Resin composition and molded article

Abstract

Provided are a resin composition and molded article having excellent slidability, high tensile fracture nominal strain, and excellent heat aging resistance. This resin composition includes, with respect to 100 parts by mass of polyacetal resin (A), 0.1-50 parts by mass of an acid-modified olefin polymer (B) having an acid value of 1.0-30.0 mgKOH / g, and 0.01-5 parts by mass of a compound (C) containing two or more primary amino groups and / or secondary amino groups in total, said compound being selected from a dihydrazone compound, dihydrazide compound, urea compound, and melamine compounds. The ratio (B) / (C) of the acid-modified olefin polymer (B) to the amino group-containing compound (C) is 20-200.

Description

[Technical Field]

[0001] The present invention relates to resin compositions and molded articles. In particular, it relates to resin compositions and molded articles containing polyacetal resin and exhibiting excellent sliding properties.

[0002] The use of polyacetal resin in sliding components has been considered for some time. For example, Patent Document 1 contains: (A) 100 parts by mass of polyacetal resin; (B) 0.01 parts by mass or more and 1 part by mass of a hindered phenol-based antioxidant; (C) 0.05 parts by mass or more and 1 part by mass of a nitrogen-containing compound; (D) 0.5 parts by mass or more and 10 parts by mass of a modified olefin polymer obtained by modifying an olefin polymer with at least one selected from unsaturated carboxylic acids, acid anhydrides of the unsaturated fatty acids, and derivatives thereof; (E) 0.01 parts by mass or more and 5 parts by mass of an alkylene glycol polymer having a primary amino group or a secondary amino group and a number average molecular weight of 400 or more and 500,000 or less; and (F) a BET specific surface area of ​​15 m². 2 A polyacetal resin composition is disclosed that contains 0.1 to 20 parts by mass of calcium carbonate which is less than or equal to / g, has an average particle size of 50 nm to 200 nm, is surface untreated, and is substantially cubic; (G) 0.1 to 10 parts by mass of a partial ester of a polyhydric alcohol which is divalent to tetravalent; and (H) 0.1 to 10 parts by mass of an alpha-olefin oligomer.

[0003] Furthermore, Patent Document 2 discloses a polyacetal resin composition obtained by melt-kneading (A) 100 parts by mass of polyacetal resin, (B) 0.5 to 100 parts by mass of a modified olefin polymer (B-1) obtained by modifying an olefin polymer (B-1) with at least one selected from the group consisting of unsaturated carboxylic acids, their acid anhydrides and derivatives thereof (B-2), and (C) 0.1 to 20 parts by mass of an inorganic filler.

[0004] Furthermore, Patent Document 3 discloses a polyacetal resin composition comprising (A) 100 parts by mass of polyacetal resin, (B) 0.1 to 50 parts by mass of an olefin polymer, (C) 0.1 to 15 parts by mass of polyethylene wax having an acid value of 1 mg KOH / g or more, and (D) 0.05 to 20 parts by mass of calcium carbonate. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-069451 [Patent Document 2] Japanese Patent Application Publication No. 10-130458 [Patent Document 3] Japanese Patent Publication No. 2019-006974 [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, resin compositions with excellent sliding properties using polyacetal resin are well known. However, in recent years, sliding components have become more diverse, and the required performance has also become more diverse, creating a demand for new resin compositions with excellent sliding properties. In particular, depending on the application, high tensile fracture strain and heat aging resistance are required. The present invention aims to solve these problems and to provide a resin composition and molded article that exhibits excellent sliding properties, high tensile fracture strain, and excellent heat aging resistance. [Means for solving the problem]

[0007] Based on the above problems, the inventors conducted investigations and found that the above problems can be solved by adjusting the amount of acid modification of the olefin polymer, using it in combination with a predetermined amine compound, and adjusting the ratio thereof. Specifically, the above problem was solved by the following means. <1> (A) Per 100 parts by mass of polyacetal resin, (B) 0.1 to 50 parts by mass of an acid-modified olefin polymer having an acid value of 1.0 to 30.0 mgKOH / g, (C) comprising 0.01 to 5 parts by mass of a compound selected from dihydrazone compounds, dihydrazide compounds, urea compounds, and melamine compounds, which contains a total of two or more primary amino groups and / or secondary amino groups, The ratio (B) / (C) of the acid-modified olefin polymer to (C) the amino group-containing compound is 20 to 200. Resin composition. <2> Furthermore, (D) hydrocarbon wax is included in an amount of 0.01 to 15.0 parts by mass per 100 parts by mass of the polyacetal resin. <1> The resin composition described above. <3> The melt viscosity of the hydrocarbon wax (D) is measured at 140°C using a B-type viscometer and is between 15 and 6000 mPa·s. <2> The resin composition described above. <4> The above (B) acid-modified olefin polymer has a Vicat softening temperature of 20°C or higher according to JIS K7206. <1> ~ <3> A resin composition as described in any one of the following. <5> The (B) acid-modified olefin polymer includes an acid-modified olefin polymer modified with at least one unsaturated carboxylic acid and its anhydride. <1> ~ <4> A resin composition as described in any one of the following. <6> The olefin polymer constituting the acid-modified olefin polymer (B) is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer. <1> ~ <5> A resin composition as described in any one of the following. <7> The olefin polymer constituting the acid-modified olefin polymer (B) includes an ethylene-butene copolymer. <1> ~ <5> A resin composition as described in any one of the following. <8> The compound (C) containing a total of two or more primary amino groups and / or secondary amino groups is included in 0.01 to 2 parts by mass per 100 parts by mass of polyacetal resin. <1> ~ <7> A resin composition as described in any one of the following. <9> For forming sliding members, <1> ~ <8> A resin composition as described in any one of the following. A molded article formed from the resin composition according to any one of <10><1> to <9>. The molded article according to <10>, which is a sliding member.

