WO2023274884A1

WO2023274884A1 - Electrically conductive yarn

Info

Publication number: WO2023274884A1
Application number: PCT/EP2022/067391
Authority: WO
Inventors: Pascal FREUND; Tim Biemelt; Thomas Rademacher
Original assignee: Trevira Gmbh
Priority date: 2021-06-28
Filing date: 2022-06-24
Publication date: 2023-01-05
Also published as: EP4363642A1

Abstract

The invention relates to an electrically conductive yarn having good physical and mechanical properties, to a process for producing same and to its use.

Description

Electrically conductive yarn

description

The invention relates to an electrically conductive yarn with good physical and mechanical properties, a method for its production, and its use.

It has long been known to produce electrically conductive yarns from thermoplastic polymers, in which an electrically conductive material is incorporated into the thermoplastic polymer or a yarn made from thermoplastic polymer is provided with an electrically conductive sheath, for example in the form of a bi-component fiber. Examples of this can be found inter alia in EP-A-1559815 and EP-A-3502327.

However, the combination of thermoplastic polymers and electrically conductive materials, e.g. graphite or carbon black, is not trivial, since carbon or carbon-loaded polymer resin in particular does not adhere well, which leads to spalling or flaking of the coating.

Another problem is the mass of electrically conductive materials, particularly carbon, required to produce a sufficient level of electrical conductivity. Historically, the carbon content required to provide adequate electrical conductivity has been greater than 25% by weight of the thermoplastic polymer. Such a high carbon content greatly affects the technical properties of yarns.

Recently, the availability of highly electrically conductive materials such as carbon nanotubes (CNT) as well as graphene and fullerenes has led to a reduction in the necessary mass of electrically conductive materials and thus at least partially eliminate the disadvantages mentioned, as in EP-A-1559815.

Nevertheless, the known electrically conductive yarns and their production have serious deficits. On the one hand there is the problem of embedding enough electrically conductive additive in the thread matrix to get over the electrical percolation threshold and at the same time to maintain the stability of the yarn during production in the spinning process and on the other hand to take into account the forces occurring during spinning draft, since these are at the necessary post-treatment, e.g. stretching, to cracking of the percolating additive network, which means that the electrical conductivity is lost.

A realization of electrically conductive yarns in a conventional spinning process, as well as a bi-component fiber spinning process, leads to yarns that were either no longer sufficiently electrically conductive or not mechanically stable enough to be able to be wound up.

There was therefore still a need for electrically conductive yarns which, on the one hand, have good electrical conductivity and, on the other hand, have good mechanical properties. In particular, these good properties should also be retained during subsequent use, for example when exposed to mechanical stress and thermal stress.

The subject matter of the present invention is an electrically conductive yarn with a core-sheath structure comprising:

(i) a core of at least one multifilament yarn,

(ii) a jacket comprising a mixture of

(iia) thermoplastic elastomer and

(iib) at least one electrically conductive material, characterized in that

(iii) the core multifilament yarn

(iiia) has a tenacity of 40 to 300 cN/tex,

(iiib) has an elongation at break of no more than 25%,

(iiic) has thermal shrinkage of at most 6% (iiid) has a linear density of 100 to 1200 dtex for a multifilament yarn made from organic polymers or has a diameter in the range from 200 to 600 pm for a multifilament yarn made from non-organic materials

(iv) the coat

(iva) is in contact with the core and completely encloses it,

(ivb) has a thickness of at least 10 μm,

(ivc) has an electrical conductivity of at least 150 S/m,

(ivd) the electrically conductive material has an electrical conductivity of at least 3x10 ² S/m,

(ive) 1 to 45% by weight of electrically conductive material.

(ivf) 99 to 55% by weight thermoplastic elastomer,

(ivg) the jacket material has a maximum thermal shrinkage of 6%. core component

The multifilament yarn present in the yarn according to the invention preferably has a tenacity of 40 to 300 cN/tex. Strengths related to the tenacity of from 50 to 280 cN/tex, in particular from 60 to 260 cN/tex, are particularly preferred.

The multifilament yarn present in the yarn according to the invention preferably has an elongation at break of at most 25%, preferably at most 20%.

The multifilament yarn present in the yarn according to the invention preferably has a thermal shrinkage of at most 6%, preferably at most 3%.

The multifilament yarn according to the invention preferably has a linear density in the range from 100 to 1200 dtex, particularly preferably 250 to 500 dtex. The dtex specification refers to fibers made of organic polymers, in particular thermoplastic polymers, particularly preferably made of polyester.

The multifilament yarn according to the invention preferably has 10 to 500 individual filaments.

The multifilament yarn according to the invention is electrically non-conductive. The term electrically non-conductive means that the yarn has an electrical conductivity of <10 ⁸ S/m.

The multifilament yarn according to the invention is preferably a multifilament yarn made from aramids, preferably so-called high-modulus aramids, polyesters, preferably so-called high-strength polyester multifilaments, polyamides, preferably so-called high-strength polyamide multifilaments, carbon, glass, mineral fibers (basalt), and based on so-called hybrid multifilament yarns that have two or more of the aforementioned materials. The term high-strength stands for a tenacity-related strength of at least 50 cN/tex, in particular of at least 60 cN/tex, particularly preferably of at least 70 cN/tex,

The multifilament yarn present in the yarn according to the invention preferably has a Young's modulus of at least 0.3 GPa, particularly preferably at least 0.5 GPa, in particular at least 0.8 GPa, particularly preferably at least 2 GPa or at least 2.5 GPa. The multifilament yarn according to the invention is particularly preferably a multifilament yarn made from a thermoplastic polymer

In the context of the present invention, the term “thermoplastic polymer” designates a plastic which can be (thermoplastically) deformed in a specific temperature range, preferably in the range from 25° C. to 350° C. This process is reversible, i.e. it can be repeated as often as you like by cooling and reheating until it is molten, as long as the material has not been damaged too much by overheating, so-called thermal decomposition, or by mechanical stress during shaping. This is where thermoplastic polymers differ from duroplastics and elastomers.

