Slidable thermoplastic resin composition and agent for improving sliding properties

Abstract

To provide a slidable molding which is excellent in slidability, a slidable thermoplastic resin composition which is used in manufacture of the molding, and a slidable improver which is suitably used in the resin composition.SOLUTION: A slidable thermoplastic resin composition contains a thermoplastic resin and a slidable improver, wherein the slidable improver contains an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) having a melt flow rate (MFR) of 20 g / 10 min or more and silicone powder, and with respect to 100 pts.mass of the thermoplastic resin, 7.5 to 3.5 pts.mass of the ABS resin having an MFR of 20 g / 10 min or more, and 2.5 to 0.5 pts.mass of the silicone powder are contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition having excellent sliding properties, and a sliding property improver for use in the resin composition. [Background technology]

[0002] Polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, etc. are thermoplastic resins that are widely used in many fields, and various properties such as scratch resistance, weather resistance, flexibility, mechanical strength, rigidity, heat resistance, and chemical resistance are required depending on the application and purpose of use. One of these properties is slidability, which is also known as smoothness, and is a physical property required for sliding parts such as gears and bearings, electrical and electronic equipment such as printer feeders, agricultural materials such as agricultural sheets, and building components such as support materials for fastening parts.

[0003] Two methods have been conventionally employed to impart slidability to resin members. One method is to provide a layer of polyethylene resin, which has excellent sliding properties, on the surface of a resin member. Although this method is excellent in terms of sliding properties, the polyethylene resin layer wears out over long-term use, resulting in a loss of sliding properties, and this has been a problem in terms of durability. Another method involves incorporating a sliding property improver into a resin component. Examples of sliding property improvers include silicone oil or silicone powder for styrene-based resins, and organopolysiloxane copolymers, higher fatty acid amides, silicone oil, and silicone surfactants for vinyl chloride resins (Patent Documents 1, 2, and 3). This method requires the sliding property improver to be uniformly dispersed in the resin. Insufficient dispersion can result in reduced sliding properties or changes over time. Furthermore, some sliding property improvers bleed onto the resin surface, causing poor appearance, molding defects, poor adhesion to other components, and reduced contamination resistance and dust resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 11-349757 [Patent Document 2] Patent Publication No. 2019-26716 [Patent Document 3] Japanese Patent Application Publication No. 9-143326 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of extensive research into sliding property improvers, the inventors discovered that, of the various sliding property improvers, silicone powder is superior in its effectiveness for thermoplastic resins, and that the coexistence of acrylonitrile-butadiene-styrene copolymer resin (ABS resin), which has specific physical properties, improves the dispersibility of the silicone powder, resulting in a significant improvement in sliding property and other physical properties as well, which led to the invention of the present invention. The present invention aims to provide a slidable molded article having excellent slidability, a thermoplastic resin composition used to produce the molded article, and a slidability improver that is suitably used in the resin composition. [Means for solving the problem]

[0006] That is, the present invention provides a sliding thermoplastic resin composition containing a thermoplastic resin and a sliding property improver, The sliding property improver comprises an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) having a melt flow rate (MFR) of 20 g / 10 min or more and silicone powder, and the sliding property thermoplastic resin composition is characterized in that it contains 3.5 to 7.5 parts by mass of ABS resin having an MFR of 20 g / 10 min or more and 0.5 to 2.5 parts by mass of silicone powder per 100 parts by mass of the thermoplastic resin. In the above-mentioned slidable thermoplastic resin composition of the present invention, it is preferable that the thermoplastic resin is a soft vinyl chloride resin.

