Laminated resin tube and forming method

Abstract

The invention provides a laminated resin tube and a molding method. A laminated resin tube (1) is provided with: an inner layer (4) containing a thermoplastic material that is a thermoplastic resin or a thermoplastic elastomer; an intermediate layer (3) that is provided on the outer periphery of the inner layer and contains a polyamide resin; and an outer layer (2) that is provided on the outer periphery of the intermediate layer and contains a fluororesin.

Description

Technical Field

[0001] The present invention relates to a laminated resin tube and a forming method. Background Art

[0002] There are known laminated resin tubes formed by laminating a plurality of layers. Japanese Patent Application Laid-Open No. 2009-127631 discloses a fuel tube formed by laminating an inner layer containing a tetrafluoroethylene-ethylene copolymer resin (ETFE) and an outer layer made of a polyamide resin having good adhesiveness to the inner layer.

[0003] Japanese Patent Application Laid-Open No. 6-234190 discloses a hose for automotive fuel piping formed by laminating an inner layer made of a fluororesin, an intermediate layer made of a synthetic resin other than a fluororesin, and an outer layer made of a rubber elastic material. An adhesive layer based on a mixture of a fluororesin and a polyamide resin can be formed between the inner layer and the intermediate layer. In addition to the formation of the adhesive layer, adhesive treatment such as flame treatment can be applied to the surface of the inner layer.

[0004] Japanese Patent Application Laid-Open No. 2012-92901 discloses a tube including: an inner layer made of a thermoplastic resin; a reinforcing layer made of a metal braid formed on the outer periphery of the inner layer; and an outer layer covering the inner layer and the reinforcing layer and made of a fluororesin. As the fluororesin forming the outer layer covering body, an adhesive fluororesin can be used.

[0005] There is a need for a laminated resin tube having excellent flexibility and bending performance (kink resistance) and capable of being produced simply. Summary of the Invention

[0006] An object of the present invention is to solve the above technical problems.

[0007] A first aspect of the present invention is a laminated resin tube including: an inner layer containing a thermoplastic material as a thermoplastic resin or a thermoplastic elastomer; an intermediate layer provided on the outer periphery of the inner layer and containing a polyamide resin; and an outer layer provided on the outer periphery of the intermediate layer and containing a fluororesin.

[0008] The second method of the present invention is a method for forming a laminated resin tube based on the first method. The inner layer material of the inner layer containing the thermoplastic resin or the thermoplastic elastomer is heated and melted by an inner layer extruder; the intermediate layer material of the intermediate layer containing the polyamide resin is heated and melted by an intermediate layer extruder; the outer layer material of the outer layer containing the fluororesin is heated and melted by an outer layer extruder; by jointly performing the extrusion of the inner layer material from the inner layer extruder to the mold based on the inner layer extruder, the extrusion of the intermediate layer material from the intermediate layer extruder to the mold based on the intermediate layer extruder, and the extrusion of the outer layer material from the outer layer extruder to the mold based on the outer layer extruder, co-extrusion molding of the inner layer, the intermediate layer, and the outer layer is performed in the mold.

[0009] According to the present invention, a laminated resin tube having excellent flexibility and bending properties and capable of being easily produced can be obtained.

[0010] The above objects, features, and advantages should be easily understood from the following description of the embodiments described with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. illustrates the structure of a laminated resin tube based on one embodiment.

[0012] Figure 2 FIG. is a schematic view for explaining a method for forming a laminated resin tube.

[0013] Figure 3 FIG. is a flowchart showing a processing sequence corresponding to the method for forming a laminated resin tube. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the past, various resin tubes have been supplied for actual use. A seamless and uniform long resin tube can be produced in large quantities. The resin tube is suitable for the transportation of gases or liquids. The resin tube is widely used in various industries. The resin tube is used, for example, in the food industry, medical treatment, transportation of fuels or paints, piping parts for introducing high-pressure air, etc.

[0015] The resin tube is an important component in the industry. Therefore, multiple types of resin tubes that have undergone various studies are provided for actual use. For example, when the resin tube needs to withstand high pressure, a resin tube made of a strong polyamide resin is selected. When the resin tube transports organic solvents, a resin tube made of a fluororesin with excellent chemical resistance is selected.

[0016] A laminated resin tube having an inner layer and an outer layer with a reinforcing layer having reinforcing filaments provided therebetween is also provided for practical use. The inner layer is made of a material having an appropriate material according to the type of gas or liquid to be transported. The outer layer is made of a material having a material that is hardly affected by the external environment and has strong friction resistance. Since the laminated resin tube has a reinforcing layer, it has high pressure resistance.

[0017] In addition, a flexible tubular body for transporting gas or liquid is also called a hose in addition to a tube. Hereinafter, a tube is a concept including a hose. In addition, the transported material transported by the resin tube is not limited to gas or liquid. A mixture of gas and liquid can also be transported by the resin tube. Solids such as powders or granules can also be transported by the resin tube together with gas or liquid. Hereinafter, transported materials such as gas, liquid, powder, and granule transported by the resin tube are collectively referred to as fluids.

[0018] A resin tube made of fluororesin has high chemical resistance. In particular, a resin tube made of tetrafluoroethylene-ethylene copolymer resin (ETFE) can be processed at a relatively low temperature, so it is widely used. However, the flexibility of many fluororesins including ETFE is low. Therefore, the flexibility of the resin tube made of fluororesin is low. Therefore, the resin tube made of fluororesin is hard and lacks flexibility, so it is difficult to bend and the usability is poor.

[0019] In addition, generally, the bending performance of a resin tube made of fluororesin is poor. The bending performance of a resin tube is also called kink resistance. When an operator wants to bend a resin tube, the resin tube may not bend but be crushed and bent. In this case, the tubular structure of the resin tube becomes narrow and a state where the fluid cannot pass through is generated. Kink resistance means how difficult it is to fall into such a state. When the kink resistance is high, the operator can bend the resin tube greatly without crushing it. That is, when the kink resistance of the resin tube is high, the bending performance of the resin tube is high.

