Thermochromic polyurethane foam, methods for its production and use for polishing wheels or sponge pores

Abstract

Thermochromic polyurethane foam for polishing discs or sponge pores produced by reacting at least one polyester polyol with at least one compound containing an isocyanate group in the presence of at least one thermochromic colorant, characterized in that the reaction takes place in the presence of at least one di- or trifunctional chain extender, wherein the at least one polyester polyol is a branched polyester polyol.

Description

The present invention relates to a polyurethane foam comprising a thermochromic colorant, a method for producing the polyurethane foam according to the invention, and the use of the polyurethane foam for a polishing wheel or a sponge pore. The invention further relates to a polishing wheel and a sponge pore containing the polyurethane foam according to the invention. Polyurethanes are typically obtained by the polyaddition of dihydric or higher alcohols with dihydric or higher isocyanates. Using alcohols or isocyanates with a valence greater than two usually results in branched and cross-linked polyurethanes. Polyurethane foams are typically obtained when the polyaddition of the alcohol and isocyanate is carried out in the presence of a blowing agent, such as a blowing gas like pentane, methylene chloride, or carbon dioxide, or in the presence of water. Colored polyurethane foams are usually obtained by adding colorants during the manufacturing process. Various types of colorants are known. Both dyes and pigments can be used as colorants, with dyes typically being soluble in a solvent, while pigments are not. Colorants can also consist of multiple components. Furthermore, some dyes are known to exhibit the same coloring effect at different temperatures. Additionally, some colorants are known to exhibit their coloring effect depending on the temperature of the object in which they are contained. For example, some colorants only show their coloring effect up to a certain temperature. At higher (or lower) temperatures, they have no coloring properties. This ability to exhibit a coloring effect depending on temperature is also known as thermochromism. Corresponding substances are called thermochromic substances or thermochromic dyes. Polyurethane foams are frequently used in the manufacture of mattresses, pillows, upholstered furniture, sponges, as packaging material, insulating material, for coating carpets, etc. It is also known to use polyurethane foams as a component of polishing discs, for example for paints. When polishing paintwork with a polyurethane foam polishing wheel, temperatures can occur that are high enough to damage the paint. To indicate this critical temperature, EP 2 253 652 A1 proposes a polyurethane foam containing a thermochromic dye, so that these thermochromic polyurethane foams exhibit color changes from colored to colorless. However, EP 2 253 652 A1 does not provide any information on the mechanical properties of the polyurethane foams. EP 0 231 030 A2 also describes polyurethane foams that, through the addition of a thermochromic composition, can indicate a specific temperature by changing color. However, the mechanical properties of these thermochromic polyurethane foams are unsatisfactory; in particular, the tensile strength of the polyurethane foams according to the embodiments described in EP 0 231 030 A2 is below 200 kN / m², corresponding to less than 200 kPa. German patent DE 10 2009 018 728 A1 describes polyurethane foams comprising a thermochromic colorant, such that these thermochromic polyurethane foams exhibit color changes, and their use as a component of a polishing wheel. However, no information is provided regarding the mechanical properties of these polyurethane foams. Based on the prior art described above, one object of the invention was to provide thermochromic polyurethane foams with good mechanical properties, in particular with good tensile strength. This problem is solved according to the invention by the thermochromic polyurethane foam according to claim 1, the manufacturing process according to claim 18, the use according to claim 23, the polishing wheel according to claim 24 and the sponge pore according to claim 25. Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below. The invention provides a thermochromic polyurethane foam for polishing discs or sponge pores produced by reacting at least one polyester polyol with at least one compound containing an isocyanate group in the presence of at least one thermochromic colorant, wherein the reaction takes place in the presence of at least one di- or trifunctional chain extender, wherein the at least one polyester polyol is a branched polyester polyol. Surprisingly, it has been shown that by reacting at least one polyester polyol with at least one compound containing isocyanates in the presence of at least one thermochromic colorant and at least one di- or trifunctional chain extender, wherein the at least one polyester polyol is a branched polyester polyol, thermochromic polyurethane foams with good mechanical properties, in particular good tensile strength, can be obtained. Furthermore, it has been shown that the invention makes it possible to obtain thermochromic polyurethane foams with a higher concentration of thermochromic colorant. This leads, in particular, to a significantly more visible color change. The invention is of particular practical importance for polishing wheels and sponge pores. In these areas, a clear visual indication through a color change upon reaching a certain, potentially critical, temperature is especially helpful. The reaction for producing the thermochromic polyurethane foam according to the invention takes place in the presence of at least one di- or trifunctional chain extender. Chain extenders are substances that carry more than one functional group capable of reacting with an isocyanate group. Difunctional chain extenders, in particular, have two functional groups, each capable of reacting with an isocyanate group. Trifunctional chain extenders, in particular, have three functional groups, each capable of reacting with an isocyanate group. The mechanical properties of the thermochromic polyurethane foam can be adjusted depending on the number of functional groups in the chain extender. Furthermore, it has been found that the amount of thermochromic colorant that can be incorporated into the thermochromic polyurethane foam decreases with the number of functional groups in the chain extender that can react with isocyanates. Examples of functional groups that can react with an isocyanate group include, in particular, hydroxyl groups (-OH) and amine groups (for example, primary amines R-NH₂ and secondary amines RR'NH₂). Furthermore, chain extenders preferably have a molecular weight in the range of 60 g / mol to 300 g / mol. Chain extenders can be monodisperse substances. In a monodisperse substance, all molecules preferably have the same molecular weight. Preferably, the at least one di- or trifunctional chain extender of the thermochromic polyurethane foam according to the invention has a molecular weight in the range of 60 g / mol to 300 g / mol and / or is a monodisperse substance. The at least one di- or trifunctional chain extender can also be a mixture of different di- or trifunctional substances, which are preferably each monodisperse. According to a preferred embodiment of the invention, the difunctional chain extender has two functional groups that can react with isocyanate groups. Various substances are suitable as difunctional chain extenders. Advantageously, in the thermochromic polyurethane foam according to the invention, the difunctional chain extender is a diol with the formula HO-R-OH, where R represents a (C1-C30) alkylene chain, in particular a (C1-C16) alkylene chain, which optionally contains 1 to 10 heteroatoms, in particular oxygen. An alkylene group is understood to be, in particular, a group described by the general formula -CnH2n-, which is obtained by abstracting two hydrogen atoms from the corresponding alkane. Alkylene groups are especially saturated. Examples of alkylene groups are methylene (-CH2-), ethylene (-C2H4-), and propylene (-C3H6-). Alkylene groups have, in particular, two free valences. Furthermore, alkylene groups can be unbranched or branched; preferably, they are unbranched. If heteroatoms are present in the alkylene group, they replace, in particular, -CH2 units in the interior of the alkylene group. Examples of alkylene groups with heteroatoms are -CH2-CH2-O-CH2-CH2-, -CH2-CH2-O-CH2-CH2-O-CH2-CH2-, and -CH2-CH2-O-CH2-CH2-O-CH2-CH2-O-CH2-CH2-. According to one embodiment of