DE102009011553B4 - Process for producing a material insulated from electric current and insulated material produced thereby - Google Patents

Abstract

A method of making a material insulated from electric current comprising (a) providing a first substrate having a surface, (b) applying a planar insulating paste comprising a dispersible uncharged thermoplastic polyurethane having free hydroxyl groups, a water-soluble thickener, a crosslinker, and water wherein the insulating paste does not comprise a conductive polymer and a conductive filler on the surface or portions of the surface; and (c) solidifying the insulating paste by crosslinking.

Description

Technical area

The invention relates to a process for the production of electrically insulated materials using an insulating paste, including, inter alia, a dispersible thermoplastic polyurethane, a water-soluble thickener and water according to the claims. The invention also relates to an insulated material produced by this method according to the claims.

State of the art

Electrical traces, such as cables or traces in printed circuit boards, are usually isolated with layers of organic polymers. In the production of thermoplastic polymers, such as polyurethanes, are often used in the extrusion or injection molding process.

In the prior art aqueous solutions of prepolymers and conductive particles are known, which are applied in liquid form on surfaces. The prepolymers are crosslinked in the solution to (thermoplastic) polyurethanes, so that conductive layers are obtained. Such solutions are usually applied to an insulating layer, such as a nonwoven fabric, to obtain a single-sided insulated conductive material.

The EP 1284278 A2 describes an aqueous coating composition for the production of electrically conductive coatings of textiles. The pastes described therein are used, for example, to coat flat layers, in particular textiles and nonwovens, and to equip them with electrical conductivity.

In the case of these pastes known from the prior art, it is disadvantageous that, as a result of the binder, after application to the material and curing, it is often no longer or not sufficiently extensible and no longer thermally deformable. A coated with the paste material is therefore also not stretchable. The paste can therefore not be used where stretchability of the material is required.

The conductive particles on the surface of the conductor are not protected against external influences and can, for. B. be attacked during cleaning operations of printed textiles.

The DE 10 2007 042 253 A1 discloses printable and conductive pastes and methods for coating a material with the paste.

The DE 197 37 685 A1 discloses a conductive ink for the preparation of a conductive surface coating containing metal powder and a resin binder.

The DE 197 57 542 A1 discloses a screen printing paste for producing electrically conductive coatings containing a solution or dispersion of a conductive polymer.

Object of the invention

The invention has for its object to overcome the problems described above. In particular, new and improved insulating coatings and processes for their preparation are to be provided, which are particularly suitable for insulating printed conductors. The coating should be easy to prepare and overcome the problems of known coatings.

The invention is in particular the object of providing an insulating coating which is flexible and stretchable. The coating should be simple and inexpensive to produce. The procedures and materials used should be as simple and safe as possible for the user and manufacturer.

Another object of the invention is to provide an electrically conductive material which is insulated from the outside and which is flexible and expandable. The material should have an electrical conductivity in the Ω range and have a high dielectric strength due to the insulation. Also multilayered Laminates of insulating and conductive layers should be simple and inexpensive to produce.

Object of the invention:

This object is achieved by methods and materials according to the claims. In advantageous embodiments, the dependent claims relate.

• (a) Bereitstellen eines ersten Substrats mit einer Oberfläche,
• (b) flächiges Auftragen einer Isolierpaste, enthaltend ein dispergierbares ungeladenes thermoplastisches Polyurethan, das freie Hydroxylgruppen aufweist, einen wasserlöslichen Verdicker, einen Vernetzer und Wasser, wobei die Isolierpaste kein leitfähiges Polymer und keinen leitfähigen Füllstoff aufweist, auf die Oberfläche oder Teilbereiche der Oberfläche und
• (c) Verfestigen der Isolierpaste durch Vernetzen.

The invention relates to a method for producing a material isolated from electrical current, comprising

• (a) providing a first substrate having a surface,
• (b) applying flat an insulating paste containing a dispersible uncharged thermoplastic polyurethane having free hydroxyl groups, a water-soluble thickener, a crosslinker and water, the insulating paste having no conductive polymer and no conductive filler on the surface or portions of the surface and
• (c) solidifying the insulating paste by crosslinking.

The term "insulating paste" means that the paste is suitable for producing an insulating coating. The insulation is against electrical current, in particular of printed conductors within an object isolated with the paste. The paste is also suitable for insulation against other influences such as heat and cold, radiation and mechanical or chemical action. The coating essentially does not conduct the electrical current after solidification. The insulating paste therefore contains no conductive polymer and no conductive filler. In contrast, since the paste itself is preferably an aqueous dispersion, it is slightly conductive in the non-solidified state because of its water content.

The thermoplastic polyurethane is stretchable and thermoformable. Thus, the paste is stretchable even after processing and can be reshaped by thermal forming processes at any time, while the stretchability is maintained.

The viscosity of the paste is determined via the water-soluble thickener. According to the invention, this is between 8,000 and 150,000 mPas, preferably between 20,000 and 150,000 mPas, so that the paste can be applied to a material by a printing process, preferably screen printing or stencil printing.

The insulating pastes may contain between 3 and 98 wt .-%, preferably between 5 and 95 wt .-% or between 20 and 85 wt .-%, particularly preferably between 30 and 75 wt .-% thermoplastic polyurethane. It is preferably between 0.1 and 15 wt .-%, preferably 0.2 and 10 wt .-%, thickener included. Preferably, 0 to 30 wt .-%, in particular 0.5 to 25% of an additional binder. In addition, greater than 0 to 30 wt .-%, in particular 0.2 to 15 wt .-% or 0.5 to 10 wt .-% crosslinker may be included.

In a preferred embodiment, the paste contains 5 to 95% by weight of thermoplastic polyurethane, 0.2 to 10% by weight of thickener, 0 to 30% by weight of an additional binder, greater than 0 to 25% by weight of crosslinking agent and 2 to 94.8% by weight of water.

In the dry substance are preferably fractions of 50 to 99.9 wt .-%, preferably 80 to 99.8 wt .-% thermoplastic polyurethane, 0.1 to 5 wt .-% thickener and 1 to 50 wt .-% additional binder contain, supplemented by up to 45 wt .-% further additives.

The thickener is provided in a preferred embodiment as an aqueous thickener solution. The thickener solution contains, for example, 0.2-15% by weight of the thickener dissolved in water. Preference is given to using distilled or bidistilled water. In the pastes, the proportion of the thickener paste is preferably 40-80% by weight, particularly preferably 55-75% by weight. The paste is preferably water-based. It thus contains no organic solvents or less than 5, 2.5 or 1 wt .-% organic solvent.

The paste may contain adjuvants such as humectants, defoamers and rheological additives to improve processability.

In a preferred embodiment of the invention, the thickener contains cellulose derivatives, a diurethane or a non-thermoplastic polyurethane.

The thickener may contain or consist of cellulose derivatives, for example methylcellulose. Cellulose derivatives are chemical compounds derived from cellulose. The result is a hydrophilic powder which forms a viscous solution with water. Cellulose derivatives are not digestible, non-allergenic and non-toxic and therefore also suitable for the production of a paste for coating clothing textiles. A suitable thickener of methyl cellulose is, for example Metylan ^® Normal (MHEC 9000; methylhydroxyethylcellulose with viscosity of a 2% solution of 9000 mPas and Henkel, Dusseldorf).

In a further preferred variant, the thickener may be an aqueous solution of a diurethane (for example a fatty alcohol ethoxylate urethane) which optionally contains water-miscible organic solvents, such as, for example, B. may contain butyl (di) glycol, propylene glycol and / or isopropanol. Such a suitable thickener is, for example, Collacral PU 75 ^® or Collacral PU85 ^® (BASF Ludwigshafen). The solids content of the thickener Collacral is about 25-28 wt .-%.

