US20180334775A1

US20180334775A1 - Cables made of phase change material

Info

Publication number: US20180334775A1
Application number: US15/757,701
Authority: US
Inventors: Loic Pierre Rolland
Original assignee: EI Du Pont de Nemours and Co
Current assignee: Performance Materials NA Inc
Priority date: 2015-11-03
Filing date: 2015-11-03
Publication date: 2018-11-22
Also published as: CN108352213B; JP6944933B2; WO2017079018A1; EP3371815A1; JP2019500441A; CN108352213A

Abstract

A phase change material (PCM) is useful for thermal management in various applications such as automotive, building, packaging, garments, and footwear, and in devices such as wires and cables. The cable described herein comprises a core and a PCM layer surrounding the core. The PCM layer comprises a PCM composition, which in turn comprises a 1,3-propanediol fatty acid ester. The core consists of a yarn, strand or wire made of a natural or synthetic polymeric material or a metal.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Appln. No. 62/250,206, filed on Nov. 3, 2015, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Provided herein is a Phase Change Material (PCM) for thermal management in a variety of applications, such as for example automotive, building, packaging, garments and footwear. In particular, cables comprising a PCM, a process for making the cables, and the use of the cables in several applications are described herein.

BACKGROUND OF THE INVENTION

Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Phase Change Materials (PCM) are latent thermal storage materials that are capable of absorbing and releasing large amounts of latent heat during melting and crystallization. The thermal energy transfer occurs when a material is transformed from a solid to a liquid phase or from a liquid to a solid phase. During such phase changes, the temperature of the PCM material remains nearly constant as does the space surrounding the PCM material, the heat flowing through the PCM being “entrapped” within the PCM itself. Among other well-known PCM, paraffin is frequently used because of its low cost and low toxicity.
PCM can be introduced in matrices made of different materials, or they can be applied as a coating. See, e.g., U.S. Pat. No. 4,003,426, U.S. Pat. No. 4,528,328, U.S. Pat. No. 5,053,446, U.S. 2006/0124892 (WO 2006/062610), WO 98/04644, and WO 2004/044345.
In order to use PCM conveniently in thermal management applications, they have been incorporated into matrix polymers that absorb and retain the PCM, even at temperatures above the melting point of the PCM, thus making it possible to manufacture the resulting PCM composite materials into slabs, panels or other shapes that are easily mounted in a wall. Most matrix polymers suffer from multiple drawbacks, however, such as limited PCM absorption capacity, or substantial loss of PCM by exudation during the product's lifetime. A partial solution to these problems has been proposed in WO 2006/062610, WO 2011/143278 and WO 2011/014636.
Nevertheless, there remains a need for PCM-containing materials that provide high heat storage capacity and high surface contact for optimum thermal exchange; that are resistant to temperatures from −20° C. to 130° C. under permanent exposure to air and also to chemicals, in particular to lubricating oil or to ethylene glycol; that retain their efficiency over time; and that provide high thermal conductivity.

SUMMARY OF THE INVENTION

Accordingly, provided herein are cables comprising a core and a PCM layer surrounding the core, wherein the PCM layer consists of a PCM composition, and wherein

- a) the PCM composition comprises a 1,3-propanediol fatty acid ester; and
- b) the core consists of a yarn, strand or wire made of a natural or synthetic polymeric material or a metal.

Preferably, the PCM composition is biobased.
In a preferred embodiment, the PCM composition comprises or consists essentially of 1,3-propanediol dibehanate or 1,3-propanediol dipalmitate.
Preferably, the yarn, strand or wire is made of polyparaphenylene terephtalamide (para-aramid) or copper.
In another embodiment, the cables further comprise one or more layer(s) of a protective polymer. Preferably the cables comprise one layer of a protective polymer. Preferably, the protective polymer is made of a blend of ionomer and polyamide. Even more preferably, the cables comprise two layers of a protective polymer. Preferably, the first layer of protective polymer is made of a blend of ionomer and polyamide and the second layer is made of a polymer selected from the group consisting of grafted or non-grafted polypropylene homopolymer, grafted or non-grafted polypropylene copolymer, perfluoro ethylene-propylene (FEP), perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE) and/or ethylene acrylate rubber (AEM).
Preferably, each layer of protective polymer has a thickness between 50 and 300 μm. More preferably, when two layers are present, the total thickness of both layers is between 50 and 600 μm.
Preferably, the amount of PCM in the cable is at least 70 weight percent, based on the total weight of the cable.
Preferred cables of the present invention have a diameter of 3 to 6 mm.
Further provided herein is a process for making the cables. The process comprises the steps of:

- a) providing a core consisting of yarn, strand or wire made of a natural or synthetic polymeric material or a metal; and
- b) extruding a PCM composition comprising or consisting essentially of a 1,3-propanediol fatty acid ester onto the core.

