Synthesis and Use of Platinum(II) Dithiocarbamate Complexes

Abstract

The process involves the following components in a solvent: The process includes (i) combining a platinum(0) complex, (ii) tetrahydrocarbyl thiuram disulfide, and (iii) a solvent to form a platinum(II) dithiocarbamate complex. The process may further include separating the platinum(II) dithiocarbamate complex from the solvent to isolate the platinum(II) dithiocarbamate complex. The process may further include preparing a curable silicone composition by combining the platinum(II) dithiocarbamate complex with a vinyl-functionalized silicone and a silyl hydride-functionalized silicone to form a curable composition.

Description

[Technical Field]

[0001] The present invention relates to a process for preparing a platinum(II) dithiocarbamate complex, optionally for isolating the platinum(II) dithiocarbamate complex, and optionally for using the platinum(II) dithiocarbamate complex in preparing a curable silicone composition.

[0002] Introduction Platinum(II) dithiocarbamate complexes are useful in applications such as cancer treatment (see U.S. Patent No. 10494394) and dye-sensitized solar cells (see U.S. Patent Application Publication No. 2020 / 0381186). These references teach the production of platinum(II) dithiocarbamate complexes by reacting platinum(II) chloride salt (PtCl2) with sodium dithiocarbamate salt. A typical reaction scheme is as follows.

[0003] [ka]

[0004] Identifying a method for preparing platinum(II) dithiocarbamate complexes without requiring salts as reactants, thereby promoting the adaptability of the reaction in a wider range of polar chemical environments and avoiding metal ion byproducts, would advance the field. In particular, it is desirable to be able to prepare platinum(II) dithiocarbamate complexes from platinum(0) reactants.

[0005] A seemingly unrelated issue exists in the field of curable silicone compositions. Curable silicone compositions are useful as secondary insulators for electric motors because they can provide desirable levels of electrical insulation and thermal protection. Curable silicone compositions for such applications typically contain a silicone having vinyl (Vi) functional groups and a silicone crosslinking agent containing multiple silyl hydride (SiH) functional groups. Curable silicone compositions also typically contain a hydrosilylation catalyst. The Vi and SiH groups undergo hydrosilylation to cure the composition. Hydrosilylation occurs more rapidly at high temperatures but can also occur at lower temperatures, which can lead to storage instability in curable silicone compositions.

[0006] One approach to improving the storage stability of curable silicone compositions is to add inhibitors to prevent hydrosilylation curing at low temperatures. For example, U.S. Patent No. 4,260,726 describes adding a compound containing a [=NC(-S-)2-] subunit to a curable silicone composition to reduce the viscosity increase of the curable composition when aged at 80°C (indicating improved storage stability) while still achieving rapid curing reactivity at 175°C. However, the method of U.S. Patent No. 4,260,726 still results in a viscosity increase of the composition at a temperature of 80°C. It is desirable to identify a method for obtaining storage stability of a curable silicone composition that results in less viscosity increase during storage than that obtained by the method disclosed in U.S. Patent No. 4,260,726, while still achieving rapid initiation of curing at temperatures above 120°C.

[0007] U.S. Patent Provisional Application No. 63 / 535620 discloses a process for preparing a curable silicone composition to achieve these objectives. However, this process requires forming a catalyst / inhibitor masterbatch containing a platinum hydrosilylation catalyst, tetrahydrocarbyl thiuram disulfide, and an aromatic silicone carrier fluid, and then combining the masterbatch with a vinyl-functionalized silicone and a silyl hydride-functionalized silicone to form a curable composition. To avoid the need for an aromatic silicone carrier fluid, it is desirable to develop a solution in a way that does not require adding a catalyst / inhibitor masterbatch containing an aromatic silicone carrier fluid to form a curable composition. [Overview of the project]

[0008] The present invention provides a process for preparing platinum(II) dithiocarbamate complexes from platinum(0) complexes without requiring salt reactants. Surprisingly, platinum(II) dithiocarbamate complexes have been found to be useful in solving the problems identified above herein with respect to curable silicone compositions. In particular, platinum(II) dithiocarbamate complexes prepared by the process of the present invention are useful as heat-induced catalysts for curable silicone compositions.

