Connector / tube connection structure

Abstract

Provided is a connector / tube connection structure that uses a dynamically crosslinked thermoplastic elastomer as a material for a laser light–absorbent tube and that not only achieves excellent weld strength but also has both flexibility and bending strength.　A connector / tube connection structure according to the present invention includes a connector 1 and a tube 2 that is laser-welded to the connector 1. The connector 1 comprises a resin composition [I] that contains a polypropylene resin, and the tube 2 comprises a dynamically crosslinked thermoplastic elastomer composition [II]. The dynamically crosslinked thermoplastic elastomer composition [II] contains components (A)–(D), the component (B) content being 10–45 mass% of the total of the component (A) and component (B) content.　(A) An ethylene / α-olefin / non-conjugated diene copolymer rubber.　(B) A polypropylene resin.　(C) An organic peroxide.　(D) A laser light absorber.

Description

Connector-tube connection structure

[0001] The present invention relates to a connector-tube connection structure in which a connector and a tube are laser-welded together.

[0002] Laser welding is a technique in which laser light that passes through a laser-transparent material is absorbed by a laser-absorbent material, generating heat and melting the material, and heat transfer also melts the laser-transparent material, thereby welding the two materials together.

[0003] For example, in paths for circulating various fluids, such as cooling water flow paths and fuel supply paths in automobiles, a connector-tube connection structure is used, which is obtained by inserting a long tube (sometimes called a "pipe" or "hose") into a connector and laser welding the tube and connector by irradiating them with laser light (Patent Document 1).

[0004] Various materials have been proposed as materials for the laser-transmittable member and the laser-absorbent member. For example, Patent Document 2 describes the use of a dynamically crosslinked thermoplastic elastomer, which is described as being low cost and having a good balance of various properties compared to other thermoplastic elastomers.

[0005] Japanese Patent No. 4161823 Japanese Patent Laid-Open No. 2005-290372

[0006] However, in connector-tube connection structures constructed by laser welding, the research and development of those using dynamically crosslinked thermoplastic elastomers as the laser-absorbent tube material has not yet progressed sufficiently. In particular, there has been almost no research and development focused on improving the weld strength and achieving both bending strength and flexibility when dynamically crosslinked thermoplastic elastomers are used as the laser-absorbent tube material.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and provides a connector-tube connection structure that uses a dynamically crosslinked thermoplastic elastomer as the material for the laser light-absorbing tube, and that has excellent welding strength while also achieving both flexibility and bending strength.

[0008] The present inventors have conducted extensive research to solve the above problems. During the course of their research, they came up with the idea of ​​using a polypropylene-based resin as the material for the connector and a dynamically crosslinked thermoplastic elastomer composition containing a polypropylene-based resin as the material for the tube, in order to increase the weld strength. As a result of further research, they discovered that by using a dynamically crosslinked thermoplastic elastomer composition having a specific composition, it is possible to increase the weld strength while simultaneously achieving both flexibility and bending strength, and thus arrived at the present invention.

[0009] That is, the gist of the present invention is the following [1] to

[11] . [1] A connector-tube connection structure having a connector and a tube laser-welded to the connector, wherein the connector is made of a resin composition [I] containing a polypropylene-based resin, and the tube is made of a dynamically crosslinkable thermoplastic elastomer composition [II], the dynamically crosslinkable thermoplastic elastomer composition [II] containing the following components (A) to (D), wherein the content of component (B) is 10 to 45 mass% relative to the total amount (100 mass%) of components (A) and (B): (A) ethylene-α-olefin-non-conjugated diene copolymer rubber; (B) polypropylene-based resin; (C) organic peroxide; (D) laser beam absorber. [2] The connector-tube connection structure according to [1], wherein the content of component (B) is 25 to 45 mass% relative to the total amount (100 mass%) of components (A) and (B). [3] The connector-tube connection structure according to [1] or [2], wherein the content of the (C) component is 0.05 to 6 parts by mass per 100 parts by mass of the total of the (A) component and the (B) component. [4] The connector-tube connection structure according to any of [1] to [3], wherein the content of the (D) component is 0.01 to 3 parts by mass per 100 parts by mass of the total of the (A) component and the (B) component. [5] The connector-tube connection structure according to any of [1] to [4], wherein the (A) component is an ethylene-propylene-non-conjugated diene copolymer rubber. [6] The connector-tube connection structure according to any of [1] to [5], wherein the (D) component is carbon black. [7] The connector-tube connection structure according to any of [1] to [6], wherein the dynamically crosslinked thermoplastic elastomer composition [II] contains an antioxidant (E), and wherein the melting point of the antioxidant (E) is 60°C or higher. [8] The connector-tube connection structure according to any one of [1] to [7], wherein the resin composition [I] contains a glass fiber filler.[9] The connector-tube connection structure according to any one of [1] to [8], wherein the end of the tube is inserted into the open end edge of the connector, and the connector and the end of the tube are connected by laser welding.

[10] The connector-tube connection structure according to any one of [1] to [9], wherein the tube is an automotive tube.

[11] The connector-tube connection structure according to any one of [1] to [9], wherein the tube is an automotive cooling system tube.

[0010] According to the present invention, it is possible to provide a connector-tube connection structure that has excellent welding strength, as well as flexibility and bending strength.

[0011] 1 is a cross-sectional view showing an example of a connector-tube connection structure of the present invention.

[0012] Next, an embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0013] In this specification, when "X to Y" (X and Y are any numbers) is stated, unless otherwise specified, it includes the meaning of "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." Furthermore, with regard to numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in one stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage. Furthermore, "X and / or Y (X and Y are any configuration)" means at least one of X and Y, and can mean three possibilities: X only, Y only, or X and Y. Furthermore, in this specification, the term "tube" also includes the meaning of "hose."

