COMPOSITION FOR THE PRODUCTION OF SILICONE RUBBER COMPOUNDS

Description

[0001] The present invention relates to a catalyst for the crosslinking of silicone rubber compounds. In particular, the present invention provides a composition for the production of a silicone rubber compound, wherein the composition comprises this catalyst. Furthermore, the present invention provides a use of the catalyst for crosslinking a silicone rubber compound, as well as a use of the composition according to the invention for the production of a silicone rubber compound, in particular for use as a sealant, adhesive, or coating agent. Background of the invention

[0002] Cold-curing silicone rubber compounds, also known as RTV (room temperature curing) silicone rubber compounds, have long been recognized as custom-made materials with elastic properties. They are commonly used as sealants or adhesives for glass, porcelain, ceramics, stone, plastics, metals, wood, etc., e.g., as joint or sealant compounds in construction and plumbing, or as coating materials, e.g., in the electronics industry (Römpp Chemie Lexikon, CD-ROM, Version 2.0, ed. J. Falbe, Thieme-Verlag, Stuttgart 1999, and Ullmanns Enzyklopädie der Technischen Chemie, 4th edition, ed. E. Bartholome, Verlag Chemie, Weinheim 1982, Volume 21, pp. 511 ff.).In particular, one-component RTV silicone rubber compounds (RTV-1) are used; these are, for example, plastically moldable mixtures of α,ω-dihydroxypolyorganosiloxanes and suitable crosslinkers (also referred to in the field as crosslinking agents or hardeners) that can be stored in the absence of moisture (e.g., in a suitable cartridge) but polymerize at room temperature under the influence of water or atmospheric humidity. Polymerization generally occurs through the condensation of SiOH groups with suitable hydrolyzable SiX groups of the crosslinkers.

[0003] Depending on the desired chemical and physical properties of the polymerization product, such as the desired degree of crosslinking, solvent resistance, etc., various polyfunctional crosslinkers (hardeners), e.g., tri- and / or tetrafunctional, are typically used together with various difunctional or multifunctional polyorganosiloxane compounds. α,ω-Dihydroxypolyorganosiloxanes are particularly frequently used as difunctional polyorganosiloxane compounds.

[0004] RTV-1 silicone rubber compounds are classified into acidic (HX = acids, such as acetic acid, etc.), basic (e.g., HX = amines, etc.), and neutral (e.g., HX = alcohols, oximes, etc.) systems based on the leaving groups (HX) released during the hydrolysis of the crosslinker. Currently available RTV-1 silicone rubber compounds generally contain acidic crosslinking systems that hydrolyze to release acetic acid, or neutral crosslinking systems that hydrolyze to release oxime compounds, such as butan-2-one oxime (or methyl ethyl ketoxime, MEKO).

[0005] For the desired broad range of applications, silicone rubber compounds should adhere to as many surfaces as possible, such as wood, painted wood, varnished wood, metals like steel, aluminum, powder-coated aluminum, glass, plastics like polyvinyl chloride (PVC), polyamide, concrete, etc. Furthermore, the silicone rubber compounds should be shelf-stable in a standard cartridge, meaning their properties should not change depending on the storage time, ideally both in a sealed cartridge after filling and in a cartridge that has already been opened and / or partially emptied. Finally, the polymerization product should be transparent or clear after the silicone rubber compound has fully cured (cross-linked).

[0006] In addition to the appropriate selection of the actual polymer components, such as crosslinkers and polyorganosiloxane, a catalyst is usually added to control the polymerization rate and / or degree of polymerization. This catalyst influences important product properties of the silicone rubber compounds, such as skin formation time (i.e., the time it takes for a complete initial skin to form on an applied compound), tack-free time (i.e., the time after which the compound is no longer tacky), curing time (i.e., the time it takes for polymerization to be complete), etc. For example, the required properties for commercial silicone sealants are a skin formation time of 5 to 15 minutes, a tack-free time of 15 to 120 minutes, and a curing time of a maximum of 7 days for an application with a height of 10 mm.Further information on skin formation time, tack time and curing time can be found, for example, in the "Practical Handbook of Sealants" (3rd edition 1990), published by the German Sealants Industry Association (IVD).

[0007] Previously, a metal-organic catalyst, such as those commonly used for condensation-curing polysiloxanes, was used as a catalyst for silicone rubber compounds, in particular a catalyst based on an organotin compound, such as an alkyltin carboxylate, especially dibutyltin dilaurate and dioctyltin dilaurate. However, such organotin compounds exhibit toxicological properties that have led to restrictions on their use in commercially available products (see EU Directive 76 / 769 / EEC of 28 May 2009).

[0008] Alternatively, in the prior art, a different catalyst, which does not include an organotin compound, has been used for the crosslinking of polysiloxanes.

[0009] For example, a titanium-based compound can be used as a catalyst, as described in EP 1 230 298 A1 and EP 2 290 007 A1. However, it is known that a titanium-based catalyst can lead to yellowing and / or surface stickiness in the products, as well as exhibiting a slow vulcanization rate, poor storage stability, and incompatibility with common aminosilane-based adhesion promoters.

[0010] Furthermore, EP 1 230 298 A1 describes a catalyst based on amines and metal salts of tin, zinc, iron, lead, barium, and zirconium, as well as on tin chelates. This catalyst leads to products with a slight yellow coloration, but according to EP 2 290 007 A1, it is a slow catalyst.

[0011] Therefore, EP 2 290 007 A1 proposes a catalyst based on metal compounds of groups I and II, i.e., Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Cu, Ag, Au, Zn, Cd, and Hg, in the form of pure carboxylates, which, upon addition of an acidic co-catalyst in the form of an organic or inorganic acid, yield a product with an acceptable curing profile. EP 2 290 007 A1 describes the use of this catalyst in silicone rubber compounds with crosslinkers (hardeners) that release acidic (acetic acid) or neutral (alcohols or MEKO) compounds upon hydrolysis, particularly using a catalyst consisting of a Li carboxylate or an Sr carboxylate.

[0012] The use of a catalyst based on Li, Na, K, Mg, Ca, Sr compounds without the additional simultaneous use of an acidic co-catalyst is described in EP 2 280 041 A1. It is further described therein that, in particular, the use of octasolitic lithium or octasolitic strontium in combination with alkoxy, acetoxy, or oximo-RTV-1 yields products with the desired properties. Object of the invention

[0013] The inventors of the present invention have found, however, that it is not possible to use the known tin-free catalysts described above in conjunction with known silicone rubber compounds optimized using catalysts based on organotin compounds while retaining the optimized product properties of the silicone rubber compounds. Simply replacing a tin-based catalyst with one of the known tin-free catalysts does not yield a product (RTV-1) with the desired properties. It was found that the sealant compounds produced with the known tin-free catalysts exhibit poor adhesion and insufficient storage stability. Furthermore, inadequate curing was observed, particularly with acetate crosslinkers.

[0014] It is therefore an object of the invention to provide an improved catalyst for silicone rubber compounds which is not only tin-free, but also maintains all the properties desired for RTV-1 in product compositions that have been optimized using catalysts based on organotin compounds.

[0015] The object of the invention is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims. Brief description of the invention

[0016] To solve the problem described above, the present invention provides: a catalyst for the crosslinking of silicone rubber compounds; a composition for producing a silicone rubber compound, wherein the composition comprises this catalyst; a use of the catalyst for crosslinking a silicone rubber compound; and a use of the composition according to the invention for producing a silicone rubber compound, in particular for use as a sealant, adhesive or coating agent.