the thermochromic polyurethane foam according to the invention, the difunctional chain extender is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, and mixtures thereof. Preferably, the difunctional chain extender is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and mixtures thereof. The difunctional chain extender ethylene glycol is particularly preferred. Practical tests have shown that thermochromic polyurethane foams with particularly good mechanical properties can be obtained with such chain extenders, especially with ethylene glycol. Furthermore, thermochromic polyurethane foams with high contents of thermochromic colorant could be obtained. Advantageously, the trifunctional chain extender has three functional groups that can react with isocyanate groups. According to one embodiment of the invention, the trifunctional chain extender is selected from the group consisting of glycerol, trimethylolpropane, 1,2,6-hexanetriol, triethanolamine and mixtures thereof. The thermochromic polyurethane foam can contain at least one di- or trifunctional chain extender in varying amounts. Advantageously, the thermochromic polyurethane foam according to the invention contains 0.5 to 5 wt.%, preferably 1 to 4 wt.%, based on the total weight of the polyurethane foam, of the at least one di- or trifunctional chain extender. Thermochromic polyurethane foams with these contents of di- or trifunctional chain extender have exhibited good mechanical properties, in particular good tensile strength, and were able to absorb a high content of thermochromic colorant. Suitable polyester polyols for conversion to the thermochromic polyurethane foam according to the invention are branched. Examples of polyester polyols are polycondensation products of a dicarboxylic acid such as succinic acid, glutaric acid, adipic acid, terephthalic acid, or phthalic acid with a polyhydroxyl compound such as diethylene glycol, glycerol, or trimethylolpropane, or ring-opening polymerization products of lactones such as epsilon-caprolactone. Copolyester polyols based on more than one dicarboxylic acid and / or more than one polyhydroxyl compound are also conceivable. Preferably, the at least one polyester polyol has a hydroxyl value, measured according to DIN 53240-2, in particular according to DIN 53240-2:2007-11, in the range of 50 to 250 mg KOH / g. According to one embodiment, the at least one polyester polyol of the polyurethane foam according to the invention has a hydroxyl value, measured according to DIN 53240-2, in particular according to DIN 53240-2:2007-11, in the range of 50 to 70 mg KOH / g. According to a further embodiment, the at least one polyester polyol of the polyurethane foam according to the invention has a hydroxyl value, measured according to DIN 53240-2, in particular according to DIN 53240-2:2007-11, in the range of 190 to 240 mg KOH / g. Preferably, the at least one polyester polyol used to convert the thermochromic polyurethane foam to 25°C is in liquid, and in particular viscous, form. According to a preferred embodiment of the invention, the at least one polyester polyol of the thermochromic polyurethane foam has a viscosity of 10,000 to 25,000 mPas, and in particular 15,000 to 23,000 mPas, at 25°C, as measured according to DIN EN ISO 3219 / B. The thermochromic polyurethane foam can contain at least one polyester polyol in varying amounts. Preferably, the thermochromic polyurethane foam according to the invention contains at least one polyester polyol in an amount of 10 to 75 wt.%, based on the total weight of the thermochromic polyurethane foam. According to one embodiment, the thermochromic polyurethane foam according to the invention contains 10 to 17 wt.%, in particular 12 to 16 wt.%, based on the total weight of the thermochromic polyurethane foam, of at least one polyester polyol, and optionally 40 to 80 wt.%, preferably 50 to 75 wt.%, based on the total weight of the thermochromic polyurethane foam, of a prepolymer, in particular a polyester polyol-based isocyanate group-containing prepolymer. According to a further embodiment, the thermochromic polyurethane foam according to the invention contains 50 to 75 wt.%, in particular 55 to 70 wt.