Method for producing polyurethane-polyisocyanurate elastomers, sealants and adhesives having long pot life

Abstract

The present invention relates to a method for producing a polyurethane elastomer, the method comprising the steps of: (A) preparing an isocyanate prepolymer (a) by mixing at least one isocyanate-reactive composition (a1) comprising a polyol selected from polyester polyols, polyether polyols or mixtures thereof, the polyol having an average functionality ranging from 1.8 to 2.5 and an OH value ranging from 20 mg KOH / g to 450 mg KOH / g, and at least one polyisocyanate (a2), and reacting the mixture to form an isocyanate prepolymer (a), wherein the isocyanate prepolymer has an isocyanate content ranging from 1% to 9% by weight; and (B) reacting at least one catalyst (c) with at least one isocyanate prepolymer (a) in the presence of at least one catalyst (c). the step of preparing a reaction mixture by mixing at least one epoxy compound (b) with an isocyanate prepolymer (a), wherein the catalyst (c) is a mixture obtainable by introducing an alkali metal salt or alkaline earth metal salt into the compound R—NH—CO—OR′, the amount of alkali metal salt or alkaline earth metal salt being 0.00001 to 0.1 moles per kg of the total mass of the isocyanate prepolymer (a), the epoxy compound (b) and the catalyst (c), and the step of heating this mixture to at least 80° C. to obtain a polyurethane elastomer. Furthermore, the present invention relates to a polyurethane elastomer obtainable by the method according to the present invention, and to the use of such polyurethane elastomer as a part of a roller or as a sealant.

Description

[Technical field]

[0001] The present invention relates to a method for producing a polyurethane elastomer, the method comprising the steps of: (A) preparing an isocyanate prepolymer (a) by mixing at least one isocyanate-reactive composition (a1) comprising a polyol selected from polyester polyols, polyether polyols or mixtures thereof, the polyols having an average functionality in the range of 1.8 to 2.5 and an OH value in the range of 20 mg KOH / g to 450 mg KOH / g, and at least one polyisocyanate (a2), and reacting the mixture to form an isocyanate prepolymer (a), the isocyanate prepolymer having an isocyanate content in the range of 1% to 9% by weight; and (B) reacting at least one epoxy compound (b) with an isocyanate in the presence of at least one catalyst (c). The process comprises the steps of preparing a reaction mixture by mixing an isocyanate prepolymer (a) with an epoxy compound (b) (wherein the catalyst (c) is a mixture obtainable by introducing an alkali metal salt or an alkaline earth metal salt into a compound R-NH-CO-OR', where R and R' can be the same or different and can be any radical known in organic chemistry, the amount of alkali metal salt or alkaline earth metal salt being between 0.00001 and 0.1 moles per kg of the total mass of the isocyanate prepolymer (a), the epoxy compound (b) and the catalyst (c) and heating this mixture to at least 80°C to obtain a polyurethane elastomer. Furthermore, the present invention relates to a polyurethane elastomer obtainable by the process according to the invention and to the use of such a polyurethane elastomer as part of a roller or as a sealant. [Background technology]

[0002] In particular, the manufacture of plastic parts with large surface areas, such as wheels and rollers for heavy load applications, requires plastic systems with long open assembly times. For this reason, for example, the mould may be filled before the plastic system has cured to provide the finished plastic. However, there is also a demand for plastic systems to cure the plastic as quickly as possible, which allows for faster demolding times and improves profitability. Furthermore, moulded articles, particularly those exposed to high loads, require high mechanical strength, especially compression set. The required long open assembly times are generally achieved by slow-reacting chain extenders, a significant reduction in catalysis or by setting in atmospheric humidity. However, this results firstly in uncontrollable demolding times and secondly in the need for long curing periods.

[0003] One option for producing polyisocyanurate-polyurethane elastomers is described in US 20110065885, where a potassium acetate based catalyst system is used, where the open assembly time is in the range of 10 minutes.

[0004] The patent document EP 0 643 086 describes the reaction of polyurethane prepolymers in the presence of the 2-ethylhexanoate salt of diazabicycloundecene (DBU) as a catalyst system. Here, the curing of the material takes place as a one-component system and can be thermally initiated from 50° C. Nevertheless, the open time still needs to be extended.

[0005] WO 10121898 describes a polyisocyanate component consisting in part of a bidentate urea prepolymer (-NH-CO-NH-) with respect to the anion, mixed with lithium chloride. When this component is mixed with a diglycidyl ether and a second component containing a polyol and the mixture is heated to 80-90°C, a rapid reaction occurs, which leads to a complete cure of the material. Nevertheless, elastomers with low compression set are not described in WO 10121898.

[0006] WO 2015 / 078740 is concerned with the production of large fiber-reinforced polyurethane parts. In order to provide a method for producing these parts with long open times and fast curing times, WO 2015 / 078740 proposes the application of polyurethane catalyst mixtures that can be obtained by introducing alkali metal salts or alkaline earth metal salts into urethane group-containing compounds. The production of elastomers is not proposed in WO 2015078740. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US 20110065885 [Patent Document 2] EP0643086 [Patent Document 3] WO 10121898 [Patent Document 4] WO 2015 / 078740 Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a method for producing polyurethane elastomers, wherein the reaction mixture for producing the polyurethane elastomers exhibits a long open time that allows for mold filling and rapid curing of even larger parts. Furthermore, it is an object of the present invention to provide polyurethane elastomers obtainable by such a method, wherein the elastomers comprise a low compression set. [Means for solving the problem]