The thermoplastic polymers used according to the invention are polymers from the group consisting of acrylonitrile-ethylene-propylene(diene)styrene copolymer, acrylonitrile-methacrylate copolymer, acrylonitrile-methyl methacrylate copolymer, chlorinated acrylonitrile, polyethylene-styrene copolymer and acrylonitrile-butadiene -styrene copolymer, acrylonitrile-ethylene-propylene-styrene copolymer cellulose acetobutyrate, cellulose acetopropionate, hydrated cellulose, carboxymethyl cellulose, cellulose nitrate, cellulose propionate, cellulose triacetate, polyvinyl chloride, ethylene acrylic acid copolymer, ethylene butyl acrylate copolymer, ethylene - chlorotrifluoroethylene copolymer, ethylene ethyl acrylate copolymer, ethylene methacrylate copolymer, ethylene methacrylic acid copolymer, ethylene tetrafluoroethylene copolymer, ethylene vinyl alcohol copolymer, ethylene butene copolymer, ethyl cellulose, polystyrene, polyfluoroethylene propylene , methyl methacrylate acrylonitrile butadiene styrene copolymer, methyl methacrylate butadiene styrene rol-copolymer, methyl cellulose, polyamide 11, polyamide 12, polyamide 46, polyamide 6, polyamide 6-3-T, polyamide 6-terephthalic acid copolymer, polyamide 66, polyamide 69, polyamide 610, polyamide 612, polyamide 6I, polyamide MXD 6, polyamide PDA-T, Polyamide, Polyarylether, Polyaryletherketone, Polyamideimide, Polyarylamide, Polyaminobismaleimide, Polyarylate, Polybutene-1, Polybutylacrylate, Polybenzimidazole, Polybismaleimide, Polyoxadiazobenzimidazole, Polybutylterephthalate, Polycarbonate, Polychlorotrifluoroethylene, Polyethylene, Polyestercarbonate, Polyaryletherketone, Polyether ether ketone, polyether imide, polyether ketone, polyethylene oxide, polyaryl ether sulfone, polyethylene terephthalate, polyimide, polyisobutylene, polyisocyanurate, polyimide sulfone, polymethacrylimide, polymethacrylate, poly-4-methylpentene, polyacetal, polypropylene, polyphenyl oxide, polypropylene oxide, polyphenylene sulfide, polyphenylene sulfone, polystyrene, polysulfone, polytetrafluoroethylene, polyurethane, polyvinyl acetate, polyvinyl alcohol, Polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, polyvinyl methyl ether, polyvinyl pyrrolidone, styrene butadiene copolymer, styrene isoprene copolymer, styrene maleic anhydride copolymer, styrene maleic anhydride butadiene copolymer, styrene methyl methacrylate copolymer, Styrene-methlystyrene copolymer, styrene-acrylonitrile copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-methacrylate copolymer, vinyl chloride-maleic anhydride copolymer, vinyl chloride-maleimide copolymer, vinyl chloride-methyl methacrylate copolymer, vinyl chloride-octlyacrylate copolymer, vinyl chloride- vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinylidene chloride-acrylonitrile copolymer.

Within the thermoplastic polymers, melt-spinnable synthetic polycondensates are preferred. Also suitable thermoplastic polymers are melt-spinnable synthetic biopolymers.

In the context of the present invention, the term “synthetic biopolymer” designates a material that consists at least predominantly of biogenic raw materials (renewable raw materials). This is a differentiation from the conventional, petroleum-based materials or plastics, such as e.g. B. polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).

Within the thermoplastic polymers, melt-spinnable synthetic polycondensates are preferred. These are aliphatic polyesters, arylaliphatic polyesters, aromatic polyesters and their co-/ter-polymers, which are produced from polyols and aliphatic and/or aromatic dicarboxylic acids or their derivatives (anhydrides, esters) by polycondensation, with the polyols being substituted or may be unsubstituted, the polyols may be linear or branched polyols.

Preferred polyols are polyols having 2 to 8 carbon atoms, polyalkylene ether glycols having 2 to 8 carbon atoms, and cycloaliphatic diols having 4 to 12 carbon atoms. Examples of polyols that can be used include, but are not limited to, ethylene glycol,

Diethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3- cyclobutanediol, triethylene glycol and tetraethylene glycol. Preferred polyols include 1,4-butanediol, 1,3-propanediol, ethylene glycol, 1,6-hexanediol, diethylene glycol, isosorbitol and 1,4-cyclohexanedimethanol. Preferred aliphatic dicarboxylic acids include substituted or unsubstituted, linear or branched, non-aromatic dicarboxylic acids selected from the group consisting of aliphatic dicarboxylic acids having 2 to 12 carbon atoms and cycloaliphatic dicarboxylic acids having 5 to 10 carbon atoms, where the cycloaliphatic dicarboxylic acids can also have heteroatoms in the ring.

The substituted non-aromatic dicarboxylic acids typically contain 1 to 4 substituents selected from halogen, C6-C10 aryl and C1-C4 alkoxy. Non-limiting examples of aliphatic and cycloaliphatic dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid. 3-cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid, 2,5-norbornanedicarboxylic acid.

Preferred aromatic dicarboxylic acids include substituted or unsubstituted aromatic dicarboxylic acids selected from the group of aromatic dicarboxylic acids having 6 to 12 carbon atoms, it also being possible for these dicarboxylic acids to have heteroatoms in the aromatic ring and/or in the substituent.

The substituted aromatic dicarboxylic acids can typically have 1 to 4 substituents selected from halogen, C6-C10 aryl and C1-C4 alkoxy. Non-limiting examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid,

naphthalene dicarboxylic acid and furandicarboxylic acid.

The multifilament yarn according to the invention has a diameter in the range from 200 μm to 600 μm, this information relating to a multifilament yarn made from non-organic fibers, in particular from carbon, glass and mineral fibers (basalt).

