Laminated Tube

Abstract

To provide a laminated tube with excellent tearing strength in a longitudinal direction, and an improved interlayer adhesive property.SOLUTION: A laminated tube including an inner layer containing polypropylene and an outer layer containing polyamide includes an adhesive layer between the inner layer and the outer layer, and the adhesive layer is constituted of a resin composition containing particles of organic polymer in a matrix of acid modification polypropylene. Or, in the laminated tube including the inner layer containing polypropylene and the outer layer containing polyamide, the inner layer is constituted of the resin composition containing particles of organic polymer in a matrix of acid modification polypropylene.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[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 a vehicle such as an automobile. [Background technology]

[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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-507436 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-082885 Summary of the Invention [Problem to be solved by the invention]

[0004] Laminated tubes made of polypropylene resin and polyamide resin have poor adhesion between the resins. Patent Document 2 discusses using acid-modified polypropylene as the polypropylene resin to improve adhesion with the polyamide resin. However, in extrusion-molded laminated tubes, each layer tends to be oriented in the longitudinal direction. When acid-modified polypropylene is used as the polypropylene resin, the polypropylene resin tends to tear easily into fibers, reducing tear strength in the longitudinal direction.

[0005] The problem to be solved by the present invention is to provide a laminated tube having excellent tear strength in the longitudinal direction and improved interlayer adhesion. [Means for solving the problem]

[0006] The laminated tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and an adhesive layer is provided between the inner layer and the outer layer, and the adhesive layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[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 inner layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[0008] 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 to 20 parts by mass per 100 parts by mass of the acid-modified polypropylene matrix. The average particle size of the organic polymer particles may be 0.1 to 10 μm.

[0009] In the laminate tube according to the present invention, the outer and inner peripheral surfaces of the adhesive layer may have one or more convex or concave portions. In another laminate tube according to the present invention, the outer peripheral surface of the inner layer may have one or more convex or concave portions. Here, the height of the convex portion or the depth of the concave portion may be 0.1 μm or more and 10 μm or less.

[0010] In the laminate tube according to the present invention, the tear strength in the longitudinal direction of the adhesive layer may be 20 N / mm or more. In another laminate tube according to the present invention, the tear strength in the longitudinal direction of the inner layer may be 20 N / mm or more.

[0011] 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.

[0012] The inner layer may further contain an antioxidant having a melting point of 60°C or higher. The antioxidant may be a phenolic antioxidant. The antioxidant may be a hindered phenolic antioxidant. The polypropylene used in the inner layer may have a melt flow rate of 0.2 g / 10 min to 2.0 g / 10 min measured at 230°C under a load of 2.16 kg, and a melting point of 145°C or higher.

[0013] 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.

[0014] (1) The laminated tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and an adhesive layer is provided between the inner layer and the outer layer, and the adhesive layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[0015] (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 inner layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene.

[0016] (3) In the above (1) or (2), the organic polymer particles may be composed of an ethylene-propylene copolymer or an ethylene polymer.

[0017] (4) In any one of the above (1) to (3), the content of the organic polymer particles may be 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the acid-modified polypropylene matrix.

[0018] (5) In any one of the above (1) to (4), the organic polymer particles may have an average particle size of 0.1 μm or more and 10 μm or less.

[0019] (6) In the above (1), the adhesive layer may have one or more projections or depressions on the outer and inner surfaces thereof.

[0020] (7) In the above (2), the outer peripheral surface of the inner layer may have one or more projections or depressions.

[0021] (8) In the above (6) or (7), the height of the convex portion or the depth of the concave portion may be 0.1 μm or more and 10 μm or less.

[0022] (9) In the above (1), the tear strength in the longitudinal direction of the adhesive layer is preferably 20 N / mm or more.

[0023] (10) In the above (2), the tear strength of the inner layer in the longitudinal direction is preferably 20 N / mm or more.

[0024] (11) In any one of the above (1) to (10), the amine value of the polyamide may be 15 mmol / kg or more and 100 mmol / kg or less.

[0025] (12) In the above (1), the adhesive strength at the interface between the adhesive layer and the outer layer is preferably 30 N / cm or more.

[0026] (13) In the above (2), the adhesive strength at the interface between the inner layer and the outer layer is preferably 30 N / cm or more.

[0027] (14) In any one of the above (1) to (13), the inner layer may further contain an antioxidant having a melting point of 60° C. or higher.

