Novel polyurethane foam catalysts with improved storage stability

Abstract

The invention relates to a polyol mixture comprising a) 10% to 99.7% by weight of at least one polyol as component A, b) 0.1% to 30% by weight of a hydrohaloolefin blowing agent as component B, c) 0.1% to 10% by weight of water as component C, d) 0.1% to 10% by weight of a catalyst as component D, e) 0% to 80% by weight of one or more additional additives, optionally as one or more additional components E, in which catalyst D comprises an imidazolium salt of general formula (I) [Formula (I)] wherein R1, R2 are independently aliphatic, alicyclic, araliphatic or aromatic groups having 1 to 20 carbon atoms, which may additionally comprise one or more heteroatoms, and optionally as one or more additional components E, in which catalyst D comprises an imidazolium salt of general formula (I) [Formula (I)] wherein R1, R2 are independently aliphatic, alicyclic, araliphatic or aromatic groups having 1 to 20 carbon atoms, which may additionally comprise one or more heteroatoms; wherein A-is a carboxylate anion having 1 to 20 carbon atoms, which may additionally comprise one or more additional heteroatoms. # imgabs0 #

Description

[0001] The present invention relates to a polyol mixture comprising a polyol, a hydrohaloolefin blowing agent, water and an imidazolium salt catalyst, to a method for producing rigid polyurethane foam, and to the use of the imidazolium salt as a catalyst.

[0002] Rigid polyurethane foams have been known for a long time and have been described in great detail. Rigid polyurethane foams are used primarily for thermal insulation, for example in refrigeration units, vehicles or buildings, and also for the production of building elements, in particular sandwich elements.

[0003] It is important that the rigid polyurethane foam fills the cavity uniformly and without gaps, so that a stable structure is formed which ensures good thermal insulation by the best possible connection to the outer layer. In order to prevent foam defects, the foamable PU reaction mixture must be introduced into the cavity to be insulated within a short time for this purpose. Low-pressure or preferably high-pressure machines are usually used for the foaming of such objects.

[0004] A comprehensive review of the production of rigid polyurethane foams and their use as outer or core layers in composite components and also their deployment as thermal insulation layers in cooling or heating technology can be found, for example, in “Polyurethane” [Polyurethanes], Kunststoff-Handbuch [Plastics Handbook], Volume 7, 3rd edition, 1993, edited by Dr. Günter Oertel, Carl-Hanser-Verlag, Munich / Vienna.

[0005] Suitable rigid polyurethane foams can be produced in a known manner by reacting organic polyisocyanates with one or more compounds containing at least two reactive hydrogen atoms in the presence of blowing agents, catalysts and optionally auxiliaries and / or additives.

[0006] The compounds having at least two hydrogen atoms reactive toward isocyanate groups used for producing polyurethanes are preferably polyetherols and / or polyesterols. The choice of the polyol is based in particular on cost and desired application properties (eg EP-A1 632 511, US Pat. No. 6,495,722, WO 2006 / 108833).

[0007] Polyurethane foam compositions are typically produced by reacting isocyanates with a premix comprising isocyanate reactive components (such as polyols, preferably polyether alcohols and / or polyester alcohols). Premixes may alternatively also comprise other components, such as water, fire retardants, blowing agents, foam stabilizing surfactants and catalysts, which promote the reaction of isocyanates with polyols to form carbamates, and also promote the reaction of isocyanates with water to form ureas and release CO . The blowing agent in the premix is ​​typically a liquid with a sufficiently low boiling point, which evaporates by the heat released during the polymerization reaction. The example of the blowing agent used in the production of thermal insulation polyurethane foams includes hydrofluorocarbons, hydrofluoroolefins, hydrofluorochloroolefins, hydrochlorofluorocarbons, formates and hydrocarbons. For some purposes, before the premix is ​​converted into polyurethane foam with isocyanates, the premix is ​​stored for up to one year. This is common in spray foam applications, wherein a barrel of a premix and a barrel of isocyanates are provided for on-site use. Therefore, it is desirable that the premix is ​​chemically and physically stable. However, catalysts suitable for promoting the polyurethane reaction may undergo or induce undesirable reactions with blowing agents present in the premix, thereby reducing the storage stability of the premix. These undesirable reactions occur in the case of blowing agents containing halogens, and particularly in the case of unsaturated halogenated blowing agents. Conventional amine catalysts suitable for the production of polyurethane foams include tertiary amines, such as N,N,N′,N″,N″-pentamethyldiethylenetriamine or 1,4-diazabicyclo[2.2.2]octane. The reaction between the tertiary amine and the halogen-containing organic compound occurs faster when the halogen atom is attached to the olefin carbon because the halogen-substituted olefin is susceptible to nucleophilic attack by the tertiary amine, which results in rapid deactivation of the tertiary amine catalyst.

