Multilayer cooling pipe

Abstract

The present invention provides a multilayer cooling pipe which contains a polymer composition layer of a modified polyolefin resin and an amide-based polymer layer, and has excellent adhesion and is not easily reduced in adhesion strength even when exposed to high temperatures. The multilayer cooling pipe of the present invention contains a polymer composition layer formed of a polymer composition containing an ethylene-α-olefin copolymer (A), a propylene-based polymer (B), and a modified propylene-based polymer (C) obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid to a propylene-based polymer, the polymer composition containing 18 mass% or more and 40 mass% or less of the ethylene-α-olefin copolymer (A), 40 mass% or more and 81 mass% or less of the propylene-based polymer (B), and 1 mass% or more and 19 mass% or less of the modified propylene-based polymer (C).

Description

Technical Field

[0001] This invention relates to a multi-layer cooling pipe. Background Technology

[0002] In recent years, electric vehicles have rapidly gained popularity amidst rising global environmental awareness. Thermal management is essential in electric vehicles to mitigate power consumption, energy loss, and battery degradation. Therefore, effectively cooling various heat-generating components using fluids (cooling water) within pipes maintains a suitable temperature, thereby improving the overall system efficiency.

[0003] Polyamides are typically used as materials for this cooling duct, considering the balance between melt formability, flexibility (shapeability), gas barrier properties, rigidity, and internal pressure creep. Furthermore, from the perspective of further weight reduction and economy, multilayering with polyolefins is known, especially multilayering with modified polyolefins known to have excellent adhesion to polyamides.

[0004] Various solutions have been proposed to date for multilayer cooling channels formed by laminating layers of amide polymers with different properties with other polymer compositions. For example, Patent Document 1 proposes a multilayer cooling channel that uses polyamide as the outer layer and modified polyolefin (maleic acid grafted polyolefin) as the inner layer.

[0005] Furthermore, to allow each pipe to be deformed into the desired shape according to its application, sometimes so-called high-temperature shaping is performed, i.e., shaping it by exposing it to a high-temperature environment such as 150°C to soften it, followed by cooling. Therefore, modified polypropylene resins, which have particularly excellent heat resistance among modified polyolefin resins, are mostly used. For example, Patent Document 2 discloses a laminated structure having: an olefin-based thermoplastic elastomer layer as the outer layer, an adhesive layer containing a modified propylene polymer as the middle layer, and a semi-aromatic polyamide layer as the inner layer. Patent Document 2 describes that the laminated structure can also be suitably used for hoses in cooling system piping.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 7-214690

[0009] Patent Document 2: Japanese Patent Application Publication No. 2017-177548 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The polyamides used in the amide-based polymer layers for this purpose are typically long-chain aliphatic polyamides such as polyamide 11, which has excellent melt-forming properties, flexibility, chemical resistance, and gas barrier properties, and polyamide 12, which is also used in Patent Document 1. However, long-chain aliphatic polyamides have low amide group concentrations and fewer reaction sites with maleic anhydride, which is present in modified polyolefins, when compared for the same molecular weight. In addition, plasticizers are sometimes included in the amide-based polymer layers to impart flexibility and melt-forming properties to the polyamide. However, these plasticizers may migrate (exude) to the adhesive interface, hindering adhesion to the polyolefin layer.

[0012] Thus, in a multilayer cooling pipe that uses polyamide as the outer layer and modified polyolefin as the inner layer, from the viewpoint of the adhesion strength to the amide polymer layer, there is room for improvement in the layers containing the modified polyolefin described in Patent Document 1 and the modified propylene polymer described in Patent Document 2.

[0013] Furthermore, when performing high-temperature shaping, the laminated structures described in Patent Documents 1-2 have room for improvement in terms of the adhesive strength between the amide polymer layer and the polymer composition layer after high-temperature shaping.

[0014] Therefore, the present invention was made in view of the following problem. That is, the object of the present invention is to provide a multilayer cooling pipe comprising a polymer composition layer containing a modified polyolefin and an amide polymer layer, wherein the polymer composition layer and the amide polymer layer have excellent adhesion and the bond strength is not easily reduced even when exposed to high temperatures.

[0015] Solution for solving the problem

[0016] Scheme 1 of the present invention is a multilayer cooling pipe comprising a polymer composition layer and an amide polymer layer. The polymer composition layer is formed of a polymer composition comprising an ethylene-α-olefin copolymer (A), a propylene polymer (B), and a modified propylene polymer (C). The modified propylene polymer (C) is obtained by grafting at least one of an unsaturated carboxylic acid and a derivative thereof onto the propylene polymer. The polymer composition comprises 18% by mass and 40% by mass of the ethylene-α-olefin copolymer (A), 40% by mass and 81% by mass of the propylene polymer (B), and 1% by mass and 19% by mass of the modified propylene polymer (C).

[0017] Solution 2 of the present invention is a multi-layer cooling pipe according to Solution 1, wherein the value shown in the following formula (1) is 0.22 or more and 0.65 or less.

[0018] PA / (PB+PC)…(1)

[0019] In equation (1),

[0020] PA represents the percentage (by mass) of the ethylene-α-olefin copolymer (A) in the polymer composition.

[0021] PB represents the percentage (by mass) of the propylene polymer (B) in the polymer composition.

[0022] PC represents the percentage (by mass) of the modified propylene polymer (C) in the polymer composition.

[0023] Scheme 3 of the present invention is a multi-layer cooling pipe according to Scheme 1 or 2, wherein the polymer composition is non-crosslinked.

[0024] Scheme 4 of the present invention is a multilayer cooling pipe according to any one of Schemes 1 to 3, wherein the MFR of the ethylene-α olefin copolymer (A) measured at 190°C, 21.2N, and 2mm pore size is 0.01g / 10min or more and 4.0g / 10min or less.

[0025] Solution 5 of the present invention is a multi-layer cooling pipe according to Solution 4, wherein the MFR is 0.1g / 10min or more and 1.5g / min or less.

[0026] Scheme 6 of the present invention is a multilayer cooling pipe according to any one of Schemes 1 to 5, wherein the ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 6 or fewer carbon atoms.

[0027] Scheme 7 of the present invention is a multi-layer cooling pipe according to Scheme 6, wherein the α-olefin constituting the ethylene-α-olefin copolymer (A) is at least one selected from the group consisting of propylene, 1-butene and 1-octene.

[0028] Solution 8 of the present invention is a multilayer cooling pipe according to any one of solutions 1 to 7, wherein the density of the ethylene-α-olefin copolymer (A) is 0.85 g / cm³. 3 Above and less than 0.88 g / cm 3 .

[0029] Scheme 9 of the present invention is a multi-layer cooling pipe according to any one of Schemes 1 to 8, wherein the propylene polymer (B) is a propylene homopolymer.

[0030] Scheme 10 of the present invention is a multi-layer cooling pipe according to any one of Schemes 1 to 9, wherein the modified propylene polymer (C) has an MFR of 0.4 g / 10 min or more and 500 g / 10 min or less at 180°C, 21.2 N and 1 mm pore size.

[0031] Scheme 11 of the present invention is a multi-layer cooling pipe according to any one of Schemes 1 to 10, wherein the modified propylene polymer (C) is a modified propylene polymer obtained by grafting maleic anhydride onto a propylene polymer.

[0032] Scheme 12 of the present invention is a multilayer cooling pipe according to any one of Schemes 1 to 11, wherein, in the polymer composition layer, at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives is present in an amount of 0.01% by mass or more and 0.30% by mass or less.

[0033] Scheme 13 of the present invention is a multilayer cooling pipe according to any one of Schemes 1 to 12, wherein the amide polymer contained in the amide polymer layer is an amide polymer containing monomers having 10 to 12 carbon atoms between amide groups.

[0034] Scheme 14 of the present invention is a multilayer cooling pipe according to any one of Schemes 1 to 13, wherein the amide polymer layer contains a plasticizer.

[0035] Solution 15 of the present invention is a multi-layer cooling pipe according to any one of solutions 1 to 14, wherein, when a test piece obtained by sheet forming the polymer composition into a thickness of 0.1 mm is measured based on JISK7161, the ratio of the tensile elongation at break TDα in the TD direction to the tensile elongation at break MDα in the MD direction, TDα / MDα, is 0.5 or more and 1.5 or less.

[0036] Solution 16 of the present invention is a multi-layer cooling pipe according to any one of solutions 1 to 15, wherein, when a test piece obtained by sheet forming the polymer composition into a thickness of 0.4 mm is measured based on JISK7136, the haze is 15% or more and 50% or less.

[0037] Solution 17 of the present invention is a multilayer cooling pipe according to any one of solutions 1 to 16, wherein the multilayer cooling pipe has a stacked structure in which the amide polymer layer and the polymer composition layer are in contact with each other, and exhibits coagulation and delamination when the amide polymer layer and the polymer composition layer are peeled off.

[0038] Solution 18 of the present invention is a multilayer cooling pipe according to any one of solutions 1 to 17, wherein the multilayer cooling pipe has a stacked structure in which the amide polymer layer and the polymer composition layer are stacked sequentially from the outer layer side.

[0039] Solution 19 of the present invention is a multilayer cooling pipe according to Solution 18, wherein the multilayer cooling pipe further comprises an propylene polymer layer, having a stacked structure in which the amide polymer layer, the polymer composition layer, and the propylene polymer layer are stacked sequentially from the outer layer side.

[0040] Solution 20 of the present invention is a multilayer cooling pipe according to Solution 19, wherein the thickness of the amide polymer layer is 0.1 to 6.0 mm, the thickness of the polymer composition layer is 0.01 to 1.0 mm, and the thickness of the propylene polymer layer is 0.1 to 3.0 mm.

[0041] Solution 21 of the present invention is based on the multilayer cooling pipe of Solution 18, wherein the multilayer cooling pipe further comprises an propylene polymer layer, having a stacked structure in which the propylene polymer layer, the polymer composition layer, the amide polymer layer, the polymer composition layer, and the propylene polymer layer are stacked sequentially from the outer layer side.

[0042] Scheme 22 of the present invention is a multilayer cooling pipe according to Scheme 21, wherein the thickness of the amide polymer layer is 0.1 to 6.0 mm, the thickness of the polymer composition layer is 0.01 to 1.0 mm, and the thickness of the propylene polymer layer is 0.1 to 3.0 mm.

[0043] Scheme 23 of the present invention is an application of a multi-layer cooling pipe in a heat exchange system of an automobile, wherein the multi-layer cooling pipe is any one of Schemes 1 to 22.

[0044] Scheme 24 of the present invention is an application of a multi-layer cooling pipe in the heat exchange system of an electric vehicle, wherein the multi-layer cooling pipe is any one of Schemes 1 to 22.

[0045] Invention Effects

[0046] According to the present invention, a multilayer cooling pipe can be provided, the multilayer cooling pipe comprising a polymer composition layer containing a modified polyolefin and an amide polymer layer, wherein the adhesion between the polymer composition layer and the amide polymer layer is improved, the adhesion between the two layers is excellent, and the adhesion strength is not easily reduced even when exposed to high temperatures. Attached Figure Description

[0047] Figure 1 This is a schematic cross-sectional view showing the structure of the multi-layer cooling pipe in this embodiment. Detailed Implementation

[0048] The embodiments of the present invention will now be described in detail. However, these embodiments are merely examples (representative examples) of the implementation of the present invention, and the present invention is not limited to them. The present invention can be implemented in any way without departing from its spirit.

[0049] In this specification, when using "~" followed by numerical values ​​or property values, the symbols are used in a manner that includes the values ​​before and after them. Furthermore, in this specification, "mass%" and "weight%", as well as "parts by mass" and "parts by weight", have the same meaning.

[0050] The multilayer cooling pipe of this embodiment includes a polymer composition layer and an amide polymer layer. The polymer composition layer is formed from a polymer composition comprising an ethylene-α-olefin copolymer (A), a propylene polymer (B), and a modified propylene polymer (C). The modified propylene polymer (C) is obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid onto the propylene polymer. The polymer composition comprises 18% by mass and 40% by mass of the ethylene-α-olefin copolymer (A), 40% by mass and 81% by mass of the propylene polymer (B), and 1% by mass and 19% by mass of the modified propylene polymer (C).

[0051] <Polymer Composition>

[0052] The polymer composition forming the polymer composition layer in the multilayer cooling pipe of this embodiment includes an ethylene-α-olefin copolymer (A), a propylene polymer (B), and a modified propylene polymer (C) obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of the unsaturated carboxylic acid onto the propylene polymer.

[0053] Composition (A): Ethylene-α-olefin copolymer (A)

[0054] Ethylene-α-olefin copolymer (A) refers to a copolymer that contains ethylene units and α-olefin units as structural units, and has the highest content (mass%) of ethylene units among all structural units.

[0055] In this specification, "unit" refers to a monomer unit contained in a copolymer. For example, "ethylene unit" in an ethylene-based polymer refers to an ethylene-based monomer unit.