Advantages of the Invention

[0008] According to the present invention, it has become possible to provide a resin composition and a molded article that are excellent in slidability, have a high tensile fracture elongation, and are excellent in heat aging resistance.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram showing a sample of the measurement result using a surface roughness measuring machine.

Modes for Carrying Out the Invention

[0010] Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention, and the present invention is not limited only to the present embodiment. In this specification, "~" is used in the sense of including the numerical values described before and after it as the lower limit value and the upper limit value. In this specification, various physical property values and characteristic values are those at 23°C unless otherwise specified. In this specification, the number average molecular weight is a polystyrene conversion value measured by the GPC (gel permeation chromatography) method unless otherwise specified. When the standards shown in this specification differ depending on the year and the measurement methods, etc., they are based on the standards as of January 1, 2021 unless otherwise specified.

[0011] The resin composition of this embodiment comprises (A) 100 parts by mass of polyacetal resin, (B) 0.1 to 50 parts by mass of an acid-modified olefin polymer having an acid value of 1.0 to 30.0 mg KOH / g, and (C) 0.01 to 5 parts by mass of a compound containing a total of two or more primary amino groups and / or secondary amino groups (sometimes referred to as "a predetermined amine compound" in this specification), selected from dihydrazone compounds, dihydrazide compounds, urea compounds, and melamine compounds, wherein the ratio (B) / (C) of the acid-modified olefin polymer to the amino group-containing compound is 20 to 200. With this configuration, a resin composition with excellent sliding properties, high tensile fracture strain, and excellent heat aging resistance can be obtained. This is presumed to be due to the following mechanism: the acid present in the olefin polymer is thought to form a crosslinked structure with a predetermined amine compound. Therefore, by setting the acid value in the olefin polymer above a predetermined value, a sufficient crosslinked structure, i.e., a hard structure, can be formed with the predetermined amine compound, thereby reducing the amount of wear on the molded product. Furthermore, by setting the acid value in the olefin polymer below a predetermined value, it is thought that the formation of crosslinked structures beyond what is necessary can be made less likely. In particular, it is presumed that the tensile fracture strain can be further increased by setting the proportion of a predetermined amine compound to 2 parts by mass or less per 100 parts by mass of polyacetal resin. The details of this embodiment will be described below.

[0012] <(A) Polyacetal resin> The resin composition of this embodiment includes (A) polyacetal resin. By including polyacetal resin, a molded product with excellent sliding properties and mechanical strength can be obtained. The (A) polyacetal resin used in this embodiment has an acetal structure -(-O-CRH-) nThe polymer has a repeating structure of -(wherein R represents a hydrogen atom or an organic group), and usually has an oxymethylene group (-CH2O-) where R is a hydrogen atom as the main constituent unit. The (A) polyacetal resin used in this embodiment may include not only acetal homopolymers consisting only of this repeating structure, but also copolymers (including block copolymers) and terpolymers that contain one or more constituent units other than the oxymethylene group, and may have not only a linear structure but also branched and crosslinked structures.

[0013] Other structural units besides the oxymethylene group include, for example, branched oxyalkylene groups having 2 to 10 carbon atoms, such as oxyethylene (-CH2CH2O-), oxypropylene (-CH2CH2CH2O-), and oxybutylene (-CH2CH2CH2CH2O-). Among these, branched oxyalkylene groups having 2 to 4 carbon atoms are preferred, and oxyethylene groups are particularly preferred. The content of such oxyalkylene structural units other than the oxymethylene group is preferably 0.1 mol% to 20 mol%, and more preferably 0.1 mol% to 15 mol% in the polyacetal resin.

