Resin composition, pellet, and molded article

Abstract

To provide a resin composition from which a molded article having high strength and high elastic modulus can be obtained, and a pellet and a molded article.SOLUTION: A resin composition contains 50 to 91 mass% of a polyacetal resin, and 9 to 50 mass% of a woody filler.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a pellet, and a molded article, and more particularly to a resin composition containing a polyacetal resin as a main component. [Background technology]

[0002] Polyacetal resin is a plastic having excellent mechanical properties, electrical properties, and chemical properties such as chemical resistance, and is used in a wide range of applications. Further, blending glass fibers into polyacetal resins to enhance mechanical strength has also been investigated. For example, Patent Document 1 discloses a polyacetal resin composition characterized by containing a polyacetal resin (A) and a polylactic acid resin (B), where the total of (A) and (B) is 100% by mass, with more than 50% by mass and not more than 90% by mass of (A), and 10% by mass or more and less than 50% by mass of (B), and a fibrous filler (C) in an amount of 10 to 120 parts by mass per 100 parts by mass of the total of (A) and (B). Patent Document 1 also discloses glass fibers as an example of the fibrous filler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-233131 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the increasing demand for polyacetal resins, new materials with excellent mechanical strength are required, and in particular, polyacetal resin compositions that can be used to produce molded products with high strength and high elastic modulus without blending glass fibers are required. The present invention aims to solve the above problems and to provide a resin composition from which molded articles having high strength and high elastic modulus can be obtained, as well as pellets and molded articles. [Means for solving the problem]

[0005] In view of the above problems, the present inventors have conducted research and found that the above problems can be solved by using a wood-based filler. Specifically, the above problems were solved by the following means. <1> A resin composition comprising 50 to 91 mass % of a polyacetal resin and 9 to 50 mass % of a wood-based filler. <2> The content of the compatibilizer contained in the resin composition is 0% by mass or more and less than 0.65% by mass, based on 100% by mass of the resin composition. <1> The resin composition according to claim 1. <3> The total content of the polyacetal resin and the wood-based filler accounts for 90% by mass or more of the resin composition. <1> or <2> The resin composition according to claim 1. <4> the content of the compatibilizer contained in the resin composition is 0% by mass or more and less than 0.65% by mass, based on 100% by mass of the resin composition; The total content of the polyacetal resin and the wood-based filler accounts for 90% by mass or more of the resin composition. <1> ~ <3> The resin composition according to any one of the above. <5> Further, the composition contains 0.1 to 5 parts by mass of a sliding agent relative to 100 parts by mass of the polyacetal resin. <1> ~ <4> The resin composition according to any one of the above. <6> The sliding agent includes polyethylene wax. <5> The resin composition according to claim 1. <7> The sliding agent contains a copolymer of 50 to 99 mol % of ethylene and 1 to 50 mol % of an α-olefin (however, the total of ethylene and the α-olefin does not exceed 100 mol %) having a number average molecular weight of 500 to 15,000. <5> or <6> The resin composition according to claim 1. <8> The sliding agent contains an acid-modified polyethylene wax having a number average molecular weight of 500 to 15,000. <5> ~ <7> The resin composition according to any one of the above. <9> The sliding agent contains silicone oil. <5> ~ <8> The resin composition according to any one of the above. <10> The sliding agent contains silicone oil and polyethylene wax, and the mass ratio thereof (silicone oil / polyethylene wax) is 0.01 to 4. <5> ~ <9> The resin composition according to any one of the above. <11> Further comprising a dispersant, <1> ~ <10> The resin composition according to any one of the above. <12> Further, the composition contains 0.1 to 1 part by mass of an ultraviolet absorber and / or 0.05 to 1 part by mass of a light stabilizer relative to 100 parts by mass of the polyacetal resin. <1> ~ <11> The resin composition according to any one of the above. <13> <1> ~ <12> A pellet of the resin composition according to any one of the above. <14> <1> ~ <12> A molded article formed from the resin composition according to any one of the above items. <15> <13> A molded article formed from the pellets according to claim 1. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a resin composition from which molded articles having high strength and high elastic modulus can be obtained, as well as pellets and molded articles. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the upper and lower limits. "A to B" means that the range is A or more and B or less. In addition, any combination of the upper and lower limit values ​​of the numerical values ​​in this specification is an example of this embodiment. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification change from year to year, they will be based on the standards in effect as of January 1, 2024, unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification are abolished as of January 1, 2024, they will be based on the standards in effect at the time of abolition.

[0008] The resin composition of this embodiment is characterized by containing 50 to 91 mass % of a polyacetal resin and 9 to 50 mass % of a wood-based filler, and by using such a composition, it is possible to provide a resin composition that can be used to obtain molded products with high strength and high elastic modulus. Blending a wood-based filler into a resin has been considered, for example, as described in JP 2020-26485 A. However, the inventors of the present invention have conducted research and found that blending a wood-based filler into the polypropylene resin specifically verified in JP 2020-26485 A does not improve the mechanical strength of the molded product (Comparative Examples 1 to 3 described below). On the other hand, it was found that blending wood-based fillers into polyacetal resin improves mechanical strength. When the reason for this was investigated, it was speculated that polyacetal resin has a relatively low melting point, and the wood-based fillers are oriented in the direction of the flow of the polyacetal resin and solidify as they are, resulting in a reinforcing effect. It was also speculated that wood-based fillers would decompose if blended into resins with high molding temperatures, resulting in no reinforcing effect. Furthermore, it was found that the addition of wood-based fillers improved the sliding properties of the resulting molded products, and that the addition of a dispersant to the resin composition further improved the flexural modulus.

