Multilayer tube

Abstract

The present invention provides a multilayer tube that has excellent interlayer adhesiveness between an inner layer containing polypropylene and an outer layer containing polyamide.　Provided is a multilayer tube 10 comprising an inner layer 12 that contains polypropylene, an outer layer 14 that contains polyamide, and an adhesive layer 16 that is therebetween and that contains an acid-modified polypropylene, wherein the ratio (b / a) of the length b of an outer peripheral surface 16a of the adhesive layer 16 to the length a of an outer peripheral surface 14a of the outer layer 14 is 1.003-1.050 in a 100-μm range in the axial direction. Also provided is a multilayer tube 20 comprising an inner layer 22 that contains polypropylene and an outer layer 24 that contains polyamide, wherein the polypropylene contains acid-modified polypropylene, and the ratio (b' / a') of the length b' of an outer peripheral surface 22a of the inner layer 22 to the length a' of an outer peripheral surface 24a of the outer layer 24 is 1.003-1.050 in a 100-μm range in the axial direction.

Description

Laminated Tube

[0001] The present invention relates to a laminate tube, and more particularly to a laminate tube suitable as a tube for transporting a coolant in a cooling system of an automobile or the like.

[0002] Coolant transport tubes are used to transport coolants in the cooling systems of gasoline-powered vehicles and electric vehicles. Polyamide resins are often used for these tubes because of their heat resistance. Cost-effective polypropylene resins are also being considered. Furthermore, laminated tubes made of polyamide and polypropylene resins are also being considered.

[0003] JP-T-2008-507436A JP-A-2012-082885A

[0004] A laminated tube of polypropylene resin and polyamide resin has poor adhesion between the resins. Patent Document 2 studies the use of acid-modified polypropylene as the polypropylene resin to improve adhesion with the polyamide resin. However, there is still room for improvement in interlayer adhesion.

[0005] An object of the present invention is to provide a laminated tube having excellent interlayer adhesion between an inner layer containing polypropylene and an outer layer containing polyamide.

[0006] The laminate tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and an adhesive layer containing acid-modified polypropylene is disposed 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 a range of 100 μm in the axial direction is 1.003 or more and 1.050 or less.

[0007] Another laminate tube according to the present invention is a laminate 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.

[0008] In the laminate tube according to the present invention, the adhesive layer may be made of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix. Also, in another laminate tube according to the present invention, the inner layer may be made of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix.

[0009] The organic polymer particles may be composed of an ethylene-propylene copolymer or an ethylene polymer. The content of the organic polymer particles may be 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 average particle size of the organic polymer particles may be 0.1 μm or more and 10 μm or less.

[0010] The amine value of the polyamide is preferably 15 mmol / kg or more and 100 mmol / kg or less. In the laminate tube according to the present invention, the adhesive strength at the interface between the adhesive layer and the outer layer is preferably 30 N / cm or more. In another laminate tube according to the present invention, the adhesive strength at the interface between the inner layer and the outer layer is preferably 30 N / cm or more.

[0011] The laminate tube according to the present invention and the other laminate tube according to the present invention may be used as a coolant transport tube for a vehicle.

[0012] (1) The laminate tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and an adhesive layer containing acid-modified polypropylene is disposed 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 a range of 100 μm in the axial direction is 1.003 or more and 1.050 or less.

[0013] (2) Another laminate tube according to the present invention is a laminate 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.

[0014] (3) In the above (1), the adhesive layer may be made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[0015] (4) In the above (2), the inner layer may be made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[0016] (5) In the above (3) or (4), the organic polymer particles may be composed of an ethylene-propylene copolymer or an ethylene polymer.

[0017] (6) In any one of the above (3) to (5), the content of the organic polymer particles may be 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acid-modified polypropylene matrix.

[0018] (7) In any one of the above (3) to (6), the average particle size of the organic polymer particles may be 0.1 μm or more and 10 μm or less.

[0019] (8) In any one of the above (1) to (7), the amine value of the polyamide may be 15 mmol / kg or more and 100 mmol / kg or less.

[0020] (9) In the above (8) which is dependent on the above (1), the adhesive strength at the interface between the adhesive layer and the outer layer may be 30 N / cm or more.

[0021] (10) In the above (8) which is dependent on the above (2), the adhesive strength at the interface between the inner layer and the outer layer may be 30 N / cm or more.

[0022] (11) In any one of (1) to (10) above, the invention may be used for a coolant transport tube for a vehicle.

[0023] The laminate tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and an adhesive layer containing acid-modified polypropylene between the inner layer and the outer layer, wherein 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 is 1.003 or more and 1.050 or less. Since the length b of the outer peripheral surface of the adhesive layer bonding the inner layer containing polypropylene and the outer layer containing polyamide is 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, resulting in excellent interlayer adhesion between the adhesive layer and the outer layer. Furthermore, since both the adhesive layer and the inner layer contain polypropylene, the interlayer adhesion between the adhesive layer and the inner layer is also excellent. This results in excellent interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide.

[0024] Another laminate tube according to the present invention is a laminate tube having an inner layer containing polypropylene and an outer layer 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 to the length b' of the outer peripheral surface of the inner layer within a 100 μm axial range is 1.003 to 1.050. Since the length b' of the outer peripheral surface of the inner layer, which forms the adhesive interface between the inner layer containing polypropylene and the outer layer containing polyamide, is 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 is increased, resulting in excellent interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide.

[0025] In the laminate tube according to the present invention, when the adhesive layer is composed of a resin composition containing organic polymer particles in an acid-modified polypropylene matrix, the organic polymer particles tend to form an uneven shape on the outer peripheral surface of the adhesive layer, making it easier to make the length b of the outer peripheral surface of the adhesive layer longer than the length a of the outer peripheral surface of the outer layer. This also improves the tear strength in the length direction of the acid-modified polypropylene matrix. This further improves the interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide.

