Resin composition, pellets, and molded article

Abstract

Provided are a resin composition, pellets, and a molded article. This resin composition includes, per 100 parts by mass of (A) a polyacetal resin, 0.25-9.0 parts by mass of (B) an ultra-high molecular weight polyethylene that has a a melt volume rate (MVR) of 0.1-10 cm3 / 10 min as measured according to the ASTM-D1238 standard and under conditions of 190°C and a load of 5.0 Kg, and 0.25-9.0 parts by weight of (C) a polyolefin that, in a 100 mm tall × 100 mm long × 3 mm thick test piece that was molded with a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C, has a shrinkage rate of 2% or more after 24 hours have passed after molding, wherein (B) / [(B)+(C)]×100, which is the mass ratio of the included quantity of (B) the ultra-high molecular weight polyethylene and the included quantity of (C) the polyolefin is in the range 10-90%.

Description

Resin composition, pellets, and molded products

[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.

[0002] Polyacetal resins have an excellent balance of mechanical properties (friction resistance, abrasion resistance, creep resistance, dimensional stability, etc.) and excellent fatigue resistance. They also have excellent chemical resistance and low water absorption. Because of these characteristics, polyacetal resins have been widely used in a variety of applications, including automobile, office equipment, building materials, and machinery components, as well as automobile interior parts, home interior parts (hot water mixer taps, etc.), clothing parts (zippers, belt buckles, etc.), and toys, and demand is growing.

[0003] As a resin composition using a polyacetal resin, Patent Document 1 discloses a resin composition for a sliding member, which contains 75 to 97 mass % of a polyacetal resin, 2 to 20 mass % of an ultra-high molecular weight polyethylene resin as an additive, 0.01 to 3 mass % of a copolymer of ethylene and an α,β-unsaturated carboxylic acid, and 0.5 to 3 mass % of a lubricant.

[0004] Japanese Patent Application Laid-Open No. 2022-083337

[0005] As described above, polyacetal resins are used in a variety of applications, one of the most common being sliding parts. For such sliding parts, molded articles with a reduced gloss appearance are sometimes required. The present invention aims to solve this problem by providing a resin composition, pellets, and molded articles that can provide molded articles with a high matte effect while maintaining sliding properties.

[0006] In light of the above-mentioned problems, it has been found that the above-mentioned problems can be solved by blending a polyacetal resin with an ultra-high molecular weight polyethylene and a predetermined polyolefin in a predetermined ratio. Specifically, the above-mentioned problems have been solved by the following means: <1> (A) For 100 parts by mass of polyacetal resin, (B) a melt volume rate (MVR) of 0.1 to 10 cm3 measured at 190°C and a load of 5.0 kg according to ASTM-D1238 standard is３A resin composition comprising: 0.25 to 9.0 parts by mass of an ultra-high molecular weight polyethylene having a shrinkage rate of 2% or more 24 hours after molding of a test piece measuring 100 mm long x 100 mm wide x 3 mm thick, molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C; and (C) 0.25 to 9.0 parts by mass of a polyolefin having a shrinkage rate of 2% or more 24 hours after molding of a test piece measuring 100 mm long x 100 mm wide x 3 mm thick, molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C, wherein the mass ratio (B) / [(B)+(C)]×100 of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin is in the range of 10 to 90%. <2> The resin composition according to <1>, wherein the total content of the (B) ultra-high molecular weight polyethylene and the (C) acid-modified polyolefin is 10.0 parts by mass or less per 100 parts by mass of the (A) polyacetal resin. <3> The resin composition according to <1> or <2>, wherein the (C) polyolefin includes an acid-modified polyolefin modified with at least one of an unsaturated carboxylic acid and an unsaturated carboxylic anhydride. <4> The resin composition according to any one of <1> to <3>, wherein the mass ratio of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin, (B) / [(B)+(C)]×100, is in the range of 15 to 90%. <5> The resin composition according to any one of <1> to <4>, further comprising a hindered amine-based light stabilizer and / or an ultraviolet absorber. <6> The resin composition according to any one of <1> to <5>, wherein the total content of the (B) ultra-high molecular weight polyethylene and the (C) polyolefin is 10 parts by mass or less per 100 parts by mass of the (A) polyacetal resin, the (B) ultra-high molecular weight thermoplastic polyolefin comprises an ultra-high molecular weight thermoplastic polyolefin modified with at least one of an unsaturated carboxylic acid and / or an unsaturated carboxylic acid anhydride, the mass ratio of the (B) ultra-high molecular weight polyethylene content to the (C) polyolefin content, (B) / [(B)+(C)]×100, is in the range of 15 to 90%, and the resin composition further contains a hindered amine-based light stabilizer and / or an ultraviolet absorber. <7> The resin composition according to any one of <1> to <6>, further containing a formaldehyde scavenger. <8> Pellets of the resin composition according to any one of <1> to <7>. <9> A molded article formed from the resin composition according to any one of <1> to <7>. <10> A molded article formed from the pellets according to <8>.

