WO2015173126A1 - Dielectric eap films with low glass transition temperature based on polyester polyols - Google Patents

Abstract

The present invention relates to a method for producing a dielectric polyurethane film from a mixture comprising A) a compound containing isocyanate groups having a content of isocyanate groups of ≥ 10 and ≤ 50 wt.% and a number-average functionality of isocyanate groups of ≥ 2.6 and ≤ 4 and B) a polyester polyol having an OH-number of ≥ 27 and ≤ 120 mg KOH/g, determined in accordance with DIN 53240, characterized in that it exhibits an ester group content of ≥ 1 and ≤ 7 mol/kg and a portion of aromatic structures of ≤ 50 wt.-% The invention also relates to the dielectric polyurethane film obtainable by this method. The invention further relates to a method for preparing an electrochemical transducer and an electrochemical transducer obtainable by said method.

Description

 Dielectric EAP films with a low glass point based on polyester polyols

The present invention relates to a process for producing a polyurethane dielectric film from a mixture comprising A) an isocyanate group-containing compound with B) a specific polyester polyol. Furthermore, the invention relates to the obtainable by this method dielectric polyurethane film. Further objects of the invention are a method for producing an electrochemical transducer and an electrochemical transducer obtainable by this method.

Transducers - also called electromechanical transducers - convert electrical energy into mechanical energy and vice versa. They can be used as part of sensors, actuators and / or generators.

The basic structure of such a transducer consists of electroactive polymers (EAP). The construction principle and the operation are similar to those of an electrical capacitor. There is a dielectric between two plates under tension. However, EAPs are a ductile dielectric that deforms in the electric field. Strictly speaking, dielectric elastomers are mostly in film form (DEAP, dielectric electroactive polymer) which have a high electrical resistance and are coated on both sides with stretchable electrodes with high conductivity (electrode), as described, for example, in WO-A 01/06575. This basic structure can be used in a variety of configurations for the production of sensors, actuators or generators. In addition to single-layered structures, multi-layered structures are also known.

Electroactive polymers as elastic dielectric in transducer systems must - depending on the application in different components: actuators / sensors or generators - have different properties. Common mechanical properties are sufficiently high elongation at break, low residual strains and sufficiently high compressive / tensile strengths. These properties provide a sufficiently large elastic deformability without mechanical damage to the energy converter. For energy converters operated in Zug, it is particularly important that these elastomers have no permanent elongation, otherwise no electroactive effect will occur after a certain number of cycles of strains and, moreover, no stress relaxation under mechanical load. However, there are also different requirements depending on the application: For actuators in the tensile mode, highly reversible elastic elastomers with high elongation at break and low tensile modulus of elasticity are required. For generators that are operated in extension, however, a high tensile modulus is useful. The requirements for the internal resistance are different; For generators, significantly higher requirements are placed on the internal resistance than for actuators.

From the literature it is known for actuators that the ductility to the dielectric constant and the applied voltage is inversely proportional to the modulus: with the relative permittivity e _r , the stiffness Find the film thickness d with the switching voltage U shows the strain s _z according to the equation

 The voltage is in turn dependent on the breakdown field strength, d. H. if the breakdown rupture field strength is very low, no high voltage can be applied. Since this value is squared in the equation for calculating the strain caused by the electromechanical attraction of the electrodes, the breakdown field strength must be correspondingly high. A typical equation can be found in: Federico Carpi, Dielectric Elastomers as Electromechanical Transducers, Elsevier, page 314, Equation 30.1, as well as similarly in R. Pelrine, Science 287, 5454, 2000, page 837, Equation 2. Actors Heretofore Known are too low in either the dielectric constant and / or the breakdown field strength or too high in the module. A disadvantage of known solutions is also the low electrical resistance, which leads to high leakage currents in actuators and in the worst case to an electrical breakdown.

For generators, it is important that they produce a high electrical current yield with low losses. Typical losses occur at interfaces, loading and unloading of the dielectric elastomer, and leakage through the dielectric elastomer. In addition, the resistance of the electrically conductive electrode layer of the EAP causes an energy loss; The electrode should therefore again have the lowest possible electrical resistance. A description can be found in: Christian Graf and Jürgen Maas, Energy harvesting cycles based on electroactive polymers, proceedings of SPIE Smart structures, 2010, vol. 7642, 764217. From the derivations of Equations 34 and 35, it follows on page 9 (12), last sentence, that the energy loss is minimal when the dielectric constant as well as the electrical resistance are particularly high. Since almost all electroactive polymers are operated under cyclic loads and pre-stretched structures, the materials must not flow with repeated cyclic loads and the creep should be as low as possible.

WO-A 2014/001272, WO-A 2012/019979 and WO-A 2014/006005 describe electrochemical converters containing polyurethanes as electroactive polymers. For the preparation of the dielectric polyurethane films used it is possible, inter alia, to use various OH-functional polymeric compounds, for example polyetherpolyols, polyesterpolyols or polycarbonatepolyols. However, in the case of polyether polyol-based polyurethane films, the transducers have too low an electrical resistance and an insufficient breakdown field strength. If polyester or polycarbonate polyols are used, the resulting converters can only be used to a limited extent at typical ambient temperatures, in particular in winter, owing to the relatively high glass transition temperatures of the resulting polyurethanes. It is also disadvantageous in this case that the polyurethane films usually have a too high modulus of elasticity, so that the actuator system according to the above equation is not sufficient. WO-A 2013/037508 A1 describes electrochemical converters which contain thermoplastic polyurethanes as electroactive polymers. However, thermoplastic polyurethanes are generally linear in construction, i. the overall functionality of the components used is <2, 1. However, such linear, uncrosslinked systems show a high stress relaxation (Creep).

It was therefore an object of the present invention to provide a process for the production of dielectric polyurethane films which are suitable for the production of electrochemical transducers, which in particular have a good electrical resistance and a high breakdown field strength and which also at typical ambient temperatures, especially in winter, can be used.

In particular, the dielectric polyurethane films should have one or more of the following properties: a) a tensile modulus (modulus of elasticity) of <5 MPa, preferably <4 MPa and more preferably <3 MPa at 25% elongation determined according to DIN 53 504, b) Elongation at break of> 20%, preferably> 50%> and especially> 70%> according to DIN 53 504, c) a glass point according to DIN 53 513 <- 10 ° C d) a stress relaxation (creep) at 10%> deformation after 30 min according to DIN 53 441 of

<30%, preferably <20% and especially <10%, e) a breakdown field strength of> 40 V / μηι according to ASTM D 149-97a, preferably> 60 V / μηι and particularly preferably> 80 V / μηι and / or f) an electrical resistance of> 1.0 * E10 ohm * m after ASTM D 257, more preferably> 1 * E11 ohm m and especially,> 5 * E11 ohm m.

The object according to the invention has been achieved by a method for producing a dielectric polyurethane film from a mixture comprising

A) an isocyanate group-containing compound having a content of isocyanate groups of> 10 and <50 wt .-% and a number average functionality of isocyanate groups of> 2.6 and <4 and

B) a polyester polyol having an OH number> 27 and <120 mg KOH / g, determined according to DIN 53240, characterized in that it has an ester group content of> 1 and <7 mol / kg and a content of aromatic structures of <50 wt .- % having.

