Two-component polyurethane filler with adjustable pot life

Description

Technical field

[0001] The invention relates to the field of two-component polyurethane compositions and their use as sandable fillers, as well as a method for filling cavities, holes or cracks, in particular in wood, with such a polyurethane composition. State of the art

[0002] Wood is a popular building and manufacturing material and is still used in a variety of ways today, for example in furniture making or as flooring in interiors. Especially in such applications, it is desirable for the wooden boards to have a smooth surface. However, wood is a natural material, and as such, flat wooden boards or planks, such as those used for flooring, regularly have defects such as cracks, knots, holes, and similar surface imperfections. These defects must be repaired—that is, glued, filled, or puttyed—to create a surface suitable for finishing. This finishing usually involves sanding or refining, followed by treatments and other finishes. Knots, in particular, pose a problem when processing the surface. Knot slices either tend to fall out, creating large holes, or often exhibit star-shaped drying shrinkage cracks.There are many proposed solutions for creating a uniform, flawless surface in wood. These range from cutting out the defects or removing the knots and inserting blanks to gluing knots together. All of these methods are time-consuming and often inefficient in terms of material utilization.

[0003] Therefore, methods have been developed in which a suitable filler is applied to the defects, which is then hardened and sanded flush with the wood. For example, DE 102 30 574 A1 discloses a thermoplastic filler that is applied to the defects and hardens rapidly. A disadvantage of this method, however, is that the thermoplastic filler must be heated significantly, which makes the process complex and can thermally stress the wood. It is generally desirable that the filler adheres well to the wood species used in this market, has a similar hardness to the wood, but at the same time possesses a certain degree of elasticity to accommodate the natural movements (such as contractions) of the wood substrate without cracking or similar defects.

[0004] For this reason, polyurethane compounds were developed specifically for this purpose. Polyurethane compounds are known to adhere well to wood and can be formulated with a wide range of properties; achieving suitable hardness, elasticity, and color is usually quite satisfactory. Two-component polyurethane compounds are particularly suitable for this. Compared to one-component compounds, they have the advantage of curing quickly after mixing and can therefore be further processed, for example, sanded, after a short time.

[0005] On the other hand, compromises always have to be made with two-component polyurethane compounds. For the application of two-component polyurethane compounds as fillers, it would generally be desirable to combine a sufficiently long working time (pot life) of the mixed compound, without an excessively rapid increase in viscosity due to the initial curing process, with very rapid curing and exceptionally fast strength development after application. However, this is hardly achievable with conventional two-component compounds. Either the pot life is very short for compounds that cure and build strength quickly, or the curing and strength development are slow when compounds with a long pot life are used.For industrial processing with rapid cycle times, it would be desirable to have a sufficiently long, ideally even adjustable, pot life for optimal processing of the uncured filler, without significant viscosity increase during processing, but then very rapid curing after processing, allowing the cured filler to be sanded immediately. This has not yet been achieved with currently manufactured polyurethane-based fillers.

[0006] For example, DE 198 58 818 A1 teaches aqueous fillers based on two-component polyurethane compositions. These are easy to sand, but require a considerable waiting time after curing before they are sandable, especially if the pot life has been set long enough for good workability.

[0007] WO 98 / 15586 A1, as another example, also describes a two-component polyurethane leveling compound for smoothing wood. This compound has a high viscosity and / or a rapid increase in viscosity after application, so that it does not run uncontrollably even from vertical surfaces. However, it is difficult to completely fill all cavities with such a highly viscous or rapidly curing compound, which, in extreme cases, can lead to acoustic disturbances, for example, in floor coverings.

[0008] From DE 39 32 171 A1, fillers based on two-component polyurethane compositions are known, which contain hollow glass spheres in addition to a tin dialkyl mercaptide as a catalyst.

[0009] Therefore, there is a need for a filler based on two-component polyurethane compounds that can be easily applied during a sufficiently long pot life without increasing viscosity, and that cures very quickly after application, regardless of the layer thickness, and can be sanded or troweled within a very short time. In addition to good sandability, it should also have a sufficiently high Shore D hardness, for example, 60 or more. Furthermore, it would be desirable to be able to adjust the pot life of such a compound for the desired application. Description of the invention

[0010] The object of the present invention is therefore to provide a filler based on a two-component polyurethane composition which hardens very quickly to a sandable, mechanically excellent and suitable wood filler with sufficiently high hardness, but at the same time has a sufficiently long pot life, adjustable within certain limits, so that it can be processed without problems.

[0011] Surprisingly, this problem is solved by the polyurethane composition according to claim 1. It comprises at least one polyol, a short-chain diol, and a compound with at least one thiol group in the first component and a high polyisocyanate content in the second component. Furthermore, the composition contains a metal catalyst for curing, which can form thio complexes, the ratio of thiol groups to metal atoms in the composition being fixed. In addition, the composition contains microscopic hollow spheres and an aluminosilicate-based drying agent. After mixing the components, it cures very quickly after a sufficiently long pot life, which can be adjusted within certain limits, and achieves very good mechanical properties after only a short time, e.g., a few minutes to a few hours, and can be easily processed further.In its hardened state, the composition has a very high hardness and good elasticity and is excellent for grinding.

[0012] Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of dependent claims. Ways to implement the invention

[0013] The present invention relates to a polyurethane composition comprising a first and a second component; wherein the first component A at least one polyol A1 with an OH functionality in the range of 1.5 to 4 and an average molecular weight in the range of 250 to 15,000 g / mol, and at least one diol A2 with two hydroxyl groups connected via a C2 to C9 carbon chain, and at least one compound T, which contains at least one thiol group; and the second component Bat least one polyisocyanate I , includes; wherein at least one metal catalyst is additionally included in one of the components K for the reaction of hydroxyl groups and isocyanate groups, which can form thio complexes; and wherein the molar ratio of all thiol groups of the at least one compound T to all metal atoms of the at least one metal catalyst K between 5:1 and 100:1; and where the molar ratio of all NCO groups of the polyisocyanates I to all OH groups of the polyols A1 and A2 = 0.9 : 1 - 1.5 : 1, in particular 1.05 : 1 - 1.3 : 1; and wherein the composition in at least one of the two components is between 3 and 25 wt.%, based on the total composition, of at least one type of microscopic hollow spheres H contains, wherein the microscopic hollow spheres Hhave a compressive strength, measured according to ASTM D3102-72, of at least 10 MPa and a density of at least 0.2 kg / L; and wherein the composition in at least one of the two components is between 2.5 and 7.5 wt.%, based on the total composition, of at least one desiccant D contains the desiccant D is an aluminosilicate.

[0014] The prefix "Poly" in substance names such as "Polyol", "Polyisocyanate", "Polyether" or "Polyamine" indicates in this document that the respective substance formally contains more than one of the functional groups appearing in its name per molecule.

[0015] In this document, the term "polymer" encompasses, on the one hand, a group of chemically uniform macromolecules that differ in degree of polymerization, molar mass, and chain length, and which are produced by a polymerization reaction (polymerization, polyaddition, polycondensation). On the other hand, the term also includes derivatives of such a group of macromolecules from polymerization reactions; that is, compounds obtained by changes, such as additions or substitutions, of functional groups on given macromolecules, and which may be chemically uniform or chemically heterogeneous. Furthermore, the term also includes so-called prepolymers, that is, reactive oligomeric pre-adducts whose functional groups are involved in the construction of macromolecules.

