a multi-color injection molded body of the resin composition (A) and other resin compositions is preferred, and a multi-color injection molded body of the resin composition (B) in which the ratio of the resin composition (A) to the polyacetal resin is 50 to 100 volume %. The preferred ranges of the resin composition (A) and the resin composition (B) are as described above.

[0130] <Application>

[0131] The resin composition of the present embodiment and the molded article formed from the resin composition can be exemplified by automobile parts such as trim clips, seat belt components, and headrest rails, building material parts, electrical / electronic parts, commercial equipment parts, daily sundry parts, and containers for frozen foods, beverages, etc., household appliances such as refrigerator gaskets, hose clamps, packaging, and strapping tapes.

[0132] Example

[0133] Below, give embodiment and the present invention is described more specifically.As long as do not depart from the gist of the present invention, the material, dosage, ratio, processing content, processing steps etc. shown in the following embodiment can be appropriately changed.Therefore, the scope of the present invention is not limited to the specific example shown below.

[0134] When the measuring equipment used in the examples is difficult to obtain due to discontinuation of production or the like, other equipment having equivalent performance may be used for measurement.

[0135] 1. Raw materials

[0136] The raw materials described in the following Table 1 or Table 2 were used.

[0137] [Table 1

[0138]

[0139] [Table 2

[0140] Element Details Hydrotalcite BASF, Hycite713 Hindered Amine Hindered amine light stabilizer, manufactured by BASF, Tinuvin 770 Magnesium hydroxide Kyowa Chemical Industry Co., Ltd., Kisuma5A Calcium stearate Made by NOF Co., Ltd., GF-200 Polyethylene glycol Made by Sanyo Chemical Co., Ltd., PEG20000, specific gravity: 1.1 Polyalphaolefin Made by Mitsui Chemicals Co., Ltd., Tafmer DF7350 Polyethylene Novatec HJ360 manufactured by Japan Polyethylene Co., Ltd. Melamine Made by Mitsui Chemicals Co., Ltd.

[0141] 2. Examples 1 to 18, Comparative Examples 1 to 6

[0142] <Production of resin composition (A) (pellets (A))>

[0143] Using a super mixer manufactured by Kawada Manufacturing Co., Ltd., the components shown in Tables 3 to 6 were uniformly mixed in the ratios (parts by mass) shown in Tables 3 to 6. The obtained mixture was melt-shear mixed using a twin-screw extruder with a screw diameter of 30 mm, a screw length of 760, and a die nozzle diameter of 3.5 mm ("PCM-30" manufactured by Ikegai Co., Ltd.) at a barrel temperature of 200° C., a screw speed of 120 rpm, and a discharge amount of 10 kg / hour to produce pellets (A) of the resin composition.

[0144] <Flexural modulus>

[0145] The pellets (A) obtained above were heat-treated in a hot air circulation dryer at a temperature of 80° C. for 4 hours.

[0146] Next, the dried pellets (A) were injection molded using an injection molding machine with the cylinder temperature set at 195° C. and the mold temperature set at 90° C. in accordance with ISO9988-2, thereby obtaining a 4 mm thick multipurpose test piece (ISO test piece).

[0147] Next, the 4 mm thick multipurpose test piece (ISO test piece) was subjected to a bending test at a bending test speed of 2 mm / min in accordance with the method described in ISO 178 using a fully automatic bending tester as a bending tester to measure the bending elastic modulus.

[0148] The pellets (A) obtained above were heat-treated in a hot air circulation dryer at a temperature of 80° C. for 4 hours.

[0149] The injection molding machine used was EC-100S manufactured by Shibaura Machine Co., Ltd. The fully automatic bending tester used was a tester manufactured by Shimadzu Corporation.

[0150] The results are shown in Tables 3 to 6. The unit is MPa.

[0151] <Resonance frequency>

[0152] One end of the ISO test piece obtained above is bonded with silkworm silk and hung in an environment that is not affected by external vibration. With a vibration sensor connected to the measurement system (DS2000) manufactured by Ono Sakuki installed at the other end, an impact hammer connected to DS2000 is used to apply an impact to the center of the test piece. The vibration generated at this time is analyzed using DS2000 to obtain the frequency response function, and the peak frequency of the frequency response function is taken as the resonance frequency. At this time, if the resonance frequency is below 120Hz, it is judged to be a material with excellent quietness.

[0153] <Productivity>

[0154] The above-mentioned pellets (A) were evaluated as follows.

[0155] A: Can be produced without any problems

[0156] B: Although a small amount of resin decomposition and foreign matter were generated, production was still possible.