[0007] According to the present invention, it is possible to provide a resin composition that can provide a molded article with a high matte effect while maintaining slidability, as well as pellets and a molded article.

[0008] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. Note that in this specification, the word "to" is used to mean that the numerical values ​​written before and after it are included as lower and upper limits. In this specification, various physical property values ​​and characteristic values ​​are those at 23°C unless otherwise specified. When the measurement methods etc. described in the standards shown in this specification vary depending on the fiscal year, they are based on the standards as of January 1, 2023, unless otherwise specified.

[0009] The resin composition of the present embodiment is a composition comprising (A) 100 parts by mass of polyacetal resin and (B) a melt volume rate (MVR) of 0.1 to 10 cm3 measured at 190°C and a load of 5.0 kg according to ASTM-D1238 standard. ３ and (C) 0.25 to 9.0 parts by mass of a polyolefin having a shrinkage rate of 2% or more 24 hours after molding of a test piece measuring 100 mm length x 100 mm width x 3 mm thickness, molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C, wherein the mass ratio of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin, (B) / [(B)+(C)]×100, is in the range of 10 to 90%. By adopting such a configuration, a resin composition can be obtained that can provide a molded product with a high matte effect while maintaining sliding properties.

[0010] Blending ultra-high molecular weight polyethylene and polyolefin into polyacetal resin tends to improve sliding properties. However, the inventors' investigations have revealed that the matte effect is inferior depending on the type and blend ratio of the ultra-high molecular weight polyethylene and polyolefin. The inventors speculate that the reasons for this are insufficient compatibility between the ultra-high molecular weight polyethylene and polyolefin, particularly insufficient mixing during melt-kneading, and a small difference in shrinkage rate between the polyacetal resin and polyolefin. In this embodiment, by using (B) ultra-high molecular weight polyethylene and a polyolefin ((C) polyolefin) with a large shrinkage rate as the ultra-high molecular weight polyethylene and further setting the mass ratio of the (B) ultra-high molecular weight polyethylene content to the (C) polyolefin content within a predetermined range, the compatibility of these components is improved, and a resin composition capable of providing a molded product with an excellent matte effect while maintaining sliding properties is obtained.

[0011] <(A) Polyacetal Resin> The resin composition of this embodiment contains a polyacetal resin. The type of the polyacetal resin is not particularly limited, and the polyacetal resin may be a homopolymer containing only divalent oxymethylene groups as structural units, or a copolymer containing divalent oxymethylene groups and divalent oxyalkylene groups having 2 to 6 carbon atoms as structural units.

[0012] Examples of the oxyalkylene group having 2 to 6 carbon atoms include an oxyethylene group, an oxypropylene group, and an oxybutylene group.

[0013] 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 %.

[0014] 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 the polyacetal resin. ２ A formyl terminal group is represented by —CHO.

[0015] The polyacetal resin used in this embodiment has a melt volume rate (MVR) of 0.5 cm3 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, and 0.8 cm ３ / 10 minutes or more is more preferable, and 1.0 cm ３ / 10 minutes or more is more preferable, ３ / 10 minutes or more is more preferable, 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, and 25 cm ３ / 10 minutes or less is more preferable, and 20 cm 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.

[0016] In addition to the above, the polyacetal resin may be the polyacetal resin described in paragraphs 0018 to 0043 of JP 2015-074724 A, 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.

[0017] The resin composition of this embodiment preferably contains polyacetal resin in a proportion of 80% by mass or more of the resin composition, more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 93% by mass or more, even more preferably 95% by mass or more, and even more preferably 97% by mass or more. Furthermore, all components other than (B) ultra-high molecular weight polyethylene and (C) polyolefin may be polyacetal resin. The resin composition of this embodiment may contain only one type of polyacetal resin, or two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0018] <(B) Ultra-high molecular weight polyethylene> The resin composition of this embodiment contains (B) ultra-high molecular weight polyethylene. By containing (B) ultra-high molecular weight polyethylene, the sliding properties of the resulting molded article can be improved. (B) ultra-high molecular weight polyethylene has a melt volume rate (MVR) of 0.1 to 10 cm, measured at 190°C and a load of 5.0 kg according to ASTM-D1238. ３ / 10 minutes. The MVR is 0.1 cm ３ / 10 minutes or more is preferable, and 0.2 cm ３ / 10 minutes or more is more preferable, and 0.3 cm ３ / 10 minutes or more is more preferable, and 0.4 cm ３ / 10 minutes or more is more preferable, and 0.5 cm ３ / 10 minutes or more is more preferable, and 10 cm ３ / 10 minutes or less is preferable, ３ / 10 minutes or less is more preferable, ３ / 10 minutes or less is more preferable, and 6 cm ３ / 10 minutes or less is more preferable, ３ It is more preferable that the time is 10 minutes or less. By setting the time to be equal to or more than the lower limit, the dispersibility in the polyacetal resin tends to be further improved. On the other hand, by setting the time to be equal to or less than the upper limit, molding defects tend to be more effectively suppressed.

