Resin molded article and method for producing the same

Abstract

To provide a resin molded article having superior durability in low-friction properties in a surface treatment layer containing fluorine atoms.SOLUTION: A resin molded article according to one embodiment of the present disclosure includes a base body composed of a crosslinked body of a resin composition. At least a part of a surface of the base body is a surface treatment layer. A main component in the resin composition is an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene, or polypropylene. The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is greater than the ratio of the number of fluorine atoms to the number of carbon atoms in a region of the base body that excludes the surface treatment layer. The average thickness of the surface treatment layer is 500 nm or more and 2000 nm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a resin molded body and a method for manufacturing the resin molded body.

Background Art

[0002] A surface treatment method has been studied in which the surface of a plastic molded product is modified by bringing it into contact with fluorine gas to improve water repellency and adhesion. As such a conventional technique, for example, a surface treatment apparatus and method using fluorine gas have been disclosed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The resin molded body according to one aspect of the present disclosure includes a base body made of a crosslinked body of a resin composition, at least a part of the surface of the base body is a surface treatment layer, the main component in the resin composition is an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the base body, and the average thickness of the surface treatment layer is 500 nm or more and 2000 nm or less.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] In the surface treatment layer of a plastic molded article that has been surface-treated with conventional fluorine gas, it is not easy to make the layer adhere stably for a long period of time, and there is a particular problem that it easily peels off when rubbed.

[0007] An object of the present disclosure is to provide a resin molded article that is excellent in the persistence of low-friction properties in a surface treatment layer containing fluorine atoms.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a resin molded article that is excellent in the persistence of low-friction properties in a surface treatment layer containing fluorine atoms.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] The resin molded article of the present disclosure (1) includes a substrate made of a crosslinked body of a resin composition, at least a part of the surface of the substrate is a surface treatment layer, the main component in the resin composition is an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, and the average thickness of the surface treatment layer is 500 nm or more and 2000 nm or less.

[0011] As described above, in the conventional surface treatment with fluorine gas, it is not easy to make the surface treatment layer of a plastic molded article adhere stably for a long period of time, and there is a particular problem that it easily peels off when rubbed. This is presumably because fluororesin has a low surface tension, so while it has high water repellency and oil repellency, it is difficult to adhere to other substances, making it easy to peel off and reducing its wear resistance. By having the above configuration, the resin molded article is excellent in the persistence of low-friction properties in the surface treatment layer containing fluorine atoms. The reason for this is presumably as follows. Because fluorine atoms have an extremely low electronegativity, while strongly bonding to the carbon in the main chain, the van der Waals force does not act between them and surrounding substances, resulting in a small interaction. The higher the proportion of fluorine atoms contained in the molecule, the more pronounced this tendency becomes. Therefore, polytetrafluoroethylene (PTFE), in which the entire periphery of the carbon chain consists of fluorine atoms, has the lowest interaction among resins and is excellent in non-stick and low-friction properties. However, since the characteristic of low interaction with surrounding substances in fluorine atoms also applies to the same molecules, resins with a high fluorine atom content generally have low intermolecular forces, making it easy for molecules to slide past each other and peel off, resulting in a decrease in wear resistance. Therefore, the surface treatment layer containing fluorine atoms provided on the resin surface is very unstable and easily peeled off and worn due to friction. The resin molded body includes a substrate made of a crosslinked body of a resin composition, thereby reducing intermolecular peeling and improving wear resistance. Also, since the surface treatment layer is a surface treatment layer of the crosslinked body, even if the surface treatment layer contains fluorine atoms, the surface treatment layer can be stably maintained. Furthermore, the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer with an average thickness of 500 nm or more and 2000 nm or less is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, so that the low-friction characteristics of the surface treatment layer can be maintained even in a situation where friction is repeatedly applied to the surface treatment layer. Therefore, it is considered that the resin molded body is excellent in the persistence of the low-friction characteristics in the surface treatment layer containing fluorine atoms. In the present disclosure, the "main component" refers to the component with the highest content, for example, a component with a content exceeding 90% by mass. The "average thickness" refers to the average value of the thickness measured at any ten points.

