Thermosetting polyurethane composition with a wide temperature window

Abstract

A hydrazide having a melting point of at least 65°C is used as a curing agent in a thermosetting polyurethane composition comprising a prepolymer having isocyanate-terminated groups obtained from at least one polyisocyanate and at least one polyol, and at least one epoxy resin. As a result of this combination, a thermosetting polyurethane composition is obtained that has better storage stability and can be cured with consistent mechanical properties over a wide temperature range.

Description

Technical Field

[0001] The present invention relates to the use of a curing agent for thermosetting in a thermosetting polyurethane composition. The present invention further relates to a thermosetting polyurethane composition and a method for curing such a composition.

Background Art

[0002] Polyurethane compositions have long been known and are used in many fields, for example, in the building and manufacturing industries as adhesives, sealants, or coatings. One-component (1K) and two-component (2K) polyurethane (PUR) compositions are distinguished. In the case of a 1K polyurethane composition in which all components are present in one liquid, a moisture-curable composition that cures under the influence of atmospheric moisture and a composition for thermosetting in which curing is induced by heating can be further distinguished.

[0003] WO 2009 / 080738 A1 (Sika Technology AG) describes, for example, a moisture-curable polyurethane composition containing a polyisocyanate and an aldehyde or a ketone-blocked amine as a moisture-activated crosslinking agent. This composition cures by moisture at room temperature or slightly elevated temperature, especially below 40 °C, to form an aldehyde and / or a ketone. In order to significantly reduce the undesirable gas evolution of aldehydes and ketones in the cured state, the composition contains a hydrazide that reacts with an aldehyde and / or a ketone at a temperature above 80 °C to form a non-volatile liquid.

[0004] Thermosetting polyurethane compositions are mainly used in industrial production as adhesives and sealants. It is specifically used as a sealant in automobile assembly, in which case the thermosetting polyurethane composition is used, for example, in an appropriate curing oven at a temperature typically > 110 °C, in parallel with the curing of the paint after liquid application.

[0005] In a thermosetting polyurethane composition, a thermally unstable curing agent or a thermally activatable curing agent that initiates the curing process of the composition at a specified temperature is used.

[0006] European Patent Application Publication No. 0255572A1 (Sika AG) describes, for example, a one-component adhesive and / or sealing compound comprising a polyurethane-based prepolymer and a thermoactivating curing agent, in which the stoichiometric ratio of the prepolymer to the curing agent is selected such that only partial crosslinking is possible when heated to a temperature of 60-180°C and a product with high viscosity to high plasticity is obtained. The curing agents mentioned are dicyandiamide or 4,4'-diaminodiphenylmethane sodium chloride complex salts.

[0007] However, currently known thermosetting polyurethane compositions typically have the problem of having to cure within a relatively narrow temperature window. If the temperature is too low, there is a risk that the curing agent will not react completely, potentially leading to the curing agent leaching out of the cured product as an oily liquid. On the other hand, if the temperature is too high, there is a risk of undesirable discoloration. Furthermore, polyurethane compositions are usually not stable at high temperatures and begin to decompose at temperatures above 180°C, or at the latest above 200°C. This results in a significant loss of mechanical properties such as tensile strength.

[0008] Furthermore, known thermosetting polyurethane compositions are often based on problematic substances such as 4,4'-methylenedianiline, which are classified as substances of very high concern (SVHC) under the REACH Act or have insufficient storage stability. [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, there is still a need for improved solutions in which the listed shortcomings are not so prevalent or not present at all. [Means for solving the problem]

[0010] Therefore, an object of the present invention is to overcome the aforementioned drawbacks and to provide an improved solution that yields a thermosetting polyurethane composition particularly suitable as a one-component adhesive and / or sealant composition. The temperature window within which the composition can be cured should preferably be as wide as possible. This is especially true when ensuring that the mechanical properties of the cured product can be reliably guaranteed to be independent of, or at least not significantly dependent on, the curing temperature. A further goal is that the composition exhibits as little discoloration as possible at high curing temperatures and does not significantly lose its mechanical properties, while also being as stable as possible with respect to liquid separation or segregation. The latter is also particularly true in the case of partial or incomplete thermosetting reactions that may occur, for example, if the curing temperature is too low. Finally, the composition should also be as long as possible of storage stability, even at relatively high ambient temperatures.

[0011] Surprisingly, we have found that the objective is achieved by the use described in claim 1. Therefore, the core of the present invention is the use of a hydrazide having a melting point of at least 65°C as a curing agent for thermosetting polyurethane composition comprising a prepolymer having isocyanate-terminated groups obtained from at least one polyisocyanate and at least one polyol, and further at least one epoxy resin.

[0012] Hydrazides have been found to be usable as curing agents in 1K polyurethane compositions comprising at least one prepolymer having isocyanate-terminated groups in combination with an epoxy resin, and to offer unexpected advantages. Therefore, it is possible to provide a storage-stable 1K polyurethane composition suitable as an adhesive and / or sealant, which can be cured under controlled conditions by thermosetting within a wide temperature window, particularly in the range of 100-120°C, possesses excellent mechanical properties when cured over the entire temperature range, and is resistant to discoloration. The composition is storage-stable from room temperature down to 60°C.

[0013] The reason for this is assumed to be that even at relatively low curing temperatures starting above the melting point of the hydrazide, the hydrazide used as a curing agent already causes effective curing without the need for a parallel epoxy resin that would negatively affect this process. Particularly at higher temperatures, such as above 150°C, the epoxy resin is likely to contribute to curing by reacting with other components of the composition, such as the hydrazide, through crosslinking. What is surprising here is that the use of the combination of hydrazide and epoxy resin according to the present invention when curing at high temperatures results in a cured product with considerably less discoloration and considerably better temperature stability of mechanical properties than in the case of thermosetting polyurethane compositions known to date.

[0014] Furthermore, even in cases of incomplete thermal curing reaction events that may occur when the curing temperature is too low, a composition that is stable against liquid separation can be obtained. Specifically, it is possible to effectively avoid the problem of oily liquid seepage from the cured product.

[0015] This may be due to the relatively high melting point of the hydrazide, which ensures that any unreacted curing agent remains unreacted in the cured product. Therefore, even if a certain proportion of the prepolymer in the thermosetting composition hardens due to moisture before actual thermal curing, it does not result in a shift in the ratio of available prepolymer to curing agent, and excess curing agent does not cause segregation problems.

[0016] The discoloration commonly observed in polyurethane compositions is, in this case, very low even at high curing temperatures up to 220°C, and can be avoided as much as possible by using stabilizers, specifically phosfit stabilizers.

[0017] The polyurethane compositions that can be obtained according to the present invention have stable mechanical properties, particularly with respect to the elastic modulus, throughout the entire range of use and especially at curing temperatures up to 220°C.

[0018] A further advantage of the present invention is that it is possible to provide an unexpectedly advantageous alternative form without using problematic substances such as 4,4'-methylenedianiline, which is classified as a substance of very high concern (SVHC) under the REACH regulation.