[0008] EP 3 091 044 A1 discloses a polyol premix composition comprising a hydrohaloolefin blowing agent, at least one polyol, water, and a catalyst comprising at least 10% by weight of tetramethylguanidine and 10 to 90% by weight of one or more tertiary amines having isocyanate-reactive groups selected from 2-[N-(dimethylaminoethoxyethyl)-N-methylamino]ethanol and N,N,N′-trimethyl-N′-3-aminopropylbis(aminoethyl)ether.

[0009] EP 2 504 372 A1 discloses a coating composition comprising:

[0010] (A) at least one polyisocyanate obtainable by reacting at least one monomeric isocyanate,

[0011] (B) at least one compound having at least two isocyanate-reactive groups, a number average molecular weight Mn of at least 1000 g / mol, and an OH number of 40 to 350 mg KOH / g,

[0012] (C) at least one imidazolium salt,

[0013] (D) optionally a solvent,

[0014] (E) optionally a further urethanization catalyst different from (C), and also

[0015] (F) Optionally further typical coating components and / or additives.

[0016] The object of the present invention is to provide a polyurethane foaming catalyst which is storage-stable and does not deactivate in a polyol mixture comprising a hydrohaloolefin blowing agent.

[0017] This object is achieved by a polyol mixture comprising:

[0018] a) at least one polyol as component A,

[0019] b) a hydrohaloolefin blowing agent as component B,

[0020] c) water as component C,

[0021] d) as a catalyst of component D,

[0022] e) optionally as one or more further additives of one or more further components E,

[0023] wherein the catalyst D comprises an imidazolium salt having the general formula (I),

[0024]

[0025] wherein R1 and R2 are independently aliphatic, alicyclic, araliphatic or aromatic groups having 1 to 20 carbon atoms, which may additionally contain one or more heteroatoms,

[0026] Here A- is a carboxylate anion having 1 to 20 carbon atoms, which may additionally also contain one or more further heteroatoms.

[0027] The heteroatoms may be selected from oxygen, nitrogen, sulfur, and phosphorus. For example, R1, R2 may contain 1 to 5 heteroatoms, and A- may contain 1 to 5 additional heteroatoms.

[0028] The polyol mixture comprises at least one polyol as component A. In a preferred embodiment, the polyol component comprises a polyol typically used to produce rigid PIR / PUR (polyisocyanurate and / or polyurethane) foams. Such polyols include, but are not limited to, polyalkylene ethers and polyester polyols. In one embodiment, polyalkylene ethers comprise poly(alkylene oxide) polymers, such as poly(ethylene oxide) polymers and poly(propylene oxide) polymers and copolymers with terminal hydroxyl groups derived from polyols, which comprise glycols and triols, such as, for example, ethylene glycol, propylene glycol, butane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, neopentyl glycol, diethylene glycol, dipropylene glycol, pentaerythritol, glycerine, diglycerine, trimethylolpropane, cyclohexanediol, sugars such as sucrose and similar low molecular weight polyols or combinations thereof. In another embodiment, the polyol component includes an amine polyether polyol, which can be produced when an amine (such as ethylenediamine, diethylenetriamine, toluenediamine, diphenylmethanediamine, triethanolamine, etc.) reacts with ethylene oxide or propylene oxide. In one embodiment involving a spray foam formulation, the polyol component includes a polyether polyol, as a result of which the reactivity of the polyurethane composition is enhanced.