The multifilament yarn according to the invention is very particularly preferably a multifilament yarn made from a polyester, preferably a polyester based on aromatic dicarboxylic acids, which preferably:

(i) have a tenacity of 40 to 300 cN/tex, in particular 60 to 100 cN/tex, and

(ii) have a titre in the range from 100 to 1200 dtex, particularly preferably 250 to 500 dtex, and

(iii) have an elongation at break of at most 25%, preferably at most 20%, and (iv) have a thermal shrinkage of at most 6%, preferably at most 3%.

Polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN) are particularly preferred.

Particularly preferred polyesters are PET and PEN with a glass transition temperature of at least 70°C.

Particularly preferred polyesters are PET which contain at least 95 mol % polyethylene terephthalate (PET).

Particularly preferred polyesters, in particular polyethylene terephthalate, have a molecular weight corresponding to a specific viscosity (pspec) of at least 0.8 dl/g, in particular at least 0.9 dl/g, measured in each case on solutions with 1 g/l of polymer in dichloroacetic acid at 25 °C

The production of such polyester multifilament yarns is known in principle, for example, from EP-A-0173221 and the places cited therein. Such high-strength polyester multifilament yarns are also referred to as tire cord and are used in technical products that require high strength.

The production on an industrial scale takes place via a melt spinning process. For this purpose, the thermoplastic, polymeric material is melted and fed into a spinning beam in the liquid state by means of an extruder. The molten material is fed from this spinning beam to so-called spinnerets. The spinneret usually has a spinneret plate with a plurality of bores from which the individual capillaries (filaments) of the fiber are extruded. In addition to the melt spinning process, wet or solvent spinning processes are also used to produce staple fibers. Here, instead of the melt, a highly viscous solution of a synthetic polymer is extruded through nozzles with fine bores. Both processes are referred to by those skilled in the art as so-called multi-station spinning processes.

The polymer fibers produced in this way are subjected to fiber post-processing in order to set the desired mechanical strength. Here, a modification or finishing of polymer fibers for each end use or for the necessary intermediate treatment steps, for example drawing and/or crimping, usually by applying suitable finishes or sizings, which are applied to the surface of the finished polymer fiber or the polymer fiber to be treated.

Additives such as antistatic agents or colored pigments may be added to the thermoplastic polymer, usually by incorporation into the molten thermoplastic polymer during the multi-spin process of the polymer fiber.

spinning oil equipment

In a further embodiment of the present invention, the thermoplastic multifilament yarn, in particular the polyester multifilament yarn, is finished with a commercially available spinning oil which decouples the multifilament yarn core from the thermoplastic sheath. Here, the spinning oil is applied to the multifilament yarn before it is sheathed.

The spinning oil used is commercially available spinning oil.

Examples of corresponding commercially available spinning oils are distillates (petroleum) consisting of dewaxed heavy paraffinic solvents (50-70%), mineral oils (25-50%), ethoxylated fatty alcohol (2.5-30%), C8-18 even amides (2.5 -10%) and C18-unsaturated, N,Nbis(hydroxyethyl) C9-C11 alcohol ethoxylate (<2.5%) Alternatively, ethylene glycol (2.5-10%), diisooctyl sodium sulfosuccinate (1-2.5%) and/or sodium alkane sulfonate (1 -<2.5%) must be included.

sheath component

The sheath present in the yarn according to the invention is in contact with the multifilament yarn. This means that at least 90% of the surface of the multifilament yarn is in direct contact with the sheath or at least 90% of the surface of the multifilament yarn is in indirect contact with the sheath, insofar as the spinning oil finish described above has taken place.

The sheath usually has a thickness of at least 10 μm, preferably at least 20 μm, particularly preferably at least 50 μm. The thickness is not limited as to the upper limit. The maximum thickness is usually 300 μm, so that the thickness is in the range from 10 μm to 300 μm, preferably from 50 μm to 300 m, especially in the range of 100 pm to 150 pm..

The sheath usually has an electrical conductivity of at least 150 S/m.

The electrically conductive material used in the casing usually has an electrical conductivity of at least 3×10 ² S/m, preferably at least 1×10 ⁶ S/m.

The sheathing comprises 55 to 99% by weight of thermoplastic elastomer and 1 to 45% by weight of electrically conductive material, preferably 85 to 99% by weight of thermoplastic elastomer and 1 to 15% by weight of electrically conductive material, particularly preferably 90 to 99% by weight thermoplastic elastomer and 1 to 10% by weight electrically conductive material, in particular 94 to 99% by weight thermoplastic elastomer and 1 to 6% by weight electrically conductive material. In addition, the casing can also have the usual additives, in particular those that make it easier to process the casing compound. The compound described above is hereinafter referred to as the sheath component.

The term thermoplastic elastomer refers to a thermoplastic elastomer according to DIN ES ISO 18064:2021-04 (replaces DIN EN ISO 18064:2015-03)

The thermoplastic elastomer used according to the invention can be (thermoplastically) deformed in a specific temperature range, preferably in the range from 25° C. to 350° C. This process is reversible, i.e. it can be repeated as often as you like by cooling and reheating until it is molten, as long as the material has not been damaged too much by overheating, so-called thermal decomposition, or by mechanical stress during shaping.

A thermoplastic elastomer is usually obtained by combining thermoplastic with an elastomer, this can usually be done in two different ways, block polymers or polymer blends

Examples of suitable block polymers as a thermoplastic elastomer are TPS, TPU, TPA and TPC.

TPS stands for styrene block copolymers, specifically styrene/butadiene/styrene (SBS), or styrene/ethylene-butylene/styrene (SEBS) or styrene/ethylene-propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS) based styrene block copolymers. These block copolymers have hard and soft segments, with the styrenic group forming the hard segment and the aliphatic groups, particularly aliphatic groups containing 2 to 6 carbon atoms, forming the soft segments. Such TPS are characterized by a hardness of 10 Shore A to 70 Shore D. Preferred within the TPS are styrene/butadiene/styrene (SBS), styrene/ethylene butylene/styrene (SEBS), styrene/ethylene propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS) with a hardness of 75 Shore A up to 40 shore D

Particularly preferred within the TPS are styrene/butadiene/styrene (SBS), styrene/ethylene butylene/styrene (SEBS), styrene/ethylene propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS) in the form of the shell component have a maximum melt flow rate of 10g/10 min (190°C, 21.60 kg).

