Thermolatent catalyst for polyurethane preparation

Abstract

The present invention concerns a novel compound for use as thermolatent catalyst in a process for preparing a polyurethane, a method of preparing said compound, a catalyst composition for use in the preparation of a polyurethane, a polyol composition for use in the preparation of a polyurethane, a method of preparing a polyurethane, a polyurethane thus obtained and an article comprising such polyurethane.

Description

[0001] Thermolatent catalyst for polyurethane preparation

[0002] The present invention lies in the field of polyurethanes. It relates to a novel compound for use as (thermolatent) catalyst in a process for preparing a polyurethane, a method of preparing said compound, a catalyst composition for use in the preparation of a polyurethane, a polyol composition for use in the preparation of a polyurethane, a method of preparing a polyurethane, a polyurethane thus obtained and an article comprising such polyurethane.

[0003] BACKGROUND OF THE INVENTION

[0004] Cellular or compact polyurethanes, in particular polyurethane casting elastomers and thermoplastic polyurethanes (TPU), have long been known from numerous patent and literature publications. Their industrial importance is based on the combination of valuable mechanical properties with the advantages of low-cost processing methods. The use of different chemical formative components in different ratios makes it possible to prepare thermoplastic processable or crosslinked, compact or cellular polyurethanes having a wide variety of mechanical and processing properties.

[0005] Some manufacturing processes require a delayed cure. For example, some manufacturing processes require a polyurethane-forming mixture to be prepared and then applied to some other material or mold before it is cured. Some "working time", which may be up to several minutes in some processes, may be needed to apply the mixture and to manipulate it further, before the mixture builds a high molecular weight and becomes too viscous to work with. In all of these processes, some delay in the initial cure is wanted, to provide enough time that the polyurethane-forming mixture can be applied and manipulated. However, after some predetermined "working time", it is usually desirable that the reaction mixture cures rapidly. The rapid cure allows manufacturing equipment to handle greater volumes of product per unit time and thus allows for increased production rates and lower manufacturing costs.

[0006] Previous efforts to provide a delayed cure have focused on the selection of the catalyst. Various types of delayed action catalysts are known. Some are simply relatively inactive catalysts, and the delayed action is mainly an artifact of a generally slow cure. These catalysts can provide for good working time, but the slow cure means that line processing speeds are slow and / or in-mold residence times are long, and for that reason these catalysts are often not useful in commercial processes.

[0007] A way to achieve better results is to use thermolatent catalysts, which will be inert at a chosen temperature, but become active at a higher temperature. Reference is made for example to WO 2011 / 094244 , EP 0 989 146, US 5,212,306 , or US 4,582,861 .

[0008] Also known from the state of the art are tertiary amine salts of carboxylic acid derivatives and the use of these compounds in processes for preparing polyurethanes. The literature describes various families of thermolatent base catalysts for the synthesis of polyurethanes which are inactive at room temperature, but become active at an elevated temperature. For instance, they are suitable for mold applications where the system's viscosity needs to remain low until the mold is filled, but the polymerization-crosslinking process must commence at a specific higher temperature and be rapid to keep the processing time as brief as feasible.

[0009] EP 2 050 775 discloses a catalyst composition for producing a polyurethane resin employing as thermolatent catalyst a salt of a tertiary amine and triazole or benzotriazole. An alternative to these triazole / benzotriazole salts are the respective phenolic salts. Of particular interest in the industry is the phenolic salt of DBU (1 ,8-Diazabicyclo[5.4.0]undec-7-en), especially the 1 :1 adduct of phenol and DBU, that is widely used as thermolatent catalyst. The 1 :1 adduct of phenol and DBU is the salt obtained by reacting 1 equivalent of phenol with 1 equivalent of DBU. The phenolic salts of DBU are also of such paramount interest as they allow for an improved curing compared to triazole and benzotriazole. However, all of triazole, benzotriazole and phenol pose severe health and environmental risks. Furthermore, many articles based on polyurethane are made for direct contact with humans. Thus, articles made from polyurethane that were prepared with e.g. phenolic salts are often susceptible to liberating phenol. However, phenol - being harmful to humans and the environment - should not be liberated and people must not be exposed to these harmful substances.

[0010] OBJECTIVE OF THE INVENTION

[0011] It is therefore the objective of the present invention to overcome the shortcomings of the prior art.

[0012] Thus, it is an objective of the present invention to provide a thermolatent catalyst with at least comparable technical results.

[0013] It is another objective of the present invention to provide a thermolatent catalyst having an ecological more benign character compared to the solutions presented in the prior art.

[0014] SUMMARY OF THE INVENTION

[0015] These objectives are solved by using the inventive compound according to formula (I) for use as catalyst in a process for preparing a polyurethane: wherein

[0016] R1is selected from the group consisting of alkyl group, aryl group and polyoxyalkylene group; and n is an integer selected from the group consisting of 0 to 6. The compound according to the invention allows for a better cure profile, giving a longer pot life time whilst having a fast back end cure (see inventive example 1 vs. comparative example 1).

[0017] It is an advantage of the present invention that less harmful substances are used to prepare the compound according to the invention compared to the solutions described in the prior art.

[0018] The liberation of malodors and harmful substances is reduced when using the compound according to the invention and formulations comprising the compound according to the invention (e.g. the polyol composition according to the invention and the catalyst composition according to the invention, vide infra) compared to prior art systems, especially those comprising phenol and salts thereof.

[0019] Advantageously, the present invention allows to limit the exposure / liberation of harmful substances from articles made therewith such as phenols.

[0020] FIGURES

[0021] Figure 1 depicts a thermogravimetric analysis of DBU (solid line), the 1 :1 adduct of phenol and DBU (dashed line) and a compound according to the invention (with n=3 and R1=n-Bu, dotted line).