[0009] Hereinafter, the embodiments of the present invention will be described in detail. However, the explanation of the constituent elements described below is an example of an embodiment of the present invention, and the present invention is not limited to these contents.

[0010] <Polyacetal resin> The resin composition of the present embodiment contains a polyacetal resin. The polyacetal resin is not particularly limited in terms of type, etc., and may be a homopolymer containing only divalent oxymethylene groups as constituent units, or a copolymer containing divalent oxymethylene groups and divalent oxyalkylene groups having 2 to 6 carbon atoms as constituent units.

[0011] Examples of the oxyalkylene group having 2 to 6 carbon atoms include an oxyethylene group, an oxypropylene group, and an oxybutylene group.

[0012] In the polyacetal resin, the proportion of oxyalkylene groups having 2 to 6 carbon atoms in the total number of moles of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms is not particularly limited, and may be 0.5 to 10 mol %.

[0013] To produce the polyacetal resin, trioxane is typically used as the main raw material. Furthermore, to introduce oxyalkylene groups having 2 to 6 carbon atoms into the polyacetal resin, cyclic formals or cyclic ethers can be used. Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, and 1,3,6-trioxocane. Specific examples of cyclic ethers include ethylene oxide, propylene oxide, and butylene oxide. To introduce oxyethylene groups into the polyacetal resin, 1,3-dioxolane can be used as the main raw material. To introduce oxypropylene groups, 1,3-dioxane can be used as the main raw material. To introduce oxybutylene groups, 1,3-dioxepane can be used as the main raw material. In addition, it is preferable that the amount of hemiformal terminal groups, formyl terminal groups, and terminal groups unstable to heat, acid, or base is small in polyacetal resins. Here, the hemiformal terminal group is represented by -OCHOH, and the formyl terminal group is represented by -CHO.

[0014] The polyacetal resin used in this embodiment has a melt volume rate (MVR) of 0.5 cm, measured at a temperature of 190°C and a load of 2.16 kg according to ASTM-D1238. 3 / 10 minutes or more is preferable, 0.8cm 3 / 10 minutes or more is more preferable, and 1.0 cm 3 / 10 minutes or more is more preferable, and 3 cm 3 / 10 minutes or more is more preferable, and 5cm 3 By setting the MVR to the above lower limit or more, the productivity of the resin composition tends to be further improved. 3 / 10 minutes or less is preferable, 25cm 3 / 10 minutes or less is more preferable, and 20cm 3 / 10 minutes or less is more preferable, and 15 cm 3 / 10 minutes or less is more preferable, and 12 cm 3 It is even more preferable that the time is 10 minutes or less.

[0015] In addition to the above, the polyacetal resins that can be used include those described in paragraphs 0018 to 0043 of JP-A No. 2015-074724, the contents of which are incorporated herein by reference. The polyacetal resin used in this embodiment may be a recycled product (including recovered products, material recycled products, chemical recycled products, etc.), a rejected product, or a waste material from molding a polyacetal resin.

[0016] The resin composition of this embodiment contains polyacetal resin in a proportion of 50% by mass or more of the resin composition, preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more, and also contains 91% by mass or less, preferably 85% by mass or less, more preferably 83% by mass or less, and even more preferably 75% by mass or less. The resin composition of the present embodiment may contain only one type of polyacetal resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0017] <Wood-based filler> The resin composition of the present embodiment contains a wood-based filler, which can further improve the mechanical strength of molded articles obtained from the polyacetal resin. Furthermore, by blending a wood-based filler, the sliding properties of the resulting molded product can be improved. In particular, blending a sliding agent improves the sliding properties, but other physical properties (mechanical properties) tend to be slightly inferior. However, in this embodiment, the sliding properties can be improved without blending a sliding agent. Examples of wood-based fillers include those derived from conifers such as cedar, red pine, spruce, Sakhalin fir, Douglas fir, western hemlock, spruce, and Japanese cypress, as well as broad-leaved trees such as paulownia, linden, beech, macaba, katsura, maple, mizunara, and zelkova, as well as powders derived from plant materials such as reed, rice straw, rice husks, and coconuts, and powders of plant materials such as bamboo, hemp, plants, and agricultural products. Furthermore, examples of wood-based fillers include waste wood boards such as wood plywood, particle board (chipboard), MDF (medium density fiberboard), and OSB (oriented strand board), which are broken up using a cutter mill or the like and then pulverized into fine powder using a ball mill or impeller mill. In this embodiment, spruce, cypress, cedar, and bamboo are preferred. The particle size of the wood filler is preferably about 100 to 500 μm, and it is preferable to use a wood filler that is sufficiently dried (with a moisture content of 3% by mass or less, preferably 2% by mass or less, and particularly 1% by mass or less).

