Sliding resin composition and sliding resin molded article

Abstract

To provide a sliding molded article which exhibits superior slidability and reduced generation of chatter noise, and a sliding resin composition employed for producing the molded article.SOLUTION: A sliding resin composition wherein, with respect to 100 pts.mass of a vinyl chloride-based resin comprising 25-75 mass% of vinyl chloride resin and 75-25 mass% of crosslinked vinyl chloride resin, there are contained 5-30 pts.mass of silicone powder and 3-20 pts.mass of resin beads having an average particle size of 5-80 μm comprising a polymethyl methacrylate resin or the like.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polyvinyl chloride resin (PVC) is a thermoplastic resin that is widely used in many fields, and depending on its application and purpose, various properties are required, such as scratch resistance, weather resistance, flexibility, mechanical strength, rigidity, heat resistance, and chemical resistance. One of these properties is slidability, which is also called smoothness, and is a physical property required for a variety of applications, including household water wipers, airtight components for automobile door window glass frames, electrical and electronic equipment components such as printer feeders, agricultural materials such as agricultural sheets, support materials for fastening parts, window frame airtight materials, and building components such as bathroom joint materials.

[0003] Two methods have been used to impart sliding properties to PVC members. One method is to provide a coating layer made of polyurethane elastomer, which has excellent sliding properties, on the surface of a PVC member (Patent Document 1). However, this method has problems such as unstable sliding properties due to uneven coating, increased manufacturing steps and higher production costs, and loss of sliding properties after long-term use. Another method involves incorporating a sliding property improver into the PVC component. Examples of sliding property improvers that have been used include organopolysiloxane copolymers, higher fatty acid amides, silicone oils, and silicone surfactants (Patent Documents 2, 3, and 4). This method requires that the sliding property improver be uniformly dispersed in the resin. Insufficient dispersion can lead to problems such as reduced sliding property or changes over time. Furthermore, some sliding property improvers bleed out onto the resin surface, causing poor appearance, molding defects, poor adhesion to other components, and reduced stain resistance and dust resistance. Furthermore, vibration noises such as scraping and creaking caused by friction, known as chatter noise, can be generated, which can impair the product value, particularly in applications for building components such as resin rails, airtight window frame seals, and bathroom joint seals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2014-84346 [Patent Document 2] Japanese Patent Publication No. 11-349757 [Patent Document 3] Patent Publication No. 2019-26716 [Patent Document 4] 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 the sliding properties of molded articles made from vinyl chloride resin as a base material, the inventors discovered that by adding cross-linked vinyl chloride resin in addition to silicone powder or resin beads, which contribute to improving sliding properties, sliding properties are dramatically improved and other physical properties such as water repellency and stain resistance are also improved, leading to the invention of the present invention. The present invention aims to provide a slidable molded article having excellent slidability, and a slidable resin composition to be used for producing the molded article. [Means for solving the problem]

[0006] That is, the present invention provides a sliding resin composition characterized by containing 5 to 30 parts by mass of silicone powder and 3 to 20 parts by mass of resin beads having an average particle size of 5 to 80 μm per 100 parts by mass of vinyl chloride resin consisting of 25 to 75% by mass of vinyl chloride resin and 75 to 25% by mass of cross-linked vinyl chloride resin.

[0007] In the above-mentioned invention of the sliding resin composition, 1) The resin beads are acrylic resin beads. 2) The sliding resin composition is a soft sliding resin composition that further contains a plasticizer. is preferred. The present invention also relates to a slidable molded article obtained by molding the above-mentioned slidable resin composition. [Effects of the Invention]