[0022] DETAILED DESCRIPTION OF THE INVENTION

[0023] Percentages throughout this specification are weight-percentages (wt.-%) unless stated otherwise. Yields are given as percentage of the theoretical yield. Concentrations given in this specification refer to the volume or mass of the entire solutions or dispersions unless stated otherwise. Measurements and experiments are usually conducted at room temperature (20 °C) and standard pressure (1013 mbar), unless stated differently hereinafter.

[0024] The term "alkyl" according to the present invention comprises branched or unbranched alkyl groups comprising cyclic and / or non-cyclic structural elements, wherein cyclic structural elements of the alkyl groups naturally require at least three carbon atoms. C1-CX-alkyl in this specification and in the claims refers to alkyl groups having 1 to X carbon atoms (X being an integer). C1 -C8-alkyl for example includes, among others, methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, sec-pentyl, tert-pentyl, neo-pentyl, hexyl, heptyl and octyl. Substituted alkyl groups may theoretically be obtained by replacing at least one hydrogen by a functional group. Unless stated otherwise, alkyl groups are preferably selected from substituted or unsubstituted C1-C8-alkyl, more preferably from substituted or unsubstituted C1 -C4-alkyl.

[0025] The term "alkanediyl" is the corresponding group having two free valences (bonding sites). Sometimes, it is referred to as "alkylene" in the art. Said residues according to the present invention comprise cyclic and / or non-cyclic structural elements and can be linear and / or branched. C1 -C4-al- kanediyl for example includes, among others, methane-1 ,1-diyl, ethane-1 ,2-diyl, ethane-1 ,1-diyl, propane-1 ,3-diyl, propane-1 ,2-diyl, propane-1 ,1-diyl, butane-1 ,4-diyl, butane-1 ,3-diyl, butane-1 ,2- diyl, butane-1 ,1-diyl, butane-2,3-diyl. Furthermore, individual hydrogen atoms bound to the alkanediyl compound may in each case be substituted by a functional group such as those defined above for the alkyl group. Unless stated otherwise, alkanediyl groups are preferably selected from substituted or unsubstituted C1 -C8-alkanediyl, more preferably from substituted or unsubstituted C1-C4-alkanediyl.

[0026] The term "aryl" according to the invention refers to ring-shaped aromatic hydrocarbon residues, for example phenyl or naphthyl where individual ring carbon atoms can be replaced by N, O and / or S, for example benzothiazolyl. Preferably, no carbon atoms are substituted, e.g. by N, O and / or S. Furthermore, aryl groups are optionally substituted by replacing a hydrogen atom in each case by a functional group. The term C5-CX-aryl refers to aryl groups having 5 to X carbon atoms (optionally replaced by N, O and / or S) in the ring-shaped aromatic group (X naturally being an integer). C5- C6-aryl is preferred unless stated otherwise.

[0027] Unless stated otherwise, above-described groups are preferably not substituted. Functional groups as substituents can be exemplarily hydroxyl (-OH), halides (such as Cl, Br, I), amino (-NH2) and carboxyl (-CO2H).

[0028] If more than one residue is to be selected from a given group, each of the residues is selected independently from each other unless stated otherwise hereinafter, meaning they can be selected to be the same members or different members of said group. The bonding sites in some chemical formulas herein may be emphasized by a wavy line (“ -~w “).

[0029] It is clear to the person skilled in the art that the compound according to the invention can be present in the form of its respective salt. The person skilled in the art knows that the compound according to the invention is in a state of equilibrium between the uncharged formula (I) and the ionic form ( / .e. the respective salt). The salts of the compound according to the invention shall be included in the scope of the present invention.

[0030] An exemplary salt of the compound according to the invention is depicted hereinafter:

[0031] In above formula (salt of I) one tautomeric form is depicted. Further tautomeric forms of above-depicted salts are known to the person skilled in the art.

[0032] R1is selected from the group consisting of alkyl group, aryl group and polyoxyalkylene group.

[0033] A polyoxyalkylene group in the context of the present invention is preferably a R2-[O-R3]k-group, wherein R2is hydrogen, an alkyl group, or an aryl group, R3is an alkanediyl group and k is an integer ranging from 1 to 20. R2is preferably selected from the group consisting of hydrogen, C1 -C8- alkyl group, and phenyl group, more preferably selected from the group consisting of hydrogen, methyl group and ethyl group. R3is preferably a C1 -C8-alkanediyl group, more preferably a C2-C4- alkanediyl group, even more preferably selected from the group consisting of ethane-1 ,2-diyl group and propane-1 ,2-diyl group, yet even more preferably an ethane-1 ,2-diyl group. The integer k preferably ranges from 2 to 15, more preferably from 3 to 10.

[0034] It is preferred that R1is selected from the group consisting of alkyl group and aryl group. It is even more preferred that R1is selected from the group consisting of C1 -C4-alkyl group and phenyl group. And it is even more preferred that R1is an alkyl group. Yet even more, R1is selected from the group consisting of methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group , t- butyl group, and s-butyl group. Most preferably, R1is selected from the group consisting of methyl group, ethyl group, n-propyl group, and n-butyl group.

[0035] In a particularly preferred embodiment of the invention R1is defined as above with the proviso that it is not methyl. Thus, it is preferred that C2-C4-alkyl group and phenyl group. And it is even more preferred that R1is an alkyl group with the proviso that R1is not a methyl group. Yet even more, R1is selected from the group consisting of, ethyl group, n-propyl group, i-propyl group, n-butyl group , t-butyl group, and s-butyl group. Even more preferably, R1is selected from the group consisting of ethyl group, n-propyl group, and n-butyl group. Most preferably R1is an ethyl group. n is preferably selected from 1 and 3, n more preferably is 3.