[0019] In addition, the polyurethane composition obtainable has very good adhesion to metal substrates and a wide variety of coatings, particularly coatings such as those applied in automotive assembly, for example by cathodic electrocoating.

[0020] The polyurethane composition obtainable by the use according to the present invention is particularly available for industrial production as an adhesive and a sealant, especially in automotive assembly as a sealant, in which case it is curable with a suitable curing open, for example a newly applied liquid, in parallel with the curing of the paint.

[0021] A further aspect of the present invention is the subject matter of the further independent claims. Particularly preferred embodiments of the present invention are the subject matter of the dependent claims.

Mode for Carrying Out the Invention

[0022] A first aspect of the present invention relates to the use of a hydrazide having a melting point of at least 65 °C in combination with an epoxy resin as a curing agent for thermosetting in a thermosetting polyurethane composition comprising a prepolymer having isocyanate end groups obtained from at least one polyisocyanate and at least one polyol.

[0023] A compound name starting with "poly" means a substance containing two or more functional groups appearing in its name per molecule. The compound can be a monomeric, oligomeric or polymeric compound. For example, a polyol is a compound having two or more hydroxyl groups. A polyisocyanate is a compound having two or more isocyanate groups.

[0024] An isocyanate-reactive compound is a compound having at least one isocyanate-reactive group capable of reacting with an isocyanate group to form a chemical bond.

[0025] A one-component polyurethane composition means a composition in which the components are present in one liquid. Generally, a one-component composition is storage-stable at room temperature (e.g., 23 °C) and - when the system is moisture-curable - excluding atmospheric moisture, for at least a certain period (e.g., at least one day or at least one month).

[0026] The term "storage-stable" means the property of a substance or composition that can be stored in a suitable container at room temperature for a period ranging from several weeks to six months or more without causing any change in its applicability and usability during storage to the extent relevant to its use.

[0027] Here, the average molecular weight means the number-average molecular weight (Mn) that can be determined by gel permeation chromatography (GPC) in comparison with polystyrene standards.

[0028] Thermal curing is understood to mean curing at a temperature increase of at least 80 °C, specifically at least 100 °C, and particularly above 120 °C. Thermal curing is specifically carried out at a temperature above the melting point of the hydrazide.

[0029] In the case of thermal curing, the polyurethane composition cures simultaneously throughout after application. In contrast, in the case of moisture curing, after application, diffusion-controlled curing of the polyurethane composition is observed from the outside inward. Moisture curing is understood to mean curing under moisture, particularly atmospheric moisture. Moisture curing is generally carried out at a temperature of 40 °C or lower, but moisture curing is usually carried out at room temperature, i.e., at a temperature of less than 35 °C, for example, about 23 °C.

[0030] Furthermore, all subsequent details, particularly those relating to polyurethane compositions, methods thereof, and uses thereof, can naturally be applied equally to the uses of the present invention, the methods thereof, the products that can be obtained therefrom, and the adhesive and / or sealant compositions of the present invention, even when separate references do not exist. The polyurethane compositions of the present invention comprise a prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol. It is also possible to use mixtures of two or more such prepolymers. Prepolymers having isocyanate-terminated groups are known to those skilled in the art. The prepolymer has at least two isocyanate-terminated groups, preferably exactly two isocyanate-terminated groups. By utilizing the isocyanate-terminated groups, the prepolymer can be chain-extended or crosslinked by reaction with compounds having isocyanate-reactive groups, such as water, a hydroxyl group, or an amino group, thereby causing curing of the polyurethane composition. The terms “curing” or “crosslinking” also encompass chain-extension reactions hereafter.

[0031] A prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol is a polyurethane prepolymer prepared by the reaction of at least one polyisocyanate and at least one polyol. Those skilled in the art can easily prepare such a prepolymer.

[0032] The reaction between at least one polyol and at least one polyisocyanate can be carried out, for example, by conventional methods, for example, by reacting the polyol component and the polyisocyanate component at a temperature of 50-100°C, in the presence of an optionally suitable catalyst, and using the polyisocyanate in stoichiometric excess. Optionally, additives such as solvents and / or plasticizers can be added to the reaction mixture as needed. The reaction product formed is a prepolymer having isocyanate-terminated groups. Furthermore, any solvent used can be removed after the reaction. Preferably, any plasticizer used may remain in the resulting product.

[0033] The polyisocyanate for forming the prepolymer having isocyanate-terminated groups is preferably a diisocyanate selected from polyisocyanates, particularly aliphatic polyisocyanates and / or aromatic polyisocyanates. One or more such polyisocyanates may be used. Aliphatic polyisocyanates are preferred.

[0034] Aliphatic polyisocyanates are aliphatic compounds having at least two isocyanate groups. Aliphatic diisocyanates are preferred. Aliphatic polyisocyanates can be acyclic or cyclic aliphatic polyisocyanates, with cyclic aliphatic polyisocyanates being preferred. Saturated aliphatic polyisocyanates are preferred. These polyisocyanates are known and commercially available.

[0035] Examples of suitable aliphatic polyisocyanates include hexamethylene 1,6-diisocyanate, 2,2,4- and 2,4,4-trimethylhexamethylene 1,6-diisocyanate, dodecamethylene 1,12-diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate and mixtures thereof of their isomers, isophorone diisocyanate (IPDI, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane), hexahydrotrylene 2,4- and 2,6-diisocyanate, hexahydrophenyl 1,3- and -1,4-diisocyanate, perhydrodiphenylmethane 2,4'- and -4,4'-diisocyanate, and mixtures of the above-mentioned isocyanates. Particularly preferred are isophorone diisocyanate (IPDI) and hexamethylene 1,6-diisocyanate (HDI).

[0036] Examples of suitable aromatic polyisocyanates include diphenylmethane 4,4'-diisocyanate (MDI), which may optionally contain a portion of diphenylmethane 2,4'- and / or 2,2'-diisocyanate; torylene 2,4-diisocyanate or a mixture thereof with torylene 2,6-diisocyanate (TDI); phenylene 1,4-diisocyanate (PDI); and / or naphthalene 1,5-diisocyanate (NDI).

[0037] The polyisocyanates are diphenylmethane 4,4'-diisocyanate (MDI), which may optionally contain a portion of diphenylmethane 2,4'- and / or 2,2'-diisocyanate; more preferably, torylene 2,4-diisocyanate or a mixture thereof with torylene 2,6-diisocyanate (TDI); and / or isophorone diisocyanate (IPDI).

[0038] To form a prepolymer having isocyanate-terminated groups, at least one polyisocyanate is reacted with one or more polyols. Any polyol commonly used in polyurethane chemistry can be used. A wide variety of suitable polyols are commercially available.

[0039] Preferably, the polyol has an average molecular weight of 250 to 30,000 g / mol, preferably 400 to 20,000 g / mol, or a molecular weight in the case of a non-polymeric polyol.

[0040] Polyols also preferably have an average number of OH functional groups in the range of 1.6 to 3. It will be understood that polymeric compounds may also include substances formed from side reactions that have, for example, only one hydroxyl group or none at all.

