Multilayer cooling pipe

Abstract

The present invention provides a multilayer cooling pipe which is excellent in adhesion between an amide-based polymer layer and a polymer composition layer containing a modified polyolefin resin, with the adhesive strength hardily reduced even when the pipe is exposed to a high temperature. The multilayer cooling pipe of the present invention comprises: a polymer composition layer including a polymer composition containing (A) an ethylene-α olefin copolymer, (B) a propylene-based polymer, and (C) a modified propylene-based polymer obtained by grafting at least one of an unsaturated carboxylic acid and a derivative of an unsaturated carboxylic acid onto a propylene-based polymer; and an amide-based polymer layer. The polymer composition contains 18%-40% by mass of the ethylene-α olefin copolymer (A), 40%-81% by mass of the propylene-based polymer (B), and 1%-19% by mass of the modified propylene-based polymer (C).

Description

multilayer cooling piping

[0001] The present invention relates to a multi-layer cooling piping.

[0002] In recent years, electric vehicles have become increasingly popular due to growing global environmental awareness. Thermal management is essential for electric vehicles to reduce power consumption, energy loss, and battery degradation. Therefore, various heat-generating devices are effectively cooled with fluid (cooling water) inside the piping, and the efficiency of the entire system is improved by maintaining an appropriate temperature.

[0003] Polyamide is generally used as a material for this cooling pipe from the viewpoint of ensuring a balance of melt moldability, flexibility (shapeability), gas barrier properties, rigidity, internal pressure creep resistance, etc. In addition, from the viewpoint of further weight reduction and economic efficiency, multilayering with polyolefin is known, and in particular multilayering with modified polyolefin, which has excellent adhesiveness to polyamide, is known.

[0004] Various proposals have been made so far as to form multilayer cooling pipes from laminates in which an amide polymer layer and another polymer composition layer having different properties are stacked together. For example, Patent Document 1 proposes a multilayer cooling pipe that uses a polyamide as an outer layer and a modified polyolefin (maleic acid-grafted polyolefin) as an inner layer.

[0005] Furthermore, in order to deform each pipe into a desired shape according to the site of use, so-called high-temperature shaping is sometimes performed, in which the pipe is exposed to a high-temperature environment, for example, 150°C, to soften it, shaping it, and then cooled. Therefore, among modified polyolefin resins, modified polypropylene resins, which have excellent heat resistance, are often used. For example, Patent Document 2 proposes a laminate structure having an olefin-based thermoplastic elastomer layer as an outer layer, an adhesive layer containing a modified propylene-based polymer as an intermediate layer, and a semi-aromatic polyamide layer as an inner layer. Patent Document 2 also describes that the laminate structure can be suitably used for cooling system piping tubes.

[0006] Japanese Patent Application Publication No. 7-214690 Japanese Patent Application Publication No. 2017-177548

[0007] Polyamides commonly used in the amide polymer layer for this application include long-chain aliphatic polyamides such as Polyamide 11, which has excellent melt moldability, flexibility, chemical resistance, and gas barrier properties, and Polyamide 12, which is also used in Patent Document 1. However, when compared at the same molecular weight, long-chain aliphatic polyamides have a low amide group concentration and fewer reaction sites with maleic anhydride in modified polyolefins. Furthermore, the amide polymer layer may contain a plasticizer to impart flexibility and melt moldability to the polyamide, and there is a concern that the plasticizer may migrate (bleed) to the adhesive interface and inhibit adhesion to the polyolefin layer.

[0008] As described above, in a multilayer cooling pipe using a polyamide as an outer layer and a modified polyolefin as an inner layer, the layer containing the modified polyolefin described in Patent Document 1 and the modified propylene-based polymer described in Patent Document 2 have room for improvement in terms of adhesive strength with the amide-based polymer layer.

[0009] Furthermore, when high-temperature shaping is performed, the laminate structures described in Patent Documents 1 and 2 have room for improvement in terms of adhesive strength between the amide polymer layer and the polymer composition layer after high-temperature shaping.

[0010] The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a multi-layer cooling piping including a polymer composition layer containing a modified polyolefin and an amide-based polymer layer, which has excellent adhesion between the polymer composition layer and the amide-based polymer layer and is less likely to lose adhesive strength even when exposed to high temperatures.

[0011] A first aspect of the present invention is a multi-layer cooling piping including an amide-based polymer layer and a polymer composition layer made 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 onto the propylene-based polymer, wherein the polymer composition contains 18% by mass or more and 40% by mass or less of the ethylene-α-olefin copolymer (A), 40% by mass or more and 81% by mass or less of the propylene-based polymer (B), and 1% by mass or more and 19% by mass or less of the modified propylene-based polymer (C).

[0012] A second aspect of the present invention is the multilayer cooling piping of the first aspect, wherein the value represented by the following formula (1) is 0.22 or more and 0.65 or less: PA / (PB+PC) (1) In formula (1), PA is the content (% by mass) of the ethylene-α-olefin copolymer (A) in the polymer composition, PB is the content (% by mass) of the propylene polymer (B) in the polymer composition, and PC is the content (% by mass) of the modified propylene polymer (C) in the polymer composition.

[0013] A third aspect of the present invention is the multi-layer cooling piping of the first or second aspect, wherein the polymer composition is non-crosslinked.

[0014] A fourth aspect of the present invention is the multilayer cooling piping of any one of the first to third aspects, wherein the ethylene / α-olefin copolymer (A) has an MFR of 0.01 g / 10 min or more and 4.0 g / 10 min or less, measured at 190°C, 21.2 N, and a 2 mm orifice diameter.

[0015] A fifth aspect of the present invention is the multilayer cooling piping of the fourth aspect, wherein the MFR is 0.1 g / 10 min or more and 1.5 g / min or less.

[0016] A sixth aspect of the present invention is the multilayer cooling piping of any one of the first to fifth aspects, wherein the ethylene / α-olefin copolymer (A) is a copolymer of ethylene and an α-olefin having 6 or less carbon atoms.

[0017] A seventh aspect of the present invention is the multilayer cooling piping of the sixth aspect, 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.

[0018] Aspect 8 of the present invention is the multilayer cooling piping of any one of Aspects 1 to 7, wherein the density of the ethylene / α-olefin copolymer (A) is 0.85 g / cm ３ 0.88g / cm or more ３ It is a multi-layer cooling piping that is less than

[0019] A ninth aspect of the present invention is the multi-layer cooling piping of any one of the first to eighth aspects, wherein the propylene polymer (B) is a propylene homopolymer.

[0020] A tenth aspect of the present invention is the multi-layer cooling piping of any one of Aspects 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, as measured at 180°C, 21.2 N, and a 1 mm orifice diameter.

[0021] An eleventh aspect of the present invention is the multilayer cooling piping of any one of the first to tenth aspects, wherein the modified propylene polymer (C) is a modified propylene polymer obtained by grafting maleic anhydride onto a propylene polymer.

[0022] A twelfth aspect of the present invention is the multilayer cooling piping of any one of Aspects 1 to 11, wherein the polymer composition layer contains at least one member selected from the group consisting of unsaturated carboxylic acids and derivatives thereof in an amount of 0.01% by mass or more and 0.30% by mass or less.

[0023] A thirteenth aspect of the present invention is the multilayer cooling pipe of any one of Aspects 1 to 12, wherein the amide polymer contained in the amide polymer layer is an amide polymer containing a monomer having 10 to 12 carbon atoms between amide groups.

[0024] A fourteenth aspect of the present invention is the multilayer cooling piping of any one of the first to thirteenth aspects, wherein the amide polymer layer contains a plasticizer.

[0025] A fifteenth aspect of the present invention is the multilayer cooling piping of any one of Aspects 1 to 14, wherein a test piece obtained by sheet-molding the polymer composition into a thickness of 0.1 mm is measured in accordance with JIS K7161, and the ratio TDα / MDα of the tensile elongation at break in the TD direction, TDα, to the tensile elongation at break in the MD direction, MDα, is 0.5 or more and 1.5 or less.

[0026] A sixteenth aspect of the present invention is the multilayer cooling piping of any one of Aspects 1 to 15, wherein the polymer composition is molded into a sheet having a thickness of 0.4 mm, and the haze of the sheet is measured in accordance with JIS K7136 and is from 15% to 50%.

[0027] A seventeenth aspect of the present invention is the multilayer cooling piping of any one of Aspects 1 to 16, which has a laminated structure in which the amide-based polymer layer and the polymer composition layer are in contact with each other, and which exhibits cohesive peeling when the amide-based polymer layer and the polymer composition layer are peeled from each other.

[0028] Aspect 18 of the present invention is the multilayer cooling piping of any one of Aspects 1 to 17, which has a laminated structure in which the amide-based polymer layer and the polymer composition layer are laminated in this order from the outer layer side.

[0029] A nineteenth aspect of the present invention is the multilayer cooling piping of Aspect 18, which further includes a propylene-based polymer layer, and has a layered structure in which the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are layered in this order from the outer layer side.

[0030] A twentieth aspect of the present invention is the multilayer cooling piping of Aspect 19, wherein the amide polymer layer has a thickness of 0.1 to 6.0 mm, the polymer composition layer has a thickness of 0.01 to 1.0 mm, and the propylene polymer layer has a thickness of 0.1 to 3.0 mm.

[0031] A twenty-first aspect of the present invention is the multilayer cooling piping of Aspect 18, which further includes a propylene-based polymer layer, and has a layered structure in which, from the outer layer side, the propylene-based polymer layer, the polymer composition layer, the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are layered in this order.

[0032] A twenty-second aspect of the present invention is the multilayer cooling piping of Aspect 21, wherein the amide polymer layer has a thickness of 0.1 to 6.0 mm, the polymer composition layer has a thickness of 0.01 to 1.0 mm, and the propylene-based polymer layer has a thickness of 0.1 to 3.0 mm.

[0033] A twenty-third aspect of the present invention is the use of the multi-layer cooling piping according to any one of aspects one to twenty-second in a heat exchange system of an automobile.

[0034] A twenty-fourth aspect of the present invention is the use of the multilayer cooling piping according to any one of aspects one to twenty-two in a heat exchange system of an electric vehicle.

[0035] According to the present invention, it is possible to provide a multilayer cooling pipe including a polymer composition layer containing a modified polyolefin and an amide-based polymer layer, in which the adhesion between the polymer composition layer and the amide-based polymer layer is improved, the adhesion between the two layers is excellent, and the adhesive strength is unlikely to decrease even when exposed to high temperatures.

[0036] FIG. 1 is a schematic cross-sectional view showing the configuration of a multilayer cooling piping according to this embodiment.

[0037] The following describes in detail the embodiments of the present invention, but the following embodiments are merely examples (representative examples) of the present invention and the present invention is not limited thereto. The present invention can be implemented by any modifications within the scope of the gist thereof. In this specification, when a numerical value or physical property value is enclosed before and after "~", the values ​​before and after the "~" are used to include the values ​​before and after the "~" in the specification. Furthermore, in this specification, "mass %" and "wt %", and "parts by mass" and "parts by weight" are synonymous.

[0038] The multilayer cooling pipe of this embodiment includes: a polymer composition layer made of a polymer composition containing 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 an unsaturated carboxylic acid onto the propylene polymer; and an amide polymer layer, wherein the polymer composition contains 18% by mass or more and 40% by mass or less of the ethylene-α-olefin copolymer (A), 40% by mass or more and 81% by mass or less of the propylene polymer (B), and 1% by mass or more and 19% by mass or less of the modified propylene polymer (C).

