Connector-tube connecting structure

Abstract

Provided is a connector-tube connecting structure having excellent welding strength, flexibility, and extraction resistance.　A connector-tube connecting structure comprising a connector made of a resin composition [I] containing a polypropylene-based resin, and a tube made of a dynamic crosslinked thermoplastic elastomer composition [II], wherein the dynamic crosslinked thermoplastic elastomer composition [II] contains components (A) to (E), the content of component (B) is 40 to 80 mass% relative to the total amount of components (A) and (B), the content ratio of component (B) relative to the total amount of components (A), (B), and (E) is 0.30 or more, and the content of component (E) is 20 to 70 parts by mass relative to the total amount of components (A) and (B).　(A) ethylene / α-olefin / non-conjugated diene copolymer rubber; (B) polypropylene-based resin; (C) crosslinking agent;(D) laser light absorber; (E) plasticizer

Description

Connector-Tube Connecting Structure

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

[0002] Laser welding is a method of welding two materials together by passing laser light through a material that is transparent to laser light, absorbing it in a material that is absorbing laser light, generating heat and melting it, and simultaneously melting the laser-transmitting material through heat transfer.

[0003] For example, in the pathways through which various fluids flow, such as the cooling water passages and fuel supply lines of 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 together by irradiating them with laser light (Patent Document 1).

[0004] Various materials have been proposed for members that transmit or absorb laser light. For example, Patent Document 2 describes the use of a dynamically crosslinked thermoplastic elastomer, stating that it offers a good balance of various properties at a lower cost compared to other thermoplastic elastomers.

[0005] Japanese Patent Publication No. 4161823, Japanese Unexamined Patent Publication No. 2005-290372

[0006] However, research and development regarding connector-tube connection structures constructed by laser welding, particularly those using dynamically cross-linked thermoplastic elastomers as the material for the laser-absorbing tube, is still insufficient. In particular, there has been very little research and development focused on the challenge of simultaneously satisfying the required flexibility and extractability of the fluid flowing through the tube when using dynamically cross-linked thermoplastic elastomers as the material for the laser-absorbing tube.

[0007] The present invention has been made in view of the above circumstances, and provides a connector-tube connecting structure that uses a dynamically crosslinked thermoplastic elastomer as the material for a tube having laser light absorption properties, and that is excellent in welding strength, flexibility, and extractability.

[0008] The inventors of the present invention have conducted extensive research from the perspective of solving the above problems and have found that by further incorporating a plasticizer along with ethylene-α-olefin-non-conjugated diene copolymer rubber, polypropylene resin, a crosslinking agent, and a laser light absorber, and by setting the content and blending ratio of the polypropylene resin and the content of the plasticizer within a specific range, the requirements for welding strength, flexibility, and extractability can be simultaneously met, leading to the present invention.

[0009] In other words, the gist of the present invention is as follows: [1] A connector-tube connecting 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 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 (E), the content of component (B) is 40 to 80% by mass relative to the total amount of components (A) and (B) (100% by mass), the content ratio of component (B) to the total amount of components (A), (B) and (E) [(B) / {(A) + (B) + (E)}] is 0.30 or more, and the content of component (E) is 20 to 70 parts by mass relative to the total amount of components (A) and (B) (100 parts by mass), the connector-tube connecting structure. [1] A connector-tube connecting structure according to [1], wherein the content ratio of component (B) above [(B) / {(A)+(B)+(E)}] is 0.50 or less. [3] A connector-tube connecting structure according to [1] or [2], wherein the melt flow rate of component (B) above at 230°C and a load of 2.16 kg is 0.1 to 50 g / 10 min. [4] A connector-tube connecting structure according to any one of [1] to [3], wherein component (C) above is a phenolic resin crosslinking agent. [5] A connector-tube connecting structure according to any one of [1] to [4], wherein component (D) above is carbon black. [6] A connector-tube connecting structure according to any one of [1] to [5], wherein component (E) above is paraffinic oil. [7] The connector-tube connecting structure according to any one of [1] to [6], wherein the component (C) is a phenol resin crosslinking agent, and the content of the phenol resin crosslinking agent is 0.1 to 10 parts by mass per 100 parts by mass of the total of the components (A) and (B).[8] The connector-tube connecting structure according to any one of [1] to [7], wherein the content of component (D) is 0.01 to 10 parts by mass per 100 parts by mass of the total of components (A) and (B). [9] The connector-tube connecting 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 connecting structure according to any one of [1] to [9], wherein the tube is an automotive tube.

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

[0010] According to the present invention, a connector-tube linking structure with excellent welding strength, flexibility, and extractability can be provided.

[0011] This is a cross-sectional view showing an example of the connector-tube connecting structure of the present invention. This is a schematic explanatory diagram showing the test method of the embodiment.

[0012] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments.

[0013] In this specification, when "X to Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Furthermore, in numerical ranges described in stages in this specification, the upper or lower limit of one numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in numerical ranges described in this specification, the upper or lower limit of that numerical range can be replaced with the values ​​shown in the examples. Furthermore, "X and / or Y (where X and Y are any configuration)" means at least one of X and Y, and can mean X only, Y only, or X and Y. Also, in this specification, when "tube" is written, it also includes the meaning of "hose."