[0029] In one embodiment, the polyether polyol is prepared by condensing phenol with formaldehyde in the presence of a hydroxyl-containing amine such as diethanolamine, ethanolamine, and the like.

[0030] The polyether polyols are prepared from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene group by known methods, for example by anionic polymerization with alkali metal hydroxides (e.g. sodium hydroxide or potassium hydroxide) or alkali metal alkoxides (e.g. sodium methoxide, sodium methoxide or potassium methoxide or potassium isopropoxide) as catalysts and addition of at least one starter molecule containing 2 to 8, preferably 2 to 6, attached reactive hydrogen atoms, or by cationic polymerization with Lewis acids (e.g. antimony pentachloride, boron fluoride etherate or Fuller's earth) as catalysts. Suitable polyether polyols can also be produced using DMC catalysts.

[0031] Examples of suitable alkylene oxides are tetrahydrofuran, 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, phenylethylene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately in sequence or as a mixture. Preferred alkylene oxides are propylene oxide and ethylene oxide; particularly preferred is propylene oxide.

[0032] Examples of useful starter molecules include: water, organic dicarboxylic acids (such as succinic acid, adipic acid, phthalic acid and terephthalic acid), aliphatic and aromatic optionally N-monoalkyl-substituted diamines and N,N- and N,N′-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl group (such as optionally monoalkyl-substituted and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, propylene-1,3-diamine, butylene-1,3- or -1,4-diamine, hexamethylene-1,2-, -1,3-, -1,4-, -1,5- and -1,6-diamine, phenylenediamine, toluene-2,3-, -2,4- and -2,6-diamine and 4,4′, 2,4′- and 2,2′-diaminodiphenylmethane).

[0033] Useful starter molecules further include alkanolamines (eg ethanolamine, N-methylethanolamine and N-ethylethanolamine), dialkanolamines (eg diethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine), and trialkanolamines (eg triethanolamine), and ammonia.

[0034] Preference is given to using dihydric or polyhydric alcohols, such as ethylene glycol, propane-1,2- and -1,3-diol, diethylene glycol, dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose. Particular preference is given to the above-mentioned primary amines, such as toluene-2,3-diamine.

[0035] The polyether polyols (preferably polyoxypropylene polyols and / or polyoxyethylene polyols) have a functionality of preferably 2 to 6 and especially 2 to 5 and a number average molecular weight of 150 to 3000, preferably 200 to 1500 and especially 250 to 750.

[0036] Suitable polyester polyols can be prepared, for example, from organic dicarboxylic acids (preferably aromatic dicarboxylic acids or mixtures of aromatic dicarboxylic acids and aliphatic dicarboxylic acids) having 2 to 12 carbon atoms and polyhydroxy alcohols (preferably glycols) having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms. Examples of useful dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid. Dicarboxylic acids can be used alone or in addition as a mixture. Instead of free dicarboxylic acids, corresponding dicarboxylic acid derivatives, such as dicarboxylic acid esters or dicarboxylic anhydrides of alcohols having 1 to 4 carbon atoms, can also be used. The aromatic dicarboxylic acids used are preferably phthalic acid, phthalic anhydride, terephthalic acid and / or isophthalic acid or themselves in the form of a mixture. The aliphatic dicarboxylic acids used are preferably dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid in a quantitative ratio of, for example, 20 to 35:35 to 50:20 to 32 parts by weight, and in particular adipic acid. Examples of dihydric and polyhydric alcohols, in particular diols, are: ethylene glycol, diethylene glycol, propane-1,2- and -1,3-diol, dipropylene glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, decane-1,10-diol, glycerol, trimethylolpropane, and pentaerythritol. Preference is given to using ethylene glycol, diethylene glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol or a mixture of at least two of the diols mentioned, in particular a mixture of butane-1,4-diol, pentane-1,5-diol and hexane-1,6-diol. It is also possible to use polyester polyols derived from lactones (eg, ε-caprolactone) or hydroxycarboxylic acids (eg, ω-hydroxycaproic acid).