The thickener may be a non-thermoplastic polyurethane. "Non-thermoplastic" means that the thickener is present in the solution in molecularly dissolved or dispersed form and not in the form of thermoplastic particles. After applying and drying the paste, however, the thickener may have thermoplastic properties. The thickener may be an electrolyte-stabilized thickener systems based on nonionic polyurethanes. Such a thickener may contain small amounts of solvents such. B. 2-butoxyethanol. A suitable thickener based on nonionic polyurethanes is, for example, ^® Ruco Coat TH 5005 (Rudolf Chemie, Geretsried). Also suitable is "Thickener 128" (Schill and Seilach).

The advantage of the said thickeners, which are not based on cellulose derivatives, is the film-forming properties during drying, so that the calendering process can be carried out with far less pressure, if necessary even completely omitted. For example, very pressure-sensitive surfaces, such. As low-melting nonwovens or demanding (3D) geometries are printed. Using these thickeners, when used in the insulating paste not only a good insulation effect, but also a significantly improved tensile strength could be determined.

The paste according to the invention contains thermoplastic polyurethanes (PU). Polyurethanes are essentially formed by the reaction of polyols (long-chain diols), diisocyanates and optionally short-chain diols. It may also contain small amounts of long or short chain tri- or higher functional alcohols and amines. The nature of the starting materials, the reaction conditions and the proportions are responsible for the properties of the product. The polyol has an increased influence, for example, the cold flexibility, the media or hydrolysis resistance or the rebound resilience; while the isocyanate and the chain extender are more likely to affect hardness, heat resistance or settling / remanence. As polyols in particular polyester, polycarbonate or polyether polyols are used. Methods are known to the person skilled in the art to select the starting materials and the reaction conditions in such a way that polyurethanes having desired properties, for example melting point, density and hardness, are obtained. Thermoplastic polyurethane elastomers are also referred to as TPUs.

The thermoplastic polyurethane may have a melting point between 80 and 250 ° C, in particular between 100 and 220 ° C, between 100 and 180 or between 110 and 150 ° C. Such polyurethanes can be used without problems on textiles and can be processed and formed by conventional methods, such as calendering or thermoforming. The melting point of the polyurethane is adjusted with regard to the desired processing method and the material to be coated. Therefore, depending on the application, higher-melting polyurethanes with melting points approximately between 120 and 220 ° C., in particular above 130 or 140 ° C., or low-melting polyurethanes with melting points approximately between 80 and 120 ° C., in particular below 110 ° C., are used. Polyurethanes usually do not have a clearly defined melting point, but a melting range in which the material changes from the solid to the liquid state. According to the invention, the melting point is the temperature at which this melting process begins. The use of ether- or carbonate-based polyols has the advantage that resulting polyurethanes are particularly resistant to hydrolysis and are therefore particularly suitable for printing on washable textiles.

The polyurethanes may be aliphatic or aromatic. Aliphatic polyurethanes have the advantage that they are generally lightfast and do not yellow.

The polyurethanes are preferably stirred into the pastes as fine powders. The thermoplastic polyurethane is preferably in the form of particles having an average particle diameter of <350 μm, preferably <200 μm or <120 μm, in particular between 20 and 350 μm, between 50 and 200 μm or between 80 and 120 μm. The small particle size makes it possible to produce a homogeneous dispersion, improves the pressure behavior and accelerates the manufacturing process due to rapid melting.

In a preferred embodiment of the invention, the polyurethane used according to the invention contains no free reactive groups, in particular no free isocyanate groups. Such thermoplastic polyurethanes are obtained, for example, when the reaction between the polyol, the chain extender and the polyisocyanate is carried out with a stoichiometric excess of diol and / or polyol, so that the polymer has only free, for example terminal, hydroxyl groups. In this embodiment, therefore, the polyurethane is not a reactive polymer, but cured. Such a polyurethane does not react under normal conditions and in aqueous solution. The polyurethane thus differs from commercially available prepolymers with free isocyanate groups. Such prepolymers are offered, for example, in the form of dispersions.

The polyurethanes are uncharged polyurethanes. Thus, no ionic polyurethanes are included. The paste usable according to the invention thus differs from compositions EP 1 284 278 , Uncharged polyurethanes are generally not or only poorly dispersible in water. Pastes with uncharged polyurethanes that can be used according to the invention are preferably suspensions in which polyurethanes are finely distributed as solids (particles). The ionic polyurethanes, for example, according to EP 1 284 278 are used, however, are dispersed in an aqueous solution in molecular form. Commercially available polyurethane dispersions (such as the brand ROTTA WS 80525 from Rotta GmbH) are usually prepared by dispersing a liquid and still reactive polyurethane prepolymer under very high shear with an emulsifier. Often, such a dispersion still contains solvents which are subsequently removed from the PU dispersion. The ionic groups of the polyurethane thereby increase the dispersibility and thus the storage stability, because settling of the polyurethane particles (density about 1.1) due to the mutual repulsion is prevented or greatly reduced. Ionic polyurethanes resulting from the drying of these (emulsifier-containing) dispersions have the disadvantage that the water absorption and swelling in water due to the hydrophilicity of the ionic groups is significantly higher than nonionic polyurethanes.

However, if the viscosity of the paste is adjusted so that the polyurethane particles do not fall, the use of emulsifiers is not required. In a preferred embodiment of the invention, the paste contains no emulsifiers.

Thermoplastic polyurethanes suitable according to the invention can be prepared, for example, from the isocyanates diphenylmethane diisocyanate (MDI), such as 2,2-, 2,4- and / or 4,4'-diphenylmethane diisocyanate, hexamethylene-1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI ), Tolylene diisocyanate (TDI), naphthylene-1,5-diisocyanate (NDI), dimethyl-diphenyl-diisocyanate TODI), dicyclohexyl-methane-4,4'-diisocyanate (HMDI).

Suitable polyols for the preparation of the polyurethanes are polyethers, for. As polytetrahydrofuran (PTHF) or polypropylene glycol (PPG), polyester, z. B. Ethylenadipatpolyol, Butylenadipatpolyol, NPG adipates, polycarbonate polyols and polycaprolactone and Polyetheresterpolyole. These may also be trifunctional and polyfunctional in a linear or too low proportion.

These are optionally used in conjunction with suitable chain extenders. Suitable chain extenders are, for example, short-chain diols such as ethylene glycol, propanediol, butanediol, pentanediol, diethylene glycol, hexanediol, cyclohexanedimethanol (CHDM), hydroquinone hydroxyethyl ether (HQEE) and diamines and in small amounts triamines or triols such as. B. trimethylolpropane and higher functional amines and alcohols or thiols.

Particularly preferred is the use of polyurethanes of ethylene glycol-adipic acid-polyester polyol, butanediol, hexanediol and diphenylmethane-4,4'-diisocyanate. Such a TPU, for example, has a melting point of about 135 ° C.

For applications at lower temperatures, for example, a TPU made of polycaprolactone polyol or carbonate polyol and 1,6-hexamethylene diisocyanate is extended with the chain extenders: 1,6-hexanediol and 1,4-butanediol. Polyols can be used to reach melting temperatures of the TPU below 110 ° C from neopentyl glycol adipate or, instead, further isomers of butanediol or other diols such as neopentyl glycol may be added.

A suitable thermoplastic polyurethane can be prepared for example from the components methylene diphenyl isocyanate, polycarbonate / hexanediol neopentyl glycol adipate and butanediol. The thermoplastic polyurethane has a melting range of 160 to 170 ° C. Such higher melting polyurethanes usually have a Shore hardness of 60 to 98 Shore (A) and are due to the crystallization especially for thermoforming processes.