[0016] The term "polyurethane polymer" encompasses all polymers produced using the so-called diisocyanate polyaddition process. This also includes polymers that are almost or entirely free of urethane groups. Examples of polyurethane polymers are polyether polyurethanes, polyester polyurethanes, polyether polyureas, polyureas, polyester polyureas, polyisocyanurates, and polycarbodiimides.

[0017] In this document, "molecular weight" refers to the molar mass (in grams per mole) of a molecule or molecular residue. "Mean molecular weight" refers to the number mean Mn of a polydisperse mixture of oligomeric or polymeric molecules or molecular residues, which is usually determined by gel permeation chromatography (GPC) against polystyrene as a standard. "Room temperature" in this document refers to a temperature of 23°C. Weight percent, abbreviated wt%, denotes the mass fraction of a component of a composition, based on the total composition, unless otherwise specified. The terms "mass" and "weight" are used synonymously in this document.

[0018] A "primary hydroxyl group" is an OH group which is bonded to a C atom with two hydrogens.

[0019] In this document, "pot life" refers to the time within which the polyurethane composition can be processed after mixing the two components, before the viscosity becomes too high for further processing due to the progress of the crosslinking reaction.

[0020] In this document, the term "strength" refers to the strength of the cured composition, whereby strength refers in particular to the tensile strength and the modulus of elasticity (E-modulus), especially in the strain range of 0.05 to 0.25%.

[0021] In this document, "room temperature" refers to a temperature of 23°C.

[0022] A substance or composition is described as "storage-stable" or "storable" if it can be stored at room temperature in a suitable container for a longer period of time, typically at least 3 months up to 6 months or more, without its application or usage properties, in particular viscosity and crosslinking rate, changing to an extent relevant to its use.

[0023] All industry standards and norms mentioned in the document refer to the versions valid at the time of the initial application.

[0024] The first component A initially contains at least one polyol A1 with an OH functionality in the range of 1.5 to 4 and an average molecular weight in the range of 250 to 15,000 g / mol.

[0025] Suitable polyols A1In principle, all common polyols are suitable for the production of polyurethane polymers. Particularly suitable are polyether polyols, polyester polyols, poly(meth)acrylate polyols, polybutadiene polyols, and polycarbonate polyols, as well as mixtures of these polyols.

[0026] Polyether polyols, also called polyoxyalkylene polyols or oligoetherols, are particularly suitable if they are polymerization products of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, oxetane, tetrahydrofuran, 1,3-propanediol, or mixtures thereof, optionally polymerized with the aid of a starter molecule with two or more active hydrogen atoms such as water, ammonia, or compounds with several OH or NH groups such as 1,2-ethanediol, 1,2- and 1,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols and tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, 1,3- and 1,4-Cyclohexandimethanol, Bisphenol A, hydrogenated Bisphenol A, 1,1,1-Trimethylolethane, 1,1,1-Trimethylolpropane, Glycerol, Aniline, and mixtures of the aforementioned compounds.Both polyoxyalkylene polyols with a low degree of unsaturation (measured according to ASTM D-2849-69 and expressed in milliequivalents of unsaturation per gram of polyol (mEq / g)), produced, for example, using so-called double metal cyanide complex catalysts (DMC catalysts), and polyoxyalkylene polyols with a higher degree of unsaturation, produced, for example, using anionic catalysts such as NaOH, KOH, CsOH, or alkali alkoxides, can be used. Polyoxyethylene polyols and polyoxypropylene polyols are particularly suitable, especially polyoxyethylene diols, polyoxypropylene diols, polyoxyethylene triols, and polyoxypropylene triols.

[0027] Particularly suitable are polyoxyalkylene diols or polyoxyalkylene triols with a degree of unsaturation lower than 0.02 mEq / g and with a molecular weight in the range of 400 to 15,000 g / mol, as well as polyoxyethylene diols, polyoxyethylene triols, polyoxypropylene diols and polyoxypropylene triols with a molecular weight of 400 to 15,000 g / mol.

[0028] Also particularly suitable are so-called ethylene oxide-terminated ("EOendcapped," ethylene oxide-endcapped) polyoxypropylene polyols. These are special polyoxypropylene polyoxyethylene polyols obtained, for example, by further alkoxylating pure polyoxypropylene polyols, especially polyoxypropylene diols and triols, after completion of the polypropoxylation reaction with ethylene oxide, thereby giving them primary hydroxyl groups. Polyoxypropylene polyoxyethylene diols and polyoxypropylene polyoxyethylene triols are preferred in this case.

[0029] Also suitable are hydroxyl group terminated polybutadiene polyols, such as those produced by polymerization of 1,3-butadiene and allyl alcohol or by oxidation of polybutadiene, as well as their hydrogenation products.

[0030] Styrene-acrylonitrile grafted polyether polyols, such as those commercially available under the trade name Lupranol ®< from Elastogran GmbH, Germany, are also suitable.

[0031] Polyester polyols are particularly suitable if they bear at least two hydroxyl groups and are produced by known processes, in particular the polycondensation of hydroxycarboxylic acids or the polycondensation of aliphatic and / or aromatic polycarboxylic acids with dihydric or polyhydric alcohols.

[0032] Particularly suitable are polyester polyols produced from dihydric to trihydric alcohols such as 1,2-ethanediol, diethylene glycol, 1,2-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol (MPD), 1,9-nonadiol (ND), glycerol, 1,1,1-trimethylolpropane, or mixtures of the aforementioned alcohols with organic dicarboxylic acids or their anhydrides or esters such as succinic acid, glutaric acid, adipic acid, trimethyladipic acid, cortic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, dimer fatty acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, dimethyl terephthalate, hexahydrophthalic acid, trimellitic acid, and Trimellitic anhydride or mixtures of the aforementioned acids, as well as polyester polyols made from lactones such as ε-caprolactone.

[0033] Polyester diols are particularly suitable, especially those produced from adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acid, phthalic acid, isophthalic acid and terephthalic acid as dicarboxylic acids or from lactones such as ε-caprolactone and from ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, dimer fatty acid diol and 1,4-cyclohexanedimethanol as dihydric alcohols.

[0034] Particularly suitable polycarbonate polyols are those obtained by reacting, for example, the alcohols mentioned above (used in the synthesis of polyester polyols) with dialkyl carbonates such as dimethyl carbonate, diaryl carbonates such as diphenyl carbonate, or phosgene. Also suitable are polycarbonates obtained from the copolymerization of CO₂ with epoxides such as ethylene oxide and propylene oxide. Polycarbonate diols, especially amorphous polycarbonate diols, are particularly suitable.

[0035] Other suitable polyols are poly(meth)acrylate polyols.