[0009] The present invention provides a curable silicone composition that exhibits improved storage stability, as demonstrated by less viscosity increase during storage than compositions obtained by simply adding an inhibitor to a composition of a catalyst and a reactive silicone composition, as described in U.S. Patent No. 426076. Furthermore, the present invention does not require the formation of a curable composition by combining a catalyst / inhibitor masterbatch containing an aromatic silicone carrier fluid with vinyl-functionalized silicones and silyl hydride-functionalized silicones.

[0010] Tests of silicone compositions prepared according to the method disclosed in U.S. Patent No. 426076 showed a viscosity increase of 40% or more after storage at 80°C for 150 hours. Silicone compositions prepared according to the process of the present invention show a viscosity increase of 20% or less, and even 10% or less, after storage at 80°C for 150 hours. Furthermore, curable silicone compositions produced according to the process of the present invention exhibit rapid curing, as indicated by a DSC exothermic sharpness of 35°C or less when using a temperature gradient rate of 20°C / min from 25°C to 300°C, and have an exothermic onset temperature (curing onset temperature) exceeding 120°C. Moreover, the process of the present invention may contain less than 5% by weight, less than 2% by weight, or less than 1% by weight of organic solvents, or may even be completely free of organic solvents, so that the curable silicone compositions prepared according to the present invention contain less than 5% by weight, less than 2% by weight, or less than 1% by weight of organic solvents, or even be completely free of organic solvents.

[0011] This invention is the result of the surprising discovery that when a platinum(0) complex is combined with tetrahydrocarbyl thiuram disulfide in a solvent, a platinum(II) dithiocarbamate complex is formed. The reaction can be represented by the following exemplary reaction scheme.

[0012] [ka]

[0013] The reaction is typically spontaneous and can result in phase separation of the platinum(II) dithiocarbamate complex from the solvent. The platinum(II) dithiocarbamate complex can be isolated from the solvent and used as desired. One particularly desirable and surprising application is as a heat-induced catalyst for curable silicone compositions cured by hydrosilylation reactions. The platinum(II) dithiocarbamate complex can then be added to vinyl-functionalized silicones and silylhydride-functionalized silicones to form curable silicone compositions without the need for an aromatic silicone carrier fluid or any carrier fluid, resulting in curable silicones with much better storage stability than those formed by adding an inhibitor to a composition already containing curable silicone and a catalyst.

[0014] In a first aspect, the present invention is a process comprising the step of (a) forming a platinum(II) dithiocarbamate complex in a solvent by combining the following components, namely (i) a platinum(0) complex, (ii) tetrahydrocarbyl thiuram disulfide, and (iii) a solvent.

[0015] In a second aspect, the present invention is a process of the first aspect, further comprising the following step (b) after step (a), namely (b) separating the platinum(II) dithiocarbamate complex from the solvent to isolate the platinum(II) dithiocarbamate complex.

[0016] In a third aspect, the present invention is a process of the first or second aspect for preparing a curable silicone composition, further comprising the step of combining the platinum(II) dithiocarbamate complex prepared in step (a) with a vinyl-functionalized silicone and a silyl hydride-functionalized silicone to form a curable composition.

[0017] The present invention is useful for preparing platinum(II) dithiocarbamate complexes. The present invention is also useful for forming curable silicone compositions with improved storage stability. MODES FOR CARRYING OUT THE INVENTION

[0018] If no date is indicated together with the test method number, the test method refers to the latest test method valid on the priority date of the present document. References to test methods include both references to the testing association and the test method number. The following abbreviations and identifiers for test methods apply herein. ASTM refers to test methods of the American Society for Testing and Materials, EN refers to European Norm, DIN refers to Deutsches Institut für Normung, ISO refers to the International Organization for Standards, and UL refers to Underwriters Laboratory.

[0019] Products identified by trade names refer to compositions available under those trade names on the priority date of the present document.

[0020] The term "multiple" means two or more. The term "and / or" means "and, or as an alternative". All ranges include their endpoints unless specifically indicated otherwise.

