WO2023238790A1

WO2023238790A1 - Resin composition and molded article

Info

Publication number: WO2023238790A1
Application number: PCT/JP2023/020627
Authority: WO
Inventors: 啓太伊久間; 裕太山元
Original assignee: グローバルポリアセタール株式会社
Priority date: 2022-06-09
Filing date: 2023-06-02
Publication date: 2023-12-14
Also published as: TW202409186A; JP7550321B2; JPWO2023238790A1

Abstract

Provided are: a resin composition that yields molded articles having exceptional moderate flexibility, exceptional sliding properties, and exceptional weld elongation; and a molded article that is formed from the resin composition. A resin composition containing a polyacetal resin (A), a core-shell elastomer (B), and silicone (C), wherein the core-shell elastomer (B) has an average secondary particle size of 10-250 nm in the polyacetal resin (A), the content value for the core-shell elastomer (B) is 5-25 mass% in the resin composition, the kinematic viscosity at 25°C of the silicone (C) is 4,000,000 to 30,000,000 cSt, and the content value for the silicone (C) is 0.3-1 mass% in the resin composition.

Description

Resin compositions and molded products

The present invention relates to a resin composition and a molded article. In particular, it relates to a resin composition containing polyacetal resin as a main component.

Polyacetal resin is used in a wide range of applications as a plastic with excellent mechanical properties, electrical properties, and chemical properties such as chemical resistance.
Here, in order to impart flexibility to the polyacetal resin, consideration has been given to incorporating an elastomer into the polyacetal resin.
For example, Patent Document 1 describes a resin composition containing a polyacetal resin and a core-shell elastomer, in which the resin composition is molded into a multipurpose test piece with a thickness of 4 mm, and the bending elastic modulus measured according to ISO178 is 1700 MPa or less. and the resin composition has a weld elongation of 20% or more when the resin composition is molded into a 1.6 mm thick test piece having a weld part in the center and pulled at 10 mm/min according to ASTM D638. things are listed.

JP 2021-011562 Publication

A molded article obtained from a resin composition containing a polyacetal resin and an elastomer described in Patent Document 1 has excellent flexibility. On the other hand, as the uses of polyacetal resins have expanded in recent years, there has been a demand for resin compositions that can yield molded products that are flexible and have excellent sliding properties.
Here, in order to improve sliding properties, it is conceivable to blend silicone into the polyacetal resin. However, when an elastomer or silicone is blended with a polyacetal resin, the weld elongation of the resulting molded product tends to be poor. When weld elongation deteriorates, the strength of the molded product decreases.
The present invention aims to solve the above-mentioned problems, and provides a resin composition from which a molded article having moderate flexibility, excellent sliding properties, and excellent weld elongation can be obtained, and It is an object of the present invention to provide a molded article formed from the resin composition.

Based on the above-mentioned problem, the present inventor conducted a study and found that a predetermined amount of a core-shell elastomer having a predetermined average secondary particle diameter in the polyacetal resin and a silicone having a predetermined kinematic viscosity are blended into the polyacetal resin. We have found that the above problems can be solved by this method.
Specifically, the above problem was solved by the following means.
<1> A resin composition containing a polyacetal resin (A), a core-shell elastomer (B), and a silicone (C),
The core-shell elastomer (B) has an average secondary particle diameter of 10 to 250 nm in the polyacetal resin (A),
The content of the core-shell elastomer (B) is 5 to 25% by mass in the resin composition,
A resin composition, wherein the silicone (C) has a kinematic viscosity at 25° C. of 4 million to 30 million cSt, and the content thereof is 0.3 to 1% by mass in the resin composition.
<2> The resin composition according to <1>, wherein the core-shell elastomer (B) has a crosslinking index in the range of 0.11 to 0.30.
<3> The resin composition according to <1> or <2>, wherein in the core-shell elastomer (B), the core contains a butadiene-containing rubber and the shell contains an acrylic resin.
<4> The resin composition according to any one of <1> to <3>, further comprising a hydrazide compound and/or a urea compound.
<5> The resin according to any one of <1> to <4>, wherein the mass ratio (B)/(C) of the core-shell elastomer (B) and silicone (C) is 8 to 40. Composition.
<6> The resin composition according to any one of <1> to <5>, which is used for trim clip molding.
<7> The core-shell elastomer (B) has a crosslinking index in the range of 0.11 to 0.30, and in the core-shell elastomer (B), the core contains a butadiene-containing rubber, the shell contains an acrylic resin, and , contains a hydrazide compound and/or a urea compound, the mass ratio (B)/(C) of the core-shell elastomer (B) and silicone (C) is 8 to 40, and is for trim clip molding, <1 ＞The resin composition described in ＞.
<8> Pellets of the resin composition according to any one of <1> to <7>.
<9> A molded article formed from the resin composition according to any one of <1> to <7>.
<10> A molded article formed from the pellets described in <8>.
<11> The molded product according to <9>, which is a trim clip.

