tube

Abstract

To provide a tube capable of improving creep resistance and flexibility.SOLUTION: A hollow tube 10 composed of a laminate 10X in which a plurality of layers are laminated in a thickness direction from an inner peripheral side to an outer peripheral side. The laminate is formed of polyamide with a bending modulus of 200 MPa or more and 1450 MPa or less, and comprises a first layer 10A having a thickness of 0.1 mm or more and 0.5 mm or less, and a second layer 10B formed of a mixture of one or both of polyurethane elastomer and polyamide elastomer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tube. [Background technology]

[0002] Single-layer polyamide tubes and single-layer polyurethane elastomer tubes are used for cooling water piping and the like. Single-layer polyamide tubes are used in places where creep resistance is important or where high temperatures are present, while single-layer polyurethane elastomer tubes are used in narrow piping spaces or places where high temperatures are not present. In this way, single-layer polyamide tubes and single-layer polyurethane elastomer tubes are used for different purposes.

[0003] Patent Document 1 discloses a flame-retardant resin tube using a polyurethane elastomer as the base resin, and a flame-retardant resin tube using a polyamide elastomer as the base resin.

[0004] Patent Document 2 discloses an antistatic tube in which an inner layer having a flow path is formed from polyamide containing an antistatic agent, and an outer layer made of polyurethane elastomer or the like is formed on the outer periphery of the inner layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-267055 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-48088 Summary of the Invention [Problem to be solved by the invention]

[0006] While single-layer polyamide tubes generally have excellent creep resistance, they have issues such as low flexibility and a tendency to kink, making them difficult to route in narrow spaces. Once kinked, they leave marks, making it difficult to transport fluids.

[0007] While single-layer polyurethane elastomer tubes generally have excellent flexibility, they also have low creep resistance, meaning that if pressure is continued to be applied, their outer diameter increases and does not return to its original size. This can lead to issues such as the tube bursting due to continued creep, or the increased outer diameter making it impossible to reinsert the fitting.

[0008] As described above, it is difficult for a single-layer polyamide tube or a single-layer polyurethane elastomer tube to have both creep resistance and flexibility.

[0009] Tubes for cooling water piping and the like are required to have improved creep resistance and flexibility. Specifically, they are required to have creep resistance such that the outer diameter increases by no more than 5% from before pressure when pressurized at an ambient temperature of 70°C and an internal pressure of 0.5 MPa for 660 hours, while also having flexibility such that the kink radius is equal to or smaller than that of a tube of the same diameter made of a single layer of polyurethane elastomer with a Shore hardness of 98A.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a tube that can improve creep resistance and flexibility. [Means for solving the problem]

[0011] The tube of the present invention is a hollow tube composed of a laminate in which multiple layers are stacked in the thickness direction from the inner periphery to the outer periphery, and the laminate includes: a first layer formed of polyamide having a flexural modulus of 200 MPa to 1450 MPa and having a thickness of 0.1 mm to 0.5 mm; and a second layer formed of a mixture of one or two of a polyurethane elastomer and a polyamide elastomer. [Effects of the Invention]

[0012] According to the present invention, creep resistance and flexibility can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] 2 is a cross-sectional view of the tube of the present embodiment taken along a plane perpendicular to the longitudinal direction thereof. FIG. [Figure 2] FIG. 1 is a diagram showing a schematic configuration of a bending stiffness testing device. [Figure 3] FIG. 1 is a diagram showing a schematic configuration of a creep resistance testing device. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are merely examples and can be appropriately modified within the scope obvious to those skilled in the art.

[0015] <Embodiment> (Tube 10 configuration) 1 is a cross-sectional view of a tube 10 of this embodiment taken along a plane perpendicular to the longitudinal direction. The tube 10 of this embodiment is a hollow tube made of a laminate 10X in which multiple layers are stacked in the thickness direction from the inner periphery to the outer periphery, and the laminate 10X includes a first layer 10A as an inner layer and a second layer 10B as an outer layer.

[0016] The first layer 10A is formed of polyamide having a flexural modulus of 200 MPa to 1450 MPa, and has a thickness of 0.1 mm to 0.5 mm. The first layer 10A is a layer that enhances the creep resistance of the tube 10. If the flexural modulus of the polyamide constituting the first layer 10A is less than 200 MPa, the creep resistance of the tube 10 may not be ensured, and if it exceeds 1450 MPa, the flexibility of the tube 10 may not be ensured. Furthermore, if the thickness of the first layer 10A is less than 0.1 mm, the creep resistance of the tube 10 may not be ensured, and if it is thicker than 0.5 mm, the flexibility of the tube 10 may not be ensured.

