Resin composition, pellet, and molded article

Abstract

The present application provides a resin composition, and a pellet and a molded article. The resin composition comprises: a polyacetal resin 100 parts by mass, a silicone rubber gum 0.4 to 10 parts by mass having a kinematic viscosity greater than 1,000,000 mm 2 / s, and a polyolefin-based lubricant 0.5 to 10 parts by mass, 25 to 80% by mass of the polyolefin-based lubricant being an oxidatively modified polyolefin-based lubricant.

Description

Technical Field

[0001] This invention relates to resin compositions, granules, and molded articles. In particular, it relates to resin compositions with polyacetal resin as the main component. Background Technology

[0002] Polyacetal resin is used in a wide range of applications as a plastic with excellent mechanical, electrical, and chemical resistance properties.

[0003] Furthermore, as one of the ways to utilize polyacetal resin, sliding components are known. As an example of using polyacetal resin as a sliding component, Patent Document 1 discloses a polyacetal resin composition, which is prepared by combining 99.8 to 80 parts by weight of polyacetal, 0.1 to 20 parts by weight of polyethylene wax, and 0.1 to 5 parts by weight of silicone oil.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 04-224856 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The resin composition described in Patent Document 1 above is a material with excellent sliding properties. However, in recent years, there has been a demand for even better sliding properties. In particular, there is a demand for resin compositions that can provide molded articles with high PV limits and low coefficients of dynamic friction.

[0009] The purpose of this invention is to solve the above-mentioned problems and provide a resin composition, granules and molded articles that can produce molded articles with high PV limit and low coefficient of dynamic friction.

[0010] Problem Solving Methods

[0011] Based on the above problems, the inventors conducted research and found that the above problems can be solved by combining a given silicone gum and a polyolefin lubricant with a polyacetal resin.

[0012] Specifically, the above problems were solved in the following way.

[0013] <1> A resin composition comprising:

[0014] 100 parts by weight of polyacetal resin

[0015] kinematic viscosity greater than 1,000,000 mm 2 / s of pure silicone rubber compound, 0.4~10 parts by weight, and

[0016] Polyolefin lubricant, 0.5-10 parts by weight.

[0017] 25-80% by mass of polyolefin lubricants are oxidically modified polyolefin lubricants.

[0018] <2> A resin composition comprising polyacetal resin, silicone rubber pure material, and polyolefin lubricant, wherein,

[0019] The above resin composition was molded into a cylindrical thrust test piece. The average length L of the micro-domain containing the organosilicon compound, as observed by a laser microscope, was 8.0 μm or more, and the average width W was 3.0 μm or less.

[0020] <3> according to <1> The resin composition, wherein the kinematic viscosity of the pure silicone rubber compound contained in the resin composition is 5,000,000 mm⁻¹ 2 / s or more.

[0021] <4> according to <1> ~ <3> The resin composition described in any one of the above statements, wherein the kinematic viscosity of the pure silicone rubber compound contained in the resin composition is 10,000,000 mm⁻¹ 2 / s or more.

[0022] <5> according to <1> ~ <4> The resin composition according to any one of the following methods, wherein the polyolefin lubricant contained in the resin composition comprises an oxidically modified polyolefin lubricant.

[0023] <6> according to <1> ~ <5> The resin composition according to any one of the following methods, wherein the proportion of the oxidized polyolefin lubricant contained in the resin composition is 35% by mass or more.

[0024] <7> according to <1> ~ <6> The resin composition described in any one of the above statements, wherein the kinematic viscosity of the pure silicone rubber compound contained in the resin composition is 10,000,000 mm⁻¹ 2 / s or more

[0025] In the above resin composition, the proportion of oxidized polyolefin lubricant is 35% or more.

[0026] <8> according to <1> ~ <7> The resin composition according to any one of the following methods, wherein the resin composition is molded into a cylindrical thrust test piece, and the average length L of the micro-region containing the organosilicon compound observed by a laser microscope is 8.0 μm or more, and the average width W is 3.0 μm or less.

[0027] <9> according to <1> ~ <8> The resin composition described in any one of the above statements, wherein the kinematic viscosity of the pure silicone rubber compound contained in the resin composition is 10,000,000 mm⁻¹ 2 / s or more

[0028] More than 35% by mass of polyolefin lubricants are oxidically modified polyolefin lubricants.

[0029] <10> according to <2> or <8> The resin composition wherein the ratio L / W of the average length L to the average width W of the microregion containing the organosilicon compound is 3.0 or more.

[0030] <11> A type of granular material, which is <1> ~ <10> Granules of the resin composition described in any one of the above statements.

[0031] <12> A molded product, which is made of <1> ~ <10> The resin composition described in any one of the above statements is formed.

[0032] <13> A molded product, which is made of <11> The aforementioned granule formation.

