Laminated pipe

Abstract

Provided is a laminated tube having excellent interlayer adhesion between an inner layer comprising polypropylene and an outer layer comprising polyamide. The laminated tube (10) has an adhesive layer (16) containing an acid-modified polypropylene between an inner layer (12) containing a polypropylene and an outer layer (14) containing a polyamide, and the ratio (b / a) of the length (a) of the outer peripheral surface (14a) of the outer layer (14) to the length (b) of the outer peripheral surface (16a) of the adhesive layer (16) within the range of 100 [mu] m in the axial direction is 1.003-1.050. Furthermore, the polypropylene of the laminated tube (20) having an inner layer (22) comprising polypropylene and an outer layer (24) comprising polyamide contains an acid-modified polypropylene, and the ratio (b ' / a') of the length a'of the outer peripheral surface (24a) of the outer layer (24) to the length b 'of the outer peripheral surface (22a) of the inner layer (22) within the range of 100 [mu] m in the axial direction is 1.003-1.050.

Description

Technical Field

[0001] The present invention relates to laminated tubes, and more specifically, to laminated tubes suitable for use as pipes for conveying coolant in cooling systems of automobiles and the like. Background Technology

[0002] Coolant delivery pipes are used in the cooling systems of gasoline vehicles, electric vehicles, and other similar vehicles to transport coolant. From a heat resistance perspective, polyamide resin is often used for coolant delivery pipes. Additionally, polypropylene resin, which is cost-effective, has also been investigated. Furthermore, laminated pipes made of polyamide and polypropylene resins have been studied.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2008-507436 Patent Document 2: Japanese Patent Application Publication No. 2012-082885 Summary of the Invention The problem that the invention aims to solve The inter-resin adhesion of laminated tubes made of polypropylene and polyamide resins is poor. Patent Document 2 investigated improving the adhesion between the polypropylene resin and the polyamide resin by using acid-modified polypropylene. However, there is still room for improvement in interlayer adhesion.

[0004] The problem to be solved by the present invention is to provide a laminated tube with excellent interlayer adhesion between an inner layer comprising polypropylene and an outer layer comprising polyamide.

[0005] means for solving problems The laminated tube involved in this invention is a laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein an adhesive layer containing acid-modified polypropylene is provided between the inner layer and the outer layer, and the ratio (b / a) of the length a of the outer peripheral surface of the outer layer to the length b of the outer peripheral surface of the adhesive layer within an axial range of 100 μm is 1.003 or more and 1.050 or less.

[0006] In addition, another type of laminated tube involved in the present invention is a laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein the polypropylene contains acid-modified polypropylene, and the ratio (b' / a') of the length a' of the outer peripheral surface of the outer layer to the length b' of the outer peripheral surface of the inner layer within an axial range of 100 μm is 1.003 or more and 1.050 or less.

[0007] Preferably, in the laminated tube according to the present invention, the adhesive layer is composed of a resin composition comprising particles of an organic polymer in an acid-modified polypropylene matrix. Additionally, preferably, in another laminated tube according to the present invention, the inner layer is composed of a resin composition comprising particles of an organic polymer in an acid-modified polypropylene matrix.

[0008] Preferably, the organic polymer particles are composed of an ethylene-propylene copolymer or an ethylene polymer. Preferably, the content of the organic polymer particles is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acid-modified polypropylene matrix. Preferably, the average particle size of the organic polymer particles is 0.1 μm or more and 10 μm or less.

[0009] Furthermore, preferably, the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less. Here, in the laminated tube according to the present invention, preferably, the adhesive force at the interface between the adhesive layer and the outer layer is 30 N / cm or more. Additionally, in another laminated tube according to the present invention, preferably, the adhesive force at the interface between the inner layer and the outer layer is 30 N / cm or more.

[0010] Moreover, preferably, the laminated tubes involved in the present invention, as well as other laminated tubes involved in the present invention, are used for coolant delivery pipes in vehicles.

[0011] (1) The laminated tube involved in the present invention is a laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein an adhesive layer containing acid-modified polypropylene is provided between the inner layer and the outer layer, and the ratio (b / a) of the length a of the outer peripheral surface of the outer layer to the length b of the outer peripheral surface of the adhesive layer in an axial range of 100 μm is 1.003 or more and 1.050 or less.

[0012] (2) Another laminated tube involved in the present invention is a laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein the polypropylene contains acid-modified polypropylene, and the ratio (b' / a') of the length a' of the outer peripheral surface of the outer layer to the length b' of the outer peripheral surface of the inner layer in the axial range of 100 μm is 1.003 or more and 1.050 or less.

[0013] (3) Preferably, in (1) above, the adhesive layer is composed of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix.

[0014] (4) Preferably, in (2) above, the inner layer is composed of a resin composition containing particles of an organic polymer in an acid-modified polypropylene matrix.

[0015] (5) Preferably, in (3) or (4) above, the particles of the organic polymer are composed of ethylene-propylene copolymer or ethylene polymer.

[0016] (6) Preferably, in any one of (3) to (5) above, the content of the organic polymer particles is 5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acid-modified polypropylene matrix.

[0017] (7) Preferably, in any one of (3) to (6) above, the average particle size of the organic polymer particles is 0.1 μm or more and 10 μm or less.

[0018] (8) Preferably, in any one of (1) to (7) above, the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less.

[0019] (9) Preferably, in (8) which is subordinate to (1) above, the adhesive force at the interface between the adhesive layer and the outer layer is 30 N / cm or more.

[0020] (10) Preferably, in (8) which is subordinate to (2) above, the adhesive force at the interface between the inner layer and the outer layer is 30 N / cm or more.

[0021] (11) Preferably, in any one of (1) to (10) above, the laminated tube is used as a coolant delivery tube for a vehicle.

[0022] Invention Effects The laminated tube of this invention has an inner layer containing polypropylene and an outer layer containing polyamide. An adhesive layer containing acid-modified polypropylene is provided between the inner and outer layers. The ratio (b / a) of the length 'a' of the outer circumferential surface of the outer layer to the length 'b' of the outer circumferential surface of the adhesive layer within a 100 μm axial direction is 1.003 or more and 1.050 or less. By making the length 'b' of the outer circumferential surface of the adhesive layer, which bonds the inner layer containing polypropylene to the outer layer containing polyamide, longer than the length 'a' of the outer circumferential surface of the outer layer, the contact area between the inner circumferential surface of the outer layer and the outer circumferential surface of the adhesive layer increases, thus resulting in excellent interlayer adhesion between the adhesive layer and the outer layer. Furthermore, since both the adhesive layer and the inner layer are polypropylene-containing layers, the interlayer adhesion between the adhesive layer and the inner layer is also excellent. Therefore, the interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide is excellent.

[0023] Furthermore, another type of laminated tube involved in this invention is a laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein the polypropylene contains acid-modified polypropylene, and the ratio (b' / a') of the length a' of the outer peripheral surface of the outer layer to the length b' of the outer peripheral surface of the inner layer within an axial range of 100 μm is 1.003 or more and 1.050 or less. By making the length b' of the outer peripheral surface of the inner layer, which forms the bonding interface between the inner layer containing polypropylene and the outer layer containing polyamide, longer than the length a' of the outer peripheral surface of the outer layer, the contact area between the inner peripheral surface of the outer layer and the outer peripheral surface of the inner layer increases, thus resulting in excellent interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide.

