WO2023032606A1

WO2023032606A1 - Resin composition, molded article, and method for producing resin composition

Info

Publication number: WO2023032606A1
Application number: PCT/JP2022/030285
Authority: WO
Inventors: 崇石井; 麻希子大島
Original assignee: 三菱エンジニアリングプラスチックス株式会社
Priority date: 2021-08-30
Filing date: 2022-08-08
Publication date: 2023-03-09
Also published as: CN117897447A

Abstract

Provided are: a resin composition from which a molded article having excellent slidability is obtained and which has excellent moldability; a molded article; and a method for producing a resin composition. This resin composition comprises, with respect to 100 parts by mass of (A) a polyacetal resin, 0.1-30.0 parts by mass of (B) an olefin polymer, 0.1-30.0 parts by mass of (C) a silicone oil having a kinematic viscosity of 1,000-55,000 cSt at 25°C, and 0.1-15.0 parts by mass of (D) a hydrocarbon wax, wherein (B)/(C), which is the mass ratio of the (B) olefin polymer to the (C) silicone oil, is at most 2.00.

Description

RESIN COMPOSITION, MOLDED PRODUCT AND METHOD FOR MANUFACTURING RESIN COMPOSITION

The present invention relates to a resin composition, a molded product, and a method for producing a resin composition.

Polyacetal resin has well-balanced mechanical properties, and is excellent in friction/wear resistance, chemical resistance, heat resistance, electrical properties, etc., so it is widely used in the fields of automobiles, electrical and electronic products, etc. .
A sliding member is known as one of the forms of utilization of polyacetal resin. Patent document 1 and patent document 2 are mentioned as an example using polyacetal resin as a sliding member.

JP 2008-214490 A WO2018/230389

The resin compositions described in

Patent Documents

1 and 2 are materials having excellent slidability, but in

Patent Documents

1 and 2, the resin composition is produced after masterbatching a silicone compound I needed it. Therefore, the present inventors have considered using silicone oil as a silicone compound that does not require masterbatching. However, even if the polyacetal resin is blended with silicone oil, the slidability is not necessarily sufficient, and the moldability is poor. That is, when a resin composition is molded by, for example, injection molding, the molten resin composition is weighed and then injected into a mold for molding, which takes a very long time.
An object of the present invention is to solve such problems, and to provide a resin composition having excellent slidability of the resulting molded product and excellent moldability, a molded product, and a method for producing the resin composition. intended to provide

Based on the above problems, the present inventors have conducted studies and found that by blending a polyacetal resin with a silicone oil having a predetermined kinematic viscosity, an olefin polymer, and a hydrocarbon wax in a predetermined ratio, the above problems can be solved. found a solution.
Specifically, the above problems have been solved by the following means.
<1> (A) 100 parts by mass of polyacetal resin, (B) 0.1 to 30.0 parts by mass of olefin polymer, and (C) silicone having a kinematic viscosity at 25°C of 1,000 to 55,000 cSt It contains 0.1 to 30.0 parts by mass of oil and 0.1 to 15.0 parts by mass of (D) hydrocarbon wax, and the mass ratio of (B) olefin polymer and (C) silicone oil is ( A resin composition in which B)/(C) is 2.00 or less.
<2> The resin composition according to <1>, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.10 or more.
<3> The resin composition according to <1> or <2>, wherein the (B) olefin polymer is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, and ethylene-butene copolymers. thing.
<4> The resin composition according to <1> or <2>, wherein the (B) olefin polymer comprises an ethylene-butene copolymer.
<5> The resin composition according to any one of <1> to <4>, wherein the (B) olefin polymer has a Vicat softening temperature according to JIS K7206 of 30° C. or higher.
<6> Any one of <1> to <5>, wherein the content of the (B) olefin polymer is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin The resin composition according to 1.
<7> Any one of <1> to <6>, wherein the content of the (C) silicone oil is 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. The resin composition according to .
<8> Any one of <1> to <7>, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.80 or less. Resin composition.
<9> Any one of <1> to <8>, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.50 or less. of the resin composition.
<10> Any one of <1> to <9>, wherein (D)/(C), which is the mass ratio of (D) hydrocarbon wax and (C) silicone oil, is 1.0 or less. of the resin composition.
<11> The resin composition according to any one of <1> to <9>, which is used for forming a sliding member.
<12> A pellet of the resin composition according to any one of <1> to <11>.
<13> A molded article formed from the resin composition according to any one of <1> to <11>.
<14> A molded article formed from the pellets according to <12>.
<15> The molded article according to <13> or <14>, which is a sliding member.
<16> A method for producing a resin composition according to any one of <1> to <11>,
(A) a polyacetal resin, (B) an olefin polymer, and (D) a hydrocarbon wax are introduced from the supply port of an extruder and kneaded, and then from a liquid supply pump, (C) the kinematic viscosity at 25 ° C. A method for producing a resin composition, comprising adding a silicone oil of 1,000 to 55,000 cSt and further kneading.

