Rhodium hydrosilylation catalyst and curable silicone compositions

Abstract

A composition contains or consists of a rhodium complex having chemical structure (I) or chemical structure (II). The composition can be a release coating composition that further contains an alkenyl-functional siloxane and a silylhydride-functional siloxane.

Description

[0001] RHODIUM HYDROSILYLATION CATALYST AND CURABLE SILICONE COMPOSITIONS FIELD The present invention relates to a rhodium compound and curable silicone composition that comprise the rhodium compound as a hydrosilylation catalyst. INTRODUCTION Silicone release coating compositions are curable compositions that, upon curing, form a silicone release coating. Generally, silicone release coating compositions are useful for coating onto a substrate and then curing to form a silicone release coating on the substrate. A common type of curing chemistry for silicone release coating compositions is hydrosilylation where silicones with carbon-carbon double bond (C=C) functionality react with crosslinkers containing silylhydride (SiH) functionality, typically in the presence of a hydrosilylation catalyst. Karstedt’s catalyst is perhaps the most widely used hydrosilylation catalyst in hydrosilylation-curable compositions, yet there are challenges with using Karstedt’s catalyst that are desirable to overcome. Karstedt’s catalyst tends to be highly effective at inducing a hydrosilylation reaction, meaning hydrosilylation reactions occur rapidly in the presence of Karstedt’s catalyst. As a result, silicone release coating compositions using Karstedt’s catalyst have a short workability timeframe once the catalyst is introduced into the silicone release coating composition. It is possible to add inhibitors such as 1-ethynyl-1-cyclohexanol (ETCH) to silicone release coating compositions containing Karstedt’s catalyst in order to slow the rapid curing reaction. ETCH inhibits Karstedt’s catalyst from catalyzing hydrosilylation reactions at lower temperatures, but allows the reaction to proceed at elevated temperatures. Use of inhibitors offer their own challenges to release coating compositions with Karstedt’s catalyst. Often, the complex of inhibitor and catalyst is not soluble in the components of the silicone release coating composition, especially those compositions with little to no solvent. Such incompatibility can result in the inhibitor / catalyst complex phase separating and even settling out of the silicone release coating composition as a precipitate over time which can result in a longer cure time for the composition. Additionally, use of an inhibitor requires including yet one more component in the release coating composition, and that would be desirable to avoid. It would advance the art to identify a new hydrosilylation catalyst for silicone release coating compositions. It would further advance the art if that catalyst serves as a hydrosilylation catalyst for silicone release coating compositions without requiring the presence of platinum as is found in Karstedt’s catalyst. Even more desirable is if such a catalyst in a silicone release coating composition does not require inhibitor to produce a silicone release coating with the following desirable properties: (a) long workability characterized by a 40 degree Celsius (°C) bathlife of greater than 60 minutes; and (b) cures to a release coating with immediate and 7-day aged anchorage to Glassine paper that demonstrates greater than 95% Rub-Off Resistance (ROR). Desirably, the silicone release coating further (c) cures to release coating having a release force with TESA™ 7475 tape that is less than 100 centiNewtons per 25 millimeters (cN / 25 mm) over a peel rate range of 0.3 to 300 meters per minute (m / min). The catalyst should also be miscible with silicone components of a silicone release coating composition as determined by visual inspection for signs of precipitation, the lack of which indicates miscibility. SUMMARY The present invention provides a solution to the challenge of identifying a new hydrosilylation catalyst for silicone release coating compositions. The catalyst even can serve as a hydrosilylation catalyst for silicone release coating compositions, does not require the presence of platinum as is found in Karstedt’s catalyst, and does not require inhibitor to produce a silicone release coating with the following desirable properties: (a) long workability characterized by a 40 degree Celsius (°C) bathlife of greater than 60 minutes; and (b) cures to a release coating with immediate and 7-day aged anchorage to Glassine paper that demonstrates greater than 95% Rub- Off Resistance (ROR). The resulting silicone release coating can also (c) cure to release coating having a release force with TESA™ 7475 tape that is less than 100 centiNewtons per 25 millimeters (cN / 25 mm) over a peel rate range of 0.3 to 300 meters per minute (m / min). The catalyst is also miscible with silicone