[0056] Ethylene-α-olefin copolymer (A) is a component used to improve the wettability of the adhesive interface and enhance adhesive strength. Additionally, it also helps to mitigate strain at the adhesive interface caused by heating / cooling during high-temperature shaping and maintain adhesive strength.

[0057] The α-olefin constituting the ethylene-α-olefin copolymer (A) is not limited. Specifically, examples include propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, etc., and one or more of these can be used. Among them, as the α-olefin, an α-olefin with 8 or fewer carbon atoms is preferred, an α-olefin with 6 or fewer carbon atoms is more preferred, and an α-olefin with 3 or more carbon atoms is also preferred. That is, the α-olefin preferably has 3 to 8 carbon atoms. In particular, from the viewpoint of improving compatibility with propylene polymers (B) and modified propylene polymers (C) and suppressing phase separation to improve material strength and thus adhesive strength, the α-olefin is more preferably propylene, 1-butene, 1-hexene, or 1-octene, and even more preferably at least one selected from the group consisting of propylene, 1-butene, and 1-octene.

[0058] The lower limit of the content of α-olefin units in the ethylene-α-olefin copolymer (A) is preferably 3% by mass, more preferably 6% by mass, further preferably 9% by mass, particularly preferably 12% by mass, and especially preferably 15% by mass. If the lower limit of the content of α-olefin units is within this range, the ethylene-α-olefin copolymer (A) and the polymer composition containing it become softer, the wettability of the adhesive interface is improved, and therefore there is a tendency for excellent adhesive strength not only at room temperature but also after high-temperature shaping. In addition, by including a certain amount or more of α-olefin components with structures similar to those of the propylene polymer (B) and the modified propylene polymer (C) in the ethylene-α-olefin copolymer (A), there is a tendency to improve the compatibility with the propylene polymer (B) and the modified propylene polymer (C) and suppress phase separation, thereby improving the material strength and thus the adhesive strength.

[0059] On the other hand, the upper limit of the content of α-olefin units in the ethylene-α-olefin copolymer (A) is preferably 40% by mass, more preferably 39% by mass, further preferably 38% by mass, particularly preferably 37% by mass, and especially preferably 36% by mass. If the upper limit of the content of α-olefin units is within this range, the crystallinity of the ethylene-α-olefin copolymer (A) can be maintained at a certain level, the material strength can be maintained, and therefore the material strength (cohesive force) of the polymer composition in which it is blended is also improved, and the adhesive strength is sufficient.

[0060] The ethylene-α-olefin copolymer (A) may contain monomer units other than ethylene and the aforementioned α-olefin. Examples of other monomer units constituting these monomer units include vinyl acetate, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, etc. Here, "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid.

[0061] The content of ethylene units, α-olefin units, and other monomer units in the ethylene-α-olefin copolymer (A) can be determined by infrared spectroscopy.

[0062] The lower limit of the melt flow rate (MFR) of the ethylene-α-olefin copolymer (A) measured at 190°C, 21.2 N, and 2 mm pore size is preferably 0.01 g / 10 min, more preferably 0.05 g / 10 min, further preferably 0.1 g / 10 min, particularly preferably 0.2 g / 10 min, and especially preferably 0.3 g / 10 min. If the lower limit of the MFR of the ethylene-α-olefin copolymer (A) is within this range, the polymer composition has sufficient fluidity, thus exhibiting excellent melt-forming properties. Furthermore, phase separation between the ethylene-α-olefin copolymer (A) and the propylene polymer (B) and modified propylene polymer (C) is suppressed, the surface area of ​​the matrix / domain interface increases, and the material strength (cohesion) is maintained, resulting in a tendency for excellent adhesive strength.

[0063] On the other hand, the upper limit of the MFR of the ethylene-α-olefin copolymer (A) measured at 190°C, 21.2 N, and 2 mm pore size is preferably 4.0 g / 10 min, more preferably 3.0 g / 10 min, further preferably 2.0 g / 10 min, particularly preferably 1.5 g / 10 min, and especially preferably 1.0 g / 10 min. If the upper limit of the MFR of the ethylene-α-olefin copolymer (A) is within this range, the molecular weight is sufficiently high, thus tending to improve the material strength (cohesive force) of the polymer composition and thereby easily exhibit excellent adhesive strength.

[0064] That is, the MFR of the ethylene-α olefin copolymer (A) is preferably in the range of 0.01 g / 10 min or more and 4.0 g / 10 min or less. Within the range, the upper and lower limits can be any combination of the above preferred values, and more preferably 0.1 g / 10 min or more and 1.5 g / min or less.

[0065] There are no particular limitations on the density (JIS K7112) of the ethylene-α-olefin copolymer (A), but from the viewpoint of maintaining cohesion and improving adhesion, the lower limit is preferably 0.80 g / cm³. 3 More preferably, it is 0.81 g / cm³. 3 Further preferred value is 0.82 g / cm³. 3 The preferred value is 0.83 g / cm³. 3 The preferred value is 0.84 g / cm³. 3 The optimal value is 0.85 g / cm³. 3 On the other hand, from the viewpoint of improving the wettability of the bonding interface and enhancing adhesion, the upper limit is preferably 0.93 g / cm³. 3More preferably, it is 0.92 g / cm³. 3 Further preferred is 0.91 g / cm³ 3 The preferred value is 0.90 g / cm³. 3 A further preferred value is 0.89 g / cm³. 3 The preferred value is 0.88 g / cm³. 3 The optimal value is less than 0.88 g / cm³. 3 .

[0066] That is, the density of the ethylene-α-olefin copolymer (A) is preferably 0.80 g / cm³. 3 Above and 0.93g / cm 3 The following range, within which the upper and lower limits can be arbitrarily combined with the above preferred values, is more preferably 0.85 g / cm³. 3 Above and less than 0.88 g / cm 3 .

[0067] As a suitable ethylene-α-olefin copolymer (A) for the present invention, commercially available products may also be used. Appropriately selected products that meet the described characteristics may be selected from the following: the "TAFMER (registered trademark)" series manufactured by Mitsui Chemicals, the "ENGAGE (registered trademark)" series manufactured by Dow Chemical, the "Solumer (registered trademark)" series manufactured by SK Chemicals, the "LUCENE (registered trademark)" series manufactured by LG Chem, the "FORTIFY (registered trademark)" series manufactured by SABIC, and polyolefin elastomers (POE) manufactured by Lotte Chemical.

[0068] The ethylene-α-olefin copolymer (A) may use only one monomer or may contain two or more monomers with different compositions and properties.

[0069] As an ethylene-α-olefin copolymer (A), its ethylene and α-olefin components can be of biomass origin. Biomass origin refers to substances synthesized from renewable biomass resources through chemical or biological means. Biomass-derived ethylene-α-olefin copolymers (A) have the following characteristics: even when incinerated, they do not increase the concentration of carbon dioxide in the atmosphere due to the carbon-neutral nature of biomass.

[0070] The above-mentioned biomass-derived ethylene-α-olefin copolymer (A) preferably uses plant-derived ethylene and α-olefins obtained from plant raw materials as raw materials.

[0071] Plant-derived ethylene-alpha olefin copolymers (A) and petroleum-derived ethylene-alpha olefin copolymers (A) can typically be distinguished by biomass (the ratio of the concentration of carbon-14C in a sample to standard modern carbon). Carbon exists in nature in different weights: carbon-12 (12C), carbon-13 (13C), and carbon-14 (14C). Carbon-14C has the property of existing in the atmosphere at a certain proportion and decreasing over a predetermined period, becoming half its original amount in 5730 years (half-life). Plant-derived ethylene-alpha olefin copolymers (A) contain carbon-14C (radioactive carbon-14, half-life 5730 years), while petroleum-derived ethylene-alpha olefin copolymers (A) do not. Therefore, by determining the concentration of carbon-14C in ethylene-alpha olefin copolymers (A) using accelerator mass spectrometry, plant-derived and petroleum-derived sources can be distinguished. Furthermore, biomass can also serve as an indicator of the proportion of plant-derived components in polymer compositions containing both plant-derived and petroleum-derived polymers.

[0072] Biometrics can be determined, for example, by the following methods.

[0073] The sample to be tested is burned to produce carbon dioxide. Using iron as a catalyst, the carbon dioxide purified in a vacuum line is reduced by hydrogen to produce graphite. The graphite is then installed in a dedicated 14C-AMS apparatus (manufactured by NEC Corporation) based on a tandem accelerator to measure the 14C count, 13C concentration (13C / 12C), and 14C concentration (14C / 12C). The ratio of the 14C concentration of the sample carbon to that of standard modern carbon is calculated from these measurements.

[0074] As an ethylene-α-olefin copolymer (A), it can be a substance obtained from biomass naphtha in a so-called mass balance manner. Biomass naphtha is obtained by decomposing and refining previously discarded animal fats, waste cooking oils, vegetable oil processing waste and residues, and vegetable oils, and is therefore preferred from an environmental protection point of view.

[0075] From an environmental protection perspective, ethylene-α-olefin copolymers (A) can be made from recycled raw materials. Recycling methods can include material recycling and chemical recycling. Material recycling refers to the process of crushing and dissolving waste plastics for reuse as raw materials for the same purpose. This includes post-consumer recycling (PCR), which involves recycling and reusing products used in the market, and post-industrial recycling (PIR), which involves regenerating and reusing materials generated during the product manufacturing process before they enter the market. Chemical recycling refers to a mechanism that restores waste plastics to their raw material state through chemical decomposition and reuses them as product raw materials. It is preferred from the perspective of preventing degradation of physical properties.

[0076] Composition (B): Acrylic polymer (B)

[0077] The polymer composition constituting the polymer composition layer of the multi-layer cooling pipe includes a propylene polymer (B). The aforementioned propylene polymer (B) refers to a polymer that contains propylene units as structural units and has the highest content (by mass%) of propylene units among all structural units.

[0078] Acrylic polymer (B) is a component that imparts heat resistance and rigidity to the polymer composition. Furthermore, in the case of a multi-layered cooling pipe having an acrylic polymer layer, it plays a role in ensuring good adhesion to the acrylic polymer layer.

[0079] There are no particular limitations on the propylene-based polymer (B), and examples include propylene homopolymers and propylene-α-olefin copolymers. Among these, propylene homopolymers are preferred from the viewpoint of balancing heat resistance and rigidity. By using propylene homopolymers, the polymer composition layer does not flow even when molded at high temperatures, thus maintaining material strength and making it easier to maintain adhesive strength.

[0080] Examples of propylene-α-olefin copolymers include propylene-ethylene copolymers, propylene-butene copolymers, propylene-pentene copolymers, propylene-hexene copolymers, propylene-octene copolymers, propylene-(4-methyl-1-pentene) copolymers, propylene-ethylene-butene copolymers, propylene-ethylene-hexene copolymers, propylene-ethylene-octene copolymers, propylene-butene-hexene copolymers, propylene-butene-octene copolymers, and propylene-hexene-octene copolymers. All of the above copolymers can be exemplified as random copolymers or block copolymers.

[0081] The content of propylene units in the propylene polymer (B) is preferably 90% by mass or more, more preferably 92% by mass or more, even more preferably 95% by mass or more, particularly preferably 97% by mass or more, and especially preferably 100% by mass.

[0082] The lower limit of the flexural modulus of the propylene polymer (B) is preferably 600 MPa, more preferably 700 MPa. On the other hand, the upper limit is preferably 2000 MPa, more preferably 1800 MPa. That is, the flexural modulus of the propylene polymer (B) is preferably in the range of 600 MPa or more and 2000 MPa or less. By setting it to the above-mentioned numerical range, it becomes easier to control the stiffness.

[0083] It should be noted that the flexural modulus of the propylene polymer (B) is based on the value determined according to JIS K 7171:2016.

[0084] The melt flow rate (MFR) of the propylene polymer (B) is not particularly limited. From the viewpoint of reducing energy load during manufacturing and improving the processing characteristics of the molded product, the lower limit is preferably 0.1 g / 10 min, more preferably 0.3 g / 10 min, and even more preferably 0.5 g / 10 min. Similarly, from the same viewpoint, the upper limit is preferably 50 g / 10 min, more preferably 20 g / 10 min, and even more preferably 5 g / 10 min. That is, the MFR of the propylene polymer (B) is preferably in the range of 0.1 g / 10 min or more and 50 g / 10 min or less.

[0085] It should be noted that, in this specification, the melt flow rate (MFR) of the propylene polymer (B) is a value determined according to JIS K 7210:2014 under the conditions of 230°C, 21.2 N load, 2 mm orifice diameter, and 10 minutes.

[0086] As one option for the propylene polymer (B), it is preferable to satisfy at least one of the following: the content of propylene units in the propylene polymer is 90% by mass or more; the flexural modulus is 600 MPa or more and 2000 MPa or less; and the melt flow rate (MFR) is 0.1 g / 10 min or more and 50 g / 10 min or less. More preferably, at least two of these conditions are met, and particularly preferably all of them are met.

[0087] It should be noted that when two or more components are mixed and used as a propylene polymer (B), the preferred mixture satisfies the above conditions.