[0039] <Polymer Composition> The polymer composition forming the polymer composition layer in the multilayer cooling piping according to this embodiment contains 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 onto a propylene-based polymer.

[0040] <Component (A): Ethylene-α-olefin copolymer (A)> The ethylene-α-olefin copolymer (A) contains ethylene units and α-olefin units as structural units, and refers to a copolymer in which the ethylene unit has the highest content (mass%) of all structural units. In this specification, the term "unit" refers to a monomer unit contained in the copolymer. For example, the term "ethylene unit" in an ethylene-based polymer refers to a monomer unit based on ethylene.

[0041] The ethylene-α-olefin copolymer (A) is a component that improves the wettability of the adhesive interface and improves adhesive strength, and also serves to relieve distortion that occurs at the adhesive interface due to heating / cooling associated with high-temperature molding, thereby maintaining adhesive strength.

[0042] The α-olefin constituting the ethylene-α-olefin copolymer (A) is not limited, but specific 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 are used. Among these, the α-olefin is preferably one having 8 or less carbon atoms, more preferably 6 or less, and also preferably one having 3 or more carbon atoms. That is, the α-olefin is preferably one having 3 to 8 carbon atoms. In particular, from the viewpoints of industrial availability, improving compatibility with the propylene-based polymer (B) and the modified propylene-based polymer (C), suppressing phase separation, and increasing material strength and, in turn, 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.

[0043] The lower limit of the α-olefin unit content in the ethylene-α-olefin copolymer (A) is preferably 3% by mass, more preferably 6% by mass, even more preferably 9% by mass, particularly preferably 12% by mass, and particularly preferably 15% by mass. When the lower limit of the α-olefin unit content is within this range, the ethylene-α-olefin copolymer (A) and polymer compositions containing it become flexible and the wettability of the adhesive interface improves, which tends to improve not only the adhesive strength at room temperature but also the maintenance of adhesive strength after high-temperature shaping. Furthermore, by containing a certain amount of an α-olefin component in the ethylene-α-olefin copolymer (A) that is similar in structure to the propylene polymer (B) or the modified propylene polymer (C), compatibility with the propylene polymer (B) or the modified propylene polymer (C) is improved, phase separation is suppressed, and material strength and, therefore, adhesive strength tend to be improved.

[0044] On the other hand, the upper limit of the content of the α-olefin units in the ethylene / α-olefin copolymer (A) is preferably 40% by mass, more preferably 39% by mass, even more preferably 38% by mass, particularly preferably 37% by mass, and particularly preferably 36% by mass. When the upper limit of the α-olefin unit content is within this range, the crystallinity of the ethylene / α-olefin copolymer (A) can be maintained at a certain level or higher, and the material strength can be maintained, so that the material strength (cohesive strength) of the polymer composition blended therewith is also improved, and sufficient adhesive strength can be achieved.

[0045] The ethylene-α-olefin copolymer (A) may contain other monomer units in addition to ethylene and the above-mentioned α-olefins. Examples of other monomers that can form the other monomer units include vinyl acetate, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. Here, "(meth)acrylic" refers to both acrylic and methacrylic.

[0046] The content of ethylene units, the content of α-olefin units, and the content of other monomer units in the ethylene / α-olefin copolymer (A) can each be determined by infrared spectroscopy.

[0047] The lower limit of the melt flow rate (MFR) of the ethylene-α-olefin copolymer (A), measured at 190°C, 21.2 N, and a 2 mm orifice diameter, is preferably 0.01 g / 10 min, more preferably 0.05 g / 10 min, even more preferably 0.1 g / 10 min, particularly preferably 0.2 g / 10 min, and particularly preferably 0.3 g / 10 min. When the lower limit of the MFR of the ethylene-α-olefin copolymer (A) is within this range, the polymer composition has sufficient fluidity and therefore excellent melt moldability. Furthermore, phase separation between the ethylene-α-olefin copolymer (A) and the propylene polymer (B) or modified propylene polymer (C) is suppressed, the surface area of ​​the matrix / domain interface is increased, and the material strength (cohesive force) is maintained, which tends to result in excellent adhesive strength.

[0048] 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 a 2 mm orifice diameter is preferably 4.0 g / 10 min, more preferably 3.0 g / 10 min, even more preferably 2.0 g / 10 min, particularly preferably 1.5 g / 10 min, and particularly preferably 1.0 g / 10 min. When the upper limit of the MFR of the ethylene / α-olefin copolymer (A) is within this range, the molecular weight is sufficiently high, so that the material strength (cohesive strength) of the polymer composition is increased, and therefore, excellent adhesive strength tends to be easily exhibited.

[0049] 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, and within the range, the upper and lower limits can be arbitrarily combined with the above-mentioned preferred values, and is more preferably 0.1 g / 10 min or more and 1.5 g / min or less.

[0050] The density (JIS K7112) of the ethylene-α-olefin copolymer (A) is not particularly limited, but from the viewpoint of maintaining cohesive force and enhancing adhesiveness, the lower limit is 0.80 g / cm ３ is preferred, and 0.81 g / cm ３ More preferably, 0.82 g / cm ３ More preferably, 0.83 g / cm ３ is particularly preferred, and 0.84 g / cm ３ is particularly preferred, and 0.85 g / cm ３ On the other hand, from the viewpoint of improving the wettability of the adhesive interface and enhancing the adhesiveness, the upper limit is 0.93 g / cm ３ is preferred, and 0.92 g / cm ３ More preferably, 0.91 g / cm ３ More preferably, 0.90 g / cm ３ is particularly preferred, and 0.89 g / cm ３ Even more preferably, 0.88 g / cm ３ is particularly preferred, and 0.88 g / cm ３ Most preferably, it is less than 1000 .mu.m.

[0051] That is, the density of the ethylene-α-olefin copolymer (A) is 0.80 g / cm ３ 0.93g / cm or more ３The following range is preferred, and the upper and lower limits within the range can be arbitrarily combined with the preferred values ​​described above, and 0.85 g / cm ３ 0.88g / cm or more ３ Less than is more preferred.

[0052] As the ethylene-α-olefin copolymer (A) suitable for the present invention, commercially available products can be used, and those having the above-mentioned properties can be appropriately selected from the "TAFMER (registered trademark)" series manufactured by Mitsui Chemicals, Inc., the "ENGAGE (registered trademark)" series manufactured by Dow Chemical Company, the "SOLMER (registered trademark)" series manufactured by SK Chemical Company, the "LUCENE (registered trademark)" series manufactured by LG Chemical Company, the "FORTIFY (registered trademark)" series manufactured by SABIC Corporation, and polyolefin elastomer (POE) manufactured by Lotte Chemical Company.

[0053] The ethylene / α-olefin copolymer (A) may be used alone or in combination with two or more different copolymers having different monomer compositions, physical properties, etc.

[0054] The ethylene / α-olefin copolymer (A) may have its ethylene component and α-olefin component derived from biomass. "Biomass-derived" means that it is obtained by chemical or biological synthesis using renewable biomass resources as raw materials. The biomass-derived ethylene / α-olefin copolymer (A) has the characteristic that, even when incinerated, it does not increase the carbon dioxide concentration in the atmosphere due to the carbon-neutrality of biomass.

[0055] The biomass-derived ethylene / α-olefin copolymer (A) is preferably one made from plant-derived ethylene and α-olefin obtained from a plant raw material.

[0056] Plant-derived ethylene-α-olefin copolymer (A) and petroleum-derived ethylene-α-olefin copolymer (A) can generally be distinguished by their biomass content (the ratio of the 14C concentration of the sample carbon to the standard modern carbon). Natural carbon exists in three forms: carbon-12 (12C), carbon-13 (13C), and carbon-14 (14C). Among these, 14C exists in the atmosphere at a constant rate and decreases periodically, reaching half its original amount in 5,730 years (half-life). While plant-derived ethylene-α-olefin copolymer (A) contains 14C (radioactive carbon-14, half-life 5,730 years), petroleum-derived ethylene-α-olefin copolymer (A) does not contain this radioactive carbon (14C). Therefore, measuring the 14C concentration of ethylene-α-olefin copolymer (A) using accelerator mass spectrometry allows for the distinction between plant-derived and petroleum-derived copolymers. The biomass ratio can also be used as an index of the content ratio of plant-derived components in a polymer composition containing a plant-derived polymer and a petroleum-derived polymer.

[0057] The biomass ratio can be measured, for example, by the following method. The sample to be measured is burned to generate carbon dioxide, which is then purified in a vacuum line and reduced with hydrogen using iron as a catalyst to generate graphite. This graphite is then installed in a tandem accelerator-based dedicated 14C-AMS device (manufactured by NEC Corporation) to measure 14C counts, 13C concentrations (13C / 12C), and 14C concentrations (14C / 12C). From these measurements, the ratio of the 14C concentration of the sample carbon to standard modern carbon is calculated.

[0058] The ethylene-α-olefin copolymer (A) may be a so-called mass balance copolymer obtained from biomass naphtha. Biomass naphtha is preferable from the viewpoint of environmental protection because it is obtained by decomposing and refining animal fats, waste cooking oils, vegetable oil processing waste and residues, vegetable oils, etc., which have conventionally been discarded.

[0059] From the viewpoint of environmental protection, the ethylene-α-olefin copolymer (A) may be made from recycled raw materials. Recycling methods may include material recycling and chemical recycling. Material recycling refers to the reuse of waste plastics as raw materials for similar applications after crushing and dissolving them. This refers to post-consumer recycling (PCR), which collects used products in the market and recycles them as recyclable resources, and post-industrial recycling (PIR), which recycles and reuses materials generated in the manufacturing process of products before they are released to the market. Chemical recycling refers to a system in which waste plastics are chemically decomposed to return them to their raw material state and reused as product raw materials, and is preferable in that it suppresses deterioration of physical properties.

[0060] <Component (B): Propylene-Based Polymer (B)> The polymer composition constituting the polymer composition layer of the multilayer cooling piping contains a propylene-based polymer (B). The propylene-based polymer (B) contains propylene units as structural units and has the highest content (mass%) of propylene units among all structural units.

[0061] The propylene polymer (B) is a component that imparts heat resistance and rigidity to the polymer composition, and also acts to improve adhesion to the propylene polymer layer when the multilayer cooling pipe has a propylene polymer layer.

[0062] The propylene polymer (B) is not particularly limited, and examples thereof include propylene homopolymers and propylene-α-olefin copolymers. Among these, propylene homopolymers are preferred from the viewpoint of the balance between heat resistance and rigidity. By using propylene homopolymers, the polymer composition layer does not flow even during high-temperature shaping, and the material strength can be maintained, which makes it easier to maintain adhesive strength.

[0063] Examples of the propylene-α-olefin copolymer include a propylene-ethylene copolymer, a propylene-butene copolymer, a propylene-pentene copolymer, a propylene-hexene copolymer, a propylene-octene copolymer, a propylene-(4-methyl-1-pentene) copolymer, a propylene-ethylene-butene copolymer, a propylene-ethylene-hexene copolymer, a propylene-ethylene-octene copolymer, a propylene-butene-hexene copolymer, a propylene-butene-octene copolymer, a propylene-hexene-octene copolymer, etc. Examples of the above copolymers include random copolymers and block copolymers.

[0064] 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 particularly preferably 100% by mass.

[0065] 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 the value in the above range, it becomes easier to control the rigidity.

[0066] The flexural modulus of the propylene polymer (B) is a value measured in accordance with JIS K 7171:2016.