Particularly preferred within the TPS are styrene/butadiene/styrene (SBS), styrene/ethylene-butylene/styrene (SEBS), styrene/ethylene-propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS) which have a maximum thermal shrinkage 3%, preferably not more than 2%, particularly preferably not more than 1%.

Very particular preference is given to styrene/butadiene/styrene (SBS), styrene/ethylene-butylene/styrene (SEBS), styrene/ethylene-propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS) which is a combination of the aforementioned features thermal shrinkage, melt flow rate, tensile stress at break and hardness, with styrene/ethylene butylene/styrene (SEBS) being particularly preferred.

Commercially available TPS's include Elastron® G and Elastron® D, Kraton® (Kraton Polymers), Septon® (Kuraray), Styroflex® (BASF), Thermolast® (Kraiburg TPE) ALLRUNA® (ALLOD Material GmbH & Co.KG) or Saxomer® TPE-S (PCW), as well as Pre-Elect® TPE (Premix). The TPS elastomers mentioned above have particularly good conductivity and are also advantageous in processing. Thus yarns according to the invention with this sheath component have a particularly smooth surface.

TPU stands for thermoplastic polyurethane, i.e. a thermoplastic elastomer based on polyurethane. Such TPUs are characterized by a hardness of about 60 Shore A and above. Commercially available TPUs include Elastollan® (BASF) or Desmopan®, Texin®, Utechllan® (Covestro).

TPA stands for Thermoplastic Polyether Polyamide, ie a block polymer based on polyamide. Such TPAs are characterized by a hardness of 60 Shore A to 70 Shore D. Commercially available TPA's include PEBAX® (Arkema), VESTAMID® E (Evonik Industries) TPC stands for thermoplastic polyester elastomer, ie a block copolymer on a copolyester basis. Such TPCs are distinguished by a flatness of 80 Shore A to 70 Shore D. Commercially available TPC's include Hytrel® (Du Pont), Keyflex® (LG Chem), Skypel® (SK Chemicals)

Examples of suitable polymer blends as thermoplastic elastomers are TPO and TPV

TPO stands for thermoplastic polyolefins, a mixture of a polyolefin-based plastic (usually PP or PE) and an elastomer such as EPDM. In contrast to TPV, TPO is not or only partially crosslinked. TPOs are polymer mixtures that are made hard or soft depending on their composition. Such TPOs are characterized by a hardness of 55 Shore A to 70 Shore D. Commercially available TPO's include Elastron® TPO, Saxomer® TPE-0 (PCW)

TPV stands for thermoplastic polyolefin vulcanizate, a mixture of a polyolefin-based plastic (primarily PP) and an elastomer such as EPDM. In contrast to TPO, the elastomer in TPV is cross-linked or vulcanized. TPV are characterized by a hardness of 35 Shore A to 50 Shore D. Commercially available TPV's include Elastron® V, Sariink® (DSM), Santoprene® (Exxon)

In a preferred embodiment, the thermoplastic elastomer is characterized by a Vicat softening point VST (50°C/10N) of at least 50°C, preferably at least 60°C, in particular at least 100°C.

In a preferred embodiment, the thermoplastic elastomer is distinguished by a melting temperature in the range from 140 to 190.degree. C., in particular in the range from 150 to 175.degree.

In a preferred embodiment, the thermoplastic elastomer is characterized by a thermal shrinkage of at most 3%, preferably at most 2%, particularly preferably at most 1%.

In a preferred embodiment, the thermoplastic elastomer in the form of the sheath component has a melt flow rate of at most 13 g/10 min (190° C.), in particular of at most 11 g/10 min (190° C.), particularly preferably of a maximum of 10g/10 min (190°C).

In a preferred embodiment, the thermoplastic elastomer in the form of the sheath component has a melt flow rate of not more than 50 g/10 min (230° C.), in particular not more than 30 g/10 min (230° C.), particularly preferably not more than 20 g/10 min. 10 min (230°C).

In a particularly preferred embodiment, the thermoplastic elastomer is a TPS and stands for styrene block copolymers, in particular styrene/butadiene/styrene (SBS), or styrene/ethylene butylene/styrene (SEBS) or styrene/ethylene propylene/styrene (SEPS) or styrene/isoprene/styrene (SIS)-based styrene block copolymers which, in the form of the shell component, have a melt flow rate of not more than 30 g/10 min (230°C), in particular not more than 20 g/10 min (230°C), particularly preferably not more than 13 g/10 min (230° C.).

In a preferred embodiment, the thermoplastic elastomer has a hardness of 75 Shore A to 40 Shore D.

In a preferred embodiment, the thermoplastic elastomer has a water absorption (23° C.) of at most 0.8%.

In a preferred embodiment, the thermoplastic elastomer has a tensile stress at break (tensile stress at break) of at least 10 MPa and at most 28 MPa.

In a preferred embodiment, a TPS styrene block copolymer is selected as the thermoplastic elastomer from the group of styrene/butadiene/styrene (SBS), styrene/ethylene butylene/styrene (SEBS), styrene/ethylene propylene/styrene (SEPS) or styrene/ Isoprene/styrene (SIS) is used, with the thermoplastic elastomer styrene/ethylene-butylene/styrene (SEBS) being particularly preferred, or a TPC thermoplastic polyester elastomer, i.e. a block copolymer on a copolyester basis, is used as the thermoplastic elastomer. deployed..

The electrically conductive material present in the casing usually has an electrical conductivity of at least 3×10 ² S/m, preferably at least 1×10 ⁶ S/m.