[0036] Particularly preferably, the compound according to the invention is represented by formula (la) or (lb) wherein R1is selected from above-defined groups. Most preferably, the compound according to the invention is represented by formula (la) as it allows for the best properties of a polyurethane to be obtained when used as catalyst in its preparation. If an even more ecologically benign compound or process is desired, the compound according to formula (lb) is preferably selected.

[0037] Advantageously, the compound according to the invention is more thermally stable compared to solutions of the prior art, in particular when compared to phenolic salts of DBU (see Figure 1 and example section). This also reduces the liberation of toxic compounds and unpleasant odors when using the compound according to the invention.

[0038] The compound according to the invention is preferably used as catalyst in a process for preparing a polyurethane. The compound according to the invention is preferably used as thermolatent catalyst in said process. Thermolatent means in this regard that a certain temperature threshold is to be reached before the catalytic effect of the catalyst in question sets into operation. Advantageously, the compound according to the invention requires a much lower temperature to be reached compared to catalysts known from the prior art.

[0039] The present invention further concerns a method of preparing the compound according to the invention, comprising the method steps:

[0040] M1) providing at least one starting material according to formula (A) wherein n is an integer selected from the group consisting of 0 to 6, preferably selected from 1 and 3, p more preferably is 3;

[0041] M2) providing at least one starting material according to formula (B) wherein R1is selected from the group consisting of alkyl group, aryl group and polyoxyalkylene group; and

[0042] M3) mixing the at least one starting material according to formula (A) and the at least one starting material according to formula (B), such that the compound according to any one of the preceding claims is obtained.

[0043] By mixing the at least one starting material according to formula (A) and the at least one starting material according to formula (B) (hereinafter referred to as “starting materials”), the compound according to the invention is formed.

[0044] Method steps M1 and M2 can be carried out in the order indicated above, simultaneously or in the reverse order. Method step M3 is performed after method step M1 and M2 have been concluded. Further steps can be included in the inventive method before, between or after the aforementioned method steps.

[0045] The temperature in method step M3 preferably ranges from 15 °C to 120 °C, more preferably from 25 °C to 90 °C, even more preferably from 60 °C to 80 °C. The duration of method step M3 can be widely varied. It can be selected based on routine experiments and depends inter alia on the specific starting materials used and the temperature in method step M3.

[0046] Optionally, the method of preparing the compound according to the invention comprises the method step M2a to be included in the method before method step M3 or during method step M3: M2a) Adding at least one solvent.

[0047] The at least one solvent can be added to one or each of the starting materials or it can be added to the mixture of method step M3.

[0048] The at least one solvent is preferably selected from those described for the catalyst composition according to the invention described hereinafter. The addition of the at least one solvent facilitates the preparation of the compound according to the invention as the viscosity of the mixture can more be easily controlled. The at least one solvent is optionally removed after method step M3. If the at least one solvent is not removed, the catalyst composition according to the invention is obtained. The removal of the at least one solvent can be accomplished by standard methods such as distillation, preferably under reduced pressure, precipitation of the compound according to the invention from the at least one solvent and the like. The person skilled in the art can select suitable methods by routine experiments if required.

[0049] The means for mixing the starting materials is not particularly limited. The person skilled in the art can select suitable means based on his knowledge or on routine experiments. A preferred means for mixing is stirring.

[0050] Another aspect of the present invention pertains to a catalyst composition for use in the preparation of a polyurethane comprising (or preferably consisting of) i) the compound according to the invention; and ii) at least one solvent, the at least one solvent being preferably a polar solvent, wherein the at least one solvent is more preferably selected from the group consisting of glycols and glycol ethers and polyglycol ether.

[0051] The compound according to the invention is preferably present in in the catalyst composition an amount ranging from 99.9 to 0.1 wt.-% , more preferably from 95 to 10 wt.-%, even more preferably from 90 to 50% wt.-%, still even more preferably from 90 to 70 wt.-%, based on the weight of the overall catalyst composition. If more than one compound according to the invention is used, the total amount of all compounds according to the invention preferably lies in above-defined ranges.

[0052] Any solvent capable of dissolving or dispersing the compound according to the invention can be used. The at least one solvent is preferably a polar solvent. A polar solvent in the context of the present invention has a dielectric constant e of at least 10, preferably of at least 20 at 25 °C. The at least one solvent is preferably protic. More preferably, the at least one solvent is polar and protic. Even more preferably, the at least one solvent is selected from the group consisting of glycols and glycol ethers. Still even more preferably, the at least one solvent is a glycol. Preferable glycols are ethane-1 ,2-diol (ethylene glycol), polyethylene glycol poly(ethylene oxide), propane-1 ,2-diol, polypropylene glycol, propane-1 ,3-diol 1 ,3-(propylene glycol), 1 ,3-polypropanediol, butane-1 ,4-diol (butylene glycol) and polytetramethylene ether glycol.

[0053] Preferable glycol ethers are represented by the following formula (P):

[0054] Rs

[0055] HO O^’<P> wherein each Rsis selected from the group consisting of hydrogen and alkyl group, R‘ is selected from the group consisting of hydrogen and alkyl group, each s is independently selected from 1 , 2, 3 and 4 and t is an integer ranging from 2 to 50.

[0056] Each Rsis independently preferably selected from the group consisting of hydrogen and methyl group. It is preferred that at most one Rsper repeating unit is an alkyl group, preferably a methyl group. At most one means 0 or 1 . The repeating unit is the entity shown in squared brackets in above formula. The preferable glycol ether consists of t repeating units. More preferably, all Rsare hydrogen. R‘ is preferably selected from the group consisting of hydrogen and C1 -C4-alkyl group, R‘ is more preferably hydrogen, s is preferably selected from 2 and 3, more preferably 2. t preferably ranges from 2 to 30, more preferably 2 to 20, t even more preferably is 2 to 8.