components of a silicone release coating composition as determined by visual inspection for signs of precipitation, the lack of which indicates miscibility. All of these properties are achieved without requiring platinum or inhibitor in the silicone release coating composition. The present invention is a result of discovering rhodium complexes shown as chemical structures (I) and (II) and further discovering that such rhodium complexes can serve as a catalyst for silicone release coating compositions in place of platinum catalysts, such as Karstedt’s catalyst. Moreover, the rhodium complex allows for release coating compositions that achieve the aforementioned desired properties. where: P is from chloride, fluoride, bromide and iodide; each R1is independently in each occurrence selected from linear alkyl groups having from one to 8 carbon atoms; RhIrefers to a rhodium atom in an oxidation state of one; the “=” bound to the rhodium atom in structure (I) is ethylene; the rhodium atom in structure (II) is bonded to the double bond in the cyclooctene, and arrows refer to dative bonding to the RhI. In a first aspect, the present invention is a composition comprising a rhodium complex having chemical structure (I) or chemical structure (II): (I) R1 where: P is phosphorous; from chloride, fluoride, bromide and iodide; each R1is independently selected from linear alkyl groups having from one to 8 carbon atoms; RhIrefers to a rhodium atom in an oxidation state of one; the “=” bound to the rhodium atom in structure (I) is ethylene; and the rhodium atom in structure (II) is bonded to the double bond in the cylooctene. The composition of the present invention can further comprise an alkenyl-functional siloxane and a silylhydride-functional siloxane. The rhodium complex of the present invention is useful as a catalyst in hydrosilylation- curable silicone release coating compositions. DETAILED DESCRIPTION Products identified by their tradename refer to the compositions available under those tradenames on the priority date of this document. “Multiple” means two or more. “And / or” means “and, or as an alternative”. All ranges include endpoints unless otherwise indicated. “Average value” when referencing a value describing a molecule refers to the average value of a sample of molecules since it is generally difficult to measure the value of a single molecule. Polysiloxanes (or just “siloxanes”) comprise multiple siloxane units linked together through siloxane bonds. Siloxane units can be characterized by the designation M, D, T or Q. There are two generally accepted usages of MDTQ nomenclature: GE method and an NMR method. Usage herein is in accordance with the following GE method. Unless expressly stated otherwise: “M” correspond to R3SiO1 / 2siloxane units. “D” correspond to the combination of R2SiO2 / 2and. “T” corresponds to RSiO3 / 2siloxane units. “Q” corresponds to SiO4 / 2siloxane units. “R” is independently in each occurrence a methyl unless otherwise stated. Notably, an oxygen atom having a multiple of “1 / 2” subscript is an oxygen of a siloxane bond that is shared with a silicon atom of two siloxane units including the one of the subject siloxane unit. The numerator of the subscript indicates how many shared oxygen atoms are attached to the silicon atom. For example, SiO3 / 2has three siloxane bonded oxygen atoms that are shared with other siloxane units. The M, D and T notations can include a superscript indicating what R groups are bound to the silicon atom of the siloxane unit. If no superscript notation is used then it is assumed the R groups are all methyl groups. For instance, TArrefers to a T unit where the R group is an aryl group. When the aryl group of a TAris phenyl, the siloxane is TPh. DHand MHrefer to D siloxane units and M siloxane units, respectively, where one of the R groups bound to the silicon atom is a hydrogen. Similarly, DViand MVirefer to D siloxane units and M siloxane units, respectively, where one of the R groups bound to the silicon atom is a vinyl group. Chemical formula designations for polysiloxanes using M, D, T, Q nomenclature typically have subscripts associated with the siloxane unit designator that can either refer to the average mole ratio of that siloxane unit relative to all siloxane units in the molecule or the average number of the associate siloxane units in the molecule. When the subscript associated with a siloxane unit is greater than or equal to one, then the subscript refers to the average number of those siloxane units in the molecule. When the subscript associated with a siloxane unit is less than one then the subscript refers to the average mole ratio of that siloxane unit relative to the number of moles of all siloxane units in the molecule. An absence of a subscript implies a subscript value of one. The present invention is a composition comprising a rhodium complex having chemical structure (I) or chemical structure (II): (I)