Optionally, the process further comprises a step c) wherein one or more layer(s) of one or more protective polymers are extruded onto the PCM composition and the core. Preferably, one layer of a protective polymer is extruded onto the PCM composition and the core. Preferably, the protective polymer is made of a blend of ionomer and polyamide. Even more preferably, two layers of protective polymer are extruded onto the PCM composition and the core. More preferably, the first layer is made of a blend of ionomer and polyamide and the second layer is made a polymer selected from the group consisting of grafted or non-grafted polypropylene homopolymer, grafted or non-grafted polypropylene copolymer, perfluoro ethylene-propylene (FEP), perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE) and/or ethylene acrylate rubber (AEM).
The cables are useful in thermal management, in particular in automotive applications.

DETAILED DESCRIPTION

Definitions

As used herein, the term “a” refers to one as well as to at least one and is not an article that necessarily limits its referent noun to the singular.
As used herein, the terms “about” and “at or about” are intended to mean that the amount or value in question may be the value designated or some other value about the same. The phrase is intended to convey that similar values promote equivalent results or effects according to the invention.
As used herein, the term “acrylate” means an ester of acrylic acid with an alkyl group. Preferred are acrylates with alkyl groups having 1 to 4 carbon atoms.
As used herein, the term “(meth)acrylic acid” refers to acrylic acid, methacrylic acid, or both acrylic and methacrylic acid. Likewise, the term “(meth)acrylate” means methacrylate and/or acrylate, and “poly(meth)acrylate” means polymers derived from the polymerization of either monomer or a mixture of both monomers.
As used herein, the term “copolymer” refers to polymers comprising copolymerized units resulting from copolymerization of two or more comonomers. In this connection, a copolymer may be described herein with reference to its constituent comonomers or to the amounts of its constituent comonomers, for example “a copolymer comprising ethylene and 18 weight percent of acrylic acid”, or a similar description. Such a description may be considered informal in that it does not refer to the comonomers as copolymerized units; in that it does not include a conventional nomenclature for the copolymer, for example International Union of Pure and Applied Chemistry (IUPAC) nomenclature; in that it does not use product-by-process terminology; or for another reason. As used herein, however, a description of a copolymer with reference to its constituent comonomers or to the amounts of its constituent comonomers means that the copolymer contains copolymerized units (in the specified amounts when specified) of the specified comonomers. It follows as a corollary that a copolymer is not the product of a reaction mixture containing given comonomers in given amounts, unless expressly stated in limited circumstances to be such. The term “copolymer” may refer to polymers that consist essentially of copolymerized units of two different monomers (a dipolymer), or that consist essentially of more than two different monomers (a terpolymer consisting essentially of three different comonomers, a tetrapolymer consisting essentially of four different comonomers, etc.).
Moreover, the amounts of all components in a polymer or composition are complementary, that is, the sum of the amounts of all the components is the amount of the entire polymer composition. For example, when an ethylene copolymer is described by specifying the weight percentage of a copolymerized comonomer, the total of the weight percentages of the copolymerized ethylene, the copolymerized comonomer, and the other copolymerized comonomers, if any, is 100 wt %.
The term “acid copolymer” refers to a polymer comprising copolymerized units of an α-olefin, an α,β-ethylenically unsaturated carboxylic acid, and optionally other suitable comonomer(s), such as an α,β-ethylenically unsaturated carboxylic acid ester.
The term “ionomer” refers to a polymer that is produced by partially or fully neutralizing an acid copolymer.
Provided herein are cables comprising a core and a PCM layer surrounding the core. The PCM layer consists of a PCM composition.
The PCM composition comprises, consists of or consists essentially of a 1,3-propanediol fatty acid ester.
More specifically, the 1,3-propanediol fatty acid esters are 1,3-propanediol esters of fatty acids, in which each propanediol molecule has reacted to form an ester with one fatty acid (“monoester”) or two fatty acids (“diester”). Preferably, the 1,3-propanediol, the fatty acids, and the 1,3-propanediol diesters and monoesters of the fatty acids are fully bio-based, renewable and biodegradable. For example, these PCM be synthesized to from food-grade raw materials.
The PCM composition comprises 1,3-propanediol diesters, 1,3-propanediol monoesters or a mixture of 1,3-propanediol diesters and 1,3-propanediol monoesters.