[0017] Through extensive studies, the inventors of the present invention have surprisingly discovered that the problem of the invention can be solved by using a mixture of at least two tin-free compounds with catalytic activity as the catalyst in a silicone rubber compound, instead of a single tin-free compound as in the prior art. Such a mixture of individual catalysts has not been used before, but in addition to its toxicological advantages, it offers the further advantage of being easily adapted to existing compositions. Detailed description of the invention

[0018] The present invention provides a composition comprising at least one organosilicone compound, at least one crosslinking agent, and a catalyst. The composition according to the invention can be used to produce a silicone rubber compound.

[0019] The present invention uses a catalyst for the crosslinking of silicone rubber compounds. The catalyst, which is contained in the composition according to the invention or is used in the use according to the invention, comprises a metal salt of a carboxylic acid, which is a zinc salt of one or more branched saturated carboxylic acids with six to nineteen carbon atoms, and a metal salt of a carboxylic acid, which is selected from a bismuth salt, a calcium salt, a potassium salt, a lithium salt, a magnesium salt and a sodium salt, each of one or more branched saturated carboxylic acids with six to nineteen carbon atoms.

[0020] The catalyst contained in the composition according to the invention, or used in the application according to the invention, is thus a mixture of at least two different compounds, preferably of two to twenty different compounds, more preferably of two to eight different compounds, and particularly preferably of two or three different compounds.

[0021] The catalyst most preferably comprises exactly two different metal salts of carboxylic acids. These are preferably two metal salts of different metals. The two metal salts of the carboxylic acids in the catalyst are most preferably present in a ratio of the number of metal atoms (numerical ratio) of 2:1 to 1:2, more preferably 1.3:1 to 1:1.3, more preferably 5:4 to 4:5, more preferably 1.2:1 to 1:1.2, even more preferably 1.1:1 to 1:1.1, and most preferably approximately 1:1.

[0022] Each of the compounds included in the catalyst is a metal salt of one or more carboxylic acids.

[0023] The term "carboxylic acid" refers to an organic compound, preferably a hydrocarbon, with at least one carboxyl group (-COOH). A carboxylic acid preferably comprises a hydrocarbon with 1 to 25 carbon atoms, preferably 5 to 20 carbon atoms, and particularly preferably 6 to 19 carbon atoms. The hydrocarbon of the carboxylic acid can be saturated, unsaturated, or aromatic, or contain corresponding bonds. The hydrocarbon of the carboxylic acid can comprise a straight-chain or branched hydrocarbon chain, and / or rings of hydrocarbons and / or suitable heteroatoms. Preferably, the carboxylic acid comprises a saturated hydrocarbon (alkane) with a straight-chain or branched hydrocarbon chain. The carboxylic acid can comprise one or more carboxyl groups, preferably one, two, or three. Monocarboxylic acids and dicarboxylic acids are particularly preferred.In particularly preferred dicarboxylic acids, the two carboxyl groups are bonded to adjacent carbon atoms. Monocarboxylic acids are especially preferred.

[0024] One particularly preferred carboxylic acid is 2-ethylhexanoic acid.

[0025] A "metal salt of a carboxylic acid" within the meaning of this invention is a compound comprising at least one carboxylate anion and at least one metal cation. The carboxylate anion is defined as the anion formed by deprotonation of a carboxyl group of a carboxylic acid. Thus, a carboxylate anion within the meaning of this invention is an organic compound, preferably a hydrocarbon, with at least one carboxylate group -COO-<, which can be formed from any of the carboxylic acids described above. The metal cation is a cation of the respective metal, preferably in an oxidation state stable under the conditions of application. Accordingly, the metal cation preferably has a positive charge of +1 to +4, more preferably +1, +2, or +3. Examples of a monovalent metal cation are K+, Li+, and Na+.Examples of a divalent metal cation (charge +2) are Ca²⁺, Mg²⁺, and Zn²⁺, and an example of a trivalent metal cation (charge +3) is Bi³⁺. For a charge-neutral compound, the charge of the metal cation can be balanced by the number of monovalent negatively charged carboxylate groups, so that the ratio of metal cation to carboxylate group in the metal salt can be 1:1, 1:2, 1:3, etc., up to the maximum charge, depending on the charge of the metal cation. For example, in the case of monocarboxylic acids, the ratio of metal to carboxylic acid is 1:1 for monovalent metal cations, 1:2 for divalent metal cations, 1:3 for trivalent metal cations, etc. In dicarboxylic acids with two carboxylate groups, the ratio is adjusted accordingly, so that, for example, in the case of divalent metal cations, the ratio of metal to dicarboxylate can be 1:1, etc.The metal salt can contain carboxylate anions of a single carboxylic acid, or carboxylate anions of several different carboxylic acids. For example, the metal salt of a divalent metal cation can contain a carboxylate anion of a first carboxylic acid (R1< -COO-< ) and a carboxylate anion of a different second carboxylic acid (R2< -COO-< ).

[0026] In addition to metal cations and carboxylate anion(s), the metal salt of a carboxylic acid may also include other components, such as other anions that are not carboxylate anions, e.g., halide anions, nitrate anions, sulfate anions, or the like, or neutral molecules, e.g., solvate molecules, or the like.

[0027] Particularly preferably, the metal salts of the carboxylic acids in the catalyst are comprised in a ratio of the number of the respective metal atoms (numerical ratio) of 2:1 to 1:2, further preferably of 1.3:1 to 1:1.3, further preferably of 5:4 to 4:5, further preferably of 1.2:1 to 1:1.2, even more preferably of 1.1:1 to 1:1.1, and particularly preferably of about 1:1.

[0028] It was surprisingly found that a catalyst for the crosslinking of silicone rubber compounds, comprising at least two different metal salts of carboxylic acids as defined above, imparts particularly advantageous product properties to the production of silicone rubber compounds, especially RTV-1 silicone rubber compounds. The catalyst can be advantageously used without the need for a co-catalyst.

[0029] It was found that products with particularly advantageous properties can be provided in this way. Anions of saturated carboxylic acids with six to ten carbon atoms are further preferred. Anions of a carboxylic acid with a branched hydrocarbon chain of eight carbon atoms are particularly preferred. A particularly preferred embodiment of a carboxylic acid is 2-ethylhexanoic acid.

[0030] The catalyst contained in the composition according to the invention, or used in the use according to the invention, comprises a metal salt of a carboxylic acid, which is a zinc salt of one or more branched saturated carboxylic acids having six to nineteen carbon atoms, and a metal salt of a carboxylic acid, which is selected from a bismuth salt, a calcium salt, a potassium salt, a lithium salt, a magnesium salt and a sodium salt, each of one or more branched saturated carboxylic acids having six to nineteen carbon atoms.

[0031] Particularly preferably, the metal salts of the carboxylic acids in the catalyst are comprised in a ratio of the number of zinc atoms of the zinc salt of a carboxylic acid to the number of metal atoms of the metal salt of a carboxylic acid (numerical ratio) of 2:1 to 1:2, further preferably of 1.3:1 to 1:1.3, further preferably of 5:4 to 4:5, further preferably of 1.2:1 to 1:1.2, even more preferably of 1.1:1 to 1:1.1, and particularly preferably of about 1:1.

[0032] It was found that this could lead to the provision of products with particularly advantageous properties.

[0033] More preferably, the catalyst contained in the composition according to the invention, or used in the use according to the invention, comprises a metal salt of a carboxylic acid, which is a zinc salt of one or more branched saturated carboxylic acids having six to nineteen carbon atoms, and a metal salt of a carboxylic acid, which is selected from a bismuth salt and a calcium salt, respectively, of one or more branched saturated carboxylic acids having six to nineteen carbon atoms.