[0009] According to the present invention, this object is achieved by a process for the preparation of polyurethane elastomers, which comprises the steps of: (A) preparing an isocyanate prepolymer (a) by mixing at least one isocyanate-reactive composition (a1) comprising a polyol selected from polyester polyols, polyether polyols or mixtures thereof, having an average functionality in the range of 1.8 to 2.5 and an OH value in the range of 20 mg KOH / g to 450 mg KOH / g, and at least one polyisocyanate (a2), and reacting this mixture to form an isocyanate prepolymer (a), wherein the isocyanate prepolymer has an isocyanate content in the range of 1% by weight to 9% by weight; (B) reacting at least one catalyst (c) with at least one isocyanate-reactive composition (a2) in the presence of at least one isocyanate-reactive composition (a1) and at least one polyisocyanate (a2) to form an isocyanate prepolymer (a), wherein the isocyanate prepolymer has an isocyanate content in the range of 1% by weight to 9% by weight; The method includes the steps of preparing a reaction mixture by mixing at least one epoxy compound (b) with an isocyanate prepolymer (a), where the catalyst (c) is a mixture obtainable by introducing an alkali metal salt or an alkaline earth metal salt into the compound R-NH-CO-OR', and the amount of the alkali metal salt or the alkaline earth metal salt is 0.00001-0.1 moles per kg of the total mass of the isocyanate prepolymer (a), the epoxy compound (b) and the catalyst (c), and heating the mixture to at least 80°C to obtain a polyurethane elastomer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The elastomers according to the invention have an elongation at break according to DIN 53504 of at least 80%, preferably at least 150%, more preferably at least 200%, in particular at least 300%, and a hardness of at most 90 Shore A, preferably at most 85 Shore A, more preferably at most 75 Shore A, most preferably at most 90 Shore A, more preferably at most 90 ... maximum It includes a Shore hardness of 70 Shore A, but preferably the Shore A hardness is greater than 20 Shore A, more preferably greater than 30 Shore A, and most preferably greater than 40 Shore A. Additionally, the elastomers according to the present invention preferably include a compression set of 40% or less, more preferably 25% or less, and most preferably 15% or less.

[0011] To prepare the isocyanate prepolymer (a) in step (A), at least one isocyanate-reactive composition (a1) containing a polyol selected from polyester polyols, polyether polyols or mixtures thereof, with an average functionality in the range of 1.8 to 2.5 and an OH value in the range of 20 mg KOH / g to 450 mg KOH / g, and at least one polyisocyanate (a2) are mixed. This mixture is then reacted to form the isocyanate prepolymer (a). This reaction can be carried out in a known manner. For example, these polyisocyanate prepolymers can be obtained by reacting an excess of isocyanate (a2) with the isocyanate-reactive component (a2) at a temperature of, for example, 30 to 100°C, preferably about 80°C, to obtain a prepolymer. The amounts of isocyanate (a2) and isocyanate-reactive component (a1) are selected so that the isocyanate content of the finished prepolymer is in the range of from 1% to 9% by weight, preferably from greater than 2% to less than 8% by weight, and most preferably from greater than 4% to less than 6% by weight.

[0012] As the isocyanate-reactive composition comprising a polyol selected from polyester polyols, polyether polyols and mixtures thereof, polyester polyols and / or polyether polyols known in the field of polyurethane chemistry can be applied, having an average functionality in the range of 1.8 to 2.5, preferably 1.9 to 2.3, more preferably 1.95 to 2.1, particularly preferably 2.0, and an OH value in the range of 20 mg KOH / g to 450 mg KOH / g, preferably 25 mg KOH / g to 200 mg KOH / g, more preferably 30 mg KOH / g to 120 mg KOH / g, particularly preferably 35 mg KOH / g to 70 mg KOH / g.

[0013] As polyetherols having an average functionality in the range of 1.8 to 2.5, preferably 1.9 to 2.3, more preferably 1.95 to 2.1, particularly preferably 2.0, and an OH value in the range of 20 mg KOH / g to 450 mg KOH / g, preferably 25 mg KOH / g to 200 mg KOH / g, more preferably 30 mg KOH / g to 120 mg KOH / g, particularly preferably 35 mg KOH / g to 70 mg KOH / g, it is possible to use conventional polyether polyols characterized by these parameters. In this specification, according to the invention, the OH value is determined according to DIN 53240, and the functionality of the applied polyol is to be understood as the theoretical functionality. In polyether polyols, this theoretical functionality can be obtained, for example, by calculating the functionality based on the functionality of the starter molecules. The influence of side reactions during the preparation of the polyether polyols, such as disproportionation, is not taken into account when determining the functionality.

[0014] As isocyanate-reactive groups, groups such as OH, SH and NH groups may be present. The polyol preferably has substantially OH groups, more preferably only OH groups, as isocyanate-reactive groups. Here, the calculation of the average OH number and the average functionality is carried out based on all polyols used.

[0015] The polyether polyols are obtained in the presence of a catalyst by known methods, for example by anionic polymerization of alkylene oxides with the addition of at least one starter molecule containing 1 to 4, preferably 2 to 3, more preferably 2 reactive hydrogen atoms in bond form. The catalysts used can be alkali metal hydroxides, such as sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, such as sodium methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide, or in the case of cationic polymerization, Lewis acids as catalysts, such as antimony pentachloride, boron trifluoride etherate or bleaching earth. As catalysts it is also possible to use double metal cyanide compounds, known as DMC catalysts.

[0016] As alkylene oxide, preferably one or more compounds having 2 to 4 carbon atoms in the alkylene group are used, such as tetrahydrofuran, 1,2-propylene oxide or 1,2- and / or 2,3-butylene oxide, in each case alone or in the form of a mixture, preferably 1,2-propylene oxide, 1,2-butylene oxide and / or 2,3-butylene oxide, in particular 1,2-propylene oxide. In a preferred embodiment, the polyether polyol comprises at least 70% by weight of propylene oxide, more preferably at least 80% by weight, in particular at least 90% by weight, based on the total weight of the alkylene oxides.