[0037] To prepare the polyester polyols, it is also possible to use biobased starting materials and / or derivatives thereof, for example castor oil, palm oil, polyhydroxy fatty acids, ricinoleic acid, hydroxyl-modified oils, grape seed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean oil, wheat germ oil, rapeseed oil, sunflower seed oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, evening primrose oil, wild rose oil, safflower oil, walnut oil, hydroxyl-modified fatty acids and fatty acid esters based on myristic acid, palmitoleic acid, stearic acid, palmitic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, α- and γ-linolenic acid, octadecatetraenoic acid, arachidonic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid.

[0038] Preferred polyester polyols are prepared from adipic acid, phthalic anhydride and / or terephthalic anhydride as dicarboxylic acids and propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, glycerol and / or trimethylolpropane as alcohol components, and also oleic acid or castor oil, and have an OH number of 150 to 400 and a functionality of 2 to 4.5.

[0039] The polyol mixture comprises as catalyst D an imidazolium salt of the general formula (I).

[0040] R1 and R2 in formula (I) are independently preferably aliphatic, alicyclic, araliphatic or aromatic organic groups having 1 to 10 carbon atoms. Examples of hydrocarbon groups include phenyl, benzyl, phenyl or benzyl substituted with one or more C1-C4 alkyl groups (e.g. mesityl), and also alkyl and alkenyl groups (especially alkyl).

[0041] Preferably, R1 and R2 are independently C1-C18 alkyl, preferably C1-C16 alkyl, more preferably C1-C14 alkyl, further preferably C1-C12 alkyl, and especially preferably C1-C10 alkyl. Very particularly preferably, R1 and R2 are independently C1-C6 alkyl, especially C1-C4 alkyl. Especially preferably, R1 and R2 are independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl, wherein methyl, ethyl, n-propyl and n-butyl are particularly preferred.

[0042] Examples of the imidazolium ion are 1,3-dimethylimidazolium (DMIM), 1-benzyl-3-methylimidazolium, 3-ethyl-1-methylimidazolium (EMIM), 1-propyl-3-methylimidazolium, 3-n-butyl-1-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-methyl-3-octylimidazolium, 1-decyl-3-methylimidazolium, 1-dodecyl-3-methylimidazolium, 1,3-diethylimidazolium (DEIM), 1,3-diisopropylimidazolium, 1,3-di-n-butylimidazolium, and 1,3-dihexylimidazolium.

[0043] Preferred imidazolium ions are 1,3-dimethylimidazolium (DMIM), 3-ethyl-1-methylimidazolium (EMIM), and 1,3-diethylimidazolium (DEIM). Particularly preferred are 1,3-dimethylimidazolium (DMIM) and 1,3-diethylimidazolium (DEIM).

[0044] The carboxylate anion A- in the formula (I) may be an anion of an aliphatic or aromatic carboxylic acid having 1 to 20 carbon atoms, preferably an anion of an aliphatic carboxylic acid having 1 to 20 carbon atoms.

[0045] Examples of anions of aromatic carboxylic acids are benzoate, salicylate, and nicotinate. Alkanoate anions (i.e., anions of alkane carboxylic acids) can be straight or branched, preferably straight chain. The parent alkane carboxylic acid has 1 to 20 carbon atoms, preferably 2 to 18, and more preferably 2 to 12 carbon atoms.

[0046] Examples of alkanoate anions are formate, acetate, propionate, 2,2-dimethylpropionate (pivalate), n-butyrate, isobutyrate, n-valerate, n-hexanoate, n-heptanoate, n-octanoate, 2-ethylhexanoate, isooctanoate, n-nonanoate, isononanoate, n-decanoate, 3-propylheptanoate, n-dodecanoate, tetradecanoate, hexadecanoate, stearate, and n-eicosanoate, preferred are acetate, formate, propionate, n-butyrate, isobutyrate, n-valerate, 2,2-dimethylpropionate (pivalate), and n-hexanoate, and particularly preferred are acetate, formate, and propionate, among which acetate is especially preferred.