[0041] The polyol is preferably a diol or triol having an OH value in the range of 8 to 185 mg KOH / g, and more particularly in the range of 10 to 120 mg KOH / g.

[0042] The polyols used are, for example, the commercially available polyols listed below or mixtures thereof.

[0043] a) Depending on the case, a starter molecule having two or more active hydrogen atoms, for example, water, ammonia, or a compound having two or more OH or NH groups, for example, ethane-1,2-diol, propane-1,2- and -1,3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, isomeric dipropylene glycol and tripropylene glycol, isomeric butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecane Polyoxyalkylene polyols, also called polyether polyols or oligoetherols, are polymerization products of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, oxetane, tetrahydrofuran, or mixtures thereof, polymerized with the help of diols, cyclohexane-1,3- and -1,4-dimethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, aniline, and mixtures thereof. For example, it is possible to use either polyoxyalkylene polyols with a low degree of unsaturation (measured according to ASTM D-2849-69 and reported in unsaturated milliequivalents / grams of polyol (meq / g)) prepared with the help of so-called binary metal cyanide complex catalysts (DMC catalysts), or polyoxyalkylene polyols with a higher degree of unsaturation prepared with the help of anionic catalysts such as NaOH, KOH, CsOH, alkali metal alkoxides.

[0044] Polyoxyalkylenediols or polyoxyalkylentriols are particularly preferred, and polyoxyethylenedi and triols, as well as polyoxypropylenedi and triols, are especially preferred. Polyoxyalkylenediols and triols having an unsaturation degree of less than 0.02 meq / g and an average molecular weight in the range of 1,000 to 30,000 g / mol are particularly preferred, as are polyoxypropylenediols and triols having an average molecular weight of 400 to 8,000 g / mol.

[0045] Similarly, particularly preferred are so-called ethylene oxide-terminated ("EO end cap") polyoxypropylene polyols. The latter are, for example, special polyoxypropylene polyoxyethylene polyols having primary hydroxyl groups, obtained when pure polyoxypropylene polyols, especially polyoxypropylene diols and triols, are further alkoxylated with ethylene oxide after the completion of the polypropoxylation reaction.

[0046] b) Styrene-acrylonitrile graft or acrylonitrile-methyl methacrylate graft polyether polyol.

[0047] c) Polyester polyols, also known as oligoesterols, prepared by known methods, particularly by polycondensation of hydroxycarboxylic acids or polycondensation of aliphatic and / or aromatic polycarboxylic acids with dihydric or polyhydric alcohols.

[0048] Particularly preferred polyester polyols are divalent to trivalent alcohols, especially divalent alcohols, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, butane-1,4-diol, pentane-1,5-diol, 3-methylhexane-1,5-diol, hexane-1,6-diol, octane-1,8-diol, decane-1,10-diol, dodecane-1,12-diol, 1,12-hydroxystearyl alcohol, 1,4-cyclohexanedimethanol, dimer fatty acid diols (dimer diols), neopentyl glycol hydroxypivalate, glycerol, and 1,1,1-trimethylol pro. Polyester polyols are prepared from a pan or a mixture of the alcohols mentioned above, and organic di or tricarboxylic acids, particularly dicarboxylic acids, or their anhydrides or esters, such as succinic acid, glutaric acid, adipic acid, trimethyladipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, dimer fatty acids, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, dimethyl terephthalate, hexahydrophthalic acid, trimellitic acid and trimellitic anhydride, or a mixture of the acids mentioned above, and are further formed from a lactone such as ε-caprolactone and a starter such as the dihydric or trihydric alcohols mentioned above.

[0049] d) Polycarbonate polyols that can be obtained by reacting the above-mentioned alcohols—used to form polyester polyols—with dialkyl carbonates, diaryl carbonates, or phosgene.

[0050] e) A block copolymer having at least two different blocks having a polyether, polyester, and / or polycarbonate structure of the type described above, particularly a polyether polyester polyol, and supporting at least two hydroxyl groups.

[0051] f) Polyacrylate polyols and polymethacrylate polyols.

[0052] g) Polyhydroxy functional fats and oils, such as natural fats and oils, particularly castor oil, or polyols obtained by chemical modification of natural fats and oils, called oleochemical polyols, such as epoxy polyesters or epoxy polyethers obtained by epoxidation of unsaturated oils and subsequent ring-opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils, or polyols obtained from natural fats and oils by decomposition processes such as alkalisis and ozonolysis and subsequent chemical linkage of the thus obtained decomposition products or derivatives by transesterification or dimerization. Preferred decomposition products of natural fats and oils are, in particular, fatty acids and fatty alcohols, and further, fatty acid esters, in particular methyl esters (FAMEs), which can be derivatized to hydroxy fatty acid esters, for example, by hydroformylation and hydrogenation.

[0053] h) Polyhydrocarbon polyols, also called oligohydrocarbonols, such as polyhydroxy-functional polyolefins, polyisobutylene, polyisoprene, polyhydroxy-functional ethylene / propylene, ethylene / butylene, or ethylene / propylene / diene copolymers; polyhydroxy-functional polymers of dienes, particularly 1,3-butadiene, which can also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes or mixtures of dienes such as 1,3-butadiene and vinyl monomers such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene, isoprene, etc., such as polyhydroxy-functional acrylonitrile / butadiene copolymers, which can also be prepared from epoxides or amino alcohols and carboxyl-terminated acrylonitrile / butadiene copolymers; and hydrogenated polyhydroxy-functional polymers or copolymers of dienes.

[0054] The NCO / OH ratio during the reaction between polyisocyanate and polyol is preferably in the range of 2 / 1 to 10 / 1, more preferably in the range of 3 / 1 to 8 / 1, and particularly in the range of 4 / 1 to 7 / 1.

[0055] Preferably, the prepolymer has an NCO content in the range of 0.5% to 10% by weight, preferably 0.6% to 8.4% by weight, and particularly 0.8% to 7% by weight.

[0056] Specifically, the prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol has a monomeric polyisocyanate, particularly monomeric diisocyanate, content of 0.5% by weight or less, preferably 0.3% by weight or less, specifically 0.2% by weight or less, and especially 0.1% by weight or less.

[0057] The prepolymer used is preferably formed of isophorone diisocyanate (IPDI) and / or diphenylmethane 2,2'-diisocyanate (MDI), in which case the prepolymer has a monomeric polyisocyanate, particularly monomeric diisocyanate, content of 0.5% by weight or less, preferably 0.3% by weight or less, specifically 0.2% by weight or less, and especially 0.1% by weight or less.

[0058] Such prepolymers are particularly suitable for the production of formulations such as elastic adhesives, sealants, and coatings having a monomeric polyisocyanate, especially monomeric diisocyanate, content of less than 0.1% by weight, which can be handled safely even without special safety precautions and are therefore marketable in many countries without hazard labeling.

