WO2010099958A2

WO2010099958A2 - Insulating pastes

Info

Publication number: WO2010099958A2
Application number: PCT/EP2010/001333
Authority: WO
Inventors: Gernot Frackmann; Jürgen GÜNTHER; Benno Schmied
Original assignee: Carl Freudenberg Kg
Priority date: 2009-03-06
Filing date: 2010-03-04
Publication date: 2010-09-10
Also published as: WO2010099958A3; DE102009011553B4; DE102009011553A1

Abstract

The invention relates to an insulating paste containing a thermoplastic polyurethane which can be dispersed, a water-soluble thickener and water. The invention also relates to insulated materials, which are provided with the insulating paste, and to methods for formulating the insulating pastes and to materials and to applications.

Description

Isolierpasten

Technical area

The invention relates to an insulating paste containing a dispersible thermoplastic polyurethane, a water-soluble thickener and water. The invention also relates to materials provided with the insulating paste and to methods of making the insulating pastes and materials and uses.

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. 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 track are also not protected against external influences and may be e.g. be attacked during cleaning processes of printed textiles.

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 used Procedures and materials 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 multilayer laminates of insulating and conductive layers should be easy and inexpensive to produce.

Object of the invention:

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

The invention relates to an insulating paste for producing an insulating coating (insulating layer) comprising a dispersible thermoplastic polyurethane, a water-soluble thickener and water.

The term "insulating paste" means that the paste is suitable for producing an insulating coating. The isolation is preferably carried out 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 thermally deformable. 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.

Insulating pastes according to the invention may contain between 3 and 98% by weight, preferably between 5 and 95% by weight or between 20 and 85% by weight, particularly preferably between 30 and 75% by weight, of 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 included. 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 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, 0 to 25% by weight of crosslinker and 2 to 94.8% by weight .% 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.% Of additional binder included, supplemented by up to 45% by weight of other additives. The thickener is provided in a preferred embodiment as an aqueous thickener solution. The thickener solution contains, for example, 0.2 to 15% by weight of the thickener dissolved in water. Preference is given to using distilled or bidistilled water. In the pastes according to the invention, the proportion of thickener paste is preferably 40-80% by weight, more preferably 55-75% by weight. The paste according to the invention is preferably water-based. It thus contains no organic solvents or less than 5, 2.5 or 1 wt.% Organic solvents.

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 _t

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 methylcellulose is, for example, Metylan® Normal (MHEC 9000; methylhydroxyethylcellulose having the viscosity of a 2% solution of 9000 MPas, Henkel, Dusseldorf).

In a further preferred variant, the thickener may be an aqueous solution of a diurethane (eg a fatty alcohol ethoxylate urethane) which may optionally contain water-miscible organic solvents such as 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 Coiiacrai is about 25-28% by weight.

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, e.g. Contain 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 much less pressure, if necessary even completely omitted. For example, very pressure sensitive areas, e.g. Low-melt 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 Starting materials, the reaction conditions and the proportions are responsible for the properties of the product. The polyo! influences, for example, cold flexibility, media or hydrolysis resistance or rebound resilience; while the isocyanate and the chain extender are more likely to be hard, heat distortion or

Settlement / Remanence influence. 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 ⁰ C, in particular between 100 and 220 ⁰ C, between 100 and 180 or between 110 and 150 ⁰ 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 with higher melting polyurethane

Melting points approximately between 120 and 220 ⁰ C, in particular above 130 or 140 ⁰ C, or low-melting polyurethanes having melting points approximately between 80 and 120 ⁰ C, in particular below 110 ⁰ C 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. Aiiphatic 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.

In a preferred embodiment of the invention, the polyurethanes are uncharged polyurethanes. Preferably, the paste contains only uncharged polyurethanes. Thus, no ionic polyurethanes are included. The paste according to the invention thus differs from compositions from EP 1 284 278. Uncharged polyurethanes are generally not or only poorly dispersible in water. Novel pastes with uncharged polyurethanes are preferably suspensions in which polyurethanes are finely dispersed as solids (particles). By contrast, the ionic polyurethanes used according to EP 1 284 278, for example, 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 then 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.

In principle, ionic polyurethanes can also be used according to the invention. However, if the viscosity of the paste is adjusted so that the polyurethane particles do not fall, neither the use of an ionic polyurethane nor the use of emulsifiers is required. In a preferred embodiment of the invention, the paste contains no emulsifiers.

Thermoplastic polyurethanes which are suitable according to the invention can be, for example, diphenylmethane diisocyanate (MDI), such as 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate, hexamethylene-1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), Naphthylene-1,5-diisocyanate (NDI) ₁ dimethyl diphenyl diisocyanate TODI), dicyclohexylmethane-4,4-diisocyanate (HMDI).