[0033] The effects of the invention

[0034] According to the present invention, a resin composition, as well as granules and molded articles, can be provided that yields molded articles with high PV limit and low coefficient of dynamic friction. Attached Figure Description

[0035] Figure 1 This is an electron microscope photograph of the test piece from Example 4.

[0036] Figure 2 This is an electron microscope photograph of the test piece from Comparative Example 7. Detailed Implementation

[0037] Hereinafter, a method for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the following embodiment is an example for illustrating the present invention, and the present invention is not limited to this embodiment.

[0038] It should be noted that in this specification, "~" is used to include the numerical values ​​recorded before and after it as the lower limit and upper limit values.

[0039] Unless otherwise specified, all physical property values ​​and characteristic values ​​in this specification are values ​​at 23°C.

[0040] Unless otherwise specified, the measurement methods described in the standards shown in this specification may differ from year to year, and are based on the standards as of January 1, 2023.

[0041] The resin composition of this embodiment comprises: 100 parts by weight of polyacetal resin with a kinematic viscosity greater than 1,000,000 mm. 2 The composition comprises 0.4 to 10 parts by weight of pure silicone rubber and 0.5 to 10 parts by weight of polyolefin lubricant, wherein 25 to 80% by weight of the polyolefin lubricant is an oxidically modified polyolefin lubricant. This composition provides a resin composition capable of producing molded articles with high PV limits and low coefficients of dynamic friction.

[0042] The silicone rubber pure compound is dispersed in polyacetal resin to form micro-regions. Furthermore, this silicone rubber pure compound can be stretched by the resin flow during injection molding. Moreover, by elongating the silicone rubber pure compound regions, the limiting PV value is increased. However, if the silicone rubber pure compound content is too high, there is a tendency for other physical properties of the resulting molded article to deteriorate.

[0043] On the other hand, polyolefin lubricants help improve initial sliding properties. Furthermore, they can improve overall sliding properties together with pure silicone rubber, reducing the coefficient of dynamic friction of the resulting molded article. However, unmodified polyolefin lubricants tend to remain on the surface of the molded article, and are presumably prone to detaching from it. In this embodiment, it is presumed that this problem is solved at least by using an oxidized polyolefin lubricant. That is, it is presumed that the oxidized polyolefin lubricant is compatible with polyacetal resin and exists not only on the surface of the molded article but also inside it. Furthermore, it is presumed that, under the influence of the oxidized polyolefin lubricant, unmodified polyolefin lubricants can also remain not only on the surface of the molded article but also inside it.

[0044] As a result, molded products with high PV limit values ​​and low coefficient of dynamic friction can be obtained.

[0045] The following is a detailed description of this embodiment.

[0046] <Polyacetal resin>

[0047] The resin composition of this embodiment comprises a polyacetal resin.

[0048] There are no particular limitations on the type of polyacetal resin. It can be a homopolymer containing only divalent oxymethylene as a constituent unit, or a copolymer containing divalent oxymethylene and divalent oxyalkylene with 2 to 6 carbon atoms as constituent units.

[0049] Examples of oxoalkylene groups with 2 to 6 carbon atoms include oxoethylene, oxopropylene, and oxobutylene.

[0050] In polyacetal resin, the proportion of alkylene groups with 2 to 6 carbon atoms in the total number of moles of oxymethylene and alkylene groups with 2 to 6 carbon atoms is not particularly limited and can be 0.5 to 10 moles.

[0051] To manufacture the aforementioned polyacetal resin, trioxane is typically used as the main raw material. Alternatively, to introduce alkylene oxides with 2 to 6 carbon atoms into the polyacetal resin, cyclic formaldehydes or cyclic ethers can be used. Specific examples of cyclic formaldehydes include 1,3-dioxolane, 1,3-dioxolane, 1,3-dioxolane-heptane, 1,3-dioxolane-octane, 1,3,5-trioxolane-heptane, and 1,3,6-trioxolane-octane. Specific examples of cyclic ethers include ethylene oxide, propylene oxide, and butane oxide. When introducing ethylene oxides into the polyacetal resin, 1,3-dioxolane can be used as the main raw material; when introducing propylene oxides, 1,3-dioxolane can be used as the main raw material; and when introducing butylene oxides, 1,3-dioxolane-heptane can be used as the main raw material. It should be noted that in polyacetal resins, it is preferable to have a lower amount of hemiacetal terminal groups, formyl terminal groups, and terminal groups that are unstable to heat, acid, and alkali. Here, hemiacetal terminal groups are represented by -OCH2OH, and formyl terminal groups are represented by -CHO.