ADVANTAGE OF THE INVENTION According to the present invention, it has become possible to provide a resin composition from which a molded article with moderate flexibility, excellent sliding properties, and excellent weld elongation can be obtained, and a molded article formed from the resin composition. Ta.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. Note that the present embodiment below is an illustration for explaining the present invention, and the present invention is not limited only to this embodiment.
In addition, in this specification, "~" is used to include the numerical values described before and after it as a lower limit value and an upper limit value.
In this specification, various physical property values and characteristic values are assumed to be at 23° C. unless otherwise stated.
If the measurement methods, etc. explained in the standards shown in this specification differ from year to year, unless otherwise stated, they shall be based on the standards as of January 1, 2022.

The resin composition of the present embodiment is a resin composition containing a polyacetal resin (A), a core-shell elastomer (B), and a silicone (C), in which the core-shell elastomer (B) is contained in the polyacetal resin (A). , the average secondary particle diameter is 10 to 250 nm, the content of the core-shell elastomer (B) is 5 to 25% by mass in the resin composition, and the kinematic viscosity of the silicone (C) at 25°C is 4 million ~30 million cSt, and the content is 0.3~1% by mass in the resin composition. By employing such a resin composition, it is possible to obtain a resin composition from which a molded article having excellent flexibility, excellent sliding properties, and excellent weld elongation can be obtained.
When an elastomer is blended with the polyacetal resin (A), the flexibility of the resulting molded product tends to improve. On the other hand, when silicone is blended, the sliding properties tend to improve. However, when an elastomer or silicone is blended with the polyacetal resin (A), weld elongation tends to be poor. In the present invention, in order to solve this problem, a core-shell elastomer (B) having an average secondary particle diameter of 10 to 250 nm is blended into the polyacetal resin (A) as an elastomer. By setting the average secondary particle diameter of the core-shell elastomer (B) within a predetermined range, the interfacial force applied between the core-shell elastomer (B) and the polyacetal resin (A) can be reduced, and weld elongation can be increased. Guessed. Furthermore, it is presumed that by using a predetermined amount of silicone (C) having a predetermined kinematic viscosity, it was possible to effectively suppress a decrease in weld elongation while maintaining sliding properties.

<Polyacetal resin (A)>
The resin composition (A) of this embodiment contains a polyacetal resin.
The polyacetal resin is not particularly limited, and even if it is a homopolymer containing only divalent oxymethylene groups as a constituent unit, it may contain a divalent oxymethylene group and a divalent oxyalkylene having 2 to 6 carbon atoms. It may also be a copolymer containing the group as a constituent unit.

Examples of the oxyalkylene group having 2 to 6 carbon atoms include oxyethylene group, oxypropylene group, and oxybutylene group.

In the polyacetal resin, the proportion of the oxyalkylene group having 2 to 6 carbon atoms in the total number of moles of the oxymethylene group and the oxyalkylene group having 2 to 6 carbon atoms is not particularly limited, and is 0.5 to 10 mol. % is sufficient.

In order to manufacture the above polyacetal resin, trioxane is usually used as the main raw material. Further, in order to introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin, a cyclic formal or a cyclic ether can be used. Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, 1,3,6-trioxocane, etc. Specific examples of the cyclic ether include ethylene oxide, propylene oxide, and butylene oxide. To introduce oxyethylene groups into polyacetal resin, 1,3-dioxolane may be used as the main raw material, and to introduce oxypropylene groups, 1,3-dioxane may be used as the main raw material. In order to introduce an oxybutylene group, 1,3-dioxepane may be used as the main raw material. In addition, in the polyacetal resin, the amount of hemiformal terminal groups, the amount of formyl terminal groups, and the amount of terminal groups unstable to heat, acids, and bases is preferably small. Here, the hemiformal end group is represented by -OCH ₂ OH, and the formyl end group is represented by -CHO.

As the polyacetal resin, in addition to the above, polyacetal resins described in paragraphs 0018 to 0043 of JP 2015-074724A can be used, the contents of which are incorporated herein.