The inventive method is particularly suitable for the production of dielectric polyurethane films, which are suitable for the production of electrochemical transducers, which in particular have a good electrical resistance and a high breakdown field strength and due to their low glass transition temperatures to that also at typical ambient temperatures, especially in winter , can be used. In addition, the polyurethane films have good mechanical strength and high elasticity.

The ester group content (dimension: mol ester groups / kg ester) is understood to mean the amount of ester groups of a polyester polyol relative to 1 kg of substance. This is calculated directly from the recipe by determining the molar amount of carboxylic acid groups or carboxylic acid group equivalents required to produce 1 kg of ester. Carboxylic acid equivalent are, for example, low molecular weight carboxylic acid esters and / or carboxylic anhydrides and / or lactones.

Aromatic components (proportion of aromatic structures, dimension:% by weight of aromatic) are likewise calculated directly from the formulation by determining the amount of aromatic carboxylic acids and / or aromatic carboxylic acid group equivalents required for preparing 100 g of the polyesterpolyol, and optionally aromatic diols , aromatic Carboxylic acid group equivalents are, for example, low molecular weight aromatic carboxylic acid esters and / or aromatic carboxylic anhydrides.

Number-average functionalities of the polyester polyols are calculated by first determining the number of molecules present before starting the reaction starting from the respective polyester polyol formulation. Furthermore, the number of moles of hydroxyl groups of all polyols before starting the reaction is determined as well as the number of moles of carboxyl groups. When carboxylic acid anhydrides and / or low molecular weight carboxylic acid esters and / or lactones are used as carboxylic acid equivalents, this number of carboxyl groups results from the fact that the anhydrides and / or esters are theoretically hydrolyzed to form carboxylic acid groups. The functionality of the reacted polyester polyol can now be determined from these data by dividing the number of moles of hydroxyl groups remaining by the number of molecules after the reaction.

The number of moles of hydroxyl groups remaining after the reaction is calculated from the number of moles of hydroxyl groups used before the reaction, minus the hydroxyl groups reacted by reaction with carboxyl groups. The latter corresponds to the number of moles of the carboxylic acid groups present before the reaction.

Since in each condensation step of a carboxyl group having a hydroxyl group, the number of remaining molecules in the reaction medium is reduced by 1 (distilling off the low molecular weight condensation product), the number of molecules after the reaction by subtracting the number of carboxyl groups from the number of all molecules before the reaction.

In a preferred embodiment of the invention, the ester group content of the polyester polyol is> 1 and <6.5 mol / kg, more preferably> 2 and <6.5 mol / kg.

In a likewise preferred embodiment of the invention, the aromatic content of the polyester polyol is <45% by weight, particularly preferably <35% by weight.

Further preferably, the OH number of the polyester polyol is> 35 and <90 mg KOH / g.

The number-average functionality of the polyester polyols is advantageously> 1.6 and <2.8, preferably> 1.8 and <2.4. In an advantageous embodiment of the invention, the polyester polyol has an OH number> 27 and <120 mg KOH / g, determined according to DIN 53240, an ester group content of> 1 and <6.5 mol / kg and a content of aromatic structures of <45 % By weight.

In a particularly advantageous embodiment of the invention, the polyester polyol has an OH number> 35 and <90 mg KOH / g, determined according to DIN 53240, an ester group content of> 2 and <6.5 mol / kg and a proportion of aromatic structures of < 35% by weight.

The polyester polyols are prepared in a conventional manner by polycondensation.

The polyesterpolyol is preferably obtainable from at least a) one or more aromatic and / or aliphatic dicarboxylic acids and / or dicarboxylic acid equivalents and b) one or more linear and / or branched aliphatic diols which have> 6 C atoms, c) optionally one or more Alcohols which are different from the alcohols b) and d) optionally at least one further constituent components which is selected from monocarboxylic acids, polycarboxylic acids having a functionality> 2 and / or hydroxycarboxylic acids and / or the carboxylic acid equivalents of the abovementioned and / or lactones.

As component a) it is possible in principle to use all aliphatic and / or aromatic dicarboxylic acids having> 4 and <50 carbon atoms, and also their anhydrides or low molecular weight esters as carboxylic acid equivalents and / or carbonic acid and their equivalents.

For example, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, suberic acid, nonanedicarboxylic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid are suitable , and dimer fatty acids and / or 2,2- Dimethylsuccinic. The acid source used may also be the corresponding analogous anhydrides and / or low molecular weight esters, which are referred to as carboxylic acid equivalents in the context of this invention.

Furthermore, carbonic acid in the context of this invention is likewise a dicarboxylic acid, which can preferably be used as dicarboxylic acid equivalent in the form of dialkyl esters, for example as dimethyl carbonate, or as diaryl esters, for example as diphenyl carbonate.

As component a) are in particular linear, unbranched dicarboxylic acids having> 8 and <18 C atoms and / or dimer fatty acids and / or phthalic acid, isophthalic acid and / or terephthalic acid and the carboxylic acid equivalents of the aforementioned.

In a preferred embodiment of the invention, component a) preferably contains> 5% by weight, more preferably> 10% by weight and very preferably> 15% by weight, based on the total weight of component a), of at least one aliphatic dicarboxylic acid having> 30 and <44 C atoms (component al) and / or their carboxylic acid equivalents. Component a) can in one embodiment consist entirely of al). Component a) preferably contains> 5% by weight and <90% by weight, more preferably> 10% by weight and <80% by weight of component a1), based on the total weight of component a).

Particularly preferably, the aliphatic dicarboxylic acid of component al) is branched.

Most preferably, component al) is one or more dimer fatty acids and / or their carboxylic acid equivalents.

By dimer fatty acids is meant dicarboxylic acids which can be prepared by dimerization of unsaturated monocarboxylic acids, such as oleic acid. Suitable dimer fatty acids are, for example, Pripol 1006, Pripol 1009, Pripol 1012, Pripol 1013, Pripol 1017, Pripol 1022, Pripol 1025 and Pripol 1027 from Croda. In addition to component a1), component a) preferably comprises at least one further aromatic and / or aliphatic dicarboxylic acid a2) and / or its dicarboxylic acid equivalent, which is different from al). The sum of the proportions of al) and a2) adds up to 100% by weight, based on the entire component a).

Suitable as component a2) are, in principle, all abovementioned dicarboxylic acids and / or their carboxylic acid equivalents, which do not correspond to component a1). The further dicarboxylic acid a2) is preferably selected from linear, unbranched dicarboxylic acids having> 8 and <18 C atoms and / or phthalic acid, isophthalic acid and / or terephthalic acid, and the carboxylic acid equivalents of the abovementioned.

In addition to the component a) or the components a1) and a2), no further dicarboxylic acids and / or dicarboxylic acid equivalents are preferably used to prepare the polyesterpolyol according to the invention.

Suitable as component b) are in principle all linear and / or branched aliphatic diols which have> 6 C atoms. Examples of suitable components (b) are 1,8-octanediol, 1,10-decanediol, 1,1,1-undecanediol, 1,6-hexanediol, 3-methylpentanediol-1,1,5,9-nonanediol and / or 1,12 -Dodecanediol, as well as dimer fatty acid diols from Croda, such as Pripol 2030 and 2033. Particularly preferably, the alcohols of component b)> 6 and <44 C-atoms, very particularly preferably> 6 and <18 C-atoms. Most preferably, component b) is selected from 1,8-octanediol, 1, 10-decanediol, 1,1,1-undecanediol, 1,6-hexanediol, methylpentanediol, 1,9-nonanediol and / or 1,12-dodecanediol.