[0036] Also suitable are polyhydroxy functional fats and oils, for example, natural fats and oils, especially castor oil, or so-called oleochemical polyols obtained by chemical modification of natural fats and oils, such as epoxy polyesters or epoxy polyethers obtained, for example, by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils. Also suitable are polyols obtained from natural fats and oils through degradation processes such as alcoholysis or ozonolysis and subsequent chemical linkage, for example, by transesterification or dimerization, of the degradation products or derivatives thereof.Suitable degradation products of natural fats and oils are in particular fatty acids and fatty alcohols as well as fatty acid esters, especially the methyl esters (FAME), which can be derivatized to hydroxy fatty acid esters, for example by hydroformylation and hydrogenation.

[0037] Also suitable are polyhydrocarbon polyols, also called oligohydrocarbonols, for example polyhydroxyfunctional ethylene-propylene, ethylene-butylene or ethylene-propylene-diene copolymers, such as those produced by Kraton Polymers, USA, or polyhydroxyfunctional copolymers of dienes such as 1,3-butanediene or diene mixtures and vinyl monomers such as styrene, acrylonitrile or isobutylene, or polyhydroxyfunctional polybutadiene polyols, for example those produced by copolymerization of 1,3-butadiene and allyl alcohol, which may also be hydrogenated.

[0038] Also suitable are polyhydroxy functional acrylonitrile / butadiene copolymers, such as those produced from epoxides or amino alcohols and carboxyl-terminated acrylonitrile / butadiene copolymers, which are commercially available under the name Hypro ®< (formerly Hycar ®< ) CTBN from Emerald Performance Materials, LLC, USA.

[0039] All the polyols mentioned have an average molecular weight of 250 to 15,000 g / mol, particularly 400 to 10,000 g / mol, preferably 1,000 to 8,000 g / mol, and an average OH functionality in the range of 1.5 to 4, preferably 1.7 to 3. However, the composition may also contain proportions of monools (polymers with only one hydroxyl group).

[0040] Particularly suitable polyols are polyester polyols and polyether polyols, especially polyoxyethylene polyol, polyoxypropylene polyol and polyoxypropylene polyoxyethylene polyol, preferably polyoxyethylene diol, polyoxypropylene diol, polyoxyethylene triol, polyoxypropylene triol, polyoxypropylene polyoxyethylene diol and polyoxypropylene polyoxyethylene triol.

[0041] The first component A also contains at least one diol A2 with two hydroxyl groups connected via a C2 to C9 carbon chain.

[0042] Suitable as a diol A2 are linear or branched alkylenediols with two primary or secondary hydroxyl groups, alkylenediols with one primary and one secondary hydroxyl group, and cycloaliphatic diols.

[0043] The diol is preferred A2A linear aliphatic diol with two primary hydroxyl groups linked via a C4 to C9 carbon chain. Such a diol has the advantage that elastic polyurethanes with particularly high moduli of elasticity in the low strain range, for example between 0 and 5%, are obtained, which is especially advantageous for wood fillers.

[0044] In particular, the Diol A2selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,3-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 2,4-pentanediol, 2-methyl-1,4-butanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,2-hexanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, 3,6-octanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,7-dimethyl-3,6-octanediol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.

[0045] Diol is particularly preferred A2 selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol and 1,9-nonanediol.

[0046] The Diol is the most preferred. A2Selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol. These diols are commercially readily available and enable polyurethanes with particularly high moduli of elasticity and low elongation after curing.

[0047] Preferably the first component contains A between 5 and 25 wt.%, in particular 10 to 20 wt.%, of diol A2.

[0048] In addition to these polyols A1 and A2Small amounts of other low-molecular-weight dihydric or polyhydric alcohols, such as diethylene glycol, triethylene glycol, the isomeric dipropylene and tripropylene glycols, the isomeric decanediols and undecanediols, hydrogenated bisphenol A, dimeric fatty alcohols, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, pentaerythritol, sugar alcohols such as xylitol, sorbitol, or mannitol, sugars such as sucrose, other higher-molecular-weight alcohols, low-molecular-weight alkoxylation products of the aforementioned dihydric and polyhydric alcohols, as well as mixtures of the aforementioned alcohols, may also be used. Furthermore, polyols containing other heteroatoms, such as methyldiethanolamine or thiodiglycol, may also be present.

[0049] The first component A still contains at least one compound T,which has at least one thiol group. Suitable compounds are those that have at least one thiol or mercapto group and that can be formulated according to the invention. A thiol group is understood here to be an -SH group bonded to an organic residue, for example, an aliphatic, cycloaliphatic, or aromatic carbon residue.

[0050] Compounds with 1 to 6, particularly 1 to 4, and most preferably 1 or 2 thiol groups are preferred. Compounds with one thiol group have the advantage that they do not form complexes with the metal catalyst, which tend to be sparingly soluble. K Compounds with two thiol groups have the advantage that the mechanical properties of the composition are improved after curing.

[0051] Suitable connections TExamples of compounds containing a thiol group are 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercapto-1,2-propanediol, 2-mercaptotoluimidazole or 2-mercaptobenzothiazole.

[0052] Suitable connections T Examples of compounds with more than one thiol group are 1,8-dimercapto-3,6-dioxaoctane, ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), 2,3-dimercapto-1,3,4-thiadiazole or pentaerythritol tetrakis(3-mercaptopropionate).

[0053] The preferred connection T selected from the group consisting of 1,8-Dimercapto-3,6-dioxaoctane, ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate) and 3-mercaptopropyl-trimethoxysilane.

[0054] Preferably contains component A, related to component A,0.25 to 5 wt.-%, preferably 1 to 3 wt.%, in particular 1.5 to 2 wt.%, of the compound T, which has at least one thiol group

[0055] The molar ratio of all thiol groups of the at least one compound T to all metal atoms of the at least one metal catalyst K The ratio must be between 5:1 and 100:1. This ratio allows the pot life to be adjusted within the intrinsic limits of the respective composition, determined, for example, by the catalyst content, the reactivity of the isocyanates, and their quantity. The lower limit of the pot life is the pot life achievable with a given composition using a specific amount of catalyst without the addition of the compound. Tis obtained. In many cases, which are suitable for the invention-related application as a structural adhesive or composite material matrix and are due to the high amount of isocyanate groups in the presence of a catalyst but without compounding T, No real pot life is achieved, and the composition practically begins to harden as soon as the two components are mixed.

[0056] The upper limit of the adjustable pot life is therefore the pot life that would be achieved without the use of a catalyst due to the uncatalyzed isocyanate-hydroxyl reaction. This reaction begins to start eventually after mixing the two components, even without a catalyst. However, without a catalyst, the reaction proceeds more slowly and results in the hardened material exhibiting inferior mechanical properties.

[0057] The key advantage achieved by the inventive two-component polyurethane composition is an exceptionally fast-curing and strength-building system that simultaneously possesses a sufficiently long pot life for user-friendly processing. This allows, for example, filling and smoothing applications on larger surfaces, which can then be sanded or sanded very soon after application. This leads, for instance, to a significant reduction in cycle times in industrial manufacturing. A further advantage of the inventive polyurethane compositions is the ability to adjust the pot life as described above.This is particularly advantageous for automated applications and can, for example, enable further optimization of cycle times in industrial manufacturing, as the pot life can be adjusted to the desired application.

[0058] The second component B initially contains at least one polyisocyanate I.