[0047] The catalyst used according to the present invention is suitable for producing rigid insulation foams and is particularly suitable for spray foam applications, device insulation, insulation building panels, and other insulation products including closed-cell rigid polyurethane foams. The present invention includes foams having an isocyanate index between 70 and 500, 90 to 270, and typically 100 to 150. The catalyst used according to the present invention can be used in combination with any halogenated blowing agent to provide improved system stability, and is particularly suitable for improving the stability of systems containing hydrohaloolefin blowing agents, especially HFCO-1234ze (trans-1,3,3,3-tetrafluoroprop-1-ene) and HFCO-1233zd (1-chloro-3,3,3-trifluoro-1-propylene)).

[0048] As one or more additives E, the polyol mixture may include cell stabilizers, chain extenders, pigments, fillers, organic acids or diacids, flame retardants, additional urethane gelling catalysts, additional urethane foaming catalysts, transition metal catalysts or combinations thereof.

[0049] Suitable cell stabilizers include silicone surfactants, anionic surfactants, cationic surfactants, zwitterionic surfactants, nonionic surfactants and combinations thereof. In one embodiment, the cell stabilizer is a silicone surfactant, such as a polyalkylsiloxane, a polyoxyalkylene polyol-modified dimethylpolysiloxane or an alkylene glycol-modified dimethylpolysiloxane. In another embodiment, the cell stabilizer is an anionic surfactant, such as a salt of a fatty acid, a salt of a sulfate ester, a salt of a phosphate ester, a salt of a sulfonic acid or a combination thereof. Suitable cationic surfactants are quaternary ammonium salts (pH-dependent or permanently charged), such as hexadecyltrimethylammonium chloride, hexadecylpyridinium chloride, polyethoxylated tallow amine, benzalkonium chloride, benzethonium chloride, and the like. Suitable zwitterionic or amphoteric surfactants include sulfobetaines, amino acids, imino acids, betaines, and phosphates. Suitable nonionic surfactants include fatty alcohols, polyoxyethylene glycol alkyl ethers, polyoxypropylene glycol alkyl ethers, glucosides (such as decyl, lauryl and octyl glucoside), polyoxyethylene glycol alkylphenol ethers, glycol alkyl esters, etc. The polyol mixture may contain, for example, a cell stabilizer in an amount of 0.1% to 20% by weight.

[0050] Suitable pigments are organic pigments, inorganic pigments or combinations thereof. In certain embodiments where the pigment is an organic pigment, the pigment is an azo / diazo dye, a phthalocyanine, a dioxazine, carbon black or a combination thereof. In other embodiments where the pigment is an inorganic pigment, the pigment is titanium dioxide, iron oxide, chromium oxide or a combination thereof. The polyol mixture may contain, for example, 0.1% to 10% pigment by weight.

[0051] Suitable fillers increase the density and load-bearing capacity of the polyurethane foam. In certain embodiments, the filler is barium sulfate, calcium carbonate, or a combination thereof. The polyol mixture may contain fillers in an amount of, for example, 0.1% to 20% by weight.

[0052] Suitable flame retardants include, for example, chlorinated phosphates, phosphate esters, chlorinated paraffins, melamine powders, or combinations thereof.The polyol mixture may include the flame retardant, for example, in an amount of 0.1% to 30% by weight.

[0053] Polyol mixtures generally contain

[0054] a) as component A 10 to 99.7% by weight, preferably 35 to 97% by weight, of at least one polyol,

[0055] b) as component B 0.1 to 30% by weight, preferably 1 to 15% by weight, of a hydrohaloolefin blowing agent,

[0056] c) as component C 0.1 to 10% by weight, preferably 0.5 to 5% by weight, of water,

[0057] d) as component D 0.1 to 10% by weight, preferably 0.5 to 5% by weight, of an imidazolium salt catalyst of the general formula (I),

[0058] e) optionally as 0 to 80% by weight, preferably 1 to 40% by weight, of component(s) E, one or more further additives.