[0067] The melt flow rate (MFR) of the propylene polymer (B) is not particularly limited, but from the viewpoints of reducing the energy load during production and the processability of molded articles, 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. From the same viewpoints, 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 to 50 g / 10 min.

[0068] In this specification, the melt flow rate (MFR) of the propylene polymer (B) is a value measured in accordance with JIS K 7210:2014 under conditions of a temperature of 230°C, a load of 21.2 N, an orifice diameter of 2 mm, and a time period of 10 minutes.

[0069] In one embodiment of the propylene polymer (B), it is preferable that the propylene polymer has at least one of the following characteristics: a propylene unit content of 90% by mass or more, a flexural modulus of 600 MPa or more and 2000 MPa or less, and a melt flow rate (MFR) of 0.1 g / 10 min or more and 50 g / 10 min or less, more preferably at least two of these characteristics, and particularly preferably all of these characteristics. When two or more types of components are mixed and used as the propylene polymer (B), it is preferable that the embodiment of the mixture satisfy the above characteristics.

[0070] The propylene polymer (B) is produced by a conventionally known method, such as a batch method, a gas phase method, or a slurry method using a catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0071] As the propylene polymer (B) suitable for the present invention, commercially available products can be used, and specific examples thereof include "Novatec (registered trademark) PP" manufactured by Japan Polypropylene Corporation, "Prim Polypro (registered trademark)" manufactured by Prime Polymer Co., Ltd., "Sumitomo Noblen (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd., "Polypropylene Block Copolymer" manufactured by SunAllomer Co., Ltd., "Moplen (registered trademark)" manufactured by LyondellBasell, "ExxonMobil PP" manufactured by ExxonMobil, "Formolene (registered trademark)" manufactured by Formosa Plastics, "Borealis PP" manufactured by Borealis, "SEETEC PP" manufactured by LG Chemical, and A. A polypropylene having the above properties can be appropriately selected from "ASI POLYPROPYLENE" manufactured by Schulman, "INEOS PP" manufactured by INEOS Olefins & Polymers, "Braskem PP" manufactured by Braskem, "Samsung 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 Corporation, and the like.

[0072] The propylene polymer (B) may be used alone or in combination with two or more polymers having different monomer compositions, physical properties, etc.

[0073] As the propylene polymer (B), similarly to the ethylene-α-olefin copolymer (A), from the viewpoint of environmental protection, a biomass-derived or recycled material can also be used.

[0074] <Component (C): Modified Propylene-Based Polymer (C) Obtained by Grafting At Least One of an Unsaturated Carboxylic Acid and an Unsaturated Carboxylic Acid Derivative to a Propylene-Based Polymer> The polymer composition constituting the polymer composition layer of the multilayer cooling pipe contains a modified propylene-based polymer (C) obtained by grafting at least one of an unsaturated carboxylic acid and an unsaturated carboxylic acid derivative to a propylene-based polymer (hereinafter, sometimes simply referred to as "modified propylene-based polymer (C)"). The modified propylene-based polymer (C) contains a reactive polar group, and therefore is a component that reacts with a functional group of an adherend to form a covalent bond, thereby exhibiting strong adhesive strength.

[0075] In this specification, "unsaturated carboxylic acid or its derivative" may be referred to as a modifier. "Grafting" means bonding an unsaturated carboxylic acid or its derivative to a propylene polymer. The bonding position of the unsaturated carboxylic acid or its derivative in the modified propylene polymer is not particularly limited, as long as it is introduced into at least one of the main chain terminal and the side chain of the propylene polymer. "Propylene polymer" means a polymer containing propylene units as structural units, with the propylene units having the highest content (mass%) of all structural units.

[0076] 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 particularly preferably 88% by mass or more. From the above-mentioned viewpoints, 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 particularly preferably 88% by mass or more.

[0077] The propylene-based polymer used as a raw material is not particularly limited, and can be arbitrarily selected from propylene homopolymers; propylene-α-olefin copolymers such as 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, and propylene-hexene-octene copolymers; propylene-based polymers in which an ethylene-based rubber component is dispersed in a propylene phase (commonly known as block PP), or combinations thereof.

[0078] When a propylene homopolymer is used as the raw material propylene polymer, its compatibility with the propylene polymer (B) improves, and fine dispersion increases the surface area of ​​the matrix / domain interface, improving the material strength (cohesive strength) and ultimately the adhesive strength. Furthermore, the propylene homopolymer has high crystallinity and its own high material strength (cohesive strength), which also contributes to improving the cohesive strength and adhesive strength of the composition. The propylene homopolymer is a commonly known propylene homopolymer, and propylene homopolymers having any structure, such as atactic, isotactic, or syndiotactic, can be used. Among these, an isotactic structure is particularly preferred from the viewpoint of heat resistance.

[0079] When a propylene-α-olefin copolymer is used as the raw propylene-based polymer, the use of a propylene-α-olefin copolymer with low crystallinity is expected to improve the wettability of the adhesive interface and increase the adhesive strength. It is also expected to alleviate the distortion of the adhesive interface that occurs after high-temperature molding and maintain the adhesive strength. As the propylene-α-olefin copolymer, a propylene-ethylene copolymer is preferred from the viewpoints of melt moldability, heat resistance, industrial availability, etc.

[0080] Even when block PP containing an ethylene-based rubber component is used, it is expected to improve the wettability of the adhesive interface, increase adhesive strength, and alleviate the distortion of the adhesive interface that occurs after high-temperature molding, thereby maintaining adhesive strength.

[0081] The density (JIS K7112) of the raw material propylene polymer is not particularly limited, but from the viewpoint of maintaining cohesive force and enhancing adhesiveness, the lower limit is 0.81 g / cm ３ is preferred, and 0.82 g / cm ３ More preferably, 0.83 g / cm ３ More preferably, 0.84 g / cm ３ is particularly preferred, and 0.85 g / cm ３ On the other hand, from the viewpoint of improving the wettability of the adhesive interface and increasing the adhesiveness, the upper limit is 0.95 g / cm ３ is preferred, and 0.94 g / cm ３ More preferably, 0.93 g / cm ３ More preferably, 0.92 g / cm ３ is particularly preferred, and 0.91 g / cm ３ That is, the density of the raw material propylene polymer is 0.81 g / cm ３ 0.95g / cm or more ３ The following ranges are preferred:

[0082] The MFR (230°C, 21.2 N, 2 mm orifice) of the raw material propylene polymer is not particularly limited. However, from the viewpoint of imparting sufficient fluidity to the polymer composition and ensuring melt moldability 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 particularly preferably 0.5 g / 10 min. On the other hand, from the viewpoint of increasing the molecular weight and thus the cohesive strength and ensuring the 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 particularly preferably 12 g / 10 min. That is, the MFR of the raw material propylene polymer is preferably in the range of 0.1 g / 10 min or more and 20 g / 10 min or less.

[0083] The propylene polymer used as the raw material for the modified propylene polymer (C) may be either a manufactured product or a commercially available product. When the raw material propylene polymer is manufactured, it is manufactured by a conventionally known method.

[0084] The propylene polymer used as the raw material for the modified propylene polymer (C) may be derived from biomass or recycled material from the viewpoint of environmental protection, similar to the ethylene-α-olefin copolymer (A) and the propylene polymer (B).

[0085] The unsaturated carboxylic acid used for modification is not particularly limited, but representative examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. The derivative of the unsaturated carboxylic acid is not particularly limited, but representative examples include acid anhydrides, esters, amides, imides, and metal salts. Specific examples of the derivative of unsaturated carboxylic acid include maleic anhydride, himic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate, maleic acid monoethyl ester, maleic acid diethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, 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-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, and potassium methacrylate.

[0086] The unsaturated carboxylic acids and their derivatives may be used singly or in any combination and ratio of two or more. Among these, maleic acid and its anhydride are particularly preferred because of their low electron density and high reactivity, with maleic anhydride being the most preferred.

[0087] The graft modification of the raw material propylene polymer can be carried out by various conventionally known methods. Examples of the modification method include a melt modification method in which the modifier is added to a molten raw material propylene polymer to perform graft copolymerization, and a solution modification method in which the modifier is added to a raw material propylene polymer dissolved in a solvent to perform graft copolymerization. These methods are not particularly limited, but the melt modification method is preferred from the viewpoints of productivity and economy. Note that, for efficient graft modification, it is preferred to perform the modification in the presence of a radical initiator.

[0088] The radical initiator is not particularly limited, but is preferably an organic peroxide or an azo compound, and more preferably an organic peroxide. Specific examples thereof include di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,4-bis(t-butylperoxyisopropyl)benzene, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,2-bis( Dialkyl peroxides such as 4,4-t-butylperoxycyclohexyl)propane, 2,2-bis(t-butylperoxy)butane, and 1,1-bis(t-butylperoxy)cyclododecane; t-butylperoxyacetate, t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylperoxylaurate, t-butylperoxybenzoate, and t-butylperoxyisopropyl carbonate. peroxyesters such as t-butylperoxymaleic acid, di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, or 2,5-dimethyl-2,5-di(benzoylperoxy)hexyne-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 t-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 are not particularly limited to these. The radical initiators can be used alone or in any combination and ratio of two or more kinds.

[0089] Among these, radical initiators having a decomposition temperature of 100°C or higher, at which the half-life is 1 minute, are preferred from the viewpoint of graft modification efficiency. Specifically, dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, and peroxyesters such as t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexyne-3 are preferred.

[0090] The amount of the radical initiator used is not particularly limited, but is preferably 0.001 to 10 parts by mass per 100 parts by mass of the raw material propylene polymer.

[0091] After the modification reaction, a treatment for removing unreacted unsaturated carboxylic acid components may be carried out. The method for this treatment is not particularly limited, but an example thereof includes a method in which the modified propylene-based polymer after the modification reaction is placed in a storage tank having a structure that allows gas to be blown in from the bottom of the apparatus, the apparatus is heated to about 100°C with a heater or thermal oil, and an inert gas such as nitrogen or air is blown in from the bottom of the apparatus for treatment for 6 to 24 hours.

[0092] The content of the modifying component in the modified propylene polymer (C), specifically, the content of the unsaturated carboxylic acid or its derivative grafted to the propylene polymer (hereinafter, sometimes referred to as the "graft ratio"), varies depending on the type of raw propylene polymer and the type of modifier, and is not particularly limited. From the viewpoint of improving adhesion to the amide polymer constituting the multilayer cooling pipe of the present embodiment, particularly an amide polymer containing a monomer having 10 to 12 carbon atoms between amide groups, having a low amide group concentration, and being unlikely to react with an unsaturated carboxylic acid to form a covalent bond, or an amide polymer containing a plasticizer that precipitates at the adhesive interface and inhibits adhesion, the graft ratio is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. On the other hand, from the viewpoint of preventing crosslinking of the raw material propylene polymer and suppressing deterioration of melt moldability and generation of foreign matter, the upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 7% by mass or less, and particularly preferably 5% by mass or less. That is, the graft ratio of the modified propylene polymer (C) is preferably in the range of 0.01% by mass or more and 20% by mass or less.

[0093] Here, the graft ratio can be measured by press-molding the modified propylene polymer (C) directly into a sheet having a thickness of 0.1 mm to prepare a test sample, and using infrared absorption spectroscopy, the graft ratio can be determined from the absorption characteristic of the modifier (carboxylic acid or its derivative) in the resin. －１ The graft ratio can be determined by measuring the characteristic carbonyl absorption band (C═O stretching vibration band). That is, the amount of the modifier (unsaturated carboxylic acid or a derivative thereof) that contributed to the grafting is calculated from the measured value of the characteristic carbonyl absorption, and the graft ratio (mass %) is calculated as the mass ratio to the raw material propylene polymer.