[0059] The polyisocyanate I is present in relatively high quantities, which is very advantageous for developing sufficiently good mechanical properties for use as a filler, especially for wood.

[0060] The second component preferably contains as much polyisocyanate as possible I that at least 5 wt.%, in particular at least 6 wt.%, preferably at least 7.5 wt.%, based on the total polyurethane composition, contain isocyanate groups.

[0061] All commercially available polyisocyanates suitable for polyurethane production, in particular diisocyanates, can be used as polyisocyanates I for the production of the polyurethane polymer in the composition according to the invention.

[0062] Suitable polyisocyanates are in particular monomeric di- or triisocyanates, as well as oligomers, polymers and derivatives of the monomeric di- or triisocyanates, and any mixtures thereof.

[0063] Suitable aromatic monomeric di- or triisocyanates include, in particular, 2,4- and 2,6-toluene diisocyanate and any mixtures of these isomers (TDI), 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers (MDI), mixtures of MDI and MDI homologs (polymeric MDI or PMDI), 1,3- and 1,4-phenylene diisocyanate, 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, naphthalene-1,5-diisocyanate (NDI), 3,3'-dimethyl-4,4'-diisocyanatodiphenyl (TODI), dianisidine diisocyanate (DADI), 1,3,5-tris-(isocyanatomethyl)benzene, tris-(4-isocyanatophenyl)methane and tris-(4-isocyanatophenyl)thiophosphate.

[0064] Suitable aliphatic monomeric di- or triisocyanates include, in particular, 1,4-tetramethylene diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 2,2,4- and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate (TMDI), 1,10-decamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, lysine and lysine ester diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate, 1-methyl-2,4- and -2,6-diisocyanatocyclohexane and any mixtures of these isomers (HTDI or H₆TDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (=isophorone diisocyanate or IPDI), perhydro-2,4'- and -4,4'-diphenylmethane diisocyanate (HMDI or H12MDI), 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis-(isocyanatomethyl)cyclohexane, and p-xylylene diisocyanate (m- and p-XDI), m- and p-tetramethyl-1,3- and -1,4-xylylene diisocyanate (m- and p-TMXDI), bis-(1-isocyanato-1-methylethyl)naphthalene, dimer and trimer fatty acid isocyanates such as 3,6-bis-(9-isocyanatononyl)-4,5-di-(1-heptenyl)cyclohexene (dimeryl diisocyanate) and α,α,α',α',α",α"-hexamethyl-1,3,5-mesitylene triisocyanate.

[0065] The preferred technologies are MDI, TDI, HDI and IPDI.

[0066] Suitable oligomers, polymers and derivatives of the aforementioned monomeric di- and triisocyanates are in particular derived from MDI, TDI, HDI and IPDI.Particularly suitable are commercially available types, especially HDI biuretes such as Desmodur® < N 100 and N 3200 (from Covestro), Tolonate® < HDB and HDB-LV (from Vencorex) and Duranate® < 24A-100 (from Asahi Kasei); HDI isocyanurates, such as Desmodur® < N 3300, N 3600 and N 3790 BA (all from Covestro), Tolonate® < HDT, HDT-LV and HDT-LV2 (from Vencorex), Duranate® < TPA-100 and THA-100 (from Asahi Kasei) and Coronate® < HX (from Nippon Polyurethane); HDI uretdiones such as Desmodur® < N 3400 (from Covestro); HDI-iminooxadiazindiones such as Desmodur®< XP 2410 (from Covestro); HDI-allophanates such as Desmodur®< VP LS 2102 (from Covestro); IPDI-isocyanurates, such as in solution as Desmodur®< Z 4470 (from Covestro) or in solid form as Vestanat®< T1890 / 100 (from Evonik); TDI-oligomers such as Desmodur®< IL (from Covestro); and mixed isocyanurates based on TDI / HDI, for example as Desmodur®< HL (from Covestro).Also particularly suitable are liquid forms of MDI at room temperature (so-called "modified MDI"), which represent mixtures of MDI with MDI derivatives, such as in particular MDI carbodiimides or MDI uretonides or MDI urethanes, known under trade names such as Desmodur®< CD, Desmodur®< PF, Desmodur®< PC (all from Covestro) or Isonate®< M 143 (from Dow), as well as mixtures of MDI and MDI homologs (polymeric MDI or PMDI), available under trade names such as Desmodur®< VL, Desmodur®< VL50, Desmodur®< VL R10, Desmodur®< VL R20, Desmodur®< VH 20 N and Desmodur®< VKS 20F (all from Covestro), Isonate®< M 309, Voranate®< M 229 and Voranate® < M 580 (both from Dow) or Lupranat® < M 10 R (from BASF). In practice, the aforementioned oligomeric polyisocyanates typically represent mixtures of substances with varying degrees of oligomerization and / or chemical structures. Preferably, they exhibit a medium NCO functionality of 2.1 to 4.0.

[0067] Preferably, the polyisocyanate is selected from the group consisting of MDI, TDI, HDI and IPDI and oligomers, polymers and derivatives of the aforementioned isocyanates, as well as mixtures thereof.

[0068] Preferably, the polyisocyanate contains isocyanurate, iminooxadiazin ione, uretdione, biuret, allophane, carbodiimide, uretonimine or oxadiazintrione groups.

[0069] Particularly preferred as polyisocyanates are liquid forms of MDI at room temperature. These are especially so-called polymeric MDI as well as MDI with proportions of oligomers or derivatives thereof. The MDI content (=4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers) of such liquid forms of MDI is particularly 50 to 95 wt.%, and more particularly 60 to 90 wt.%.

[0070] Particularly preferred as a polyisocyanate is polymeric MDI and MDI types that are liquid at room temperature and contain proportions of MDI carbodiimides or their adducts.

[0071] These polyisocyanates provide particularly good processing properties and especially high strengths.

[0072] The polyisocyanate of the second component may contain proportions of polyurethane polymers containing isocyanate groups. Either the second component may comprise a separately produced polyurethane polymer containing isocyanate groups, or the polyisocyanate may have been mixed with at least one polyol, in particular a polyether polyol, wherein the isocyanate groups are present in a stoichiometric excess relative to the OH groups.

[0073] In the composition according to the invention, polyisocyanate is Ipreferably present in an amount of 10 wt.% to 50 wt.%, in particular 15 wt.% to 45 wt.%, especially preferably 20 wt.% to 35 wt.%, based on the total composition.

[0074] The first component A and / or the second component B It also contains at least one metal catalyst. K for the reaction of hydroxyl and isocyanate groups, which can form thio complexes. As a metal catalyst K Therefore, all metal catalysts are suitable which can be used as crosslinking catalysts in polyurethane chemistry and which can simultaneously form thio complexes with thiols in the presence of these thiols.

[0075] The metal catalyst is preferred. K only in the first component A Included. This has the advantage of achieving better storage stability.

[0076] Suitable metal catalysts include, for example, bismuth, zinc, tin or zirconium compounds, which includes complexes and salts of these metals.

[0077] Preferably, the metal catalyst comprises K A bismuth compound, in particular a bismuth(III) compound. A bismuth compound has the advantage that, in addition to its desirable properties as a catalyst and thiocomplex former, it possesses low acute toxicity.