[0012] (2) In the above (1), the main component of the resin composition may be an ethylene-tetrafluoroethylene copolymer or polyvinylidene fluoride. By the main component of the resin composition being an ethylene-tetrafluoroethylene copolymer or polyvinylidene fluoride, the processability and wear resistance can be improved.

[0013] (3) In the above (1) or (2), the main component of the resin composition is an ethylene-tetrafluoroethylene copolymer, and the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer may exceed 1.0. When the main component of the resin composition is an ethylene-tetrafluoroethylene copolymer and the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer exceeds 1.0, the resin molded body can further improve the persistence of the low friction characteristics in the surface treatment layer containing fluorine atoms.

[0014] (4) Further, the method for manufacturing a resin molded body of the present disclosure is a method for manufacturing a resin molded body including a substrate and a surface treatment layer provided on at least a part of the surface of the substrate. The method includes a step of molding a resin composition, a step of crosslinking the resin composition after the molding step by electron beam irradiation, and a step of bringing a fluorine-containing gas into contact with at least a part of the surface of the resin composition after the crosslinking step. The main component in the resin composition is an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene, or polypropylene. The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate. The average thickness of the surface treatment layer formed by the step of bringing the fluorine-containing gas into contact is 500 nm or more and 2000 nm or less.

[0015] The method for manufacturing the resin molded body crosslinks the entire resin composition after the above-mentioned molding step by electron beam irradiation in the above-mentioned crosslinking step. And, by including a step of bringing a fluorine-containing gas into contact with at least a part of the surface of the resin composition after the above-mentioned crosslinking step, a resin molded body having a surface treatment layer with a high fluorine content and an average thickness of 500 nm or more and 2000 nm or less can be manufactured. Since the surface treatment layer of the resin molded body obtained by the method for manufacturing the resin molded body is the surface treatment layer of the crosslinked body, even if the surface treatment layer contains fluorine atoms, the surface treatment layer can be stably maintained. Further, since the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer having an average thickness of 500 nm or more and 2000 nm or less is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, the wear resistance of the surface treatment layer can be improved. Therefore, the method for manufacturing the resin molded body can manufacture a resin molded body excellent in the persistence of the low friction characteristics in the surface treatment layer containing fluorine atoms.

[0016] [Details of Embodiments of the Present Disclosure] Preferred embodiments of the present disclosure will be described.

[0017] <Resin Molded Body> The resin molded body according to an embodiment of the present disclosure includes a substrate made of a crosslinked body of a resin composition. Further, in the resin molded body, at least a part of the surface of the substrate is a surface treatment layer. Examples of the shape of the resin molded body include a tube shape, a plate shape, a rod shape, a cube, a rectangular parallelepiped, and a cylinder. The resin molded body may have a through hole. Further, the surface of the resin molded body does not need to be flat, and patterns such as a convex shape, a concave shape, and a continuous corrugated shape in which protrusions alternate between the outside and the inside may be formed on the surface. In the case of a continuous corrugated shape, the cross-sectional shapes of the convex shape and the concave shape are not particularly limited, and various shapes such as an isosceles triangle, an arc shape, an isosceles trapezoid, and a rectangle can be adopted. Further, when the resin molded body is tube-shaped, the cross-sectional shape may be either an annular shape or a polygonal annular shape, and those manufactured by a normal molding method such as an extrusion molding method can be used.

[0018] FIG. 1 is a schematic perspective view showing a resin molded body 1 according to an embodiment of the present disclosure. The resin molded body 1 is a cylindrical tube. In the resin molded body 1, at least a part of the surface of the base body 2 is a surface treatment layer 3. That is, the base body 2 has a surface treatment layer 3 and a region 4 other than the surface treatment layer 3 in the base body 2.

[0019] In the resin molded body 1, the main component in the resin composition is ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polyethylene (PE) or polypropylene (PP). Since the main component in the resin composition is ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, the main chain is made of a carbon chain, so the strength is good. On the other hand, resins containing oxygen or nitrogen in the main chain cannot withstand fluorine gas treatment, so they are likely to cause strength deterioration and are not suitable as the main component. Among these, as the main component in the resin composition, ethylene-tetrafluoroethylene copolymer or polyvinylidene fluoride may be used from the viewpoints of corrosion resistance to fluorine gas, the surface composition approaching polytetrafluoroethylene (PTFE) by treatment with a fluorine-containing gas, and further processability.