[0018] The content of wood-based filler in the resin composition of this embodiment is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of polyacetal resin.

[0019] The content of the wood-based filler in the resin composition of this embodiment is 9% by mass or more, preferably 15% by mass or more, more preferably 17% by mass or more, and 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less. By making the content equal to or greater than the lower limit, the effect of improving mechanical strength tends to be further improved. The resin composition of the present embodiment may contain only one type of wood-based filler, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0020] <Sliding agent> The resin composition of the present embodiment may contain a sliding agent, which can improve the sliding properties of the resulting molded article. The type of the sliding agent is not particularly limited, and a wide range of sliding agents that are used to improve the sliding properties of polyacetal resin molded articles can be used. An example of the sliding agent is polyolefin wax, and another example of the sliding agent is silicone oil.

[0021] The polyolefin wax is preferably a polyethylene wax, and more preferably a polyethylene wax that is a copolymer of 50 to 99 mol % of ethylene and 1 to 50 mol % of an α-olefin (however, the total of ethylene and the α-olefin does not exceed 100 mol %). By setting the content within the above range, the effects of the present invention tend to be more effectively exhibited. Furthermore, in the polyethylene wax, which is a copolymer of 50 to 99 mol % of ethylene and 1 to 50 mol % of an α-olefin, the total of ethylene and the α-olefin preferably accounts for 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more, of the monomer units constituting the copolymer, and may even account for 100 mol %. The α-olefins include propylene and / or butylene.

[0022] The polyolefin wax may be an acid-modified polyolefin wax or an acid-modified polyethylene wax. The acid-modified polyolefin wax is preferably an acid-modified polyolefin modified with at least one of an unsaturated carboxylic acid and an unsaturated carboxylic acid anhydride, and more preferably an acid-modified polyolefin modified with maleic acid and / or maleic acid anhydride. The lower limit of the amount of such ethylenically unsaturated carboxylic acid or its anhydride added to the polyolefin or grafted thereto (modification degree) is preferably 0.01% by mass, more preferably 0.02% by mass, relative to the acid-modified polyolefin. The upper limit of this amount of addition or grafting (modification degree) is preferably 15% by mass, more preferably 10% by mass. By setting the amount within the above range, the effects of the present invention tend to be more effectively exhibited.

[0023] The number average molecular weight of the polyolefin wax is preferably 500 or more, more preferably 1,000 or more, and even more preferably 5,000 or more, and is preferably 15,000 or less, more preferably 10,000 or less, and even more preferably 8,000 or less. By keeping it within the above range, the effects of the present invention tend to be more effectively exhibited. The number average molecular weight of the polyolefin wax is a polystyrene equivalent value measured by GPC (gel permeation chromatography). When the resin composition of the present embodiment contains two or more types of polyolefin waxes, the number average molecular weight of the polyolefin waxes is the number average molecular weight of the mixture.

[0024] Silicone oil is particularly effective in improving the sliding properties and in maintaining the sliding properties. Silicone oils include straight silicone oils and modified silicone oils in which organic groups are introduced into the side chains or terminals. Examples of straight silicone oils include dimethyl silicone oil, methyl phenyl silicone oil, and methyl hydrogen silicone oil.

[0025] Modified silicone oils are classified into side chain, both end, one end, and both end side chain types depending on the bonding position of the substituted organic group. Modified silicone oils are also classified into reactive silicone oils and non-reactive silicone oils depending on the properties of the organic group introduced.

[0026] Examples of reactive silicone oils include various modified types of reactive silicone oils such as amino-modified, epoxy-modified, carboxy-modified, carbinol-modified, methacryl-modified, mercapto-modified, phenol-modified, and heterofunctional group-modified. Examples of non-reactive silicone oils include reactive silicone oils of various modified types such as polyether-modified, methylstyryl-modified, alkyl-modified, higher fatty acid ester-modified, specially hydrophilic-modified, higher fatty acid-containing, and fluorine-modified.

[0027] As the silicone oil used in the resin composition of this embodiment, straight silicone oil is preferred, and dimethyl silicone oil is more preferred, because of its superior chemical stability.

[0028] The dynamic viscosity of the silicone oil used in the resin composition of this embodiment is preferably 10 to 106 mPa·s, and more preferably 102 to 105 mPa·s. When the dynamic viscosity of the silicone oil is equal to or greater than the lower limit of the preferred range, long-term sliding properties are improved. When the dynamic viscosity of the silicone oil is equal to or less than the upper limit of the preferred range, the initial coefficient of friction is reduced. The dynamic viscosity in this specification is the viscosity measured at 25°C using a Brookfield viscometer.

[0029] The molecular weight of the silicone oil used in the resin composition of this embodiment is preferably 1000 to 15000, and more preferably 6000 to 100000. When the molecular weight of the silicone oil is within the preferred range, the dynamic viscosity of the silicone oil can be easily adjusted to the above preferred range. The molecular weight of the silicone oil is measured by gel permeation chromatography using a polystyrene standard polymer as the standard.