[0052] In this embodiment, the melt volumetric flow rate (MVR) of the polyacetal resin, measured according to ISO 1133 at a temperature of 190°C and a load of 2.16 kg, is preferably 0.5 cm⁻¹. 3 / 10 minutes or more, preferably 0.6cm 3 / 10 minutes or more, further preferably 0.8cm 3 / 10 minutes or more, with 1cm being a further preferred size 3 / 10 minutes or more, and further optimized to 5cm 3 / 10 minutes or more. By setting it to the lower limit value or above, there is a tendency to further improve the productivity of the resin composition. In addition, the MVR of the above-mentioned polyacetal resin is preferably 20 cm. 3 / less than 10 minutes, preferably 18cm 3 / less than 10 minutes, further preferably 14cm 3 / less than 10 minutes, and more preferably 10cm 3 / less than 10 minutes, with 8cm being a further preferred size 3 / Less than 10 minutes.

[0053] In addition to the above, the polyacetal resin described in paragraphs 0018 to 0043 of Japanese Patent Application Publication No. 2015-074724 may also be used as the polyacetal resin, and these contents are incorporated into this specification.

[0054] The polyacetal resin used in this embodiment can be recycled (including recycled products, recycled materials, recycled chemicals, etc.), defective products, or scraps from thermoplastic resin molding.

[0055] The resin composition of this embodiment preferably contains polyacetal resin at a proportion of 80% or more by mass, more preferably at a proportion of 85% or more by mass, even more preferably at a proportion of 90% or more by mass, even more preferably at a proportion of 93% or more by mass, even more preferably at a proportion of 95% or more by mass, and even more preferably at a proportion of 97% or more by mass. Additionally, except for a kinematic viscosity greater than 1,000,000 mm⁻¹, the resin composition of this embodiment preferably contains polyacetal resin at a proportion of 80% or more by mass, more preferably at a proportion of 85% or more by mass, and even more preferably at a proportion of 97% or more by mass. 2 The components of / s other than pure silicone rubber and polyolefin lubricants can also be all polyacetal resin.

[0056] The resin composition of this embodiment may contain only one type of polyacetal resin, or it may contain two or more types. When two or more types are contained, the total amount is preferably within the range described above.

[0057] Kinematic viscosity greater than 1,000,000 mm³ 2 / s of pure silicone rubber compound>

[0058] The resin composition of this embodiment preferably contains a kinematic viscosity greater than 1,000,000 mmHg. 2 / s of pure silicone rubber compound. By including such pure silicone rubber compound, the limiting PV value of the obtained molded article can be improved. Pure silicone rubber compound refers to liquid organosilicon or silicone oil with a high molecular weight. In this embodiment, its molecular weight is defined by kinematic viscosity.

[0059] The kinematic viscosity used in this embodiment is greater than 1,000,000 mm³. 2 The kinematic viscosity of the pure silicone rubber compound is preferably 5,000,000 mm³ / s. 2 / s or higher, more preferably 10,000,000 mm 2 / s or higher, further preferably 15,000,000 mm 2 / s or higher, and more preferably 17,000,000 mm 2 / s or higher, and preferably 30,000,000 mm 2 / s or less, more preferably 25,000,000 mm 2 Below / s, further preferably 22000000mm 2 / s or less. By setting it above the lower limit value mentioned above, the ultimate PV value can be maintained at a high level. In addition, by setting it below the upper limit value mentioned above, the ultimate PV value can be maintained at a high level while suppressing mold contamination and delamination of the molded sheets.

[0060] The resin composition of this embodiment may contain only one resin with a kinematic viscosity greater than 1,000,000 mmHg. 2 The pure silicone rubber compound can contain two or more types of materials. When two or more types of materials are contained, the kinematic viscosity of the mixture is preferably within the range described above.

[0061] For kinematic viscosity, the viscosity of a toluene solution (0.1 g / L) of each pure silicone rubber compound at 25°C was measured using a cone-plate viscometer, and calculated based on the calibration curve of the kinematic viscosity of silicone oil and the viscosity of toluene solution.

[0062] As the measuring device, the instrument used can be the TVE-25L cone-plate viscometer manufactured by Toki Sangyo Co., Ltd.

[0063] The silicone rubber compound used in this embodiment is a compound having a structure linked by siloxane bonds. The silicone rubber compound is preferably a polyorganosiloxane, preferably a compound represented by -(Si(R)2-O)-, where each R is independently a hydrogen atom, a hydrocarbon group, an -O-hydrocarbon group, or a hydroxyl group (wherein at least one of R is a hydrocarbon group or an -O-hydrocarbon group). Preferably, each R is independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, an -O-hydrocarbon group having 1 to 6 carbon atoms, or a hydroxyl group; more preferably, a hydrogen atom, methyl, ethyl, phenyl, methoxy, ethoxy, phenoxy, or hydroxyl; more preferably, a hydrogen atom, methyl, or methoxy; and even more preferably, a hydrogen atom or methyl.

[0064] The -(Si(R)2-O)- in pure silicone rubber compound can be of two or more types.

