Laminated resin tube

Abstract

To provide an easy-to-use laminated resin tube which has high flexibility and excellent bend performance while having proper chemical resistance, and which enables good visual recognition of an internally-carried fluid.SOLUTION: A laminated resin tube comprises: an inner layer that is made of a polyurethane elastomer; an intermediate layer that is made of a polyamide resin provided around it; and a tetrafluoroethylene resin outer layer that is provided around it. The thickness of the outer layer is set to be one third or less of the sum of the thicknesses of the inner layer, the intermediate layer and the outer layer. Additionally, the arithmetic mean roughness of the outer layer is 0.1 μm or less, and its maximum height roughness is 1 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin tube. More specifically, it relates to a laminated resin tube having at least two resin layers, and at least one of the resin layers is made of a fluororesin.

Background Art

[0002] Conventionally, resin tubes having various characteristics have been put into practical use. Resin tubes that can be mass-produced in a seamless, uniform, and long form are convenient for transporting gases and liquids, and are widely used in large quantities in almost all industries, including the food and medical fields, as well as for transporting fuels, paints, and piping components for introducing high-pressure air.

[0003] Since they are industrially important components, many types of resin tubes with various ingenuities have been put into practical use. For example, when high pressure resistance is required, a resin tube made of tough polyamide resin is selected, and when transporting organic solvents, a resin tube made of fluororesin with excellent chemical resistance is selected. Furthermore, an inner layer of an appropriate material according to the type of gas or liquid to be transported, an outer layer made of a material that is less affected by the external environment or resistant to friction, and a reinforcing layer provided with reinforcing threads between the inner layer and the outer layer are provided to provide a laminated resin tube with high pressure resistance, which has also been put into practical use. Note that a flexible tubular body used for transporting gases and liquids is sometimes called a hose, but it is said that there is no clear difference between a tube and a hose, and in this application, the term "tube" is used as a concept including a hose. In addition, not only gases and liquids alone, but also mixtures of these, and solids such as powders and granules together with gases and liquids are transported by resin tubes, but these are used by users of resin tubes by appropriately devising according to the purpose, and in this application, those transported by resin tubes such as gases, liquids, powders, and granules are collectively referred to as fluids.

[0004] As described above, although resin tubes having various features have already been put into practical use, there is still no resin tube that is easy to handle and has chemical resistance and is fully satisfactory. In terms of chemical resistance, a resin tube made of a fluororesin provides high performance. In particular, a resin tube made of ethylene tetrafluoride-ethylene copolymer resin (hereinafter referred to as "ETFE"), which can be processed at a relatively low temperature, is widely used. However, many fluororesins including ETFE have difficulty in flexibility. When processed into a resin tube, it lacks flexibility, that is, it gives a hard impression when held in the hand, lacks flexibility, is difficult to bend, and is not easy to use. Also, although not unrelated to low flexibility, resin tubes made of fluororesin generally have inferior bending performance. The bending performance of a resin tube is a characteristic that may also be expressed as kink resistance, which means how difficult it is for the resin tube to buckle and bend when trying to bend it, resulting in a state where the tubular structure narrows and gas / liquid cannot pass through. A resin tube with inferior bending performance or kink resistance has strict restrictions on the bending radius and requires careful handling during use. In the present application, the terms "flexibility" and "bending performance (kink resistance)" are used as different concepts. For example, there are cases where a tube that is hard and lacks flexibility and is difficult to bend easily actually has excellent bending performance and can be bent at a small bending radius without kinking when carefully bent with force.

[0005] In a single-layer resin tube made of ETFE, there are obvious problems as described above. Therefore, various improvements have been made conventionally. For example, in the invention disclosed in Japanese Patent Application Laid-Open No. 2009-127631, a fuel tube is formed by laminating an inner layer containing ETFE and an outer layer made of a polyamide resin. Further, in the invention disclosed in Japanese Patent Application Laid-Open No. 6-234190, a hose for an automobile fuel pipe is formed by laminating an inner layer formed of a fluororesin, an intermediate layer formed of a synthetic resin other than the fluororesin, and an outer layer using a rubber elastic material. These inventions aim to reduce the difficulty of bending by making the ETFE layer lacking in flexibility thinner, and to ensure strength and the like by an outer layer made of another resin material. They can improve the low flexibility and low bending performance, which are problems of a single-layer resin tube made of ETFE, to a certain extent.

[0006] However, fluororesins containing ETFE have low adhesiveness to other resins and extremely little friction due to their low surface energy. If it peels off from other layers, the inner layer made of fluororesin has no substantial difference from a single-layer fluororesin tube. Therefore, there is a risk of kinking in a laminated resin tube simply formed by laminating other resin layers on the fluororesin layer. In the above-mentioned inventions, an intermediate layer made of a resin capable of ensuring a certain adhesiveness to the fluororesin is provided, or the resin material is modified to improve the adhesiveness (for example, by chemical etching, etc.) to reduce such problems. Although there is a difference in degree, the tendency that the inner layer tube made of fluororesin is likely to kink and the bending radius is severely restricted remains unchanged. In addition, there are concerns about an increase in the manufacturing cost of the resin tube and a decrease in long-term stability due to the use of special materials or surface treatments.