[0028] (15) In the above (14), the antioxidant may be a phenol-based antioxidant.

[0029] (16) In the above (14), the antioxidant may be a hindered phenol-based antioxidant.

[0030] (17) In any one of the above (14) to (16), the polypropylene of the inner layer may be polypropylene having a melt flow rate of 0.2 g / 10 min or more and 2.0 g / 10 min or less, measured at 230°C under a load of 2.16 kg, and a melting point of 145°C or more.

[0031] (18) In any one of the above (1) to (17), the invention may be used for a coolant transport tube for a vehicle. [Effects of the Invention]

[0032] The laminate tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, and further has an adhesive layer between the inner layer and the outer layer, the adhesive layer being made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene, thereby providing excellent tear strength in the longitudinal direction of the acid-modified polypropylene matrix and excellent interlayer adhesion.

[0033] Another laminate tube according to the present invention has an inner layer containing polypropylene and an outer layer containing polyamide, wherein the inner layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene, thereby providing excellent tear strength in the longitudinal direction of the acid-modified polypropylene matrix and excellent interlayer adhesion.

[0034] Here, when the organic polymer particles are composed of an ethylene-propylene copolymer or an ethylene polymer, the effect of improving the tear strength in the length direction of the acid-modified polypropylene matrix is ​​excellent.

[0035] 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 tear strength in the length direction of the acid-modified polypropylene matrix and adhesiveness.

[0036] When the average particle size of the organic polymer particles is 0.1 μm or more and 10 μm or less, an excellent balance between the effect of improving the tear strength in the length direction of the acid-modified polypropylene matrix and adhesiveness is achieved.

[0037] When the adhesive layer of the laminate tube according to the present invention has one or more convex portions or concave portions on the outer peripheral surface and inner peripheral surface thereof, the adhesive layer and the outer layer, and the adhesive layer and the inner layer, respectively, are bonded together by an anchoring effect. When the adhesive layer of another laminate tube according to the present invention has one or more convex portions or concave portions on the outer peripheral surface thereof, the adhesive layer and the inner layer, respectively, are bonded together by an anchoring effect. When the height of the convex portions or the depth of the concave portions is 0.1 μm or more and 10 μm or less, the adhesive layer and the outer layer, and the adhesive layer and the inner layer, and the adhesive layer and the outer layer, respectively, are bonded together by an anchoring effect.

[0038] In the laminate tube according to the present invention, if the tear strength in the longitudinal direction of the adhesive layer is 20 N / mm or more, the laminate tube has excellent tear strength in the longitudinal direction. Also, in another laminate tube according to the present invention, if the tear strength in the longitudinal direction of the inner layer is 20 N / mm or more, the laminate tube has excellent tear strength in the longitudinal direction.

[0039] When the amine value of the polyamide is 15 mmol / kg or more and 100 mmol / kg or less, the polyamide has excellent adhesion to acid-modified polypropylene, thereby improving the adhesion between the adhesive layer and the outer layer or the adhesion between the inner layer and the outer layer.

[0040] 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.

[0041] Furthermore, when the inner layer further contains an antioxidant having a melting point of 60°C or higher, the heat resistance and extraction resistance of the inner layer are improved. When the antioxidant is a phenolic antioxidant, the heat resistance of the inner layer is improved. Furthermore, when the antioxidant is a hindered phenolic antioxidant, the heat resistance is particularly improved.

[0042] Furthermore, if the polypropylene used in the inner layer has a melt flow rate of 0.2 g / 10 min or more and 2.0 g / 10 min or less, measured at 230°C under a load of 2.16 kg, and a melting point of 145°C or more, the heat resistance and extraction resistance of the inner layer are improved.

[0043] 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. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a structural view showing a laminated tube according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the laminated state of the laminate tube shown in FIG. [Figure 3] FIG. 4 is a structural view showing a laminated tube according to another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the laminated state of the laminate tube shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0045] 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 schematic diagram of the laminated state of the laminate tube shown in Fig. 1.

[0046] As shown in FIG. 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. The inner layer 12, the outer layer 14, and the adhesive layer 16 are each 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, the adhesive layer 16, and the 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.

[0047] 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. Because 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, interlayer adhesion between the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide is important. Because polypropylene and polyamide generally have poor adhesive properties, the laminate tube 10 has an adhesive layer 16 arranged thereon to bond the inner layer 12 and outer layer 14 together.