[0008] Molded articles of the sliding resin composition provided by the present invention are widely used as parts requiring sliding properties, including airtight parts such as household water wipers and window glass frames for automobile doors, sliding parts such as gaskets, sealing materials, packing materials, and conductor insertion pipes, parts for electrical and electronic equipment such as printer feeders, agricultural materials such as agricultural films and sheets, and building parts such as support materials for fastening parts, airtight window frame materials, and bathroom joint materials. In particular, since the generation of rattle noise due to poor sliding properties is suppressed, it is suitable for use as sliding components such as resin rails, bathroom fitting components that generate noise due to thermal expansion caused by temperature changes, window frame airtight materials, etc. Furthermore, since it has excellent water repellency and stain resistance, it is also suitable for use as building components for wet areas such as flooring materials, bathroom joint materials, bathroom counters, and bathroom baseboards. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Vinyl chloride resin] This is a component that becomes the base material of the slidable molded body. Specific examples include vinyl chloride resins such as rigid vinyl chloride resins and vinyl chloride copolymer resins, but do not include crosslinked vinyl chloride resins, which will be described later. As the rigid vinyl chloride resin, any known general-purpose vinyl chloride resin can be used without any restrictions. From the viewpoints of ease of molding, ensuring physical properties, and dispersibility of other blended components, it is generally preferable that the average polymerization degree is 2000 to 3000. Examples of vinyl chloride copolymer resins include vinyl chloride-vinylidene chloride copolymer resins, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-ethylene copolymer resins, and vinyl chloride-(meth)acrylic acid ester copolymer resins.

[0010] [Cross-linked vinyl chloride resin] The cross-linked vinyl chloride resin is a component that further enhances the sliding property improvement effect achieved by the silicone powder and resin beads described below, and also becomes part of the base material of the resin molded body while also enhancing water repellency and stain resistance. Cross-linked vinyl chloride resin is a resin in which vinyl chloride polymer is cross-linked by a radiation chemical method using electron beam irradiation or a chemical method using a cross-linking agent. It has the major characteristic of having a high heat resistance temperature, and is generally used to achieve a matte design. From the viewpoint of ease of molding and ensuring physical properties, a cross-linked vinyl chloride resin having an average degree of polymerization of 800 to 1500 is preferably used. Such cross-linked vinyl chloride resins are commercially available from Kaneka Corporation, Sumitomo Electric Industries, Ltd., Shin-Etsu Chemical Co., Ltd., etc.

[0011] [Vinyl chloride resin] The vinyl chloride resin must be composed of 25 to 75% by mass of the vinyl chloride resin and 75 to 25% by mass of cross-linked vinyl chloride resin. If the cross-linked vinyl chloride resin is less than 25% by mass, no significant improvement in sliding properties will be observed, and if it exceeds 75% by mass, the surface will become rough and moldability will be impaired, resulting in poor design and gelation. From the perspective of surface roughness and moldability, it is particularly preferable for the resin to be composed of 60 to 75% by mass of vinyl chloride resin and 40 to 25% by mass of cross-linked vinyl chloride resin. The vinyl chloride resin is preferably a soft vinyl chloride resin, since it significantly improves the sliding properties. The soft vinyl chloride resin is usually a resin softened by adding a plasticizer, and is flexible. Typical physical properties include a specific gravity of 1.16 to 1.35 and a tensile strength of 6.9 to 25 MPa.

[0012] [Plasticizer] Examples of plasticizers include phthalate ester-based plasticizers such as dibutyl phthalate, phosphate ester-based plasticizers such as trioctyl phosphate, aliphatic polycarboxylic acid ester-based plasticizers such as dioctyl adipate, trimellitate ester-based plasticizers such as tris-2-ethylhexyl trimellitate and tributyl trimellitate, and epoxy-based plasticizers such as epoxy soybean oil. Trimellitate ester-based plasticizers are particularly preferred because they bleed out little and do not impair sliding properties. The amount of plasticizer to be added is appropriately selected depending on the properties of the vinyl chloride resin used, the degree of softening, etc., but is usually added in the range of 10 to 150 parts by mass per 100 parts by mass of vinyl chloride resin.