[0007] Incidentally, Japanese Patent Application Laid-Open No. 2012-92901 discloses a tube characterized by comprising an inner layer made of a thermoplastic resin such as nylon (registered trademark), a reinforcing layer made of a braid formed of metal wires on the outer periphery thereof, and an outer layer coating made of a fluororesin covering these. The detailed structure and effects thereof are described in paragraphs

[0021] and below of the specification of the said publication. In this invention, the bending performance, pressure resistance performance, and slipperiness are ensured for each of the inner layer, the reinforcing layer, and the outer layer coating. Incidentally, the slipperiness means that the friction on the outer surface of the tube is low, there is no catching with other tubes or the like, and it is easy to handle. Further, in this invention, since the outermost layer is made of a fluororesin, it has excellent slipperiness and excellent chemical resistance on the outer surface of the tube.

[0008] However, since it has a reinforcing layer made of a braid formed of metal wires to obtain high pressure resistance performance, it is heavy. Further, since the metal wires are exposed on the cross section at the time of cutting, care is required for the use and usage method. Further, in order to achieve good adhesion between the fluororesin constituting the outer layer coating and the reinforcing layer or the like, it is necessary to select an adhesive fluororesin or perform a defluorination treatment such as chemical etching, and it was not satisfactory from the viewpoints of raw material and processing costs and productivity.

[0009] Furthermore, generally, fluororesins are inferior in transparency except for some exceptions, and it is difficult to clearly visually recognize the inside of the laminated resin tube even for the invention shown in the prior art document. In particular, when an inner layer made of a fluororesin is provided, if the adhesiveness with the resin constituting the outer layer is not extremely high, delamination or the like will occur and the bending performance cannot be obtained. In order to enhance the adhesiveness, various methods are known such as performing chemical etching of the adhesive surface or using an adhesive resin having many functional groups with a high amine value, but these also impair the transparency of the adhesive surface and impair the visibility inside the tube. Whether the presence or absence of liquid inside the tube can be visually confirmed has a great influence on the usability during actual use, and it is not unusual that the presence or absence of transparency is a major concern.

Prior Art Document

Patent Document

[0010] Patent Document 1 Japanese Patent Application Laid-Open No. 2009-127631 Patent Document 2 Japanese Patent Application Laid-Open No. 6-234190 Patent Document 3 Japanese Patent Application Laid-Open No. 2012-92901 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The problem to be solved by the present invention is, as described above, to provide a laminated resin tube that is flexible, has excellent bending performance, has good chemical resistance, and is user-friendly in that the fluid conveyed inside can be clearly visible. MEANS FOR SOLVING THE PROBLEMS

[0012] (1) In order to solve the above problems, in the present invention, an inner layer made of a thermoplastic resin or a thermoplastic elastomer, an intermediate layer made of a polyamide resin provided on the outer periphery of the inner layer, and an outer layer made of a fluororesin provided on the outer periphery of the intermediate layer are provided, and it is a laminated resin tube.

[0013] The inner layer of the laminated resin tube according to the present invention, that is, the innermost circular tubular layer in contact with the fluid to be transported, is composed of a thermoplastic resin or a thermoplastic elastomer. Specific resin materials of the thermoplastic resin or the flexible elastomer can be appropriately selected according to the use and necessary functions. However, if it is a thermoplastic resin, it is preferably a polyurethane resin or a polyvinyl chloride resin. Further, as the thermoplastic elastomer, it is preferably any one of a polyurethane-based elastomer, a polyamide-based elastomer, an olefin-based elastomer, and a polystyrene-based elastomer. By configuring with a material having appropriate strength and elasticity, a tube excellent in flexibility and bending performance (kink resistance) can be obtained. Since many grades are available for these materials, it is possible to select one having both strength and elasticity according to the use.

[0014] Incidentally, the thermoplastic resin or the flexible elastomer constituting the inner layer of the laminated resin tube according to the present invention does not contain a fluororesin. If the inner layer is composed of a fluororesin, the tube will lack flexibility as a tube, have strict restrictions on the bending radius, be inferior in flexibility, and be inconvenient to use. In addition, it is inferior in bending performance and is likely to cause an accident in which it easily buckles (kinks) and the tubular structure narrows and gas / liquid cannot pass through.

[0015] The intermediate layer of the laminated resin tube according to the present invention is composed of a polyamide resin. As will be described later, in the present invention, since a fluororesin layer is provided as the outer layer, a situation where the inner layer, which is a fluororesin layer, buckles due to bending and the layers are easily peeled off and the bending performance is inferior as in the case of a laminated resin tube with a fluororesin inner layer does not occur. However, it goes without saying that it is preferable that each layer of the laminated resin tube is firmly fixed integrally without peeling. Therefore, in order to favorably adhere the inner layer made of a thermoplastic resin or a thermoplastic elastomer and the outer layer made of a fluororesin, an intermediate layer made of a polyamide resin is provided. Incidentally, improving the adhesiveness by providing a polyamide resin layer between a fluororesin and other resins has been conventionally performed.