[0034] Particularly preferably, the catalyst comprises a zinc salt of a branched carboxylic acid with six to ten carbon atoms in combination with a bismuth salt of a branched carboxylic acid with six to ten carbon atoms and / or a calcium salt of a branched carboxylic acid with six to ten carbon atoms. In a particularly preferred embodiment, the catalyst comprises a zinc salt of a branched carboxylic acid with eight carbon atoms in combination with a bismuth salt of a branched carboxylic acid with eight carbon atoms and / or a calcium salt of a branched carboxylic acid with eight carbon atoms.

[0035] The catalyst contained in the composition according to the invention, or used in the invention, particularly preferably comprises zinc bis(2-ethylhexanoate). It has been found that products with particularly advantageous properties can be obtained using zinc bis(2-ethylhexanoate).

[0036] The catalyst contained in the composition according to the invention, or used in the invention, particularly preferably comprises bismuth tris(2-ethylhexanoate). It has been found that products with particularly advantageous properties can be obtained using bismuth tris(2-ethylhexanoate).

[0037] The catalyst contained in the composition according to the invention, or used in the invention, particularly preferably comprises calcium bis(2-ethylhexanoate). It has been found that products with particularly advantageous properties can be obtained using calcium bis(2-ethylhexanoate).

[0038] The catalyst contained in the composition according to the invention, or used in the invention, particularly preferably comprises sodium (2-ethylhexanoate). It has been found that products with particularly advantageous properties can be obtained using sodium (2-ethylhexanoate).

[0039] The catalyst contained in the composition according to the invention, or used in the application according to the invention, particularly preferably comprises a mixture of calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). A catalyst comprising calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) is particularly preferably used together with an oxime crosslinking agent.

[0040] The catalyst most preferably comprises a mixture of calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) in a ratio of 1:1 to 1:3 (weight ratio), more preferably in a ratio of 1:1 to 1:2, and most preferably 4:5.

[0041] This corresponds to a numerical ratio of calcium bis(2-ethylhexanoate) to zinc bis(2-ethylhexanoate) of about 1.1:1 to 1:2.8, preferably of about 1.1:1 to 1:1.9, and particularly preferably of about 1:1.2.

[0042] It has been found that products with particularly advantageous properties can be provided using a catalyst comprising calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of 1:1 to 1:3 (weight ratio).

[0043] It has been found that products with particularly advantageous properties can be provided with a catalyst comprising calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of approximately 1:1, in particular of about 1.3:1 to 1:1.3 (numerical ratios).

[0044] The catalyst contained in the composition according to the invention, or used in the application according to the invention, particularly preferably comprises a mixture of sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate). A catalyst comprising sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate) is particularly preferably used together with an oxime crosslinking agent.

[0045] The catalyst most preferably comprises a mixture of sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate) in a ratio of 4:1 to 1:4 (weight ratio), more preferably in a ratio of 1:1 to 1:3, and most preferably 1:2.

[0046] This corresponds to a numerical ratio of sodium (2-ethylhexanoate) to zinc bis(2-ethylhexanoate) of about 8.5:1 to 1:1.9, preferably of about 2.1:1 to 1:1.4, and particularly preferably of about 1:1.1.

[0047] It has been found that products with particularly advantageous properties can be provided using a catalyst comprising sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of 4:1 to 1:4 (weight ratio).

[0048] It has been found that products with particularly advantageous properties can be provided using a catalyst comprising sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of approximately 1:1, in particular of about 1.3:1 to 1:1.3 (numerical ratios).

[0049] The catalyst contained in the composition according to the invention, or used in the application according to the invention, particularly preferably comprises a mixture of bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). A catalyst comprising bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) is particularly preferably used together with an acetate crosslinker and / or an alkoxy crosslinker.

[0050] The catalyst most preferably comprises a mixture of bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) in a ratio of 4:1 to 1:4 (weight ratio), more preferably in a ratio of 2:1 to 3:1, and most preferably in a ratio of 7:3.

[0051] This corresponds to a numerical ratio of bismuth tris(2-ethylhexanoate) to zinc bis(2-ethylhexanoate) of about 2.2:1 to 1:7.3, preferably of about 1.1:1 to 1:1.7, and particularly preferably of about 1.3:1.

[0052] It has been found that products with particularly advantageous properties can be provided using a catalyst comprising bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of 4:1 to 1:4 (weight ratio).

[0053] It has been found that products with particularly advantageous properties can be provided with a catalyst comprising bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a ratio of approximately 1:1, in particular of about 1.3:1 to 1:1.3 (numerical ratios).

[0054] A composition according to the invention comprises at least one organosilicon compound, preferably two, three, or more different organosilicon compounds. An organosilicon compound contained in the composition is preferably an oligomeric or polymeric compound. The polymeric organosilicon compound is preferably a difunctional polyorganosiloxane compound, particularly preferably an α,ω-dihydroxyl-terminated polyorganosiloxane. α,ω-dihydroxyl-terminated polydiorganosiloxanes are especially preferred, in particular α,ω-dihydroxyl-terminated polydialkylsiloxanes, α,ω-dihydroxyl-terminated polydialkenylsiloxanes, or α,ω-dihydroxyl-terminated polydiarylsiloxanes.In addition to homopolymeric α,ω-dihydroxyl-terminated polydiorganosiloxanes, heteropolymeric α,ω-dihydroxyl-terminated polydiorganosiloxanes with different organic substituents can also be used. This includes both copolymers of monomers with identical organic substituents on a silicon atom and copolymers of monomers with different organic substituents on a silicon atom, e.g., those with mixed alkyl, alkenyl, and / or aryl substituents. Preferred organic substituents include straight-chain and branched alkyl groups with 1 to 8 carbon atoms, in particular methyl, ethyl, n- and iso-propyl, and n-, sec- and tert-butyl, vinyl, and phenyl. In the individual organic substituents, one or all carbon-bound hydrogen atoms can be substituted by common substituents, such as halogen atoms or functional groups such as hydroxyl and / or amino groups.Thus, α,ω-dihydroxyl-terminated polydiorganosiloxanes with partially fluorinated or perfluorinated organic substituents can be used, or α,ω-dihydroxyl-terminated polydiorganosiloxanes with organic substituents substituted by hydroxyl and / or amino groups on the silicon atoms.

[0055] Particularly preferred examples of organosilicon compounds are α,ω-dihydroxyl-terminated polydialkylsiloxanes, such as α,ω-dihydroxyl-terminated polydimethylsiloxanes, α,ω-dihydroxyl-terminated polydiethylsiloxanes, or α,ω-dihydroxyl-terminated polydivinylsiloxanes, as well as α,ω-dihydroxyl-terminated polydiarylsiloxanes, such as α,ω-dihydroxyl-terminated polydiphenylsiloxanes. Polyorganosiloxanes having a kinematic viscosity of 5,000 to 120,000 cSt (at 25°C) are preferred, especially those with a viscosity of 20,000 to 100,000 cSt, and particularly preferably those with a viscosity of 40,000 to 90,000 cSt.

[0056] Mixtures of polydiorganosiloxanes with different viscosities can also be used.

[0057] A composition according to the invention comprises at least one crosslinking agent. Any known crosslinking agent can be used. Crosslinking agents based on silane compounds with hydrolyzable acetate groups and / or crosslinking agents based on silane compounds with hydrolyzable oxime groups are preferred. In addition to the hydrolyzable acetate and / or oxime groups, the crosslinking agents can comprise non-hydrolyzable groups, such as alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and the like.

