Resin composition, pellets, and molded article

Abstract

The invention provides a resin composition, pellets, and a molded article. The resin composition contains a polyacetal resin (A), a silicone resin (B) having a weight-average molecular weight of 800,000 or more, and a silicone resin (C) having a weight-average molecular weight of 100,000 or more and less than 800,000, the mass ratio of the silicone resin (B) to the silicone resin (C), i.e., (B) / (C), being 10 / 90-90 / 10.

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 widely used as a plastic with excellent mechanical, electrical, and chemical resistance properties.

[0003] Furthermore, as one of the uses of 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 made of 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 that the invention aims to solve

[0008] The resin composition described in Patent Document 1 is a material with excellent lubricity. However, in recent years, there has been a demand for even better lubricity. However, if the amount of lubricant added increases, mold contamination during molding becomes a problem.

[0009] The purpose of this invention is to solve the above-mentioned problems, and to provide resin compositions, granules, and molded articles that can provide molded articles with excellent sliding properties and low mold contamination.

[0010] Problem Solving Methods

[0011] Based on the above problems, the inventors conducted research and found that the above problems can be solved by using a silicone resin of a given molecular weight in combination with polyacetal resin.

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

[0013] <1> A resin composition comprising: a polyacetal resin (A), an organosilicon resin (B) with a weight average molecular weight of 800,000 or more, and an organosilicon resin (C) with a weight average molecular weight of 100,000 or more and less than 800,000, wherein the mass ratio of the organosilicon resin (B) to the organosilicon resin (C), i.e. (B) / (C), is 10 / 90 to 90 / 10.

[0014] <2> According to the resin composition described in <1>, wherein,

[0015] The total content of the above-mentioned silicone resins (B) and (C) is more than 0.1 parts by weight and less than 10 parts by weight relative to 100 parts by weight of polyacetal resin (A).

[0016] <3> The resin composition according to <1> or <2>, wherein,

[0017] The resin composition is molded into test pieces as specified in ISO 9988-2 standard, and spherical silica (D) is projected onto the test pieces. 50 A 1mm × 1mm nozzle with a nozzle diameter of 1mm was used to spray a 3% (w / w) aqueous solution (5μm) at a distance of 4mm from the test piece. Under the conditions of a projection force of 16.15~17.85μm with a depth range when the test was conducted using a polymethyl methacrylate plate of the same shape, and with a projection treatment condition of 0.5g × 30 times, the erosion depth was less than 35μm, and the erosion rate at a test depth of 15μm was less than 3μm / g.

[0018] <4> A particle, which is a particle of the resin composition described in any one of <1> to <3>.

[0019] <5> A molded article formed from any one of <1> to <3>.

[0020] <6> A molded article formed from the particles described in <4>.

[0021] The effects of the invention

[0022] According to the present invention, resin compositions, granules, and molded articles that provide molded articles with excellent sliding properties and low mold contamination can be provided. Detailed Implementation

[0023] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the following embodiments are examples for illustrating the present invention, and the present invention is not limited to these embodiments.

[0024] It should be noted that in this specification, "~" is used to indicate the lower and upper limits of the values ​​contained before and after it.

[0025] Unless otherwise specified, all physical property values ​​and characteristic values ​​in this specification refer to values ​​at 23°C.

[0026] Unless otherwise specified, in cases where the measurement methods described in the standards shown in this instruction manual vary depending on the year, the standards at the time of January 1, 2023 shall prevail.

[0027] The resin composition of this embodiment is characterized by comprising: a polyacetal resin (A), a silicone resin (B) with a weight-average molecular weight of 800,000 or more, and a silicone resin (C) with a weight-average molecular weight of 100,000 or more and less than 800,000, wherein the mass ratio of silicone resin (B) to silicone resin (C), i.e., (B) / (C), is 10 / 90 to 90 / 10. With this configuration, it is possible to provide molded articles with less mold contamination during molding and excellent sliding properties.

[0028] If a silicone resin (B) with a weight-average molecular weight of 800,000 or higher is used, the sliding properties of the resulting molded article can be improved. This is presumably because if the molecular weight of the silicone resin is large, the dispersion diameter in the polyacetal resin becomes larger, and the silicone resin is more likely to appear on the surface of the molded article.