[0024] In the laminated tubes of this invention, if the adhesive layer is composed of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix, the organic polymer particles easily create an uneven shape on the outer peripheral surface of the adhesive layer, making it easier for the length b of the outer peripheral surface of the adhesive layer to be longer than the length a of the outer peripheral surface of the outer layer. Furthermore, the tear strength in the longitudinal direction of the acid-modified polypropylene matrix can be improved. Therefore, the interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide can be further improved.

[0025] In another laminated tube according to the present invention, if the inner layer is composed of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix, the organic polymer particles tend to create an uneven shape on the outer peripheral surface of the inner layer, making it easier for the length b' of the outer peripheral surface of the inner layer to be longer than the length a' of the outer peripheral surface of the outer layer. Furthermore, the tear strength in the longitudinal direction of the acid-modified polypropylene matrix can be improved. This further enhances the interlayer adhesion between the polypropylene-containing inner layer and the polyamide-containing outer layer.

[0026] Here, if the organic polymer particles are composed of ethylene-propylene copolymer or ethylene polymer, it is easy to form an uneven shape on the outer peripheral surface of the adhesive layer or inner layer. Furthermore, the acid-modified polypropylene matrix exhibits excellent improvement in tear strength along its length.

[0027] Furthermore, if the content of the organic polymer particles is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acid-modified polypropylene matrix, the effect of forming an uneven shape on the outer peripheral surface of the adhesive layer or inner layer to increase the contact area and thereby improve the adhesion between the adhesive layer or inner layer and the outer layer is excellent, and the effect of improving the adhesion based on the acid-modified polypropylene and polyamide is well balanced.

[0028] Furthermore, if the average particle size of the organic polymer particles is 0.1 μm or more and 10 μm or less, the effect of forming an uneven shape on the outer peripheral surface of the adhesive layer or inner layer to increase the contact area and thereby improve the adhesion between the adhesive layer or inner layer and the outer layer is excellent, achieving a balance between the effect of improving the adhesion based on acid-modified polypropylene and polyamide.

[0029] Furthermore, if the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less, the adhesion between the acid-modified polypropylene and the polyamide is excellent. This improves the adhesion between the adhesive layer and the outer layer, or the adhesion between the inner layer and the outer layer.

[0030] Furthermore, in the laminated tubes according to the present invention, if the adhesive force at the interface between the adhesive layer and the outer layer is 30 N / cm or more, the adhesion between the adhesive layer and the outer layer is excellent. Additionally, in another laminated tube according to the present invention, if the adhesive force at the interface between the inner layer and the outer layer is 30 N / cm or more, the adhesion between the inner layer and the outer layer is excellent.

[0031] Furthermore, the laminated tubes involved in this invention, as well as other laminated tubes involved in this invention, are suitable for use as coolant delivery pipes for vehicles. Attached Figure Description

[0032] Figure 1 This is a structural diagram illustrating a laminated tube according to one embodiment of the present invention.

[0033] Figure 2 yes Figure 1 The cross-sectional view of the laminated tube shown is within an axial range of 100 μm.

[0034] Figure 3 This is a diagram illustrating the configuration of a laminated tube according to another embodiment of the present invention.

[0035] Figure 4 yes Figure 3 The cross-sectional view of the laminated tube shown is within an axial range of 100 μm. Detailed Implementation

[0036] The laminated tubes involved in this invention will now be described in detail. Figure 1 This is a structural diagram of a laminated tube according to one embodiment of the present invention. Figure 2 yes Figure 1 The cross-sectional view of the laminated tube shown is within an axial range of 100 μm.

[0037] like Figure 1As shown, a laminated tube 10 according to one embodiment of the present invention has an inner layer 12, an outer layer 14, and an adhesive layer 16. Each of the inner layer 12, outer layer 14, and adhesive layer 16 is configured as a tube. The laminated tube 10 has a three-layer laminated structure formed by stacking the inner layer 12, adhesive layer 16, and outer layer 14 in a tubular shape from the inside. The adhesive layer 16 is disposed between the inner layer 12 and the outer layer 14 as a layer for bonding the inner layer 12 and the outer layer 14. The adhesive layer 16 is disposed in contact with the inner layer 12 on the outer peripheral surface of the inner layer 12. The outer layer 14 is disposed in contact with the adhesive layer 16 on the outer peripheral surface of the adhesive layer 16.

[0038] The laminated tube 10 has an inner layer 12 containing polypropylene and an outer layer 14 containing polyamide. The outer layer 14 containing polyamide ensures strength and heat resistance. The inner layer 12 containing polypropylene prevents the fluid flowing within the laminated tube 10 from contacting the outer layer 14 containing polyamide, thereby suppressing strength reduction caused by hydrolysis. The inner layer 12 containing polypropylene is protected by the outer layer 14 containing polyamide relative to the internal pressure of the fluid flowing within the laminated tube 10; therefore, the interlayer adhesion between the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide is important. Generally, polypropylene and polyamide have low adhesion; therefore, in the laminated tube 10, an adhesive layer 16 is provided as a layer to bond the inner layer 12 and the outer layer 14. The adhesive layer 16 is a layer containing acid-modified polypropylene.

[0039] exist Figure 2 In the diagram, 14a is the outer peripheral surface of the outer layer 14. 16a is the outer peripheral surface of the adhesive layer 16. 16b is the inner peripheral surface of the adhesive layer 16. The axial direction of the laminated tube 10 is the direction in which the laminated tube 10 extends. Figure 1 , Figure 2 The X direction in the equation.

[0040] like Figure 2 As shown, in the laminated tube 10, the ratio (b / a) of the length a of the outer peripheral surface 14a of the outer layer 14 to the length b of the outer peripheral surface 16a of the adhesive layer 16 within a 100 μm axial range is 1.003 or more and 1.050 or less. The outer peripheral surface 14a of the outer layer 14 is the part that contacts the forming die during extrusion molding and is the part that suppresses the generation of undulations during extrusion molding. Therefore, it can be represented as a length that is undulating and close to a straight line. The ratio (b / a) of the length b of the outer peripheral surface 16a of the adhesive layer 16 to the length a of the outer peripheral surface 14a is greater than 1. By making the length b of the outer peripheral surface 16a of the adhesive layer 16, which bonds the inner layer 12 containing polypropylene to the outer layer 14 containing polyamide, longer than the length a of the outer peripheral surface 14a of the outer layer 14, the contact area between the inner peripheral surface of the outer layer 14 and the outer peripheral surface 16a of the adhesive layer 16 becomes larger, thus the interlayer adhesion between the adhesive layer 16 and the outer layer 14 is excellent.

[0041] In this invention, the undulation of the outer peripheral surface 16a of the adhesive layer 16 is intentionally increased to increase the contact area between the outer peripheral surface 16a of the adhesive layer 16 and the inner peripheral surface of the outer layer 14, thereby improving the interlayer adhesion between the adhesive layer 16 and the outer layer 14. If the ratio (b / a) is less than 1.003, the improvement in adhesion due to the increase in contact area is insufficient. Furthermore, if the ratio (b / a) is greater than 1.050, the undulation of the outer peripheral surface 16a of the adhesive layer 16 becomes excessive, and the adhesion decreases. Methods for increasing the undulation of the outer peripheral surface 16a of the adhesive layer 16 include: changing the extrusion temperature of each layer during extrusion molding to increase the viscosity difference between layers, thus creating undulations larger than those naturally occurring and unavoidable; or incorporating organic polymer particles 18 into the material of the adhesive layer 16 to create protrusions or depressions on the outer peripheral surface 16a of the adhesive layer 16 caused by the organic polymer particles 18.