[0026] In another laminate tube according to the present invention, when 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 form an uneven shape on the outer peripheral surface of the inner layer, making it easier to make the length b' of the outer peripheral surface of the inner layer longer than the length a' of the outer peripheral surface of the outer layer. This also improves the tear strength in the length direction of the acid-modified polypropylene matrix. This further improves the interlayer adhesion between the polypropylene-containing inner layer and the polyamide-containing outer layer.

[0027] When the organic polymer particles are composed of an ethylene-propylene copolymer or an ethylene polymer, it is easy to form an uneven shape on the outer peripheral surface of the adhesive layer or the inner layer, and the tear strength in the longitudinal direction of the acid-modified polypropylene matrix is ​​excellently improved.

[0028] Furthermore, when 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, an excellent balance is achieved between the effect of improving the adhesion between the adhesive layer or inner layer and the outer layer by forming an uneven shape on the outer surface of the adhesive layer or inner layer to increase the contact area, and the effect of improving the adhesion by the acid-modified polypropylene and polyamide.

[0029] Furthermore, when the average particle size of the organic polymer particles is 0.1 μm or more and 10 μm or less, an excellent balance is achieved between the effect of improving the adhesion between the adhesive layer or inner layer and the outer layer by forming an uneven shape on the outer surface of the adhesive layer or inner layer to increase the contact area, and the effect of improving the adhesion by the acid-modified polypropylene and polyamide.

[0030] When 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, thereby improving the adhesion between the adhesive layer and the outer layer or the adhesion between the inner layer and the outer layer.

[0031] In the laminate tube according to the present invention, when the adhesive strength at the interface between the adhesive layer and the outer layer is 30 N / cm or more, the adhesiveness between the adhesive layer and the outer layer is excellent. In another laminate tube according to the present invention, when the adhesive strength at the interface between the inner layer and the outer layer is 30 N / cm or more, the adhesiveness between the inner layer and the outer layer is excellent.

[0032] The laminate tube according to the present invention and the other laminate tube according to the present invention are suitable for use as a coolant transport tube for a vehicle.

[0033] 1 is a structural diagram showing a laminate tube according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of the laminate tube shown in FIG. 1 taken along a range of 100 μm in the axial direction; FIG. 3 is a structural diagram showing a laminate tube according to another embodiment of the present invention; and FIG. 4 is a cross-sectional view of the laminate tube shown in FIG. 3 taken along a range of 100 μm in the axial direction.

[0034] The laminate tube according to the present invention will be described in detail below. Fig. 1 is a structural diagram of a laminate tube according to one embodiment of the present invention. Fig. 2 is a cross-sectional view of the laminate tube shown in Fig. 1 in the range of 100 µm in the axial direction.

[0035] As shown in Figure 1, a laminate 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 in a tubular shape. The laminate tube 10 has a three-layer laminate structure in which, from the inside out, the inner layer 12, adhesive layer 16, and outer layer 14 are laminated in a tubular shape. The adhesive layer 16 is disposed between the inner layer 12 and the outer layer 14 as a layer that bonds the inner layer 12 and the outer layer 14. The adhesive layer 16 is disposed on the outer peripheral surface of the inner layer 12 in contact with the inner layer 12. The outer layer 14 is disposed on the outer peripheral surface of the adhesive layer 16 in contact with the adhesive layer 16.

[0036] The laminate 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 fluid flowing through the laminate tube 10 from coming into contact with the outer layer 14 containing polyamide, thereby preventing a decrease in strength due to hydrolysis. The inner layer 12 containing polypropylene is protected by the outer layer 14 containing polyamide against the internal pressure of the fluid flowing through the laminate tube 10, so interlayer adhesion between the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide is important. Because polypropylene and polyamide generally have low adhesive properties, the laminate tube 10 includes an adhesive layer 16 that bonds the inner layer 12 and the outer layer 14. The adhesive layer 16 is a layer containing acid-modified polypropylene.

[0037] 2, 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 laminate tube 10 is the direction in which the laminate tube 10 extends, which is the X direction in FIGS.

[0038] As shown in Figure 2, in the laminate 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 portion that comes into contact with the molding die during extrusion molding, and is the portion where the generation of undulations during extrusion molding is suppressed. Therefore, it can be expressed as a length that is nearly straight and free of undulations. 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 exceeds 1. Since the length b of the outer surface 16a of the adhesive layer 16 that bonds the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide is longer than the length a of the outer surface 14a of the outer layer 14, the contact area between the inner surface of the outer layer 14 and the outer surface 16a of the adhesive layer 16 is increased, resulting in excellent interlayer adhesion between the adhesive layer 16 and the outer layer 14.

[0039] In the present invention, the waviness 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 increased contact area is insufficient. Furthermore, if the ratio (b / a) is greater than 1.050, the waviness of the outer peripheral surface 16a of the adhesive layer 16 becomes too large, resulting in reduced adhesion. Methods for increasing the waviness 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 the layers, thereby creating waviness greater than the naturally occurring, unavoidable waviness, and incorporating organic polymer particles 18 into the material of the adhesive layer 16 to create protrusions or depressions due to the organic polymer particles 18 on the outer peripheral surface 16a of the adhesive layer 16.

[0040] The ratio (b / a) is preferably 1.005 or more, more preferably 1.007 or more, from the viewpoint of improving adhesiveness due to an increased contact area, and is preferably 1.040 or less, more preferably 1.030 or less, from the viewpoint of suppressing a decrease in adhesiveness due to an increased waviness.

[0041] 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 cutting the laminated tube 10 in half in the axial direction, photographing the cross section observed with a scanning electron microscope (SEM) at a magnification of 5000 times, and connecting ten of the images.

[0042] The inner layer 12 is composed of a composition containing polypropylene. The inner layer 12 contains polypropylene 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.