[0029] However, it is known that using silicone resins with high molecular weights can easily lead to mold contamination during molding. In this embodiment, to address this issue, a silicone resin (C) with a weight-average molecular weight of 100,000 or more but less than 800,000 is used. That is, sufficient lubricity cannot be achieved using only silicone resin (C) with a weight-average molecular weight of 100,000 or more but less than 800,000, but by blending two silicone resins, excellent lubricity can be maintained while suppressing mold contamination.

[0030] Furthermore, if a high molecular weight silicone resin is used, there is a tendency for the resulting molded product to deteriorate in terms of layering. From the above perspective, this can also be suppressed by using it in combination with a silicone resin (C) with a weight-average molecular weight of 100,000 or more but less than 800,000.

[0031] It should be noted that the silicones used to improve the lubrication of polyacetal resins are usually silicones with a weight average molecular weight of less than 100,000.

[0032] The following is a detailed description of this embodiment.

[0033] <Polyacetal Resin (A)>

[0034] The resin composition of this embodiment comprises a polyacetal resin.

[0035] There are no particular limitations on the type of polyacetal resin. It can be a homopolymer containing only divalent oxymethylene as a structural unit, or a copolymer containing divalent oxymethylene and divalent oxyalkylene with 2 to 6 carbon atoms as structural units.

[0036] Examples of oxoalkylene groups with 2 to 6 carbon atoms include oxoethylene, oxopropylene, and oxobutylene.

[0037] In polyacetal resins, there is no particular limitation on the proportion of 2-6 carbon alkylene groups in the total molar number of oxymethylene and 2-6 carbon alkylene groups, as long as it is 0.5-10 mol%.

[0038] To manufacture the aforementioned polyacetal resin, trialkylene is typically used as the main raw material. Additionally, to introduce alkylene groups with 2 to 6 carbon atoms into the polyacetal resin, cyclic methylal and cyclic ethers can be used. Specific examples of cyclic methylal include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxane-heptane, 1,3-dioxane-octane, 1,3,5-trioxane-heptane, and 1,3,6-trioxane-octane. Specific examples of cyclic ethers include ethylene oxide, propylene oxide, and butane oxide. To introduce ethylene into the polyacetal resin, only 1,3-dioxolane is needed as the main raw material; to introduce propylene oxide, only 1,3-dioxane is needed; and to introduce butylene, only 1,3-dioxane-heptane is needed. It should be noted that in polyacetal resins, the amount of hemiacetal terminal groups, formyl terminal groups, and terminal groups that are unstable to heat, acid, and alkali are preferred. Here, hemiacetal terminal groups refer to groups represented by -OCH2OH, and formyl terminal groups refer to groups represented by -CHO.

[0039] In this embodiment, the melt volumetric velocity (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 points or more, preferably 0.6cm 3 / 10 points or above, further optimized to 0.8cm 3 / 10 points or higher, with an even better option of 1cm 3 / 10 points or above, further preferred to be 5cm 3 / 10 points or more. By setting it to the lower limit value mentioned 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 20cm. 3 / 10 points or less, preferably 18cm 3 / 10 points or less, further preferred to be 14cm 3 / 10 points or less, more preferably 10cm 3 / 10 points or less, further preferred to be 8cm 3 / Below 10 points.

[0040] In addition to the above, polyacetal resins described in paragraphs 0018 to 0043 of Japanese Patent Application Publication No. 2015-074724 may be used as polyacetal resins, and these contents are incorporated into this specification.

[0041] 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.

[0042] 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. In addition, all components except silicone resin (B) and silicone resin (C) may be polyacetal resin.

[0043] The resin composition of this embodiment may contain only one type of polyacetal resin, or it may contain two or more types. When it contains two or more types, the total amount is preferably within the range described above.

[0044] <Organic silicone resins with a weight-average molecular weight of over 800,000 (B)>

[0045] The resin composition of this embodiment contains an organosilicon resin (B) with a weight-average molecular weight of 800,000 or more. By containing an organosilicon resin (B) with a weight-average molecular weight of 800,000 or more, the sliding properties can be improved. In particular, the limiting PV value can be increased and the coefficient of kinetic friction can be reduced.