The resin composition (A) of the present embodiment preferably contains 70% by mass or more of polyacetal resin, more preferably 75% by mass or more, and further preferably contains 80% by mass or more. Preferably, it is more preferably contained in an amount of 85% by mass or more. The upper limit is preferably 95% by mass or less, more preferably 92% by mass or less.
The resin composition of this embodiment may contain only one type of polyacetal resin, or may contain two or more types of polyacetal resin. When two or more types are included, it is preferable that the total amount falls within the above range.

<Core shell elastomer (B)>
The resin composition of this embodiment includes a core-shell elastomer (B). By using an elastomer, flexibility can be imparted to the resulting molded product. Further, by using a core-shell elastomer as the elastomer, a decrease in weld elongation can be effectively suppressed. Furthermore, by adjusting the core-shell elastomer (B) to have an average secondary particle size of 10 to 250 nm in the polyacetal resin (A), it is possible to effectively reduce weld elongation while maintaining high flexibility. can be suppressed to
A core-shell elastomer is a polymer with a multilayer structure having a core part and a shell layer covering part or all of the core part, and Kaneka Corporation's Kane Ace series and Mitsubishi Chemical Corporation's Metablen series are known.

The average secondary particle diameter of the core-shell elastomer (B) in the polyacetal resin (A) is 10 to 250 nm. By setting the average secondary particle diameter of the core-shell elastomer (B) to 250 nm or less, the core-shell elastomer (B) is easily dispersed in the polyacetal resin (A), and weld elongation can be increased. This is because when the average secondary particle diameter of the core-shell elastomer (B) becomes large, the core-shell elastomer (B) becomes a starting point for fracture in the molded product. Moreover, the interfacial force applied between the core-shell elastomer (B) and the polyacetal resin (A) is also reduced, and weld elongation can be increased. Such an average secondary particle diameter of the core-shell elastomer (B) in the polyacetal resin (A) can be achieved by adjusting the selection of the type of core-shell elastomer (B), the fluidity of the polyacetal resin, the melt-kneading conditions, etc. be done.

The average secondary particle diameter of the core-shell elastomer (B) is preferably 240 nm or less, more preferably 210 nm or less, even more preferably 180 nm or less, even more preferably 150 nm or less, and even more preferably 120 nm or less. It is even more preferable that Moreover, it is more preferably 30 nm or more, even more preferably 50 nm or more, even more preferably 80 nm or more, and even more preferably 100 nm or more.
The average secondary particle diameter of the core-shell elastomer (B) is measured according to the description in the examples below.

The core-shell elastomer (B) used in this embodiment preferably has a crosslinking index in the range of 0.11 to 0.30.
The crosslinking index of the core-shell elastomer (B) is more preferably 0.15 or more, further preferably 0.19 or more, and preferably 0.29 or less, more preferably 0.28 or less, and even more preferably 0.27 or less. . The crosslinking index means the degree of intermolecular crosslinking in the core portion of the core-shell elastomer. That is, the larger the crosslinking index, the harder the elastomer, and the smaller the crosslinking index, the softer the elastomer. By setting the crosslinking index to the lower limit value or more, weld elongation becomes high. This is presumably because the harder the elastomer is, the more it will not be deformed by the force applied to the weld portion during molding, and will be able to maintain its spherical shape. Furthermore, by setting the crosslinking index to be less than or equal to the upper limit value, the impact resistance, which is the role of the elastomer, cannot be absorbed, and impact resistance tends to be more effectively exhibited.
The crosslinking index of the core-shell elastomer (B) can be adjusted, for example, by the polymerization conditions during production of the core-shell elastomer.
The crosslinking index of the core-shell elastomer (B) is measured and calculated by the method described in the Examples below.

Although the type of core-shell elastomer (B) used in this embodiment is not particularly limited, the core is preferably a rubber-based polymer. The rubber-based polymer preferably contains at least one selected from butadiene-containing rubber, butyl acrylate-containing rubber, 2-ethylhexyl acrylate-containing rubber, and silicone-based rubber, and preferably contains butadiene-containing rubber. More preferred. The shell is preferably a polymer of one or more monomers such as (meth)acrylic esters and aromatic vinyl compounds, and units derived from (meth)acrylic esters account for 50% by mass or more of the whole. Polymers (acrylic resins) are more preferred.
In the core-shell elastomer (B) used in this embodiment, it is preferable that the core contains a rubber-based polymer and the shell contains an acrylic resin. When such a core-shell elastomer is used, the effects of the present invention tend to be more effectively exhibited.