[0007] The present invention also relates to a slidable molded article obtained by molding the above-mentioned slidable thermoplastic resin composition. Furthermore, the present invention relates to a sliding property improver comprising 70 to 90 parts by mass of an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) having an MFR of 20 g / 10 min or more and 30 to 10 parts by mass of silicone powder, and it is preferable that the sliding property improver is a pellet-shaped melt-kneaded product. [Effects of the Invention]

[0008] The sliding property improver provided by the present invention is versatile and can improve the sliding properties of various thermoplastic resins, with the effect being particularly pronounced for soft vinyl chloride resins. Molded articles of thermoplastic resin compositions obtained by blending the sliding property improver are widely used as components requiring sliding properties. For example, molded articles of styrene-based resins are used as sliding components such as printer housings, various electrical and electronic components, gears, and bearings. Molded articles of ABS resins are suitable for bathroom components, etc., where noise caused by interference between components due to thermal expansion is a problem. Molded articles of polyvinyl chloride resins are suitable for agricultural films and sheets, interior materials, and building components, and molded articles of soft polyvinyl chloride resins in particular are suitable for applications such as gaskets, sealing materials, packing materials, and lead-insertion pipes. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Sliding property improver> The sliding property improver of the present invention contains a silicone powder and an ABS resin with an MFR of 20 g / 10 min or more (hereinafter also referred to as MFR20 ABS resin). There are no limitations on the form in which these two components are present, as long as they are dispersed and mixed. A pellet-shaped melt-kneaded product, known as a master pellet, made by melt-kneading and then granulating the two components is highly preferred, as it disperses extremely well with the thermoplastic resin described below and exhibits a significant improvement in sliding property. The compounding ratio of silicone powder to MFR20ABS resin varies depending on the thermoplastic resin to be compounded. However, when the sliding property improver is melt-kneaded in advance and then granulated to form pellets (master pellets), from the viewpoints of dispersibility of both components and versatility applicable to any thermoplastic resin, a ratio of MFR20ABS resin:silicone powder of 70 to 90 parts by mass:30 to 10 parts by mass (total amount of both components being 100 parts by mass) is preferred. If the amount of MFR20ABS resin is less than 70 parts by mass, when blended with a thermoplastic resin, the silicone powder will not disperse uniformly within the thermoplastic resin composition, resulting in unstable quality. If the amount of silicone powder is less than 10 parts by mass, no improvement in sliding properties will be observed. If the amount of silicone powder exceeds 30 parts by mass, poor dispersion of the components is likely to occur, leading to molding defects and poor appearance of the molded product, which is not preferable. In consideration of moldability, surface properties and physical properties of the molded product, as well as cost, a blending ratio of 80-90 parts by mass:20-10 parts by mass is preferred. The sliding property improver may contain various additives as described below if necessary, but usually consists of the above two components.

[0010] [Silicone powder] Silicone powder is a spherical powder generally having an average particle size of 1 to 30 μm that disperses uniformly in thermoplastic resins and exhibits remarkable sliding properties. Specific examples of silicone powders include silicone rubber powders obtained by curing oily silicone, silicone resin powders, silicone composite powders, etc. Among these, silicone resin powders are particularly preferred because of their good dispersibility and excellent improvement in sliding properties.

[0011] The silicone rubber powder is a spherical powder of silicone rubber having a structure in which linear dimethylpolysiloxane is crosslinked. Silicone resin powder has a three-dimensional structure obtained by hydrolysis and condensation of silane, and typically has a siloxane bond of (CH3SiO 3 / 2 ) is a spherical powder of polymethylsilsesquioxane, which has a three-dimensional network-like cross-linked structure. Silicone composite powder is a spherical powder with a composite structure in which the surface of silicone rubber spherical powder is coated with silicone resin. These silicone powders are commercially available from Shin-Etsu Chemical Co., Ltd. as the "KMP" series with various average particle sizes and characteristics, and can be selected according to the properties of the thermoplastic resin to be blended.

