Plastic line for conveying air conditioning refrigerant in an electric or plug-in hybrid vehicle

Abstract

The invention relates to a plastic line for conveying air-conditioning refrigerant in an electric or plug-in hybrid vehicle, which consists of only two layers: a first layer which directly surrounds the inner space of the line, and a second layer which directly adjoins the first layer, and wherein the first layer is based on an aliphatic polyamide molding compound A based on PA 6, the second layer is based on an aliphatic polyamide molding compound B based on PA 610, PA 612, or mixtures or copolyamides thereof, wherein the sum of the thicknesses of the first layer and the second layer is in the range from 1.5 mm to 5 mm, and the thickness ratio of the first layer to the second layer is in the range from 0.54 to 5.66.

Description

Technical Field

[0001] This invention relates to the field of plastic tubing, and more specifically, to plastic tubing for delivering air conditioning refrigerant in electric vehicles or plug-in hybrid electric vehicles (PHEVs). Background Technology

[0002] Current air conditioning systems are typically based on rubber hoses and metal pipes and are primarily designed for internal combustion engine vehicles. Internal combustion engines generate a significant amount of heat, therefore air conditioning ducts and systems need to meet stringent regulations regarding aspects such as thermal stability.

[0003] However, with the advent of electric vehicles and plug-in hybrid vehicles, air conditioning systems no longer need to meet the requirements of pure internal combustion engine vehicles. In particular, because electric vehicles do not have an internal combustion engine, and plug-in hybrid vehicles do not, the temperatures in electric vehicles and plug-in hybrid vehicles are lower. This change in the operating environment brings new applicability requirements.

[0004] In particular, refrigerant lines, such as those transporting refrigerant for air conditioning systems, need to operate at high pressures (e.g., 3.5 MPa or higher), and the burst pressure of refrigerant lines can even reach 8.3 MPa at 125°C. However, existing technologies do not specifically address plastic lines used to transport refrigerant in electric vehicles or plug-in hybrid vehicles while meeting the desired operating and burst pressures. If the operating and burst pressure requirements are not met, there is a risk of refrigerant leakage when these lines are used to transport refrigerant in electric vehicles or plug-in hybrid vehicles.

[0005] Various plastic tubing systems have been disclosed in the prior art. For example, document EP4155068B1 describes a multilayer tubular structure with three layers (an inner layer, a barrier layer, and an outer layer) intended for transporting hydrogen (rather than an air conditioning refrigerant). The inner and outer layers are based on polyamide, while the barrier layer is based on an EVOH layer, a fluoropolymer layer, or a PPA layer. PPA stands for polyphthalamide.

[0006] Document CN114851669B describes a multi-layered conduit for transporting vehicle fuel (not air conditioning refrigerant), which, from the outside in, includes: a nylon outer layer, an amphiphilic branched polymer adhesive layer, a fluoropolymer barrier layer, an amphiphilic branched polymer adhesive layer, and a conductive nylon inner layer.

[0007] Document BR102020004872A2 describes a multilayer pipe for use in fuel (not air conditioning refrigerant) piping systems for motor vehicles, characterized by comprising the following layers: an inner PA 6 layer, an intermediate EVOH layer, and an outer PA 612 or PA 610 layer.

[0008] The multi-layer pipes used as fuel lines do not meet the application requirements of refrigerant lines because: the working pressure of fuel lines is usually 1 MPa, while the working pressure of refrigerant lines is as high as 3.5 MPa, which is 3.5 times that of fuel lines; in addition, the burst pressure of fuel lines is usually 3.0-4.0 MPa, while the burst pressure of refrigerant lines can even reach 8.3 MPa at 125°C.

[0009] Furthermore, document CN113165305A describes a multilayer pipe for transporting air conditioning fluids in general-purpose vehicles. Its technical concept requires a combined structure of a short-chain (4-9 carbon atoms per nitrogen atom) aliphatic polyamide inner layer and a long-chain (10-15 carbon atoms per nitrogen atom) aliphatic polyamide outer layer. Examples of short-chain aliphatic polyamides include PA6, PA66, PA6 / 66, PA610, PA410, PA412, and PA612; examples of long-chain aliphatic polyamides include PA11, PA12, PA1010, PA1012, PA1210, and PA1212. However, it fails to recognize the differences in operating conditions between electric vehicles or plug-in hybrid vehicles and ordinary internal combustion engine vehicles, and does not address the related issues of air conditioning piping in electric vehicles or plug-in hybrid vehicles. Moreover, according to this document, a long-chain aliphatic polyamide outer layer is necessary. As shown in counterexamples 1 and 2 in the literature, the desired technical effect cannot be achieved without an outer layer made of long-chain aliphatic polyamide. However, long-chain aliphatic polyamide is expensive, and its introduction would significantly increase costs.

[0010] Therefore, providing a plastic pipeline that can replace the existing pipelines used in internal combustion engine vehicles, and that meets the requirements for the working environment, pressure, and burst pressure for delivering air conditioning refrigerant in electric vehicles or plug-in hybrid vehicles, has become an unsolved problem. Summary of the Invention

[0011] Therefore, one object of the present invention is to provide a plastic tubing for conveying air conditioning refrigerant in electric vehicles or plug-in hybrid vehicles, characterized by improved operating characteristics and features, such as improved barrier properties (particularly barrier properties / leakage resistance to air conditioning refrigerant) and good burst pressure characteristics, and which improves upon the prior art for these types of plastic tubing and has cost advantages.