[0057] Particularly preferably, R‘ is selected from the group consisting of hydrogen and C1 -C4-alkyl group, R‘ is most preferably hydrogen, s is selected from 2 and 3, s is most preferably 2, and t ranges from 2 to 30, more preferably 2 to 10, most preferably t is 2 or 3. Much preferred glycol ethers are selected from the group consisting of diethylene glycol (IUPAC name: 2,2'-[Ethane-1 ,2- diylbis(oxy)]di(ethan-1-ol)), triethylene glycol, dipropylene glycol (IUPAC names: 4-Oxa-2,6-heptan- diol and 4-Oxa-1 ,6-heptandiol) and tripropylene glycol (also referred to as [(1 -Methyl-1 ,2- ethanediyl)bis(oxy)]bispropanol).

[0058] The at least one solvent is particularly preferably selected from the group consisting of ethane-1 ,2- diol, propane-1 ,2-diol, propane-1 ,3-diol and butane-1 ,4-diol, diethylene glycol, dipropylene glycol and tripropylene glycol.

[0059] The at least one solvent is preferably present in the catalyst composition according to the invention in an amount ranging from 0.1 to 99 wt.-%, more preferably from 5 to 90 wt.-%, even more preferably from 10 to 50 wt.-%, still even more preferably from 10 to 30 wt.-%, based on the weight of the overall catalyst composition. If more than one solvent is used, the total amount of all solvents preferably lies in above-defined ranges. Optionally, the catalyst composition according to the invention comprises further compounds which can function as a catalyst in a process for preparing a polyurethane. These further compounds might be catalysts generally used in the preparation of a polyurethane. Suitable further catalysts for preparing a polyurethane, which, in particular, accelerate the reaction between the NCO groups (isocyanate groups) of the diisocyanates and the hydroxyl groups of the polyol are the customary catalysts known from the prior art, for example tertiary amines such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'- dimethylpiperazine, diazabicyclo[2.2.2]octane and the like, and also, in particular, organic metal compounds such as titanate esters, iron compounds, tin compounds, e.g. tin diacetate, tin dioctoate, tin dilaurate or the dialkyltin salts of aliphatic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate or the like.

[0060] The further compound which can function as a catalyst is preferably present in the catalyst composition in an amount ranging from 1 to 10 wt.-%, preferably from 5 to 10 wt.-%, more preferably from 7 to 9.9 wt.-%, based on the weight of the overall catalyst composition. If more than one further compound which can function as a catalyst is used, the total amount of all further compound which can act as a catalyst preferably lies in above-defined ranges.

[0061] The catalyst composition according to the invention is preferably a solution. Alternatively, it is a dispersion. In the latter case, at least one surfactant is present in the dispersion. One or more suitable surfactants can be selected by routine experiments and based on the general knowledge of the person skilled in the art.

[0062] The catalyst composition according to the invention can be prepared by various means, notably by mixing the compound according to the invention, the at least one solvent and optionally any one of the aforementioned compounds to be included in the catalyst composition according to the invention. It is also possible to prepare the catalyst composition according to the invention using the above-described method of preparing the compound according to the invention when at least one solvent is added in optional method step M2a.

[0063] The viscosity of the catalyst composition according to the invention advantageously can be tailored by selecting its components and the amounts thereof such that its dosing can be facilitated.

[0064] In a further aspect, the present invention is directed at a polyol composition comprising (or preferably consisting of) a) at least one polyol; b) the compound according to the invention; and optionally, c) at least one solvent, the at least one solvent being preferably a polar solvent, wherein the at least one solvent is more preferably selected from the group consisting of glycols and glycol ethers. The at least one polyol is not limited. The person skilled in the art can select the at least one polyol based on his general knowledge and the desired properties of the polyurethane to be formed. The at least one polyol is preferably selected from the group consisting of polyether polyol, polyester polyol, polymer polyol, flame-retardant polyol such as a phosphorus-containing polyol or a halogencontaining polyol, phenol-type polyol such as a Mannich base polyol and mixtures of the aforementioned. Typically, the at least one polyol comprises 2 to 4 hydroxyl groups capable of reacting with at least one NCO group. Additionally, it is possible to include diamines that are conventionally used in the manufacturing of polyurethanes (giving urea groups in the polyurethanes or polyureas entirely). Preferably, no diamines are used in the polyol composition according to the invention.

[0065] The polyether polyols can be produced, for example, by an addition reaction of an alkylene oxide such as ethylene oxide or propylene oxide to a starting material which is a compound having at least two active hydrogen groups, such as a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerol, trimethylolpropane or pentaerythritol, an aliphatic amine such as ethylenediamine, an aromatic amine such as toluenediamine, an alkanolamine such as ethanolamine or diethanolamine, sorbitol or sucrose, for example, by a method disclosed in "Polyurethane Handbook," edited by Gunter Oertel (1985), Hanser Publishers (Germany), p. 42-53.

[0066] The polyester polyol may, for example, be one obtainable by a reaction of a dibasic acid such as adipic acid with glycol, DMT residue, a polyester polyol obtained from phthalic anhydride as the starting material, waste material from the production of nylon, TMP, waste material of pentaerythritol, waste material of a phthalic acid-type polyester, or a polyester polyol obtained by treatment of waste articles (see e.g. Keiji Iwata (Ed.), "Polyurethane Resin Handbook" (1stedition, 1987), published by Nikkan Kogyo Shinbunsha, p. 116 - p. 117).

[0067] The polymer polyol may, for example, be a polymer polyol obtained by reacting the above polyether polyol with an ethylenically unsaturated monomer (such as butadiene, acrylonitrile, or styrene) in the presence of a radical-polymerization catalyst.

