Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/26—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment
  • C08L23/30—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment by oxidation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L59/00—Compositions of polyacetals; Compositions of derivatives of polyacetals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes

Definitions

• the present invention relates to a resin composition, pellets, and molded products.
• the present invention relates to a resin composition whose main component is polyacetal resin.
• Polyacetal resin is a plastic having excellent mechanical properties, electrical properties, and chemical properties such as chemical resistance, and is used in a wide range of applications.
• One of the known uses of polyacetal resin is as a sliding member.
• Patent Document 1 discloses a polyacetal resin composition obtained by blending 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.
• the resin composition described in Patent Document 1 is a material having excellent sliding properties.
• a resin composition capable of providing a molded product having a high PV limit value and a low dynamic friction coefficient aims to solve such problems, and to provide a resin composition capable of providing a molded article having a high PV limit value and a low dynamic friction coefficient, as well as pellets and a molded article.
• the present inventors have conducted research and found that the above problems can be solved by blending a specific silicone gum and a polyolefin-based lubricant with a polyacetal resin. Specifically, the above problems were solved by the following means. ⁇ 1> 100 parts by mass of polyacetal resin, 0.4 to 10 parts by weight of a silicone gum having a kinetic viscosity of more than 1,000,000 mm 2 /s; and 0.5 to 10 parts by mass of a polyolefin-based lubricant; 25 to 80 mass % of the polyolefin-based lubricant is an oxidatively modified polyolefin-based lubricant. Resin composition.
• a resin composition comprising a polyacetal resin, a silicone gum, and a polyolefin-based lubricant, The resin composition is molded into a cylindrical thrust test piece, and domains containing a silicone compound observed with a laser microscope have an average length L of 8.0 ⁇ m or more and an average width W of 3.0 ⁇ m or less.
• Resin composition. ⁇ 3> The resin composition according to ⁇ 1>, wherein the silicone gum contained in the resin composition has a kinetic viscosity of 5,000,000 mm 2 /s or more.
• ⁇ 4> The resin composition according to any one of ⁇ 1> to ⁇ 3>, wherein the silicone gum contained in the resin composition has a kinetic viscosity of 10,000,000 mm 2 /s or more.
• ⁇ 5> The resin composition according to any one of ⁇ 1> to ⁇ 4>, wherein the polyolefin-based lubricant contained in the resin composition includes an oxidatively modified polyolefin-based lubricant.
• ⁇ 6> The resin composition according to any one of ⁇ 1> to ⁇ 5>, wherein the proportion of the oxidized polyolefin-based lubricant in the polyolefin-based lubricant contained in the resin composition is 35 mass% or more.
• the silicone gum contained in the resin composition has a kinetic viscosity of 10,000,000 mm 2 /s or more;
• the resin composition according to any one of ⁇ 1> to ⁇ 6>, wherein the proportion of the oxidized polyolefin-based lubricant in the polyolefin-based lubricant contained in the resin composition is 35 mass% or more.
• the silicone gum contained in the resin composition has a kinetic viscosity of 10,000,000 mm 2 /s or more; ⁇ 1> to ⁇ 8>, wherein 35 mass% or more of the polyolefin-based lubricant is an oxidatively modified polyolefin-based lubricant.
• ⁇ 12> A molded article formed from the resin composition according to any one of ⁇ 1> to ⁇ 10>.
• ⁇ 13> A molded article formed from the pellets according to ⁇ 11>.
• the present invention makes it possible to provide a resin composition capable of producing molded articles with a high PV limit value and a low dynamic friction coefficient, as well as pellets and molded articles.
• the present embodiment is an example for explaining the present invention, and the present invention is not limited to the present embodiment.
• the word "to” is used to mean that the numerical values before and after it are included as the lower limit and upper limit.
• various physical properties and characteristic values are those at 23° C. unless otherwise specified. If the measurement methods, etc. described in the standards shown in this specification vary from year to year, they will be based on the standards as of January 1, 2023, unless otherwise specified.