[0058] Preferred non-hydrolyzable groups are methyl, ethyl, propyl, isopropyl, isobutyl, vinyl, phenyl, and the like. The silane compound used as a crosslinker preferably has the general formula SiX n Y (4-n) , where X denotes the hydrolyzable groups and Y the non-hydrolyzable groups, and n is an integer from 1 to 4. Preferably, a crosslinker comprises three (n = 3) or four (n = 4) hydrolyzable groups.

[0059] Preferably, the crosslinker is selected from silane compounds comprising acid residues, in particular silane compounds with acetate residues, and silane compounds comprising oxime residues, in particular silane compounds with acetone oxime groups, silane compounds with methyl ethyl ketoxime groups, silane compounds with methyl propyl ketoxime groups, silane compounds with methyl isobutyl ketoxime groups and / or silane compounds with methyl isopropyl ketoxime groups.

[0060] Examples of preferred acetate crosslinkers include methyl triacetoxysilane, ethyl triacetoxysilane, propyl triacetoxysilane, vinyl triacetoxysilane, phenyl triacetoxysilane, tetraacetoxysilane, and the like.

[0061] The acetate crosslinkers can be used as a single compound, or as a mixture of two or more acetate crosslinkers.

[0062] In addition to mixtures consisting solely of acetate crosslinkers, crosslinker mixtures can also be used that additionally include crosslinkers based on silane compounds with hydrolyzable alkoxy groups. Crosslinkers based on silane compounds with hydrolyzable alkoxy groups are structurally similar to acetate crosslinkers, except that each acetoxy group is replaced by an alkoxy group. Upon hydrolysis or polymerization (polycondensation), alkoxy crosslinkers release neutral alcohol molecules. Examples of preferred alkoxy groups are methoxy, ethoxy, propoxy, and the like. Examples of preferred alkoxy crosslinkers include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, and the like.

[0063] Beispiele bevorzugter Oximvernetzer umfassen Methyl-tris(acetonoximo)silan, Ethyl-tris(acetonoximo)silan, Propyl-tris(acetonoximo)silan, Vinyl-tris(acetonoximo)silan, Phenyl-tris(acetonoximo)silan, Tetra(acetonoximo)silan, Methyl-tris(methyl-ethyl-ketoximo)silan, Ethyl-tris(methyl-ethyl-ketoximo)silan, Propyl-tris(methyl-ethyl-ketoximo)silan, Vinyl-tris(methyl-ethyl-ketoximo)silan, Phenyl-tris(methyl-ethyl-ketoximo)silan, Tetra(methyl-ethyl-ketoximo)silan, Methyl-tris(methyl-propyl-ketoximo)silan, Ethyl-tris(methyl-propyl-ketoximo)silan, Propyl-tris(methyl-propyl-ketoximo)silan, Vinyl-tris(methyl-propyl-ketoximo)silan, Phenyl-tris(methyl-propyl-ketoximo)silan, Tetra(methyl-propyl-ketoximo)silan, Methyl-tris(methyl-isopropyl-ketoximo)silan, Ethyl-tris(methyl-isopropyl-ketoximo)silan, Propyl-tris(methyl-isopropyl-ketoximo)silan, Vinyl-tris(methyl-isopropyl-ketoximo)silan, Phenyl-tris(methyl-isopropyl-ketoximo)silan, Tetra(methyl-isopropyl-ketoximo)silan,Methyl-tris(methyl-isobutyl-ketoximo)silane, ethyl-tris(methyl-isobutyl-ketoximo)silane, propyl-tris(methyl-isobutyl-ketoximo)silane, vinyl-tris(methyl-isobutyl-ketoximo)silane, phenyl-tris(methyl-isobutyl-ketoximo)silane, tetra(methyl-isobutyl-ketoximo)silane, and the like.

[0064] Oxime crosslinkers can be used as a single compound or as a mixture of two or more oxime crosslinkers.

[0065] It was found that the composition can be stored in the absence of moisture for periods of more than 12 months and polymerizes under the influence of water or humidity at room temperature.

[0066] A composition according to the invention, comprising acetate crosslinkers, particularly preferably comprises a catalyst comprising bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). A composition according to the invention, comprising oxime crosslinkers, particularly preferably comprises a catalyst comprising calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), or a catalyst comprising sodium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate).

[0067] In the presence of water or atmospheric humidity, the crosslinking agent (hardener) and organosilicon compound components of the composition according to the invention polymerize or condense, forming Si-O-Si bonds to form silicone rubber masses. The polymerization products produced using the composition according to the invention are free of specks, transparent, and clear. Therefore, the composition according to the invention can be used as a sealant, adhesive, coating agent, or the like.

[0068] The composition according to the invention particularly preferably comprises 40 to 90 wt.% of the organosilicone compound, 1 to 15 wt.% of the crosslinking agent, and 0.1 to 5.0 wt.% of the catalyst, more preferably 0.5 to 2.0 wt.% of the catalyst, the remainder being made up of conventional additives.

[0069] If desired, the composition according to the invention can include further conventional additives. Conventional additives are fillers, colorants, plasticizers, thixotropic agents, wetting agents, adhesives, and others.

[0070] Both reinforcing and non-reinforcing fillers can be used. Inorganic fillers are preferred, such as highly dispersed, pyrogenic, or precipitated silicas, carbon black, quartz powder, chalk, or metal salts or metal oxides, such as titanium oxides. A particularly preferred filler is highly dispersed silica, such as that available from Cabot under the name Cabosil 150. Fillers such as highly dispersed silicas, especially pyrogenic silicas, can also be used as thixotrophic agents. Metal oxides can also be used as colorants, e.g., titanium oxides as a white colorant. The fillers can also be surface-modified by conventional methods; for example, silane-hydrophobized silicas can be used.

[0071] Suitable plasticizers include polydiorganosiloxanes known per se without functional end groups, which thus differ from the organosilicon compounds used according to the invention, and / or liquid aliphatic or aromatic hydrocarbons, preferably those with molecular weights of about 50 to about 5000, which have low volatility and are sufficiently compatible with polysiloxanes. Plasticizers preferably have a kinematic viscosity of 1 to 5000 cSt (at 25°C), particularly 50 to 500 cSt, and especially 90 to 200 cSt. Examples of plasticizers include polydimethylsiloxanes with a viscosity of 90 to 120 cSt, particularly 100 cSt, paraffin oils, and polysubstituted alkylbenzenes.

[0072] Preferably, known silane compounds with reactive group-bearing organic substituents on the silicon atom are used as wetting and / or adhesion promoters. These differ from the organosilicone compounds used according to the invention, such as organosilanes with reactive amine, carboxylic acid, epoxy, or thiol groups. Particularly preferred examples include aminosilanes, such as aminoethylaminopropyl trialkoxysilanes. Specific examples of particularly preferred adhesion promoters are 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, aminoethylaminopropyl trimethoxysilane, butylaminopropyl triethoxysilane, butylaminopropyl trimethoxysilane, propylaminopropyl triethoxysilane, propylaminopropyl trimethoxysilane, N-cyclohexyl-3-aminopropyl trimethoxysilane, N-cyclohexyl-3-aminopropyl triethoxysilane, and co-oligomers of diamino / alkyl functional silanes, which is available, for example, as Dynasylan 1146 from Degussa.Other oligomeric adhesion promoters can also be used.

[0073] In a further aspect, the present invention provides for the use of the composition according to the invention as a sealant, adhesive, coating agent, or the like. The composition is preferably used in the construction industry as a sealant or adhesive, particularly for joints in building construction, civil engineering, glass and window construction (preferred), and in sanitary installations. Further uses exist in mechanical engineering, e.g., in the automotive industry (preferred), the electrical industry, the textile industry, or in industrial plant construction.