[0014] A connector-tube connecting structure according to one embodiment of the present invention (hereinafter sometimes referred to as "this connecting structure") is a connector-tube connecting 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 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 (E), the content of component (B) is 40 to 80% by mass relative to the total amount of components (A) and (B) (100% by mass), the content ratio of component (B) to the total amount of components (A), (B) and (E) [(B) / {(A) + (B) + (E)}] is 0.30 or more, and the content of component (E) is 20 to 70 parts by mass relative to the total amount of components (A) and (B) (100 parts by mass). (A) Ethylene-α-olefin-non-conjugated diene copolymer rubber (B) Polypropylene resin (C) Crosslinking agent (D) Laser light absorber (E) Plasticizer

[0015] This connecting structure is used as a connecting structure applicable to various fluid flow paths, such as cooling water flow paths, lubricating oil flow paths, and fuel supply lines in automobiles. Because this connecting structure has excellent welding strength, it improves the fastening force between the connector and the tube, effectively suppressing fluid leakage. In addition, it also has excellent flexibility and resistance to extraction, making it extremely useful when used as one of the above-mentioned flow paths.

[0016] One embodiment of this connecting structure will be described with reference to the figures. Referring to Figure 1, this connecting structure comprises a connector 1 and a tube 2. The connector 1 is a molded body that transmits laser light, and the tube 2 is a molded body that absorbs laser light. As shown in Figure 1, with the end of the tube 2 inserted into the open 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, and a connecting structure having a laser-welded portion is formed. Specifically, the laser light that passes through the laser-transmitting connector 1 is absorbed by the laser-absorbing tube 2, generating heat, which melts the constituent material of the tube 2. This heat is then transferred to the connector 1, which also melts the constituent material of the connector 1, welding the interface between the connector 1 and the tube 2, and forming the connecting structure.

[0017] Furthermore, the term "having laser light transmittance" means, for example, that even if it partially absorbs and / or reflects the laser light, it transmits the remaining laser light without melting much, allowing the laser light to reach the tube. The term "having laser light absorbance" means that even if it partially transmits and / or reflects the laser light, it absorbs the remainder, resulting in heating or melting.

[0018] The laser irradiation conditions are not particularly limited and should be set to provide the energy necessary to melt the joint interface between connector 1 and tube 2. For example, the laser output and irradiation time (scan speed) should be appropriately set according to the laser light transmittance and thickness of connector 1.

[0019] As the laser used in this linked structure, for example, a laser having an oscillation wavelength of 800 to 1200 nm can be used, and known lasers such as YAG lasers, semiconductor lasers, glass lasers, ruby ​​lasers, He-Ne lasers, nitrogen lasers, chelate lasers, and dye lasers can be applied. The output power of these lasers is not limited, but for example, about 5 to 40 W is preferred.

[0020] A specific example of this connecting structure is a structure in which a connector 1, particularly a quick connector, is laser-welded to one or both ends of a long tube 2 in the longitudinal direction. The quick connector has a structure that can be connected to components (including piping, etc.) such as a cooling device or a device to be cooled. For example, it can be used in a manner in which a quick connector laser-welded to one end of a long tube 2 in the longitudinal direction is connected to a component such as a cooling device, and a quick connector laser-welded to the other end of the long tube 2 in the longitudinal direction is connected to another component such as a device to be cooled.

[0021] Furthermore, as a specific example of this connecting structure, it can also be used to connect tubes together. That is, it can be used in a configuration where tube 2 is laser-welded at one end of connector 1, and another tube 2 is laser-welded at the other end of connector 1.

[0022] The connector 1 and tube 2 that constitute this connecting structure will be described in detail below.

[0023] <<Connector>> Connector 1 is composed of a member that is transparent to laser light. In this connecting structure, the laser light transparent connector 1 is a molded body made of a resin composition [I] containing a polypropylene resin.

[0024] <Resin composition [I]> Resin composition [I] contains a polypropylene resin and may optionally contain other components such as reinforcing fillers.

[0025] [Polypropylene Resins] Examples of polypropylene resins include homopolymers of propylene (homopolypropylene), 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 polypropylene modified with acid anhydrides such as maleic anhydride. Among these, homopolymers of propylene (homopolypropylene) are preferred. These may be used individually or in combination of two or more. For example, one or more selected from the group consisting of homopolymers of propylene (homopolypropylene), and 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 polypropylene modified with acid anhydrides.

[0026] Examples of the above-mentioned α-olefins include 2 to 20 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 (excluding propylene, which has 3 carbon atoms). These may be used individually or in combination of two or more.

[0027] The melt flow rate (MFR) of the polypropylene resin is preferably, for example, 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 7210:2014, under conditions of a measurement temperature of 230°C and a load of 2.16 kg.

[0028] 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 refers to the refractive index with respect to laser light at 1060 nm. An approximate curve was created using a precision refractometer (KPR-3000, manufactured by Shimadzu Corporation) from the d-line (587.6 nm), e-line (546.1 nm), and t-line (1013.98 nm) to determine the refractive index at 1060 nm.

[0029] The polypropylene resin content is preferably, for example, 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, based on the total amount (100% by mass) of the resin composition [I].

[0030] [Reinforcement Filler] The resin composition [I] may optionally contain a reinforcement filler from the viewpoint of increasing the strength of the connector 1. Examples of reinforcement fillers include glass fiber filler, carbon fiber filler, potassium titanate, glass beads, milled fiber, and talc. These may be used alone or in combination of two or more. Among these, glass fiber filler is preferred.

[0031] Examples of glass fibers used as material for glass fiber fillers 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 2.5 to 20 μm, and more preferably 5 to 15 μm. The fiber length of the glass fiber filler is preferably 2 to 6 mm, and more preferably 3 to 5 mm. Note that glass fibers break and become finer in the melting and mixing machine or injection molding machine, so the above fiber length is usually different from the glass fiber length in the molded connector.

[0032] When glass fiber filler is used as a 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.