[0002] R1 where: P is phosphorous; from chloride, fluoride, bromide and alkyl groups having from one to 8 carbon atoms; RhIrefers to a rhodium atom in an oxidation state of one; the “=” bound to the rhodium atom in structure (I) is ethylene; and the rhodium atom in structure (II) is bonded to the double bond in the cylooctene. The composition of the present invention can consist of or comprise the rhodium complex of structure (I), structure (II), or a combination of rhodium complexes of structure (I) and structure (II). In the broadest scope, the composition of the present invention can be solely the rhodium complex of structure (I), the rhodium complex of structure (II), or a combination of rhodium complexes of structure (I) and (II). It is particularly desirable for the composition of the present invention to further comprise components of a release coating composition, as described herein below. A particularly desirable composition of the present invention consists of or comprises a rhodium complex of structure (Ib), which is the rhodium complex of structure (I) where each R1is methyl and X is chloride (Rh Complex 1 in Table 1). The experimental section, below, provides a synthetic procedure for making the rhodium complex of structure (Ib). Other rhodium complexes of structure (I) as well as rhodium complexes of structure (II) can be prepared in a similar manner by substituting in the desired reactant to the procedure for preparing a rhodium complex of structure (Ib). For example, the rhodium complex of structure (II) can be prepared from chlorobis(cyclotene)rhodium dimer (available from Strem Chemical, CAS#12279-09-3). R1modifications can be made through selection of what to use for “Ligand 1” in Table 1 and the synthesis of Rh Complex 1, below. Ligand 1 and various derivatives of Ligand 1 can be made by lithium-halogen exchange of 2- OR1-1-halobenzene with a reagent, such as n-buthyl lithium, followed by a reaction of this intermediate with chlorodiphenylphosphine to make the P(Ph)2PhOR1ligand: Desirably, the composition of the present invention further comprises components of a hydrosilylation-curable silicone release coating composition and can be a fully formulated hydrosilylation-curable silicone release coating composition. A silicone release coating composition is a composition that can be applied to a substrate and cured to form a silicone release coating. One of the surprising and desirable features of the present invention is the discovery that the rhodium complexes of the present invention serve as catalysts for hydrosilylation curing of a silicone release coating composition, thereby obviating a need to for platinum catalysts while still achieving hydrosilylation curing. The composition of the present invention can comprise any one or any combination of more than one of the following components of a hydrosilylation-curable silicone release coating in addition to the rhodium complex: (a) alkenyl-functional siloxane; (b) silylhydride-function siloxane; (c) hydrosilylation inhibitor; and (d) a solvent. Desirably, when the composition comprises the components to form a hydrosilylation-curable silicone release coating, then the concentration of rhodium complex is sufficient to provide a concentration of rhodium that is in a range of greater than 10 to less than 40 mass-parts, preferably in a range of 20 to 30 mass- parts, per million mass parts composition. It is also desirable for the molar ratio of silylhydride- functionality from component (b) to alkenyl-functionality from component (a) is in a range of 5:1 to 1:1. The composition can be free of platinum. The composition can be free of any hydrosilylation catalyst other than the rhodium complex having chemical structure (I) or (II). (a) Alkenyl-functional siloxane The alkenyl-functional siloxane component contains an average of at least 2 alkenyl groups per molecule. The alkenyl groups are desirably terminally unsaturated. Preferably, the alkenyl groups contain 2 or more, and can contain 3 or more, 4 or more 5 or more, 6 or more, even 7 or more carbon atoms while at the same time typically contain 8 or fewer, and can contain 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, even 3 or fewer carbon atoms. Typically, the alkenyl groups are selected from vinyl and allyl groups. The alkenyl-functional siloxane component can be free of silylhydride (SiH) groups. The alkenyl-functional siloxane can be linear, branched, resinous, or any combination thereof. Linear siloxanes typically contain fewer than 5 branching points on average per molecule. Resinous siloxanes typically comprise more than 50 mole-percent (mol%) of siloxane units that are selected from T and Q type siloxane units, which introduce branching point. Branched siloxanes have more branching point that linear siloxanes but fewer T and Q type siloxane units that siloxane resins. The alkenyl-functional siloxane can comprise or consist of one or more than one siloxane having an average chemical composition (III): (R2R’SiO1 / 2)m(R2SiO2 / 2)d(SiO4 / 2)q(III) where: R is independently in each