[0020] The average thickness of the base body 2 is not particularly limited as long as sufficient strength can be maintained, and can be, for example, 100 μm or more and 100 mm or less.

[0021] The surface treatment layer 3 is provided on the inner peripheral surface of the base body 2. As will be described later, the surface treatment layer 3 is formed by bringing a fluorine-containing gas into contact with the surface of the base body 2 and substituting hydrogen of the cross-linked body of the main component resin of the resin composition constituting the resin molded body 1 with fluorine atoms. The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer 3 is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region 4 other than the surface treatment layer 3 of the base body 2. By the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer 3 being larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region 4 other than the surface treatment layer 3 of the base body 2, the persistence of the low friction characteristics in the surface treatment layer 3 can be improved.

[0022] The lower limit of the average thickness of the surface treatment layer 3 is 500 nm, and it may be 550 nm or 600 nm. When the average thickness is 500 nm or more, the surface treatment layer 3 containing fluorine atoms is excellent in durability against friction. On the other hand, the upper limit of the average thickness is 2000 nm, and it may be 1950 nm or 1900 nm. Although it depends on the type of resin that is the main component of the resin composition, there is a limit to the depth to which fluorine gas can reach from the surface of the resin by fluorine gas treatment. To treat deeper than 2000 nm, additional measures such as increasing the treatment time or reaction temperature will increase the cost. When the average thickness is 2000 nm or less, sufficiently excellent durability can be obtained without making the surface treatment layer 3 unnecessarily thick.

[0023] The main component of the resin composition constituting the resin molded body 1 is an ethylene-tetrafluoroethylene copolymer. The lower limit of the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer 3 is more than 1.0, and it may be 1.1 or 1.2. On the other hand, the upper limit of the ratio of the number of fluorine atoms to the number of carbon atoms is theoretically 2.0 for tetrafluoroethylene. Since the main component of the resin composition is an ethylene-tetrafluoroethylene copolymer and the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer 3 exceeds 1.0, the resin molded body 1 can further improve the persistence of the low friction characteristics in the surface treatment layer 3 containing fluorine atoms.

[0024] As other optional components, the resin molded body 1 can use additives such as an antifoaming agent, a coloring pigment, an antioxidant, an ultraviolet absorber, an antistatic agent, a surfactant, a leveling agent, and a rheology control agent.

[0025] According to the resin molded body, since the friction coefficient of the surface treatment layer containing fluorine atoms is low, it is excellent in slipperiness. Furthermore, the resin molded body includes a substrate made of a crosslinked body of a resin composition, and at least a part of the surface of the substrate is a surface treatment layer, so that the durability of the low friction property in the surface treatment layer containing fluorine atoms is excellent. The following reasons are presumed for this. Since the resin molded body includes a substrate made of a crosslinked body of a resin composition, the entire substrate is connected and integrated by covalent bonds. Further, since the surface treatment layer is a surface treatment layer of the crosslinked body, even if the surface treatment layer contains fluorine atoms, the surface treatment layer can be stably maintained. Furthermore, the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer having an average thickness of 500 nm or more and 2000 nm or less is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, so that the low friction property of the surface treatment layer can be maintained even in a situation where friction is repeated against the surface treatment layer. Therefore, it is considered that the resin molded body has excellent slipperiness and abrasion resistance in the surface treatment layer containing fluorine atoms.

[0026] <Method for manufacturing resin molded body> The manufacturing method of the resin molded body is a method for manufacturing a resin molded body comprising a base body made of a crosslinked body of a resin composition, with at least a part of the surface being a surface treatment layer. The manufacturing method of the resin molded body includes a step of molding the resin composition (molding step), a step of crosslinking the resin composition after the molding step by electron beam irradiation (crosslinking step), and a step of bringing a fluorine-containing gas into contact with at least a part of the surface of the resin composition after the crosslinking step (bringing the fluorine-containing gas into contact step). And, the resin molded body obtained by the manufacturing method of the resin molded body has a main component in the resin composition being ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer being larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the base body, and the average thickness of the surface treatment layer formed by the step of bringing the fluorine-containing gas into contact being 500 nm or more and 2000 nm or less. The resin molded body obtained by the manufacturing method of the resin molded body has the above configuration, so that the surface treatment layer containing fluorine atoms is excellent in slipperiness and wear resistance.