[0042] From the viewpoint of improving adhesion by increasing the contact area, the ratio (b / a) is preferably 1.005 or more, and more preferably 1.007 or more. Furthermore, from the viewpoint of suppressing the decrease in adhesion caused by increased undulations, the ratio (b / a) is preferably 1.040 or less, and more preferably 1.030 or less.

[0043] The length a of the outer peripheral surface 14a of the outer layer 14 and the length b of the outer peripheral surface 16a of the adhesive layer 16 can be determined by taking a cross-section of the laminated tube 10 along the axial direction by taking a scanning electron microscope (SEM) at 5000x magnification and connecting 10 of these images.

[0044] The inner layer 12 is composed of a composition containing polypropylene. The inner layer 12 contains polypropylene as the main component. The main component is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0045] The polypropylene used as the inner layer 12 can be propylene homopolymer, propylene-α-olefin random copolymer, propylene-α-olefin block copolymer, or other propylene-based polymers. Among these, propylene-α-olefin block copolymers are preferred. Examples of α-olefins include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among these, ethylene, 1-butene, and 1-hexene are preferred, with ethylene being particularly preferred.

[0046] A propylene-α-olefin block copolymer refers to a block copolymer that is not limited to having blocks continuously composed of propylene monomers and blocks continuously composed of α-olefin monomers. For example, it also includes blends (alloys) with an island structure where polypropylene, such as a homopolymer of propylene, forms the sea phase, and polyethylene and / or ethylene-based rubber forms the island phase. Examples of polyethylene components include ethylene homopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and copolymers of ethylene and α-olefins (ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers), etc. Examples of ethylene-based rubber components include ethylene-propylene-diene terpolymers (EPDM), ethylene-propylene copolymers (EPR), ethylene-butene copolymers (EBR), ethylene-octene copolymers (EOR), etc. Furthermore, the proportion of polyethylene and / or ethylene-based rubber components relative to the total blend (alloy) is, for example, 1 to 49% by mass, or 2.5 to 20% by mass.

[0047] The composition constituting the inner layer 12 may, as needed, incorporate stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, anti-aging agents, etc., based on polypropylene. Furthermore, the composition constituting the inner layer 12 may, as needed, be a material formed by granulating a material obtained by melting and mixing these materials.

[0048] The outer layer 14 is composed of a composition containing polyamide. The outer layer 14 contains polyamide as a main component. The main component is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The polyamide can be an aliphatic polyamide or an aromatic polyamide. From the viewpoint of affinity with polypropylene, an aliphatic polyamide is more preferred as the polyamide.

[0049] From the viewpoint of improving adhesion to acid-modified polypropylene, the amine value of the polyamide is preferably 15 mmol / kg or more. More preferably, it is 20 mmol / kg or more, and even more preferably, it is 25 mmol / kg or more. On the other hand, from the viewpoint of excellent extrusion moldability, the above-mentioned amine value is preferably 100 mmol / kg or less. More preferably, it is 80 mmol / kg or less, and even more preferably, it is 60 mmol / kg or less. The amine value of the polyamide represents the number of mmol of amine contained in 1 kg of the solid component of the polyamide. The outer layer 14 may contain 50% by mass or more of polyamide exhibiting a specific amine value. Preferably, it is 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0050] Examples of polyamides exhibiting specific amine values ​​include aliphatic polyamides such as polyamide 46 (PA46), polyamide 410 (PA410), polyamide 6 (PA6), polyamide 66 (PA66), polyamide 610 (PA610), polyamide 612 (PA612), polyamide 11 (PA11), polyamide 12 (PA12), and polyamide 1010 (PA1010), as well as aromatic polyamides such as polyamide 6T (PA6T), polyamide 9T (PA9T), and polyamide 10T (PA10T). The polyamide used as the outer layer 14 can be one of these polyamides alone or in combination with two or more.

[0051] From the viewpoint of heat resistance, the melting point of polyamide is preferably 160°C or higher, more preferably 170°C or higher. On the other hand, from the viewpoint of ensuring adhesion, the melting point is preferably 280°C or lower, more preferably 270°C or lower.

[0052] The composition constituting the outer layer 14 may, as needed, incorporate stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, anti-aging agents, etc., in addition to polyamide. Furthermore, the composition constituting the outer layer 14 may, as needed, be a material formed by granulating a material obtained by melt-blending these materials.

[0053] The adhesive layer 16 comprises acid-modified polypropylene as the base polymer. This results in excellent adhesion to the outer layer 14, which comprises polyamide. The adhesive layer 16 may be composed of a resin composition comprising acid-modified polypropylene as the base polymer and containing particles 18 of an organic polymer within the acid-modified polypropylene matrix. The base polymer is the main component of the adhesive layer 16. The main component is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The polymer component in the adhesive layer 16 may consist only of acid-modified polypropylene, or it may include polymer components such as unmodified polypropylene. In this case, the acid-modified polypropylene in the polymer component of the adhesive layer 16 is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Furthermore, the adhesive layer 16 may not necessarily contain particles 18 of an organic polymer.

[0054] Acids used in acid-modified polypropylene can be unsaturated carboxylic acids and their derivatives. Examples of unsaturated carboxylic acids include maleic acid, fumaric acid, acrylic acid, and methacrylic acid. Examples of unsaturated carboxylic acid derivatives include acid anhydrides, esters, amides, imides, and metal salts. From the viewpoint of reactivity with polyamides, maleic acid and maleic anhydride are particularly preferred.

[0055] From the viewpoint of improving adhesion to the outer layer 14, the amount of acid modification in the acid-modified polypropylene is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. On the other hand, from the viewpoint of ensuring heat resistance, the above-mentioned amount of acid modification is preferably 7% by mass or less, more preferably 5% by mass or less. Furthermore, from the viewpoint of ensuring heat resistance, the melting point of the acid-modified polypropylene is preferably 130°C or more, more preferably 140°C or more. On the other hand, from the viewpoint of ensuring adhesion, the melting point is preferably 180°C or less, more preferably 170°C or less.

[0056] Organic polymer particles 18 are disposed within the matrix polymer (acid-modified polypropylene) of the adhesive layer 16. Through the inclusion of organic polymer particles 18, such as... Figure 2 As shown, protrusions and recesses (concave-convex shapes) are easily formed on the outer peripheral surface 16a and inner peripheral surface 16b of the adhesive layer 16. This makes it easy for the length b of the outer peripheral surface 16a of the adhesive layer 16 to be longer than the length a of the outer peripheral surface 14a of the outer layer 14. Furthermore, in the extruded laminated tube 10, the matrix polymer (acid-modified polypropylene) of the adhesive layer 16, oriented along the length direction, easily tears in a fibrous manner, weakening the tear strength in the length direction. The organic polymer particles 18 disposed within the matrix polymer of the adhesive layer 16 act as barriers against tearing forces in the length direction, thereby increasing the tear strength in the length direction.