occurrence selected from hydrocarbyls having from one to 10 carbon atoms, and can have one or more, 2 or more 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, even 9 or more while at the same time typically has 10 or fewer, and can have 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, even 2 or fewer carbon atoms. Each R can be a methyl group. R' is independently in each occurrence selected from a group consisting of terminally unsaturated alkenyl group, typically having from 2 to 10 carbon atoms, and can have 2 or more 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, even 9 or more while at the same time typically has 10 or fewer, and can have 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, even 3 or fewer carbon atoms. Each R’ group can be a vinyl group. Subscript m refers to the average number of (R2R’SiO1 / 2) siloxane units per molecule and is generally 2 or more, 3 or more, even 4 or more, while at the same time is typically 8 or less, and can be 7 or less, 6 or less, 5 or less, or even 4 or less. Subscript d refers to the average number of (R2SiO2 / 2) siloxane units per molecule and is generally 50 or more, even 75 or more, 100 or more, 120 or more, 140 or more, 150 or more, even 160 or more, while at the same time is typically 250 or less, and can be 200 or less, 180 or less, 170 or less, even 160 or less. Subscript q refers to the average number of (SiO4 / 2) siloxane units per molecule and is generally one or more while at the same time 4 or less, preferably 3 or less, 2 or less, and most preferably is one. The alkenyl-functional siloxane can have the chemical formula (III) where each R is a methyl group, R’ is a vinyl group, m has an average value of 4, d has an average value in a range of 150 to 170, preferably an average value of 160, and q has an average value of one. The alkenyl-functional siloxane can be a linear siloxane having an average chemical formula (IV): [(CH3)(3-x-y)(OH)x(R’)ySiO1 / 2]2[(CH3)2SiO2 / 2]m[(CH3)XSiO2 / 2]n(IV) where: subscripts x and y are each selected from zero or one, provided one or both of subscripts x and y is zero; R’ is a hydrocarbyl group with 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, even 7 or more while at the same time 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, even 3 or fewer carbon atoms; subscript m has an average value in a range of 20 to 10,000 and can be 20 or more 40 or more, 50 or more 100 or more, 250 or more, 500 or more, 750 or more, 1000 or more, 2000 or more, 3000 or more, 4000 or more, 5000 or more, 6000 or more, even 70000 or more while at the same time is typically 10,000 or less, 9000 or less, 8000 or less, 8000 or less, 6000 or less, 5000 or less, 1000 or less, 750 or less, even 500 or less; Subscript n has an average value in a range of 2 to 1000 and can be 2 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 250 or more, 300 or more, 400 or more, 500 or more, 600 or more, 700 or more, 800 or more, 900 or more, while at the same time is typically 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, 250 or less, 200 or less, 170 or less, 150 or less, 130 or less, 110 or less, 100 or less, and can be 90 or less; and X is independently in each occurrence selected from a group consisting of R’ and perfluoro alkyl groups. Examples of suitable X groups include vinyl groups, hexenyl groups, and perfluoro alkyl groups such a perfluorobutylethyl (“PFBE”) group (CF3CF2CF2CF2CH2CH2-). (b) Silylhydride-functional siloxane The silylhydride-functional (SiH-functional) siloxane has an average of at least 2 SiH groups per molecule. The SiH-functional siloxane can be free of alkenyl groups, even free of any unsaturated groups. The SiH-functional siloxane is desirably one or any combination of more than one linear SiH-functional siloxane. Desirably, the SiH-functional siloxane has pendant SiH groups. Pendant groups attach to non-terminal atoms of a backbone (such as D and T type siloxane units). In contrast, “terminal” groups attach to terminal atoms of a backbone (such as M type siloxane units). For example, the SiH-functional siloxane can be any one or any combination of more than one SiH-functional siloxane selected from those having the following average chemical structures: [(CH3)3SiO1 / 2][(CH3)2SiO2 / 2]x[(CH3)HSiO1 / 2]y[(CH3)3SiO1 / 2] (V) and [(CH3)3SiO1 / 2][(CH3)(PFA)SiO2 / 2]z[(CH3)HSiO2 / 2]y[(CH3)3SiO1 / 2] (VI) where: subscript x has a value in a range of zero to 50, and can be zero or more, 2 or more, 4 or more, 8 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, even 45 or more, while at the same time is typically 50 or less, and can be 40 or less, 30 or less, 20 or less, even 10 or less; subscript y has a value in a range of 10 to 50, and can be 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, even 45 or more, while at the same time is typically 50 or less, and can be 40 or less, 30 or less, 20 or less, even 10 or less; subscript z has a value in a range of zero to 20, and can be zero or more, 2 or more, 4 or more, 8 or more, 10 or more, even 15 or more, while at the same time