[0017] The first layer 10A preferably contains at least one of a plasticizer and an impact-resistant agent in a content greater than 0 wt% and not greater than 30 wt%. The plasticizer may be, for example, butylbenzenesulfonamide (BBSA). The impact-resistant agent may be, for example, an olefin-based rubber component. The plasticizer and impact-resistant agent may be those commonly used in polyamides. Adding at least one of a plasticizer and an impact-resistant agent minimizes the loss of flexibility. However, if the content of the plasticizer and impact-resistant agent exceeds 30 wt%, the creep resistance of the tube 10 may not be ensured.

[0018] The first layer 10A contains, as a polyamide having a flexural modulus of elasticity of 200 MPa or more and 1450 MPa or less, for example, any one of PA11, PA12, and PA1012, or a mixture of two or more thereof.

[0019] The second layer 10B is formed of a mixture of one or two of a polyurethane elastomer and a polyamide elastomer. The second layer 10B is a layer that increases the flexibility of the tube 10. The polyurethane elastomer is a copolymer of a hard segment having a urethane bond and a soft segment having an ester bond or an ether bond. The polyamide elastomer is a copolymer of a hard segment having an amide bond and a soft segment having an ester bond or an ether bond.

[0020] The second layer 10B is preferably formed of an elastomer having a Shore hardness of 85 A or more and 95 A or less. If the Shore hardness of the elastomer constituting the second layer 10B exceeds 95 A, the flexibility of the tube 10 may not be ensured.

[0021] In the tube 10 shown in FIG. 1, the first layer 10A is the inner layer and the second layer 10B is the outer layer, but the first layer 10A may be the outer layer and the second layer 10B may be the inner layer.

[0022] One or both of the first layer 10A and the second layer 10B may have a multilayer structure. In this case, the layer structures of the first layer 10A and the second layer 10B can be selected arbitrarily. For example, the first layer 10A may have a multilayer laminated structure, or the second layer 10B may have a multilayer laminated structure. Furthermore, the second layer 10B may be disposed between a plurality of first layers 10A, or the first layer 10A may be disposed between a plurality of second layers 10B, or the first layer 10A and the second layer 10B may be alternately laminated.

[0023] The laminate 10X constituting the tube 10 may include a layer (not shown) other than the first layer 10A and the second layer 10B. The layer other than the first layer 10A and the second layer 10B may be provided between the first layer 10A and the second layer 10B, on the inner peripheral side of the first layer 10A and the second layer 10B, or on the outer peripheral side of the first layer 10A and the second layer 10B.

[0024] For example, an adhesive layer (not shown) may be provided between the first layer 10A and the second layer 10B as a layer other than the first layer 10A and the second layer 10B. The adhesive layer may have the function of increasing the creep resistance of the tube 10, similar to the first layer 10A. Alternatively, the adhesive layer may have the function of increasing the flexibility of the tube 10, similar to the second layer 10B. Furthermore, the laminate 10X constituting the tube 10 may include a layer other than an adhesive layer in addition to the first layer 10A and the second layer 10B, or may further include an adhesive layer.

[0025] The tube of this embodiment can be preferably used as a tube for piping cooling water.

[0026] (Action and effect of Tube 10) According to the tube 10 of this embodiment, by having a laminated structure of a first layer 10A that improves creep resistance and a second layer 10B that improves flexibility, after being pressurized for 660 hours at an ambient temperature of 70°C and an internal pressure of 0.5 MPa, the tube 10 has creep resistance such that the outer diameter increases by 5% or less from before pressurization, while maintaining flexibility such that the kink radius is equal to or less than that of a tube of the same diameter made of a single layer of polyurethane elastomer with a Shore hardness of 98A.

[0027] (Manufacturing method of tube 10) Next, a method for manufacturing the tube configured as described above will be described. The tube is formed by extrusion molding. The tube 10 shown in Fig. 1 can be manufactured by forming a first layer 10A, which will be the inner layer, using an inner layer extruder, and then forming a second layer 10B on the outer surface of this first layer 10A using an outer layer extruder, or by co-extrusion molding the material that will form the first layer 10A and the material that will form the second layer 10B in a molten state and heat-sealing them.

[0028] Even when the first layer 10A is the outer layer and the second layer 10B is the inner layer, they can be formed in the same manner as above. Also, even when layers other than the first layer 10A and the second layer 10B, such as an adhesive layer, are included, the layers can be laminated by sequentially extruding them with an extruder, as in the above, or by co-extrusion molding the materials for the layers.