Another polyurethane comprises the components methylene diphenyl isocyanate, polycaprolactone and hexanediol. This thermoplastic polyurethane has a melting range of 125 to 135 ° C. Low-melting polyurethanes often have a Shore hardness of 40 to 85 Shore (A) and are then particularly suitable for use on low-melting materials.

A preferred hydrolysis-stable, low-melting polyurethane comprises the components hexamethylene diisocyanate, polycarbonate polyol and hexanediol and butanediol (isomers). By suitable selection and combination of chain extenders and the proportions of the respective polyols and isocyanates, the melting point of such described polyurethanes can be set arbitrarily between about 80 ° C to about 230 ° C.

The paste contains a crosslinker. The polyurethane contains crosslinkable hydroxyl groups. It is, for example, a polyurethane which has a low characteristic number, for example <99, <98, or <95, in particular> 80, or from 70 to 98 (characteristic number = n (NCO) / n (OH) x 100). In a preferred embodiment of the invention, the polyurethanes in crosslinking pastes have a melting point below 120 ° C., in particular below 110 ° C. The melting point is then for example between 80 and 120 ° C or 90 and 110 ° C. The crosslinker is a compound capable of linking hydroxyl groups, preferably a diisocyanate or polyisocyanate. In a preferred embodiment of the invention, the crosslinker is a blocked isocyanate, which has a crosslinking effect above a defined temperature, for example 70-10 ° C.

The melting point of the thermoplastic polyurethane can be adjusted to values below 120 ° C or 110 ° C by selection of suitable polyols and chain extender combinations. Such polyurethanes can be used if the substrate to be printed has a low melting point itself (eg in the case of a stretchable PU nonwoven fabric). A melting point below 110 ° C. can be achieved, for example, with polycaprolactone polyol and additionally polyol from neopentyl glycol adipate and use of several chain extenders (1,6-hexanediol, 1,4-butanediol and 2,3-butanediol) and 1,6-hexamethylene diisocyanate , To increase the temperature stability of the coated materials, it is possible to add a crosslinker to this low-melting paste. An inventively employable crosslinker which is added to these pastes, z. B. ground isocyanate, such as. Example, diphenylmethane-4,4'-diisocyanate (MDI) or 3,3'-dimethylbiphenyl-4,4'-diisocyanate (TODI), having a melting point below 110 ° C. In the aqueous paste, a thin urea layer is formed on the isocyanate powder surface by reaction of isocyanate and water, which causes the water permeability and thus the urea reaction inside the isocyanate particles to be greatly slowed down. The paste is therefore storage stable. During the calendering process, the polyurethane and the isocyanate melt and the crosslinking reaction of the isocyanate with the free OH groups of the polyurethane occurs. In this case, the crosslinkability of advantage, since sensitive substrates can be printed and the crosslinking reaction, the temperature stability of the coated materials is increased.

In a preferred embodiment, latent reactive and / or capped isocyanates are used. The paste is latently reactive and crosslinks in the calendering process, so that the melting point increases; As a result, a further printing and calendering process on the previously prepared conductor track is possible. Suitable for a latent-reactive isocyanate system is z. MDI powder, TODI powder, HDT or HDB (Bayer). As a capping agent for isocyanates z. B. pyrazole (eg triazole, reacts at about 120 ° C), oxime (react at 130 ° C), caprolactam (reacts at about 155 ° C) in question. By adding a catalyst (eg DABCO) to the paste, the reaction temperature (and the cleavage temperature of the capped system) can be lowered.

The addition of a solid, at temperatures above about 50 ° C liquid, polyhydric alcohol, such as di-trimethylolpropane, which additionally reacts with the isocyanate, leads to a further increase in melting point by crosslinking. Instead of Di-TMP and MDI can also be used as Cross-linking components other polyols and isocyanates such. As trimethylolpropane, HQEE and TODI or NDI powder can be used.

Another variant is the addition of a polyfunctional, less reactive in room temperature, liquid isocyanate such as the biuret or trimer of z. As hexamethylene diisocyanate (Tolonate ^® HDB or Tolonate ^® HDT) or isophorone diisocyanate (Tolonate ^® IDT), (Rhodia, Freiburg).

In a preferred embodiment, a prepolymer is used as crosslinker. This is especially solid at room temperature and preferably long-chain. Preferred are a prepolymer of a polyisocyanate having at least 2 free isocyanate groups and a prepolymer of a polyhydric alcohol having at least 2 hydroxyl groups, which may additionally contain free isocyanate. Preference is given to a di- or higher-functional polyol which has been reacted terminally with a diisocyanate. The prepolymer itself may also contain free isocyanate. The prepolymer is cooled after production and added as a powder to the insulating or conductive paste. This type of post-crosslinking is generally possible not only in aqueous systems, but also generally in thermoplastic, OH-terminated polyurethanes.

Postcrosslinking pastes are particularly suitable for a multilayer construction. The PU is after the post-crosslinking, which takes place for example during the lamination, no longer thermoplastic and has a higher melting point. When applying or processing an overlying layer, for example during lamination, the crosslinked layer is no longer melted or deformed.

As an alternative to the use of post-crosslinking pastes, multilayer printing also makes it possible to use pastes in which the melting temperature of the TPU decreases from the first to the next printed layer. Thus, the next layer can be laminated at a lower temperature without the underlying layer being melted again.

In a preferred embodiment, the paste contains an additional binder. This serves in particular to improve the film-forming properties. Preferably, the additional binder is a polymer dispersion, which is preferably molecular. A preferred binder is, for example, a polyurethane dispersion. This forms a film during drying of the paste and combines the TPU powder contained in the paste even better together. A suitable binder according to the invention is, for example Emuldur ^® DS2360 Fa. BASF (Ludwigshafen, Germany). Emuldur ^® DS2360 is an anionic aqueous polyurethane dispersion having a solids content of 39-41 wt .-%. Such binders differ from the thermoplastic polyurethane particles of the pastes in that the polyurethanes are present substantially in molecularly dispersed form and not in particulate form.

Another preferred binder is, for example, the aqueous dispersion of a polymer based on acrylic ester and / or styrene. A suitable binder according to the invention is, for example, Acronal DS2337 (BASF, Ludwigshafen). Acronal DS2337 is an aqueous dispersion of a polymer based on acrylic acid ester and styrene with a solids content of 54-56%.

The preparation of the paste is preferably carried out by first an aqueous solution is provided from the thickener (thickener solution). Preferably, the thickener swells while being stirred for a sufficient time, for example 10 to 30 minutes. A suitable viscosity is set, for example between 1,500 and 20,000 mPas.

Subsequently, the thermoplastic polyurethane and the crosslinker are added and mixed by stirring to a homogeneous paste. The paste is preferably degassed. If a pulverulent crosslinker is used, it is preferably first mixed with the PU powder in order to achieve a more homogeneous distribution.

In one embodiment of the invention, the paste has a pH of from 6 to 8.5, preferably from 7 to 7.5. The pH is in a preferred embodiment at about pH 7.0. These pHs are also preferably adjusted when antioxidants are included. By adjusting the pH in this range, by using antioxidants and by producing and storing in the absence of air, undesirable changes in the pastes can be avoided.

The first substrate is a solid substrate and may have a layered structure or other three-dimensional structure. The application of the insulating paste (b) is carried out by conventional methods, such as printing, brushing, spraying, dipping the substrate or rolling. "Flat" means a movie or a layer arises. "Subregions of the surface" means that structures can be produced on the surface during application, the insulating paste being applied only in specific areas and other subregions being omitted.