Component c) of the polyester polyols according to the invention is preferably selected from difunctional or polyhydric aromatic alcohols having> 8 C atoms and / or aliphatic diols having> 2 and <5 C atoms and / or trihydric or polyhydric aliphatic alcohols, more preferably from aliphatic diols with> 2 and <C atoms and / or trihydric or more aliphatic alcohols, very particularly preferably from dihydric or polyhydric aliphatic alcohols.

Suitable components c) are, for example, ethylene glycol, butylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, trimethylolpropane, glycerol, pentaerythritol and / or trimethylolbenzene.

Component c) is preferably present in proportions of <10% by weight, based on the total weight of the polyester polyol, particularly preferably <5% by weight and very particularly preferably <2% by weight.

Most preferably, the proportion of component c), based on the total weight of the polyester polyol at 0 wt .-%. In a further embodiment of the invention, component c) is in proportions of> 0.5% by weight and <10% by weight, based on the total weight of the polyester polyol, particularly preferably> 0.5% by weight and <5 Wt .-% and most preferably> 0.5 wt .-% and <2 wt .-% before.

As component d) monocarboxylic acids, such as benzoic acid, caproic acid, oleic acid and / or ricinoleic acid can be used.

Furthermore, as component d), hydroxycarboxylic acids can also be used as reactants in the preparation of a polyester polyol having terminal hydroxyl groups. Suitable hydroxycarboxylic acids are, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid or hydroxystearic acid or mixtures thereof.

Likewise, as component d), it is also possible to use lactones for the preparation of the polyesterpolyols. Preferably, caprolactone is used.

As component d) also polycarboxylic acids with a functionality> 2 can be used. Suitable polycarboxylic acids of component d) are, for example, pyromellitic acid, pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, as well as trimer fatty acids, such as, for example, Pripol 1040 from Croda.

Preferably used as component d) are mono- and / or polycarboxylic acids having a functionality of> 2, more preferably ricinoleic acid and / or trimer fatty acids. Component d) is preferably present in proportions of <10% by weight, based on the total weight of the polyesterpolyol, particularly preferably <5% by weight and very particularly preferably <2% by weight.

Most preferably, the proportion of component d), based on the total weight of the polyester polyol at 0 wt .-%. In a further embodiment of the invention, component d) is in proportions of> 0.5% by weight and <10% by weight, based on the total weight of the polyester polyol, more preferably> 0.5% by weight and <5 Wt .-% and most preferably> 0.5 wt .-% and <2 wt .-% before. The sum of components c) and d) is preferably <20% by weight, particularly preferably <10% by weight and very particularly preferably <5% by weight, based on the total weight of the polyester polyol.

Single or more of the compounds suitable as component a) to d) may be biobased, i. be made from renewable raw materials and / or by means of at least one fermentative process step.

The polyesterpolyol is preferably obtainable from at least a) one or more linear, unbranched dicarboxylic acids with> 8 and <18 C atoms and / or dimer fatty acids and / or phthalic acid, isophthalic acid and / or terephthalic acid and the carboxylic acid equivalents of the abovementioned, b) one or more linear and / or branched aliphatic diols which have> 6 and <18 C atoms, c) optionally one or more alcohols which are selected from difunctional or polyhydric aromatic alcohols with> 8 C atoms and / or aliphatic diols with> 2 and <5 C atoms and / or trihydric or polyhydric aliphatic alcohols and d) optionally at least one further synthesis component which is selected from monocarboxylic acids, polycarboxylic acids having a functionality> 2 and / or hydroxycarboxylic acids and / or the carboxylic acid equivalents of the abovementioned and / or lactones.

In a particularly preferred embodiment of the invention, the polyesterpolyol is obtainable from at least ai)> 5% by weight, based on the total weight of the polyesterpolyol, of at least one aliphatic dicarboxylic acid which has> 30 and <44 carbon atoms and / or their carboxylic acid equivalents and a2) at least one further aromatic and / or aliphatic dicarboxylic acid a2) and / or its dicarboxylic acid equivalent, which is different from al), the sum of the proportions of al) and a2) being 100% by weight (corresponding to component a) added, b) one or more linear and / or branched aliphatic diols having> 6 and <18 C atoms, c) optionally one or more alcohols selected from di- or polyhydric aromatic alcohols having> 8 C atoms and / or aliphatic diols having> 2 and <5 C atoms and / or trihydric or more aliphatic alcohols and d) optionally at least one further synthesis component which is selected from monocarboxylic acids, polycarboxylic acids having a functionality> 2 and / or

Hydroxycarboxylic acids and / or the carboxylic acid equivalents of the aforementioned and / or lactones.

In a very particularly preferred embodiment of the invention, the polyesterpolyol is obtainable from at least ai)> 5% by weight, based on the total weight of the polyesterpolyol, of at least one dimer fatty acid and / or its carboxylic acid equivalent and a2) at least one further aromatic and / or aliphatic dicarboxylic acid a2) and / or their dicarboxylic acid equivalent, which is selected from linear, unbranched dicarboxylic acids having> 8 and <18 C atoms and / or phthalic acid, isophthalic acid and / or terephthalic acid, and the carboxylic acid equivalents of the aforementioned, wherein the sum of the proportions of al ) and a2) to 100 wt .-% (corresponding to component a) added, b) one or more linear and / or branched aliphatic diols, which are selected from 1,8-octanediol, 1, 10-decanediol, 1, 11th Undecanediol, 1,6-hexanediol, methylpentanediol, 1,9-nonanediol and / or 1,12-dodecanediol, c) <10% by weight, based on the total weight of the polyesterpolyol s, one or more alcohols, which are selected from di- or polyhydric aromatic alcohols having> 8 C atoms and / or aliphatic diols having> 2 and <5 C atoms and / or tri- or more aliphatic alcohols and d) <10% by weight, based on the total weight of the polyester polyol, of at least one further constituent component which is selected from monocarboxylic acids, polycarboxylic acids having a functionality of> 2 and / or hydroxycarboxylic acids and / or the carboxylic acid equivalents of the abovementioned and / or lactones.

In a preferred embodiment of the invention, the polyester polyol is exclusively from components a), b), c) and d), more preferably exclusively from components a), b) and c) and very particularly preferably exclusively from components a) and b) constructed.

The compound A) has a number average functionality of isocyanate groups of> 2.6 and <4.

Isocyanates or modifications of isocyanates having a number average functionality of isocyanate groups of> 2.6 and <4, for example based on 1, 4-butylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2 are suitable according to the invention as compound A) , 2,4 and / or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis (4,4'-isocyanatocyclohexyl) methanes (H12-MDI) or mixtures thereof of any isomer content, 1,4-cyclohexylene diisocyanate, 4-isocyanatomethyl-1 , 8-octane diisocyanate (nonane triisocyanate), 1, 4-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate (TDI), 1,5-naphthylene diisocyanate, 2,2'- and / or 2,4'- and or 4,4'-diphenylmethane diisocyanate (MDI), 1,3- and / or 1,4-bis (2-isocyanato-prop-2-yl) -benzene (TMXDI), 1,3-bis (isocyanatomethyl) benzene (XDI), alkyl 2,6-diisocyanatohexanoates (lysine diisocyanates) having alkyl groups of 1 to 8 carbon atoms and mixtures thereof. Preferred are modifications such as allophanate, uretdione, urethane, isocyanurate, biuret, iminooxadiazinedione or oxadiazinetrione containing compounds based on the diisocyanates mentioned, as well as polynuclear compounds, such as polymeric MDI (pMDI) and combinations of all mentioned compounds. Preference is given to using modified diisocyanates from the series HDI, IPDI, H12-MDI, TDI and MDI.