[0078] A variety of conventional bismuth catalysts can be used as bismuth compounds. These include, for example, bismuth carboxylates such as bismuth acetate, oleate, octoate, or neodecanoate; bismuth nitrate; bismuth halides such as bromide, chloride, iodide, and bismuth sulfide; basic bismuth carboxylates such as bismutyl neodecanoate, bismuth subgallate, or bismuth subsalicylate; and mixtures thereof.

[0079] In a preferred embodiment, the metal catalyst KA bismuth(III) complex comprising at least one 8-hydroxyquinoline-based ligand. Such complexes are described in EP 1551895. Preferably, this is a bismuth(III) carboxylate comprising one molar equivalent of an 8-hydroxyquinoline ligand.

[0080] In another preferred embodiment, the metal catalyst K A bismuth(III) complex comprising at least one 1,3-ketoamide-based ligand. Such complexes are described in EP 2791153. Preferably, this is a bismuth(III) carboxylate comprising 1 to 3 molar equivalents of a 1,3-ketoamide ligand.

[0081] The composition according to the invention further comprises between 3 and 25 wt.%, preferably between 4 and 20 wt.%, particularly preferably between 5 and 20 wt.%, based on the total composition, at least one type of microscopic hollow spheres. H.

[0082] The microscopic hollow spheresH These exhibit a compressive strength, measured according to ASTM D3102-72, of at least 10 MPa, preferably at least 15 MPa. The compressive strength can be determined using ASTM D3102-72. A detailed method for measuring preferred microscopic hollow spheres is described. H Further information based on this industry standard can be found in WO 2012 / 033810, p. 15, second paragraph.

[0083] When microscopic hollow spheres H Using materials with a compressive strength of less than 10 MPa not only impairs pumpability and density stability after pumping during the manufacture or conveying of the composition, but surprisingly also results in a material with lower strength, a rougher surface, poorer grindability, and inferior application properties. Therefore, it is essential for the invention that microscopic hollow spheres H must be used with a compressive strength of at least 10 MPa.

[0084] Furthermore, the microscopic hollow spheres exhibit H The composition has a density (bulk density) of at least 0.2 kg / L, preferably at least 0.3 kg / L, and particularly at least 0.4 kg / L. If hollow spheres with a lower density are used, the strength of the composition becomes too weak, and the hardness and surface finish of the hardened composition no longer meet the requirements for use as a filler, especially wood filler. Preferably, the microscopic hollow spheres have... HThe material has a mean particle size (volume-based median value D50) of at most 60 µm, preferably at most 45 µm, and particularly at most 30 µm, as measured by laser diffraction. Such hollow spheres produce a surface on the cured composition that is particularly well-suited for fillers and is especially easy to sand, resulting in a particularly smooth and uniform surface after grinding. When using hollow spheres with a much larger particle size, for example, over 200 µm, the surface may exhibit unevenness after grinding.

[0085] The microscopic hollow spheres H Essentially, they are spherical bodies comprising a shell and an interior gas. The gas can be, for example, air, CO₂, nitrogen, oxygen, hydrogen, a noble gas, or mixtures of these gases. The shell can be made of, for example, glass, especially borosilicate glass, silicates, or other materials.

[0086] Microscopic hollow spheres are preferred. H made of glass, in particular borosilicate glass, wherein the microscopic hollow spheres H They are preferably white or colorless. Besides ideal mechanical properties, these allow for a wide range of colorations of the polyurethane composition, which is advantageous for aesthetic reasons in visible joint fillers.

[0087] Suitable microscopic hollow spheres H Glass and its manufacture are taught, for example, in US 8,261,577 and WO 2012 / 033810.

[0088] Preferred suitable, commercially available microscopic hollow spheres H Made of glass, 3M™ Glass Bubbles are available from 3M Germany GmbH. The preferred types are S60, K37, iM16K and S28HS.

[0089] The microscopic hollow spheres H are preferably in component B before. In this case, component contains Bpreferably 6 to 50 wt.%, preferably 7 to 40 wt.%, in particular 8 to 30 wt.%, microscopic hollow spheres H, related to component B.

[0090] The composition according to the invention further comprises between 2.5 and 7.5 wt.%, preferably between 3 and 6 wt.%, based on the total composition, at least one drying agent. D, where the desiccant D is an aluminosilicate.

[0091] The desiccant DThis is particularly important for applications as a wood filler or on other moisture-containing substrates, as residual moisture, for example in the wood, can interfere with the curing of the polyurethane composition and lead to blistering or insufficient curing, especially in thin layers. Surprisingly, it was found experimentally that only aluminosilicate drying agents are suitable for the present invention. Reactive silanes or isocyanates, which are otherwise used as drying agents in polyurethane compositions, lead to a deterioration of the pot life during application and / or the sandability after curing.

[0092] It is also necessary that at least 2.5% by weight of desiccant be used. D,These additives are included in the total polyurethane composition to achieve the desired workability and sandability. An amount exceeding 7.5% by weight, based on the total composition, reduces the open time and is therefore not recommended.

[0093] Suitable as a drying agent D This includes all aluminosilicates that can be used as drying agents, such as molecular sieves or zeolites.

[0094] The desiccant is preferred D a molecular sieve with a pore size of at least 2.5 Å.

[0095] The desiccant D is preferably located in component B before. In this case, component contains B preferably 5 to 15 wt.%, preferably 8 to 14 wt.%, in particular 9 to 13 wt.%, drying agent D, related to component B.

[0096] Further preferred components include inorganic and organic fillers, such as, in particular, natural, ground or precipitated calcium carbonates, which may optionally be coated with fatty acids, especially stearic acid, barite (barytes), talcs, quartz flours, quartz sand, dolomites, wollastonites, kaolins, calcined kaolins, mica (potassium aluminum silicate), aluminum oxides, aluminum hydroxides, magnesium hydroxide, silicic acids including highly dispersed silicic acids from pyrolysis processes and their hydrophobized variants, industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver or steel, PVC powders or hollow spheres, as well as flame-retardant fillers such as hydroxides or hydrates, in particular hydroxides or hydrates of aluminum, preferably aluminum hydroxide.

[0097] The addition of fillers is advantageous in that it increases the strength of the cured polyurethane composition. Preferably, the polyurethane composition contains at least one filler selected from the group consisting of calcium carbonate, carbon black, kaolin, barite, talc, quartz flour, dolomite, wollastonite, kaolin, calcined kaolin, and mica. Ground calcium carbonate, calcined kaolin, or carbon black are particularly preferred as fillers.

[0098] It can be advantageous to use a mixture of different fillers. Combinations of ground calcium carbonates or calcined kaolins and carbon black are most preferred.

[0099] The filler content F The proportion of the composition is preferably in the range of 5 wt.% to 50 wt.%, in particular 10 wt.% to 40 wt.%, especially preferably 15 wt.% to 30 wt.%, based on the total composition.

[0100] Other components may include, in particular, solvents, plasticizers and / or extenders, pigments, rheology modifiers such as amorphous silicas, drying agents such as zeolites, adhesion promoters such as organofunctional trialkoxysilanes, stabilizers against oxidation, heat, light and UV radiation, flame retardants, and surfactants, especially wetting agents and defoamers.