The 1,3-propanediol esters may be produced by direct esterification using an excess of fatty acids and 1,3-propanediol. After esterification, residual free fatty acids and alcohol are removed by distillation. The remaining ester can be directly applied or further purified, e.g., by an additional distillation of the product, as described in WO08/123845.
In a preferred embodiment, the PCM composition is biobased. More specifically, the PCM is produced from biological products in an environmentally friendly way. For illustration, plant oil serves as the source of the fatty acids, and the 1,3-propanediol is produced by fermentation of corn syrup (bioseparation of 1,3-propanediol). This process uses 40% less energy than the conventional 1,3-propanediol production via chemical methods beginning with fossil fuels, and reduces greenhouse gas emissions by 20% (reference: http://brew.geo.uu.nl/BREWsymbosiumWiesbaden11mei2005/WEBSITEBrewPresentations51105.PDF).
Bio-based and renewable 1,3-propanediol can be produced, for example, as described in WO1996/035796.
In a further embodiment, the 1,3-propanediol diester is a “symmetric diester”. This term, as used herein, refers to diesters in which two identical fatty acids have reacted with a single 1,3-propanediol molecule. Symmetrical diesters are typically characterized by more regular crystalline packing.
In a further embodiment, the diester is a “non-symmetric diester”. This term, as used herein, refers to diesters in which two different fatty acids have reacted with a single 1,3-propanediol molecule. By varying the fatty acids and the symmetry of the diester, the melting temperature of the PCM can be varied and finely adjusted.
In a further embodiment, the 1,3-propanediol ester is a monoester. In general, the melting temperature of the 1,3-propanediol monoesters is reduced compared to that of the corresponding 1,3-propanediol diesters.
In a further embodiment, the esters comprise reacted residues of fatty acids having a chain length of 2 to 24 carbon atoms (C₃to C₂₅fatty acids). Preferred chain length is 8 to 22 carbon atoms (C₉to C₂₃fatty acids). In general, PCM having a higher melting temperature will also have a higher latent heat. Also typically, the longer the chain length of the fatty acid, the higher the melting temperature of its 1,3-propanediol ester, and the more heat can be absorbed and released by the PCM composition. Thus, by changing the chain length of the fatty acids, it is possible to change the PCM's characteristics.
The fatty acids can be saturated or unsaturated fatty acids, such as but not limited to propionic acid, butyric acid, valeric acid, caproic acid, enathic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, luric acid, tridecylic acid myristic acid, pentadecylic acid, palmitic acid, margaric acid, staric acid, nonadecylic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, docosatetraenoic acid, palmitoleic acid, vaccenic acid, paullinic acid, oleic acid, elaidic acid, gondoic acid, erucic acid, nervonic acid, and mead acid.
The PCM composition can comprise esters of saturated, unsaturated, linear or fatty acids, or mixtures of fatty acids that are saturated or unsaturated, branched or unbranched.
In a preferred embodiment, the fatty acids are linear and saturated.
In a more preferred embodiment, the PCM composition comprises, consists of, or consists essentially of 1,3-propanediol dibehanate or 1,3-propanediol dipalmitate. Again, these diesters are preferably biobased.
The PCM composition may further comprise from 0.01 to 15, 0.01 to 10, or 0.01 to 5 weight percent, based on the total weight of the PCM composition, of one or more additives including, without limitation, plasticizers; stabilizers, including viscosity stabilizers and hydrolytic stabilizers; primary and secondary antioxidants; ultraviolet absorbers; anti-static agents; dyes, pigments or other coloring agents; inorganic fillers; fire-retardants; lubricants; reinforcing agents such as glass fiber and flakes, synthetic (for example, aramid) fiber or pulp; foaming or blowing agents; processing aids (e.g. ethylene copolymer such as ethylene vinyl acetate (EVA)); slip additives; antiblock agents such as silica or talc; release agents; seed additives for reducing the occurrence of supercooling; and tackifying resins. These additives are described in the Kirk Othmer Encyclopedia of Chemical Technology. Examples of suitable antioxidants for the thermal stabilization of 1,3-propanediol esters include, for example, tert-butylhydroquinone (TBHQ), pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), butylated hydroxytoluene (BHT), tris(2,4-ditert-butylphenyl)phosphite, and propyl-3,4,5-trihydroxybenzoate.
The additives may be incorporated into the composition by any known process such as by dry blending, extruding a mixture of the various constituents, masterbatch techniques, and the like.
The cables provided herein comprise a PCM layer surrounding a core and optionally one or more polymer layer(s) surrounding the PCM layer and the core.
The cables may be made by extruding the PCM composition onto a yarn, strand or wire. Alternately, the cables may be made by other methods, such as for example drawing the yarn through or dipping it into a molten PCM composition.