[0094] In the modification with the unsaturated carboxylic acid component, 100% of the added unsaturated carboxylic acid component may not be subjected to the reaction, and some of the unsaturated carboxylic acid component that has not reacted with the raw material propylene polymer may remain in the modified propylene polymer (C). However, the above-mentioned modification amount (graft ratio) in this specification means the value measured by the above-mentioned method.

[0095] The density (JIS K7112) of the modified propylene polymer (C) is not particularly limited, but from the viewpoint of maintaining cohesive force and enhancing adhesiveness, the lower limit is 0.81 g / cm ３ is preferred, and 0.82 g / cm ３ More preferably, 0.83 g / cm ３ More preferably, 0.84 g / cm ３ is particularly preferred, and 0.85 g / cm ３ On the other hand, from the viewpoint of improving the wettability of the adhesive interface and increasing the adhesiveness, the upper limit is 0.95 g / cm ３ is preferred, and 0.94 g / cm ３ More preferably, 0.93 g / cm ３ More preferably, 0.92 g / cm ３ is particularly preferred, and 0.91 g / cm ３ is particularly preferred.

[0096] That is, the density of the modified propylene polymer (C) is 0.81 g / cm ３ 0.95g / cm or more ３ The following ranges are preferred, and the upper and lower limits within the ranges can be arbitrarily combined with the preferred values ​​described above.

[0097] The MFR of the modified propylene polymer (C) is not particularly limited, but from the viewpoint of imparting sufficient fluidity 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, still more preferably 0.1 g / 10 min, particularly preferably 0.2 g / 10 min, still more preferably 0.3 g / 10 min, particularly preferably 0.4 g / 10 min, especially preferably 0.5 g / 10 min, and most preferably 1 g / 10 min. On the other hand, from the viewpoint of increasing the molecular weight and therefore the cohesive strength and ensuring the adhesive strength, the upper limit of the MFR is preferably 1000 g / 10 min, more preferably 900 g / 10 min, even more preferably 800 g / 10 min, particularly preferably 700 g / 10 min, even more preferably 600 g / 10 min, particularly preferably 500 g / 10 min, even more preferably 450 g / 10 min, and most preferably 430 g / 10 min.

[0098] That is, the MFR of the modified propylene polymer (C) is preferably in the range of 0.01 g / 10 min to 1000 g / 10 min, and the upper and lower limits within the range can be any combination of the above-mentioned preferred values. Specifically, the MFR of the modified propylene polymer (C) is more preferably 0.4 g / 10 min to 500 g / 10 min, and even more preferably 0.4 g / 10 min to 430 g / 10 min.

[0099] Here, the MFR of the modified propylene polymer (C) means the value measured at 180° C., under a load of 21.2 N, and through an orifice diameter of 1 mm.

[0100] As a suitable modified propylene polymer (C), a commercially available product can be used. For example, a product having the above-mentioned properties can be appropriately selected from the "Modic (registered trademark)" series manufactured by Mitsubishi Chemical Corporation and used.

[0101] The modified propylene polymer (C) may be used alone or in combination of two or more types having different monomer compositions, physical properties, etc.

[0102] <<Contents of Components (A) to (C)>> In this embodiment, the polymer composition contains 18% by mass or more and 40% by mass or less of the ethylene-α-olefin copolymer (A), 40% by mass or more and 81% by mass or less of the propylene polymer (B), and 1% by mass or more and 19% by mass or less of the modified propylene polymer (C). When the contents of Components (A) to (C) are within the above ranges, the release mode is cohesive release, and therefore, it is possible to maintain adhesive strength even when shaped in a heat-resistant environment.

[0103] The content of the ethylene-α-olefin copolymer (A) in the polymer composition is 18% by mass or more and 40% by mass or less. The lower limit of the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 19% by mass, more preferably 20% by mass, even more preferably 21% by mass, and particularly preferably 22% by mass. When the lower limit of the content of the ethylene-α-olefin copolymer (A) is within this range, the wettability of the adhesive interface tends to be improved, and the adhesive strength tends to be excellent. In addition, when a film is generally exposed to a high-temperature environment, such as during shaping of a cooling pipe, and then cooled, the linear expansion coefficients of the polymer composition layer and the amide-based polymer layer are different, so that distortion occurs at the adhesive interface, and reactive sites are broken, which tends to reduce the adhesive strength. However, when the content of the ethylene-α-olefin copolymer (A) is within this range, the distortion occurring at the adhesive interface can be alleviated and reactive sites can be maintained, so that the adhesive strength tends to be easily maintained even after high-temperature shaping. On the other hand, the upper limit of the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 35% by mass, more preferably 33% by mass, even more preferably 32% by mass, particularly preferably 31% by mass, and most preferably 30% by mass. When the upper limit of the content of the ethylene-α-olefin copolymer (A) is within this range, the polymer composition does not become too flexible and can maintain sufficient material strength (cohesion), thereby tending to increase adhesive strength. Furthermore, phase separation with the propylene-based polymer (B) or the modified propylene-based polymer (C) is suppressed, and the surface area of ​​the matrix / domain interface is increased, thereby maintaining material strength (cohesion), and as a result, sufficient adhesive strength can be achieved. Furthermore, since ethylene-α-olefin copolymers generally have a lower melting point than general-purpose polyolefin-based polymers, they flow in high-temperature environments when forming multilayer cooling pipes, making it difficult to maintain sufficient material strength (cohesion). However, by setting the content within the above upper limit, material strength (cohesion), and therefore adhesive strength, tend to be easily maintained even in high-temperature environments.

[0104] The content of the propylene polymer (B) in the polymer composition is 40% by mass or more and 81% by mass or less from the viewpoints of material strength (cohesive strength), heat resistance, and adhesive strength. The lower limit of the content of the propylene polymer (B) in the polymer composition is preferably 45% by mass, more preferably 46% by mass, even more preferably 49% by mass, even more preferably 50% by mass, particularly preferably 51% by mass, particularly preferably 53% by mass, especially preferably 55% by mass, even more preferably 60% by mass, and most preferably 70% by mass. When the lower limit of the content of the propylene polymer (B) is within this range, the material strength (cohesive strength) and heat resistance tend to be excellent. The upper limit of the content of the propylene polymer (B) in the polymer composition is preferably 80% by mass, more preferably 79% by mass, even more preferably 78% by mass, particularly preferably 77% by mass, and most preferably 76% by mass. When the upper limit of the content of the propylene polymer (B) is within this range, the adhesive strength tends to be excellent.

[0105] A larger amount of the modified propylene polymer (C) is preferred from the viewpoint of increasing the number of reactive sites with the amide polymer layer and improving adhesive strength, but a smaller amount is preferred from the viewpoint of material strength (cohesive strength). Therefore, from the viewpoint of optimizing the balance between the reactivity with the amide polymer layer and material strength (cohesive strength), the content of the modified propylene polymer (C) in the polymer composition is 1% by mass or more and 19% by mass or less. The lower limit of the content of the 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 may be 2% by mass. When the lower limit of the content of the modified propylene polymer (C) is within this range, the adhesive strength tends to be excellent. The upper limit of the content of the 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. When the upper limit of the content of the modified propylene polymer (C) is within this range, the strength of the material tends to be easily maintained.

[0106] Specific preferred content ranges of each component are as follows: the content of the ethylene-α-olefin copolymer (A) is 18% by mass or more and 40% by mass or less, the content of the propylene polymer (B) is 41% by mass or more and 81% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, relative to the entire polymer composition.

[0107] With respect to the content of each component, it is more preferable that the content of the ethylene-α-olefin copolymer (A) is 19% by mass or more and 35% by mass or less, the content of the propylene polymer (B) is 46% by mass or more and 80% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, relative to the entire polymer composition.

[0108] Furthermore, with regard to the content of each component, it is more preferable that the content of the ethylene-α-olefin copolymer (A) is 20% by mass or more and 33% by mass or less, the content of the propylene polymer (B) is 49% by mass or more and 79% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 18% by mass or less, relative to the entire polymer composition.

[0109] Furthermore, with regard to the content of each component, it is particularly preferable that the content of the ethylene-α-olefin copolymer (A) is 21% by mass or more and 32% by mass or less, the content of the propylene polymer (B) is 51% by mass or more and 78% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 17% by mass or less, relative to the entire polymer composition.

[0110] Furthermore, with regard to the content of each component, it is particularly preferred that the content of the ethylene-α-olefin copolymer (A) is from 22% by mass to 31% by mass, the content of the propylene polymer (B) is from 53% by mass to 77% by mass, and the content of the modified propylene polymer (C) is from 1% by mass to 16% by mass, relative to the entire polymer composition.

[0111] Furthermore, with respect to the content of each component, the content of the ethylene-α-olefin copolymer (A) may be 22% by mass or more and 30% by mass or less, the content of the propylene polymer (B) may be 55% by mass or more and 76% by mass or less, and the content of the modified propylene polymer (C) may be 2% by mass or more and 15% by mass or less, relative to the entire polymer composition.

[0112] The polymer composition of this embodiment preferably has a value calculated from the contents of components (A) to (C) and represented by the following formula (1): PA / (PB+PC) (1) In formula (1), PA is the content (% by mass) of the ethylene-α-olefin copolymer (A) in the polymer composition, PB is the content (% by mass) of the propylene polymer (B) in the polymer composition, and PC is the content (% by mass) of the modified propylene polymer (C) in the polymer composition.

[0113] In the polymer composition, the lower limit of the value represented by formula (1) is preferably 0.22, more preferably 0.23, even more preferably 0.24, and particularly preferably 0.25, from the viewpoint of adhesive strength. In the polymer composition, the upper limit of the value represented by formula (1) is preferably 0.65, more preferably 0.55, even more preferably 0.50, and particularly preferably 0.45, from the viewpoint of maintaining adhesive strength even after high-temperature shaping and maintaining material strength to ensure high adhesive strength.

[0114] The polymer composition preferably satisfies both the specifically preferred content ranges of each component in the polymer composition and the preferred numerical range of the value represented by formula (1). Specifically, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is 18% by mass or more and 40% by mass or less, the content of the propylene polymer (B) is 41% by mass or more and 81% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, and the numerical range represented by formula (1) preferably satisfies 0.22 to 0.65, more preferably 0.23 to 0.55, even more preferably 0.24 to 0.50, and particularly preferably 0.25 to 0.45.

[0115] In addition, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 19% by mass or more and 35% by mass or less, the content of the propylene polymer (B) is 46% by mass or more and 80% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 19% by mass or less, and the numerical range represented by formula (1) is preferably 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.

[0116] In addition, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 20% by mass or more and 33% by mass or less, the content of the propylene polymer (B) is 49% by mass or more and 79% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 18% by mass or less, and the numerical range represented by formula (1) is preferably 0.22 to 0.65, more preferably 0.23 to 0.55, even more preferably 0.24 to 0.50, and particularly preferably 0.25 to 0.45.

[0117] In addition, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 21% by mass or more and 32% by mass or less, the content of the propylene polymer (B) is 51% by mass or more and 78% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 17% by mass or less, and the numerical range represented by formula (1) is preferably 0.22 to 0.65, more preferably 0.23 to 0.55, even more preferably 0.24 to 0.50, and particularly preferably 0.25 to 0.45.

[0118] In addition, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 22% by mass or more and 31% by mass or less, the content of the propylene polymer (B) is 53% by mass or more and 77% by mass or less, and the content of the modified propylene polymer (C) is 1% by mass or more and 16% by mass or less, and the numerical range represented by formula (1) preferably satisfies 0.22 to 0.65, more preferably 0.23 to 0.55, even more preferably 0.24 to 0.50, and particularly preferably 0.25 to 0.45.