%, based on the total weight of the thermochromic polyurethane foam, of at least one polyester polyol. In this way, the mechanical properties of the thermochromic polyurethane foam according to the invention can be adjusted. Various compounds are suitable as isocyanate-containing compounds used for the production of the thermochromic polyurethane foam according to the invention. The isocyanate-containing compound is preferably used in an amount of 5 to 90 wt%, more preferably 10 to 85 wt%, and more preferably 15 to 80 wt%, in each case based on the total weight of the thermochromic polyurethane foam. According to a preferred embodiment of the invention, the at least one isocyanate-containing compound is an isocyanate-containing prepolymer based on a polyester polyol and / or a polyisocyanate. A polyester polyol obtained by reacting a polyester polyol as described above with a compound containing more than one isocyanate group can be used as a polyester polyol-based isocyanate group-containing prepolymer. For example, a polyester polyol-based isocyanate group-containing prepolymer can be obtained by reacting a polyester polyol with a hydroxyl number of 60 mg KOH / g with a polyisocyanate, such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and mixtures thereof. Preferably, the polyester polyol-based isocyanate group-containing prepolymer has an isocyanate group content in the range of 5 to 20%, particularly 7 to 15%. The thermochromic polyurethane foam can contain the polyester polyol-based isocyanate group-containing prepolymer, particularly in an amount of 40 to 80 wt.%, preferably 50 to 75 wt.%.%, each based on the total weight of the thermochromic polyurethane foam. Preferably, aliphatic or aromatic polyisocyanates with at least two isocyanate groups per molecule are used. Aliphatic polyisocyanates exhibit better light stability. According to a preferred embodiment, a polyisocyanate selected from the group consisting of ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate and mixtures of these isomers, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate and mixtures of these isomers, 2,2'-methylenediphenyl diisocyanate, 2,4'-methylenediphenyl diisocyanate, 4,4'-methylenediphenyl diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate and mixtures thereof, can be used as the isocyanate-containing compound. A mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate with a 2,4-toluene diisocyanate content of 60-70 wt.% is particularly preferred as the polyisocyanate. 66-68 wt.%, based on the total weight of the toluene diisocyanate mixture, were used. The polyisocyanate can preferably be used in an amount of 10 to 50 wt.%, more preferably 15 to 40 wt.%, and even more preferably 15 to 35 wt.%, in each case based on the total weight of the thermochromic polyurethane foam. If a prepolymer and a polyisocyanate are used as the isocyanate group-containing compound, the prepolymer is preferably used in an amount of 50 to 75 wt.% and the polyisocyanate preferably in an amount of 15 to 20 wt.%, each based on the total weight of the thermochromic polyurethane foam. The at least one thermochromic colorant, in the presence of which the reaction for the production of the thermochromic polyurethane foam according to the invention takes place, can contain a dye or a pigment. The dye or pigment can be inorganic or organic. The thermochromic colorant can comprise several components. In particular, the thermochromic colorant can contain a matrix, an auxiliary compound, and a dye or a pigment. According to a preferred embodiment of the invention, the at least one thermochromic colorant, preferably containing a matrix, an auxiliary compound, and a dye or a pigment, is enclosed in a microcapsule. The outer shell of the microcapsule is preferably transparent to allow the visual perception of a color change. The encapsulation of the thermochromic colorant improves the reversibility of the color change. A solvent that is preferably solid below the color change temperature is used as the matrix. This solvent is preferably selected from waxes, low-melting thermoplastic resins, rubber, natural resins, and synthetic resins. Examples include low molecular weight polyethylenes, low-melting polyesters, ethylene vinyl acetate copolymer, chlorinated rubber, a polyvinyl acetate emulsion, a polyethylene emulsion, an acrylic emulsion, a styrene resin emulsion, a butadiene nitrile emulsion, shellac, teain, an unsaturated polyester resin, an epoxy resin, a cellulose resin, a