[0048] 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.

[0049] Examples of 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.

[0050] The term "propylene-α-olefin block copolymer" is not limited to block copolymers having at least a block of continuous propylene monomer and a block of continuous α-olefin monomer. It also encompasses alloys (mixtures) with a sea-island structure, in which a polypropylene component such as a propylene homopolymer constitutes the sea phase and a polyethylene component and / or an ethylene-based rubber component constitutes the island phase. Examples of polyethylene components include ethylene-based copolymers such as 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, and ethylene-octene copolymers). Examples of ethylene-based rubber components include ethylene-propylene-diene terpolymers (EPDM), ethylene-propylene copolymers (EPR), ethylene-butene copolymers (EBR), and ethylene-octene copolymers (EOR). The content of the polyethylene component and / or the ethylene-based rubber component in the entire alloy (mixture) is, for example, 1 to 49 mass %, or 2.5 to 20 mass %.

[0051] In addition to polypropylene, the composition constituting the inner layer 12 may contain stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, antioxidants, etc. as needed. Furthermore, the composition constituting the inner layer 12 may be prepared by melt-kneading these materials and then pelletizing them, as needed.

[0052] 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.

[0053] 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.

[0054] 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), as well as 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.

[0055] 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.

[0056] 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.

[0057] The adhesive layer 16 is composed of a resin composition containing acid-modified polypropylene as a matrix polymer and 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 component of the adhesive layer 16.

[0058] 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.

[0059] 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, the melting point is preferably 180°C or less, and more preferably 170°C or less.

[0060] The organic polymer particles 18 are disposed within the matrix polymer (acid-modified polypropylene) of the adhesive layer 16. In the extrusion-molded laminated 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. It is presumed that 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.

[0061] 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 and superior effect of improving the tear strength in the longitudinal direction of the acid-modified polypropylene matrix.

[0062] 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.

[0063] The content of 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 viewpoint of achieving an excellent effect of improving the tear strength in the length direction of the acid-modified polypropylene matrix. More preferably, it is 10 parts by mass or more. On the other hand, from the viewpoint of ensuring the adhesiveness of the acid-modified polypropylene, the content is preferably 20 parts by mass or less per 100 parts by mass of the acid-modified polypropylene matrix, more preferably 15 parts by mass or less. The content of organic polymer particles 18 in adhesive layer 16 can be determined by taking an image at 1000x magnification using a scanning electron microscope (SEM) and performing binarization processing, for example.

[0064] The average particle size of the organic polymer particles 18 is preferably 0.1 μm or more from the viewpoint of achieving an excellent effect of improving the tear strength in the length direction of the acid-modified polypropylene matrix. It is more preferably 0.3 μm or more. On the other hand, from the viewpoint of ensuring the adhesiveness of the acid-modified polypropylene, 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 particle sizes.

[0065] The composition constituting the adhesive layer 16 may contain stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, antioxidants, etc. as needed in addition to the acid-modified polypropylene and organic polymer particles 18. Furthermore, the composition constituting the adhesive layer 16 may be prepared by melt-kneading these materials and then pelletizing them, as needed.

[0066] As shown in FIG. 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 anchoring 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 anchoring 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.

[0067] From the viewpoint of the anchoring effect, the number of the convex 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 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 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 or concave portions is 100 or less per 100 μm in the circumferential direction at any given position. The number of the convex 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.

[0068] 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.

[0069] 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 forming the adhesive layer 16 from a resin composition containing organic polymer particles 18 in a matrix of acid-modified polypropylene. The tear strength can be measured by extruding a 0.3 mm thick film 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.

[0070] 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 amount of organic polymer particles 18, etc. 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.

[0071] 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.

[0072] 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). When the melt extrusion (co-extrusion) is performed 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, the organic polymer particles 18 in the adhesive layer 16 tend to be unevenly distributed near the interface between the adhesive layer 16 and the outer layer 14 or the interface between the adhesive layer 16 and the inner layer 12. This facilitates the formation of protrusions or recesses due to the organic polymer particles 18 on the outer peripheral surface 16a and inner peripheral surface 16b of the adhesive layer 16.