[0059] The present invention further relates to a process for producing a rigid polyurethane foam by reacting:

[0060] (i) an organic polyisocyanate or a modified organic polyisocyanate and

[0061] (ii) The polyol mixture of the present invention.

[0062] Useful organic polyisocyanates (i) are the aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyfunctional isocyanates known per se. The organic polyisocyanates may optionally be modified.

[0063] Specific examples include: alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene group, such as dodecane 1,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and preferably hexamethylene 1,6-diisocyanate; alicyclic diisocyanates such as cyclohexane 1,3- and 1,4-diisocyanate and also any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), hexahydrotoluene 2,4- and 2,6-diisocyanate and also the corresponding isomer mixtures, dicyclohexylmethane 4,4′-, 2,2′- and 2,4′-diisocyanates and also the corresponding isomer mixtures, and preferably aromatic diisocyanates and polyisocyanates, for example toluene 2,4- and 2,6-diisocyanate and the corresponding isomer mixtures, diphenylmethane 4,4′-, 2,4′- and 2,2′-diisocyanate and the corresponding isomer mixtures, mixtures of diphenylmethane 4,4′- and 2,2′-diisocyanate, polyphenylpolymethylene polyisocyanates, mixtures of diphenylmethane 2,4′-, 2,4′- and 2,2′-diisocyanate and polyphenylpolymethylene polyisocyanates (crude MDI), and mixtures of crude MDI and toluene diisocyanate. The organic diisocyanates and polyisocyanates can be used individually or in the form of mixtures thereof.

[0064] Preferred polyisocyanates are toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and especially mixtures of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanates (polymeric MDI or PMDI).

[0065] Modified polyfunctional isocyanates are also commonly used, i.e. products obtained by chemical reaction of organic polyisocyanates. Examples include polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups.

[0066] For the production of the rigid polyurethane foams according to the invention, very particular preference is given to using polymeric MDI.

[0067] The present invention also relates to the use of an imidazolium salt of the general formula (I) as a catalyst in a polyol mixture comprising a hydrohaloolefin blowing agent for producing rigid polyurethane foams.

[0068] The present invention is more specifically explained by the following examples.

[0069] Examples

[0070] Components used:

[0071] Lupranol 3300: Polyether triol with OH value of 400 mg KOH / g

[0072] Foam stabilizer: Silicone-based foaming agent: R-1233zd(E) = 1-chloro-3,3,3-trifluoro-1-propene

[0073] Lupranat M20S: polymerized MDI, NCO 31.5%, viscosity 210 mPa·s

[0074] Method 1

[0075] A polyol mixture was prepared by mixing 100 g of Lupranol 3300, 4 g of water and 2 g of foam stabilizer. 15 g of this mixture and an additional 1% by weight of catalyst were mixed with 17.1 g of Lupranat M20S in a 0.5 L plastic beaker with a propeller stirrer at 2000 rpm for 5 seconds and measured.

[0076] The following parameters were determined:

[0077] Cream time: the time until the PU mixture starts to rise;

[0078] Half height: time until the beaker reaches half its height (7 cm);

[0079] Time until the edge of the beaker is reached;

[0080] Time until the foaming ends;

[0081] Foam height.

[0082] The results are shown in Table 1.

[0083] Method 2

[0084] For this, a stock solution consisting of Lupranol 3300, foam stabilizer and water was prepared. In each container, 52 g of this stock solution (comprising 50 g Lupranol 3300, 1 g foam stabilizer and 1 g water) was weighed into a 500 mL pressure-resistant laboratory glass bottle, and then 1 g catalyst and 7.5 g blowing agent R-1233zd (E) were added. The containers were stored at 45° C. for periods of 2 and 4 weeks. 17 g of the polyol mixture from each bottle was mixed with 17.1 g Lupranat M20S in a 0.5 L plastic beaker with a propeller stirrer at 2000 rpm for 5 seconds and measured.