[0020] A resin tube with poor bending performance cannot be bent greatly. That is, the bending radius of a resin tube with poor bending performance cannot be reduced. When an operator uses a resin tube with a large limitation on the bending radius, the operator needs to handle the resin tube very carefully.

[0021] In addition, the concepts of flexibility and bending performance (kink resistance) are different from each other. For example, there is a case where a tube that lacks flexibility and is hard and thus difficult to bend easily has excellent bending performance. If the operator carefully bends the tube with force, the tube can be bent with a small bending radius without kinking.

[0022] As described above, a single-layer ETFE resin tube has technical problems of low flexibility and poor bending performance. For such technical problems, improvement can be achieved through the technologies disclosed in Japanese Patent Application Laid-Open No. 2009-127631 and Japanese Patent Application Laid-Open No. 6-234190. That is, by making the inner layer formed of ETFE lacking flexibility into a thin wall, the difficulty in bending is alleviated. In addition, the strength and the like are improved by an outer layer made of another resin material. Thus, the low flexibility and bending performance can be improved to a certain extent.

[0023] However, the surface energy of fluororesin containing ETFE is low. Therefore, the adhesiveness between the fluororesin and other resins is low. The friction between the layer of the fluororesin and the layer of other resins is also extremely small. That is, the layer of the fluororesin is likely to peel off from other layers. If peeling occurs, there is no substantial difference between the inner layer formed of the fluororesin and the single-layer fluororesin tube. Therefore, kinking may still occur in the laminated resin tube formed by simply laminating other resin layers on the fluororesin layer.

[0024] Japanese Patent Application Laid-Open No. 2009-127631 and Japanese Patent Application Laid-Open No. 6-234190 disclose technologies for reducing the peeling between the layer of the above-mentioned fluororesin and other layers. For example, it is disclosed that an intermediate layer is provided, and the intermediate layer is made of a resin capable of ensuring a certain adhesiveness to the fluororesin. In addition, it is also disclosed that the adhesiveness can be improved by modifying the resin material constituting the layer of the fluororesin (for example, by chemical etching).

[0025] However, by using such special materials or surface treatments, problems such as an increase in the manufacturing cost of the laminated resin tube and a decrease in the long-term stability of the laminated resin tube occur. In addition, even if the adhesiveness is improved, kinking may still occur in the inner layer tube made of fluororesin. In this case, the limitation of the bending radius of the laminated resin tube is still large.

[0026] In addition, generally, the transparency of the fluororesin is poor, so the operator may not be able to visually confirm the inside of the laminated resin tube well. The reason will be described below. When the laminated resin tube has an inner layer made of fluororesin, if the adhesiveness between the fluororesin and the resin constituting the outer layer is not very high, the possibility of the above-mentioned interlayer peeling is high. Therefore, the bending performance of the laminated resin tube is low. In order to improve the above-mentioned adhesiveness, various methods such as chemical etching of the adhesive surface of the inner layer or using an adhesive resin having a high amine value and many functional groups can be applied.

[0027] However, even when any of the techniques is applied, the transparency of the inner adhesive surface is impaired. As a result, the visual confirmability inside the laminated resin tube is impaired. That is, the operator cannot visually confirm the inside of the laminated resin tube well. Whether the operator can visually confirm the presence or absence of fluid inside the tube greatly affects the usability of the laminated resin tube. Therefore, the above transparency is very important for the operator.

[0028] According to the technique disclosed in Japanese Patent Application Laid-Open No. 2012-92901, the inner layer, the reinforcing layer, and the outer covering of the tube respectively achieve the ensuring of bending performance, pressure resistance performance, and slidability. In addition, the slidability means low friction on the outer surface of the tube. In the case of a tube with low slidability, no snagging with other tubes or the like occurs, so the handling of the tube becomes easy. Since the outer covering as the outermost layer of the tube is made of fluororesin, the tube has excellent slidability and chemical resistance on the outer surface of the tube.

[0029] However, for the purpose of improving the pressure resistance and kink resistance of the tube, the tube has a reinforcing layer composed of a braid formed of metal wires. Therefore, the tube is heavy. In addition, when the tube is cut, the metal wires are exposed from the cross section. Therefore, the operator needs to pay sufficient attention when using the tube, and it also limits the uses of the tube.

[0030] In addition, in order to ensure good adhesion between the fluororesin constituting the outer covering and the reinforcing layer or the like, a selective adhesive fluororesin is disclosed as the fluororesin. Instead of selecting a selective adhesive fluororesin as the fluororesin, a defluorination treatment such as chemical etching is also disclosed for the fluororesin. Therefore, the laminated resin tube cannot be produced simply, and improvement is desired from the viewpoints of raw material cost, processing cost, and productivity.

[0031] The laminated resin tube based on one embodiment will be described with reference to the drawings. Figure 1 It is a diagram illustrating the structure of the laminated resin tube 1 based on the present embodiment. The laminated resin tube 1 has a tubular structure integrally formed by laminating an inner layer 4, an intermediate layer 3, and an outer layer 2 in this order from the inside. The central portion of the laminated resin tube 1 is a hollow formed inside the inner layer 4. The central portion of the laminated resin tube 1 is used as a flow path for transporting fluid.

[0032] The inner layer 4 of the laminated resin tube 1 is a circular tubular layer located on the innermost side of the laminated resin tube 1. Therefore, the inner layer 4 comes into contact with the fluid transported inside the laminated resin tube 1. The inner layer 4 contains a thermoplastic material having thermoplasticity. The thermoplastic material used for the inner layer 4 is a thermoplastic resin or a thermoplastic elastomer. Thermoplastic resins and thermoplastic elastomers have excellent elasticity and high flexibility. Specific materials used as the thermoplastic resin or the thermoplastic elastomer can be appropriately selected according to the use or required functions of the laminated resin tube 1.