According to the present invention, it has become possible to provide a resin composition, a molded product, and a method for producing a resin composition, in which the obtained molded product has excellent slidability and excellent moldability.

FIG. 1 is a schematic illustration of an example of an extruder used in the method for producing a resin composition of the present embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail. In addition, the following embodiment is an example for explaining the present invention, and the present invention is not limited only to this embodiment.
In this specification, the term "~" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.
In this specification, various physical property values and characteristic values are at 23° C. unless otherwise specified.
If the standards shown in this specification differ from year to year in terms of measurement methods, etc., the standards as of January 1, 2021 shall be used unless otherwise specified.

The resin composition of the present embodiment comprises (A) 100 parts by mass of polyacetal resin, (B) 0.1 to 30.0 parts by mass of olefin polymer, and (C) kinematic viscosity at 25 ° C. of 1,000 to 0.1 to 30.0 parts by mass of a silicone oil of 55,000 cSt, and (D) 0.1 to 15.0 parts by mass of a hydrocarbon wax, wherein the (B) olefin polymer and (C) the silicone oil (B)/(C), which is the mass ratio of , is 2.00 or less. With such a configuration, the resulting molded article has excellent slidability, and a resin composition having excellent moldability can be obtained.

<(A) Polyacetal resin>
The resin composition of this embodiment contains a polyacetal resin. By containing the polyacetal resin, a molded article having excellent slidability and mechanical strength can be obtained.
The polyacetal resin used in the present embodiment is a polymer having an acetal structure -(-O-CRH-) _n - (wherein R represents a hydrogen atom or an organic group) in a repeating structure, and usually R is It has an oxymethylene group (--CH ₂ O--), which is a hydrogen atom, as a main structural unit. The polyacetal resin used in the present embodiment includes, in addition to the acetal homopolymer consisting only of this repeating structure, copolymers (including block copolymers) and terpolymers containing one or more structural units other than the oxymethylene group, and further. It may have not only a linear structure but also a branched or crosslinked structure.

Examples of _structural units other than the oxymethylene group include an oxyethylene group ( _{--CH.sub.2CH.sub.2O--} ), _an oxypropylene group ₍ _{--CH.sub.2CH.sub.2CH.sub.2O--} ), and an oxybutylene group ( _{--CH.sub.2CH.sub.2CH} _. ₂ CH ₂ O—) and other optionally branched oxyalkylene groups having 2 to 10 carbon atoms, among which optionally branched oxyalkylene groups having 2 to 4 carbon atoms are preferred; An oxyethylene group is particularly preferred. In addition, the content of such oxyalkylene structural units other than oxymethylene groups is preferably 0.1 mol % or more and 20 mol % or less, and 0.1 mol % or more and 15 mol % or less in the polyacetal resin. is more preferable.

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

Among them, the polyacetal resin used in the present invention is preferably a copolymer of a cyclic oligomer such as trioxane or tetraoxane and ethylene oxide and/or 1,3-dioxolane, particularly a copolymer of trioxane and 1,3-dioxolane. A copolymer is preferred. In this case, the total content of ethylene oxide and/or 1,3-dioxolane is preferably 1 to 20% by mass with respect to 80 to 99% by mass of the cyclic oligomer.
The melt flow rate (MFR) of the polyacetal resin is arbitrary, but according to ASTM-D1238, the value measured at 190 ° C. under a load of 2.16 kg is usually 1 g / 10 minutes or more, and 10 g / 10 minutes or more. is preferably 13 g/10 min or more, more preferably 20 g/10 min or more, still more preferably 32 g/10 min or more, and even more preferably 35 g/10 min or more. Preferably, it is still more preferably 40 g/10 minutes or more. The MFR is usually 150 g/10 minutes or less, preferably 100 g/10 minutes or less, more preferably 70 g/10 minutes or less, and even more preferably 60 g/10 minutes or less. , 50 g/10 minutes or less.
When the resin composition of the present embodiment contains two or more polyacetal resins, the MFR of the mixture preferably satisfies the above range.

The resin composition of the present embodiment preferably contains a polyacetal resin in a proportion of 80% by mass or more of the resin composition, more preferably 85% by mass or more, and more preferably 90% by mass or more. is more preferred. The upper limit is the amount in which the total amount other than (B) the olefin polymer, (C) the silicone oil, and (D) the hydrocarbon wax becomes a polyacetal resin.
The resin composition of the present embodiment may contain only one type of polyacetal resin, or may contain two or more types. When two or more kinds are included, the total amount is preferably within the above range.