[0073] According to the laminated tube 10 having the above-described configuration, the adhesive layer 16 is formed between the inner layer 12 containing polypropylene and the outer layer 14 containing polyamide, and is made of a resin composition containing organic polymer particles 18 in a matrix of acid-modified polypropylene. This results in excellent tear strength in the longitudinal direction of the acid-modified polypropylene matrix and excellent interlayer adhesion.

[0074] The laminated tube 10 is used as a radiator hose, a heater hose, an air conditioner hose, or a cooling tube for a battery pack of an electric vehicle or a fuel cell vehicle. The laminated 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.).

[0075] The laminate tube 10 preferably has an inner diameter of 2 to 40 mm, more preferably 4 to 35 mm. The thickness of the inner layer 12 is preferably 0.1 to 1.9 mm, more preferably 0.2 to 1.8 mm. The thickness of the outer layer 14 is preferably 0.1 to 1.9 mm, more preferably 0.2 to 1.8 mm. The thickness of the adhesive layer 16 is preferably 0.05 to 0.5 mm, more preferably 0.05 to 0.3 mm.

[0076] When the laminated tube 10 is used to transport 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.

[0077] 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.

[0078] 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 extracted into the coolant, thereby achieving a high level of both heat resistance and extraction resistance.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Examples of the antiaging agent include phenol-based antiaging agents, amine-based antiaging agents, imidazole-based antiaging agents, and phosphoric acid-based 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, phenol-based antiaging agents are preferred from the viewpoint of superior heat resistance. Furthermore, among the phenol-based antiaging agents, hindered phenol-based antiaging agents are particularly preferred from the viewpoint of heat resistance.

[0084] Examples of hindered phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., BASF's "Irganox 1010," melting point 110-125°C, 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°C, molecular weight 784), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (e.g., BASF's "Irganox 1330," 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, BASF's "Irganox 565", melting point 91 to 96 ° C.), 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, BASF's "Irganox 1035", melting point 63 to 78 ° C.), N,N'-hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] (for example, BASF's "Irganox 1098", melting point 156 to 161 ° C., molecular weight 637), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, BASF's "Irganox 259", melting point 104 to 108 ° C., molecular weight 639), and the like.

[0085] 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.

[0086] The laminate tube according to the present invention may be a laminate tube of a three-layer structure as shown in Fig. 1, or may be a laminate tube of 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.

[0087] Fig. 3 shows a laminate tube according to another embodiment of the present invention, and Fig. 4 shows the laminated state of the laminate tube shown in Fig. 3.

[0088] 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 out, 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 22a of the inner layer 22 in contact with the inner layer 22.

[0089] 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 the fluid flowing inside 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 inside 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 poor adhesion, the laminate tube 20 uses acid-modified polypropylene for the inner layer 22 that comes into contact with the outer layer 24 containing polyamide.

[0090] The inner layer 22 is composed of a resin composition containing acid-modified polypropylene as a matrix polymer and containing organic polymer particles 28 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.

[0091] 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, and the configuration of other added components 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.

[0092] 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 .

[0093] As shown in FIG. 4, in the laminate tube 20, the outer peripheral surface 22a of the inner layer 22 preferably has one or more convex portions or concave portions. The anchor effect improves the adhesion between the inner layer 22 and the outer layer 24. The height of the convex portions or the depth of the concave portions 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.

[0094] From the viewpoint of the anchoring effect, the number of the convex 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 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 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 or concave portions is 100 or less per 100 μm in the circumferential direction at any given position. The number of the convex 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.

[0095] 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.

[0096] 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 above tear strength can be satisfied by making the inner layer 22 from a resin composition containing organic polymer particles 18 in a matrix of acid-modified polypropylene. The above tear strength can be measured in the same manner as the tear strength of the adhesive layer 16 of the laminate tube 10.

[0097] 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 amount of organic polymer particles 28, etc. 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.

[0098] 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, respectively. 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.

[0099] 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). When melt extrusion (co-extrusion) is performed 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, the organic polymer particles 28 in the inner layer 22 tend to be unevenly distributed near the interface between the inner layer 22 and the outer layer 24. This facilitates the formation of protrusions or recesses due to the organic polymer particles 28 on the outer peripheral surface 22a of the inner layer 22.

[0100] According to the laminated tube 20 having the above-described configuration, the laminated tube 20 has an inner layer 22 containing polypropylene and an outer layer 24 containing polyamide, and since the inner layer 22 is composed of a resin composition containing organic polymer particles 28 in a matrix of acid-modified polypropylene, the acid-modified polypropylene matrix has excellent tear strength in the longitudinal direction and excellent interlayer adhesion.