[0033] The difference between the refractive index of the polypropylene resin and the refractive index of the reinforcing filler is preferably approximated in order to avoid obstructing the transmission of laser light and to reduce variations in the transmittance of laser light. For example, the difference in refractive index is preferably within 0.02. More preferably, the difference in refractive index is within 0.01, particularly preferably within 0.005, and most preferably 0.

[0034] When reinforcing fillers are used, the content of the reinforcing fillers is preferably 1 to 35% by mass, more preferably 10 to 32% by mass, and even more preferably 20 to 30% by mass, relative to the total content (100% by mass) of the polypropylene resin and the reinforcing fillers.

[0035] [Other Components] In addition to the above components, the resin composition [I] in this connected structure may contain, as necessary, resins other than polypropylene resins (other resins), colorants (dyes and pigments), heat stabilizers, antioxidants, inorganic fillers, nucleating agents, weathering agents, plasticizers, lubricants, etc., in a type and range that does not impair the effects of the present invention and laser light transmittance.

[0036] Examples of the "other resins" mentioned above 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, and polyphenylene sulfide resins. These can be used individually or in combination of two or more.

[0037] When the resin composition [I] contains "other resins", it is necessary that the content thereof is 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, or may be about 5 to 50% by mass, 5 to 40% by mass, 3 to 30% by mass, 1 to 20% by mass, or 1 to 10% by mass, based on the total content (100% by mass) of the polypropylene-based resin and the "other resins".

[0038] Examples of dyes that are colorants include oil-based dyes, acid dyes, basic dyes, and disperse dyes of azo, anthraquinone, perinone, perylene, phthalocyanine, carbonium, and indigoid types from the viewpoint of laser light transmittance. Examples of pigments that are colorants include organic pigments such as phthalocyanine, anthraquinone, isoindolinone, quinacridone, perylene, and azo types from the viewpoint of laser light transmittance.

[0039] Since the colorant is used within a range that does not impair laser light transmittance, normally the content of the colorant in the total amount (100% by mass) of the resin composition [I] is less than 1% by mass, preferably less than 0.75% by mass, and more preferably less than 0.5% by mass.

[0040] <Method for Manufacturing Connector> The method for manufacturing connector 1 is not limited. For example, a polypropylene-based resin and optional components such as a reinforcing filler are melt-kneaded at a cylinder temperature of 200 to 260°C using a twin-screw extruder. Then, pellets are obtained from the melt-kneaded product. Next, using the pellets, injection molding is performed into a mold for connector 1 at a set temperature of 200 to 280°C by an injection molding machine. Connector 1 can be manufactured in this manner.

[0041] As another manufacturing method, for example, the connector 1 may be manufactured by injection molding in which a polypropylene resin and optional components such as a reinforcing filler are directly charged into an injection molding machine in the required amount for each shot, and then the injection molding is performed. Alternatively, after a part of each of the above materials is mixed in advance, the mixture together with the remaining materials is directly charged into the injection molding machine in the required amount for each shot, and the target connector 1 may be manufactured by the injection molding.

[0042] <Shape of Connector etc.> The shape of connector 1 may be any shape as long as it can be laser-welded in a state where the end of tube 2 is inserted into the opening edge 1a of the connector 1. For example, from the viewpoint of laser weldability, it is preferably a substantially cylindrical molded body having 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 still 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 still more preferably 1.0 to 3 mm. The above length is preferably 25 to 500 mm, more preferably 30 to 250 mm, and still more preferably 35 to 100 mm.

[0043] When the total light transmittance at 1060 nm of connector 1 is measured using a spectrophotometer (e.g., V-770 manufactured by JASCO Corporation), the total light transmittance is preferably 30% or more, more preferably 40% or more, and still more preferably 50% or more.

[0044] <<Tube>> The tube 2 is formed of a member having laser light absorptivity. The laser light-absorbing tube 2 is formed of a dynamically crosslinked thermoplastic elastomer composition [II]. The tube 2 has at least one layer formed 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.

[0045] Figure 1 shows an example of a single-layer tube, but for examples of multi-layer tubes having two or more layers, it is preferable that at least the outer layer is a layer that absorbs laser light. Specifically, examples include a three-layer structure having an outer layer that abuts the inner surface of the connector 1, an intermediate layer (e.g., a reinforcing thread 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 layer that absorbs laser light.

[0046] <Dynamic Crosslinking Thermoplastic Elastomer Composition [II]> The dynamic crosslinking thermoplastic elastomer composition [II] contains at least (A) ethylene-α-olefin-non-conjugated diene copolymer rubber, (B) polypropylene resin, (C) crosslinking agent, (D) laser light absorber, and (E) plasticizer. The dynamic crosslinking thermoplastic elastomer composition [II] is produced by kneading at least components (A), (B), (D), and (E) in a molten or semi-molten state in the presence of the crosslinking agent (C), while simultaneously crosslinking component (A) under shear (dynamic crosslinking).

[0047] [Component (A): Ethylene-α-olefin-non-conjugated diene copolymer rubber] Ethylene-α-olefin-non-conjugated diene copolymer rubber is a copolymer having ethylene, α-olefin, and a non-conjugated diene compound as copolymer components. Component (A) may be used alone, or two or more components with different types of constituent units, compositions, and physical properties may be used.

[0048] Examples of α-olefins in component (A) include 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, which have 3 to 20 carbon atoms. These may be used individually or in combination of two or more. Among these, propylene, 1-butene, 3-methyl-1-butene, and 1-pentene are preferred, and propylene is more preferred.