In a preferred embodiment of the invention, the compound A) comprises or consists of an aliphatic polyisocyanate.

Particularly preferably, the compound A) comprises or consists of hexamethylene diisocyanate and / or a polyisocyanate based on HDI having a functionality of> 2.6, this being Polyisocyanate particularly preferably has a biuret, allophanate, isocyanurate, Iminooxadiazindion- or Oxadiazintrionstruktur.

Most preferably, the compound A) comprises or consists of hexamethylene diisocyanate and / or a biuret and / or isocyanurate of hexamethylene diisocyanate. Preference is furthermore given to using as component A) modified aliphatic isocyanates based on HDI with a free, unreacted monomeric fraction of free isocyanate of <0.5% by weight.

The compound A) has a content of isocyanate groups of> 10 and <50 wt .-%, preferably of> 15 and <40% by weight, particularly preferably of> 18 and <25% by weight.

The isocyanate groups of compound A) may also be partially or completely blocked until they react with the isocyanate-reactive groups so that they can not react directly with the isocyanate-reactive group. This ensures that the reaction takes place only at a certain temperature (blocking temperature). Typical blocking agents are found in the prior art and are selected so that they split off again at temperatures between 60 and 220 ° C, depending on the substance, from the isocyanate group and only then react with the isocyanate-reactive group. There are blocking agents which are incorporated into the polyurethane and also those which remain in the polyurethane as a solvent or plasticizer or outgas from the polyurethane. One speaks also of blocked NCO values. If NCO values are mentioned in the invention, this is always based on the unblocked NCO value. Most are blocked up to <0.5%. Typical blocking agents are for example caprolactam, methyl ethyl ketoxime, pyrazoles such as 3,5-dimethyl-l, 2-pyrazole or 1-pyrazole, triazoles such as 1,2,4-triazole, diisopropylamine, diethyl malonate, diethylamine, phenol or its derivatives or imidazole.

In addition to the components A) and B), the mixture may also contain further polymeric compounds i) containing at least 2 isocyanate-reactive groups, these being preferred for <20% by weight, based on the total weight of the polyester polyols B) and the compounds i) <15 wt .-% and particularly preferably <10 wt .-% present. Further preferably, the mixture contains no compounds i). As polymeric compounds i) for the purposes of this invention are meant compounds having a number average molecular weight of> 400 g / mol. The isocyanate-reactive groups of compound i) are functional groups that can react to form covalent bonds with isocyanate groups. In particular, it can be here be amine, epoxy, hydroxyl, thiol, mercapto, acrylic, anhydride, vinyl, and / or carbinol groups. The isocyanate-reactive groups are particularly preferably hydroxyl and / or amine groups.

It is advantageous if the compound i) has a number-average functionality of isocyanate-reactive groups of> 2.0 and <4, wherein the isocyanate-reactive groups are preferably hydroxyl and / or amine groups, more preferably hydroxy groups.

The compound i) may preferably have an OH number> 27 and <120 mg KOH / g, more preferably> 35 and <90 mg KOH / g.

As compound i) it is possible to use polyetherpolyols, polyetheramines, polyetheresterpolyols, polycarbonatepolyols, polyethercarbonatepolyols, polybutadiene derivatives and polysiloxanes, and mixtures thereof. I) are preferably polyether, polycarbonate and polyetherester polyols, polybutadiene polyols and / or polysiloxane polyols and more preferably polycarbonate polyols.

The compounds i) mentioned are prepared by the processes known to the person skilled in the art and comprise all compounds known to those skilled in the art under these terms.

Furthermore, the mixture may also comprise monofunctional compounds ii) which have an isocyanate-reactive group. Examples of such monofunctional compounds are ethanol, n-butanol, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, dipropylene glycol mono-propyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, 2-ethylhexanol, 1-octanol, 1-dodecanol or 1-hexadecanol or mixtures thereof.

Optionally, the mixture may additionally contain chain extenders and / or crosslinking agents iii), which are proportionally added to compound B). In this case, compounds having a functionality of 2 to 3 and a molecular weight of 62 to 400 g / mol are preferably used. It is possible to use aromatic or aliphatic aminic chain extenders, for example diethyltoluenediamine (DETDA), 3,3'-dichloro-4,4'-diaminodiphenylmethane (MBOCA), 3,5-diamino-4-chloro-isobutylbenzoate, 4- Methyl 2,6-bis (methylthio) -1,3-diaminobenzene (Ethacure 300), trimethylene glycol di-p-aminobenzoate (Polacure 740M) and 4,4'-diamino-2,2'-dichloro-5 , 5'-Diethyldiphenylmethane (MCDEA) can be used. Particularly preferred are MBOCA and 3,5-diamino-4-chloro-isobutylbenzoate. Components suitable for chain extension according to the invention are organic diamines or polyamines. For example, ethylenediamine, 1,2-diaminopropane, 1, 3 Diaminopropane, 1, 4-diaminobutane, 1,6-diaminohexane, isophorone diamine, isomer mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylenetriamine, diaminodicyclohexylmethane or dimethylethylenediamine or mixtures thereof.

In addition, as component iii), compounds which, in addition to a primary amino group, also have secondary amino groups or, in addition to an amino group (primary or secondary), also OH groups, can be used. Examples of these are primary / secondary amines, such as diethanolamine, 3-amino-1-methylaminopropane, 3-amino-1-ethylaminopropane, 3-amino-1-cyclohexylaminopropane, 3-amino-1-methylaminobutane, alkanolamines, such as N-aminoethylethanolamine, ethanolamine , 3-aminopropanol, neopentanolamine. For chain termination are usually amines having an isocyanate-reactive group such as methylamine, ethylamine, propylamine, butylamine, octylamine, laurylamine, stearylamine, isononyloxypropylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylaminopropylamine, diethyl (methyl) aminopropylamine, morpholine, piperidine, or suitable substituted derivatives thereof, amide amines from diprimary amines and monocarboxylic acids, monoketim of diprimary amines, primary / tertiary amines, such as Ν, Ν-dimethylaminopropylamine. Often these have a thixotropic effect due to their high reactivity, so that the rheology is changed so that the mixture has a higher viscosity on the substrate.

Examples of non-aminic chain extenders which are often used are, for example, 2,2'-thiodiethanol, 1,2-propanediol, 1,3-propanediol, glycerol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol. propanediol-1,3, pentanediol-1,2, pentanediol-1,3, pentanediol-1,4, pentanediol-1,5, 2,2-dimethyl-1,3-propanediol, 2-methylbutanediol-1,4 2-Methylbutanediol-1,3,1,1,1-trimethylolethane, 3-methyl-1,5-pentanediol, 1,1,1-trimethylolpropane, 1,6-hexanediol, 1,7-heptanediol, 2-ethyl- 1, 6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1, 10-decanediol 1, 11-undecanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanediol, 1,3-cyclohexanediol and water used. In a preferred embodiment of the invention, the mixture contains neither component ii) nor iii). In a particularly preferred embodiment of the invention, the mixture does not contain any of components i), ii) and iii).