The resin composition of the present embodiment contains the core-shell elastomer (B) in an amount of 5% by mass or more, preferably 6% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. When the content is equal to or more than the lower limit, the resulting molded product tends to have improved flexibility. The upper limit of the content of the core-shell elastomer (B) is 25% by mass or less, preferably 22% by mass or less, more preferably 18% by mass or less, and more preferably 16% by mass or less. More preferably, it may be 14% by mass or less. By setting it below the above-mentioned upper limit, softness and weld elongation can be improved in a well-balanced manner.
The resin composition of this embodiment may contain only one type of core-shell elastomer (B), or may contain two or more types of core-shell elastomer (B). When two or more types are included, it is preferable that the total amount falls within the above range.

<Silicone (C)>
The resin composition of this embodiment contains silicone (C). By including silicone (C), the slidability of the obtained molded product can be improved.
The kinematic viscosity at 25° C. of the silicone compound (C) used in this embodiment is 4 million cSt or more, preferably 7 million cSt or more, and more preferably 10 million cSt or more. By setting it above the lower limit value, the limit PV value tends to be further improved. Further, the kinematic viscosity at 25°C of the silicone compound (C) is 30 million cSt or less, preferably 28 million cSt or less, more preferably 25 million cSt or less, and 20 million cSt or less. It is even more preferable. By setting it below the above-mentioned upper limit, the dispersibility of silicone (C) in the polyacetal resin is improved, and weld elongation tends to be further improved.

The silicone compound (C) is not specifically defined, but polyorganosiloxane is preferable. Examples of organic groups that polyorganosiloxane may have include alkyl groups having 2 to 20 carbon atoms, phenyl groups, halogenated phenyl groups, silicone-containing groups, epoxy groups, amino groups, alcoholic hydroxyl groups, and polyether groups. Examples include.
In this embodiment, the silicone compound (C) is preferably silicone gum.

The content of silicone (C) in the resin composition of this embodiment is preferably 0.3% by mass or more, more preferably 0.4% by mass or more. By making it equal to or more than the lower limit, sliding properties can be improved. Further, the upper limit of the content of silicone (C) in the resin composition is 1% by mass or less, preferably 0.9% by mass or less, and more preferably 0.8% by mass or less. It is preferably 0.7% by mass or less, more preferably 0.6% by mass or less, and even more preferably 0.6% by mass or less. By setting it below the above-mentioned upper limit, weld elongation can be maintained at a high level.
The resin composition of this embodiment may contain only one type of silicone (C), or may contain two or more types of silicone (C). When two or more types are included, it is preferable that the total amount falls within the above range.

In the resin composition of the present embodiment, the total amount of polyacetal resin (A), core shell elastomer (B), and silicone (C) preferably accounts for 96% by mass or more, and preferably 97% by mass or more of the resin composition. is more preferable, more preferably 98% by mass or more, and may be 99% by mass or more. However, the total amount of polyacetal resin (A), core-shell elastomer (B), and silicone (C) does not exceed 100% by mass.
Further, in the resin composition of the present embodiment, the mass ratio (B)/(C) of the core-shell elastomer (B) and silicone (C) is preferably 8 or more, and more preferably 9 or more. It is preferably 10 or more, and more preferably 10 or more. By setting it above the lower limit value, weld elongation tends to be further improved. Further, the ratio (B)/(C) is preferably 40 or less, more preferably 35 or less, even more preferably 32 or less, even more preferably 30 or less, and 25 or less. It is even more preferable that there be. By setting it below the above-mentioned upper limit value, slidability tends to be further improved.

<Formaldehyde scavenger>
The resin composition of this embodiment may contain a formaldehyde scavenger. By including a formaldehyde scavenger, the generation of formaldehyde from the resulting molded product can be effectively suppressed.
The formaldehyde scavenger preferably contains at least one selected from the group consisting of a hydrazide compound, a hydrazone compound of a hydrazine compound, a guanamine compound, and a urea compound, and more preferably a hydrazide compound and/or a urea compound.

For details of these formaldehyde scavengers, the descriptions in paragraphs 0021 to 0036 of JP-A No. 2020-132662 can be referred to, the contents of which are incorporated herein.

The resin composition of the present embodiment preferably contains 0.05 parts by mass or more, and more preferably 0.10 parts by mass, of a formaldehyde scavenger based on 100 parts by mass of the polyacetal resin (A). Further, the formaldehyde scavenger is preferably contained in an amount of 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, based on 100 parts by mass of the polyacetal resin.
The resin composition of this embodiment may contain only one type of formaldehyde scavenger, or may contain two or more types of formaldehyde scavengers. When two or more types are included, the total amount falls within the above range.