[0065] When combined with pure silicone rubber compound, a masterbatch can be prepared. Polyacetal resin can be used as a resin for the masterbatch. Furthermore, the proportion of pure silicone rubber compound in the masterbatch is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less.

[0066] The kinematic viscosity of the resin composition of this embodiment is greater than 1,000,000 mmHg relative to 100 parts by weight of polyacetal resin. 2 The content of pure silicone rubber compound per s is preferably 0.4 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, even more preferably 2.5 parts by mass or less, particularly preferably 1.8 parts by mass or less, and especially preferably 1.5 parts by mass or less. By setting it to the lower limit or the upper limit mentioned above, there is a tendency to further improve the slip properties.

[0067] The resin composition of this embodiment may contain only one resin with a kinematic viscosity greater than 1,000,000 mmHg. 2 The pure silicone rubber compound per second may also contain two or more types. When two or more types are included, the preferred total quantity is within the range described above.

[0068] <Polyolefin Lubricants>

[0069] The resin composition of this embodiment contains a polyolefin lubricant. By including a polyolefin lubricant, initial sliding properties can be improved, and together with the pure silicone rubber compound, the coefficient of dynamic friction can be reduced.

[0070] Polyolefin lubricants refer to homopolymers or copolymers of olefins.

[0071] Examples of polyolefin lubricants include polyethylene wax, polypropylene wax, and polyethylene propylene wax, with polyethylene wax being the most preferred.

[0072] Polyolefin lubricants can be unmodified or modified. Examples of modified polyolefin lubricants include vinyl ester-modified polyolefin lubricants, acid-modified polyolefin lubricants, and oxidized polyolefin lubricants (polyolefin lubricants modified by oxidation), with oxidized polyolefin lubricants being preferred. Oxidized polyolefin lubricants are easily mixed with polyacetal resins and dispersed throughout the molded article, further improving the sliding properties of the resulting molded article.

[0073] The polyethylene wax can be formed from ethylene homopolymer or from ethylene-α-olefin copolymer. Examples of α-olefins in ethylene copolymers include propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene, and 4-methyl-1-pentene, which have 3 to 20 carbon atoms. The ethylene unit content in the ethylene-α-olefin copolymer wax is preferably greater than 50 mol%, more preferably 60 to 100 mol%. The polyethylene wax can be unmodified or modified. Examples of unmodified polyethylene waxes include Clariant Chemicals' Licowax (registered trademark) PE520, Licowax PE130, and Licowax PE190; Licocene (registered trademark) PE3101TP, Licocene PE4201, and Licocene PE5301; and Ceridust (registered trademark) 3620 and Ceridust 3610.

[0074] The polypropylene wax can be formed from propylene homopolymer or from propylene-α-olefin copolymer. Examples of α-olefins in propylene copolymers include ethylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene, and 4-methyl-1-pentene, which have 3 to 20 carbon atoms. The propylene unit content in the propylene-α-olefin copolymer wax is preferably greater than 50 mol%, more preferably 60 to 100 mol%. The polypropylene wax can be unmodified or modified. Examples of unmodified polypropylene waxes include Licocene (registered trademark) PP6102, Licocene PP6502, Licocene PP7502, Licocene PP1302, Licocene PP1502, Licocene PP1602, Licocene PP2602, and Licocene PP3602 manufactured by Clariant Chemicals; and Ceridust (registered trademark) 6050M, etc.

[0075] The resin composition of this embodiment preferably contains an oxidized polyolefin lubricant. By including an oxidized polyolefin lubricant, the initial sliding properties can be further improved, and together with the pure silicone rubber compound, the coefficient of dynamic friction can be further reduced.

[0076] Oxidized polyolefin lubricants can be obtained by oxidizing the corresponding unmodified polyolefin lubricant. In this embodiment, oxidized polyethylene wax is preferred.

[0077] Examples of oxidized polyethylene waxes include Clariant Chemicals' Licowax (registered trademark) PED521, Licowax PED522, and Licowax PED121; and Ceridust (registered trademark) 3715.

[0078] In this embodiment, it preferably includes oxidized polyolefin lubricant and unmodified polyolefin lubricant, and more preferably includes oxidized polyethylene wax and unmodified polyethylene wax.

[0079] The content of the oxidized polyolefin lubricant in the resin composition of this embodiment is preferably 25% by mass or more, more preferably 30% by mass or more, further preferably 35% by mass or more, even more preferably 40% by mass or more, particularly preferably 45% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 74% by mass or less. By setting it to the above-mentioned lower limit value or above, there is a tendency to further reduce the coefficient of kinetic friction of the obtained molded article. In addition, by setting it to the above-mentioned upper limit value or below, there is a tendency to further increase the PV limit value of the obtained molded article.

[0080] The resin composition of this embodiment may contain only one oxidized polyolefin lubricant, or it may contain two or more. When two or more are contained, the total amount is preferably within the range described above.