[0033] In the case where a thermoplastic resin is used as the thermoplastic material for the inner layer 4, the thermoplastic resin is, for example, a polyurethane resin or a polyvinyl chloride resin. In the case where a thermoplastic elastomer is used as the thermoplastic material for the inner layer 4, the thermoplastic elastomer is, for example, a polyurethane-based elastomer, a polyamide-based elastomer, an olefin-based elastomer, or a polystyrene-based elastomer.

[0034] That is, the inner layer 4 contains any one of, for example, a polyurethane resin, a polyvinyl chloride resin, a polyurethane-based elastomer, a polyamide-based elastomer, an olefin-based elastomer, and a polystyrene-based elastomer.

[0035] Both the above-mentioned thermoplastic resin and thermoplastic elastomer for the inner layer 4 have appropriate strength and elasticity corresponding to the use of the laminated resin tube 1. Thus, a laminated resin tube 1 with excellent flexibility and bending performance (kink resistance) can be obtained. Therefore, the usability of the laminated resin tube 1 is good.

[0036] In addition, when the above-mentioned thermoplastic material is used for the inner layer 4, various grades of resin materials with both strength and elasticity can be selected according to the use of the laminated resin tube 1. When a polyurethane resin or a polyurethane-based elastomer is used for the inner layer 4, grades of materials with particularly excellent softness and elasticity can be selected. In this case, a laminated resin tube 1 that is softer overall and has excellent bending performance can be obtained.

[0037] Among polyurethane-based elastomers, there are materials that have particularly excellent softness, sufficient strength, and can be produced at a relatively low cost. Therefore, the laminated resin tube 1 with a polyurethane-based elastomer used for the inner layer 4 has remarkable flexibility and bending performance and can be provided at a low cost.

[0038] The thermoplastic material used for the inner layer 4 preferably does not contain a fluororesin. Thereby, the softness of the inner layer 4 can be ensured. Therefore, it is possible to avoid obtaining a laminated resin tube 1 with poor usability, large limitations on the bending radius, and poor flexibility.

[0039] In addition, when the inner layer 4 is a fluororesin layer, since the layers are likely to peel due to the bending of the laminated resin tube 1, the bending performance of the inner layer 4 is poor. When the bending performance of the inner layer 4 is poor, the inner layer 4 is easily buckled (kinked), and thus the above-mentioned tubular structure will become narrow. In this case, accidents where gas or liquid does not flow in the laminated resin tube 1 are likely to occur. When the thermoplastic material used for the inner layer 4 does not contain a fluororesin, such accidents can be prevented.

[0040] The intermediate layer 3 of the laminated resin tube 1 is provided on the outer periphery of the inner layer 4. The intermediate layer 3 contains a polyamide resin. The outer layer 2 of the laminated resin tube 1 is provided on the outer periphery of the intermediate layer 3. The outer layer 2 contains a fluororesin with low adhesiveness as described later. However, since the intermediate layer 3 contains a polyamide resin, it adheres well to the inner layer 4 and the outer layer 2.

[0041] That is, the adhesiveness between the thermoplastic resin or thermoplastic elastomer contained in the inner layer 4 and the fluororesin contained in the outer layer 2 is improved by providing a polyamide resin layer as the intermediate layer 3 between the inner layer 4 and the outer layer 2. Since the layers of the laminated resin tube 1 are integrally bonded and fixed without peeling, it is possible to prevent defects such as the intrusion of the transported fluid between the layers.

[0042] The fluororesin contained in the outer layer 2 generally has high chemical resistance and excellent sliding properties. Therefore, the outer layer 2 has excellent chemical resistance and good sliding properties in the external environment where the laminated resin tube 1 is used. Dirt and the like are difficult to adhere to the outer layer 2.

[0043] Various types of fluororesins can be used for the outer layer 2. The fluororesin used for the outer layer 2 is, for example, tetrafluoroethylene-ethylene copolymer resin (ETFE), or tetrafluoroethylene-perfluoroalkyl vinyl ether-trifluorochloroethylene copolymer resin. That is, the outer layer 2 contains, for example, any one of polyurethane resin, polyvinyl chloride resin, polyurethane-based elastomer, polyamide-based elastomer, olefin-based elastomer, and polystyrene-based elastomer.

[0044] The fluororesin used for the outer layer 2 is preferably ETFE. ETFE has good mechanical properties among fluororesins, characteristics such as being relatively easy to form, and sufficiently high chemical resistance. Regarding chemical resistance, ETFE has sufficient performance for various types of solvents, acids, alkalis, and other fluids. ETFE also has high chemical resistance even compared to the thermoplastic resin or thermoplastic elastomer used for the inner layer 4.

[0045] The laminated resin tube 1 is a tubular structure. Therefore, due to the bending or twisting of the laminated resin tube 1, strong tensile stress is generated at the outermost peripheral portion of the laminated resin tube 1. In addition, various fluids can be transported in the laminated resin tube 1 for a long period of time. Even in such a case, the outer layer 2 using ETFE is difficult to deteriorate. Therefore, in the use of the laminated resin tube 1, the possibility of an accident causing the breakage of the laminated resin tube 1 due to the deterioration of the outer layer 2 is suppressed to a low level.

[0046] In addition, as described above, tetrafluoroethylene-perfluoroalkyl vinyl ether-trifluorochloroethylene copolymer resin can also be used for the outer layer 2. Tetrafluoroethylene-perfluoroalkyl vinyl ether-trifluorochloroethylene copolymer resin also has sufficient performance similar to that of ETFE.

[0047] The purpose of using the laminated resin tube 1 is to convey fluid. Usually, the types and states of the fluids in contact with the inner layer 4 are managed in advance. The outer layer 2 exposed to the external environment may face pressures such as high heat during an accident or momentary electric sparks. The outer layer 2 has the high heat resistance and flame retardancy peculiar to fluororesin.