[0014] The method for producing the (A) polyacetal resin used in this embodiment is arbitrary and can be any conventionally known method. For example, a polyacetal resin having an oxymethylene group and an oxyalkylene group having 2 to 4 carbon atoms as constituent units can be produced by copolymerizing a cyclic oligomer of an oxymethylene group, such as a trimer (trioxane) or tetramer (tetraoxane) of formaldehyde, with a cyclic oligomer containing an oxyalkylene group having 2 to 4 carbon atoms, such as ethylene oxide, 1,3-dioxolane, 1,3,6-trioxocane, or 1,3-dioxepane.

[0015] In particular, the (A) polyacetal resin used in this embodiment is preferably a copolymer of a cyclic oligomer such as trioxane or tetraoxane with ethylene oxide and / or 1,3-dioxolane, and especially preferably a copolymer of trioxane and 1,3-dioxolane. In this case, it is preferable that the total amount of ethylene oxide and / or 1,3-dioxolane is 1 to 20% by mass, relative to 80 to 99% by mass of the cyclic oligomer. (A) The melt flow rate (MFR) of the polyacetal resin is arbitrary, but according to ASTM-D1238, the value measured at 190°C under a 2.16 kg load is usually 0.01 to 150 g / 10 min, preferably 0.1 to 100 g / 10 min, more preferably 1 to 70 g / 10 min, even more preferably 1 to 40 g / 10 min, and most preferably 1 to 30 g / 10 min.

[0016] The resin composition of this embodiment preferably contains (A) polyacetal resin in an amount of 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. The upper limit is when the entire amount other than the acid-modified olefin polymer and the predetermined amine compound is (A) polyacetal resin. The resin composition of this embodiment may contain only one type of (A) polyacetal resin, or it may contain two or more types. If it contains two or more types, it is preferable that the total amount is within the above range.

[0017] <(B) Acid-modified olefin polymer> The resin composition of this embodiment contains (A) 100 parts by mass of polyacetal resin and (B) 0.1 to 50 parts by mass of an acid-modified olefin polymer having an acid value of 1.0 to 30.0 mgKOH / g. By including the acid-modified olefin polymer, molded articles with excellent sliding properties and mechanical strength can be obtained. (B) The acid value in the acid-modified olefin polymer is preferably 2.0 mg KOH / g or higher, more preferably 5.0 mg KOH / g or higher, even more preferably 8.0 mg KOH / g or higher, even more preferably 10.0 mg KOH / g or higher, and even more preferably 12.0 mg KOH / g or higher. Setting it above the lower limit tends to further improve sliding properties. Also, (B) the acid value in the acid-modified olefin polymer is preferably 25.0 mg KOH / g or lower, and more preferably 20.0 mg KOH / g or lower. Setting it below the upper limit tends to further improve tensile fracture strain. Here, the acid value is the sum of the values ​​obtained by multiplying the acid value of each olefin polymer by the proportion (mass) of each olefin polymer in the mixture, when two or more olefin polymers are included. The same applies to molecular weight and melt flow rate (MFR), which will be discussed later.

[0018] The olefin polymer constituting the (B) acid-modified olefin polymer used in this embodiment can be any known polymer. The olefin polymer is preferably selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer, and more preferably contains an ethylene-butene copolymer. In this embodiment, (B) the acid-modified olefin polymer has a number-average molecular weight of 1 × 10 4 It is preferable that the above is true, 2 × 10 4 It is more preferable that it be greater than or equal to 50 × 10 4 The following is preferable: By using a number-average molecular weight above the lower limit, a harder molded product can be formed, and the sliding properties of the resulting molded product can be further improved. Furthermore, by using a number-average molecular weight below the upper limit, uniform dispersion can be achieved during shearing during kneading, and a decrease in mechanical properties tends to be suppressed. Furthermore, according to ASTM-D1238, the melt flow rate (MFR) measured at 190°C and a load of 2.16 kg is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 15 g / 10 min or less, and may also be 10 g / 10 min or less, or 5 g / 10 min or less. By setting it below the upper limit, a harder molded product can be formed, and the sliding properties of the resulting molded product tend to improve. The lower limit of the melt flow rate (MFR) can be, for example, 0.1 g / 10 min or more. By setting it above the lower limit, uniform dispersion can be achieved during shearing during kneading, and a decrease in mechanical properties can be effectively suppressed.

[0019] The olefin polymer in this embodiment is preferably an acid-modified olefin polymer modified with at least one unsaturated carboxylic acid and its anhydride, and more preferably an acid-modified olefin polymer modified with at least one anhydride of an unsaturated carboxylic acid (preferably maleic anhydride). Examples of unsaturated carboxylic acids include maleic acid, acrylic acid, methacrylic acid, maleic acid, citraconic acid, itaconic acid, tetrahydrophthalic acid, nadic acid, methylnadic acid, and allyl succinic acid, with maleic acid being preferred. Details of modified olefin polymers modified with at least one unsaturated carboxylic acid and its anhydride can be found in paragraph 0005 of Japanese Patent Publication No. 10-130458, and these contents are incorporated herein by reference.