[0088] Propylene polymers (B) are manufactured using methods known in the art. Examples include batch processes, gas-phase processes, and slurry processes using catalysts such as Ziegler-Natta catalysts and metallocene catalysts.

[0089] As a suitable propylene polymer (B) for the present invention, commercially available products can be used. Specifically, products that meet the aforementioned characteristics can be appropriately selected from the following: NOVATEC PP manufactured by Nippon Polypropylene Co., Ltd., Prim Polypro PP manufactured by Prim Polypro Co., Ltd., SUMITOMONOBLEN PP manufactured by Sumitomo Chemical Co., Ltd., polypropylene block copolymer manufactured by SunAllomer Ltd., Moplen PP manufactured by LyondellBasell, ExxonMobil PP manufactured by ExxonMobil, Formolene PP manufactured by Formosa Plastics, Borealis PP manufactured by Borealis, SEETEC PP manufactured by LG Chem, ASI POLYPROPYLENE manufactured by A. Schulman, INEOS PP manufactured by INEOS Olefins & Polymers, and Braskem PP manufactured by Braskem. PP, "Sumsung Total" manufactured by Samsung Total Petrochemicals, "Sabic (registered trademark) PP" manufactured by Sabic, "TOTAL PETROCHEMICALS Polypropylene" manufactured by TOTAL PETROCHEMICALS, "YUPLENE (registered trademark)" manufactured by SK, etc.

[0090] Acrylic polymers (B) can be a single type or contain two or more different monomer compositions and properties.

[0091] As a propylene-based polymer (B), similar to the ethylene-α-olefin copolymer (A), from an environmental protection perspective, biomass-derived or recycled materials can also be used.

[0092] Composition (C): Modified propylene polymer (C) obtained by grafting at least one of unsaturated carboxylic acids and derivatives of unsaturated carboxylic acids onto a propylene polymer.

[0093] The polymer composition constituting the polymer composition layer of the multilayer cooling pipe includes a modified propylene polymer (C) grafted with at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid (hereinafter, sometimes simply referred to as "modified propylene polymer (C)"). The modified propylene polymer (C) contains reactive polar groups and is therefore a component used to exhibit strong adhesive strength by reacting with the functional groups of the adherend to form covalent bonds.

[0094] In this specification, "unsaturated carboxylic acids or their derivatives" are sometimes referred to as modifiers. Additionally, "grafting" refers to bonding unsaturated carboxylic acids or their derivatives to a propylene polymer. It should be noted that there are no particular restrictions on the bonding position of the unsaturated carboxylic acids or their derivatives in the modified propylene polymer, as long as they are introduced to at least one of the main chain ends or side chains of the propylene polymer. "Propylene polymer" refers to a polymer that contains propylene units as structural units, and where the content (mass%) of propylene units is the highest among all structural units.

[0095] The content of propylene units in the modified propylene polymer (C) is preferably 80% by mass or more, more preferably 82% by mass or more, even more preferably 84% by mass or more, particularly preferably 86% by mass or more, and especially preferably 88% by mass or more. Based on the above viewpoint, the content of propylene units in the propylene polymer used as a raw material is preferably 80% by mass or more, more preferably 82% by mass or more, even more preferably 84% by mass or more, particularly preferably 86% by mass or more, and especially preferably 88% by mass or more.

[0096] There are no particular restrictions on the propylene-based polymers used as raw materials, and they can be selected arbitrarily from the following substances or combinations thereof: propylene homopolymers; propylene-ethylene copolymers (commonly known as random PP), propylene-butene copolymers, propylene-pentene copolymers, propylene-hexene copolymers, propylene-octene copolymers, propylene-(4-methyl-1-pentene) copolymers, propylene-ethylene-butene copolymers, propylene-ethylene-hexene copolymers, propylene-ethylene-octene copolymers, propylene-butene-hexene copolymers, propylene-butene-octene copolymers, propylene-hexene-octene copolymers, and other propylene-α-olefin copolymers; propylene-based polymers in which ethylene rubber components are dispersed in the propylene phase (commonly known as block PP).

[0097] When propylene homopolymers are used as the raw material for propylene-based polymers, the compatibility with propylene-based polymers (B) is improved. The increased surface area at the matrix / domain interface due to micro-dispersion leads to improved material strength (cohesion) and consequently, increased adhesive strength. Furthermore, the high crystallinity of propylene homopolymers contributes to their inherent high material strength (cohesion), further enhancing the cohesion and adhesive strength of the composition. Propylene homopolymers are commonly known, and propylene homopolymers with arbitrary structures such as atactic, isotactic, and syndiotactic can be used. From a heat resistance perspective, isotactic structures are particularly preferred.

[0098] When using propylene-α-olefin copolymers as raw materials in propylene-based polymers, it is expected that using propylene-α-olefin copolymers with low crystallinity can improve the wettability of the adhesive interface and increase the adhesive strength. Furthermore, it is expected that the strain at the adhesive interface generated after high-temperature molding can be mitigated, maintaining the adhesive strength. From the viewpoints of melt molding properties, heat resistance, and industrial availability, propylene-ethylene copolymers are preferred as propylene-α-olefin copolymers.

[0099] When using block PP containing vinyl rubber components, improved interfacial wettability and increased bond strength can be expected. Furthermore, it can mitigate interfacial strain generated after high-temperature molding, thus maintaining bond strength.

[0100] There are no particular restrictions on the density (JIS K7112) of the propylene polymer in the raw material. From the viewpoint of maintaining cohesion and improving adhesion, the lower limit is preferably 0.81 g / cm³. 3 More preferably, it is 0.82 g / cm³. 3 Further preferred value is 0.83 g / cm³. 3 The preferred value is 0.84 g / cm³. 3 The preferred value is 0.85 g / cm³. 3 On the other hand, from the viewpoint of improving the wettability of the adhesive interface and enhancing adhesion, the upper limit is preferably 0.95 g / cm³. 3 More preferably 0.94 g / cm³ 3 A further preferred value is 0.93 g / cm³. 3 The preferred value is 0.92 g / cm³. 3 The preferred value is 0.91 g / cm³. 3 That is, the density of the propylene polymer in the raw material is preferably 0.81 g / cm³. 3 Above and 0.95g / cm 3 The following range.

[0101] The molecular weight flow rate (MFR, 230°C, 21.2 N, 2 mm orifice) of the propylene polymer in the raw material is not particularly limited. From the viewpoint of imparting sufficient fluidity to the polymer composition and ensuring melt molding properties and wettability at the adhesive interface, the lower limit is preferably 0.1 g / 10 min, more preferably 0.2 g / 10 min, even more preferably 0.3 g / 10 min, particularly preferably 0.4 g / 10 min, and especially preferably 0.5 g / 10 min. On the other hand, from the viewpoint of increasing molecular weight and thus increasing cohesive force to ensure adhesive strength, the upper limit is preferably 20 g / 10 min, more preferably 18 g / 10 min, even more preferably 16 g / 10 min, particularly preferably 14 g / 10 min, and especially preferably 12 g / 10 min. That is, the MFR of the propylene polymer in the raw material is preferably in the range of 0.1 g / 10 min or more and 20 g / 10 min or less.

[0102] The propylene polymer that forms the raw material of the modified propylene polymer (C) can be manufactured or commercially available products can be used. In the case of manufacturing the propylene polymer as a raw material, it is manufactured using methods known in the art.

[0103] The propylene polymers that make up the raw materials of the modified propylene polymer (C) are also biomass-derived or recycled materials, just like the ethylene-α-olefin copolymer (A) and the propylene polymer (B). From an environmental protection point of view, these polymers can also be biomass-derived or recycled materials.

[0104] There are no particular limitations on the unsaturated carboxylic acids used for modification; representative examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. Furthermore, there are no particular limitations on the derivatives of unsaturated carboxylic acids; representative examples include acid anhydrides, esters, amides, imides, and metal salts. Specific examples of derivatives of unsaturated carboxylic acids include: maleic anhydride, nadic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate, monoethyl maleate, diethyl maleate, monomethyl itaconic acid, diethyl itaconic acid, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N,N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-n-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, or potassium methacrylate.

[0105] Unsaturated carboxylic acids and their derivatives can be used alone, or in any combination and ratio of two or more. Among them, maleic acid and its anhydride are particularly suitable due to their low electron density and high reactivity, with maleic anhydride being the most preferred.

[0106] Graft modification of propylene-based polymers in raw materials can be carried out by various methods known to exist. Examples of modification methods include melt modification, which involves adding the modifier to the molten propylene-based polymer of the raw material to induce graft copolymerization, and solution modification, which involves adding the modifier to the propylene-based polymer of the raw material dissolved in a solvent to induce graft copolymerization. These methods are not particularly limited, but melt modification is preferred from the viewpoint of productivity and economy. It should be noted that, for efficient graft modification, modification is preferably carried out in the presence of a free radical initiator.

[0107] There are no particular limitations on the free radical initiator, but organic peroxides or azo compounds are preferred, with organic peroxides being particularly preferred. Specifically, examples include: di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyn-3, 1,4-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)cyclohexane, 4,4-bis(tert-butylperoxy)valerate n-butyl ester, 2,2-bis(4,4-tert-butylperoxycyclohexyl)propane, 2,2-bis(tert-butylperoxy)butane, or 1,1-bis(tert-butylperoxy)cyclododecane and other dialkyl peroxides; tert-butyl peroxyacetate, tert-butyl peroxy2-ethylhexanoate, tert-butyl peroxyneoplate, tert-butyl perlaurate, tert-butyl peroxybenzoate, etc. Peroxides such as tert-butyl peroxyisopropyl carbonate, tert-butyl peroxymaleic acid, di-tert-butyl peroxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, or 2,5-dimethyl-2,5-di(benzoylperoxy)hexyn-3, 2,5-dimethyl-2,5-di(toluylperoxy)hexane; diacyl peroxides such as di-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, or dibenzoyl peroxide; hydroperoxides such as tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, or 2,5-dimethyl-2,5-di(hydroperoxy)hexane; or ketone peroxides such as methyl ethyl ketone peroxide or cyclohexanone peroxide, but not particularly limited to these.

[0108] Free radical initiators can be used alone, or two or more can be used in any combination and ratio.

[0109] From the perspective of grafting modification efficiency, free radical initiators with a half-life of 1 minute and a decomposition temperature of 100°C or higher are preferred. Specifically, dialkyl peroxides such as di-tert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 are preferred; or peroxide esters such as tert-butyl peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, or 2,5-dimethyl-2,5-di(benzoylperoxy)hexyne-3 are preferred.

[0110] There is no particular limitation on the amount of free radical initiator used, but it is preferably 0.001 to 10 parts by mass relative to 100 parts by mass of the propylene polymer in the raw material.

[0111] After the above modification reaction, unreacted unsaturated carboxylic acid components can be removed. This treatment method is not particularly limited; for example, the following method can be used: The modified propylene polymer after the modification reaction is placed in a storage tank with a structure that allows gas to be blown in from the bottom of the device. The device is heated to approximately 100°C using a heater or hot oil, and inert gases such as nitrogen or air are blown in from the bottom of the device for 6 to 24 hours.

[0112] The proportion (hereinafter sometimes referred to as "grafting rate") of the modifying component in the modified propylene polymer (C), specifically the unsaturated carboxylic acid grafted onto the propylene polymer, and its derivatives, varies depending on the type of propylene polymer and modifier used as the raw material, and is not particularly limited. From the viewpoint of improving the adhesiveness of the amide polymer constituting the multilayer cooling pipe of this embodiment, especially amide polymers containing monomers with 10 to 12 carbon atoms between amide groups, having a low amide group concentration and being less likely to react with unsaturated carboxylic acids to form covalent bonds, or amide polymers containing plasticizers that precipitate at the bonding interface and hinder adhesion, the grafting rate is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and especially preferably 1% by mass or more. On the other hand, from the viewpoint of preventing cross-linking of the propylene polymer in the raw material and suppressing the deterioration of melt molding properties and the generation of foreign matter, the upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, particularly preferably 7% by mass or less, and especially preferably 5% by mass or less. That is, the grafting rate of the modified propylene polymer (C) is preferably in the range of 0.01% by mass or more and 20% by mass or less.

[0113] Here, the grafting rate can be determined by directly pressing the modified propylene polymer (C) into a 0.1 mm thick sheet as the test sample, and using infrared absorption spectroscopy based on the specific absorption characteristics of the modifier (carboxylic acid and its derivatives) in the resin. Specifically, it can be determined by measuring the 1900–1600 cm⁻¹... -1 The characteristic absorption of the carbonyl group in the (C=O stretching vibration band) is used to determine the value.

[0114] That is, the amount of the modifier (unsaturated carboxylic acid, or its derivative) involved in the grafting is calculated based on the measured value of the carbonyl characteristic absorption, and the grafting rate (mass %) is calculated as its mass ratio relative to the propylene polymer of the raw material.