Suitable polyols for preparing the polyurethanes are polyethers, e.g. Polytetrahydrofuran (PTHF) or polypropylene glycol (PPG), polyesters, e.g. Ethylenadipatpolyol, Butylenadipatpolyol, NPG adipates, polycarbonate polyols and polycaprolactone and Polyetheresteφolyole. These may also be trifunctional and polyfunctional in a linear or too low proportion.

These are optionally used in conjunction with suitable Kettenveriängerern. 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 e.g. Trimethylolpropane and higher functional amines and alcohols or thiols.

Especially preferred is the use of polyurethanes of ethylene glycol adipic acid polyester polyol, butanediol, hexanediol and diphenylmethane-4,4 ¹ - 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 with the Kettenveriängerern: 1, 6-hexanediol and 1, 4-butanediol extended. To reach melting temperatures of the TPU below 110 ⁰ C polyols may be added from neopentyl glycol adipate or instead more isomers of butanediol or other diols such as neopentyl glycol. 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 ⁰ 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 the Kettenveriängerer and the proportions of the respective polyols and isocyanates, the melting point of such described polyurethanes can be arbitrarily set between about 80 ⁰ C to about 230 ⁰ C.

In one embodiment of the invention, the paste contains no crosslinker. It is then added before or during processing no crosslinker. In this way, an uncrosslinked thermoplastic coating is obtained. Due to the thermoplastic properties, the possibility of deformability (for example by deep drawing) is given. Such post-treatment is not possible with known highly crosslinked polyurethanes. In a preferred embodiment of the invention, the Polyurethanes in non-crosslinked pastes have a melting point above 120 ⁰ C.

In a further embodiment of the invention, a crosslinker is contained in the 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 index, for example <99, <98, or <95, in particular> 80, or from 70 to 98 (characteristic number = n (NCO) / n (OH) * 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 ⁰ C or 90 and 110 ⁰ C. The crosslinker is a compound that can link hydroxyl groups, preferably a diisocyanate or polyisocyanate. In a preferred embodiment of the invention the crosslinker is a blocked isocyanate, of reticulating only above a defined temperature, for example 70- 100 ⁰ C.

The melting point of the thermoplastic polyurethane can be adjusted to values below 12O ⁰ C or 110 ⁰ C by selecting 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 11O ⁰ C can be achieved, for example, with polycaprolactone polyol and additionally polyol from neopentyl glycol adipate and using multiple 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. A crosslinker according to the invention which is added to these pastes is, for example, ground isocyanate, such as diphenylmethane-4,4'-diisocyanate (MDI) or a.S'-dimethylbiphenyl-M ¹ - diisocyanai (TODi), with a melting point below 110 ⁰ C. In the aqueous paste, a thin urea layer is formed on the isocyanate powder surface Reaction of isocyanate and water, which causes the water permeability and thus the urea reaction inside the isocyanate particles is slowed down very much. 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 through 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 latently reactive isocyanate system is, for example, MDI powder, TODI powder, HDT or HDB (Bayer). As capping agents for isocyanates such as pyrazole come (for example, triazole, reacted at about 120 ⁰ C), oximes (react at 130 ⁰ C), caprolactam (reacted 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 5O ⁰ 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, other polyalcohols and isocyanates such as trimethylolpropane, HQEE and TODI or NDI powders can be used as crosslinking components. Another variant is the addition of a mehrfunktiöneiien, less reactive in room temperature, liquid isocyanate such as the biuret or trimer of eg 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. So can the next layer is laminated at a lower temperature without resurfacing the underlying layer.

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. An inventive binder is, for example

Emuldur® DS2360 from BASF (Ludwigshafen). Emuldur® DS2360 is an anionic aqueous polyurethane dispersion having a solids content of 39-41% by weight. 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. An inventive binder is, for example, Acronal DS 2337 (BASF, Ludwigshafen). Acronal DS 2337 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 according to the invention is preferably carried out by first providing an aqueous solution of 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 optionally 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 invention also provides a process for the preparation of an insulated material comprising

(a) providing a first substrate having a surface,

(B) surface application of an insulating paste according to any one of the preceding claims on the surface or portions of the

Surface and

(c) solidifying the insulating paste.

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 that a film or a layer is created. "Subregions of the surface" means that structures can be created on the surface during application, wherein the insulating paste is applied only in specific places and other parts are 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, the solidification (c) of the insulating paste is preferably carried out by drying, heating and / or crosslinking. 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 can too 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 are applied to the insulated material obtained in step (c) and optionally a further isolated layer, which is preferably an insulating layer according to the invention.