[0029] In general, it is preferable to pelletize the resins forming the first layer 10A and the second layer 10B in advance. For example, the polyamide forming the first layer 10A and the polyurethane elastomer forming the second layer 10B are melt-kneaded and pelletized using a single-screw extruder, a twin-screw extruder, a twin-screw kneader, or the like.

[0030] By laminating the first layer 10A, which improves creep resistance, and the second layer 10B, which improves flexibility, as described above, it is possible to manufacture a tube that has creep resistance such that the outer diameter increases by 5% or less from before pressure after being pressurized at an ambient temperature of 70°C and an internal pressure of 0.5 MPa for 660 hours, while maintaining flexibility such that the kink radius is equal to or less than that of a tube of the same diameter made of a single layer of polyurethane elastomer with a Shore hardness of 98A.

[0031] (Example) Tubes according to Examples 1 to 8 and Comparative Examples 1 to 5 were produced and evaluated according to the procedures shown in the above manufacturing method. The tubes according to Examples 1 to 8 and Comparative Examples 1 to 3 and 5 had an outer diameter of 8.0 mm, an inner diameter of 5.0 mm, and an overall thickness of 1.5 mm. The tube according to Comparative Example 4 had an outer diameter of 8.0 mm, an inner diameter of 6.0 mm, and an overall thickness of 1.0 mm. In Examples 1 to 8 and Comparative Examples 1 to 3, the tubes were produced by co-extrusion. In Comparative Examples 4 and 5, the tubes were produced by single-layer extrusion.

[0032] The tube of Example 1 was produced by forming the first layer 10A, which is the inner layer, from PA11 (flexural modulus of elasticity 350 MPa) to a thickness of 0.1 mm, and the second layer 10B, which is the outer layer, from an ether-based polyurethane elastomer (Shore hardness 95A) to a thickness of 1.4 mm.

[0033] A tube according to Example 2 was produced in the same manner as in Example 1, except that the thickness of the inner layer was 0.2 mm and the thickness of the outer layer was 1.3 mm.

[0034] A tube according to Example 3 was produced in the same manner as in Example 1, except that the thickness of the inner layer was 0.3 mm and the thickness of the outer layer was 1.2 mm.

[0035] A tube according to Example 4 was produced in the same manner as in Example 1, except that the thickness of the inner layer was 0.5 mm and the thickness of the outer layer was 1.0 mm.

[0036] The tube of Example 5 was produced by forming the first layer 10A, which is the inner layer, from PA12 (flexural modulus 1450 MPa) to a thickness of 0.5 mm, and the second layer 10B, which is the outer layer, from an ether-based polyurethane elastomer (Shore hardness 95A) to a thickness of 1.0 mm.

[0037] The tube of Example 6 was produced by forming the first layer 10A, which is the inner layer, from PA12 (flexural modulus of elasticity 200 MPa) to a thickness of 0.1 mm, and the second layer 10B, which is the outer layer, from an ether-based polyurethane elastomer (Shore hardness 85A) to a thickness of 1.4 mm.

[0038] The tube of Example 7 was produced by forming the first layer 10A, which is the inner layer, from PA12 (flexural modulus 1450 MPa) to a thickness of 0.5 mm, and the second layer 10B, which is the outer layer, from polyamide elastomer (Shore hardness 95A) to a thickness of 1.0 mm.

[0039] The tube of Example 8 was produced by forming the first layer 10A, which is the inner layer, from PA12 (flexural modulus 200 MPa) to a thickness of 0.1 mm, and the second layer 10B, which is the outer layer, from polyamide elastomer (Shore hardness 85A) to a thickness of 1.4 mm.

[0040] The tube according to Comparative Example 1 was produced by forming the first layer 10A, which is the inner layer, from PA11 (flexural modulus 350 MPa) to a thickness of 0.75 mm, and forming the second layer 10B, which is the outer layer, from an ether-based polyurethane elastomer (Shore hardness 95A) to a thickness of 0.75 mm.

[0041] A tube according to Comparative Example 2 was produced in the same manner as Comparative Example 1, except that the thickness of the inner layer was 1.0 mm and the thickness of the outer layer was 0.5 mm.

[0042] The tube according to Comparative Example 3 was produced by forming the first layer 10A, which is the inner layer, from PA12 (flexural modulus 1700 MPa) to a thickness of 0.1 mm, and forming the second layer 10B, which is the outer layer, from an ether-based polyurethane elastomer (Shore hardness 95A) to a thickness of 1.4 mm.

[0043] A tube according to Comparative Example 4 was produced using a single layer of PA12 (flexural modulus: 400 MPa) with a thickness of 1.0 mm.

[0044] A tube according to Comparative Example 5 was produced using a single layer of ether-based polyurethane elastomer (Shore hardness 98A) with a thickness of 1.5 mm.