is typically 20 or less, 18 or less, 16 or less, 14 or less, 12 or less, 10 or less, 8 or less, 6 or less, 4 or less, even 2 or less; and PFA refers to a perfluoro alkyl group, preferably a perfluorobutylethyl (“PFBE”) group (CF3CF2CF2CF2CH2CH2-). One desirable SiH-functional siloxane has an average chemical structure: [(CH3)3SiO1 / 2][(CH3)HSiO2 / 2]A[(CH3)3SiO1 / 2]; where subscript A has an average value in a range of 10 to 50, preferably in a range of 20 to 30. The concentration of SiH-functional siloxane in the composition is desirably sufficient to provide a molar ratio of SiH groups relative to alkenyl groups from the alkenyl-functional siloxane gum that is one or more and that can be 1.5 or more, 2 or more, 2.5 or more, even 3 or more, while at the same time is typically 5 or less, and can be 4 or less, 3 or less, 2 or less, 1.50 or less, even 1.40 or less. (c) Hydrosilylation inhibitor Examples of suitable hydrosilylation inhibitors include those selected from the group consisting of : acetylenic alcohols; silylated acetylenic compounds; cycloalkenylsiloxanes; ene- yne compounds; triazoles; phosphines; mercaptans; hydrazines; amines; fumarates such as dialkyl fumarates, dialkenyl fumarates, and dialkoxyalkyl fumarates; maleates, nitriles, ethers, and combinations of two or more of the aforementioned materials. Suitable acetylenic alcohols include dimethyl hexynol, and 3,5-dimethyl-1-hexyn-3- ol, methyl butynol such as 1-butyn-3-ol, 1-propyn-3-ol, 2-methyl 3-butyn-2-o1, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3- phenyl-1-butyn-3-ol, 4-ethyl-1-octyn-3-ol , 3,5 dimethyl-1-hexyn-3-ol , and 1-ethynyl-1- cyclohexanol, and a combination thereof . Suitable cycloalkenylsiloxanes include methylvinylcyclosiloxanes exemplified by 1,3,5,7 tetramethyl-1,3,5,7- tetravinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane, combination thereof. Suitable ene-yne compounds include 3-methyl-3-penten-1-yne, 3,5- dimethyl-3-hexen-1-yne . Suitable triazoles include benzotriazole . Suitable amines include tetramethyl ethylenediamine. Silylated acetylenic compounds include (3-methyl-1-butyn-3-oxy ) trimethylsilane, ((1,1-dimethyl-2-propynyl)oxy) trimethylsilane , bis(3-methyl-1 butyn-3- oxy)dimethylsilane, bis(3-methyl-1-butyn-3-oxy) silanemethylvinylsilane, bis ((1,1-dimethyl-2- propynyl)oxy) dimethylsilane, methyl(tris(1,1-dimethyl-2-propynyloxy))silane, methyl(tris(3- methyl-1-butyn-3-oxy))silane, (3-methyl-1-butyn-3-oxy)dimethylphenylsilane, (3-methyl 1- butyn-3-oxy)dimethylhexenylsilane, (3-methyl-1-butyn 3-oxy)triethylsilane, bis(3-methyl-1- butyn-3-oxy)methyltrifluoropropylsilane, (3,5-dimethyl-1-hexyn-3-oxy)trimethylsilane, (3- phenyl-1-butyn-3-oxy)diphenylmethylsilane, (3-phenyl-1-butyn-3-oxy)dimethylphenyls dimethylvinylsilane, (3-phenyl-1-butyn-3-oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyn-1- oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyn-1-oxy)dimethylvinylsilane, (cyclohexyl-1- ethyn-1-oxy)diphenylmethylsilane, (cyclohexyl -1-ethyn-1-oxy)trimethylsilane, and combinations thereof. The amount of inhibitor is zero weight-percent (wt%) or more and can be 0.001 wt% or more, 0.0025 wt% or more, even 0.01 wt% or more while at the same time is typically 5 wt% or less, and can be one wt% or less, 0.5 wt% or less, or even 0.025 wt% or less based on the weight of the curable silicone release coating composition. (d) Solvent The composition can contain or be free of organic solvents. Examples of organic solvents include tetrahydrofuran, toluene, and hexane. The composition of the present invention desirably comprises the rhodium complex of structure (I) and / or structure (II), alkenyl-functional siloxane, SiH-functional siloxane, optionally hydrosilylation inhibitor and optionally solvent, where the concentration of rhodium from the rhodium complex is in a range of greater than 10 to less than 40, preferably 20 to 30, mass-parts per million mass parts of composition and the molar ratio of SiH-functionality from the SiH-functional siloxane to alkenyl-functionality from the alkenyl-functional siloxane is in a range of 5:1 to 1:1 (which is the same as a range of 5 to one). The composition of the present invention can comprise the rhodium complex of structure (I) and / or structure (II), alkenyl-functional siloxane, SiH-functional siloxane, optionally hydrosilylation inhibitor and optionally solvent, where the alkenyl-functional siloxane has an average chemical composition: [(CH3)2ViSiO1 / 2]4[(CH3)2)SiO2 / 2]dSiO4 / 4; where “Vi” refers to a vinyl group and subscript d has a value in a range of 150 to 170; the SiH-functional siloxane has an average chemical structure: [(CH3)3SiO1 / 2][(CH3)HSiO2 / 2]y[(CH3)3SiO1 / 2]; where subscript y has a value in a range of 20 to 30; and wherein the molar ratio of SiH- functionality from the SiH-functional siloxane to alkenyl-functionality from alkenyl-functional siloxane is in a range of 3:1 to 1:1 (that is, in a range of 3 to 1). EXAMPLES Table 1 lists materials for use in the following samples. SYL-OFF is a trademark of Dow Silicones Corporation.