Also preferred is the sum of the number average functionality of isocyanate groups and isocyanate-reactive groups of compounds A) and B), and optionally i), ii) and iii)> 2.6 and <6.0, more preferably> 2.8 and < 5.0, most preferably> 2.8 and <4.0. Most preferably, A) and B) and optionally i) have low levels of free water, residual acids and metal contents. The residual water content of B) is preferably <1% by weight, more preferably <0.7% by weight (based on B)). The residual acid content of B) is preferably <1% by weight, more preferably <0.7% by weight (based on B). The residual metal contents, caused, for example, by residues of catalyst constituents used in the preparation of the starting materials should preferably be less than 1000 ppm and more preferably less than 500 ppm, based on A) or B).

The ratio of isocyanate-reactive groups to isocyanate groups in the mixture is preferably between 1: 3 to 3: 1, more preferably between 1: 1.5 to 1.5: 1, most preferably between 1: 1, 3 to 1, 3: 1 and more preferably between 1: 1, 02 to 1: 0.95.

The components A) and B), and optionally i), ii) and iii) can be reacted with one another in one step, the so-called one-shot process. In addition to the one-shot process, the prepolymer process can also be used in the reaction of A) with B). In this case, a part A) is reacted with B) to form a prepolymer and later reacted further with further component B). In this case, the prepolymer thus prepared can be further processed directly or first filled and stored and later used as component A).

In addition to the compounds A) and B, and optionally also i) to iii), the mixture may additionally contain auxiliaries and additives. Examples of such auxiliaries and additives are crosslinkers, thickeners, solvents, thixotropic agents, stabilizers, antioxidants, light stabilizers, emulsifiers, surfactants, adhesives, plasticizers, water repellents, pigments, fillers rheology improvers, plasticizers, degassing and defoaming agents, wetting additives and catalysts and fillers.

Typical catalysts are organometallic compounds such as tin salts or amines or amidines. Very particular preference is given to using organotin compounds as catalysts.

In a preferred embodiment of the invention, the mixture furthermore comprises C) a solvent which has a vapor pressure at 20 ° C. of> 0.1 and <200 mbar and D) a wetting additive. In a further preferred embodiment of the invention, the mixture also comprises a filler E).

As solvent C) aqueous and organic solvents can be used, more preferably organic solvents are used. Preferably, a solvent can be used which has a vapor pressure at 20 ° C. of> 0.1 mbar and <200 mbar, preferably> 0.2 mbar and <150 mbar and particularly preferably> 0.3 mbar and <120 mbar. It is particularly advantageous that the films of the invention can be produced on a roller coating system.

Usually, the wetting additive D) in an amount of 0.05 to 1.0 wt .-%, based on the total weight of the mixture, in the mixture. Typical wetting additives are available, for example, from Altana (Byk additives such as: polyester-modified polydimethylsiloxane, polyether-modified polydimethylsiloxane or acrylate copolymers, and, for example, CeFo fluorotelomers).

Preferably, the mixture comprises fillers E) with a high dielectric constant. Examples of these are ceramic fillers, in particular barium titanate, strontium titanate, copper titanate, calcium titanate, titanium dioxide and piezoelectric ceramics such as quartz or lead zirconium titanate, and mixed oxides of all compounds mentioned above and organic fillers, especially those having a high electrical polarizability, for example phthalocyanines, poly-3-hexylthiophene , By adding these fillers, the dielectric constant of the polyurethane film can be increased.

In addition, a higher dielectric constant can also be achieved by introducing electrically conductive fillers below the percolation threshold. Examples of such materials are, besides metals such as silver, aluminum and copper, carbon black, graphite, graphene, fibers, single or multi-walled carbon nanotubes, electrically conductive polymers such as polythiophenes, polyanilines or polypyrroles, or mixtures thereof. Of particular interest in this connection are those types of carbon black which have a surface passivation and therefore at higher concentrations below the percolation threshold increase the dielectric constant and nevertheless do not lead to an increase in the conductivity of the polymer. Here, such carbon black types with a particularly high BET surface area are preferred. In the context of the present invention, additives for increasing the dielectric constant and / or the electrical breakdown field strength can also be added after the filming of polyurethanes. This can be done, for example, by generating one or more further layers or by penetration of the polyurethane film, for example, by diffusion.

In a further preferred embodiment of the process according to the invention, at least the following steps are carried out: I) the mixture is prepared.

II) the mixture is applied to a support in the form of a wet film immediately after its preparation,

III) the wet film is cured to form the polyurethane film and

IV) the polyurethane film is separated from the carrier. Particularly preferably, the steps I) to IV) are repeated continuously.

The polyurethane film may have a layer thickness of 0.1 μιη to 1000 μηι, preferably from 1 μιη to 500 μηι, more preferably from 5 μιη to 200 μιη and most preferably from 10 μιη to 100 μιη.

The application of the mixture of step I) to the support in step II) can be carried out, for example, by knife coating, brushing, casting, spinning, spraying, extrusion in a roll-to-roll process. Preferably, the mixture is applied to the carrier with a squeegee (such as a squeegee, quark, or the like), rollers (such as anilox rollers, gravure rollers, burnishing rollers, or the like) or a nozzle. The nozzle may be part of a nozzle application. It is also possible to operate several commissioned works simultaneously or in succession. Several layers can be applied simultaneously with a commissioned work. Preferably, a nozzle is used, and more preferably a residence time optimized and / or recirculation-free nozzle. Most preferably, the distance of the nozzle to the carrier is less than three times the thickness of the wet film, preferably less than twice the thickness of the wet film, and more preferably less than one and a half times the thickness of the wet film. If, for example, 150 μm of wet film is coated (if the wet film contains 20% by weight of solvent, this corresponds to 120 μm of cured film), then the distance between the nozzle and the substrate should be selected to be less than 300 μm. If the distance of the nozzle to the support is chosen as described above, a roller coater can be used to make the films. According to a further preferred embodiment of the method according to the invention, a wet film with a thickness of 10 to 300 μm, preferably of 15 to 150 μm, more preferably of 20 to 120 μm, and very particularly preferably of 20 to 80 μm can be produced in step II).

It is also preferred if the wet film is cured in step III) by being passed through a first drying section, which preferably has a temperature> 40 ° C and <120 ° C, more preferably> 60 ° C and <110 ° C and especially preferably> 60 ° C and <100 ° C.

The wet film can also be passed through a second drying section after the first drying section, which preferably has a temperature> 60 ° C and <130 ° C, more preferably> 80 ° C and <120 ° C and particularly preferably> 90 ° C and < 120 ° C has. In addition, after the second drying section, the wet film can also be passed through a third drying section which preferably has a temperature of> 110 ° C. and <180 ° C., more preferably> 110 ° C. and <150 ° C. and particularly preferably> 110 ° C. <140 ° C has.

Drying can be carried out in suspension or in roller dryers, such as those offered by, for example, Krönert, Coatema, Drytec or Polytype on the market. The typical rate at which the wet film on the support passes through the drying section (s) is> 0.5 m / min and <600 m / min, more preferably> 0.5 m / min and <500 m / min and more preferably> 0.5 m / min and <100 m / min.

The dry section length and the supply air of the dry sections are adapted to the speed. Most commonly, the total residence time of the wet film in the dry section or sections is> 10 seconds and <60 minutes, preferably> 30 seconds and <40 minutes, more preferably> 40 seconds and <30 minutes, and most preferably> 40 seconds and < 10 mins.