[0014] A connector-tube connection structure according to one embodiment of the present invention (hereinafter sometimes referred to as "the connection structure") is a connector-tube connection structure having a connector and a tube laser-welded to the connector, wherein the connector is made of a resin composition [I] containing a polypropylene-based resin, and the tube is made of a dynamically crosslinked thermoplastic elastomer composition [II], characterized in that the dynamically crosslinked thermoplastic elastomer composition [II] contains the following components (A) to (D), with the content of component (B) being 10 to 45 mass% relative to the total amount (100 mass%) of components (A) and (B): (A) ethylene-α-olefin-non-conjugated diene copolymer rubber; (B) polypropylene-based resin; (C) organic peroxide; and (D) laser light absorber.

[0015] In the course of research and development into a connector-tube connection structure connected by laser welding, the inventors conceived of a connection structure formed by laser welding a connector made of a resin composition containing a polypropylene-based resin to a tube made of a dynamically crosslinked thermoplastic elastomer composition, and conducted extensive research focusing on the weld strength of laser welding. As a result of this extensive research, the inventors discovered that by using a dynamically crosslinked thermoplastic elastomer composition of a specific composition, the weld strength can be sufficiently increased even if a relatively small amount of polypropylene-based resin is contained. In other words, while it is common technical knowledge that increasing the weld strength with a connector made of a resin composition containing a polypropylene-based resin usually involves containing a relatively large amount of polypropylene-based resin as a tube material, the inventors have succeeded in developing a new technology that can increase the weld strength by containing a relatively small amount of polypropylene-based resin, without using a large amount of polypropylene-based resin. Although the principle behind the excellent effects of the present linked structure is not entirely clear, the present inventors speculate that the interaction between the two components in the dynamically crosslinkable thermoplastic elastomer composition containing (B) a polypropylene-based resin and (C) an organic peroxide reduces the molecular weight of component (B) and improves its meltability, thereby sufficiently increasing the weld strength even when a small amount of polypropylene-based resin is included. After further research, the present inventors discovered that by setting the polypropylene-based resin content within a specific range, not only is the weld strength sufficiently increased, but also high flexibility and bending strength can be achieved. In other words, the present linked structure is extremely useful in that it has excellent weld strength and can achieve both flexibility and bending strength.

[0016] For example, this connection structure is used as a connection structure applied to various fluid flow passages in automobiles, such as cooling water flow passages, lubricating oil flow passages, and fuel supply passages. Because this connection structure has excellent welding strength, it improves the fastening force between the connector and the tube, effectively suppressing fluid leakage, and also has excellent flexibility and bending strength, making it extremely useful when used as each of the above-mentioned flow passages. It is also suitable because it can reduce costs compared to connecting the connector and the tube by press-fitting.

[0017] One embodiment of the present connection structure will be described with reference to the drawings. Referring to FIG. 1 , the connection structure includes a connector 1 and a tube 2, where the connector 1 is a laser-transmissive molded body and the tube 2 is a laser-absorbent molded body. As shown in FIG. 1 , with the end of the tube 2 inserted into the opening edge 1a of the connector 1, laser light is irradiated from the outside of the connector 1, welding the interface between the connector 1 and the tube 2, thereby forming a connection structure having a laser weld. Specifically, laser light transmitted through the laser-transmissive connector 1 is absorbed by the laser-absorbent tube 2, generating heat, which melts the constituent material of the tube 2. The heat is then transferred to the connector 1, melting the constituent material of the connector 1 as well, welding the interface between the connector 1 and the tube 2, thereby forming the connection structure.

[0018] The above-mentioned "having laser light transparency" means, for example, a property of transmitting the remaining laser light without melting even if the laser light is partially absorbed and / or reflected, and having a transmittance that allows the laser light to reach the tube, and the above-mentioned "having laser light absorption" means a property of transmitting and / or reflecting the laser light partially, but absorbing the remainder, and being heated or melted.

[0019] The conditions for irradiating the laser beam are not particularly limited, and may be set so as to provide the energy necessary to melt the joining interface between the connector 1 and the tube 2. For example, the output power and irradiation time (scanning speed) of the laser beam may be appropriately set depending on the laser beam transmittance, thickness, etc. of the connector 1.

[0020] The laser used in this connected structure may be, for example, a laser having an oscillation wavelength of 800 to 1200 nm, and known lasers such as a YAG laser, a semiconductor laser, a glass laser, a ruby ​​laser, a He—Ne laser, a nitrogen laser, a chelate laser, a dye laser, etc. The output of these lasers is not limited, but is preferably, for example, about 5 to 40 W.

[0021] A specific example of this connection structure is a structure in which a connector 1, particularly a quick connector, is laser welded to one or both longitudinal ends of the long tube 2. The quick connector has a structure that allows it to be connected to components (including piping, etc.) such as a cooling device or a device to be cooled, and can be used in such a manner that, for example, the quick connector laser welded to one longitudinal end of the long tube 2 is connected to a component such as a cooling device, and the quick connector laser welded to the other longitudinal end of the long tube 2 is connected to another component such as a device to be cooled.

[0022] As a specific example of the connection structure, it can be used to connect tubes together, i.e., a tube 2 is laser welded to one end of the connector 1, and another tube 2 is laser welded to the other end of the connector 1.

[0023] The connector 1 and the tube 2 that constitute this connection structure will be described in detail below.

[0024] <<Connector>> The connector 1 is made of a laser-transparent material. In this connection structure, the laser-transparent connector 1 is a molded article made of a resin composition [I] containing a polypropylene-based resin.