[0003] Table 1 Component Description Source Alkenyl-functional Vinyl end-blocked Q-branched liquid polymer Prepare at taught in siloxane (a) having formula: US6806339 e Synthesis of Rh Complex 1 Conduct the following synthesis in a nitrogen-filled glovebox. Add 100 milligrams (mg) of Rh Complex 3 (0.257 millimole (mmol), 0.5 equivalents (equiv)) and 6 milliliter (mL) of Solvent 2 to a reaction vial to obtain a yellow / brown solution. Pass the solution through a 0.2 micrometer polytetrafluoroethylene syringe filter to remove Rh black. Wash the filter with two rinses of one mL of Solvent 2. Combine the filtrates to obtain Rh Complex 3 solutions and use in the following reaction. In a separate reaction vial add 301 mg of Ligand 1 (1.028 mmol, 2 equiv) and 2 mL of Solvent 2 to form a Ligand 1 solution. Add the Ligand 1 solution to the Rh Complex 3 solution prepared above. Rinse the vial used to prepare the Ligand 1 solution twice with one mL of Solvent 2 and add the rinses to the Rh Complex 3 solution. Stir the resulting solution at 23-25 degrees Celsius (°C) for one hour to obtain a precipitate of a yellow solid in an orange solution. Filter the solid by vacuum filtration using a fritted funnel and wash three times with 2 mL of Solvent 3. Dry the resulting solid in vacuo to obtain a yellow solid (302 mg, 78% yield) comprising Rh Complex 1 as evidenced by an ethylene31P NMR (202 MHz, THF-d8) peak at δ 31.12 (d, JRh-P= 132.6 Hz). Catalyst Solutions Prepare Catalyst Solution 1 by combining 0.175 g of Rh Complex 1 and 7 g of Solvent 1. Prepare Catalyst Solution 2 by combining 0.02 g of Rh Complex 1 and 1 g of Solvent 1. Prepare Catalyst Solution 3 by combining 0.02 g of Rh Complex 2 with 1 g of Solvent 1. Release Coating Compositions Prepare release coating compositions according to the formulations in Table 2. Amounts of each component are listed in grams. Combine Alkenyl-functional siloxane (a) and SiH- functional siloxane (b) in a dental cup and then mix at 3000 revolutions per minute for 30 seconds in a Flaktek mixer. Add the designated catalyst or catalyst solution and mix again at 3000 revolutions per minute for 30 seconds to obtain the release coating composition.