[0119] Furthermore, the content of the ethylene-α-olefin copolymer (A) in the polymer composition is preferably 22% by mass or more and 30% by mass or less, the content of the propylene polymer (B) is 55% by mass or more and 76% by mass or less, and the content of the modified propylene polymer (C) is 2% by mass or more and 15% by mass or less, and the numerical range represented by formula (1) preferably satisfies 0.22 to 0.65 or less, more preferably 0.23 to 0.55 or less, even more preferably 0.24 to 0.50 or less, and particularly preferably 0.25 to 0.45 or less.

[0120] The total content of the ethylene-α-olefin copolymer (A), the propylene polymer (B), and the 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 may be 100% by mass.

[0121] <<Other Components>> In addition to the components (A) to (C) described above, the polymer composition according to this embodiment may contain other optional additives, resins, etc. (hereinafter, sometimes referred to as "other components") depending on various purposes, as long as the effects of the present invention are not significantly impaired. However, since tackifiers may cause smoke during molding, leach into oil, and reduce heat resistance, it is preferable that the polymer composition according to this embodiment does not contain a tackifier. This means that the content of tackifier in the polymer composition is 5% by mass or less.

[0122] The other components may be contained alone or in any combination and ratio of two or more.

[0123] Among the other components, additives that can be used include auxiliary additives generally used in polyolefins, such as process oils, neutralizing agents, processing aids, plasticizers, nucleating agents, impact modifiers, flame retardants, flame retardant aids, antistatic agents, lubricants, fillers, compatibilizers, heat stabilizers, weather stabilizers (antioxidants, light stabilizers, ultraviolet absorbers, etc.), antifogging agents, slip agents, antiblocking agents, antibacterial agents, carbon black, and colorants (pigments, dyes, etc.).

[0124] Among additives, flame retardants are broadly classified into halogen-based flame retardants and non-halogen-based flame retardants, with non-halogen-based flame retardants being preferred.Specific examples of non-halogen-based flame retardants include metal hydroxides, phosphorus-based flame retardants, nitrogen-containing compound (melamine-based, guanidine-based) flame retardants, and inorganic compound (borate, molybdenum compound) flame retardants.

[0125] Among the additives, examples of the heat stabilizer and antioxidant include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, and alkali metal halides.

[0126] Among additives, fillers can be broadly classified into organic fillers and inorganic fillers. Organic fillers include naturally derived polymers such as starch, cellulose fine particles, wood flour, soybean pulp, rice husks, and bran, as well as modified versions of these. Inorganic fillers include talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, glass balloons, carbon black, zinc oxide, antimony trioxide, zeolite, metal fibers, metal whiskers, ceramic whiskers, potassium titanate, boron nitride, graphite, and carbon fibers.

[0127] Here, the total content of the additives relative to the entire polymer composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is preferably 5% by mass or less, more preferably 2% by mass or less. That is, the total content of the additives is preferably in the range of 0.01% by mass or more and 5% by mass or less.

[0128] When the polymer composition according to this embodiment is used as a masterbatch, the content of the additives can be 2 to 50 times, preferably 3 to 30 times, the above range.

[0129] Among the other components, specific examples of resins 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. These may be used alone or in combination of two or more.

[0130] When the polymer composition according to the present embodiment contains resins as other components, the total content of these resins relative to the entire polymer composition is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0131] <<Method for Producing Polymer Composition>> The polymer composition according to this embodiment is obtained by blending components (A) to (C) with other components that are added as needed. The blending method is not particularly limited, and examples thereof include a melting method, a solution method, a suspension dispersion method, etc., and from a practical standpoint, the melting method is preferred, and the melt-kneading method is more preferred.

[0132] The melt-kneading method involves, for example, uniformly mixing and kneading powdery or granular components (A) to (C) and other components added as needed at a predetermined blending ratio. The order in which the components are mixed and kneaded is not particularly limited, and may involve, for example, mixing components (A) to (C) and other components added as needed all at once and kneading them together, or mixing components (A) to (C) and some of the other components added as needed in advance, and then mixing the remaining components all at once and kneading them together.

[0133] For mixing, for example, a Henschel mixer, a ribbon blender, a V-type blender, a tumbler blender, or the like can be used.

[0134] The kneading can be carried out using a common kneading machine such as a Banbury mixer, a kneader, a roll, or a multi-screw kneading extruder such as a single-screw or twin-screw extruder.

[0135] The melt-kneading 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 temperature is preferably 100° C. or higher, more preferably 120° C. or higher, and even more preferably 150° C. or higher, and is preferably 300° C. or lower, more preferably 280° C. or lower, and even more preferably 250° C. or lower.

[0136] <<Physical Properties of Polymer Composition>> The content of at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives in the polymer composition (the content of the unsaturated carboxylic acid or its derivative grafted to the propylene-based polymer 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 particularly preferably 0.05% by mass or more and 0.10% by mass or less. Because the number of reactive groups in the amide-based polymer layer is limited, even if the number of reactive groups in the polymer composition is significantly increased, saturation occurs at a certain point, and not only does not improve the adhesive strength, but the unreacted reactive groups remaining in the composition may act as adhesion-inhibiting components, thereby reducing the adhesive strength. Furthermore, an increase in the number of unreacted reactive groups can also cause problems such as an increase in the color and odor of the composition. From this viewpoint, the content of at least one selected from the group consisting of unsaturated carboxylic acids and derivatives thereof in the polymer composition is preferably in the above-mentioned range. Here, the reactive group in the polymer composition refers to a site derived from the unsaturated carboxylic acid or derivative thereof grafted onto the polypropylene.

[0137] The polymer composition according to this embodiment is preferably non-crosslinked. When the polymer composition is non-crosslinked, molecular mobility during adhesion is increased, and therefore adhesive strength can be increased. Note that "the polymer composition is non-crosslinked" means that molecular chains are not constrained by chemical bonds.

[0138] The polymer composition according to this embodiment preferably has a melt flow rate (MFR) of 0.2 g / 10 min or more and 10 g / 10 min or less. From the viewpoints of easily maintaining a good viscosity balance with the amide polymer containing a monomer having 10 to 12 carbon atoms between amide groups and / or containing a plasticizer when the polymer composition is co-extruded as a polymer composition layer and suppressing variation in the thickness of each layer constituting the obtained laminate, the 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. The MFR of the polymer composition can be any combination of the upper and lower limits described above within the above-mentioned range, and specifically, the MFR is more preferably 0.5 g / 10 min or more and 5 g / 10 min or less. When the polymer composition according to the present embodiment is used as an adhesive layer, particularly when used in extrusion molding to form a laminate such as a tube or a multilayer cooling pipe, the MFR is particularly preferably 0.5 g / 10 min or more and 3 g / 10 min or less.

[0139] In this specification, the melt flow rate (MFR) of the polymer composition is a value measured in accordance with JIS K 7210:2014 under conditions of a temperature of 230°C, a load of 21.2 N, and a time of 10 minutes.

[0140] When the polymer composition used in the multilayer cooling pipe of this embodiment is formed into a sheet having a thickness of 0.1 mm, the tensile elongation at break in the transverse direction (TD) of the sheet, as 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 is sufficient when the multilayer cooling pipe is inserted into a connector, and the sheet can be prevented from becoming a starting point for cracks. The upper limit of the tensile elongation at break in the TD direction of the sheet-molded product formed from the polymer composition is not particularly limited, but from the viewpoint of rigidity as a 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-molded product is preferably in the range of 500% to 1000%.

[0141] The polymer composition used in the multilayer cooling piping of this embodiment preferably has a ratio TDα / MDα of the tensile breaking elongation in the TD direction to the tensile breaking elongation in the MD (Machine Direction) direction MDα, TDα / MDα, of 0.5 to 1.5, more preferably 1.0 to 1.2, when measured based on JIS K 7161 using the above-mentioned 0.1 mm-thick sheet molded product as a test piece. When the ratio TDα / MDα of the tensile breaking elongation in the TD direction to the tensile breaking elongation in the MD direction is within the above range, excessive orientation is unlikely to occur during molding of the multilayer cooling piping, and the occurrence of cracks can be suppressed.

[0142] Furthermore, when the 0.1 mm thick sheet molding is used as a test piece and measurement is performed in accordance with JIS K7161, the ratio of the TD direction breaking stress TDβ to the MD direction breaking stress MDβ, TDβ / MDβ, is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. When the breaking stress ratio TDβ / MDβ is within the above range, excessive orientation is unlikely to occur during molding of the multilayer cooling pipe, and the occurrence of cracks can be suppressed.

[0143] Furthermore, the polymer composition used in the multilayer cooling pipe of this embodiment preferably has a haze of 15% to 50% as measured in accordance with JIS K7136 on a test piece obtained by molding the polymer composition into a sheet having a thickness of 0.4 mm. The inventors have discovered that when the polymer composition contains too much component (Y) derived from an α-olefin monomer other than propylene monomer, the haze value of the sheet molding increases, and therefore haze can serve as an indicator of the susceptibility to cracking of the polymer composition layer. When the haze of the sheet molding is within the above range, cracking of the polymer composition layer can be suppressed and adhesion to the amide polymer layer can be improved. Furthermore, when the haze of the sheet molding is 15% or more, a matrix-domain structure is easily formed in the polymer composition, and the required adhesive strength tends to be easily achieved. The haze of the sheet molding is preferably 15% or more, more preferably 20% or more, even more preferably 25% or more, and preferably 50% or less, more preferably 48% or less, and even more preferably 46% or less.

[0144] <Multilayer Cooling Pipe> The multilayer cooling pipe of this embodiment includes a polymer composition layer and an amide polymer layer, each of which is made of a polymer composition containing 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 an unsaturated carboxylic acid derivative onto the propylene polymer. The polymer composition forming the polymer composition layer contains 18% by mass to 40% by mass of the ethylene-α-olefin copolymer (A), 40% by mass to 81% by mass of the propylene polymer (B), and 1% by mass to 19% by mass of the modified propylene polymer (C). The polymer composition layer has excellent adhesive strength and heat resistance, and therefore has good adhesion to the amide polymer layer constituting the laminate, resulting in a multilayer cooling pipe with excellent heat resistance.

[0145] The multilayer cooling pipe preferably has a two-type, two-layer laminate structure in which the amide-based polymer layer and the polymer composition layer are laminated in this order from the outer layer side of the multilayer cooling pipe. That is, the amide-based polymer layer and the polymer composition layer are preferably in direct contact with each other. The multilayer cooling pipe of this embodiment may further include a propylene-based polymer layer, and may have a three-type, three-layer laminate structure in which the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are laminated in this order from the outer layer side. FIG. 1 is a schematic cross-sectional view showing the configuration of a multilayer cooling pipe having a three-type, three-layer laminate structure. As shown in FIG. 1, an amide-based polymer layer 1, a polymer composition layer 2, and a propylene-based polymer layer 3 are laminated in this order from the outer layer side. Alternatively, the multilayer cooling pipe may have a three-type, five-layer laminate structure in which the propylene-based polymer layer, the polymer composition layer, the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are laminated in this order from the outer layer side. By providing a layer other than the amide polymer layer and the polymer composition layer to form a three or more layer laminate structure, it is possible to impart greater flexibility and chemical resistance to the multilayer cooling pipe while maintaining the rigidity and gas barrier properties that are characteristic of the amide polymer. Here, in the case of a three-kind five-layer structure, the two propylene-based polymer layers may have the same or different compositions, and the two polymer composition layers may have the same or different compositions. The laminate structure may be three or more layers, and may have a symmetric or asymmetric structure.