[0025] <Resin Composition [I]> The resin composition [I] contains a polypropylene-based resin, and may contain optional components such as a reinforcing filler, if necessary.

[0026] [Polypropylene-Based Resin] Examples of polypropylene-based resins include propylene homopolymers (homopolypropylenes), copolymers such as block copolymers, random copolymers, and graft copolymers of propylene with α-olefins other than propylene, such as ethylene and 1-butene, and modified polypropylenes modified with acid anhydrides such as maleic anhydride. Among these, propylene homopolymers (homopolypropylenes) are preferred. These may be used alone or in combination of two or more. For example, one or more selected from the group consisting of propylene homopolymers (homopolypropylenes), copolymers such as block copolymers, random copolymers, and graft copolymers of propylene with α-olefins other than propylene, such as ethylene and 1-butene, may be used in combination with modified polypropylenes modified with acid anhydrides.

[0027] Examples of the α-olefin include α-olefins having 2 to 20 carbon atoms (excluding propylene having 3 carbon atoms), such as ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene. These may be used alone or in combination of two or more.

[0028] The melt flow rate (MFR) of the polypropylene resin is, for example, preferably 0.1 to 50 g / 10 min, more preferably 0.3 to 30 g / 10 min, even more preferably 0.5 to 15 g / 10 min, and particularly preferably 1 to 10 g / 10 min. The MFR of the polypropylene resin is measured in accordance with JIS K 7210 at a measurement temperature of 230°C and a load of 2.16 kg.

[0029] The refractive index of the polypropylene resin is preferably 1.470 to 1.510, more preferably 1.475 to 1.505, even more preferably 1.480 to 1.500, and particularly preferably 1.485 to 1.495. The refractive index indicates the refractive index at 1060 nm of laser light, and was determined by creating an approximation curve from the d-line (587.6 nm), e-line (546.1 nm), and t-line (1013.98 nm) using a precision refractometer KPR-3000.

[0030] The content of the polypropylene resin is, for example, preferably 50 to 100% by mass, more preferably 55 to 90% by mass, even more preferably 60 to 85% by mass, and particularly preferably 65 to 80% by mass, relative to the total amount (100% by mass) of the resin composition [I].

[0031] [Reinforcing Filler] The resin composition [I] may optionally contain a reinforcing filler in order to increase the strength of the connector 1. Examples of reinforcing fillers include glass fiber filler, carbon fiber filler, potassium titanate, glass beads, milled fiber, and talc. Among these, glass fiber filler is preferred.

[0032] Examples of glass fibers that are the material for the glass fiber filler include D-glass (low dielectric constant glass), NE-glass (acid-resistant alkali glass), A-glass (alkali glass), S-glass (high-strength, high-elasticity glass), and alkali-resistant glass. The fiber diameter of the glass fiber filler is preferably, for example, 2.5 to 20 μm, and more preferably 5 to 15 μm. The fiber length of the glass fiber filler is preferably, for example, 2 to 6 mm, and more preferably 3 to 5 mm. Note that, because the glass fibers break and become finer in the melt-kneader or injection molding machine, the above-mentioned fiber length is usually different from the glass fiber length in the connector, which is the molded product.

[0033] When a glass fiber filler is used as the reinforcing filler, the refractive index of the glass fiber filler is, for example, 1.4 to 1.7, more preferably 1.44 to 1.64, and even more preferably 1.48 to 1.58.

[0034] The difference in refractive index between the polypropylene resin and the reinforcing filler is preferably close to each other from the viewpoint of not hindering the transmission of the laser light and reducing variations in the transmittance of the laser light, and for example, the difference in refractive index is preferably within 0.02, more preferably within 0.01, particularly preferably within 0.005, and most preferably 0.

[0035] When a reinforcing filler is used, the content of the reinforcing filler is, for example, preferably 1 to 35 mass %, more preferably 10 to 32 mass %, and even more preferably 20 to 30 mass %, relative to the total content (100 mass %) of the polypropylene-based resin and the reinforcing filler.

[0036] [Other Components] In addition to the above-described components, the resin composition [I] in the present linked structure may contain, as necessary, resins other than polypropylene-based resins (other resins), colorants (dyes and pigments), heat stabilizers, antioxidants, inorganic fillers, crystal nucleating agents, weathering agents, plasticizers, lubricants, and the like, within the types and ranges that do not impair the effects of the present invention and laser light transmittance.

[0037] Examples of the "other resins" include polyamide resins, polyethylene resins, polystyrene resins, polycarbonate resins, acrylonitrile butadiene styrene copolymer resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polyacetal resins, modified polyphenylene ether resins, polyphenylene sulfide resins, etc. These may be used alone or in combination of two or more.

[0038] When the resin composition [I] contains "other resins," the amount must be within a range that does not impair the effects of the present invention. The content of the "other resins" is not limited to the following, but may be about 90% by mass or less, 5 to 85% by mass, or 5 to 75% by mass relative to the total content (100% by mass) of the polypropylene resin and the "other resins."

[0039] From the viewpoint of laser light transmittance, examples of dyes that serve as colorants include azo-based, anthraquinone-based, perinone-based, perylene-based, phthalocyanine-based, carbonium-based, and indigoid-based oil dyes, acid dyes, basic dyes, and disperse dyes. From the viewpoint of laser light transmittance, examples of pigments that serve as colorants include phthalocyanine-based, anthraquinone-based, isoindolinone-based, quinacridone-based, perylene-based, and azo-based organic pigments.

[0040] The colorant is used in an amount that does not impair laser light transmittance. Therefore, the content of the colorant in the total amount (100 mass%) of the resin composition [I] is usually less than 1 mass%, preferably less than 0.75 mass%, and more preferably less than 0.5 mass%.