The dielectric polyurethane film according to the invention can be provided with further functional layers, for example conductive layers, barrier layers against solvents and gases, and / or adhesive layers. This can be done on one side or on both sides, in one layer or in several layers one above the other, by complete or by surface partial coating.

Glass, release paper, films and plastics from which the produced polyurethane dielectric film can be easily separated are particularly suitable as carriers for the production of a polymer film from the reaction mixture. Particularly preferred paper or films are used. Paper can be coated on one or both sides, for example, with silicone or plastics be. The coating and / or the film can be made, for example, of plastics such as polyethylene, polypropylene, polymethylpentene, polyethylene terephthalate, polypropylene, polyethylene, polyvinyl chloride, teflon, polystyrene, polybutadiene, polyurethane, acrylester-styrene-acrylonitrile, acrylonitrile / butadiene / acrylate, acrylonitrile-butadiene Styrene, acrylonitrile / chlorinated polyethylene / styrene, acrylonitrile / methyl methacrylate, butadiene rubber, butyl rubber, casein plastics, artificial horn, cellulose acetate, cellulose hydrate, cellulose nitrate, chloroprene rubber, chitin, chitosan, cyclo-olefin copolymers, epoxy resin, ethylene oxide Ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene rubber, ethylene-vinyl acetate, fluororubber, urea-formaldehyde resin, isoprene rubber, lignin, melamine-formaldehyde resin, melamine / phenol-formaldehyde, methyl acrylate / butadiene / styrene, natural rubber ( Gum arabic), phenol-formaldehyde resin, perfluoroalkoxylalkane, polyacrylonitrile, polyamide, polybutylene sensor cinate, polybutylene terephthalate, polycaprolactone, polycarbonate, polychlorotrifluoroethylene, polyester, polyesteramide, polyether-block-amide, polyetherimide, polyetherketones, polyethersulfone, polyhydroxyalkanoates, polyhydroxybutyrate, polyimide, polyisobutylene, polylactic acid, polymethacrylmethylimide, polymethylene terephthalate, polymethylmethacrylate, polymethylpentene, polyoxymethylene or polyacetal , Polyphenylene ether, polyphenylene sulfide, polyphthalamide, polypyrrole, polystyrene, polysulfone, polytetrafluoroethylene, polyurethane PUR, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyvinylidene fluoride, polyvinylpyrrolidone, silicone, styrene-acrylonitrile copolymer, styrene-butadiene rubber, styrene-butadiene-styrene, thermoplastic starch , Thermoplastic polyurethane, vinyl chloride / ethylene, vinyl chloride / ethylene / methacrylate. Alternatively, these plastics can also be used directly as support materials and / or additionally provided with further internal or external release agents or layers. The layers may have barrier functions or may also contain conductive structures which may optionally be transferred to the polyurethane dielectric film. The plastics may be axially or biaxially oriented or stretched and may be pretreated by pressure or corona. The films can also be reinforced. Typical reinforcements are fabrics such as textile or glass fibers.

According to a particularly preferred embodiment, a carrier made of glass, plastic or paper and preferably made of silicone or plastic-coated paper can be used. The film or paper can be peeled off directly after coating and reused. In a particular embodiment, the film may be circulated and the dielectric polyurethane film transferred directly to a new carrier during stripping. In a preferred embodiment, the carrier is provided with a structure. This is also called an imprint. The embossing is such that the structure on the dielectric Polyurethane film transfers in such a way that the embossing is formed only in the surface of the dielectric polyurethane film. The embossing is smooth when the film is stretched. The embossment is made such that an electrode layer on the film is stretched when stretched without significantly stretching that layer itself. The embossment is preferably embossed in a roll-to-roll process in the carrier. For example, hot or coagulated hot through a roll into a thermoplastic is applied here. Typical embossings are described for example in EP 1 919 071.

A further subject of the present invention is a dielectric polyurethane film obtainable by the process according to the invention. The polyurethane dielectric film of the present invention is also useful for the production of multi-layered electroactive polymer film systems known in the art comprising layers of dielectric polyurethane and, for example, conductive electrode layer. Such systems are described, for example, in WO-A 2014/001272 or WO-A 2014/006005.

Likewise provided by the invention is a method for producing an electromechanical transducer, in which a dielectric polyurethane film is produced in a first step by a method according to the invention and in a second step an electrode is arranged on opposite sides of the dielectric polyurethane film.

The electrodes can be applied, for example, via a printing process such as ink-jet, flexographic printing, screen printing or via a doctor blade, a nozzle or roller and via a metallization in a vacuum. Typical materials are carbon based or based on metals such as silver, copper, aluminum, gold, nickel, zinc or other conductive metals as well as materials. The metal can be applied as a salt or as a solution, as a dispersion or emulsion and also as a precursor.

In addition, an obtainable by this method electromechanical transducer is the subject of the invention.

In the electromechanical transducer, the electrode layer on the layers is preferably applied so that it can be contacted from the sides and not over the dielectric film edge, otherwise there will be breakdowns. It is usual to allow a safety margin between the electrode and the dielectric so that the electrode area is smaller than the dielectric area. The electrode is structured such that a conductor track is led out for electrical contacting. The converter can be advantageously used in a variety of configurations for the production of sensors, actuators and / or generators.

Another object of the present invention is therefore an electronic and / or electrical device, in particular a module, automaton, instrument or a component comprising an electromechanical transducer according to the invention.

Furthermore, the present invention relates to the use of an electromechanical transducer according to the invention in an electronic and / or electrical device, in particular in an actuator, sensor or generator. Advantageously, the invention in a variety of different applications in the electro-mechanical and electro-acoustic field, in particular in the field of energy from mechanical vibrations (energy harvesting), acoustics, ultrasound, medical diagnostics, acoustic microscopy, mechanical sensors, in particular pressure - Force and / or strain sensors, robotics and / or communication technology can be realized. Typical examples include pressure sensors, electroacoustic transducers, microphones, loudspeakers, vibration transducers, light deflectors, diaphragms, optical fiber modulators, pyroelectric detectors, capacitors and control systems, and "intelligent" floors, as well as systems for converting mechanical energy, particularly rotating or oscillating motions electrical power.

Examples:

The invention will be explained in more detail below with reference to examples.

Unless otherwise indicated, all percentages are by weight.

Unless otherwise noted, all analytical measurements would be carried out at temperatures of 23 ° C under normal conditions.

methods:

NCO contents were determined volumetrically in accordance with DIN EN ISO 11909, unless expressly stated otherwise. Hydroxyl numbers (OHN in mg KOH / g substance) were determined according to DIN 53240 (December 1971).

Acid numbers were determined according to DIN EN ISO 2114 (June 2002).

The ester group contents and aromatics contents were determined as explained in the description section.

The indicated viscosities were determined by means of rotational viscometry according to DIN 53019 at 23 ° C. using a rotational viscometer from Anton Paar Germany GmbH, Germany, Helmuth-Hirth-Str. 6, 73760 Ostfildern.

For the coating experiments of the examples, a laboratory doctor blade from Zehntner was used for laboratory experiments.

Measurements of film thicknesses were made with a mechanical probe from Dr. Ing. Johannes Heidenhain GmbH, Germany, Dr.-Johannes-Heidenhain-Str. 5, 83301 Traunreut. The specimens were measured at three different locations and the mean value was used as a representative measurement.