[0017] Possible starter molecules include, in particular, dihydric alcohols, such as, for example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine, diethanolamine, triethanolamine, etc.

[0018] In another preferred embodiment, the polyether polyol comprises polytetraethylene ether glycol (PTMEG), also known as polytetrahydrofuran (PTHF). When PTHF is present as the polyether polyol, the amount of PTHF in the isocyanate-reactive component (a1) is preferably at least 50%, more preferably at least 80%, and most preferably at least 90%, based on the total weight of the isocyanate-reactive component (a1).

[0019] As polyester polyols having an average functionality in the range of 1.8 to 2.5, preferably 1.9 to 2.3, more preferably 1.95 to 2.1 and particularly preferably 2.0, and an OH value in the range of 20 mg KOH / g to 150 mg KOH / g, preferably 25 mg KOH / g to 200 mg KOH / g, more preferably 30 mg KOH / g to 120 mg KOH / g and particularly preferably 35 mg KOH / g to 70 mg KOH / g, it is possible to use customary polyether polyols characterized by these parameters.

[0020] The polyester alcohols used are usually prepared by condensation of polyfunctional alcohols, preferably having 1 to 12 carbon atoms, such as ethylene glycol, diethylene glycol, butanediol, trimethylolpropane, glycerol or pentaerythritol, with polyfunctional carboxylic acids having 2 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid isomers, or their anhydrides. Besides or in addition to polyfunctional alcohols having 1 to 12 carbon atoms, alkoxylation products of preferably difunctional starter molecules can also be used. Such alkoxylation products preferably have an OH value of less than 610 mg KOH / g, preferably more than 100 mg KOH / g, more preferably more than 200 mg KOH / g, most preferably more than 400 mg KOH / g. In a preferred embodiment of the present invention, the polyester polyol is obtained by esterification of adipic acid and butanediol. In a more preferred embodiment, the polyester comprises at least 70% by weight, even more preferably at least 80% by weight, and most preferably at least 90% by weight, of adipic acid and butanediol, based on the diacids and diols used in the preparation of the polyester of the present invention.

[0021] As further starting materials in the preparation of the polyesters, it is possible to use hydrophobic substances. Hydrophobic substances are water-insoluble substances containing non-polar organic radicals and having at least one reactive group selected from hydroxyl, carboxylic acid, carboxylic acid ester or mixtures thereof. The equivalent weight of the hydrophobic material is preferably 130 to 1000 g / mol. For example, fatty acids such as stearic acid, oleic acid, palmitic acid, lauric acid or linoleic acid, and also for example fats and oils such as castor oil, corn oil, sunflower oil, soybean oil, coconut oil, olive oil or tall oil may be used. If the polyester comprises a hydrophobic substance, the proportion of the hydrophobic substance in the total monomer content of the polyester alcohol is preferably 1 to 30 mol%, more preferably 4 to 15 mol%.

[0022] A further group of polyols derived from fatty acids which are preferably used are obtained by ring opening of epoxidized fatty acid esters with simultaneous reaction of alcohols and, optionally, subsequent further transesterification reactions. The introduction of hydroxyl groups into fats and oils is mainly achieved by epoxidizing the olefinic double bonds present in these products and subsequently reacting the resulting epoxide groups with mono- or polyhydric alcohols. This produces structures with hydroxyl groups from the epoxide ring or, in the case of polyfunctional alcohols, more OH groups. Since fats and oils are usually glycerol esters, a parallel transesterification reaction is further carried out during the above-mentioned reaction. The compounds thus obtained preferably have a molecular weight in the range of 500 to 1500 g / mol. Products of this kind are sold, for example, by BASF under the name Sobermole®.

[0023] In a preferred embodiment, besides the isocyanate-reactive component (a1) less than 30% by weight, more preferably less than 10% by weight, of further compounds having isocyanate-reactive groups, and most preferably no further compounds having isocyanate-reactive groups, are used to prepare the isocyanate prepolymer (a).

[0024] As polyisocyanate (a2), all aliphatic, cycloaliphatic and aromatic isocyanates known for preparing polyurethanes can be used. They preferably have an average functionality of less than 2.5. Examples include 2,2'-, 2,4'- and 4,4'-diphenylmethane diisocyanate, mixtures of monomeric diphenylmethane diisocyanate and higher polycyclic homologues of diphenylmethane diisocyanate (polymeric MDI), isophorone diisocyanate (IPDI) or its oligomers, 2,4- or 2,6-tolylene diisocyanate (TDI) or its mixtures, tetramethylene diisocyanate or its oligomers, hexamethylene diisocyanate (HDI) or its oligomers, naphthylene diisocyanate (NDI), or their mixtures. Preferred polyisocyanates (a2) are monomeric aromatic diisocyanates, preferably 2,4- and 2,6-TDI, or particularly preferably monomeric diphenylmethane diisocyanates, such as 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, or mixtures thereof. Here, diphenylmethane diisocyanates can also be used as mixtures with their derivatives. In that case, the diphenylmethane diisocyanates may particularly preferably contain up to 10% by weight, more particularly preferably up to 5% by weight, of diphenylmethane diisocyanates modified with carbodiimides, uretdione or uretonimines, in particular diphenylmethane diisocyanates modified with carbodiimides.

[0025] In step (B), the isocyanate (a) and at least one epoxy compound (b) are mixed in the presence of at least one catalyst (c). In the mixing step, the order does not matter. In one embodiment, the epoxide (b) is already present during the formation of the isocyanate prepolymer (a). In a preferred embodiment, the isocyanate prepolymer is first prepared, and then the epoxide is added. Furthermore, in a preferred embodiment, the catalyst (c) is not present during the formation of the isocyanate prepolymer (a).