The yarn, strand or wire is preferably made of a natural or synthetic polymeric material or a metal. Suitable polymeric materials include, without limitation, cotton, polyester, polyamide or polyphenylene terephtalamide (aramid) and/or mixtures or blends thereof. Preferably, the yarn, strand or wire is made of polyparaphenylene terephtalamide (para-aramid) or copper. Some suitable polyparaphenylene terephtalamide (para-aramid) yarns, strands or wires are commercially available from DuPont, under the trademark Kevlar®.
The use of the yarn, strand or wire allows pulling of the overall cable during extrusion process of the PCM composition without breaking due to the weakness or brittleness of the PCM material. The use of a PCM composition comprising a 1,3-propanediol fatty acid ester allows for the extrusion of the PCM composition by itself without the need for other thermoplastic polymers. Without wishing to be bound by theory, it is hypothesized that the melting ranges of compositions comprising 1,3-propanediol fatty acid esters are broad enough to provide suitable and stable melt viscosities, thus guaranteeing a stable process during extrusion.
Preferably, the PCM composition is fed into a wire coating extrusion line and is extruded at a temperature above its melting point, at the desired thickness, onto the yarn, strand or wire.
Optionally, one or more additional layer(s) can be extruded onto the cable obtained by extruding the PCM composition onto the yarn, strand or wire. Polymeric layers are preferred as additional layers.
The cross-section of the cable need not be circular and can be of any shape, as determined by the shape of the die that is mounted at the exit of the extruder.
The amount of PCM in the cables is desirably as high as possible, because the thermal performance of the compositions is in general directly proportional to the concentration of PCM in the PCM composition. The amount of PCM in the cable is at least about 70 weight percent, about 70 to about 95 weight percent, or about 75 to about 85 weight percent, based on the total weight of the cable.
Optionally, the cables comprising a core and a PCM layer further comprise one or more layer(s) of a protective polymer. The layer of protective polymer is generally surrounding the PCM layer; however, the layer of protective polymer could be inserted between the PCM layer and the core.
The protective polymer may be any polymer; however, the layer(s) of protective polymer(s) preferably provide some properties to the cables such as for example heat resistance, chemical resistance, sealability, or the like. In particular, the cables described herein are capable of bending 180° without breakage after 1000 hours of exposure at 95° C. to air, glycol or lubricating oil. In addition, the protective polymers are preferably impermeable to the PCM composition. More preferably, the protective layer is impermeable to PCM composition when it is in the molten state. Preferred protective polymers include, without limitation, an ionomer, a polyamide, a grafted or non-grafted polypropylene homopolymer, a grafted or non-grafted polypropylene copolymer, a perfluoro ethylene-propylene (FEP), a perfluoroalkoxy alkane (PFA), an ethylene tetrafluoroethylene (ETFE), an ethylene methylacrylate copolymer with a methyl acrylate content above 50 weight percent; or mixtures or blends of two or more of these polymers.
In one embodiment, a layer of protective polymer is made of a blend of an ionomer and a polyamide. In particular, the layer is made of a blend of an ionomer of an ethylene acid copolymer and a polyamide.
The ionomer is a polymer that is produced by partially or fully neutralizing an acid copolymer. Suitable ethylene acid copolymers and ionomers are described in U.S. Pat. No. 7,641,965, issued to Bennison et al., for example. Briefly, however, the ethylene acid copolymer comprises copolymerized units of an α-olefin having from 2 to 10 carbon atoms and about 8 to about 30 weight percent, preferably about 15 to about 30 weight percent, more preferably about 20 to about 30 weight percent, yet more preferably about 20 to about 25 weight percent, or still more preferably about 21 to about 23 weight percent of copolymerized units of an α,β-ethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms. The weight percentage is based on the total weight of the ethylene acid copolymer. Preferably, the α-olefin comprises ethylene; more preferably, the α-olefin consists of or consists essentially of ethylene. Also preferably, the α,β-ethylenically unsaturated carboxylic acid comprises (meth)acrylic acid. More preferably, the α,β-ethylenically unsaturated carboxylic acid consists of or consists essentially of (meth)acrylic acid.
The ethylene acid copolymers may further comprise copolymerized units of other comonomer(s), such as derivatives of unsaturated carboxylic acids having 2 to 10, or preferably 3 to 8 carbon atoms or derivatives thereof. Suitable acid derivatives include acid anhydrides, amides, and esters. Esters are preferred derivatives. Preferably, the esters are α,β-ethylenically unsaturated carboxylic acid ester comonomers and include, but are not limited to, methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate and combinations thereof.