[0115] It should be noted that, in modifications based on unsaturated carboxylic acids, sometimes not 100% of the added unsaturated carboxylic acid is used in the reaction; instead, unreacted unsaturated carboxylic acids remain in the modified propylene polymer (C). However, the modification amount (grafting rate) mentioned above in this specification refers to the value measured using the above method.

[0116] There are no particular limitations on the density (JIS K7112) of the modified propylene polymer (C), but from the viewpoint of maintaining cohesion and improving adhesion, the lower limit is preferably 0.81 g / cm³. 3 More preferably, it is 0.82 g / cm³. 3 Further preferred value is 0.83 g / cm³. 3 The preferred value is 0.84 g / cm³. 3 The preferred value is 0.85 g / cm³. 3 On the other hand, from the viewpoint of improving the wettability of the adhesive interface and enhancing adhesion, the upper limit is preferably 0.95 g / cm³. 3 More preferably, it is 0.94 g / cm³. 3 Further preferred is 0.93 g / cm³ 3 The preferred value is 0.92 g / cm³. 3 The preferred value is 0.91 g / cm³. 3 .

[0117] That is, the density of the modified propylene polymer (C) is preferably 0.81 g / cm³. 3 Above and 0.95g / cm 3 The following ranges, within which the upper and lower limits can be arbitrarily combined with the above preferred values.

[0118] The melt flow rate (MFR) of the modified propylene polymer (C) is not particularly limited. From the viewpoint of imparting sufficient flowability to the polymer composition and ensuring melt moldability, the lower limit is preferably 0.01 g / 10 min, more preferably 0.05 g / 10 min, further preferably 0.1 g / 10 min, particularly preferably 0.2 g / 10 min, even more preferably 0.3 g / 10 min, especially preferably 0.4 g / 10 min, particularly preferably 0.5 g / 10 min, and most preferably 1 g / 10 min. On the other hand, from the viewpoint of increasing molecular weight and thus increasing cohesive force to ensure adhesive force, the upper limit of the MFR is preferably 1000 g / 10 min, more preferably 900 g / 10 min, further preferably 800 g / 10 min, particularly preferably 700 g / 10 min, even more preferably 600 g / 10 min, particularly preferably 500 g / 10 min, especially preferably 450 g / 10 min, and most preferably 430 g / 10 min.

[0119] That is, the MFR of the modified propylene polymer (C) is preferably in the range of 0.01 g / 10 min or more and 1000 g / 10 min, and the upper and lower limits can be arbitrarily combined within the range of the above preferred values. Specifically, the MFR of the modified propylene polymer (C) is more preferably 0.4 g / 10 min or more and 500 g / 10 min or less, and even more preferably 0.4 g / 10 min or more and 430 g / 10 min or less.

[0120] Here, the MFR of the modified propylene polymer (C) refers to the value at 180°C, a load of 21.2 N, and a pore size of 1 mm.

[0121] As a suitable modified propylene polymer (C), commercially available products can be used, for example, products that meet the aforementioned properties can be appropriately selected from the "Modic (registered trademark)" series manufactured by Mitsubishi Chemical Corporation.

[0122] Modified propylene polymers (C) can be used alone or by mixing two or more substances with different monomer compositions and properties.

[0123] Content of Ingredients (A) to (C)

[0124] In this embodiment, the polymer composition comprises 18% by mass and 40% by mass of an ethylene-α-olefin copolymer (A), 40% by mass and 81% by mass of a propylene polymer (B), and 1% by mass and 19% by mass of a modified propylene polymer (C). If the contents of components (A) to (C) are within the aforementioned range, the peeling morphology is agglomerated peeling, and thus the adhesive strength can be maintained even when the material is shaped in a heat-resistant environment.

[0125] The content of ethylene-α-olefin copolymer (A) in the polymer composition is more than 18% by mass and less than 40% by mass.

[0126] The lower limit of the content of ethylene-α-olefin copolymer (A) in the polymer composition is preferably 19% by mass, more preferably 20% by mass, further preferably 21% by mass, and particularly preferably 22% by mass. If the lower limit of the content of ethylene-α-olefin copolymer (A) is within this range, there is a tendency to improve the wettability of the adhesive interface and achieve excellent adhesive strength. Furthermore, generally, when exposed to high-temperature environments such as during the shaping of cooling channels and then cooled, the linear expansion coefficients of the polymer composition layer and the amide polymer layer are different, thus strain occurs at the adhesive interface, and reaction sites are cut off, making it easy for adhesive strength to decrease. However, if the content of ethylene-α-olefin copolymer (A) is within the above-mentioned range, the strain generated at the adhesive interface can be mitigated, and reaction sites can be maintained, thus there is a tendency to maintain adhesive strength even after high-temperature shaping. On the other hand, the upper limit of the content of ethylene-α-olefin copolymer (A) in the polymer composition is preferably 35% by mass, more preferably 33% by mass, further preferably 32% by mass, particularly preferably 31% by mass, and most preferably 30% by mass. If the content of ethylene-α-olefin copolymer (A) is within this upper limit, the polymer composition will not become too soft and will be able to maintain sufficient material strength (cohesion), thus tending to have higher adhesive strength. Furthermore, since phase separation with the propylene polymer (B) and modified propylene polymer (C) is suppressed, the surface area of ​​the matrix / domain interface increases, thus maintaining material strength (cohesion), resulting in sufficient adhesive strength. Moreover, generally speaking, ethylene-α-olefin copolymers are low-melting-point materials compared to general polyolefin polymers; therefore, they tend to flow at high temperatures when shaping multilayer cooling channels, making it difficult to maintain sufficient material strength (cohesion). However, by setting the content within the aforementioned upper limit, there is a tendency to maintain material strength (cohesion) even at high temperatures, thereby maintaining adhesive strength.

[0127] From the perspective of material strength (cohesion), heat resistance, and adhesive strength, the content of propylene polymer (B) in the polymer composition is 40% by mass or more and 81% by mass or less.

[0128] The lower limit of the content of propylene polymer (B) in the polymer composition is preferably 45% by mass, more preferably 46% by mass, further preferably 49% by mass, even more preferably 50% by mass, particularly preferably 51% by mass, especially preferably 53% by mass, particularly preferably 55% by mass, especially more preferably 60% by mass, and most preferably 70% by mass. If the lower limit of the content of propylene polymer (B) is within this range, there is a tendency for excellent material strength (cohesion) and heat resistance. The upper limit of the content of propylene polymer (B) in the polymer composition is preferably 80% by mass, more preferably 79% by mass, further preferably 78% by mass, particularly preferably 77% by mass, and most preferably 76% by mass. If the upper limit of the content of propylene polymer (B) is within this range, there is a tendency for excellent adhesive strength.

[0129] From the viewpoint of increasing the number of reaction sites with the amide polymer layer to improve adhesive strength, it is preferable to contain a larger amount of the modified propylene polymer (C), while from the viewpoint of material strength (cohesion), it is preferable to contain a smaller amount. Therefore, from the viewpoint of optimizing the balance between reactivity with the amide polymer layer and material strength (cohesion), the content of the modified propylene polymer (C) in the polymer composition is 1% by mass or more and 19% by mass or less.

[0130] The lower limit of the content of modified propylene polymer (C) in the polymer composition is preferably 1.2% by mass, more preferably 1.4% by mass, even more preferably 1.6% by mass, particularly preferably 1.8% by mass, and can be 2% by mass. If the lower limit of the content of modified propylene polymer (C) is within this range, there is a tendency for excellent adhesive strength. The upper limit of the content of modified propylene polymer (C) in the polymer composition is preferably 18% by mass, more preferably 17% by mass, even more preferably 16% by mass, and particularly preferably 15% by mass. If the upper limit of the content of modified propylene polymer (C) is within this range, there is a tendency for material strength to be easily maintained.

[0131] Regarding the specific preferred content range of each component, relative to the overall polymer composition, the content of ethylene-α-olefin copolymer (A) is 18% by mass or more and 40% by mass or less, the content of propylene polymer (B) is 41% by mass or more and 81% by mass or less, and the content of modified propylene polymer (C) is 1% by mass or more and 19% by mass or less.

[0132] More preferably, relative to the overall polymer composition, the content of the ethylene-α-olefin copolymer (A) is 19% or more and 35% or less by mass, the content of the propylene polymer (B) is 46% or more and 80% or less by mass, and the content of the modified propylene polymer (C) is 1% or more and 19% or less by mass.

[0133] Furthermore, the preferred content of each component is that, relative to the overall polymer composition, the content of ethylene-α-olefin copolymer (A) is 20% or more and 33% or less by mass, the content of propylene polymer (B) is 49% or more and 79% or less by mass, and the content of modified propylene polymer (C) is 1% or more and 18% or less by mass.

[0134] In addition, the preferred content of each component is that, relative to the polymer composition as a whole, the content of ethylene-α-olefin copolymer (A) is 21% or more and 32% or less by mass, the content of propylene polymer (B) is 51% or more and 78% or less by mass, and the content of modified propylene polymer (C) is 1% or more and 17% or less by mass.

[0135] Furthermore, the content of each component is particularly preferred to be such that, relative to the polymer composition as a whole, the content of ethylene-α-olefin copolymer (A) is 22% or more and 31% or less by mass, the content of propylene polymer (B) is 53% or more and 77% or less by mass, and the content of modified propylene polymer (C) is 1% or more and 16% or less by mass.

[0136] Furthermore, the content of each component may be, relative to the polymer composition as a whole, ethylene-α-olefin copolymer (A) having a content of 22% or more and 30% or less by mass, propylene polymer (B) having a content of 55% or more and 76% or less by mass, and modified propylene polymer (C) having a content of 2% or more and 15% or less by mass.

[0137] The polymer composition of this embodiment preferably has a value of 0.22 or more and 0.65 or less, as shown in the following formula (1) calculated from the content of components (A) to (C).

[0138] PA / (PB+PC)…(1)

[0139] In equation (1),

[0140] PA represents the percentage (by mass) of ethylene-α-olefin copolymer (A) in the polymer composition.

[0141] PB represents the percentage (by mass) of propylene polymer (B) in the polymer composition.

[0142] PC represents the percentage (by mass) of the modified propylene polymer (C) in the polymer composition.

[0143] In the polymer composition, from the viewpoint of adhesive strength, the lower limit of the value shown in Formula (1) is preferably 0.22, more preferably 0.23, further preferably 0.24, and especially preferably 0.25. In the polymer composition, from the viewpoint of maintaining adhesive strength and material strength after high-temperature shaping to ensure high adhesive strength, the upper limit of the value shown in Formula (1) is preferably 0.65, more preferably 0.55, further preferably 0.50, and especially preferably 0.45.

[0144] The polymer composition preferably satisfies both the specific preferred content range of each component in the polymer composition and the preferred numerical range of the value shown in formula (1).

[0145] Specifically, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 18% by mass or more and 40% by mass or less, the content of propylene polymer (B) is 41% by mass or more and 81% by mass or less, and the content of modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, and the numerical range shown in formula (1) is 0.22 or more and 0.65 or less, more preferably 0.23 or more and 0.55 or less, further preferably 0.24 or more and 0.50 or less, and especially preferably 0.25 or more and 0.45 or less.

[0146] In addition, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 19% by mass or more and 35% by mass or less, the content of propylene polymer (B) is 46% by mass or more and 80% by mass or less, and the content of modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, and the numerical range shown in formula (1) is 0.22% or more and 0.65% or less, more preferably 0.23% or more and 0.55% or less, further preferably 0.24% or more and 0.50% or less, and especially preferably 0.25% or more and 0.45% or less.

[0147] In addition, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 20% or more and 33% or less by mass, the content of propylene polymer (B) is 49% or more and 79% or less by mass, and the content of modified propylene polymer (C) is 1% or more and 18% or less by mass, and the numerical range shown in formula (1) is 0.22 or more and 0.65 or less, more preferably 0.23 or more and 0.55 or less, further preferably 0.24 or more and 0.50 or less, and especially preferably 0.25 or more and 0.45 or less.

[0148] In addition, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 21% or more and 32% or less by mass, the content of propylene polymer (B) is 51% or more and 78% or less by mass, and the content of modified propylene polymer (C) is 1% or more and 17% or less by mass, and the numerical range shown in formula (1) is 0.22 or more and 0.65 or less, more preferably 0.23 or more and 0.55 or less, even more preferably 0.24 or more and 0.50 or less, and particularly preferably 0.25 or more and 0.45 or less.

[0149] In addition, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 22% by mass or more and 31% by mass or less, the content of propylene polymer (B) is 53% by mass or more and 77% by mass or less, and the content of modified propylene polymer (C) is 1% by mass or more and 16% by mass or less, and the numerical range shown in formula (1) is 0.22% or more and 0.65% or less, more preferably 0.23% or more and 0.55% or less, further preferably 0.24% or more and 0.50% or less, and especially preferably 0.25% or more and 0.45% or less.