[0021] "Silicone" refers to polysiloxane, which is a molecule comprising a plurality of siloxane units. For identifying siloxane units, the abbreviations M, D, T and Q are often used to refer to siloxane units in a siloxane molecule. M-type siloxane units have the chemical formula: R a ₃SiO 1 / 2 refers to a unit having . D-type siloxane units have the chemical formula: R a ₂SiO 2 / 2 refers to a unit having . T-type siloxane units have the chemical formula: R a SiO 3 / 2 refers to a unit having . Q-type siloxane units have the chemical formula: SiO 4 / 2This refers to a unit having R. a The oxygen atom is independently selected at each occurrence from hydrogen, a hydrocarbyl group (substituted or unsubstituted), hydroxyl, alkoxyl, or essentially any other group bonded to the silicon atom. O refers to the oxygen atom bonded to the silicon atom of another siloxane unit. The subscript is a multiple of 1 / 2 to reflect that oxygen is bonded to this silicon atom and, likewise, to another silicon atom of another siloxane unit having a multiple of 1 / 2 in the denominator, so that both siloxane units reflect 1 / 2 ownership of the same oxygen atom. The number in the subscript for oxygen reflects the number of oxygen atoms bonded to that particular silicon atom, also bonded to the silicon atom of another siloxane unit. Typically, a subscript exists accompanying the siloxane unit itself to indicate the relative amount of siloxane units in the molecule. If the subscript accompanying a siloxane unit is greater than 1, the subscript refers to the average number of those siloxane units in the molecule. If the subscript accompanying a siloxane unit is less than 1, the subscript indicates the average molar ratio of the siloxane unit associated with the subscript to the total number of moles of all siloxane units in the molecule. Since the subscript 1 is typically not present, a siloxane unit is understood to have a subscript 1 if it does not contain one. While the chemical formulas of silicones typically list siloxane units in blocks, this does not necessarily imply block polymerization (i.e., the siloxane units exist in the molecule as blocks), but rather they are presented as blocks for convenience to indicate how many of each siloxane unit are present in total in the polymer.

[0022] "Resinous polysiloxane" or "resin" contains 30 mole percent (mol%) or more and may contain 50 mol% or more, 70 mol% or more, 90 mol% or more, or even 100 mol% of Q-type siloxane units, T-type siloxane units, or a total of Q-type siloxane units and T-type siloxane units. In contrast, "non-resinous" silicones often simply refer to "polymers," "polymeric," or "linear" silicones, siloxanes, or polysiloxanes, containing less than 30 mol% of a combination of Q-type siloxane units and T-type siloxane units, and often containing only M-type and D-type siloxane units.

[0023] The "silyl hydride" functional group refers to a group that has a hydrogen atom directly bonded to a silicon atom, forming a SiH group.

[0024] "DSC thermal sharpness" refers to the temperature range defined by the temperature from the onset of heating to the peak heating temperature. In other words, DSC thermal sharpness is the value of (peak heating temperature) - (onset of heating temperature). DSC thermal sharpness is a measure of how quickly a composition hardens after curing has started, with a smaller value indicating faster hardening.

[0025] "Solid" refers to a state of matter that is not perceptibly flowing to the naked eye.

[0026] The "pour point" refers to the melting point for crystalline materials and the glass transition temperature for amorphous materials. If a material has both a melting point and a glass transition temperature, the pour point is the higher of the two. Essentially, the pour point is the temperature at which a solid (non-flowable) material transitions to a flowable state. The pour point of a material is determined by differential scanning calorimetry (DSC) using the ASTM method D3418.

[0027] The present invention relates to a process for preparing a platinum(II) dithiocarbamate complex by combining (i) a platinum(0) complex, (ii) tetrahydrocarbyl thiuram disulfide, and (iii) a solvent in a solvent. The platinum(0) complex and tetrahydrocarbyl thiuram disulfide react to form a platinum(II) dithiocarbamate complex in the solvent. Typically, the platinum(II) dithiocarbamate complex is formed spontaneously when the components are combined in the solvent. For example, the combination of components can be stirred by mechanical stirring. In the broadest range, the temperature at which the combinations of components (i) to (iii) occur is not important, but typically they combine at temperatures above 0°C, preferably above 10°C, and may also be above 15°C, above 20°C, above 23°C, above 25°C, or even above 30°C, while at the same time typically they are below 70°C, below 60°C, below 50°C, below 40°C, or even below 30°C.

[0028] Platinum(0) complexes are complexes of platinum(0) and complexing agents that form solvent-soluble compounds. In other words, it is desirable that platinum(0) complexes be solvent-soluble. Examples of desirable platinum(0) complexes include those useful as hydrosilylation catalysts, such as platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Karstedt catalyst), platinum-carbonyl complexes, platinum(0)-divinyltetramethyldisiloxane complexes, platinum(0)-cyclovinylmethylsiloxane complexes, platinum-carbene complexes, and any one or any combination of two or more platinum(0) complexes with phosphine, olefins, and / or carbonyl ligands.