[0085] The following parameters were determined:

[0086] Cream time: the time until the PU mixture starts to rise;

[0087] Half height: time until the beaker reaches half its height (7 cm);

[0088] Time until the edge of the beaker is reached;

[0089] Time until the foaming ends;

[0090] Foam height.

[0091] The results are shown in Table 2.

[0092] As can be seen in Table 2, BDMAEE exhibits insufficient storage stability in the presence of R-1233zd(E).

[0093] From a toxicological point of view (skin sensitization), DMI is not completely harmless.

[0094]

[0095]

[0096]

Claims

1. A polyol mixture comprising: a) as component A 10 to 99.7% by weight of at least one polyol, b) as component B 0.1 to 30% by weight of a hydrohaloolefin blowing agent, c) as component C, 0.1 to 10% by weight of water, d) from 0.1 to 10% by weight of catalyst, based on component D, e) optionally as 0 to 80% by weight of one or more further additives of one or more further components E, wherein the catalyst D comprises an imidazolium salt of the general formula (I), wherein R1 and R2 are independently aliphatic, alicyclic, araliphatic or aromatic groups having 1 to 20 carbon atoms, which may additionally contain one or more heteroatoms, Here A- is a carboxylate anion having 1 to 20 carbon atoms, which may additionally also contain one or more further heteroatoms.

2. The polyol mixture according to claim 1, wherein The hydrohaloolefin blowing agent includes trans-1-chloro-3,3,3-trifluoropropene.

3. The polyol mixture according to claim 1 or 2, wherein In the general formula (I), R1 and R2 are selected from methyl and ethyl.

4. The polyol mixture according to any one of claims 1 to 3, wherein The carboxylate anion A- is selected from the group consisting of formate, acetate, propionate, 2,2-dimethylpropionate (neopentanoate), n-butyrate, isobutyrate, n-valerate, n-hexanoate, n-heptanoate, n-octanoate, 2-ethylhexanoate, isooctanoate, n-nonanoate, isononanoate, n-decanoate, 3-propylheptanoate, n-dodecanoate, tetradecanoate, hexadecanoate, stearate, and n-eicosanoate.

5. The polyol mixture according to any one of claims 1 to 4, wherein The carboxylate anion A- is acetate.

6. The polyol mixture according to any one of claims 1 to 5, wherein The polyol A includes polyether polyols and optionally polyester polyols.

7. The polyol mixture according to any one of claims 1 to 6, wherein The one or more additional additives E are selected from cell stabilizers, chain extenders, pigments, fillers, organic acids or diacids, flame retardants, additional urethane gelling catalysts, additional urethane foaming catalysts, transition metal catalysts or combinations thereof.

8. Use of the polyol mixture according to any one of claims 1 to 7 for spray foam applications.

9. The use according to claim 8 for producing rigid thermal insulation foam.

10. The use according to claim 9 for thermal insulation of an apparatus.

11. A process for producing rigid polyurethane foams having an isocyanate index between 70 and 500 by reacting: (i) an organic polyisocyanate or a modified organic polyisocyanate and (ii) The polyol mixture according to any one of claims 1 to 7.

12. Imidazolium salts having the general formula (I) wherein R1 and R2 are independently aliphatic, alicyclic, araliphatic or aromatic groups having 1 to 20 carbon atoms, which may additionally contain one or more heteroatoms, wherein A- is a carboxylate anion having 1 to 20 carbon atoms, which may additionally also contain one or more further heteroatoms, Use of a polyol mixture comprising a hydrohaloolefin blowing agent according to any one of claims 1 to 7 as a catalyst for producing rigid polyurethane foams.

13. The use according to claim 12, wherein The hydrohaloolefin blowing agent includes trans-1-chloro-3,3,3-trifluoropropene.

14. The use according to claim 12 or 13, wherein In the general formula (I), R1 and R2 are selected from methyl and ethyl.

15. The use according to any one of claims 12 to 14, wherein A- in formula (I) is acetate.

16. Use according to any one of claims 12 to 15 for spray foam applications.

17. The use according to claim 16 for producing rigid thermal insulation foam.

18. The use according to claim 17 for thermal insulation of an apparatus.

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