[0012] According to one aspect of the invention, a plastic conduit is provided, characterized in that it comprises only two layers: a first layer directly surrounding the internal space of the conduit, and a second layer directly adjacent to the first layer, wherein the first layer is made of an aliphatic polyamide molding compound A comprising a polyamide based on PA 6, and the second layer is made of an aliphatic polyamide molding compound B comprising a polyamide based on PA 610, PA 612, or a mixture thereof or a copolyamide, wherein the sum of the thicknesses of the first and second layers is in the range of 1.5 mm to 5 mm, and the thickness ratio of the first layer to the second layer is in the range of 0.54 to 5.66.

[0013] According to one aspect of the invention, the plastic tubing can be configured to be located between the compressor and the condenser.

[0014] According to one aspect of the invention, the minimum burst pressure of the first layer made of aliphatic polyamide molding compound A and the second layer made of aliphatic polyamide molding compound B at 125°C can be 6.0 MPa, and / or the minimum burst pressure at 23°C can be 10.4 MPa.

[0015] According to one aspect of the invention, the first layer and the second layer may be separated by no adhesive layer and / or barrier layer.

[0016] According to one aspect of the invention, aliphatic polyamide molding A may contain an impact modifier in an amount of 2.0% to 12.0% by weight of the total weight of aliphatic polyamide molding A, and / or aliphatic polyamide molding B may contain an impact modifier in an amount of 2.0% to 12.0% by weight of the total weight of aliphatic polyamide molding B.

[0017] According to one aspect of the invention, the impact modifier in aliphatic polyamide molding A and / or aliphatic polyamide molding B may be an acid-modified ethylene-α-olefin copolymer.

[0018] According to one aspect of the invention, the aliphatic polyamide molding A may contain a nonionic surfactant in an amount of 0% to 0.5% by weight of the total weight of the aliphatic polyamide molding A.

[0019] According to one aspect of the present invention, the nonionic surfactant may be Tween-20 (chemical name: polyoxyethylene (20) dehydrated sorbitan monolaurate; CAS No.: 9005-64-5).

[0020] According to one aspect of the invention, aliphatic polyamide molding A may contain minerals in an amount of 0% to 0.50% by weight of the total weight of aliphatic polyamide molding A, and / or aliphatic polyamide molding B may contain minerals in an amount of 0% to 0.50% by weight of the total weight of aliphatic polyamide molding B.

[0021] According to one aspect of the invention, the mineral may be a layered silicate mineral.

[0022] According to one aspect of the invention, the layered silicate mineral may be kaolinite.

[0023] According to one aspect of the invention, the melt temperature of the aliphatic polyamide molding B can be in the range of 180°C to 240°C, wherein the melt temperature is measured according to ISO 11357-3:2025.

[0024] According to the technical solution of the present invention, it is possible to provide plastic tubing for conveying air conditioning refrigerant in electric vehicles or plug-in hybrid vehicles, which has improved operating characteristics and features, such as improved barrier properties (especially barrier properties against air conditioning refrigerant) and good burst pressure characteristics. Detailed Implementation

[0025] In the context of this invention, the term "polyamide" (abbreviated PA) is understood as an inclusive term; it includes homopolymers and copolymers. Selected names and abbreviations of polyamides and their monomers correspond to the names and abbreviations defined in ISO standard 16396-1 (2015, (D)).

[0026] The symbol "." is used as a decimal separator in numbers.

[0027] The terms "comprising" and "including" in these claims and specification mean that additional components are not excluded. Within the scope of this invention, the term "composed of / constituting of" is understood to refer to the preferred embodiment of the terms "comprising" or "including," meaning that in addition to the listed components, it contains only other components that do not affect the function of the invention, and that these other components are present in amounts that do not affect the function of the invention. If a group is defined as "comprising" or "including" at least a certain number of components, this should also be understood to mean that a group / technical solution preferably "composed / constituting" of these components is disclosed.

[0028] Weight % is an abbreviation for weight percentage, and unless otherwise defined, weight % is based on the total weight of the polyamide molding composition.

[0029] For the purposes of this invention, if a range from a to b is stated, then endpoints a and b are included. Furthermore, for any stated range from a to b, all subranges from a1 to b1 are also disclosed, where a ≤ a1, b1 ≤ b, and a1 <b1。

[0030] The term "nylon" is used here as a synonym for "polyamide".

[0031] As used herein, the term “aliphatic” refers to acyclic or cyclic, saturated or unsaturated carbon compounds, excluding aromatic compounds. This definition follows the IUPAC definition in the Gold Book (IUPAC Chemical Terminology Compendium, 5th Edition, “aliphatic compounds” in the International Union of Pure and Applied Chemistry; online version 5.0.0, 2025; https: / / doi.org / 10.1351 / goldbook.A00217).