polyurethane resin, a phenolic resin, a vinyl chloride resin, a vinyl acetate resin, a silicone resin, polyvinyl alcohol, polyvinyl methyl ether, and mixtures thereof.It is particularly preferred that the solid solvent has a melting point in the range of -5 to 100 °C, especially from 0 °C to 90 °C, or from 10 °C to 80 °C, or from 20 °C to 60 °C, or from 30 °C to 50 °C. A dye component of the thermochromic colorant is characterized in particular by being soluble with respect to the matrix. In one embodiment of the invention, it is further preferred that the solid solvent has a boiling point of less than 150 °C. It is also preferred that the solid solvent has a boiling point of more than 90 °C or more than 100 °C. By melting the solvent at approximately the temperature of the color change, the dye or pigment can interact with the auxiliary compound in such a way that the thermochromic colorant undergoes a reversible color change. According to one embodiment, the auxiliary compound is able, upon contact with the dye or pigment in the molten matrix, to induce a color change of the thermochromic colorant from colored to colorless. Examples of suitable auxiliary compounds include organic acids, such as carboxylic acids, phenols and phenol derivatives, 5-hydroxybenzotriazoles, tetrazoles, or triazoles such as 1,2,3-triazole. According to a further embodiment, the color impression of the thermochromic colorant is generated by contact of the auxiliary compound with the dye or pigment. The color change from colored to colorless in the molten matrix is ​​produced by the auxiliary compound losing contact with the dye or pigment. Accordingly, the thermochromic polyurethane foam according to the invention, in a preferred embodiment, exhibits a color change from colored to colorless or from a first color to a second color at a temperature of -5 °C to 100 °C, in particular from 0 °C to 90 °C, or from 10 °C to 80 °C, or from 20 °C to 60 °C, or from 30 °C to 50 °C. The color change points can be set very precisely, preferably in increments of 3 ± 2 °C to 5 ± 2 °C. For example, the thermochromic polyurethane foam can be blue at the beginning and change to colorless upon reaching the color change temperature.Furthermore, it is conceivable that by adding another dye, for example in the form of an ink, to the thermochromic polyurethane foam during its production, in addition to the at least one thermochromic colorant, a thermochromic polyurethane foam with a color change from a first color to a second color, for example from blue to red, could be achieved. The added dye could also be another thermochromic dye. This would allow for multiple temperature-dependent color changes. According to a preferred embodiment of the invention, the at least one thermochromic colorant is added as a mixture with the at least one di- or trifunctional chain extender. This allows, firstly, a high concentration of thermochromic colorant to be achieved in the thermochromic polyurethane foam. Furthermore, the manufacturing process can be carried out very economically in this way. The thermochromic colorant can be contained in the thermochromic polyurethane foam according to the invention in an amount of 0.01 to 10 wt.%, preferably 0.1 to 5 wt.%, more preferably 0.2 to 3 wt.%, in each case based on the total weight of the thermochromic polyurethane foam. According to a further embodiment of the invention, the reaction for producing the thermochromic polyurethane foam is carried out in the presence of a fatty acid. This allows polyurethane foams with an anisotropic cell structure to be obtained. This is particularly advantageous when a natural sponge appearance of the thermochromic polyurethane foam according to the invention is desired, for example in the case of sponge pores, such as for bath sponges. The thermochromic polyurethane foam according to the invention can be open-cell, closed-cell, or mixed-cell, in particular partially closed-cell. In closed-cell polyurethane foams, the walls between the individual cells are completely closed. This is recognizable to those skilled in the art, for example, by the fact that gases cannot pass through the polyurethane foam, or can only do so with great difficulty. In open-cell polyurethane foams, the walls between the individual cells are not closed. This is recognizable to those skilled in the