[0026] In a preferred embodiment, the isocyanate prepolymer (a) used in step (B) contains less than 1% by weight, more preferably less than 0.5% by weight, most preferably less than 0.1% by weight of monomeric diisocyanate, based on the total weight of isocyanate (a), which can be ensured, for example, by removing excess unreacted isocyanate by distillation, for example thin film distillation.

[0027] As epoxide (b), any compound containing one or more epoxide groups, it is possible to use all epoxide-containing compounds commonly used in the preparation of epoxy resins. The epoxide (b) containing epoxide groups is preferably liquid at 25° C. It is also possible here to use mixtures of such compounds, which are preferably also liquid at 25° C.

[0028] Examples of such compounds containing epoxide groups that can be used in the context of the present invention include the following I) to VI).

[0029] I) Polyglycidyl and poly([beta]-methylglycidyl) esters obtainable by reacting compounds having at least two carboxyl groups in the molecule with epichlorohydrin and [beta]-methylepichlorohydrin in each case, the reaction being advantageously catalyzed by the presence of a base.

[0030] As the compound having at least two carboxyl groups, for example, aliphatic polycarboxylic acids can be used. Examples of such aliphatic polycarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, dimerized or trimerized linoleic acid. In addition, it is also possible to use cyclic aliphatic acids, such as tetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, hexahydrophthalic acid or 4-methylhexahydrophthalic acid. It is also possible to use aromatic carboxylic acids, such as phthalic acid, isophthalic acid or terephthalic acid, and also any desired mixtures of these carboxylic acids.

[0031] II) Polyglycidyl or poly([beta]-methylglycidyl) ethers which can be obtained by reacting a compound having at least two alcoholic and / or phenolic hydroxyl groups with epichlorohydrin or [beta]-methylepichlorohydrin under alkaline conditions or in the presence of an acid catalyst, followed by treatment with a base.

[0032] Glycidyl ethers of this type are derived, for example, from linear alcohols such as ethylene glycol, diethylene glycol or higher poly(oxyethylene) glycols, propane-1,2-diol or poly(oxypropylene) glycol, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene) glycol, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol or sorbitol, and from polyepichlorohydrins.

[0033] Furthermore, glycidyl ethers of this type can be obtained from alicyclic alcohols, such as 1,4-cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane or 2,2-bis(4-hydroxycyclohexyl)propane, or from alcohols carrying aromatic and / or other functional groups, such as N,N-bis(2-hydroxyethyl)aniline or p,p'-bis(2-hydroxyethylamino)diphenylmethane.

[0034] The glycidyl ethers may also be based on monocyclic phenols such as p-tert-butylphenol, resorcinol or hydroquinone, or polycyclic phenols such as bis(4-hydroxyphenyl)methane, 4,4'-dihydroxybiphenyl, bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane or 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.

[0035] Further compounds which contain hydroxyl groups and are suitable for the preparation of glycidyl ethers are the novolaks which can be obtained by condensing aldehydes, such as formaldehyde, acetaldehyde, chloroaldehyde or furfuraldehyde, with phenols or bisphenols, such as phenol, 4-chlorophenol, 2-methylphenol or 4-tert-butylphenol, which may or may not be substituted by chlorine atoms or C1-C9 alkyl groups.

[0036] III) Poly(N-glycidyl) compounds obtainable by dehydrochlorination of the reaction products of epichlorohydrin with amines containing at least two amine-bound hydrogen atoms. Such amines include, for example, aniline, n-butylamine, bis(4-aminophenyl)methane, m-xylylenediamine or bis(4-methylaminophenyl)methane. Poly(N-glycidyl) compounds also include triglycidyl isocyanurate, N,N'-diglycidyl derivatives of cycloalkyleneureas, such as ethyleneurea or 1,3-propyleneurea, and diglycidyl derivatives of hydantoins, such as 5,5-dimethylhydantoin.

[0037] IV) Poly(S-glycidyl) compounds, such as di-S-glycidyl derivatives, which can be obtained from dithiols, such as ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.

[0038] V) Cycloaliphatic epoxy resins, such as bis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, 1,2-bis(2,3-epoxycyclopentyloxy)ethane or 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexane carboxylate.

[0039] VI) Monofunctional epoxy resins, such as 2-ethylhexyl glycidyl ether, isopropyl glycidyl ether, butyl glycidyl ether or cresyl glycidyl ether.

[0040] In the context of the present invention, it is likewise possible to use epoxy resins in which the 1,2-epoxy groups are bonded to different heteroatoms or functional groups. These compounds include the N,N,O-triglycidyl derivatives of 4-aminophenol, the glycidyl ether glycidyl esters of salicylic acid, N-glycidyl-N'-(2-glycidyloxypropyl)-5,5-dimethylhydantoin and 2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.

[0041] Particularly preferred epoxides (b) are the compounds of classes (I) and (II), more particularly the compounds of class (II).

[0042] The epoxide (b) is preferably used in an amount of 0.3 to 15% by weight, preferably 0.5 to 10% by weight, more in particular 0.8 to 5% by weight, based on the total weight of the isocyanate prepolymer (a) and the epoxide (b).

[0043] Catalyst (c) is a mixture obtainable by introducing an alkali metal salt or an alkaline earth metal salt into the compound R-NH-CO-OR'.

