Resin composition, molded article, and sliding member

Abstract

This resin composition does not contain any fibrous fillers and contains a liquid crystal polyester resin, a fluororesin, and an oxide of a metal element belonging to Group 2 of the long-form periodic table. The content of the metal element belonging to Group 2 with respect to 100 mass% of the total mass of the resin composition is 0.01-2.0 mass%.

Description

Resin composition, molded article, and sliding member

[0001] The present invention relates to a resin composition, a molded article, and a sliding member. This application claims priority to Japanese Patent Application No. 2023-135578, filed on August 23, 2023, the contents of which are incorporated herein by reference.

[0002] It is known that molded articles made from a resin composition containing a liquid crystal polyester resin and a fluororesin undergo little dimensional change even when a constant load is continuously applied to the molded article. Patent Document 1 discloses a liquid crystal polyester resin composition containing, per 100 parts by weight of liquid crystal polyester, 5 to 180 parts by weight of at least one compound selected from oxides, peroxides, double oxides, and carbonates of metal elements belonging to Group 1A or 2A of the short periodic table, and 0.1 to 80 parts by weight of a fluororesin.

[0003] Japanese Patent Application Publication No. 10-25402

[0004] Industrial products and their materials are sometimes transported by sea. For example, when a ship passes through the equator on its sea route, it is said that the inside of the ship's container becomes an environment with higher temperatures and humidity (for example, 40°C or higher and a relative humidity of 80% or higher) than the outside air. However, molded products using the liquid crystal polyester resin composition described in Patent Document 1 as a molding material have problems in that corrosive gases are generated from the molded products and the molded products are prone to wear under high-temperature and humid conditions, such as when a ship passes through the equator during transportation.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide a resin composition containing a liquid crystal polyester resin, which can produce a molded article that suppresses the generation of corrosive gases and maintains wear resistance, and also aims to provide a molded article containing the resin composition, and a sliding member including the molded article.

[0006] In order to solve the above problems, the present disclosure includes the following aspects.

[0007] [1] A resin composition containing a liquid crystal polyester resin, a fluororesin, and an oxide of a metal element belonging to Group 2 of the long form periodic table, and not containing a fibrous filler, wherein the content of the metal element belonging to Group 2 relative to 100% by mass of the total mass of the resin composition is 0.01% by mass or more and 2.0% by mass or less.

[0008] [2] The resin composition according to [1], wherein the content of the metal element belonging to Group 2 relative to 100 parts by mass of the fluororesin is 0.04 parts by mass or more and 8 parts by mass or less.

[0009] [3] The resin composition according to [1] or [2], wherein the content of the oxide of the metal element belonging to Group 2 relative to the total mass of the resin composition (100 mass%) is more than 0.01 mass% and less than 3.0 mass%.

[0010] [4] The resin composition according to any one of [1] to [3], wherein the content of the fluororesin relative to 100 parts by mass of the liquid crystal polyester resin is 10 parts by mass or more and 50 parts by mass or less.

[0011] [5] The resin composition according to any one of [1] to [4], wherein the metal element belonging to Group 2 is at least one selected from the group consisting of calcium and magnesium. [6] The resin composition according to [5], wherein the metal element belonging to Group 2 is calcium.

[0012] [7] The resin composition according to any one of [1] to [6], wherein the liquid crystal polyester resin has a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2), and a repeating unit represented by the following formula (3): １ -CO- (2) -CO-Ar ２ -CO- (3)-X-Ar ３ -Y- [In formulas (1) to (3), Ar １ represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar ２ and Ar ３each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group (—NH—). １ , Ar ２ or Ar ３ One or more hydrogen atoms in the group represented by the formula (4) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.] (4) -Ar ４ -Z-Ar ５ - [In formula (4), Ar ４ and Ar ５ each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group having 1 to 10 carbon atoms. ４ or Ar ５ One or more hydrogen atoms in the group represented by the formula (I) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.]

[0013] [8] A molded article comprising the resin composition according to any one of [1] to [7]. [9] A sliding member comprising the molded article according to [8].

[0014] According to the present disclosure, it is possible to provide a resin composition containing a liquid crystalline polyester resin, which can produce a molded article that suppresses the generation of corrosive gases and maintains abrasion resistance. Also, according to the present disclosure, it is possible to provide a molded article that maintains abrasion resistance under high-temperature and high-humidity conditions, and a sliding member including the molded article.

[0015] (Resin Composition) One embodiment of the resin composition is a resin composition containing a liquid crystal polyester resin, a fluororesin, and an oxide of a metal element belonging to Group 2 of the long form periodic table, and containing no fibrous filler, and in which the content of the metal element belonging to Group 2 relative to the total mass of the resin composition (100 mass%) is 0.01 mass% or more and 2.0 mass% or less.

[0016] In this specification, the term "resin composition" refers to a mixture obtained by mixing a liquid crystal polyester resin, a fluororesin, an oxide of a metal element belonging to Group 2 of the long-form periodic table, and, if necessary, other components. The resin composition may be in the form of pellets.

[0017] The resin composition in the present embodiment does not contain a fibrous filler, and therefore is unlikely to damage a mating material that comes into contact with a sliding member containing the resin composition, even if the mating material is a soft metal (for example, SUS or aluminum).

[0018] <Liquid Crystal Polyester Resin> The liquid crystal polyester resin is not particularly limited as long as it is a polyester resin that exhibits liquid crystallinity in a molten state. The liquid crystal polyester resin is preferably one that melts at a temperature of 450° C. or less.