[0150] Furthermore, it is preferable that the content of ethylene-α-olefin copolymer (A) in the polymer composition is 22% by mass or more and 30% by mass or less, the content of propylene polymer (B) is 55% by mass or more and 76% by mass or less, and the content of modified propylene polymer (C) is 2% by mass or more and 15% by mass or less, and the numerical range shown in formula (1) is 0.22% by mass or more and 0.65% by mass or less, more preferably 0.23% by mass or more and 0.55% by mass or less, even more preferably 0.24% by mass or more and 0.50% by mass or less, and particularly preferably 0.25% by mass or more and 0.45% by mass or less.

[0151] The total content of the ethylene-α-olefin copolymer (A), propylene polymer (B) and modified propylene polymer (C) in the polymer composition is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and can be 100% by mass.

[0152] Other Ingredients

[0153] The polymer composition of this embodiment, based on components (A) to (C) described above, may contain other arbitrary additives, resins, etc. (hereinafter sometimes referred to as "other components") for various purposes, without significantly impairing the effects of the present invention. However, since tackifiers may produce smoke during molding, leach into oil, or reduce heat resistance, the polymer composition of this embodiment preferably does not contain tackifiers. This means that the tackifier content in the polymer composition is 5% by mass or less.

[0154] Other ingredients may be contained in only one form, or in any combination and ratio of two or more.

[0155] Among the other components, as additives, auxiliary additives commonly used in polyolefins can be adopted. Specifically, these include processing oils, neutralizers, processing aids, plasticizers, crystallizing nucleating agents, impact modifiers, flame retardants, flame retardant additives, antistatic agents, lubricants, fillers, compatibilizers, heat stabilizers, weather stabilizers (antioxidants, light stabilizers, UV absorbers, etc.), antifogging agents, slip agents, antiblocking agents, antibacterial agents, carbon black, and colorants (pigments, dyes, etc.).

[0156] Among additives, flame retardants are broadly classified into halogenated flame retardants and non-halogenated flame retardants, with non-halogenated flame retardants being preferred.

[0157] As non-halogenated flame retardants, specific examples include metal hydroxides, phosphorus-based flame retardants, nitrogen-containing compound (melamine-based, guanidine-based) flame retardants, and inorganic compound (borate, molybdenum compound) flame retardants.

[0158] Among additives, examples of heat stabilizers and antioxidants include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, and alkali metal halides.

[0159] In additives, fillers are broadly classified into organic fillers and inorganic fillers.

[0160] Examples of organic fillers include polymers from natural sources such as starch, cellulose microparticles, wood flour, soybean residue, rice husks, and wheat bran, as well as their modified forms.

[0161] Examples of inorganic fillers include talc, calcium carbonate, zinc carbonate, wollastonite, silicon dioxide, aluminum oxide, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, hollow glass spheres, carbon black, zinc oxide, antimony trioxide, zeolite, metal fibers, metal whiskers, ceramic whiskers, potassium titanate, boron nitride, graphite, and carbon fiber.

[0162] Here, the total content of additives relative to the polymer composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 5% by mass or less, more preferably 2% by mass or less. That is, the total content of additives is preferably in the range of 0.01% by mass or more and 5% by mass or less.

[0163] It should be noted that when the polymer composition of this embodiment is used as a masterbatch, the content of the above-mentioned additives may also be 2 to 50 times, preferably 3 to 30 times, within the above range.

[0164] Other components, specifically resins, may include: polyphenylene ether polymers; polycarbonate; polyamide polymers such as nylon 66 and nylon 11; polyester polymers such as polyethylene terephthalate and polybutylene terephthalate; styrene polymers such as polystyrene; and acrylic / methacrylic polymers such as polymethyl methacrylate polymers. One or more of these may be used.

[0165] When the polymer composition of this embodiment contains resin as another component, its total content relative to the entire polymer composition is preferably 10% by mass or less, more preferably 5% by mass or less.

[0166] Methods for Manufacturing Polymer Compositions

[0167] The polymer composition of this embodiment is obtained by combining components (A) to (C) with other components added as needed.

[0168] There are no particular limitations on the mixing method. Examples include melting, solution, and suspension dispersion. In terms of practicality, melting is preferred, and melt mixing is even more preferred.

[0169] Melt blending, for example, involves uniformly mixing and blending powdered or granular components (A) to (C), and other components added as needed, in a prescribed proportion.

[0170] There is no particular limitation on the order in which the components are mixed and kneaded. For example, it can be a method of mixing and kneading components (A) to (C) and other components used as needed all at once; or a method of pre-mixing a portion of components (A) to (C) and other components used as needed, and then mixing and kneading the remaining components all at once.

[0171] Mixing can be done using, for example, a Henschel mixer, a ribbon mixer, a V-type mixer, a drum mixer, etc.

[0172] Mixing can be carried out using conventional mixing machines such as Banbury internal mixers, kneaders, rollers, multi-screw mixing extruders such as single-screw or twin-screw extruders.

[0173] The melting and mixing temperature is preferably in the range of 100°C to 300°C, more preferably 120°C to 280°C, and even more preferably 150°C to 250°C. Here, the above-mentioned temperature is preferably above 100°C, more preferably above 120°C, and even more preferably above 150°C. In addition, it is preferably below 300°C, more preferably below 280°C, and even more preferably below 250°C.

[0174] Properties of Polymer Compositions

[0175] The proportion of at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives in the polymer composition (the proportion of unsaturated carboxylic acids grafted onto propylene-based polymers and their derivatives in the polymer composition) is preferably 0.01% by mass or more and 0.30% by mass or less, more preferably 0.02% by mass or more and 0.25% by mass or less, even more preferably 0.03% by mass or more and 0.20% by mass or less, particularly preferably 0.04% by mass or more and 0.15% by mass or less, and especially preferably 0.05% by mass or more and 0.10% by mass or less. Since the number of reactive groups in the amide polymer layer is limited, even if the number of reactive groups in the polymer composition is significantly increased, saturation will occur after a certain point. Not only will the adhesive strength not increase, but the remaining unreacted reactive groups in the composition will act as adhesion-inhibiting components, potentially reducing the adhesive strength. Furthermore, if the number of unreacted reactive groups increases, problems such as a change in color and a stronger odor in the composition may occur. From this viewpoint, the proportion of at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives in the polymer composition is preferably within the above-mentioned range. Here, the reactive group in the polymer composition refers to the site from which the unsaturated carboxylic acid grafted onto polypropylene and its derivatives originate.

[0176] The polymer composition in this embodiment is preferably non-crosslinked. If the polymer composition is non-crosslinked, the molecular mobility during bonding is increased, thus improving the bond strength. It should be noted that "non-crosslinked polymer composition" means that the molecular chains are not bound together by chemical bonds.

[0177] The melt flow rate (MFR) of the polymer composition in this embodiment is preferably 0.2 g / 10 min or more and 10 g / 10 min or less. From the viewpoint of easily maintaining a good viscosity balance with monomers containing 10 to 12 carbon atoms between amide groups and / or amide polymers containing plasticizers when co-extruding the polymer composition as a polymer composition layer, and suppressing uneven thickness of each layer of the resulting laminate, the above-mentioned MFR is preferably 0.2 g / 10 min or more, more preferably 0.5 g / 10 min or more, and preferably 10 g / 10 min or less, more preferably 5 g / 10 min or less, and even more preferably 3 g / 10 min or less.

[0178] The MFR of the polymer composition can be arbitrarily combined with the above-mentioned preferred values ​​within the range. Specifically, the MFR is more preferably 0.5 g / 10 min or more and 5 g / 10 min or less. When the polymer composition of this embodiment is used as an adhesive layer, especially for extrusion molding of laminates such as hoses and multilayer cooling pipes, the above-mentioned MFR is particularly preferably 0.5 g / 10 min or more and 3 g / 10 min or less.

[0179] It should be noted that, in this specification, the melt flow rate (MFR) of the polymer composition is the value determined according to JIS K7210:2014 under the conditions of 230°C, 21.2 N load, and 10 minutes.

[0180] When the polymer composition used in the multilayer cooling pipe of this embodiment is formed into a sheet with a thickness of 0.1 mm, the tensile elongation at break in the TD direction (traverse direction) when the sheet is measured according to JIS K7161 is preferably 500% or more, more preferably 600% or more. If the tensile elongation at break in the TD direction is 500% or more, the elongation in the TD direction when the multilayer cooling pipe is inserted into the connector is sufficient, which can suppress the initiation of cracking. There is no particular upper limit to the tensile elongation at break in the TD direction of the sheet formed from the polymer composition, but from the viewpoint of rigidity of the multilayer cooling pipe, it is preferably 1000% or less, more preferably 900% or less, and even more preferably 800% or less. That is, the tensile elongation at break in the TD direction of the sheet is preferably in the range of 500% or more and 1000% or less.

[0181] Regarding the polymer composition used in the multilayer cooling channel of this embodiment, when a sheet molded to a thickness of 0.1 mm is used as a test piece and measurements are performed based on JIS K7161, the ratio of the tensile elongation at break TDα in the TD direction to the tensile elongation at break MDα in the MD (Machine Direction) direction, TDα / MDα, is preferably 0.5 or more and 1.5 or less, more preferably 1.0 or more and 1.2 or less. If the ratio of tensile elongation at break TDα / MDα is within the aforementioned range, excessive orientation is less likely to occur during the molding of the multilayer cooling channel, and the occurrence of cracks can be suppressed.

[0182] Furthermore, when using the 0.1 mm thick sheet as a test piece and measuring according to JIS K7161, the ratio of the fracture stress TDβ in the TD direction to the fracture stress MDβ in the MD direction, TDβ / MDβ, is preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less. If the fracture stress ratio TDβ / MDβ is within the aforementioned range, excessive orientation is less likely to occur during the molding of multilayer cooling channels, thus suppressing the occurrence of cracks.

[0183] Furthermore, the polymer composition used in the multilayer cooling pipe of this embodiment preferably has a haze of 15% or more and 50% or less, as measured by JIS K7136 on a test piece obtained by molding the polymer composition sheet into a thickness of 0.4 mm. The inventors have discovered that if the polymer composition contains too much α-olefin monomer (Y) other than propylene monomer, the haze value of the sheet molded body becomes high; therefore, haze can be an indicator of the ease with which the polymer composition layer can break. If the haze of the sheet molded body is within the aforementioned range, the breakage of the polymer composition layer can be suppressed, and the adhesion to the amide polymer layer can be improved. Additionally, when the haze of the sheet molded body is 15% or more, there is a tendency for a matrix-domain structure to be sufficiently formed in the polymer composition, and the required adhesive strength to be easily achieved. The haze of the sheet molded body is preferably 15% or more, more preferably 20% or more, further preferably 25% or more, and preferably 50% or less, more preferably 48% or less, and even more preferably 46% or less.

[0184] Multi-layer cooling pipes

[0185] The multilayer cooling pipe of this embodiment includes a polymer composition layer and an amide polymer layer. The polymer composition layer is formed from a polymer composition comprising an ethylene-α-olefin copolymer (A), a propylene polymer (B), and a modified propylene polymer (C). The modified propylene polymer (C) is obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid onto the propylene polymer. Furthermore, the polymer composition used to form the polymer composition layer comprises 18% by mass and 40% by mass of the ethylene-α-olefin copolymer (A), 40% by mass and 81% by mass of the propylene polymer (B), and 1% by mass and 19% by mass of the modified propylene polymer (C). Because the polymer composition layer exhibits excellent adhesive strength and heat resistance, a multilayer cooling pipe with good adhesion to the amide polymer layer constituting the laminate and excellent heat resistance can be obtained.

[0186] The multi-layer cooling pipe preferably has a stacked structure with two double-layer structures: an amide polymer layer and a polymer composition layer, which are sequentially stacked from the outer side of the multi-layer cooling pipe. That is, it is preferable that the amide polymer layer and the polymer composition layer are in direct contact.

[0187] The multilayer cooling pipe of this embodiment may also have a propylene polymer layer, and has a stacked structure with three three-layer structures, namely an amide polymer layer, a polymer composition layer and a propylene polymer layer, stacked sequentially from the outer layer side. Figure 1 This is a schematic cross-sectional view illustrating a multi-layer cooling pipe structure with three different three-layer configurations. (Example:) Figure 1As shown, from the outermost layer, an amide polymer layer 1, a polymer composition layer 2, and a propylene polymer layer 3 are stacked sequentially. Alternatively, the multilayer cooling pipe can have a stacked structure with three five-layer structures, where the propylene polymer layer, polymer composition layer, amide polymer layer, polymer composition layer, and propylene polymer layer are stacked sequentially from the outermost layer.

[0188] By incorporating layers other than the amide polymer layer and the polymer composition layer to create a stacked structure of three or more layers, it is possible to impart further flexibility and chemical resistance to multi-layer cooling channels while maintaining the rigidity and gas barrier properties characteristic of amide polymers. Here, in the three five-layer structures, the compositions of the two propylene polymer layers can be the same or different, and the compositions of the two polymer composition layers can also be the same or different. The stacked structure can have three or more layers, and can be a symmetrical / asymmetrical structure.

[0189] Polymer Composition Layer

[0190] The polymer composition layer in the laminate of this embodiment is a layer formed from the composition described in the above <Polymer Composition>.