<(B) Olefin polymer>
The resin composition of the present embodiment contains (B) the olefin polymer in a proportion of 0.1 to 30.0 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. By including an olefin polymer, a molded article having excellent slidability can be obtained. Furthermore, a resin composition having excellent moldability can be obtained. In addition, there is a tendency to obtain molded articles having excellent mechanical strength.
A known olefin polymer can be used as the olefin polymer used in the present embodiment. The olefin polymer is preferably selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer and ethylene-butene copolymer, and more preferably contains ethylene-butene copolymer. These olefin polymers are intended to include acid-modified polyolefin polymers having the polyolefin skeleton. That is, for example, polyethylene is intended to include both acid-unmodified polyethylene and acid-modified polyethylene.
The olefin polymer in the present embodiment preferably has a number average molecular weight of 1×10 ⁴ or more, more preferably 2×10 ⁴ or more, and preferably 50×10 ⁴ or less. By using one having a number average molecular weight equal to or higher than the lower limit, a harder molded article can be formed, and the slidability of the resulting molded article can be further improved. Further, by using one having a number average molecular weight of not more than the above upper limit, it is possible to disperse uniformly by shearing during kneading, and there is a tendency that deterioration of mechanical properties can be suppressed.
In addition, according to ASTM-D1238, the melt flow rate (MFR) measured at 190 ° C. and a load of 2.16 kg is preferably 70 g / 10 minutes or less, more preferably 50 g / 10 minutes or less, and 25 g / 10 minutes or less, more preferably 15 g/10 minutes or less. By making it equal to or less than the above upper limit, a harder molded article can be formed, and the slidability of the obtained molded article tends to be further improved. The lower limit of the melt flow rate (MFR) can be, for example, 0.1 g/10 minutes or more. When the content is at least the above lower limit, uniform dispersion can be achieved by shearing during kneading, and deterioration of mechanical properties can be effectively suppressed.
When the resin composition of the present embodiment contains two or more polyolefin polymers, the MFR of the mixture is used.

The olefin polymer in this embodiment preferably has a Vicat softening temperature of 30°C or higher according to JIS K7206. The Vicat softening temperature is a measure of the temperature at which a thermoplastic begins to soften rapidly, and is an indicator of short-term heat resistance. In this embodiment, by using such an olefin polymer, excellent heat resistance during sliding can be obtained. In this embodiment, the Vicat softening temperature is the Vicat softening temperature at a load of 50 N and a heating rate of 50° C./hour. Although the upper limit of the Vicat softening temperature is not particularly defined, it is usually lower than the melting point of the polyacetal resin, preferably 150° C. or lower.

The olefin polymer in the present embodiment may be an acid-modified polyolefin polymer as described above, an olefin polymer modified with at least one of an unsaturated carboxylic acid and its anhydride, or an unsaturated It may be an olefin polymer modified with at least one carboxylic acid anhydride (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 allylsuccinic acid, with maleic acid being preferred.
Details of the modified olefin polymer modified with at least one of an unsaturated carboxylic acid and its anhydride can be referred to paragraph 0005 of JP-A-10-130458, the contents of which are incorporated herein.

The acid value of the acid-modified olefin polymer may be 0 mgKOH/g, may be 2.0 mgKOH/g or more, or may be 5.0 mgKOH/g or more. The acid value of the acid-modified olefin polymer is, for example, 70.0 mgKOH/g or less, may be 30.0 mgKOH/g or less, or may be 20.0 mgKOH/g or less. By making it equal to or less than the above upper limit, there is a tendency that the tensile fracture nominal strain is further improved.
When two or more kinds of olefin polymers are included, the acid value here is the sum of the values obtained by multiplying the acid value of each olefin polymer by the blending amount (mass) fraction of each olefin polymer.

The content of the olefin polymer in the resin composition of the present embodiment is 0.1 parts by mass or more, preferably 0.4 parts by mass or more, and 0.8 parts by mass with respect to 100 parts by mass of the polyacetal resin. It is more preferable to be above. When the content is at least the above lower limit, the resulting molded article tends to be more excellent in slidability and moldability. Further, the content of the olefin polymer in the resin composition of the present embodiment is 30.0 parts by mass or less, preferably 20.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin, and 10.0 parts by mass or less. It is more preferably not more than 5.0 parts by mass, even more preferably not more than 3.0 parts by mass, and even more preferably not more than 2.5 parts by mass. It is even more preferable that it is 1.5 parts by mass or less. By making it equal to or less than the above upper limit, there is a tendency that the nominal strain at break of the resulting molded product is further improved.
The resin composition of the present embodiment may contain only one type of olefin polymer, or may contain two or more types. When two or more types are included, the total amount is preferably within the above range.