[0019] The flow initiation temperature of the liquid crystal polyester resin is preferably 250° C. or higher, more preferably 270° C. or higher, and even more preferably 280° C. or higher. The flow initiation temperature of the liquid crystal polyester resin is preferably 400° C. or lower, more preferably 360° C. or lower, and even more preferably 340° C. or lower. For example, the flow initiation temperature of the liquid crystal polyester resin is preferably 250° C. or higher and 400° C. or lower, more preferably 270° C. or higher and 360° C. or lower, and even more preferably 280° C. or higher and 340° C. or lower.

[0020] In this specification, the flow initiation temperature of the liquid crystal polyester resin is measured by using a flow tester to test the liquid crystal polyester resin at a pressure of 9.8 MPa (100 kg / cm ２ When the liquid crystal polyester resin is melted under a load of 1000 kJ / min while being heated at a rate of 4°C / min and extruded through a nozzle having an inner diameter of 1 mm and a length of 10 mm, the liquid crystal polyester resin exhibits a viscosity of 4800 Pa·s (48,000 poise).

[0021] The liquid crystal polyester resin is preferably a wholly aromatic liquid crystal polyester having only repeating units derived from aromatic compounds.

[0022] In this specification, the term "derived from" means that during polymerization of the raw material monomer, the chemical structure of the functional group that contributes to polymerization changes, but other chemical structures do not change. The term "derived from" as used herein is a concept that also encompasses cases where the raw material monomer is derived from a polymerizable derivative thereof.

[0023] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include esters in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group; acid halides in which the carboxy group is converted to a haloformyl group; and acid anhydrides in which the carboxy group is converted to an acyloxycarbonyl group.

[0024] Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include acylated products in which the hydroxy group is acylated to convert it into an acyloxyl group, etc. Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include acylated products in which the amino group is acylated to convert it into an acylamino group, etc.

[0025] The liquid crystal polyester resin preferably has a repeating unit represented by the following formula (1) (hereinafter also referred to as "repeating unit (1)"), and more preferably has the repeating unit (1), a repeating unit represented by the following formula (2) (hereinafter also referred to as "repeating unit (2)"), and a repeating unit represented by the following formula (3) (hereinafter also referred to as "repeating unit (3)").

[0026] (1) -O-Ar １ -CO- (2) -CO-Ar ２ -CO- (3)-X-Ar ３ -Y- [In formulas (1) to (3), Ar １ represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar ２ and Ar ３ each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group (—NH—).１ , Ar ２ or Ar ３ One or more hydrogen atoms in the group represented by the formula (I) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.]

[0027] (4)-Ar ４ -Z-Ar ５ - [In formula (4), Ar ４ and Ar ５ each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group having 1 to 10 carbon atoms. ４ or Ar ５ One or more hydrogen atoms in the group represented by the formula (I) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.]

[0028] Ar １ , Ar ２ , Ar ３ , Ar ４ or Ar ５ Examples of halogen atoms that can substitute for hydrogen atoms in include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0029] Ar １ , Ar ２ , Ar ３ , Ar ４ or Ar ５ The alkyl group that can substitute for a hydrogen atom in is an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group. The alkyl group may be linear or branched.

[0030] Ar １ , Ar ２ , Ar ３ , Ar ４ or Ar ５The aryl group that can substitute for a hydrogen atom in is an aryl group having 6 to 20 carbon atoms, such as a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, or a 2-naphthyl group. The aryl group may be a monocyclic group or a condensed ring. The aryl group may also be a group in which a hydrogen atom in an aromatic ring is substituted with an alkyl group, such as a tolyl group.

[0031] Ar １ , Ar ２ , Ar ３ , Ar ４ or Ar ５ When a hydrogen atom of is substituted with the above-mentioned group, the number of substitutions is preferably one or two, and more preferably one.

[0032] The alkylidene group for Z in formula (4) is an alkylidene group having 1 to 10 carbon atoms, and examples thereof include a methylene group, an ethylidene group, an isopropylidene group, an n-butylidene group, and a 2-ethylhexylidene group.

[0033] The repeating unit (1) may be Ar １ A repeating unit in which is a 1,4-phenylene group or a repeating unit in which is a 2,6-naphthylene group is preferred.

[0034] The repeating unit (2) may be Ar ２ is preferably a repeating unit in which Ar is a 1,4-phenylene group, a 1,3-phenylene group, a 2,6-naphthylene group, a 2,7-naphthylene group, a 4,4'-biphenylylene group, or a diphenylether-4,4'-diyl group, ２ More preferred are repeating units in which R is a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthylene group.

[0035] The repeating unit (3) is Ar ３ A repeating unit in which R is a 1,4-phenylene group or a repeating unit in which R is a 4,4'-biphenylylene group is preferred.

[0036] The repeating unit (3) preferably has a repeating unit in which X and Y are each an oxygen atom, since this tends to reduce the melt viscosity of the liquid crystal polyester resin. It is more preferable that the repeating unit (3) contains only repeating units in which X and Y are each an oxygen atom.

[0037] More specifically, the liquid crystal polyester resin having the above repeating units (1) to (3) preferably has a repeating unit represented by the following formula (11) (hereinafter also referred to as "repeating unit (11)"), a repeating unit represented by the following formula (12) (hereinafter also referred to as "repeating unit (12)"), and a repeating unit represented by the following formula (13) (hereinafter also referred to as "repeating unit (13)").