[0191] Amide polymer layers

[0192] The amide polymer layer in a laminate used to form a multi-layer cooling channel not only provides gas barrier properties but also imparts mechanical strength, heat resistance, and other properties to the laminate. The amide polymer layer contains amide polymers. Examples of amide polymers include condensation polymers of diamines and dicarboxylic acids, and their copolymers: polymers of lactams such as ε-caprolactam and ω-laurolactam; polymers of aminocarboxylic acids such as 6-aminohexanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid; aliphatic diamines such as hexamethylenediamine, decamethyldiamine, dodecylmethylenediamine, 2,2,4-trimethylhexamethylenediamine, or 2,4,4-trimethylhexamethylenediamine; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane, or 1,4-bis(aminomethyl)cyclohexane, or bis(p-aminocyclohexylmethane); aromatic diamines such as m-phenylenediamine and terephthalic acid; aliphatic dicarboxylic acids such as adipic acid, octanoic acid, and sebacic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid.

[0193] More specifically, examples of amide polymers include polyamide 6, polyamide 9, polyamide 9T, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 611, polyamide 612, polyamide 1010, polyamide 1012, polyamide 6T, polyamide 6I, and polyamide MXD6. Among these, from the perspectives of low amide group concentration and low susceptibility to hydrolysis, low melting point among amide polymers and ease of co-extrusion molding with the polymer composition of this embodiment, which is mainly composed of polypropylene polymers, and the polyolefin layer, polyamide 11, polyamide 12, polyamide 610, polyamide 611, polyamide 612, polyamide 1010, and polyamide 1012, which contain monomers with 10 to 12 carbon atoms between the amide groups, are particularly preferred.

[0194] The amide polymer layer may contain a plasticizer. The inclusion of a plasticizer increases flexibility and makes it easier to shape. Examples of such plasticizers include one or more sulfonamide compounds selected from the group consisting of N-butylbenzenesulfonamide, N-(2-hydroxypropyl)benzenesulfonamide, N-ethyl-o-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, o-toluenesulfonamide, and p-toluenesulfonamide.

[0195] When the amide polymer layer contains a plasticizer, the plasticizer may precipitate at the bonding interface over time or when exposed to high temperatures, intervening between the polymer composition layer and the amide polymer layer. Therefore, it may sometimes have a tendency to reduce the bonding strength. However, since the polymer composition has extremely excellent bonding strength and heat resistance, structures using amide polymer layers containing such plasticizers can also be used appropriately.

[0196] It should be noted that, without compromising its purpose, the amide polymer layer of this embodiment may contain the polymer composition of this embodiment, its constituent components, or other components that may be contained in the polymer composition.

[0197] From an environmental perspective, amide polymers containing monomers derived from biomass can be used as amide polymers. Specifically, biomass-derived amide polymers refer to amide polymers obtained by polymerizing plant-derived monomers. Polyamides derived from biomass, such as polyamide 610, polyamide 1010, and polyamide 1012 (starting from plant-derived sebacic acid and decamethyldiamine), and polyamide 11 (starting from plant-derived 11-aminoundecanoic acid), are well-known examples. For other amide polymers, as long as the monomer is derived from biomass, they can be appropriately used. Furthermore, amide polymers obtained by polymerizing monomers derived from biomass naphtha can also be appropriately used.

[0198] From an environmental protection perspective, amide polymers can be made from recycled raw materials. Recycling methods can include material recycling or chemical recycling. Material recycling can be either post-consumer recycling (PCR) or post-industrial recycling (PIR).

[0199] As a recyclable amide polymer, commercially available products can be used, such as those that meet the aforementioned characteristics and can be appropriately selected from the following: "Mingamid (registered trademark)" manufactured by Mitsubishi Chemical Advanced Materials Co., Ltd., "Rilsan (registered trademark)" or "Rilsamid (registered trademark)" manufactured by Arkema Co., Ltd., and the "DINALON (registered trademark)" series manufactured by UBE Co., Ltd.

[0200] Acrylic polymer layer

[0201] The propylene polymer layer in the laminate used to form multi-layer cooling pipes is a layer with propylene polymer as the main component, which has excellent rigidity and heat resistance.

[0202] The propylene polymer contained in the propylene polymer layer preferably contains propylene units at a rate of 50 mol% or more.

[0203] It should be noted that the propylene polymer layer is a layer formed from a composition containing a propylene polymer having a different composition from the polymer composition of this embodiment, and is distinct from the polymer composition layer described above.

[0204] Examples of such propylene-based polymers include: propylene homopolymers, propylene-ethylene random copolymers, propylene-butene random copolymers, propylene-ethylene-butene random copolymers, propylene-ethylene-hexene random copolymers, propylene-ethylene-octene random copolymers, propylene-butene-hexene random copolymers, propylene-butene-octene random copolymers, propylene-hexene-octene random copolymers, propylene-ethylene block copolymers, and other propylene-based polymers.

[0205] Of the above, propylene homopolymers, propylene-ethylene random copolymers, propylene-butene random copolymers, propylene-ethylene-butene random copolymers, propylene-ethylene-hexene random copolymers, propylene-ethylene-octene random copolymers, propylene-butene-hexene random copolymers, and propylene-butene-octene random copolymers with a melt flow rate (MFR) of 0.1 to 30 g / 10 min are particularly preferred.

[0206] It should be noted that, in this specification, the melt flow rate (MFR) of the above-mentioned propylene polymers is the value measured according to JIS K 7210:2014 under the conditions of 230°C, 21.2 N load, and 10 minutes.

[0207] It should be noted that, without compromising its purpose, the propylene polymer layer may contain the polymer composition of this embodiment, its constituent components, or other components that may be contained in the polymer composition described above.

[0208] Other Layers

[0209] In addition to the polymer composition layer, amide polymer layer and propylene polymer layer mentioned above, other layers may be laminated in the laminate used to form multi-layer cooling pipes.

[0210] There are no particular limitations on other layers. For example, resin layers formed from styrene-based polymers such as polycarbonate, polystyrene (GPPS), high-impact polystyrene (HIPS), and styrene-acrylonitrile graft copolymer (ABS resin) can be listed; olefin polymers other than propylene polymers and polyethylene polymers can be listed; cyclic polyolefin polymers can be listed; polyphenylene ether polymers can be listed; polyoxymethylene homopolymers and polyoxymethylene copolymers can be listed; acrylic / methacrylic polymers such as polymethyl methacrylate polymers can be listed; and other thermoplastic polymer layers such as polyethylene terephthalate, polybutylene terephthalate, and amorphous polyester can be listed.

[0211] The total thickness of the multi-layer cooling pipes in this embodiment is preferably 0.5 to 10 mm, more preferably 0.6 to 9 mm. From the viewpoint of mechanical strength, the total thickness is preferably 0.5 mm or more, more preferably 0.6 mm or more. Furthermore, from the viewpoint of hose shaping, the total thickness is preferably 10 mm or less, more preferably 9 mm or less.

[0212] The thickness of the amide polymer layer constituting the multilayer cooling pipe of this embodiment is preferably 0.1 to 6.0 mm, more preferably 0.1 to 3.0 mm, and even more preferably 0.2 to 2.0 mm. Here, from the viewpoint of mechanical strength, the thickness of the amide polymer layer is preferably 0.1 mm or more, more preferably 0.2 mm or more. In addition, from the viewpoint of hose shaping, the thickness of the amide polymer layer is preferably 6.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.0 mm or less.

[0213] The thickness of the polymer composition layer constituting the multilayer cooling pipe of this embodiment is preferably 0.01 to 1.0 mm, more preferably 0.01 to 0.5 mm, and even more preferably 0.05 to 0.4 mm. Here, from the viewpoint of adhesion, the thickness of the polymer composition layer is preferably 0.01 mm or more, more preferably 0.05 mm or more. In addition, from the viewpoint of flexibility, the thickness of the polymer composition layer is preferably 1.0 mm or less, more preferably 0.5 mm or less, and even more preferably 0.4 mm or less.

[0214] The thickness of the propylene polymer layer constituting the multilayer cooling pipe of this embodiment is preferably 0.1 to 3.0 mm, more preferably 0.1 to 1.1 mm, and even more preferably 0.15 to 1.0 mm. Here, from the viewpoint of coolant resistance, the thickness of the propylene polymer layer is preferably 0.1 mm or more, more preferably 0.15 mm or more. In addition, from the viewpoint of hose shaping, the thickness of the propylene polymer layer is preferably 3.0 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less.

[0215] The thickness of each layer of the multilayer cooling pipe constituting this embodiment is preferably 0.1 to 6.0 mm for the amide polymer layer, 0.01 to 1.0 mm for the polymer composition layer, and 0.1 to 3.0 mm for the propylene polymer layer.

[0216] In this embodiment, the preferred ratio of the thickness of the polymer composition layer to the thickness of the amide polymer layer is 1:0.2 to 1:300, more preferably 1:1 to 1:100, and even more preferably 1:2 to 1:10. Forming both the polymer composition layer and the amide polymer layer to achieve thicknesses within the aforementioned range allows for a balance between rigidity and flexibility.

[0217] The adhesive strength of the multilayer cooling pipe of this embodiment can be evaluated by a T-peel test. Specifically, as shown in one of the embodiments described later, a test piece cut to a specified width (1 cm wide in the embodiments described later) is used. The interface at which the strength is to be measured is peeled off using a cutter or the like. Using a general tensile testing machine, the peeling is performed at 23°C using a T-peel method at a specified speed (50 mm / min in the embodiments described later). The peel strength can then be measured and taken as the adhesive strength of the multilayer cooling pipe. The interface to be measured in this invention refers to the adhesive interface between the polymer composition layer and the amide polymer layer.

[0218] Although it also depends on the application, the bonding strength of the multi-layer cooling pipe as determined by the above-mentioned T-peel test is preferably 7.0 N / cm or more, more preferably 10.0 N / cm or more, and even more preferably 15.0 N / cm or more.

[0219] The multilayer cooling pipe of this embodiment can maintain good bonding strength between its layers even after being heated. As an indicator, the greater the retention rate of bonding strength measured after the multilayer cooling pipe has been heated at 150°C for 10 minutes relative to the bonding strength before heat treatment, the better the evaluation. From the viewpoint of heat resistance, it is preferable to have a retention rate of 80% or more, and more preferably 85% or more.

[0220] The multilayer cooling pipe of this embodiment has a laminated structure in which a polymer composition layer and an amide polymer layer are in contact with each other. There are no particular limitations on the peeling mode when peeling occurs between the polymer composition layer and the amide polymer layer, but cohesive peeling is preferred. Cohesive peeling refers to the phenomenon where, because the interfacial adhesive strength is greater than the material strength (cohesion) of the polymer composition layer or the amide polymer layer, peeling does not occur at the adhesive interface during peeling, but rather the polymer composition layer or the amide polymer layer undergoes material failure (cohesive failure) while peeling occurs. In contrast, the phenomenon where the polymer composition layer or the amide polymer layer does not fail but peels off at their interface is called interfacial peeling. Cohesive peeling is preferred in that the adhesive strength is sufficiently high compared to the material strength, exhibiting stable peel strength. In particular, the inventors have found that when the adhesive strength is measured after cooling following exposure to a high-temperature environment, the rate of decrease in peel strength is low in cases exhibiting cohesive peeling.

[0221] Manufacturing Method of Multi-Layer Cooling Pipes

[0222] The method for manufacturing the multilayer cooling pipe of this embodiment can employ various methods known in the art. Examples include blow molding, tube extrusion molding, and hose extrusion molding, which involve co-extrusion by feeding individual molten resins melted in an extruder to a multilayer die and stacking them in the die.

[0223] The co-extrusion process will be explained in detail below.

[0224] The polymers and compositions constituting the above layers are prepared in advance by melt mixing or dry mixing. Then, they are extruded using a single-screw, twin-screw, or other extrusion molding method, and the layers are formed by merging the feed blocks and manifold dies. Then, the product is extruded from a die of a specified shape, cooled, and the hollow molded product is wound up using a winding machine or cut directly in a straight line.

[0225] The extrusion temperature of the co-extrusion method is appropriately selected according to the characteristics of the resins constituting each layer of the laminate, and is usually preferably suppressed to below 300°C.

[0226] The traction speed (m / min) can be set appropriately according to the desired thickness.

[0227] The discharge rate (kg / h) of the base material of the extruder can be appropriately selected according to the type of raw material used and the thickness of each layer of the target material.

[0228] The cooling method can be any existing known method, such as cooling by air knife, air cooling, or cooling in water via a pelletizer, etc.