<(C) Silicone oil>
The resin composition of the present embodiment comprises (A) 100 parts by mass of polyacetal resin and (C) 0.1 to 30.0 parts by mass of silicone oil having a kinematic viscosity at 25° C. of 1,000 to 55,000 cSt. included in the ratio of By including silicone oil, a molded article having excellent slidability can be obtained. Furthermore, unlike conventional slidability improvers, it can be compounded with polyacetal resin or the like without being masterbatched, facilitating the production of resin compositions.

The silicone oil used in the present embodiment has a kinematic viscosity at 25° C. of 1,000 cSt or more, preferably 2,000 cSt or more, more preferably 4,000 cSt or more, and 6,000 cSt or more. is more preferably 8,000 cSt or more. When the content is at least the above lower limit, the moldability (measurability) tends to be further improved. The kinematic viscosity of the silicone oil at 25° C. is also 55,000 cSt or less, preferably 45,000 cSt or less, more preferably 35,000 cSt or less, and further preferably 25,000 cSt or less. It is preferably 15,000 cSt or less, and even more preferably 12,000 cSt or less. Limit PV tends to be improved by making it equal to or less than the upper limit.
When the resin composition of the present embodiment contains two or more types of silicone oils, the mixing ratio is determined as follows so as to achieve the desired kinematic viscosity. In the graph, the kinematic viscosity is plotted on a logarithmic scale on the vertical axis and the percentage of use is plotted on the horizontal axis. A vertical line is drawn from the intersection of the horizontal line passing through the memory of the desired kinematic viscosity and the preceding straight line, and the usage amounts of the upper and lower viscosities are read to determine the amount to be added.

Any conventionally known silicone oil can be used as the silicone oil used in this embodiment. Specifically, for example, in addition to silicone oil made of polydimethylsiloxane, some or all of the methyl groups in polydimethylsiloxane are hydrogen, alkyl groups having 2 or more carbon atoms, phenyl groups, halogenated phenyl groups, and esters. substituted silicone oils substituted with groups, halogenated ester groups such as fluorine, polyether groups, etc.; modified silicone oils having epoxy groups, amino groups, alcoholic hydroxyl groups, polyether groups, etc. in addition to polydimethylsiloxane; dimethyl Alkylaralkylsilicone oils containing siloxane units and phenylmethylsiloxane units; Alkylaralkylpolyether-modified silicones containing siloxane units and phenylmethylsiloxane units having a structure in which a portion of the methyl groups of the dimethylsiloxane units are substituted with polyether oils; and the like. Preferred among these are polymers of dimethylsiloxane and copolymers of dimethylsiloxane and methylphenylsiloxane.

The content of (C) silicone oil in the resin composition of the present embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, relative to 100 parts by mass of (A) polyacetal resin. It is more preferably 1.0 parts by mass or more, still more preferably 1.5 parts by mass or more, and even more preferably 2.1 parts by mass or more. By making it more than the said lower limit, there exists a tendency for slidability to improve more. In addition, the content of (C) silicone oil in the resin composition of the present embodiment is 30.0 parts by mass or less and 20.0 parts by mass or less with respect to 100 parts by mass of (A) polyacetal resin. It is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. Formability tends to be further improved by making it equal to or less than the above upper limit.
The resin composition of the present embodiment may contain only one type of (C) silicone oil, or may contain two or more types. When two or more types are included, the total amount is preferably within the above range.

The resin composition of the present embodiment preferably does not substantially contain silicone oils other than those having a kinematic viscosity of 1,000 to 55,000 cSt at 25°C. "Substantially free" means that the content of the silicone oil other than the silicone oil having a kinematic viscosity at 25°C of 1,000 to 55,000 cSt is a silicone having a kinematic viscosity at 25°C of 1,000 to 55,000 cSt. It is 5% by mass or less of the oil content, preferably 1% by mass or less.

In the resin composition of the present embodiment, (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 2.00 or less. With such a configuration, slidability can be improved. The (B)/(C) is preferably 1.50 or less, more preferably 1.00 or less, further preferably 0.80 or less, and 0.60 or less. It is more preferably 0.50 or less, even more preferably 0.45 or less. The lower limit of (B)/(C) is preferably 0.10 or more, more preferably 0.15 or more.

<(D) Hydrocarbon wax>
The resin composition of the present embodiment contains 0.1 to 15.0 parts by mass of (D) hydrocarbon wax with respect to 100 parts by mass of (A) polyacetal resin. Containing the hydrocarbon wax tends to further improve the slidability of the obtained molded article. Among hydrocarbon waxes, if they can also correspond to the above olefin polymers, those having a Vicat softening temperature of 30° C. or higher are considered to correspond to the above olefin polymers. Those whose softening temperature cannot be measured shall be regarded as hydrocarbon waxes. Examples of those for which the Vicat softening temperature cannot be measured include those for which a test piece for measuring the Vicat softening temperature cannot be molded. Generally, hydrocarbon waxes cannot be made into test specimens for measuring the Vicat softening temperature.
A hydrocarbon wax is a wax containing a hydrocarbon as a main component, and may have a functional group such as an acid group.