[0032] As used in this patent application, the term "mixture" refers to a polymer blend (or simply "blend"), that is, a physical mixture of two or more different polymers. Therefore, a mixture is different from a copolyamide.

[0033] As used in this patent application, the term "copolyamide" refers to a copolymer containing amide bonds (–CO–NH–) and formed from monomers (comonomers) that are different from the monomers required for polymerization according to the corresponding reaction mechanism. This definition follows the definition provided in the RÖMPP online dictionary (https: / / roempp.thieme.de / lexicon / RD-03-02510).

[0034] As used in this patent application, the "first layer" can also be referred to as the "inner layer" because it directly surrounds the internal space of the pipeline; and the "second layer" can also be referred to as the "outer layer" because it is located outside the first layer.

[0035] In a preferred embodiment of the invention, the aliphatic polyamide molding compound A of the first / inner layer may be specified as being based on PA 6. PA 6 (polyamide 6, nylon 6) is a polyamide that can be produced by ring-opening polymerization of caprolactam, having a C / N atomic ratio of 6, i.e., 6 carbon atoms per nitrogen atom. The phrase "based on PA 6" means that the polyamide molding compound A consists of at least 50 weight percent PA 6. PA 6 is particularly preferred for the first / inner layer due to its excellent barrier properties, strength at elevated temperatures, and its compliance with refrigerant leakage requirements.

[0036] Preferably, PA 6 is present in polyamide molding compound A in an amount of 85.5% to 98% by weight of the total weight of polyamide molding compound A. More preferably, PA 6 is present in polyamide molding compound A in an amount of 87.85% to 96.45% by weight. Most preferably, PA 6 is present in polyamide molding compound A in an amount of 92.36% to 95.31% by weight. Here, weight percent is based on the total weight of polyamide molding compound A.

[0037] Similarly, the term "PA X-based" means that the corresponding polyamide molding compound consists of at least 50% by weight of PA X, where X is the type of polyamide, such as 610 or 612.

[0038] In a preferred embodiment of the invention, the second / outer layer aliphatic polyamide molding compound B may be specified as being based on PA 610, PA 612, or a mixture thereof or a copolyamide. PA 610 (polyamide 610, nylon 610) is a polyamide that can be produced by the condensation polymerization of hexamethylenediamine and sebacic acid, having a C / N atomic ratio of 8, i.e., 8 carbon atoms per nitrogen atom. PA 612 (polyamide 612, nylon 612) is a polyamide that can be produced by the condensation polymerization of hexamethylenediamine and dodecanoic acid, having a C / N atomic ratio of 9, i.e., 9 carbon atoms per nitrogen atom. PA 6, PA 610, and PA 612 are not long-chain polyamides with a C / N atomic ratio of 10 or greater.

[0039] Preferably, the aliphatic polyamide molding compound B of the second / outer layer is based on PA 610. A particular advantage of PA 610 is its resistance to chlorides in road de-icing salt.

[0040] Preferably, the aliphatic polyamide (e.g., PA 610) in the polyamide molding compound B is present in an amount of 86% to 98% by weight of the polyamide molding compound B. More preferably, the aliphatic polyamide (e.g., PA 610) is present in the polyamide molding compound B in an amount of 88.25% to 96.55% by weight. Most preferably, the aliphatic polyamide is present in an amount of 92.45% to 95.35% by weight. Here, weight percent is based on the total weight of the polyamide molding compound B.

[0041] Therefore, according to one aspect of the invention, double-layered plastic conduits can meet the requirements for strength and leak resistance as well as resistance to external influences (e.g., road de-icing salt).

[0042] In a preferred embodiment of the invention, a plastic conduit may be specified to be located between the compressor and the condenser. The compressor and condenser are part of an air conditioning refrigeration system. A compressor is a mechanical device that increases gas pressure by reducing gas volume. A condenser is a heat exchanger used to condense gaseous substances into a liquid state through cooling.

[0043] In a preferred embodiment of the invention, the minimum burst pressure at 125°C for the first layer made of polyamide molding compound A and the second layer made of polyamide molding compound B can be specified as 6.0 MPa. Preferably, the minimum burst pressure at 125°C is 7.0 MPa. More preferably, the minimum burst pressure at 125°C is 8.0 MPa. Most preferably, the minimum burst pressure at 125°C is 8.3 MPa. Alternatively or additionally, the minimum burst pressure at 23°C can be specified as 10.4 MPa. The burst pressure test is performed against the specimens and procedures defined in SAE International standard SAE J3143 (July 2019).

[0044] In a preferred embodiment of the invention, the first and second layers may be provided without any adhesive layer and / or barrier layer between them. Prior art multilayer tubular structures are typically characterized by the presence of an adhesive layer, barrier layer, or intermediate layer between the first and second layers. The adhesive layer may be made of ethylene-vinyl alcohol (EVOH), a fluoropolymer layer, or a polyphthalamide (PPA) layer, etc. Alternatively, the adhesive layer or intermediate layer may be made of maleic anhydride (MAH)-grafted polypropylene (PP) (PP-g-MAH). Therefore, the present invention provides an improvement over the prior art because the plastic tubing of the present invention does not require an adhesive layer and / or barrier between the first and second layers and still achieves its purpose (objective).