[0030] The resin composition of this embodiment preferably contains silicone oil and polyethylene wax as the sliding agent, with the mass ratio thereof (silicone oil / polyethylene wax) being 0.01 to 4. By making the mass ratio equal to or greater than the lower limit, the effect of improving the dynamic friction coefficient at low surface pressure tends to be further enhanced. Meanwhile, by making the mass ratio equal to or less than the upper limit, mechanical properties can be effectively maintained. The mass ratio (silicone oil / polyethylene wax) is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.5 or more, even more preferably 0.8 or more, and is preferably 4 or less, more preferably 3 or less, even more preferably 2.5 or less, even more preferably less than 2.3, and even more preferably 2.1 or less.

[0031] The content of the sliding agent in the resin composition of this embodiment is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, even more preferably 2.0 parts by mass or more, even more preferably 2.5 parts by mass or more, and preferably 5 parts by mass or less, more preferably 4.5 parts by mass or less, even more preferably 4 parts by mass or less, even more preferably 3.5 parts by mass or less, and even more preferably 3.3 parts by mass or less, relative to 100 parts by mass of the polyacetal resin. By setting the content at or above the lower limit, the dynamic friction coefficient can be reduced. Meanwhile, by setting the content at or below the upper limit, deterioration of mechanical properties tends to be effectively suppressed. The resin composition of the present embodiment may contain only one type of sliding agent, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0032] <Dispersant> The resin composition of this embodiment may contain a dispersant. The dispersant improves the dispersibility of the wood-based filler and can more effectively suppress cracking in the resulting molded article. In particular, the addition of a dispersant can further improve the flexural modulus of the resulting molded article. The dispersant can be used without any particular limitation as long as it contributes to the dispersion of the wood-based filler. The dispersant preferably has a functional group such as a hydroxyl group or an amino group. Since wood-based fillers contain many hydroxyl groups, it is presumed that these dispersants penetrate between the wood-based fillers and maintain the distance between them. The dispersant is preferably polyethylene glycol, lignin polymer, nitrogen-containing compound (urea, melamine), sugar-derived wax (sugar wax), or the like, and more preferably lignin polymer and / or melamine.

[0033] When the resin composition of this embodiment contains a dispersant, the content thereof is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyacetal resin, and is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less. By setting the content at or above the lower limit, the rigidity of the obtained molded article tends to be improved. Furthermore, by setting the content at or below the upper limit, gas generation during molding tends to be effectively suppressed. The resin composition of the present embodiment may contain only one dispersant, or may contain two or more dispersants. When two or more dispersants are contained, the total amount is preferably in the above range.

[0034] <Other ingredients> The resin composition of this embodiment may contain known additives and fillers as long as the object of the present invention is not impaired. Examples of additives and fillers that can be used in this embodiment include known thermoplastic polymers other than polyacetal resins, polymers, formaldehyde scavengers, inorganic particles, antioxidants, UV absorbers, light stabilizers, colorants, nucleating agents, plasticizers, fluorescent brighteners, mold release agents, antistatic agents, flame retardants, and flame retardant aids. The resin composition of this embodiment preferably further contains at least one selected from the group consisting of antioxidants, UV absorbers, and light stabilizers, and more preferably contains a UV absorber and / or a light stabilizer. The total amount of these other components is preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass or more and less than 5% by mass, and even more preferably 0% by mass or more and less than 3% by mass, relative to 100 parts by mass of the polyacetal resin. The other components may be contained in one kind or in two or more kinds. When two or more kinds are contained, it is preferable that the total amount is in the above range. In addition, the resin composition of this embodiment can be blended with additives described in paragraphs 0047 to 0103 of WO 2021 / 241471 within the scope of the present invention, the contents of which are incorporated herein by reference.

[0035] The resin composition of this embodiment is prepared so that the total amount of the polyacetal resin, the wood-based filler, and other components that are blended as necessary is 100% by mass. In the resin composition of this embodiment, the total content of the polyacetal resin and wood-based filler preferably accounts for 90% by mass or more of the resin composition, more preferably 93% by mass or more, and even more preferably 95% by mass or more. Depending on the application, etc., it may account for 97% by mass or more, 98% by mass, or 100% by mass or more. In the resin composition of the present embodiment, the total amount of the polyacetal resin, wood-based filler, and at least one selectively blended agent selected from the group consisting of a sliding agent, a dispersant, an antioxidant, an ultraviolet absorber, and a light stabilizer preferably accounts for 90% by mass or more of the resin composition, more preferably 95% by mass or more, even more preferably 97% by mass or more, and even more preferably 99% by mass or more, with the upper limit being 100% by mass.

[0036] The resin composition of this embodiment may or may not contain a filler other than a wood-based filler. An example of this embodiment is one that is substantially free of a wood-based filler. "Substantially free" means that the content of fillers other than a wood-based filler contained in the resin composition of this embodiment is less than 9% by mass, preferably less than 5% by mass, more preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.1% by mass. Examples of fillers other than wood-based fillers include glass fiber, glass beads, and talc.