[0157] C: Resin decomposition occurred obviously, foreign matter was generated, and production was difficult

[0158] <Multi-color injection molding / adhesion>

[0159] Using the pellets (A) obtained above and polyacetal resin pellets (B) (manufactured by Mitsubishi Engineering-Plastics Corporation, F20-03, polyacetal resin), a Figure 1 The two-color injection molded articles shown were evaluated as follows: Comparative Example 4 was difficult to produce in terms of the above-mentioned productivity, and therefore the multi-color injection moldability was not evaluated.

[0160] Using an injection molding machine (DCE-140 manufactured by Nissei Plastic Industry Co., Ltd.), a laminate A was obtained by a two-color molding method. Specifically, the polyacetal resin particles (B) were injection molded under the conditions of a resin temperature of 230°C and a mold temperature of 80°C to form a test film of 123mm×13mm×0.8mm (thickness). Then, the mold was rotated, and then the particles (A) were injection molded. On the test film, a part of the particles (A) (laminated portion) was laminated on the test film so that the remaining part (bent portion) was bent 90° relative to the laminated portion to form an L-shaped shape. The size of the laminated portion was set to 63mm×13mm×2.0mm (thickness), and the size of the bent portion was set to 15mm×13mm×2.0mm (thickness). In addition, the laminated portion and the test film were laminated in a manner consistent with the length direction. The multi-color injection molded body thus obtained was fixed to the upper fixture (fixed side) of a tensile tester (manufactured by INSTRON, product name "5544"), and the test film was fixed to the lower fixture (movable side). Next, the upper fixture was displaced upward at a speed of 200 mm / min, thereby implementing a peeling test of the multi-color injection molded body.

[0161] <<Moldability>>

[0162] Based on the above-mentioned molding state, evaluation was performed as follows.

[0163] A: Can be molded without any problems

[0164] B: Although the flow channel is damaged, it can be formed.

[0165] C: Demolding failure occurs and molding is impossible

[0166] <<Peelability>>

[0167] Based on the results of the above peel test, evaluation was performed as follows.

[0168] A: Good adhesion between components

[0169] B: Poor adhesion between components (easy to peel off at the bonding interface)

[0170] C: The adhesion between the components is poor (not bonded when removed from the mold) [Table 3]

[0171] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Polyacetal resin 50 50 50 50 30 20 Core-shell elastomer A 50 Core-shell elastomer B 50 70 80 Core-shell elastomer C 50 Core-shell elastomer D 50 Elastomer E Hydrotalcite Hindered Amine Magnesium hydroxide Calcium stearate Polyethylene glycol Polyalphaolefin Polyethylene Melamine 0.1 0.1 0.1 0.1 0.1 0.1 POM volume ratio 44 44 44 44 25 16 Core-shell elastomer volume ratio 56 56 56 56 75 84 Flexural modulus (MPa) 700 700 680 700 300 200 Resonance frequency(Hz) 107 107 107 107 90 86 Productivity A A A A B B Formability A A A A A B Adhesion A A A A A A

[0172] [Table 4]

[0173] Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 7 Example 8 Example 9 Polyacetal resin 50 80 80 30 30 30 Core-shell elastomer A 20 70 70 70 Core-shell elastomer B Core-shell elastomer C Core-shell elastomer D Elastomer E 50 20 Hydrotalcite 0.1 Hindered Amine 0.1 Magnesium hydroxide Calcium stearate Polyethylene glycol Polyalphaolefin Polyethylene Melamine 0.1 0.1 0.1 0.1 POM volume ratio 44 76 76 25 25 25 Core-shell elastomer volume ratio - - 24 75 75 75 Flexural modulus (MPa) 700 1600 1600 300 300 300 Resonance frequency(Hz) 107 146 146 90 90 90 Productivity A A A B A B Formability B A A A A A Adhesion C A A A A A

[0174] [Table 5]

[0175] Example 10 Embodiment 11 Example 12 Comparative Example 4 Example 13 Embodiment 14 Polyacetal resin 30 30 30 30 50 50 Core-shell elastomer A 70 70 70 70 45 40 Core-shell elastomer B Core-shell elastomer C Core-shell elastomer D Elastomer E 5 10 Hydrotalcite Hindered Amine Magnesium hydroxide 0.1 Calcium stearate 0.1 Polyethylene glycol Polyalphaolefin Polyethylene Melamine 0.03 0.1 POM volume ratio 25 25 25 25 44 44 Core-shell elastomer volume ratio 75 75 75 75 51 45 Flexural modulus (MPa) 300 300 300 300 700 700 Resonance frequency(Hz) 90 90 90 90 107 107 Productivity B A B C A A Formability A A A A A Adhesion A A A A A