[0020] In this embodiment, the (B) acid-modified olefin polymer preferably has a Vicat softening temperature of 20°C or higher, and more preferably 23°C or higher, according to JIS K7206. The Vicat softening temperature is an indicator of the temperature at which thermoplastics begin to soften rapidly, and is an indicator of short-term heat resistance. In this embodiment, by using such an acid-modified olefin resin, the crosslinked structure formed by reaction with a predetermined amine compound has excellent heat resistance during sliding. In this embodiment, the Vicat softening temperature is the Vicat softening temperature when the load is 50N and the heating rate is 50°C / hour. There is no particular upper limit for the Vicat softening temperature, but it is usually below the melting point of the polyacetal resin, and preferably 150°C or lower.

[0021] The content of (B) acid-modified olefin polymer in the resin composition of this embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of (A) polyacetal resin. Setting it above the lower limit tends to result in molded articles with better sliding properties. Furthermore, the content of (B) acid-modified olefin polymer in the resin composition of this embodiment is 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of (A) polyacetal resin. Setting it below the upper limit tends to result in improved tensile fracture strain of the molded articles. The resin composition of this embodiment may contain only one type of (B) acid-modified olefin polymer, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0022] <(C) Compounds containing a total of two or more primary amino groups and / or secondary amino groups> The resin composition of this embodiment contains (A) 100 parts by mass of polyacetal resin, and (C) 0.01 to 5 parts by mass of a compound (a predetermined amine compound) selected from dihydrazone compounds, dihydrazide compounds, urea compounds, and melamine compounds, which contains a total of two or more primary amino groups and / or secondary amino groups. The (C) predetermined amine compound forms a crosslinked structure with the acid-modified olefin polymer, resulting in a molded article with excellent sliding properties. Furthermore, a molded article with excellent heat aging resistance is obtained. In this embodiment, it is presumed that the primary amine and / or secondary amine of the predetermined amine compound (C) react with the acid of the acid-modified olefin polymer. Since the predetermined amine compound (C) has two or more primary amines and / or secondary amines in one molecule, it is presumed that it forms a crosslinked structure between the acid-modified olefin polymers. As a result, the hardness of the resulting molded article is increased and the wear resistance of the molded article is improved.

[0023] (C) The specified amine compound contains a primary amino group and / or a secondary amino group, but more preferably contains at least a primary amine. The presence of a primary amine tends to facilitate the formation of crosslinked structures with the acid-modified olefin polymer. (C) The specified amine compound contains two or more primary amino groups and / or secondary amino groups in one molecule, preferably 2 to 5, more preferably 2 or 3, and even more preferably 2. (C) The molecular weight of the specified amine compound is not particularly defined, but from the viewpoint of ease of forming a crosslinked structure, it is preferably 80 to 500, and more preferably 80 to 300.

[0024] In this embodiment, (C) the predetermined amine compound is selected from dihydrazone compounds, dihydrazide compounds, urea compounds, and melamine compounds, and is preferably at least one selected from compounds containing dihydrazide compounds, urea compounds, and melamine compounds, and more preferably a dihydrazide compound.

[0025] Dihydrazone compounds can be described with reference to paragraphs 0015 to 0023 of Japanese Patent Publication No. 2022-015084, the contents of which are incorporated herein by reference.

[0026] The hydrazide compound is not particularly defined as long as it has two or more hydrazide groups. The hydrazide compound preferably has a molecular weight of 200 to 1000. Furthermore, the hydrazide compound is preferably a dihydrazide compound or a trihydrazide compound, and more preferably a dihydrazide compound. Examples of dihydrazide compounds include aliphatic dihydrazide compounds and aromatic dihydrazide compounds.

[0027] Examples of aliphatic dihydrazide compounds include carbodihydrazide, oxalate dihydrazide, malonic acid dihydrazide, succinate dihydrazide, glutarate dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacate dihydrazide, dodecandioic acid dihydrazide (1,12-dodecanedicarbohydrazide), 1,18-octadecanedicarbohydrazide, stearate dihydrazide, maleate dihydrazide, fumarate dihydrazide, and 7,11-octadecadiene-1,18-dicarbohydrazide.

[0028] Examples of aromatic dihydrazide compounds include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 1,5-naphthalenedicarbohydrazide, 1,8-naphthalenedicarbohydrazide, 2,6-naphthalenedicarbohydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, and 1,5-diphenylcarbonohydrazide.

[0029] The hydrazide compound used in this embodiment is preferably represented by the following formula (1). Formula (1) [ka] In the above equation (1), R 1represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms; R 2 ~R 5 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R 2 and R 3 , and R 4 and R 5 may be bonded to each other to form a ring.