[0081] The molecular weight (viscosity method) of polyolefin lubricants (oxidized polyolefin lubricants, unmodified polyolefin lubricants, etc.) is preferably 1000 or more, more preferably 2000 or more, and even more preferably 3000 or more. For unmodified polyolefin lubricants, it is even more preferably 4500 or more, particularly preferably 5000 or more, and especially preferably 6000 or more. By setting these values ​​to the lower limit or above, a high level of slippage can be maintained without exudation from the molded article. Furthermore, the molecular weight (viscosity method) of polyolefin lubricants is preferably 20000 or less, more preferably 15000 or less, even more preferably 10000 or less, and especially preferably 8000 or less. By setting these values ​​to the upper limit or below, there is a tendency for further improvement in slippage.

[0082] The molecular weight of polyolefin lubricants was determined by gel permeation chromatography (viscosity method).

[0083] In the case where the resin composition of this embodiment contains two or more polyolefin lubricants, the molecular weight is the weighted average of the molecular weights of each polyolefin lubricant.

[0084] Relative to 100 parts by weight of polyacetal resin, the content of polyolefin lubricant in the resin composition of this embodiment is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more, even more preferably 1.0 parts by weight or more, even more preferably 1.2 parts by weight or more, particularly preferably 1.4 parts by weight or more, especially preferably 1.6 parts by weight or more, and preferably 10 parts by weight or less, more preferably 8 parts by weight or less, even more preferably 6 parts by weight or less, even more preferably 5 parts by weight or less, especially preferably 3 parts by weight or less, and especially preferably 2.5 parts by weight or less. By setting the content to the lower limit or above and the upper limit or below the above-mentioned values, there is a tendency to further improve the sliding properties.

[0085] The resin composition of this embodiment may contain only one type of polyolefin lubricant, or it may contain two or more types. When two or more types are contained, the total amount is preferably within the range described above.

[0086] <Other Ingredients>

[0087] The resin composition of this embodiment can be supplemented with known additives and fillers without prejudice to the purpose of the present invention. Examples of additives and fillers that can be used in this embodiment include, as needed, known thermoplastic polymers other than polyacetal resins, acid-modified polymers, weathering agents, formaldehyde scavengers, inorganic particles, antioxidants (hindered amines, hindered phenols, etc.), heat stabilizers, colorants, nucleating agents, plasticizers, fluorescent whitening agents, release agents, antistatic agents, ultraviolet absorbers, flame retardants, flame retardant additives, etc.

[0088] The resin composition in this embodiment is a polyacetal resin with a kinematic viscosity greater than 1,000,000 mmHg. 2 The resin composition of this embodiment is prepared by comprising 100% by mass of pure silicone rubber compound, polyolefin lubricant, and other components as needed. Preferably, the kinematic viscosity of the resin composition in this embodiment is greater than 1,000,000 mm⁻¹. 2 The total amount of silicone rubber pure rubber and polyolefin lubricant in the resin composition is 85% or more by mass, more preferably 90% or more by mass, even more preferably 95% or more by mass, and may also be 98% or more by mass.

[0089] <Other methods>

[0090] Furthermore, the resin composition in this embodiment is preferably a resin composition comprising polyacetal resin, pure silicone rubber, and a polyolefin lubricant. The resin composition is molded into a cylindrical thrust-molded sheet, and the average length of the micro-regions containing the organosilicon compound, as observed by a laser microscope, is 8.0 μm or more, and the average width is (3.0) μm or less. By forming fine and long micro-regions containing the organosilicon compound in the molded article in this way, a molded article with a low coefficient of dynamic friction and a high limiting PV value can be obtained. Preferably, 90% by mass of the aforementioned micro-regions are formed of the organosilicon compound.

[0091] The average length of the aforementioned microregions is preferably 8.0 μm or more, more preferably 9.0 μm or more, even more preferably 10.0 μm or more, even more preferably 11.0 μm or more, particularly preferably 12.0 μm or more, and preferably 30.0 μm or less, more preferably 25.0 μm or less. Depending on the application, it may also be 20.0 μm or less, 15.0 μm or less, or 10.0 μm or less. By setting it to the lower limit or above, the limiting PV value can be maintained at a high level. Furthermore, by setting it to the upper limit or below, the limiting PV value can be maintained at a high level without accompanying a decrease in toughness expressed as tensile elongation or Charpy impact value.

[0092] The average width of the aforementioned micro-region is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.5 μm or more, even more preferably 0.8 μm or more, and particularly preferably 1.0 μm or more. Furthermore, the average width of the aforementioned micro-region is preferably 3.0 μm or less, more preferably 2.8 μm or less, even more preferably 2.5 μm or less, even more preferably 2.3 μm or less, and particularly preferably 2.0 μm or less.