The ethylene acid copolymers may be synthesized by any suitable polymerization process. For example, the ethylene acid copolymers may be polymerized as described in U.S. Pat. Nos. 3,404,134; 5,028,674; 6,500,888; and 6,518,365.
Preferably, the ethylene acid copolymer has a melt index (MI) of about 60 g/10 min or less, more preferably about 45 g/10 min or less, yet more preferably about 30 g/10 min or less, or yet more preferably about 25 g/10 min or less, or still more preferably about 10 g/10 min or less, as measured by ASTM method D1238 at 190° C. and 2.16 kg.
Some suitable ethylene acid copolymer resins are commercially available from E.I. du Pont de Nemours and Company of Wilmington, Del. (“DuPont”), under the trademark Nucrel®.
To obtain the ionomers, at least a portion of the carboxylic acid moieties of the ethylene acid copolymers is neutralized to form carboxylate groups. Preferably about 5 to about 90%, more preferably about 10 to about 50%, yet more preferably about 20 to about 50%, or still more preferably about 20 to about 35% of the carboxylic acid groups are neutralized, based on the total carboxylic acid content of the ethylene acid copolymers. An example of a suitable procedure for neutralizing the ethylene acid copolymers is also described in U.S. Pat. No. 3,404,134.
The ionomers comprise cations as counterions to the carboxylate anions. Suitable cations include any positively charged species that is stable under the conditions in which the ionomer composition is synthesized, processed and used. Preferably, the cations are metal cations that may be monovalent, divalent, trivalent or multivalent. Combinations of two or more cations that may have different valencies, for example mixtures of Na⁺ and Zn²⁺, or mixtures of NH⁴⁺ and K⁺, are also suitable. The cations are more preferably monovalent or divalent metal ions. Still more preferably, the metal ions are selected from the group consisting of ions of sodium, lithium, magnesium, zinc, and potassium and combinations of two or more thereof. Still more preferably, the metal ions are selected from the group consisting of ions of sodium, ions of zinc and combinations thereof. Still more preferably, the metal ions comprise or consist essentially of zinc ions.
The ionomer preferably has a MI of about 10 g/10 min or less, more preferably about 5 g/10 min or less, or still more preferably about 3 g/10 min or less, about 1.0 g/10 min or less, about 0.5 g/10 min or less, about 0.2 g/10 min or less, or about 0.1 g/10 min or less, as measured by ASTM method D1238 at 190° C. and 2.16 kg. The ionomer also preferably has a flexural modulus greater than about 40,000 psi (276 MPa), more preferably greater than about 50,000 psi (345 MPa), or still more preferably greater than about 60,000 psi (414 MPa), as measured by ASTM method D790 (Procedure A).
Some suitable ionomeric resins are commercially available from DuPont, under the trademarks Surlyn® resins.
Suitable polyamides may be chosen from semi-aromatic polyamides, aliphatic polyamides, and blends thereof having a melting temperature of from 150 to 330° C.
The polyamide may be a fully aliphatic polyamide. Fully aliphatic polyamide resins may be formed from aliphatic and alicyclic monomers such as diamines, dicarboxylic acids, lactams, aminocarboxylic acids, and their reactive equivalents. A suitable aminocarboxylic acid includes 11-aminododecanoic acid. As used herein, the term “fully aliphatic polyamide resin” also includes fully aliphatic polyamides having three or more distinct copolymerized repeat units, and blends of two or more fully aliphatic polyamide resins. Linear, branched, and cyclic monomers are suitable.
Suitable dicarboxylic acid monomers for use in synthesizing fully aliphatic polyamide resins include, but are not limited to, aliphatic dicarboxylic acids, such as for example adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), sebacic acid (C10), dodecanedioic acid (C12) and tetradecanedioic acid (C14), and mixtures of two or more thereof. Suitable diamines for use in synthesizing fully aliphatic polyamide resins have four or more carbon atoms, and include, but are not limited to, tetramethylene diamine, hexamethylene diamine, octamethylene diamine, decamethylene diamine, 2-methylpentamethylene diamine, 2-ethyltetramethylene diamine, 2-methyloctamethylene diamine; trimethylhexamethylene diamine, and mixtures of two or more thereof.
Suitable examples of fully aliphatic polyamide resins include PA6; PA6,6; PA4,6; PA6,10; PA6,12; PA6,14; P 6,13; PA 6,15; PA6,16; PA11; PA 12; PA10; PA 9,12; PA9,13; PA9,14; PA9,15; P 6,16; PA9,36; PA10,10; PA10,12; PA10,13; PA10,14; PA12,10; PA12,12; PA12,13; 12,14 and copolymers and blends of the same. Preferred examples of fully aliphatic polyamide resins include PA6, PA11, PA12, PA4,6, PA6,6, PA, 10; PA6,12; PA10,10; and copolymers and blends of these polyamides.
The layer of protective polymer comprising a blend of ionomer and polyamide may have a thickness of from 50 to 500 μm, preferably from 50 to 250 μm, and more preferably of from 100 to 200 μm.