[0037] The resin composition of this embodiment may or may not contain a compatibilizer. An example of a compatibilizer is maleic anhydride. In this embodiment, the resin composition is substantially free of a compatibilizer. "Substantially free" means that the content of the compatibilizer contained in the resin composition of this embodiment is 0% by mass or more and less than 0.65% by mass, preferably 0% by mass or more and less than 0.5% by mass, more preferably 0% by mass or more and less than 0.3% by mass, even more preferably 0% by mass or more and less than 0.1% by mass, even more preferably 0% by mass or more and less than 0.01% by mass, and even more preferably 0% by mass or more and less than 0.001% by mass. By not including a compatibilizer, deterioration of other physical properties can be effectively suppressed.

[0038] <<Antioxidants>> The resin composition of the present embodiment preferably contains an antioxidant, which can improve the heat resistance of the resulting molded article. Examples of antioxidants include phenolic antioxidants (preferably hindered phenolic antioxidants), amine antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants, with phenolic antioxidants and / or phosphorus-based antioxidants being preferred, and phenolic antioxidants being more preferred.

[0039] Specifically, the phenolic antioxidant is preferably a hindered phenolic antioxidant. Here, the hindered phenolic antioxidant is, for example, a compound having a hindered phenol structure in which at least one of the carbon atoms on either side of the carbon atom to which the OH group of the phenyl group is bonded has a bulky substituent, and the bulky substituent is generally a t-butyl group. Hindered phenolic antioxidants are generally classified into hindered and less hindered types, and the hindered type is preferred. The hindered type is a compound in which a bulky substituent is present on each of the carbon atoms on either side of the carbon atom to which the OH group of the phenyl group is bonded. On the other hand, the less hindered type is a hindered phenolic antioxidant in which a bulky substituent is present on only one of the carbon atoms on either side of the carbon atom to which the OH group of the phenyl group is bonded, or a hindered phenolic antioxidant in which no bulky substituent is present on either of the carbon atoms at both ends. In particular, in this embodiment, a hindered phenol-based antioxidant having 2 to 6 hindered phenol structures is preferred, and a hindered phenol-based antioxidant having two hindered phenol structures is more preferred. In this embodiment, a hindered phenol-based antioxidant having an amide bond is preferred, a hindered hindered phenol-based antioxidant having an amide bond is more preferred, a hindered phenol-based antioxidant having 2 to 6 amide bonds and 2 to 6 hindered hindered phenol structures is more preferred, a hindered phenol-based antioxidant having 2 to 6 di-tert-butyl-4 hydroxyphenylalkylcarbonylamide groups (the number of carbon atoms in the alkyl chain portion is preferably 1 to 5, and more preferably 2 to 4), is even more preferred, and N,N'-hexane-1,6diylbis[3-(3,5-di-tert-butyl-4 hydroxyphenylpropionamide] is particularly preferred. As commercially available hindered phenol-based antioxidants, antioxidants sold by BASF as the Irganox series and antioxidants sold by ADEKA as the Adeka STAB series (e.g., AO-20, AO-50, AO-50F, AO-60, AO-60G, AO-330) are preferred, and Irganox 1098 is preferred.

[0040] When the resin composition of this embodiment contains an antioxidant, the content thereof is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, even more preferably 0.01 parts by mass or more, even more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the polyacetal resin. It is also preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.5 parts by mass or less. By setting the content at or above the lower limit, the thermal stability improving effect tends to be further improved. Furthermore, by setting the content at or below the upper limit, gas generation during molding tends to be effectively suppressed. The resin composition of the present embodiment may contain only one type of antioxidant, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0041] <<Ultraviolet absorber>> The resin composition of the present embodiment preferably contains an ultraviolet absorber, which can improve the weather resistance of the resulting molded article. The ultraviolet absorber is preferably selected from benzotriazole compounds, benzophenone compounds, aromatic benzoate compounds, cyanoacrylate compounds, and oxalic acid anilide ultraviolet absorbers, with benzotriazole compounds being more preferred.

[0042] Specific examples of ultraviolet absorbers include 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2'-hydroxy-3',5'-di-isoamyl-phenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis-(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, Examples of the oxalic acid diamide include 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-oxybenzylbenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, pt-butylphenyl salicylate, p-octylphenyl salicylate, 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenylacrylate, N-(2-ethoxy-5-t-butylphenyl)oxalic acid diamide, and N-(2-ethylphenyl)-N'-(2-ethoxyphenyl)oxalic acid diamide. In addition to the above, the ultraviolet absorbers described in paragraphs 0116 to 0117 of WO 2017 / 018210 may be referred to, the contents of which are incorporated herein by reference.

[0043] A preferred ultraviolet absorber is a benzotriazole compound, and particularly preferred is a compound having a vapor pressure of 1×10 at 20° C. -8 These are benzotriazole-based ultraviolet absorbers with a UV absorbency of less than 100 Pa. Specific examples include 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol and 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol].