[0057] The particles 18, which are organic polymers, can be exemplified by rubber, resin, or other organic polymers. Examples of rubber materials include ethylene-propylene copolymers, ethylene-octene copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, and ethyl acrylate. Examples of resins include polyethylene. The particles 18, which are organic polymers, can be used alone or in combination of two or more. From the viewpoints of superior compatibility with the matrix polymer, ease of forming an uneven shape on the outer peripheral surface 16a of the adhesive layer 16, and excellent improvement in tear strength along the length direction of the acid-modified polypropylene matrix, ethylene-propylene copolymers and polyethylene are more preferred.

[0058] The organic polymer particles 18 can be added to the matrix polymer by pre-granulating the particles, or the ungranulated organic polymer and the matrix polymer can be melt-blended and granulated under specific conditions, and then melt-extruded under specific conditions, thereby containing the organic polymer particles 18 in the matrix of acid-modified polypropylene.

[0059] From the viewpoints of improving the adhesion between the adhesive layer 16 and the outer layer 14 by increasing the contact area through the formation of an uneven shape on the outer peripheral surface 16a of the adhesive layer 16, and improving the tear strength in the longitudinal direction of the acid-modified polypropylene matrix, the content of organic polymer particles 18 is preferably 5 parts by mass or more relative to 100 parts by mass of the acid-modified polypropylene matrix. More preferably, it is 10 parts by mass or more. On the other hand, from the viewpoints of improving the adhesion between acid-modified polypropylene and polyamide, the content is preferably 20 parts by mass or less relative to 100 parts by mass of the acid-modified polypropylene matrix. More preferably, it is 15 parts by mass or less. The content of organic polymer particles 18 in the adhesive layer 16 can be determined by taking a picture at 1000x magnification using a scanning electron microscope (SEM) and performing binarization processing.

[0060] From the viewpoints of improving the adhesion between the adhesive layer 16 and the outer layer 14 by increasing the contact area through the formation of an uneven shape on the outer peripheral surface 16a of the adhesive layer 16, and improving the tear strength in the longitudinal direction of the acid-modified polypropylene matrix, the average particle size of the organic polymer particles 18 is preferably 0.1 μm or more. More preferably, it is 0.3 μm or more. On the other hand, from the viewpoints of improving the adhesion of acid-modified polypropylene and polyamide, the above-mentioned average particle size is preferably 10 μm or less. More preferably, it is 5 μm or less, and even more preferably, it is 3 μm or less. The average particle size of the organic polymer particles 18 can be expressed by taking a cross-section of the adhesive layer 16 at 5000x magnification using a scanning electron microscope (SEM) and measuring the particle size of any 10 confirmed organic polymer particles 18.

[0061] The composition constituting the adhesive layer 16, based on acid-modified polypropylene, may also include, as needed, stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, anti-aging agents, etc. Furthermore, the composition constituting the adhesive layer 16 may, as needed, use a material formed by granulating a material obtained by melting and mixing these materials.

[0062] like Figure 2 As shown, the adhesive layer 16 preferably has one or more protrusions or recesses on its outer peripheral surface 16a and inner peripheral surface 16b. Through the anchoring effect, the adhesion between the adhesive layer 16 and the outer layer 14, and the adhesion between the adhesive layer 16 and the inner layer 12, are improved. The height of the protrusion or the depth of the recess can be 0.1 μm or more and 10 μm or less. More preferably, it is 0.1 μm or more and 5 μm or less. Through the anchoring effect, the adhesion between the adhesive layer 16 and the outer layer 14, and the adhesion between the adhesive layer 16 and the inner layer 12, are improved. The protrusions and recesses are relative and can be arbitrary in their appearance.

[0063] From the perspective of the anchoring effect described above, it is preferable that the number of protrusions or recesses is 2 or more per 100 μm in the length direction at any location. Furthermore, it is preferable that the number is 2 or more per 100 μm in the circumferential direction at any location. On the other hand, from the viewpoint of ensuring the adhesion of acid-modified polypropylene, it is preferable that the number is 100 or less per 100 μm in the length direction at any location. Furthermore, it is preferable that the number is 100 or less per 100 μm in the circumferential direction at any location. The number of protrusions or recesses can be calculated from an image obtained by taking a cross-section of the adhesive layer 16 in a predetermined direction using a scanning electron microscope (SEM) at 5000x magnification and then binding 10 such images together.

[0064] The aforementioned protrusions or recesses are caused by the coordination of organic polymer particles 18, or are formed by changing the extrusion temperature of each layer, increasing the viscosity difference between each layer, etc.

[0065] The tear strength in the longitudinal direction of the adhesive layer 16 is preferably 20 N / mm or more. More preferably, it is 25 N / mm or more, and even more preferably 30 N / mm or more. For example, the above-mentioned tear strength can be achieved by making the adhesive layer 16 a resin composition containing organic polymer particles 18 in an acid-modified polypropylene matrix. The above-mentioned tear strength can be measured as follows: a film with a thickness of 0.3 mm is extruded, and the measurement is performed according to JIS K 6252 using a trouser-type test piece at room temperature and a tensile speed of 100 mm / min.

[0066] The adhesive force at the interface between the adhesive layer 16 and the outer layer 14 is preferably 30 N / cm or more. More preferably, it is 35 N / cm or more, and even more preferably 40 N / cm or more. For example, the adhesive force at the interface can be satisfied by adjusting the acid modification amount of the acid-modified polypropylene, the amine value of the polyamide, the ratio (b / a) of the length a of the outer peripheral surface 14a of the outer layer 14 to the length b of the outer peripheral surface 16a of the adhesive layer 16, and the amount of organic polymer particles 18. The adhesive force can be measured as follows: a 10 mm long strip test piece is made from the laminated tube 10 that is axially halved. The end of the test piece is peeled off with pliers or the like, and the peeled part is grasped. Interlayer peeling is performed using a tensile testing machine, and the result is measured. The tensile speed is set to 25 mm / min, and the average value of the adhesive force (N / cm) when the peel strength is stable for 30 seconds is taken as the adhesive force.

[0067] The laminated tube 10 can be manufactured as follows: First, a composition constituting the inner layer 12, a composition constituting the outer layer 14, and a composition constituting the adhesive layer 16 are prepared separately. Each composition is granulated as needed. Next, using an extruder, each composition is melt-extruded onto a mandrel (co-extrusion molding) to form a tube. Thus, a laminated tube 10 with a three-layer structure, formed by stacking the inner layer 12, adhesive layer 16, and outer layer 14 in a tubular shape from the inside out, can be obtained.

[0068] Preferably, the extrusion molding of each layer is carried out at a temperature of 200~350°C (preferably 220~280°C) and a traction speed of 1~15 m / min (preferably 3~5 m / min). Here, if melt extrusion molding (co-extrusion molding) is carried out at a temperature 20~100°C higher than the melting point of the polyamide of the outer layer 14 (preferably 20~80°C higher), the organic polymer particles 18 in the adhesive layer 16 tend to be located near the interface between the adhesive layer 16 and the outer layer 14 or near the interface between the adhesive layer 16 and the inner layer 12. As a result, the undulation of the outer peripheral surface 16a of the adhesive layer 16 caused by the organic polymer particles 18 can be increased, the contact area between the inner peripheral surface of the outer layer 14 and the outer peripheral surface 16a of the adhesive layer 16 can be increased, and the interlayer adhesion between the adhesive layer 16 and the outer layer 14 can be improved.