[0012] [MFR20ABS resin] In the sliding improver of the present invention, it is important that the component that contributes to improving sliding properties has an MFR of 20 g / 10 min or more. ABS resins with an MFR of less than 20 g / 10 min have high viscosity, so the silicone powder does not disperse uniformly in the ABS resin, and a high-quality sliding improver cannot be obtained. Because the MFR20ABS resin is highly compatible with thermoplastic resins, it is believed that silicone powder disperses extremely well in systems where both thermoplastic resins and MFR20ABS resin coexist, resulting in significantly improved sliding properties. Furthermore, when the resin is made into master pellets, shear heat generation during high-mix extrusion is suppressed, making it less likely to cause problems such as burning. ABS resin is a general-purpose copolymer resin of acrylonitrile, butadiene, and styrene, and is commercially available from Nippon A&L as the "Clarastic" series, from Toray Industries as the "Toyolac" series, from Denka as the "Denka ABS" series, and from Techno UMG as the "UMG ABS" series; therefore, it is sufficient to select and use one of the commercially available products with an MFR of 20 g / 10 min or more.

[0013] [Method for producing a sliding property improver] The silicone powder and MFR20 ABS resin are dry-blended in a conventional manner using a mixer such as a tumbler mixer or a Henschel mixer to prepare a sliding property improver. For the above reasons, it is preferably made into a pellet-shaped melt-kneaded product (master pellet). A known method can be used without limitation for the production of master pellets, and typically, the dry-blended sliding property improver is melt-kneaded in a single-screw or twin-screw extruder, followed by granulation. There are no particular limitations on the particle size, but the particle size is usually about 1 to 4 mm.

[0014] <Slidable Thermoplastic Resin Composition> The sliding property improver is prepared as a sliding thermoplastic resin composition by dry-blending the following thermoplastic resin and, if necessary, the additives described below, using a tumbler mixer, ribbon blender, Henschel mixer, high-speed mixer, or the like. The blending ratio of the sliding property improver to the thermoplastic resin is such that the content of silicone powder in the sliding thermoplastic resin composition is 0.5 to 2.5 parts by mass per 100 parts by mass of the thermoplastic resin. If the content is less than 0.5 parts by mass, the sliding property improvement effect is not achieved. If the content exceeds 2.5 parts by mass, the improvement effect saturates and the cost becomes high. The blending ratio of the thermoplastic resin to the sliding property improver is determined so that the blending amount of silicone powder satisfies the above range, but is usually selected from the range of 1 to 10 parts by mass of sliding property improver per 100 parts by mass of thermoplastic resin. If the blending amount exceeds 10 parts by mass, the desired properties of the thermoplastic resin tend to be lost due to the influence of the ABS resin in the sliding property improver. The thermoplastic resin composition having sliding properties is preferably melt-kneaded in a single-screw or twin-screw extruder and then granulated into pellets.

[0015] [Thermoplastic resin] As the resin to be blended with the sliding property improver to improve sliding property, known thermoplastic resins can be used without any restrictions. Specifically, these include polyolefin resins such as polyethylene resin, copolymer resins of ethylene and other α-olefins, polypropylene resin, and block copolymer resins of propylene and ethylene; vinyl chloride resins such as hard vinyl chloride resin, soft vinyl chloride resin, and thermoplastic polyvinyl chloride elastomer (TPVC); styrene resins such as acrylonitrile-ethylene-propylene-rubber-styrene copolymer resin (AES resin), ABS resin, polystyrene resin, and acrylonitrile-styrene copolymer resin; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resin; polyurethane resin; polyamide resin; polyacetal resin, etc. Among these thermoplastic resins, vinyl chloride resins, particularly soft vinyl chloride resins, are highly effective in incorporating the sliding property improver of the present invention, reducing the dynamic friction coefficient by approximately 50%. Soft vinyl chloride resins are made by incorporating a plasticizer into vinyl chloride resin, and are flexible. Typical physical properties include a specific gravity of 1.16 to 1.35 and a tensile strength of 6.9 to 25 MPa. From the perspectives of ease of molding and ensuring physical properties, soft vinyl chloride resins with an average degree of polymerization of 700 to 1500 are typically used.

[0016] [Additives] If necessary, conventionally known additives such as lubricants, plasticizers, release agents, flame retardants, antioxidants, ultraviolet absorbers, antistatic agents, colorants, fillers, etc. may be blended into the slidable thermoplastic resin composition. The additives may be added separately when blending the slidability improver in preparing the slidable thermoplastic resin composition, but it is preferable to mix them with the thermoplastic resin in advance.