[0045] In a preferred embodiment of the invention, the thickness ratio of the first layer to the second layer can be specified to be in the range of 0.54 to 5.66. Preferably, the thickness ratio of the first layer to the second layer is in the range of 0.8 to 3. Most preferably, the thickness ratio of the first layer to the second layer is in the range of 1 to 2. Surprisingly, it has been found that ratios within such defined ranges result in the minimum burst pressure as defined in the preceding paragraphs.

[0046] In a preferred embodiment of the invention, the sum of the thicknesses of the first and second layers can be specified to be in the range of 1.5 mm to 5 mm. Preferably, the upper limit of the sum of the thicknesses of the first and second layers can be 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, or 2 mm. Preferably, the lower limit of the sum of the thicknesses of the first and second layers can be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2 mm. Preferably, the sum of the thicknesses of the first and second layers can be in the range of 1.7 mm to 2.3 mm. Most preferably, the sum of the thicknesses of the first and second layers can be in the range of 1.8 mm to 2.2 mm, for example, 2.0 mm. Surprisingly, within such a defined thickness range, the minimum burst pressure as defined in the preceding paragraphs is achieved.

[0047] In a preferred embodiment of the invention, the polyamide molding compound A may contain an impact modifier in an amount of 2.0 wt% to 12.0 wt%. Preferably, the amount of impact modifier is in the range of 3.0 wt% to 10.0 wt%. Most preferably, the impact modifier is present in an amount of 4.0 wt% to 6.0 wt%. Here, wt% is based on the total weight of the polyamide molding compound A.

[0048] In a preferred embodiment of the invention, the polyamide molding compound B may contain an impact modifier in an amount of 2.0 wt% to 12.0 wt%. Preferably, the amount of impact modifier is in the range of 3.0 wt% to 10.0 wt%. Most preferably, the impact modifier is present in an amount of 4.0 wt% to 6.0 wt%. Here, wt% is based on the total weight of the polyamide molding compound B.

[0049] According to one aspect of the invention, an impact modifier may be added to improve the toughness, ductility and impact resistance of the polyamide molding compound.

[0050] Impact modifiers can be thermoplastic elastomers, such as styrene-based elastomers like SEBS or SBS, or polyolefin-based elastomers like EVA or EPDM. Alternatively, impact modifiers can be rubber-modified polyolefins, such as maleic anhydride-grafted polyolefins (PO-g-MA).

[0051] In a preferred embodiment of the present invention, the impact modifier in polyamide molding compound A and / or polyamide molding compound B may be specified as an acid-modified ethylene-α-olefin copolymer.

[0052] In an alternative embodiment of the invention, the impact modifier may be specified as an ethylene-glycidyl methacrylate polymer and / or a core-shell impact modifier, preferably a methacrylate-butadiene-styrene (MBS) core-shell impact modifier.

[0053] This type of impact modifier (i.e., core-shell impact modifier) ​​is mentioned, for example, in EP 1847569 A1, WO 2007 / 076108 A1, or US 2006 / 0293438 A1. Further disclosures indicating the structure and chemical structure of preferred core-shell impact modifiers are, for example, U.S. Patent No. 6,869,497 B2, EP 0 208 187 B1, or EP 0 654 505 B1.

[0054] Impact modifiers can also be mixtures of the impact modifiers mentioned above.

[0055] Examples of commercially available impact modifiers that can be used include TAFMER MC201, TAFMER MH5010, TAFMER MH7010, and TAFMER MH7020 from Mitsui Chemicals; EXXELORVA1801, EXXELOR VA1803, EXXELOR VA1810, and EXXELOR MDEX 94-11 from Exxon Mobile Chemicals; FUSABOND MN493D and FUSABOND A EB560D; and ELVALOY from DuPont.

[0056] Most preferably, the impact modifier is a blend comprising 67% by weight of ethylene-propylene copolymer (containing 20% ​​by weight of propylene) and 33% by weight of ethylene-but-1-ene copolymer (containing 15% by weight of but-1-ene) grafted with 0.5% by weight of maleic anhydride, which can be commercially available from Mitsui Chemicals (Japan) as TAFMER MC201.

[0057] In a preferred embodiment of the invention, the polyamide molding compound A may optionally contain 0% to 0.5% by weight of a nonionic surfactant, wherein the weight percentage is based on the total weight of the polyamide molding compound A. More preferably, the nonionic surfactant is present in an amount of 0.1% to 0.4% by weight. Most preferably, the nonionic surfactant is present in an amount of 0.15% to 0.35% by weight.

[0058] According to one aspect of the invention, the purpose of the nonionic surfactant is to act as a dispersant, wetting agent, and processing aid, thereby promoting uniform filler distribution, improved melt flow, and enhanced surface quality, while maintaining chemical neutrality and compatibility with the polyamide matrix. As previously defined, the use of the nonionic surfactant is optional.

[0059] In a preferred embodiment of the present invention, the nonionic surfactant may be specified as Tween-20 (chemical name: polyoxyethylene (20) dehydrated sorbitan monolaurate; CAS number: 9005-64-5).