[0049] Examples of non-conjugated diene compounds 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, and 6-methyl Examples include -1,5-heptadiene, 7-methyl-1,6-octadiene, tetrahydroindene, methyltetrahydroindene, 5-isopropylidene-2-norbornene, 5-vinyl-2-norbornene, vinylidenenorbornene, ethylidenenorbornene such as 5-ethylidene-2-norbornene (ENB), and methylenenorbornene such as 5-methylene-2-norbornene (MNB). These may be used individually or in combination of two or more. Among these, ethylidenenorbornene is preferred.

[0050] (A) Specific examples of component include, for example, ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, ethylene-propylene-dicyclopentadiene copolymer rubber, ethylene-propylene-1,4-hexadiene copolymer rubber, ethylene-propylene-5-vinyl-2-norbornene copolymer rubber, and other ethylene-propylene-non-conjugated diene copolymer rubbers (EPDM), as well as ethylene-1-butene-5-ethylidene-2-norbornene copolymer rubber. These may be used individually or in combination of two or more. Among these, ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) is preferred.

[0051] The ethylene content in component (A) is not particularly limited, but from the viewpoint of significantly achieving the effects of the present invention, it is preferably 50 to 90% by mass, more preferably 55 to 85% by mass, and even more preferably 60 to 80% by mass.

[0052] The α-olefin content in component (A) is not particularly limited, but from the viewpoint of significantly achieving the effects of the present invention, it is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and even more preferably 20 to 40% by mass.

[0053] The non-conjugated diene content in component (A) is not particularly limited, but from the viewpoint of significantly achieving the effects of the present invention, it is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and even more preferably 2 to 10% by mass.

[0054] (A) Mooney viscosity of component (ML 1+4 The temperature (125°C) is not particularly limited, but from the viewpoint of significantly achieving the effects of the present invention, it is preferably 20 to 90°C, more preferably 30 to 80°C, and even more preferably 40 to 70°C.

[0055] The content of component (A) is not particularly limited, but is usually 8% by mass or more, preferably 10 to 70% by mass, and more preferably 10 to 60% by mass, relative to the dynamic cross-linked thermoplastic elastomer composition [II] (100% by mass). Furthermore, component (A) is the main component of the rubber component contained in the dynamic cross-linked thermoplastic elastomer composition [II], and is preferably 70% by mass or more, relative to the total amount of rubber component contained in the dynamic cross-linked thermoplastic elastomer composition [II] (100% by mass), and may be 70 to 100% by mass, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 100% by mass, etc.

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

[0057] Examples of the above-mentioned α-olefins include 2 to 20 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 (excluding propylene, which has 3 carbon atoms). These may be used individually or in combination of two or more.

[0058] The melt flow rate (MFR) of component (B) is preferably 0.1 to 50 g / 10 min, more preferably 0.3 to 30 g / 10 min, and even more preferably 0.5 to 15 g / 10 min. The melt flow rate (MFR) of component (B) can be appropriately set within the above range, for example, 1 to 10 g / 10 min or 1 to 5 g / 10 min. The MFR of the polypropylene resin is measured in accordance with JIS K 7210:2014, under conditions of a measurement temperature of 230°C and a load of 2.16 kg.

[0059] It is important that the content of component (B) be within a specific range of 40 to 80% by mass relative to the total amount (100% by mass) of components (A) and (B). The content (ratio) of component (B) relative to the total amount of components (A) and (B) can be set appropriately within the above range, for example, 40 to 50% by mass, 60 to 80% by mass, etc. In other words, the mass ratio of component (A):B can be set appropriately within the range of 60:40 to 20:80.

[0060] Furthermore, in the dynamically crosslinked thermoplastic elastomer composition [II] of the present invention, it is important to set the content of component (B) within a specific range, and to set the content ratio of component (B) to the total amount of components (A), (B), and (E) [(B) / {(A)+(B)+(E)}] to 0.30 or more. That is, by setting the content of component (B) within a specific range of 40 to 80% by mass, and setting the above content ratio [(B) / {(A)+(B)+(E)}] to 0.30 or more, a linked structure with excellent welding strength, flexibility, and extractability can be obtained. The above content ratio [(B) / {(A)+(B)+(E)}] can be appropriately set within the above range, but from the viewpoint of significantly exhibiting the effects of the present invention, and in particular from the viewpoint of exhibiting good flexibility, the above content ratio [(B) / {(A)+(B)+(E)}] is preferably 0.30 to 0.50.

[0061] Furthermore, the total content of component (A) and component (B) relative to the total amount (100% by mass) of the dynamically crosslinked thermoplastic elastomer composition [II] (total amount of component (A) and component (B) / total amount of dynamically crosslinked thermoplastic elastomer composition [II] × 100 [%]) is preferably 70 to 95% by mass, and more preferably 70 to 90% by mass.

[0062] [Component (C): Crosslinking agent] Examples of component (C) include phenol resin-based crosslinking agents and organic peroxide-based crosslinking agents.

[0063] (Phenol resin-based crosslinking agents) Examples of phenol resin-based crosslinking agents include condensates of phenols and aldehydes, resol-type phenol resins, novolac-type phenol resins, and rosin-modified phenol resins. These can be used alone or in combination of two or more. Examples of the condensates of phenols and aldehydes include alkylphenol resins.

[0064] Alkylphenol resins are condensates of alkylphenol components and aldehydes. Examples of alkylphenol components include phenols having alkyl groups with 1 to 18 carbon atoms, such as cresol, isopropylphenol, t-butylphenol, amylphenol, octylphenol (e.g., p-octylphenol), nonylphenol, dodecylphenol, allylphenol, and cyclohexylphenol, as well as various derivatives such as methylolated and halogenated derivatives of these compounds.

[0065] Examples of the above-mentioned aldehydes include formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, propionaldehyde, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, and paraxylenedimethyl ether.