[0176] [Table 6]

[0177] Embodiment 15 Example 16 Embodiment 17 Comparative Example 5 Comparative Example 6 Embodiment 18 Polyacetal resin 50 50 50 50 70 65 Core-shell elastomer A 45 45 45 25 30 35 Core-shell elastomer B Core-shell elastomer C Core-shell elastomer D Elastomer E 25 Hydrotalcite Hindered Amine Magnesium hydroxide Calcium stearate Polyethylene glycol 5 Polyalphaolefin 5 Polyethylene 5 Melamine POM volume ratio 44 44 44 44 65 59 Core-shell elastomer volume ratio 45 45 45 28 35 41 Flexural modulus (MPa) 680 690 720 700 1200 950 Resonance frequency(Hz) 107 107 108 107 129 118 Productivity A A A A A A Formability A A A B A A Adhesion A A A C A A

[0178] In Tables 3 to 6 above, “POM volume ratio” refers to the volume ratio of the polyacetal resin relative to the total volume of the resin components in the resin composition, and “elastomer volume ratio” refers to the volume ratio of the elastomer relative to the total volume of the resin components in the resin composition.

[0179] According to the above results, it is clear that when the resin composition (A) of the present embodiment is used, a good two-color injection molded body with a hard polyacetal resin component (B) obtained from the resin composition (B) is obtained. In contrast, in Comparative Example 1, an elastomer other than the core-shell elastomer is used, and the result is a low bending elastic modulus. Although softness can be ensured, two-color molding with a hard polyacetal resin component (B) cannot be performed. In addition, in Comparative Example 2, an elastomer other than the core-shell elastomer is used and its proportion is reduced. As a result, although two-color molding with a hard polyacetal resin component (B) can be performed, softness cannot be ensured. In addition, in Comparative Example 3, a core-shell elastomer is used and the proportion of the elastomer is reduced. As a result, although two-color molding with a hard polyacetal resin component (B) can be performed, softness cannot be ensured. In Comparative Example 4, although a core-shell elastomer is used, no compound capable of capturing ions is used, and the volume ratio of the elastomer is increased, and as a result, particles cannot be produced. In Comparative Example 5, no compound capable of capturing ions was blended and an elastomer other than the core-shell elastomer was used. As a result, two-color injection molding could not be performed.

Claims

1. A resin composition comprising a polyacetal resin and a core-shell elastomer, The resin composition is molded into a multi-purpose test piece (ISO test piece) with a thickness of 4 mm, and the bending elastic modulus measured according to ISO178 is 50 to 1000 MPa. The resin composition is a resin composition for multi-color injection molding.

2. The resin composition according to claim 1, wherein The bending elastic modulus is 800 MPa or less.

3. The resin composition according to claim 1, wherein The ratio of the polyacetal resin is 10 to 50% by volume relative to the total volume of the resin components in the resin composition.

4. The resin composition according to claim 1, wherein The core-shell elastomer accounts for 30 to 90 volume % of the total volume of the resin components in the resin composition.

5. The resin composition according to claim 1, wherein The shell of the core-shell elastomer comprises an acrylic resin.

6. The resin composition according to claim 1, wherein The resin composition contains 0.01 to 1 parts by mass of a compound capable of capturing ions, based on 100 parts by mass of the total resin components in the resin composition.

7. The resin composition according to claim 6, wherein The compound capable of capturing ions comprises at least one selected from a triazine skeleton-containing compound, a hindered amine, an alkaline earth metal hydroxide, a hydrotalcite, and a fatty acid metal salt.

8. The resin composition according to claim 1, which is a resin composition for multi-color injection molding in which the ratio of the resin composition (B) to the polyacetal resin is 50 to 100 volume %.

9. The resin composition according to claim 1, wherein The core-shell elastomer accounts for 30 to 90% by volume of the total volume of the resin components in the resin composition, and the ion-capturing compound accounts for 0.01 to 1 part by mass of the compound based on 100 parts by mass of the total resin components in the resin composition.

10. The resin composition according to claim 1, wherein With respect to the total volume of the resin components in the resin composition, 35 to 50 volume % is the polyacetal resin, and 35 to 50 volume % is the core-shell elastomer. 11 . Pellets, which are particles of the resin composition according to claim 1 . 12 . A molded product formed from the resin composition according to claim 1 .

13. A shaped body formed from the particles according to claim 11.

14. A multi-color injection-molded article, which is a multi-color injection-molded article of a resin composition (B) wherein the ratio of the resin composition according to any one of claims 1 to 10 to the polyacetal resin is 50 to 100% by volume.

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