[0048] The melting point of fluororesin is relatively high. Fluororesin meets the flame retardancy level V-0 of the specification UL94 "Combustion Test Specification for Plastic Materials of Devices and Equipment" determined by UL Solutions, a certification body in the United States. Therefore, even when facing the above-mentioned pressures, the outer layer 2 can maintain high heat resistance and flame retardancy.

[0049] In conventional laminated resin tubes, hard fluororesin, which is poor in terms of elasticity, is used for the inner layer, and soft thermoplastic resin or thermoplastic elastomer, which is excellent in terms of elasticity, is used for the outer layer. Such a conventional laminated resin tube can be analogized to a state where a soft rubber is wound around a hard tube. When the inner hard tube is bent, it will buckle regardless of the surrounding wound rubber. That is, when a conventional laminated resin tube is bent, buckling is likely to occur.

[0050] The laminated resin tube 1 according to this embodiment can be analogized to a state where a soft rubber tube as the inner layer 4 is surrounded by a hard sheath as the outer layer 2. When the inner soft rubber tube is bent, it is not likely to buckle easily. That is, when the laminated resin tube 1 according to this embodiment is bent, buckling is difficult to occur.

[0051] Therefore, compared with conventional laminated resin tubes, in the laminated resin tube 1 according to this embodiment, delamination between the inner layer 4 and the outer layer 2 is less likely to occur. In the laminated resin tube 1, as described above, a polyamide resin layer as the intermediate layer 3 is provided between the inner layer 4 and the outer layer 2. Since the intermediate layer 3 contains polyamide resin, the adhesiveness between the inner layer 4 and the outer layer 2 is improved. That is, the adhesiveness between the layers of the laminated resin tube 1 is improved.

[0052] Therefore, during the normal use of the laminated resin tube 1, the possibility of interlayer delamination occurring is low. It is possible to prevent defects such as the intrusion of the conveyed fluid between the layers due to interlayer delamination.

[0053] In the present embodiment, the thickness Ti of the inner layer 4 among the inner layer 4, the intermediate layer 3, and the outer layer 2 is the thickest. That is, the thickness Tm of the intermediate layer 3 and the thickness To of the outer layer 2 are both thinner than the thickness Ti of the inner layer 4. When the outer layer 2 is thin enough, the outer layer 2 becomes easily and softly bendable. Thereby, the influence of the fluororesin contained in the outer layer 2 on the flexibility and bending performance of the laminated resin tube 1 as a whole can be suppressed. The thickness To of the outer layer 2 is preferably, for example, 1 / 3 or less of the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2. In this case, a laminated resin tube 1 with excellent flexibility and excellent bending performance, and better usability can be obtained.

[0054] Laminated resin tubes 1 with various inner diameters and outer diameters can be manufactured. Generally, a requirer selects and uses a laminated resin tube 1 with a suitable size according to the purpose. For example, Figure 1 The inner diameter Di of the laminated resin tube 1 shown is 6 mm, and the outer diameter Do is 8 mm. That is, the inner diameter of the inner layer 4 of the laminated resin tube 1 is 6 mm, and the thickness (wall thickness) T of the wall of the laminated resin tube 1 is 1 mm.

[0055] The thickness T of the wall of the laminated resin tube 1 is the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2. In Figure 1 In the example shown, the thickness Ti of the inner layer 4 is 0.7 mm, the thickness Tm of the intermediate layer 3 is 0.1 mm, and the thickness To of the outer layer 2 is 0.2 mm. Therefore, 0.2 mm as the thickness To of the outer layer 2 is 1 / 3 or less of 1 mm, which is the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2.

[0056] If the thickness Tm of the intermediate layer 3 becomes large, the laminated resin tube 1 becomes hard, and thus it becomes difficult to bend the laminated resin tube 1. In addition, since the amount of moisture absorption increases, the dimensions of the laminated resin tube 1 change. That is, the performance of the laminated resin tube 1 as a whole deteriorates. Moreover, the polyamide resin contained in the intermediate layer 3 is relatively expensive, so the manufacturing cost of the intermediate layer 3 increases.

[0057] Therefore, it is preferable to make the thickness Tm of the intermediate layer 3 thin enough. For example, if the thickness Tm of the intermediate layer 3 is 0.2 mm or less, problems in the actual use of the laminated resin tube 1 can be suppressed. In the present embodiment, as described above, the thickness Tm of the intermediate layer 3 is 0.1 mm which is 0.2 mm or less. Thereby, the flexibility of the laminated resin tube 1 is maintained, and the dimensional change due to moisture absorption of the laminated resin tube 1 is suppressed. In addition, since the amount of polyamide resin is small, the raw material cost is suppressed.

[0058] The ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 is an important parameter in the design of the laminated resin tube 1. The ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 is expressed by the formula "rd = Do / Di".

[0059] The thickness T of the wall of the laminated resin tube 1 is obtained by multiplying the difference between the outer diameter Do and the inner diameter Di of the laminated resin tube 1 by 1 / 2. If the ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 becomes larger, the thickness T of the wall of the laminated resin tube 1 also becomes larger. Therefore, the laminated resin tube 1 is strong and has excellent shape stability. That is, the laminated resin tube 1 has excellent bending performance. However, the laminated resin tube 1 becomes hard and difficult to bend. That is, the laminated resin tube 1 has poor flexibility.

[0060] The smaller the ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 and the closer it is to 1, the smaller the thickness T of the wall of the laminated resin tube 1. Therefore, the laminated resin tube 1 becomes soft and easy to bend. That is, the laminated resin tube 1 has excellent flexibility. However, the laminated resin tube 1 is easily buckled and has poor shape stability. That is, the laminated resin tube 1 has poor bending performance. In addition, the strength of the laminated resin tube 1 will also decrease.