[0146] <Polymer Composition Layer> The polymer composition layer in the laminate according to this embodiment is a layer made of the composition described in the above <Polymer Composition>.

[0147] <<Amide-Based Polymer Layer>> The amide-based polymer layer in the laminate that forms the multilayer cooling pipe not only has gas barrier properties but also can impart mechanical strength, heat resistance, and other durability to the laminate. The amide-based polymer layer contains an amide-based polymer. Examples of the amide polymer include polymers of lactams such as ε-caprolactam and ω-laurolactam; polymers of aminocarboxylic acids such as 6-aminocaproic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid; polycondensates of diamines such as aliphatic diamines such as hexamethylenediamine, decamethylenediamine, dodecamethylenediamine and 2,2,4- or 2,4,4-trimethylhexamethylenediamine; alicyclic diamines such as 1,3- or 1,4-bis(aminomethyl)cyclohexane and bis(p-aminocyclohexylmethane); and aromatic diamines such as m- or p-xylylenediamine, and dicarboxylic acids such as aliphatic dicarboxylic acids such as adipic acid, suberic acid and sebacic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; and copolymers thereof.

[0148] More specifically, examples of the amide polymer 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, amide polymers containing a monomer having 10 to 12 carbon atoms between amide groups, such as polyamide 11, polyamide 12, polyamide 610, polyamide 611, polyamide 612, polyamide 1010, and polyamide 1012, are particularly preferred because they have a low amide group concentration and are less likely to undergo hydrolysis, have a low melting point among amide polymers, are easily co-extruded with the polymer composition of the present embodiment containing a polypropylene polymer as the main component, or with a polyolefin layer, and have low rigidity among amide polymers.

[0149] The amide polymer layer may contain a plasticizer. The inclusion of a plasticizer improves flexibility and facilitates shaping. 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.

[0150] When the amide-based polymer layer contains a plasticizer, the plasticizer precipitates at the adhesive interface over time or when exposed to a high-temperature environment, and intervenes between the polymer composition layer and the amide-based polymer layer, which may tend to reduce the adhesive strength. However, since the polymer composition has extremely excellent adhesive strength and heat resistance, it can also be suitably used in a configuration using an amide-based polymer layer containing such a plasticizer.

[0151] The amide polymer layer in the present embodiment may contain the polymer composition in the present embodiment or its constituent components, or may contain other components that the polymer composition may contain, within the scope of not impairing the object of the present embodiment.

[0152] From the viewpoint of environmental protection, amide polymers containing biomass-derived monomers can be used. Biomass-derived amide polymers specifically refer to amide polymers obtained by polymerizing plant-derived monomers. Well-known biomass-derived amide polymers include polyamide 610, polyamide 1010, and polyamide 1012, which are made from plant-derived sebacic acid or decamethylenediamine as starting materials, and polyamide 11, which is made from plant-derived 11-aminoundecanoic acid as starting material. However, other amide polymers can also be suitably used as long as the monomer is biomass-derived. In addition, amide polymers obtained by polymerizing monomers made from biomass naphtha as a starting material can also be suitably used.

[0153] From the viewpoint of environmental protection, the amide polymer may be made from recycled raw materials. The recycling method may be material recycling or chemical recycling. Material recycling may be the above-mentioned post-consumer recycling (PCR) or post-industrial recycling (PIR).

[0154] As the recyclable amide polymer, a commercially available product can be used. For example, a product meeting the above-mentioned properties can be appropriately selected from "Mingamid (registered trademark)" manufactured by Mitsubishi Chemical Advanced Materials Corporation, "Rilsan (registered trademark)" or "Rilsamid (registered trademark)" manufactured by Arkema, and the "DINALON (registered trademark)" series manufactured by UBE.

[0155] <<Propylene-Based Polymer Layer>> The propylene-based polymer layer in the laminate forming the multilayer cooling pipe is a layer containing a propylene-based polymer as a main component, and is excellent in rigidity and heat resistance. The propylene-based polymer contained in the propylene-based polymer layer preferably has a propylene unit content of 50 mol % or more. The propylene-based polymer layer is a layer made of a propylene-based polymer-containing composition having a composition different from the polymer composition of the present embodiment, and is distinguished from the above-described polymer composition layer.

[0156] 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, and propylene-ethylene block copolymers.

[0157] Among the above, propylene homopolymers (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, all of which have a melt flow rate (MFR) of 0.1 to 30 g / 10 min, are more preferred, and propylene homopolymers (propylene homopolymers), propylene-ethylene random copolymers, and propylene-butene random copolymers, all of which have an MFR of 0.1 to 30 g / 10 min, are particularly preferred.

[0158] In this specification, the melt flow rate (MFR) of the propylene-based polymer is a value measured in accordance with JIS K 7210:2014 under conditions of a temperature of 230°C, a load of 21.2 N, and a time of 10 minutes.

[0159] The propylene-based polymer layer may contain the polymer composition of the present embodiment or its constituent components, or may contain other components that the polymer composition may contain, within the scope of not impairing the object of the propylene-based polymer layer.

[0160] <<Other Layers>> The laminate forming the multilayer cooling pipe may have other layers laminated therein in addition to the polymer composition layer, the amide-based polymer layer, and the propylene-based polymer layer described above.

[0161] The other layers are not particularly limited, and examples thereof include resin layers made of styrene polymers such as polycarbonate, polystyrene (GPPS), high impact polystyrene (HIPS), and styrene-acrylonitrile graft copolymers (ABS resins), and other thermoplastic polymer layers such as olefin polymers other than propylene polymers and polyethylene polymers, cyclic polyolefin polymers, polyphenylene ether polymers, polyoxymethylene polymers such as polyoxymethylene homopolymers and polyoxymethylene copolymers, acrylic / methacrylic polymers such as polymethyl methacrylate polymers, and ester polymers such as polyethylene terephthalate, polybutylene terephthalate, and amorphous polyesters.

[0162] The total thickness of the multilayer cooling pipe 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. From the viewpoint of tube shaping, the total thickness is preferably 10 mm or less, more preferably 9 mm or less.

[0163] The thickness of the amide polymer layer constituting the multilayer cooling pipe in 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. From the viewpoint of mechanical strength, the thickness of the amide polymer layer is preferably 0.1 mm or more, and more preferably 0.2 mm or more. From the viewpoint of tube 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.

[0164] The thickness of the polymer composition layer constituting the multilayer cooling pipe in 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. From the viewpoint of adhesiveness, the thickness of the polymer composition layer is preferably 0.01 mm or more, and more preferably 0.05 mm or more. 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.

[0165] The thickness of the propylene-based polymer layer constituting the multilayer cooling pipe in 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. From the viewpoint of coolant resistance, the thickness of the propylene-based polymer layer is preferably 0.1 mm or more, and more preferably 0.15 mm or more. From the viewpoint of tube shaping, the thickness of the propylene-based 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.

[0166] With regard to the layers constituting the multilayer cooling pipe in this embodiment, it is preferred that the amide polymer layer has a thickness of 0.1 to 6.0 mm, the polymer composition layer has a thickness of 0.01 to 1.0 mm, and the propylene polymer layer has a thickness of 0.1 to 3.0 mm.

[0167] In the present embodiment, the ratio of the thickness of the polymer composition layer to the thickness of the amide-based polymer layer is preferably 1:0.2 to 1:300, more preferably 1:1 to 1:100, and even more preferably 1:2 to 1:10. When the polymer composition layer and the amide-based polymer layer are formed so as to have thicknesses within the above ranges, both rigidity and flexibility can be achieved.

[0168] The adhesive strength of the multilayer cooling pipe of this embodiment can be evaluated by a T-peel test. Specifically, as shown in the Examples section below, a test piece cut to a predetermined width (1 cm width in the Examples below) is used, and the interface where strength is to be measured is peeled off with a cutter or the like. The peel strength can be measured by peeling off the test piece at a predetermined speed (50 mm / min in the Examples below) using a general tensile tester at 23°C using the T-peel method, and this peel strength is defined as the adhesive strength of the multilayer cooling pipe. In the present invention, the interface to be measured refers to the adhesive interface between the polymer composition layer and the amide polymer layer.

[0169] Although it depends on the application, the adhesive strength of the multilayer cooling pipe measured by the 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.

[0170] The multilayer cooling pipe of this embodiment can maintain good adhesive strength between the layers even after heating. As an indicator of this, the higher the retention rate of adhesive strength measured after heat treatment of the multilayer cooling pipe at 150°C for 10 minutes relative to the adhesive strength before the heat treatment, the better the evaluation. From the viewpoint of heat resistance, a retention rate of 80% or more is preferable, and 85% or more is more preferable.

[0171] The multilayer cooling pipe of this embodiment has a laminated structure in which a polymer composition layer and an amide-based polymer layer are in contact with each other. The peeling mode between the polymer composition layer and the amide-based polymer layer is not particularly limited, but preferably exhibits cohesive peeling. Cohesive peeling is a phenomenon in which the interfacial adhesive strength is greater than the material strength (cohesive force) of the polymer composition layer or the amide-based polymer layer, and therefore peeling does not occur at the adhesive interface, but rather the polymer composition layer or the amide-based polymer layer undergoes material failure (cohesive failure) during peeling. In contrast, a phenomenon in which the polymer composition layer or the amide-based polymer layer does not break down and peels at their interface is called interfacial peeling. Exhibiting cohesive peeling means that the adhesive strength is sufficiently greater than the material strength, and is preferred in the sense that stable peel strength is achieved. In particular, the inventors have found that when exposed to a high-temperature environment, cooled, and adhesive strength is measured, cohesive peeling results in a lower rate of decrease in peel strength.

[0172] <<Manufacturing Method of Multilayer Cooling Pipe>> The multilayer cooling pipe of this embodiment can be manufactured by various conventionally known methods, such as blow molding, pipe extrusion molding, and tube extrusion molding, which are co-extrusion methods in which individual molten resins melted in an extruder are supplied to a multilayer die and laminated in the die.

[0173] The co-extrusion method is described in detail below. The polymers and compositions constituting each of the above layers are prepared in advance by melt kneading or dry blending. Next, they are extruded by a single-screw or twin-screw extrusion molding method, and the extrusions are joined together in a feed block, multi-manifold die, or the like to form a laminate structure. The extrusion is then performed through a die of a predetermined shape. After cooling, the hollow molded product is either wound up on a winder or cut straight.

[0174] The extrusion temperature in the co-extrusion method is appropriately selected depending on the properties of the resins in each layer constituting the laminate, but it is generally preferable to keep it at 300° C. or less.

[0175] The take-up speed (m / min) may be appropriately set depending on the desired thickness.

[0176] The extrusion rate (kg / h) of the base material from the extruder may be appropriately selected depending on the type of material used, the desired thickness of each layer, and the like.

[0177] The cooling method can be a conventionally known method, such as cooling with an air knife or air cooling, or cooling in water through a sizer or the like.