[0101] 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.

[0102] 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. [Example]

[0103] The present invention will be described in detail below using examples and comparative examples.

[0104] (Examples 1-7, Comparative Example 1) (outer layer material) The following commercially available polyamides were used as the outer layer materials.

[0105] (Preparation of adhesive layer material) The components were blended in the proportions (parts by mass) shown in the table, and mixed at 200°C for 5 minutes using a twin-screw kneading extruder (Toshiba Machine's "TEM-18SS") to obtain a mixture, which was then pelletized to prepare the adhesive layer material.

[0106] (Preparation of inner layer material) The components were blended in the proportions (parts by mass) shown in the table, and mixed at 200°C for 5 minutes using a twin-screw kneading extruder (Toshiba Machine's "TEM-18SS") to obtain a mixture, which was then pelletized to prepare the inner layer material.

[0107] (Fabrication of laminated tube) The outer layer material, adhesive layer material, and inner layer material were melt-extruded (co-extruded) into a tubular shape using a multi-layer extruder (manufactured by the Plastics Engineering Research Institute) in the combinations shown in the table to produce 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 at 20°C higher than the melting point, and the take-up speed was 3 m / min.

[0108] (Example 8, Comparative Example 2) (outer layer material) The following commercially available polyamides were used as the outer layer materials.

[0109] (Preparation of inner layer material) The components were blended in the proportions (parts by mass) shown in the table, and mixed at 200°C for 5 minutes using a twin-screw kneading extruder (Toshiba Machine's "TEM-18SS") to obtain a mixture, which was then pelletized to prepare the inner layer material.

[0110] (Fabrication of laminated tube) The outer and inner layer materials were melt-extruded (co-extruded) into a tubular shape using a multi-layer extruder (manufactured by the Plastics Engineering Research Institute) in the combinations shown in the table to produce 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 at 20°C higher than the melting point, and the take-up speed was 3 m / min.

[0111] The materials used are as follows: (Material for outer layer) PA <1> Polyamide, Daicel Evonik "SX8002", melting point 211°C, amine value 70.7mmol / g PA <2> Polyamide, DuPont "Zytel RSLC3060", melting point 223°C, amine value 52.0 mmol / g PA <3> Polyamide, Toray "CM2001", melting point 222°C, amine value 18.0 mmol / g

[0112] (Material for adhesive layer) Acid-modified PP <1> Maleic anhydride modified polypropylene, Mitsui Chemicals "Admer QF500", 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] (Inner layer material) Block PP: Propylene-α-olefin block copolymer, Prime Polymer "E-702MG", MFR 1.4g / 10min, melting point 162℃ Antioxidant: Phenolic antioxidant, BASF "IRGANOX 1010", melting point 110-125°C Acid-modified PP <1> Maleic anhydride modified polypropylene (Mitsui Chemicals "Admer QF500"), modification amount 0.27% by mass, melting point 165°C ·EP copolymer <1> : Ethylene-propylene copolymer (Mitsui Chemicals "Tafmer DF840") ·EP copolymer <2> : Ethylene-propylene copolymer (Mitsui Chemicals "Tafmer DF8200")

[0114] The resulting laminated tube was cut in half, and its cross section was photographed at 5000x magnification using a scanning electron microscope (SEM). Ten images were then joined together. Based on the images, the particle sizes of any 10 organic polymer particles observed in the adhesive layer or the inner layer were measured, and their average particle size (μm) was calculated. Furthermore, for images in which convexities were observed on the adhesive layer or inner layer side at the interface between the adhesive layer or the inner layer and the outer layer, the number of convexities (numbers / 100 μm) along the linear distance at the interface was counted. The results are shown in the table below.

[0115] 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.

[0116] <Tear strength> A 0.3 mm thick film was extruded using the adhesive layer material or inner layer material, and the tear strength was measured at room temperature at a tensile speed of 100 mm / min using trouser-type test pieces in accordance with JIS K 6252. Tear strength of 40 N / mm or more was marked "◎", 20 N / mm or more but less than 40 N / mm was marked "○", and less than 20 N / mm was marked "×".