[0027] (molding step) In the molding step, the resin composition is molded into a desired shape. The resin composition is prepared by mixing the main components, namely ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, and components added as required, using a kneader or the like. As the kneader, a known kneader can be used. Alternatively, a commercially available resin composition as a material previously mixed with a conductive substance can be used as a raw material. The method for molding the resin composition is not particularly limited, and known extrusion molding, injection molding, etc. can be used.

[0028] (crosslinking step) In the crosslinking step, the resin composition after the molding step is crosslinked by electron beam irradiation.

[0029] The electron beam is irradiated onto the resin composition after the above-mentioned shaping process. By irradiating the electron beam, the crosslinking of the resin composition proceeds, reducing the deformation of the resulting resin molded body in a high-temperature environment and enhancing its mechanical strength.

[0030] The ambient temperature during electron beam irradiation can be equal to or higher than room temperature and equal to or lower than the melting point of the resin composition.

[0031] Also, in the above-mentioned electron beam irradiation, the electron beam can be irradiated in the air. Therefore, since no equipment or energy for adjusting the atmosphere is required, the manufacturing efficiency can be further enhanced.

[0032] The irradiation dose of the electron beam in electron beam irradiation may be 50 kGy or more and 250 kGy or less, or may be 100 kGy or more and 200 kGy or less, although it depends on the type of resin to be irradiated. If the irradiation dose of the above-mentioned electron beam is less than 50 kGy, the effect of reducing the deformation and the abrasion resistance of the resulting molded body in a high-temperature environment may not be sufficiently improved. On the other hand, if the irradiation dose of the above-mentioned electron beam exceeds 250 kGy, there is a possibility that the strength deterioration and the cost-effectiveness of electron beam irradiation cannot be sufficiently obtained.

[0033] (Step of contacting with a fluorine-containing gas) In the step of contacting with a fluorine-containing gas, the fluorine-containing gas is brought into contact with at least a part of the surface of the resin composition after the above-mentioned crosslinking step. By bringing the surface of the crosslinked body into contact with the fluorine-containing gas, a surface treatment layer with an average thickness of 500 nm or more and 2000 nm or less is obtained. The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the above-mentioned substrate. For example, in the case of a tubular resin molded body, it can be manufactured by bringing a fluorine-containing gas into contact with the inner peripheral surface of the tubular resin molded body.

[0034] As the fluorine-containing gas, any gaseous fluorine-containing compound can be contained without particular limitation. Examples include fluorine gas, hydrogen fluoride gas, ammonium fluoride, fluorine-containing organic compounds (CF4, C2F6, etc.), carbonyl fluoride (COF2), and nitrogen trifluoride (NF3). The fluorine-containing gas can be used alone or as a mixed gas with an inert gas or the like. Examples of the inert gas include inert gases such as nitrogen gas and argon gas.

[0035] The temperature at which the fluorine-containing gas is contacted and the time for contacting the fluorine-containing gas are not particularly limited. The reaction of fluorine gas itself occurs instantaneously upon contact with the object to be treated. However, the reactivity changes due to factors such as the time required for fluorine gas to penetrate from the surface in the depth direction, the amount of fluorine gas supplied, and the surface area of the object to be treated, resulting in the consumption of fluorine gas and a decrease in the concentration of the effective gas. Therefore, the temperature and contact time need to be carried out within an appropriate range.

[0036] The method for manufacturing the resin molded body crosslinks the entire resin composition after the molding step in the crosslinking step. By providing a step of contacting at least a part of the surface of the resin composition after the crosslinking step with a fluorine-containing gas, a resin molded body having a surface treatment layer with a high fluorine content and an average thickness of 500 nm or more and 2000 nm or less can be manufactured. Since the surface treatment layer of the resin molded body obtained by the method for manufacturing the resin molded body is the surface treatment layer of the crosslinked body of the resin composition, the surface treatment layer can be stably maintained even if it contains fluorine atoms. Furthermore, by making the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer with an average thickness of 500 nm or more and 2000 nm or less larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, the wear resistance of the surface treatment layer can be improved. Therefore, the method for manufacturing the resin molded body can manufacture a resin molded body excellent in the persistence of the low friction characteristics in the surface treatment layer containing fluorine atoms.