[0101] The polyurethane composition preferably contains less than 0.5 wt%, and in particular less than 0.1 wt%, of carboxylic acids based on the total composition, as these can impair curing. Any carboxylate ligands introduced by the metal catalyst are not considered carboxylic acids in this context.

[0102] A preferred polyurethane composition contains a first component A, which, each relating to component A, 30 to 90 wt.%, preferably 40 to 80 wt.%, in particular 50 to 70 wt.%, polyol A1, 5 to 25 wt.%, preferably 10 to 20 wt.%, in particular 12 to 18 wt.%, Diol A2, 0.25 to 5 wt.%, preferably 1 to 3 wt.%, in particular 1.5 to 2 wt.%, of a compound T, comprising at least one thiol group, 0.05 to 2 wt.%, preferably 0.1 to 1.5 wt.%, in particular 0.3 to 1 wt.%, of a metal catalyst K, and 10 to 50 wt.%, preferably 15 to 40 wt.%, in particular 20 to 30 wt.%, fillers, and may contain other components.

[0103] A preferred polyurethane composition contains a second component B, which, each relating to component B, 30 to 80 wt.%, preferably 40 to 70 wt.%, in particular 50 to 70 wt.%, polyisocyanate I,5 to 15 wt.%, preferably 8 to 14 wt.%, in particular 9 to 13 wt.% drying agent D, 6 to 50 wt.%, preferably 7 to 40 wt.%, in particular 8 to 30 wt.%, microscopic hollow spheres H, and 0 to 40 wt.%, preferably 10 to 30 wt.%, in particular 15 to 25 wt.%, fillers, and may contain other components.

[0104] A preferred two-component polyurethane composition consists of the two aforementioned preferred components. A and B.

[0105] In all embodiments, the first and second components are advantageously formulated such that their mixing ratio in parts by weight is in the range of 5:1 to 1:5, preferably between 3:1 and 1:3, and particularly preferably between 2:1 and 1:2.

[0106] In all embodiments, the first and second components are advantageously formulated such that their mixing ratio in parts by volume is in the range of 5:1 to 1:5, preferably between 3:1 and 1:3, and particularly preferably between 2:1 and 1:2.

[0107] In the mixed polyurethane composition, the molar ratio between the number of isocyanate groups and the number of groups reactive towards isocyanates, in particular hydroxyl groups of the polyols, before curing is in the range of 0.9 : 1 - 1.4 : 1, preferably 1.05 : 1 - 1.3 : 1.

[0108] The polyurethane composition is determined immediately after mixing the components. A and BAt 23 °C, it is preferably flowable, particularly self-leveling. This means that it can be used as a self-filling compound and can completely or almost completely fill cavities. It is possible and can be advantageous for the composition to exhibit slight thixotropy. In some preferred embodiments, the composition is self-leveling after mixing.

[0109] The polyurethane composition has a specific properties immediately after mixing the components. A and B preferably a viscosity, measured at 20°C on a plate-plate viscometer with plate spacing of 1 mm and plate diameter of 25 mm, of < 5000 Pa·s, preferably < 4000 Pa·s, at a shear rate of 0.01 s⁻¹ and < 500 Pa·s, preferably < 200 Pa·s, at a shear rate of 1 s⁻¹ and < 50 Pa·s, preferably < 30 Pa·s, at a shear rate of 10 s⁻¹.

[0110] The viscosity can be adjusted through formulation measures, for example the selection of polyols and / or fillers and the use of low-viscosity additives such as plasticizers, through routine tests.

[0111] The two components are manufactured separately and preferably in the absence of moisture. Both components are typically stored in separate containers. The other components of the polyurethane composition can be present as part of either the first or the second component, with any additional components reactive towards isocyanate groups preferably being part of the first component. Suitable containers for storing each component include, in particular, a drum, pail, bag, bucket, can, cartridge, or tube. Both components are stable for storage, meaning they can be kept for several months up to a year or longer before use without any significant change in their respective properties relevant to their application.

[0112] The two components are stored separately before the composition is mixed and only combined at or immediately before use. They are advantageously contained in a package consisting of two separate compartments.

[0113] In another aspect, the invention comprises a package consisting of a package with two separate chambers, each containing the first component and the second component of the composition, respectively.

[0114] Mixing is typically carried out using static or dynamic mixers. During mixing, it is important to ensure that the two components are mixed as homogeneously as possible. If the two components are not mixed completely, local deviations from the advantageous mixing ratio can occur, which can result in a deterioration of the mechanical properties.

[0115] Upon contact of the first component with the second component, after the catalyst's latency period, the reaction with the thiols of the compound begins. T, The curing process occurs through a chemical reaction. In this reaction, the hydroxyl groups and any other substances reactive towards isocyanate groups react with the isocyanate groups. Excess isocyanate groups react primarily with moisture. As a result of these reactions, the polyurethane composition cures into a solid material. This process is also known as cross-linking.

[0116] Another object of the invention is therefore also a cured polyurethane composition obtained from the curing of the polyurethane composition as described in the present document.

[0117] Therefore, the described polyurethane composition can be advantageously used as a filler, in particular as a filler for filling gaps, cavities, holes, cracks and joints, especially for wood.

[0118] The polyurethane composition is further preferably used as a filler, particularly as a wood filler. In another aspect, the invention therefore encompasses the use of a two-component polyurethane composition as a filler, especially as a filler for smoothing the surface of wood.

[0119] In another aspect, the invention therefore comprises a method for smoothing a surface by filling cavities, cracks, holes and crevices in a substrate, in particular a wood substrate, comprising the steps a) Mixing the first component A and the second component Ba) a two-component polyurethane composition as described above; b) filling the cavities, cracks, holes, or crevices on the surface of the substrate with the mixed polyurethane composition within its pot life; c) optionally pressing the polyurethane composition applied in step b) onto the substrate and / or into the cavities, cracks, holes, or crevices on the surface of the substrate using a preferably heated roller or press; d) curing of the filled, mixed polyurethane composition in the cavities, cracks, holes, or crevices on the surface of the substrate; e) smoothing of the filled substrate surface by grinding, abrasion, or sanding.

[0120] Step c) is optional, but preferred, for example, for processing larger wooden substrates in industrial processes. This allows the filling or smoothing of cavities, cracks, holes, or gaps on the substrate's surface to be carried out even more efficiently, and the use of a heated roller or press has the additional advantage of allowing the composition to harden even faster, thus enabling even shorter cycle times.