In the method according to the invention, the two-dimensional application (b) is preferably carried out by printing. Decisive for the printability are the particle size and the dependent on the proportion of thickener viscosity of the paste. The printing process makes it possible to easily and inexpensively print large areas with a reproducible pattern. After the printing process, the paste is dried, for example, in a continuous furnace. In a preferred embodiment, the paste is printed on at least one material and then dried and subjected to the material printed with the paste of a combined heat and pressure treatment.

According to the invention, solidification (c) of the insulating paste takes place by crosslinking. The solidification (c) may be in conjunction with drying and / or heating. The material provided with the paste may be subjected to a combined heat and pressure treatment before, during or after solidification (c).

In a preferred embodiment, the upper insulating layer and / or the insulated material are thermally deformed following the combined heat and pressure treatment.

In a preferred embodiment of the invention, the first substrate has at least one conductor track in step (a). These may be known printed conductors and structures, such as wires or foils of metals, for example of copper, silver or gold, in particular copper wires and foils, or other metal tracks, as are common in electronic components such as printed circuit boards, circuit boards and chips. The first substrate may also have semiconductor structures, for example based on silicon, germanium and gallium.

The advantage of the printing technique is given by the simplicity of the process, even complex geometries easily produce and can also isolate them. Likewise, this insulation as well as the conductor track thus produced is stretchable and thermally deformable. For each insulation further conductor structures consisting of conductor tracks can be printed, so that a multi-layered, extensible or thermally deformable conductor system is produced. Consequently, a conductor system consists of several superimposed and also penetrating planes of conductor structures, which are electrically insulated from one another by layers of insulating paste. Furthermore, it is conceivable to electrically shield a conductor system on the two main sides of a flat layer, consisting of conductive paste to the outside. This shield is also electrically separated from the conductor system by a layer of insulating paste.

In a preferred embodiment of the invention, prior to step (a), the first substrate of step (a) is prepared by printing at least one conductive line on the surface of a second substrate using a conductive paste.

In a preferred embodiment of the invention, a conductive paste containing a dispersion of a polyurethane and a conductive filler is used in step (a1) for printing.

In a preferred embodiment of the invention, prior to step (a1), the method comprises the step of (a2) producing the second substrate by printing an insulating layer on a third substrate.

In a preferred embodiment, conductor tracks and optionally a further insulated layer, which is preferably an insulating layer according to the invention, are applied to the isolated material obtained in step (c).

In a preferred embodiment of the invention, the insulating paste and the conductive paste are crosslinkable. Preferably, the insulating paste is crosslinked after printing so that a cross-linking of the conductor track or the conductive paste is carried out with the insulating paste. In these embodiments, it is preferred that the layers to be crosslinked contain polymers having free hydroxyl groups. The use of layers or pastes with polyurethanes having free hydroxyl groups is preferred. However, the crosslinking, in particular the insulating paste, can also be carried out to other polymers which have free hydroxyl groups on the surface, such as silicones or other hydrophilic or hydrophilicized plastics.

In this case, the insulating paste and the conductive paste preferably each contain a thermoplastic polyurethane having free hydroxyl groups and at least one crosslinker consisting of a polyisocyanate with at least 2 isocyanate groups and / or a polyhydric alcohol is selected with at least 2 hydroxyl groups.

As a conductive and printable paste pastes known in the art can be used according to the invention. Such conductive pastes contain, for example, polymers, binders, thickeners and / or fillers. The conductivity is effected by conductive polymers, metals, metal salts, metal oxides, carbon in a suitable form, fibers or other additives. Printable pastes are for example off EP 1 284 278 A2 . US 5,389,403 A. or DE 197 57 542 A2 known.

It is inventively preferred to use pressure and conductive pastes, which in PCT / EP2008 / 007235 or DE 102007042253 to be discribed. Among other things, these pastes are distinguished from known pastes in that they are both flexible and extensible. The printed and conductive pastes disclosed in these two applications are incorporated herein by reference. The printable and conductive pastes described therein contain a dispersible thermoplastic polyurethane, a conductive filler, a water-soluble thickener, and water. The thermoplastic polyurethane forms the binder of the paste and is both ductile and thermoformable. Thus, the paste is stretchable even after processing and can be formed by thermal forming processes, while maintaining the stretchability. The conductive filler is mixed in such a way that the conductive particles touch each other after processing, thus establishing the conductivity. The viscosity of the paste is determined via the water-soluble thickener. According to the invention, this is between 8,000 and 150,000 mPas, preferably between 20,000 and 150,000 mPas, so that the paste can be applied to a material by a printing process, preferably screen printing or stencil printing.

Conductive pastes which can be used according to the invention can contain, for example, between 2-40% by weight, preferably 4-25% by weight, particularly preferably 5-15% by weight of thermoplastic polyurethane. The proportion of the conductive filler is preferably 2-40 wt .-%, in particular 15-40 wt .-%, particularly preferably 20-35 wt .-%. It is preferably between 1 to 5 wt .-%, preferably 1.5-3 wt .-%, thickener included. Preferably, 0 to 30 wt .-%, in particular 0.5 to 25% of an additional binder. In addition, from 0 to 30% by weight, in particular from 0.2 to 15% by weight, or from 0.5 to 10% by weight, of crosslinking agent may be present. In the dry substance thus proportions of 15 to 80 wt .-%, preferably 15 to 40 wt .-% thermoplastic polyurethane, 15 to 85 wt .-% of conductive filler and 0.5 to 4.5 wt .-% thickener.

The sheet resistance of the conductive paste after drying and calendering is preferably between 0.05 to 0.5 ohms, wherein the resistance increases by a factor of 10 to 1000 when the paste is stretched by 20%, depending on the composition. In this case, the higher the proportion of the conductive filler, the lower the resistance.

The paste may contain adjuvants such as humectants, rheological additives and defoamers to improve processability. Preferred defoamers are silicone-free (BYK-A-535, BYK-Chemie).

The thickener of the conductive paste is preferably selected as described above for the insulating paste. It may contain, for example, corresponding cellulose derivatives, a diurethane or a non-thermoplastic polyurethane.

The thermoplastic polyurethanes (PU) of the conductive paste and their properties, such as melting point and particle size, can be selected as described above for the isolator paste.

In one embodiment of the invention, a crosslinker is included in the conductive paste, or a crosslinker is added to the paste before or during processing. The polyurethane in this embodiment contains crosslinkable hydroxyl groups. It is, for example, a polyurethane which has a low characteristic number, for example <99, <98, or <95, in particular> 80, or of 80-98 (characteristic number = n (NCO) / n (OH) x 100). In a preferred embodiment of the invention, the polyurethanes in crosslinked pastes have a melting point below 120 ° C., in particular below 110 ° C. The melting point is then for example between 80 and 120 ° C or 90 and 110 ° C. The crosslinker is a compound capable of linking hydroxyl groups, preferably a diisocyanate or polyisocyanate or a dialcohol or polyhydric alcohol. In a preferred embodiment of the invention, the crosslinker is a blocked isocyanate, which has a crosslinking effect only above a defined temperature, for example 70-100 ° C.

The conductive filler is preferably selected as in PCT / EP2008 / 007235 or DE 102007042253 disclosed. The conductive filler is then in particular selected from metallic particles, carbon nanotubes, low-melting alloys and / or copper flakes.

The conductive filler may consist of metallic particles, preferably copper- and / or silver-based. Such metal-based particles have a particularly good conductivity. Silver-based particles are also corrosion resistant. The particles may be spherical, fibrous or flat. The advantage of the planar fillers is that they align themselves parallel to each other after a pressure treatment and overlap. This results in a particularly low sheet resistance. Spherical particles are particularly easy to disperse. By "metallic" particles are meant particles which are largely or wholly metal, i. H. to more than 95%,> 99% or 100%.