[0045] The flexural moduli of PA11 and PA12 mentioned above are flexural moduli measured in accordance with ISO178.

[0046] The configuration of the prepared tube is shown in Table 1. The tube prepared as described above was subjected to the following various evaluations.

[0047] (Flexibility) Flexibility was evaluated using a bending stiffness tester 11 shown in FIG. 2. First, the tube 10 was left to stand in a constant temperature and humidity chamber (23°C, 50% RH) for 24 hours or more and then attached to the bending stiffness tester. The tube 10 was cut to a length calculated by the formula: length (mm) = π((R + OD) / 2) + (2 × OD). Here, R: tube bending radius (mm) at the start of the test, OD: tube outer diameter (mm), which was set to 343 mm in this test. The movable part 14 mounted on the rail was moved toward the fixed part 12 at a speed of 100 mm / min to gradually bend the tube 10, and the kink radius was measured. The kink radius was the bending radius of the tube 10 when a kink occurred in the tube 10. Five tests were conducted, and the average kink radius for each example and comparative example was calculated. A kink radius equal to or smaller than that of the tube of Comparative Example 5 was marked with an O, and a kink radius greater than that of the tube of Comparative Example 5 was marked with an X. The results are shown in the "Flexibility" column of Table 1.

[0048] (Creep resistance) A creep resistance test was conducted to evaluate creep resistance using a creep resistance test device 32 shown in Figure 3. The tube 10 was cut to a length of 150 mm, and a blank cap 21 was attached to one end via a joint 20. The other end of the tube 10 was attached to a manifold 30 via the joint 20. A pressurized air supply line 31 was connected to the manifold 30, and pressure could be applied to the inside of the tube 10 via the manifold 30.

[0049] First, the outer diameter A (mm) of the tube 10 before pressurization in the creep resistance test was measured using a constant-pressure vernier caliper. Next, while the tube 10 was immersed in a 70°C water bath, pressurized air was supplied from the pressurized air supply line 31 to apply a pressure of 0.5 MPa to the inside of the tube 10. After 660 hours, the outer diameter B (mm) of the tube 10 in the pressurized state was measured using a constant-pressure vernier caliper. The outer diameter increase rate was calculated using the formula: outer diameter increase rate (%) = (B / A) × 100 - 100. Three tests were conducted, and the average outer diameter increase rate for each example and comparative example was calculated. An outer diameter increase rate of 5% or less was marked with ◯, and an outer diameter increase rate of more than 5% was marked with ×. The results are listed in the "Creep Resistance" column in Table 1.

[0050] [Table 1]

[0051] As shown in Table 1, Examples 1 to 8 had a laminated structure in which an inner layer made of polyamide with a flexural modulus of 200 MPa or more and 1450 MPa or less and a thickness of 0.1 mm or more and 0.5 mm or less was formed, and an outer layer made of an ether-based polyurethane elastomer or polyamide elastomer, and therefore had good evaluation results for flexibility and creep resistance.

[0052] The creep resistance evaluation results were good for Comparative Examples 1 to 4, but the flexibility was not good. The creep resistance evaluation result for Comparative Example 5 was not good, although flexibility was used as the evaluation standard. [Explanation of symbols]

[0053] 10 tubes 10A 1st layer 10B 2nd layer 10X laminate 11. Bending stiffness testing device 12 Fixed part 14 Moving parts 20 Joints 21 Blank Cap 30 Manifold 31 Pressurized air supply line 32 Creep resistance test equipment R bending radius

Claims

1. A hollow tube composed of a laminate in which multiple layers are stacked in a thickness direction from the inner periphery to the outer periphery, The laminate comprises: A first layer is formed of polyamide having a flexural modulus of 200 MPa or more and 1450 MPa or less and has a thickness of 0.1 mm or more and 0.5 mm or less; A second layer formed of a mixture of one or two of a polyurethane elastomer and a polyamide elastomer; Including, After pressurizing for 660 hours at an atmospheric temperature of 70°C and an internal pressure of 0.5 MPa, the increase in outer diameter from before pressurization is 5% or less. Tube for cooling water piping.

2. The first layer contains at least one of a plasticizer and an impact resistance agent in an amount greater than 0 wt % and less than 30 wt %. The tube of claim 1.

3. The first layer contains one or a mixture of two or more of PA11, PA12, and PA1012.

3. The tube according to claim 1 or 2.

4. The second layer is formed of an elastomer having a Shore hardness of 85A or more and 95A or less. The tube according to any one of claims 1 to 3.

5. An adhesive layer is provided between the first layer and the second layer. The tube according to any one of claims 1 to 4.

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