In another embodiment, a layer of protective polymer comprises one or more polymers selected from the group consisting of grafted or non-grafted polypropylene homopolymer, grafted or non-grafted polypropylene copolymer, perfluoro ethylene-propylene (FEP), perfluoroalkoxy alkane (PFA), ethylene tetrafluoroethylene (ETFE), and ethylene acrylate rubber (AEM).
The grafted or non-grafted polypropylene and grafted or non-grafted copolymer of propylene may be obtained by grafting and/or copolymerizing the propylene polymers or monomers with organic functionalities including acid, anhydride, or epoxide functionalities. Examples of the acids and anhydrides used to modify polypropylene are mono-, di- or polycarboxylic acids such as (meth)acrylic acid, maleic acid, maleic acid monoethylester, fumaric acid, fumaric acid, itaconic acid, crotonic acid, itaconic anhydride, maleic anhydride and substituted maleic anhydride, e.g., dimethyl maleic anhydride or citrotonic anhydride, nadic anhydride, nadic methyl anhydride, and tetrahydrophthalic anhydride, or combinations of two or more thereof, with maleic anhydride being preferred.
Preferred protective polymer layers comprise grafted polypropylene or grafted copolymer of propylene. Some suitable grafted polypropylenes and grafted copolymers of propylene are commercially available from DuPont, under the trademarks Bynel®.
The fluoropolymer FEP (fluorinated ethylene propylene copolymer) is generally a copolymer of tetrafluoroethylene and hexafluoropropylene. Usually, FEPs comprise from 87 weight percent to 94 weight percent of tetrafluoroethylene and from 6 weight percent to 13 weight percent of hexafluoropropylene, more preferably from 88 weight percent to 90 weight percent of tetrafluoroethylene and from 10 weight percent to 12 weight percent hexafluoropropylene, all based on the total weight of the FEP.
The fluoropolymer PFA (perfluoroalkoxy copolymer) is generally a copolymer of tetrafluoroethylene and a perfluoroalkylvinylether such as perfluoropropylvinylether, perfluoroethylvinylether or perfluoromethylvinylether. Usually, PFA comprises from 90 weight percent to 98 or 99 weight percent of tetrafluoroethylene and from 1 or 2 weight percent to 10 weight percent of perfluoropropylvinylether, perfluoroethylvinylether or perfluoromethylvinylether. More preferably from 92 weight percent to 97 weight percent of tetrafluoroethylene and from 3 weight percent to 8 weight percent of perfluoropropylvinylether, perfluoroethylvinylether or perfluoromethylvinylether, all based on the total weight of the PFA.
The fluoropolymer ETFE (ethylene tetrafluoroethylene copolymer) is generally a copolymer of ethylene and tetrafluoroethylene. Usually, ETFEs comprise from 15 weight percent to 25 weight percent of ethylene and from 75 weight percent to 85 weight percent of tetrafluoroethylene, more preferably from 15 weight percent to 20 weight percent of ethylene and from 80 weight percent to 85 weight percent of tetrafluoroethylene, based on the total weight of the ETFE.
Ethylene acrylate rubbers (AEM) are curable compositions of copolymers of ethylene and alkyl (meth)acrylate. The term “curable” denotes a material that may be cross-linked through a chemical reaction or irradiation. The curable composition may be cured by any suitable means or by a curing agent, such as, for example chemical additives or radiation. AEM may contain at least 45 weight percent of the alkyl (meth)acrylate, preferably from 45 to 70 weight percent, more preferably from 55 to 65 weight percent, based on the total weight of the AEM. The alkyl (meth)acrylate may be chosen among methyl (meth)acrylate, ethyl (meth)acrylate and butyl (meth)acrylate, and is preferably methyl (meth)acrylate.
Ethylene Acrylate Rubbers or AEMs are commercially available from DuPont under the trademark VAMAC®.
The cables of the present invention can be used in several applications where thermal management is needed. While temperature management inside buildings is one of the most relevant applications, the PCM composition may also be used in automotive applications (for example for latent heat batteries, or thermal management of electrical batteries, ceiling and seats of vehicles); air filters in air ducts; air conditioners; transportation applications; food packaging (to keep food chilled or warm); medical packaging (for example organ or vaccine transportation); woven and nonwoven fabrics for garments, clothes and sport wear; footwear; tree wraps; hand grips (for example, in tools, sporting goods and vehicles); bedding; carpets; wood composites; electric cables; and plastic tubes for hot media including water.
A particularly preferred application is in latent heat batteries of cars, where energy is stored in the cables of the present invention while the engine is in operation and where the cables are able to release the energy stored when necessary (for instance for start-up in cold environment or cold season). This energy release allows the viscosity of lubricating oils and cooling fluids to be reduced and ultimately leads to lower fuel consumption and reduced CO₂emissions.
The following examples are provided to describe the invention in further detail. These examples, which set forth specific embodiments and a preferred mode presently contemplated for carrying out the invention, are intended to illustrate and not to limit the invention.