[0004] Table 2 Component Comp Ex Ex 1 Ex 2 Comp Ex Comp Ex Comp Ex A B C D Alkenyl-functional 3812 3806 3786 3772 3786 3818 Coat a release coating composition onto a substrate using a Euclid single roll coater. Pour a release coating composition into the coater. Pass through the coater a UPM Glassine paper substrate to coat the paper substrate with the release coating composition. Place the coated substrate into an oven at 204 °C (400 degrees Fahrenheit) for 21 seconds to obtain a release coating on the Glassine paper substrate, which is a now a “release liner”. The release coating coat weight is approximately 1.3 grams per square meter. Release Coating Characterization Use the following characterization methods to characterize the release coating composition performance. Miscibility of Rh Complex. Determine miscibility by visual observation of a composition containing the Rh Complex. If the composition is hazy or there is other evidence of particulates then the Rh Complex is considered not to be miscible. If the composition appears transparent with no visual particulates, then the Rh Complex is considered miscible. Bathlife (Workability). Maintain a release coating composition in a bath at 40 °C while continually measuring the viscosity of the release coating composition using a Brookfield DV2T-LV viscometer with SC4-24 spindle and SC4-13rd sample chamber. Record the time required to reach a viscosity greater than 96% torque. A time of greater than 60 minutes is desirable. Curability (Extractables). Cut a coated substrate immediately after forming the release liner into three sample discs using a die cutter (3.49 centimeter diameter). Handle the sample discs only with tweezers to avoid contamination. Analyze each disc by x-ray fluorescence (XRF) to quantify silicon atoms (which is proportional to coat weight) to determine initial silicone coat weight (Wis). Place the sample discs into individual 100 -milliliter (mL) bottles containing 40 mL of methyl isobutyl ketone. Cap the bottles and allow to sit for 30 minutes at 23-25 °C. Remove the sample disc from the methyl isobutyl ketone and place coated-side up on a clean tissue paper to allow residual methyl isobutyl ketone to evaporate. Analyze again by XRF to determine a final silicone coat weight (Wfs). Determine the extractable % for each sample using the following formula: Extractable % = [Wfs / Wi s]x100%. A lower value for Extractable% corresponds to a higher degree of cure performance. Lower Extractable% values are desirable. Anchorage (Rub-Off Resistance). Evaluate the anchorage of a release coating on a Glassine substrate for a release liner using an anchorage index by determining a percent rub-off resistance (ROR%) value. Immediately after curing a release coating on a Glassine substrate as described above, cut the sample into two sample discs using a die cutter (3.49 centimeter diameter). Analyze each sample disc by XRF for silicon atom concentration to determine an initial silicone coat weight (Wia). Abrade each sample disc four times with felt (Needle-TEX: Synthetic needle felt; IF-202 from IdealFELT in Brussels Belgium) under a 1.9 kilogram load using automated abrading equipment. After abrading, analyze the coatings for silicon atom content by XRF again to get a final coat weight (Wfa). Determine ROR% for the sample with the following formula: ROR%=[ Wfa / Wi a]x100%. Measure ROR% on sample discs immediately after curing and also on sample discs after allowing to age 7 days at 23-25 °C after curing. Release Force. Laminate onto a release liner prepared as described above with Tesa 7475 industrial standard tape (25 millimeters wide and 200 millimeters long) and then age the laminated sheets under weight (200 grams per square centimeter) at 23 °C and 50% relative humidity for 7 days. Cut the aged laminated sheets into strips (2.54 centimeters wide by 20.32 centimeters long). Evaluate the delaminate force for the Tesa 7475 industrial tape from the release liner sheets on IMASS SP-2100 slip / peel tester at a delamination speed of 0.3 meter per minute and on IMASS ZPE-1100W at delamination speeds of 10, 100 and 300 meters per minute. Peel the tape at a 180° angle. Measure each value in triplicate and average to present final result. Report values as release force in units of centiNewtons per 25 millimeters (cN / 25mm). Characteristics for the release coatings described above are summarized in Table 3. Table 3 Characteristics Comp Ex Ex 1 Ex 2 Comp Ex Comp Ex Comp Ex A B C D Mi i ilit f Mi i l Mi i l Mi i l Mi i l Mi i l N t Comp Ex C and Ex 2 have similar formulations and use Rh Complexes of similar, but not the same, structure. Yet, Ex 2 (which uses the Rh Complex of the present invention) achieves much lower and more desirable Release Force values. Ex 2 also achieves a longer Bathlife (worakability) time, which is desirable. Ex 1 and Ex 2, relative to Comp Ex A and Comp Ex B, illustrate that the most desirable release coating compositions using the Rh complex of the present invention have a mass parts Rh per million mass parts composition in a range of greater than 10 to less than 40, preferably in a range of 20 to 30. Comp Ex D illustrates that a precursor used to make the Rh complex of the present invention does not work as a hydrosilylation catalyst in the release coating compositions.