[0041] <Method for Manufacturing Connector> The method for manufacturing the connector 1 is not limited, but for example, a polypropylene resin and optional components such as a reinforcing filler are melt-kneaded using a twin-screw extruder at a cylinder temperature of 200 to 260°C. Pellets are then obtained from the melt-kneaded mixture. Next, the pellets are injection-molded into a mold for the connector 1 using an injection molding machine at a set temperature of 200 to 280°C. In this manner, the connector 1 can be manufactured.

[0042] As another manufacturing method, for example, the required amounts of polypropylene resin and optional components such as a reinforcing filler may be directly injected into an injection molding machine for each shot, and then injection molding may be performed to manufacture the connector 1. Alternatively, a portion of each of the above materials may be premixed, and then the mixture may be directly injected into an injection molding machine together with the remaining materials in the required amounts for each shot, and then the desired connector 1 may be obtained by injection molding.

[0043] <Shape of Connector, etc.> The shape of the connector 1 may be any shape that allows laser welding with the end of the tube 2 inserted into its open edge 1a. For example, from the standpoint of laser weldability, the connector 1 is preferably a substantially cylindrical molded body with an inner diameter of 2.5 to 50 mm, a wall thickness of 0.25 to 10 mm, and a length of 20 to 1000 mm. The inner diameter is preferably 3 to 45 mm, more preferably 3.5 to 40 mm, and even more preferably 4 to 35 mm. The wall thickness is preferably 0.5 to 7.5 mm, more preferably 0.75 to 5 mm, and even more preferably 1.0 to 3.0 mm. The length is preferably 25 to 500 mm, more preferably 30 to 250 mm, and even more preferably 35 to 100 mm.

[0044] When the total light transmittance of the connector 1 is measured at 1060 nm using a spectrophotometer (for example, V-770 manufactured by JASCO Corporation), the total light transmittance is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more.

[0045] <<Tube>> The tube 2 is composed of a laser-absorbent material. The laser-absorbent tube 2 is made of a dynamically crosslinked thermoplastic elastomer composition [II]. The tube 2 has at least one layer made of the dynamically crosslinked thermoplastic elastomer composition [II]. The tube 2 may be either a single-layer tube or a multi-layer tube having two or more layers.

[0046] 1 shows an example of a single-layer tube, but in the case of a multi-layer tube having two or more layers, it is preferable that at least the outer layer is a laser-absorbent layer. Specifically, for example, a three-layer structure can be used, which has an outer layer that abuts against the inner surface of the connector 1, an intermediate layer (e.g., a reinforcing fiber layer) formed radially inward of the outer layer, and an inner layer formed radially inward of the intermediate layer, and it is preferable that at least the outer layer is a laser-absorbent layer.

[0047] <Dynamically crosslinkable thermoplastic elastomer composition [II]> The dynamically crosslinkable thermoplastic elastomer composition [II] contains at least (A) an ethylene-α-olefin-non-conjugated diene copolymer rubber, (B) a polypropylene resin, (C) an organic peroxide, and (D) a laser beam absorber. The dynamically crosslinkable thermoplastic elastomer composition [II] is produced by kneading at least components (A), (B), and (D) in a molten or semi-molten state in the presence of the organic peroxide (C), while simultaneously crosslinking component (A) under shear (dynamic crosslinking).

[0048] [Component (A): Ethylene / α-olefin / non-conjugated diene copolymer rubber] The ethylene / α-olefin / non-conjugated diene copolymer rubber is a copolymer having ethylene, an α-olefin, and a non-conjugated diene compound as copolymerization components. Only one type of component (A) may be used, or two or more types differing in the type, composition, physical properties, etc. of structural units may be used.

[0049] Examples of the α-olefin in component (A) include those having 3 to 20 carbon atoms, such as propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene. These may be used alone or in combination of two or more. Of these, propylene, 1-butene, 3-methyl-1-butene, and 1-pentene are preferred, with propylene being more preferred.

[0050] Examples of the non-conjugated diene compound in component (A) include dicyclopentadiene, 1,4-hexadiene, cyclohexadiene, cyclooctadiene, dicyclooctadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene, 2-methyl-1,5-hexadiene, 6-methyl Examples of suitable cyclopentadiene include 1,5-heptadiene, 7-methyl-1,6-octadiene, tetrahydroindene, methyltetrahydroindene, 5-isopropylidene-2-norbornene, 5-vinyl-2-norbornene, vinylidene norbornene, ethylidene norbornenes such as 5-ethylidene-2-norbornene (ENB), and methylene norbornenes such as 5-methylene-2-norbornene (MNB). These may be used alone or in combination of two or more. Among these, dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene are preferred, and dicyclopentadiene, 5-ethylidene-2-norbornene, and vinylidene norbornene are more preferred.

[0051] Specific examples of component (A) include ethylene-propylene-non-conjugated diene copolymer rubbers (EPDM) such as ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, ethylene-propylene-dicyclopentadiene copolymer rubber, ethylene-propylene-1,4-hexadiene copolymer rubber, and ethylene-propylene-5-vinyl-2-norbornene copolymer rubber, and ethylene-1-butene-5-ethylidene-2-norbornene copolymer rubber. These may be used alone or in combination of two or more. Of these, ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) is preferred.

[0052] The ethylene content in component (A) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 50 to 90 mass%, more preferably 55 to 85 mass%, and even more preferably 60 to 80 mass%.

[0053] The α-olefin content in component (A) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 10 to 50 mass%, more preferably 15 to 45 mass%, and even more preferably 20 to 40 mass%.

[0054] The non-conjugated diene content in component (A) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 0.5 to 30 mass%, more preferably 1 to 20 mass%, and even more preferably 2 to 10 mass%.