[0044] The resin composition of this embodiment preferably contains 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, of the ultraviolet absorber per 100 parts by mass of the polyacetal resin, and preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, of the ultraviolet absorber per 100 parts by mass of the polyacetal resin. The resin composition of the present embodiment may contain only one type of ultraviolet absorber, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0045] <<Light stabilizers>> The resin composition of the present invention may contain a light stabilizer, such as a hindered amine light stabilizer. The resin composition of the present embodiment preferably contains a hindered amine-based light stabilizer, which can improve weather resistance. The hindered amine light stabilizer preferably used is one represented by formula (4). Formula (4) [ka] (In formula (4), R represents an organic group whose bond to the nitrogen atom is a carbon atom, and X represents an organic group bonded to the 4-position of the piperidyl group via an oxygen atom or a nitrogen atom, or a hydrogen atom.)

[0046] R can be a linear or branched alkyl group having 1 to 10 carbon atoms. Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, a t-butyl group, a hexyl group, an octyl group, and a decyl group, with a methyl group being preferred.

[0047] Specific examples of preferred hindered amine light stabilizers include bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, 1-[2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl and tridecyl-1,2,3,4 butanetetracarboxylate (a mixture of compounds in which some of the four ester moieties of butanetetracarboxylate are 1,2,2,6,6-pentamethyl-4-piperidyl groups and the others are tridecyl groups), 1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl groups and tridecyl groups, and 1,2,3,4-butanetetracarboxylate. Condensation product of ethanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β,β-tetramethyl-3,9(2,4,8,10-tetraoxaspiro[5,5]udencane)-diethanol, condensation product of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, N ,N',N''',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1 dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate. In addition to the above, the hindered amine light stabilizers described in paragraph 0113 of WO 2017 / 018210 may be referred to, the contents of which are incorporated herein by reference.

[0048] The resin composition of this embodiment preferably contains 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, of a light stabilizer (preferably a hindered amine-based light stabilizer) per 100 parts by mass of the polyacetal resin. The resin composition of this embodiment preferably contains 1 part by mass or less, and more preferably 0.5 parts by mass or less, of a light stabilizer (preferably a hindered amine-based light stabilizer) per 100 parts by mass of the polyacetal resin. By setting the content at or above the lower limit, weather resistance tends to be further improved. By setting the content at or below the upper limit, mold fouling can be effectively suppressed. The resin composition of the present embodiment may contain only one type of light stabilizer, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0049] <Physical properties of resin composition> The resin composition of this embodiment preferably has a high tensile modulus. Specifically, the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece, and the tensile modulus measured according to the method described in JIS K 7127 is preferably 3,500 MPa or more, more preferably 4,500 MPa or more, and even more preferably 5,500 MPa or more. The resin composition of this embodiment preferably has high tensile strength. Specifically, the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece, and the tensile strength measured according to the method described in JIS K 7127 is preferably 45 MPa or more, more preferably 55 MPa or more, and even more preferably 65 MPa or more. The resin composition of this embodiment preferably has a high flexural modulus. Specifically, the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece, and the flexural modulus measured according to the method specified in ISO 178 is preferably 3,400 MPa or more, more preferably 4,400 MPa or more, and even more preferably 5,400 MPa or more. The resin composition of this embodiment preferably has high flexural strength. Specifically, the resin composition of this embodiment is molded into a 4 mm thick multipurpose test piece, and the flexural strength measured according to the method specified in ISO 178 is preferably 85 MPa or more, more preferably 95 MPa or more, and even more preferably 105 MPa or more.

[0050] <Method of manufacturing resin composition> The resin composition of this embodiment can be easily prepared by a known method commonly used for preparing conventional thermoplastic resin compositions. For example, (1) a method in which all components constituting the resin composition are mixed, fed into an extruder, and melt-kneaded to obtain a pellet-shaped resin composition, (2) a method in which some of the components constituting the resin composition are fed through a main feed port of an extruder and the remaining components are fed through a side feed port, and melt-kneaded to obtain a pellet-shaped resin composition, or (3) a method in which pellets of different compositions are prepared by extrusion or the like, and the pellets are mixed to obtain a resin composition having a predetermined composition, etc., can be employed. Examples of the kneading machine include a kneader, a Banbury mixer, an extruder, etc. There are no particular limitations on the various conditions and devices for mixing and kneading, and they may be appropriately selected from any conventionally known conditions. Kneading is preferably carried out at a temperature above the melting point of the polyacetal resin, specifically above the melting point of the polyacetal resin (generally 180°C or higher).

[0051] <Molded products> The molded article of this embodiment is formed from the resin composition or pellets of this embodiment. The pellets obtained by pelletizing the resin composition of this embodiment are molded into a molded article by various molding methods. Alternatively, a resin composition melt-kneaded in an extruder can be directly molded into a molded article without going through pelletization. The shape of the molded article is not particularly limited and can be appropriately selected depending on the application and purpose of the molded article. Examples of the shape of the molded article include plate-like, plate-like, rod-like, sheet-like, film-like, cylindrical, ring-like, circular, elliptical, gear-like, polygonal, irregular-shaped, hollow, frame-like, box-like, and panel-like shapes. The molded article of this embodiment may be a finished product or a part.

[0052] The method for molding the molded article is not particularly limited, and any conventionally known molding method can be used, such as injection molding, injection compression molding, extrusion molding, profile extrusion, transfer molding, blow molding, gas-assisted blow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding), rotational molding, multilayer molding, two-color molding, insert molding, sandwich molding, foam molding, and pressure molding.