[0074] The composition according to the invention can be applied as an RTV silicone rubber compound to any substrate, depending on the desired application, where it then polymerizes at room temperature under the influence of water or atmospheric humidity. For example, when used as a sealant, the composition according to the invention is applied to a joint or the like. When used as an adhesive, the composition according to the invention is applied to one or both of the parts to be joined, and these are then joined together. The composition according to the invention is characterized by excellent adhesion to all important materials, such as wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials. The resulting polymer is transparent and exhibits advantageous elasticity and hardness.Furthermore, the composition according to the invention is characterized by a short skin formation time, short tack-free time, and early load-bearing capacity. In addition, the composition according to the invention exhibits advantageous storage properties in the cartridge.

[0075] In another aspect, the present invention provides a use of a catalyst for crosslinking a silicone rubber mass, wherein the catalyst comprises at least two different compounds which are selected independently of each other from metal salts of carboxylic acids.

[0076] The catalyst used in the application according to the invention has been described in detail above.

[0077] Preferably, a catalyst is used comprising at least one metal salt of a carboxylic acid selected from bismuth tris(2-ethylhexanoate), calcium bis(2-ethylhexanoate), sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate).

[0078] Particularly preferably, the catalyst used comprises calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3.

[0079] A catalyst comprising calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) together with an oxime crosslinker is particularly preferred.

[0080] Particularly preferably, the catalyst used comprises B-tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3.

[0081] A catalyst comprising bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) is particularly preferred, in combination with an acetate wetting agent.

[0082] Particularly preferably, the catalyst used comprises sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3.

[0083] A catalyst comprising sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate) together with an oxime crosslinker is particularly preferred.

[0084] The catalyst is particularly preferably used for crosslinking a silicone rubber mass comprising at least one organosilicone compound and at least one crosslinking agent, wherein the at least one organosilicone compound and the at least one crosslinking agent are preferably the compounds described above.

[0085] Particularly preferably, the organosilicon compound used comprises at least one α,ω-dihydroxyl-terminated polyorganosiloxane compound, in particular an α,ω-dihydroxyl-terminated polydialkylsiloxane.

[0086] Particularly preferably, the crosslinking agent used comprises at least one compound selected from the group consisting of silane compounds comprising acid residues, in particular silane compounds with acetate residues, and silane compounds comprising oxime residues, in particular silane compounds with acetone oxime groups, silane compounds with methyl ethyl ketoxime groups, silane compounds with methyl propyl ketoxime groups, silane compounds with methyl isobutyl ketoxime groups and / or silane compounds with methyl isopropyl ketoxime groups.

[0087] Particularly preferred are 0.1 to 5.0 wt.% of the catalyst with 40 to 90 wt.% of the organosilicone compound and 1 to 15 wt.% of the crosslinking agent.

[0088] By using the described catalyst according to the invention, the crosslinking of a silicone rubber mass can be advantageously controlled according to a desired application, so that polymerization products with desired properties are formed. Examples

[0089] The following metal salts of carboxylic acids, available from various manufacturers such as Gelest (Morrisville, USA), are used in the examples and comparisons. The sodium and potassium salts of 2-ethylhexanoic acid were obtained from Alfa Aesar GmbH & Co. KG, Karlsruhe, Germany.

[0090] Bismuth tris(2-ethylhexanoate), classified under CAS No. 67874-71-9, is used as the bismuth salt of carboxylic acids.

[0091] Calcium bis(2-ethylhexanoate), classified under CAS No. 68409-80-3, is used as the calcium salt of carboxylic acids.

[0092] Potassium 2-ethylhexanoate, classified under CAS No. 3164-85-0, is used as the potassium salt of carboxylic acids.

[0093] Lithium 2-ethylhexanoate, classified under CAS No. 15590-62-2, is used as the lithium salt of carboxylic acids.

[0094] Sodium 2-ethylhexanoate, classified under CAS No. 19766-89-3, is used as the sodium salt of carboxylic acids.

[0095] Strontium bis(2-ethylhexanoate), classified under CAS No. 2457-02-5, is used as the strontium salt of carboxylic acids.

[0096] Zinc bis(2-ethylhexanoate), classified under CAS No. 85203-81-2, is used as the zinc salt of carboxylic acids.

[0097] The other chemicals used in the examples and comparisons are available from the manufacturers listed below: Polydimethylsiloxane (80,000 cSt) from Wacker Chemie, Burghausen, Germany; Polymethylsiloxane (100 cSt) from Dow Corning, Seneffe, Belgium; Filler (highly dispersed silica) from Cabot Rheinfelden, Germany; Aminopropyltriethoxysilane from Nitrochemie Aschau GmbH, Germany; Adhesion promoter (co-oligomers based on aminoethylaminopropyltrimethoxysilane) from Nitrochemie Aschau GmbH, Germany; Adhesion promoter (diacetoxy-di-tert-butoxysilane) from Nitrochemie Aschau GmbH, Germany; Crosslinking mixtures from Nitrochemie Aschau GmbH, Germany. Measurement of the product properties of the manufactured sealants

[0098] The product properties skin formation time, tack-free time, early stress resistance, complete curing, appearance, and Shore A hardness were determined for all manufactured sealants according to standard procedures (e.g., "Practical Handbook of Sealants" by the German Sealants Association, 3rd edition, 1990). All measurements were carried out under conditions of 23°C and 50% relative humidity.

[0099] To determine the skin formation time, the time was measured at which a complete layer of solidified material (skin) was observed on the surface of a sample strand.

[0100] To determine the stickiness time, the time was measured at which the surface of a sample strand no longer exhibits stickiness.

[0101] To determine early stress resistance, a 10 mm high silicone strip was applied to a metal strip. The load-bearing capacity was tested by bending the strip at a 90° angle. The time during which the silicone strip's surface does not tear is recorded.

[0102] To determine complete curing, the sealant is applied to a glass plate with a height of 4 mm and the time it takes for the sealant to cure through to the glass plate is measured.

[0103] To determine surface cross-linking (notch strength), a 10 mm high strip of sealant is applied to a glass plate. After 24 hours under standard conditions (21 to 25°C; 40 to 60% relative humidity), a notch is pressed into the surface. After 10 seconds, it is checked whether the indentation is reversible.

[0104] The appearance was determined by organoleptic examination.

[0105] The Shore A hardness was determined using a Zwick-Roell measuring instrument (reference: ASTM D 2240; DIN 53505; ISO 868). For this purpose, the respective sealant sample was applied to a thickness of 10 mm and stored for 7 days under standard conditions (23°C / 50% RH). The measurement was then taken after 7 days of storage under standard conditions. Example 1: Catalyst A

[0106] A catalyst according to the invention is produced, comprising calcium and zinc salts of carboxylic acids.

[0107] For catalyst A, calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) are mixed in a ratio of 4:5 (weight ratio). Example 2: Catalyst B

[0108] A catalyst according to the invention is produced, comprising bismuth and zinc salts of carboxylic acids.