[0017] [Preparation of Slidable Thermoplastic Resin Composition] There are no particular limitations on the method for preparing the thermoplastic resin composition of the present invention. For example, the thermoplastic resin, the sliding property improver, and various additives used as desired are dry-blended in predetermined proportions using a blender, Henschel mixer, or the like to obtain the composition. Furthermore, the composition can also be homogeneously kneaded and dispersed using a melt kneader such as a single-screw or twin-screw extruder, a Banbury mixer, a pressure kneader, or a co-kneader to obtain the desired composition. Usually, the thermoplastic resin composition is pelletized and then subjected to the subsequent molding process.

[0018] <Production of Slidable Molded Body> The thermoplastic resin composition of the present invention can be mixed with various additives as needed to produce a molded article using known molding methods such as injection molding, extrusion molding, vacuum molding, blow molding, etc. The molding machine and molding conditions can be selected from among conventionally known molding methods in consideration of the type of thermoplastic resin used and the shape of the molded article. For example, from the viewpoint of mass productivity and continuous and stable production, an extrusion molding method is preferably adopted, and a molded article according to the desired cross-sectional shape is obtained. For the sliding molded article by the extrusion molding method, a method of melting the material in an extruder and then extruding it from a T-die, or a method of extruding it into a sheet form from an extruder and then biaxially stretching it by a tenter system or an inflation system, etc., is adopted. The stretching may be uniaxial stretching, sequential biaxial stretching, homogeneous biaxial stretching, or biaxial stretching by an inflation system. The injection-molded sliding molded article can be molded by a normal injection molding method, and the injection molding temperature, injection molding pressure, etc. are appropriately selected depending on the shape and material of the desired sliding molded article. [Example]

[0019] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Furthermore, not all of the combinations of features described in the examples are necessarily essential to the solution of the present invention. The various components, abbreviations, and test methods used in the following examples and comparative examples are as follows:

[0020] [ABS resin] nABS: "Clarastic GA-101" manufactured by Nippon A&L Co., Ltd. MFR = 26g / 10min (220℃ / 10kg) mABS: "Toyolac 100" manufactured by Toray Industries, MFR = 15g / 10min (220℃ / 10kg) [Silicone powder] Silicone powder: "KMP-590" manufactured by Shin-Etsu Chemical Co., Ltd. [Thermoplastic resin] PVC: Polyvinyl chloride resin Average degree of polymerization = 1000 TPVC: Polyvinyl chloride thermoplastic elastomer Average degree of polymerization=1300 ABS: ABS resin "Clarastic SR" manufactured by Nippon A&L Co., Ltd. PP: Polypropylene resin "Pripe Polypro E701" Prime Polymer Made PE: Polyethylene resin "Hi-Zex 5100B" manufactured by Prime Polymer

[0021] <Physical property measurement> [Dynamic friction coefficient] Measurement was performed using a dynamic friction coefficient measuring device "HM-3" manufactured by Toyo Seiki Co., Ltd. The friction element was made of stainless steel, the speed was 100 mm / min, and the load was 200 g. [Contact angle] The contact angle of the surface was measured using "DMs-401" manufactured by Kyowa Interface Science Co., Ltd. The contact angle (degrees) is an index of antifouling properties.