[0016] The outer layer of the laminated resin tube according to the present invention is made of a fluororesin. Fluororesins generally have high chemical resistance and excellent lubricity, and various types of fluororesins can be used in the present invention. Preferably, ETFE can be used. This is because among fluororesins, they have excellent mechanical properties, are relatively easy to mold, and have sufficiently high chemical resistance.

[0017] Now, in the present invention, since the outer layer is made of a fluororesin, it is obvious that it has characteristics such as excellent chemical resistance to the outside, good lubricity, and being difficult to adhere to dirt. Also, it is a preferable characteristic that the outer layer has the high heat resistance and flame retardancy peculiar to fluororesins. Since the purpose of the laminated resin tube is originally to transport a fluid, it is always the case that the type and state of the fluid in contact with the inner layer are managed. On the other hand, for the outer layer exposed to the external environment, it cannot be denied that it may be exposed to stresses such as high heat during an accident or momentary electric sparks. However, since the outer layer is made of a fluororesin with a high melting point and satisfying V-0 flame retardancy (according to UL94 "Test Standard for Combustion of Plastic Materials for Equipment and Appliances"), it can be expected that the function can be maintained even when exposed to such stresses.

[0018] In addition, since the inner layer is made of a thermally flexible elastomer having appropriate elasticity, it has good flexibility, is supple, and becomes a user-friendly laminated resin tube with excellent bending performance. To supplement the explanation, there are many conventional examples of resin laminated tubes in which the inner layer is made of a hard fluororesin with poor elasticity and the outer layer is made of a supple thermoplastic resin or thermoplastic elastomer with excellent elasticity. Such tubes are like those with soft rubber wrapped around a hard pipe, and when bent, the hard pipe inside buckles regardless of the surrounding rubber. On the other hand, in the configuration of the present invention, it is like a soft rubber tube wrapped in a hard sheath, and the rubber tube inside does not easily buckle when bent. For such reasons, in the present invention, delamination between the inner layer and the outer layer is less likely to be a problem compared to the resin laminated tubes with a hard fluororesin inner layer having poor elasticity, which have many conventional examples. However, in the present invention, an intermediate layer made of polyamide resin is provided in this part to further enhance the adhesiveness, so there is almost no concern about delamination occurring in normal use.

[0019] Also, as described above, the inner layer of the laminated resin tube according to the present invention is composed of a thermoplastic resin or a thermoplastic elastomer, and it is preferable to select those with high transparency. Further, in this case, it is more preferable not to perform surface treatment such as chemical etching or defluorination treatment on its surface (that is, the outer surface of the inner layer tube). The normal purpose of the laminated resin tube is to transport fluids, and the fact that the fluid during transportation can be visually confirmed from the outside of the laminated resin tube greatly contributes to the convenience during actual use. Needless to say, if the laminated resin tube is completely transparent, the visibility of the fluid during transportation will be maximized. However, for example, even if the laminated resin tube is in a state like frosted glass visually and the presence or absence of the fluid during transportation can be discriminated, its value is still high. In the present invention, the ratio of the thickness of the inner layer to the total thickness of the tube wall (that is, the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer) tends to be high, and the transparency of the inner layer resin has a great influence on the transparency of the entire laminated resin tube. Therefore, it is preferable that this constituent resin has high transparency. Also, for the purpose of enhancing the adhesiveness between the layers of the laminated resin tube, chemical etching of the outer surface of the inner layer tube is widely performed, but this is not preferable because it greatly impairs the transparency of the laminated resin tube. As already explained, the present invention has a structure in which an inner layer made of a flexible thermoplastic resin or thermoplastic elastomer with excellent elasticity is wrapped like a sheath with an outer layer made of a hard fluororesin, making it difficult for layer peeling to occur. Therefore, surface treatment of the outer surface of the inner layer tube that impairs transparency is not necessary.

[0020] Furthermore, regarding the intermediate layer of the laminated resin tube according to the present invention, it is preferable to select those with high transparency in the same manner as in the case of the inner layer, and it is also preferable not to perform surface treatment such as chemical etching or defluorination treatment on its surface (that is, the outer surface of the intermediate layer tube). The reason is the same as in the case of the inner layer.

[0021] (2) To solve the above problems, in the present invention, the thickness of the outer layer is set to be 1 / 3 or less of the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer It is the laminated resin tube described in (1), characterized in that.

[0022] Regarding the laminated resin tube provided with an inner layer made of a thermoplastic resin or a thermoplastic elastomer that is rich in elasticity and has high flexibility, if the outer layer made of a fluororesin is thick, the overall flexibility will be lost and the bending performance will also be inferior. On the other hand, if the outer layer made of a fluororesin with inferior elasticity is sufficiently thin, it will be flexible and easy to bend, and the influence on the overall flexibility and bending performance will be small. The inventor of the present application has conducted intensive research and found that if the thickness of the outer layer made of a fluororesin is 1 / 3 or less of the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer, that is, the wall thickness of the laminated resin tube, a laminated resin tube with excellent flexibility, excellent bending performance, and good usability can be obtained. Therefore, the laminated resin tube according to the present invention is characterized in that the thickness of the outer layer is 1 / 3 or less of the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer.

[0023] (2.2) In order to solve the above problems, in the present invention, The thickness of the intermediate layer is set to 0.2 mm or less. It is the laminated resin tube described in (2), characterized in that.