[0037] [Other Embodiments] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0038] In the above embodiments, it was tubular, but as described above, the shape of the resin molded body is not particularly limited, and for example, it may be plate-shaped. Further, for example, when the shape of the resin molded body is plate-shaped, the cross-sectional shape may be rectangular, square, parallelogram, or trapezoid, and these cross-sectional shapes may have rounded corners.

[0039] FIG. 2 is a schematic cross-sectional view showing a resin molded body 10 according to another embodiment of the present disclosure. The resin molded body 10 is plate-shaped. In the resin molded body 10, at least a part of the surface of the base 12 is a surface treatment layer 13. That is, the base 12 has the surface treatment layer 13 and a region 14 other than the surface treatment layer 13 in the base 12. As a method for molding the plate-shaped resin molded body 10, it is not particularly limited, and known extrusion molding, injection molding, compression molding, cutting processes, etc. can be used. Since the configurations of the base 12 and the surface treatment layer 13 in the resin molded body 10, as well as the manufacturing process, are the same as those of the base 2 and the surface treatment layer 3 in the above resin molded body 1, the description is omitted. Also in the resin molded body 10, by having the above configuration, the durability of the low friction characteristics in the surface treatment layer 13 containing fluorine atoms is excellent.

Examples

[0040] Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples.

[0041] <Test Nos. 1 to 3 and No. 7> (1) Preparation of Resin Molded Body As the material of the resin molded body, a commercially available ETFE (ethylene tetrafluoroethylene copolymer) tube manufactured by Chukyo Kasei Kogyo Co., Ltd. (ETFE raw material: Fluon ETFE "C-55AXP" manufactured by AGC Inc.) was used. The inner diameter (diameter) of the ETFE tube was 1.68 mm, and the outer diameter (diameter) was 2.28 mm. In this way, the tubular molded bodies of Test Nos. 1 to 3 and No. 7 were obtained. Among these, the tubular molded body of Test No. 1 was used as the resin molded body of Test No. 1. (2) Electron beam irradiation Next, in No. 3 and No. 7, crosslinking was performed by electron beam irradiation. The electron beam irradiation was performed using a Dynamitron type electron beam accelerator manufactured by RDI. As the irradiation conditions, the acceleration voltage was 4.6 MeV and 20 mA, the irradiation dose was 20 kGy × 10 irradiations (total 200 kGy), and the irradiation was performed at normal temperature in the atmosphere. In this way, the resin molded body of Test No. 3 was obtained. (3) Fluorine gas treatment Furthermore, in No. 7, after electron beam irradiation, fluorine gas treatment was performed on the inner peripheral surface. In No. 2, fluorine gas treatment was performed on the inner peripheral surface without electron beam irradiation. The sample was placed in a sealed container, and the inside of the container was evacuated to a sub-vacuum with a vacuum pump. Then, nitrogen gas with a fluorine gas concentration of 1.5% by volume was introduced until atmospheric pressure and sealed. Next, after a certain period of time, the gas inside the container was exhausted, and after returning to atmospheric pressure, the sample was taken out. In this way, the resin molded bodies of Test Nos. 2 and 7 were obtained.

[0042] <Test Nos. 4 to 6 and No. 8> (1) Preparation of resin molded body As the material of the resin composition, polyethylene (PE) was pelletized. The obtained pellets were heated and melted and then molded into a square plate shape with a thickness of 5 mm and a size of 4 cm × 4 cm using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.) with a clamping force of 18 t. After that, it was cooled to normal temperature to produce a plate-shaped molded body. In this way, the plate-shaped molded bodies of Test Nos. 4 to 6 and No. 8 were obtained. Among these, the plate-shaped molded body of Test No. 4 was used as the resin molded body of Test No. 4. (2) Electron beam irradiation Next, in No. 5 and No. 8, crosslinking was performed by electron beam irradiation. The electron beam irradiation was performed using a Dynamitron-type electron beam accelerator manufactured by RDI. As the irradiation conditions, the acceleration voltage was 4.6 MeV and 20 mA, the irradiation dose was 20 kGy × 3 irradiations (total 60 kGy), and one-sided irradiation was performed at room temperature in the air. In this way, the resin molded body of Test No. 5 was obtained. (3) Fluorine treatment Furthermore, in No. 8, after electron beam irradiation, fluorine gas treatment was performed on the outer surface. In No. 6, fluorine gas treatment was performed on the outer surface without electron beam irradiation. The sample was placed in a sealed container, and the inside of the container was made into a sub-vacuum with a vacuum pump. Then, nitrogen gas with a fluorine gas concentration of 1.5 vol% was introduced until atmospheric pressure and sealed. Next, after a certain period of time had passed, the gas inside the container was exhausted, and after returning to atmospheric pressure, the sample was taken out. In this way, the resin molded bodies of Test No. 6 and Test No. 8 were obtained.