<Other ingredients>
The resin composition of the present embodiment may contain any conventionally known additives and fillers within a range that does not impair the object of the present invention. Examples of additives and fillers used in this embodiment include thermoplastic resins other than polyacetal resins, ultraviolet absorbers, antioxidants, heat stabilizers, stabilizers, antistatic agents, carbon fibers, dyes, and carbon black. Examples include organic pigments such as, inorganic pigments such as titanium oxide, glass fibers, glass flakes, potassium titanate whiskers, and the like. For these details, the descriptions in paragraphs 0113 to 0124 of JP 2017-025257 A can be referred to, and the contents thereof are incorporated herein.

<Physical properties of resin composition>
It is preferable that the resin composition of this embodiment has excellent weld elongation and does not break before yielding. Specifically, when the resin composition of this embodiment is molded into an ASTM tensile test piece (thickness 1.6 mm) and a tensile test is performed according to ASTM D638, the weld elongation is 14% or more. It is preferably 17% or more, more preferably 18% or more, and even more preferably 20% or more. Further, the upper limit of the weld elongation is, for example, 300% or less.

The resin composition (A) of this embodiment has a flexural modulus of 1000 MPa or more when the resin composition (A) is molded into a 4 mm thick multipurpose test piece (ISO test piece) and measured according to ISO178. It is preferably at least 1,500 MPa, more preferably at most 3,000 MPa, and more preferably at most 2,500 MPa.
In this embodiment, by setting it within the above range, a molded product having appropriate flexibility can be obtained.
The above flexural modulus is achieved primarily by blending a core elastomer.

<Method for manufacturing resin composition>
The resin composition of this embodiment contains the above-mentioned essential components and, if necessary, the above-mentioned arbitrary components. Any manufacturing method is selected so that the average secondary particle diameter falls within the above-mentioned range. These raw materials may be mixed and kneaded using any conventionally known method for producing a resin composition.

One method for making the average secondary particle size within the above range is to mix the polyacetal resin and core-shell elastomer in a tumbler, extrude it in a melt kneader, make it into strands, and then cut it into pellets. Can be mentioned. At this time, it is preferable to use a twin-screw extruder as the melt-kneading machine, since a single-screw extruder tends to cause secondary agglomeration. Among them, L/D, which is the ratio of the length L (mm) of the screw to the diameter D (mm) of the same screw, is preferably 20 or more, more preferably 30 or more, and 100 or less. It is preferably 70 or less, and more preferably 70 or less. By setting the L/D to 20 or more, the core-shell elastomer becomes easily finely dispersed, and secondary aggregation of the core-shell elastomer can be effectively suppressed. Further, by setting the L/D to 100 or less, discoloration of the resin composition due to thermal deterioration tends to be effectively suppressed.
The shape of the die nozzle is also not particularly limited, but in terms of pellet shape, a circular nozzle with a diameter of 1 mm or more is preferable, a circular nozzle with a diameter of 2 mm or more is more preferable, a circular nozzle with a diameter of 10 mm or less is preferable, and a circular nozzle with a diameter of 7 mm or less is preferable. Nozzles are more preferred.

Further, the melting temperature of the resin composition during melt-kneading is preferably 170°C or higher, more preferably 190°C or higher, and preferably 250°C or lower, and preferably 230°C or lower. More preferred. By setting the melting temperature to 170° C. or higher, melting becomes sufficient and production volume tends to improve. Moreover, by setting the temperature to 250° C. or lower, discoloration of the resin composition due to thermal deterioration tends to be effectively suppressed.

Although the screw configuration of the twin-screw extruder is not particularly limited, one preferred embodiment includes having at least two kneading sections. The kneading section has a kneading disk and mainly contributes to melting the resin and dispersing the elastomer.

The screw rotation speed during melt-kneading is preferably 50 rpm or more, more preferably 70 rpm or more, and preferably 500 rpm or less, and more preferably 350 rpm or less. By setting the screw rotation speed to 50 rpm or more, the core-shell elastomer tends to be finely dispersed, and the occurrence of secondary aggregation can be more effectively suppressed. Furthermore, by setting the speed to 500 rpm or less, heat generation during melt-kneading can be suppressed, and discoloration of the resin composition due to thermal deterioration tends to be effectively suppressed. Further, the discharge rate is preferably 5 kg/hr or more, more preferably 7 kg/hr or more, preferably 1,000 kg/hr or less, and more preferably 800 kg/hr or less. By setting the rate to 5 kg/hr or more, the core-shell elastomer becomes more easily finely dispersed, and the occurrence of secondary aggregation can be effectively suppressed. Further, by controlling the amount to be 1,000 kg/hr or less, heat generation during melt-kneading can be effectively suppressed, and discoloration of the resin composition due to thermal deterioration tends to be effectively suppressed.