[0024] The laminated resin tube according to the present invention has a flexible inner layer with excellent elasticity, which is wrapped like a sheath by an outer layer that is inferior in elasticity but hard and has excellent properties such as chemical resistance, heat resistance, and slipperiness, so as to have the advantages of both the inner layer and the outer layer. As already described, the function of the intermediate layer is to enhance the adhesiveness between the inner layer and the outer layer, and to further enhance the value of the present invention by preventing the occurrence of failures such as delamination. However, if the thickness of the intermediate layer is too thick, the properties of the intermediate layer may appear in an undesirable form as the performance of the entire laminated resin tube. For example, it becomes hard to bend, and there are large moisture absorption and dimensional changes. From another perspective, the polyamide resin constituting the intermediate layer is relatively expensive, which is also a problem. According to the research of the inventors of the present application, such problems can be avoided by making the thickness of the intermediate layer sufficiently thin. In the configuration of the present invention, it has been found that no practical problems occur by setting the thickness to 0.2 mm or less. Therefore, the thickness of the intermediate layer is preferably 0.2 mm or less.

[0025] (2.3) In order to solve the above problems, in the present invention, The ratio of the outer diameter to the inner diameter of the laminated resin tube is 1.3 to 1.6 The laminated resin tube according to (2), which is characterized by this.

[0026] The ratio (Do / Di) of the outer diameter Do to the inner diameter Di of the laminated resin tube is an important parameter in the design of the laminated resin tube. Since half of the difference between the outer diameter Do and the inner diameter Di corresponds to the wall thickness of the laminated resin tube, a large ratio of the outer diameter to the inner diameter means that the laminated resin tube is thick with respect to the inner diameter, and conversely, a small ratio of the outer diameter to the inner diameter close to 1 indicates that the laminated resin tube is thin. Naturally, a thick laminated resin tube with a large ratio of the outer diameter to the inner diameter can be expected to be strong and have excellent shape stability, but it tends to become hard and difficult to bend. On the other hand, a thin laminated resin tube with a small ratio of the outer diameter to the inner diameter is soft and easy to bend, but it is inferior in shape stability, so it is prone to buckling (inferior in kink resistance) and tends to be inferior in strength. Since the present invention aims to realize a laminated resin tube that is highly flexible, has excellent bending performance, and is easy to use, an appropriate range of the ratio of the outer diameter to the inner diameter must be selected to make the laminated resin tube have the above excellent performance. According to the research of the inventor of the present invention, in the case of the laminated resin tube according to the present invention, it has been found that a desired performance can be obtained by setting the ratio (Do / Di) of the outer diameter Do to the inner diameter Di to 1.3 to 1.6. Therefore, it is preferable to use such a laminated resin tube.

[0027] (2.4) In order to solve the above problems, in the present invention, the ratio of the inner diameter of the laminated resin tube to the thickness of the inner layer is set to 3.33 to 6.0 and the laminated resin tube according to (2) is characterized by this.

[0028] As described above, the inner diameter of the laminated resin tube and the wall thickness of the laminated resin tube (the sum of the inner diameter thickness, the intermediate layer thickness, and the outer layer thickness) are important parameters in the design of the laminated resin tube. However, in the present invention, the contribution of the inner layer made of a material having appropriate strength and elasticity is significant for the manifestation of its good flexibility and bending performance. Therefore, not only the wall thickness of the entire laminated resin tube but also a preferable relationship exists between the thickness of the inner layer and the inner diameter of the laminated resin tube in order to obtain excellent performance. According to the research of the inventor of the present invention, in the case of the laminated resin tube according to the present invention, it has been found that desired performance can be obtained by setting the ratio of the inner diameter to the intermediate layer thickness to be from 3.33 to 6.0. Therefore, it is preferable to use such a laminated resin tube.

[0029] (3) In order to solve the above problems, in the present invention, the fluororesin is ethylene tetrafluoride-ethylene copolymer resin or ethylene tetrafluoride-perfluoroalkyl vinyl ether-chlorotrifluoroethylene copolymer resin which is the laminated resin tube according to (2).

[0030] The fluororesin constituting the outer layer of the laminated resin tube according to the present invention is preferably tetrafluoroethylene-ethylene copolymer resin (ETFE). Although ETFE is somewhat inferior in chemical resistance and the like compared to tetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), etc., it still has sufficient performance against most solvents, acids, alkalis and other fluids. Since a thermoplastic resin or a thermoplastic elastomer, which is inferior in chemical resistance to ETFE, is used for the inner layer of the laminated resin tube according to the present invention, it is obvious that ETFE has sufficient performance for the requirements. However, the outer layer made of ETFE brings benefits not limited to the chemical resistance of the outer surface. Tubular structures such as tubes often generate strong tensile stress at the outermost peripheral part due to bending or torsion, and destruction often starts from here and progresses. However, since the outer layer is made of ETFE, even if the inner layer deteriorates somewhat during the long-term conveyance of various fluids, the presence of the non-deteriorated outer layer prevents the start of destruction as a laminated resin tube, and the occurrence of accidents during the use period is suppressed. Also, the fact that the melt viscosity is low and extrusion molding is possible is a feature suitable for the present invention. By the way, laminated resin tubes are often required to be seamless and extremely long, and it is preferable that they can be manufactured by extrusion molding. ETFE can be molded at a relatively low temperature among fluororesins, and extrusion molding can be performed relatively easily, which is also a preferable choice in this regard.