[0059] Furthermore, it has been found that prepolymers with a low proportion of monomeric polyisocyanate yield particularly advantageous polyurethane compositions when used with curing agents used according to the present invention, to a certain extent, exhibiting the advantages of the present invention. In particular, in the case of MDI-based prepolymers, it is advantageous to remove excess MDI monomer after preparation, because otherwise, as will be further described below, particularly in embodiments already coated with MDI, the hydrazide may slow down and affect the curing of the isocyanate group-containing polymer. However, in the case of IPDI or TDI-based prepolymers, the presence of residual monomeric diisocyanate has no effect on curing at all.

[0060] Preferably, the reaction between the polyisocyanate and the polyol is carried out in the presence of an optionally suitable catalyst at a temperature in the range of 20 to 160°C, particularly 40 to 140°C, with moisture removed.

[0061] After the reaction, residual monomeric polyisocyanate, and specifically residual monomeric diisocyanate, in the reaction mixture can be removed to the described residual content using a suitable separation method.

[0062] Preferred separation methods include distillation, particularly thin-film distillation or short-path distillation, preferably using reduced pressure.

[0063] Particularly preferred is a multi-stage method in which monomeric polyisocyanate or diisocyanate is removed in a short-path evaporator with a jacket temperature in the range of 120 to 200°C and a pressure of 0.001 to 0.5 mbar.

[0064] In the case of IPDI, which is a preferred monomeric diisocyanate, the jacket temperature is preferably in the range of 140 to 180°C.

[0065] Preferably, monomeric polyisocyanate, particularly monomeric diisocyanate, and polyol are reacted, followed by the removal of any remaining monomeric polyisocyanate from the reaction mixture without the use of a solvent and / or an entraining agent.

[0066] Preferably, the monomeric polyisocyanate removed after the reaction is subsequently reused, i.e., it is used again for the preparation of a polymer containing isocyanate groups.

[0067] During the reaction, the OH groups of the polyol react with the isocyanate groups of the monomeric polyisocyanate, specifically the monomeric diisocyanate. This results in a so-called chain extension reaction, where the OH groups and / or isocyanate groups of the reaction products of the polyol and monomeric polyisocyanate undergo the reaction. A higher NCO / OH ratio leads to a lower level of chain extension, lower polydispersity, and consequently, lower viscosity of the resulting polymer. The degree of chain extension is measured by the average molecular weight or peak width and peak distribution of the polymer in GPC analysis. A further measure is the effective NCO content of the polymer after monomer removal, compared to the theoretical NCO content calculated assuming that every OH group reacts with the monomeric polyisocyanate.

[0068] Polymers containing isocyanate groups and having a low monomeric polyisocyanate content preferably have a viscosity at 20°C of 50 Pa·s or less, particularly 40 Pa·s or less, and more preferably 30 Pa·s or less. Viscosity is measured here with a cone diameter of 25 mm, a cone angle of 1°, a cone tip-to-plate distance of 0.05 mm, and 10s -1 This is determined by a cone-plate viscometer with a shear rate of [value].

[0069] Preferred polymers or prepolymers containing isocyanate groups can be used to obtain high-quality, easily processable thermosetting polyurethane compositions.

[0070] Particularly preferred polymers having a low monomeric polyisocyanate content are obtained from the reaction of an IPDI with an IPDI having an NCO content in the range of 1% to 2.5% by weight, preferably 1.1% to 2.1% by weight, 80% to 100% by weight, particularly 80% to 90% by weight of 1,2-propyleneoxy groups, and 0% to 20% by weight, particularly 10% to 20% by weight of 1,2-ethyleneoxy groups, and a monomeric polyisocyanate content of 0.3% by weight or less, and having an average number of OH functional groups in the range of 2.2 to 3, preferably 2.2 to 2.8, particularly 2.2 to 2.6, and an OH value in the range of 10 to 42 mg KOH / g, particularly 20 to 35 mg KOH / g.

[0071] Further, particularly preferred prepolymers having a low monomeric polyisocyanate content are obtained from the reaction of IPDI with at least one polyetherdiol having an NCO content in the range of 2.8% to 7% by weight, 100% propyleneoxy groups, and a monomeric polyisocyanate content of 0.3% by weight or less, based on all repeating units of the polyether segment, and having an OH value in the range of 44 to 120 mg KOH / g.

[0072] The proportion of the prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol in the polyurethane composition is, for example, in the range of 10% to 90% by weight, particularly 15% to 70% by weight, preferably 20% to 50% by weight, and specifically 25% to 45% by weight.

[0073] In this case, the hydrazide in combination with epoxy resin is specifically used as a curing agent.

[0074] Hydrazides are a class of compounds having a functional group in which two nitrogen atoms are covalently bonded. Specifically, in relation to the present invention, hydrazides are organic hydrazides. These are typically derivatives of organic acids such as carboxylic acids and / or sulfonic acids. Carbonyl hydrazides have at least one acyl group as a substituent in addition to at least one hydrazide group, while sulfonyl hydrazides have at least one sulfonyl group as a substituent in addition to at least one hydrazide group.

[0075] The hydrazide used is in particulate form, preferably powder form. In advantageous embodiments, the hydrazide is in powder form with a D50 particle size value of ≤50 μm, particularly ≤20 μm, preferably ≤10 μm, more preferably ≤7.5 μm, and most preferably ≤5 μm. The D50 particle size means the value at which 50% by weight of the particles have a size less than or equal to the specified value. The D50 particle size can typically be determined by laser light scattering in accordance with standard ISO 13320:2020, for example, with a CILAS920 instrument from CILAS.

[0076] In the use according to the present invention, the hydrazide is preferably mixed with the prepolymer so that the hydrazide is uniformly distributed within the prepolymer. Specifically, the prepolymer before curing disperses particulate hydrazide to form a continuous phase.

[0077] The hydrazide is preferably used in a ratio of 1.5 to 10 parts by weight, more preferably 2.0 to 7.5 parts by weight, and particularly 2.5 to 5.5 parts by weight, per 1 part by weight of isocyanate groups in the prepolymer present in the thermosetting polyurethane composition. This means, for example, that when using 100 grams of prepolymer having a 2% by weight NCO content, preferably 3 to 20 grams of hydrazide are used.

[0078] Preferably, the hydrazide is used in a proportion of 0.5 to 15% by weight, preferably 1 to 10% by weight, and particularly 1.5 to 23.0% by weight, based on the total weight of the thermosetting polyurethane composition.

[0079] In preferred embodiments, the hydrazide is coated with an isocyanate monomer, specifically a diisocyanate monomer, and in particular, diphenylmethane diisocyanate monomer. Specifically, the isocyanate monomer is diphenylmethane 4,4'-diisocyanate, which may optionally contain a portion of diphenylmethane 2,4'- and / or 2,2'-diisocyanate. The isocyanate monomer coating specifically results in the encapsulation of the hydrazide. The isocyanate monomer allows for control, specifically increase, of the activation temperature and storage stability of the polyurethane composition.

[0080] When used in coatings, the isocyanate monomers used are specifically chemically bonded to a hydrazide. Therefore, they are not free isocyanate monomers. Coatings can be made, for example, by mixing the hydrazide and the isocyanate monomer. This is done before mixing with other components of the thermosetting polyurethane composition, in particular.