[0055] Mooney viscosity (ML) of component (A) 1+4 , 125°C) is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 20 to 90, more preferably 30 to 80, and even more preferably 40 to 70.

[0056] [Component (B): Polypropylene-Based Resin] Examples of component (B) include propylene homopolymers (homopolypropylenes), copolymers such as block copolymers, random copolymers, and graft copolymers of propylene with α-olefins other than propylene, such as ethylene and 1-butene, and modified polypropylenes modified with acid anhydrides, such as maleic anhydride-modified polypropylene and imine-modified polypropylene. These may be used alone or in combination of two or more.

[0057] Examples of the α-olefin include α-olefins having 2 to 20 carbon atoms (excluding propylene having 3 carbon atoms), such as ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene. These may be used alone or in combination of two or more.

[0058] The melt flow rate (MFR) of component (B) is, for example, preferably 0.1 to 50 g / 10 min, more preferably 0.3 to 30 g / 10 min, even more preferably 0.5 to 15 g / 10 min, and particularly preferably 1 to 10 g / 10 min. The MFR of polypropylene resins is measured in accordance with JIS K 7210 at a temperature of 230°C and a load of 2.16 kg.

[0059] It is important that the content of the (B) component be within a specific range of 10 to 45% by mass, based on the total amount (100% by mass) of the (A) and (B) components. By setting the content of the (B) component within this range, a connected structure with excellent welding strength, bending strength, and flexibility can be obtained. To further enhance the above-described effects, the content of the (B) component is preferably 15 to 45% by mass, more preferably 20 to 45% by mass, and particularly preferably 25 to 45% by mass, based on the total amount (100% by mass) of the (A) and (B) components. The content of the (B) component can be appropriately set within the above range, and may be, for example, 22 to 45% by mass, more preferably 25 to 40% by mass.

[0060] [Component (C): Organic Peroxide] Examples of organic peroxides include 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)butane, n-butyl-4,4-bis(t-butylperoxy)butane, and n-butyl-4,4-bis(t-butylperoxy)cyclohexane. peroxyketals such as di-t-butylperoxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, α,α'-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, and the like; acetyl peroxide, isobutyryl peroxide, Diacyl peroxides such as octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and m-trioyl peroxide, as well as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, and di-t-butyl peroxy Examples of the peroxyesters include isophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and cumylperoxyoctate, and hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, and 1,1,3,3-tetramethylbutyl peroxide. These may be used alone or in combination of two or more.

[0061] The content of component (C) is not limited to the following, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, 0.05 to 6 parts by mass, more preferably 0.08 to 5 parts by mass, and even more preferably 0.1 to 4 parts by mass per 100 parts by mass of component (A). Note that when a 100% pure organic peroxide is not used as the active ingredient, the organic peroxide is blended so that the proportion calculated as the active ingredient falls within the above range.

[0062] The content of component (C) is not limited to the following, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, 0.05 to 6 parts by mass, more preferably 0.08 to 5 parts by mass, and even more preferably 0.1 to 4 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). When a 100% pure organic peroxide is not used as the organic peroxide, it is blended so that the proportion calculated as the organic peroxide falls within the above range.

[0063] [Component (D): Laser Beam Absorbent] The component (D) is not particularly limited as long as it has an absorption wavelength within the wavelength range of the irradiated laser beam (e.g., 800 to 1200 nm) and absorbs the laser beam to generate heat. For example, pigments, dyes, etc. can be used as appropriate, and black pigments and black dyes are preferred.

[0064] Specific examples of component (D) include inorganic pigments such as carbon black, oxides, sulfides, and sulfates. Organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene pigments, perinone pigments, quinacridone pigments, and dioxazine pigments. Dyes include oil-soluble dyes such as anthraquinone pigments, indigoid pigments, perylene pigments, perinone pigments, azo pigments, methine pigments, phthalocyanine pigments, and anthrapyridone pigments.

[0065] The carbon black is not particularly limited, and examples thereof include SAF grade, ISAF grade, HAF grade, MAF grade, MAF-HS grade, FEF grade, GPF grade, SRF grade, SRF-HS grade, FT grade, MT grade, etc. These may be used alone or in combination of two or more types.

[0066] The average particle size of the carbon black is, for example, preferably 5 to 130 nm, more preferably 7 to 70 nm, and even more preferably 10 to 50 nm.

[0067] The nitrogen adsorption specific surface area of ​​carbon black is 10 to 150 m 2 / g is preferred, and 15 to 100m 2 / g, and even more preferably 20 to 80 m 2 / g, particularly preferably 25 to 65 m 2 / g.

[0068] The nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with the method described in JIS K 6217-2.

[0069] The iodine adsorption capacity of carbon black is, for example, preferably 10 to 150 mg / g, more preferably 15 to 100 mg / g, and even more preferably 20 to 80 mg / g. The DBP (dibutyl phthalate) absorption capacity of carbon black is preferably 20 to 180 mL / 100 g, more preferably 20 to 150 mL / 100 g. The iodine adsorption capacity of carbon black is a value measured in accordance with JIS K 6217-1 (Method A), and the DBP absorption capacity of carbon black is a value measured in accordance with JIS K 6217-4.

[0070] The content of component (D) is not limited to the following, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, 0.01 to 10 parts by mass, preferably 0.01 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, even more preferably 0.05 to 3 parts by mass, and particularly preferably 0.1 to 3 parts by mass, per 100 parts by mass of the total of component (A) and component (B).

[0071] The content of carbon black is not limited to the following, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, 0.01 to 3 parts by mass, more preferably 0.05 to 1.5 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the total of the components (A) and (B).