[0038] (11) -O-Ar １１ -CO- (12)-CO-Ar １２ -CO- (13)-O-Ar １３ -O- [In formulas (11) to (13), Ar １１ represents a 2,6-naphthylene group or a 1,4-phenylene group. １２ represents a 2,6-naphthylene group, a 2,7-naphthylene group, a 1,4-phenylene group, a 1,3-phenylene group, a 4,4'-biphenylylene group, or a diphenylether-4,4'-diyl group. １３ represents a 1,4-phenylene group or a 4,4'-biphenylylene group. １１ , Ar １２ or Ar １３ One or more hydrogen atoms in the group represented by the formula (I) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.]

[0039] Preferred liquid crystal polyester resins having the repeating units (11) to (13) include Ar １１ A repeating unit (11) in which Ar is a 1,4-phenylene group, and １２ A repeating unit (12) in which Ar is a 1,4-phenylene group, and １２ A repeating unit (12) in which Ar is a 1,3-phenylene group, and １３ and a repeating unit (13) in which is a 4,4'-biphenylylene group.

[0040] The number of repeating units (1) is preferably 30% or more and 80% or less, more preferably 40% or more and 70% or less, and even more preferably 45% or more and 70% or less, of the total number (100%) of all repeating units constituting the liquid crystal polyester resin (hereinafter referred to as the "total number of all repeating units").

[0041] The number of repeating units (2) is preferably 10% to 35%, more preferably 15% to 30%, and even more preferably 15% to 27.5%, of the total number of all repeating units.

[0042] The number of repeating units (3) is more preferably 10% to 35%, more preferably 15% to 30%, and even more preferably 15% to 27.5%, of the total number of all repeating units.

[0043] The liquid crystal polyester resin having repeating units (1) to (3) is preferably one in which the number of repeating units (1) is 30% or more and 80% or less of the total number of all repeating units, and the number of repeating units (2) and the number of repeating units (3) are both 10% or more and 35% or less of the total number of all repeating units.

[0044] Furthermore, it is more preferable that the number of repeating units (1) is 40% or more and 70% or less of the total number of all repeating units in the liquid crystal polyester resin, and the number of repeating units (2) and the number of repeating units (3) are both 15% or more and 30% or less of the total number of all repeating units.

[0045] Furthermore, it is particularly preferred that the liquid crystal polyester resin has a number of repeating units (1) of 45% or more and 70% or less of the total number of all repeating units, and that the number of repeating units (2) and the number of repeating units (3) are both 15% or more and 27.5% or less of the total number of all repeating units.

[0046] The ratio of the content of repeating units (2) to the content of repeating units (3), expressed as [number of repeating units (2)] / [number of repeating units (3)], is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0047] The liquid crystal polyester resin may have two or more types of each of the repeating units (1), (2), and (3). The liquid crystal polyester resin may also have repeating units other than the repeating units (1), (2), and (3), but the number of such repeating units is preferably 10% or less, more preferably 5% or less, of the total number of all repeating units.

[0048] In a liquid crystal polyester resin having repeating units (1), (2), and (3), the sum of the content of repeating units (1) (the number of repeating units (1)), the content of repeating units (2) (the number of repeating units (2)), and the content of repeating units (3) (the number of repeating units (3)) does not exceed 100% of the total number of all repeating units.

[0049] In this specification, the number of each repeating unit constituting the liquid crystal polyester resin is determined by the analytical method described in JP 2000-19168 A. Specifically, the liquid crystal polyester resin is depolymerized by reacting it with a lower alcohol in a supercritical state, and the depolymerized product (monomers that derive each repeating unit) is quantified by liquid chromatography, whereby the number of each repeating unit relative to the total repeating units can be calculated.

[0050] The resin composition may contain one type of liquid crystal polyester, or may contain two or more types of liquid crystal polyesters.

[0051] The liquid crystal polyester resin can be produced by melt-polymerizing raw material monomers corresponding to the repeating units constituting the liquid crystal polyester resin, and then solid-phase polymerizing the resulting polymer. For example, it can be produced by a production method including the following acylation step and polymerization step, such as the method described in Japanese Patent No. 6439027.

[0052] In the acylation step, the phenolic hydroxyl groups of the raw material monomers are acylated with a fatty acid anhydride (e.g., acetic anhydride) to obtain an acylated product. The acylation reaction in the acylation step is preferably carried out at a temperature range of 130°C to 180°C for 30 minutes to 20 hours, more preferably at 140°C to 160°C for 1 to 5 hours. In the polymerization step, the acyl groups of the acylated product are polymerized with the carboxyl groups of the acylated products of aromatic dicarboxylic acids and aromatic hydroxycarboxylic acids to cause transesterification, thereby obtaining a liquid crystal polyester resin. The transesterification reaction in the polymerization step is preferably carried out while increasing the temperature from 130°C to 400°C at a rate of 0.1 to 50°C / min, and more preferably while increasing the temperature from 150°C to 350°C at a rate of 0.3 to 5°C / min.

[0053] <Fluororesin> In this specification, the term "fluororesin" refers to a resin containing a fluorine atom in the molecule, and includes polymers having a structural unit containing a fluorine atom. Examples of fluororesins contained in the resin composition of this embodiment include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride (PVDF), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA). Among these, the fluororesin is preferably polytetrafluoroethylene (PTFE) from the viewpoints of miscibility with liquid crystal polyester resin and excellent sliding properties and heat resistance of molded articles. The resin composition may contain one type of fluororesin, or may contain two or more types of fluororesins.