Claims

CLAIMS:

1. A composition comprising a rhodium complex having chemical structure (I) and / or chemical structure (II):where: P is phosphorous; “Ph” refers to a phenyl group; X is a halide selected from chloride, fluoride, bromide and iodide; each R1is independently selected from linear alkyl groups having from one to 8 carbon atoms; RhIrefers to a rhodium atom in an oxidation state of one; the “=” bound to the rhodium atom in structure (I) is ethylene; and the rhodium atom in structure (II) is bonded to the double bond in the cylooctene.

2. The composition of claim 1, where the rhodium complex has the chemical structure (I) where each R1is methyl and X is chloride.

3. The composition of claim 1 or claim 2, wherein the composition further comprises the following components: (a) an alkenyl-functional siloxane; and (b) a silylhydride- functional siloxane.

4. The composition of claim 3, wherein the alkenyl-functional siloxane has an average chemical composition: (R2R’SiO1 / 2)m(R2SiO2 / 2)d(SiO4 / 2)qwhere R is independently in each occurrence selected from hydrocarbyls having from one to 10 carbon atoms, R’ isindependently in each occurrence selected from terminally unsaturated alkenyl groups having from 2 to 10 carbon atoms, subscript m has a value in a range of 2 to 8, subscript d has an average value in a range of 50 to 250, and q has an average value in a range of 1 to 4.

5. The composition of claim 4, wherein the alkenyl-functional siloxane has an average chemical composition: [(CH3)2ViSiO1 / 2]4[(CH3)2)SiO2 / 2]dSiO4 / 2; where “Vi” refers to a vinyl group and subscript d has a value in a range of 100 to 200.

6. The composition of any one of claims 3-5, wherein the silylhydride-functional siloxane is a linear siloxane with pendant SiH groups.

7. The composition of claim 6, wherein the silylhydride-functional siloxane has an average chemical structure: [(CH3)3SiO1 / 2][(CH3)HSiO2 / 2]y[(CH3)3SiO1 / 2]; where subscript y has an average value in a range of 10 to 50.

8. The composition of any one of claim 3-7, wherein the concentration of rhodium complex is sufficient to provide a concentration of rhodium that is in a range of greater than 10 to less than 40 mass-parts per million mass parts composition and the molar ratio of silylhydride-functionality from component (b) to alkenyl-functionality from component (a) is in a range of 5:1 to 1:

1.

9. The composition of any one of claim 3-8, wherein the composition further comprises a hydrosilylation inhibitor, a solvent, or both a hydrosilylation inhibitor and a solvent.

10. The composition of any one of claim 3-9, wherein the alkenyl-functional siloxane has an average chemical composition: [(CH3)2ViSiO1 / 2]4[(CH3)2)SiO2 / 2]dSiO4 / 4; where “Vi” refers to a vinyl group and subscript d has a value in a range of 150 to 170; the silylhydride-functional siloxane has an average chemical structure: [(CH3)3SiO1 / 2][(CH3)HSiO2 / 2]y[(CH3)3SiO1 / 2]; where subscript y has a value in a range of 20 to 30; and wherein the molar ratio of silylhydride-functionality from component (b) to alkenyl-functionality from component (a) is in a range of 3:1 to 1:1.

Images