[0229] Applications of Multi-Layer Cooling Pipes

[0230] The polymer composition layer constituting the multilayer cooling pipe of this embodiment exhibits excellent adhesion to the amide polymer layer, as well as excellent heat resistance and rigidity. Therefore, the multilayer cooling pipe of this embodiment displays excellent adhesive strength characteristics, and consequently, excellent strength, heat resistance, and gas barrier properties. Thus, the multilayer cooling pipe of this embodiment is suitable for use in heat exchange systems for automobiles, particularly electric vehicles, and is also suitable for applications requiring high cooling efficiency in limited spaces, such as cooling pipes for automobiles (especially electric vehicles). In electric vehicles, there is a trend towards larger batteries to achieve higher output and extended driving range. To maintain the interior volume (indoor space) of the vehicle, a cooling system with efficiently configured cooling pipes in a more limited space is required. The multilayer cooling pipe of this embodiment exhibits excellent flexibility and excellent adhesion that prevents the adhesive layer from peeling off from the polyamide layer even when bent into complex shapes, thus making it suitable for applications such as electric vehicles. Examples of automotive heat exchange systems include radiators, intercoolers, and oil coolers.

[0231] Example

[0232] The present invention will now be described in more detail through embodiments. However, the present invention is not limited to these embodiments without departing from its spirit. It should be noted that the various manufacturing conditions and evaluation results in the following embodiments have the meaning of preferred values ​​as upper or lower limits in the implementation of the present invention. The preferred range can be defined by a combination of the aforementioned upper or lower limits with the values ​​in the following embodiments, or by a combination of the values ​​of the embodiments themselves.

[0233] [raw materials]

[0234] The following examples use the following raw materials.

[0235] <Ethylene-α-olefin copolymer (A)>

[0236] • A-1: ​​Ethylene-propylene copolymer (propylene ratio: 30% by mass), MFR: 0.4 g / 10 min (190°C, load 21.2 N, orifice diameter 2 mm), density: 0.858 g / cm³ 3

[0237] • A-2: Ethylene-(1-Butene) copolymer (1-butene ratio: 33% by mass), MFR: 0.5 g / 10 min (190 °C, load 21.2 N, orifice diameter 2 mm), density: 0.860 g / cm³ 3

[0238] • A-3: Ethylene-(1-Butene) copolymer (1-butene ratio: 27% by mass), MFR: 1.0 g / 10 min (190 °C, load 21.2 N, orifice diameter 2 mm), density: 0.862 g / cm³ 3

[0239] • A-4: Ethylene-(1-Butene) copolymer (1-butene ratio: 21% by mass), MFR: 0.5 g / 10 min (190 °C, load 21.2 N, orifice diameter 2 mm), density: 0.870 g / cm³ 3

[0240] • A-5: Ethylene-(1-octene) copolymer (1-octene ratio: 45% by mass), MFR: 1.0 g / 10 min (190 °C, load 21.2 N, orifice diameter 2 mm), density: 0.857 g / cm³ 3

[0241] <Propylene Polymers (B)>

[0242] • B-1: Propylene homopolymer, MFR: 0.5 g / 10 min (230℃, load 21.2 N, orifice diameter 2 mm)

[0243] • B-2: Propylene homopolymer, MFR: 7.0 g / 10 min (230℃, load 21.2 N, orifice diameter 2 mm)

[0244] • B-3: Propylene-ethylene random copolymer, MFR: 1.3 g / 10 min (230 °C, load 21.2 N, orifice diameter 2 mm, ethylene ratio: 3%)

[0245] • B-4: Propylene-ethylene random copolymer, MFR: 0.8 g / 10 min (230 °C, load 21.2 N, orifice diameter 2 mm, ethylene ratio: 3%)

[0246] • B-5: Propylene-ethylene random copolymer, MFR: 7.0 g / 10 min (230℃, load 21.2 N, orifice diameter 2 mm, ethylene ratio: 3%)

[0247] • B-6: Propylene-ethylene random copolymer, MFR: 2.0 g / 10 min (230 °C, load 21.2 N, orifice diameter 2 mm, ethylene ratio: 3%)

[0248] • B-7: Propylene homopolymer, MFR: 10g / 10min (230℃, load 21.2N, orifice diameter 2mm)

[0249] • B-8: Propylene homopolymer, MFR: 0.8 g / 10 min (230℃, load 21.2 N, orifice diameter 2 mm)

[0250] • B-9: Propylene-ethylene random copolymer, MFR: 1.9 g / 10 min (230 °C, load 21.2 N, orifice diameter 2 mm, ethylene ratio: 4%)

[0251] • B-10: Propylene homopolymer (biomass source), MFR: 3.2 g / 10 min (230℃, load 21.2 N, orifice diameter 2 mm)

[0252] <Propylene polymers modified with at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives (C)>

[0253] • C-1: Modified propylene homopolymer grafted with maleic anhydride

[0254] (Manufacturing method)

[0255] Propylene homopolymer (density: 0.90 g / cm³) was dissolved in 6 L of chlorobenzene at 130 °C. 3 5 kg of powder with an MFR (230℃, 21.2 N load): 11 g / 10 min and 500 g of maleic anhydride were prepared. Then, a chlorobenzene solution of dicumyl peroxide (200 g / 400 L) was added to the solution. The reaction was further continued at 130℃ for 8 hours, followed by cooling to 40℃ to precipitate the resin. The precipitated resin was filtered, repeatedly washed with acetone, and dried under reduced pressure at 90℃ to obtain modified propylene homopolymer C-1 with a modification content of 2.2% by mass and grafted with maleic anhydride. The MFR (180℃, 21.2 N load, 1 mm pore size) of C-1 was 400 g / 10 min.

[0256] • C-2: Modified propylene homopolymer grafted with maleic anhydride

[0257] (Manufacturing method)

[0258] 100 parts by mass of propylene homopolymer (MFR (230°C, 21.2 N load): 0.5 g / 10 min), 4 parts by mass of maleic anhydride (manufactured by Fujifilm and Koichi Chemical Co., Ltd.), and 0.7 parts by mass of organic peroxide (PERBUTYL I manufactured by Nippon Oil Co., Ltd.) were dry-blended. The resulting mixture was then melt-blended using a twin-screw extruder (D=30 mm φ, L / D=32, TEX30 manufactured by Nippon Steel Co., Ltd.) at 200°C, 300 rpm, and 10 kg / h to produce granules. This yielded modified propylene homopolymer C-2 grafted with maleic anhydride, with a modification content of 1.3% by mass. The MFR (180°C, 21.2 N load, 1 mm pore size) of C-2 was 12 g / 10 min.

[0259] • C-3: Modified propylene-ethylene random copolymer grafted with maleic anhydride

[0260] (Manufacturing method)

[0261] 100 parts by mass of propylene-ethylene random copolymer (MFR (230°C, 21.2N load): 2 g / 10 min, ethylene ratio: 11% by mass), 1.5 parts by mass of maleic anhydride (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.), and 1.5 parts by mass of organic peroxide (PERBUTYL O manufactured by Nippon Oil Co., Ltd.) were dry-blended. The resulting mixture was then melt-blended using a twin-screw extruder (D=30 mm φ, L / D=32, TEX30 manufactured by Nippon Steel Co., Ltd.) at 200°C, 300 rpm, and 10 kg / h to produce granules. This yielded modified propylene-ethylene random copolymer C-3 grafted with maleic anhydride, with a modification amount of 1.1% by mass. The MFR (180°C, 21.2N load, 1 mm orifice diameter) of C-3 was 0.5 g / 10 min.

[0262] • C-4: Modified propylene-ethylene random copolymer grafted with maleic anhydride

[0263] (Manufacturing method)

[0264] 56 parts by mass of propylene-ethylene random copolymer (MFR (230℃, load 21.2N): 7g / 10min, ethylene ratio: 1% by mass), 44 parts by mass of propylene-ethylene random copolymer (MFR (230℃, load 21.2N): 7g / 10min, ethylene ratio: 11% by mass), 1.5 parts by mass of maleic anhydride (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.), and 0.3 parts by mass of organic peroxide (PERHEXA 25B manufactured by Nippon Oil Co., Ltd.) were dry-blended. The resulting mixture was then melt-blended using a twin-screw extruder (D=30mmφ, L / D=32, TEX30 manufactured by Nippon Steel Co., Ltd.) at 200℃, 300rpm, and 10kg / h to produce granules. This yielded modified propylene-ethylene random copolymer C-4 grafted with maleic anhydride, with a modification content of 0.9% by mass. The MFR (180℃, 21.2N load, 1mm pore size) of C-4 is 8.0g / 10min.

[0265] • C-5: Modified block propylene polymer grafted with maleic anhydride

[0266] (Manufacturing method)

[0267] 100 parts by weight of block propylene polymer (MFR (230°C, 21.2 N load): 2 g / 10 min), 1.5 parts by weight of maleic anhydride (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.), and 0.7 parts by weight of organic peroxide (PERBUTYL I manufactured by Nippon Oil Co., Ltd.) were dry-blended. The resulting mixture was then melt-blended using a twin-screw extruder (D=30 mm φ, L / D=32, TEX30 manufactured by Nippon Steel Co., Ltd.) at 200°C, 300 rpm, and 10 kg / h to produce granules. This yielded modified block propylene polymer C-5 grafted with maleic anhydride, with a modification content of 0.9% by weight. The MFR (180°C, 21.2 N load, 1 mm pore size) of C-5 was 4.0 g / 10 min.

[0268] • C-6: Modified propylene-ethylene random copolymer grafted with maleic anhydride

[0269] (Manufacturing method)

[0270] 100 parts by mass of propylene-ethylene random copolymer (MFR (230℃, load 21.2N): 2 g / 10 min, ethylene ratio: 3% by mass), 2 parts by mass of maleic anhydride (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.), and 1.5 parts by mass of organic peroxide (PERBUTYL O manufactured by Nippon Oil Co., Ltd.) were dry-blended. The resulting mixture was then melt-blended using a twin-screw extruder (D=30 mm φ, L / D=32, TEX30 manufactured by Nippon Steel Co., Ltd.) at 200℃, 300 rpm, and 10 kg / h to produce granules. This yielded modified propylene-ethylene random copolymer C-6 grafted with maleic anhydride, with a modification amount of 1.1% by mass. The MFR (180℃, load 21.2N, 1 mm orifice diameter) of C-6 was 25 g / 10 min.

[0271] <Other Ingredients>

[0272] • N-1: Low-density polyethylene, MFR: 2.8g / 10min (190℃, load 21.2N, orifice diameter 2mm)

[0273] • N-2: Linear low-density polyethylene, MFR: 1.7 g / 10 min (190℃, load 21.2 N, orifice diameter 2 mm)

[0274] • N-3: High-density polyethylene, MFR: 1.8g / 10min (190℃, load 21.2N, orifice diameter 2mm)

[0275] <Experimental Example 1>

[0276] (Examples 1-19, Comparative Examples 1-11)

[0277] Using the components listed in [Raw Materials] above, dry-mix them according to the proportions listed in Tables 1 to 5. The resulting mixture is then melt-blended using a single-screw extruder (40 mm φ, L / D = 32) at a set temperature of 210°C, a screw speed of 60 rpm, and an extrusion rate of 20 kg / h. The resulting granular, non-crosslinked polymer composition is obtained by wire cutting.

[0278] The MFR (230℃, 21.2N) of the obtained polymer composition and the content ratio of maleic anhydride in the polymer composition were determined, and the results are shown in Tables 1 to 5.

[0279] Next, the obtained polymer composition is used as a polymer composition layer, and a multilayer sheet simulating a multilayer cooling pipe is obtained through the following steps.

[0280] It should be noted that, as the propylene polymer layer, the polypropylene "NOVATEC PP EG7F" (MFR (230℃, load 21.2N): 1.3g / 10min) manufactured by Japan Polypropylene Co., Ltd. was used.

[0281] The amide polymer layer uses polyamide 12 (nylon 12) (Grilamid L25W20X manufactured by EMS).

[0282] First, a multilayer sheet forming machine equipped with three single-screw extruders was used to obtain three types of three-layer multilayer sheets. The extruders for each layer in the multilayer sheet forming machine were set as follows: propylene polymer layer 20mmφ, amide polymer layer 30mmφ, and polymer composition layer 20mmφ, using a 300mm wide die (die lip opening 1mm).

[0283] The three three-layer multilayer structures employ an amide polymer layer, a polymer composition layer, and an propylene polymer layer, with thicknesses of 0.6 mm, 0.1 mm, and 0.3 mm respectively (totaling 1 mm).

[0284] The molding temperature is set to 230℃ for the amide polymer layer, 230℃ for the polymer composition layer, 230℃ for the propylene polymer layer, and 230℃ for the die head. The total extrusion rate for the three layers is set to approximately 3 kg / h, and the roller cooling temperature is set to 80℃.

[0285] [Evaluation: Bond strength]

[0286] The laminated sheets obtained above were cut into strips with a width of 1 cm along the extrusion direction to serve as test pieces. For the test pieces, a T-type peel test was conducted on the interface between the amide polymer layer and the polymer composition layer at a speed of 50 mm / min under an atmosphere of 23°C to determine the peel strength, which was taken as the adhesive strength of the laminated sheets. The results are shown in Tables 1 to 5.

[0287] A strength of 7.0 N / cm or higher but less than 15.0 N / cm can be evaluated as excellent adhesion strength between the amide polymer layer and the polymer composition layer, while a strength of 15.0 N / cm or higher can be evaluated as very excellent adhesion strength between the amide polymer layer and the polymer composition layer.