art, for example, by the fact that gases can easily pass through the polyurethane foam. Furthermore, these polyurethane foams can also absorb liquids. Mixed-cell, in particular partially closed-cell, polyurethane foams contain both closed and open cells. According to one embodiment of the invention, the thermochromic polyurethane foam is 80 to 90% closed-cell. This is particularly the case for freshly produced thermochromic polyurethane foams according to the invention. According to another embodiment of the invention, the thermochromic polyurethane foam is open-cell. Methods for producing the open-cell thermochromic polyurethane foam, especially starting from the 80 to 90% closed-cell thermochromic polyurethane foam, are known to those skilled in the art. For example, the open-cell structure of the thermochromic polyurethane foam can be achieved by reticulation. In this process, the thermochromic polyurethane foam can be subjected, particularly in an autoclave, to an explosion of a gas containing an oxyhydrogen mixture of hydrogen and oxygen in a molar ratio of essentially 2:1.This allows the mechanical properties of the thermochromic polyurethane foam to be further improved. Furthermore, the reaction to produce the thermochromic polyurethane foam can also be carried out in the presence of other substances, if required. For example, catalysts such as tin di-2-ethylhexanoate, dibutyltin dilaurate, and dibutyltin di-2-ethylhexanoate can be used in the reaction. Cocatalysts, such as amine catalysts like triethylenediamine, N-methylmorpholine, tetramethyl-1,4-butanediamine, N-methylpiperazine, dimethylpiperazine, dimethylethanolamine, triethylamine, and mixtures thereof, can also be used. Stabilizers, emulsifiers, surfactants, in particular organosiloxane compounds, and / or flame retardants can also be added. The catalysts, cocatalysts, stabilizers, emulsifiers, and surfactants can each be used in an amount of 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the at least one polyester polyol. Furthermore, the invention provides a method for producing the thermochromic polymer foam according to the invention. Accordingly, the method for producing the thermochromic polyurethane foam comprises: a. providing at least one polyester polyol, wherein the at least one polyester polyol is a branched polyester polyol; b. providing at least one thermochromic colorant; c. providing at least one compound containing isocyanates; d. providing at least one di- or trifunctional chain extender; e. mixing and foaming the components a., b., c., and d. to form a thermochromic polyurethane foam. Steps a. to e. of the method according to the invention can be carried out in any order, preferably they are carried out in the order given above. The above statements concerning the thermochromic polyurethane foam and the functional chain extender also apply equally to the functional chain extender of the inventive method. The above statements concerning the thermochromic polyurethane foam and the trifunctional chain extender also apply equally to the trifunctional chain extender of the inventive method. According to a preferred embodiment of the inventive method, the at least one di- or trifunctional chain extender is provided together with the at least one thermochromic colorant. This allows the method to be carried out very economically and enables the production of thermochromic polyurethane foams with a high thermochromic colorant content and good mechanical properties. The foregoing in connection with the thermochromic polyurethane foam and the at least one polyester polyol applies equally to the at least one polyester polyol of the process according to the invention. Likewise, what has been said above in connection with the thermochromic polyurethane foam and the at least one thermochromic colorant also applies equally to the at least one thermochromic colorant of the process according to the invention. Furthermore, what has been said above in connection with the thermochromic polyurethane foam and the at least one isocyanate group-containing compound also applies equally to the at least one isocyanate group-containing compound of the process according to the invention. The thermochromic polyurethane foam produced by the inventive method preferably exhibits a color change from colored to colorless or from a first color to