[0093] When the average length of the micro-region is set to L and the average width of the micro-region is set to W, the ratio L / W is preferably 3.0 or higher, more preferably 3.5 or higher, even more preferably 3.8 or higher, and particularly preferably 4.0 or higher. By setting L / W to a lower limit or higher, the limiting PV value can be maintained at a higher level. The upper limit of L / W is not particularly limited, but is actually 20 or lower.

[0094] The aforementioned micro-regions are mainly achieved by incorporating a given amount of polyacetal resin with a kinematic viscosity greater than 1,000,000 mm. 2 This can be achieved using pure silicone rubber and polyolefin lubricants. Alternatively, it can be achieved by combining a given amount of oxidized polyolefin lubricant. Of course, it goes without saying that the aforementioned microregions can also be formed by other methods.

[0095] The preferred range of the resin compositions described above in other ways is the same as the preferred range of the resin compositions of this embodiment described above in this specification.

[0096] <Physical Properties of Resin Compositions>

[0097] The resin composition of this embodiment preferably has excellent lubricity.

[0098] The coefficient of kinetic friction of the resin composition in this embodiment when molded into a cylindrical push-formed sheet is preferably 0.30 or less, more preferably 0.29 or less, even more preferably 0.24 or less, even more preferably 0.23 or less, and particularly preferably 0.20 or less. The lower limit is, for example, practically 0.01 or more. Such a coefficient of kinetic friction can be achieved primarily by incorporating a given amount of polyacetal resin with a kinematic viscosity greater than 1,000,000 mm⁻¹. 2 This is achieved by using pure silicone rubber material and polyolefin lubricants per second.

[0099] The coefficient of kinetic friction was measured according to the description of the embodiments described later.

[0100] The resin composition of this embodiment has a contact area of ​​2 cm². 2 The limiting PV value (MPa·cm / s) for the thrust ring friction and wear test specified in JIS K7218 A method at 23°C is preferably 14.0 MPa·cm / s or higher, more preferably 15.0 MPa·cm / s or higher, even more preferably 15.5 MPa·cm / s or higher, even more preferably 16.0 MPa·cm / s or higher, and particularly preferably 16.5 MPa·cm / s or higher. There is no particular upper limit, but it is practically 50.0 MPa·cm / s or lower.

[0101] The limiting PV value was determined according to the description in the embodiments described later.

[0102] <Method for manufacturing resin composition>

[0103] The resin composition of this embodiment can be easily prepared by known methods commonly used in the preparation of conventional thermoplastic resin compositions. For example, the following methods can be employed: (1) mixing all the components constituting the resin composition, feeding it to an extruder for melt mixing to obtain a granular resin composition; (2) feeding a portion of the components constituting the resin composition from the main feed port of an extruder and the remaining components from the side feed port, performing melt mixing to obtain a granular resin composition; (3) temporarily preparing granules with different compositions by extrusion or the like, and then mixing these granules to adjust them into a resin composition having a given composition.

[0104] In this embodiment, it is preferable to prepare the pure silicone rubber material into a masterbatch beforehand, and then melt-mix it with the remaining components.

[0105] Examples of mixing machines include kneaders, Banbury mixers, and extruders. There are no particular restrictions on the various conditions and apparatus used for mixing / blending; any conventionally known conditions can be appropriately selected. Blending is preferably carried out above the melting temperature of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally above 180°C).

[0106] Molded Products

[0107] The molded article of this embodiment is formed from the resin composition or granules of this embodiment. The granules obtained by granulating the resin composition of this embodiment can be molded into molded articles by various molding methods. Alternatively, the molded article can be directly molded from the resin composition after melt mixing in an extruder without going through the granulation process.

[0108] The shape of the molded article is not particularly limited and can be appropriately selected according to the use and purpose of the molded article. Examples include plate-shaped, flat plate-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, ring-shaped, circular, elliptical, gear-shaped, polygonal, irregular-shaped, hollow, frame-shaped, box-shaped, and panel-shaped articles. The molded article in this embodiment can be a finished product or a component.

[0109] There are no particular restrictions on the method of molding the product. Commonly known molding methods 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.

[0110] The resin composition of this embodiment is preferably used for forming sliding members. Therefore, the molded article formed from the resin composition of this embodiment is preferably used as a sliding member (sliding component).

[0111] Specific examples of sliding components include gears, rotating shafts, bearings, various transmission devices, cams, end face materials of mechanical seals, valve seats, V-rings, piston rod seals, piston rings, guide rings and other sealing components, as well as rotating shafts, rotating sleeves, pistons, impellers, rollers and other sliding components of compressors, which are required to achieve high quality in electrical / electronic equipment, office equipment, vehicles (automobiles), industrial equipment, etc.

[0112] The sliding member of this embodiment can of course be used as a sliding member combined with the sliding member of this embodiment. In addition, it can also be used as a sliding member combined with other resin sliding members, fiber-reinforced resin sliding members, and ceramic or metal sliding members.