[0043] Examples of the polypropylene for the inner layer 12 include propylene-based polymers such as propylene homopolymers, propylene-α-olefin random copolymers, and propylene-α-olefin block copolymers. Of 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. Of these, ethylene, 1-butene, and 1-hexene are preferred, with ethylene being particularly preferred.

[0044] The propylene-α-olefin block copolymer is not limited to a block copolymer having at least a block of continuous propylene monomer and a block of continuous α-olefin monomer, but also encompasses, for example, an alloy (mixture) having an island-sea structure in which a polypropylene component such as a propylene homopolymer constitutes a sea phase and a polyethylene component and / or an ethylene-based rubber component constitutes an island phase. Examples of the polyethylene component include ethylene-based copolymers such as ethylene homopolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and copolymers of ethylene and α-olefins (ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer). Examples of the ethylene-based rubber component include ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), and ethylene-octene copolymer (EOR). The content of the polyethylene component and / or ethylene rubber component in the entire alloy (mixture) is, for example, 1 to 49 mass %, or 2.5 to 20 mass %.

[0045] In addition to polypropylene, the composition constituting the inner layer 12 may contain, as needed, stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, antioxidants, etc. Furthermore, the composition constituting the inner layer 12 may be prepared by melt-kneading these materials and then pelletizing them, as needed.

[0046] 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 may be an aliphatic polyamide or an aromatic polyamide. As the polyamide, an aliphatic polyamide is more preferred from the viewpoint of affinity with polypropylene, etc.

[0047] From the viewpoint of improving adhesion to acid-modified polypropylene, the polyamide preferably has an amine value of 15 mmol / kg or more. It is more preferably 20 mmol / kg or more, and even more preferably 25 mmol / kg or more. On the other hand, from the viewpoint of excellent extrusion moldability, the amine value is preferably 100 mmol / kg or less. It is more preferably 80 mmol / kg or less, and even more preferably 60 mmol / kg or less. The amine value of polyamide indicates the number of mmoles of amine contained in 1 kg of polyamide solids. The outer layer 14 preferably contains 50% by mass or more of a polyamide exhibiting a specific amine value. It is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0048] Examples of polyamides exhibiting a specific amine value 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), and aromatic polyamides such as polyamide 6T (PA6T), polyamide 9T (PA9T), and polyamide 10T (PA10T). As the polyamide for the outer layer 14, one of these may be used alone, or two or more may be used in combination.

[0049] From the viewpoint of heat resistance, the polyamide preferably has a melting point of 160°C or higher, more preferably 170°C or higher. On the other hand, from the viewpoint of ensuring adhesiveness, the melting point is preferably 280°C or lower, more preferably 270°C or lower.

[0050] In addition to polyamide, the composition constituting the outer layer 14 may contain, as needed, stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, antioxidants, etc. Furthermore, the composition constituting the outer layer 14 may be prepared by melt-kneading these materials and then pelletizing them, as needed.

[0051] The adhesive layer 16 contains acid-modified polypropylene as a matrix polymer. This provides excellent adhesion to the outer layer 14, which contains polyamide. The adhesive layer 16 preferably contains acid-modified polypropylene as a matrix polymer and is composed of a resin composition containing organic polymer particles 18 in the acid-modified polypropylene matrix. The matrix 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 of the adhesive layer 16 may be composed solely of acid-modified polypropylene, or may also contain a polymer component such as polypropylene that is not modified with acid. In this case, the acid-modified polypropylene preferably accounts for 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of the polymer components of the adhesive layer 16. Note that the adhesive layer 16 does not necessarily have to contain organic polymer particles 18.

[0052] The acid in the acid-modified polypropylene includes 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. Among these, maleic acid and maleic anhydride are particularly preferred from the viewpoint of reactivity with polyamide.

[0053] The amount of acid modification in the acid-modified polypropylene is preferably 0.05% by mass or more, from the viewpoint of improving adhesion to the outer layer 14, and more preferably 0.1% by mass or more. On the other hand, from the viewpoint of ensuring heat resistance, the amount of acid modification is preferably 7% by mass or less, and more preferably 5% by mass or less. Furthermore, from the viewpoint of ensuring heat resistance, the acid-modified polypropylene preferably has a melting point of 130°C or more, and more preferably 140°C or more. On the other hand, from the viewpoint of ensuring adhesion, and the like, the melting point is preferably 180°C or less, and more preferably 170°C or less.

[0054] The organic polymer particles 18 are disposed within the matrix polymer (acid-modified polypropylene) of the adhesive layer 16. The inclusion of the organic polymer particles 18 facilitates the formation of convex and concave portions (uneven shapes) on the outer peripheral surface 16a and inner peripheral surface 16b of the adhesive layer 16, as shown in FIG. 2 . This facilitates making the length b of the outer peripheral surface 16a of the adhesive layer 16 longer than the length a of the outer peripheral surface 14a of the outer layer 14. Furthermore, in the extrusion-molded laminate tube 10, the matrix polymer (acid-modified polypropylene) of the adhesive layer 16, which is oriented in the longitudinal direction, is prone to fibrous tearing, weakening the tear strength in the longitudinal direction. The organic polymer particles 18 disposed within the matrix polymer of the adhesive layer 16 act as an obstacle to tear forces in the longitudinal direction, thereby improving the tear strength in the longitudinal direction.

[0055] Examples of the organic polymer particles 18 include organic polymer particles 18 such as rubber and resin. Examples of rubber materials include ethylene-propylene copolymer, ethylene-octene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, and ethyl acrylate. Examples of resins include polyethylene. As the organic polymer particles 18, one of these materials may be used alone, or two or more may be used in combination. Among these, ethylene-propylene copolymer and polyethylene are more preferred 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 superior effect of improving the tear strength of the acid-modified polypropylene matrix in the length direction.

[0056] The organic polymer particles 18 may be pre-granulated and added to the matrix polymer, or an ungranulated organic polymer may be melt-kneaded with the matrix polymer under specific conditions to form pellets, and then melt-extruded under specific conditions to contain the organic polymer particles 18 in the acid-modified polypropylene matrix.