[0081] Preferably, the isocyanate monomer is present in an amount of 0.01 to 1% by weight, preferably 0.02 to 1% by weight, and particularly 0.1 to 0.3% by weight, based on the total weight of the thermosetting polyurethane composition.

[0082] The weight ratio of isocyanate monomer to hydrazide is preferably in the range of 0.01 to 0.20, specifically 0.03 to 0.15, and particularly 0.05 to 0.12.

[0083] These proportions and ratios have proven particularly advantageous for controlling the activation temperature and storage stability of polyurethane compositions within an industrial context.

[0084] However, it is also possible to avoid using isocyanate monomers. In this case, the hydrazide preferably comes into direct contact with the prepolymer in the polyurethane composition. Therefore, the hydrazide in this case is in a free and / or unencapsulated form. Direct contact between the hydrazide and the prepolymer has the advantage of enabling controlled rapid curing, as the liquefaction of the hydrazide directly activates the thermosetting process.

[0085] More preferably, the hydrazide has a melting point of at least 75°C, preferably at least 100°C, particularly at least 110°C, specifically at least 120°C, and more preferably at least 150°C. This makes it possible to achieve particularly high storage stability while effectively reducing segregation in events involving only partial conversion of the curing agent.

[0086] In a particularly preferred embodiment, the hydrazide includes or consists of a dihydrazide.

[0087] The hydrazide is preferably a hydrazide of a carboxylic acid and / or sulfonic acid. Specifically, it is of formula (Ia), (Ib), or (Ic): [ka] (In the formula, W is the p-valent group of the carboxylic acid after the removal of p carboxylic acid groups. X is the q-valent group of the sulfonic acid after the removal of q sulfonic acid groups. m is either 0 or 1. p is 1, 2, 3, or 4, preferably 2, and (q is 1, 2, 3, or 4) It is hydrazide.

[0088] Specifically, the hydrazide is a carbonyl hydrazide, particularly a carbonyl dihydrazide, preferably selected from the group consisting of carbodihydrazide, oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacate acid dihydrazide, dodecandioic acid dihydrazide, and isophthalic acid dihydrazide, most preferably adipic acid dihydrazide.

[0089] When using such hydrazides, which are commercially available from various suppliers, it is possible to produce polyurethane compositions, particularly within a wide temperature window.

[0090] Suitable and preferred commercially available hydrazides include, for example, Ajicure® VDH (manufactured by Venture Chemical Ltd.) and Technicure® ADH (manufactured by A&C Catalysts).

[0091] It is even more preferable when the polyurethane composition is aldehyde and / or ketone-blocking amine-free. Specifically, the polyurethane composition is aldimine, ketimine, enamine, and / or oxazolidine-free. This specifically reduces the risk of undesirable gas release of aldehydes and / or ketones.

[0092] A suitable epoxy resin is a standard industrial epoxy resin, which can be obtained by known methods, for example, from the oxidation of a corresponding olefin, or from the reaction of epichlorohydrin with a corresponding polyol, polyphenol, or amine.

[0093] Specifically, epoxy resin is polyepoxide.

[0094] Particularly preferred epoxy resins are those referred to as "liquid resins," or so-called liquid polyepoxide resins. These have a glass transition temperature of less than 25°C. So-called solid resins, which have a glass transition temperature greater than 25°C and can be granulated into a powder that can be poured at 25°C, can also be used as epoxy resins. However, liquid epoxy resins are advantageous.

[0095] A suitable epoxy resin is, specifically, one of the following: [ka] (In the formula, substituents R' and R'' are each independently either H or CH3. The exponent s has a value between 0 and 20.) It is an epoxy resin.

[0096] Compounds of formula (I) with an exponent s >1.5, particularly between 2 and 12, are called solid epoxy resins. Such solid epoxy resins are commercially available, for example, from Dow Chemical, Huntsman, or Hexion.

[0097] Compounds of formula (I) having an exponent s of 1 to 1.5 are referred to by those skilled in the art as semi-solid epoxy resins. In the present invention, they are considered equivalent to solid epoxy resins. The term "solid epoxy resin" is very well known to those skilled in the field of epoxy and is used in contrast to "liquid epoxy resin."

[0098] Compounds of formula (I) having an exponent s between 0 and 1 are liquid epoxy resins. Preferably, s has a value less than 0.2.

[0099] Suitable epoxy resins are, in particular, aromatic epoxy resins, and especially glycidylation products of the following: - Bisphenol A, bisphenol F, or bisphenol A / F (where A is an abbreviation for acetone and F is an abbreviation for formaldehyde, and these are used as reactants in the preparation of these bisphenols. In the case of bisphenol F, positional isomers, particularly those derived from 2,4'- or 2,2'-hydroxyphenylmethane, may also exist.) - Dihydroxybenzene derivatives, for example, resorcinol, hydroquinone, or catechol, - Further bisphenols or polyphenols, e.g., bis(4-hydroxy-3-methylphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane (bisphenol C), bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane (bisphenol B), 3,3-bis(4-hydroxyphenyl)pentane, 3,4-bis(4-hydroxyphenyl)hexane, 4,4-bis(4-hydroxyphenyl)heptane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl) bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,4-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol P), 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol M), 4,4'-dihydroxydiphenyl (DOD), 4,4'-dihydroxybenzophenone, bis(2-hydroxynaphtho-1-yl)methane, bis(4-hydroxynaphtho-1-yl)methane, 1,5-dihydroxynaphthalene, tris(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl) ether, or bis(4-hydroxyphenyl) sulfone, - Condensation products of phenol with formaldehyde obtained under acidic conditions, such as phenol novolac and cresol novolac, also known as bisphenol F novolac. - Aromatic amines, such as aniline, toluidine, 4-aminophenol, 4,4'-methylenediphenyldiamine, 4,4'-methylenediphenyldi(N-methyl)amine, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline (bisaniline P), or 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline (bisaniline M).

[0100] Further preferred epoxy resins are aliphatic or cyclic aliphatic polyepoxides, in particular the following: - Saturated or unsaturated, branched or unbranched, cyclic or open-chain 2, 3, or 4-functional C2-C30 alcohols, in particular ethylene glycol, propylene glycol, butylene glycol, hexanediol, octanediol, polypropylene glycol, dimethylolcyclohexane, neopentyl glycol, dibromo-neopentyl glycol, castor oil, trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol, or glycerol, or glycidyl ethers of alkoxylated glycerol or alkoxylated trimethylolpropane. - Hydrogenated liquid bisphenol A, F, or A / F resin, or glycidylation products of hydrogenated bisphenol A, F, or A / F, - N-glycidyl derivatives of amides or heterocyclic nitrogen bases, such as triglycidyl cyanurate or triglycidyl isocyanurate, or reaction products of epichlorohydrin with hydantoin. - Epoxy resins derived from olefins, for example, vinylcyclohexene, dicyclopentadiene, cyclohexadiene, cyclododecadiene, cyclododecatriene, isoprene, 1,5-hexadiene, butadiene, polybutadiene, or divinylbenzene.

[0101] Preferred epoxy resins are liquid resins, particularly bisphenol-based liquid resins.