The ratio (Q/Ns) between the screw rotation speed (Ns) and the discharge amount (Q) during melt-kneading depends on the screw diameter and screw configuration of the extruder, but is preferably 0.5 or more, and 0.7 The above is more preferable, 0.9 or more is particularly preferable, 1.5 or less is preferable, 1.3 or less is even more preferable, and 1.2 or less is particularly preferable. The above Q/Ns is particularly preferable in an embodiment in which the screw diameter is 18 to 75 mm (even 58 mm) and the screw configuration has two kneading sections.

Examples of the kneading machine include a kneader, a Banbury mixer, and an extruder. The various conditions and equipment for mixing and kneading are also not particularly limited, and may be determined by appropriately selecting from any conventionally known conditions. The kneading is preferably carried out 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).

<Molded product>
The molded article of this embodiment is formed from the resin composition of this embodiment. Further, the resin composition of the present embodiment is usually made into a molded product by injection molding the pellets obtained by directly or by pelletizing the resin composition.
That is, a preferable example of the molded product of this embodiment is an injection molded product. An injection molded product is a molded product formed by injection molding, and a weak portion (weld portion) is usually formed at a portion where molten resin joins within a mold.
The shape of the molded product is not particularly limited and can be appropriately selected depending on the use and purpose of the molded product, such as plate, plate, rod, sheet, film, cylindrical, annular, etc. Examples include circular shapes, elliptical shapes, gear shapes, polygonal shapes, irregularly shaped products, hollow products, frame shapes, box shapes, panel shapes, cap shapes, and the like. The molded product of the present invention may be a component or a finished product.

<Application>
The resin composition of the present embodiment and molded products formed from the resin composition are, for example, automotive parts such as trim clips, seatbelt members, and headrest guides, building material parts, electric/electronic parts, office equipment parts, and daily miscellaneous goods. In addition to parts, examples include containers for frozen foods and beverages, home appliances such as refrigerator gaskets, hose bands, gaskets, and cable ties.
In particular, the resin composition and molded article of this embodiment are suitable for trim clips.

The present invention will be explained in more detail 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 spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
If the measuring equipment used in the examples is difficult to obtain due to discontinuation or the like, measurements can be made using other equipment with equivalent performance.
1. Raw Materials The raw materials shown in Table 1 below were used.

The above MVR is a melt volume rate measured under the conditions of a temperature of 190° C. and a load of 2.16 kg in accordance with ISO1133.
The kinematic viscosity of the silicone oil and silicone gum described above is a value measured by the following method.
(i) 1.0 g of silicone oil or silicone gum was weighed out and dissolved in 10 mL of toluene, and the viscosity of the silicone-toluene solution was measured using a cone-plate viscometer TPE100.
(ii) Using the same method, the viscosity of silicone oil whose kinematic viscosity was known was measured, and a calibration curve was prepared.
(iii) The kinematic viscosity of silicone oil or silicone gum was calculated by extrapolation using a calibration curve.

<Core-shell elastomer crosslinking index>
For each core-shell elastomer used in each Example and Comparative Example, the T ₂ relaxation time was measured using Minispec mq20 manufactured by Bruker. Measurements were performed at -40°C, 0°C, 23°C, and 80°C, and the respective _T2 relaxation times were obtained. Regarding the approximate straight line of the plot obtained when the measurement temperature is set on the X axis and the _T2 relaxation time is set on the Y axis, the larger the slope, the higher the molecular mobility.In other words, there are fewer crosslinked structures that restrict the movement of molecules, and the slope is smaller. Considering that the lower the molecular mobility, that is, there are more crosslinked structures that restrict the movement of molecules, the reciprocal of the slope of the approximate straight line was used as the crosslinking index. The measurement temperatures of -40°C and 0°C were assumed by the solid echo method, and the measurement temperatures of 23°C and 80°C were measured by the spin echo method.
_T2 relaxation time was measured under the following conditions.
Observation frequency: 25MHz
Measurement method: Solid echo method/Spin echo method Repetition time: 4sec/4sec
Total number of times: 16 times/4 times Measurement temperature: -40℃, 0℃/23℃, 80℃

2. Examples 1 to 14, Comparative Examples 1 to 9, Reference Examples 1 to 3
<Manufacture of resin composition (pellets)>
The components shown in Tables 2 to 6 were uniformly mixed in the proportions (parts by mass) shown in Tables 2 to 6 using a super mixer manufactured by Kawada Seisakusho. The obtained mixture was heated at a cylinder temperature of 200° C. and a screw rotation speed of 120 rpm using a vented twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) with a screw diameter of 30 mm, a screw length of 760 mm, and a die nozzle diameter of 3.5 mm. , melting and shear mixing were carried out at a discharge rate of 10 kg/hour to produce pellets of the resin composition.