[0057] The content of the organic polymer particles 18 is preferably 5 parts by mass or more per 100 parts by mass of the acid-modified polypropylene matrix, from the viewpoints of achieving an excellent effect of improving the adhesion between the adhesive layer 16 and the outer layer 14 by forming an uneven shape on the outer peripheral surface 16a of the adhesive layer 16 to increase the contact area, and of achieving an excellent effect of improving the tear strength in the longitudinal direction of the acid-modified polypropylene matrix. It is more preferably 10 parts by mass or more. On the other hand, from the viewpoint of achieving an excellent effect of improving the adhesion between the acid-modified polypropylene and polyamide, it is preferably 20 parts by mass or less per 100 parts by mass of the acid-modified polypropylene matrix, and more preferably 15 parts by mass or less. The content of the organic polymer particles 18 in the adhesive layer 16 can be determined by taking an image at a magnification of 1000 times using a scanning electron microscope (SEM) and binarizing it.

[0058] The average particle size of the organic polymer particles 18 is preferably 0.1 μm or more from the viewpoints of achieving an excellent effect of improving the adhesion between the adhesive layer 16 and the outer layer 14 by forming an uneven shape on the outer peripheral surface 16a of the adhesive layer 16 to increase the contact area, and of achieving an excellent effect of improving the tear strength in the longitudinal direction of the acid-modified polypropylene matrix. It is more preferably 0.3 μm or more. On the other hand, from the viewpoint of achieving an excellent effect of improving the adhesion between the acid-modified polypropylene and polyamide, the average particle size is preferably 10 μm or less. It is more preferably 5 μm or less, and even more preferably 3 μm or less. The average particle size of the organic polymer particles 18 can be expressed by photographing a cross section of the adhesive layer 16 at a magnification of 5000 times using a scanning electron microscope (SEM), measuring the particle sizes of any 10 organic polymer particles 18 observed, and averaging the measured values.

[0059] In addition to the acid-modified polypropylene, the composition constituting the adhesive layer 16 may contain stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, antioxidants, etc. as needed. Furthermore, the composition constituting the adhesive layer 16 may be prepared by melt-kneading these materials and then pelletizing them, as needed.

[0060] As shown in Figure 2, the outer peripheral surface 16a and inner peripheral surface 16b of the adhesive layer 16 preferably have one or more convex or concave portions. The anchor effect improves the adhesion between the adhesive layer 16 and the outer layer 14, and between the adhesive layer 16 and the inner layer 12. The height of the convex portion or the depth of the concave portion is preferably 0.1 µm or more and 10 µm or less, and more preferably 0.1 µm or more and 5 µm or less. The anchor effect improves the adhesion between the adhesive layer 16 and the outer layer 14, and between the adhesive layer 16 and the inner layer 12. The terms convex portion and concave portion are relative terms, and either can be used in expression.

[0061] From the viewpoint of the anchoring effect, it is preferable that the number of the convex portions or concave portions is 2 or more per 100 μm in the longitudinal direction at any position. It is also preferable that the number of the convex portions or concave portions is 2 or more per 100 μm in the circumferential direction at any position. On the other hand, from the viewpoint of ensuring adhesiveness by the acid-modified polypropylene, it is preferable that the number of the convex portions or concave portions is 100 or less per 100 μm in the longitudinal direction at any position. It is also preferable that the number of the convex portions or concave portions is 100 or less per 100 μm in the circumferential direction at any position. The number of the convex portions or concave portions can be calculated by photographing a cross section of the adhesive layer 16 in a predetermined direction at a magnification of 5000 times using a scanning electron microscope (SEM) and connecting 10 of the images.

[0062] The convex or concave portions can be formed by blending the organic polymer particles 18 or by changing the extrusion temperature of each layer to increase the difference in viscosity between the layers.

[0063] The tear strength in the longitudinal direction of the adhesive layer 16 is preferably 20 N / mm or more, more preferably 25 N / mm or more, and even more preferably 30 N / mm or more. For example, the above tear strength can be satisfied by the adhesive layer 16 being composed of a resin composition containing organic polymer particles 18 in a matrix of acid-modified polypropylene. The tear strength can be measured by extruding a film with a thickness of 0.3 mm and using a trouser-type test piece in accordance with JIS K 6252 at room temperature and at a tensile speed of 100 mm / min.

[0064] The adhesive strength at the interface between the adhesive layer 16 and the outer layer 14 is preferably 30 N / cm or more, more preferably 35 N / cm or more, and even more preferably 40 N / cm or more. For example, the 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 (b / a) of the length a of the outer surface 14a of the outer layer 14 to the length b of the outer surface 16a of the adhesive layer 16, and the amount of organic polymer particles 18. The adhesive strength can be measured by preparing a 10 mm strip-shaped test piece from the laminated tube 10 split in half axially, peeling the end of the test piece with nippers or the like, grasping the peeled portion, and performing interlayer delamination using a tensile tester. The tensile speed is 25 mm / min, and the average adhesive strength (N / cm) after the peel strength remains stable for 30 seconds is defined as the adhesive strength.

[0065] The laminate tube 10 can be produced as follows. First, the composition constituting the inner layer 12, the composition constituting the outer layer 14, and the composition constituting the adhesive layer 16 are each prepared. Each composition is pelletized as needed. Next, using an extruder, each composition is melt-extruded (co-extruded) into a tubular shape on a mandrel. This allows for the production of a laminate tube 10 having a three-layer laminate structure in which, from the inside out, the inner layer 12, the adhesive layer 16, and the outer layer 14 are laminated in a tubular shape.