[0117] <Adhesive strength after heat resistance> The prepared laminated tube was heat-treated at 160°C for 1 hour, then split in half. 10 mm-wide strip test pieces were prepared from the split laminated tube. 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 delamination. The average adhesive strength (N / cm) after the peel strength stabilized for 30 seconds was measured and expressed as "adhesive strength (N / cm)." Adhesive strengths of 40 N / cm or greater after heat resistance were evaluated as "◎," those between 20 N / cm and 40 N / cm as "○," and those less than 20 N / cm as "△."

[0118] [Table 1]

[0119] [Table 2]

[0120] In Comparative Example 1, a laminated tube having a three-layer structure consisting of an inner layer, an outer layer, and an adhesive layer is used. The adhesive layer is made of only acid-modified polypropylene, and does not contain organic polymer particles in its matrix. Comparative Example 1 exhibits poor tear strength in the adhesive layer. In contrast, Examples 1-7 exhibit adhesive layers made of acid-modified polypropylene and organic polymer particles, with the organic polymer particles contained in the acid-modified polypropylene matrix. The Examples exhibit excellent tear strength in the adhesive layer. This allows for satisfactory interlayer adhesion.

[0121] In Comparative Example 2, the inner layer of a laminated tube having a two-layer structure of an inner layer and an outer layer is made only of acid-modified polypropylene, and does not contain organic polymer particles in its matrix. Comparative Example 2 exhibits poor tear strength for the inner layer. In contrast, Example 8 exhibits an inner layer made of acid-modified polypropylene and organic polymer particles, with the organic polymer particles contained in the acid-modified polypropylene matrix. Example 8 exhibits excellent tear strength for the inner layer. This allows for satisfactory interlayer adhesion.

[0122] 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. [Explanation of symbols]

[0123] 10. Laminated tube 12 Inner layer 14 Outer layer 16 Adhesive layer 16a (Adhesive layer) outer surface 16b (Adhesive layer) inner surface 18 Organic polymer particles 20 laminated tube 22 Inner layer 22a (inner layer) outer surface 24 Outer layer 28 Organic polymer particles

Claims

1. A laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, an adhesive layer between the inner layer and the outer layer; the adhesive layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene, A laminate tube, 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.

2. A laminated tube having an inner layer containing polypropylene and an outer layer containing polyamide, the inner layer is made of a resin composition containing organic polymer particles in a matrix of acid-modified polypropylene, A laminate tube, 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.

3. 3. The laminate tube according to claim 1, wherein the organic polymer particles are composed of an ethylene-propylene copolymer or an ethylene polymer.

4. 3. The laminate tube according to claim 1, wherein the organic polymer particles have an average particle size of 0.1 μm or more and 10 μm or less.

5. 2. The laminate tube according to claim 1, wherein the adhesive layer has one or more convex or concave portions on the outer and inner peripheral surfaces thereof.

6. 3. The laminate tube according to claim 2, wherein the outer peripheral surface of the inner layer has one or more convex or concave portions.

7. 7. The laminate tube according to claim 5, wherein the height of the convex portions or the depth of the concave portions is 0.1 μm or more and 10 μm or less.

8. 2. The laminate tube according to claim 1, wherein the adhesive layer has a tear strength in the longitudinal direction of 20 N / mm or more.

9. 3. The laminate tube according to claim 2, wherein the inner layer has a tear strength in the longitudinal direction of 20 N / mm or more.

10. 3. The laminate tube according to claim 1, wherein the polyamide has an amine value of 15 mmol / kg or more and 100 mmol / kg or less.

11. 2. The laminate tube according to claim 1, wherein the adhesive strength at the interface between the adhesive layer and the outer layer is 30 N / cm or more.

12. 3. The laminate tube according to claim 2, wherein the adhesive strength at the interface between the inner layer and the outer layer is 30 N / cm or more.

13. 3. The laminate tube according to claim 1, wherein the inner layer further contains an antioxidant having a melting point of 60°C or higher.

14. 14. The laminate tube according to claim 13, wherein the antioxidant is a phenol-based antioxidant.

15. 14. The laminate tube according to claim 13, wherein the antioxidant is a hindered phenol-based antioxidant.

16. 14. The laminate tube according to claim 13, wherein the polypropylene used for the inner layer has a melt flow rate of 0.2 g / 10 min or more and 2.0 g / 10 min or less, measured at 230°C under a load of 2.16 kg, and a melting point of 145°C or more.

17. 3. The laminate tube according to claim 1, which is used as a coolant transport tube for vehicles.

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