[0046] The weight-average molecular weight of the aforementioned organosilicon resin (B) is preferably 850,000 or more, more preferably 900,000 or more, even more preferably 950,000 or more, and even more preferably 980,000 or more. In addition, it is preferably 2,000,000 or less, more preferably 1,800,000 or less, even more preferably 1,500,000 or less, and may also be 1,200,000 or less.

[0047] Setting the value above the aforementioned lower limit tends to further improve slippage. Conversely, setting the value below the aforementioned upper limit tends to further improve the suppression of mold contamination and delamination of the molded sheet.

[0048] In this embodiment, the molecular weight of the silicone resin (B) was determined according to the following method.

[0049] Organosilicon was extracted from the organosilicon resin using dichloromethane. The extracted organosilicon was adjusted with 0.2% (w / w) toluene eluent and allowed to stand at room temperature for 12 hours. The filtrate was then filtered through a 0.45 μm membrane filter and analyzed by gel permeation chromatography (GPC). AQCUITY APC (Waters) was used for GPC analysis.

[0050] In the case where the resin composition of this embodiment contains two or more silicone resins (B), the Mw of the silicone resin (B) is set as the Mw of the mixture.

[0051] The same applies to silicone resin (C).

[0052] The organosilicon resin (B) used in this embodiment is preferably a polyorganosiloxane, preferably a compound represented by -(Si(R)2-O)- and where 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). R is preferably 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, preferably a hydrogen atom, methyl, ethyl, phenyl, methoxy, ethoxy, phenoxy, or hydroxyl group, more preferably a hydrogen atom, methyl, or methoxy group, and even more preferably a hydrogen atom or methyl group.

[0053] The -(Si(R)2-O)- in organosilicon resin (B) can be one type or two or more types.

[0054] When combined with silicone resin (B), masterbatch production can be performed. Polyacetal resin is preferably used as the resin in the masterbatch. Furthermore, the proportion of silicone resin (B) in the masterbatch is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and more preferably 60% by mass or less.

[0055] Relative to 100 parts by weight of polyacetal resin (A), the content of silicone resin (B) in the resin composition of this embodiment is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, further preferably 0.3 parts by weight or more, even more preferably 0.5 parts by weight or more, and still more preferably 0.6 parts by weight or more. It is also preferably 9 parts by weight or less, more preferably 7 parts by weight or less, further preferably 5 parts by weight or less, even more preferably 3 parts by weight or less, still more preferably 1 part by weight or less, and still more preferably 0.9 parts by weight or less. By setting the content to the lower limit or above, there is a tendency for further improvement in slip properties. Furthermore, by setting the content to the upper limit or below, there is a tendency for further improvement in mold contamination and delamination suppression effect on the molded sheet.

[0056] The resin composition of this embodiment may contain only one type of silicone resin (B), or it may contain two or more types. When it contains two or more types, the total amount is preferably within the range described above.

[0057] <Organic silicone resins with a weight-average molecular weight of 100,000 or more but less than 800,000 (C)>

[0058] The resin composition of this embodiment comprises a silicone resin (C) with a weight-average molecular weight of 100,000 or more and less than 800,000. By using a silicone resin (C) with a weight-average molecular weight of 100,000 or more and less than 800,000 in combination with a silicone resin (B), mold contamination and delamination can be effectively suppressed while maintaining slip properties.

[0059] Silicone resins (C) with such molecular weights are easier to disperse internally compared to the surface of the molded product, thus increasing the erosion depth.

[0060] The weight-average molecular weight of the aforementioned organosilicon resin (C) is preferably 150,000 or more, more preferably 200,000 or more, further preferably 300,000 or more, even more preferably 350,000 or more, even more preferably 400,000 or more, even more preferably 450,000 or more, and preferably 750,000 or less, more preferably 700,000 or less, even more preferably 650,000 or less, even more preferably 600,000 or less, even more preferably 550,000 or less, and may also be 520,000 or less.