[0066] Each layer is preferably extruded at a temperature of 200 to 350°C (preferably 220 to 280°C) at a take-up speed of 1 to 15 m / min (preferably 3 to 5 m / min). Melt extrusion (co-extrusion) at a temperature 20 to 100°C (preferably 20 to 80°C) higher than the melting point of the polyamide of the outer layer 14 facilitates uneven distribution of the organic polymer particles 18 in the adhesive layer 16 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. This increases the waviness of the outer peripheral surface 16a of the adhesive layer 16 due to the organic polymer particles 18, thereby increasing the contact area between the inner peripheral surface of the outer layer 14 and the outer peripheral surface 16a of the adhesive layer 16, resulting in excellent interlayer adhesion between the adhesive layer 16 and the outer layer 14.

[0067] The laminated tube 10 having the above configuration has an adhesive layer 16 containing acid-modified polypropylene between an inner layer 12 containing polypropylene and an outer layer 14 containing 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 a 100 μm axial range is 1.003 to 1.050. Since the length b of the outer peripheral surface 16a of the adhesive layer 16 bonding the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide is 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 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, adhesion to the outer layer 14 containing polyamide is further improved. Furthermore, since both the adhesive layer 16 and the inner layer 12 contain polypropylene, excellent interlayer adhesion is achieved between the adhesive layer 16 and the inner layer 12. This results in excellent interlayer adhesion between the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide.

[0068] The laminate tube 10 is used as a radiator hose, a heater hose, an air conditioning hose, or a cooling tube for a battery pack of an electric vehicle or a fuel cell vehicle. The laminate tube 10 can also be used not only for automobiles but also for other transportation machinery (industrial transportation vehicles such as airplanes, forklifts, excavators, and cranes, railway vehicles, etc.).

[0069] The inner diameter of the laminate tube 10 is preferably in the range of 2 to 40 mm, more preferably in the range of 4 to 35 mm. 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. 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. 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.

[0070] When the laminate tube 10 is used for transporting vehicle coolant, the polypropylene-containing inner layer 12 may be required to have a certain level of heat resistance. In this case, it is possible to incorporate an antioxidant into the polypropylene-containing composition of the inner layer 12. When an antioxidant is incorporated into the material of a vehicle coolant transport tube, components derived from the antioxidant tend to be extracted (eluted) into the coolant, which may cause clogging of filters in the vehicle cooling system, or the extracted components may increase the conductivity of the coolant, leading to short circuits, electric leakage, etc. Therefore, excellent heat resistance and extraction resistance are required.

[0071] When an antioxidant is used, heat resistance and extraction resistance are at odds with each other. In other words, increasing the amount of antioxidant is required to improve heat resistance. However, increasing the amount of antioxidant makes it difficult to suppress the amount of antioxidant-derived components extracted into the coolant, making it impossible to ensure extraction resistance. In contrast, using a specific polypropylene and a specific antioxidant in combination and keeping the content ratio of both within a specific range results in excellent heat resistance and extraction resistance.

[0072] The polypropylene of the inner layer 12 preferably has a melt flow rate (MFR) of 0.2 g / 10 min or more and less than 2.0 g / 10 min. It also preferably has a melting point of 145°C or higher. This provides excellent extraction resistance and heat resistance. Having an MFR of less than 2.0 g / 10 min and a melting point of 145°C or higher improves the compatibility between the polypropylene and the antioxidant, reducing the amount of extraction into the coolant, thereby achieving a high level of both heat resistance and extraction resistance.

[0073] From the above viewpoints, the MFR of the polypropylene is more preferably 1.8 g / 10 min or less, even 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 the polypropylene is preferably 0.3 g / 10 min or more, more preferably 0.4 g / 10 min or more, and even more preferably 0.5 g / 10 min or more. The MFR is measured in accordance with JIS K7210:1999 under conditions of 230°C and a load of 2.16 kg.

[0074] From the above viewpoints, the melting point of the polypropylene is more preferably 148° C. or higher, even more preferably 150° C. or higher, and particularly preferably 155° C. or higher. On the other hand, the upper limit of the melting point of the polypropylene is not particularly limited, but is preferably 175° C. or lower. The melting point of the polypropylene can be measured by a method in accordance with JIS K7121-2012.

[0075] From the viewpoint of heat resistance and extraction resistance, the antioxidant preferably has a melting point of 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, and particularly preferably 80°C or higher or 90°C or higher. The melting point is preferably 300°C or lower, more preferably 250°C or lower.

[0076] The molecular weight of the antioxidant is not particularly limited, but is preferably 550 to 1,300, more preferably 580 to 1,280, even more preferably 600 to 1,250, and particularly preferably 700 to 1,200, for example.

[0077] Examples of the antiaging agent include phenolic antiaging agents, amine antiaging agents, imidazole antiaging agents, and phosphoric acid antiaging agents. The antiaging agent may be composed of only one of these, or may be composed of two or more of these. Among these, phenolic antiaging agents are preferred from the viewpoint of superior heat resistance. Furthermore, among the phenolic antiaging agents, hindered phenolic antiaging agents are particularly preferred from the viewpoint of heat resistance.

[0078] Examples of hindered phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., "Irganox 1010" manufactured by BASF, melting point 110-125°C, molecular weight 1178), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (e.g., "Irganox 3114" manufactured by BASF, melting point 220-222°C, molecular weight 784), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (e.g., "Irganox 1330" manufactured by BASF, melting point 248-252°C, molecular weight 775), and 6-(4-hydroxy-3,5-di-tert-butylanilino)-2,4-bis(octyl thio)-1,3,5-triazine (for example, "Irganox 565" manufactured by BASF, melting point 91 to 96°C), 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, "Irganox 1035" manufactured by BASF, melting point 63 to 78°C), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] (for example, "Irganox 1098" manufactured by BASF, melting point 156 to 161°C, molecular weight 637), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, "Irganox 259" manufactured by BASF, melting point 104 to 108°C, molecular weight 639), and the like.

[0079] From the viewpoint of heat resistance and extraction resistance, the content of the antioxidant is preferably relatively small relative to the polypropylene, specifically, preferably 0.1 part by mass or more and 1.0 part by mass or less relative to 100 parts by mass of polypropylene.