[0054] <Oxide of a Metal Element Belonging to Group 2 of the Long Periodic Table> The resin composition of this embodiment contains an oxide of a metal element belonging to Group 2 of the Long Periodic Table. Metal elements belonging to Group 2 include beryllium, magnesium, calcium, strontium, barium, and radium. An oxide of any of magnesium, calcium, strontium, barium, and radium that can react with water is preferred. In this embodiment, the metal element belonging to Group 2 is preferably at least one selected from the group consisting of calcium and magnesium, and more preferably calcium, in order to further suppress the generation of corrosive gas from the molded article. The oxide contained in the resin composition of this embodiment is preferably at least one selected from the group consisting of calcium oxide and magnesium oxide, and more preferably calcium oxide. The resin composition may contain one or more of the oxides.

[0055] The content of the liquid crystal polyester resin relative to the total mass (100 mass%) of the resin composition of this embodiment may be more than 57 mass% and less than 89.99 mass%, more than 57 mass% and less than 89.9 mass%, more than 62 mass% and less than 84.9 mass%, 67.5 mass% or more and 79.5 mass% or less, or 72.5 mass% or more and less than 75.0 mass%.

[0056] The content of the fluororesin relative to the total mass (100 mass%) of the resin composition of the present embodiment may be 10 mass% or more and 40 mass% or less, 15 mass% or more and 35 mass% or less, or 20 mass% or more and 30 mass% or less.

[0057] In this embodiment, the content of the oxide of the metal element belonging to Group 2 relative to the total mass (100 mass%) of the resin composition is preferably more than 0.01 mass% and less than 3.0 mass%, more preferably 0.1 mass% or more and less than 3.0 mass%, even more preferably more than 0.1 mass% and less than 3.0 mass%, even more preferably more than 0.1 mass% and less than 2.5 mass%, and particularly preferably 0.5 mass% or more and less than 2.5 mass%. When the content of the oxide of the metal element belonging to Group 2 is equal to or more than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when it is equal to or less than the upper limit of the preferred range, the wear resistance of the molded article is easily maintained.

[0058] Furthermore, the content of the oxide of the metal element belonging to Group 2 relative to the total mass (100 mass%) of the resin composition of this embodiment is preferably 0.1 mass% to 2 mass%, and particularly preferably 0.5 mass% to 2 mass%. When the content of the oxide of the metal element belonging to Group 2 is equal to or greater than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed. On the other hand, when the content is equal to or less than the upper limit of the preferred range, the abrasion resistance of the molded article is easily maintained under high-temperature and high-humidity conditions, and the color change of the resin composition is also less likely to occur.

[0059] The content of the metal element belonging to Group 2 relative to 100% by mass of the total mass of the resin composition of this embodiment is 0.01% by mass to 2.0% by mass, preferably 0.05% by mass to 2.0% by mass, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.3% by mass to 1.8% by mass. When the content of the metal element belonging to Group 2 is equal to or greater than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when it is equal to or less than the upper limit of the preferred range, the wear resistance of the molded article is easily maintained.

[0060] Furthermore, the content of the metal element belonging to Group 2 relative to the total mass (100 mass%) of the resin composition of this embodiment is preferably 0.05 mass% or more and 1.5 mass% or less, and particularly preferably 0.3 mass% or more and 1.5 mass% or less. When the content of the metal element belonging to Group 2 is equal to or more than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed. On the other hand, when the content is equal to or less than the upper limit of the preferred range, the abrasion resistance of the molded article is easily maintained under high-temperature and high-humidity conditions, and the appearance of the resin composition is less likely to change.

[0061] In this specification, the content of the metal element belonging to Group 2 relative to 100% by mass of the total mass of the resin composition is defined as a value measured by the following measurement method.

[0062] [Method for measuring the content of metal elements belonging to Group 2 in a resin composition] The resin composition is heated, for example, at a temperature of 500 to 700°C, and the resin component is removed. The content of metal elements in the resulting residue can be measured by a known method. A preferred method for measuring the content of metal elements is, for example, inductively coupled plasma mass spectrometry (ICP-MS), which allows for highly sensitive measurement.

[0063] In the resin composition of this embodiment, the content of the fluororesin relative to 100 parts by mass of the liquid crystal polyester resin may be 10 parts by mass or more and 50 parts by mass or less, 20 parts by mass or more and 45 parts by mass or less, or 30 parts by mass or more and 40 parts by mass or less.

[0064] In the resin composition of this embodiment, the content of the oxide of the metal element belonging to Group 2 relative to 100 parts by mass of the liquid crystal polyester resin may be 0.1 parts by mass or more and 4 parts by mass or less, 0.2 parts by mass or more and 3.5 parts by mass or less, or 0.5 parts by mass or more and 3 parts by mass or less.

[0065] In the resin composition of this embodiment, the content of the metal element belonging to Group 2 relative to 100 parts by mass of the liquid crystal polyester resin may be 0.05 parts by mass or more but less than 3 parts by mass, 0.2 parts by mass or more but 2.5 parts by mass or less, or 0.4 parts by mass or more but 2 parts by mass or less. When the content of the metal element belonging to Group 2 is equal to or more than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when it is equal to or less than the upper limit of the preferred range, the color change of the resin composition is more unlikely to occur under high-temperature and high-humidity conditions.

[0066] In the resin composition of this embodiment, the content of the oxide of the metal element belonging to Group 2 relative to 100 parts by mass of the fluororesin may be 0.3 parts by mass or more but less than 12 parts by mass, 0.5 parts by mass or more but 11 parts by mass or less, or 1 part by mass or more but 10 parts by mass or less. When the content of the oxide of the metal element belonging to Group 2 is equal to or more than the lower limit of the above-mentioned preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when it is equal to or less than the upper limit of the above-mentioned preferred range, the wear resistance of the molded article is easily maintained.