[0068] The flame-retardant polyol may, for example, be a phosphorus-containing polyol obtained by adding an alkylene oxide to a phosphoric acid compound, a halogen-containing polyol obtained by ring-opening polymerization of epichlorohydrin or trichlorobutylene oxide, or a phenol-type polyol such as Mannich base polyol.

[0069] More preferably, the at least one polyol is selected from the group consisting of polyester polyol and polyether polyol.

[0070] A preferred polyester polyol is one having a mass average molar mass (Mw) of from 1 ,000 to 2,500 g / mol. A polyester polyol obtained from the reaction of adipic acid with a glycol is preferred. As the polyester polyol, one having a mass average molar mass (Mw) of from 1 ,000 to 2,500 g / mol and obtained from the reaction of adipic acid with a glycol, is more preferred. It is preferred that the polyether polyol has a mass average molar mass (Mw) of from 1 ,000 to 6,000 g / mol. A polyether polyol obtained by reacting propylene oxide to propylene glycol or glycerol as an initiator, followed by reacting ethylene oxide to the terminal, is preferred. As the polyether polyol, one having a mass average molar mass (Mw) of from 1 ,000 to 6,000 g / mol, obtained by reacting propylene oxide to propylene glycol or glycerol as an initiator, followed by reacting ethylene oxide to the terminal, is more preferred.

[0071] The mass average molar mass (Mw) in both cases is preferably measured by gel permeation chromatography using a column combination SDV 1000 / 10000 A (length 65 cm), temperature 30 °C, THF as mobile phase, flow rate 1 ml / min, sample concentration 10 g / l, Rl-Detector, calibration vs. polypropylene glycol standard.

[0072] Preferably, the hydroxyl value of such a polyol is within a range of from 20 to 1 ,000 mg KOH / g. Specifically, the polyester polyol preferably has a hydroxyl value within a range of from 50 to 1 ,000 mg KOH / g, and the polyether polyol preferably has a hydroxyl value within a range of from 20 to 800 mg KOH / g. The hydroxyl value is measured in accordance with ASTM D4274D.

[0073] The at least one polyol according to the invention is preferably present in in the polyol composition an amount ranging from 10 to 99.98 wt.-%, preferably from 50 to 99.9 wt.-%, more preferably from 80 to 98 wt.-%, based on the weight of the overall catalyst composition. If more than one polyol is used, the total amount of all polyols preferably lies in above-defined ranges.

[0074] The compound according to the invention is preferably present in in the polyol composition an amount ranging from 0.02 to 5 wt.-%, preferably from 0.05 to 3 wt.-%, more preferably from 0.1 to 2 wt.-%, based on the weight of the overall catalyst composition. If more than one compound according to the invention is used, the total amount of all compounds according to the invention preferably lies in above-defined ranges.

[0075] The polyol composition according to the invention optionally comprises water. The amount of water in the polyol composition according to the invention preferably ranges from 0.0001 to 5.0 wt.-%, more preferably 0.001 to 2.0 wt.-% and even more preferably from 0.05 to 0.25 wt.-%, based on the total weight of the polyol composition according to the invention. It is known that phenolic systems of the prior art suffer from age-induced drift of pot life time, i.e. the reactivity reduces over time. This is especially the case if water is present in such a system. In case of the invention, this effect does not occur or is less pronounced.

[0076] A blowing agent is optionally included in the polyol composition according to the invention when it is desirable to produce a cellular polyurethane foam. Suitable chemical and physical blowing agents are known to the person skilled in the art. The polyol composition according to the invention optionally comprises one or more of conventionally used components selected from the group consisting of filling agents (also referred to as fillers in the art), colorants, odor masks, flame retardants, biocides, antioxidants, UV stabilizers, antistatic agents, viscosity modifiers, drying agents and mixtures of the aforementioned. These components are known in the art and the person skilled in the art can select them based on his knowledge.

[0077] In accordance with the present invention, the compound according to the invention, the catalyst composition according to the invention and / or the polyol composition according to the invention can be used for preparing a polyurethane.

[0078] The present invention also concerns a method of preparing a polyurethane comprising reacting at least one polyisocyanate with at least one polyol in the presence of the compound according to the invention.

[0079] Polyurethane (PU) in the context of the present invention is in particular understood as meaning a product obtainable through reaction of at least one polyisocyanate with at least one polyol or compounds having multiple isocyanate-reactive groups, preferably with at least one polyol. In addition to the polyurethane, further functional groups may also be formed in the reaction, for example uretdi- ones, carbodiimides, isocyanu rates, allophanates, biurets, ureas and / or uretonimines. For the purposes of the present invention, therefore, polyurethane means not just polyurethane but also polyi- socyanurate, polyureas, and polyisocyanate reaction products containing uretdione, carbodiimide, allophanate, biuret and / or uretonimine groups. It is, however, preferred that the polyurethane according to the invention is free of such groups including polyisocyanurate, polyureas, and polyisocyanate reaction products containing uretdione, carbodiimide, allophanate, biuret and / or uretonimine groups.

[0080] Suitable polyisocyanates are known to the person skilled in the art. The at least one polyisocyanate is preferably selected from the group consisting of aliphatic, cycloaliphatic, araliphatic and aromatic diisocyanates.

[0081] Preferred aromatic isocyanates are selected from the group consisting of 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'- diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, urethane-modified liquid 4,4'- diphenylmethane diisocyanates, urethane-modified liquid 2,4-diphenylmethane diisocyanates, 4,4'-diisocyanatodiphenylethane, the mixtures of monomeric methanediphenyl diisocyanates, toluene diisocyanate (TDI), methanediphenyl diisocyanate (MDI), more highly polycyclic homologues of methanediphenyl diisocyanate (polymeric MDI), 1 ,2- naphthylene diisocyanate, 1 ,5-naphthylene diisocyanate and mixtures of the aforementioned.