In a preferred embodiment of the invention, the insulating paste and / or the conductive paste are crosslinkable. In particular, the insulator 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.

The insulating paste and the conductive paste preferably each contain a thermoplastic polyurethane having free hydroxyl groups and at least one crosslinker which is selected from a polyisocyanate having at least 2 isocyanate groups and / or a polyhydric alcohol having 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 known, for example, from EP 1 284 278 A2, US Pat. No. 5,389,403 A or DE 197 57 542 A2. It is preferred according to the invention to use pressure and conductive pastes which are described in PCT / EP2008 / 007235 or DE 102007042253. 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, from 2 to 40% by weight, preferably from 4 to 25% by weight, particularly preferably from 5 to 15% by weight, of thermoplastic polyurethane. The proportion of the conductive filler is preferably 2-40% by weight, in particular 15-40% by weight, particularly preferably 20-35% by weight. 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 included. 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.% Result. thermoplastic polyurethane, 15 to 85% by weight conductive filler and 0.5 to 4.5% by weight 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) * 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 ⁰ 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 polyalcohol. In a preferred embodiment of the invention, the crosslinker is a blocked isocyanate, which acts crosslinking only above a defined temperature, for example 70-100 ⁰ C.

The conductive filler is preferably selected as disclosed in PCT / EP2008 / 007235 or DE 102007042253. 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 according to the invention refers to particles that are largely or entirely made of metal, i. 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 copper flakes which can be used according to the invention 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 with a Precious metal, in particular silver, coated. The proportion of the coating is preferably from 1 to 25, in particular from 5 to 2,% by weight. 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 proportion 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 melt at the processing temperatures of the pastes, particularly 100-220 ⁰ C, between 100 and 180 ° C or between 110 and 150 ⁰ C.

The invention also provides 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 as crosslinking agent is a polyhydric alcohol having at least 2 or at least 3 free hydroxyl groups and a di- or polyisocyanate are included. A Such conductive paste is particularly suitable for crosslinking with an isolator paste according to the invention, 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. For example, ascorbic acid or ascorbates such as sodium ascorbate, glucose and metal salts, in particular reducing salts such as ammonium iron (II) sulfate, are suitable. 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 on.

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 in a preferred embodiment at about pH 7.0. These pH values are preferably also adjusted when antioxidants are included. By adjusting the pH in this area, by using Antioxidants and by preparation and storage 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. This achieves elongation, i. 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.

According to the invention, 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. It can provide several materials with the paste and bonded by pressure and heat treatment through the paste cohesively become. 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 paste according to the invention. 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).

According to the invention, "flat" denotes any two-dimensional structure, without this being limited by the lateral extent. Layers according to the invention, such as insulating layers and conductive layers, can 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 portion of a surface of a substrate or material is printed with the insulating paste according to the invention, 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. It is according to the invention also possible in principle a layer has subregions that insulate and subregions that are conductive or perform another function. Such complex structures according to the invention 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.

Particular preference is given to insulated materials which contain two outer insulating layers according to the invention and inner conductor tracks arranged therebetween.

The insulating coating of the invention may be bonded or laminated with other known and suitable materials. Suitable examples are materials such as plates, which serve for stabilization. It is also possible to add polymer films as insulating layers. Such polymer films based on, for example, polyurethanes are known.

An inventive structure of an isolated material according to the invention is shown for example in Figures 1 and 2. Figure 1 shows in plan view of an inventive material with insulating layers 1 and conductor tracks 2, 3, wherein the insulating layers 1 are each arranged between two conductor tracks 2, 3. In this case, the tracks 2, 3 intersect and are separated at the intersections by the insulating layer 1 from each other. Figure 2 shows in cross-section the material according to FIG. 1 with an additional lower substrate 4.

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

According to the invention, 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 can be insulating layers according to the invention 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 ⁰ 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. These

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 according to the invention has the advantage that even complicated geometries of insulating layers can be printed in a simple manner. Another advantage is that according to the invention it is possible to produce insulated materials and coatings which 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 is on which the conductive paste and the insulating paste are printed, designed as a stretchable nonwoven fabric. A stretchable nonwoven fabric printed in such a way with the paste according to the invention 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 designed circuit, produced with the paste according to the invention, with non-printed areas and provided with a conductor system substrate is permeable to water vapor and is particularly suitable for clothing. It is also conceivable to print the paste according to the invention on a stretchable film.