[0030] In formula (1), R 1 represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms, preferably an aliphatic hydrocarbon group having 4 to 18 carbon atoms, more preferably an aliphatic hydrocarbon group having 8 to 12 carbon atoms. The above aliphatic hydrocarbon group may be saturated or unsaturated, and may be linear or branched. Examples of the aliphatic hydrocarbon group include alkylene groups such as butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and nonadecylene group.

[0031] The above alicyclic hydrocarbon group may be saturated or unsaturated. Examples of the alicyclic hydrocarbon group include cycloalkylene groups having 6 to 10 carbon atoms. Examples of the cycloalkylene group include cyclohexylene group.

[0032] Examples of the aromatic hydrocarbon group include arylene groups such as phenylene group and naphthylene group. Substituents may be bonded to at least a part of the carbon atoms of the aromatic hydrocarbon group. Examples of this substituent include halogen group, nitro group, alkyl group having 1 to 20 carbon atoms and the like.

[0033] In formula (1), R 2 ~R5 Each of these is independently preferably a hydrogen atom, a methyl group, and an ethyl group, with a hydrogen atom being more preferred.

[0034] The urea compound used in this embodiment refers to a compound having a -(HN)2C(=O) structure, and its type and other characteristics are not specifically defined. The urea compound used in this embodiment preferably includes a compound having a skeleton represented by formula (N). Having such a structure makes it possible to more significantly suppress the generation of formaldehyde when the polyacetal resin is left in the molding machine for a long time. [ka] Here, the term "compound having a skeleton represented by formula (N)" includes not only the compound represented by formula (N) (ethylene urea), but also compounds having a structure in which the hydrogen atoms bonded to the nitrogen atom and / or carbon atom forming the cyclic structure of formula (N) are substituted by substituents. When substituents are present, it is preferable that the hydrogen atoms bonded to the carbon atom are substituted by substituents. Examples of substituents include oxygen atoms (=O), urea groups, and (methyl groups).

[0035] The molecular weight of the urea compound used in this embodiment is preferably 60 or more, and more preferably 86 or more. The upper limit is preferably 500 or less, more preferably 300 or less, and even more preferably 200 or less. Examples of urea compounds include urea, ethyleneurea, allantoin, and biurea, with the inclusion of ethyleneurea and / or allantoin being preferred, and more preferably ethyleneurea being included.

[0036] The melamine compound used in this embodiment is a compound (melamine) or a derivative thereof that has a triazine ring at the center of its structure and three amino groups around it. Examples include melamine, melamine cyanurate, acetoganaamine, benzoguanamine, melamine condensates (melam, melem, melon), methylolmelamine, etc., with melamine being the preferred compound among them.

[0037] The content of the predetermined amine compound (C) in the resin composition of this embodiment is 0.01 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.04 parts by mass or more, per 100 parts by mass of the polyacetal resin (A). Setting it above the lower limit tends to result in molded articles with superior sliding properties. Furthermore, the content of the predetermined amine compound (C) in the resin composition of this embodiment is 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, even more preferably 1 part by mass or less, even more preferably 0.7 parts by mass or less, and even more preferably 0.3 parts by mass or less, per 100 parts by mass of the polyacetal resin (A). Setting it below the upper limit, and in particular setting it to 2 parts by mass or less, tends to result in improved tensile fracture strain of the molded articles. The resin composition of this embodiment may contain only one of the specified amine compounds (C), or it may contain two or more. When it contains two or more, it is preferable that the total amount is within the above range.

[0038] In this embodiment, the ratio (B) / (C) of the acid-modified olefin polymer to the amino group-containing compound is 20 to 200. Setting the ratio within this range tends to improve sliding properties. The above (B) / (C) is preferably 23 or more, more preferably 28 or more, and preferably 180 or less, and may also be 150 or less.

[0039] <(D) Hydrocarbon waxes> The resin composition of this embodiment preferably contains (D) hydrocarbon wax in an amount of 0.1 to 15 parts by mass per 100 parts by mass of (A) polyacetal resin. Including (D) hydrocarbon wax tends to further improve the sliding properties of the resulting molded article. In the case where (D) hydrocarbon wax may also be the above-mentioned acid-modified olefin polymer, those with a Vicat softening temperature of 20°C or higher shall be considered the above-mentioned (B) acid-modified olefin polymer, and those whose Vicat softening temperature cannot be measured shall be considered (D) hydrocarbon wax. An example of a substance whose Vicat softening temperature cannot be measured is one for which a test piece for measuring the Vicat softening temperature cannot be molded. Typically, it is not possible to manufacture a test piece for measuring the Vicat softening temperature of (D) hydrocarbon wax. (D) Hydrocarbon wax is a wax whose main component is hydrocarbons, and which may have functional groups such as acidic groups.