The electrically conductive material is preferably a particulate material, for example a powder or granules. In addition to spherical particles, non-spherical particles up to rod, fibrous, platelet-shaped or branched particles possible. The introduction of the electrically conductive material into the jacket makes it possible for larger particles to be added, which usually interfere with the production of spun filaments in the extrusion process. Within the scope of the present invention, the electrically conductive material can also have particles larger than 2 μm, preferably larger than 3 μm, in particular particles with a spherical size of more than 2 μm, preferably larger than 3 μm. Particle sizes of this type cannot be used in conventional thread spinning processes, since a filter is usually used in front of the spinning beam. The presence of such large particles of electrically conductive material, on the other hand, allows the electrical percolation threshold to be overcome more easily. With the help of the present invention, it is thus also possible to introduce large particles of electrically conductive material into the yarn according to the invention.

The electrically conductive material is usually mixed with the thermoplastic polymer for the sheath, and this can be done in the melt, for example in an extruder, or by metering in in some other way. So-called masterbatches are also advantageous for better distribution of the electrically conductive material in the thermoplastic elastomer of the sheath.

Preferred electrically conductive materials for the thermoplastic sheath are disclosed, for example, in US-A-6,228,492; US-A-6,528,572; US-A-2003/158,323; US-A-6,621,970; CN-A-1431342; US-A-2003/236,588 and US-A-5,840,425. These are also part of this description and disclosure by reference.

Other preferred electrically conductive materials for the thermoplastic sheath are suitable carbon nanotubes, such as those described in US Pat. Nos. 6,099,960; US-A-6,280,697; US-A-2002/172,639; US-A-2003/102,222; US-A-2002/113,335 and US-A-2003/102,444. These are also part of this description and disclosure by reference.

Particularly preferred electrically conductive materials for the thermoplastic jacket are so-called CNTs (Carbon Nano Tubes) with an average diameter in the range from 8 to 12 nm, preferably in the range from 9 to 10 nm, determined by means of transmission electron microscopy (TEM),

Particularly preferred electrically conductive materials for the thermoplastic jacket are so-called CNTs (Carbon Nano Tubes) with an average diameter in the range from 8 to 12 nm, preferably in the range from 9 to 10 nm, and an average length in the range 1 to 3 gm, preferably in the range 1 to 2 gm, as determined by transmission electron microscopy (TEM).

Particularly preferred electrically conductive materials for the thermoplastic sheath are so-called graphene, in particular graphene with a height of <10nm and a lateral extent of 1.5pm, determined by transmission electron microscopy (TEM). have a BET specific surface area of more than 600m ² /g.

The enclosing application of the sheath to the multifilament yarn is carried out by extrusion from the melt. Here, the multifilament yarn is pulled through a ring-shaped extrusion nozzle around which another, larger extrusion nozzle is installed, which applies the melted sheath component to the multifilament yarn. The yarn thickness is determined by the thickness of the core yarn, the difference in diameter of the extrusion nozzles and the take-off speed of the yarn. The multi-component yarn is then cooled in a water bath and wound up.

As already explained, the introduced (electrically conductive) materials can have sizes of >3 pm in one or more dimensions, contrary to conventional spinning methods, without lastingly disturbing the production process.

The electrically conductive material used according to the invention can also form aggregates in the jacket. These aggregates of the particulate material, for example a powder or granules, can be determined using optical methods. For this purpose, a film is formed from the cladding component and the size of the aggregate is determined using optical methods. The determination can be made, for example, using an FSA100 analyzer from OCS Optical Control Systems GmbH, Witten, Germany. For this purpose, a small amount of the cladding component (usually 1% by weight of cladding in RT5030 from OCS) is formed into a film (d=20mm, >10pm) and examined (area 1m ² , gray value 150, filter size 100, resolution 10pm, film thickness 30pm ). The individual defect size can, in individual cases, be up to 500 pm and usually 90% of the defects are smaller than 100 pm. Preferably, the average numerical defect size is typically up to 50pm. Additives in the thermoplastics of the multifilament core and sheath

The thermoplastic polymers described above have customary additives. These are typically antioxidants, pigments, stabilizers, surfactants, waxes, flow promoters, solid solvents, plasticizers and other materials such as nucleating agents that are added to improve the processability of the thermoplastic composition.

The additives mentioned above are not the electrically conductive material used according to the invention.

yarn

The electrically conductive yarn according to the invention with a core-sheath structure made of a multifilament yarn core and an electrically conductive sheath has good mechanical properties on the one hand and good electrical conductivity on the other.

The yarn according to the invention preferably has a diameter in the range from 0.1 mm to 2.5 mm.

The yarn according to the invention preferably has 10 to 500 individual filaments in the multifilament yarn core.

The yarn according to the invention is electrically non-conductive in the multifilament yarn core.

The yarn according to the invention preferably has an elongation at break (=elongation at break) of at most 25%, in particular at most 20%, particularly preferably at most 15%.

The yarn according to the invention preferably has a maximum tensile strength in the range from 1500 to 3600 cN, in particular 1700 to 3600 cN, particularly preferably 2000 to 3600 cN.

The yarn according to the invention preferably has a tenacity in the range from 35 to 100 cN/tex, in particular from 50 to 100 cN/tex. The tenacity of the yarn according to the invention is thus lower than the tenacity of the core, since the sheath material is included in the determination of the tenacity, but makes no appreciable contribution to the tenacity. The yarn according to the invention preferably has a maximum bending force in the range from 0.5 to 20 cN, in particular 1 to 20 cN, particularly preferably from 2 to 20 cN, particularly preferably 5 to 20 cN.

The yarn according to the invention preferably has a flexural modulus in the range from 5 to 200 daN/mm ² , in particular from 10 to 200 daN/mm ² , particularly preferably 50 to 200 daN/mm ² , particularly preferably 100 to 200 daN/mm ² in the range from 120 to 180 daN/mm ² .

The yarn according to the invention preferably has a thermal shrinkage of at most 6%, preferably at most 5%.

The yarn according to the invention is electrically non-conductive in the multifilament yarn core. The term electrically non-conductive means an electrical conductivity of <10 ⁸ S/m.