The conductive filler may comprise copper flakes. Copper flakes are flat particles. They can be aligned in parallel in a combined pressure and heat treatment. You can then overlap each other and thus have a low sheet resistance. The usable copper flakes have, for example, average diameters of 5 to 100 μm, in particular 20 to 60 μm, and heights of 0.2 to 10 μm, in particular 0.5 to 8 μm. The copper flakes are preferably coated with a noble metal, in particular silver. The proportion of the coating is preferably 1 to 25, in particular 5 to 20 wt .-%. Suitable copper flakes are available, for example, under the trade name Conduct-O-Fil SC230F9.5 (Potters Industries Inc.). These are flat copper plates with a mean diameter of approx. 40 μm and a height of approx. 1-5 μm. They are silvered with a weight fraction of about 9-10 wt .-%.

The conductive filler may include carbon nanotubes. Carbon nanotubes (CNT) are tubular structures made of carbon. These have a diameter of 1 to 50 nm.

The conductive filler may include a low melting alloy. Such an alloy is, for example, a tin-bismuth alloy. Such alloys melt during a heat and pressure treatment, for example during calendering. The low melting alloy particles may be mixed with other particles, such as silver or copper. It is advantageous that the other particles are materially connected by the low-melting particles and thus sets a particularly low surface resistance. For the purposes of the invention, "low-melting" means that the alloy melts at the processing temperatures of the pastes, in particular between 100 and 220 ° C., between 100 and 180 ° C. or between 110 and 150 ° C.

Also usable according to the invention is a conductive paste comprising a dispersible thermoplastic polyurethane, a conductive filler, a water-soluble thickener and water, wherein the thermoplastic polyurethane has free hydroxyl groups and the paste contains a crosslinker, wherein the crosslinker is a polyalcohol having at least 2 or at least 3 free hydroxyl groups and a di- or polyisocyanate are included. Such a conductive paste is particularly suitable for crosslinking with an isolator paste, which also has a thermoplastic polyurethane with free hydroxyl groups.

In a preferred embodiment of the invention, the conductive and / or the insulating paste additionally contain at least one antioxidant. Suitable examples are ascorbic acid or ascorbates such as sodium ascorbate, glucose and metal salts, in particular reducing salts such as ammonium iron (II) sulfate. Preferably, in the preparation of the paste, an aqueous solution of the antioxidants is first prepared in distilled water. This has, for example, 0.2 to 5 wt .-%, preferably 1.5 to 3 wt .-% antioxidants.

The preparation of the insulating paste and / or the conductive paste is preferably carried out by first an aqueous solution of the thickener and optionally the antioxidant is provided (thickener solution). Preferably, the thickener swells while being stirred for a sufficient time, for example 10 to 30 minutes. A suitable viscosity is set, for example between 1500 and 20,000 mPas. Subsequently, the thermoplastic polyurethane, optionally the conductive filler and optionally the crosslinker are added and mixed by stirring to a homogeneous paste. The paste is preferably degassed. If a crosslinker is used, it is preferably first mixed with the PU powder and / or the filler in order to achieve a more homogeneous distribution.

In one embodiment of the invention, the insulating paste and / or the conductive paste has a pH of from 6 to 8.5, preferably from 7 to 7.5. The pH is approximately in a preferred embodiment at pH 7.0. These pHs are also preferably adjusted when antioxidants are included. By adjusting the pH in this range, by using antioxidants and by producing and storing in the absence of air, undesirable changes in the pastes can be avoided.

In a preferred embodiment of the invention, the conductive paste is exposed to the conductive particles in a subsequent to the drying heat and pressure treatment, preferably a calendering. The paste is solidified, the contact and the adhesion to the material are improved and the conductive particles are aligned.

In a preferred embodiment of the invention, a material provided with the conductive paste is stretched in a thermal post-treatment. For example, a deep-drawing process is suitable for this. As a result, an elongation is achieved, d. H. The PU matrix softens under pressure and heat and is stretched. After cooling, it maintains the stretched shape. However, the silver-plated copper platelets still overlap so that the electrical conductivity is maintained. During deep drawing, the orientation of the platelets is further improved, so that even with a stretch or elongation of the substrate still enough platelets overlap.

The insulating paste and / or the conductive paste can be printed by screen or stencil printing. Depending on the choice of screen printing fabrics, large layer thicknesses of the printed paste are possible. The material with the printed conductive paste may be thermoformed following the combined heat and pressure treatment. An advantage of using a thermoplastic polyurethane is that such pastes can be reshaped at any time by melting the polyurethane. Therefore, the already provided with the paste materials can be repeatedly transformed later. Several materials can be provided with the paste and bonded together by pressure and heat treatment via the paste. As a result, textiles can be conductively connected to each other. This is particularly advantageous for garments, since here the conductive and cohesive connection of several clothing sections is possible with simple means.

The invention also provides an isolated material obtainable by a method according to the invention. The material according to the invention contains at least one insulating layer which has been produced from the insulating paste. In addition, further layers may be present in any arrangement. The insulating layer may also be applied to a solid substrate which has no layer structure. Further layers may be, for example, shielding layers or stabilizing layers. Suitable substrates are, for example, nonwovens, films or other flexible, stretchable or solid substrates. Suitable films are, for example, polyurethane films (trademark Epurex, Bayer).

"Layer" refers to any two-dimensional structure without being limited by the lateral extent. Layers, such as insulating layers and conductive layers, may for example be applied in the form of webs. Within a layer, there may be a multiplicity of paths, for example in a parallel arrangement or in any other structure. The insulating layers may be insular within a layer, for example, as circles that insulate contact points of traces. In one embodiment of the invention, only a fraction of a surface of a substrate or material is printed with the insulating paste, for example up to 80%, up to 50% or up to 20%. However, it is also possible to provide a substrate completely or substantially (more than 80 or 90%) with an insulating layer. In general, several subareas that are not connected to one another can exist within a layer. In principle, it is also possible for a layer to have subregions which insulate, and subregions which are conductive or fulfill another function. Such complex structures can be produced in a simple manner, in particular in printing processes. Recesses of the insulating layer in partial areas can serve for contacting, the conductor structures exposed there can be used as contacting points.

In one embodiment, the insulated material includes at least one conductive layer and at least two insulating layers, wherein the conductive layer is disposed between the insulating layers. The material is completely isolated in this way.

Particularly preferred are insulated materials containing two outer insulating layers and interposed inner conductor tracks.

The insulating coating may be bonded or laminated with other known and suitable materials. Suitable examples are materials such as plates, which serve for stabilization. It In addition, polymer films may additionally be added as insulating layers. Such polymer films based on, for example, polyurethanes are known.

A structure of an isolated material according to the invention is for example in the 1 and 2 shown. 1 shows in plan view of an inventive material with insulating layers 1 and tracks 2 . 3 , wherein the insulating layers 1 each between two tracks 2 . 3 are arranged. The interconnects intersect 2 . 3 and are at the intersections through the insulating layer 1 separated from each other. 2 shows in cross section the material according to 1 with an additional lower substrate 4 ,

3 shows in cross-section another inventive material with insulating layers 1 , Tracks 2 , outer substrates 4 and additional shields 5 , For the shielding, a conductive paste is applied to the substrate in a flat or at least close meshed manner, thus providing electrical shielding.

For example, a non-flexible stabilizer layer or a flexible insulator film can first be printed with conductor structures and then printed with an insulating layer.