[0102] The epoxy resin is most preferably a liquid resin based on bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, or bisphenol A / F diglycidyl ether. Such liquid resins are commercially available, for example, from Dow, Huntsman, or Momentive. These epoxy resins have easily manageable viscosity and allow for high strength and resistance. Such liquid resins may also contain a solid bisphenol A resin or phenol novolac portion.

[0103] The epoxy equivalent weight (EEW) of epoxy resins is typically between 100 and 500 g / eq, and more specifically between 130 and 250 g / eq. Here, the epoxy equivalent weight is measured specifically in accordance with the standard ASTM D1652-11 (2019).

[0104] Such epoxy resins react at relatively high temperatures, for example, above 150°C, which leads to further crosslinking of the polyurethane composition.

[0105] The epoxy resin is used in particular in a proportion of 0.1 to 15% by weight, preferably 1 to 10% by weight, especially 1.5 to 5% by weight, and most preferably 2 to 4% by weight, based on the total weight of the thermosetting polyurethane composition.

[0106] Specifically, epoxide-amine adducts are not used at all in polyurethane compositions, in particular epoxide-amine adducts that can be obtained by reacting bisphenol diglycidyl ether with an aliphatic polyamine are not used at all, and / or polyurethane compositions do not contain such epoxide-amine adducts. In this case, the aliphatic polyamine is specifically a diamine, in particular a diamine having one primary amine group and one secondary amine group, and / or a diamine having one primary amine group and one tertiary amine group. The epoxide-amine adducts that are not used are, in particular, the adducts described on page 5, lines 8-16 of European Patent Application Publication No. 0365984A2. Such adducts are not suitable for compositions according to the present invention.

[0107] The polyurethane composition of the present invention may also optionally contain one or more further auxiliary agents and additives commonly used in the polyurethane industry.

[0108] Examples of such additives include plasticizers, solvents, inorganic and organic fillers, such as pulverized or precipitated calcium carbonate, carbon black, kaolin, alumina, silica, and / or PVC powder, fibers, such as polyethylene fibers, pigments, rheology modifiers, such as thixotropic agents, thickeners, such as urea compounds, polyamide waxes, bentonite, or fumed silica, adhesion promoters, in particular silanes, such as epoxysilane, vinylsilane, and isocyanatosilane, desiccants, such as p-tosyl isocyanates and other reactive isocyanates, orthoformates, calcium oxide, or molecular sieves, stabilizers against heat, light, and UV rays, flame retardants, surfactants, such as wetting agents, leveling agents, deaeration agents, or defoaming agents, and fungicidal agents or substances that inhibit fungal growth.

[0109] Additives may be added in suitable amounts according to convention, depending on the end use as required. Generally, polyurethane compositions preferably contain at least one plasticizer and / or at least one filler.

[0110] The plasticizers are selected from, for example, carboxylic acid esters, such as phthalates, particularly diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and / or di(2-propylheptyl) phthalate (DPHP), hydrogenated phthalates, particularly hydrogenated diisononyl phthalate (DINCH), terephthalates, particularly dioctyl terephthalate, trimellitates, particularly trioctyl trimellitate, adipates, particularly dioctyl adipate, azelates, sebacates, polyols, particularly polyoxyalkylene polyols and / or polyester polyols, benzoates, glycol ethers, glycol esters, organophosphoric acids, phosphonic acids, and / or sulfonic acid esters, polybutenes, polyisobutenes, and / or plasticizers derived from natural oils and fats, particularly epoxidized soybean oil and / or linseed oil.

[0111] Preferably, the plasticizer has a vapor pressure of less than 0.1 mbar at 20°C, and / or the plasticizer has a boiling point of at least 250°C, preferably at least 300°C, and particularly at least 350°C, at a standard pressure of 101.325 kPa. This makes it possible to prevent excessive gas release from the plasticizer, especially at higher curing temperatures, for example, above 180°C.

[0112] Particularly preferred are plasticizers selected from phthalates and / or trimellites, and more specifically from diisodecylphthalate (DIDP) and / or trioctyl trimellites. These have proven particularly advantageous for the thermosetting polyurethane composition.

[0113] Preferably, the plasticizer is used in a proportion of 0.1 to 30% by weight, preferably 5 to 25% by weight, and particularly 10 to 20% by weight, based on the total weight of the thermosetting polyurethane composition.

[0114] More preferably, the thermosetting polyurethane composition contains one or more stabilizers against heat, oxygen, moisture, light, and / or UV rays.

[0115] Suitable stabilizers include, for example, hindered amines (HALS stabilizers), hindered phenols, phosphites, and / or aromatic amines. Such stabilizers are commercially available under product names such as Irganox, Kinox, Dovernox, Weston, Irgaphos, Doverphos, and / or Ionol.

[0116] Phosphates, and more specifically organophosphates, are particularly preferred as stabilizers. Organophosphates, also called phosphate esters, are specifically defined by formula (II): [ka] (In the formula, R 1 , R 2 , and R 3 Each of these is independently an organic group, for example, a group having 1 to 25 carbon atoms. It has one or more groups. The organic group may contain one or more heteroatoms, or may consist exclusively of carbon and hydrogen atoms.

[0117] Preferably, base R 1 , R 2 , and R 3 At least one of them contains an aromatic group.

[0118] Specifically, the stabilizer is an organodiphosphine having two groups of formula II.

[0119] Such phosfit stabilizers are commercially available, for example, under the name Doverphos®.

[0120] Surprisingly, phosfit further reduced any discoloration of the polyurethane composition, and in this case, discoloration was found to be very mild even at curing temperatures typically above 200°C. In contrast, stabilizers in the form of phenol are not as suitable for stabilization at such high curing temperatures.

[0121] The proportions of components in a polyurethane composition can vary over a wide range depending on the components used and the final use. The amounts specified below for suitable preferred embodiments are based on the total weight of the polyurethane composition.

[0122] More preferably, the thermosetting polyurethane composition comprises the following components based on the total weight of the thermosetting polyurethane composition. a) 0.5 to 15% by weight, preferably 1 to 10% by weight, particularly 1.5 to 3.0% by weight of hydrazide, b) 0.1 to 15% by weight, preferably 1 to 10% by weight, and particularly 2 to 5% by weight of epoxy resin, c) 15-70% by weight, preferably 20-50% by weight, particularly 25-40% by weight of a prepolymer, d) 0-1% by weight, preferably 0.02-1% by weight, and particularly 0.1-0.3% by weight of isocyanate monomer, e) 0-70% by weight, preferably 10-60% by weight, particularly 40-50% by weight of inorganic and / or organic fillers, specifically those described above. f) 0-30% by weight, preferably 5-25% by weight, particularly 10-20% by weight of a plasticizer, specifically those described above. g) 0-5% by weight, preferably 0.5-4% by weight, particularly 1-3% by weight of a stabilizer, specifically those described above, preferably phosphite. h) 0-1% by weight, preferably 0.01-0.8% by weight, particularly 0.05-0.6% by weight of catalyst, i) Optionally, one or more additional additives, in proportion to the total weight of the mixture.