[0043] [Evaluation] (Average depth in the surface treatment layer and ratio of fluorine atoms to carbon atoms) The average depth [nm] of the surface treatment layer and the ratio of fluorine atoms to carbon atoms in the surface treatment layer were analyzed for the depth direction distribution by X-ray photoelectron spectroscopy (XPS) each time while gradually scraping the surface of the resin molded bodies of Test No. 1 to No. 8 by sputtering. The measurement method of XPS measurement is as follows. (Sputtering) Sputtering conditions: In the depth from the surface of 0 nm to 2000 nm, data was acquired every 40 nm. (Acceleration voltage 10 kV, acceleration current 20 nA, sputtering area 2 mm × 2 mm) Sputtering speed: It was performed at 135.14 nm / min in terms of standard PMMA (polymethyl methacrylate). (XPS measurement) Scanning-type dual X-ray photoelectron spectrometer "PHI Quantes" manufactured by ULVAC-PHI, Inc. X-ray source: MONO AlKα Beam conditions: 100μmφ, 25W, 15kV Transmitted energy: 55eV, 112eV, 280eV Analytical elements: C, N, O, F, Si

[0044] (Average maximum frictional force) For resin molded bodies (fluorine-treated ETFE tubes) in Test Nos. 1 to 3 and No. 7, a polyamide layer-coated wire was inserted into the holes, and a friction test was conducted based on the following method to calculate the average maximum frictional force [N] between the inner peripheral surface of the resin molded body and the polyamide layer-coated wire. As the polyamide layer-coated wire (diameter 1.0 mm), a wire rope made of stainless steel (diameter 0.81 mm) coated with an outer coating layer made of polyamide was used. (1) Measuring device: Tensile test device "SDT-503NB" manufactured by Imada Seisakusho Co., Ltd. (2) Measuring method The resin molded body to be measured was set along the 2.5 mm-wide groove of the measuring device, and a polyamide layer-coated wire was inserted into the inner cavity of the resin molded body. Next, the upper end of the wire was connected to a load cell, and a 1 kg weight (9.8 N) was connected to the lower end of the wire. Then, with the weight of the weight applied as a load to the load cell, the wire was moved up and down to measure the frictional resistance between the inner cavity of the resin molded body and the wire. (3) Measuring procedure After raising the upper end of the wire from a height of 0 mm to 12 mm, it was stationary at the upper end for 20 seconds. Next, it was lowered to 0 mm. The stroke speed was set at 10 mm / min. This was repeated 100 cycles to measure the maximum frictional force [N]. Then, the average maximum frictional force [N] for 100 cycles was calculated. The results are shown in Table 1.

[0045] (Change amount of the maximum frictional force after repeating the friction test) The difference between the maximum frictional force at the 100th cycle and the maximum frictional force at the 1st cycle of the resin molded bodies in Test Nos. 1 to 3 and No. 7 for which the maximum frictional force was measured was obtained and taken as the change amount [N] of the maximum frictional force after repeating the friction test. The results are shown in Table 1.