[0072] [Component (E): Antiaging Agent] The dynamically crosslinkable thermoplastic elastomer composition [II] may optionally contain an antioxidant (E). Examples of antioxidants include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, phenylamine-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, and waxes. These may be used alone or in combination of two or more.

[0073] The content of the antioxidant is not particularly limited, but is, for example, 0.05 to 10 parts by mass, preferably 0.1 to 8 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the component (A).

[0074] From the viewpoint of significantly exhibiting the effects of the present invention, the melting point of the antioxidant is preferably 60° C. or higher, more preferably 70° C. or higher, even more preferably 75° C. or higher, particularly preferably 80° C. or higher, and especially preferably 90° C. or higher. The melting point of the antioxidant is preferably 300° C. or lower, more preferably 250° C. or lower.

[0075] 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.

[0076] As the anti-aging agent, a phenol-based anti-aging agent is preferred, and among the phenol-based anti-aging agents, a hindered phenol-based anti-aging agent is particularly preferred from the viewpoint of heat resistance. 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 Corporation; melting point: 110 to 125°C), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (e.g., "Irganox 3114" manufactured by BASF Corporation; melting point: 218 to 223°C), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (e.g., "Irganox 1330" manufactured by BASF Corporation; melting point: 240 to 245°C), 6-(4-hydroxy-3,5-di-tert-butylanilino)-2,4-bis(octyl)methylpropional, and 1,3,5-tris(4-hydroxy-3,5-di-tert-butylanilino)methylpropional. N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, "Irganox 1035" manufactured by BASF Corporation; melting point 63 to 78°C), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] ("Irganox 1098" manufactured by BASF Corporation; melting point 156 to 161°C), and 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("Irganox 259" manufactured by BASF Corporation; melting point 104 to 108°C).

[0077] [Other Components] In addition to the above-mentioned components, various additives such as co-crosslinking agents, heat stabilizers, inorganic fillers, crystal nucleating agents, weathering agents, plasticizers, and lubricants may be blended into the resin composition [II] in the present linked structure, as needed, within the types and ranges that do not impair the effects of the present invention and laser light absorbency.

[0078] [Co-crosslinking agent] Examples of the co-crosslinking agent include sulfur-containing compounds, polyfunctional monomers, maleimide compounds, quinone compounds, etc. These may be used alone or in combination of two or more.

[0079] Examples of the sulfur-containing compound include sulfur, dipentamethylenethiuram tetrasulfide, and mercaptobenzothiazole. Examples of the polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate, diallyl phthalate, trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate (TAIC), triallyl trimellitate, and triallyl tricyanurate. Examples of the maleimide compound include N,N'-m-phenylene bismaleimide and toluylene bismaleimide. Examples of the quinone compound include quinone dioxime and dibenzoyl-p-quinone dioxime.

[0080] The content of the co-crosslinking agent is not particularly limited, but is, for example, 0.1 to 8 parts by mass, preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3.5 parts by mass, relative to 100 parts by mass of the component (A).

[0081] <Method for preparing dynamically crosslinked thermoplastic elastomer composition [II]> The dynamically crosslinked thermoplastic elastomer composition [II] is produced by kneading a mixture containing components (A), (B), and (D), and optional additives, in a molten or semi-molten state in the presence of an organic peroxide (C), while simultaneously crosslinking component (A) under shear (dynamic crosslinking). The dynamically crosslinked thermoplastic elastomer composition [II] has a sea-island structure in which crosslinked component (A) is finely dispersed as domains in a matrix of component (B).

[0082] The conditions for producing the dynamically crosslinkable thermoplastic elastomer composition [II] by kneading it in an extruder or the like are to melt-knead it in a heated state usually at 80 to 300° C., preferably 100 to 250° C. The treatment time for the dynamic heat treatment is not particularly limited, but is usually about 0.1 to 30 minutes.

[0083] <Physical Properties of Dynamically Crosslinked Thermoplastic Elastomer Composition [II]> The hardness of the dynamically crosslinked thermoplastic elastomer composition [II] is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, for example, the Shore A hardness measured in accordance with JIS K 6253 (2012) is preferably 70 to 98, more preferably 75 to 96. The Shore A hardness can be determined as an instantaneous value by using a durometer to measure a sheet-like molded product having a thickness of 2 mm prepared by the method described in the Examples below.

[0084] The 25% modulus (M25) of the dynamically crosslinkable thermoplastic elastomer composition [II] is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 1 to 20 MPa, more preferably 2 to 10 MPa. The 25% modulus (M25) can be determined in accordance with JIS K 6250, 6251 (2019) by conducting a tensile test using a 2 mm thick sheet-like molded product prepared by the method described in the Examples below, at a measurement temperature of 23°C and a tensile speed of 500 mm / min.

[0085] The breaking strength of the dynamically crosslinked thermoplastic elastomer composition [II] is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, preferably 5 to 30 MPa, more preferably 10 to 20 MPa. The breaking strength can be determined in accordance with JIS K 6250, 6251 (2019) by conducting a tensile test using a 2 mm thick sheet-like molded product prepared by the method described in the Examples below, at a measurement temperature of 23°C and a tensile speed of 500 mm / min.

[0086] <Tube Manufacturing Method, etc.> The tube 2 can be obtained by a known manufacturing method using the dynamically crosslinkable thermoplastic elastomer composition [II]. Specifically, for example, the tube 2 can be produced by extruding the dynamically crosslinkable thermoplastic elastomer composition [II] into a tubular shape using an extruder or the like under conditions of 180 to 250°C.

[0087] The inner diameter, thickness, and length of the tube 2 are not particularly limited, but for example, it is preferable that the inner diameter of the tube 2 is in the range of 2.5 to 30 mm, the thickness of the tube 2 is in the range of 0.5 to 5 mm, and the length of the tube 2 is in the range of 100 to 1500 mm.