[0123] Further components of the prepolymer and composition may be mixed with each other in any order to obtain a polyurethane composition. Some components, such as hydrazides optionally coated with isocyanate monomers, may also be added, for example, as a mixture with a plasticizer. Mixing can be carried out at room temperature (e.g., 23°C). It may also be carried out with a slight increase in temperature, either partially or whole, to facilitate homogenization or dispersion. The mixing device used may be any mixing device known in the art. Viscosity may be set, if desired, taking into account the intended use. For example, the polyurethane composition may be paste-like and preferably have structural viscosity.

[0124] The present invention also relates to thermosetting polyurethane compositions obtained by use according to the present invention.

[0125] In other words, it is a thermosetting polyurethane composition comprising: (i) a prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol; (ii) a hydrazide; and (iii) an epoxy resin. Optionally, one or more of the further components described above may be additionally present.

[0126] All the above details and descriptions relating to the use and thermosetting polyurethane compositions according to the present invention shall apply mutatis mutandis to, for example, preferred components.

[0127] The thermosetting polyurethane composition may be a multi-component, for example, a two-component thermosetting polyurethane composition. However, it is preferably a one-component thermosetting polyurethane composition.

[0128] Polyurethane compositions, preferably one-component polyurethane compositions, are generally suitable for bonding one or more materials having the same or different properties, particularly for bonding in automotive assembly or repair. Polyurethane compositions are also suitable as sealants for sealing components, particularly for sealing in automotive assembly or repair. Components include, for example, substrates, surfaces, joints, and / or cavities.

[0129] The present invention also relates to a method for curing the polyurethane composition described above, in which case the polyurethane composition is cured by the action of heat.

[0130] The operating temperature for thermosetting can vary within a wide range, depending on the polyurethane composition used, the desired degree of crosslinking, and the duration of thermosetting. Thermosetting can be performed at temperatures within the range of, for example, 100 to 220°C. The duration of thermosetting can be within the range of, for example, 1 to 120 minutes.

[0131] The present invention also, a) Applying a thermosetting polyurethane composition to the surface of one or both of the adherends to be bonded, b) Bringing the surfaces of the adherends to be bonded into contact, c) In particular, curing the polyurethane composition by thermosetting at the temperatures described above, The present invention relates to a method for bonding adherends, particularly vehicle parts, using the thermosetting polyurethane composition described above.

[0132] The present invention further, a) Applying a thermosetting polyurethane composition to and / or within the components to be sealed, b) In particular, curing the polyurethane composition by thermosetting at the temperatures described above, The present invention relates to a method for sealing components using the thermosetting polyurethane composition described above, including the above-described method.

[0133] The components to be sealed are, in particular, the substrate, surfaces, joints, and / or cavities of the vehicle. In step a), the thermosetting polyurethane composition may be applied to the substrate or surface, and / or introduced into the joints and / or cavities.

[0134] The adherends or adherend surfaces and / or components to be bonded may be made of any desired material, and the adherend surfaces to be bonded may be made of the same or different materials. Examples of suitable materials include metals, metal alloys, glass, plastics, ceramics, textiles, or painted components or adherends.

[0135] The thermosetting polyurethane composition can be applied to one or both adherend surfaces to be bonded or to components to be sealed in a manner conventionally known to those skilled in the art. The adherend surfaces to be bonded are brought into contact with each other while optionally pressing them together.

[0136] Next, the polyurethane composition is cured by heat, for example, by thermosetting at a temperature in the range of 100 to 220°C, and particularly in the temperature range of 150 to 220°C.

[0137] The present invention also relates to articles comprising adherends and cured polyurethane compositions as bonded combinations of adherends that can be obtained by the method of the present invention. The adherends are, in particular, vehicle components.

[0138] The present invention also relates to a vehicle component, in particular, which includes the cured polyurethane composition described above as a sealant.

[0139] The present invention will be further described by examples hereafter, but this is not intended to limit the present invention. [Examples]

[0140] Examples are presented hereafter, intended to further illustrate the present invention as described. Of course, the present invention is not limited to these described examples.

[0141] Unless otherwise specified, the chemicals used are obtained from Sigma-Aldrich (Switzerland).

[0142] Preparation of prepolymers: Polymer P1: 780.0 g of Desmophen® 5031BT (glycerol-start ethylene oxide-terminated polyoxypropylene triol, OH value 28.0 mg KOH / g, approximately 2.3 OH functional groups, manufactured by Covestro) and 220 g of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (Vestanat® IPDI, manufactured by Evonik) were converted at 80°C by a known method to a polyether urethane polymer having a 6.4 wt% NCO content, a viscosity of 4.1 Pa·s at 20°C, and a monomeric IPDI content of approximately 12 wt%.

[0143] Next, the volatile components, specifically the majority of monomeric IPDI, were removed by distillation in a short-circuit evaporator (jacket temperature 160°C, pressure 0.1-0.005 mbar). The resulting polyether urethane polymer had an NCO content of 1.9 wt%, a viscosity of 8.2 Pa·s at 20°C, and a monomeric IPDI content of 0.02 wt%.

[0144] Polymer P1 is a prepolymer (a polymer containing isocyanate groups) having a low monomeric diisocyanate content.

[0145] Viscosity was measured using a Rheotec RC30 cone-plate viscometer with thermostat (cone diameter 25mm, cone angle 1°, cone tip / plate distance 0.05mm, shear rate 10s). -1 ) was used for measurement.

[0146] The monomeric diisocyanate content was determined by HPLC (detection via photodiode array, with 0.04 M sodium acetate / acetonitrile as the mobile phase) after prior derivatization using N-propyl-4-nitrobenzylamine.

[0147] Polyurethane composition The components specifically shown in Table 1 were mixed under reduced pressure using a planetary mixer in the amounts (parts by weight) specified, removing moisture, to obtain one-component polyurethane compositions R and C1-C5. These compositions were then stored after removing moisture until use.

[0148] [Table 1]

[0149] The composition could be stored at temperatures up to 60°C for several months without any problems.

[0150] Experiments with uncoated hydrazides using isocyanate monomers However, an additional composition C6 was produced without coating the hydrazide with an isocyanate monomer. Composition C6 was formulated similarly to composition C5, except that it used 1.73% by weight of pure hydrazide (without prior treatment with an isocyanate monomer) and 13.77% by weight of plasticizer to compensate for the mass difference due to the missing isocyanate monomer. Therefore, C6 differed from C5 only in that the hydrazide was not coated with an isocyanate monomer.

[0151] Thermosetting and properties of the sample Films of compositions R and C1-C6, each with a thickness of 2 mm, were cured at various curing temperatures for 30 minutes and stored for 7 days under standard climatic conditions (23°C, 50% relative humidity). No oily liquids or other seepage from the cured material occurred during or after the heat curing process.

[0152] Next, the tensile strength, elongation at fracture, and modulus of elasticity were determined in accordance with DIN 53504 (strain rate: 200 mm / min). Table 2 provides an overview of the results.