[0109] For catalyst B, bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate) are mixed in a ratio of 7:3 (weight ratio). Reference example 1:

[0110] A standard tin-containing silicone rubber mixture with oxime crosslinker is produced according to the following formulation: 556,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 266,0 g Polydimethylsiloxane with a viscosity of 100 cSt 109,0 g Highly dispersed silica (filler) 50,5 g Cross-linking mixture made of 14.5 g vinyl-tris(ethylmethylketoximo)silane and 36.0 g methyl tris(ethylmethylketoximo)silane 18,0 g 3-Aminopropyltriethoxysilane (thixotropic agent) 4,0 g Dibutyltin laurate as a catalyst

[0111] The sealant behaves after exposure to air: a skin formation time of 10 min, an tack-free time of 30 min, early use after 80 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 24

[0112] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0113] Reference example 1 illustrates the product properties of a currently common tin-containing sealant mixture. Comparative example 1: Sealant formulation 1 (with oxime crosslinker)

[0114] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 3,0 g Zinc bis(2-ethylhexanoate) 1,0 g 2-Ethylhexanoic acid (co-catalyst)

[0115] The sealant behaves after exposure to air: a skin formation time of 7 min, an tack-free time of 20 min, early use after 160 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 22

[0116] Furthermore, it was found that the sealant exhibits good adhesion to wood, varnished wood, aluminum, and glass. In contrast, adhesion to powder-coated aluminum, PVC, polyamide, steel, and concrete is only moderate to poor.

[0117] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the sealant only achieves a Shore A hardness of 12 after 7 days of air curing. In addition, the sealant shows only moderate to poor adhesion to all substrates. Comparative example 2: Sealant formulation 1 (with oxime crosslinker)

[0118] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,9 g Zinc bis(2-ethylhexanoate) 1,1 g Octylphosphonic acid (co-catalyst)

[0119] The sealant behaves after exposure to air: a skin formation time of 10 min, an tack-free time of 25 min, early use after 250 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0120] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0121] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 16; yellowing of the sealant. Comparative example 3: Sealant formulation 1 (with oxime crosslinker)

[0122] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,9 g Strontium bis(2-ethylhexanoate) 1,1 g Octylphosphonic acid (co-catalyst)

[0123] The sealant behaves after exposure to air: a skin formation time of 13 min, an tack-free time of 30 min, early use after 360 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0124] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0125] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 17; yellowing of the sealant. Comparison example 4: Sealant formulation 1 (with oxime crosslinker)

[0126] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,9 g Lithium 2-ethylhexanoate 1,1 g Octylphosphonic acid (co-catalyst)

[0127] The sealant behaves after exposure to air: a skin formation time of 13 min, an tack-free time of 30 min, early use after 420 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0128] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0129] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 15; yellowing of the sealant. Comparative example 5: Sealant formulation 1 (with oxime crosslinker)

[0130] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 4,0 g Zinc bis(2-ethylhexanoate)

[0131] The sealant behaves after exposure to air: a skin formation time of 5 min, an tack-free time of 25 min, early use after 280 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0132] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0133] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 17; yellowing of the sealant. Comparative example 6: Sealant formulation 1 (with oxime crosslinker)

[0134] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 4,0 g Bismuth tris(2-ethylhexanoate)

[0135] The sealant behaves after exposure to air: a skin formation time of 5 min, an tack-free time of 15 min, early use after 300 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0136] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0137] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 15; yellowing of the sealant. Comparative example 7: Sealant formulation 1 (with oxime crosslinker)

[0138] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(acetonoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 4,0 g Calcium bis(2-ethylhexanoate)

[0139] The sealant behaves after exposure to air: a skin formation time of 5 min, an tack-free time of 18 min, early use after 320 min (unacceptable), complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0140] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0141] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: No notch strength after 24 hours in air; Shore A hardness after 7 days in air only 14; yellowing of the sealant. Comparative example 8: Sealant formulation 2 (with oxime crosslinker)

[0142] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g vinyl-tris(ethylmethylketoximo)silane and 21.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,0 g Sodium (2-ethylhexanoate)

[0143] The sealant behaves after exposure to air: a skin formation time of 8 min, an tack-free time of 30 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 23

[0144] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0145] However, the sealant exhibits insufficient storage stability in the cartridge. After just 4 weeks of storage at 60°C in the cartridge, the following parameters deteriorated: Adhesion insufficient; Shore hardness A only 5 after 7 days in the air.

[0146] From comparative examples 1 to 8, it is evident that it is not possible to produce a sealant compound with oxime crosslinkers using known tin-free catalysts that exhibits good product properties comparable to those of a conventional tin-containing sealant compound (e.g., reference example 1). In particular, the sealants produced with known tin-free catalysts exhibit poor adhesion to many materials and insufficient storage stability. Example 3: Sealant formulation 1 (with oxime crosslinker)

[0147] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g ethyl tris(ethylmethylketoximo)silane, 15.0 g vinyl-tris(ethylmethylketoximo)silane and 6.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,0 g Catalyst A (from Example 1)

[0148] The sealant behaves after exposure to air: a skin formation time of 12 min, an tack-free time of 23 min, early use after 180 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0149] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0150] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 4 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 4: Sealant formulation 2 (with oxime crosslinker)

[0151] A silicone rubber compound is produced according to the following formulation: 525,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 103,0 g Highly dispersed silica (filler) 42,0 g Cross-linking mixture made of 21.0 g vinyl-tris(ethylmethylketoximo)silane and 21.0 g methyl tris(ethylmethylketoximo)silane 13,0 g Adhesion promoter (based on aminoethylaminopropyltrimethoxysilane) 2,0 g Catalyst A (from Example 1)

[0152] The sealant behaves after exposure to air: a skin formation time of 10 min, an tack-free time of 20 min, early use after 140 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 26

[0153] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0154] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 4 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 5: Sealant formulation 2 (with oxime crosslinker)

[0155] Three exemplary catalysts (A1 to A3) are prepared from calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). The mixing ratio (weight ratio) of calcium bis(2-ethylhexanoate) to zinc bis(2-ethylhexanoate) is 1:1 in catalyst A1, 2:3 in catalyst A2, and 1:3 in catalyst A3.

[0156] A silicone rubber mixture is prepared according to the formulation described in Example 4, wherein instead of 2.0 g of catalyst A, 2.0 g each of catalysts A1, A2, and A3 are added.

[0157] The sealant behaves after exposure to air: a skin formation time of 6 min (A1, A2, A3), a tack-free time of 30 min (A1) or 25 min (A2, A3), complete curing after 24 h (A1, A2, A3) (notch strength), a transparent appearance, a Shore A hardness of 24 (A1) or 26 (A2, A3)

[0158] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0159] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 4 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 6: Sealant formulation 2 (with oxime crosslinker)

[0160] Three exemplary catalysts (C1 to C3) are prepared from sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate). The mixing ratio (weight ratio) of sodium (2-ethylhexanoate) to zinc bis(2-ethylhexanoate) is 4:1 in catalyst C1, 2:3 in catalyst C2, and 1:4 in catalyst C3.

[0161] A silicone rubber mixture is prepared according to the formulation described in Example 4, wherein instead of 2.0 g of catalyst A, 2.0 g each of catalysts C1, C2, and C3 are added.

[0162] The sealant behaves after exposure to air: a skin formation time of 6 min (C1, C3) or 7 min (C2), a tack-free time of 25 min (C1, C2, C3), complete curing (notch strength) after 24 h (C1, C2, C3), a transparent appearance, a Shore A hardness of 24 (C1) or 25 (C2, C3)

[0163] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials. Example 7: Sealant formulation 2 (with oxime crosslinker)

[0164] A silicone rubber mixture is prepared according to the formulation described in Example 4, wherein instead of 2.0 g of catalyst A, 2.0 g of a catalyst of potassium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate) in a ratio of 2:3 is used.