• the resin composition of the present embodiment is characterized in that it contains 100 parts by mass of polyacetal resin, 0.4 to 10 parts by mass of silicone gum having a kinetic viscosity of more than 1,000,000 mm2 /s, and 0.5 to 10 parts by mass of polyolefin-based lubricant, and 25 to 80% by mass of the polyolefin-based lubricant is an oxidatively modified polyolefin-based lubricant.
• the silicone gum disperses in the polyacetal resin to form domains.
• Such silicone gum is stretched by the flow of the resin during injection molding of the resin composition.
• the silicone gum region is stretched to a long length, improving the limit PV value.
• the polyolefin-based lubricant contributes to improving the initial sliding properties.
• the silicone gum it is possible to improve the overall sliding properties and reduce the dynamic friction coefficient of the resulting molded product.
• the polyolefin-based lubricant that is not oxidized is likely to be present on the surface of the molded product and is likely to be removed from the molded product.
• Examples of oxyalkylene groups having 2 to 6 carbon atoms include oxyethylene groups, oxypropylene groups, and oxybutylene groups.
• the polyacetal resin used in this embodiment has a melt volume rate (MVR) measured according to ISO1133 at a temperature of 190°C and a load of 2.16 kg of preferably 0.5 cm3 /10 min or more, more preferably 0.6 cm3 /10 min or more, even more preferably 0.8 cm3 /10 min or more, even more preferably 1 cm3 /10 min or more, and even more preferably 5 cm3 /10 min or more.
• MVR melt volume rate
• polyacetal resins described in paragraphs 0018 to 0043 of JP-A-2015-074724 can be used as the polyacetal resin, 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 scrap from thermoplastic resin molding.
• the resin composition of the present embodiment preferably contains a silicone gum having a kinetic viscosity of more than 1,000,000 mm 2 /s.
• silicone gum means a liquid silicone or silicone oil having a large molecular weight. In the present embodiment, the molecular weight is defined by the kinetic viscosity.
• the resin composition of the present embodiment may contain only one type of silicone gum having a kinetic viscosity of more than 1,000,000 mm2 /s, or may contain two or more types. When two or more types are contained, it is preferable that the kinetic viscosity of the mixture is in the above range.
• the kinetic viscosity is calculated from a calibration curve of the kinetic viscosity of the silicone oil and the viscosity of the toluene solution by measuring the viscosity of a toluene solution (0.1 g/L) of each silicone gum at 25° C. using a cone-plate viscometer.
• a cone-plate type viscometer TVE-25L manufactured by Toki Sangyo Co., Ltd. can be used.
• the silicone gum used in this embodiment is a compound having a structure linked by siloxane bonds.
• the silicone gum is preferably a polyorganosiloxane, and is preferably a compound represented by -(Si(R) 2 -O)-, where R is each independently a hydrogen atom, a hydrocarbon group, -O-hydrocarbon group, or a hydroxyl group (provided that at least one of R is a hydrocarbon group or an -O-hydrocarbon group).
• Each R is preferably independently a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, -O-a hydrocarbon group having 1 to 6 carbon atoms, or a hydroxyl group, and is preferably a hydrogen atom, a methyl group, an ethyl group, a phenyl group, a methoxy group, an ethoxy group, a phenoxy group, or a hydroxyl group, more preferably a hydrogen atom, a methyl group, or a methoxy group, and even more preferably a hydrogen atom or a methyl group.
• the silicone gum may contain two or more types of —(Si(R) 2 —O)—.
• silicone gum When compounding silicone gum, it may be made into a masterbatch.
• An example of a resin used in a masterbatch is polyacetal resin.
• the proportion of silicone gum in the masterbatch is preferably 10% by mass or more, more preferably 20% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less.
• the content of the silicone gum having a kinetic viscosity of more than 1,000,000 mm2 /s in the resin composition of this embodiment is preferably 0.4 parts by mass or more, more preferably 0.6 parts by mass or more, and even more preferably 0.8 parts by mass or more, relative to 100 parts by mass of the polyacetal resin, and is preferably 10 parts by mass or less, more preferably 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, even more preferably 1.8 parts by mass or less, and even more preferably 1.5 parts by mass or less.