[0121] Suitable substrates for these processes include, in particular: Glass, glass ceramics, glass mineral fiber mats; metals and alloys, such as aluminum, iron, steel and non-ferrous metals, as well as surface-treated metals and alloys, such as galvanized or chrome-plated metals; coated and painted substrates, such as powder-coated metals or alloys and painted sheets; plastics, such as polyvinyl chloride (rigid and flexible PVC), acrylonitrile butadiene styrene copolymers (ABS), polycarbonate (PC), polyamide (PA), polymethyl methacrylate (PMMA), polyesters, epoxy resins, in particular epoxy-based thermosets, polyurethanes (PUR), polyoxymethylene (POM), polyolefins (PO), polyethylene (PE) or polypropylene (PP), ethylene / propylene copolymers (EPM) and ethylene / propylene / diene terpolymers (EPDM), wherein the plastics may preferably be surface-treated by plasma, corona or flame; Fiber-reinforced plastics, such as carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GFRP) and sheet moulding compounds (SMC);Wood, including natural wood or wood treated with resins, for example phenolic, melamine or epoxy resins, bonded wood-based materials, resin-textile composites and other so-called polymer composites; as well as concrete, asphalt, mortar, bricks, gypsum and natural stones such as granite, limestone and sandstone or marble.

[0122] Suitable substrates include concrete, natural stone, plastics, wood, glass, ceramics, and fiber-reinforced plastics, especially wood and fiber-reinforced plastics. The most suitable and preferred substrates are wood or wood-based materials such as wood treated with resins (e.g., phenolic, melamine, or epoxy resins), bonded wood-based materials, resin-textile composites, and other so-called wood-polymer composites.

[0123] After application of the polyurethane composition according to the invention using the above-mentioned method, it hardens very quickly to form a high-strength, hard-elastic mass with a Shore D hardness of at least 60 and a homogeneous, dry surface.

[0124] A significant advantage of the polyurethane composition according to the invention is a sufficiently long pot life, which enables trouble-free application, followed by exceptionally rapid curing and sandability. This allows not only for fillings with exceptionally fast cycle and processing times, but also with exceptionally good mechanical properties.

[0125] The cycle time, especially in automated filling processes, can be further increased by heating the applied polyurethane compound, for example, using a heated production line or a heated roller or press. The pressure applied to the polyurethane compound also improves the filling of narrow cavities, cracks, or similar features. Heating further accelerates the curing reaction; temperatures of 40°C to 60°C or higher already accelerate curing without thermally affecting the substrate.

[0126] Once cured, the composition can be easily sanded, for example by sandblasting or other suitable grinding methods known to experts for all substrates. In principle, the composition can be sanded using any grinding technique. The substrate, preferably wood, can be removed with the same grinding process, resulting in a smooth surface with homogeneous compressive and tensile strength.

[0127] For optical or aesthetic needs, the polyurethane composition according to the invention can also be colored, for example with pigments or dyes.

[0128] In another aspect, the invention therefore also includes an article whose surface has been smoothed according to the method described above. Examples

[0129] Table 1: Substances used Voranol CP 4755 Voranol®< CP 4755 (Dow Chemical); Polyethertriol, CAS No. 9082-00-2; Mw: 5000 g / mol; OH number: 35 mg KOH / g Lupranol 3422 Lupranol® < 3422 (BASF); High-functionality polyether polyol; OH number: 490 mg KOH / g 1,5-Pentanediol (Sigma Aldrich) Thiocure GDMP Thiocure®<GDMP (Bruno Bock Thiochemicals); Glycol di(3-mercaptopropionate) Desmodur CD-S Desmodur® < CD-S (Covestro); modified diphenylmethane-4,4'-diisocyanate (MDI); NCO content: 29.5 wt.% Glass Bubbles iM16K 3M™ Glass Bubbles iM16K (3M); White hollow spheres made of borosilicate glass; Density: 0.46 kg / m³; Compressive strength (ASTM D3102-72): 110.3 MPa (microscopic hollow spheres) H ) Sylosiv A3 Sylosiv® < A3 (WR: Grace); micronized molecular sieve (aluminosilicate); pore size: 3 Å (desiccant) D ) Monarch 570 Monarch® < 570 (Cabot Corp.); Russ (filler) Whitetex Satintone® < W (Whitetex) (BASF); calcined kaolin (filler) HDK H18 HDK ®< H18 (Wacker); hydrophobic pyrogenic silica (filler) Omyacarb 5-GU Omyacarb® < 5-GU (Omya); ground, natural chalk (filler) Bi-Cat. (2.68 mmol Bi / g) 35 wt% Coscat 83 (organobismuth catalyst; Coscat ®< 83 (Vertellus Specialties Inc.)) in plasticizer with 1 molar equivalent of 8-hydroxyquinoline (based on Bi) Sn-Cat. Dibutyltin dilaurate (Sigma Aldrich) Production of polyurethane compositions

[0130] For each composition, the ingredients listed in Table 2, in the specified quantities (in parts by weight) of the first component A, were processed into a homogeneous paste using a vacuum dissolver under exclusion of moisture and stored. Similarly, the ingredients listed in the tables for the second component B were processed and stored. Subsequently, the two components were processed into a homogeneous paste using a SpeedMixer® (DAC 150 FV, Hauschild) for 30 seconds and immediately tested as follows: Examination of the example compositions

[0131] The ShoreD-hardness was determined according to DIN 53505 on test specimens cured for 7 days at 23°C and 50% relative humidity (standard climate) with a layer thickness of 4 mm. The exact storage time (curing time) until each measurement is given in Table 3. Waiting time until grinding is possible was determined by measuring the time in minutes until the surface of test specimens prepared according to ASTM D4060-19 from the mixed two-component composition under test had dried sufficiently through curing under standard climate conditions to allow them to be sanded. Sandability after curing The quality was assessed by visually and tactilely evaluating the grinding result. Smooth, dry, sufficiently hard, and homogeneously ground surfaces were rated as "very good." For less than ideal results (observed inhomogeneities or insufficient hardness), the assessment was accordingly rated as "good," "poor," or "very poor."

[0132] The Potting time The viscosity was measured in a viscometer as the time until the viscosity reached 500 Pa·s after mixing the two components. The viscosity was measured on a plate-plate rheometer MCR 302 (Anton Paar) with a plate diameter of 25 mm and a plate spacing of 1 mm at a frequency of 0.1 s⁻¹ and a temperature of 20°C. For this purpose, the two components were first mixed for 30 seconds in a speed mixer (Hauschild) and immediately applied to the plates for measurement. Table C-1 2: Sample compositions produced up to C-4. Example C-1 (Ref.) C-2 (Ref.) C-3 C-4 (Ref.) First component A (Quantities in parts by weight) Voranol CP 4755 50.5 50.5 50.5 50.5 Lupranol 3422 3.0 3.0 3.0 3.0 1,5-Pentanediol 17.0 17.0 17.0 17.0 Thiocure GDMP 2.4 2.4 2.4 2.4 Bi-Cat. (2.68 mmol Bi / g) 0.6 0.6 0.6 0.6 HDK H18 6.0 6.0 6.0 6.0 Omyacarb 5-GU 20.5 20.5 20.5 20.5 TOTAL 100 100 100 100 Second component B (Quantities in parts by weight) Desmodur CD-S 60.0 60.0 60.0 60.0 HDK H18 6.0 6.0 6.0 6.0 Monarch 570 4.0 4.0 4.0 4.0 Whitetex 17.5 20.0 7.5 30.0 Glass Bubbles iM16K 12.5 - 12.5 - Sylosiv A3 - 10.0 10.0 - TOTAL 100 100 100 100 mixture A and B Mixing ratio (weight) AWAY 1 : 1 1 : 1 1 : 1 1 : 1 Table 3: Properties of the example compositions and suitability as wood filler. composition C-1 (Ref.) C-2 (Ref.) C-3 C-4 (Ref.) Pot life (processing time) Shortened Extended Optimal and adjustable Optimal and adjustable Surface after curing Hard, sticky in thin layers Soft and dry Hard and dry Soft, sticky in thin layers Sandability after curing Good Bad Very good Very bad Waiting time until grinding is possible 35 min 23 min 23 min 35 min Shore D hardness 62 40 60 25

[0133] Table 3 shows that only composition C-3 exhibits sufficiently high hardness, a sufficiently long and adjustable pot life, and a sufficiently short waiting time before it can be sanded. Furthermore, it is very easy to sand. While composition C-4 is very easy to apply (long, adjustable pot life), its sandability and waiting time before it can be sanded are poor, and the material is too soft after curing.