[0080] The laminate tube according to the present invention may be a laminate tube having a three-layer structure as shown in Fig. 1, or may be a laminate tube having a two-layer structure consisting of an inner layer and an outer layer, omitting the adhesive layer 16. Furthermore, other resin layers, rubber layers, or reinforcing layers (layers formed by braiding reinforcing yarns such as PET yarns) may be laminated on the outer peripheral surface of the outer layer.

[0081] Fig. 3 shows a laminate tube according to another embodiment of the present invention, and Fig. 4 shows a cross-sectional view of the laminate tube shown in Fig. 3 taken along a 100 µm axial direction.

[0082] As shown in Fig. 3, a laminate tube 20 according to another embodiment of the present invention has an inner layer 22 and an outer layer 24. Each of the inner layer 22 and the outer layer 24 is configured in a tubular shape. The laminate tube 20 has a two-layer laminate structure in which, from the inside, the inner layer 22 and the outer layer 24 are laminated in a tubular shape. The outer layer 24 is disposed on the outer peripheral surface of the inner layer 22 in contact with the inner layer 22.

[0083] The laminate 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 prevents fluid flowing through the laminate tube 20 from coming into contact with the outer layer 24 containing polyamide, thereby preventing a decrease in strength due to hydrolysis. Because the inner layer 22 containing polypropylene is protected by the outer layer 24 containing polyamide against the internal pressure of the fluid flowing through the laminate tube 20, interlayer adhesion between the inner layer 22 containing polypropylene and the outer layer 24 containing polyamide is important. Because polypropylene and polyamide generally have low adhesiveness, the laminate tube 20 uses acid-modified polypropylene for the inner layer 22 that comes into contact with the outer layer 24 containing polyamide.

[0084] In Fig. 4, 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 laminate tube 20 is the direction in which the laminate tube 20 extends, which is the X direction in Figs. 3 and 4 .

[0085] As shown in FIG. 4 , in the laminate 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 greater and 1.050 or less. The outer peripheral surface 24a of the outer layer 24 is the portion that comes into contact with the molding die during extrusion molding, and is the portion where the generation of undulations during extrusion molding is suppressed. Therefore, it can be expressed as a length that is free of undulations 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 exceeds 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 is increased, resulting in excellent interlayer adhesion between the inner layer 22 and the outer layer 24.

[0086] In the present invention, the waviness 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 increased contact area is insufficient. Furthermore, if the ratio (b' / a') is greater than 1.050, the waviness of the outer peripheral surface of the inner layer 22 becomes too large, resulting in reduced adhesion. Methods for increasing the waviness of the outer peripheral surface of the inner layer 22 include changing the extrusion temperature of each layer during extrusion molding to increase the viscosity difference between the layers, thereby forming waviness larger than the naturally occurring, unavoidable waviness, and incorporating organic polymer particles 18 into the material of the inner layer 22 to generate protrusions or depressions due to the organic polymer particles 18 on the outer peripheral surface of the inner layer 22.

[0087] The ratio (b' / a') is preferably 1.005 or more, more preferably 1.007 or more, from the viewpoint of improving adhesiveness due to an increased contact area. The ratio (b' / a') is preferably 1.040 or less, more preferably 1.030 or less, from the viewpoint of suppressing a decrease in adhesiveness due to an increase in waviness.

[0088] 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 of a cross section taken with a scanning electron microscope (SEM) after axially dividing the laminate tube 20 in half. The lengths a' and b' can be measured in the same manner as the lengths a and b of the laminate tube 10.

[0089] The inner layer 22 contains acid-modified polypropylene. The matrix polymer is acid-modified polypropylene. This provides excellent adhesion to the outer layer 14, which contains polyamide. The inner layer 22 preferably contains acid-modified polypropylene as the matrix polymer and is composed of a resin composition containing organic polymer particles 18 in the acid-modified polypropylene matrix. 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 of the inner layer 22 may be composed solely of acid-modified polypropylene, or may also contain a polymer component such as polypropylene that is not modified with acid. In this case, the acid-modified polypropylene preferably accounts for 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of the polymer component of the inner layer 22. The inner layer 22 does not necessarily have to contain organic polymer particles 18.

[0090] The configuration of the inner layer 22 of the laminate tube 20 is the same as the configuration of the adhesive layer 16 of the laminate tube 10. The configuration of the acid-modified polypropylene, the configuration of the organic polymer particles 28, the configuration of other added components, and the like are the same as the configuration of the adhesive layer 16 of the laminate tube 10. Furthermore, a predetermined antioxidant may be added to the inner layer 22 of the laminate tube 20, as with the inner layer 12 of the laminate tube 10. Furthermore, the polypropylene of the inner layer 22 of the laminate tube 20 may have a predetermined MFR, as with the inner layer 12 of the laminate tube 10.

[0091] The configuration of the outer layer 24 of the laminate tube 20 is similar to the configuration of the outer layer 14 of the laminate tube 10 .

[0092] As shown in Figure 4, in the laminate tube 20, the outer peripheral surface 22a of the inner layer 22 preferably has one or more convex or concave portions. The anchor effect improves the adhesion between the inner layer 22 and the outer layer 24. The height of the convex portion or the depth of the concave portion is preferably 0.1 µm or more and 10 µm or less, more preferably 0.1 µm or more and 5 µm or less. The anchor effect improves the adhesion between the inner layer 22 and the outer layer 24. The terms convex portion and concave portion are relative terms, and either can be used in expression.