EXAMPLES

Example 1: Encapsulated PCM Cable Encapsulated in PA6-Ionomer Coating

In a first step, a powder of 1,3-propanediol dibehanate was fed into a wire coating extrusion line and extruded at a temperature of 72° C. and at a thickness of 1.675 mm onto a copper wire having a diameter of 250μ to form a cable having a diameter of 3.6 mm.
In a second step, a melt blend of 60 weight percent PA6 and 40 weight percent ionomer (methacrylic acid copolymer neutralized with zinc) was extruded at a temperature of 250° C. using another wire coating line. A coating of ionomer/PA blend having a thickness of 200 μm was applied to the 3.6 mm diameter cable. The final encapsulated PCM cable had a diameter of around 4 mm.
Samples (10 cm lengths) were cut from the 4 mm cable. Both ends of each sample were sealed at a temperature of 250° C. using impulse sealing equipment (“Medseal 410/610 MSI” from the company Audion Elektro). The sealed samples were exposed to:

- Air at a temperature of 130° C. during 24 hours
- A mixture of ethylene glycol (product “G12 plus plus” distributed by the company Volkswagen AG) and demineralized water (50/50 by weight at a temperature of 130° C. during 24 hours)
- A lubricating oil for cars (product “ATF-SP4(M)” from the company Michang Oil) at a temperature of 130° C. during 24 hours