[0013] [Silicone powder] Silicone powder is a spherical powder generally having an average particle size of 1 to 30 μm, which is uniformly dispersed in vinyl chloride resin and exhibits remarkable sliding properties. The average particle size of the powder used in the present invention refers to the particle size at 50% of the cumulative value (D50) in the particle size distribution determined by laser diffraction / scattering method. Specific examples of silicone powder include silicone rubber powder obtained by curing oily silicone, silicone resin powder, silicone composite powder, etc. Among these, silicone rubber powder is particularly preferred because it has good dispersibility and is excellent in improving sliding properties.

[0014] 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 or alkyl (meth)acrylate resin. These silicone powders are commercially available from Shin-Etsu Chemical Co., Ltd. and Mitsubishi Chemical Corporation, and come in a variety of chemical structures, average particle sizes, and properties.

[0015] The silicone powder is blended in an amount of 5 to 30 parts by mass per 100 parts by mass of vinyl chloride resin consisting of vinyl chloride resin and cross-linked vinyl chloride resin. If the amount is less than 5 parts by mass, the effect of improving sliding properties is not observed, and if the amount is more than 30 parts by mass, the effect saturates. From the viewpoints of effectiveness and cost, an amount of 10 to 20 parts by mass is particularly suitable.

[0016] [Resin beads] This component acts synergistically with the improvement in sliding properties provided by the silicone powder to further improve sliding properties, and powder having an average particle size of 5 to 80 μm is used. Specific examples of resins that can be used to make the beads include polyethylene resin, polystyrene resin, polymethyl methacrylate resin, polyacrylonitrile resin, ethylene-acrylic acid copolymer resin, and acrylic-urethane copolymer resin. Resin beads made of acrylic resins such as polymethyl methacrylate resin are preferred in terms of their sliding properties. These resin beads are commercially available from Negami Chemical Industrial Co., Ltd., Nippon Exlan Industrial Co., Ltd., Sekisui Plastics Co., Ltd., and others, with a variety of chemical structures and average particle sizes. The resin beads are blended in an amount of 3 to 20 parts by mass per 100 parts by mass of vinyl chloride resin consisting of vinyl chloride resin and cross-linked vinyl chloride resin. If the amount is less than 3 parts by mass, no synergistic improvement effect on sliding properties is observed, while if the amount is more than 20 parts by mass, defects such as roughening of the surface, brittleness resulting in reduced physical properties, and hardening occur. From the viewpoints of design, physical properties of the molded product, and the expression of sliding properties, an amount of 5 to 10 parts by mass is particularly suitable.

[0017] [Additives] If necessary, conventionally known additives such as lubricants, release agents, flame retardants, antioxidants, ultraviolet absorbers, antistatic agents, colorants, and fillers can be blended into the resin composition within a range that does not impair the effects of the present invention. The additives may be added when preparing the resin composition, but it is preferable to mix them with the vinyl chloride resin in advance.

[0018] [Preparation of Slidable Resin Composition] There are no particular limitations on the method for preparing the sliding resin composition of the present invention. For example, the vinyl chloride resin, cross-linked vinyl chloride resin, silicone powder, resin beads, 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, Banbury mixer, pressure kneader, or co-kneader to obtain the desired sliding resin composition. Typically, the melt-kneaded sliding resin composition is pelletized and then subjected to the subsequent molding process.

[0019] [Production of Slidable Molded Body] The 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 appropriately selected and determined taking into consideration the structure and shape of the molded article, the components and compounding ratios of the resin composition used, etc. For example, from the viewpoint of mass productivity and continuous and stable production, extrusion molding or profile extrusion molding is preferably used, and a molded article according to the desired cross-sectional shape is obtained. For the sliding molded article by extrusion molding, a method of melting the material in an extruder and then extruding it from a T-die, or a method of extruding the material into a sheet form from an extruder and then biaxially stretching it by a tenter system or an inflation system, etc., is used. 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]

[0020] The present invention will be specifically described below using 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 and abbreviations used in the following examples and comparative examples, as well as the test and evaluation methods, are as follows:

[0021] [Vinyl chloride resin] PVC: Hard polyvinyl chloride resin, average degree of polymerization = 2500 [Cross-linked vinyl chloride resin] Cross-linked PVC: Cross-linked vinyl chloride resin, average degree of polymerization = 1300 [Plasticizer] TOTM: Trimellitate ester plasticizer [Silicone powder] SLP: Silicone rubber powder [Resin beads] ACB: Cross-linked polymethyl methacrylate beads True spherical shape, average particle size 30μm

[0022] <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. From the viewpoint of sliding properties, it is preferable that the coefficient is 0.4 or less, and if it is 0.3 or less, the sliding properties are extremely excellent. [Appearance (surface roughness)] The surface of the test piece was visually inspected and evaluated according to the following criteria. ○: No noticeable surface roughness △: Slightly rough surface ×: The surface is very rough [Contact angle] The contact angle of the surface was measured using the DMs-401 manufactured by Kyowa Interface Science Co., Ltd. Although the contact angle (degrees) is a physical property that serves as an indicator of antifouling properties, it is also affected by other physical properties such as the coefficient of dynamic friction. [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 [Weather resistance] A weather resistance test was carried out using a sunshine carbon arc lamp in accordance with JIS b 7753 under conditions of BP 63°C, rain, and for 500 hours. 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. [Rattling noise] A test piece was placed on a glass plate, a 1 kg iron weight was applied to the test piece, and the test piece was pulled with a string at a speed of 100 mm / min. The occurrence of chatter noise at this time was evaluated according to the following criteria. ○: No chattering noise occurred △: A slight rattle noise occurred ×: Chattering noise occurred

[0023] Examples 1 to 4, Comparative Examples 1 to 6 The components were mixed in the proportions shown in Tables 1 and 2 using a Kawata Supermixer SMV-Ba series to produce resin compositions suitable for sliding. These resin compositions were then molded using a Toyo Seiki Labo Plastomill 4C150 at a melt temperature of 185°C to obtain flat test pieces (50 x 30 x 2 mm). Note that although the amounts of vinyl chloride resin and cross-linked vinyl chloride resin in the tables are listed in parts by mass, the total amount of both is 100 parts by mass, so these values represent % by mass. The coefficient of dynamic friction, appearance (surface roughness), contact angle, stain resistance, weather resistance, and chatter noise of this test piece were measured according to the respective test and evaluation methods described above. The results are shown in Tables 1 and 2.

[0024] [Table 1]

[0025] [Table 2]

[0026] Comparative Example 1 is a case where the content of cross-linked vinyl chloride resin is low, and the coefficient of dynamic friction is large, the sliding properties are insufficient, and the stain resistance is poor. Comparative Example 2 is a case where the content of cross-linked vinyl chloride resin is high, and the coefficient of dynamic friction is small and the sliding property is excellent, but the surface roughness is large. Comparative Example 3 is a case where the content of silicone powder is small, and the coefficient of dynamic friction is large, the sliding properties are insufficient, and the stain resistance is poor. Comparative Example 4 is a case where the content of silicone powder is large, and although the coefficient of dynamic friction is small and the sliding property is excellent, the surface is rough and the antifouling property is insufficient. Comparative Example 5 is a case where the content of resin beads is small, and the dynamic friction coefficient is large, the sliding properties are insufficient, and the antifouling properties are poor. Comparative Example 6 is a case where the content of resin beads is large, and although the coefficient of dynamic friction is small and the sliding property is excellent, the surface is rough and the antifouling property is poor.

Claims

1. A sliding resin composition comprising 100 parts by mass of a vinyl chloride resin consisting of 25 to 75% by mass of vinyl chloride resin and 75 to 25% by mass of cross-linked vinyl chloride resin, 5 to 30 parts by mass of silicone powder, and 3 to 20 parts by mass of resin beads having an average particle size of 5 to 80 μm.

2. 2. The sliding resin composition according to claim 1, wherein the resin beads are acrylic resin beads.

3. 2. The sliding resin composition according to claim 1, wherein the sliding resin composition is a soft sliding resin composition further containing a plasticizer.

4. A sliding molded article obtained by molding the sliding resin composition according to any one of claims 1 to 3.

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