[0029] The tetrahydrocarbyl thiuram disulfide component (ii) is preferably any one component selected from the group consisting of tetraalkyl thiuram disulfides and tetraaryl thiuram disulfides, or any combination of two or more components. Preferably, tetrahydrocarbyl thiuram disulfide is any one component selected from the group consisting of tetrabenzyl thiuram disulfide (pour point 124°C according to Sigma-Aldrich), tetramethyl thiuram disulfide (pour point 156-158°C according to Sigma-Aldrich), tetraethyl thiuram disulfide (pour point 69-71°C according to Sigma-Aldrich), tetra(isopropyl) thiuram disulfide (pour point 115-117°C according to Sigma-Aldrich), tetra(isobutyl) thiuram disulfide (pour point 73.5-74.5°C according to ChemBK), and tetra(n-butyl) thiuram disulfide (pour point 33°C according to Fisher Scientific), or any combination of two or more components.

[0030] The concentration of tetrahydrocarbyl thiuram disulfide is preferably such that the molar ratio of tetrahydrocarbyl thiuram disulfide to platinum in the platinum(0) complex is in the range of 1 to 3, although it may be in the range of 1 to 2. Such a ratio is desirable to avoid excess platinum(0) complex.

[0031] Solvent component (iii), in the broadest scope of the present invention, is any material capable of dissolving the platinum(0) complex and tetrahydrocarbyl thiuram disulfide in the process. Examples of suitable solvents include any one or any combination of two or more selected from the group consisting of aromatic hydrocarbons, halogenated hydrocarbons, ethers, and aprotic polar solvents. To facilitate the isolation of the platinum(II) dithiocarbamate complex from the solvent by evaporation of residual solvent, it is generally desirable to use a solvent with the lowest possible boiling point in the process. Particularly useful solvents include halogenated hydrocarbons, such as chloroform (CHCl3) and / or deuterated chloroform (CDCl3). Preferably, the solvent is silicon-free.

[0032] It is desirable to use as little solvent as possible to dissolve the platinum(0) complex and tetrahydrocarbyl thiuram disulfide, promote easy contact between the two reactants, and, if desired, remove the solvent afterward. Examples of suitable concentration ranges for each of the platinum(0) complex and tetrahydrocarbyl thiuram disulfide in the solvent are 0.01 mol(M) or more, preferably 0.1 M or more, while simultaneously typically 2.5 M or less, and may also be 1.0 M or less.

[0033] During step (a), the platinum(0) complex reacts with tetrahydrocarbyl thiuram disulfide to form a platinum(II) dithiocarbamate complex. The platinum(II) dithiocarbamate complex is typically solid at 25°C and is soluble or dispersed in a solvent. The platinum(II) dithiocarbamate complex can be phase-separated from the solvent to obtain a precipitate or dispersion.

[0034] The process of the present invention may further include the following step (b) after step (a), namely, (b) separating the platinum(II) dithiocarbamate complex from the solvent to isolate the platinum(II) dithiocarbamate complex.

[0035] In the broadest scope of the present invention, separation can be carried out by any means capable of isolating the platinum(II) dithiocarbamate complex from the solvent. For example, evaporation of the solvent from the platinum(II) dithiocarbamate complex is a preferred method for separating the platinum(II) dithiocarbamate complex from the solvent. Another possible method for separating the platinum(II) dithiocarbamate complex from the solvent includes, preferably, decanting the solvent from the platinum(II) dithiocarbamate complex after centrifugation. Yet another possible method is to filter the solvent from the platinum(II) dithiocarbamate complex, preferably then wash with the platinum(II) dithiocarbamate complex using a low-boiling point solvent, and evaporate the solvent from the platinum(II) dithiocarbamate complex. It is also possible to isolate the platinum(II) dithiocarbamate complex by spray drying the mixture of platinum(II) dithiocarbamate complexes in the solvent to remove the solvent.

[0036] The objective of step (b) is to isolate the platinum(II) dithiocarbamate complex by removing the solvent, preferably any excess reactants and by-products, from the platinum(II) dithiocarbamate complex. This step (b) reduces the amount of solvent, preferably reactants and by-products, introduced by the platinum(II) dithiocarbamate complex when the platinum(II) dithiocarbamate complex is used in further applications. In the broadest scope of the present invention, some solvent may remain with the platinum(II) dithiocarbamate complex. However, it is desirable that the amount of solvent remaining with the platinum(II) dithiocarbamate complex after step (b) be less than 1% by weight, preferably less than 0.1% by weight. It is most desirable to remove all solvent from the platinum(II) dithiocarbamate complex.