In a particular embodiment of the invention, the material according to the invention has at least two thermoplastic layers which have a different melting temperature. These at least two layers may be insulating layers or conductive layers. Preferably, layers with different melting temperatures lie directly above one another and were applied by printing. The melting temperatures are preferably at least 10, 20, 30 or 50 ° C apart. In this case, preferably, the respective lower layer, which was printed first, the higher melting temperature. In such laminates, a thermal post-processing may be carried out at a temperature which is below the melting temperature of the upper layer and above the melting temperature of the lower layer. This embodiment has the advantage that the top last applied layer can be post-processed in a thermal process, without the underlying layer is changed.

In general, the method has the advantage that even complicated geometries of insulating layers can be printed in a simple manner. Another advantage is that it is possible to produce insulated materials and coatings that are stretchable and thermoformable. Another advantage is that the insulating layer and the conductive layer can be made to be both malleable and thermoformable. On this insulating layer further printed conductors can be printed, so that a multilayer, expandable or thermally deformable conduit system is formed. Another advantage is that the paste is non-toxic and can not escape or degas during manufacture and later use any harmful substances.

The breakdown resistance of the isolated material or an insulated coating according to the invention is preferably greater than 10 ⁷ ohms or greater than 10 ⁸ ohms and in particular greater than 10 ⁹ or 10 ¹¹ ohms. The breakdown resistance is measured after. The electrical resistance is measured using the method DIN IEC 93 or ISO 6722. With any layer structure, the four-point method has proven itself to avoid incorrect measurements due to contact resistance.

The thickness of the conductive or insulator layer in the solidified state is preferably less than 5 mm or less than 1 mm, preferably less than 0.7 mm and particularly preferably less than 0.5 mm. The thickness can be greater than 0.02 or 0.05 mm.

In preferred embodiments, the insulated material according to the invention is selected from a printed circuit board, a console, a fabric, a nonwoven fabric, a textile, a garment, a heating element, a wound dressing, a flat cable and a piece of furniture. Advantageously, the substrate on which the conductive paste and also the insulating paste are printed, designed as a stretchable nonwoven fabric. Such a stretchable nonwoven fabric printed with the insulating paste and provided with an electrical and insulated circuit is stretchable and is therefore particularly suitable for applications in which the substrate should be flexible and also extensible. Furthermore, the nonwoven fabric can also be formed permeable to water vapor. In a suitably formed circuit, made with the insulating paste, with non-printed areas, the provided with a conductor system substrate is permeable to water vapor and is particularly suitable for clothing. It is also conceivable to print the insulating paste on a stretchable film.

The invention also provides the use of an insulating paste for insulating and / or shielding materials against electrical current. Preference is given to shielding (EMC protection), for example by multilayer construction of combinations of conductive paste and insulating pastes.

The materials are particularly suitable for the insulation of printed conductors of flexible and / or stretchable electronic components. In this way, the protection of the conductor against external mechanical, chemical or other impairments is ensured. Thus, an insulating layer on textiles can cause washability.

Flexible or stretchable interconnects, even multi-layered, are also suitable for the automotive interior, such as consoles. Another preferred application is the insulation of printed circuit traces for the shoe inner region for the pressure sensor system. Insulated materials according to the invention, in particular those with printed conductors, are also suitable for textile and medical products such as compression stockings, electric blankets, wound dressings, ECG accessories. The invention also relates to heating elements in general, for. B. for seat heaters, for example in the automotive sector.

Materials coated with the insulating paste are particularly useful in automotive applications such as dashboards and headliners having a three-dimensional, arcuate geometry, wherein the material provided with the paste is thermally deformed and takes on the shape of the material. Furthermore, the insulating paste is suitable for use in clothing, in particular functional clothing with integrated electronic components. Here the paste isolates flexible tracks on the clothing. Another field of application is the functional coating of aggregates and pipelines, for example the isolation of antistatic equipment.

The use of the insulating paste is particularly advantageous because the substrate to be printed, for example a nonwoven fabric, is not necessarily electrically insulating and, in particular in the region of pores that are printed, can lead to short circuits. Common insulating substrates such as films are not permeable to water vapor, which limits the utility of clothing. The insulating paste can be applied so that water vapor permeable spaces remain.

Brief description of the pictures:

1 shows in supervision a material with insulating layers 1 and tracks 2 . 3 , wherein the insulating layers at least at the intersection points in each case between two conductor tracks 2 . 3 are arranged.

2 shows in cross section a material according to 1 which additionally has a lower substrate 4 having.

3 shows in cross section a material with insulating layers 1 , Tracks 2 , outer substrates 4 and additional shieldings 5 ,

embodiments

Example 1: Preparation of a conductive paste

The polyurethane used is a nonionic, thermoplastic, non-crosslinked, OH-terminated polyurethane. This is prepared from ethylene glycol-adipic acid-polyester polyol and diphenylmethane-4,4'-diisocyanate with the addition of the chain extenders butanediol and hexanediol. The index, which describes the ratio of isocyanate groups to hydroxyl groups in the polymer, is less than 100. The TPU has a melting point of about 135 ° C and is used as a fine powder. To prepare the paste, an aqueous solution of the thickener methylcellulose (Metylan ^Normal® , Henkel) is prepared with stirring. The thickener swells with stirring for another 20 minutes. Depending on the concentration of the thickener, the aqueous solution has a viscosity of between 1,500 and 20,000 mPas. In the solution, the TPU powder and the conductive filler are stirred, processed with further stirring to a homogeneous paste and then degassed under vacuum. When using a crosslinker, this is weighed together with the PU powder and / or the filler and mixed. When using antioxidants, an approximately 2.8% solution with a pH of 7.0 is first prepared with demineralized water, into which the thickener is stirred.

A first example of a conductive paste contains 60 wt .-% of a solution consisting of 1.5% Metylan ^® Normal (Henkel KGaA) in water, 32 wt .-% of a conductive filler, in this embodiment silver-coated copper flakes (Conduct-O-Fil, SC230F9.5 from Potters Industries Inc.) and 8% by weight of a thermoplastic polyurethane having a particle size of less than 120 μm.

The paste has a viscosity of 56,000 mPas and can be printed on a material, for example by screen printing. After drying in an oven and after-treatment in a heating calender, the paste has a sheet resistance of 0.19 ohms as the dried solid.

Example 2: Preparation of a conductive paste

A paste was prepared according to Example 1, with the following different conditions were set. The paste contains 70 wt .-% of a solution consisting of 2.1% Metylan ^® Normal (Henkel KGaA) a thermoplastic polyurethane in water, 24 wt .-% of a conductive filler, silver-coated copper flakes, in this embodiment, and 6 wt .-% with a particle size less than 120 microns.

The paste has a viscosity of 50,200 mPas and can be printed on a material, for example by screen printing. After drying in an oven and after-treatment in a heating calender, the paste has a sheet resistance of 0.44 ohms as the dried solid.

Example 3: Preparation of a conductive paste

A paste was prepared according to Example 1, with the following different conditions were set. The paste contains 60 wt .-% of a solution consisting of 2.5% Metylan ^® Normal (Henkel KGaA) in water, 32 wt .-% of a conductive filler, in this embodiment, copper flakes, and 8 wt .-% of a thermoplastic polyurethane with a particle size less than 120 microns.

The paste has a viscosity of 125,000 mPas and can be printed on a material, for example by means of stencil printing. After drying in an oven and after-treatment in a heating calender, the paste has a sheet resistance of 0.39 ohms as the dried solid.

In Examples 1 to 3, a distensibility of the dried and calendered paste results to 25%. The extensibility of the paste is limited primarily by the large increase in resistance.