• the sliding properties tend to be further improved.
• the resin composition of the present embodiment may contain only one type of silicone gum having a kinetic viscosity of more than 1,000,000 mm 2 /s, or may contain two or more types. When two or more types are contained, it is preferable that the total amount is in the above range.
• the resin composition of the present embodiment contains a polyolefin-based lubricant, which improves initial sliding properties and, together with the silicone gum, reduces the dynamic friction coefficient.
• Polyolefin-based lubricants are homopolymers or copolymers of olefins. Examples of polyolefin-based lubricants include polyethylene wax, polypropylene wax, and polyethylene propylene wax, with polyethylene wax being preferred.
• the polyolefin-based lubricant may be unmodified or modified.
• the modified polyolefin-based lubricant may include vinyl ester modified polyolefin-based lubricant, acid modified polyolefin-based lubricant, oxidized polyolefin-based lubricant (oxidized modified polyolefin-based lubricant), etc., and preferably contains oxidized polyolefin-based lubricant.
• the oxidized polyolefin-based lubricant is easily mixed with polyacetal resin, and is uniformly dispersed throughout the entire molded product, which further improves the sliding property of the obtained molded product.
• the polyethylene wax may be made of an ethylene homopolymer or an ethylene- ⁇ -olefin copolymer.
• ⁇ -olefins as ethylene copolymers include ⁇ -olefins having 3 to 20 carbon atoms, such as propylene, 1-butene, isobutylene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene, and 4-methyl-1-pentene.
• the content of ethylene units in the ethylene- ⁇ -olefin copolymer wax is preferably more than 50 mol%, and more preferably 60 to 100 mol%.
• the polyethylene wax may be unmodified or modified.
• unmodified polyethylene waxes include Licowax (registered trademark) PE520, PE130, and PE190, all manufactured by Clariant Chemicals; Licocene (registered trademark) PE3101TP, PE4201, and PE5301; Ceridust (registered trademark) 3620, and 3610.
• the polypropylene wax may be made of a propylene homopolymer or a propylene- ⁇ -olefin copolymer.
• ⁇ -olefins as propylene copolymers include ⁇ -olefins having 3 to 20 carbon atoms, such as ethylene, 1-butene, isobutylene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, 1-octadecene, and 4-methyl-1-pentene.
• the content of propylene units in the propylene- ⁇ -olefin copolymer wax is preferably more than 50 mol%, and more preferably 60 to 100 mol%.
• the polypropylene wax may be unmodified or modified. Examples of unmodified polypropylene waxes include Licocene (registered trademark) PP6102, PP6502, PP7502, PP1302, PP1502, PP1602, PP2602, and PP3602 manufactured by Clariant Chemicals; Ceridust (registered trademark) 6050M, and the like.
• the resin composition of the present embodiment preferably contains an oxidized polyolefin-based lubricant.
• an oxidized polyolefin-based lubricant By containing an oxidized polyolefin-based lubricant, the initial sliding property can be further improved, and together with the silicone gum, the dynamic friction coefficient can be further reduced.
• the oxidized polyolefin lubricant can be obtained by oxidizing the corresponding unmodified polyolefin lubricant, and in this embodiment, oxidized polyethylene wax is preferred. Examples of oxidized polyethylene waxes include Licowax (registered trademark) PED521, PED522, and PED121; Ceridust (registered trademark) 3715, and the like, all of which are manufactured by Clariant Chemicals.
• the lubricant contains an oxidized polyolefin-based lubricant and an unmodified polyolefin-based lubricant, and it is more preferable that the lubricant contains an oxidized polyethylene wax and an unmodified polyethylene wax.
• the content of the oxidized polyolefin-based lubricant in the resin composition of this embodiment is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, and also preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 74% by mass or less.
• the resin composition of the present embodiment may contain only one type of oxidatively modified polyolefin-based lubricant, or may contain two or more types. When two or more types are contained, it is preferable that the total amount is in the above range.