[0061] Therefore, the ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 is preferably a value within a specified range K in which the flexibility and bending performance of the laminated resin tube 1 become appropriate. The specified range K is, for example, a range from 1.3 to 1.6. That is, the ratio rd is preferably a value within a specified range K of 1.3 or more and 1.6 or less. In the present embodiment, the ratio rd of the outer diameter Do to the inner diameter Di of the laminated resin tube 1 is 8 / 6 = 1.33..., which is a value within a specified range K of 1.3 or more and 1.6 or less. Thus, the laminated resin tube 1 can have appropriate flexibility and bending performance.

[0062] As described above, the inner layer 4 has appropriate strength and elasticity. Based on the laminated resin tube 1 exhibiting good flexibility and bending performance, the contribution of the inner layer 4 is great. The ratio ri of the inner diameter of the inner layer 4 to the thickness T of the wall of the laminated resin tube 1 is preferably a value within a specified range L. The inner diameter of the inner layer 4 is equal to the inner diameter Di of the laminated resin tube 1. The thickness T of the wall of the laminated resin tube 1 is equal to the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2. Therefore, the ratio ri is expressed by the formula "ri = Di / (Ti + Tm + To)". The specified range L is, for example, a range of 3.33 or more and 6.0 or less. That is, the ratio ri is preferably a value within a specified range L of 3.33 or more and 6.0 or less. Thus, the laminated resin tube 1 can exhibit good flexibility and bending performance.

[0063] In the present embodiment, the ratio ri of the inner diameter of the inner layer 4, which is equal to the inner diameter Di of the laminated resin tube 1, to the thickness T of the tube wall of the laminated resin tube 1, which is equal to the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2, is 6 / (0.7 + 0.1 + 0.2) = 6, which is a value within the specified range L of 3.33 or more and 6.0 or less.

[0064] As described above, the outer layer 2 contains a fluororesin. Most fluororesins including ETFE have low transparency. The thicker the outer layer 2 is, the lower the transparency of the laminated resin tube 1 becomes. If the transparency of the laminated resin tube 1 decreases, it becomes difficult to visually confirm the fluid transported inside the laminated resin tube 1. In this case, the usability of the laminated resin tube 1 deteriorates. In order to ensure the transparency of the laminated resin tube 1, the thickness To of the outer layer 2 is preferably 1 / 2 or less of the sum of the thickness Ti of the inner layer 4 and the thickness Tm of the intermediate layer 3 and 0.5 mm or less.

[0065] Thereby, the outer layer 2 can be made thinner. Since the transparency of the laminated resin tube 1 is ensured, the fluid transported inside the laminated resin tube 1 can be visually confirmed well. Therefore, the usability of the laminated resin tube 1 is good. In addition, even with a thinner outer layer 2, the chemical resistance, heat resistance, and flame retardancy possessed by the fluororesin contained in the outer layer 2 can be obtained.

[0066] In the present embodiment, the thickness To of the outer layer 2 is 0.2 mm, and thus it is 0.5 mm or less. 1 / 2 of the sum of 0.7 mm as the thickness Ti of the inner layer 4 and 0.1 mm as the thickness Tm of the intermediate layer 3 is 0.4 mm. Therefore, the thickness To of the outer layer 2 is 1 / 2 or less of the sum of the thickness Ti of the inner layer 4 and the thickness Tm of the intermediate layer 3.

[0067] As described above, the inner layer 4 contains a thermoplastic resin or a thermoplastic elastomer. Thermoplastic resins or thermoplastic elastomers are transparent but are easily colored by various colors. However, since it is convenient and practical to be able to visually confirm well from the outside of the laminated resin tube 1 the fluid transported inside the laminated resin tube 1, there are necessary cases. In this case, even when the inner layer 4 is colored, it is preferably transparent. That is, the inner layer 4 is colorless transparent or colored transparent.

[0068] Including being colorless, the color of the inner layer 4 can be regarded as the color of the entire laminated resin tube 1. By using a plurality of laminated resin tubes 1 including a colorless laminated resin tube 1 and laminated resin tubes 1 of various colors, the plurality of laminated resin tubes 1 can be easily distinguished visually.

[0069] In various applications such as industrial and medical uses, there are cases where multiple laminated resin tubes 1 are used simultaneously. For example, different types of fluids are respectively transported by multiple laminated resin tubes 1 inside a device or the like. In this case, the multiple laminated resin tubes 1 can be visually distinguished based on the colors of the respective laminated resin tubes 1. Therefore, it is possible to detect or prevent accidents of misconnecting one or more laminated resin tubes 1 to their connection targets.

[0070] By coloring the entire inner layer 4, the multiple laminated resin tubes 1 can be visually distinguished even when they are partially bundled. For example, the multiple laminated resin tubes 1 can be distinguished based on the colors of the unbundled parts of the respective laminated resin tubes 1. In addition, the colored inner layer 4 is covered by the intermediate layer 3 and the outer layer 2. Therefore, the color will not disappear due to wear on the outer surface of the laminated resin tube 1. Also, the color will not disappear when removing dirt attached to the outer surface of the laminated resin tube 1.

[0071] As described above, the thermoplastic resin or thermoplastic elastomer used for the inner layer 4 is transparent. It is preferable to select a thermoplastic resin or thermoplastic elastomer with high transparency. In addition, it is more preferable that no surface treatment based on chemical etching or defluorination treatment is applied to the surface of the inner layer 4.

[0072] The ability to visually confirm from the outside of the laminated resin tube 1 the fluid being transported inside the laminated resin tube 1 by the laminated resin tube 1 can greatly contribute to the convenience of the laminated resin tube 1. However, for example, even when the transparency of the laminated resin tube 1 is reduced to a state like that of frosted glass, it is sufficient to be able to determine the presence or absence of the fluid inside the laminated resin tube 1.