[0037] A particularly desirable embodiment of the process of the present invention is a process for preparing a curable silicone composition, comprising, in addition to step (a), preferably in addition to step (b), and after step (b), combining the platinum (II) dithiocarbamate complex prepared in step (a) with a vinyl-functional silicone and a silylhydride-functional silicone to form a curable composition. The term "curable" means that the composition has components capable of reacting with each other in an additive manner to form a crosslinked material. In the case of the curable silicone composition of the present invention, curable refers to the ability to undergo a hydrosilylation curing reaction. Platinum (II) dithiocarbamate functions as a hydrosilylation catalyst for the curable silicone composition. The curable silicone composition may be a liquid composition, which means it is flowable at 25°C and a pressure of 101 kilopascals.

[0038] The vinyl-functional silicone and the silylhydride-functional silicone may be different silicone molecules, or may be the same molecule having both vinyl and silylhydride functional groups. Both the vinyl-functional silicone and the silylhydride-functional silicone may be linear silicones, both may be silicone resins, or one may be a linear silicone and the other may be a silicone resin.

[0039] Examples of suitable vinyl-functional silicones that are linear silicones include those having chemical structure (I): ViR₂SiO(R₂SiO) d SiR₂Vi (I) (wherein "Vi" refers to a vinyl group, "R" is independently a hydrocarbyl in each instance, preferably a hydrocarbyl having 1 to 10 carbon atoms, and may have 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, and even 9 or more carbon atoms, while simultaneously having typically 10 or fewer, 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, and even 2 or fewer carbon atoms. This includes any one silicone or any combination of two or more silicones. Typically, each R is methyl.

[0040] The subscript d is a value of 10 or more, preferably 20 or more, and may also be 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, 160 or more, 170 or more, and even 175 or more, while at the same time typically being 1000 or less, and can be 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, and may also be 270 or less, 250 or less, 225 or less, 200 or less, 190 or less, and even 180 or less.

[0041] A suitable example of a linear silicone with silyl hydride functionality is the chemical structure (II): R3SiO(R2SiO) x (HRSiO) y SiR3(II) (In the formula, "R" is independently a hydrocarbyl in each instance, preferably a hydrocarbyl having 1 to 10 carbon atoms, and can have 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, and even 9 or more carbon atoms, while simultaneously having typically 10 or fewer, 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, and even 2 or fewer carbon atoms. This includes any one silicone or any combination of two or more silicones. Typically, each R is methyl. The subscript x is a value of 1 or more, preferably 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 15 or more, 20 or more, and may also be a value of 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, 160 or more, 170 or more, and even 175 or more, while at the same time it is typically a value of 300 or less, and may also be a value of 270 or less, 250 or less, 225 or less, 200 or less, 190 or less, and even 180 or less. The subscript y is a value of 2 or greater, 3 or greater, 4 or greater, 5 or greater, 6 or greater, 7 or greater, 8 or greater, 9 or greater, 10 or greater, 15 or greater, and 20 or greater, and may also be a value of 30 or greater, 40 or greater, 50 or greater, 60 or greater, 70 or greater, 80 or greater, 90 or greater, 100 or greater, 110 or greater, 120 or greater, 130 or greater, 140 or greater, 150 or greater, 160 or greater, 170 or greater, and even 175 or greater, while at the same time it is typically a value of 300 or less, and may also be a value of 270 or less, 250 or less, 225 or less, 200 or less, 190 or less, and even 180 or less.

[0042] Vinyl-functionalized silicones and silyl hydride-functionalized silicones may be the same silicone resin having both vinyl and silyl hydride functional groups. If vinyl-functionalized silicones and silyl hydride-functionalized silicones are the same silicone, the composition may further contain additional vinyl-functionalized silicones and / or silyl hydride-functionalized silicones. Alternatively, if vinyl-functionalized silicones and silyl hydride-functionalized silicones are the same silicone, the composition may not contain additional vinyl-functionalized silicones and / or silyl hydride-functionalized silicones.