[0066] Suitable examples of alkylphenol resins include alkylphenol acetylene resins, alkylphenol formaldehyde resins, and alkylphenol acetaldehyde resins.

[0067] The softening point of the phenolic resin crosslinking agent is not particularly limited, but is preferably 50 to 200°C, more preferably 60 to 150°C, and even more preferably 70 to 120°C. The softening point is measured by the ring-sphere method in accordance with JIS K 2207:2006.

[0068] Examples of commercially available phenolic resin crosslinking agents include Schenectady SP1059, Schenectady SP1045, Schenectady SP-1055, Schenectady SP-1056 (all manufactured by Schenectady Chemicals), Tackirol® 201 (alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), Tackirol® 250-I (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), and Tackirol® 250-III (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.).

[0069] (Organic peroxide crosslinking agents) Examples of organic peroxide crosslinking agents 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( Peroxyketals such as t-butylperoxy)valerate, dialkylperoxides such as di-t-butylperoxide, dicumylperoxide, t-butylcumylperoxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, α,α'-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, as well as acetylperoxide and isobutylperoxide. Diacyl peroxides such as oxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-tolyloyl peroxide, and t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, di-t-butyl peroxy Examples include peroxyesters such as cyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and cumylperoxyoctate, as well as hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, and 1,1,3,3-tetramethylbutylperoxide. These can be used individually or in combination of two or more.

[0070] The content of component (C) is not limited to the following, but from the viewpoint of significantly achieving the effects of the present invention, it is, for example, 0.1 to 10 parts by mass, more preferably 0.2 to 9 parts by mass, and even more preferably 0.3 to 8 parts by mass, based on 100 parts by mass of the total of components (A) and (B).

[0071] Furthermore, when a phenolic resin-based crosslinking agent is used as component (C), the content of the phenolic resin-based crosslinking agent is not limited to the following, but is for example 0.1 to 10 parts by mass, more preferably 1 to 9 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0072] Furthermore, when an organic peroxide-based crosslinking agent is used as component (C), the content of the organic peroxide-based crosslinking agent is not limited to the following, but from the viewpoint of significantly achieving 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 the total of components (A) and (B). In addition, when a 100% pure raw material is not used as the organic peroxide-based crosslinking agent, it is formulated so that the ratio on a raw material basis falls within the above range.

[0073] [Component (D): Laser light absorber] Component (D) is not particularly limited as long as it has an absorption wavelength within the range of the irradiated laser light wavelength (e.g., 800 to 1200 nm) and absorbs laser light to generate heat. For example, pigments and dyes can be used as appropriate, and black pigments and black dyes are preferred.

[0074] (D) Specific examples of component include, for example, inorganic pigments such as carbon black, oxides, sulfides, and sulfates. Examples of organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, and dioxazine. Examples of dyes include oil-soluble dyes such as anthraquinone, indigoid, perylene, perinone, azo, methine, phthalocyanine, and anthrapyridone.

[0075] Carbon black is not particularly limited and can include grades such as SAF, ISAF, HAF, MAF, MAF-HS, FEF, GPF, SRF, SRF-HS, FT, and MT. These can be used individually or in combination of two or more types.

[0076] The average particle size of the carbon black is preferably 5 to 130 nm, more preferably 7 to 70 nm, and even more preferably 10 to 50 nm.

[0077] The specific surface area for nitrogen adsorption of carbon black is 10 to 150 m². 2 A value of / g is preferred, and more preferably 15 to 100 m 2 / g, more preferably 20 to 80 m 2 / g, particularly preferably 25 to 65 m 2 The value is / g. The specific surface area of ​​nitrogen adsorption of carbon black can be measured according to the method described in JIS K 6217-2:2017.

[0078] The amount of iodine adsorbed by carbon black is preferably 10 to 150 mg / g, more preferably 15 to 100 mg / g, and even more preferably 20 to 80 mg / g. The amount of DBP (dibutyl phthalate) absorbed by carbon black is preferably 20 to 180 mL / 100g, and more preferably 20 to 150 mL / 100g. The iodine adsorbed by carbon black is a value measured in accordance with JIS K 6217-1 (Method A):2017, and the DBP absorbed by carbon black is a value measured in accordance with JIS K 6217-4:2017.

[0079] The content of component (D) is not limited to the following, but from the viewpoint of significantly achieving 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, based on 100 parts by mass of the total of components (A) and (B).

[0080] When carbon black is used as component (D), the carbon black content is not limited to the following, but from the viewpoint of significantly achieving 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, per 100 parts by mass of the total of components (A) and (B).

[0081] [Component (E): Plasticizer] In embodiments of the present invention, it is important that the dynamically crosslinked thermoplastic elastomer composition [II] contains a specific amount of (E) plasticizer. If the plasticizer content is outside the range specified in the present invention, it tends to be difficult to achieve a high balance of weld strength, flexibility, and extractability.

[0082] Examples of plasticizers include aromatic oils, ether ester plasticizers, and process oils. These can be used individually or in combination of two or more.

[0083] Examples of aromatic oils include Diana Process AC-12, Diana Process AC-460, Diana Process AH-16 (all manufactured by Idemitsu Kosan Co., Ltd.), JSO Aroma 790 (manufactured by Nippon Sun Oil Co., Ltd.), Aromax 1, and Aromax 3 (both manufactured by Fuji Kosan Co., Ltd.). Examples of ether ester plasticizers include those that have both ether and ester bonds in a single molecule. Specifically, examples include adipic acid ether ester plasticizers such as bis[2-(2-butoxyethoxy)ethyl] adipate. Examples of process oils include naphthenic oils and paraffinic oils.