[0040] The hydrocarbon wax (D) used in this embodiment preferably has a melt viscosity of 15 mPa·s or more, preferably 20 mPa·s or more, more preferably 80 mPa·s or more, and may be 100 mPa·s or more, as measured using a B-type viscometer. Setting it above the lower limit can more effectively prevent bleed-out from occurring on the surface of the molded product. The melt viscosity is preferably 6000 mPa·s or less, more preferably 5000 mPa·s or less, and may be 4000 mPa·s or less. Setting it below the upper limit can further improve friction and wear characteristics and moldability. Molecular weight measurement by viscometers shall be based on values ​​obtained using a Type B viscometer at 140°C.

[0041] (D) Hydrocarbon waxes include paraffin wax, polyolefin wax, and Fischer-Tropsch wax. In this embodiment, polyolefin wax is preferred, and polyethylene wax is more preferred. (D) Examples of hydrocarbon waxes include FT-100 and FT-0070 sold by Nippon Seiro, and paraflint manufactured by SASOL. Examples of polyolefin waxes include Hiwax (manufactured by Mitsui Chemicals), Sanwax (manufactured by Sanyo Chemical Industries), Eporen (manufactured by Eastman Chemical), and Allied Wax (manufactured by Allied Synthetics).

[0042] The (D) polyethylene wax used in this embodiment is preferably a modified polyethylene wax obtained by acid-modifying low molecular weight polyethylene or a low molecular weight polyethylene copolymer. The acid modification treatment can be carried out by treating the wax with an inorganic acid, organic acid, or unsaturated carboxylic acid, etc., in the presence of peroxide or oxygen as needed, to introduce polar groups such as carboxyl groups or sulfonic acid groups.

[0043] These polyethylene waxes are commercially available under names such as medium-acid value polyethylene wax, high-acid value polyethylene wax, and acid-modified polyethylene wax, and can be easily obtained from the market. Furthermore, the polyethylene wax used in this embodiment preferably has an acid value of 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, and may be 26 mgKOH / g or more. The upper limit of the acid value of the polyethylene wax is preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, even more preferably 40 mgKOH / g or less, even more preferably 37 mgKOH / g or less, and may also be 35 mgKOH / g or less, or 30 mgKOH / g or less. By setting it within this range, high frictional properties and wear resistance can be achieved. The acid value is measured according to the example described below.

[0044] The content of (D) hydrocarbon wax in the resin composition of this embodiment is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and may be 0.8 parts by mass or more, and particularly may be 1.2 parts by mass or more, per 100 parts by mass of (A) polyacetal resin. Setting it above the lower limit tends to improve sliding properties. Furthermore, the content of (D) hydrocarbon wax in the resin composition of this embodiment is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, even more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, per 100 parts by mass of (A) polyacetal resin. Setting it below the upper limit effectively suppresses the decrease in mechanical strength. The resin composition of this embodiment may contain only one type of (D) hydrocarbon wax, or it may contain two or more types. If it contains two or more types, it is preferable that the total amount is within the above range.

[0045] <Other ingredients> In addition to the above, the resin composition of this embodiment may optionally contain other additives such as waxes, inorganic particles such as calcium carbonate, antioxidants (hindered amine type, hindered phenol type), heat stabilizers, colorants, nucleating agents, plasticizers, fluorescent whitening agents, mold release agents (fatty acid ester type compounds, silicon type compounds, etc.), antistatic agents, and ultraviolet absorbers (benzotriazole type or benzophenone type compounds, etc.). The resin composition of this embodiment is prepared so that the total of (A) polyacetal resin, (B) acid-modified olefin polymer, (C) a predetermined amine compound, and other components added as needed is 100% by mass. Preferably, the total of (A) polyacetal resin, (B) acid-modified olefin polymer, (C) a predetermined amine compound, and polyethylene wax accounts for 85% by mass or more of the resin composition, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0046] <Physical properties of resin compositions> The resin composition of this embodiment preferably has a high tensile fracture strain. Specifically, when the resin composition is molded into a test piece as specified in ISO 9988-2 and the tensile fracture strain measured according to ISO 527 is preferably 5% or more, more preferably 10% or more, even more preferably 13% or more, and even more preferably 15% or more. There is no upper limit to the tensile fracture strain, but 50% or less is practical, and even 40% or less is sufficient to meet the required performance. The resin composition of this embodiment preferably has excellent sliding properties. Specifically, the resin composition is molded into a pin-shaped test piece with a tip diameter of 10 mm and a height of 30 mm, as specified in the ISO 9988-2 standard. The pin-shaped test piece and the test piece specified in the ISO 9988-2 standard are brought into contact under the conditions of a load of 200 gf, a linear speed of 1200 mm / min, a travel distance of 10 mm, and 8000 reciprocating cycles, and a reciprocating sliding test is performed. After that, the width and depth of the wear grooves formed on the test piece specified in the ISO 9988-2 standard are measured, and the area of ​​the portion enclosed by the width and depth is defined as the wear groove area. The measured wear area is 15,000 μm². 2 Preferably, the following, 10,000 μm 2 It is more preferable that the following is true: 8,000 μm 2 It is even more preferable that the following is the case: 5,000 μm 2 It is even more preferable that the following is true: 4,000 μm 2 The following is even more preferable: The lower limit of the wear area obtained by the reciprocating sliding test is not specifically defined, but is 100 μm. 2 The above is practical, and 700 μm 2 Even with these specifications, the required performance is fully met. The resin composition of this embodiment preferably exhibits excellent heat aging resistance. Specifically, it is preferable that the ΔE of a test specimen molded from the resin composition of this embodiment (as specified in ISO 9988-2) before and after 500 hours of treatment at 80°C is 1.5 or less, and more preferably less than 1.0. An ideal lower limit is 0, but a value of 0.1 or higher is sufficient to meet the required performance.