[0043] Vinyl-functionalized silicones and silyl hydride-functionalized silicones have the following chemical structure (III): (PhSiO 3 / 2 ) a (ViMeSiO 2 / 2 ) b (HMeSiO 2 / 2 )c [(Me)3SiO 1 / 2 ] d (III) The same silicone resin may have the following characteristics (wherein "Ph" refers to a phenyl group, "Vi" refers to a vinyl group, "Me" refers to a methyl group, and the subscripts a, b, c, and d refer to the molar ratio of the associated siloxane units to the total number of moles of siloxane units in the molecule): Subscript a has a value of 0.3 or greater, and may be 0.4 or greater, or 0.43, and at the same time typically 0.7 or less, 0.5 or less, and even 0.45 or less. Subscript b has a value of 0.05 or greater, and may be 0.10 or greater, 0.12 or greater, and even 0.14 or greater, while at the same time typically 0.2 or less, and may be 0.15 or less. The subscript c is typically a value of 0.05 or greater, and may also be 0.13 or greater, 0.14 or greater, 0.15 or greater, and even 0.16 or greater, while at the same time typically being 0.2 or less, and may also be 0.18 or less, and even 0.17 or less. The subscript d is generally a value of 0.15 or greater, and may also be 0.20 or greater, and even 0.25 or greater, while at the same time typically being 0.35 or less, and may also be 0.30 or less, and even 0.26 or less.

[0044] The molar ratio of SiH functional groups to vinyl functional groups in the curable silicone composition is preferably 0.8 or higher, and may also be 1.0 or higher, 1.1 or higher, 1.2 or higher, 1.3 or higher, 1.4 or higher, or even 1.5 or higher, while simultaneously preferably being 2 or lower.

[0045] The process of the present invention may not include an aromatic silicone carrier fluid when combining the platinum(II) dithiocarbamate complex with a vinyl-functionalized silicone and a silyl hydride-functionalized silicone to form a curable silicone composition.

[0046] The curable silicone composition of the present invention exhibits rapid curing reactivity, as indicated by a DSC exothermic sharpness of 35°C or less when using a temperature gradient rate of 20° / min from 25°C to 300°C. Curing can be initiated at temperatures of 200°C or higher, 175°C or higher, 150°C or higher, or even 120°C or higher. Curing typically has a peak temperature of less than 275°C, as measured by the DSC exothermic sharpness evaluation. The curable silicone composition exhibits stability from curing at a temperature of 80°C, even after aging for more than 150 hours, as evidenced by a viscosity increase of less than 20% after aging. [Examples]

[0047] The examples are prepared using the materials listed in Table 1.

[0048] [Table 1] DOWSIL is a trademark of The Dow Chemical Company. SYL-OFF is a trademark of Dow Silicones Corporation.

[0049] Preparation of platinum(II) dithiocarbamate complexes Pt(0) complex with complex 1-tetrahydrocarbyl thiuram disulfide 1 Add 400 mg of Pt(0) complex and 3 mL of solvent 1 to a 10 ml (mL) vial to obtain a clear yellow solution. Add 170 mg of tetrahydrocarbyl thiuram disulfide 1 to the vial in 3 mL of solvent 1. The molar ratio of tetrahydrocarbyl thiuram disulfide 1 to Pt from the Pt(0) complex is 1.5. A precipitate forms rapidly. Mix the contents of the vial at 23°C for 10 minutes, then centrifuge the vial to obtain a clear orange supernatant on top of the solid precipitate. Remove the clear orange supernatant with a pipette. Add 1 mL of solvent 1, then centrifuge, and complete two rinses of the precipitate by removing the solvent with a pipette after each rinse. Dry the residual yellow solid in air under atmospheric conditions (23°C and 101 kPa pressure) to allow the solvent to evaporate, leaving complex 1.

[0050] Pt(0) complex with complex 2-tetrahydrocarbyl thiuram disulfide 2 Add 400 mg of Pt(0) complex and 3 mL of solvent 1 to a 10 ml (mL) vial to obtain a clear yellow solution. Add 140 mg of tetrahydrocarbyl thiuram disulfide 2 in 3 mL of solvent 1 to the vial. The molar ratio of tetrahydrocarbyl thiuram disulfide 2 to Pt from the Pt(0) complex is 1. The contents of the vial rapidly change color from yellow to dark red / brown. Mix the contents of the vial at 23°C for 10 minutes to induce the formation of a brown precipitate / crystal. Dry the mixture in air under atmospheric conditions (23°C and 101 kPa pressure) to allow the solvent to evaporate. Wash the residual solid with hexane to obtain a clean brown solid. Dry the clean brown solid in air under atmospheric conditions to allow the hexane to evaporate to obtain complex 2.