[0073] Assume that the ratio of the thickness Ti of the inner layer 4 to the thickness T of the tube wall of the laminated resin tube 1 (the sum of the thickness Ti of the inner layer 4, the thickness Tm of the intermediate layer 3, and the thickness To of the outer layer 2) is high. In this case, the transparency of the resin used for the inner layer 4 greatly affects the overall transparency of the laminated resin tube 1. In other words, it is preferable that the resin used for the inner layer 4 has high transparency.

[0074] Assume that chemical etching is applied to the surface of the inner layer 4 for the purpose of improving the adhesion between the layers of the laminated resin tube 1. In this case, the transparency of the inner layer 4 is reduced, and as a result, the overall transparency of the laminated resin tube 1 is also reduced. In the laminated resin tube 1 according to the present embodiment, the inner layer 4 made of a soft thermoplastic resin or thermoplastic elastomer with excellent elasticity is surrounded like a sheath by the outer layer 2 made of a hard fluororesin. Therefore, as described above, compared with conventional laminated resin tubes, it is difficult for peeling to occur between the inner layer 4 and the outer layer 2 in the laminated resin tube 1 according to the present embodiment. Therefore, the necessity of applying surface treatments such as chemical etching to the surface of the inner layer 4 is low.

[0075] Like the inner layer 4, the intermediate layer 3 also preferably has high transparency. Moreover, it is also preferable that no surface treatment based on chemical etching or defluorination treatment is applied to the surface of the intermediate layer 3.

[0076] In addition, consider the usage mode of the laminated resin tube 1 where it is not necessary to visually confirm the fluid transported inside the laminated resin tube 1. In this usage mode, when the fluid is required to be shielded from light, the inner layer 4 can be colored opaque. In this case, for example, the inner layer 4 is colored opaque black. The thermoplastic resin or thermoplastic elastomer contained in the inner layer 4 can be easily colored into various opaque colors. Thereby, the fluid transported inside the laminated resin tube 1 is not exposed to light. Since the opaque color of the inner layer 4 is maintained even if the surface of the outer layer 2 of the laminated resin tube 1 is worn, the possibility of reduced light shielding property is low.

[0077] Figure 2 It is a schematic diagram for explaining the forming method of the laminated resin tube 1. The inner layer material M4 of the inner layer 4 contains the above-mentioned thermoplastic resin or thermoplastic elastomer. The inner layer extruder P4 heats the inner layer material M4 inside the inner layer extruder P4 to melt it. The intermediate layer material M3 of the intermediate layer 3 contains the above-mentioned polyamide resin. The intermediate layer extruder P3 heats the intermediate layer material M3 inside the intermediate layer extruder P3 to melt it. The outer layer material M2 of the outer layer 2 contains the above-mentioned fluororesin. The outer layer extruder P2 heats the outer layer material M2 inside the outer layer extruder P2 to melt it.

[0078] The inner layer extruder P4 can extrude the inner layer material M4 from the inner layer extruder P4 towards the die D. The intermediate layer extruder P3 can extrude the intermediate layer material M3 from the intermediate layer extruder P3 towards the die D. The outer layer extruder P2 can extrude the outer layer material M2 from the outer layer extruder P2 towards the die D.

[0079] The extrusion of the inner layer material M4 based on the inner layer extruder P4, the extrusion of the intermediate layer material M3 based on the intermediate layer extruder P3, and the extrusion of the outer layer material M2 based on the outer layer extruder P2 are carried out simultaneously. Thereby, in the die D, co-extrusion forming of the inner layer 4, the intermediate layer 3, and the outer layer 2 is performed. The molten resin materials of the respective layers constituting the inner layer 4, the intermediate layer 3, and the outer layer 2 are laminated inside the die D, thereby forming the laminated resin tube 1.

[0080] Next, the inner layer 4, the intermediate layer 3, and the outer layer 2 are supported by the forming die E and cooled in the cooling device C. Thereby, the forming of the laminated resin tube 1 is continuously carried out. Therefore, a seamless and extremely long laminated resin tube 1 can be obtained. In addition, since the productivity of the laminated resin tube 1 can be improved, it can be mass-produced. In other words, the manufacturing cost of the laminated resin tube 1 can be suppressed.

[0081] Figure 3 FIG. is a flowchart exemplifying the processing sequence corresponding to the forming method of the laminated resin tube 1. When this processing sequence starts, in step S1, the inner layer material M4 is heated and melted by the extruder P4 for the inner layer. In step S2, the intermediate layer material M3 is heated and melted by the extruder P3 for the intermediate layer. In step S3, the outer layer material M2 is heated and melted by the extruder P2 for the outer layer.

[0082] In step S4, the inner layer material M4 is extruded into the die D by the extruder P4 for the inner layer. The intermediate layer material M3 is extruded into the die D by the extruder P3 for the intermediate layer. The outer layer material M2 is extruded into the die D by the extruder P2 for the outer layer. The extruder P4 for the inner layer, the extruder P3 for the intermediate layer, and the extruder P2 for the outer layer simultaneously extrude the respective materials into the die D. That is, co-extrusion molding of the inner layer 4, the intermediate layer 3, and the outer layer 2 is performed. When the processing of step S4 is completed, this processing sequence ends.

[0083] As described above, the fluororesin used for the outer layer 2 is preferably ETFE. ETFE has a low melt viscosity. Therefore, ETFE can be easily extrusion-molded at a lower temperature among fluororesins. In addition, ETFE has adhesiveness among fluororesins. Therefore, the outer layer 2 using ETFE can easily obtain an adhesive state with the intermediate layer 3 by co-extrusion molding of the inner layer 4, the intermediate layer 3, and the outer layer 2.

[0084] As described above, the fluororesin used for the outer layer 2 can be a tetrafluoroethylene-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin. As the tetrafluoroethylene-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin, a material with better formability and / or adhesiveness than ETFE can be used. The productivity of the laminated resin tube 1 can be further improved, and the possibility of interlayer peeling can be suppressed to a lower level.