[0031] In addition, while having sufficiently high chemical resistance, ETFE has relatively good adhesiveness among fluororesins, and it is also preferable in that it is easy to obtain an adhesive state with other layers when extrusion molding is performed. In addition, as already mentioned in (1), the fact that high heat resistance and flame retardancy can be obtained is also an advantage.

[0032] Furthermore, the fluororesin constituting the outer layer of the laminated resin tube according to the present invention is preferably a tetrafluoroethylene - perfluoroalkyl vinyl ether - chlorotrifluoroethylene copolymer resin. The tetrafluoroethylene - perfluoroalkyl vinyl ether - chlorotrifluoroethylene copolymer resin has sufficient performance for most applications, similar to ETFE. In addition, grades with better moldability and adhesiveness than ETFE are available, which can make the characteristics of the laminated resin tube according to the present invention more prominent and at the same time further improve productivity.

[0033] (4) To solve the above problems, in the present invention, the thermoplastic resin or thermoplastic elastomer is any one of polyurethane resin, polyvinyl chloride, resin polyurethane - based elastomer, polyamide - based elastomer, olefin - based elastomer, and polystyrene - based elastomer and is characterized as the laminated resin tube according to (3).

[0034] As already described, the inner layer of the resin - laminated tube is a part that greatly affects the flexibility and bending resistance of the tube as a tube. There are a variety of grade options as resin materials having both strength and elasticity according to the application, and it is preferable to select any one of polyurethane - based elastomers, polyamide - based elastomers, olefin - based elastomers, polystyrene - based elastomers, and polyvinyl chloride that can manufacture the resin - laminated tube by extrusion molding.

[0035] More preferably, a polyurethane resin or a polyurethane-based elastomer may be used as the thermoplastic resin or the thermoplastic elastomer. This is because a material of a grade that is particularly excellent in flexibility and elasticity can be used, and a resin laminated tube that is more flexible and has excellent bending performance as a whole tube can be realized. In particular, among polyurethane-based elastomers, those that are particularly excellent in flexibility, have sufficient strength, and are relatively low in cost are available, so they are optimal as the inner layer material of the laminated resin tube according to the present invention. This is because a laminated resin tube can be provided in which characteristics such as flexibility and bending performance become more prominent while suppressing the cost.

[0036] (5) To solve the above problems, in the present invention, the outer layer has an arithmetic mean roughness of the surface of 0.1 μm or less and is the laminated resin tube according to any one of (1) to (4).

[0037] The laminated resin tube according to the present invention has an inner layer made of a thermoplastic resin or a thermoplastic elastomer and an intermediate layer made of a polyamide resin. Many of these resin materials have high transparency. However, except for some exceptions, fluororesins are often inferior in transparency. In particular, when the outer layer is made of a fluororesin, a strong cloudiness like ground glass is derived on the resin surface, and the transparency is increasingly impaired. For this reason, regardless of whether it is a single-layer resin tube or a laminated resin tube, it has been difficult to visually recognize well from the outside the fluid conveyed inside the tube when the outer layer is made of a fluororesin.

[0038] However, according to the research of the inventor of the present application, by setting the arithmetic mean roughness of the surface of the outer layer to 0.1 μm or less, the resin surface's frosted glass-like cloudiness is greatly improved. In addition, in the laminated resin tube according to the present invention, since the outer layer thickness can be set thin, the influence of the low transparency of the fluororesin itself is also reduced, and a laminated resin tube in which the fluid conveyed inside the tube can be extremely well visually recognized from the outside is realized. In addition to the requirements that the arithmetic mean roughness of the surface of the outer layer should satisfy, it is more preferable that the maximum height roughness is 1 μm or less. When the maximum height roughness is large, although the transparency of the laminated resin tube is ensured, it may look like there are fine scratches, and even if it does not affect the essential performance of the laminated resin tube, there is a risk that the commerciality will decrease. Also, even if it does not affect the essential performance, the appearance of fine scratches makes it difficult to notice the scratches generated on the surface during use and makes it difficult to judge replacement or the like for maintaining performance. In this sense too, it is preferable that the maximum height roughness is 1 μm or less.

[0039] (5.2) In order to solve the above problems, in the present invention, the outer layer has a thickness that is one-half or less of the sum of the thickness of the inner layer and the thickness of the intermediate layer and is 0.5 mm or less which is characterized as the laminated resin tube according to (5).