The yarn according to the invention is electrically conductive in the sheath and has an electrical conductivity of at least 150 S/m.

The sheathing of the yarn according to the invention usually has a thickness of at least 10 μm, preferably at least 20 μm, particularly preferably at least 50 μm. The thickness is not limited as to the upper limit. The maximum thickness is usually 300 μm, so that the thickness is in the range from 10 μm to 300 μm, preferably from 50 μm to 300 μm, in particular in the range from 100 μm to 150 μm.

The sheath of the yarn according to the invention comprises 55 to 99% by weight thermoplastic elastomer and 1 to 45% by weight electrically conductive material, preferably 85 to 99% by weight thermoplastic elastomer and 1 to 15% by weight electrically conductive material, especially preferably 90 to 99% by weight thermoplastic elastomer and 1 to 10% by weight electrically conductive material, in particular 94 to 99% by weight thermoplastic elastomer and 1 to 6% by weight electrically conductive material.

In addition, the casing can also have the usual additives, in particular those that make it easier to process the casing compound.

Using the electrically conductive yarn

Another subject of the present invention are textile fabrics, in particular nonwovens, woven fabrics, knitted fabrics, knitted fabrics, grids, cables containing the yarn according to the invention.

The yarns according to the invention can be used in sensory applications, for example as pressure sensors in tires, and in biosensors in textiles. Furthermore, the yarns according to the invention can be used as an antistatic material, for example in assembly and conveyor belts and screens. Another application can be as a cable in data transmission or the yarn can be used in flexible electronic applications, for example as intelligent clothing or as a textile fleece material.

Production of the electrically conductive yarn

Another object of the present invention is a method for producing the electrically conductive yarn according to the invention.

The process for producing the electrically conductive yarn according to the invention comprises the steps: a) supplying a multifilament yarn with

(i) a tenacity of 40 to 300 cN/tex and

(ii) an elongation at break of not more than 25% and

(iii) a maximum thermal shrinkage of 6% and

(iv) a linear density of 100 to 1200 dtex for a multifilament yarn made from organic polymers or a diameter in the range from 200 to 600pm for a multifilament yarn made from non-organic materials, into the orifice of a round extrusion die, b) sheathing of the multifilament yarn supplied according to step a) by means of a round extrusion nozzle by extrusion of a mixture

(v) 55 to 99% by weight thermoplastic elastomer and

(vi) 45 to 1% by weight electrically conductive material,

(vii) electrically conductive material with an electrical conductivity of at least 3x10 ² S/m ,

(viii) the mixture forming the sheath with an electrical conductivity of at least 150 S/m

(ix) the sheath material, which has a thermal shrinkage of at most 6% c) cooling the sheathed yarn, preferably to room temperature (25°C), the yarn after cooling

(x) has an electrically conductive coating with a thickness of at least 10 pm, d) winding the yarn onto a suitable support, preferably in the form of a spool.

The sheathing, consisting essentially of thermoplastic elastomer and electrically conductive material, is usually extruded at temperatures in the range from 180 to 250° C., but at least 30° C. above the melting temperature of the thermoplastic elastomer of the sheath.

The sheathing is extruded in such a way that the sheathing material has little or no orientation, i.e. has predominantly amorphous structures and only small crystalline portions. The lower orientation can be determined by DSC or wide-angle diffraction. Further methods can be found in the dissertation by S. Bogner (2002) Institute for Textile and Fiber Research Stuttgart.

In addition, it is advantageous if the multifilament yarn to be sheathed is kept under tension. Depending on the viscosity of the molten casing, this is also built up - at least in part - by the braking effect of the molten component. A typical tensile stress is 5-15 cN, for example.

In addition, it is advantageous if the difference in the melting points of core and shell is at least 15°C, preferably at least 25°C, in particular at least 30-80°C.

The material forming the casing is usually dried beforehand and then fed to the extruder, with the extruder having a plurality of heating zones and cooling in the intake. In addition to the fleiz zones in the extruder, further fleiz zones can also be present outside in the direction of the spinning head. After installing the nozzles with the core yarn in the spinning head, the melted jacket material is directed laterally through a combination of nozzles onto the yarn (multifilament thread). This is followed by cooling, preferably in a water bath, and relaxation in a “chili unit”, with the covered yarn usually running over several godets without tension and then being wound up. If a thick sheathing occurs, the resulting weight of the sheathed yarn can lead to unsteady running, which can be corrected by applying a slight tension. In this case, a low voltage is usually applied across two godets, with the different speeds of the two godets being in the range of <0.5% lie.

The electrically conductive yarn according to the invention has the properties according to the invention without further stretching, so that damage by breaking up the percolating additive network does not occur. In addition, the special properties of the multifilament core, in particular the high specific strength, the low elongation at break and the high Young's modulus allow mechanical tension to be applied that can be maintained during the sheathing. The other special properties of the multifilament core, in particular the orientation and the low thermal shrinkage, mean that no thermal shrinkage is triggered during the sheathing and thus forces that occur that damage the percolating additive network in the sheathing are avoided. In addition, a very uniform thickness of the cladding is obtained.

Test Methods:

Unless already stated in the above description, the following measurement and test methods are used:

Denier of the multifilament yarn:

The titre is determined in accordance with DIN EN IS01973 for fibers made from organic polymers

Multifilament yarn diameter

The diameter is determined by optical methods using a microscope. Suitable microscopes are SEM, digital microscope, light microscope.

Young module

The Young's modulus is determined together with the determination of the maximum tensile force or the maximum tensile force elongation.

elongation at break

The elongation at break is determined in accordance with DIN EN ISO 2062:04/2010. heat shrink

The thermal shrinkage of the multifilament yarn (core) and the sheath is determined at 180° C. in accordance with the historical DIN 53866 T3 (03/1987). thickness

The thickness of the jacket material is determined using optical methods, i.e. examining the cross section using a microscope. Suitable microscopes are SEM, digital microscope, light microscope.