[0084] It is important that the plasticizer content is within the range of 20 to 70 parts by mass per 100 parts by mass of the total of components (A) and (B). If the plasticizer content is outside this range, for example, the extractability may be insufficient, and it tends to be difficult to achieve a high balance between welding strength, flexibility, and extractability. The plasticizer content can be appropriately set within the above range, for example, 20 to 40 parts by mass, 50 to 70 parts by mass, etc.

[0085] [Other Components] In addition to the above components, the resin composition [II] in this connected structure may contain various additives as needed, such as crosslinking aids, antioxidants, co-crosslinking agents, heat stabilizers, inorganic fillers, crystal nucleating agents, and weathering agents, in a type and range that does not impair the effects of the present invention and the laser light absorption.

[0086] (Crosslinking aids) When used with organic peroxide-based crosslinking agents, examples of crosslinking aids include divinyl compounds such as divinylbenzene, oxime compounds such as p-quinone dioxime, nitroso compounds such as N-methyl-N-4-dinitrosoaniline and nitrosobenzene, maleimide compounds such as N,N'-m-phenylenedimaleimide, and polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate. When used with phenolic resin-based crosslinking agents, examples of crosslinking aids include iron oxide, titanium oxide, magnesium oxide, silicon dioxide, zinc oxide, stannous chloride, ferric chloride, chlorinated paraffin, chlorinated polyethylene, and chlorosulfonated polyethylene.

[0087] The amount of crosslinking aid can be appropriately set depending on the amount of component (A), the type and amount of crosslinking agent, etc. For example, although not particularly limited, the amount of crosslinking aid is 0.1 to 5 parts by mass, or about 0.1 to 3 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0088] <Method for preparing the dynamically crosslinked thermoplastic elastomer composition [II]> The dynamically crosslinked thermoplastic elastomer composition [II] is produced by kneading a mixture containing component (A), component (B), component (D), component (E), and additives as needed, in a molten or semi-molten state in the presence of a crosslinking agent (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).

[0089] The conditions for producing the dynamically crosslinked thermoplastic elastomer composition [II] by kneading in an extruder or the like are typically 150 to 300°C, preferably 180 to 250°C, during melt kneading. The processing time during the dynamic heat treatment is not particularly limited, but is usually about 0.1 to 30 minutes.

[0090] <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 demonstrating the effects of the present invention, a Shore A hardness (Type A durometer hardness) of 95 or less is preferred. The lower limit is not particularly limited, but for example, it may be 60 or more, 80 or more, etc. The above Shore A hardness can be determined as the Shore A hardness (instantaneous value) using a durometer with a sheet-like molded body of 2 mm thickness, as described in the example below.

[0091] <Method of manufacturing the tube, etc.> The tube 2 is obtained by a known manufacturing method using the above-mentioned dynamic crosslinking thermoplastic elastomer composition [II]. Specifically, for example, the dynamic crosslinking thermoplastic elastomer composition [II] is extruded into a tube shape using an extrusion molding machine or the like under conditions of 180 to 250°C.

[0092] The inner diameter, thickness, and length of tube 2 are not particularly limited, but for example, the inner diameter of tube 2 is preferably in the range of 2.5 to 30 mm, the thickness of tube 2 is preferably in the range of 0.5 to 5 mm, and the length of tube 2 is preferably in the range of 100 to 1500 mm.

[0093] In the case of a single-layer tube, the thickness of tube 2 is in the range of 0.5 to 5 mm, and preferably in the range of 1 to 3 mm. In the case of a multi-layer tube with two or more layers, the thickness of the outer layer that contacts the inner surface of connector 1 is preferably in the range of 0.1 to 2.5 mm.

[0094] <Applications of Connector-Tube Connecting Structure> This connecting structure can be used as a connecting structure applicable to various fluid flow paths. Specifically, it is preferably used in automotive tubes. In particular, it can be preferably used as an automotive tube, such as a radiator tube used to connect the engine and radiator in vehicles such as automobiles, a heater tube used to connect the engine and heater core, an automotive cooling system tube such as a refrigerant transport tube for coolers, a fuel cell vehicle tube such as a methanol fuel tube and a hydrogen fuel tube, and a gasoline fuel tube. Furthermore, this connecting structure is particularly suitable for electric vehicle tubes because it can satisfy the pressure resistance, flexibility, and extractability required for electric vehicle tubes in a well-balanced manner. In addition, this connecting structure can be applied not only to automotive applications but also as an industrial tube, for example, to transportation machinery other than automobiles (industrial transport vehicles such as airplanes, forklifts, excavators, and cranes, and railway vehicles).

[0095] The following describes the examples along with comparative examples. However, the present invention is not limited to these examples unless it exceeds the essence of the invention. Unless otherwise specified, "parts," "%," etc., refer to mass.

[0096] First, I prepared the following materials.

[0097] <Materials for the 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 (at 125°C), ethylene content 65%, diene content 4.6%)

[0098] [(B) Polypropylene resin] ・Polypropylene (Prime Polymer Co., Ltd., Prime Polypropylene E200GP [homopolypropylene, MFR (230℃) 2.0g / 10min])

[0099] [(C) Crosslinking agent] ・Phenolic resin crosslinking agent (Schenectady Chemicals, SP-1055) ・Organic peroxide crosslinking agent (Nippon Oil & Fats Co., Ltd., Perhexine 25B [purity 40%, half-life temperature at 1 hour = 149.9°C]) Note that the "0.4 parts by mass" in Table 2 indicates the product concentration, and the raw material equivalent blending amount is "0.16 parts by mass".