[0019] When the resin composition of the present embodiment contains two or more types of ultra-high molecular weight polyethylene (B), the MVR of the ultra-high molecular weight polyethylene (B) is the MVR of the mixture.

[0020] The (B) ultra-high molecular weight polyethylene typically has an intrinsic viscosity [η] of 10 dL / g or more (e.g., 40 dL / g or less) measured in decaphosphoric acid at 135°C, and a viscosity-average molecular weight of 500,000 to 6,000,000. When the resin composition of this embodiment contains two or more types of (B) ultra-high molecular weight polyethylene, the intrinsic viscosity and viscosity-average molecular weight are those of the (B) ultra-high molecular weight polyethylene mixture. Specifically, the (B) ultra-high molecular weight polyethylene may be a mixture of an ultra-high molecular weight polyethylene resin having an intrinsic viscosity of 10 to 40 dL / g at 135°C and a low- or high-molecular weight polyethylene resin having an intrinsic viscosity of 0.1 to 5 dL / g. Specific examples include "Lubmer (trade name)" manufactured by Mitsui Chemicals, Inc. Furthermore, acid-modified ultra-high molecular weight polyethylene resins can also be used, such as "Modified Lubmer (trade name)" manufactured by Mitsui Chemicals, Inc., modified with maleic anhydride.

[0021] The (B) ultra-high molecular weight polyethylene may be either acid-modified or unmodified, but is preferably acid-modified. The use of acid-modified ultra-high molecular weight polyethylene further improves compatibility with the (A) polyacetal resin, tending to result in molded articles with superior matte properties. When the resin composition of this embodiment contains acid-modified ultra-high molecular weight polyethylene, it is preferably an acid-modified ultra-high molecular weight thermoplastic polyolefin modified with at least one of an unsaturated carboxylic acid and an unsaturated carboxylic acid anhydride, and more preferably an acid-modified ultra-high molecular weight thermoplastic polyolefin modified with maleic acid and / or maleic anhydride. The lower limit of the amount of such ethylenically unsaturated carboxylic acid or its anhydride added or grafted to the olefin-based polymer (modification degree) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, relative to the olefin-based polymer. On the other hand, the upper limit of this amount of addition or grafted (modification degree) is preferably 15% by mass or less, more preferably 10% by mass or less. By setting the addition amount or graft amount to the above lower limit or more, molded articles with better matte properties tend to be obtained. Conversely, by setting the addition amount or graft amount to the above upper limit or less, adhesion of molded articles obtained from the resin composition can be more effectively suppressed, and the appearance tends to be improved.

[0022] The content of the (B) ultra-high molecular weight polyethylene in the resin composition of this embodiment is, relative to 100 parts by mass of the (A) polyacetal resin, 0.25 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, even more preferably 4.0 parts by mass or more, and 9.0 parts by mass or less, preferably 8.0 parts by mass or less, more preferably 7.5 parts by mass or less, even more preferably 7.0 parts by mass or less, even more preferably 6.5 parts by mass or less, even more preferably 6.0 parts by mass or less. By setting the content at or above the lower limit, the matte effect tends to be further improved. Furthermore, by setting the content at or below the upper limit, mechanical properties such as impact resistance tend to be further improved. The resin composition of this embodiment may contain only one type of (B) ultra-high molecular weight polyethylene, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0023] <(C) Polyolefin> The resin composition of this embodiment contains (C) a polyolefin having a shrinkage rate of 2% or more 24 hours after molding a test piece measuring 100 mm in length, 100 mm in width, and 3 mm in thickness, molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C. The polyolefin may be either an acid-modified polyolefin or an unmodified polyolefin, but an acid-modified polyolefin is preferred. By including the polyolefin (C), the matte effect can be further improved while maintaining high sliding properties of the resulting molded article. The shrinkage rate is preferably 2.1% or more, more preferably 2.5% or more, even more preferably 3% or more, even more preferably 3.5% or more, and even more preferably 4% or more. It is also preferably 10% or less, more preferably 7% or less, even more preferably 6% or less, even more preferably 5% or less, and even more preferably 4.10% or less. When two or more types of polyolefin (C) are included, the shrinkage rate is the shrinkage rate after molding a mixture of the acid-modified polyolefins (C) as described above. In this embodiment, the polyolefin constituting the polyolefin (C) is preferably polyethylene and / or an ethylene-butene copolymer, more preferably polyethylene. The polyethylene and / or ethylene-butene copolymer referred to here may contain other monomer units within the scope of this embodiment. The proportion of other monomer units is typically less than 10% by mass, preferably less than 5% by mass, more preferably less than 3% by mass, and even more preferably less than 1% by mass.