[0022] [Anti-fouling] The test piece was contaminated with carbon dispersed water and then heated in an oven at 60°C to fix the contaminants. It was then washed with running water and the degree of surface contamination was visually observed and evaluated according to the following criteria. 〇: Slight stains remain △: About half of the stain remains ×: Almost no dirt comes off

[0023] [Weather resistance] A weather resistance test was carried out using a sunshine carbon arc lamp at BP63°C, 50% RH (relative humidity) for 500 hours in accordance with JIS b 7753. Evaluation was based on the following criteria. 〇: No change △: Slight changes such as slight discoloration are observed ×: Significant changes such as noticeable discoloration and brittleness of the surface are observed. 〔exterior〕 The surface of the test piece was visually inspected and evaluated according to the following criteria. ○: No noticeable defects △: One visible defect is found ×: Two or more visible defects are found

[0024] [Sliding property improver] Manufacturing Example 1 70 kg of nABS and 30 kg of silicone powder were mixed at 100°C using a Henschel mixer, and then granulated using a co-rotating twin-screw extruder to produce a sliding property improver (pellets; MB1). Manufacturing Example 2 A sliding property improver (pellets; MB2) was produced in the same manner as in Example 1, except that the amount of nABS was 80 kg and the amount of silicone powder was 20 kg. Manufacturing Example 3 A sliding property improver (pellets; MB3) was produced in the same manner as in Example 1, except that the amount of nABS was 90 kg and the amount of silicone powder was 10 kg. Production Example 4 A sliding property improver (pellets; MB4) was produced in the same manner as in Example 1, except that 60 kg of nABS and 40 kg of silicone powder were used. Production Example 5 A sliding property improver (pellets; MB5) was produced in the same manner as in Example 1, except that the amount of nABS was 95 kg and the amount of silicone powder was 5 kg. Manufacturing Example 6 A sliding property improver (pellets; MB6) was produced in the same manner as in Example 1, except that 80 kg of mABS with an MFR of 15 g / 10 min and 20 kg of silicone powder were used.

[0025] [Slidable thermoplastic resin composition and molding] Examples 1 to 15, Comparative Examples 1 to 11 Sliding thermoplastic compositions were produced by mixing the sliding property improvers prepared in Production Examples 1 to 6 with the thermoplastic resins shown in Tables 1 and 2 in the blending ratios shown in Tables 1 and 2. These sliding thermoplastic resin compositions were then molded using a Toyo Seiki Co., Ltd. "Labo Plastomill 4C150" at a melting temperature of 185°C to obtain flat plate-shaped test pieces (30 x 50 x 2 mm). The dynamic friction coefficient, contact angle, antifouling property, weather resistance and appearance of this test piece were measured according to the respective test methods described above and are shown in Tables 1 and 2.

[0026] [Table 1]

[0027] [Table 2]

[0028] In Comparative Examples 1, 2, 4 and 5, the content of MFR20ABS resin in the slidable thermoplastic resin composition was low, and the stain resistance and weather resistance were poor, and further the appearance was poor. Comparative Example 3 was a case in which the content of silicone powder in the slidable thermoplastic resin composition was high, and similarly, the stain resistance and weather resistance were poor, and furthermore, the appearance was poor. Comparative Examples 6, 7, 9 and 10 are cases where the content of silicone powder in the slidable thermoplastic resin composition is low, and the dynamic friction coefficient is high, no improvement in slidability is observed, and furthermore, the stain resistance is very poor. Comparative Example 8 is a case where the content of MFR20ABS resin in the slidable thermoplastic resin composition is high, and the stain resistance is very poor and the weather resistance is also poor. In Comparative Example 11, the ABS resin blended in the slidable thermoplastic resin composition had an MFR of less than 20 g / 10 min, and the dynamic friction coefficient was high, resulting in no improvement in slidability, and the stain resistance and weather resistance were poor.

Claims

1. A sliding thermoplastic resin composition comprising a thermoplastic resin and a sliding property improver, the sliding property improver is a pellet-shaped melt-kneaded product containing 70 to 90 parts by mass of an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) having a melt flow rate (MFR) of 20 g / 10 min or more, and 30 to 10 parts by mass of a silicone powder; The slidable thermoplastic resin composition is characterized in that the slidability improver is blended in a ratio of 5 to 8 parts by mass per 100 parts by mass of the thermoplastic resin.

2. 2. The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is a soft vinyl chloride resin.

3. A slidable molded article obtained by molding the slidable thermoplastic resin composition according to claim 1 or 2.

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