[0040] In the laminated resin tube according to the present invention, the fluororesin constituting the outer layer provides chemical resistance, heat resistance, and flame retardancy, and these are performance that can be obtained even with a relatively thin outer layer. On the other hand, except for some exceptions, fluororesins generally tend to be inferior in transparency, and this is the same for ETFE, which is one of the fluororesins preferred as a constituent material of the present invention. For this reason, if the outer layer is too thick, the transparency of the laminated resin tube is impaired, and it becomes difficult to visually observe the fluid being transported, which deteriorates the usability of the laminated resin tube. Therefore, in the present invention, the thickness of the outer layer is set to be less than or equal to one-half of the sum of the thickness of the inner layer and the thickness of the intermediate layer (which corresponds to the outer layer thickness being less than or equal to one-third of the wall thickness of the laminated resin tube), and the thickness is set to 0.5 mm or less. By making the outer layer have such a thickness, the transparency of the laminated resin tube is ensured to a certain extent, and it becomes a user-friendly product that allows for good visual recognition of the fluid being transported.

[0041] (6) In order to solve the above problems, in the present invention, the thermoplastic resin or thermoplastic elastomer constituting the inner layer is transparent or colored transparent, and the fluid transported from the outside can be visually recognized and is characterized as the laminated resin tube according to (5).

[0042] Multilayer resin tubes are used in various applications including industrial and medical uses, and often multiple multilayer resin tubes are used simultaneously. For example, inside a single device or the like, each multilayer resin tube is used to convey different types of fluids. In such cases, it is preferable for the multilayer resin tube to be colorable in order to prevent and detect accidents such as accidentally connecting a large number of multilayer resin tubes incorrectly. On the other hand, it is inconvenient in actual operation if the fluid conveyed inside the multilayer resin tube cannot be visually recognized. Here, it is also conceivable to perform partial coloring or the like on the surface of the multilayer resin tube by printing or the like. However, in the case of partial display, it is easy to overlook when a large number of multilayer resin tubes are bundled together, and there is also concern that the display may become difficult to visually recognize due to dirt or wear on the surface of the multilayer resin tube.

[0043] Therefore, in the multilayer resin tube according to the present invention, by making the thermoplastic resin or thermoplastic elastomer constituting the inner layer transparent or colored transparent, the fluid conveyed inside can be visually recognized from the outside, and at the same time, various color variations are provided to facilitate mutual distinction. The thermoplastic resin or thermoplastic elastomer is easy to color, and since the inner layer constituting these is covered with the intermediate layer and the outer layer, there is no concern that the distinction of the multilayer resin tube will be lost due to dirt or friction from the outside.

[0044] By the way, the multilayer resin tube according to (6) is transparent or colored transparent as a whole and the fluid during transportation can be visually recognized from the outside. Separately from this invention, a multilayer resin tube in which the thermoplastic resin or thermoplastic elastomer constituting the inner layer is opaque-colored is also useful. For example, the inner layer of the multilayer resin tube according to (5) can be made opaque black. Such a multilayer resin tube cannot visually recognize the internal fluid from the outside, but is useful when conveying a fluid that is preferably not exposed to light.

[0045] (7) In order to solve the above problems, in the present invention, The inner layer, the intermediate layer, and the outer layer are co-extrusion molded, and an adhesive state is formed between the layers. The laminated resin tube according to (6), which is characterized by this.

[0046] The laminated resin tube according to the present invention is preferably molded by co-extrusion. That is, since the resin materials constituting the inner layer, the intermediate layer, and the outer layer are simultaneously supplied to an extrusion molding die and the laminated resin tube is continuously molded, there is an advantage that an extremely long laminated resin tube without joints can be obtained, and the manufacturing cost can be reduced during mass production. Further, in addition to the molten resin materials constituting the respective layers being laminated and molded inside the extrusion molding die, in the present invention, since an intermediate layer made of a polyamide resin is provided, a laminated resin tube in which the layers including the outer layer made of a fluororesin having poor adhesiveness are in an adhesive state can be formed. In the present invention, the outer layer is made of a fluororesin. Although the influence of the adhesive strength between the layers on the bending resistance is relatively small, since the delamination between the layers can cause other problems such as the intrusion of the conveyance fluid between the layers, it is clearly a desirable state as a laminated resin tube that the layers are in an adhesive state.

Effect of the Invention

[0047] (1) Since it is provided with an inner layer made of a thermoplastic resin or a thermoplastic elastomer, there is an effect that a laminated resin tube having high flexibility and high bending performance can be obtained. Since an intermediate layer made of a polyamide resin is provided on the outer periphery of the inner layer, there is an effect that the adhesiveness with the outer layer made of a fluororesin is improved and the occurrence of problems such as delamination between the layers is suppressed. Since an outer layer made of a fluororesin is provided, there is an effect that an easy-to-use laminated resin tube can be obtained in which the excellent flexibility and high bending performance derived from the thermoplastic resin or the thermoplastic elastomer of the inner layer are hardly impaired despite having excellent chemical resistance and flame retardancy derived from the fluororesin. Further, since such a selection of the inner layer, the intermediate layer, and the outer layer makes it difficult for delamination to occur in the first place, there is no need to perform chemical etching or defluorination treatment on the outer surface of the inner layer tube or the outer surface of the intermediate layer tube to enhance the adhesiveness, and there is an effect that the transparency of the laminated resin tube can be easily ensured.

[0048] (2) Since the thickness of the outer layer is set to be 1 / 3 or less of the wall thickness of the laminated resin tube, that is, the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer, the effect is achieved that the characteristics of the present invention, namely, a laminated resin tube having excellent chemical resistance derived from the fluororesin and being highly flexible with high bending performance, become more prominent.