[0060] In a preferred embodiment of the invention, polyamide molding compound A and additional or alternative polyamide molding compound B may optionally contain 0.0% to 0.50% by weight of minerals. Preferably, the minerals are present in an amount of 0.25% to 0.45% by weight. Most preferably, the minerals are present in an amount of 0.30% to 0.40% by weight. The weight percentages are based on the total weight of the respective polyamide molding compounds. The minerals act as functional fillers. Their primary purpose is mechanical reinforcement, dimensional stability, and processing support. According to the invention, the use of minerals is optional.

[0061] In a preferred embodiment of the present invention, the mineral may be specified as a layered silicate mineral.

[0062] Layered silicates are defined as a large class of minerals characterized by a layered structure, including mica, montmorillonite, and kaolinite, which can be formed in both surface and subsurface environments through processes such as diagenesis and hydrothermal alteration.

[0063] In a preferred embodiment of the invention, the layered silicate mineral may be specified as kaolinite. Surprisingly, kaolinite has been found to possess particularly good properties as a functional filler and / or crystallizer. It also exhibits advantageous properties in terms of mechanical reinforcement, dimensional stability, and thermal stability.

[0064] In a preferred embodiment of the invention, the melt temperature of the polyamide molding compound B can be specified to be in the range of 180°C to 240°C. Preferably, the melt temperature is in the range of 190°C to 230°C. Most preferably, the melt temperature is in the range of 210°C to 225°C. The melt temperature is measured herein according to standard ISO 11357-3:2025.

[0065] In a preferred embodiment of the invention, the polyamide molding compound A may optionally contain 0.0% to 0.5% by weight, preferably 0.1% to 0.4% by weight, and most preferably 0.15% to 0.35% by weight of a heat and oxidation stabilizer. Here, % by weight is based on the total weight of the polyamide molding compound A.

[0066] In a preferred embodiment of the invention, the polyamide molding compound B may optionally contain 0.0% to 0.5% by weight, preferably 0.1% to 0.4% by weight, and most preferably 0.15% to 0.35% by weight of a heat and oxidation stabilizer. Here, % by weight is based on the total weight of the polyamide molding compound B.

[0067] The preferred heat and oxidation stabilizer is copper iodide (CuI; CAS No.: 7681-65-4). Alternatively, the heat and oxidation stabilizer may be potassium iodide (KI; CAS No.: 7681-11-0) or a mixture of copper iodide and potassium iodide. When using a mixture of copper iodide and potassium iodide, the preferred weight ratio between copper iodide and potassium iodide is 1:(2 to 8).

[0068] Other heat and oxidation stabilizers that can be used include copper compounds such as copper halides, copper acetate, copper propionate, copper benzoate, copper adipate, copper terephthalate, copper isophthalate, copper salicylate, copper nicotinate, and copper stearate, as well as copper complex salts coordinated with chelating agents such as ethylenediamine and ethylenediaminetetraacetic acid. These copper compounds can be used alone or in combination of both or more.

[0069] Metal halides can also be used as heat and oxidation stabilizers (provided that copper halides are not included). Metal halides are salts of metals from Group 1 or Group 2 of the periodic table and halogens, examples of which include potassium iodide, potassium bromide, potassium chloride, sodium iodide, and sodium chloride, with potassium iodide and potassium bromide being preferred. Metal halides can be used alone or in combination of two or more. Potassium iodide is preferred because of its excellent resistance to long-term heat aging and its ability to inhibit metal corrosion.

[0070] In a preferred embodiment of the invention, the weight ratio of the heat and oxidation stabilizer to the polyamide (PA 6) in the polyamide molding compound A can be specified to be in the range of 0.04 to 0.06. Surprisingly, such a ratio has been found to result in favorable thermal stability.

[0071] In a preferred embodiment of the invention, the polyamide molding compound A may optionally contain a lubricant in an amount of 0% to 1.0% by weight. More preferably, the lubricant is present in an amount of 0.1% to 0.9% by weight. Most preferably, the lubricant is present in an amount of 0.2% to 0.8% by weight. Here, weight% is based on the total weight of the polyamide molding compound A.

[0072] In a preferred embodiment of the invention, the polyamide molding compound B may optionally contain a lubricant in an amount of 0% to 1.0% by weight. More preferably, the lubricant is present in an amount of 0.1% to 0.9% by weight. Most preferably, the lubricant is present in an amount of 0.2% to 0.8% by weight. Here, weight% is based on the total weight of the polyamide molding compound B.

[0073] Lubricants may be selected from the group consisting of: stearates / esters such as metal stearates, fatty acid amides (e.g., ethylene bis-stearamide, oleamide, erucamide, stearamide), fatty acid esters (e.g., pentaerythritol tetrastearate, trimethylolpropane ester), lignite waxes (e.g., calcium lignite, lignite ester wax), and silicone-based lubricants (e.g., silicone oil) or mixtures thereof.

[0074] Preferably, the lubricant is a stearate / ester. The stearate / ester is a salt or ester of stearic acid.