[0088] If the tube 2 is a single-layer tube, the thickness of the tube 2 is in the range of 0.5 to 5 mm, preferably in the range of 1 to 3 mm. If the tube is a multi-layer tube with two or more layers, the thickness of the outer layer that abuts against the inner surface of the connector 1 is in the range of 0.1 to 3.0 mm, preferably in the range of 0.1 to 2.5 mm.

[0089] <Uses of Connector-Tube Connection Structure> The present connection structure is used as a connection structure applied to various fluid flow passages. Specifically, it is suitable for use as, for example, automotive tubing. In particular, it can be suitably used as automotive tubing, such as radiator tubes used to connect the engine and radiator in vehicles such as automobiles, heater tubes used to connect the engine and heater core, engine cooling system tubing such as refrigerant transport tubing for coolers, fuel cell vehicle tubing such as methanol fuel tubing and hydrogen fuel tubing, and gasoline fuel tubing. Furthermore, the present connection structure is particularly suitable as an electric vehicle tubing because it can satisfy the balance of pressure resistance, flexibility, heat resistance, and economy required for electric vehicle tubing. Furthermore, the present connection structure can be used not only for automobiles but also as an industrial tubing, for example, for transportation machinery other than automobiles (industrial transportation vehicles such as airplanes, forklifts, excavators, and cranes, railway vehicles, etc.).

[0090] Examples will be described below together with comparative examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

[0091] First, the following materials were prepared.

[0092] <Materials for Dynamically Crosslinked Thermoplastic Elastomer Composition [II] (Tube)> [(A) Ethylene-α-olefin-non-conjugated diene copolymer rubber] EPDM (manufactured by Mitsui Chemicals, Inc., EPT3092M [ethylene-propylene-ENB copolymer rubber, Mooney viscosity 61 (ML 1+4 , 125°C), ethylene content 65%, diene content 4.6%]

[0093] [(B) Polypropylene Resin] Polypropylene (Prime Polypro E200GP [homopolypropylene, MFR (230°C) 2.0 g / 10 min], manufactured by Prime Polymer Co., Ltd.)

[0094] [(C) Organic peroxide] 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 (Perhexyne 25B [purity 40%; 1-hour half-life temperature = 149.9°C], manufactured by NOF Corporation) The blending amount "0.4 parts by mass" in Table 1 indicates the product concentration, and the blending amount converted to the active ingredient is "0.16 parts by mass."

[0095] [(D) Laser Light Absorber] Carbon black (manufactured by Tokai Carbon Co., Ltd., SEAT S [nitrogen adsorption specific surface area 27 m 2 / g, average particle size 66 nm])

[0096] [Co-crosslinking agent]: A mixture of divinylbenzene and ethylvinylbenzene (manufactured by Nippon Steel Chemical Co., Ltd., DVB-570 [mass ratio of divinylbenzene:ethylvinylbenzene = 55:45])

[0097] <Materials for resin composition [I] (connector) containing polypropylene resin> Polypropylene (manufactured by Hanwha Total Petroleum Co., Ltd., PPGF-30 (homopolypropylene, MFR (230°C) 6.7 g / 10 min, GF (glass fiber) 30%))

[0098] [Examples 1 to 3, Comparative Examples 1 and 2] The above components (A) to (D) and the co-crosslinking agent were mixed in the proportions shown in Table 1 below to prepare a dynamically crosslinked thermoplastic elastomer composition [II]. Specifically, components (A), (B), and (D) were fed into the hopper of a twin-screw extruder ("TEM-18SS" manufactured by Toshiba Machine Co., Ltd.) and kneaded at 180°C for 1 minute. Component (C) and the co-crosslinking agent were then added and kneaded at 120°C for 0.5 minutes to obtain a kneaded mixture. The screw rotation speed was 200 rpm, and the extrusion rate was 10 kg / hour. The kneaded mixture was then cut into pellets of the dynamically crosslinked thermoplastic elastomer composition [II].

[0099] <Weld Strength Test> (Preparation of Test Pieces for Weld Strength Test) First, a sheet-shaped molded body (2 mm thick) of polypropylene (PPGF-30, manufactured by Hanwha Total Petroleum) was prepared using an injection molding machine, and a test piece (Is) measuring 60 mm in length, 10 mm in width, and 2 mm in thickness was prepared from the sheet-shaped molded body. <Molding Conditions> Injection molding machine: SH100A (φ32 mm), manufactured by Sumitomo Heavy Industries, Ltd. Cylinder temperature: 220°C ± 10°C Mold temperature: 80°C ± 20°C Injection speed: 39 ± 5 cm 2 / sec Holding pressure: 30 MPa Screw back pressure: 5 MPa

[0100] Next, a sheet-like molded article (thickness: 2 mm) was prepared from the dynamically crosslinked thermoplastic elastomer composition [II] (pellets) using an injection molding machine, and test pieces (IIs) measuring 60 mm in length, 10 mm in width, and 2 mm in thickness were prepared from the sheet-like molded article. <Molding conditions> Injection molding machine: SH100A (φ32 mm), manufactured by Sumitomo Heavy Industries, Ltd. Cylinder temperature: 220°C ± 10°C Mold temperature: 80°C ± 20°C Injection speed: 39 ± 5 cm 2 / sec Holding pressure: 30 MPa Screw back pressure: 5 MPa

[0101] The test piece (Is) and the test piece (IIs) were brought into contact with each other so that a 20 mm long portion was overlapped as shown in FIG. 2, and a semiconductor laser (L) (wavelength: 800 to 1000 nm) with an output of 30 W was irradiated from the test piece (Is) side at the contact portion over a range of 10 mm while scanning in the width direction (W direction), thereby welding both test pieces (Is and IIs) together to prepare a test piece for a weld strength test.