[0093] From the viewpoint of the anchoring effect, the number of the convex portions or concave portions is preferably 2 or more per 100 μm in the longitudinal direction at any given position. It is also preferable that the number of the convex portions or concave portions is 2 or more per 100 μm in the circumferential direction at any given position. On the other hand, from the viewpoint of ensuring adhesiveness due to the acid-modified polypropylene, it is preferable that the number of the convex portions or concave portions is 100 or less per 100 μm in the longitudinal direction at any given position. It is also preferable that the number of the convex portions or concatenated portions is 100 or less per 100 μm in the circumferential direction at any given position. The number of the convex portions or concatenated portions can be calculated by photographing a cross section of the inner layer 22 in a predetermined direction at a magnification of 5000 times using a scanning electron microscope (SEM) and connecting 10 of the images.

[0094] The convex or concave portions can be formed by blending the organic polymer particles 28 or by changing the extrusion temperature of each layer to increase the difference in viscosity between the layers.

[0095] The tear strength of the inner layer 22 in the longitudinal direction is preferably 20 N / mm or more, more preferably 25 N / mm or more, and even more preferably 30 N / mm or more. For example, the tear strength can be satisfied by the inner layer 22 being composed of a resin composition containing organic polymer particles 18 in a matrix of acid-modified polypropylene. The tear strength can be measured in the same manner as the tear strength of the adhesive layer 16 of the laminate tube 10.

[0096] 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 35 N / cm or more, and even more preferably 40 N / cm or more. For example, the 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 (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, and the amount of organic polymer particles 28 blended. The adhesive strength at the interface can be measured in the same manner as the adhesive strength at the interface between the adhesive layer 16 and the outer layer 14 of the laminate tube 10.

[0097] The laminate tube 20 can be produced as follows. First, a composition constituting the inner layer 22 and a composition constituting the outer layer 24 are prepared. Each composition is pelletized as needed. Next, using an extruder, each composition is melt-extruded (co-extruded) into a tubular shape on a mandrel. This allows for the production of a laminate tube 20 having a two-layer laminate structure in which, from the inside out, the inner layer 22 and the outer layer 24 are laminated in a tubular shape.

[0098] Each layer is preferably extruded at a temperature of 200 to 350°C (preferably 220 to 280°C) at a take-up speed of 1 to 15 m / min (preferably 3 to 5 m / min). Melt-extrusion (co-extrusion) at a temperature 20 to 100°C (preferably 20 to 80°C) higher than the melting point of the polyamide of the outer layer 24 facilitates uneven distribution of the organic polymer particles 28 in the inner layer 22 near the interface between the inner layer 22 and the outer layer 24. This increases the waviness of the organic polymer particles 28 on the outer peripheral surface of the inner layer 22, thereby increasing the contact area between the inner peripheral surface of the outer layer 24 and the outer peripheral surface of the inner layer 22, resulting in excellent interlayer adhesion between the inner layer 22 and the outer layer 24.

[0099] The laminate tube 20 having the above-described configuration has 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 a 100 μm axial range is 1.003 or greater and 1.050 or less. Since the length b' of the outer peripheral surface of the inner layer 22, which forms the adhesive interface between the polypropylene-containing inner layer 22 and the polyamide-containing outer layer 24, is 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 is increased, resulting in excellent interlayer adhesion between the polypropylene-containing inner layer 22 and the polyamide-containing outer layer 24. Furthermore, since the inner layer 22 contains acid-modified polypropylene, adhesion to the polyamide-containing outer layer 24 is further improved. This results in excellent interlayer adhesion between the polypropylene-containing inner layer 22 and the polyamide-containing outer layer 24.

[0100] The laminate tube 20 can be used for the same purposes as the laminate tube 10. The inner diameter, thickness of the inner layer 22, and thickness of the outer layer 24 of the laminate tube 20 can also be configured in the same manner as the laminate tube 10.

[0101] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0102] The present invention will be described in detail below using examples and comparative examples.

[0103] (Examples 1 to 7, Comparative Examples 1 to 2) (Outer Layer Materials) The following commercially available polyamides were used as outer layer materials.

[0104] (Preparation of adhesive layer material) Each component was blended in the blending ratio (parts by mass) shown in the table, and the blend was mixed at 200°C for 5 minutes using a twin-screw kneading extruder (Toshiba Machine "TEM-18SS") to obtain a blend, which was then pelletized to prepare an adhesive layer material.

[0105] (Preparation of Inner Layer Material) The following commercially available polypropylene was used as the inner layer material.

[0106] (Preparation of Laminated Tubes) The outer layer material, adhesive layer material, and inner layer material in the combinations shown in the table were melt-extruded (co-extrusion molded) into a tubular shape using a multi-layer extruder capable of co-extrusion molding (manufactured by Plastics Engineering Research Institute) to prepare 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 a temperature 20°C higher than the melting point, and the take-up speed was 3 m / min.

[0107] (Example 8, Comparative Example 3) (Outer Layer Material) The commercially available polyamides shown below were used as outer layer materials.

[0108] (Preparation of inner layer material) Each component was blended in the blending ratio (parts by mass) shown in the table, and blended at 200°C for 5 minutes using a twin-screw blender extruder (Toshiba Machine "TEM-18SS") to obtain a blend, which was then pelletized to prepare an inner layer material.

[0109] (Preparation of Laminated Tubes) The outer layer materials and inner layer materials in the combinations shown in Table 1 were melt-extruded (co-extrusion molded) into a tubular shape using a multi-layer extruder capable of co-extrusion molding (manufactured by Plastics Engineering Research Institute) to prepare two-layer laminated tubes (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 a temperature 20°C higher than the melting point, and the take-up speed was 3 m / min.