[0113] Example

[0114] The present invention will be further described in detail below with reference to specific embodiments. The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0115] If the measuring equipment used in the embodiments is difficult to obtain due to production stoppages or other reasons, other equipment with equivalent performance can be used for measurement.

[0116] 1. Raw materials

[0117] The raw materials shown in Table 1 below were used.

[0118]

[0119] In Table 1 above, POM is an abbreviation for polyacetal resin.

[0120] 2. Examples 1-9, Comparative Examples 1-10

[0121] <Preparation of Resin Composition (Grit)>

[0122] Using a twin-screw extruder (manufactured by Ikegai Co., Ltd., PCM-30, screw diameter 30mm), at a screw speed of 120rpm and a barrel temperature of 190°C, the components shown in Table 1 were melt-blended in the proportions shown in Tables 2 to 5 (the proportions of each component are parts by mass), extruded into a filament, and then cut into granules using a granulator to produce granules of the resin composition.

[0123] <Manufacturing of Cylindrical Thrust Test Piece>

[0124] The granules of the above-obtained polyacetal resin composition were injection molded using a SE-30DUZ manufactured by Sumitomo Heavy Industries, Ltd. at a barrel temperature of 200°C and a mold temperature of 80°C to form a cylindrical thrust test piece (JIS K7218 method, dimensions: outer diameter 25.6mm × inner diameter 20.0mm × height 15.0mm).

[0125] <Average length and average width of micro-regions>

[0126] The average length and average width of the micro-regions were determined using a cylindrical thrust test piece. The surface of the cylindrical thrust test piece was prepared free of impurities by ultrasonic cleaning with ethanol. Brightness images of the surface of the cylindrical thrust test piece were obtained using a laser microscope, and the average length and average width of the micro-regions formed by the organosilicon compound were evaluated using image analysis software.

[0127] The following shows the shooting conditions and image analysis methods for brightness images.

[0128] <<Brightness Image Shooting Conditions>>

[0129] Brightness images were captured using a Lasertec HYBRID L7 hybrid laser microscope. The field of view was set to four locations around 90°, 180° (reverse gate side weld line), and 270°, with the top of the gate as the reference point (0°). A 20x objective lens was used.

[0130] The laser microscope used a light source with a brightness of 200 and a light intensity of 100% during shooting. The resolution was set to 0.24μm, and the image was taken using the confocal function.

[0131] The obtained brightness image is processed by automatic surface correction and a 5×5 median filter on the device to serve as the analysis image.

[0132] Image Analysis

[0133] Image analysis of the photographs used to calculate the average length and average width employed image analysis software (WinROOF 2018) manufactured by Mitani Corporation. For all micro-regions appearing in the photograph, the length and width of each micro-region and its average value were automatically calculated.

[0134] Image analysis was performed using the aforementioned image analysis software, following these steps.

[0135] First, the image obtained under the above conditions was read using the image analysis software described above. After monochrome image conversion, the scale bar was calibrated. The method is as follows: Using the "Manual Calibration" function, the line was aligned with the 100μm scale bar recorded at the bottom of the brightness image, and 100μm was entered in the actual size value field. Next, the entire area except for the approximately 30μm × 740μm area at the bottom of the captured image containing the above analysis conditions was selected using a rectangular ROI, and the selected area was cropped to extract the image region. The box mode for setting the boundary line processing method of the rectangular ROI was set to "Cut at the boundary".

[0136] Next, within the selected ROI range, thresholds related to brightness were set using discriminant analysis. Specifically, to distinguish between the "parts being measured" and the "parts not being measured" based on these thresholds, binarization was performed by selecting pixels with a brightness level of 200 or higher. It should be noted that the number of binarization operations was set to 2. After this processing, pixels with brightness values ​​within the range (200-255) specified in the binarization process, and with an area of ​​0.525 μm, were selected. 2 The above collection of pixels is used as the measurement object.

[0137] For the obtained image of the measurement object, select "Skeleton Length" and "Diagonal Width" from the "Shape Features" function to calculate the length and width of the binarized selection region. Perform the above analysis on the four specified fields of view, add up the average values ​​of each field of view automatically calculated by the image analysis software, divide by the number of fields of view (4), and use the resulting values ​​as the average length and average width of the micro-region. It should be noted that "Skeleton Length" represents the length of the free curve, and "Diagonal Width" represents the shortest distance between two straight lines parallel to the absolute maximum length when the figure is sandwiched between them. The average skeleton length calculated by the above method corresponds to the average length of the micro-region, and the average diagonal width corresponds to the width of the micro-region.

[0138] Electron microscope images of Example 4 and Comparative Example 7 are shown respectively. Figure 1 and Figure 2 In Example 4, it can be seen that elongated micro-regions are formed; in contrast, in Comparative Example 7, it can be seen that elongated micro-regions are not formed.