[0069] The laminated tube 10 constructed as described above has an adhesive layer 16 containing acid-modified polypropylene between an inner layer 12 containing polypropylene and an outer layer 14 containing polyamide. Within an axial range of 100 μm, the ratio (b / a) of the length a of the outer peripheral surface 14a of the outer layer 14 to the length b of the outer peripheral surface 16a of the adhesive layer 16 is 1.003 or more and 1.050 or less. The length b of the outer peripheral surface 16a of the adhesive layer 16, which bonds the inner layer 12 containing polypropylene to the outer layer 14 containing polyamide, is longer than the length a of the outer peripheral surface 14a of the outer layer 14. Therefore, the contact area between the inner peripheral surface of the outer layer 14 and the outer peripheral surface 16a of the adhesive layer 16 is increased, resulting in excellent interlayer adhesion between the adhesive layer 16 and the outer layer 14. Furthermore, since the adhesive layer 16 contains acid-modified polypropylene, its adhesion to the outer layer 14 containing polyamide is further improved. Furthermore, both the adhesive layer 16 and the inner layer 12 are layers containing polypropylene, thus the interlayer adhesion between the adhesive layer 16 and the inner layer 12 is also excellent. Consequently, the interlayer adhesion between the polypropylene-containing inner layer 12 and the polyamide-containing outer layer 14 is excellent.

[0070] The laminated tube 10 is used for cooling radiator hoses, heater hoses, air conditioning hoses, and battery packs for electric vehicles and fuel cell vehicles. In addition, the laminated tube 10 can be used not only in automobiles, but also in other transportation machinery (aircraft, forklifts, loaders, cranes and other industrial transport vehicles, railway vehicles, etc.).

[0071] In the laminated tube 10, the inner diameter is preferably in the range of 2 to 40 mm, more preferably in the range of 4 to 35 mm. Furthermore, the thickness of the inner layer 12 is preferably in the range of 0.1 to 1.9 mm, more preferably in the range of 0.2 to 1.8 mm. Additionally, the thickness of the outer layer 14 is preferably in the range of 0.1 to 1.9 mm, more preferably in the range of 0.2 to 1.8 mm. Furthermore, the thickness of the adhesive layer 16 is preferably in the range of 0.05 to 0.5 mm, more preferably in the range of 0.05 to 0.3 mm.

[0072] In the case where the laminated tube 10 is used for transporting vehicle coolant, a predetermined heat resistance is sometimes required for the inner layer 12 containing polypropylene. In this case, it is possible to incorporate an anti-aging agent into the polypropylene-containing composition of the inner layer 12. If an anti-aging agent is incorporated as the material of the vehicle coolant transport pipe, there is a tendency for components from the anti-aging agent to be extracted (leaked) into the coolant. This poses a risk of clogging filters in the vehicle cooling system, and the extracted components may increase the conductivity of the coolant, leading to short circuits, leakage, etc. Therefore, excellent heat resistance and resistance to extraction are required.

[0073] When using anti-aging agents, heat resistance and extraction resistance are inversely related. That is, from the perspective of improving heat resistance, it is necessary to increase the amount of anti-aging agent; however, if the amount of anti-aging agent is increased, it becomes difficult to suppress the extraction of components from the anti-aging agent into the coolant, thus failing to ensure extraction resistance. Conversely, if specific polypropylene and specific anti-aging agents are used together in a specific ratio within a certain range, both heat resistance and extraction resistance are excellent.

[0074] The melt flow rate (MFR) of the polypropylene in the inner layer 12 is preferably 0.2 g / 10 min or more and less than 2.0 g / 10 min. Furthermore, the melting point is preferably 145°C or more. This results in excellent extraction resistance and heat resistance. By ensuring that the MFR is less than 2.0 g / 10 min and the melting point is 145°C or more, the compatibility of the polypropylene with the anti-aging agent is improved, and the amount of extraction into the coolant is suppressed. Therefore, a high balance between heat resistance and extraction resistance can be achieved.

[0075] Furthermore, based on the above viewpoints, the MFR of polypropylene is more preferably 1.8 g / 10 min or less, more preferably 1.6 g / 10 min or less, and particularly preferably 1.5 g / 10 min or less. On the other hand, from the viewpoint of ensuring flowability, the MFR of polypropylene is preferably 0.3 g / 10 min or more, more preferably 0.4 g / 10 min or more, and more preferably 0.5 g / 10 min or more. The MFR was measured according to JIS K7210:1999 under conditions of 230°C and 2.16 kg load.

[0076] Furthermore, based on the above viewpoints, the melting point of polypropylene is more preferably 148°C or higher, more preferably 150°C or higher, and particularly preferably 155°C or higher. On the other hand, there is no particular upper limit to the melting point of polypropylene, but it is preferably 175°C or lower. The melting point of polypropylene can be determined according to the method of JIS K7121-2012.

[0077] From the viewpoint of heat resistance and extractability, the melting point of the anti-aging agent is preferably 60°C or higher. More preferably, it is 70°C or higher, even more preferably 75°C or higher, and particularly preferably 80°C or higher or 90°C or higher. Furthermore, it is preferably 300°C or lower, and more preferably 250°C or lower.

[0078] The molecular weight of the anti-aging agent is not particularly limited, but is preferably 550-1300, more preferably 580-1280, even more preferably 600-1250, and particularly preferably 700-1200.

[0079] Examples of anti-aging agents include phenolic anti-aging agents, amine-based anti-aging agents, imidazole-based anti-aging agents, and phosphate-based anti-aging agents. An anti-aging agent can consist of only one of these types or two or more. From the viewpoint of superior heat resistance, phenolic anti-aging agents are preferred. Furthermore, among phenolic anti-aging agents, hindered phenolic anti-aging agents are particularly preferred from the viewpoint of heat resistance.

[0080] Examples of hindered phenolic anti-aging agents include pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., BASF's "Irganox 1010", melting point 110-125℃, molecular weight 1178), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (e.g., BASF's "Irganox 3114", melting point 220-222℃, molecular weight 784), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)trimethylbenzylene (e.g., BASF's "Irganox 1330", melting point 248-252℃, molecular weight 775), and 6-(4-hydroxy-3,5-di-tert-butylaniline)-2,4-bis(octylthio)- 1,3,5-Triazine (e.g., BASF's "Irganox 565", melting point 91~96℃), 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., BASF's "Irganox 1035", melting point 63~78℃), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] (e.g., BASF's "Irganox 1098", melting point 156~161℃, molecular weight 637), 1,6-hexanediolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., BASF's "Irganox 259", melting point 104~108℃, molecular weight 639), etc.

[0081] From the viewpoint of heat resistance and extractability, the content of the anti-aging agent is preferably a small amount relative to polypropylene. Specifically, it is preferably 0.1 parts by weight or more and 1.0 parts by weight or less relative to 100 parts by weight of polypropylene.

[0082] The laminated tubes involved in this invention can be as follows: Figure 1 The three-layer laminated tube shown can also be a two-layer laminated tube with the inner and outer layers of the adhesive layer 16 omitted. In addition, other resin layers, rubber layers, and reinforcing layers (layers formed by braiding or weaving reinforcing filaments such as PET filaments) can be laminated on the outer peripheral surface of the outer layer.