[0067] Furthermore, in the resin composition of this embodiment, the content of the oxide of the metal element belonging to Group 2 relative to 100 parts by mass of the fluororesin is preferably 0.4 parts by mass to 9 parts by mass, and particularly preferably 1.5 parts by mass to 9 parts by mass. When the content of the oxide of the metal element belonging to Group 2 is equal to or greater than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when the content is equal to or less than the upper limit of the preferred range, the abrasion resistance of the molded article is easily maintained under high-temperature and high-humidity conditions, and the appearance of the resin composition is less likely to change.

[0068] In the resin composition of this embodiment, the content of the metal element belonging to Group 2 relative to 100 parts by mass of the fluororesin is preferably 0.04 parts by mass to 8 parts by mass, more preferably 0.2 parts by mass to 8.5 parts by mass, even more preferably 0.4 parts by mass to 8 parts by mass, and particularly preferably 1 part by mass to 7.5 parts by mass. When the content of the metal element belonging to Group 2 is equal to or greater than the lower limit of the preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when it is equal to or less than the upper limit of the preferred range, the wear resistance of the molded article is easily maintained.

[0069] Furthermore, in the resin composition of this embodiment, the content of the metal element belonging to Group 2 relative to 100 parts by mass of the fluororesin is preferably 0.2 parts by mass or more and 6 parts by mass or less, and particularly preferably 1.4 parts by mass or more and 6 parts by mass or less. When the content of the metal element belonging to Group 2 is equal to or more than the lower limit of the above-mentioned preferred range, the generation of corrosive gas from the molded article is easily suppressed, while when the content is equal to or less than the upper limit of the above-mentioned preferred range, the abrasion resistance of the molded article is easily maintained under high-temperature and high-humidity conditions, and the appearance of the resin composition is less likely to change.

[0070] In the resin composition of this embodiment, the contents of the liquid crystal polyester resin, the fluororesin, and the oxide of the metal element belonging to Group 2 of the long periodic table can be adjusted to the above-mentioned contents by adjusting the blending amount of each raw material when preparing the resin composition. In the resin composition of this embodiment, the contents of the metal element belonging to Group 2 can be controlled to the above-mentioned preferred contents by adjusting the blending amount of the corresponding metal element oxide belonging to Group 2 when preparing the resin composition.

[0071] <Fibrous Filler> The resin composition of this embodiment does not contain a fibrous filler. In this specification, the phrase "does not contain a fibrous filler" means that the content of the fibrous filler is 0% by mass or more and 1% by mass or less, and preferably 0% by mass, relative to 100% by mass of the total mass of the resin composition.

[0072] The fibrous filler may be an inorganic filler or an organic filler. Examples of the fibrous inorganic filler include glass fiber, modified cross-section glass fiber, carbon fiber, silica fiber, alumina fiber, ceramic fiber, metal fiber, silicon carbide fiber, or whisker. Examples of the fibrous organic filler include polyester fiber, para- or meta-aramid fiber, and polyparaphenylene benzobisoxazole (PBO) fiber.

[0073] <Other Components> The resin composition of this embodiment may optionally contain other components in addition to the liquid crystal polyester resin, fluororesin, and oxide of a metal element belonging to Group 2 of the long periodic table described above. Examples of other components include fillers other than fibrous fillers, other resins other than the liquid crystal polyester resin and fluororesin, flame retardants, conductivity imparting agents, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration dampers, antibacterial agents, insect repellents, deodorizers, color inhibitors, heat stabilizers, release agents, antistatic agents, plasticizers, lubricants, dyes, foaming agents, foam control agents, viscosity modifiers, surfactants, etc.

[0074] <Fillers> Examples of fillers other than fibrous fillers include plate-like fillers, spherical fillers, and powder fillers. Examples of plate-like fillers include talc, mica, glass flakes, and graphite. The plate-like fillers may be surface-treated or untreated. Examples of mica include natural mica such as muscovite, phlogopite, fluorphlogopite, and tetrasilicic mica, as well as artificially produced synthetic mica. Examples of spherical fillers include glass beads and glass balloons. Examples of powder fillers include calcium carbonate, dolomite, clay barium sulfate, titanium oxide, carbon black, conductive carbon, and fine silica. The resin composition of this embodiment may contain fillers other than fibrous fillers, but preferably does not contain fillers other than fibrous fillers from the viewpoint of preventing damage to the mating material with which the sliding member comes into contact. In this specification, "containing no filler other than fibrous filler" means that the content of the filler is 0% by mass or more and 1% by mass or less relative to 100% by mass of the total mass of the resin composition.

[0075] <<Other Resins Other Than Liquid Crystal Polyester Resin and Fluorine Resin>> Examples of other resins include polyolefin resins, vinyl resins, polystyrene resins, polyamide resins, polyester resins, polysulfone resins, polyphenylene sulfide, polyether ketone, polycarbonate, polyphenylene ether, and polyimide resins.

[0076] In the resin composition of this embodiment, the content of other resins other than the liquid crystal polyester resin and the fluororesin relative to the total mass of the resin composition (100 mass%) is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 1 mass% or less. It is particularly preferable that the resin composition of this embodiment does not contain other resins.

[0077] In the resin composition of this embodiment, the content of the metal element belonging to Group 2 is 0.01% by mass or more relative to 100% by mass of the total mass of the resin composition, thereby suppressing the generation of corrosive gas from the molded article. In addition, the content of the metal element belonging to Group 2 is 2.0% by mass or less, thereby providing a molded article that maintains wear resistance, particularly under high-temperature and high-humidity conditions.