[0134] Composition C-1 is easy to grind and exhibits good hardness. However, the waiting time until it can be ground is too long, and the application is hampered by a shortened pot life.

[0135] Composition C-2 exhibits an unfavorable extension of the pot life, which impairs cycle times, and the composition is too soft and difficult to grind after hardening. Comparative experiments with other drying agents and other microscopic hollow spheres

[0136] A number of compositions were produced that demonstrated the influence of the drying agents according to the invention. D and microscopic hollow cones H They should show. Composition C-5 (Ref.)

[0137] Composition C-5 corresponds to composition C-3 as described above, with the sole difference being that instead of Sylosiv A3 as a drying agent, 10 parts by weight of Dynasylan®< A (tetraethoxysilane; from Evonik) are used in component B were used. Compared to composition C-3, the pot life of C-5 was reduced, and the waiting time until it could be ground increased to 30 minutes. Composition C-6 (Ref.)

[0138] Composition C-6 corresponds to composition C-3 as described above, with the sole difference being that instead of Sylosiv A3 as a drying agent, 10 parts by weight of calcium oxide are used in component Bwere used. Compared to composition C-3, the pot life of C-6 was drastically reduced and the material was no longer processable. Composition C-7 (Ref.)

[0139] Composition C-7 is identical to composition C-3 as described above, with the sole difference being that instead of iM16K glass bubbles, 12.5 parts by weight of Omyasphere® < 220 (density: 0.27 kg / L; compressive strength (ASTM D3102-72): 2.5 MPa; from Omya) are used as microscopic hollow spheres in component C-7. B were used. Compared to composition C-3, composition C-7 showed a rough, poorly sandable surface after curing.

Claims

1. Polyurethane composition consisting of a first component A and a second component B; wherein - the first component A comprises - at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a mean molecular weight (number average) Mn, measured by means of GPC against polystyrene, in the range from > 500 to 15'000 g / mol, and - at least one polyol A2 having an OH functionality in the range from 2 to 6 and a mean molecular weight (number average) Mn, measured by means of GPC against polystyrene, in the range from 50 to 500 g / mol, and - at least one compound T that has at least one thiol group; and - the second component B comprises - at least one polyisocyanate I; wherein one of the components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes; and wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 5 : 1 and 100 : 1; and wherein the molar ratio of all NCO groups in the polyisocyanates I to all OH groups in the polyols A1 and A2 = 0.9 : 1 - 1.4 : 1, especially 1.05 : 1 - 1.3 : 1; and wherein the composition, in at least one of the two components, contains between 3% and 25% by weight, based on the overall composition, of at least one type of hollow microspheres H, where the hollow microspheres H have a compressive strength measured to ASTM D3102-72 of at least 10 MPa and a density of at least 0.2 kg / L; and wherein the composition, in at least one of the two components, contains between 2.5% and 7.5% by weight, based on the overall composition, of at least one desiccant D, where the desiccant D is an aluminosilicate.

2. Polyurethane composition according to Claim 1, characterized in that the metal catalyst K comprises a bismuth(III) compound, preferably a bismuth(III) carboxylate.

3. Polyurethane composition according to either of Claims 1 and 2, characterized in that the diol A2 is selected from the group consisting of butane-1,3-diol, butane-1,4-diol, butane-2,3-diol, 2-methylpropane-1,3-diol, pentane-1,2-diol, pentane-2,4-diol, 2-methylbutane-1,4-diol, 2,2-dimethylpropane-1,3-diol, hexane-1,2-diol, 3-methylpentane-1,5-diol, octane-1,2-diol, octane-3,6-diol, 2-ethylhexane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, 2-butyl-2-ethylpropane-1,3-diol, 2,7-dimethyloctane-3,6-diol, cyclohexane-1,4-diol, cyclohexane-1,3-dimethanol and cyclohexane-1,4-dimethanol.

4. Polyurethane composition according to any of the preceding claims, characterized in that the at least one compound T comprises a polythiol compound having 2 to 6 thiol groups, or a mercaptosilane.

5. Polyurethane composition according to Claim 4, characterized in that the at least one compound T is selected from the group consisting of ethylene glycol di(3-mercaptopropionate), 1,8-dimercapto-3,6-dioxaoctane, ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), and 3-mercaptopropyltrimethoxysilane.

6. Polyurethane composition according to any of the preceding claims, characterized in that the metal catalyst K is present in the first component A.

7. Polyurethane composition according to any of the preceding claims, characterized in that the polyol A1 comprises at least one polyether polyol.

8. Polyurethane composition according to any of the preceding claims, characterized in that the polyisocyanate I is a form of diphenylmethane 4,4'-, 2,4'- or 2,2'-diisocyanate that is liquid at room temperature or any desired mixtures of these isomers (MDI) in the form of polymeric MDI or MDI containing proportions of oligomers or derivatives, in particular carbodiimides.

9. Polyurethane composition according to any of the preceding claims, characterized in that the second component B comprises a polyurethane polymer containing isocyanate groups.

10. Polyurethane composition according to any of the preceding claims, characterized in that the hollow microspheres H comprise hollow glass beads that are preferably white or colourless.

11. Polyurethane composition according to any of the preceding claims, characterized in that the desiccant D comprises a molecular sieve having a pore size of at least 2.5 Å.

12. Polyurethane composition according to any of the preceding claims, characterized in that the mixing ratio in parts by volume between the first and second components is in the range from 5:1 to 1:5, especially 3:1 to 1:3, more preferably 2:1 to 1:2.

13. Use of a polyurethane composition according to any of Claims 1 to 12 as filling compound, especially as filling compound for smoothing of a wood surface.

14. Method of smoothing a surface by filling cavities, fissures, holes and gaps in a substrate, especially a wood substrate, comprising the steps of a) mixing the first component A and second component B of a two-component polyurethane composition according to any of Claims 1 to 10, b) filling the cavities, fissures, holes or gaps to be filled on the surface of the substrate with the mixed polyurethane composition within the pot life thereof; c) optionally pressing the polyurethane composition applied in step b) onto the substrate and / or into the cavities, fissures, holes or gaps on the surface of the substrate by means of a preferably heated roller or press; d) curing the filled mixed polyurethane composition in the cavities, fissures, holes or gaps on the surface of the substrate; e) smoothing the filled substrate surface by means of grinding, abrasion or sanding.