The invention also provides the use of an insulating paste according to the invention for insulating and / or shielding materials, preferably a shield (EMC protection), for example by multilayer construction of combinations of conductive paste and insulating pastes.

The materials of the invention are particularly suitable for the isolation 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, including multi-day, 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. Materials isolated 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 example for seat heaters, for example in the automotive sector.

Materials coated with the paste according to the invention are particularly suitable for automotive applications, such as dashboards and headliners having a three-dimensional, curved geometry, wherein the material provided with the paste is thermally deformed and assumes the shape of the material. Furthermore, the paste according to the invention is suitable for use in clothing, in particular functional clothing with integrated electronic components. Here the paste isolates flexible tracks on the clothing. Another area of application is functional coatings of aggregates and pipelines, for example the isolation of antistatic equipment and heating / cooling applications.

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:

Figure 1 shows in plan view of an inventive material with insulating layers 1 and conductors 2, 3, wherein the insulating layers are arranged at least at the intersection between each two interconnects 2, 3. FIG. 2 shows in cross-section a material according to the invention according to FIG. 1, which additionally has a lower substrate 4.

FIG. 3 shows in cross-section a material according to the invention with insulating layers 1, conductor tracks 2, outer substrates 4 and additional shields 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 paste according to the invention contains 60% by weight of a solution consisting of 1.5% Metylan® Normal (Henkel KGaA) in water, 32% by weight of a conductive filler, in this embodiment silver-coated copper flakes (Conduct-O-Fil, SC230F9 .5 of the company Potters Industries Inc.) and 8 wt.% Of a thermoplastic polyurethane having a particle size of less than 120 microns. 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 according to the invention contains 70% by weight of a solution consisting of 2.1% Metylan® Normal (Henkel KGaA) in water, 24% by weight of a conductive filler, in this embodiment silver-coated copper flakes, and 6% by weight of a thermoplastic polyurethane with a Particle size less than 120 μm.

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 according to the invention contains 60% by weight of a solution consisting of 2.5% Metylan® Normal (Henkel KGaA) in water, 32% by weight of a conductive filler, in this embodiment copper flakes, and 8% by weight of a thermoplastic polyurethane having a particle size less than 120 μm.

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 In an oven and after-treatment in a heating calender, the paste has a dried solids content of 0.39 ohms.

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 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, as well as di- or higher-functional isocyanates.

Abbreviations:

Basic Polvole:

D: Desmophen ™ (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 ™ (Solvay Polycaprolactone Polyols) C200: Polycaprolactone (Mw: 535)

C2200: polycaprolactone (Mw: 2000)

DG: Diexter ™ G (polyols from Coim)

DG200: saturated polyester oladipate:

T: Terathane ™ (Invista's Polyetheφolyol) T2000: Polytetramethylene ether glycol.

Chain Ver .: B: Butanediol (1,4-B: 1,4 butanediol); H: 1,6-hexanediol; D:

Diethylene glycol (3-oxapentane-1, 5-diol); N: neopentyl glycol (2,2-dimethyl-1,3-propanediol).

Isocvanate: 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 not yellowing and therefore suitable, inter alia, for applications in the field of vision. The polyurethanes PUi to PU9 are aromatic polymers.

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.

Examples 8-10: Preparation of postcrosslinking conductive pastes

In accordance with Examples 1 to 3, conductive pastes are prepared, with the TPU powder additionally containing di-TMP powder (di-trimethylolpropane) and MDI powder (Diphenylmethane-4,4'-diisocyanate) is added. The non-crosslinked TPU of the reactive paste in this case has Oπ end groups and may have a melting point of about 110 ⁰ C to about 160 ⁰ C. The compositions are summarized in Table 4.

Table 4: Example formulations of postcrosslinking conductive pastes

The addition of up to 0.1% catalyst (e.g., Dabco: 1, 4-diazabicyclo [2.2.2] octane) is possible. Instead of di-TMP and MDI, as crosslinking components it is also possible to use other polyalcohols and isocyanates, such as e.g. Trimethylolpropane or HQEE powder and TODI or NDI powder can be used.

Examples 11 - 13: Production of post-crosslinking 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. Tabeiie b: Öeispieirezepiuren of postcrosslinking Isoüerpasten

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 base TPU is OH-terminated and has a melting point of about 125-130 ⁰ C. For this purpose, each 5 g of the paste were dried at 40 ⁰ 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:

Examples 19-21: Insulating pastes crosslinked with prepolymer

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 ⁰ C to about 160 ° C.