Once the ageing period of 24 hours was over, the sealed samples were carefully checked and following observations were made and summarized in Table 1:

- Damages on the samples aged in ethylene glycol
- No damage or melting of the cable samples after ageing in hot air and lubricating oil
- No opening of the sealed edges after ageing in hot air and lubricating oil
- No exudation or loss of the PCM from the cable samples after ageing in hot air and lubricating oil, as determined by weight difference

Example 2: Encapsulated PCM Cable Encapsulated in PA6/12-Ionomer Coating

In a first step, a powder of 1,3-propanediol dibehanate was fed into a wire coating extrusion line and extruded at a temperature of 72° C. and at a thickness of 1.675 mm onto a copper wire having a diameter of 250μ to form a cable having a diameter of 3.6 mm.
In a second step, a melt blend of 60 weight percent PA6/12 and 40 weight percent ionomer (methacrylic acid copolymer neutralized with zinc) was extruded at a temperature of 250° C. using another wire coating line. A coating of ionomer-PA6/12 blend having a thickness of 200 μm was applied to the 3.6 mm diameter cable. The final encapsulated PCM cable had a diameter of around 4 mm.
Samples were cut and sealed according to the procedures used in Example 1, and they were exposed to the same test conditions as the sealed samples in Example 1.
Once the ageing period of 24 hours was over, the sealed samples were carefully checked and the following observations were made and summarized in Table 2:

- No damage or melting of any of the cable samples under the test conditions
- No opening of the sealed edges under the test conditions
- No exudation or loss of the PCM from the cable samples under the test conditions

TABLE 1

Ageing results after 24 hours ageing at 130° C.

Ageing medium	Air	Ethylene glycol	Lubricating oil

Cable appearance	Perfect	Damaged	Perfect
Edge seal tightness	Tight	Opened	Tight
Weight loss due to	0%	Not applicable	0%
exuded PCM		since opened
		seals

TABLE 2

Ageing results after 24 hours ageing at 130° C.

Ageing medium	Air	Ethylene glycol	Lubricating oil

Cable appearance	Perfect	Perfect	Perfect
Edge seal tightness	Tight	Tight	Tight
Weight loss due to	0%	0%	0%
exuded PCM

While certain of the preferred embodiments of this invention have been described and specifically exemplified above, it is not intended that the invention be limited to such embodiments. Various modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.

Claims

1. A cable comprising a core and a PCM layer surrounding the core, wherein the PCM layer consists of a PCM composition, and

a) the PCM composition is biobased; and

b) the core consists of a filament, yarn, strand or wire comprising a polymeric material or a metal.

2. The cable of claim 1 wherein the PCM composition is a 1,3-propanediol fatty acid ester.

3. The cable of claim 1 or claim 2, wherein the PCM composition comprises 1,3-propanediol dibehanate or 1,3-propanediol dipalmitate.

4. The cable of any preceding claim, wherein the filament, yarn, strand or wire comprises polyamide, polyparaphenylene terephtalamide or copper.

5. The cable of any preceding claim, wherein the amount of PCM is at least 70 weight percent, based on the total weight of the cable.

6. The cable of any preceding claim, wherein the cable has a diameter of 3 to 6 mm.

7. The cable of any preceding claim, further comprising one or more layers of a protective polymer.

8. The cable of claim 7, wherein at least one of the one or more layers of a protective polymer comprises a blend of ionomer and polyamide.

9. The cable of claim 7 or claim 8, wherein the one or more layers of a protective polymer have a thickness of 50 to 600 μm.

10. The use of the cable of any preceding claim in thermal management.

11. The use of the cable of any preceding claim in the automotive industry.

12. The use of the cable of any preceding claim in an electrical battery or in a latent heat battery.

13. A process for making the cable of any of claims 1 to 9, said process comprising the steps of:

a) providing a core consisting of a yarn, strand or wire made of a polymeric material or a metal; and

b) extruding a PCM composition comprising 1,3-propanediol fatty acid ester onto the core.

14. The process of claim 13, further comprising the step of extruding one or more layers of a protective polymer onto the PCM composition and the core.

15. The process of claim 14, wherein the protective polymer comprises a blend of an ionomer and a polyamide.