Example 4: Preparation of polyurethanes

Various suitable polyurethanes were prepared. Table 1 shows an overview of the components used. By selecting the components, the melting range can be varied. For the production of polyurethanes which can be used according to the invention, it is also possible to use further, not specifically listed, difunctional or polyfunctional short- or long-chain alcohols, amines and thiols, and di- or higher-functional isocyanates. Table 1: Production of TPUs description isocyanate Polyol (s) Chain extender (Molverh.) melting range PU1 MDI D2028 B / H 80:20 PU2 MDI D2000 B / H 80:20 130-135 PU3 MDI D2000 B / H 80:20 150-155 PU4 MDI D2000 B / H / D 80:10:10 130 PU5 MDI D2001 KS B / H 75:25 from 145 PU6 MDI DG200 B / H / N 80:10:10 from 135 PU7 MDI C200 none 205 PU8 MDI T2000 B / H / N 80:10:10 165 PU9 MDI DG200 B / H 75:25 165 PU10 HDI C2200 B / H 50:50 112-117 PU11 HDI C2200 / D2028 2,3-B / H 58:42 100-105 PU12 HDI C2200 / D2028 1,4-B / 2,3-B / H 29:29:42 95-100 PU13 HDI D C2201 2,3-B / H 58:42 100-105 PU14 HDI D C2201 1,4-B / 2,3-B / H 29:29:42 95-100 PU15 HDI D C2201 B / H / N 80:10:10 from 135

Abbreviations:

Based polyols:

• D:

  Desmophen ^TM (polyols from Bayer)

  D2000:

  Polyethylene adipate diol (Mw: 2000)

  D2001 KS:

  Polyethylene / polybutylene adipate diol (Mw: 2000)

  D2028:

  Neopentyl glycol adipate (Mw: 2000)

  D C2201:

  Polycarbonate polyol (Mw .: 2000)

  C:

  Capa ^™ (Polycaprolactone Polyols from Solvay)

  C200:

  Polycaprolactone (Mw: 535)

  C2200:

  Polycaprolactone (Mw: 2000)

  DG:

  Diexter ^TM G (polyols from Coim)

  DG200:

  saturated polyester oladipate:

  T:

  Terathane ^™ (Invista's polyether polyol)

  T2000:

  Polytetramethylene.

Chain extenders .:

• B:

  Butanediol (1,4-B: 1,4 butanediol)

  H:

  1,6-hexanediol

  D:

  Diethylene glycol (3-oxapentane-l, 5-diol)

  N:

  Neopentyl glycol (2,2-dimethyl-1,3-propanediol).

isocyanates:

• MDI:

  Diphenylmethane-4,4'-diisocyanate (methylenedi (phenyl isocyanate))

  HDI:

  1,6-hexamethylene diisocyanate.

The aliphatic polyurethanes PU10 to PU15 are particularly suitable for the production of pastes with a deep melting range. They are lightfast and non-yellowing and therefore suitable for applications in the field of vision. The polyurethanes PU1 to PU9 are aromatic polymers. Table 2: Example formulations of conductive pastes example base paste Wt .-% base paste % By weight of conductive powder Wt% TPU Viscosity mPas 1 Metylan, 1.5% in water 60 32 8th 56,000 2 Metylan, 2.1% in water 70 24 6 50,200 3 Metylan, 2.5% in water 60 32 8th 125000

Examples 5-7: Preparation of insulating pastes

Pastes were prepared according to Examples 1-3, wherein the proportion of conductive powder was replaced by equal amounts of TPU powder.

Example formulations are listed in Tab. 3. Table 3: Example formulations of insulating pastes example base paste Wt .-% base paste Wt% TPU Viscosity mPas 5 Metylan, 1.5% in water 60 40 56,000 6 Metylan, 2.1% in water 70 30 50,200 7 Metylan, 2.5% in water 60 40 125000

Examples 8-10: Preparation of postcrosslinking conductive pastes

In accordance with Examples 1-3, conductive pastes are prepared by adding with the TPU powder additionally di-TMP powder (di-trimethylolpropane) and MDI powder (diphenylmethane-4,4'-diisocyanate). The non-crosslinked TPU of the reactive paste in this case has OH end groups and may have a melting point of about 110 ° C to about 160 ° C. The compositions are summarized in Table 4. Table 4: Example formulations of postcrosslinking conductive pastes example base paste Wt .-% base paste % By weight conductive powder. Wt% TPU % By weight of di-TMP Wt .-% MDI Viscosity mPas 8th Metylan, 1.5% in water 58.6 32 7.72 0.08 0.2 56,000 9 Metylan, 2.1% in water 67.9 24 5.58 0.12 0.3 50,200 10 Metylan, 2.5% in water 54.4 32 6.88 0.32 0.8 125000

The addition of up to 0.1% catalyst (eg Dabco: 1,4-diazabicyclo [2.2.2] octane) is possible. Instead of di-TMP and MDI can be used as crosslinking components, other polyols and isocyanates such. As trimethylolpropane or HQEE powder and TODI or NDI powder can be used.

Examples 11-13: Preparation of Postcrosslinking Insulating Pastes

According to Examples 8-10 pastes are prepared, wherein the proportion of conductive powder has been replaced by equal amounts of TPU powder.

Example formulations are listed in Tab. 5. Table 5: Example formulations of post-crosslinking insulating pastes example base paste Wt .-% base paste Wt% TPU % By weight of di-TMP Wt .-% MDI Viscosity mPas 11 Metylan, 1.5% in water 58.6 40 0.4 1 100000 12 Metylan, 2.1% in water 67.9 30 0.6 1.5 100000 13 Metylan, 2.5% in water 54.4 40 1.6 4 100000

Examples 14-18: Production of Films

According to Example 11, pastes were prepared based on a 2.1% Metylanlösung. However, the proportion of crosslinking component (di-TMP and MDI) was varied. The basic TPU is OH-terminated and has a melting point of approx. 125-130 ° C. For this purpose, in each case 5 g of the paste were dried at 40 ° C and then pressed to the film. Press for 5 minutes at 125 ° C and 7 bar (produced film about 10 cm in Diameter); a shortening of the pressing time is possible by addition of catalyst. The results in Table 6 show that the melting point can be adjusted via the crosslinker content. Table 6: Melting point change as a function of the crosslinker fraction: example Base paste meth. 2.1%; in% by weight Wt% TPU % By weight of di-TMP Wt .-% MDI Viscosity mPas Additional Temp ° C 14 59.65 40 0.1 0.25 about 100,000 145 15 59.3 40 0.2 0.5 about 100,000 150-155 16 58.6 40 0.4 1 about 100,000 about 165 ° C 17 57.9 40 0.6 1.5 about 100,000 about 180 ° C 18 about 57 40 1 2.5 about 100,000 180-185

Examples 19-21: Prepolymer crosslinked insulating pastes

Insulator pastes are prepared according to Examples 11-13, but the crosslinking components Di-TMP and MDI are replaced by ground prepolymer. Example formulations are shown in Tab. 7.

The TPU of the reactive paste in this case has OH end groups and a melting point of about 110 ° C to about 160 ° C. Table 7: Example formulations for prepolymer-crosslinked insulator pastes: example base paste Wt .-% base paste Wt% TPU Wt .-% prepolymer Viscosity mPas 19 Metylan, 1.5% in water 58.6 40 1.4 about 100,000 20 Metylan, 2.1% in water 67.9 30 2.1 about 100,000 21 Metylan, 2.5% in water 54.4 40 5.6 about 100,000

For the preparation of prepolymer-crosslinked conductive pastes, part of the TPU powder can be replaced by conductive powder according to Example 8-10.