[0078] The corrosive gases generated from the molded article are believed to be due to the thermal decomposition of the resin composition when molding is carried out at temperatures exceeding 300°C, and have been confirmed to be mainly acetic acid, phenol, aromatic ester, etc. It is presumed that the oxides of the metal elements belonging to Group 2 in the resin composition act as basic compounds and exhibit the effect of capturing mainly acetic acid, thereby suppressing the generation of corrosive gases from the molded article.

[0079] The presence of hydroxides of metal elements belonging to Group 2 in the resin composition may affect the stability of the structure constituting the molded article, resulting in deterioration of abrasion resistance and color changes, so the content of such hydroxides is preferably small. The content of hydroxides of metal elements belonging to Group 2 is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and even more preferably 0.3% by mass or less, relative to the total mass of the resin composition (100% by mass). For example, the content of hydroxides of metal elements belonging to Group 2 may be 0% by mass or more and 0.4% by mass or less, or 0.1% by mass or more and 0.3% by mass or less, relative to the total mass of the resin composition (100% by mass).

[0080] In addition, in the resin composition of the present embodiment, by controlling the upper limit of the content of the metal element belonging to Group 2, the color difference ΔE of the resin composition can be kept small under high temperature and high humidity conditions, making it difficult for color changes to occur.

[0081] (Molded Article) One embodiment of the molded article is a molded article containing the resin composition of the above-described embodiment. The molded article of this embodiment can be obtained by a known molding method using the resin composition. As a molding method using the resin composition of the above-described embodiment, a melt molding method is preferred, and examples thereof include injection molding, extrusion molding such as a T-die method and an inflation method, compression molding, blow molding, vacuum molding, and press molding. Among these, injection molding is preferred.

[0082] For example, a molded article can be obtained by melting the resin composition of the embodiment using a known injection molding machine and injecting the molten resin composition into a mold. Examples of known injection molding machines include the TR450EH3 manufactured by Sodick Co., Ltd. and the PS40E5ASE and ES400 hydraulic horizontal molding machines manufactured by Nissei Plastic Industrial Co., Ltd.

[0083] Regarding the temperature conditions for injection molding, the cylinder temperature of the injection molding machine is preferably set to a temperature 10 to 80°C higher than the flow initiation temperature of the resin composition used. The temperature of the mold is preferably set in the range of 25°C to 180°C, taking into account the time required to cool the resin composition and productivity. Other injection conditions such as the screw rotation speed, back pressure, injection speed, dwell pressure, and dwell time may be appropriately adjusted.

[0084] The molded article of the present embodiment uses the resin composition described above, and therefore maintains wear resistance in high-temperature environments and suppresses the generation of corrosive gases. The molded article of the present embodiment is useful for, for example, damper rings, oil seals, piston rings, etc.

[0085] (Slide member) One embodiment of the slide member is a slide member including the molded article of the above-described embodiment. The slide member of this embodiment is suitable for, for example, dampers and bearings, and is particularly suitable as an automobile part from the viewpoints that wear resistance is maintained and generation of corrosive gas is suppressed.

[0086] The present disclosure will be described below with reference to examples, but the present disclosure is not limited to these examples.

[0087] [Measurement of the Content of Metal Elements Belonging to Group 2 in Resin Composition] The content of metal elements in the resin composition was determined by heating the resin composition at 600°C and measuring the resulting residue by inductively coupled plasma mass spectrometry (ICP-MS).

[0088] [Measurement of Flow Initiation Temperature of Liquid Crystal Polyester Resin and Pellets] A liquid crystal polyester resin and a pellet-shaped resin composition were used as samples. First, using a flow tester ("CFT-500" manufactured by Shimadzu Corporation), about 2 g of the sample was filled into a cylinder equipped with a die having a nozzle with an inner diameter of 1 mm and a length of 10 mm. Next, the sample was subjected to a pressure of 9.8 MPa (100 kg / cm ２ The sample was melted and extruded from the nozzle while being heated at a rate of 4°C / min under a load of 1000 kJ / min, and the temperature at which the sample showed a viscosity of 4800 Pa·s (48000 poise) was measured and defined as the flow initiation temperature of the sample.

[0089] [Measurement of Lightness and Chromaticity of Pellets] Using a color difference meter ("CM-3600A" manufactured by Konica Minolta, Inc.), the lightness (L*: SCE method) and chromaticity (a*, b*: SCE method) of the pellets were measured according to the L*a*b* color system without UV blocking under the conditions of an illumination and light-receiving optical system D65, a C light source, an observation field of view of 10°, and a measurement diameter of 25.4 mm.

[0090] [Measurement of the amount of acetic acid generated from pellets] 4 g of pellets of the liquid crystal polyester resin composition were weighed out, washed with distilled water, and placed in a vacuum-dried 25 cc vial. The vial was sealed with a polytetrafluoroethylene packing and then heated for 20 hours in a hot air dryer set at 150°C. The sealed vial was attached to a headspace gas chromatograph (GC-15A / HSS-3A) manufactured by Shimadzu Corporation. After the vial was kept at 150°C for 1 hour, the vial was injected into a 15 m column containing DBWAX (manufactured by J&W SCIENTIFIC) as a packing material. Simultaneously with the injection of the vial, the column temperature was raised from 80°C at 2°C / min, and the gas was detected with a detector up to a retention time of 25 minutes. An FID type detector was used, and helium was used as the carrier gas. From the detected gas peaks, the amount of acetic acid generated in the gas generated from the pellets was calculated using the peak at the retention time of acetic acid, which had been confirmed in advance using a standard substance, as a reference.