[0044] The alkali metal salts or alkaline earth metal salts used herein are compounds that accelerate the curing reaction of the isocyanate prepolymer (1) in the presence of epoxide. These compounds include, in particular, sodium, lithium, magnesium and potassium, and ammonium compounds, preferably lithium or magnesium salts, with any desired anion, preferably anions of organic acids, such as carboxylates, more preferably anions of inorganic acids, such as nitrates, halides, sulfates, sulfites and phosphates, and even more preferably anions of monobasic acids, such as nitrates or halides, especially nitrates, chlorides, bromides or iodides. Particularly preferably, lithium chloride, lithium bromide and magnesium dichloride, especially lithium chloride, are used. The alkali metal salts or alkaline earth metal salts of the present invention can be used alone or as a mixture.

[0045] Besides the alkali metal salts or alkaline earth metal salts, preferably no further compounds are used which promote the reaction of isocyanate-reactive groups with isocyanates.

[0046] The compound R-NH-CO-OR' is a compound containing at least one urethane group. This compound is preferably solid or preferably liquid at 20° C. In a preferred embodiment, R does not represent hydrogen and / or COR″. In this specification, R, R' and R″ can be the same or different and can be any group known in organic chemistry.

[0047] Here, the compound containing urethane groups in catalyst (c) is preferably obtainable by reaction of a second polyisocyanate with a compound having at least one OH group. Here, compounds that are liquid at 50°C, more preferably compounds that are liquid at room temperature, are preferred. A substance or component that is "liquid" in the context of the present invention means one that has a viscosity of 10 Pas or less at a certain temperature. If no temperature is specified, 20°C is the reference. In this specification, measurements are made according to ASTM D445-11. The compound containing urethane groups preferably has at least two urethane groups. The molecular weight of these compounds containing urethane groups is preferably in the range of 200 to 15000 g / mol, more preferably 300 to 10000 g / mol, more particularly 500 to 1300 g / mol. Compounds containing urethane groups are obtained, for example, by reacting the aforementioned isocyanates (a1) as second isocyanates with compounds having at least one hydrogen atom reactive towards isocyanates, for example monoalcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, or long-chain propoxylated or ethoxylated monools, such as the monofunctional products Pluriol® from BASF, dialcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, hexanediol, and / or are reaction products of said isocyanates with the above polyols (a1) and / or chain extenders (individually or in mixtures). To prepare compounds containing urethane groups, it is possible to use not only isocyanates but also stoichiometric excesses of polyols. When using monoalcohols, it is also possible to use isocyanate groups and OH groups in a stoichiometric ratio. When compounds containing urethane groups have two or more isocyanate groups per molecule, they may completely or partially replace the polyisocyanate (a2), in which case the prepolymer (a) is the compound containing urethane groups in the catalyst (c) and no further addition of prepolymer (a) is necessary.

[0048] The reaction is generally carried out at a temperature of 20 to 120°C, for example at 80°C. The second isocyanate used to prepare the compound containing urethane groups is preferably an isomer or homologue of diphenylmethane diisocyanate. More preferably, the second isocyanate is a monomeric diphenylmethane diisocyanate, such as 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, or a mixture thereof. This diphenylmethane diisocyanate may also be used as a mixture with its derivatives. In that case, the diphenylmethane diisocyanate may contain, particularly preferably, 10% by weight or less, more particularly preferably 5% by weight or less of diphenylmethane diisocyanate modified with carbodiimide, uretdione or uretonimine, in particular diphenylmethane diisocyanate modified with carbodiimide. In a particularly preferred embodiment, the first isocyanate (a) and the second isocyanate for preparing the compound containing urethane groups are the same.

[0049] Compounds containing urethane groups can also be obtained via an alternative reaction route, for example by reacting carbonates with monoamines to form urethane groups. For this purpose, for example, a slight excess (1.1 eq) of propylene carbonate is reacted with a monoamine, for example Jeffamin M 600, at 100° C. The urethane obtained can likewise be used as a compound containing urethane groups.

[0050] The mixture comprising an alkali metal salt or alkaline earth metal salt and a compound containing urethane groups can be obtained, for example, by mixing the alkali metal salt or alkaline earth metal salt with the compound containing urethane groups, for example at room temperature or at elevated temperature. This can be done, for example, using any mixer, for example a simple stirrer. In this case, the alkali metal salt or alkaline earth metal salt can be used as a pure substance or in the form of a solution in a monofunctional or polyfunctional alcohol, for example methanol, ethanol, or a chain extender, or in water. In a particularly preferred embodiment, commercially available prepolymer-based isocyanates are directly mixed with the dissolved salt. Suitable for this purpose are, for example, isocyanate prepolymers with an NCO content of 15% to 30%, in particular based on diphenylmethane diisocyanate and polyether polyols. Isocyanates of this kind are commercially available, for example, under the trade name Lupranat® MP 102 from BASF.

[0051] In one particularly preferred embodiment of the invention, an alkali metal salt or alkaline earth metal salt is dissolved in a compound having a hydrogen atom reactive towards an isocyanate and this solution is subsequently mixed with the isocyanate, optionally at elevated temperature.

[0052] It is particularly preferred to prepare a compound containing a urethane group using a monol having a molecular weight of 30 to 15,000 g / mol, preferably 100 to 900 g / mol, and in a particularly preferred embodiment, 400 to 600 g / mol.

[0053] According to the present invention, the amount of alkali metal salt or alkaline earth metal salt is adjusted so that these salts are present in an amount of 0.00001-0.1 mol per kg of the total mass of the isocyanate prepolymer (a), the epoxy compound (b) and the catalyst (c). In a preferred embodiment, the amount of alkali metal ion or alkaline earth metal ion per urethane group in the catalyst (c) is 0.0001-3.5 based on the number of alkali metal ions or alkaline earth metal ions and urethane groups in the catalyst (c).