[0100] [(D) Laser light absorber] ・Carbon black (manufactured by Tokai Carbon Co., Ltd., Seast S [Nitrogen adsorption specific surface area 27 m²] ２ / g, average particle size 66 nm])

[0101] [(E) Plasticizer] ・Plasticizer (process oil, manufactured by Idemitsu Kosan Co., Ltd., Diana Process Oil PW-100)

[0102] [Crosslinking Aids] ・Crosslinking Aid (1) (Manufactured by Nippon Steel Chemical Co., Ltd., DVB-570 [Mixture of divinylbenzene and ethylvinylbenzene (mass ratio divinylbenzene:ethylvinylbenzene = 55:45)]) ・Crosslinking Aid (2) (Two types of zinc oxide manufactured by Hakusui Tech Co., Ltd.)

[0103] <Materials for the resin composition containing polypropylene resin [I] (connector)> ・Polypropylene (manufactured by Hanwha Total, PPGF-30 (homopolypropylene, MFR (230℃) 6.7g / 10min, containing 30% GF (glass fiber)))

[0104] [Examples 1-2, Comparative Examples 1-4] Dynamically crosslinked thermoplastic elastomer compositions [II] were prepared by mixing each material in the proportions shown in Table 1. Specifically, components (A), (B), (D), and (E) were supplied to the hopper of a twin-screw extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.), kneaded at 180°C for 1 minute, and then (C) crosslinking agent and crosslinking aid were added and kneaded at 120°C for 0.5 minutes to obtain a kneaded product. The screw rotation speed was 200 rpm and the discharge rate was 10 kg / hour. After that, the kneaded product was cut to obtain pellets of the dynamically crosslinked thermoplastic elastomer composition [II].

[0105] <Flexibility Evaluation> Pellets of the dynamic crosslinked thermoplastic elastomer composition [II] obtained above were press-molded at 210°C for 8 minutes, and then cooled and pressed at room temperature for 5 minutes to produce a 2 mm thick press sheet. Three of the obtained sheets were stacked to form a test specimen, and the hardness was measured using a hardness tester (ASKER P2-A type, manufactured by Polymer Instruments Co., Ltd.) in accordance with JIS K 6253-3:2012. Immediately after the indenter and the test specimen came into contact, the scale was read and the hardness was expressed as Type A durometer hardness (HA), and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) ○ (very good) ... less than 97 × (poor) ... 97 or more

[0106] <Evaluation of Extraction Resistance> A 10 g pellet test specimen of the dynamic cross-linked thermoplastic elastomer composition [II] obtained above was immersed in 100 mL of a 50% by mass aqueous solution of LLC (Long Life Coolant) at 100°C for 72 hours. After immersion, the test specimen was filtered, air-dried, and its mass was measured and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) ○ (very good) ... Mass ratio before and after immersion (mass after immersion / mass before immersion) is less than 0.5 × (poor) ... Mass ratio before and after immersion (mass after immersion / mass before immersion) is 0.5 or more

[0107] <Welding Strength Evaluation> (Preparation of Test Pieces for Welding Strength Test) First, a sheet-like molded body of polypropylene (Hanwha Total, PPGF-30) was prepared using an injection molding machine (thickness 2 mm), and a test piece (Is) with a length of 60 mm, a width of 10 mm, and a thickness of 2 mm was prepared from the sheet-like molded body. <Molding Conditions> ・Injection molding machine: Sumitomo Heavy Industries, Ltd., SH100A (φ32 mm) ・Cylinder temperature: 200℃±10℃ ・Mold temperature: 60℃±20℃ ・Injection speed: 39±5 cm ２ / sec • Holding pressure: 30 MPa • Screw back pressure: 5 MPa

[0108] Next, using an injection molding machine, a sheet-shaped molded article (with a thickness of 2 mm) is produced from the dynamically crosslinked thermoplastic elastomer composition [II] (pellets), and a test piece (IIs) having a length of 60 mm, a width of 10 mm, and a thickness of 2 mm is produced from the sheet-shaped molded article. <<Molding Conditions>> ・Injection molding machine: SH100A (φ32 mm), manufactured by Sumitomo Heavy Industries, Ltd. ・Cylinder temperature: 200°C±10°C ・Mold temperature: 60°C±20°C ・Injection speed: 39±5 cm 2 / sec ・Holding pressure: 30 MPa ・Screw back pressure: 5 MPa

[0109] As shown in Fig. 2, the above test piece (Is) and the above test piece (IIs) are brought into contact with each other such that a portion of 20 mm in length overlaps, and in the contacted portion, a semiconductor laser (L) with an output of 30 W (wavelength 800 to 1000 nm) is irradiated from the test piece (Is) side over a range of 10 mm while scanning in the width direction (W direction), and both test pieces (Is and IIs) are welded to prepare a test piece for welding strength test.

[0110] Using the test piece for welding strength test obtained above, a tensile test is performed under the condition of 25 mm / min in the shear direction, the strength at break is taken as the welding strength, and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) 〇(very good)…Welding strength is 90 N / cm or more ×(poor) …Welding strength is less than 90 N / cm

[0111]

[0112] As shown in Table 1, in Comparative Example 1, where the polypropylene content in the dynamically cross-linked thermoplastic elastomer composition [II] is below the range specified in the present invention, and furthermore, the polypropylene content relative to the total amount of polypropylene, EPDM, and plasticizer is also below the range specified in the present invention, the welding strength is insufficient. In Comparative Example 2, where the polypropylene content in the dynamically cross-linked thermoplastic elastomer composition [II] is above the range specified in the present invention, and furthermore, the polypropylene content relative to the total amount of polypropylene, EPDM, and plasticizer is also above the range specified in the present invention, the flexibility is insufficient. In Comparative Example 3, where the polypropylene content in the dynamically cross-linked thermoplastic elastomer composition [II] is within the range specified in the present invention, but the polypropylene content relative to the total amount of polypropylene, EPDM, and plasticizer is below the range specified in the present invention, the welding strength is insufficient. Furthermore, although the polypropylene content in the dynamically crosslinked thermoplastic elastomer composition [II] is within the range specified in the present invention, and the polypropylene content ratio relative to the total amount of polypropylene, EPDM, and plasticizer is also within the range specified in the present invention, it can be seen that in Comparative Example 4, where the plasticizer content exceeds the range specified in the present invention, the extractability is insufficient.