• the molecular weight (viscosity method) of the polyolefin lubricant is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 3,000 or more, and for the unmodified polyolefin lubricant, it is more preferably 4,500 or more, even more preferably 5,000 or more, and even more preferably 6,000 or more. By making it equal to or more than the lower limit, it is possible to maintain high sliding properties without bleeding out from the molded product.
• the molecular weight (viscosity method) of the polyolefin lubricant is preferably 20,000 or less, more preferably 15,000 or less, more preferably 10,000 or less, and even more preferably 8,000 or less. By making it equal to or less than the upper limit, sliding properties tend to be further improved.
• the molecular weight of the polyolefin-based lubricant is measured according to gel permeation chromatography (viscosity method). In the case where the resin composition in this embodiment contains two or more polyolefin-based lubricants, the molecular weight is the weighted average value of the molecular weights of the respective polyolefin-based lubricants.
• the content of the polyolefin lubricant in the resin composition of this embodiment is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 1.2 parts by mass or more, even more preferably 1.4 parts by mass or more, even more preferably 1.6 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 6 parts by mass or less, even more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2.5 parts by mass or less, relative to 100 parts by mass of polyacetal resin.
• the resin composition of the present embodiment may contain only one type of polyolefin-based lubricant, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.
• the resin composition of the present embodiment may contain known additives and fillers within the scope of the present invention.
• additives and fillers that can be used in the present embodiment include 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 brighteners, release agents, antistatic agents, ultraviolet absorbers, flame retardants, and flame retardant assistants, etc., which may be added as necessary.
• the resin composition of this embodiment is adjusted so that the total of the polyacetal resin, the silicone gum with a kinetic viscosity of more than 1,000,000 mm2 /s, the polyolefin-based lubricant, and other components blended as necessary is 100 mass%.
• the total of the silicone gum with a kinetic viscosity of more than 1,000,000 mm2 /s and the polyolefin-based lubricant preferably accounts for 85 mass% or more of the resin composition, more preferably 90 mass% or more, even more preferably 95 mass% or more, and may even account for 98 mass% or more.
• the resin composition of the present embodiment is also a resin composition containing a polyacetal resin, a silicone gum, and a polyolefin-based lubricant, and the resin composition is molded into a cylindrical thrust molded piece, and the domain containing the silicone compound observed by a laser microscope preferably has an average length of 8.0 ⁇ m or more and an average width of (3.0) ⁇ m or less.
• the domain containing the silicone compound observed by a laser microscope preferably has an average length of 8.0 ⁇ m or more and an average width of (3.0) ⁇ m or less.
• the average length of the domain is preferably 8.0 ⁇ m or more, more preferably 9.0 ⁇ m or more, even more preferably 10.0 ⁇ m or more, even more preferably 11.0 ⁇ m or more, even more preferably 12.0 ⁇ m or more, and is preferably 30.0 ⁇ m or less, more preferably 25.0 ⁇ m or less, and may be 20.0 ⁇ m or less, 15.0 ⁇ m or less, or 10.0 ⁇ m or less depending on the application.
• By making it equal to or more than the lower limit it becomes possible to maintain the limit PV value high. Also, by making it equal to or less than the upper limit, it becomes possible to maintain the limit PV value high without accompanied by a decrease in toughness indicated by tensile elongation or Charpy impact value.
• the silicone gum is made into a master batch in advance, and then melt-kneaded with the remaining components.
• the kneading machine include a kneader, a Banbury mixer, and an extruder.
• Kneading is preferably performed at a temperature at which the polyacetal resin melts or higher, specifically at the melting temperature of the polyacetal resin or higher (generally 180° C. or higher).
• the resin composition of the present embodiment is preferably used for forming a sliding member, and therefore, a molded article formed from the resin composition of the present embodiment is preferably used as a sliding member (sliding part).
• the sliding members include sliding members such as gears, rotating shafts, bearings, various gears, cams, end face materials of mechanical seals, valve seats of valves, sealing members such as V-rings, rod packings, piston rings, and rider rings, rotating shafts of compressors, rotating sleeves, pistons, impellers, and rollers, which are intended to meet the high quality demands of electric/electronic devices, office equipment, vehicles (automobiles), industrial equipment, and the like.