[0051] Pt(0) complex with complex 3-tetrahydrocarbyl thiuram disulfide 3 Add 400 mg of Pt(0) complex and 3 mL of solvent 1 to a 10 ml (mL) vial to obtain a clear yellow solution. Add 193 mg of tetrahydrocarbyl thiuram disulfide 3 to the vial in 3 mL of solvent 1. The molar ratio of tetrahydrocarbyl thiuram disulfide 3 to Pt from the Pt(0) complex is 1. The contents of the vial rapidly change color from yellow to dark red / brown. Mix the contents of the vial at 23°C for 10 minutes to form a dark red / brown solution. Dry the mixture in air under atmospheric conditions (23°C and 101 kPa pressure) to allow the solvent to evaporate. Wash the residual solid with hexane to obtain a clean brown solid. Dry the clean brown solid in air under atmospheric conditions to allow the hexane to evaporate to obtain complex 3.

[0052] Preparation of curable silicone compositions Curable silicone composition samples 1 to 4 are prepared by combining the components of each sample listed in Table 2 (values ​​in grams) in a 200-gram dental mixer cup, and then blending them together using a planetary mixer at 3500 revolutions per minute for 1 minute to obtain curable silicone composition samples.

[0053] Sample A is prepared by combining 0.0978 g of Pt(0) complex and 19.91 g of carrier fluid in a first 40 g dental mixer cup and blending them with a planetary mixer at 3000 rpm for 2 minutes. Sample A is then obtained by adding 10.015 g of bifunctional silicone resin and 0.207 g of the contents of the first 40 g dental mixer cup to a second 40 g dental mixer cup and blending them with a planetary mixer at 3000 rpm for 2 minutes.

[0054] Sample B is prepared by combining 4.972 g of vinyl-functional linear siloxane 1 and 0.034 g of diluted Pt(0) complex in a first 40 g dental mixer cup, and then mixing with a planetary mixer at 3000 rpm for 2 minutes. In a second 40 g mixer cup, 4.978 g of vinyl-functional linear siloxane 1, 0.0087 g of silyl hydride-functional linear siloxane 1, and 0.005 g of inhibitor 1 are added, and the mixture is mixed with a planetary mixer at 3000 rpm for 2 minutes. The components of the first and second 40 g dental mixer cups are combined and mixed with a planetary mixer at 3000 rpm for 2 minutes to obtain Sample B.

[0055] [Table 2] * The viscosity increased too much, preventing the aging process from completing within the target timeframe.

[0056] Characterization of the sample Each sample of the curable silicone composition was characterized for storage stability and rapid curing. The test method was as follows, and the results are shown in Table 2.

[0057] Storage stability Storage stability is evaluated by measuring the degree to which the viscosity of the sample increases as it ages. The objective is to achieve a viscosity increase of less than 20% after aging at 80°C (50°C for samples 3 and B) for 142–191 hours. The viscosity of the sample is measured using a Brookfield DV3T cone / plate (CP40) viscometer with a Haake K20 / DC3 water circulating bath, with the sample temperature maintained at 25°C. The initial viscosity is measured immediately after the sample is prepared. Then, as shown in Table 3, the sample is aged at 50°C or 80°C for 142–191 hours, and the viscosity of the sample after aging is measured to obtain the post-aging viscosity.

[0058] Rapid curing test The curing rate of the sample is evaluated using differential scanning calorimetry (DSC). A TA instruments Q2000 DSC with a liquid nitrogen cooling system is used. A 10 milligram sample is used in a perforated DSC pan. DSC scans are collected at a sampling interval of 1 second per point. First, the sample is equilibrated at -100°C, and then the sample is heated to 300°C at a rate of 20°C / min. The initial exothermic temperature (onset temperature) and the achieved peak temperature (peak exothermic temperature) are recorded. If the difference between the onset temperature and the peak exothermic temperature, i.e., the DSC exothermic sharpness, is less than 35°C, the sample is considered to have "rapidly cured". If the temperature difference (DSC exothermic sharpness) is greater than 35°C, the sample is not considered to have "rapidly cured". In other words, if curing continues for more than 35 minutes (temperature gradient of 1 degree / min), the curing is not considered "rapidly cured".