[0049] (2.2) Since the thickness of the intermediate layer is set to be 0.2 mm or less, the effect is achieved that while maintaining the characteristics of the laminated resin tube according to the present invention such as flexibility, dimensional changes such as moisture absorption do not pose a problem, and the raw material cost can also be suppressed.

[0050] (2.3) Since the ratio of the outer diameter to the inner diameter of the laminated resin tube is set to be 1.3 to 1.6, the effect is achieved that the characteristics of the present invention, namely, being highly flexible and having excellent bending performance, can be made reliable.

[0051] (2.4) Since the ratio of the inner diameter of the laminated resin tube to the thickness of the inner layer is set to be 3.33 to 6.0, the effect is achieved that while maintaining the characteristics of the laminated resin tube according to the present invention such as flexibility, dimensional changes such as moisture absorption do not pose a problem, and the raw material cost can also be suppressed.

[0052] (3) Since the fluororesin constituting the outer layer is ETFE, the effect is achieved that extrusion molding becomes possible and an extremely long laminated resin tube without joints can be obtained. Also, while having excellent chemical resistance derived from the fluororesin, a laminated resin tube can be obtained in which a good adhesion state is obtained with the inner layer made of polyamide resin and accidents such as delamination are suppressed. Further, even when the inner layer resin deteriorates slightly due to long-term use or the like, the deterioration of the outermost peripheral part is extremely small, so the effect is achieved that the start and progression of breakage of the laminated resin tube are suppressed.

[0053] In addition, since the fluororesin constituting the outer layer is a tetrafluoroethylene / perfluoroalkyl vinyl ether / chlorotrifluoroethylene copolymer resin, the characteristics of the present invention, namely, that a laminated resin tube having the above-described chemical resistance and suppressing accidents such as delamination can be obtained, can be made even more remarkable, and at the same time, productivity can be further improved.

[0054] (4) Since the thermoplastic resin or thermoplastic elastomer constituting the inner layer is any one of polyurethane resin, polyvinyl chloride, resin polyurethane-based elastomer, polyamide-based elastomer, olefin-based elastomer, and polystyrene-based elastomer, various grade resin materials having both strength and elasticity according to the application can be selected, and the effect that a laminated resin tube having high flexibility and high bending performance suitable for various applications can be obtained becomes even more remarkable.

[0055] In addition, it is preferable to select a polyurethane resin as the thermoplastic resin or thermoplastic elastomer constituting the inner layer. This is because the polyurethane resin has a rich selection of grades with high flexibility and elasticity, is excellent in processability during extrusion molding, and can mass-produce laminated resin tubes with high flexibility and high bending performance at a higher productivity and lower cost.

[0056] Furthermore, it is preferable to select a polyurethane-based elastomer as the thermoplastic resin or thermoplastic elastomer constituting the inner layer. This is because the extremely small Young's modulus and large fracture strain of the polyurethane-based elastomer make the flexibility and bending performance even more remarkable, so that a laminated resin tube that is extremely easy to handle and use can be obtained for applications that do not require pressure resistance performance or the like.

[0057] (5) Since the arithmetic mean roughness of the outer layer made of fluororesin is 0.1 μm or less, there is an effect that a laminated resin tube having excellent chemical resistance and high transparency and enabling the fluid conveyed inside the tube to be extremely well visible from the outside can be obtained.

[0058] Since the maximum height roughness of the outer layer made of fluororesin is set to 1 μm or less, the surface of the laminated resin tube becomes smooth and has a uniform appearance, and its marketability can be improved. In addition, it has the effect of facilitating the visual recognition and discrimination of scratches generated on the surface during use, and enabling appropriate judgment for replacement and the like to maintain performance.

[0059] (5.2) Since the thickness is set to be less than or equal to one-half of the sum of the thickness of the inner layer and the thickness of the intermediate layer and 0.5 mm or less, while having the characteristics of the present invention such as chemical resistance, heat resistance, and flame retardancy, a laminated resin tube with excellent transparency and good visibility of the fluid to be transported can be obtained.

[0060] (6) Since the thermoplastic resin or thermoplastic elastomer constituting the inner layer is made transparent or colored transparent, the fluid being transported inside can be visually recognized from the outside, and various color variations are provided for easy mutual distinction. In addition, it is possible to provide a laminated resin tube that has no concern about a decrease in discriminability even when exposed to dirt or abrasion from the outside.

[0061] Since the thermoplastic resin or thermoplastic elastomer constituting the inner layer is opaque-colored, it is possible to provide a laminated resin tube in which the fluid being transported inside is not exposed to light and there is no concern about a decrease in light-shielding properties even when the outer layer surface is exposed to abrasion.

[0062] (7) Since the inner layer, intermediate layer, and outer layer are formed by coextrusion and are in an adhesive state between each layer, it is possible to obtain an extremely long laminated resin tube without joints, and it has the effect of being able to be mass-produced at low cost.

Brief Description of the Drawings

[0063]

Figure 1

Modes for Carrying Out the Invention

[0064] Hereinafter, an embodiment of the laminated resin tube according to the present invention will be described with reference to the drawings.