[0024] When the (C) polyolefin is an acid-modified polyolefin, it 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 (modification degree) is preferably 0.01% by mass, more preferably 0.02% by mass, relative to the (C) acid-modified polyolefin. On the other hand, the upper limit of this amount of addition or grafting (modification degree) is preferably 15% by mass, more preferably 10% by mass. If the amount of addition or grafting is greater than the lower limit, molded products with better matte properties tend to be obtained. Conversely, if the amount of addition or grafting exceeds the upper limit, the resin composition may become severely colored, resulting in a poor appearance.

[0025] In addition, (C) polyolefin has a melt volume rate (MVR) of 0.1 cm under the condition of 190 ° C / 2.16 kg. ３ / 10 minutes or more is preferable, and 0.3 cm ３ / 10 minutes or more is more preferable, and ３ / 10 minutes or less is preferable, ３ / 10 minutes or less is more preferable, ３ / 10 minutes or less is even more preferable. When the resin composition of this embodiment contains two or more types of polyolefin (C), the MVR of the polyolefin (C) is the MVR of the mixture. The MVR is a value measured in accordance with ASTM-D1238 standard.

[0026] The number average molecular weight of the (C) polyolefin is preferably 10,000 or more, more preferably 30,000 or more, even more preferably 50,000 or more, even more preferably 70,000 or more, even more preferably 100,000 or more, and is preferably 500,000 or less, more preferably 480,000 or less, even more preferably 460,000 or less, even more preferably 440,000 or less, and even more preferably 420,000 or less. By adjusting the number average molecular weight to be above the lower limit and below the upper limit, the matte effect tends to be further improved. The number average molecular weight of the (C) polyolefin is a polystyrene-equivalent value measured by GPC (gel permeation chromatography). When the resin composition of this embodiment contains two or more (C) polyolefins, the number average molecular weight of the (C) polyolefin is the number average molecular weight of the mixture.

[0027] The content of the (C) polyolefin in the resin composition of this embodiment is, relative to 100 parts by mass of the (A) polyacetal resin, 0.25 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and 9.0 parts by mass or less, preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, even more preferably 4.5 parts by mass or less, even more preferably 3.5 parts by mass or less, even more preferably 3.0 parts by mass or less. By setting the content at or above the lower limit, the matte effect tends to be further improved. Furthermore, by setting the content at or below the upper limit, mechanical properties such as impact resistance tend to be further improved. The resin composition of this embodiment may contain only one type of (C) polyolefin, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0028] In the resin composition of this embodiment, the total content of (B) ultra-high molecular weight polyethylene and (C) polyolefin is, relative to 100 parts by mass of (A) polyacetal resin, 0.5 parts by mass or more, preferably 1.0 parts by mass or more, more preferably 2.0 parts by mass or more, even more preferably 3.0 parts by mass or more, even more preferably 4.0 parts by mass or more, and even more preferably 4.5 parts by mass or more, and is 18.0 parts by mass or less, preferably 10.0 parts by mass or less, more preferably 9.0 parts by mass or less, even more preferably 8.0 parts by mass or less, even more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By setting it to the lower limit or more, the matte effect tends to be further improved. On the other hand, by setting it to the upper limit or less, mechanical properties such as impact resistance tend to be further improved.

[0029] In the resin composition of this embodiment, the mass ratio of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin, (B) / [(B)+(C)]×100, is 10% or more, preferably 11% or more, more preferably 15% or more, even more preferably 25% or more, even more preferably 30% or more, still more preferably 45% or more, and is 90% or less, preferably 80% or less, more preferably 70% or less, even more preferably 65% ​​or less, still more preferably 60% or less, and still more preferably 55% or less. By setting it to be equal to or greater than the lower limit or equal to or less than the upper limit, the matte effect tends to be further improved.