[0102] Using the test pieces for the weld strength test obtained above, a tensile test was carried out at a shear rate of 25 mm / min. The strength at break was taken as the weld strength and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) × (poor): Weld strength less than 90 N / cm ◯ (good): Weld strength 90 N / cm or more

[0103] <Flexural modulus test (flexibility and flexural strength)> ISO multipurpose test pieces (Type A) were prepared from each dynamically crosslinked thermoplastic elastomer composition (pellet) using an injection molding machine. <Molding conditions> Injection molding machine: SH100A (φ32 mm), manufactured by Sumitomo Heavy Industries, Ltd. Cylinder temperature: 220°C ± 10°C Mold temperature: 80°C ± 20°C Injection speed: 39 ± 5 cm 2 / sec Holding pressure: 50 MPa Screw back pressure: 5 MPa

[0104] Using the ISO multipurpose test specimen obtained above, the flexural modulus was measured in accordance with ISO 178 at a speed of 2 mm / min and a span distance of 64 mm, and the flexural modulus was evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) × (poor)...flexural modulus is 40 MPa or less or exceeds 500 MPa. ○ (good)...flexural modulus is more than 40 MPa and 500 MPa or less.

[0105]

[0106] From the results in Table 1 above, it can be seen that Examples 1 to 3 are excellent in welding strength, flexibility, and bending strength. Furthermore, among Examples 1 to 3, Examples 2 and 3 are particularly excellent in welding strength, and are also particularly excellent in the balance between flexibility and bending strength.

[0107] In contrast, in Comparative Example 1, the content of the polypropylene-based resin contained in the dynamically crosslinked thermoplastic elastomer composition is below the lower limit specified in the present invention, and therefore the welding strength and bending strength (shape retention) are insufficient. In Comparative Example 2, the content of the polypropylene-based resin contained in the dynamically crosslinked thermoplastic elastomer composition is above the upper limit specified in the present invention, and therefore the flexibility is insufficient.

[0108] From the above, it can be seen that in a connector made of a resin composition [I] containing a polypropylene-based resin and a tube made of a dynamically crosslinked thermoplastic elastomer composition [II] laser-welded to the connector, by containing the dynamically crosslinked thermoplastic elastomer composition [II] as components (A) to (D) and adjusting the content of component (B) to 10 to 45 mass% relative to the total amount (100 mass%) of components (A) and (B), a connector-tube connection structure can be obtained which has excellent weld strength between the connector and the tube and an excellent balance between flexibility and bending strength.

[0109] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0110] The connector-tube connection structure of the present invention is used as a connection structure applied to various fluid flow passages. Specifically, it is suitable, for example, as an automobile tube. In particular, it can be suitably used as an automobile tube such as an engine cooling system tube, such as a radiator tube used to connect the engine and radiator in a vehicle such as an automobile, a heater tube used to connect the engine and heater core, a cooler refrigerant transport tube, a fuel cell vehicle tube, such as a methanol fuel tube or a hydrogen fuel tube, or a gasoline fuel tube. It is particularly suitable as an electric vehicle tube. Furthermore, the connector-tube connection structure of the present invention can be used not only for automobiles, but also for other transportation machinery (industrial transportation vehicles, such as airplanes, forklifts, excavators, and cranes, and railway vehicles, etc.).

[0111] 1 Connector 2 Tube 1a Open end edge of connector

Claims

1. A connector-tube connection structure having a connector and a tube laser-welded to the connector, wherein the connector is made of a resin composition [I] containing a polypropylene-based resin, and the tube is made of a dynamically crosslinked thermoplastic elastomer composition [II], wherein the dynamically crosslinked thermoplastic elastomer composition [II] contains the following components (A) to (D), with the content of component (B) being 10 to 45 mass% relative to the total amount (100 mass%) of components (A) and (B): (A) ethylene-α-olefin-non-conjugated diene copolymer rubber; (B) polypropylene-based resin; (C) organic peroxide; (D) laser light absorber.

2. A connector-tube connection structure according to claim 1, wherein the content of component (B) is 25 to 45% by mass relative to the total amount (100% by mass) of components (A) and (B).

3. A connector-tube connection structure according to claim 1 or 2, wherein the content of said component (C) is 0.05 to 6 parts by mass per 100 parts by mass of the total of said components (A) and (B).

4. A connector-tube connection structure according to any one of claims 1 to 3, wherein the content of the (D) component is 0.01 to 3 parts by mass per 100 parts by mass of the total of the (A) component and the (B) component.

5. A connector-tube connection structure according to any one of claims 1 to 4, wherein component (A) is an ethylene-propylene-non-conjugated diene copolymer rubber.

6. A connector-tube connection structure according to any one of claims 1 to 5, wherein component (D) is carbon black.

7. A connector-tube connection structure according to any one of claims 1 to 6, wherein the dynamically crosslinked thermoplastic elastomer composition [II] contains (E) an antioxidant, and the melting point of the (E) antioxidant is 60°C or higher.

8. The connector-tube connection structure according to any one of claims 1 to 7, wherein the resin composition [I] contains a glass fiber filler.

9. A connector-tube connection structure as described in any one of claims 1 to 8, in which the end of the tube is inserted into the open end edge of the connector, and the connector and the end of the tube are connected by laser welding.

10. A connector-tube connection structure according to any one of claims 1 to 9, wherein the tube is an automotive tube.

11. A connector-tube connection structure according to any one of claims 1 to 9, wherein the tube is a tube for an automobile cooling system.

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