[0083] Figure 3 This refers to a laminated tube according to another embodiment of the present invention. Figure 4 express Figure 3 The cross-sectional view of the laminated tube shown is within an axial range of 100 μm.

[0084] like Figure 3As shown, another embodiment of the present invention relates to a laminated tube 20 having an inner layer 22 and an outer layer 24. Each of the inner layer 22 and the outer layer 24 is configured as a tube. The laminated tube 20 has a two-layer laminated structure formed by stacking the inner layer 22 and the outer layer 24 in a tubular shape from the inside. The outer layer 24 is disposed in contact with the inner layer 22 on the outer peripheral surface of the inner layer 22.

[0085] The laminated tube 20 has an inner layer 22 containing polypropylene and an outer layer 24 containing polyamide. The outer layer 24 containing polyamide ensures strength and heat resistance. The inner layer 22 containing polypropylene inhibits the contact between the fluid flowing within the laminated tube 20 and the outer layer 24 containing polyamide, thereby suppressing strength reduction caused by hydrolysis. The inner layer 22 containing polypropylene is protected by the outer layer 24 containing polyamide relative to the internal pressure of the fluid flowing within the laminated tube 20; therefore, the interlayer adhesion between the inner layer 22 containing polypropylene and the outer layer 24 containing polyamide is important. Generally, polypropylene and polyamide have low adhesion; therefore, in the laminated tube 20, the inner layer 22 in contact with the outer layer 24 containing polyamide uses acid-modified polypropylene.

[0086] exist Figure 4 In the diagram, 24a is the outer peripheral surface of the outer layer 24. 22a is the outer peripheral surface of the inner layer 22. 22b is the inner peripheral surface of the inner layer 22. The axial direction of the laminated tube 20 is the direction in which the laminated tube 20 extends. Figure 3 , Figure 4 The X direction in the equation.

[0087] like Figure 4 As shown, in the laminated tube 20, the ratio (b' / a') of the length a' of the outer peripheral surface 24a of the outer layer 24 to the length b' of the outer peripheral surface 22a of the inner layer 22 within a 100 μm axial range is 1.003 or more and 1.050 or less. The outer peripheral surface 24a of the outer layer 24 is the part that contacts the forming die during extrusion molding and is the part that suppresses the generation of undulations during extrusion molding. Therefore, it can be expressed as a length that is undulating and close to a straight line. The ratio (b' / a') of the length b' of the outer peripheral surface 22a of the inner layer 22 to the length a' of the outer peripheral surface 24a is greater than 1.000. By making the length b' of the outer peripheral surface of the inner layer 22 longer than the length a' of the outer peripheral surface of the outer layer 24, the contact area between the inner peripheral surface of the outer layer 24 and the outer peripheral surface of the inner layer 22 increases, thus the interlayer adhesion between the inner layer 22 and the outer layer 24 is excellent.

[0088] In this invention, the undulation of the outer peripheral surface of the inner layer 22 is intentionally increased to increase the contact area between the outer peripheral surface of the inner layer 22 and the inner peripheral surface of the outer layer 24, thereby improving the interlayer adhesion between the inner layer 22 and the outer layer 24. If the ratio (b' / a') is less than 1.003, the improvement in adhesion due to the increase in contact area is insufficient. Furthermore, if the ratio (b' / a') is greater than 1.050, the undulation of the outer peripheral surface of the inner layer 22 becomes excessive, and the adhesion decreases. Methods for increasing the undulation of the outer peripheral surface of the inner layer 22 include changing the extrusion temperature of each layer during extrusion molding, increasing the viscosity difference between layers, etc., to form undulations larger than naturally occurring unavoidable undulations, and incorporating organic polymer particles 18 into the material of the inner layer 22 to create protrusions or depressions on the outer peripheral surface of the inner layer 22 caused by the organic polymer particles 18.

[0089] From the viewpoint of improving adhesion by increasing the contact area, the ratio (b' / a') is preferably 1.005 or more, more preferably 1.007 or more. Furthermore, from the viewpoint of suppressing the decrease in adhesion caused by increased undulations, the ratio (b' / a') is preferably 1.040 or less, more preferably 1.030 or less.

[0090] The length a' of the outer peripheral surface 24a of the outer layer 24 and the length b' of the outer peripheral surface 22a of the inner layer 22 can be determined from an image obtained by scanning electron microscopy (SEM) of a cross-section observed by dividing the laminated tube 20 in half along the axial direction. The aforementioned lengths a' and b' can be measured in the same manner as the lengths a and b of the laminated tube 10.

[0091] The inner layer 22 comprises acid-modified polypropylene. As the matrix polymer, acid-modified polypropylene is included. This results in excellent adhesion to the outer layer 14, which comprises polyamide. Preferably, the inner layer 22 is composed of a resin composition comprising particles 18 of an organic polymer within the matrix of acid-modified polypropylene, using acid-modified polypropylene as the matrix polymer. The matrix polymer is the main component of the inner layer 22. The main component is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The polymer component in the inner layer 22 may consist only of acid-modified polypropylene, or it may include polymer components such as unmodified polypropylene. In this case, the acid-modified polypropylene in the polymer component of the inner layer 22 is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Furthermore, the inner layer 22 may not necessarily contain particles 18 of an organic polymer.

[0092] The inner layer 22 of the laminated tube 20 has the same composition as the adhesive layer 16 of the laminated tube 10. The composition of the acid-modified polypropylene, the composition of the organic polymer particles 28, and other related additives are the same as those of the adhesive layer 16 of the laminated tube 10. Furthermore, a predetermined anti-aging agent may be added to the inner layer 22 of the laminated tube 20, similar to that of the inner layer 12 of the laminated tube 10. Additionally, the polypropylene of the inner layer 22 of the laminated tube 20 may have a predetermined MFR, similar to that of the inner layer 12 of the laminated tube 10.

[0093] The outer layer 24 in the laminated tube 20 has the same structure as the outer layer 14 in the laminated tube 10.

[0094] like Figure 4 As shown, in the laminated tube 20, the outer peripheral surface 22a of the inner layer 22 may have one or more protrusions or recesses. Through the anchoring effect, the adhesion between the inner layer 22 and the outer layer 24 is improved. The height of the protrusion or the depth of the recess is preferably 0.1 μm or more and 10 μm or less. More preferably, it is 0.1 μm or more and 5 μm or less. Through the anchoring effect, the adhesion between the inner layer 22 and the outer layer 24 is improved. The protrusions and recesses are relative and can be arbitrary in appearance.

[0095] From the perspective of the anchoring effect described above, it is preferable that the number of protrusions or recesses is 2 or more per 100 μm in the length direction at any given location. Furthermore, it is preferable that the number is 2 or more per 100 μm in the circumferential direction at any given location. On the other hand, from the viewpoint of ensuring the adhesion of acid-modified polypropylene, it is preferable that the number is 100 or less per 100 μm in the length direction at any given location. Furthermore, it is preferable that the number is 100 or less per 100 μm in the circumferential direction at any given location. The number of protrusions or recesses can be calculated from an image obtained by taking a cross-section of the inner layer 22 in a predetermined direction using a scanning electron microscope (SEM) at 5000x magnification and then binding 10 of these images together.