[0075] Stearates / esters can be metallic stearates, such as calcium stearate, zinc stearate, magnesium stearate, or aluminum stearate. Alternatively or alternatively, stearates / esters can be organic stearates, such as glyceryl monostearate or sorbitan monostearate. Stearates / esters can be mixtures of metallic stearates and organic stearates.

[0076] Most preferably, the stearate / ester is glyceryl monostearate and / or magnesium stearate.

[0077] In a most preferred embodiment of the invention, the polyamide molding compound A may be specified to consist of or contain the following combinations:

[0078] (A1) 88.5% to 98% by weight of PA 6, and

[0079] (B1) 0% to 0.5% by weight of nonionic surfactants, particularly Tween-20, and

[0080] (C1) 0% to 0.5% by weight layered silicate minerals, particularly kaolinite, and

[0081] (D1) 0% to 1% by weight of lubricants, particularly metal stearates and / or glyceryl monostearate, and

[0082] (E1) 0% to 0.5% by weight of heat and oxidation stabilizers, particularly copper iodide and / or potassium iodide, and

[0083] (F1) 2% to 9% by weight of impact modifiers, particularly polyolefin-based impact modifiers, and

[0084] The sum of the weight percentages of components (A1) to (F1) is equal to 100 by weight.

[0085] In a most preferred embodiment of the invention, the polyamide molding compound B may be specified to consist of or contain the following combinations:

[0086] (A2) 89% to 98% by weight of PA 610, and

[0087] (B2) 0% to 0.5% by weight layered silicate minerals, particularly kaolinite, and

[0088] (C2) 0% to 1% by weight of lubricants, particularly metal stearates and / or glyceryl monostearate, and

[0089] (D2) 0% to 0.5% by weight of heat and oxidation stabilizers, particularly copper iodide and / or potassium iodide, and

[0090] (E2) 2% to 9% by weight of impact modifiers, particularly polyolefin-based impact modifiers, and

[0091] The sum of the weight percentages of components (A2) to (E2) is equal to 100 by weight.

[0092] Exemplary Implementation

[0093] The following describes exemplary embodiments of the present invention, which are given for illustrative purposes and should not be construed as limiting.

[0094] Examples and Comparative Examples

[0095] Examples EXB1 to EXB4 are based on the present invention.

[0096] Comparative Examples VB1 to VB5 are not based on the present invention and are used to illustrate the advantages of Embodiments EXB1 to EXB4.

[0097] Measurement method:

[0098] Perform burst pressure testing and leak resistance testing according to the procedures given in SAE International's SAE J3143 (July 2019) (https: / / www.sae.org / standards / j3143_201907-non-metallic-non-reinforced-automotive-air-conditioning-refrigerant-line-assembly-requirements; accessed February 4, 2026).

[0099] Example EXB1:

[0100] Example EXB1 is a two-layer structure according to the present invention, comprising a second layer of aliphatic polyamide molding compound B containing PA 610 type polyamide and a first layer of aliphatic polyamide molding compound A containing PA 6 type polyamide. The thickness of the second layer is 0.3 mm, while the thickness of the first layer is 1.7 mm. The thickness ratio of the first layer to the second layer is 5.66. The total outer diameter of the pipe is 11 mm. An explosion pressure test was performed on Example EXB1, and a explosion pressure of 9.0 MPa was measured at 125°C, which is greater than 8.3 MPa. The explosion pressure test was successfully completed. Leakage resistance tests for a typical refrigerant (HFC-R134a; 1,1,1,2-tetrafluoroethane) were successfully completed.

[0101] The polyamide molding compound B (second layer) of Example EXB1 has the following composition: 93.4 wt% PA 610, 0.3 wt% kaolinite, 0.2 wt% glyceryl monostearate, 0.35 wt% copper iodide and potassium iodide, 5 wt% impact modifier (TAFMER MC201 from Mitsui) and 0.75 wt% colorant.

[0102] Example EXB1's polyamide molding compound A (first layer) has the following composition: 94.2 wt% PA 6, 0.19 wt% polyoxyethylene (20) dehydrated sorbitan monolaurate (Tween-20 from Sigma-Aldrich), 0.28 wt% kaolinite, 0.2 wt% glyceryl monostearate, 0.33 wt% copper iodide and potassium iodide, and 4.8 wt% impact modifier (TAFMER MC201 from Mitsui).

[0103] The components used were purchased from commercial suppliers.

[0104] Example EXB2:

[0105] Example EXB2 is a two-layer structure according to the present invention, comprising a second layer of aliphatic polyamide molding compound B containing PA 610 type polyamide and a first layer of aliphatic polyamide molding compound A containing PA 6 type polyamide. The thickness of the second layer is 1.3 mm, while the thickness of the first layer is 0.7 mm. The thickness ratio of the first layer to the second layer is 0.54. The total outer diameter of the pipe is 11 mm. An explosion pressure test was performed on Example EXB2, and a explosion pressure of 8.9 MPa was measured at 125°C, which is greater than 8.3 MPa. The explosion pressure test was successfully completed. Leakage resistance testing for a typical refrigerant (HFC-R134a) was successfully completed.

[0106] Polyamide molding compound A and polyamide molding compound B have the same composition as given in Example EXB1.