Table 7: Example formulations for prepolymer-crosslinked insulator pastes:

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

A further crosslinking according to the invention takes place by adding a water-dispersible polyisocyanate which is less reactive at room temperature instead of. An isocyanate according to the invention is, for example, Tolonate® HDB or Toionate® 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 cross-linking agent (Tolonate®HDB or Tolonate®HDT) is stirred into the paste when mixing the paste or during prolonged storage until approx. 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 11O ⁰ C to about 160 ⁰ C.

Table 8: Example formulations for polyisocanate crosslinked insulator pastes:

For the corresponding conductive paste, the TPU according to the above examples z.T. replaced by lead powder (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. Subsequently, the PU was added, stirred and also mixed in 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 according to the invention comprise 56-57% by weight of a solution consisting of the described, alternatively to be used thickeners in water, and 43-44% by weight of a thermoplastic polyurethane having a particle size of less than 120 μm (see Table 9).

Table 9: Example formulations for isolator pastes based on different thickeners:

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

Example 28-30: Pastes with additional binders

To prepare the paste, water and Collacral® (from BASF Ludwigshafen) were first mixed and mixed in a speed mixer for 1 min. Subsequently, the TPU powder and as a binder Emuldur® DS2360 BASF was added, stirred and blended just 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 solid content in wt.%: 0

B: thickener: Collacral PU75 / 85% by weight in% by weight: 26

C: PU base: TPU powder Solids content in% by weight: 100 D: Binder: Emuldur DS 2360 solids content in% by weight: 40

E: Binder Acronal DS 2337 solid content in wt.%: 55

Table 10: Insulating pastes with additional binder

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. So For example, the next layer can be laminated at a lower temperature without remelting the underlying layer.

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 printed circuit was then printed on the isolated nonwoven and also subjected to a combined pressure / heat treatment (130 ⁰ C ₁ at 2 bar pressing pressure). An exemplary result is shown schematically in FIG.

Claims

claims

An insulating paste for producing an insulating coating containing a dispersible thermoplastic polyurethane, a water-soluble thickener and water.

2. insulating paste according to claim 1, characterized in that the thickener contains cellulose derivatives, a diurethane or a non-thermoplastic polyurethane.

3. insulating paste according to any 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.

4. insulating paste according to any one of the preceding claims, characterized in that the thermoplastic polyurethane has a melting point between 80 ⁰ C and 25O ⁰ C.

5. insulating paste according to any one of the preceding claims, characterized in that the thermoplastic polyurethane has free hydroxyl groups and the paste contains a crosslinker.

6. A process for producing an insulated material, comprising

(a) providing a first substrate having a surface,

(B) surface application of an insulating paste according to any one of the preceding claims on the surface or portions of the surface and

(c) solidifying the insulating paste.

7. The method according to claim 6, wherein the surface application (b) is effected by printing.

8. The method according to at least one of claims 6 or 7, wherein the solidification (c) of the insulating paste by drying, heating and / or crosslinking takes place.

9. The method according to at least one of claims 6 to 8, wherein the material provided with the paste before, during or after the solidification (c) is subjected to a combined heat and pressure treatment.

10. The method according to claim 9, characterized in that the insulated material is thermally deformed following the combined heat and pressure treatment.

11. The method according to at least one of claims 6 to 10, wherein the first substrate in step (a) comprises at least one conductor track.

12. The method according to at least one of claims 6 to 11, 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.

13. The method according to claim 12, wherein in step (a1) for printing a conductive paste is used, comprising a dispersion of a

Polyurethane and a conductive filler.

14. The method according to claim 12 or 13, comprising before step (a1)

(a2) forming the second substrate by printing an insulating layer on a third substrate.

15. The method according to any one of claims 12 to 14, wherein the insulating paste and / or the conductive paste are crosslinkable.

16. The method of claim 15, 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 with the insulating paste takes place.

17. The method according to any one of claims 12 to 16, 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.

18. The method according to any one of claims 6 to 17, wherein on the isolated material obtained in step (c) conductor tracks and optionally a further isolated layer are applied.

19. An isolated material obtainable by a method according to at least one of claims 6 to 18.

The insulated material of claim 19, wherein the breakdown resistance of the isolated material is greater than 10 ⁷ ohms.

21. An insulated material according to claim 19 or 20, comprising at least one conductive layer and at least two insulating layers, wherein the conductive layer is disposed between the insulating layers.

22. An insulated material according to any one of claims 19 to 21, 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.

23. Use of an insulating paste according to at least one of claims 1 to 5 for insulating and / or shielding of materials.

24. 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 selected from a polyhydric alcohol having at least 2 free hydroxyl groups in combination with a Di- or polyisocyanate; a prepolymer with free isocyanate groups.