[0085] As described above, the inner layer 4 uses a resin material with thermoplasticity. As the resin material that can manufacture the laminated resin tube 1 by co-extrusion molding, any one of polyurethane elastomers, polyamide elastomers, olefin elastomers, polystyrene elastomers, and polyvinyl chloride resins is preferably selected.

[0086] As the inner layer material M4, the intermediate layer material M3, and the outer layer material M2, for example, polyurethane elastomers, polyamide resins, and ETFE can be used respectively. As the inner layer material M4, for example, a colorless and transparent polyurethane elastomer that is not colored, a transparent polyurethane elastomer colored blue, a slightly transparent polyurethane elastomer colored white, an opaque polyurethane elastomer colored black, etc. can be used.

[0087] The material M4 for the inner layer, the material M3 for the intermediate layer, and the material M2 for the outer layer are simultaneously supplied to the die D and the subsequent forming die E. Thus, the laminated resin tube 1 is manufactured by co-extrusion molding of the inner layer 4, the intermediate layer 3, and the outer layer 2. The material M4 for the inner layer, the material M3 for the intermediate layer, and the material M2 for the outer layer are extruded by the die D in a state of being melted by high temperature and laminated. Therefore, a uniform bonding state is formed between the layers, and the occurrence of delamination between the layers is suppressed.

[0088] The forming die E controls the surface roughness and lubrication of the outer layer 2. The arithmetic mean roughness of the surface of the outer layer 2 is preferably 0.1 μm or less. Thereby, the strong blurring like frosted glass generated on the surface of the fluororesin contained in the outer layer 2 is suppressed. As described above, by making the outer layer 2 containing a fluororesin with low transparency thin, the transparency of the laminated resin tube 1 is ensured. In addition, by further making the arithmetic mean roughness of the surface of the outer layer 2 0.1 μm or less, the transparency of the laminated resin tube 1 can be improved.

[0089] That is, the surface of the laminated resin tube 1 where the outer layer 2 made of ETFE is exposed is uniform and smooth. Therefore, the fluid conveyed in the laminated resin tube 1 can be visually confirmed well from the outside of the laminated resin tube 1.

[0090] More preferably, the arithmetic mean roughness of the surface of the outer layer 2 is 0.1 μm or less, and the maximum height roughness of the surface of the outer layer 2 is 1 μm or less. In this case, fine damages are hardly visible on the surface of the laminated resin tube 1, so the surface of the laminated resin tube 1 has a smooth and uniform appearance. Thereby, the reduction in commercial value due to the appearance of the laminated resin tube 1 can be prevented.

[0091] In addition, when a damage occurs on the surface of the laminated resin tube 1, since there are no fine damages around it, the damage is easily noticeable. Therefore, when using the laminated resin tube 1, it is easy to visually confirm and / or distinguish the damage generated on the surface of the laminated resin tube 1. The judgment such as replacement for the purpose of maintaining the performance of the laminated resin tube 1 can be appropriately made.

[0092] The above-described embodiment can also be modified as follows. In the following modification examples, the description overlapping with the embodiment is omitted.

[0093] (Modification example)

[0094] In the above-described embodiment, the intermediate layer 3 of the laminated resin tube 1 is provided on the outer periphery of the inner layer 4. However, a reinforcing layer having resin reinforcing wires can also be provided between the inner layer 4 and the intermediate layer 3. The reinforcing wires of the reinforcing layer are wound around the inner layer 4. By providing such a reinforcing layer, the laminated resin tube 1 can have high pressure resistance performance.

[0095] Regarding the above-described embodiments and modifications, the following remarks are also disclosed.

[0096] (Remark 1)

[0097] The laminated resin tube 1 of the present invention includes: an inner layer 4 containing a thermoplastic material as a thermoplastic resin or a thermoplastic elastomer; an intermediate layer 3 provided on the outer periphery of the inner layer and containing a polyamide resin; and an outer layer 2 provided on the outer periphery of the intermediate layer and containing a fluororesin. Since the inner layer contains a thermoplastic material, a laminated resin tube with excellent flexibility and high bending performance can be obtained. Since the intermediate layer is provided on the outer periphery of the inner layer, the adhesiveness of the outer layer containing a fluororesin is improved, and the occurrence of defects such as interlayer peeling is suppressed. Since the outer layer contains a fluororesin, excellent chemical resistance and flame retardancy are provided. Therefore, a laminated resin tube with good usability can be obtained. In addition, since interlayer peeling hardly occurs, it is not necessary to apply chemical etching or defluorination treatment to the outer surface of the inner layer and the outer surface of the intermediate layer to improve adhesiveness. Therefore, it is easy to ensure the transparency of the laminated resin tube.

[0098] (Remark 2)

[0099] In the laminated resin tube described in Remark 1, it is also possible that the thickness To of the outer layer is 1 / 3 or less of the sum of the thickness Ti of the inner layer, the thickness Tm of the intermediate layer, and the thickness of the outer layer. According to such a structure, a laminated resin tube with better flexibility and higher bending performance can be obtained.

[0100] (Remark 3)

[0101] In the laminated resin tube described in Remark 1, it is also possible that the fluororesin is tetrafluoroethylene-ethylene copolymer resin (ETFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin. When the fluororesin used for the outer layer is ETFE, extrusion molding of the outer layer can be performed. Through co-extrusion molding of the inner layer, the intermediate layer, and the outer layer, a seamless and extremely long laminated resin tube can be obtained. In addition, the outer layer using ETFE adheres well to the intermediate layer. Therefore, defects such as interlayer peeling are suppressed. Moreover, even when the inner layer deteriorates due to long-term use of the laminated resin tube or the like, deterioration of the outer layer can be suppressed. That is, deterioration of the laminated resin tube as a whole is suppressed. When the fluororesin used for the outer layer is tetrafluoroethylene-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin, defects such as interlayer peeling are further suppressed. In addition, the productivity of the laminated resin tube can be further improved.