[0113] In contrast, if the dynamic crosslinking thermoplastic elastomer composition [II] is one of Examples 1-2, which satisfies all the requirements of the present invention, it can be seen that it is superior in terms of flexibility, extractability, and welding strength.

[0114] From the above, it can be seen that a connector-tube connecting structure with an excellent balance of welding strength, flexibility, and extractability can be obtained by comprising a connector made of a resin composition [I] containing a polypropylene resin and a tube made of a dynamically cross-linked thermoplastic elastomer composition [II] laser-welded to the connector, wherein the dynamically cross-linked thermoplastic elastomer composition [II] contains components (A) to (E), the content of component (B) is 40 to 80% by mass relative to the total amount of components (A) and (B) (100% by mass), the content of component (E) is 20 to 70 parts by mass relative to the total amount of components (A) and (B) (100 parts by mass), and the content ratio of component (B) to the total amount of components (A), (B) and (E) [(B) / {(A) + (B) + (E)}] is 0.30 or more.

[0115] <Investigation of Crosslinking Agent Types> In addition, the following sag resistance tests were conducted to investigate the effects of different crosslinking agent types.

[0116] [Example 3] The materials were mixed in the proportions shown in Table 2, and a dynamic crosslinking thermoplastic elastomer composition [II] was prepared in the same manner as in Example 1 (Example 3). The following degradation resistance tests were performed on Example 3 and Example 1.

[0117] [Evaluation of deformation resistance] A sheet-like molded body (2 mm thick) was prepared from the pellets of the dynamic crosslinked thermoplastic elastomer composition [II] obtained above, and six sheets were stacked and pre-compressed to form a test specimen. The compression set of the test specimen was measured after 24 hours at 23°C (RT) while the specimen was compressed to 25%. The results are shown in Table 2. Note that in Table 2, the measured compression set in Example 3 is set to 100, and the measured compression set in Example 1 is shown as an indexed value.

[0118]

[0119] From the results in Table 2 above, it can be seen that, from the viewpoint of resistance to deformation, a phenolic resin-based crosslinking agent is suitable as the type of crosslinking agent used in the present invention.

[0120] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0121] The connector-tube connecting structure of the present invention can be used as a connecting structure applied to various fluid flow passages. Specifically, it is suitable as, for example, an automotive tube. In particular, it can be suitably used as an automotive tube, such as a radiator tube used to connect the engine and radiator in vehicles such as automobiles, a heater tube used to connect the engine and heater core, an engine cooling system tube, a refrigerant transport tube for coolers, a fuel cell vehicle tube such as a methanol fuel tube and a hydrogen fuel tube, and a gasoline fuel tube. It is especially suitable as an electric vehicle tube. Furthermore, the connector-tube connecting structure of the present invention can be used not only for automobiles but also for other transport machinery (airplanes, industrial transport vehicles such as forklifts, excavators, and cranes, railway vehicles, etc.).

[0122] 1. Connector 2. Tube 1a. Open end of the connector

Claims

1. A connector-tube connecting 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 resin, and the tube is made of a dynamically cross-linked thermoplastic elastomer composition [II], the dynamically cross-linked thermoplastic elastomer composition [II] contains the following components (A) to (E), the content of component (B) is 40 to 80% by mass relative to the total amount of components (A) and (B) (100% by mass), the content ratio of component (B) to the total amount of components (A), (B) and (E) [(B) / {(A) + (B) + (E)}] is 0.30 or more, and the content of component (E) is 20 to 70 parts by mass relative to the total amount of components (A) and (B) (100 parts by mass), the connector-tube connecting structure. (A) Ethylene-α-olefin-non-conjugated diene copolymer rubber (B) Polypropylene resin (C) Crosslinking agent (D) Laser light absorber (E) Plasticizer 2. The connector-tube connecting structure according to claim 1, wherein the content ratio of component (B) above [(B) / {(A) + (B) + (E)}] is 0.50 or less.

3. The connector-tube connecting structure according to claim 1 or 2, wherein the melt flow rate of component (B) at 230°C and a load of 2.16 kg is 0.1 to 50 g / 10 min.

4. The connector-tube connecting structure according to any one of claims 1 to 3, wherein component (C) is a phenol resin-based crosslinking agent.

5. The connector-tube connecting structure according to any one of claims 1 to 4, wherein the above component (D) is carbon black.

6. The connector-tube connecting structure according to any one of claims 1 to 5, wherein component (E) is a paraffin-based oil.

7. The connector-tube connecting structure according to any one of claims 1 to 6, wherein component (C) is a phenolic resin-based crosslinking agent, and the content of the phenolic resin-based crosslinking agent is 0.1 to 10 parts by mass per 100 parts by mass of the total of component (A) and component (B).

8. The connector-tube connecting structure according to any one of claims 1 to 7, wherein the content of component (D) is 0.01 to 10 parts by mass per 100 parts by mass of the total of component (A) and component (B).

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

11. The connector-tube connecting structure according to any one of claims 1 to 9, wherein the tube is a tube for an automotive cooling system.

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