[0059] Consideration Samples 1-4 represent curable liquid silicone compositions prepared by adding a platinum(II) dithiocarbamate complex, which contains neither a solvent nor a carrier fluid, to a reactive silicone component. Samples 1-3 utilize silicones containing both vinyl and SiH functional groups on the same molecule. Sample 4 utilizes separate reactive silicone components, one having vinyl functional groups and the other having SiH functional groups.

[0060] Samples 1-3 showed a viscosity increase of less than 20% when stored at 80°C for 150 hours. Similarly, sample 4 showed a viscosity increase of less than 20% when stored at 50°C for 142 hours, and the data suggests that it will have a viscosity increase of less than 20% when stored at 80°C for 150 hours. Furthermore, the silicone compositions produced according to the process of the present invention exhibit rapid curing, as indicated by a DSC exothermic sharpness of 35°C or less when using a temperature gradient rate of 20°C / min from 25°C to 300°C, and the exothermic onset temperature (curing onset temperature) exceeds 120°C.

[0061] Comparing Sample 1 with Sample A, the advantage of using a Pt(II) dithiocarbamate complex as a hydrosilylation catalyst to maintain viscosity stability (storage stability) is clear when the reactive silicone composition contains both SiH and SiVi on the same molecule, compared to a formulation using only the Karsetedt catalyst.

[0062] Furthermore, comparing Sample 4 and Sample B, it is clear that when a reactive silicone composition contains both SiH and SiVi on different silicone components, the advantage of using a Pt(II) dithiocarbamate complex as a hydrosilylation catalyst to maintain viscosity stability (storage stability) is evident for certain formulations containing a Karrstedt catalyst along with an inhibitor such as 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

Claims

1. (a) In the solvent, the following components, namely, (i) Platinum(0) complex and (ii) Tetrahydrocarbyl thiuram disulfide and (iii) Solvent and, A process comprising the step of combining to form a platinum(II) dithiocarbamate complex.

2. The process according to claim 1, wherein the platinum(0) complex is a platinum(0) hydrosilylation catalyst.

3. The process according to claim 1 or 2, wherein the platinum (0) complex is a Karstedt catalyst.

4. The process according to any one of claims 1 to 3, wherein the tetrahydrocarbyl thiuram disulfide is selected from the group consisting of tetrabenzyl thiuram disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetra(isopropyl) thiuram disulfide, tetra(n-butyl) thiuram disulfide, and tetra(isobutyl) thiuram disulfide.

5. The process according to any one of claims 1 to 4, wherein the molar ratio of tetrahydrocarbyl thiuram disulfide to platinum in the hydrosilylation catalyst is in the range of 1 to 3.

6. The process according to any one of claims 1 to 5, wherein the solvent is selected from the group consisting of aromatic hydrocarbons, halogenated hydrocarbons, ethers, and aprotic polar solvents.

7. The process described above proceeds as follows: step (a) followed by step (b), (b) The process according to any one of claims 1 to 6, further comprising the step of separating the platinum(II) dithiocarbamate complex from the solvent to isolate the platinum(II) dithiocarbamate complex.

8. The process according to any one of claims 1 to 7, further comprising the step of combining the platinum(II) dithiocarbamate complex prepared in step (a) with a vinyl-functionalized silicone and a silyl hydride-functionalized silicone to form a curable composition.

9. The process according to any one of claims 1 to 8, wherein the vinyl-functionalized silicone and the silyl hydride-functionalized silicone are the same silicone containing both vinyl functional groups and silyl hydride functional groups.

10. The vinyl-functionalized silicone has the chemical formula: (PhSiO ３／２ ) ａ (ViMeSiO ２／２ ) ｂ (HMeSiO ２／２ ) ｃ [(Me) ３ SiO １／２ ｄ The process according to claim 9, having the formula (wherein Ph represents a phenyl group, Vi represents a vinyl group, Me represents a methyl group; subscripts a, b, c and d each represent the molar ratio of the corresponding siloxane unit to the total number of moles of all siloxane units in the molecule, subscript a is in the range of 0.3 to 0.7, subscript b is in the range of 0.05 to 0.2, subscript c is in the range of 0.05 to 0.2, and subscript d is in the range of 0.15 to 0.35).​

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