[0053] The resin composition and pellets of this embodiment are preferably used for forming sliding members, and therefore, molded articles formed from the resin composition of this embodiment are preferably used as sliding members (sliding parts). Specific examples of sliding members include gears, rotating shafts, bearings, various gears, cams, end face materials for mechanical seals, valve seats for valves, sealing members such as V-rings, rod packings, piston rings, and rider rings, as well as sliding members such as rotating shafts, rotating sleeves, pistons, impellers, and rollers for compressors, all of which are intended to meet the high quality demands of electrical and electronic equipment, office equipment, vehicles (automobiles), industrial equipment, and the like. The sliding member of this embodiment can be used as a sliding member in combination with not only another sliding member of this embodiment but also other resin sliding members, fiber-reinforced resin sliding members, and ceramic or metal sliding members.

[0054] The resin composition, pellets, and molded article of the present embodiment can also be suitably used in applications requiring a reduced amount of formaldehyde emissions, such as automobile parts, electrical and electronic parts, precision machinery parts, building materials and piping parts, daily necessities, cosmetic parts, and medical device parts. More specifically, examples of automotive parts include interior parts such as inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, and clips; electrical system parts such as meters and connectors; in-vehicle electrical and electronic parts such as audio equipment and car navigation equipment; parts that come into contact with metal such as window regulator carrier plates; door lock actuator parts, mirror parts, wiper motor system parts, and fuel system parts.

[0055] Examples of electrical and electronic components include components or members of devices with many metal contacts, such as audio equipment such as cassette tape recorders and CD / DVD players, video equipment such as VTRs, 8mm video cameras, and digital video cameras, and office automation equipment such as copiers, facsimiles, word processors, and computers. Specific examples of these components or members include chassis, gears, levers, cams, pulleys, and bearings. Furthermore, the present invention can be applied to optical and magnetic media components, at least a portion of which is molded, such as metal music tape cassettes, digital audio tape cassettes, 8mm video tape cassettes, digital video cassettes, floppy disk cartridges, minidisk cartridges, and DVD disk cartridges.

[0056] Furthermore, the molded product of this embodiment can be suitably used for a wide range of lifestyle-related, cosmetic-related, and medical-related parts, such as lighting fixtures, fittings, pipes, cocks, faucets, toilet peripheral equipment parts, and other building materials and piping parts, fasteners, stationery, lip balm and lipstick containers, cleaning devices, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, and syringe needle holders. [Example]

[0057] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0058] 1. Raw materials The following raw materials were used: [Table 1] *Wood flour refers to wood-based filler.

[0059] <Synthesis example: Synthesis of POM2> To a twin-screw continuous polymerization reactor equipped with a self-cleaning paddle and having a jacket set at a temperature of 65°C, 100 parts by mass of trioxane, 4 parts by mass of 1,3-dioxolane, and a benzene solution of boron trifluoride diethyl etherate as a catalyst in an amount of 0.05 mmol relative to 1 mol of total monomers (trioxane and 1,3-dioxolane), and a benzene solution of methylal as a molecular weight modifier in an amount of 500 ppm relative to all monomers were continuously added, and a polymerization reaction was carried out continuously so that the residence time of the raw materials and the polymerization reaction product in the continuous polymerization reactor was 20 minutes.

[0060] To the resulting polymerization reaction product, triphenylphosphine was added as a benzene solution in an amount of 2 mol per 1 mol of boron trifluoride diethyl etherate used. After deactivating the catalyst, the product was pulverized to obtain POM2.

[0061] Examples 1 to 11, Comparative Examples 1 to 6 <Production of Resin Composition (Pellets)> The components shown in Table 1 were mixed uniformly in the proportions shown in Tables 2 to 6 (proportions of each component are in parts by mass) using a Super Mixer manufactured by Kawada Manufacturing Co., Ltd. The resulting mixture was melt-shear mixed using a vented twin-screw extruder with a screw diameter of 30 mm ("PCM30" manufactured by Ikegai Corporation) at a cylinder temperature of 190°C, a screw rotation speed of 120 rpm, and a discharge rate of 10 kg / hour to produce pellets of the resin composition.

[0062] <Density measurement> The pellets obtained above were heat-treated in a hot air circulation dryer at a temperature of 80°C for 4 hours. Next, the dried pellets were injection molded in accordance with ISO 9988-2 standard using an injection molding machine with a cylinder temperature set to 195° C. and a mold temperature set to 90° C. In this way, a 4 mm thick multipurpose test piece (ISO test piece) was obtained. A 10 mm wide strip was cut out from the 4 mm thick multipurpose test piece (ISO test piece) obtained above, and measured according to JIS K7112-1 Method A. The unit of density is g / cm 3 As shown.