Electric conductivity

The electrical conductivity of the electrically conductive material is determined using a powder conductivity measuring stand, in which the powdery material is filled into a cylinder and compressed using a piston with a pressure of 30 MPa. The electrical resistance is continuously measured between two gold electrodes located on the top of the piston and on the bottom of the cylinder. The resistance measurements are carried out using 4-point technology (resistance less than 1000 ohms) or 2-point technology (resistance greater than 1000 ohms), with switching being carried out programmatically on the basis of the measurement data determined. The device is controlled as well as the data acquisition and evaluation is carried out by a tailor-made software based on Agilent VEE Version 9.3. Further information can be found in Composites Science and Technology 2015, 114, 119-125 by Beate Krause, Regine Boldt, Liane Häußler, Petra Pötschke, "Ultralow percolation threshold in polyamide 6.6 / MWCNT composites".

The electrical conductivity of the electrically conductive jacket material is determined in accordance with DIN 54345-5:07/1985

strength

The fineness-related strength is determined in accordance with DIN EN ISO 2062:04/2010

glass transition temperature

Determination by means of differential scanning calorimetry (DSC for short) with the following procedure:

Carrying out the DSC measurement under nitrogen, calibration against indium. nitrogen flow is 50 ml/min; Weight for fibers in the range of 2 - 3 mg. Temperature range from -50 °C to 210 °C @ 10 K/min then isothermal for 5 min and finally back to -50 °C @ 10 K/min

In general, the final temperature is always around 50 °C above the highest melting point to be expected.

DSC measurement is performed using a TA/Waters model Q100. Intrinsic viscosity (Hspez) (= specific viscosity)

The determination of the specific viscosity is measured on solutions with 1 g/l polymer in dichloroacetic acid at 25°C.

hardness

The hardness Shore A and Shore D is determined according to ISO 868 (DIN EN ISO 868:2003-10)

Vicat softening point VST

The Vicat softening point (A50) is determined according to ISO 306 at 50°C/10N (DIN EN ISO 306:2014-03)

melting temperature

The melting temperature is determined according to ISO 11357-1/-3 at 10°C/min. (DIN EN ISO 11357-1:2017-02 and DIN EN ISO 11357-3:2018-07)

melt flow rate

The melt mass flow rate is determined in accordance with DIN EN ISO 1133 (2012) at 190° C. and 230° C. (21.6 kg).

water absorption

The water absorption is determined at 23°C according to DIN EN ISO 62 (2008)

Tensile stress at break

Tensile stress at break is determined in accordance with DIN EN ISO 527-2/1A (2012).

maximum tensile strength

The maximum tensile force is determined in accordance with DIN EN ISO 2062:04/2010 maximum bending force

To determine the maximum bending force, the yarn is placed on a suitable measuring head on 2 supports. The natural curvature points downwards. The bending pin moves downwards and pushes the yarn through. At the end of the test section, the bending pin moves up again. The force is recorded, the maximum bending force and possibly the force at 10° deflection are evaluated. flexural modulus

The flexural modulus is determined according to the bending force.

Examples:

The present invention is illustrated by the following examples without being restricted thereby.

example 1

Coating with the composition/properties .

The compound used for the jacket is a SEBS TPS with 20-40% by weight carbon black as an electrically conductive additive. The compound has relatively large agglomerates of up to 90 pm in diameter, is black and in the form of granules. Its melting point is 152.2 °C.

Other properties are:

Before processing, the compound is dried at 60 °C for at least 4 hours and fed to the extruder without contact with air.

Yarn fed

A 280 dtex f 48 high-tenacity yarn with an elongation at break of 17.6%, a maximum tensile strength of 18.3 N and a maximum relative tensile strength of 683 mN/tex is used as the core yarn. The yarn is twisted /60.

test execution

A spinneret combination with a 0.3 mm inner and 0.65 mm outer nozzle is used to produce a conductive yarn with a thickness of 0.65 mm from a conductive SEBS/additive compound. The yarn presented is fed through the inner of the two spinnerets and the spinning head and through the water bath and via the gallettes to the winding unit. The spinnerets are firmly screwed into the spinning head and the winding process is started. The previously dried electrically conductive compound is fed into the extruder and heated there in 3 heating zones to approx. 210 °C until the appropriate viscosity is reached. The melt is fed to the running yarn via the extruder, with the start of the coating process being clearly indicated by the color change of the yarn from white to black recognizable. Depending on the winding speed, the extruder speed is adjusted so that the yarn reaches the maximum diameter of 0.65 mm and then no longer increases.

Covered Yarn Test Data

The figures show the force/elongation diagram of the yarn described in Example 1, as well as microscopic photographs of the same yarn.

FIG. 2 shows a micrograph of a yarn according to the invention from example 1.

FIG. 3 shows a micrograph of a yarn according to the invention from Example 1.

FIG. 4 shows a microscopic photograph of the cross section of a yarn according to the invention according to example 1.

Claims

patent claims

1. Electrically conductive yarn with a core-sheath structure comprising:

(i) a core of at least one multifilament yarn,

(ii) a jacket comprising a mixture of

(iia) thermoplastic elastomer and

(iib) at least one electrically conductive material, characterized in that

(iii) the core multifilament yarn

(iiia) has a tenacity of 40 to 300 cN/tex, (iiib) has an elongation at break of at most 25%,

(iv) the coat

(iva) is in contact with the core and completely encloses it,

(ivb) has a thickness of at least 10 μm,

(ivc) has an electrical conductivity of at least 150 S/m,

(ive) 1 to 45% by weight of electrically conductive material.

(ivf) 99 to 55% by weight thermoplastic elastomer,

(ivg) the jacket material has a maximum thermal shrinkage of 6%.

2. Yarn according to claim 1, characterized in that the tenacity of the multifilament yarn in the core is 50 to 280 cN/tex, preferably 60 to 260 cN/tex.

3. Yarn according to claim 1 or 2, characterized in that the core of the multifilament yarn has an elongation at break of at most 20%.