[0107] The components used were purchased from commercial suppliers.

[0108] Example EXB3:

[0109] Example EXB3 is a two-layer structure according to the present invention, comprising a second layer of aliphatic polyamide molding compound B containing PA 612 type polyamide and a first layer of aliphatic polyamide molding compound A containing PA 6 type polyamide. Dimensions (e.g., layer thickness) are the same as in Example EXB1. An explosion pressure test was performed on Example EXB3, and an explosion pressure of 8.8 MPa was measured at 125°C, greater than 8.3 MPa. The explosion pressure test was successfully completed. Leakage resistance tests for a typical refrigerant (HFC-R134a) were successfully completed.

[0110] Polyamide molding compound B (second layer) has the composition as given in Example EXB1, provided that the amount of PA 610 is replaced with the same amount of PA 612.

[0111] The polyamide molding compound A (first layer) has the composition given in Example EXB1.

[0112] The components used were purchased from commercial suppliers.

[0113] Example EXB4:

[0114] Example EXB4 is a two-layer structure according to the present invention, comprising a second layer of aliphatic polyamide molding compound B containing PA 612 type polyamide and a first layer of aliphatic polyamide molding compound A containing PA 6 type polyamide. Dimensions (e.g., layer thickness) are the same as in Example EXB2. An explosion pressure test was performed on Example EXB4, and an explosion pressure of 8.6 MPa was measured at 125°C, greater than 8.3 MPa. The explosion pressure test was successfully completed. Leakage resistance tests for a typical refrigerant (HFC-R134a) were successfully completed.

[0115] Polyamide molding compound B (second layer) has the composition as given in Example EXB1, provided that the amount of PA 610 is replaced with the same amount of PA 612.

[0116] The polyamide molding compound A (first layer) has the composition given in Example EXB1.

[0117] The components used were purchased from commercial suppliers.

[0118] Comparative example VB1:

[0119] Comparative Example VB1 is a single-layer structure made of PA 612-based polyamide molding compound. The thickness of the single layer is 1.5 mm. The total outer diameter of the pipe is 12 mm. A burst pressure test was performed on Comparative Example VB1, and a burst pressure of 5.0 MPa was measured at 125°C, which is less than 8.3 MPa. The burst pressure test failed. Leakage resistance testing for a typical refrigerant (HFC-R134a) also failed.

[0120] The polyamide molding compound of Comparative Example VB1 has the following composition: 98.3% by weight PA 612, 0.35% by weight copper iodide and potassium iodide, 0.6% by weight antioxidant (Irganox MD1024 from BASF) and 0.75% by weight colorant.

[0121] The components used were purchased from commercial suppliers.

[0122] Comparative example VB2:

[0123] Comparative Example VB2 is a two-layer structure with a second layer of aliphatic polyamide molding compound based on PA 610 and a first layer of aliphatic polyamide molding compound based on PA 6. The total outer diameter of the pipe is 14 mm. The thickness of the second layer is 1.5 mm, while the thickness of the first layer is 0.5 mm. The thickness ratio of the first layer to the second layer is 0.33. A burst pressure test was performed on Comparative Example VB2, and a burst pressure of 5.7 MPa was measured at 125°C, which is less than 8.3 MPa. The burst pressure test failed. Leakage resistance testing for a typical refrigerant (HFC-R134a) also failed.

[0124] The aliphatic polyamide molding compound of the second layer has the same composition as the second layer given in Example EXB1.

[0125] The aliphatic polyamide molding compound of the first layer has the same composition as the first layer given in Example EXB1.

[0126] The components used were purchased from commercial suppliers.

[0127] Comparative example VB3:

[0128] Comparative Example VB3 is a two-layer structure with a second layer of aliphatic polyamide molding compound based on PA 610 and a first layer of aliphatic polyamide molding compound based on PA 6. The total outer diameter of the pipe is 14 mm. The thickness of the second layer is 0.2 mm, while the thickness of the first layer is 1.8 mm. The thickness ratio of the first layer to the second layer is 0.11. A burst pressure test was performed on Comparative Example VB3, and a burst pressure of 5.9 MPa was measured at 125°C, which is less than 8.3 MPa. The burst pressure test failed. Leakage resistance testing for a typical refrigerant (HFC-R134a) also failed.

[0129] The aliphatic polyamide molding compound of the second layer has the same composition as the second layer given in Example EXB1.

[0130] The aliphatic polyamide molding compound of the first layer has the same composition as the first layer given in Example EXB1.

[0131] The components used were purchased from commercial suppliers.

[0132] Comparative example VB4:

[0133] Comparative Example VB4 is a two-layer structure with a second layer of aliphatic polyamide molding compound based on PA 610 and a first layer of aliphatic polyamide molding compound based on PA 6. The total outer diameter of the pipe is 12 mm. The thickness of the second layer is 0.5 mm, and the thickness of the first layer is 0.5 mm. The thickness ratio of the first layer to the second layer is 1.0. A burst pressure test was performed on Comparative Example VB4, and a burst pressure of 2.9 MPa was measured at 125°C, which is less than 8.3 MPa. The burst pressure test failed. Leakage resistance testing for a typical refrigerant (HFC-R134a) also failed.