a second color at a temperature of -5 °C to 100 °C, in particular from 0 °C to 90 °C or from 10 °C to 80 °C or from 20 °C to 60 °C or from 30 °C to 50 °C. According to a further embodiment of the method according to the invention, step e. is carried out in the presence of a fatty acid. The thermochromic polyurethane foam according to the invention is suitable for a variety of possible uses. In particular, the present invention relates to the use of the thermochromic polyurethane foam according to the invention for a polishing wheel and / or for a sponge pore. Furthermore, the present invention relates to a polishing wheel containing a thermochromic polyurethane foam according to the invention. Furthermore, the present invention relates to a sponge pore containing a thermochromic polyurethane foam according to the invention. The principle of the invention will be explained in more detail below using examples that serve for illustration and are not to be interpreted as restrictive. EXAMPLES materials Polyol 1 (branched polyester polyol with an OH number of 210); Polyol 2 (branched polyester polyol with an OH number of 60); Polyol 3 (polyester polyol-based prepolymer with an isocyanate group content of 11.5%); IE (ionic emulsifier); SIT (silicone surfactant); Amine 1 (tertiary amine); Kat (tin carboxylic acid salt); TDI65 (mixture of 2,4- and 2,6-toluene diisocyanate); TF1 (thermochromic dye, 25 wt% in ethane-1,2-diol); TF2 (thermochromic dye, 25 wt% in ethane-1,2-diol); TF3 (thermochromic dye, 25 wt% in ethane-1,2-diol); Amine 2 (30% solution of a tertiary amine in dipropylene glycol); Amine 3 (30% solution of a 1:1 mixture of two tertiary amines in dipropylene glycol); SA 10% (stearic acid 10% in ethane-1,2-diol); ink (polyester polyol ink red). Recipes The following formulations A to I, containing a polyester polyol and shown in Tables 1 and 2, were prepared; dosages are given in wt.%. Table 1 BestandtailABCD Polyol 185.52--- Polyol 2–85.6382,5182.85 IE3,493,061,241,24 SIT3,843,673,143,15 Amen 11.9--- Amen 2-1.59-- Kat0,050,06-- Amen 3--1,161,16 TF1--6,196,21 SA 10%–-2,061.66 Wasser5,205,993,73,73 Table 2 Table 2 BestandtailEFGHI Polyol 1— Polyol 284,2584,9686,0682,8584,25 IE1,261,271,291,241,26 SIT3,23,233,273,153,2 Amen 1----- Amen 2----- Kat----- Amen 31,181,191,201,161,18 TF14,213,4--- TF2---6,214,21 TF3—2.58— SA 10%2,112,121,721,662.11 Wasser3,793,833,883,733.79 The resulting formulations A to I were subsequently processed with a polyisocyanate, ink, and, if necessary, a thermochromic colorant via a mixing head to produce foams AS to IS with the foam compositions specified in Tables 3 and 4, with dosages given in parts by weight. After the specified start time and reaction time, the foam compositions were foamed into block foams with a length of 5 to 7 m. Tables 3 and 4 also contain information on the color change of the foams as well as characteristic values ​​of the foams' mechanical properties. Table 3 Component A-SB-SC-SD-S Formula A77--- Formula B-77-- Formula C--121.2- Formula D---120.7 TF119,319,3-- Polyol 3277277-- TDI6576,9276,9252,352,3 Ink 0.20.20.50.05 Start time [s] 35321825 Reaction time [s] 15614510592 Color change (temperature): Blue to red (40 °C) Blue to yellow (40 °C) Blue to red (40 °C) Blue to red (40 °C) Density [kg / m³] according to ISO 84545, 145, 231, 431, 1 Tensile strength [kPa] according to ISO1798340343268263 Compression hardness CLD, 40% [kPa] according to ISO 33869, 619, 674, 414, 23 Table 4 Table 4 Component E-SF-SG-SH-SI-S Formula E118.7---- Formula F-117.7--- Formula G--116.2-- Formula H---120.7- Recipe I----118.7 TDI653540354535 Ink 110.50.11 Start time [s] 3528283035 Response time [s] 90938810090 Color change (temperature): Green to yellow (40°C), Orange to yellow (40°C), Orange to yellow (35°C), Gray to red (45°C), Green to yellow (45°C) Density [kg / m³] according to ISO 84529, 329, 828, 329, 128, 6 Tensile strength [kPa] according to ISO1798253245237249241 Compression hardness CLD, 40% [kPa] according to ISO 33864, 013, 953, 793, 993, 86 Tables 3 and 4 show that the present invention yields thermochromic polyurethane foams in which the initial color, the target color, and the color change temperature are adjustable. Furthermore, the foams according to the invention exhibit good mechanical properties, in particular a tensile strength exceeding 200 kPa.