[0030] <Other Components> 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, weathering agents, formaldehyde scavengers, inorganic particles, light stabilizers, heat stabilizers, colorants, nucleating agents, plasticizers, fluorescent brighteners, mold release agents, antistatic agents, UV absorbers, flame retardants, and flame retardant aids, which may be added as needed. The resin composition of this embodiment preferably further contains a hindered amine-based light stabilizer and / or UV absorber. The resin composition of this embodiment is adjusted so that the total content of the (A) polyacetal resin, the (B) ultra-high molecular weight polyethylene, and the (C) polyolefin, as well as other components added as needed, totals 100% by mass. In the resin composition of this embodiment, the total amount of (A) polyacetal resin, (B) ultra-high molecular weight polyethylene, and (C) polyolefin preferably accounts for 90 mass% or more of the resin composition, more preferably 95 mass% or more, and even more preferably 97 mass% or more, with the upper limit being 100 mass%. In the resin composition of this embodiment, the total amount of (A) polyacetal resin, (B) ultra-high molecular weight polyethylene, and (C) polyolefin, and optionally blended formaldehyde scavenger, heat stabilizer, and UV absorber preferably accounts for 93 mass% or more of the resin composition, more preferably 97 mass% or more, and even more preferably 99 mass% or more, with the upper limit being 100 mass%.

[0031] <<Formaldehyde Scavenger>> The resin composition of this embodiment may contain a formaldehyde scavenger. The type and other properties of the formaldehyde scavenger are not particularly limited, and a wide variety of compounds used as formaldehyde scavengers for polyacetal resins can be used. The formaldehyde scavenger is preferably a compound containing a nitrogen atom, more preferably at least one selected from the group consisting of hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds, and even more preferably at least one selected from the group consisting of hydrazide compounds and urea compounds.

[0032] The hydrazide compound is preferably a hydrazide compound having two or more hydrazide groups. Examples of the dihydrazide compound include aliphatic dihydrazide compounds and aromatic dihydrazide compounds.

[0033] Examples of the aliphatic dihydrazide compounds include carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide (1,12-dodecanedicarbohydrazide), 1,18-octadecanedicarbohydrazide, stearic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and 7,11-octadecadiene-1,18-dicarbohydrazide.

[0034] Examples of aromatic dihydrazide compounds include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 1,5-naphthalenedicarbohydrazide, 1,8-naphthalenedicarbohydrazide, 2,6-naphthalenedicarbohydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, and 1,5-diphenylcarbonohydrazide.

[0035] The hydrazide compound used in this embodiment is preferably represented by the following formula (1): (In formula (1), R １１represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms; R １２ ~R １５ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R １２ and R １３ , and R １４ and R １５ may be bonded to each other to form a ring.

[0036] In formula (1), R １１ represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms, with an aliphatic hydrocarbon group having 2 to 18 carbon atoms being preferred. The number of carbon atoms in the aliphatic hydrocarbon group having 2 to 18 carbon atoms is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less. The aliphatic hydrocarbon group may be saturated or unsaturated, and may be linear or branched. Specific examples of the aliphatic hydrocarbon group include alkylene groups such as butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, and nonadecylene.

[0037] The alicyclic hydrocarbon group may be saturated or unsaturated. Examples of the alicyclic hydrocarbon group include a cycloalkylene group having 6 to 10 carbon atoms. Examples of the cycloalkylene group include a cyclohexylene group.

[0038] Examples of aromatic hydrocarbon groups include arylene groups such as phenylene and naphthylene. Substituents may be bonded to at least some of the carbon atoms of the aromatic hydrocarbon group. Examples of such substituents include halogen groups, nitro groups, and alkyl groups having 1 to 20 carbon atoms.

[0039] In formula (1), R １２ ~R １５ are each independently preferably a hydrogen atom, a methyl group or an ethyl group, more preferably a hydrogen atom.

[0040] Specific examples of the compound represented by formula (1) include adipic acid dihydrazide and 1,12-dodecanedioic acid dihydrazide.

[0041] The hydrazone compound of the hydrazine compound is preferably at least one hydrazine compound selected from the group consisting of compounds represented by the following formula (2) and compounds represented by the following formula (3): Formula (2): (In formula (2), R １ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. ２ ~R ５ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms; R ２ and R ３ At least one of R represents an alkyl group having 1 or 2 carbon atoms; ４ and R ５ At least one of these represents an alkyl group having 1 or 2 carbon atoms.