• POM is an abbreviation for polyacetal resin.
• a cylindrical thrust test specimen was used to measure the average length and width of the domains.
• the surface of the cylindrical thrust test specimen was prepared by ultrasonic cleaning using ethanol to ensure that no impurities were attached.
• a luminance image of the surface of the cylindrical thrust test specimen was obtained using a laser microscope, and the average length and width of the domains formed from the silicone compound were evaluated using image analysis software. The conditions for capturing the luminance image and the method for analyzing the image are shown below.
• ⁇ Image analysis>> The image analysis of the photographs taken to calculate the average length and average width was performed using image analysis software (WinROOF 2018 (product name)) manufactured by Mitani Shoji Co., Ltd. The length and width of each domain and their average value were automatically calculated for all domains shown in the photograph. All image analyses were performed using the above-mentioned image analysis software in the following procedure. First, the analysis image obtained under the above conditions was read into the above image analysis software, and after conversion to a monochrome image, the scale was calibrated. The method used was to use the "manual calibration" function to align the line with the 100 ⁇ m scale bar written at the bottom of the luminance image, and to input 100 ⁇ m as the actual value.
• the entire area except for the approximately 30 ⁇ m ⁇ 740 ⁇ m area at the bottom of the captured image including the above analysis condition column was selected using a rectangular ROI, and the selected area was cut out to extract the image area.
• the box mode for setting the border processing method for the rectangular ROI was selected as "cut at the boundary and process.”
• the ROI range was selected, and a threshold value for brightness was set by discriminant analysis. Specifically, in order to distinguish between the "part to be measured” and the other "part not to be measured” based on the threshold value, binarization was performed so that pixels having a luminance of 200 or more were selected, and a closing process was performed. The number of closing processes was set to 2.
• the above process was performed, and a collection of pixels having a luminance value within the range (200-255) of the two threshold values specified in the binarization process and an area of 0.525 ⁇ m2 or more was set as the measurement target.
• "skeleton length” and “diagonal width” were selected from the "shape feature” function, and the length and width of the binarized selected region were calculated.
• the above analysis was performed for the four specified fields of view, and the average values for each field of view automatically calculated by the image analysis software were added and divided by the number of fields of view, which was four, to determine the average length and average width of the domain.
• skeleton length refers to the length of the free curve
• diagonal width refers to the shortest distance between two straight lines when a figure is sandwiched between two straight lines parallel to the absolute maximum length.
• the average value of the skeleton length calculated by the above method corresponds to the average length of the domain
• the average value of the diagonal width corresponds to the width of the domain.
• Example 4 and Comparative Example 7 Electron microscope photographs of Example 4 and Comparative Example 7 are shown in Figures 1 and 2, respectively. It can be seen that elongated domains are formed in Example 4, whereas elongated domains are not formed in Comparative Example 7.
• portion of C2 indicates the proportion (unit: mass %) of the oxidatively modified polyolefin-based lubricant in the total amount of polyolefin-based lubricant in each resin composition.
• the PV limit value was low when the sample did not contain any oxidatively modified polyolefin-based lubricant or contained only a small amount of the oxidatively modified polyolefin-based lubricant (Comparative Examples 3, 5, and 10), and when the sample did not contain any polyolefin-based lubricant (Comparative Examples 6 and 9).
• the PV limit value was also low when the sample contained a large amount of oxidatively modified polyolefin-based lubricant (Comparative Examples 2 and 4).
• silicone oil was used instead of silicone gum
• the PV limit value was further lower.
• the PV limit was particularly low.

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Citations (14)

• 2024
  • 2024-12-12 WO PCT/JP2024/043985 patent/WO2025134911A1/ja active Pending
  • 2024-12-12 JP JP2025516958A patent/JPWO2025134911A1/ja active Pending
  • 2024-12-17 TW TW113149083A patent/TW202536103A/zh unknown

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