[0096] The aforementioned protrusions or recesses are caused by the coordination of organic polymer particles 28, or are formed by changing the extrusion temperature of each layer, increasing the viscosity difference between each layer, etc.

[0097] The tear strength of the inner layer 22 in the longitudinal direction is preferably 20 N / mm or more. More preferably, it is 25 N / mm or more, and even more preferably 30 N / mm or more. For example, the above-mentioned tear strength can be achieved by making the inner layer 22 a resin composition containing organic polymer particles 18 in an acid-modified polypropylene matrix. The above-mentioned tear strength can be measured in the same way as the tear strength of the adhesive layer 16 of the laminated tube 10.

[0098] The adhesive strength at the interface between the inner layer 22 and the outer layer 24 is preferably 30 N / cm or more. More preferably, it is 35 N / cm or more, and even more preferably 40 N / cm or more. For example, the above-mentioned adhesive strength at the interface can be satisfied by adjusting the amount of acid modification of the acid-modified polypropylene, the amine value of the polyamide, the ratio of the length a' of the outer peripheral surface of the outer layer 24 to the length b' of the outer peripheral surface of the inner layer 22 (b' / a'), and the amount of organic polymer particles 28. The adhesive strength at the interface can be measured in the same way as the adhesive strength at the interface between the adhesive layer 16 and the outer layer 14 of the laminated tube 10.

[0099] The laminated tube 20 can be manufactured as follows: First, a composition constituting the inner layer 22 and a composition constituting the outer layer 24 are prepared separately. Each composition is granulated as needed. Next, using an extrusion molding machine, each composition is melt-extruded onto a mandrel to form a tube (co-extrusion molding). Thus, a laminated tube 20 having a two-layer structure formed by stacking the inner layer 22 and the outer layer 24 in a tubular shape from the inside can be obtained.

[0100] The extrusion molding of each layer can be carried out at a temperature of 200~350°C (preferably 220~280°C) and a traction speed of 1~15 m / min (preferably 3~5 m / min). Here, if melt extrusion molding (co-extrusion molding) is carried out at a temperature 20~100°C higher than the melting point of the polyamide of the outer layer 24 (preferably 20~80°C higher), the organic polymer particles 28 in the inner layer 22 tend to be located near the interface between the inner layer 22 and the outer layer 24. As a result, the undulation of the outer peripheral surface of the inner layer 22 caused by the organic polymer particles 28 can be increased, the contact area between the inner peripheral surface of the outer layer 24 and the outer peripheral surface of the inner layer 22 can be increased, and the interlayer adhesion between the inner layer 22 and the outer layer 24 can be excellent.

[0101] The laminated tube 20 constructed as described above, having an inner layer 22 containing polypropylene and an outer layer 24 containing polyamide, wherein the polypropylene comprises acid-modified polypropylene, and the ratio (b' / a') of the length a' of the outer peripheral surface of the outer layer 24 to the length b' of the outer peripheral surface of the inner layer 22 within an axial range of 100 μm is 1.003 or more and 1.050 or less. By making the length b' of the outer peripheral surface of the inner layer 22, which forms the bonding interface between the inner layer 22 containing polypropylene and the outer layer 24 containing polyamide, longer than the length a' of the outer peripheral surface of the outer layer 24, the contact area between the inner peripheral surface of the outer layer 24 and the outer peripheral surface of the inner layer 22 increases, thus resulting in excellent interlayer adhesion between the inner layer 22 containing polypropylene and the outer layer 24 containing polyamide. Furthermore, since the inner layer 22 contains acid-modified polypropylene, its adhesion to the outer layer 24 containing polyamide becomes even better. Therefore, the interlayer adhesion between the inner layer 22 containing polypropylene and the outer layer 24 containing polyamide is excellent.

[0102] The laminated tube 20 can also be used for the same purpose as the laminated tube 10. In addition, the inner diameter, the thickness of the inner layer 22, and the thickness of the outer layer 24 of the laminated tube 20 can also be configured to be the same as those of the laminated tube 10.

[0103] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

[0104] Example The present invention will now be described in detail using examples and comparative examples.

[0105] (Examples 1-7, Comparative Examples 1-2) (Outer layer material) Use the commercially available polyamide shown below as the outer layer material.

[0106] (Preparation of adhesive layer material) The components were mixed in the proportions (parts by mass) shown in the table, and then mixed at 200°C for 5 minutes using a twin-screw compounding extruder (Toshiba Machine Manufacturing's "TEM-18SS") to obtain a compound. This compound was then granulated to prepare an adhesive layer material.

[0107] (Preparation of inner layer material) Use commercially available polypropylene as shown below as the inner layer material.

[0108] (Fabrication of laminated tubes) Using the combinations shown in the table, a multilayer extrusion molding machine (manufactured by the Plastics Engineering Research Institute) capable of co-extrusion molding was used to melt-extrude the outer layer material, adhesive layer material, and inner layer material into a tubular shape, producing a three-layer laminated tube (inner layer thickness 0.6 mm, adhesive layer thickness 0.1 mm, outer layer thickness 0.3 mm, inner diameter 12 mm). The extrusion temperature of each material was set to 20°C above its melting point, and the traction speed was set to 3 m / min.

[0109] (Example 8, Comparative Example 3) (Outer layer material) Use the commercially available polyamide shown below as the outer layer material.

[0110] (Preparation of inner layer material) The components were mixed in the proportions (parts by mass) shown in the table, and then mixed at 200°C for 5 minutes using a twin-screw compounding extruder (Toshiba Machine Manufacturing's "TEM-18SS") to obtain a compound. This compound was then granulated to prepare the inner layer material.

[0111] (Fabrication of laminated tubes) Using the combinations shown in the table, a multilayer extrusion molding machine (manufactured by the Plastics Engineering Research Institute) capable of co-extrusion molding was used to melt-extrude the outer and inner layer materials into a tubular shape, producing a two-layer laminated tube (inner layer thickness 0.7 mm, outer layer thickness 0.3 mm, inner diameter 12 mm). The extrusion temperature of each material was set to 20°C above its melting point, and the traction speed was set to 3 m / min.

[0112] The materials used are as follows.