To determine the modulus of elasticity at 25% elongation and the elongation at break were carried out by means of a tractor from Zwick, model number 1455 equipped with a load cell of the total measuring range lkN according to DIN 53 504 tensile tests with a pulling speed of 50 mm / min. S2 specimens were used as specimens. Each measurement was carried out on three uniformly prepared specimens and the mean of the data obtained Rating used. The tensile strength in [MPa] and the elongation at break in [%] and the stress in [MPa] at 25% elongation were determined. The modulus at 25% elongation corresponds to the tangent to the stress-strain curve at 25% strain.

The determination of the stress relaxation (Creep) was also carried out on the tractor Zwicki; the instrumentation corresponds to the attempt to determine the permanent strain. The sample used was a strip-shaped sample of the dimension 60 × 10 mm ² , which was clamped with a clamp spacing of 50 mm. After a very fast deformation to 55 mm, this deformation was kept constant for a period of 30 minutes and during this time the force curve was determined. The stress relaxation after 30 minutes is the percentage decrease in stress, relative to the initial value immediately after deformation to 55 mm.

The determination of the glass transition temperature was carried out by means of a dynamic mechanical analysis (DMS 6100 from SEIKO, German representation: THASS GmbH, Pfingstweide 21, 61169 Friedberg) under forced oscillations according to DIN 51513. The glass transition temperature is the maximum of the loss modulus curve.

The electrical resistance was determined by means of a laboratory setup from Keithley Instruments (Keithley Instruments GmbH, Landsberger Strasse 65, D-82110 Germering Germany) Model No .: 6517 A and 8009 according to ASTM D 257, a method for determining the insulation resistance of materials , Fracture field strength was determined according to ASTM D 149-97a using a model HypotMAX high voltage power source supplied by Associated Research Inc, 13860 W Laurel Drive, Lake Forest, IL 600045-4546, USA, and a self-constructed sample holder. The sample holder contacts the homogeneous-thickness polymer samples with little mechanical preload and prevents the operator from coming in contact with the stress. The non-prestressed polymer film is statically loaded in this structure with increasing voltage until an electrical breakdown takes place through the film. The result of measurement is the voltage reached at breakthrough, based on the thickness of the polymer film in [V / μιη]. There are 5 measurements per slide and the mean value is given. Substances used and abbreviations:

Desmodur® N100 biuret based on hexamethylene diisocyanate, NCO content 220 ±

 0.3% (according to DIN EN ISO 11 909), viscosity at 23 ° C. 10000 ± 2000 mPa-s, Bayer MaterialScience AG, Leverkusen, DE P200H / DS Polyesterpolyol based on 1,6-hexanediol and

 Phthalic anhydride, molecular weight 2000 g / mol, ester group content 7.6 mol / kg and aromatic content 62.7 wt .-%, Bayer MaterialScience AG, Leverkusen, DE

Tib Kat 220 Butyltin tris (2-ethylhexanoate), from Tib Chemicals AG, Mannheim

DBTDL dibutyl-tin dilaurate from E-Merck KGaA, Frankfurter Str.

 250, D-64293 Darmstadt, Germany

Phthalic anhydride: My-Chem GmbH & Co KG

Dimethyl terephthalate: Creanova Spezialchemie GmbH

Terephthalic acid Sigma-Aldrich

Decanedicarboxylic acid Sigma-Aldrich

1,12-Dodecanediol: Beckmann Kenko GmbH

1,6-hexanediol: Sigma-Aldrich

3-methyl-pentanediol-1, 5: Beckmann Kenko GmbH

Pripol 1009: hydrogenated dimer fatty acid, Croda Europe Ltd. Titanium tetrabutoxide: Sigma-Aldrich

Tin (II) chloride dihydrate: Sigma-Aldrich

Hostaphan RN 2SLK: release film from Mitsubishi based on polyethylene terephthalate with silicone coating. A 300 mm wide film was used. polyester production

Table 1 shows the starting materials used for the preparation of the polyester polyols 1 to 4, the ester group contents and aromatic proportions of the resulting polyester polyols.

Table 1: Polyester polyols

Edukte Ex. 1 Ex. 2 Ex. 3 Ex. 4

Phthalic anhydride [% by weight] 26.9

Pripol 1009 [% by weight] 15.8 39.8 41.9 77.9

Terephthalic acid [wt%] 30.0

Dimethyl terephthalate [wt%] 20.9

Decanedicarboxylic acid [% by weight] 15.8

1,6-hexanediol [wt%] 38.4 22.1

Methylpentanediol [wt%] 33.2 18.6

1,12-Dodecanediol [wt%] 18.6

Ester group content [mol / kg] 6.2 5.1 4.3 2.9

Aromatic content [% by weight] 33.3 29.4 22.6 0

OH number [mg KOH / g] 55.5 54.8 55.5 54.3

Acid number 1.7 3.0 1.7 0.7 Preparation of the polyester polyol 1

(In a 4-liter four-necked flask equipped with mechanical stirrer, 50 cm Vigreux column, thermometer, nitrogen inlet, and column head, distillation bridge and vacuum membrane pump, put 351 g Pripol 1009 (0.613 mol, corresponding to 15.8 wt .-% ), 351 g of decanedicarboxylic acid (1.523 mol, corresponding to 15.8 wt.%) And 853 g of 1,6-hexanediol (7.221 mol, corresponding to 38.41 wt.%) And heated under nitrogen over a period of 60 min to 130 ° C. A total of 666 g of terephthalic acid (4.015 mol, corresponding to 30% by weight) were added in three portions, the reaction temperature after addition at about 130 ° to 140 ° C. in each case being raised to 230 ° C. and at this temperature, the reaction continued until no more water of reaction distilled off, which was the case after a running time of about 20 hours.The reaction was completed by adding 40 mg of stannous chloride dihydrate, by applying Vacuum the pressure gradually over about 2 hrs. lowered to last 15 mbar and the reaction continued at 200 ° C for a further 50 hours

Analysis of the polyester:

Hydroxyl value: 55.5 mg KOH / g Acid value: 1.7 mg KOH / g Viscosity: free-flowing at 100 ° C

Preparation of the polyester polyol 2

In a 4-liter four-necked flask equipped with mechanical stirrer, 50 cm Vigreux column, thermometer, nitrogen inlet, and column head, distillation bridge and vacuum membrane pump, 525 g of phthalic anhydride (26.95 wt .-% = 3.544 mol), 725 g ( 32.46% by weight = 6.132 moles) of 3-methylpentanediol, 1.5 and 869 g (39.83% by weight = 1.519 moles) of Pripol 1009 were initially charged and under nitrogen over a period of 60 minutes. heated to 200 ° C. After no further reaction water distilled off (about 3 hours), 40 mg of tin (II) chloride dihydrate were added and the pressure was slowly reduced to 15 mbar and completed the reaction over a further 36 hours. The intermediate analysis gave a value of 3.06 mg KOH for the acid number and a value of 48.6 mg KOH / g for the OH number. The batch was prepared by adding 0.75 wt .-% = 16.7 g of 3-methyl-pentanediol-l, 5 and stirring the Reaction batch at 200 ° C at atmospheric pressure for 6 hours to the desired OH number and determined again OH and acid number.