[0082] Aliphatic diisocyanates used are customarily aliphatic and / or cycloaliphatic diisocyanates, preferably selected from the group consisting of tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene-1 ,5-diisocyanate, 2-ethylbutylene-1 ,4-diisocyanate, 1-isocy- anato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1 ,4-bis(iso- cyanatomethyl)cyclohexane, 1 ,3-bis(isocyanatomethyl)cyclohexane (HXDI), 1 ,4-cyclohexane diisocyanate, 1 -methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, 4,4'-dicy- clohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate and mixtures of the aforementioned.

[0083] Polyisocyanate prepolymers are obtainable by reacting above described polyisocyanates in excess, at temperatures of 30 to 100°C, for example, preferably at about 80°C, with at least one polyol to give the prepolymer. For the preparation of the prepolymers of the invention, preference is given to using polyisocyanates and commercial polyols, preferably the preferred polyols described above.

[0084] It is preferred that the at least one polyisocyanate is selected from the group consisting of MDI, polymeric MDI, TDI or prepolymers of the aforementioned. Prepolymers of the aforementioned polyisocyanates are known in the art and can be obtained by reacting the polyisocyanates with at least one polyol wherein the first-mentioned is used in an excess such that a prepolymer is obtained (having reactive isocyanate groups).

[0085] Accordingly, the present invention is also directed to a process of preparing a polyurethane as disclosed above, wherein the polyisocyanate is selected from the group consisting of MDI, polymeric MDI, and TDI, and derivatives thereof or prepolymers of these polyisocyanates.

[0086] Polyols useful in the inventive method have been described above (vide supra).

[0087] To prepare the polyurethane, the at least one polyisocyanate is mixed with at least one polyol in the presence of the compound according to the invention. The thus obtained mixture (hereinafter: PU-forming mixture) is preferably heated to a temperature ranging from 20 to 110 °C, more preferably from 20 to 80 °C, even more preferably from 20 to 50 °C, to activate the compound according to the invention as it is preferably used here as thermolatent catalyst.

[0088] The means of mixing the at least one polyisocyanate is mixed with at least one polyol in the presence of the compound according to the invention are not particularly limited. The person skilled in the art knows suitable means such as stirring.

[0089] The compound according to the invention is used in catalytically sufficient amounts. A preferable amount of the compound according to the invention is from about 0.02 to about 2 wt.-%, especially from about 0.05 to about 0.5 wt.-%, of the compound according to the invention based on the overall weight of the at least one polyol(s). The polyisocyanate and polyol are preferably reacted at an isocyanate index of from 70 to 500 or more, although a more preferable isocyanate index is from 80 to 130. Isocyanate index is calculated as the number of reactive isocyanate groups provided by the polyisocyanate component divided by the number of isocyanate-reactive groups (in particular hydroxyl groups of the polyol) in the PU-forming mixture (including isocyanate-reactive blowing agents such as water, if present) and multiplying by 100. Water is considered to have two isocyanate-reactive groups per molecule for purposes of calculating isocyanate index. A preferred isocyanate index is from 100 to 125.

[0090] In case of preparing a foam, the PU-forming mixture optionally contains at least one surfactant, whose presence is preferred when a cellular polyurethane is formed. The surfactant helps to stabilize the cells of the composition as gas evolves to form bubbles and expand the foam. Organosili- cone surfactants are generally preferred types. A wide variety of these organosilicone surfactants are commercially available, including those sold by Goldschmidt under the Tegostab® name (such as Tegostab B-8462, B8427, B8433 and B-8404 surfactants), as well as various surfactant products commercially available from Dow Chemicals, such as Vorasurf DC-193 Additive, Vorasurf DC- 198 Additive, Vorasurf DC-5000 Additive, Vorasurf DC-5043 Additive and Vorasurf DC-5098 Additive surfactants.

[0091] In addition to the foregoing ingredients, the PU-forming mixture optionally includes one or more auxiliary components, such as fillers, colorants, odor masks, flame retardants, biocides, antioxidants, UV stabilizers, antistatic agents, viscosity modifiers, and the like.

[0092] Examples of suitable flame retardants include phosphorus compounds, halogen containing compounds and melamine.

[0093] Examples of fillers and pigments include calcium carbonate, titanium dioxide, iron oxide, chromium oxide, azo / diazo dyes, phthalocyanines, dioxazines and carbon black.

[0094] Examples of UV stabilizers include hydroxybenzotriazoles, zinc dibutyl thiocarbamate, 2,6-diter- tiary butyl catechol, hydroxybenzophenones, hindered amines and phosphites.

[0095] Except for fillers, the foregoing additives are generally used in small amounts, such as from 0.01 percent to 3 weight-% based on the total weight of the PU-forming mixture. Fillers are optionally used in quantities as high as 50 weight-% based on the total weight of the PU-forming mixture.

[0096] A viscosity modifier may be used in either the polyol (composition) or isocyanate components if needed or desired to bring the viscosity of that component into a particular range. A viscosity modifier will be used most commonly in cases in which the polyol is viscous relative to the polyisocyanate. In such a case, a viscosity modifier can be added to more closely match the viscosity of the polyol component with that of the polyisocyanate. The viscosity modifier preferably is not reactive with the polyol, water or polyisocyanate, although it may perform other functions (such as providing flame retardancy). It is generally preferred, for some applications such as producing fiber-rein- forced polyurethanes, to use components that have a viscosity of 1500 mPa s (cps) or less at 25°C, and in such a case, a viscosity modifier may be blended with one or more of the components in order to bring the viscosity down into that range. Viscosity modifiers are known in the art.