[0042] In formula (2), R １represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. The aliphatic hydrocarbon group may be saturated or unsaturated, linear, or branched. Specific examples of the aliphatic hydrocarbon group include alkylene groups such as butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and icosylene. The aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 6 to 12 carbon atoms. In this case, the reactivity of the hydrazone of the hydrazine compound with formaldehyde is enhanced, and formaldehyde generation is more effectively suppressed. Furthermore, contamination of the mold during molding can be more sufficiently suppressed. The alicyclic hydrocarbon group may be saturated or unsaturated. Examples of the alicyclic hydrocarbon group include a cycloalkylene group having 6 to 10 carbon atoms. Examples of the cycloalkylene group include a cyclohexylene group. Examples of the aromatic hydrocarbon group include arylene groups such as a phenylene group and a naphthylene group. A substituent may be bonded to at least a portion of the carbon atoms of the aromatic hydrocarbon group. Examples of the substituent include a halogen group, a nitro group, and an alkyl group having 1 to 20 carbon atoms. In formula (2), R ２ ~R ５ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms; R ２ and R ３ At least one of R represents an alkyl group having 1 or 2 carbon atoms; ４ and R ５ At least one of R represents an alkyl group having 1 or 2 carbon atoms. ２ and R ４ is an ethyl group, R ３ and R ５ is a hydrogen atom, and R ２ and R ４ When is a methyl group, R ３ and R ５is preferably a hydrogen atom or a methyl group. In this case, the reactivity of the hydrazone of the hydrazine compound with formaldehyde is increased, and the generation of formaldehyde is more effectively suppressed.

[0043] Specific examples of the compound represented by the formula (2) include 1,12-bis[2-(1-methylethylidene)hydrazino]]-1,12-dodecanedione, 1,12-bis(2-ethylidenehydrazino)-1,12-dodecanedione, 1,12-bis(2-propylidenehydrazino)-1,12-dodecanedione, 1,12-bis[2-(1-methylpropylidene)hydrazino]-1,12-dodecanedione, 1,12-bis[2-(1-ethylpropylidene)hydrazino]-1,12-dodecanedione, 1,10-bis[2-(1-methylethylidene)hydrazino]]-1,10-decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10-bis( 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis(2-ethylidenehydrazino)-1,6-hexanedione, 1,6-bis(2-propylidenehydrazino)-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-ethylpropylidene)hydrazino]-1,6-hexanedione, and 1,6-bis[2-(1-ethylpropylidene)hydrazino]-1,6-hexanedione.

[0044] Formula (3) (In formula (3), R ８ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. ６ and R ７ each independently represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms.

[0045] In formula (3), R ８ is R １The same applies to the preferred ranges. ６ and R ７ each independently represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms. Examples of the alicyclic hydrocarbon group having 3 to 12 carbon atoms include a cyclohexylene group. Specific examples of the compound represented by formula (3) above include 1,12-bis(2-cyclohexylidenehydrazino)-1,12-dodecanedione, 1,10-bis(2-cyclohexylidenehydrazino)-1,10-decanedione, and 1,6-bis(2-cyclohexylidenehydrazino)-1,6-hexanedione.

[0046] Examples of the guanamine compound include benzoguanamine and N-methylol benzoguanamine.

[0047] The urea compound is -(HN) ２ The term "urea compound" refers to a compound having a C(=O) structure, and the type thereof is not particularly limited. Examples of the urea compound include urea, ethylene urea, allantoin, biurea, dimethylethylene urea, propylene urea, and tetrabutyl urea, and preferably contains ethylene urea and / or allantoin, more preferably contains ethylene urea.

[0048] The molecular weight of the formaldehyde scavenger used in this embodiment is preferably 60 or more, and more preferably 86 or more. The upper limit is preferably 1,000 or less, more preferably 800 or less, and even more preferably 500 or less.

[0049] When included, the content of the formaldehyde scavenger in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and preferably 1.0 part by mass or less, more preferably 0.5 part by mass or less, per 100 parts by mass of the polyacetal resin (A). By ensuring that the content is equal to or greater than the lower limit, the generation of formaldehyde, particularly the generation of formaldehyde when the residence time in the molding machine is long, tends to be more effectively suppressed. By ensuring that the content is equal to or less than the upper limit, the effect of suppressing mold contamination is more effectively exerted. The resin composition of this embodiment may contain only one type of formaldehyde scavenger, or may contain two or more types. When two or more types are included, the total amount is preferably within the above range.

[0050] <<Light Stabilizer>> The resin composition of the present invention may contain a light stabilizer. Examples of the light stabilizer include hindered amine light stabilizers. The resin composition of this embodiment preferably contains a hindered amine light stabilizer. By containing a hindered amine light stabilizer, weather resistance can be improved. As the hindered amine light stabilizer, one represented by formula (4) is preferably used. Formula (4) (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.)

[0051] R may 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, and a methyl group is preferred.

[0052] 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 the others are 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 can be referred to, and the contents of these references are incorporated herein by reference.

[0053] 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 (A). The resin composition of this embodiment also preferably contains 0.5 parts by mass or less, and more preferably 0.3 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 (A). 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 this 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 within the above range.