[0054] In addition to catalyst (c), the remaining compounds (a) and (b), and potentially any further compounds present, preferably comprise less than 0.0001% by weight of alkali metal or alkaline earth metal ions, based on the total weight of components (a) and (b). Particularly preferably, the amount of alkali metal or alkaline earth metal ions in components (a) and (b) is less than 0.00005% by weight, more preferably less than 0.00003% by weight, more particularly 0.00001% by weight, based on the total weight of components (a) and (b) and, if present, any further compounds.

[0055] The amount of alkali metal ions or alkaline earth metal ions per epoxy group is preferably greater than 0.00001, more preferably between 0.00005 and 0.3, based on the number of alkali metal ions or alkaline earth metal ions and epoxy groups in each case.

[0056] The reaction mixture in step (B) may further comprise additional isocyanate-reactive compounds as polyols, chain extenders or crosslinkers.

[0057] As polyols, it is possible to use, for example, polyethers, polycarbonate polyols or polyesters, which are the same or different from compound (a1), known in polyurethane chemistry. If in step (B) an additional polyol is added to the reaction mixture, in a preferred embodiment, the additional polyol is added after the formation of the isocyanate prepolymer (a) is complete. As additional polyols, for the purposes of the present invention, it is possible to use compounds having at least two isocyanate-reactive groups and having a molecular weight of at least 350, preferably at least 400 g / mol, more preferably at least 500 g / mol. The isocyanate-reactive groups present can be groups such as OH-, SH-, NH- and CH-acid groups. The polyol preferably has essentially OH groups, more preferably exclusively OH groups, as isocyanate-reactive groups. In a preferred embodiment, the polyol has at least 40%, preferably at least 60%, more preferably at least 80%, more particularly at least 95% secondary OH groups, based on the number of isocyanate-reactive groups.

[0058] The polyols preferably used are polyetherols and / or polyesterols having a number average molecular weight of 350 to 12 000, preferably 400 to 6 000, more in particular 500 to less than 3 000, and preferably having an average nominal functionality of 2 to 6, preferably 2 to 3. In a preferred embodiment, the further polyol, when used in the mixing step (B), is identical to polyol (a1).

[0059] When using low molecular weight chain extenders and / or crosslinkers, it is possible to use chain extenders known in the context of polyurethane production, but with a functionality of 2 and crosslinkers with a functionality of 3 or more. These are preferably low molecular weight compounds having at least two isocyanate-reactive groups, with a molecular weight of less than 350 g / mol, more preferably between 60 and 300 g / mol. Chain extenders and / or crosslinkers can be used to adjust mechanical properties such as hardness or elongation. This is known to the person skilled in the art. Examples of chain extenders and crosslinkers include aliphatic, cycloaliphatic and / or araliphatic or aromatic diols having 2 to 14, preferably 2 to 10, carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol and bis(2-hydroxyethyl)hydroquinone, 1,2-, 1,3-, 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, triols such as 1,2,4-, 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane, as well as ethylene oxide and / or 1,2-propylene oxide and low molecular weight hydroxyl-containing polyalkylene oxides based on the aforementioned diols and / or triols as starter molecules. Further usable low molecular weight chain extenders and / or crosslinkers are described, for example, in "Kunststoffhandbuch, volume 7, Polyurethane", Carl Hanser Verlag, 3rd Edition 1993, Sections 3.2 and 3.3.2. If a chain extender is used, preferably propanediol, 1,4 butanediol or 1,6-hexanediol is used. Preferably, no chain extender is used.

[0060] The addition of further polyol to the reaction mixture produced in the mixing step (B) is optional. Preferably, no further polyol is used. If further polyol is used, the proportion of polyol (d) based on the total weight of components (a), (b) and (c) is preferably such that the mixing according to step (B) is carried out with an isocyanate index of more than 200, preferably more than 500, more preferably more than 1000, most preferably without further addition of compounds having isocyanate reactive groups in step (B). For the purposes of the present invention, the isocyanate index is the stoichiometric ratio of the isocyanate groups of the isocyanate prepolymer (a) to the isocyanate reactive groups added to the mixture in step (B) multiplied by 100. The isocyanate reactive groups are all the isocyanate reactive groups present in the reaction mixture, including those of chemical blowing agents and compounds having epoxy groups, but not including the isocyanate groups themselves.

[0061] It is possible to add further additives to the reaction mixture produced in step (B). Such additives are well known in polyurethane chemistry and include fillers, additives for water absorption, flame retardants, hydrolysis inhibitors, antioxidants, and internal mold release agents. Such substances are described, for example, in "Kunststoffhandbuch, volume 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, sections 3.4.4 and 3.4.6 to 3.4.11.

[0062] The water-absorbing additive used is preferably an aluminosilicate selected from the group consisting of sodium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate, cesium aluminosilicate, barium aluminosilicate, magnesium aluminosilicate, strontium aluminosilicate, sodium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate and mixtures thereof. Particularly preferred is a mixture of sodium, potassium and calcium aluminosilicates used with castor oil as carrier material.

[0063] The water absorbing additive preferably has an average particle size of 200 μm or less, more preferably 150 μm or less, more particularly 100 μm or less. The pore size of the water absorbing additive of the present invention is preferably 2 to 5 angstroms. As well as inorganic water absorbing additives, it is also possible to use known organic water absorbing additives, such as orthoformates, triisopropyl orthoformates.

[0064] When a water absorbing additive is added, it is preferably added in an amount greater than 1 part by weight, more preferably in the range of 1.2 to 2 parts by weight, based on the total weight of the polyisocyanurate system.