[0165] The sealant behaves after exposure to air: a skin formation time of 6 min, an tack-free time of 25 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0166] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials. Example 8: Sealant formulation 2 (with oxime crosslinker)

[0167] A silicone rubber mixture is prepared according to the formulation described in Example 4, wherein instead of 2.0 g of catalyst A, 2.0 g of a catalyst of lithium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate) in a ratio of 2:3 is used.

[0168] The sealant behaves after exposure to air: a skin formation time of 7 min, an tack-free time of 25 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 25

[0169] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0170] In contrast to the sealants produced in comparative examples 1 to 8, the sealants produced with the catalyst according to the invention and containing oxime crosslinkers are characterized not only by excellent product properties but also by excellent storage stability. The advantageous effect of the catalyst according to the invention is independent of the composition used, the mixing ratio, and the crosslinkers used. A particularly advantageous catalyst comprises calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). In particular, it was found that catalyst A produces especially good properties in the sealants produced, especially in combination with oxime crosslinkers. Furthermore, an additional co-catalyst is not required. Comparative example 9: Sealant formulation 3 (with acetate crosslinker)

[0171] A silicone rubber compound is produced according to the following formulation: 562,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 79,0 g Highly dispersed silica (filler) 40,0 g Cross-linking mixture made of 28.0 g propyl triacetoxysilane and 12.0 g ethyl triacetoxysilane 5,0 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 2,9 g Zinc bis(2-ethylhexanoate) 1,1 g Octylphosphonic acid (co-catalyst)

[0172] The sealant behaves after exposure to air: a skin formation time of 11 min, an tack-free time of 75 min, early use after 30 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 23

[0173] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, glass, polyamide, steel, etc.

[0174] However, the sealant exhibits insufficient storage stability in the cartridge. After just 8 weeks of storage at room temperature in the cartridge, the following parameters had deteriorated: Adhesive time: 420 min; no notch strength after 24 h in air; early loading after 90 min. Comparative example 10: Sealant formulation 3 (with acetate crosslinker)

[0175] A silicone rubber compound is produced according to the following formulation: 562,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 79,0 g Highly dispersed silica (filler) 40,0 g Cross-linking mixture made of 28.0 g propyl triacetoxysilane and 12.0 g ethyl triacetoxysilane 5,0 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Zinc bis(2-ethylhexanoate)

[0176] The sealant behaves after exposure to air: a skin formation time of 11 minutes, an tack-free time of more than five hours, early stress testing after more than five hours, no complete curing after 24 hours (notch strength), a transparent appearance, a Shore A hardness of 22

[0177] Furthermore, it was found that the sealant exhibits good adhesion to aluminum, glass, polyamide, steel, etc. In contrast, adhesion to wood, painted wood, and varnished wood is poor.

[0178] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, the following parameters deteriorated: Adhesive time: no notch strength after more than 48 hours in air; early stress after more than 48 hours; Shore A hardness after 7 days in air only 15 Comparative example 11: Sealant formulation 3 (with acetate crosslinker)

[0179] A silicone rubber compound is produced according to the following formulation: 562,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 79,0 g Highly dispersed silica (filler) 40,0 g Cross-linking mixture made of 28.0 g propyl triacetoxysilane and 12.0 g ethyl triacetoxysilane 5,0 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Bismuth tris(2-ethylhexanoate)

[0180] The sealant behaves after exposure to air: a skin formation time of 7 minutes, an tack-free time of more than 5 hours, early stress testing after more than 5 hours, no complete curing after 24 hours (notch strength), a transparent appearance, a Shore A hardness of 21

[0181] Furthermore, it was found that the sealant exhibits good adhesion to aluminum, glass, polyamide, steel, etc. In contrast, adhesion to wood, painted wood, and varnished wood is poor.

[0182] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, the following parameters deteriorated: Adhesive time: no notch strength after more than 48 hours in air; early stress after more than 48 hours; Shore A hardness after 7 days in air only 14. Comparative example 12: Sealant formulation 3 (with acetate crosslinker)

[0183] A silicone rubber compound is produced according to the following formulation: 562,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 79,0 g Highly dispersed silica (filler) 40,0 g Cross-linking mixture made of 28.0 g propyl triacetoxysilane and 12.0 g ethyl triacetoxysilane 5,0 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Calcium bis(2-ethylhexanoate)

[0184] The sealant behaves after exposure to air: a skin formation time of 9 minutes, an tack-free time of more than 5 hours, early stress testing after more than 5 hours, no complete curing after 24 hours (notch strength), a transparent appearance, a Shore A hardness of 23

[0185] Furthermore, it was found that the sealant exhibits good adhesion to aluminum, glass, polyamide, steel, etc. In contrast, adhesion to wood, painted wood, and varnished wood is poor.

[0186] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, the following parameters deteriorated: Adhesive time: no notch strength after more than 48 hours in air; early stress after more than 48 hours; Shore A hardness after 7 days in air only 12. Comparative example 13: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0187] A silicone rubber compound is produced according to the following formulation: 555,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 312,0 g Polydimethylsiloxane with a viscosity of 100 cSt 84,0 g Highly dispersed silica (filler) 45,0 g Cross-linking mixture made of 31.5 g methyl triacetoxysilane, 9.0 g propyl triacetoxysilane and 4.5 g methyl trimethoxysilane 2,5 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Lithium (2-ethylhexanoate)

[0188] The sealant behaves after exposure to air: a skin formation time of 6 min, an tack-free time of 30 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 16

[0189] Furthermore, it was found that the sealant exhibits only moderate adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0190] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, it no longer cures completely. Consequently, no adhesion to substrates is observed. Comparative example 14: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0191] A silicone rubber mixture is prepared according to the formulation described in Comparative Example 13, wherein 4.0 g of sodium (2-ethylhexanoate) is used as the catalyst instead of 4.0 g of lithium (2-ethylhexanoate).

[0192] The sealant behaves after exposure to air: a skin formation time of 6 min, an tack-free time of 28 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 1

[0193] Furthermore, it was found that the sealant exhibits only moderate adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0194] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, it no longer cures completely. Consequently, no adhesion to substrates is observed. Comparative example 15: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0195] A silicone rubber mixture is prepared according to the formulation described in Comparative Example 13, wherein 4.0 g of potassium (2-ethylhexanoate) is used as the catalyst instead of 4.0 g of lithium (2-ethylhexanoate).

[0196] The sealant behaves after exposure to air: a skin formation time of 5 minutes, an tack-free time of 30 minutes, complete curing after 24 hours (notch strength), a transparent appearance, a Shore A hardness of 16

[0197] Furthermore, it was found that the sealant exhibits only moderate adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0198] Furthermore, the sealant exhibits insufficient storage stability in the cartridge. After just four weeks of storage at 60°C in the cartridge, it no longer cures completely. Consequently, no adhesion to substrates is observed.