[0091] [Measurement of surface roughness Ra and wear amount of molded product] The surface roughness Ra of the molded product defined in JIS B0601-2001 was measured using a 3D scanner-type three-dimensional measuring machine (manufactured by KEYENCE). Measurements were performed at at least four different positions for one molded product, and the arithmetic mean value was calculated. For the molded products whose surface roughness Ra was measured, the wear amount of each molded product was determined by the sliding test shown below using a Suzuki friction and wear tester (manufactured by A&D Co., Ltd., EFM-3-H-S) (ring-on-disc).

[0092] Sliding test: A silicone oil having a kinematic viscosity of 450 to 600 Pa s at 25°C was applied to the molded product, a metal ring was placed on the molded product, and the molded product was rotated at 123 rpm in a constant temperature bath at 120°C with a load of 105 N applied to the metal ring for 24 hours.

[0093] The specific test conditions were as follows: Metal ring: SUS304 (Ra: 0.02 mm or less) Rotation speed of molded product: 0.15 m / s Measurement temperature: 120°C Contact area between metal ring and molded product: 2.0 cm ２

[0094] After the sliding test, the molded product was removed and cooled to room temperature. After the cooling, the silicone oil adhering to the molded product surface was wiped off, and the maximum surface roughness Rt of the sliding surface as defined in JIS B0601-2001 was measured using a 3D scanner-type coordinate measuring machine (manufactured by KEYENCE Corporation). Measurements were performed at at least four different positions for each molded product, and the arithmetic mean value was calculated. The wear amount of the molded product was calculated using the following formula.

[0095] Wear amount of molded product (m ３ / m) = {maximum surface roughness Rt (μm) x 2.0 (cm ２ ) x 10 －６ (m / μm) × 10 －４ (m ２ / cm ２ )} / {0.15 (m / s) x 24 (h) x 3600 (s / h)})

[0096] In the above sliding test, the larger the maximum surface roughness after the test, the deeper the abrasion, so the maximum surface roughness Rt (μm) is used as the standard for the amount of wear of the molded product. ２) refers to the contact area between the metal ring and the molded product, and the numerator in the above formula, which is the product of this contact area and the maximum surface roughness Rt, represents the actual volume of the molded product that has been worn. The x10 to the -6th power and x10 to the -4th power in the numerator of the above formula are multiplications for unit conversion. Since the amount of wear of the molded product depends on the test distance (i.e., the total length of contact between the molded product and the metal ring due to rotation), the above formula normalizes it by dividing by the test distance. In the sliding test, the molded product was rotated for 24 hours at a rotation speed of 0.15 (m / s), and the denominator in the above formula represents the total length of contact between the molded product and the metal ring due to continuous rotation for 24 hours.

[0097] The amount of wear of a molded product is a value that serves as an index of sliding properties. The smaller this value, the better the sliding properties.

[0098] Liquid Crystal Polyester Resin Used Production of Liquid Crystal Polyester Resin (LCP): A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 994.5 g (7.2 mol) of p-hydroxybenzoic acid, 299.0 g (1.8 mol) of terephthalic acid, 99.7 g (0.6 mol) of isophthalic acid, 446.9 g (2.4 mol) of 4,4'-dihydroxybiphenyl, and 1347.6 g (13.2 mol) of acetic anhydride. The gas in the reactor was replaced with nitrogen gas, and then 0.18 g of 1-methylimidazole was added. The mixture was heated from room temperature to 150°C over 30 minutes with stirring under a nitrogen gas stream, and refluxed at 150°C for 30 minutes. Next, 2.4 g of 1-methylimidazole was added, and the temperature was raised from 150°C to 320°C over 2 hours and 50 minutes while distilling off by-product acetic acid and unreacted acetic anhydride. When an increase in torque was observed, the contents were removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a grinder and, under a nitrogen gas atmosphere, the temperature was raised from room temperature to 250°C over 1 hour, then from 250°C to 295°C over 5 hours, and held at 295°C for 3 hours to cause solid-state polymerization. After cooling, a powdered liquid crystal polyester resin (LCP) was obtained. The flow initiation temperature of the resulting liquid crystal polyester resin (LCP) was 327°C.

[0099] Fluorine resin used: Polytetrafluoroethylene (product name "Dyneon (registered trademark) TF9205" manufactured by 3M Japan Ltd.).

[0100] Oxides of metal elements belonging to Group 2 of the long-form periodic table: calcium oxide (trade name "VESTA PP" manufactured by Inoue Lime Industry Co., Ltd., particle size 12 μm) and magnesium oxide (trade name "Kyowamag 150" manufactured by Kyowa Chemical Industry Co., Ltd., particle size 6.9 μm).

[0101] - Hydroxide of metal elements: Calcium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0102] <Production of pellet-shaped resin composition> (Examples 1 to 7, Comparative Examples 1 to 4) A liquid crystal polyester resin composition obtained by mixing each component in the proportions shown in Table 1 was supplied to a co-rotating twin-screw extruder having a screw diameter of 30 mm ("PCM-30" manufactured by Ikegai Iron Works Co., Ltd.), melt-kneaded, and pelletized to obtain a pellet-shaped resin composition for each example.

[0103] <<Measurement of Pellet-Shaped Resin Composition>> Immediately after production, the flow initiation temperature (°C) and the amount of corrosive gas generated (ppm) of the pellet-shaped resin composition of each example were measured. The measurement results are shown in Table 1. In addition, the brightness and chromaticity of the pellet-shaped resin composition of each example were measured immediately after production.

[0104] Next, approximately 10 g of the pellet-shaped resin composition of each example immediately after production was stored for 500 hours in a thermo-hygrostat (PJ-2L manufactured by Espec Corporation) at a temperature of 40°C and a relative humidity of 90%RH. After this, the flow initiation temperature (°C) and the brightness and chromaticity of the pellet-shaped resin composition of each example were measured in the same manner as before storage.