[0110] The materials used are as follows: (Outer layer materials) PA<1>: Polyamide, "SX8002" manufactured by Daicel-Evonik, melting point 211°C, amine value 70.7 mmol / g PA<2>: Polyamide, "Zytel RSLC3060" manufactured by DuPont, melting point 223°C, amine value 52.0 mmol / g PA<3>: Polyamide, "CM2001" manufactured by Toray, melting point 222°C, amine value 18.0 mmol / g

[0111] (Materials for adhesive layer) Acid-modified PP<1>: maleic anhydride-modified polypropylene, "Admer QF500" manufactured by Mitsui Chemicals, modification amount 0.27 mass%, melting point 165°C EP copolymer<1>: ethylene-propylene copolymer, "Tafmer DF840" manufactured by Mitsui Chemicals EP copolymer<2>: ethylene-propylene copolymer, "Tafmer DF8200" manufactured by Mitsui Chemicals

[0112] (Inner layer materials) Block PP: propylene-α-olefin block copolymer, "E-702MG" manufactured by Prime Polymer, MFR 1.4 g / 10 min, melting point 162°C Acid-modified PP<1>: maleic anhydride-modified polypropylene ("Admer QF500" manufactured by Mitsui Chemicals), modification amount 0.27 mass%, melting point 165°C EP copolymer<1>: ethylene-propylene copolymer ("Tafmer DF840" manufactured by Mitsui Chemicals) EP copolymer<2>: ethylene-propylene copolymer ("Tafmer DF8200" manufactured by Mitsui Chemicals)

[0113] The resulting laminate tube was split in half axially, and its cross section was photographed at 5000x magnification using a scanning electron microscope (SEM). Ten images were then joined together. For three-layer laminate tubes, the length a of the outer surface of the outer layer and the length b of the outer surface of the adhesive layer were measured within a 100 μm axial range, and the ratio (b / a) was calculated. For two-layer laminate tubes, the length a' of the outer surface of the outer layer and the length b' of the outer surface of the inner layer were measured within a 100 μm axial range, and the ratio (b' / a') was calculated. Furthermore, based on the images, the particle sizes of 10 random organic polymer particles observed in the adhesive layer or the inner layer were measured, and their average particle size (μm) was calculated. Furthermore, for those images in which convex portions were observed on the adhesive layer or the inner layer side at the interface between the adhesive layer or the inner layer and the outer layer, the number of convex portions (particles / 100 μm) along the linear distance at the interface was counted. The results are shown in the table below.

[0114] Each of the laminated tubes obtained was evaluated for various properties according to the following criteria, and the results are shown in the table below.

[0115] <Interfacial Adhesion> The prepared laminated tube was cut in half, and a 10 mm wide strip-shaped test piece was prepared from each half. The end of the test piece was then peeled off with nippers, the peeled portion was gripped, and the test piece was pulled at a speed of 25 mm / min using a tensile tester to perform interlayer delamination. The average adhesive strength (N / cm) when the peel strength remained stable for 30 seconds was measured and expressed as "adhesive strength (N / cm)." An adhesive strength of 40 N / cm or more was evaluated as "◎", an adhesive strength of 20 N / cm or more but less than 40 N / cm was evaluated as "◯", and an adhesive strength of less than 20 N / cm was evaluated as "×".

[0116]

[0117]

[0118] In Comparative Example 1, a laminate tube having a three-layer structure consisting of an inner layer, an outer layer, and an adhesive layer has a 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 of 1.000, less than 1.003. Furthermore, in Comparative Example 1, the effect of increasing the contact area is not obtained, resulting in insufficient interlayer adhesion between the adhesive layer and the outer layer. In Comparative Example 2, the length ratio (b / a) is 1.058, greater than 1.050. Furthermore, in Comparative Example 2, the waviness of the outer peripheral surface of the adhesive layer becomes too great, resulting in insufficient interlayer adhesion between the adhesive layer and the outer layer. On the other hand, in Examples 1-7, the length ratio (b / a) is 1.003 or more and 1.050 or less. Since the length b of the outer peripheral surface of the adhesive layer bonding the inner layer containing polypropylene and the outer layer containing polyamide is 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, resulting in excellent interlayer adhesion between the adhesive layer and the outer layer. Furthermore, since both the adhesive layer and the inner layer contain polypropylene, the adhesive layer and the inner layer also have excellent interlayer adhesion, which results in excellent interlayer adhesion between the inner layer containing polypropylene and the outer layer containing polyamide.

[0119] In Comparative Example 3, in a laminate tube having a two-layer structure of an inner layer 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, the effect of increasing the contact area was not obtained, resulting in insufficient interlayer adhesion between the inner layer and the outer layer. On the other hand, in Example 8, the length ratio (b' / a') was 1.003 or more and 1.050 or less. Since 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, is 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 is increased, resulting in excellent interlayer adhesion between the polypropylene-containing inner layer and the polyamide-containing outer layer.

[0120] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention.

[0121] 10 Laminated tube 12 Inner layer 14 Outer layer 16 Adhesive layer 18 Organic polymer particles 14a Outer surface (of outer layer) 16a Outer surface (of adhesive layer) 16b Inner surface (of adhesive layer) 20 Laminated tube 22 Inner layer 24 Outer layer 28 Organic polymer particles 22a Outer surface (of inner layer) 24a Outer surface (of outer layer) X Axial direction of laminated tube

Claims

1. A laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, wherein an adhesive layer containing acid-modified polypropylene is disposed 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.

2. A laminate 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.

3. The laminate tube according to claim 1, wherein the adhesive layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

4. The laminate tube according to claim 2, wherein the inner layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

5. A laminate tube according to claim 3 or 4, wherein the organic polymer particles are composed of an ethylene-propylene copolymer or an ethylene polymer.

6. A laminate tube according to any one of claims 3 to 5, wherein 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.

7. A laminate tube according to any one of claims 3 to 6, wherein the average particle size of the organic polymer particles is from 0.1 μm to 10 μm.

8. A laminate tube according to any one of claims 1 to 7, wherein the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less.

9. A laminate tube according to claim 8 dependent on claim 1, wherein the adhesive strength at the interface between the adhesive layer and the outer layer is 30 N / cm or more.

10. A laminate tube according to claim 8 dependent on claim 2, wherein the adhesive strength at the interface between the inner layer and the outer layer is 30 N / cm or more.

11. The laminate tube according to any one of claims 1 to 10, which is used as a cooling liquid transport tube for vehicles.

Images