The hydrocarbon wax used in the present embodiment preferably has a molecular weight of 1,000 or more, more preferably 1,500 or more, even more preferably 2,000 or more, and may be 2,500 or more as determined by the viscosity method. When the content is at least the above lower limit, it is possible to more effectively prevent the occurrence of bleeding out onto the surface of the molded article. The upper limit of the molecular weight determined by the viscosity method is preferably 7,000 or less, more preferably 6,000 or less, and may be 5,500 or less. By adjusting the content to be equal to or less than the above upper limit, it is possible to further improve frictional wear characteristics, moldability, and the like.

Hydrocarbon waxes include paraffin waxes, polyolefin waxes, and Fischer-Tropsch waxes. In the present embodiment, polyolefin wax is preferred, and polyethylene wax is more preferred.
Examples of hydrocarbon waxes include FT-100 and FT-0070 sold by Nippon Seiro, and Paraflint manufactured by SASOL.
In particular, examples of polyolefin waxes include Hiwax (manufactured by Mitsui Chemicals), Sanwax (manufactured by Sanyo Chemical Industries), Epolen (manufactured by Eastman Chemical), and Allied Wax (manufactured by Allied Signals).

The polyethylene wax used in this embodiment is preferably modified polyethylene wax obtained by acid-modifying low-molecular-weight polyethylene or low-molecular-weight polyethylene copolymer. The acid modification treatment may be carried out by treating the wax with an inorganic acid, an organic acid, an unsaturated carboxylic acid, or the like in the presence of peroxide or oxygen, if necessary, to introduce a polar group such as a carboxyl group or a sulfonic acid group.

These polyethylene waxes are commercially available under the names of medium-acid-value polyethylene wax, high-acid-value polyethylene wax, acid-modified polyethylene wax, and the like, and are readily available on the market.
The polyethylene wax used in the present 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, and 37 mgKOH/g or less. More preferably, it may be 35 mgKOH/g or less, or 30 mgKOH/g or less. By setting it as such a range, high frictional characteristics and wear resistance can be achieved.
The acid value is measured according to the description in the examples below.

The content of the (D) hydrocarbon wax in the resin composition of the present embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, relative to 100 parts by mass of the (A) polyacetal resin. , more preferably 0.8 parts by mass or more, more preferably 1.0 parts by mass or more, still more preferably 1.2 parts by mass or more, and preferably 1.3 parts by mass or more Even more preferable. By making it more than the said lower limit, there exists a tendency for slidability to improve more. In addition, the content of the (D) hydrocarbon wax is 15.0 parts by mass or less, preferably 10.0 parts by mass or less, and 5.0 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. parts by mass or less, more preferably 3.5 parts by mass or less, even more preferably 2.5 parts by mass or less, and even more preferably 2.0 parts by mass or less. Formability tends to be further improved by making it equal to or less than the above upper limit.
The resin composition of the present embodiment may contain only one type of (D) hydrocarbon wax, or may contain two or more types. When two or more types are included, the total amount is preferably within the above range.

In the resin composition of the present embodiment, (D)/(C), which is the mass ratio of (D) hydrocarbon wax and (C) silicone oil, is preferably 1.0 or less, and is 0.9 or less. is more preferably 0.8 or less, even more preferably 0.7 or less, and even more preferably 0.65 or less. It is practical that the lower limit of (D)/(C) is 0.1 or more.

<Other ingredients>
Known additives and fillers may be added to the resin composition of the present embodiment as long as the objects of the present invention are not impaired. Specific examples of additives and fillers that can be used in the present embodiment include known thermoplastic polymers, antistatic agents, ultraviolet absorbers, light stabilizers, carbon fibers, glass fibers, glass flakes, and talc. , mica, calcium carbonate, potassium titanate whiskers, and the like.
The total content of these components is preferably 10 mass % or less of the resin composition.
The resin composition of the present embodiment comprises (A) a polyacetal resin, (B) an olefin polymer, (C) a silicone oil having a kinematic viscosity at 25° C. of 1,000 to 55,000 cSt, and (D) a hydrocarbon wax. The total content of the resin composition is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 99% by mass or more.