[0105] The amount of corrosive gas generated was evaluated by measuring the amount of acetic acid generated from the pellet-shaped resin composition. The change in color of the pellet-shaped resin composition was evaluated by calculating the color difference ΔE (SCE method) from the measured values ​​before and after storage. These results are shown in Table 1.

[0106] The color difference ΔE is defined by the following formula: ΔE={(ΔL*) ２ + (△a*)２ + (△b*) ２} １／２ Here, ΔL*, Δa*, and Δb* are the differences in the measured values ​​of L*, a*, and b* before and after storage, respectively.

[0107] <Production of molded article> The pellet-shaped resin composition of each example obtained above was placed in an injection molding machine ES400 (manufactured by Nissei Plastic Industrial Co., Ltd.) with a cylinder temperature of 340°C, and injected into a mold with a mold temperature of 130°C at an injection speed of 40 mm / s, a screw rotation speed of 100 rpm, a holding pressure of 50 MPa, and a back pressure of 3 MPa, to produce an injection-molded test piece of 64 mm × 64 mm × 3 mm thick as a molded article.

[0108] <Evaluation of Molded Articles> The surface roughness Ra of the molded articles prepared in the above <Production of Molded Articles> immediately after production was measured. The molded articles were cut into 35 mm x 35 mm x 3 mm thick pieces, and the amount of wear of the molded articles was measured. The results of these measurements are shown in Table 1. The cut molded articles were dried at 120°C for 5 hours or more to remove moisture, and then the weights of the molded articles were measured.

[0109] Next, the cut molded product was stored for 500 hours in a thermo-hygrostat (PJ-2L manufactured by Espec Corporation) at a temperature of 40°C and a relative humidity of 90%RH. After this, the surface roughness Ra (μm) and the wear amount (m ３ / m) were measured. These results are shown in Table 1. After storage, the weight of each molded article was measured. Then, the water absorption rate (%) of the molded article was calculated based on the change in weight before and after storage using the following formula. These results are shown in Table 1. Water absorption rate (%) of molded article = {(weight of molded article after storage - weight of molded article before storage) / (weight of molded article before storage)} x 100

[0110]

[0111] From the results shown in Table 1, it was confirmed that the resin compositions of Examples 1 to 7, in which the content of metal elements belonging to Group 2 was 0.01 mass% or more and 2.0 mass% or less relative to 100 mass% of the total mass of the resin composition, suppressed the generation of corrosive gases and produced molded articles that maintained their abrasion resistance under high-temperature and high-humidity conditions.

[0112] Furthermore, it was also confirmed that the resin compositions of Examples 1 to 5 and 7, in which the content of the metal element belonging to Group 2 was 0.05 mass% or more and 1.5 mass% or less relative to the total mass (100 mass%) of the resin composition, had a small color difference ΔE under high temperature and high humidity conditions and were less likely to undergo color change.

[0113] The resin composition of Comparative Example 1, which did not contain any metal element belonging to Group 2, resulted in a large amount of corrosive gas generation. The resin compositions of Comparative Examples 2 to 4, in which the content of metal elements belonging to Group 2 exceeded 2 mass% relative to 100 mass% of the total mass of the resin composition, showed a large color difference ΔE under high-temperature and high-humidity conditions, were prone to color change, and the abrasion resistance of the molded product was poor.

[0114] The resin composition of the present invention can produce a molded article that suppresses the generation of corrosive gases, suppresses changes in appearance even under high-temperature and high-humidity conditions, and maintains abrasion resistance. The molded article of the present invention and a sliding member containing the molded article also suppress changes in appearance even under high-temperature and high-humidity conditions, and maintains abrasion resistance.

Claims

1. A resin composition comprising a liquid crystal polyester resin, a fluororesin, and an oxide of a metal element belonging to Group 2 of the long form periodic table, and not containing a fibrous filler, wherein the content of the metal element belonging to Group 2 relative to the total mass of the resin composition (100 mass%) is 0.01 mass% or more and 2.0 mass% or less.

2. The resin composition according to claim 1, wherein the content of the metal element belonging to Group 2 is 0.04 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the fluororesin.

3. A resin composition according to claim 1 or 2, wherein the content of the oxide of the metal element belonging to Group 2 is more than 0.01 mass% and less than 3.0 mass% relative to 100 mass% of the total mass of the resin composition.

4. The resin composition according to claim 1, wherein the content of the fluororesin is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the liquid crystal polyester resin.

5. The resin composition according to claim 1, wherein the metal element belonging to Group 2 is at least one selected from the group consisting of calcium and magnesium.

6. The resin composition according to claim 5, wherein the metal element belonging to the second group is calcium.

7. The resin composition according to claim 1, wherein the liquid crystal polyester resin has a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2), and a repeating unit represented by the following formula (3): (1) -O-Ar １ -CO- (2) -CO-Ar ２ -CO- (3)-X-Ar ３ -Y- [In formulas (1) to (3), Ar １ represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar ２ and Ar ３ each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group (-NH-). １ , Ar ２ Or Ar ３ One or more hydrogen atoms in the group represented by the formula (4) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. ４ -Z-Ar ５ - [In formula (4), Ar ４ and Ar ５ each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group having 1 to 10 carbon atoms. ４ Or Ar ５ One or more hydrogen atoms in the group represented by the formula (I) may be substituted, independently of one another, with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.] 8. A molded article comprising the resin composition according to claim 1.

9. A sliding member comprising the molded article according to claim 8.

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