[0153] Films of compositions C1-C2, which contain hydrazide and epoxy resin as curing agents, can be cured at temperatures of 100-200°C. Here, tensile strength, elongation at break, and modulus are maintained within industrial-relevant ranges throughout the entire temperature range. For films of compositions C2, C3, C4, and C5, this is true even up to 220°C.

[0154] Specifically, the modulus of elasticity is relatively constant, and the film of composition C4 has a particularly stable modulus of elasticity over the entire temperature range, while also exhibiting relatively high tensile strength and elongation at break.

[0155] In contrast, the modulus of elasticity of comparative sample R at 200°C was only 1.5 MPa, and at 220°C, the value could no longer be measured ("nm"). However, the described examples should be considered merely illustrative examples that can be modified as desired within the scope of the invention.

[0156] [Table 2]

[0157] The storage stability of the composition in the container can be determined by the pressure output.

[0158] To determine the pressure force, the composition was filled into an internally coated aluminum cartridge (outer diameter 46.9 mm, inner diameter 46.2 mm, length 215 mm, opening 15-M) and airtightly sealed with a polyethylene stopper (diameter 46.1 mm) manufactured by Novelis Deutschland GmbH. After conditioning at 23°C for 24 hours, the cartridge was opened and the contents were extruded using an extrusion device. For this purpose, a nozzle with an orifice of 2 mm inner diameter was screwed onto the threaded portion of the cartridge. Using an extrusion device (Zwick / Roell Z005), the force required to extrude the composition at an extrusion rate of 60 mm / min was determined. The reported values ​​are the average of the forces measured after extrusion distances of 22 mm, 24 mm, 26 mm, and 28 mm. Measurement was stopped after an extrusion distance of 30 mm.

[0159] To test storage stability, compositions C5 and C6 were filled into cartridges as described above. In a fresh state, composition C5 had a pressure output of 893 N. Composition C6 had a pressure output of 885 N in a fresh state.

[0160] To simulate aging in a container, each of composition C5 and composition C6 was stored in an oven at 60°C for 7 days in one additional sealed cartridge. After this heated storage, the cartridges were cooled again to 23°C for 24 hours, and their pressures were measured again as described above. Composition C5 showed a moderate increase in pressure to 1029N, while composition C6 showed a pressure of 3500N. This indicates that coating the hydrazide with an isocyanate monomer significantly improves storage stability.

Claims

1. The use of a hydrazide having a melting point of at least 65°C as a curing agent for thermosetting in a thermosetting polyurethane composition comprising a prepolymer having isocyanate-terminated groups obtained from at least one polyisocyanate and at least one polyol, and further at least one epoxy resin.

2. The use according to claim 1, wherein the hydrazide is a carbonyl hydrazide, particularly a carbonyl dihydrazide, preferably selected from the group consisting of carbodihydrazide, oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacate acid dihydrazide, dodecandioic acid dihydrazide, and isophthalic acid dihydrazide, most preferably selected from adipic acid dihydrazide.

3. The use according to claim 1 or 2, wherein the hydrazide is coated with an isocyanate monomer, more specifically a diisocyanate monomer, and in particular diphenylmethane diisocyanate.

4. The use according to claim 3, wherein the weight ratio of isocyanate monomer to hydrazide is in the range of 0.01 to 0.20, specifically 0.03 to 0.15, and more particularly 0.05 to 0.

12.

5. The use according to any one of claims 1 to 4, wherein the hydrazide is used in a proportion of 1.5 to 10 parts by weight, preferably 2.0 to 7.5 parts by weight, and particularly 2.5 to 5.5 parts by weight, per 1 part by weight of isocyanate groups in the prepolymer present in the thermosetting polyurethane composition.

6. The use according to any one of claims 1 to 5, wherein the epoxy resin is a polyepoxide, in particular a diglycidyl ether of bisphenol A, bisphenol F, and / or bisphenol A / F.

7. The use according to any one of claims 1 to 6, wherein the epoxy resin is used in a proportion of 0.1 to 15% by weight, preferably 1 to 10% by weight, and particularly 2 to 5% by weight, based on the total weight of the thermosetting polyurethane composition.

8. The use according to any one of claims 1 to 7, wherein a plasticizer is additionally used, the plasticizer preferably having a vapor pressure of less than 0.1 mbar at 20°C and / or a boiling point of at least 250°C, preferably at least 300°C, and particularly at least 350°C at a standard pressure of 101.325 kPa.

9. The use according to claim 8, wherein the plasticizer is selected from phthalates and / or trimellitates, particularly diisodecylphthalate (DIDP) and / or trioctyl trimellitate.

10. The use according to claim 8 or 9, wherein the plasticizer is used in a proportion of 0.1 to 30% by weight, preferably 5 to 25% by weight, and particularly 10 to 20% by weight, based on the total weight of the thermosetting polyurethane composition.

11. The use according to any one of claims 1 to 10, wherein the prepolymer having an isocyanate-terminated group formed from at least one polyisocyanate and at least one polyol has a monomeric polyisocyanate, particularly monomeric diisocyanate, in a content of 0.5% by weight or less, preferably 0.3% by weight or less, specifically 0.2% by weight or less, and more particularly 0.1% by weight or less.

12. The thermosetting polyurethane composition comprises the following components based on the total weight of the thermosetting polyurethane composition: a) 0.5 to 15% by weight, preferably 1 to 10% by weight, and particularly 1.5 to 3.0% by weight of the hydrazide, b) 0.1 to 15% by weight, preferably 1 to 10% by weight, and particularly 2 to 5% by weight of the epoxy resin, c) 15 to 70% by weight, preferably 20 to 50% by weight, and particularly 25 to 40% by weight of the prepolymer, d) 0 to 1% by weight, preferably 0.02 to 1% by weight, and particularly 0.1 to 0.3% by weight of the isocyanate monomer, e) 0 to 70% by weight, preferably 10 to 60% by weight, and particularly 40 to 50% by weight of inorganic and / or organic fillers, f) 0 to 30% by weight, preferably 5 to 25% by weight, and more particularly 10 to 20% by weight of a plasticizer. g) 0 to 5% by weight, preferably 0.5 to 4% by weight, and especially 1 to 3% by weight of a stabilizer, h) 0 to 1% by weight, preferably 0.01 to 0.8% by weight, particularly 0.05 to 0.6% by weight of catalyst, i) Optionally one or more additional additives, The use according to any one of claims 1 to 11, including the use described in any one of claims 1 to 11.

13. The use according to any one of claims 1 to 12, wherein the polyurethane composition is a one-component composition, particularly a one-component adhesive and / or sealant, and especially preferably for vehicle assembly.

14. A thermosetting polyurethane composition comprising (i) a prepolymer having isocyanate-terminated groups formed from at least one polyisocyanate and at least one polyol, (ii) a hydrazide, and (iii) an epoxy resin, particularly the thermosetting polyurethane composition according to any one of claims 1 to 13 and / or a thermosetting polyurethane composition that can be obtained by use according to any one of claims 1 to 13.

15. A method for curing a polyurethane composition according to claim 14, wherein the polyurethane composition is cured by the action of heat, particularly in a temperature range of 150°C to 220°C.

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