[0178] <<Uses of Multilayer Cooling Pipe>> The polymer composition constituting the polymer composition layer in the multilayer cooling pipe of this embodiment has excellent adhesion to the amide-based polymer layer and also has excellent heat resistance and rigidity. Therefore, the multilayer cooling pipe of this embodiment exhibits excellent adhesive strength characteristics and can also be excellent in strength, heat resistance, gas barrier properties, and the like. Therefore, the multilayer cooling pipe of this embodiment is suitable for use in heat exchange systems for automobiles, particularly electric vehicles, and can also be used in applications requiring high cooling efficiency in a limited space, such as cooling pipes for automobiles (particularly electric vehicles). Electric vehicles tend to have larger batteries for the purposes of higher power output and extended driving range. However, to maintain the interior volume (interior space) of the automobile, a cooling system that efficiently arranges cooling pipes in a more limited space is required. The multilayer cooling pipe of this embodiment has excellent flexibility and excellent adhesion such that the adhesive layer and polyamide layer do not peel off even when bent into a complex shape, making it suitable for use in applications such as electric vehicles. Examples of automotive heat exchange systems include cooling systems such as radiators, intercoolers, and oil coolers.

[0179] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Note that the values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present invention, and a preferred range may be defined by a combination of the above-mentioned upper or lower limit values ​​and the values ​​in the following examples or values ​​between the examples.

[0180] [Materials] The following materials were used in the examples below.

[0181] <Ethylene / α-olefin copolymer (A)> 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 / cm ３A-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 / cm ３ 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 / cm ３ 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 / cm ３ 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 / cm ３

[0182] <Propylene Polymers (B)> B-1: Propylene homopolymer, MFR: 0.5 g / 10 min (230°C, load 21.2 N, orifice diameter 2 mm) B-2: Propylene homopolymer, MFR: 7.0 g / 10 min (230°C, load 21.2 N, orifice diameter 2 mm) 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%) 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%) B-5: Propylene-ethylene random copolymer, MFR: 7.0 g / 10 min (230°C, load 21.2 N, orifice 2 mm diameter, ethylene ratio: 3%) B-6: Propylene-ethylene random copolymer, MFR: 2.0 g / 10 min (230°C, load 21.2 N, orifice 2 mm diameter, ethylene ratio: 3%) B-7: Propylene homopolymer, MFR: 10 g / 10 min (230°C, load 21.2 N, orifice 2 mm diameter) B-8: Propylene homopolymer, MFR: 0.8 g / 10 min (230°C, load 21.2 N, orifice 2 mm diameter) B-9: Propylene-ethylene random copolymer, MFR: 1.9 g / 10 min (230°C, load 21.2 N, orifice 2 mm diameter, ethylene ratio: 4%) B-10: Propylene homopolymer (biomass-derived), MFR: 3.2 g / 10 min (230°C, load 21.2 N, orifice diameter 2 mm)

[0183] <Propylene polymer (C) modified with at least one selected from the group consisting of unsaturated carboxylic acids and derivatives thereof> C-1: Modified propylene homopolymer grafted with maleic anhydride (Production method) A propylene homopolymer (density: 0.90 g / cm 3) was added to 6 L of chlorobenzene. ３5 kg of a powder having an MFR (230°C, load 21.2N): 11 g / 10 min) and 500 g of maleic anhydride were dissolved at 130°C. Next, a chlorobenzene solution of dicumyl peroxide (200 g / 400 L) was added to this solution. The reaction was continued for an additional 8 hours at 130°C, and then cooled to 40°C to precipitate a resin. The precipitated resin was filtered, washed repeatedly with acetone, and dried under reduced pressure at 90°C to obtain a modified propylene homopolymer C-1 grafted with maleic anhydride and having a modification level of 2.2 mass%. The MFR of C-1 (180°C, load 21.2 N, 1 mm orifice diameter) was 400 g / 10 min.

[0184] C-2: Modified propylene homopolymer grafted with maleic anhydride (Production method) 100 parts by mass of propylene homopolymer (MFR (230°C, load 21.2N): 0.5g / 10min), 4 parts by mass of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.7 parts by mass of organic peroxide (manufactured by NOF Corporation, Perbutyl I) were dry blended and mixed. Next, the resulting mixture was melt-kneaded using a twin-screw extruder (D = 30mmφ, L / D = 32, manufactured by Nippon Steel Corporation, TEX30) at a temperature of 200°C, a screw rotation speed of 300 rpm, and an extrusion rate of 10 kg / h, and then pelletized. As a result, a modified propylene homopolymer C-2 grafted with maleic anhydride having a modification amount of 1.3% by mass was obtained. The MFR of C-2 (180° C., 21.2 N load, 1 mm orifice diameter) was 12 g / 10 min.

[0185] C-3: Modified propylene-ethylene random copolymer grafted with maleic anhydride (Production method) 100 parts by mass of a propylene-ethylene random copolymer (MFR (230°C, load 21.2N): 2 g / 10 min, ethylene ratio: 11 mass%), 1.5 parts by mass of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 1.5 parts by mass of an organic peroxide (manufactured by NOF Corporation, Perbutyl O) were dry-blended and mixed. The resulting mixture was then melt-kneaded using a twin-screw extruder (D = 30 mmφ, L / D = 32, manufactured by Nippon Steel Corporation, TEX30) at a temperature of 200°C, a screw rotation speed of 300 rpm, and an extrusion rate of 10 kg / h, and pelletized. This yielded a modified propylene-ethylene random copolymer C-3 grafted with maleic anhydride having a modification amount of 1.1 mass%. The MFR of C-3 (180° C., 21.2 N load, 1 mm orifice diameter) was 0.5 g / 10 min.

[0186] C-4: Modified propylene-ethylene random copolymer grafted with maleic anhydride (Production method) 56 parts by mass of propylene-ethylene random copolymer (MFR (230°C, load 21.2N): 7 g / 10 min, ethylene ratio: 1 mass%), 44 parts by mass of propylene-ethylene random copolymer (MFR (230°C, load 21.2N): 7 g / 10 min, ethylene ratio: 11 mass%), 1.5 parts by mass of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and organic peroxide (Perhexa 25B, manufactured by NOF Corporation). 0.3 parts by mass of the above were dry-blended and mixed. The resulting mixture was then melt-kneaded and pelletized using a twin-screw extruder (D=30 mmφ, L / D=32, manufactured by Nippon Steel Corporation, TEX30) at a temperature of 200°C, a screw rotation speed of 300 rpm, and an extrusion rate of 10 kg / h. This resulted in a modified propylene-ethylene random copolymer C-4 grafted with maleic anhydride and having a modification level of 0.9% by mass. The MFR (180°C, 21.2 N load, 1 mm orifice diameter) of C-4 was 8.0 g / 10 min.

[0187] C-5: Modified block propylene polymer grafted with maleic anhydride (Production method) 100 parts by mass of block propylene polymer (MFR (230°C, load 21.2N): 2 g / 10 min), 1.5 parts by mass of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.7 parts by mass of organic peroxide (manufactured by NOF Corporation, Perbutyl I) were dry blended and mixed. Next, the resulting mixture was melt-kneaded using a twin-screw extruder (D = 30 mmφ, L / D = 32, manufactured by The Japan Steel Works, Ltd., TEX30) at a temperature of 200°C, a screw rotation speed of 300 rpm, and an extrusion rate of 10 kg / h, and then pelletized. This yielded a modified block propylene polymer C-5 grafted with maleic anhydride having a modification amount of 0.9% by mass. The MFR of C-5 (180° C., 21.2 N load, 1 mm orifice diameter) was 4.0 g / 10 min.

[0188] C-6: Modified propylene-ethylene random copolymer grafted with maleic anhydride (Production method) 100 parts by mass of a propylene-ethylene random copolymer (MFR (230°C, load 21.2N): 2 g / 10 min, ethylene ratio: 3 mass%), 2 parts by mass of maleic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 1.5 parts by mass of an organic peroxide (manufactured by NOF Corporation, Perbutyl O) were dry-blended and mixed. The resulting mixture was then melt-kneaded using a twin-screw extruder (D = 30 mmφ, L / D = 32, manufactured by Nippon Steel Corporation, TEX30) at a temperature of 200°C, a screw rotation speed of 300 rpm, and an extrusion rate of 10 kg / h, and pelletized. This yielded a modified propylene-ethylene random copolymer C-6 grafted with maleic anhydride having a modification amount of 1.1 mass%. The MFR of C-6 (180° C., 21.2 N load, 1 mm orifice diameter) was 25 g / 10 min.

[0189] <Other ingredients> N-1: Low-density polyethylene, MFR: 2.8 g / 10 min (190°C, load 21.2 N, orifice diameter 2 mm) N-2: Linear low-density polyethylene, MFR: 1.7 g / 10 min (190°C, load 21.2 N, orifice diameter 2 mm) N-3: High-density polyethylene, MFR: 1.8 g / 10 min (190°C, load 21.2 N, orifice diameter 2 mm)

[0190] Test Example 1 (Examples 1 to 19, Comparative Examples 1 to 11) The components listed in the above [Raw Materials] were dry-blended and mixed in the amounts listed in Tables 1 to 5. The resulting mixture was melt-kneaded using a single-screw extruder (diameter 40 mmφ, L / D = 32) at a set temperature of 210°C, a screw rotation speed of 60 rpm, and an extrusion rate of 20 kg / h, and pellets of a non-crosslinked polymer composition were obtained by strand cutting. The MFR (230°C, load 21.2 N) of the resulting polymer composition and the content of maleic anhydride in the polymer composition were measured, and the results are shown in Tables 1 to 5.

[0191] Next, a multilayer sheet simulating a multilayer cooling pipe was obtained by the following procedure using the obtained polymer composition as a polymer composition layer. The propylene-based polymer layer used was a polypropylene "Novatec PP EG7F" (MFR (230°C, load 21.2N): 1.3 g / 10 min) manufactured by Japan Polypropylene Corporation. The amide-based polymer layer used was polyamide 12 (nylon 12) (Grilamid L25W20X manufactured by EMS).

[0192] First, a three-kind, three-layer multilayer sheet was obtained using a multilayer sheet molding machine equipped with three single-screw extruders. The extruders for each layer in the multilayer sheet molding machine were 20 mmφ for the propylene-based polymer layer, 30 mmφ for the amide-based polymer layer, and 20 mmφ for the polymer composition layer, and a 300 mm wide die (lip opening 1 mm) was used. The three-kind, three-layer multilayer structure was amide-based polymer layer / polymer composition layer / propylene-based polymer layer, with layer thicknesses of 0.6 mm / 0.1 mm / 0.3 mm (total 1 mm). The molding temperatures were 230°C for the amide-based polymer layer, 230°C for the polymer composition layer, and 230°C for the propylene-based polymer layer, with a die temperature of 230°C. The total extrusion rate for the three layers was approximately 3 kg / h, and the roll cooling temperature was 80°C.

[0193] [Evaluation: Adhesion Strength] Each of the laminate sheets obtained above was cut into a strip having a width of 1 cm in the extrusion direction to prepare a test piece. The test piece was subjected to a T-peel test at the interface between the amide polymer layer and the polymer composition layer in an atmosphere of 23°C at a speed of 50 mm / min to measure the peel strength, and the value was taken as the adhesive strength of the laminate sheet. The results are shown in Tables 1 to 5. A strength of 7.0 N / cm or more but less than 15.0 N / cm can be evaluated as excellent adhesive strength between the amide polymer layer and the polymer composition layer, and a strength of 15.0 N / cm or more can be evaluated as very excellent adhesive strength between the amide polymer layer and the polymer composition layer.