[0134] The aliphatic polyamide molding compound of the second layer has the same composition as the second layer given in Example EXB1.

[0135] The aliphatic polyamide molding compound of the first layer has the same composition as the first layer given in Example EXB1.

[0136] The components used were purchased from commercial suppliers.

[0137] Comparative example VB5:

[0138] Comparative Example VB5 is a two-layer structure with a second layer of aliphatic polyamide molding compound based on PA 610 and a first layer of aliphatic polyamide molding compound based on PA 6. The total outer diameter of the pipe is 14 mm. The thickness of the first layer is 1.6 mm, while the thickness of the second layer is 0.2 mm. The thickness ratio of the first layer to the second layer is 8.0. A burst pressure test was performed on Comparative Example VB5, and a burst pressure of 3.2 MPa was measured at 125°C, which is less than 8.3 MPa. The burst pressure test failed. Leakage resistance testing for a typical refrigerant (HFC-R134a) also failed.

[0139] The aliphatic polyamide molding compound of the second layer has the same composition as the second layer given in Example EXB1.

[0140] The aliphatic polyamide molding compound of the first layer has the same composition as the first layer given in Example EXB1.

[0141] The components used were purchased from commercial suppliers.

[0142] Discussion of Results:

[0143] Embodiments EXB1 to EXB4 of the present invention demonstrate that there exists a specific range of thickness ratios between the first and second layers that satisfy the minimum burst pressure requirement. Embodiments EXB1 to EXB4 further demonstrate that the leak-resistance requirement for refrigerant HFC-R134a is successfully met. Comparative Example VB1 shows that a single layer of polyamide molding compound based on PA 612 cannot meet the burst pressure and leak-resistance requirements. Comparative Examples VB2 and VB3 show that if the thickness ratio of the first to second layer is too low, the burst pressure requirement will fail. Comparative Example VB4 shows that if the sum of the thicknesses of the first and second layers is too small, the burst pressure requirement will fail. Comparative Example VB5 shows that if the thickness ratio of the first to second layer is too high, the burst pressure requirement will also fail. While the thickness of PA 612 could theoretically be increased until the burst pressure requirement is met, such a structure would be very rigid, expensive, and likely undesirable or impractical for industrial applications.

Claims

1. A plastic pipeline, characterized in that, It consists of only the following two layers: The first layer directly surrounding the internal space of the pipeline, and The second layer directly adjacent to the first layer, and The first layer is made of an aliphatic polyamide molding compound A based on PA 6, and the second layer is made of an aliphatic polyamide molding compound B based on PA 610, PA 612, or mixtures thereof or copolyamides, wherein the sum of the thicknesses of the first and second layers is in the range of 1.5 mm to 5 mm, and the thickness ratio of the first layer to the second layer is in the range of 0.54 to 5.

66. The plastic tubing is configured to be located between the compressor and the condenser. The first layer made of aliphatic polyamide molding compound A and the second layer made of aliphatic polyamide molding compound B have a minimum burst pressure of 6.0 MPa at 125°C and / or a minimum burst pressure of 10.4 MPa at 23°C. There are no adhesive layers and / or barrier layers between the first layer and the second layer. The PA 6 is present in the aliphatic polyamide molding compound A in an amount of 85.5% to 98% by weight of the total weight of the aliphatic polyamide molding compound A. In the aliphatic polyamide molding compound B, PA 610, PA 612, or a mixture thereof or copolyamide is present in an amount of 86% to 98% by weight of the aliphatic polyamide molding compound B.

2. The plastic pipeline according to claim 1, characterized in that, The aliphatic polyamide molding A contains an impact modifier in an amount of 2.0% to 12.0% by weight of the total weight of the aliphatic polyamide molding A, and / or the aliphatic polyamide molding B contains an impact modifier in an amount of 2.0% to 12.0% by weight of the total weight of the aliphatic polyamide molding B.

3. The plastic pipeline according to claim 2, characterized in that, The impact modifier in the aliphatic polyamide molding A and / or the aliphatic polyamide molding B is an acid-modified ethylene-α-olefin copolymer.

4. The plastic pipeline according to claim 1, characterized in that, The aliphatic polyamide molding A contains 0% to 0.5% by weight of a nonionic surfactant.

5. The plastic pipeline according to claim 4, characterized in that, The nonionic surfactant is Tween-20.

6. The plastic pipeline according to claim 1, characterized in that, The aliphatic polyamide molding A contains minerals in an amount of 0% to 0.50% by weight of the total weight of the aliphatic polyamide molding A, and / or the aliphatic polyamide molding B contains minerals in an amount of 0% to 0.50% by weight of the total weight of the aliphatic polyamide molding B.

7. The plastic pipeline according to claim 6, characterized in that, The mineral is a layered silicate mineral.

8. The plastic pipeline according to claim 7, characterized in that, The layered silicate mineral is kaolinite.

9. The plastic pipeline according to claim 1, characterized in that, The melt temperature of the aliphatic polyamide molding B is in the range of 180°C to 240°C, wherein the melt temperature is measured according to ISO 11357-3:2025.