[0046] (Limiting PV value by ring-on-disk type thrust wear test) The limiting PV value of the surface of the surface treatment layer of the resin molded body was measured by a ring-on-disk type thrust wear test. Here, the "limiting PV value" is a value measured in accordance with JIS-K7218:1986 "Method for sliding wear test of plastics", and the larger the numerical value, the better the slidability represented by the wear resistance. The measurement was carried out under the condition that the temperature was adjusted to 23 ± 2 °C, the load was kept constant at 10 MPa, and the speed was increased step by step every 3 minutes. Specifically, as the ring-shaped mating material, a material with S45C (carbon steel for machine structures), ring dimensions (outer diameter / inner diameter) of φ11.6 mm / φ7.4 mm, and a surface roughness Ra of 0.28 μm was used. Then, with a predetermined load (surface pressure: P) applied to the mating material under dry lubrication conditions, the test piece was rotated at a predetermined speed (rotation speed: V), and the coefficient of dynamic friction was measured by the reaction torque generated on the mating material. At this time, for the speed, it started at 1 m / min in step (1), increased to 5 m / min in step (2), and 10 m / min in step (3), and thereafter, the speed was increased by 10 m / min every time one step was increased, and the limiting PV value was measured. In the present disclosure, the PV value immediately before the surface treatment layer peels off is defined as the limiting PV value. For the above measurement, "FEM-3-1010-ADX-S" manufactured by AND Corporation was used as the test device. The results are shown in Table 1.

[0047]

Table 1

[0048] As shown in Table 1, the resin molded body comprises a substrate made of a crosslinked body of a resin composition in which the main component resin is ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene. At least a part of the surface of the substrate is a surface treatment layer. The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is larger than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate. In Test Nos. 7 and 8 where the average thickness of the surface treatment layer is 500 nm or more and 2000 nm or less, Test No. 7 had small fluctuations in the average maximum frictional force and the average maximum frictional force after repeated friction tests. Also, Test No. 8 had a low minimum coefficient of kinetic friction and a good limiting PV value. From this, it can be seen that the resin molded body has high surface slipperiness, good sustainability of slipperiness, and excellent wear resistance.

[0049] On the other hand, in Test No. 2 where the substrate is not a crosslinked body and Test No. 3 which does not have a surface treatment layer, the average maximum frictional force was high and the fluctuations in the average maximum frictional force due to repeated friction tests became large. In Test No. 5 which does not have a surface treatment layer, the limiting PV value was low and the minimum coefficient of friction was high. In Test No. 6 where the substrate is not a crosslinked body, the limiting PV value became a low value. Also, in Test No. 1 where the substrate is not a crosslinked body and does not have a surface treatment layer, the average maximum frictional force and the fluctuations in the average maximum frictional force due to repeated friction tests became very large. In Test No. 4 where the substrate is not a crosslinked body and does not have a surface treatment layer, the limiting PV value was very low and the minimum coefficient of friction was high.

[0050] From the above results, it was shown that the resin molded body is excellent in the sustainability of the low friction characteristics in the surface treatment layer containing fluorine atoms.

Explanation of Symbols

[0051] 1, 10 Resin molded body 2, 12 Substrate 3, 13 Surface treatment layer 4, 14 Region other than the surface treatment layer in the substrate

Claims

1. Comprising a substrate made of a crosslinked body of a resin composition, At least a part of the surface of the substrate is a surface treatment layer, The main component in the resin composition is ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is greater than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, A resin molded body having an average thickness of the surface treatment layer of 500 nm or more and 2000 nm or less.

2. The resin molded body according to claim 1, wherein the main component of the resin composition is ethylene-tetrafluoroethylene copolymer or polyvinylidene fluoride.

3. The main component of the resin composition is ethylene-tetrafluoroethylene copolymer, The resin molded body according to claim 1, wherein the ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer exceeds 1.

0.

4. A method for manufacturing a resin molded body comprising a substrate made of a crosslinked body of a resin composition and having at least a part of the surface as a surface treatment layer, A step of molding a resin composition, A step of crosslinking the resin composition after the molding step by electron beam irradiation, A step of bringing a fluorine-containing gas into contact with at least a part of the surface of the resin composition after the crosslinking step And comprising, The main component in the resin composition is ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyethylene or polypropylene, The ratio of the number of fluorine atoms to the number of carbon atoms in the surface treatment layer is greater than the ratio of the number of fluorine atoms to the number of carbon atoms in the region other than the surface treatment layer of the substrate, A method for manufacturing a resin molded body having an average thickness of the surface treatment layer formed by the step of bringing the fluorine-containing gas into contact of 500 nm or more and 2000 nm or less.

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