[0047] <Method for producing resin compositions> The resin composition of this embodiment can be easily prepared by known methods commonly used for preparing conventional thermoplastic resin compositions. For example, (1) a method of mixing all the components constituting the composition, supplying it to an extruder and melt-kneading it to obtain a pelletized composition, (2) a method of supplying a portion of the components constituting the composition from the main feed port of an extruder and the remaining components from the side feed port and melt-kneading them to obtain a pelletized composition, or (3) a method of preparing pellets with different compositions by extrusion or the like, and then mixing the pellets to adjust them to a predetermined composition.

[0048] Examples of mixing machines include kneaders, Banbury mixers, and extruders. There are no particular restrictions on the various conditions and equipment for mixing and kneading; they can be appropriately selected from any conventionally known conditions. It is preferable to perform kneading at a temperature above the melting temperature of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally 180°C or higher).

[0049] <Molded products> The molded articles of this embodiment are formed from the resin composition of this embodiment. Pelletized from the resin composition of this embodiment are then molded into molded articles using various molding methods. Alternatively, the resin composition, which has been melt-kneaded in an extruder, can be directly molded into molded articles without going through the pellet stage. There are no particular restrictions on the shape of the molded product, and it can be appropriately selected according to the application and purpose of the molded product. Examples include plate-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, annular, circular, elliptical, gear-shaped, polygonal, irregularly shaped, hollow, frame-shaped, box-shaped, and panel-shaped products. The molded product in this embodiment may be a finished product or a component.

[0050] The method for molding the molded product is not particularly limited, and conventionally known molding methods can be used. Examples include injection molding, injection compression molding, extrusion molding, shape extrusion, transfer molding, hollow molding, gas-assisted hollow 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.

[0051] The resin composition of this embodiment is preferably used for forming sliding members. Therefore, molded articles formed from the resin composition of this embodiment are preferably used as sliding members (sliding parts). Specific examples of sliding components include gears, rotating shafts, bearings, various gears, cams, end face materials for mechanical seals, valve seats for valves, sealing components such as V-rings, rod packings, piston rings, and rider rings, as well as sliding components such as the rotating shafts, rotating sleeves, pistons, impellers, and rollers of compressors, all aimed at achieving high quality as required in electrical and electronic equipment, office equipment, vehicles (automobiles), and industrial equipment.

[0052] The sliding members of this embodiment can be used not only with other sliding members of this embodiment, but also in combination with other resin sliding members, fiber-reinforced resin sliding members, and even with ceramic or metal sliding members. [Examples]

[0053] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0054] 1. Raw materials The raw materials shown in Table 1 below were used. [Table 1]

[0055] Ethylene urea [ka] melamine [ka]

[0056] <Measurement of Acid Value> The amount of potassium hydroxide required to neutralize 1 g of the sample (acid-modified olefin polymer, polyethylene wax, etc.) was measured and determined as the acid value. Specifically, the measurement was performed by neutralization titration in accordance with JIS K0070. 1 g of the sample was accurately weighed and dissolved in 100 mL of xylene with stirring at approximately 120°C. After complete dissolution, phenolphthalein solution was added, and neutralization titration was performed using a 0.1 mol / L potassium hydroxide ethanol solution whose concentration had been precisely determined beforehand. The acid value was calculated using the following formula based on the titration volume (T), the factor of the 0.1 mol / L potassium hydroxide ethanol solution (f), 1 / 10 of the formula weight of potassium hydroxide (56.11) (5.611), and the mass of the sample (S). Acid value = T × f × 5.611 / S The unit is expressed as mgKOH / g.

[0057] 2. Examples 1-7, Comparative Examples 1-9 Each component was blended as shown in Table 2 or Table 3 below (the unit for each component in Table 2 or Table 3 is parts by mass), pre-blended, and then fed into the main feed port of a 30 mm diameter twin-screw extruder with one vent port for melt mixing (extrusion conditions: L / D=35, extrusion temperature=190°C, screw rotation speed=120 rpm, vent vacuum pressure=-0.08 MPa, discharge rate=10 kg / hr) to prepare a pelletized resin composition. The following evaluations were performed using the obtained resin composition.