[0199] From comparative examples 9 to 15, it is evident that it is not possible to produce a sealant compound with acetate crosslinkers using known tin-free catalysts that exhibits good product properties comparable to those of a conventional tin-containing sealant compound (e.g., reference example 1). In particular, the sealants produced with known tin-free catalysts exhibit poor adhesion to many materials and inadequate curing. Furthermore, these sealants show insufficient storage stability. Example 9: Sealant formulation 3 (with acetate crosslinker)

[0200] A silicone rubber compound is produced according to the following formulation: 562,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 313,0 g Polydimethylsiloxane with a viscosity of 100 cSt 79,0 g Highly dispersed silica (filler) 40,0 g Cross-linking mixture made of 28.0 g propyl triacetoxysilane and 12.0 g Methyl triacetoxysilane 5,0 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Catalyst B (from example 2)

[0201] The sealant behaves after exposure to air: a skin formation time of 12 min, an tack-free time of 25 min, early use after 40 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 15

[0202] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0203] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 8 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 10: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0204] A silicone rubber compound is produced according to the following formulation: 555,0 g α,ω-dihydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt 312,0 g Polydimethylsiloxane with a viscosity of 100 cSt 84,0 g Highly dispersed silica (filler) 45,0 g Cross-linking mixture made of 31.5 g methyl triacetoxysilane, 9.0 g propyl triacetoxysilane and 4.5 g methyl trimethoxysilane 2,5 g Adhesion promoter (diacetoxy-di-tert-butoxysilane) 4,0 g Catalyst B (from example 2)

[0205] The sealant behaves after exposure to air: a skin formation time of 15 min, an tack-free time of 27 min, early use after 40 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 20

[0206] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0207] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 8 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 11: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0208] Four exemplary catalysts (B1 to B4) are prepared from bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). The mixing ratio of bismuth tris(2-ethylhexanoate) to zinc bis(2-ethylhexanoate) is 4:1 in catalyst B1, 1:1 in catalyst B2, 2:1 in catalyst B3, and 1:4 in catalyst B4.

[0209] A silicone rubber mixture is prepared according to the formulation described in Example 10, wherein instead of 4.0 g of catalyst B, 4.0 g each of catalysts B1, B2, B3 and B4 are added.

[0210] The sealant behaves after exposure to air: a skin formation time of 8 min (B1, B2, B3, B4), an tack-free time of 25 min (B1, B2, B3) or 45 min (B4), complete curing after 24 h (notch strength) (B1, B2, B3, B4), a transparent appearance, a Shore A hardness of 20 (B2, B3, B4) or 21 (B1)

[0211] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0212] Furthermore, the sealant is characterized by its excellent storage stability in the cartridge. After 8 weeks of storage at 60°C in the cartridge, the sealant still exhibits the same properties as upon initial application. Example 12: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0213] A silicone rubber mixture is prepared according to the formulation described in Example 10, wherein instead of 4.0 g of catalyst B, 4.0 g of a catalyst of bismuth tris(2-ethylhexanoate) and sodium(2-ethylhexanoate) in a ratio of 2:1 is used.

[0214] The sealant behaves after exposure to air: a skin formation time of 6 min, an tack-free time of 23 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 17

[0215] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials. Example 13: Sealant formulation 4 (with acetate and alkoxy crosslinkers)

[0216] A silicone rubber mixture is prepared according to the formulation described in Example 10, wherein instead of 4.0 g of catalyst B, 4.0 g of a catalyst of bismuth tris(2-ethylhexanoate) and calcium bis(2-ethylhexanoate) in a ratio of 1:1 is used.

[0217] The sealant behaves after exposure to air: a skin formation time of 7 min, an tack-free time of 32 min, complete curing after 24 h (notch strength), a transparent appearance, a Shore A hardness of 17

[0218] Furthermore, it was found that the sealant exhibits good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, and many other materials.

[0219] In contrast to the sealants produced in comparative examples 9 to 15, the sealants produced with the catalyst according to the invention, using acetate crosslinkers or acetate and alkoxide crosslinkers from examples 9 to 13, are characterized not only by excellent product properties but also by excellent storage stability. The advantageous effect of the catalyst according to the invention is independent of the composition used, the mixing ratio, and the crosslinkers used. A particularly advantageous catalyst comprises bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate). In particular, it was found that catalyst B produces especially good properties in the sealants produced, especially in combination with acetate crosslinkers.

[0220] An additional co-catalyst is also not required.

Claims

1. Composition comprising at least one organosilicone compound, at least one crosslinker, and a catalyst, wherein the catalyst comprises a metal salt of a carboxylic acid which is a zinc salt of one or more branched saturated carboxylic acids with six to nineteen carbon atoms, and a metal salt of a carboxylic acid selected from a bismuth salt, a calcium salt, a potassium salt, a lithium salt, a magnesium salt and a sodium salt, each of one or more branched saturated carboxylic acids having six to nineteen carbon atoms.

2. Composition according to claim 1, characterized in that the ratio of the number of zinc atoms of the zinc salt of a carboxylic acid to the number of metal atoms of the metal salt of a carboxylic acid is from 2:1 to 1:2, preferably from 1.3:1 to 1:1.3.

3. Composition according to any of the preceding claims, characterized in that it comprises calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3, or characterised in that they contain bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3, or characterised in that it comprises sodium (2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3.

4. Composition according to any of the preceding claims, characterized in that the organosilicone compound is a α, ω-dihydroxy terminated polyorgano siloxane compound, in particular a α, ω-dihydroxy terminated polydialkyl siloxane.

5. Composition according to one of the preceding claims, characterized in that the crosslinker comprises at least one compound selected from the group consisting of silane compounds comprising acid residues, in particular silane compounds containing acetate residues, and silane compounds, which comprise oxime residues, in particular silane compounds with acetone oxime groups, silane compounds with methyl ethyl ketoxime groups, silane compounds with methyl propyl ketoxime groups, silane compounds with methyl isobutyl ketoxime groups and / or silane compounds with methyl isopropyl ketoxime groups.

6. Composition according to any of the preceding claims, characterized in that the crosslinker comprises at least one silane compound containing acetate residues and one silane compound containing alkoxy residues.

7. Composition according to any of the preceding claims, characterized in that it comprises 40 to 90 wt.-% of the organosilicone compound, 1 to 15 wt.-% of the crosslinker, and 0.1 to 5.0 wt.-% of the catalyst according to any of claims 1 to 10.

8. Use of a composition according to one of the preceding claims for the preparation of a silicone rubber mass, in particular for use as a sealant, adhesive or coating agent.

9. Use of a catalyst for crosslinking a silicone rubber mass, wherein the catalyst comprises a metal salt of a carboxylic acid which is a zinc salt of one or more branched saturated carboxylic acids having from six to nineteen carbon atoms, and a metal salt of a carboxylic acid selected from a bismuth salt, a calcium salt, a potassium salt, a lithium salt, a magnesium salt and a sodium salt each of one or more branched saturated carboxylic acids having from six to nineteen carbon atoms, characterized in that the catalyst comprises calcium bis(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3, or characterized in that the catalyst comprises bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3, or characterized in that the catalyst comprises sodium (2-ethylhexanoate) and zinc bis(2ethylhexanoate), preferably in a numerical ratio of 1.3:1 to 1:1.3.

10. Use according to claim 9, characterized in that the silicone rubber mass comprises at least one organosilicone compound which is a a, ω-dihydroxy terminated polyorganosiloxane compound, in particular a a, ω-dihydroxy terminated polydialkylsiloxane.

11. Use according to claim 9 or 10, characterized in that the silicone rubber mass comprises at least one crosslinker, wherein the crosslinker comprises at least one compound selected from the group consisting of silane compounds comprising acid radicals, in particular silane compounds comprising acetate radicals, and silane compounds comprising oxime radicals, in particular silane compounds having acetone oxime groups, silane compounds having methyl ethyl ketoxime groups, silane compounds having methyl propyl ketoxime groups, silane compounds having methyl isobutyl ketoxime groups and / or silane compounds having methyl isopropyl ketoxime groups.

12. Catalyst comprising a metal salt of a carboxylic acid which is a zinc salt of one or more branched saturated carboxylic acids having six to nineteen carbon atoms, and a metal salt of a carboxylic acid selected from a bismuth salt, a calcium salt, a potassium salt, a lithium salt, a magnesium salt and a sodium salt, each of one or more branched saturated carboxylic acids having six to nineteen carbon atoms.