[0097] In a preferred embodiment of the present invention, the method of preparing the polyurethane comprises the following method steps:

[0098] P1) providing the polyol composition according to the invention;

[0099] P2) providing at least one polyisocyanate;

[0100] P3) mixing the polyol composition and the at least one polyisocyanate; and

[0101] P4) heating the mixture of the polyol composition and the at least one polyisocyanate to a temperature sufficiently high to start the reaction of the at least one polyol and the at least one isocyanate; such that the polyurethane is obtained.

[0102] Auxiliary components are optionally added to the polyol composition.

[0103] The temperature in method step P4 preferably lies in above defined ranges.

[0104] The duration of method step P4 is not particularly limited and depends in particular on the at least one polyol, the at least one polyisocyanate and the temperature used. Useful durations range from 10 to 80 seconds, preferably from 10 to 60 seconds, more preferably from 20 to 40 seconds.

[0105] In another embodiment of the present invention, the method of preparing a polyurethane comprises the following method step to be carried out in the given order:

[0106] Q1) mixing the at least one polyol with the at least one solvent;

[0107] Q2) adding the compound according to the invention to the mixture of method step Q1 to give the polyol composition;

[0108] Q3) adding the polyisocyanate to the polyol composition of method step Q2;

[0109] Q4) mixing the mixture of method step Q3; and thereby obtaining the polyurethane.

[0110] Auxiliary components are optionally added in one of method steps Q2, Q3 and / or Q4, preferably in Q2.

[0111] The temperature in method step Q4 preferably lies in above defined ranges.

[0112] The duration of method step Q4 is not particularly limited and depends in particular on the at least one polyol, the at least one polyisocyanate and the temperature used. Useful durations range from 1 min to 3 h, preferably from 10 min to 2 h, more preferably from 30 min to 1 h. The present invention further concerns a polyurethane obtained from the inventive method of preparing a polyurethane.

[0113] The polyurethanes obtained according to the present invention are in particular suitable for applications such as coatings, laminating, sealants, adhesives, elastomers, and production of moldings for applications in which components of very high surface area are being produced, such as rotor blades for wind turbines, boat hulls, or plastic vehicle bodies for automobiles.

[0114] In addition to the above-mentioned aspects of the present invention, it is directed at an article, preferably an artificial leather, more preferably a 2 component artificial leather, comprising or consisting of the polyurethane according to the invention.

[0115] The invention will now be illustrated by reference to the following non-limiting examples.

[0116] EXAMPLES

[0117] Commercial products were used as described in the technical datasheet available on the date of filing of this specification unless stated otherwise hereinafter.

[0118] Materials and Methods:

[0119] Arcol Polyol 1374 (a polyether triol obtained from Covestro AG, Germany) and 1 ,4-butandiol were dried over 3 A molecular sieve. Suprasec 2015 (NCO % 27.4) was obtained from Huntsman Polyurethanes, Belgium.

[0120] All blends were mixed using a Hausschild Speedmixer DAC 400 (from HAUSCHILD GMBH & CO. KG, Germany). The Shore A hardness was measured in accordance with DIN ISO 7619-1 :2012-02 at 25°C.

[0121] Gel time measurement:

[0122] Gel times were measured with a Standard Gel Timer 220v / 50Hz from Gardco, USA. The sample was evaluated at room temperature until the rotating hook reached its maximum torque level. This time was defined as “gel time.”

[0123] Rheometer Analysis:

[0124] The viscosity was measured with a MCR 702 from Anton Paar GmbH, Austria in oscillation mode with a plate geometry. The disposable spindle plates have a diameter of 25 mm. The sample was kept for 3 minutes at 25 °C and was then heated with 2 °C / min to 70 °C. The increase in complex viscosity was recorded. Preparation of Compound 1 according to the invention (n=3, R1=Et)

[0125] 46.9 g (1 equivalent) Ethylparaben (ethyl para-hydroxybenzoate) was molten at 120 °C and was then added to a mixture of 43.0 g (1 equivalent) 1 ,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and

[0126] 10.10 g Dipropyleneglycol which was kept at room temperature. The mixture was stirred for 30 min to give Compound 1 .

[0127] Compound 2 (n=3, R1=n-Prop; molten at 100°C) and Compound 3 (n=3, R1=n-Bu; molten at 70°C) were prepared in the same manner as Compound 1 . A comparative compound using phenol was prepared analogously. The used masses of the components are given in the following table:

[0128] Table 1 : Preparation of inventive Compounds 2 and 3 and a comparative compound.

[0129] Preparation of a polyurethane

[0130] In a 250 mL cup, Arcol Polyol 1374 was mixed with 1 ,4-Butandiol in the amounts given in table 2. To the thus obtained mixture, the catalyst (compound 1 to 3 or the 1 :1 adduct of phenol and DBU) was added in the amount given in table 2 using a Hausschild Speedmixer DAC 400 for 2 min with 2500 rpm. Then, the polyisocyanate was added and the mixture was blended for 13 seconds at 2750 rpm in the Speedmixer. 70 g of the product obtained were poured into a metal cup and placed in a gel timer at room temperature. A small sample was placed into the rheometer.

[0131] Table 2: Inventive Example 1 and Comparative Example 1. The substitution of the harmful comparative compound (a 1 :1 adduct of phenol and DBU) by the compound according to the invention in inventive example 1 allowed for at least equally good polyurethanes to be obtained. Notably, the gel time was shortened when using the compound according to the invention indicating an improved catalyst effect of the compound according to the invention compared to the prior art catalyst.