[0065] good Examples of suitable flame retardants include brominated ethers (Ixol B 251), brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl alcohol and PHT-4-diol, and also chlorinated phosphates such as tris(2-chloroethyl)phosphate, tris(2-chloroisopropyl)phosphate (TCPP), tris(1,3-dichloroisopropyl)phosphate, tris(2,3-dibromopropyl)phosphate and tetrakis(2-chloroethyl)ethylene diphosphate, or mixtures thereof.

[0066] Besides the halogen-substituted phosphates mentioned above, inorganic flame retardants can be used, such as red phosphorus, preparations containing red phosphorus, expandable graphite, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, or cyanuric acid derivatives, such as melamine, mixtures of at least two flame retardants, such as a mixture of ammonium polyphosphate and melamine, and also, optionally, starch, which render the rigid polyurethane foam produced according to the invention flame retardant.

[0067] Further liquid halogen-free flame retardants may be used such as diethyl ethane phosphonate (DEEP), triethyl phosphate (TEP), dimethyl propyl phosphonate (DMPP), diphenyl cresyl phosphate (DPC), and the like.

[0068] For the purposes of the present invention, the flame retardant is preferably used in an amount of 0 to 60% by weight, more preferably 5 to 50% by weight, more especially 5 to 40% by weight, based on the total weight of components (a) to (c).

[0069] As internal release agents it is possible to use all release agents customarily used in polyurethane production, for example metal salts in diamine solutions, such as zinc stearate, and derivatives of polyisobutylene succinic acid.

[0070] The polyurethane system of the present invention preferably has less than 0.5 wt. % water, more preferably less than 0.3 wt. %, based on the total weight of components (a)-(c).

[0071] The reaction mixture of the invention has a long open time at 25°C, for example more than 60 minutes, preferably more than 90 minutes, more preferably more than 120 minutes. This open time is determined via the increase in viscosity, as described above. If the temperature is increased to at least above 80°C, preferably to above 80-200°C, more preferably to 90-150°C, the reaction mixture of the invention cures rapidly, for example in less than 50 minutes, preferably less than 30 minutes, more preferably less than 10 minutes, more particularly less than 5 minutes. For the purposes of the present invention, the curing of the reaction mixture of the invention is understood as a 10-fold increase in the initial viscosity. Here, the difference between the open time at 25°C and the open time at 130°C is preferably at least 40 minutes, more preferably at least 1 hour, very preferably at least 2 hours. In a preferred embodiment, the curing is carried out in a heated mould.

[0072] The process of the present invention preferably results in a compact material, i.e. no blowing agent is added. Small amounts of blowing agents, such as small amounts of water, which pass through the reaction mixture or starting components via atmospheric moisture by condensation during processing, are not included here. Compact polyurethanes are polyurethanes that are substantially free of gas inclusions. The density of compact polyurethanes is preferably 0.8 g / cm3 or less. 3 Greater than 0.9 g / cm 3 Larger, more especially 1.0g / cm 3 Greater than.

[0073] The polyurethane elastomer obtainable by the method according to the invention shows good mechanical properties, such as low compression set, high elasticity and high tensile strength, with relatively low hardness values, preferably less than 90 Shore A, and low abrasion values.Furthermore, the preparation of polyurethane according to the invention results in low shrinkage values.Therefore, the method according to the invention is perfectly suitable for the preparation of polyurethane sealants or polyurethane rollers, especially large rollers or large sealants that require long open times and fast curing.

[0074] In the following, the present invention will be explained using examples. EXAMPLES

[0075] Input materials: Isocyanate 1 is 4,4'-diphenylmethane diisocyanate (4,4'-MDI) with a molar mass of 250.26 g / mol; Isocyanate 2 is a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (80:20); Isocyanate 3 is a carbodiimide-modified 4,4'-diphenylmethane diisocyanate (4,4'-MDI) with an NCO of 29.5% (e.g., Lupranat® MM 103 from BASF); Polyol 1: A polyether diol (MW: about 2000) composed of tetrahydrofuran and having an OH value of about 56; Polyol 2: A polyether diol (MW: about 2000) composed of propylene glycol and propylene oxide (PO) with a functionality of about 2 and having an OH number of about 56; Polyol 3: A polyester diol (MW: about 2000) composed of adipic acid, 1,2-ethanediol and 1,4-butanediol having a functionality of 2 and an OH number of about 56; Polyol 4: A polyester diol (MW: about 2500) composed of adipic acid and 1,4-butanediol with a functionality of 2 and having an OH number of about 56; Polyol 5: A polyether diol (MW: about 1000) composed of propylene glycol and propylene oxide (PO) having a functionality of about 2 and having an OH number of about 104; Polyol 6: A polyether diol (MW: about 450) composed of propylene glycol and propylene oxide (PO) with a functionality of about 2 and having an OH number of about 248. Polyol 7: A polyether diol (MW: about 4000) composed of propylene glycol and propylene oxide (PO) with a functionality of about 2 and with an OH number of about 28; Epoxy: Diglycidyl ether based on bisphenol A, e.g. Araldite GY 250 from Huntsman; Additive 1: Diethylene glycol bischloroformate, Additive 2: Antifoaming agent, such as AF9000 NE Silicone Antifoam from Momentive; Additive 3: K-Ca-Na-Zeolite A in castor oil; Catalyst 1: reaction product of isocyanate 3 with a monofunctional polyethylene oxide having a number average molecular weight of 500 g / mol, available from BASF under the trade name "Pluriol® A 500 E" as a mixture with LiCl containing 0.50 eq LiCl based on the number of urethane compounds according to the invention; Catalyst 2: Potassium acetate, Catalyst 3: a non-inventive mixture of LiCl and urea prepolymer, obtainable by reaction of Jeffamin M600 with isocyanate 3, containing an amount as described in WO10121898, for example 0.70 eq LiCl based on the number of urea compounds in the prepolymer, Chain extender 1: 1,4-butanediol

[0076] Comparative Examples and Inventive Examples: 1. Prepolymer Prepolymer Production The isocyanate was initially placed in a 4000 ml round neck flask equipped with a PT100 thermocouple, nitrogen supply, stirrer and heating mantle at about 50° C., at which temperature the polyol was added. The reaction mixture was heated to 80° C. and stirred at 80° C. for 2 hours. The resulting prepolymer was then allowed to reach room temperature and used in the following application without further processing.