[0139] <Coefficient of dynamic friction (surface pressure 4.9 MPa)>

[0140] For cylindrical thrust test specimens of resin compositions, in a thrust-type friction and wear test relative to carbon steel S45C, at a linear velocity of 10 cm / s, and with the surface pressure increased by 3 kg, 5 kg, 10 kg, and then by 5 kg every 3 minutes, the average value of the dynamic friction coefficient was recorded over 3 minutes, focusing on the dynamic friction coefficient that is prone to differences caused by the formulation under high surface pressure (load 100 kg, surface pressure 4.9 MPa).

[0141] The results are shown in Tables 2-5 below.

[0142] <Limiting PV value (MPa·cm / s)>

[0143] For cylindrical thrust test pieces of resin compositions, a thrust-type friction and wear test was conducted relative to polyamide 6 test pieces at a linear velocity of 10 cm / s, with the surface pressure increased by 3 kg, 5 kg, 10 kg every 3 minutes, and then by 5 kg each time after 5 kg. The product of the surface pressure and velocity in the stage before the adhesion due to frictional heat occurred was taken as the limiting PV value (unit: MPa·cm / s).

[0144] The results are shown in Tables 2-5 below.

[0145]

[0146]

[0147]

[0148]

[0149] In the table above, "C2 ratio" represents the proportion of oxidized polyolefin lubricant in the total amount of polyolefin lubricant in each resin composition (unit: mass %).

[0150] Based on the above results, the molded articles formed from the resin composition of the present invention have a low coefficient of dynamic friction and a high limiting PV value (Examples 1-9).

[0151] In contrast, when the content of pure silicone rubber is low (Comparative Example 1), the sliding properties are poor.

[0152] The PV limit values ​​are low in cases where oxidized polyolefin lubricants are not present, or are present but in small amounts (Comparative Examples 3, 5, 10), and in cases where polyolefin lubricants are not present (Comparative Examples 6, 9). Additionally, the PV limit values ​​are low in cases where the content of oxidized polyolefin lubricants is high (Comparative Examples 2, 4).

[0153] On the other hand, when silicone oil was used instead of pure silicone rubber (Comparative Examples 7 and 8), the PV limit value was lower.

[0154] Furthermore, in the absence of silicone (Comparative Example 9), the PV limit value is particularly low.

Claims

1. A resin composition comprising: 100 parts by weight of polyacetal resin kinematic viscosity greater than 1,000,000 mm 2 / s of pure silicone rubber compound, 0.4~10 parts by weight, and Polyolefin lubricant, 0.5-10 parts by weight. 25-80% by mass of polyolefin lubricants are oxidically modified polyolefin lubricants.

2. A resin composition comprising a polyacetal resin, a silicone rubber compound, and a polyolefin lubricant, wherein, The resin composition was molded into a cylindrical thrust test piece, and the average length L of the micro-region containing the organosilicon compound, as observed by a laser microscope, was greater than 8.0 μm, and the average width W was less than 3.0 μm.

3. The resin composition according to claim 1, wherein, The resin composition contains a silicone rubber pure rubber compound with a kinematic viscosity of 5,000,000 mm⁻¹. 2 / s or more.

4. The resin composition according to claim 1 or 2, wherein, The resin composition contains a silicone rubber compound with a kinematic viscosity of 10,000,000 mm⁻¹. 2 / s or more.

5. The resin composition according to claim 2, wherein, The polyolefin lubricant contained in the resin composition includes an oxidically modified polyolefin lubricant.

6. The resin composition according to claim 1 or 5, wherein, The proportion of oxidized polyolefin lubricant in the resin composition is 35% or more by mass.

7. The resin composition according to claim 1, wherein, The resin composition contains a silicone rubber compound with a kinematic viscosity of 10,000,000 mm⁻¹. 2 / s or more The proportion of oxidized polyolefin lubricant in the resin composition is 35% or more by mass.

8. The resin composition according to claim 7, wherein, The resin composition was molded into a cylindrical thrust test piece, and the average length L of the micro-region containing the organosilicon compound, as observed by a laser microscope, was greater than 8.0 μm, and the average width W was less than 3.0 μm.

9. The resin composition according to claim 2, wherein, The resin composition contains a silicone rubber compound with a kinematic viscosity of 10,000,000 mm⁻¹. 2 / s or more More than 35% by mass of polyolefin lubricants are oxidically modified polyolefin lubricants.

10. The resin composition according to claim 2 or 8, wherein, The ratio of the average length L to the average width W of the microregion containing the organosilicon compound, L / W, is 3.0 or higher.

11. A granule, which is a granule of the resin composition according to claim 1, 3, 5, 7, 8 or 9.

12. A molded article formed from the resin composition of claim 1, 3, 5, 7, 8 or 9.

13. A molded article formed from the granules of claim 11.

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