[0102] (Remark 4)

[0103] In the laminated resin tube described in Supplementary Note 1, the thermoplastic material may be any one of polyurethane resin, polyvinyl chloride resin, polyurethane-based elastomer, polyamide-based elastomer, olefin-based elastomer, and polystyrene-based elastomer. With such a structure, the thermoplastic material used for the inner layer can have both the strength and elasticity corresponding to the use of the laminated resin tube. As the thermoplastic material used for the inner layer, resin materials of various grades can be selected. Therefore, a laminated resin tube with flexibility and bending performance suitable for various uses can be obtained. When polyurethane resin is used for the inner layer, there are a rich variety of resin materials with excellent softness and elasticity. In addition, the processability of polyurethane resin during the extrusion molding of the inner layer is also excellent. Moreover, by using polyurethane resin, the productivity of the laminated resin tube can be improved, and the inexpensive production of the laminated resin tube can be achieved. That is, mass production of the laminated resin tube can be realized. Polyurethane-based elastomers have an extremely small Young's modulus and a large fracture strain. When a polyurethane-based elastomer is used for the inner layer, the flexibility and bending performance of the laminated resin tube become more remarkable. In this case, the use of the laminated resin tube becomes extremely easy. Therefore, a laminated resin tube that is easy to use can be obtained. The laminated resin tube obtained in this way can be used as long as it is not for applications that require pressure resistance performance, etc.

[0104] (Supplementary Note 5)

[0105] In the laminated resin tube described in any one of Supplementary Notes 1 to 4, the arithmetic mean roughness of the surface of the outer layer may be 0.1 μm or less. With such a structure, a laminated resin tube with excellent chemical resistance and high transparency can be obtained. The fluid transported inside the laminated resin tube obtained in this way can be visually confirmed extremely well from the outside.

[0106] (Supplementary Note 6)

[0107] In the laminated resin tube described in Supplementary Note 5, the inner layer may be colorless transparent or colored transparent. With such a structure, various color changes can be set for the laminated resin tube. Thus, it is easy to distinguish between multiple laminated resin tubes. In addition, the color of the inner layer will not disappear due to the dirt or wear of the outer surface of the laminated resin tube. Therefore, the distinguishability between multiple laminated resin tubes is difficult to reduce.

[0108] (Supplementary Note 7)

[0109] In the laminated resin tube described in Supplementary Note 1, the inner layer, the intermediate layer, and the outer layer may be co-extrusion molded. With such a structure, a seamless and extremely long laminated resin tube can be obtained. In addition, the laminated resin tube can be mass-produced at low cost.

[0110] (Supplementary Note 8)

[0111] The forming method of the present invention is the forming method of the laminated resin tube described in Supplementary Note 1. The inner layer material M4 containing the thermoplastic resin or the thermoplastic elastomer is heated and melted by the inner layer extruder P4; the intermediate layer material M3 containing the polyamide resin is heated and melted by the intermediate layer extruder P3; the outer layer material M2 containing the fluororesin is heated and melted by the outer layer extruder P2. By jointly performing the extrusion of the inner layer material from the inner layer extruder to the mold D by the inner layer extruder, the extrusion of the intermediate layer material from the intermediate layer extruder to the mold by the intermediate layer extruder, and the extrusion of the outer layer material from the outer layer extruder to the mold by the outer layer extruder, co-extrusion molding of the inner layer, the intermediate layer, and the outer layer is performed in the mold. According to such a structure, laminated resin tubes can be mass-produced at low cost.

[0112] The present invention has been described in detail, but the present invention is not limited to the above-described respective embodiments. These embodiments can be variously added, replaced, changed, partially deleted, etc. within the scope of not departing from the gist of the present invention or within the scope of not departing from the gist of the present invention derived from the content described in the claims and its equivalents. In addition, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each action and the order of each process only show an example and are not limited thereto. The same applies to the case where numerical values or mathematical formulas are used in the description of the above-described embodiments.

Claims

1. A laminated resin tube, characterized in that: have: an inner layer containing a thermoplastic material which is a thermoplastic resin or a thermoplastic elastomer; an intermediate layer disposed on the periphery of the inner layer and containing a polyamide resin; and The outer layer is provided on the periphery of the intermediate layer and contains a fluororesin.

2. The laminated resin tube according to claim 1, characterized in that The thickness of the outer layer is 1 / 3 or less of the sum of the thickness of the inner layer, the thickness of the intermediate layer, and the thickness of the outer layer.

3. The laminated resin tube according to claim 1, characterized in that The fluororesin is tetrafluoroethylene-ethylene copolymer resin (ETFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin.

4. The laminated resin tube according to claim 1, characterized in that The thermoplastic material is any one of polyurethane resin, polyvinyl chloride resin, polyurethane elastomer, polyamide elastomer, olefin elastomer and polystyrene elastomer.

5. The laminated resin tube according to any one of claims 1 to 4, characterized in that The arithmetic mean roughness of the surface of the outer layer is 0.1 μm or less.

6. The laminated resin tube according to claim 5, characterized in that The inner layer is colorless and transparent or colored and transparent.

7. The laminated resin tube according to claim 1, characterized in that The inner layer, the middle layer and the outer layer are co-extruded.

8. A method for forming a laminated resin tube, the laminated resin tube being the laminated resin tube according to claim 1, characterized in that: heating and melting the inner layer material of the inner layer containing the thermoplastic resin or the thermoplastic elastomer by an inner layer extruder; heating and melting the intermediate layer material of the intermediate layer containing the polyamide resin by an intermediate layer extruder; heating and melting the outer layer material of the outer layer containing the fluororesin by an outer layer extruder; By jointly extruding the inner layer material from the inner layer extruder to the die, extruding the intermediate layer material from the intermediate layer extruder to the die, and extruding the outer layer material from the outer layer extruder to the die, the inner layer, the intermediate layer and the outer layer are co-extruded in the die.

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