[0194] [Evaluation: Heat Resistance] Test pieces were cut out in the same manner as in the above [Evaluation: Adhesive Strength] and placed in a precision oven for 10 minutes at 150°C for heat treatment. After the test pieces were sufficiently cooled, a T-peel test was performed on the heat-treated test pieces at the interface between the amide polymer layer and the polymer composition layer in an atmosphere of 23°C at a speed of 50 mm / min to measure the peel strength, and this value was taken as the adhesive strength of the laminate sheet. The results are shown in Tables 1 to 5. Regarding strength, the greater the retention rate of adhesive strength after heat treatment relative to the adhesive strength before heat treatment, the better the heat resistance. A retention rate of 80% or more but less than 85% was evaluated as excellent heat resistance, and a retention rate of 85% or more was evaluated as very excellent heat resistance.

[0195]

[0196]

[0197]

[0198]

[0199]

[0200] Examples 1 to 19 had sufficient initial adhesive strength, excellent adhesion between the polymer composition layer and the amide polymer layer, and showed little decrease in adhesive strength even after heat treatment, demonstrating excellent adhesiveness. Comparative Examples 1 to 5 had insufficient adhesive strength, with a peel strength of less than 7.0 N / cm in a 23°C atmosphere, and Comparative Examples 6 to 11 showed a decrease in adhesive strength after heat treatment compared to Examples 1 to 19.

[0201] Test Example 2 Examples 20 to 23 Pellet-shaped non-crosslinked polymer compositions were obtained using the blending amounts shown in Table 6 in the same manner as in Test Example 1. The MFR (230°C, load 21.2 N) of the obtained polymer compositions and the content of maleic anhydride in the polymer compositions were measured, and the results are shown in Table 6.

[0202] Next, a multilayer sheet simulating a multilayer cooling pipe was obtained by the following procedure using the obtained polymer composition as a polymer composition layer. Note that for the propylene-based polymer layer, polypropylene "Novatec PP EG7F" (MFR (230°C, load 21.2N): 1.3 g / 10 min) manufactured by Japan Polypropylene Corporation was used. For the amide-based polymer layer, a polyamide listed in Table 6 was used as a recycled polyamide. Details of the polyamide used in each example are as follows. P-1: Polyamide 6 (Mitsubishi Chemical Corporation, Mingamid PA6G24N), MFR: 6.7 (230°C, load 21.2N, orifice diameter 2mm) P-2: Polyamide 11 (Mitsubishi Chemical Corporation, Mingamid 14SP40), MFR: 8.9 (230°C, load 21.2N, orifice diameter 2mm) P-3: Polyamide 12 (Mitsubishi Chemical Corporation, Mingamid 12SP20), MFR: 7.9 (230°C, load 21.2N, orifice diameter 2mm) P-4: Polyamide 12 (Mitsubishi Chemical Corporation, Mingamid 14SP40), MFR: 6.6 (230°C, load 21.2N, orifice diameter 2mm)

[0203] First, a three-kind, three-layer multilayer sheet was obtained using a multilayer sheet molding machine equipped with three single-screw extruders. The extruders for each layer in the multilayer sheet molding machine were 20 mmφ for the propylene-based polymer layer, 30 mmφ for the amide-based polymer layer, and 20 mmφ for the polymer composition layer, and a 300 mm wide die (lip opening 1 mm) was used. The three-kind, three-layer multilayer structure was amide-based polymer layer / polymer composition layer / propylene-based polymer layer, with the thicknesses of each layer being 0.6 mm / 0.1 mm / 0.3 mm (total 1 mm). The molding temperatures were 230°C for the amide-based polymer layer, 230°C for the polymer composition layer, and 230°C for the propylene-based polymer layer, with a die temperature of 230°C. The total extrusion rate for the three layers was approximately 3 kg / h, and the roll cooling temperature was 80°C. However, when P-1 (polyamide 6) was used for the amide-based polymer layer, the molding temperature was 240°C.

[0204] [Evaluation: Adhesion Strength] Peel strength was measured in the same manner as in Test Example 1. The results are shown in Table 6.

[0205] [Evaluation: Heat Resistance] The peel strength of the heat-treated test piece was measured in the same manner as in Test Example 1. The results are shown in Table 6.

[0206]

[0207] In Examples 20 to 23, the initial adhesive strength was sufficient, the adhesiveness between the polymer composition layer and the amide-based polymer layer was excellent, and the decrease in adhesive strength was small even after heat treatment, showing excellent adhesiveness. These results demonstrate that the polymer composition layer made of the polymer composition of the present invention has excellent adhesiveness with various amide-based polymer layers and is resistant to decrease in adhesive strength even after exposure to high temperatures.

[0208] Test Example 3 (Example 24, Comparative Example 12) Based on the blending amounts shown in Table 7, pellet-shaped non-crosslinked polymer compositions were obtained in the same manner as in Test Example 1. Note that Comparative Example 12 has the same composition as Comparative Example 5.

[0209] [Evaluation: Proportion of Component (Y) Derived from α-olefin Monomers Other Than Propylene Monomer] 30 mg of the polymer composition was weighed into a 5 mm outer diameter NMR sample tube, and 0.53 mL of deuterated orthodichlorobenzene (ODCB) was added. The mixture was heated in a block heater at 130°C. The proportion of component (Y) derived from α-olefin monomers other than propylene monomer was measured by measuring the C NMR spectrum using a Bruker AVANCE 600 spectrometer. The resonance frequency was 150.9 MHz, the flip angle was 90°, the data acquisition time was 2.0 seconds, the pulse repetition time was 20 seconds, the number of integrations was 256, the temperature was 120°C, and the 1-hour irradiation was performed using the fully decoupled method. The chemical shift references were the polyethylene main chain signal at 30.0 ppm and the isotactic methyl group signal at 21.8 ppm. The results are shown in Table 7.

[0210] [Evaluation: Tensile Breaking Elongation] A 20 mmφ single-screw T-die extruder was used to obtain a 0.1 mm thick single-layer sheet of the polymer composition. This sheet was punched out with a JIS No. 2 dumbbell specimen, and a tensile test was performed in accordance with JIS K7161 at a temperature of 23°C and a speed of 300 mm / min to measure the tensile breaking elongation in the TD and MD directions. From the obtained values, the ratio of the tensile breaking elongation in the TD direction to the tensile breaking elongation in the MD direction was calculated. The results are shown in Table 7.

[0211] [Evaluation: Haze] Using an electric press, the polymer composition was pressed at a molding temperature of 200°C to prepare a test piece having a thickness of 0.4 mm and a size of 50 mm square. Using this test piece, the external haze was measured in accordance with JIS K7136. The results are shown in Table 7.

[0212]

[0213] As can be seen from Table 7, Example 24 had a significantly higher tensile break elongation in the TD direction than Comparative Example 12, and the tensile break elongation in the TD direction was greater than the tensile break elongation in the MD direction. These results also indicate that Example 24 is less likely to be excessively oriented during molding of the multilayer cooling piping, making it less likely to crack. Furthermore, Example 24 had a haze of 27%, making it less likely to crack.

[0214] Although the present invention has been described in detail and with reference to specific embodiments, 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 present invention. This application is based on a Japanese patent application (Patent Application No. 2024-056468) filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0215] 1 Amide-based polymer layer 2 Polymer composition layer 3 Propylene-based polymer layer

Claims

1. A multi-layer cooling pipe comprising an amide-based polymer layer and a polymer composition layer made 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 an unsaturated carboxylic acid derivative onto the propylene-based polymer, wherein the polymer composition contains 18% by mass or more and 40% by mass or less of the ethylene-α-olefin copolymer (A), 40% by mass or more and 81% by mass or less of the propylene-based polymer (B), and 1% by mass or more and 19% by mass or less of the modified propylene-based polymer (C).

2. The multilayer cooling piping according to claim 1, wherein the value represented by the following formula (1) is 0.22 or more and 0.65 or less: PA / (PB+PC) (1) In formula (1), PA is the content (mass%) of the ethylene-α-olefin copolymer (A) in the polymer composition, PB is the content (mass%) of the propylene polymer (B) in the polymer composition, and PC is the content (mass%) of the modified propylene polymer (C) in the polymer composition.

3. The multi-layer cooling piping of claim 1, wherein said polymer composition is non-crosslinked.

4. The multilayer cooling pipe according to claim 1, wherein the MFR of the ethylene-α-olefin copolymer (A) measured at 190°C, 21.2 N, and a 2 mm orifice diameter is 0.01 g / 10 min or more and 4.0 g / 10 min or less.

5. The multilayer cooling piping according to claim 4, wherein the MFR is 0.1 g / 10 min or more and 1.5 g / min or less.

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 having 6 or less carbon atoms.

7. The multi-layer cooling piping 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 density of the ethylene / α-olefin copolymer (A) is 0.85 g / cm ３ 0.88g / cm or more ３ The multi-layer cooling piping of claim 1 , wherein the thickness is less than 1 / 2 mm.

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

10. The multi-layer cooling piping according to claim 1, wherein the modified propylene polymer (C) has an MFR of 0.4 g / 10 min or more and 500 g / 10 min or less, as measured at 180°C, 21.2 N, and a 1 mm orifice diameter.

11. The multi-layer cooling piping 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. A multilayer cooling pipe as described in claim 1, wherein the content of at least one member selected from the group consisting of unsaturated carboxylic acids and derivatives thereof in the polymer composition layer is 0.01% by mass or more and 0.30% by mass or less.

13. The multilayer cooling pipe according to claim 1, wherein the amide polymer contained in the amide polymer layer is an amide polymer containing a monomer having 10 to 12 carbon atoms between the amide groups.

14. The multi-layer cooling piping of claim 1, wherein the amide-based polymer layer includes a plasticizer.

15. A multilayer cooling pipe as described in claim 1, wherein when a test piece obtained by molding the polymer composition into a sheet having a thickness of 0.1 mm is measured in accordance with JIS K7161, the ratio TDα / MDα of the tensile breaking elongation in the TD direction to the tensile breaking elongation in the MD direction MDα is 0.5 or more and 1.5 or less.

16. The multi-layer cooling piping according to claim 1, wherein the polymer composition is molded into a sheet having a thickness of 0.4 mm, and the haze of the sheet is measured in accordance with JIS K7136 and is 15% or more and 50% or less.

17. The multilayer cooling pipe according to claim 1, which has a laminated structure in which the amide-based polymer layer and the polymer composition layer are in contact with each other, and which exhibits cohesive peeling when the amide-based polymer layer and the polymer composition layer are peeled off.

18. The multilayer cooling pipe according to claim 1, having a laminated structure in which the amide polymer layer and the polymer composition layer are laminated in this order from the outer layer side.

19. The multilayer cooling pipe according to claim 18, further comprising a propylene-based polymer layer, and having a layered structure in which the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are layered in this order from the outer layer side.

20. The multilayer cooling pipe according to claim 19, wherein the amide polymer layer has a thickness of 0.1 to 6.0 mm, the polymer composition layer has a thickness of 0.01 to 1.0 mm, and the propylene polymer layer has a thickness of 0.1 to 3.0 mm.

21. The multilayer cooling pipe according to claim 18, further comprising a propylene-based polymer layer, and having a layered structure in which, from the outer layer side, the propylene-based polymer layer, the polymer composition layer, the amide-based polymer layer, the polymer composition layer, and the propylene-based polymer layer are layered in this order.

22. The multilayer cooling pipe according to claim 21, wherein the amide polymer layer has a thickness of 0.1 to 6.0 mm, the polymer composition layer has a thickness of 0.01 to 1.0 mm, and the propylene polymer layer has a thickness of 0.1 to 3.0 mm.

23. Use of the multilayer cooling piping according to any one of claims 1 to 22 in a heat exchange system of an automobile.

24. Use of the multilayer cooling piping according to any one of claims 1 to 22 in a heat exchange system of an electric vehicle.

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