[0288] [Evaluation: Heat resistance]

[0289] Similar to the [Evaluation: Adhesive Strength] above, test pieces were cut out and placed in a precision oven for heat treatment at 150°C for 10 minutes. After the test pieces were fully cooled, a T-type peel test was performed on the interface between the amide polymer layer and the polymer composition layer at 23°C and a speed of 50 mm / min. The peel strength was determined and taken as the adhesive strength of the laminated sheet. The results are shown in Tables 1 to 5.

[0290] Regarding this strength, the greater the retention rate of the bond strength after heat treatment relative to the bond strength before heat treatment, the better the heat resistance. A retention rate of 80% or more but less than 85% is rated as excellent heat resistance, and a retention rate of 85% or more is rated as very excellent heat resistance.

[0291] [Table 1]

[0292]

[0293] [Table 2]

[0294]

[0295] [Table 3]

[0296]

[0297] [Table 4]

[0298]

[0299] [Table 5]

[0300]

[0301] Examples 1-19 exhibited sufficient initial bond strength, excellent adhesion between the polymer composition layer and the amide polymer layer, and minimal decrease in bond strength after heat treatment, demonstrating excellent adhesion. Comparative Examples 1-5 showed insufficient peel strength (less than 7.0 N / cm) at 23°C, indicating inadequate bond strength. Comparative Examples 6-11 showed decreased bond strength after heat treatment compared to Examples 1-19.

[0302] <Experimental Example 2>

[0303] (Examples 20-23)

[0304] Based on the formulation amounts recorded in Table 6, a particulate, non-crosslinked polymer composition was obtained using the same method as in Experimental Example 1.

[0305] The MFR (230℃, 21.2N) of the obtained polymer composition and the content ratio of maleic anhydride in the polymer composition were determined, and the results are shown in Table 6.

[0306] Next, the obtained polymer composition is used as a polymer composition layer, and a multilayer sheet simulating a multilayer cooling pipe is obtained through the following steps.

[0307] It should be noted that, as the propylene polymer layer, the polypropylene "NOVATEC PP EG7F" (MFR (230℃, load 21.2N): 1.3g / 10min) manufactured by Japan Polypropylene Co., Ltd. was used.

[0308] The amide polymer layer uses the polyamides listed in Table 6 as recycled polyamides. Details of the polyamides used in each example are as follows.

[0309] • P-1: Polyamide 6 (Mingamid PA6G24N manufactured by Mitsubishi Chemical Corporation), MFR: 6.7 (230℃, load 21.2N, orifice diameter 2mm)

[0310] • P-2: Polyamide 11 (Mingamid 14SP40 manufactured by Mitsubishi Chemical Corporation), MFR: 8.9 (230℃, load 21.2N, orifice diameter 2mm)

[0311] • P-3: Polyamide 12 (Mingamid 12SP20 manufactured by Mitsubishi Chemical Corporation), MFR: 7.9 (230°C, load 21.2N, orifice diameter 2mm)

[0312] • P-4: Polyamide 12 (Mingamid 14SP40 manufactured by Mitsubishi Chemical Corporation), MFR: 6.6 (230°C, load 21.2N, orifice diameter 2mm)

[0313] First, a multilayer sheet forming machine equipped with three single-screw extruders was used to obtain three types of three-layer multilayer sheets. The extruders for each layer in the multilayer sheet forming machine were set as follows: propylene polymer layer 20mmφ, amide polymer layer 30mmφ, and polymer composition layer 20mmφ, using a 300mm wide die (die lip opening 1mm).

[0314] The three three-layer multilayer structures employ an amide polymer layer, a polymer composition layer, and an propylene polymer layer, with thicknesses of 0.6 mm, 0.1 mm, and 0.3 mm respectively (totaling 1 mm).

[0315] The molding temperature is set at 230℃ for the amide polymer layer, 230℃ for the polymer composition layer, 230℃ for the propylene polymer layer, and 230℃ for the die head. The total extrusion rate for the three layers is set to approximately 3 kg / h, and the roller cooling temperature is 80℃. When using P-1 (polyamide 6) for the amide polymer layer, the molding temperature is set to 240℃.

[0316] [Evaluation: Bond strength]

[0317] Peel strength was determined using the same method as in Test Example 1. The results are shown in Table 6.

[0318] [Evaluation: Heat resistance]

[0319] Peel strength was measured on the heat-treated test pieces using the same method as in Example 1. The results are shown in Table 6.

[0320] [Table 6]

[0321]

[0322] Examples 20-23 exhibit sufficient initial bond strength, excellent adhesion between the polymer composition layer and the amide polymer layer, and minimal decrease in bond strength after heat treatment, demonstrating excellent adhesion. These results indicate that the polymer composition layer formed from the polymer composition of the present invention exhibits excellent adhesion to various amide polymer layers, and the bond strength does not easily decrease even after exposure to high temperatures.

[0323] <Experimental Example 3>

[0324] (Example 24, Comparative Example 12)

[0325] Based on the formulation amounts recorded in Table 7, a particulate, non-crosslinked polymer composition was obtained using the same method as in Experimental Example 1.

[0326] It should be noted that Comparative Example 12 and Comparative Example 5 have the same composition.

[0327] [Evaluation; the proportion of α-olefin monomers (Y) other than propylene monomers]

[0328] 30 mg of the polymer composition was measured into NMR sample tubes with an outer diameter of 5 mm, and 0.53 mL of deuterated o-dichlorobenzene (ODCB) was added. The tubes were then heated using an engine block heater at 130 °C. The 13C NMR spectrum was measured using an AVANCE 600 spectrometer manufactured by Bruker, thereby determining the proportion of α-olefin monomer-derived components (Y) other than the propylene monomer.

[0329] The resonant frequency was set to 150.9 MHz, the deflection angle to 90°, the data acquisition time to 2.0 s, the pulse repetition time to 20 seconds, the cumulative number of pulses to 256, and the temperature to 120°C. A 1-hour irradiation was performed using a fully decoupled method. For the chemical shift reference, the signal from the polyethylene backbone was 30.0 ppm, and the signal from isotactic methyl groups was 21.8 ppm.

[0330] The results are shown in Table 7.

[0331] [Evaluation: Elongation at break]

[0332] A single-screw T-die extruder with a 20mm φ was used to obtain a 0.1mm thick sheet of polymer composition. This sheet was punched according to JIS No. 2 dumbbell sheet specifications, and a tensile test was conducted based on JIS K7161 at 23°C and a speed of 300mm / min to determine the elongation at break in both the TD and MD directions. The ratio of the elongation at break in the TD direction to the elongation at break in the MD direction was calculated from the obtained values. The results are shown in Table 7.

[0333] [Evaluation: Haze]

[0334] The polymer composition was pressed using a pressure press at a molding temperature of 200°C to produce test pieces with a thickness of 0.4 mm and a square diameter of 50 mm. External haze was measured using these test pieces based on JIS K7136. The results are shown in Table 7.

[0335] [Table 7]

[0336]

[0337] As shown in Table 7, Example 24 exhibits a significantly higher elongation at break in the TD direction compared to Comparative Example 12. Furthermore, the elongation at break in the TD direction is greater than that in the MD direction. This result also indicates that Example 24 is less prone to over-orientation and cracking during the molding of multi-layer cooling channels. Additionally, Example 24 has a haze of 27%, further indicating its resistance to cracking.

[0338] The invention has been described in detail and with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-056468, filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0339] Symbol Explanation

[0340] 1: Amide polymer layer

[0341] 2: Polymer composition layer

[0342] 3: Propylene polymer layer

Claims

1. A multilayer cooling pipe comprising a polymer composition layer and an amide polymer layer, the polymer composition layer being formed of a polymer composition comprising an ethylene-α-olefin copolymer (A), a propylene polymer (B), and a modified propylene polymer (C), wherein the modified propylene polymer (C) is obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid onto the propylene polymer. The polymer composition comprises 18% by mass and 40% by mass of the ethylene-α-olefin copolymer (A), 40% by mass and 81% by mass of the propylene polymer (B), and 1% by mass and 19% by mass of the modified propylene polymer (C).

2. The multi-layer cooling pipe according to claim 1, wherein, The value shown in equation (1) below is greater than 0.22 and less than 0.

65. PA / (PB+PC)…(1) In equation (1), PA represents the percentage of the ethylene-α-olefin copolymer (A) in the polymer composition, expressed as a percentage by mass. PB represents the percentage of the propylene polymer (B) in the polymer composition, expressed as % by mass. PC represents the percentage of the modified propylene polymer (C) in the polymer composition, expressed in mass.

3. The multi-layer cooling pipe according to claim 1, wherein, The polymer composition is non-crosslinked.

4. The multi-layer cooling pipe according to claim 1, wherein, The MFR of the ethylene-α-olefin copolymer (A) measured at 190°C, 21.2 N, and 2 mm pore size was greater than 0.01 g / 10 min and less than 4.0 g / 10 min.

5. The multi-layer cooling pipe according to claim 4, wherein, The MFR is above 0.1 g / 10 min and below 1.5 g / min.

6. The multi-layer cooling pipe according to claim 1, wherein, The ethylene-α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin with 6 or fewer carbon atoms.

7. The multi-layer cooling pipe according to claim 6, wherein, The α-olefin constituting the ethylene-α-olefin copolymer (A) is at least one selected from the group consisting of propylene, 1-butene and 1-octene.

8. The multi-layer cooling pipe according to claim 1, wherein, The density of the ethylene-α-olefin copolymer (A) is 0.85 g / cm³. 3 Above and less than 0.88 g / cm 3 .

9. The multi-layer cooling pipe according to claim 1, wherein, The propylene-based polymer (B) is a propylene homopolymer.

10. The multi-layer cooling pipe according to claim 1, wherein, The modified propylene polymer (C) has an MFR of ≥0.4 g / 10 min and ≤500 g / 10 min as measured at 180 °C, 21.2 N, and 1 mm pore size.

11. The multi-layer cooling pipe according to claim 1, wherein, The modified propylene polymer (C) is a modified propylene polymer obtained by grafting maleic anhydride onto a propylene polymer.

12. The multi-layer cooling pipe according to claim 1, wherein, In the polymer composition layer, at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives is present in an amount of 0.01% by mass or more and 0.30% by mass or less.

13. The multi-layer cooling pipe according to claim 1, wherein, The amide polymer layer contains amide polymers that are monomers containing 10 to 12 carbon atoms between amide groups.

14. The multi-layer cooling pipe according to claim 1, wherein, The amide polymer layer contains a plasticizer.

15. The multi-layer cooling pipe according to claim 1, wherein, When measuring the tensile elongation at break (TDα) in the TD direction relative to the tensile elongation at break (MDα) in the MD direction (MDα) according to JIS K7161, the ratio of TDα to MDα is 0.5 or more and 1.5 or less.

16. The multi-layer cooling pipe according to claim 1, wherein, When measuring the haze of a test piece obtained by sheet forming the polymer composition to a thickness of 0.4 mm according to JIS K7136, the haze is 15% or more and 50% or less.

17. The multi-layer cooling pipe according to claim 1, wherein, The multilayer cooling pipe has a stacked structure in which the amide polymer layer and the polymer composition layer are in contact with each other, and when the amide polymer layer and the polymer composition layer are peeled off, agglomeration and delamination are observed.

18. The multi-layer cooling pipe according to claim 1, wherein, The multilayer cooling pipe has a stacked structure in which the amide polymer layer and the polymer composition layer are stacked sequentially from the outer layer side.

19. The multi-layer cooling pipe according to claim 18, wherein, The multi-layer cooling pipe also has a propylene polymer layer, which has a stacked structure in which the amide polymer layer, the polymer composition layer and the propylene polymer layer are stacked sequentially from the outer layer side.

20. The multi-layer cooling pipe according to claim 19, wherein, The thickness of the amide polymer layer is 0.1–6.0 mm, the thickness of the polymer composition layer is 0.01–1.0 mm, and the thickness of the propylene polymer layer is 0.1–3.0 mm.

21. The multi-layer cooling pipe according to claim 18, wherein, The multi-layer cooling pipe also has a propylene polymer layer, which has a stacked structure in which the propylene polymer layer, the polymer composition layer, the amide polymer layer, the polymer composition layer, and the propylene polymer layer are stacked sequentially from the outer layer side.

22. The multi-layer cooling pipe according to claim 21, wherein, The thickness of the amide polymer layer is 0.1–6.0 mm, the thickness of the polymer composition layer is 0.01–1.0 mm, and the thickness of the propylene polymer layer is 0.1–3.0 mm.

23. The use of a multi-layer cooling pipe in a heat exchange system of an automobile, wherein the multi-layer cooling pipe is a multi-layer cooling pipe according to any one of claims 1 to 22.

24. Use of a multi-layer cooling pipe in a heat exchange system of an electric vehicle, wherein the multi-layer cooling pipe is a multi-layer cooling pipe according to any one of claims 1 to 22.

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