[0054] <<UV Protective Agent>> The resin composition of this embodiment preferably contains an ultraviolet absorber. By containing an ultraviolet absorber, it is possible to improve weather resistance. The ultraviolet absorber is preferably selected from a benzotriazole compound, a benzophenone compound, an aromatic benzoate compound, a cyanoacrylate compound, and an oxalic acid anilide ultraviolet absorber.

[0055] 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, p-t-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 can be referred to, the contents of which are incorporated herein by reference.

[0056] 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 viscosity of not more 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].

[0057] The resin composition of this embodiment preferably contains 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more, of the ultraviolet absorber per 100 parts by mass of the polyacetal resin (A). The resin composition of this embodiment preferably contains 0.7 parts by mass or less, and more preferably 0.5 parts by mass or less, of the ultraviolet absorber per 100 parts by mass of the polyacetal resin (A). The resin composition of this 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 within the above range.

[0058] <Method for Producing 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 through a side feed port, and melt-kneaded to obtain a pellet-shaped resin composition; or (3) a method in which pellets with different compositions are prepared by extrusion or the like, and the pellets are mixed to obtain a resin composition having a predetermined composition. Examples of kneading machines include kneaders, Banbury mixers, and extruders. There are no particular limitations on the various conditions and devices for mixing and kneading, and these may be appropriately selected from any conventionally known conditions. Kneading is preferably performed at a temperature above the melting point of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally 180°C or higher).

[0059] <Molded Article> 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.

[0060] 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.

[0061] The resin composition and pellets of this embodiment are preferably used for forming sliding members. 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, V-rings, rod packings, piston rings, rider rings, and other sealing members, as well as rotating shafts, rotating sleeves, pistons, impellers, rollers, and other sliding members for compressors, 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 members of this embodiment can be used not only between sliding members of this embodiment, but also as sliding members combined with other resin sliding members, fiber-reinforced resin sliding members, and ceramic or metal sliding members.

[0062] The resin composition, pellets, and molded articles of this embodiment can also be suitably used in applications requiring reduced formaldehyde emissions, such as automobile parts, electrical and electronic parts, precision machinery parts, building materials and piping parts, daily necessities, cosmetic parts, medical equipment parts, etc. More specific examples of automobile parts include interior parts such as inner handles, fuel trunk openers, seatbelt buckles, assist wraps, various switches, knobs, levers, and clips, electrical system parts such as meters and connectors, on-board 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, and mechanical parts such as door lock actuator parts, mirror parts, wiper motor system parts, and fuel system parts.

[0063] 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 also be applied to optical and magnetic media components, at least a portion of which is made of molded products, 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.

[0064] Furthermore, the molded article of this embodiment can be suitably used for a wide range of lifestyle-related, cosmetic-related, and medical-related parts, such as building materials and piping parts, including lighting fixtures, fittings, piping, cocks, faucets, and toilet peripheral equipment parts, fasteners, stationery, lip balm and lipstick containers, cleaning devices, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, and syringe needle holders.

[0065] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate 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.

[0066] 1. Raw Materials The raw materials shown in Table 1 below were used. In Table 1 above, PE stands for polyethylene, PP stands for polypropylene, LLDPE stands for linear low-density polyethylene, and LDPE stands for low-density polyethylene. C-1 to C-3 are modified with maleic anhydride, and C-4 and C-5 are unmodified.

[0067] The shrinkage rate is the shrinkage rate of a test piece measuring 100 mm long x 100 mm wide x 3 mm thick molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C, 24 hours after molding.

[0068] 2. Examples 1 to 14 and Comparative Examples 1 to 12 <Production of Resin Composition (Pellets)> The components shown in Table 1 were uniformly mixed 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.

[0069] <Gloss Value (60°)> The pellets obtained above were molded into a 100 mm × 40 mm × 2 mm plate using an SE-30 molded by Sumitomo Heavy Industries, Ltd. at a cylinder temperature of 215° C. and a mold temperature of 40° C. The gloss of this test piece was measured at a reflection angle of 60° using a gloss meter (VG2000) manufactured by Nippon Denshoku Industries Co., Ltd.

[0070] <Sliding property> The pellets obtained above were used in an injection molding machine with a cylinder temperature of 195°C and a mold temperature of 80°C to prepare cylindrical thrust test pieces with a contact area of ​​2 cm2. These test pieces were subjected to friction and wear testing using a Suzuki-type friction and wear tester at a temperature of 23°C, a humidity of 50%, a load of 3 kgf, a linear velocity of 30 cm / s, and a running time of 20 hours between identical materials, and the specific wear rate was calculated based on the mass of the cylindrical thrust test piece before and after the test. The specific wear rate was the sum of the specific wear rates of both test pieces used in the wear test.