[0061] Setting the value above the aforementioned lower limit tends to further improve slippage. Conversely, setting the value below the aforementioned upper limit tends to further improve the mold contamination and delamination suppression effect of the molded sheet.

[0062] The organosilicon resin (C) used in this embodiment is preferably a polyorganosiloxane, preferably a compound represented by -(Si(R)2-O)- and where 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). R is preferably 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, preferably a hydrogen atom, methyl, ethyl, phenyl, methoxy, ethoxy, phenoxy, or hydroxyl group, more preferably a hydrogen atom, methyl, or methoxy group, and even more preferably a hydrogen atom or methyl group.

[0063] The -(Si(R)2-O)- in organosilicon resin (C) can be one type or two or more types.

[0064] When combined with silicone resin (C), masterbatch production can be performed. Polyacetal resin is preferably used as the resin for the masterbatch. Furthermore, the proportion of silicone resin (C) in the masterbatch is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and further preferably 60% by mass or less, more preferably 55% by mass or less, and more preferably 45% by mass or less.

[0065] Relative to 100 parts by weight of polyacetal resin (A), the content of organosilicon resin (C) in the resin composition of this embodiment is preferably 0.1 parts by weight or more, more preferably 0.15 parts by weight or more, even more preferably 0.18 parts by weight or more, and also preferably 9 parts by weight or less, more preferably 5 parts by weight or less, even more preferably 3 parts by weight or less, even more preferably 1 part by weight or less, even more preferably 0.6 parts by weight or less, even more preferably 0.4 parts by weight or less, and even more preferably 0.3 parts by weight or less. By setting it to the lower limit or above, there is a tendency for the sliding properties to be further improved. In addition, by setting it to the upper limit or below, there is a tendency for the delamination suppression effect to be further improved.

[0066] The resin composition of this embodiment may contain only one type of silicone resin (C), or it may contain two or more types. When it contains two or more types, the total amount is preferably within the range described above.

[0067] <Blending of Organosilicon Resin (B) and Organosilicon Resin (C)>

[0068] In the resin composition of this embodiment, the mass ratio of silicone resin (B) to silicone resin (C), i.e., (B) / (C), is 10 / 90 to 90 / 10. By setting it in this way, it is possible to achieve a good balance between improved slipability and suppression of mold contamination.

[0069] Regarding the blending ratio of the aforementioned silicone resin (B) and silicone resin (C), relative to a total of 100 parts by mass of silicone resin (B) and silicone resin (C), silicone resin (B) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 22 parts by mass or more, and may also be 24 parts by mass or more. It is also preferably 85 parts by mass or less, more preferably 80 parts by mass or less, and may also be 77 parts by mass or less.

[0070] In the resin composition of this embodiment, the total content of the above-mentioned silicone resin (B) and silicone resin (C) is preferably more than 0.1 parts by weight and less than 10 parts by weight relative to 100 parts by weight of polyacetal resin (A). By setting it to the lower limit or above, there is a tendency for the slip properties to be further improved. In addition, by setting it to the upper limit or below, there is a tendency for the mold contamination and delamination suppression effect of the molded sheet to be further improved.

[0071] Relative to 100 parts by weight of polyacetal resin (A), the total content of the above-mentioned silicone resin (B) and silicone resin (C) is more preferably 0.1 parts by weight or more, further preferably 0.11 parts by weight or more, even more preferably 0.2 parts by weight or more, even more preferably 0.3 parts by weight or more, even more preferably 0.5 parts by weight or more, even more preferably 0.8 parts by weight or more, and preferably 9 parts by weight or less, more preferably 8 parts by weight or less, even more preferably 7 parts by weight or less, even more preferably 5 parts by weight or less, even more preferably 3 parts by weight or less, even more preferably 2 parts by weight or less, even more preferably 1.5 parts by weight or less, and particularly preferably 1.0 parts by weight or less.

[0072] The resin composition of this embodiment may or may not contain organosilicon compounds (silicone oil, organosilicon resin, etc.) with a weight average molecular weight of less than 100,000. One example of this embodiment substantially does not contain organosilicon compounds with a weight average molecular weight of less than 100,000. "Substantially does not contain" means that the content of organosilicon compounds with a weight average molecular weight of less than 100,000 in the resin composition is less than 10% by mass of the total content of organosilicon resin (B) and organosilicon resin (C), preferably less than 5% by mass, more preferably less than 3% by mass, and may be less than 1% by mass.