Embodiment

[0065] FIG. 1 is an explanatory view showing an embodiment of the laminated resin tube according to the present invention.

[0066] The laminated resin tube (1) has a tubular structure in which an inner layer (4), an intermediate layer (3), and an outer layer (2) are laminated in order from the inside and integrated. Needless to say, the central part of the tubular structure is hollow and is used as a flow path for conveying fluid. In this embodiment, the thickness of the inner layer (4) is made the thickest, and the thicknesses of the intermediate layer (3) and the outer layer (2) are set to be thinner than the thickness of the inner layer (4).

[0067] Although laminated resin tubes with various inner diameters and outer shapes are generally manufactured, and consumers generally select and use those with appropriate dimensions according to their purposes, in this embodiment, a laminated resin tube with an inner diameter of 6 mm, an outer diameter of 8 mm, a thickness of the inner layer (4) of 0.7 mm, a thickness of the intermediate layer (3) of 0.1 mm, and a thickness of the outer layer (2) of 0.2 mm was manufactured.

[0068] The inner layer (4) is a polyurethane-based elastomer, the intermediate layer (3) is a polyamide resin, and the outer layer (2) uses ETFE as the raw material resin. Further, the laminated resin tube (1) was manufactured by simultaneously supplying the resins constituting the inner layer, the intermediate layer, and the outer layer to a metal mold and co-extrusion molding. Since each resin in a molten state at a high temperature is extruded and laminated in the metal mold, a uniform adhesion state is achieved between the layers, and delamination between the layers does not occur.

[0069] The metal mold (including a so-called sizing die) was managed for surface roughness and lubrication by a conventional method, and a laminated resin tube having an arithmetic mean surface roughness of 0.1 μm or less and a maximum height roughness of 1 μm or less was obtained.

[0070] In addition, polyurethane-based elastomers constituting the inner layer (4) were prepared in the forms of non-colored and transparent ones, ones colored in transparent blue, ones colored in white while retaining transparency, and ones colored in opaque black. Laminated resin tubes were manufactured using each of these raw materials.

[0071] The laminated resin tube (1) obtained as described above had excellent chemical resistance from the outside of the tube, was highly flexible and had excellent bending performance, and was extremely easy to handle.

[0072] Also, in each of the laminated resin tubes when the polyurethane-based elastomer constituting the inner layer (4) was left non-colored and transparent and when it was colored in transparent blue, the fluid being conveyed inside was clearly visible from the outside. Furthermore, in the case where the polyurethane-based elastomer constituting the inner layer (4) was colored in white while retaining transparency, although it was not as clear as the former two cases, it was possible to visually recognize that a fluid was being conveyed inside. Furthermore, in the case where the polyurethane-based elastomer constituting the inner layer (4) was colored in opaque black, light transmission was not observed, and it was impossible to visually recognize the fluid being conveyed inside from the outside. On the contrary, it was found that the fluid being conveyed inside was not exposed to the light entering from the outside.

[0073] Furthermore, the surface of the laminated resin tube (1) was uniform and smooth even though the surface of the outer layer (2) made of ETFE was exposed.

[0074] Incidentally, the present invention is not limited to the embodiments described above. For example, the present invention can take various modified forms such as winding a resin reinforcing thread around the inner layer to form a reinforcing layer to achieve high pressure resistance performance.

Industrial Applicability

[0075] As described above, the present invention provides a user-friendly laminated resin tube that has good chemical resistance, is highly flexible, has excellent bending performance, and allows for good visual recognition of the fluid conveyed inside, and has a very high industrial applicability.

Explanation of Signs

[0076] 1 Laminated resin tube 2 Outer layer 3 Intermediate layer 4 Inner layer

Claims

1. An inner layer made of a thermoplastic resin or a thermoplastic elastomer, an intermediate layer made of a polyamide resin provided on the outer periphery of the inner layer, and an outer layer made of a fluororesin provided on the outer periphery of the intermediate layer characterized by comprising a laminated resin tube.

2. The thickness of the outer layer is 1 / 3 or less of the sum of the thicknesses of the inner layer, the intermediate layer, and the outer layer characterizing the laminated resin tube according to Claim 1.

3. The fluororesin is a tetrafluoroethylene / ethylene copolymer resin or a tetrafluoroethylene / perfluoroalkyl vinyl ether / chlorotrifluoroethylene copolymer resin characterizing the laminated resin tube according to Claim 2.

4. The thermoplastic resin or the thermoplastic elastomer is any one of a polyurethane resin, a polyvinyl chloride resin, a polyurethane-based elastomer, a polyamide-based elastomer, an olefin-based elastomer, and a polystyrene-based elastomer characterizing the laminated resin tube according to Claim 3.

5. The outer layer has an arithmetic mean roughness of its surface of 0.1 μm or less characterizing the laminated resin tube according to any one of Claims 1 to 4.

6. The thermoplastic resin or the thermoplastic elastomer constituting the inner layer is transparent or colored transparent, and the fluid conveyed from the outside can be visually recognized characterizing the laminated resin tube according to Claim 5.

7. The inner layer, the intermediate layer, and the outer layer are coextrusion molded, and an adhesive state is provided between the layers characterizing the resin tube according to Claim 6.

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