[0132] Thermogravimetric analysis (TGA)

[0133] The TGA was measured from 25 °C to 375 °C with a heating rate of 2K / min. It was measured on a TA Instruments Discovery TGA.

[0134] The TGA is depicted in Figure 1 . Figure 1 depicts the thermogravimetric analysis of DBU (solid line), a phenolic salt of DBU (1 :1 adduct of phenol and DBU, dashed line) and a compound according to the invention (with n=3 and R1=n-Bu, dotted line).

[0135] It can be seen that the temperature-dependent weight loss of DBU and the phenolic salt of DBU occurs at much lower temperatures compared to the compound according to the invention. This indicates an improvement in reduction of hazardous vapors during a manufacturing process.

[0136] Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being defined by the following claims only.

Claims

Claims1. A compound according to formula (I) for use as catalyst in a process for preparing a polyurethane:. vr <»Ri_0 / ^z whereinR1is selected from the group consisting of alkyl group, aryl group and polyoxyalkylene group; and n is an integer selected from the group consisting of 0 to 6.

2. The compound according to claim 1 , characterized in that R1is selected from the group consisting of alkyl group and aryl group.

3. The compound according to any one of claims 1 or 2, characterized in that R1is selected from the group consisting of C1-C4-alkyl group and phenyl group.

4. The compound according to any one of the preceding claims, characterized in that R1is an alkyl group.

5. The compound according to any one of the preceding claims, characterized in that R1is selected from the group consisting of methyl group, ethyl group, n-propyl group, and n-butyl group.

6. The compound according to any one of the preceding claims, characterized in that R1is selected with the proviso that it is not a methyl group.

7. The compound according to any one of the preceding claims, characterized in that R1is an ethyl group.

8. The compound according to claim 1 , characterized in that the polyoxyalkylene group is a R2-[O-R3]k-group, wherein R2is hydrogen, an alkyl group, or an aryl group, R3is an alkanediyl group and k is an integer ranging from 1 to 20.

9. The compound according to any one of the preceding claims, characterized in that n is selected from 1 and 3, n preferably is 3.

10. A method of preparing the compound according to any one of claims 1 to 7, comprising the method steps:M1) providing at least one starting material according to formula (A)wherein n is an integer selected from the group consisting of 0 to 6, preferably selected from 1 and 3, p more preferably is 3;M2) providing at least one starting material according to formula (B)wherein R1is selected from the group consisting of alkyl group, aryl group and polyoxyalkylene group; andM3) mixing the at least one starting material according to formula (A) and the at least one starting material according to formula (B); such that the compound according to any one of the preceding claims is obtained.

11. The method according to claim 10 characterized in that R1from the group consisting of alkyl group, aryl group and polyoxyalkylene group with the proviso that R1 is not methyl.

12. A catalyst composition for use in the preparation of a polyurethane comprising i) the compound according to any one of claims 1 to 9; and ii) at least one solvent, the at least one solvent being preferably a polar solvent, wherein the at least one solvent is more preferably selected from the group consisting of glycols and glycol ethers.

13. The catalyst composition according to claim 12, characterized in that the polar solvent has a dielectric constant e of at least 10, preferably of at least 20, at 25 °C.

14. The catalyst composition according to claim 12 or 13, characterized in that the glycol is selected from the group consisting of ethane-1 ,2-diol (ethylene glycol), polyethylene glycol poly(ethylene oxide), propane-1 ,2-diol, polypropylene glycol, propane-1 ,3-diol 1 ,3-(propylene glycol), 1 ,3-pol- ypropanediol, butane-1 ,4-diol (butylene glycol) and polytetramethylene ether glycol.

15. The catalyst composition according to claim 12 or 13, characterized in that the glycol either adheres to general formula (P):wherein each Rsis selected from the group consisting of hydrogen and alkyl group, R‘ is selected from the group consisting of hydrogen and alkyl group, each s is independently selected from 1 , 2, 3 and 4 and t is an integer ranging from 2 to 50.

16. A composition for use in the preparation of a polyurethane comprising a) at least one polyol; b) the compound according to any one of claims 1 to 9; and optionally, c) at least one solvent, the at least one solvent being preferably a polar solvent, wherein the at least one solvent is more preferably selected from the group consisting of glycols and glycol ethers.

17. The polyol composition according to claim 16, characterized in that the polar solvent has a dielectric constant e of at least 10, preferably of at least 20, at 25 °C.

18. The polyol composition according to claim 16 or 17, characterized in that the glycol is selected from the group consisting of ethane-1 ,2-diol (ethylene glycol), polyethylene glycol poly(ethylene oxide), propane-1 ,2-diol, polypropylene glycol, propane-1 ,3-diol 1 ,3-(propylene glycol), 1 ,3-pol- ypropanediol, butane-1 ,4-diol (butylene glycol) and polytetramethylene ether glycol.

19. The polyol composition according to claim 16 or 17, characterized in that the glycol either adheres to general formula (P):wherein each Rsis selected from the group consisting of hydrogen and alkyl group, R‘ is selected from the group consisting of hydrogen and alkyl group, each s is independently selected from 1 , 2, 3 and 4 and t is an integer ranging from 2 to 50.

20. Use of the compound according to any one of claims 1 to 9, the catalyst composition according to any one of claims 12 to 15 and / or the polyol composition according to any one of claims 16 to 19 for preparing a polyurethane.21 . A method of preparing a polyurethane comprising reacting at least one polyisocyanate with at least one polyol in the presence of the compound according to any one of claims 1 to 9.

22. The method according to claim 21 characterized in that the at least one polyisocyanate is selected from the group consisting of MDI, polymeric MDI, TDI and prepolymers of the aforementioned.

23. A polyurethane obtained from the method according to any one of claims 21 or 22.

24. An article comprising or consisting of the polyurethane according to claim 23.

Images