<Physical property values of the resin composition>
The limit PV value of the resin composition of the present embodiment is preferably 10.0 or more, more preferably 11.0 or more. A practical upper limit of the limit PV value is, for example, 25.0 or less. The limiting PV values were obtained by forming a cylindrical thrust test piece, and applying a surface pressure of 0.15, 0.25, 0.49, 0.74, 0.98, 1.0 in an atmosphere of 23° C. and 50% humidity. It is a value obtained by multiplying the surface pressure immediately before the surface pressure at which the test piece melted or abnormally worn and the linear velocity by increasing the pressure to 23 and 1.47 MPa every 3 minutes.
The resin composition of the present embodiment has a dynamic friction coefficient of 0.17 when molded into a cylindrical thrust test piece and measured at a surface pressure of 0.49 MPa and a linear velocity of 0.1 m / sec at a temperature of 23 ° C. and a humidity of 50%. It is preferably 0.15 or less, more preferably 0.14 or less, and even more preferably 0.13 or less. A practical lower limit is, for example, 0.01 or more.
The limit PV value and dynamic friction coefficient are measured according to the description of the examples below.

<Method for producing resin composition>
The resin composition of the present embodiment is easily prepared by a known method generally used as a method for preparing conventional thermoplastic resin compositions. For example, (1) a method of mixing all the components that make up the composition, feeding this to an extruder and melt-kneading to obtain a pellet-like composition, (2) a method of obtaining a pellet-like composition, A method of obtaining a composition in the form of pellets by supplying the remaining components from the main feed port of the extruder and melt-kneading them from the side feed port. It is also possible to adopt a method of adjusting the composition to a predetermined composition.

Examples of kneaders include kneaders, Banbury mixers, and extruders. Various conditions and devices for mixing and kneading are not particularly limited, and may be determined by appropriately selecting from conventionally known arbitrary conditions. The kneading is preferably performed at a temperature higher than the melting temperature of the polyacetal resin, specifically at a temperature higher than the melting temperature of the polyacetal resin (generally 180° C. or higher).

In particular, in the present embodiment, (A) polyacetal resin, (B) olefin polymer, and (D) hydrocarbon wax are introduced from the supply port of the extruder, kneaded, and then (C) is supplied from the liquid supply pump. It is preferable to include adding a silicone oil having a kinematic viscosity of 1,000 to 55,000 cSt at 25° C. and further kneading.
FIG. 1 is a schematic illustration of an example of an extruder used in the method for producing a resin composition of the present embodiment. This extruder 1 is composed of a raw material supply port 2 , a resin melting section 3 , a kneading and dispersing section 4 , a liquid supply pump 5 , an extrusion section 6 and a take-out section 7 . First, (A) a polyacetal resin, (B) an olefin polymer, (D) a hydrocarbon wax, and, if necessary, other components are supplied from a raw material supply port 2 provided in a resin melting section 3 . At this time, (C) silicone oil is not supplied. Next, these are sent to the kneading and dispersing section 4 and uniformly mixed. Further, (C) silicone oil is introduced from the liquid supply pump 5 and further kneaded. Next, the resin composition is extruded from the extruding section 6, cooled, taken out from the take-out section 7, and cut after cooling to obtain a resin composition in the form of pellets.

<Molded product>
The molded article of this embodiment is formed from the resin composition of this embodiment. Pellets obtained by pelletizing the resin composition of the present embodiment are molded by various molding methods to obtain molded articles. Alternatively, the resin composition melted and kneaded by an extruder can be directly molded into a molded product without going through pellets.
The shape of the molded product is not particularly limited and can be appropriately selected according to the use and purpose of the molded product. Circular, elliptical, gear-shaped, polygonal, odd-shaped, hollow, frame-shaped, box-shaped, panel-shaped and the like can be mentioned. The molded product of this embodiment may be a finished product or a part.

The method for molding the molded article is not particularly limited, and conventionally known molding methods can be employed, such as injection molding, injection compression molding, extrusion molding, profile extrusion, transfer molding, blow molding, Gas-assisted blow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding) molding, rotational molding, multi-layer molding, two-color molding, insert molding, sandwich molding, foam molding, additive A compression molding method and the like can be mentioned.

The resin composition of the present embodiment is preferably used for forming sliding members. Therefore, the molded article formed from the resin composition of this embodiment is preferably used as a sliding member (sliding part).
Specific examples of sliding members include gears, rotary shafts, bearings, gears, End face materials for cams and mechanical seals, valve seats for valves, sealing members such as V-rings, rod packings, piston rings and rider rings, rotating shafts for compressors, rotating sleeves, pistons, impellers, rollers and other sliding members mentioned.

The sliding member of the present embodiment can be used not only with the sliding members of the present embodiment, but also with other resin sliding members, fiber-reinforced resin sliding members, ceramics, and metal sliding members. It can also be used as a member.

EXAMPLES The present invention will be described more specifically with reference to examples below. The materials, usage amounts, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Accordingly, the scope of the present invention is not limited to the specific examples shown below.
If the measuring instruments and the like used in the examples are discontinued and difficult to obtain, other instruments having equivalent performance can be used for measurement.