[0063] <Tensile properties> The tensile modulus (unit: GPa) and tensile strength (unit: MPa) of the 4 mm thick multipurpose test specimen (ISO test specimen) obtained above were measured at a test speed of 50 mm / min in accordance with JIS K 7127. The test specimen was tensile tested in the MD direction with a chuck distance of 50 mm and a tensile speed of 50 mm / min. The measurement environment was an atmosphere of 23°C and relative humidity (RH) of 50%. The evaluation was carried out according to the following classification, and the results are shown in Tables 2 to 5. <<Tensile modulus>> A:5,500MPa or more B:4,500MPa or more C:3,500MPa or more D: Less than 3,500 MPa <<Tensile strength>> A: 65 MPa or more B:55MPa or more C:45MPa or more D: Less than 45 MPa

[0064] <Bending properties> The 4 mm thick multipurpose test piece (ISO test piece) obtained above was cut into 10 mm wide strips, and the flexural modulus and flexural strength were measured using a fully automatic flexural tester according to the method described in ISO178. The injection molding machine used was an EC-100S manufactured by Shibaura Machine Co., Ltd. The fully automatic bending tester used was a machine manufactured by Shimadzu Corporation. The evaluation was carried out according to the following classification, and the results are shown in Tables 2 to 5. <<Flexural modulus>> S: Among Examples 8 to 10, the bending modulus was higher than that of Example 2 A:5,400MPa or more B:4,400MPa or more C:3,400MPa or more D: Less than 3,400 MPa <<Bending strength>> A:105MPa or more B:95MPa or more C: 85MPa or more D: Less than 85 MPa

[0065] <Sliding characteristics> The pellets obtained above were used in an injection molding machine, with the cylinder temperature set to 195°C and the mold temperature set to 80°C to form cylindrical thrust test specimens with a contact area of ​​2 cm. 2 The coefficient of dynamic friction of this test piece was evaluated using a Suzuki friction and wear tester in an atmosphere of 23°C and 50% humidity, with the mating material being S45C, the linear velocity being 30 cm / s, and the load being 3 kgf, which was increased to 5 kgf after 3 minutes, and thereafter the load was increased by 5 kgf every 3 minutes. In Comparative Examples 1 to 3, the test pieces melted when the load reached 35 kgf.

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] [Table 5]

[0070] As is clear from the above results, molded articles formed from the resin composition of the present invention had high strength and a high modulus of elasticity (Examples 1 to 11). Furthermore, molded articles formed from the resin composition of the present invention also had excellent sliding properties (Examples 1 to 11). In particular, when a sliding agent was blended, the sliding properties were significantly excellent (Examples 7 to 10). In contrast, even when a wood-based filler was blended into the polypropylene resin, the mechanical strength did not improve and the sliding properties were poor (Comparative Examples 1 to 3). Furthermore, by blending a dispersant (Examples 8 to 10), the flexural modulus of the resulting molded article was significantly improved compared to Example 2, in which no dispersant was blended. In addition, the density was low enough to be comparable to that of polyacetal resin containing no filler. The density of a resin composition containing 43 parts by mass of glass fiber per 100 parts by mass of polyacetal resin was 1.64 g / cm. 3 This indicates that the resin composition is significantly lighter than the glass fiber reinforced polyacetal resin composition. Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A resin composition comprising 50 to 91% by mass of a polyacetal resin and 9 to 50% by mass of a wood-based filler.

2. The resin composition according to claim 1 , wherein the content of the compatibilizer contained in the resin composition is 0% by mass or more and less than 0.65% by mass, based on 100% by mass of the resin composition.

3. The resin composition according to claim 1 , wherein the total content of the polyacetal resin and the wood-based filler is 90% by mass or more of the resin composition.

4. the content of the compatibilizer contained in the resin composition is 0% by mass or more and less than 0.65% by mass, based on 100% by mass of the resin composition; The resin composition according to claim 1 , wherein the total content of the polyacetal resin and the wood-based filler is 90% by mass or more of the resin composition.

5. The resin composition according to any one of claims 1 to 4, further comprising 0.1 to 5 parts by mass of a sliding agent relative to 100 parts by mass of the polyacetal resin.

6. The resin composition according to claim 5 , wherein the sliding agent comprises polyethylene wax.

7. The resin composition according to claim 5, wherein the sliding agent contains a copolymer of 50 to 99 mol % of ethylene and 1 to 50 mol % of an α-olefin (provided that the total of ethylene and the α-olefin does not exceed 100 mol %) having a number average molecular weight of 500 to 15,000.

8. 6. The resin composition according to claim 5, wherein the sliding agent comprises an acid-modified polyethylene wax having a number average molecular weight of 500 to 15,000.

9. The resin composition according to claim 5 , wherein the sliding agent comprises silicone oil.

10. 6. The resin composition according to claim 5, wherein the sliding agent comprises silicone oil and polyethylene wax, and the mass ratio thereof (silicone oil / polyethylene wax) is 0.01 to 4.

11. The resin composition according to any one of claims 1 to 4, further comprising a dispersant.

12. The resin composition according to any one of claims 1 to 4, further comprising 0.1 to 1 part by mass of an ultraviolet absorber and / or 0.05 to 1 part by mass of a light stabilizer relative to 100 parts by mass of the polyacetal resin.

13. Pellets of the resin composition according to any one of claims 1 to 4.

14. A molded article formed from the resin composition according to any one of claims 1 to 4.

15. A molded article formed from the pellets of claim 13.

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