4. Yarn according to claim 1, 2 or 3, characterized in that the core of the multifilament yarn is electrically non-conductive.

5. Yarn according to one or more of claims 1 to 4, characterized in that the multifilament yarn in the core is a multifilament yarn of aramids, polyesters, polyamides, carbon, glass, mineral fibres, or mixtures of two or more of the aforementioned materials.

6. Yarn according to one or more of claims 1 to 4, characterized in that the multifilament yarn comprises one or more thermoplastic polymers in the core, preferably the thermoplastic polymers comprise melt-spinnable synthetic polycondensates, in particular aliphatic polyesters, aryl-aliphatic polyesters, aromatic polyesters and their co-/ter-polymers.

7. Yarn according to one or more of claims 1 to 6, characterized in that the core of the multifilament yarn consists of a polyester, preferably a polyester based on aromatic dicarboxylic acids, and which

(i) a tenacity of 40 to 300 cN/tex, in particular of 60 to 100 cN/tex,

(ii) a titre in the range from 100 to 1200 dtex, particularly preferably 250 to 500 dtex, and

(iii) an elongation at break of at most 25%, preferably at most 20%, and

(iv) a thermal shrinkage of at most 6%, preferably at most 3%.

8. Yarn according to one or more of claims 1 to 7, characterized in that the sheath is in direct contact with at least 90% of the surface of the multifilament yarn in the core.

9. Yarn according to one or more of claims 1 to 8, characterized in that the sheath contains 85 to 99% by weight of thermoplastic elastomer and 1 to 15% by weight of electrically conductive material, preferably 90 to 99% by weight of thermoplastic elastomer and 1 to 10% by weight of electrically conductive material, in particular 94 to 99% by weight of thermoplastic elastomer and 1 to 6% by weight of electrically conductive material.

10. Yarn according to one or more of claims 1 to 9, characterized in that the sheath comprises one or more thermoplastic elastomers selected from the group TPO, TPV, TPS, TPU, TPA and/or TPC.

11. Yarn according to one or more of claims 1 to 10, characterized in that the sheath has one or more thermoplastic elastomers whose Vicat softening point VST (50°C/10N) is at least 50°C, preferably at least 60°C, in particular at least 100°C.

12. Yarn according to one or more of claims 1 to 11, characterized in that the sheath has one or more thermoplastic elastomers whose melting point is in the range from 140 to 190°C, in particular in the range from 150 to 175°C.

13. Yarn according to one or more of claims 1 to 12, characterized in that the thermoplastic elastomer in the form of the sheath component has a melt flow rate of at most 13 g/10 min (190°C), in particular of at most 11 g/10 min (190 ° C), particularly preferably of a maximum of 10 g / 10 min (190 ° C).

14. Yarn according to one or more of claims 1 to 13, characterized in that the thermoplastic elastomer in the form of the sheath component has a melt flow rate of at most 50 g/10 min (230°C), in particular of at most 30 g/10 min ( 230°C), particularly preferably not more than 20 g/10 min (230°C).

15. Yarn according to one or more of claims 1 to 14, characterized in that the sheath comprises one or more electrically conductive materials selected from the group of carbon nanotubes (CNT) and/or graphene.

16. Yarn according to one or more of claims 1 to 15, characterized in that the sheath comprises one or more electrically conductive materials, and these comprises particles with a particle size of more than 2 μm.

17. Yarn according to one or more of claims 1 to 16, characterized in that the diameter is 0.1 mm to 2.5 mm.

18. Yarn according to one or more of claims 1 to 17, characterized in that the yarn has an elongation at break of at most 25%, preferably at most 20%, particularly preferably at most 15%.

19. Yarn according to one or more of claims 1 to 18, characterized in that the yarn has a maximum tensile strength in the range from 1500 to 3600 cN, preferably 1700 to 3600 cN, in particular 2000 to 3600 cN.

20. Yarn according to one or more of claims 1 to 19, characterized in that the yarn has a maximum bending force in the range from 0.5 to 20 cN, preferably 1 to 20 cN, in particular 2 to 20 cN, particularly preferably 5 to 20 cN , having.

21. Yarn according to one or more of claims 1 to 20, characterized in that the yarn has a flexural modulus in the range from 5 to 200 daN/mm ² , preferably 10 to 200 daN/mm ² , in particular 50 to 200 daN/mm ² , particularly preferably 100 to 200 daN/mm ² , in particular in the range from 120 to 180 daN/mm ² .

22. Yarn according to one or more of claims 1 to 21, characterized in that the yarn has a thermal shrinkage of at most 6%, preferably at most 5%.

23. Yarn according to one or more of claims 1 to 22, characterized in that the sheath has a thickness of at least 20 μm, preferably at least 50 μm

24. A method for producing the yarn defined in claims 1 to 23, comprising the steps of: a) feeding a multifilament yarn with

(i) a tenacity of 40 to 300 cN/tex and

(ii) an elongation at break of not more than 25% and

(iii) a maximum thermal shrinkage of 6% and

(iv) a linear density of 100 to 1200 dtex for a multifilament yarn made from organic polymers or a diameter in the range from 200 to 600pm for a multifilament yarn made from non-organic materials, into the orifice of a round extrusion die, b) sheathing of the multifilament yarn supplied according to step a) by means of a round extrusion nozzle by extrusion of a mixture (v) 55 to 99% by weight thermoplastic elastomer and

(vi) 45 to 1% by weight electrically conductive material,

(x) has an electrically conductive coating with a thickness of at least 10 μm, d) winding the yarn onto a suitable carrier, preferably in the form of a spool.

25. Use of the yarn defined in claims 1 to 23 for the production of (i) textile fabrics, in particular nonwovens, woven fabrics, knitted fabrics, knitted fabrics, grids, (ii) cables, (iii) sensors, (iv) as an antistatic material, in particular in, for example, assembly and conveyor belts or screens, (v) in data transmission or (vi) in flexible electronics applications.

26. Textile fabric containing one or more yarns defined in claims 1 to 23.