A-1: Polyacetal resin (MFR: 45)
Mitsubishi Engineering-Plastics Iupital F40-03, melt flow rate (MFR) (measured at 190 ° C., load 2.16 kg, hereinafter the same for MFR of polyacetal resin): 52 g / 10 minutes A-2: Polyacetal resin (MFR :30)
Iupital F30-03 manufactured by Mitsubishi Engineering-Plastics, melt flow rate (MFR): 27 g/10 minutes A-3: polyacetal resin (MFR: 12)
Iupital A25-03 manufactured by Mitsubishi Engineering-Plastics, melt flow rate (MFR): 14 g/10 minutes

B-1: Toughmer MA9015
Maleic anhydride-modified ethylene-butene copolymer, acid value 11.6 mgKOH/g, MFR (measured at 190°C under a load of 2.16 kg, hereinafter the same for polyolefin MFR): 11.0 g/min, Vicat softening temperature 30 ~40°C, Mitsui Chemicals B-2: Toughmer MH5020
Maleic anhydride-modified olefin polymer, acid value 15.5 mg KOH/g, MFR 0.6 g/min, Vicat softening temperature 30 to 40° C., Mitsui Chemicals B-3: Toughmer MH7510
Maleic anhydride-modified olefin polymer, acid value 7.3 mgKOH/g, MFR 40.0 g/min, Vicat softening temperature of about 30 to 40°C, Mitsui Chemicals B-4: Novatec LC522
Acid-unmodified olefin polymer, acid value 0 mgKOH/g, MFR 4.0 g/min, Vicat softening temperature of about 90°C, manufactured by Japan Polyethylene Co., Ltd.

C-1: Silicone oil 1000cSt
Manufacturer: Shin-Etsu Chemical Co., Ltd., KF-96H-1,000 cs, kinematic viscosity at 25 ° C. is 1000 cSt
C-2: Silicone oil 6000cSt
Manufacturer: Shin-Etsu Chemical Co., Ltd., KF-96H-6,000cs, kinematic viscosity at 25 ° C. is 6000cSt
C-3: Silicone oil 10000cSt
Manufacturer: Shin-Etsu Chemical Co., Ltd., KF-96H-10,000cs, kinematic viscosity at 25 ° C. is 10000cSt
C-4: Silicone oil 30000cSt
Manufacturer: Shin-Etsu Chemical Co., Ltd., KF-96H-30,000, kinematic viscosity at 25 ° C. is 30000 cSt
C-5: Silicone oil 60000cSt
Manufacturer: Shin-Etsu Chemical Co., Ltd., KF-96H-60,000, kinematic viscosity at 25 ° C. is 60000 cSt

D-1: Paraffin wax 155F
Manufacturer: Nihon Seiro Co., Ltd. Vicat Softening temperature: Unmeasurable, molecular weight (viscosity method) 300-550
D-2: High wax 720P
Low molecular weight polyethylene, Vicat softening temperature: not measurable, molecular weight (viscosity method) 2700, Mitsui Chemicals D-3: Sanwax 151P
Sanyo Kasei Co., Ltd., low molecular weight polyethylene, Vicat softening temperature: not measurable, number average molecular weight: 2000

<Measurement of acid value>
The mass of potassium hydroxide required for neutralizing 1 g of a sample (acid-modified olefin polymer, polyethylene wax, etc.) was measured and taken as the acid value.
Specifically, it was measured by neutralization titration according to JIS K0070. 1 g of the sample was precisely weighed and dissolved in 100 mL of xylene with stirring at about 120°C. After complete dissolution, a phenolphthalein solution was added, and neutralization titration was performed using a 0.1 mol/L potassium hydroxide ethanol solution whose exact concentration had been determined in advance. The amount of dropping (T), the factor (f) of 0.1 mol / L potassium hydroxide ethanol solution, 1/10 (5.611) of the formula weight of potassium hydroxide 56.11, and the mass (S) of the sample, the following formula The acid value was calculated by
Acid value = T x f x 5.611/S
Units are given as mgKOH/g.

<Measurement of kinematic viscosity>
Measured with an Ubbelohde viscometer according to ASTM D 445-46T.

Examples 1-11, Comparative Examples 1-5
<Compound>
Each component was blended as shown in Tables 1 and 2 below (the unit of each component in Tables 1 and 2 is parts by mass), preblended, and then a 30 mm diameter twin-screw extrusion having one vent port. (Extrusion conditions: L/D = 35, extrusion temperature = 190°C, screw speed = 120 rpm, vent vacuum pressure = -0.08 MPa, discharge rate = 10 kg/hr). , to prepare a resin composition in the form of pellets. The mixture was put into a twin-screw extruder with a diameter of 26 mm (manufactured by Shibaura Kikai Co., Ltd.) from the root, and after melting, silicone oil was supplied using a liquid supply pump to prepare resin pellets. Extrusion temperature was 190° C., screw rotation speed was 120 rpm, bend vacuum pressure was −0.08 MPa, and discharge rate was 12 kg/hr.
The following evaluation was performed using the obtained resin composition.