[0113] (Outer layer material) ·PA <1> Polyamide, "SX 8002" manufactured by Daicel Evonik, melting point 211℃, amine value 70.7 mmol / g ·PA <2> Polyamide, DuPont's "Zytel RSLC3060", melting point 223℃, amine value 52.0 mmol / g ·PA <3> Polyamide, Toray's "CM2001", melting point 222℃, amine value 18.0 mmol / g (Materials for adhesive layer) Acid-modified PP <1> Maleic anhydride modified polypropylene, "ADMER QF500" manufactured by Mitsui Chemicals, with a modification amount of 0.27% by mass and a melting point of 165℃. ·EP copolymer <1> Ethylene-propylene copolymer, "TAFMER DF840" manufactured by Mitsui Chemicals. ·EP copolymer <2> Ethylene-propylene copolymer, "TAFMER DF8200" manufactured by Mitsui Chemicals. (Inner layer material) • Block PP: Propylene-α-olefin block copolymer, Prime Polymer's "E-702MG", MFR 1.4g / 10min, melting point 162℃ Acid-modified PP <1> Maleic anhydride modified polypropylene (Mitsui Chemicals' "ADMER QF500"), modification amount 0.27% by mass, melting point 165℃ ·EP copolymer <1> : Ethylene-propylene copolymer ("TAFMER DF840" manufactured by Mitsui Chemicals) ·EP copolymer <2> : Ethylene-propylene copolymer ("TAFMER DF8200" manufactured by Mitsui Chemicals) The resulting laminated tube was halved axially, and its cross-section was photographed at 5000x magnification using a scanning electron microscope (SEM). Ten of these images were then linked together. Based on these images, in a three-layer laminated tube, the length 'a' of the outer circumferential surface of the outer layer and the length 'b' of the outer circumferential surface of the adhesive layer within a 100μm axial range were measured, and their ratio (b / a) was calculated. In a two-layer laminated tube, the length 'a' of the outer circumferential surface of the outer layer and the length 'b' of the outer circumferential surface of the inner layer within a 100μm axial range were measured, and their ratio (b' / a') was calculated. Furthermore, based on these images, the particle size of any 10 organic polymer particles identified within the adhesive layer or inner layer was measured, and their average particle size (μm) was determined. Additionally, in the images, regarding cases where protrusions were identified at the interface between the adhesive layer or the inner layer and the outer layer, the number of protrusions (number per 100μm) at the straight-line distance of the interface was counted. The results are shown in the table described later.

[0114] The characteristics of each of the resulting stacked tubes were evaluated according to the following criteria. The results are shown in the table below.

[0115] <Interface stickiness> The fabricated laminated tube is cut in half, and a 10mm wide strip test piece is made from each half. Then, the end of the test piece is peeled off using pliers. Holding the peeled portion, a tensile testing machine is used to stretch the strip at a speed of 25mm / min to perform interlayer peeling. The average adhesive force (N / cm) is measured when the peel strength remains stable for 30 seconds and recorded as "adhesive force (N / cm)". A bond force of 40N / cm or higher is marked with "◎", 20N / cm or higher but less than 40N / cm is marked with "○", and less than 20N / cm is marked with "×".

[0116]

[0117]

[0118] In Comparative Example 1, in the laminated tube consisting of an inner layer, an outer layer, and an adhesive layer, the ratio (b / a) of the length 'a' of the outer peripheral surface of the outer layer to the length 'b' of the outer peripheral surface of the adhesive layer within an axial range of 100 μm was 1.000, less than 1.003. Furthermore, in Comparative Example 1, no increase in contact area was achieved, and the interlayer adhesion between the adhesive layer and the outer layer was insufficient. In Comparative Example 2, the aforementioned length ratio (b / a) was 1.058, greater than 1.050. Moreover, in Comparative Example 2, the undulation of the outer peripheral surface of the adhesive layer became excessive, and the interlayer adhesion between the adhesive layer and the outer layer became insufficient. On the other hand, the aforementioned length ratio (b / a) of Examples 1-7 was 1.003 or more and 1.050 or less. By making the length 'b' of the outer peripheral surface of the adhesive layer that bonds the inner layer containing polypropylene to the outer layer containing polyamide longer than the length 'a' of the outer peripheral surface of the outer layer, the contact area between the inner peripheral surface of the outer layer and the outer peripheral surface of the adhesive layer is increased, thus resulting in excellent interlayer adhesion between the adhesive layer and the outer layer. Furthermore, since both the adhesive layer and the inner layer are polypropylene-containing layers, the interlayer adhesion between the adhesive layer and the inner layer is also excellent. Therefore, the interlayer adhesion between the polypropylene-containing inner layer and the polyamide-containing outer layer is excellent.

[0119] In Comparative Example 3, in the laminated tube consisting of an inner and an outer layer, the ratio (b' / a') of the length a' of the outer peripheral surface of the outer layer to the length b' of the outer peripheral surface of the adhesive layer within a 100 μm axial range was 1.000, less than 1.003. Furthermore, in Comparative Example 3, no increase in contact area was achieved, and the interlayer adhesion between the inner and outer layers was insufficient. On the other hand, in Example 8, the aforementioned length ratio (b' / a') was 1.003 or more and 1.050 or less. By making the length b' of the outer peripheral surface of the inner layer, which forms the adhesive interface between the polypropylene-containing inner layer and the polyamide-containing outer layer, longer than the length a' of the outer peripheral surface of the outer layer, the contact area between the inner peripheral surface of the outer layer and the outer peripheral surface of the inner layer increases, thus resulting in excellent interlayer adhesion between the polypropylene-containing inner layer and the polyamide-containing outer layer.

[0120] The embodiments and examples of the present invention have been described above, but the present invention is not limited to any of the above embodiments and examples, and various changes can be made without departing from the spirit of the present invention.

[0121] Explanation of reference numerals in the attached figures 10: Laminated tubes; 12: Inner layer; 14: Outer layer; 16: Adhesive layer; 18: Particles of organic polymers; 14a: (Outer) peripheral surface; 16a: (Outer peripheral surface of the adhesive layer); 16b: (Inner circumferential surface of the adhesive layer); 20: Laminated tubes; 22: Inner layer; 24: Outer layer; 28: Particles of organic polymers; 22a: (Inner layer) Outer peripheral surface; 24a: (Outer layer) outer peripheral surface; X: Axial direction of the laminated tube.

Claims

1. A layered pipe which is a layered pipe having an inner layer containing polypropylene and an outer layer containing polyamide, wherein, between the inner layer and the outer layer, there is a bonding layer containing acid-modified polypropylene, the ratio (b / a) of the length a of the outer circumferential surface of the outer layer in the range of 100 μm in the axial direction to the length b of the outer circumferential surface of the bonding layer is 1.003 or more and 1.050 or less.

2. A layered pipe which is a layered pipe having an inner layer containing polypropylene and an outer layer containing polyamide, wherein, the polypropylene contains acid-modified polypropylene, the ratio (b' / a') of the length a' of the outer circumferential surface of the outer layer in the range of 100 μm in the axial direction to the length b' of the outer circumferential surface of the inner layer is 1.003 or more and 1.050 or less. the bonding layer is composed of a resin composition containing particles of an organic polymer in a matrix of acid-modified polypropylene. the inner layer is composed of a resin composition containing particles of an organic polymer in a matrix of acid-modified polypropylene. the particles of the organic polymer are composed of ethylene-propylene copolymer or ethylene polymer. the content of the particles of the organic polymer is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the matrix of the acid-modified polypropylene.

3. The laminate tube of claim 1, wherein, the average particle diameter of the particles of the organic polymer is 0.1 μm or more and 10 μm or less.

4. The laminate tube of claim 2 wherein, the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less.

5. The laminate tube according to claim 3 or 4, wherein the bonding force at the interface of the bonding layer and the outer layer is 30 N / cm or more.

6. The layered tube of any one of claims 3 to 5, wherein, the bonding force at the interface of the inner layer and the outer layer is 30 N / cm or more.

7. The layered tube of any one of claims 3 to 6, wherein, the layered pipe is used for a cooling liquid delivery pipe for a vehicle.

8. The layered tube of any one of claims 1 to 7, wherein, ​ 9. The laminate tube according to claim 8 when dependent on claim 1, wherein, ​ 10. The laminate tube according to claim 8 when dependent on claim 2, wherein ​ 11. The layered tube of any one of claims 1 to 10, wherein, ​

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