<Average secondary particle diameter (nm) of core-shell elastomer>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were molded into an ASTM tensile test piece (thickness: 3.2 mm) using an injection molding machine, with the cylinder temperature set at 195°C and the mold temperature set at 90°C. ) was created.
From this ASTM tensile test piece, a test piece for scanning electron microscopy (SEM) observation was cut out using a diamond knife parallel to the flow direction during molding and including the weld portion.
After osmium tetroxide was deposited on the observation surface of the obtained SEM observation specimen, a SEM image was obtained using a scanning electron microscope (SEM).
From the obtained SEM image, the average value of the maximum length of the island-shaped portions derived from the elastomer was defined as the average secondary particle diameter of the elastomer.
The injection molding machine used was EC-100S manufactured by Shibaura Kikai Co., Ltd.
The osmium tetroxide was vapor-deposited using an "Osmium Coater" manufactured by Meiwaforsys under conditions of 8 mA and 60 seconds. The scanning electron microscope was a "Scanning Electron Microscope (SEM) S-4800" manufactured by Hitachi High Technologies, and the SEM was performed under the following conditions: acceleration voltage: 1 kV, signal: LA100 (U), emission current: 6 μA, probe current: Normal. The image was acquired.

<Weld elongation>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were molded into an ASTM tensile test piece (thickness 1.6 mm) using an injection molding machine, with the cylinder temperature set at 195°C and the mold temperature set at 90°C. ) was prepared and subjected to a tensile test according to ASTM D638 to measure weld elongation.
The injection molding machine used was EC-100S manufactured by Shibaura Kikai Co., Ltd.
The unit is shown in %. The measurement results were evaluated according to the following criteria.
A: 14% or more B: 10% or more, less than 14% C: less than 10% The results are shown in Tables 2 to 6 below.

<Dynamic friction coefficient>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were used in an injection molding machine, with the cylinder temperature set at 195°C and the mold temperature set at 80°C, to produce a cylindrical thrust test piece and a test piece with a contact area of ^2cm2 . did. This test piece was measured using a Suzuki friction and wear tester at a temperature of 23°C and a humidity of 50%, with a load of 10 kgf and a linear velocity of 10 cm/s, and the coefficient of dynamic friction (μ) was determined. Ta. The measurement results were evaluated according to the following criteria.
A: Less than 0.32 B: 0.32 or more, less than 0.34 C: 0.34 or more The results are shown in Tables 2 to 6 below.

<Specific wear amount>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were used in an injection molding machine, with the cylinder temperature set at 195°C and the mold temperature set at 80°C, to produce a cylindrical thrust test piece and a test piece with a contact area of ^2cm2 . did. This test piece was tested using a Suzuki type friction and wear tester in an atmosphere of temperature 23°C and humidity 50%, load 3 kgf, linear speed 30 cm/s, and running time of 20 hours between the same materials. The specific wear amount was calculated based on the mass of the cylindrical thrust test piece. The specific wear amount is the sum of the specific wear amounts of both test pieces used in the wear test.
The unit is ×10 ⁻² (mm ³ /kgf·km).
In addition, the measurement results were evaluated based on the following criteria.
A: Less than 20×10 ⁻² (mm ³ /kgf・km) B: 20×10 ⁻² (mm ³ /kgf・km) or more and less than 30×10 ⁻² (mm ³ /kgf・km) C: 30× 10 ⁻² (mm ³ /kgf·km) or more The results are shown in Tables 2 to 6 below.

<Bending elastic modulus>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were injection molded using an injection molding machine, with the cylinder temperature set at 195°C and the mold temperature set at 90°C, in accordance with the ISO9988-2 standard. The injection molding machine used was EC-100S manufactured by Shibaura Kikai Co., Ltd. In this way, a multi-purpose test piece (ISO test piece) with a thickness of 4 mm was obtained.
Next, this 4 mm thick multi-purpose test piece (ISO test piece) was subjected to a bending test using a fully automatic bending tester at a bending test speed of 2 mm/min according to the method described in ISO178. , the flexural modulus was measured. A fully automatic bending tester manufactured by Shimadzu Corporation was used. The unit is MPa. The evaluation criteria are as follows.
A: 1500 MPa or more, less than 2400 MPa B: 1300 MPa or more, less than 1500 MPa, or 2400 MPa or more, less than 2450 MPa C: Less than 1300 MPa, or 2450 MPa or more The results are shown in Tables 2 to 6 below.