Claims

Thermochromic polyurethane foam for polishing discs or sponge pores produced by reacting at least one polyester polyol with at least one compound containing an isocyanate group in the presence of at least one thermochromic colorant, characterized in that the reaction takes place in the presence of at least one di- or trifunctional chain extender, wherein the at least one polyester polyol is a branched polyester polyol. Thermochromic polyurethane foam according to claim 1, characterized in that the difunctional chain extender has two functional groups that can react with isocyanate groups. Thermochromic polyurethane foam according to claim 1 or 2, characterized in that the difunctional chain extender is a diol with the formula HO-R-OH, wherein R is a (C1-C30) alkylene chain, in particular a (C1-C16) alkylene chain, which optionally contains 1 to 10 heteroatoms, in particular oxygen. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the difunctional chain extender is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol and mixtures thereof. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the difunctional chain extender is ethylene glycol. Thermochromic polyurethane foam according to claim 1, characterized in that the trifunctional chain extender has three functional groups that can react with isocyanate groups. Thermochromic polyurethane foam according to claim 1 or 6, characterized in that the trifunctional chain extender is selected from the group consisting of glycerin, trimethylolpropane, 1,2,6-hexanetriol, triethanolamine and mixtures thereof. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the thermochromic polyurethane foam contains 0.5 to 5 wt.%, based on the total weight of the polyurethane foam, of at least one di- or trifunctional chain extender. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the at least one polyester polyol has a viscosity of 10000 to 25000 mPas, in particular of 15000 to 23000 mPas, at 25°C, as measured according to DIN EN ISO 3219 / B. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the thermochromic polyurethane foam contains 10 to 75 wt.%, based on the total weight of the thermochromic polyurethane foam, of at least one polyester polyol. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the at least one isocyanate-containing compound is an isocyanate-containing prepolymer based on a polyester polyol and / or a polyisocyanate. Thermochromic polyurethane foam according to claim 11, characterized in that the polyisocyanate is selected from the group consisting of ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate and mixtures of these isomers, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate and mixtures of these isomers, 2,2'-methylenediphenyl diisocyanate, 2,4'-methylenediphenyl diisocyanate, 4,4'-methylenediphenyl diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate and mixtures thereof. Thermochromic polyurethane foam according to one of claims 11 or 12, characterized in that the polyisocyanate is a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate with a 2,4-toluene diisocyanate content of 60-70 wt.%, in particular 66-68 wt.%, in each case based on the total weight of the mixture of toluene diisocyanates. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the at least one thermochromic colorant is enclosed in a microcapsule. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the at least one thermochromic colorant is added as a mixture with the at least one di- or trifunctional chain extender. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the thermochromic polyurethane foam exhibits a color change from colored to colorless or from a first color to a second color at a temperature of -5 °C to 100 °C, in particular from 0 °C to 90 °C or from 10 °C to 80 °C or from 20 °C to 60 °C or from 30 °C to 50 °C. Thermochromic polyurethane foam according to one of the preceding claims, characterized in that the reaction for the production of the thermochromic polyurethane foam is carried out in the presence of a fatty acid. A method for producing a thermochromic polyurethane foam for polishing wheels or sponge pores according to any one of claims 1 to 17, comprising: a. providing at least one polyester polyol, wherein the at least one polyester polyol is a branched polyester polyol, b. providing at least one thermochromic colorant, c. providing at least one compound containing isocyanates, d. providing at least one di- or trifunctional chain extender, e. mixing and foaming the components a., b., c. and d. to form a thermochromic polyurethane foam. Method according to claim 18, characterized in that the difunctional chain extender is characterized by at least one feature of claims 2 to 5. Method according to claim 18, characterized in that the trifunctional chain extender is characterized by at least one feature of claims 6 or 7. Method according to one of claims 18 to 20, characterized in that the at least one di- or trifunctional chain extender is provided together with the at least one thermochromic dye. A method according to any one of claims 18 to 21, characterized in that the at least one polyester polyol has a viscosity of 10,000 to 25,000 mPas at 25°C, in particular 15,000 to 23,000 mPas, in each case measured according to DIN EN ISO 3219 / B, and / or that the at least one thermochromic colorant is enclosed in a microcapsule, and / or that the at least one isocyanate-containing compound is characterized by at least one feature of claims 11 to 13, and / or that the thermochromic polyurethane foam exhibits a color change from colored to colorless or from a first color to a second color at a temperature of -5°C to 100°C, in particular from 0°C to 90°C or from 10°C to 80°C or from 20°C to 60°C or from 30°C to 50°C, and / or that step e. is carried out in the presence of a fatty acid. Use of a thermochromic polyurethane foam according to one of claims 1 to 17 for a polishing wheel and / or for a sponge pore. Polishing disc containing a thermochromic polyurethane foam according to any one of claims 1 to 17. Sponge pore containing a thermochromic polyurethane foam according to any one of claims 1 to 17.