[0073] Furthermore, in the resin composition of this embodiment, the total content of polyacetal resin (A), silicone resin (B), and silicone resin (C) is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 97% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more, and may be 100% by mass or less.

[0074] <Other Ingredients>

[0075] Without prejudice to the purpose of this invention, the resin composition of this embodiment may contain known additives and fillers. 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.

[0076] The resin composition of this embodiment is adjusted such that the total of polyacetal resin, silicone resin (B) and silicone resin (C), and other components as needed, is 100% by mass.

[0077] <Other methods>

[0078] Furthermore, regarding the resin composition of this embodiment, the above-mentioned resin composition is molded into a test piece as specified in the ISO 9988-2 standard, and spherical silica (D) is projected onto it. 50 A 1mm × 1mm nozzle with a nozzle diameter of 1 mm was used to spray a 3% (by mass) aqueous solution of 5 μm. The nozzle was positioned 4 mm away from the test piece. When the projection force of the spherical silica was measured using a polymethyl methacrylate plate of the same shape, the projection force range was 16.15~17.85 μm. When the projection treatment was 0.5g × 30 times, the erosion depth was 35 μm or less, and the erosion rate at a measurement depth of 15 μm was 3 μm / g or less.

[0079] The aforementioned erosion depth is preferably 35 μm or less, more preferably 33 μm or less, even more preferably 32 μm or less, even more preferably 31 μm or less, and still more preferably 30 μm or less. By setting it to the above-mentioned upper limit value or less, there is a tendency for the fatigue resistance of the obtained molded article to be improved. In addition, when the erosion depth is shallow, 0 μm (no erosion) is ideal, but in practice it is 5 μm or less.

[0080] The aforementioned erosion rate is preferably 3.0 μm / g or less, more preferably 2.5 μm / g or less, even more preferably 2.3 μm / g or less, even more preferably 2.2 μm / g or less, and still more preferably 2.1 μm / g or less. By setting it below the aforementioned upper limit, there is a tendency for the fatigue resistance of the obtained molded article to increase. In addition, the lower limit of the aforementioned erosion rate is not particularly limited, and is actually 0.1 μm / g or more.

[0081] 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 as originally described in this specification.

[0082] <Physical Properties of Resin Compositions>

[0083] The resin composition of this embodiment preferably exhibits excellent lubricity.

[0084] The coefficient of dynamic friction of the resin composition in this embodiment when molded into a cylindrical thrust test piece is preferably 0.25 or less. The lower limit is, for example, actually 0.01 or more. This low coefficient of dynamic friction is mainly achieved by combining an organosilicon resin (C) with the polyacetal resin (A).

[0085] The coefficient of kinetic friction was measured according to the description of the embodiments described later.

[0086] The resin composition of this embodiment is molded into a cylindrical thrust test piece, with a contact area of ​​2 cm². 2When conducting the thrust ring friction and wear test as specified in JIS K7218 A method at 23℃, the limiting PV value (MPa·cm / s) is preferably 16.0 MPa·cm / s or higher. There is no specific upper limit, but it is practically 50.0 MPa·cm / s or lower. Such a high limiting PV value is mainly achieved by combining silicone resin (B) with polyacetal resin (A).

[0087] The limiting PV value was determined according to the embodiments described later.

[0088] <Method for manufacturing resin composition>

[0089] 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 used: (1) mixing all the components constituting the resin composition, feeding it to an extruder, and performing 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, mixing the granules, and preparing a resin composition having a given composition, etc.

[0090] In this embodiment, it is preferable to pre-master the silicone resin (B) and / or silicone resin (C) separately before melt-blending them with the remaining components.

[0091] Examples of mixing machines include kneaders, Banbury mixers, and extruders. There are no particular restrictions on the various conditions and equipment used for mixing / blending; any suitable conditions can be selected from those currently known. Blending is preferably carried out at a temperature above the melting point of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally above 180°C).