<Compared to F20-03 limit PV value>
Cylindrical thrust test pieces were produced by injection molding at a cylinder temperature of 200°C and a mold temperature of 80°C. Using a thrust type friction wear tester manufactured by Orientec Co., Ltd., the surface pressure is 0.15, 0.25, 0.49, 0.74, 0.98, 1.23 in an atmosphere of 23 ° C. and 50% humidity. , and 1.47 MPa every 3 minutes, and the value obtained by multiplying the surface pressure immediately before the surface pressure at which the test piece was melted or abnormally worn by the linear velocity was defined as the limit PV.

<Compared to F20-03 (10kg) dynamic friction coefficient (-)>
Cylindrical thrust test pieces were produced by injection molding at a cylinder temperature of 200°C and a mold temperature of 80°C. Using a thrust-type friction wear tester manufactured by Orientec Co., Ltd., the measurement was performed at a temperature of 23° C. and a humidity of 50% at a surface pressure of 0.49 MPa and a linear velocity of 0.1 m/sec.

<Compared to F20-03 wear (F20-03 / own material)>
Cylindrical thrust test pieces were produced by injection molding at a cylinder temperature of 200°C and a mold temperature of 80°C. Using an Orientec thrust type friction wear tester, the temperature is 23 ° C., the humidity is 50%, the surface pressure is 0.15 MPa, the linear velocity is 0.3 m / sec. Calculated.

<Moldability>
Using an injection molding machine, the cylinder temperature is set to 200 ° C., the mold temperature is set to 80 ° C., the injection time is 45 seconds, and the cooling time is 20 seconds. A compact was obtained. Moldability was evaluated by the time required for weighing.
A: Within 15 seconds B: Within 18 seconds C: More than 18 seconds

As is clear from the above results, the resin composition of the present invention was excellent in slidability and moldability (Examples 1 to 11).
On the other hand, when the kinematic viscosity of the silicone oil was high (Comparative Example 1), the slidability was poor. Moreover, when silicone oil was not contained (Comparative Example 2), the slidability was inferior. Moreover, when the hydrocarbon wax was not contained (Comparative Example 3), the slidability was poor. Moreover, when the mass ratio of (B)/(C) exceeded 2.0 (Comparative Example 4), the slidability was poor. Further, when the olefin polymer was not contained (Comparative Example 5), the moldability was inferior.

1 extruder 2 raw material supply port 3 resin melting section 4 kneading and dispersing section 5 liquid supply pump 6 extruding section 7 taking-out section

Claims

(A) for 100 parts by mass of polyacetal resin,
(B) 0.1 to 30.0 parts by mass of an olefin polymer;
(C) 0.1 to 30.0 parts by mass of a silicone oil having a kinematic viscosity at 25°C of 1,000 to 55,000 cSt;
(D) 0.1 to 15.0 parts by mass of a hydrocarbon wax,
The mass ratio (B)/(C) of the (B) olefin polymer and (C) the silicone oil is 2.00 or less.
Resin composition.
2. The resin composition according to claim 1, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.10 or more.
3. The resin composition according to claim 1, wherein the (B) olefin polymer is selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, and ethylene-butene copolymers.
3. The resin composition according to claim 1, wherein the (B) olefin polymer comprises an ethylene-butene copolymer.
3. The resin composition according to claim 1, wherein the (B) olefin polymer has a Vicat softening temperature of 30° C. or higher according to JIS K7206.
3. The resin composition according to claim 1, wherein the content of the (B) olefin polymer is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin.
3. The resin composition according to claim 1, wherein the content of said (C) silicone oil is 0.5 to 5.0 parts by mass with respect to 100 parts by mass of said (A) polyacetal resin.
3. The resin composition according to claim 1, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.80 or less.
The resin composition according to claim 1 or 2, wherein (B)/(C), which is the mass ratio of (B) the olefin polymer and (C) the silicone oil, is 0.50 or less.
(D)/(C), which is the mass ratio of (D) hydrocarbon wax and (C) silicone oil
is 1.0 or less, the resin composition according to claim 1 or 2.
3. The resin composition according to claim 1, which is used for forming a sliding member.
A pellet of the resin composition according to claim 1 or 2.
A molded article formed from the resin composition according to claim 1 or 2.
A shaped article formed from the pellets of claim 12 .
14. The molded article according to claim 13, which is a sliding member.
A method for producing the resin composition according to claim 1 or 2,
(A) Polyacetal resin, (B) olefin polymer, and (D) hydrocarbon wax are charged from the feed port of the extruder and kneaded. A method for producing a resin composition, comprising adding a silicone oil of 1,000 to 55,000 cSt and further kneading.