Analysis of the polyester:

Hydroxyl value: 54.8 mg KOH / g Acid value: 3.0 mg KOH / g

Viscosity: 1500 mPas (75 ° C)

Preparation of the polyester polyol 3

In a 4-liter four-necked flask equipped with mechanical stirrer, 50 cm Vigreux column, thermometer, nitrogen inlet, and column head, distillation bridge and vacuum membrane pump, 451 g of dimethyl terephthalate (20.95 wt .-% = 2.717 mol), 400 g ( 18.57 wt .-% = 3.386 mol) 3-Methylpentandiol-l, 5 and 400 g (18.57 wt .-% = 1.958 mol) of 1,12-dodecanediol and under nitrogen over a period of 60 min. heated to 80 ° C. After adding 40 mg of titanium tetrabutoxide, the temperature was increased stepwise in the course of 8 hours to 200 ° C., which distilled off methanol. When methanol was no longer formed at 200 ° C. and atmospheric pressure, 903 g (41.9% by weight = 1.557 mol) of Pripol 1009 were added to the reaction mixture and the reaction water was distilled off in the course of a further 3 hours. Thereafter, the pressure was slowly reduced to 15 mbar and completed the reaction over a further 24 hours. Analysis of the polyester:

Hydroxyl number: 55.5 mg KOH / g

Acid number: 1.7 mg KOH / g

Viscosity: 1910 mPas (75 ° C)

Preparation of the polyester polyol 4

In a 4-liter four-necked flask equipped with mechanical stirrer, 50 cm Vigreux column, thermometer, nitrogen inlet, and column head, distillation bridge and Vacuum membrane pump, 1475 g (2.576 mol, corresponding to 77.91 wt .-%) of Pripol 1009 and 418 g (3.539 mol, corresponding to 22.09 wt%) of 1,6-hexanediol were submitted and under nitrogen overcure in the course of 60 min. heated to 200 ° C, with water of reaction distilled off. After 3 hours, the formation of water of reaction came to a standstill. It was cooled to about 80 ° C and added 36 mg of stannous chloride II dihydrate, the temperature was raised to 200 ° C and then lowered the pressure gradually over 60 minutes to 15 mbar. Under these reaction conditions, the reaction was completed in the course of another 18 hours.

Analysis of the polyester:

Hydroxyl value: 54.3 mg KOH / g Acid value: 0.7 mg KOH / g

Viscosity: 1050 mPas (75 ° C)

Preparation of the films using the polyester polyols 1 to 4 according to the invention and the comparative polyester polyol P200H / DS: 21.39 parts by wt. Desmodur® N100, with a polyol mixture of 0.01 part by wt. DBTL and 100 wt. Parts of the respective polyester polyol from Examples 1 to 4 or the polyester polyol P200H / DS (comparative) reacted with each other. The isocyanate (Desmodur® N100) was used at 40 ° C, the polyol blend (polyester polyol with DBTL) at 80 ° C. The ratio of NCO to OH groups was 1.07. It was poured onto the Hostaphan film and dried for 1 h at 100 ° C in a heating cabinet.

Evaluation of Examples 5 to 8 and Comparison 9:

Table 2 shows the properties of the polyurethane films produced from the individual polyesters determined by the abovementioned measuring methods. It was found that the films according to the invention offer distinct advantages over those of the prior art.

Particularly advantageous in the films of the invention, the combination of the deep glass point with a good electrical resistance and a high breakdown field strength. The Films of the invention can be used in particular for the production of electromechanical converters with particularly good efficiencies, which can also be used at the usual ambient temperatures, especially in winter. In addition, the polyurethane films have good mechanical strength and high elasticity.

Table 2:

Measured variable Ex. 5 Ex. 6 Ex. 7 Ex. 8 Comparison 9

 (P200H / DS)

Ester group content 6.2 5.1 4.3 2.9 7.6

[Mol / kg]

Aromatic content 33.3 29.4 22.6 0 62.7

[Wt .-%]

Tg [° C] -15.5 -18.2 -27.7 -45.9 +3.3

Breakthrough field strength 102.7 105.2 115.5 124.5 74.7

Electrical resistance 1.08 * E12 1.23 * E12 1.09 * E12 1.43 * E12 1.2 * E12 [Ohm * m]

Modulus of elasticity at 25% 2.15 1.73 1.80 1.82 2.21

Elongation [MPa]

Elongation at break [%] 174.5 102 87.9 79.3 195.2

Stress relaxation 1.28 0.50 1.85 2.31 1.55

(Creep) [%]

Film thickness [mm] 0.161 0.109 0.119 0.125 0.216

Claims

 claims

A process for producing a polyurethane dielectric film from a mixture comprising

A) a Isocyanatgrappen-containing compound having a content of isocyanate groups of> 10 and <50 wt .-% and a number average functionality of Isocyanatgrappen of> 2.6 and <4 and

B) a polyester polyol having an OH number> 27 and <120 mg KOH / g, determined according to DIN 53240, characterized in that it has an ester fragment content of> 1 and <7 mol / kg and a content of aromatic structures of <50 wt .- % having.

Process according to claim 1, characterized in that the polyester polyol has a proportion of aromatic structures of <35% by weight.

Process according to claim 1 or 2, characterized in that the polyester polyol is obtainable from at least a) one or more aromatic and / or aliphatic dicarboxylic acids or dicarboxylic acid equivalents and b) one or more linear and / or branched aliphatic diols which contain> 6 C atoms c) optionally one or more alcohols which are different from the alcohols b) and d) optionally at least one further constituent components which are selected from monocarboxylic acids, polycarboxylic acids having a functionality of> 2 and / or hydroxycarboxylic acids and / or the carboxylic acid equivalents of the abovementioned and / or lactones.

A method according to claim 3, characterized in that the component a)> 5% by weight, based on the total weight of component a), of at least one aliphatic Dicarboxylic acid al) which has> 30 and <44 C atoms and / or contains their carboxylic acid equivalents.

5. The method according to claim 4, characterized in that component a) contains> 15% by weight, based on the total weight of component a), of component al). 6. The method according to any one of claims 4 or 5, characterized in that the component al) is one or more dimer fatty acids and / or their carboxylic acid equivalents.

7. The method according to any one of claims 4 to 6, characterized in that the component a) in addition to the component al), contains at least one further aromatic and / or aliphatic dicarboxylic acid a2) and / or their dicarboxylic acid equivalent, which is different from al), wherein the sum of the proportions of al) and a2) to 100% by weight, based on the total component a), complements.

Process according to any one of Claims 1 to 7, characterized in that the sum of the number-average functionality of isocyanate groups and hydroxyl groups of compounds A) and B) is> 2.6 and <6.

A method according to any one of claims 1 to 8, characterized in that the mixture further comprises C) a solvent having a vapor pressure at 20 ° C of> 0, 1 and <200 mbar and D) comprises a wetting additive.

Method according to one of claims 1 to 9, characterized in that the compound A) comprises or consists of an aliphatic hexamethylene diisocyanate and / or a biuret and / or isocyanurate of hexamethylene diisocyanate.

Method according to one of claims 1 to 10, characterized in that at least the following steps are carried out:

I) the mixture is prepared.

II) the mixture is applied to a support in the form of a wet film immediately after its preparation,

III) the wet film is cured to form the polyurethane film and the polyurethane film is separated from the support.

12. Dielectric polyurethane film, obtainable by a process according to one of claims 1 to 11.

13. A method for producing an electromechanical transducer, wherein in a first step by a method according to any one of claims 1 to 12, a dielectric polyurethane film is prepared and in a second step on opposite sides of the dielectric polyurethane film in each case an electrode is arranged.

14. Electromechanical transducer, obtainable by a method according to claim 13.