[0092] <Molded Products>

[0093] 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 are molded using various molding methods to produce the molded article. Alternatively, the resin composition, after melt-mixing through an extruder, can be directly molded without granulation to produce the molded article.

[0094] 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, disc-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, ring-shaped, circular, elliptical, gear-shaped, polygonal, irregular-shaped, hollow, frame-shaped, box-shaped, and flat-shaped articles. The molded article in this embodiment can be a finished product or a component.

[0095] There are no particular restrictions on the molding method for molded products. Existing well-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.

[0096] The resin composition of this embodiment is preferably used as a resin composition 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).

[0097] Specific examples of sliding components include: gears, shafts, bearings, various gears, cams, end face materials for mechanical seals, valve seats, V-rings, piston rod seals, piston rings, guide rings and other sealing components, as well as compressor shafts, rotating sleeves, pistons, actuators, rollers and other sliding components, which are designed to meet the high-quality requirements of electrical / electronic equipment, office equipment, vehicles (automobiles), industrial equipment, etc.

[0098] Regarding the sliding member of this embodiment, the sliding members of this embodiment can of course be used in combination with each other, or they can be used as a sliding member combined with other resin sliding members, fiber-reinforced resin sliding members, and ceramic or metal sliding members.

[0099] Example

[0100] The present invention will be described in more detail below with examples. The materials, amounts, proportions, processing contents, processing order, etc., shown in the following examples can be appropriately changed without departing from the spirit of the invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0101] 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.

[0102] 1. Raw materials

[0103] The following raw materials were used.

[0104]

[0105] 2. Example 1, Example 2, Comparative Example 1, Comparative Example 2

[0106] <Preparation of Resin Composition (Particles)>

[0107] Using a high-speed mixer manufactured by Kawada Manufacturing Co., Ltd., the components shown in Table 1 were uniformly mixed according to the proportions shown in Table 2 (the proportions of each component are parts by mass). The resulting mixture was melt-shear mixed using a vented twin-screw extruder (PCM30 manufactured by Ikegai Co., Ltd.) with a screw diameter of 30 mm, at a cylinder temperature of 190°C, a screw speed of 120 rpm, and an ejection rate of 10 kg / hour to produce granules of the resin composition.

[0108] <Coefficient of kinetic friction>

[0109] Using a Sumitomo Heavy Industries SE-30DUZ screw with a diameter of 32mm, the above-obtained particles were molded into cylindrical thrust test pieces under conditions of cylinder temperature 195°C and mold temperature 80°C.

[0110] The obtained cylindrical thrust test piece was subjected to a thrust-type friction and wear test, and the dynamic friction coefficient was determined.

[0111] The thrust test used EFM-3-G manufactured by A&D Corporation.

[0112] For cylindrical thrust test pieces, in the thrust friction and wear test on polyacetal resin test pieces, the focus was on the dynamic friction coefficient under low surface pressure (load 3 kg, surface pressure 0.15 MPa), which easily generates a difference in dynamic friction coefficient due to the formulation. The average dynamic friction coefficient was recorded over 3 minutes and evaluated as described below. The thrust friction and wear test was conducted at a linear velocity of 10 cm / s, and the surface pressure was increased every 3 minutes to 3 kg, 5 kg, and 10 kg, with the surface pressure increasing by 5 kg each time after 5 kg.

[0113] A: The coefficient of kinetic friction is below 0.25.

[0114] B: The coefficient of kinetic friction is less than 0.25.

[0115] <Limited PV Value>

[0116] The above-obtained particles were injection molded using a SE30DUZ (manufactured by Sumitomo Heavy Industries, Ltd.) with a screw diameter of 32mm and a cylinder temperature of 195°C and a mold temperature of 80°C. Thrust wear tests were then conducted using the resulting cylindrical thrust test piece.

[0117] For cylindrical thrust test pieces, a thrust-type friction and wear test is conducted. The test is carried out at a linear velocity of 10 cm / s, and the surface pressure is increased to 3 kg, 5 kg, and 10 kg every 3 minutes. After 5 kg, the surface pressure is increased by 5 kg each time. The product of the surface pressure and the velocity at the level one level lower than the level of welding due to frictional heat is taken as the limit PV value (unit: MPa·cm / s).