Examples 22-24: conductive paste crosslinked with polyisocyanate

Another crosslinking which can be used according to the invention takes place by adding a water-dispersible polyisocyanate which is less reactive at room temperature. An isocyanate according to the invention applicable, for example, Tolonate ^® HDB and Tolonate ^® HDT from Rhodia. Insulator pastes are prepared according to Examples 11-13, but the crosslinking components Di-TMP and MDI are replaced by a liquid, water-dispersible polyisocyanate. Example formulations are shown in Tab. 8. The crosslinker (Tolonate ^® HDB or Tolonate ^® HDT) is stirred into the paste when mixing the paste or during prolonged storage until about 24 hours before using the paste. The TPU of the reactive paste in this case has OH end groups and a melting point of about 110 ° C to about 160 ° C. Table 8: Example formulations for polyisocanate crosslinked insulator pastes: example base paste Wt .-% base paste Wt% TPU % By weight HDT Viscosity mPas 22 Metylan, 1.5% in water 58.6 40 1.4 about 100,000 23 Metylan, 2.1% in water 67.9 30 2.1 about 100,000 24 Metylan, 2.5% in water 54.4 40 5.6 about 100,000

For the corresponding conductive paste, the TPU according to the above examples z. T. replaced by Leitpulver (see Example 8-10).

Examples 25-27: Addition of thickeners

Instead of the cellulose-based thickener (Metylan or MHEC 9000), alternative thickeners are used which have improved film-forming properties.

To prepare the pastes, water and thickener were first mixed and mixed in the Speed Mixer for 1 min. Then the PU was added, stirred and also mixed in the Speed Mixer. The stirred paste was then tested for airability without venting. The paste was screen printed on foils. The paste is easy to print. When printing on a Duplocoll film (Lohmann) no holes are visible in the print. When printing on a stretchable non-woven polyurethane (XO90) no holes in the print can be seen.

The pastes contain 56-57% by weight of a solution consisting of the described alternatively to be used thickeners in water, and 43-44 wt .-% of a thermoplastic polyurethane having a particle size less than 120 microns (see Table 9). Table 9: Example formulations for isolator pastes based on different thickeners: example Base paste (thickener, in water) Wt .-% base paste Wt% TPU 25 Ruco-Coat TH5005, 14.6% in water 57 43 26 Colacral PU85, 11.4% in water 56 44 27 Collacral PU75, 11.4% in water 56 44

Depending on the desired viscosity, both the concentration of the thickener in water and the proportion of the TPU powder can be varied. To prepare conductive pastes, part of the TPU powder is replaced by conductive powder according to Example 8-10.

Example 28-30: Pastes with additional binders

For the preparation of the paste were first water and Collacral ^® (BASF Ludwigshafen). mixed and blended in Speed Mixer for 1 min.

Then the TPU powder and as a binder Emuldur ^® DS2360 Fa was. Added BASF, stirred, and also mixed in the speed mixer. The stirred paste was then tested for airability without venting. Results and composition of the paste are shown in Tab: 10a. Insulating pastes were made from the following components: A: Solvent water Solids content in wt.%: 0 B: Thickener: Collacral PU75 / 85 Solids content in wt .-%: 26 C: PU Foundation: TPU powder Solids content in% by weight: 100 D: Binder: Emuldur DS2360 Solids content in wt.%: 40 e: Binder Acronal DS2337 Solid content in wt.%: 55 Table 10: Insulating pastes with additional binder Example 28: without Emuldur Example 29: with Emuldur Example 30: with Acronal component Weight (g) Solid (g) Solids content (%) Weighing (g) Solid (g) Solids content (%) Weighing (g) Solid (g) Solids content (%) A 77 0 0 77 0 0 77 0 0 B 11 2.86 4.4 11 2.86 4.0 11 2.86 3.8 C 62 62 95.6 62 62 85 62 62 81.7 D 0 0 0 20 8th 11 0 0 0 e 0 0 0 0 0 0 20 11 14.5 good consistency, film formation not optimal Lighter, still very printable paste, is dried but very flexible

As an alternative to the use of postcrosslinking pastes, multilayer printing also makes it possible to use pastes in which the melting temperature of the TPUs decreases from the first to the next higher printed layer. Thus, the next layer can be laminated at a lower temperature without the underlying layer being melted again.

Examples 31-34: Making a laminate of conductive and insulating paste

First, the Isolierbaste was screen printed on a nonwoven fabric (Evolon) and then subjected to a combined pressure / heat treatment (130 ° C, at 6 bar pressing pressure). The conductor was then printed on the isolated nonwoven and also subjected to a combined pressure / heat treatment (130 ° C, at 2 bar pressing pressure). An exemplary result is shown schematically in FIG 1 shown.

Claims (19)

A method of making a material insulated from electrical current, comprising (a) providing a first substrate having a surface, (b) applying flat an insulating paste containing a dispersible uncharged thermoplastic polyurethane having free hydroxyl groups, a water-soluble thickener, a crosslinker and water, the insulating paste having no conductive polymer and no conductive filler on the surface or portions of the surface and (c) solidifying the insulating paste by crosslinking. A method according to claim 1, characterized in that the thickener contains cellulose derivatives, a diurethane or a non-thermoplastic polyurethane. Method according to one of the preceding claims, characterized in that the thermoplastic polyurethane in the form of particles having an average particle diameter of less than 350 microns, preferably less than 120 microns, is present. Method according to one of the preceding claims, characterized in that the thermoplastic polyurethane has a melting point between 80 ° C and 250 ° C. A method according to any one of claims 1 to 4, wherein the solidification (c) of the insulating paste is carried out in conjunction with drying and / or heating. A method according to any one of claims 1 to 5, wherein the material provided with the paste is subjected to a combined heat and pressure treatment before, during or after solidification (c). A method according to claim 6, characterized in that the insulated material is thermally deformed following the combined heat and pressure treatment. Method according to at least one of claims 1 to 7, wherein the first substrate in step (a) comprises at least one conductor track. Method according to at least one of claims 1 to 8, comprising before step (a) (a1) producing the first substrate of step (a) by printing at least one conductive line on the surface of a second substrate using a conductive paste. A method according to claim 9, wherein in step (a1) a conductive paste containing a dispersion of a polyurethane and a conductive filler is used for printing. Method according to claim 9 or 10, comprising before step (a1) (a2) forming the second substrate by printing an insulating layer on a third substrate. A method according to any one of claims 9 to 11, wherein the insulating paste and the conductive paste are crosslinkable. The method of claim 12, wherein the insulator paste and the conductive paste are crosslinkable and crosslinked after printing the insulating paste, so that a crosslinking of the conductor or the conductive paste is carried out with the insulating paste. A method according to any one of claims 10 to 13, wherein the insulating paste and the conductive paste each contain a thermoplastic polyurethane having free hydroxyl groups and at least one crosslinker selected from a polyisocyanate having at least 2 isocyanate groups and a polyhydric alcohol having at least 2 hydroxyl groups. Method according to one of claims 1 to 14, wherein on the isolated material obtained in step (c) conductor tracks and optionally a further isolated layer are applied. An isolated material obtainable by a process according to any one of claims 1 to 15. The insulated material of claim 16, wherein the breakdown resistance of the isolated material is greater than 10 ohms. An insulated material according to claim 16 or 17, comprising at least one conductive layer and at least two insulating layers, the conductive layer being disposed between the insulating layers. An insulated material according to any one of claims 16 to 18, selected from a printed circuit board, a console, a fabric, a nonwoven fabric, a textile, a garment, a heating element, a wound dressing, a flat cable and a piece of furniture.

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