[0071] <Charpy (kJ / m ２ )> A 4 mm thick ISO dumbbell test piece was molded from a single gate with a mold temperature of 90°C and a cylinder temperature of 195°C. The ISO dumbbell test piece obtained above was notched with a notch radius of 0.25 mm and a depth of 2 mm using a notching machine in accordance with JIS K7111. The notched Charpy impact strength was then measured using a 1J hammer in accordance with ISO179-1 using a Charpy impact tester equipped with a thermostatic chamber. The unit is kJ / m ２ As shown.

[0072] <Measurement of Formaldehyde Generation Amount> The pellets obtained above were heated for 1 minute in a cylinder heated to 215°C using an SE-30 manufactured by Sumitomo Heavy Industries, Ltd., and then injection molded at a mold temperature of 80°C to prepare flat test pieces measuring 100 mm x 40 mm x 2 mm.

[0073] The flat test specimens were left to stand for 24 hours in an atmosphere of 23°C and 50% relative humidity. The amount of formaldehyde generated per 1 g of polyacetal resin (unit: μg / g-POM) was then measured using the following method, in accordance with the method described in German Automotive Industry Standard VDA275 (Automotive Interior Parts - Determination of Formaldehyde Emission by the Revised Flask Method). (i) 50 mL of distilled water was placed in a polyethylene container, and the flat test specimen was suspended in the air with the lid closed. The container was then heated in a sealed state at 60°C for 3 hours. (ii) After leaving the container at room temperature for 60 minutes, the flat test specimen was removed. (iii) The amount of formaldehyde absorbed in the distilled water in the polyethylene container was measured using a UV spectrometer by the acetylacetone colorimetric method. The amount of formaldehyde thus absorbed was divided by the mass of POM in the flat test specimen, and the resulting value was used as the amount of formaldehyde generated.

[0074]

[0075]

[0076]

[0077]

[0078]

[0079] As is clear from the above results, the resin composition of this embodiment had a low gloss value and an excellent matte effect. Furthermore, it also had excellent sliding properties (Examples 1 to 14). Furthermore, the resin composition of this embodiment maintained high impact resistance. Furthermore, when a formaldehyde scavenger was blended into the resin composition of this embodiment (Example 14), the scavenging effect of the formaldehyde scavenger was fully exhibited.

Claims

1. (A) For 100 parts by mass of polyacetal resin, (B) the melt volume rate (MVR) measured according to the ASTM-D1238 standard at 190°C and a load of 5.0 kg is 0.1 to 10 cm ３ (B) 0.25 to 9.0 parts by mass of an ultra-high molecular weight polyethylene having a shrinkage rate of 2% or more 24 hours after molding of a test piece having a length of 100 mm, a width of 100 mm, and a thickness of 3 mm, which is molded at a mold temperature of 40°C, a holding pressure of 30 MPa, and a resin temperature of 190°C, wherein the mass ratio (B) / [(B)+(C)]×100 of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin is in the range of 10 to 90%.

2. The resin composition according to claim 1, wherein the total content of the ultra-high molecular weight polyethylene (B) and the polyolefin (C) is 10.0 parts by mass or less per 100 parts by mass of the polyacetal resin (A).

3. The resin composition according to claim 1 or 2, wherein the polyolefin (C) comprises a polyolefin modified with at least one of an unsaturated carboxylic acid and an unsaturated carboxylic acid anhydride.

4. The resin composition according to claim 1 or 2, wherein the mass ratio of the content of the (B) ultra-high molecular weight polyethylene to the content of the (C) polyolefin, (B) / [(B)+(C)]×100, is in the range of 15 to 90%.

5. The resin composition according to claim 1 or 2, further comprising a hindered amine-based light stabilizer and / or an ultraviolet absorber.

6. The resin composition according to claim 1, wherein the total amount of the ultra-high molecular weight polyethylene (B) and the polyolefin (C) is 10 parts by mass or less per 100 parts by mass of the polyacetal resin (A), the ultra-high molecular weight thermoplastic polyolefin (B) comprises an ultra-high molecular weight thermoplastic polyolefin modified with at least one kind of unsaturated carboxylic acid and / or unsaturated carboxylic acid anhydride, the mass ratio of the ultra-high molecular weight polyethylene (B) to the polyolefin (C), (B) / [(B)+(C)]×100, is in the range of 15-90%, and further comprises a hindered amine light stabilizer and / or an ultraviolet absorber.

7. The resin composition according to claim 1, 2 or 6, further comprising a formaldehyde scavenger.

8. Pellets of the resin composition according to claim 1, 2 or 6.

9. A molded article formed from the resin composition according to claim 1, 2 or 6.

10. A molded article formed from the pellets of claim 8.

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