<Formaldehyde generation amount>
The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, the dried pellets were used in an injection molding machine, with the cylinder temperature set at 210°C and the mold temperature set at 80°C, to produce a flat test piece of 100 mm x 40 mm x 2 mm. Regarding this test piece, the amount of formaldehyde generated in 1 g of polyacetal resin was determined by the following method in accordance with the method described in the German Automobile Industry Association standard VDA275 (Automotive interior parts - Determination of formaldehyde release amount by revised flask method). It was measured.
(i) 50 mL of distilled water was placed in a polyethylene container, the lid was closed with the flat test piece hanging in the air, and the container was heated at 60° C. for 3 hours in a sealed state.
(ii) After being left at room temperature for 60 minutes, the flat test piece was taken out.
(iii) The amount of formaldehyde absorbed in the distilled water in the polyethylene container is measured using the acetylacetone colorimetric method using a UV spectrometer, and the amount of formaldehyde generated is calculated by dividing the amount of formaldehyde by the mass of POM in the flat test piece. And so.
The unit is the amount of formaldehyde generated (μg) per gram of polyacetal resin, ie, μg/g-POM. The measurement results were evaluated according to the following criteria.
A: Less than 5 μg/g-POM B: 5 μg/g-POM or more and less than 10 μg/g-POM C: 10 μg/g-POM or more The results are shown in Tables 2 to 6 below.

<Comprehensive evaluation>
Among the evaluation results of the weld elongation, dynamic friction coefficient, specific wear amount, flexural modulus, and formaldehyde generation amount, the worst result was taken as the overall evaluation.
The results are shown in Tables 2 to 6.

As is clear from Tables 2 to 6 above, the resin compositions of the present invention had excellent sliding properties and excellent abrasion resistance (Examples 1 to 14).
On the other hand, when the average secondary particle diameter of the core-shell elastomer (B) in the polyacetal resin (A) was large (Comparative Examples 1 and 2), the weld elongation was small or the resin composition (pellet) could not be obtained. .
In addition, when the content of the core-shell elastomer (B) is small (Comparative Example 3), the elastic modulus is high, and when it is too large (Comparative Example 4), the elastic modulus is too low. I couldn't keep it.
Moreover, when the content of the silicone compound (C) was too high (Comparative Examples 5 and 7), weld elongation was low, and when the content was too high (Comparative Example 6), the sliding properties were poor.
Furthermore, when the kinematic viscosity of the silicone compound (C) was low (Comparative Examples 8 and 9), the sliding properties were poor.
Furthermore, when a sliding property improver other than the silicone compound (C) was used (Reference Examples 1 to 3), the sliding property was insufficient or formaldehyde was generated.

Claims

A resin composition comprising a polyacetal resin (A), a core-shell elastomer (B) and a silicone (C),
The core-shell elastomer (B) has an average secondary particle diameter of 10 to 250 nm in the polyacetal resin (A),
The content of the core-shell elastomer (B) is 5 to 25% by mass in the resin composition,
A resin composition, wherein the silicone (C) has a kinematic viscosity at 25° C. of 4 million to 30 million cSt, and the content thereof is 0.3 to 1% by mass in the resin composition.
The resin composition according to claim 1, wherein the core-shell elastomer (B) has a crosslinking index in the range of 0.11 to 0.30.
The resin composition according to claim 1 or 2, wherein in the core-shell elastomer (B), the core contains a butadiene-containing rubber and the shell contains an acrylic resin.
The resin composition according to claim 1 or 2, further comprising a hydrazide compound and/or a urea compound.
The resin composition according to claim 1 or 2, wherein the mass ratio (B)/(C) of the core-shell elastomer (B) and silicone (C) is 8 to 40.
The resin composition according to claim 1 or 2, which is used for trim clip molding.
The core-shell elastomer (B) has a crosslinking index in the range of 0.11 to 0.30,
In the core-shell elastomer (B), the core contains a butadiene-containing rubber, the shell contains an acrylic resin,
Furthermore, it contains a hydrazide compound and/or a urea compound,
The mass ratio (B)/(C) of the core-shell elastomer (B) and silicone (C) is 8 to 40,
The resin composition according to claim 1, which is used for trim clip molding.
Pellets of the resin composition according to claim 1, 2 or 7.
A molded article formed from the resin composition according to claim 1, 2, or 7.
A molded article formed from the pellet according to claim 8.
The molded article according to claim 9, which is a trim clip.