[0077] [Table 1]

[0078] [Table 2]

[0079] [Table 3]

[0080] 2. Elastomers, sealants and adhesives Production of polyurethanes based on prepolymers The ingredients (see recipe) were mixed in a vacuum speed mixer at 1800 rpm for 20 seconds and then poured into a step mold (110° C.). The cured test sheets were then conditioned at 90° C. for 24 hours.

[0081] Properties of the solid polyurethane and the resulting test samples: The following properties of the resulting polyurethanes were determined by the following methods: Density: DIN EN ISO 1183-1, A. Hardness (Shore A / D): DIN ISO 7619-1 Tensile strength / elongation at break: DIN 53504 Tear resistance: DIN ISO 34-1,B(b) Wear measurement: DIN ISO 4649 Glass transition temperature: T measured by differential scanning calorimetry g It was decided.

[0082] Cure and mechanical properties: Reaction mixture formulation:

[0083] [Table 4]

[0084] [Table 5]

[0085] [Table 6]

[0086] [Table 7]

[0087] [Table 8]

[0088] The examples show that in the selected NCO range of the prepolymer, when the polyol according to the invention is used to prepare the prepolymer, very good mechanical properties are obtained, especially elongation and compression set with hardness less than 90 Shore A. When non-inventive catalysts that are bidentate to the anion are used, such as those disclosed in WO10121898, the curing at high temperatures is not sufficient with reasonable catalyst amounts. When used in large amounts, for example 10 parts by weight instead of 1 part by weight, the curing can be carried out at high temperatures, but such large amounts of catalyst are undesirable and lead to undesirable deterioration of the mechanical properties of the resulting elastomer.

[0089] The following table shows formulations that are cured in the presence of additional isocyanate-reactive components.

[0090] [Table 9]

[0091] [Table 10]

[0092] Additionally, formulations according to the invention cured in the presence of additional isocyanate-reactive components exhibit long open times at room temperature and fast cures at temperatures above 80°C.

Claims

1. A method for producing a polyurethane elastomer, comprising the steps of: A) (a1) at least one isocyanate-reactive composition comprising a polyol selected from polyester polyols, polyether polyols or mixtures thereof, having an average functionality in the range of 1.8 to 2.5 and an OH number in the range of 20 mg KOH / g to 450 mg KOH / g; and (a2) at least one polyisocyanate and reacting the mixture to form an isocyanate prepolymer (a), wherein the isocyanate prepolymer has an isocyanate content in the range of 1% to 9% by weight; B) preparing a reaction mixture by mixing at least one epoxy compound (b) with said isocyanate prepolymer (a) in the presence of at least one catalyst (c), said catalyst (c) being a mixture obtainable by introducing an alkali metal salt or an alkaline earth metal salt into a compound R-NH-CO-OR', where R and R' can be the same or different and can be any radical known in organic chemistry, the amount of said alkali metal salt or alkaline earth metal salt being between 0.00001 and 0.1 moles per kg of the total mass of said isocyanate prepolymer (a), said epoxy compound (b) and said catalyst (c); C) heating the mixture to at least 80° C. to obtain a polyurethane elastomer; Including, When a further polyol is used, the proportion of polyol (d) based on the total weight of components (a), (b) and (c) is preferably such that the mixing according to step (B) is carried out with an isocyanate index of more than 1000, The method wherein the polyurethane elastomer exhibits a compression set of 40% or less at 23°C.

2. 2. The process of claim 1, wherein the catalyst (c) is obtained by introducing an alkali metal salt or an alkaline earth metal salt into at least a portion of the isocyanate prepolymer (a).

3. 2. The process according to claim 1, wherein a first polyisocyanate is used as the polyisocyanate (a2) and the compound containing urethane groups in the catalyst (c) is a reaction product of a second polyisocyanate with a compound having an OH group.

4. 4. The method of claim 1, wherein the amount of alkali metal ion or alkaline earth metal ion per urethane group in the catalyst (c) is from 0.0001 to 3.5, based on the number of alkali metal ions or alkaline earth metal ions and urethane groups in the catalyst (c).

5. 5. The method of claim 1, wherein the alkali metal salt or alkaline earth metal salt is lithium chloride.

6. 6. The method of claim 1, wherein the isocyanate-reactive component (a1) comprises polytetrahydrofuran.

7. 7. The method according to claim 1, wherein the isocyanate-reactive component (a1) comprises a polyether polyol obtained by alkoxylation of starter molecules, the alkylene oxide of which comprises at least 70% by weight of propylene oxide.

8. 8. The method of claim 1, wherein the isocyanate-reactive component (a1) comprises a polyesterol obtained by esterification of adipic acid with butanediol.

9. 9. The method of claim 1, wherein the isocyanate (a2) comprises a monomeric aromatic diisocyanate.

10. 10. The method of claim 1, wherein the isocyanate prepolymer used in step (B) contains less than 1% by weight of monomeric diisocyanates.

11. A polyurethane elastomer obtainable by the process according to any one of claims 1 to 10.

12. 12. Use of the polyurethane elastomer according to claim 11 as a roller part or sealant.

Images