[0118] The limiting PV value was evaluated as described below.

[0119] A: The limiting PV value is above 16.0 MPa·cm / s.

[0120] B: The limiting PV value is less than 16.0 MPa·cm / s

[0121] <Layering>

[0122] Using a Sumitomo Heavy Industries SE-30DUZ, the resin composition obtained above was molded at a cylinder temperature of 215°C, a mold temperature of 80°C, and an injection speed of 30 mm / s to produce a test piece of 40 mm × 100 mm × 2 mm.

[0123] The evaluation was conducted in tiers as described below. A and B represent the actual usage level.

[0124] A: 3cm or more but less than 5cm from the gate

[0125] B: 5cm or more but less than 7cm from the gate

[0126] C: 7cm or more from the gate

[0127] <Mold Contamination>

[0128] Using a Sumitomo Heavy Industries SE7MII molding machine and a teardrop-shaped mold with a cylinder temperature of 230°C, the resin composition obtained above was continuously molded 500 times (shots) at a mold temperature of 40°C. The mold condition was then confirmed. The evaluation was conducted by five experts, and a majority vote was used to determine the performance. A and B represent the practical application level.

[0129] A: There are absolutely no mold residues; the mold contamination suppression effect is excellent.

[0130] B: Although there is a small amount of mold residue, the mold contamination suppression effect is good (worse than A above).

[0131] C: Excessive deposits on the mold result in poor mold contamination control (worse than B above).

[0132] <Erosion Depth>

[0133] After drying the resin composition obtained above at 80°C for more than 3 hours, the test piece specified in ISO9988-2 was formed using an injection molding machine (manufactured by Shibaura Machinery Co., Ltd., "EC-100S") under the conditions of cylinder temperature 195°C and mold temperature 90°C.

[0134] A spray nozzle (1mm diameter × 1mm) was positioned 4mm vertically relative to the surface of the test piece.

[0135] Spherical silica (D) was sprayed onto the test piece from the aforementioned nozzle. 50 A 3% by mass aqueous solution (5 μm).

[0136] The injection speed at this point was set based on the projection force of a polymethyl methacrylate plate of the same shape onto spherical silica, with a depth range of 16.15~17.85μm.

[0137] The erosion depth (in μm) and erosion rate (in μm / g) at a measurement depth of 15 μm were determined under the projection treatment conditions of 0.5 g × 30 measurements.

[0138]

[0139] Based on the above results, it is clear that the molded articles obtained from the resin composition of this embodiment exhibit excellent sliding properties. Furthermore, mold contamination is also suppressed.

Claims

1. A resin composition comprising: a polyacetal resin (A), an organic silicon resin (B) having a weight average molecular weight of 800,000 or more, and an organic silicon resin (C) having a weight average molecular weight of 1,000,000 or more and less than 80,000,000, a mass ratio of the organic silicon resin (B) to the organic silicon resin (C), i.e., (B) / (C), is 10 / 90 to 90 / 10.

2. The resin composition according to claim 1, wherein, a total content of the organic silicon resin (B) and the organic silicon resin (C) is more than 0.1 parts by mass and less than 10 parts by mass with respect to 100 parts by mass of the polyacetal resin (A).

3. The resin composition according to claim 1 or 2, wherein, The resin composition was molded into a test piece specified in ISO 9988-2 standard, and a spray nozzle having a nozzle diameter of 1 mm x 1 mm for a 3 mass% water solution of projected spherical silica (D 50 The erosion depth was 35 μm or less, and the erosion rate at a measurement depth of 15 μm was 3 μm / g or less when the measurement was performed under a projection force setting condition in which the depth range was 16.15 to 17.85 μm when measured with a polymethyl methacrylate plate of the same shape, and the projection processing condition was 0.5 g x 30 times at a distance of 4 mm from the test piece.

4. A pellet which is the resin composition according to claim 1 or 2.

5. A molded article formed from the resin composition according to claim 1 or 2.

6. A molded article formed from the pellet according to claim 4.

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