[0058] <Tensile fracture nominal strain> The resin composition obtained above was dried at 80°C for 3 hours, and then molded into test specimens as specified in ISO 9988-2 using an injection molding machine (Shibaura Machine Co., Ltd. "EC-100S") under conditions of cylinder temperature 195°C and mold temperature 90°C. The tensile fracture strain was measured according to ISO 527. The units are shown in percentages (%).

[0059] <Reciprocating sliding test> A test specimen conforming to the ISO9988-2 standard and a pin-shaped test specimen with a tip diameter of 10 mm and a height of 30 mm were formed. The ISO9988-2 standard test specimen and the pin-shaped test specimen were brought into contact and tested under the conditions of a load of 200 gf, a linear speed of 1200 mm / min, a travel distance of 10 mm, and 8000 reciprocating cycles. The width and depth of the wear grooves on the ISO9988-2 standard test specimen were measured using a surface roughness measuring instrument, and the area enclosed by the width and depth was measured as the wear groove area. The unit is μm. 2 As shown. Figure 1 shows a sample of measurement results using a surface roughness measuring instrument, indicating the area of ​​wear grooves. The shaded area in Figure 1 represents the wear groove area. Abrasion resistance testing was performed using a Tribogear surface quality measuring instrument, TYPE:38 (manufactured by Shinto Kagaku Co., Ltd.), and surface roughness testing was performed using a Surfcom 3000A (manufactured by ACCRETECH). The unit is μm. 2 As shown.

[0060] <Heat aging resistance test> The test specimens were formed according to the ISO9988-2 standard, and the resulting specimens were left standing in an 80°C environment for 500 hours. The color difference ΔE before and after this period was measured using a SE6000 model (light source: C / 2, reflected light) manufactured by Nippon Denshoku Industries Co., Ltd.

[0061] [Table 2]

[0062] [Table 3]

[0063] As is clear from the above results, the resin composition of the present invention exhibited a small wear area and excellent sliding properties in the sliding reciprocating test. In contrast, when the acid value of (B) the olefin polymer was low (Comparative Example 1), the wear area was large and the sliding properties were poor. Similarly, when the amine compound was not included (Comparative Example 2), the wear area was large and the sliding properties were poor. When (B) / (C) was outside the range of the present invention (Comparative Examples 3-5), the tensile nominal strain was low or the wear resistance was poor. Even when an amine compound was included, when (C) the specified amine compound was not included (Comparative Examples 6-8), the heat aging resistance was poor. Also, when the acid value of (B) the acid-modified olefin polymer was outside the range of the present invention (Comparative Example 9), the tensile nominal strain was low. Furthermore, by adjusting the content of a predetermined amine compound (C), the tensile fracture strain could be increased, resulting in a resin composition with an excellent balance of sliding properties and mechanical properties.

Claims

1. (A) Per 100 parts by mass of polyacetal resin, (B) 0.1 to 50 parts by mass of an acid-modified olefin polymer having an acid value of 1.0 to 25.0 mgKOH / g, (C) comprising 0.01 to 5 parts by mass of a compound selected from dihydrazone compounds, dihydrazide compounds, urea compounds, and melamine compounds, which contains a total of two or more primary amino groups and / or secondary amino groups, The ratio (B) / (C) of the acid-modified olefin polymer to (C) the amino group-containing compound is 23 to 200. Furthermore, (D) hydrocarbon wax is included in an amount of 0.01 to 15.0 parts by mass per 100 parts by mass of the polyacetal resin. Resin composition.

2. The resin composition according to claim 1, wherein the melt viscosity of the hydrocarbon wax (D), as measured at 140°C using a B-type viscometer, is 15 mPa·s or more and 6000 mPa·s or less.

3. The resin composition according to claim 1 or 2, wherein the Vicat softening temperature of the acid-modified olefin polymer (B) according to JIS K7206 is 20°C or higher.

4. The resin composition according to any one of claims 1 to 3, wherein the (B) acid-modified olefin polymer comprises an acid-modified olefin polymer modified with at least one unsaturated carboxylic acid and its anhydride.

5. The resin composition according to any one of claims 1 to 4, wherein the olefin polymer constituting the acid-modified olefin polymer is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer.

6. The resin composition according to any one of claims 1 to 4, wherein the olefin polymer constituting the acid-modified olefin polymer (B) comprises an ethylene-butene copolymer.

7. The resin composition according to any one of claims 1 to 6, comprising 0.01 to 2 parts by mass of the compound containing a total of two or more primary amino groups and / or secondary amino groups, per 100 parts by mass of the polyacetal resin.

8. A resin composition according to any one of claims 1 to 7, for forming a sliding member.

9. A molded article formed from the resin composition according to any one of claims 1 to 8.

10. A molded article according to claim 9, which is a sliding member.

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