Inhibitors for hydrosilylation catalysts

Abstract

To provide an effective and reversible inhibitor of a hydrosilylation catalyst for extending the pot life of a hydrosilylation reaction mixture.SOLUTION: There is provided a composition comprising the following components: (a) a hydrosilylation catalyst containing a metal-ligand complex and (b) an inhibitor of a catalyst represented by the formula (1) which is different from a ligand of a metal-ligand complex, X-CHR-CO-Y (I) (wherein, -X is -NO2, -S(=O)R or Rc2RaC-CO-; Y is 2-furyl, -NO2 or -CRbXRd3-x; Ra and Rb are independently selected from -O-R, -NO2, -F, -Cl, -Br or the like; R are each independently selected from -H, an optionally fluorinated alkyl having 1 to 8 carbon atoms, -F or the like; Rc and Rd are independently selected from -H, an optionally fluorinated alkyl having 1 to 8 carbon atoms, -F or the like; x is 0 or 1.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to the use of novel inhibitors of hydrosilylation catalysts, compositions containing the catalyst and inhibitor, and processes for carrying out hydrosilylation reactions using the catalyst and inhibitor. [Background technology]

[0002] Organoplatinum catalysts, such as Karstedt's catalyst (e.g., the adduct of divinyltetramethyldisiloxane and chloroplatinic acid), are used to catalyze hydrosilylation reactions, for example, to obtain crosslinked polydimethylsiloxanes (PDMS). Typically, the reaction composition is premixed before applying the catalyst. The high activity of platinum catalysts reduces the pot life of the composition. A pot life of several hours at room temperature is sufficient for applications in which the composition is cast or screen printed. However, other applications of the composition require a longer pot life, such as the inkjet printing applications disclosed by Sturgess ("3D reactive inkjet printing of polydimethylsiloxane", J. Mater. Chem. C, 2017, 5, 9733-9743) and Mikkonen et al. ("Inkjet Printable Polydimethylsiloxane for All-Inkjet-Printed Multilayered Soft Electrical Applications"; ACS Appl. Mater. Interfaces 2020, 12, 10, 11990-11997). To extend the pot life of a composition used for inkjet printing, it may be refrigerated immediately after transfer to a print cartridge. Refrigerated ink may be usable for several days. Another approach to reducing the viscosity of inkjet-printable compositions and thereby extending their pot life is to add a solvent. A known solvent is octyl acetate (OA), which is miscible with PDMS and provides a suitable vapor pressure for printing. The addition of OA dilutes the composition and extends the pot life of the formulation. Summary of the Invention [Problem to be solved by the invention]

[0003] The content of solvents as viscosity modifiers and pot-life extenders in inkjet-printable formulations must not be too high. Therefore, the pot-life of inkjet-printable formulations is limited to a maximum of a few hours. This poses significant practical and technical limitations for inkjet printing applications. Pot-life and formulation viscosity are also an issue in applications where solvents are not used in the formulation, such as in LED manufacturing processes that involve dispensing the formulation with a syringe.

[0004] Accordingly, the problem underlying the present invention was to provide an effective and reversible inhibitor of a hydrosilylation catalyst to extend the pot life of a hydrosilylation reaction mixture. [Means for solving the problem]

[0005] The problem underlying the present invention is solved by providing a composition comprising an inhibitor of a hydrosilylation catalyst, wherein the inhibition is effective and is based on a reversible interaction. This application covers the following points [1] to

[15] . [1] A composition comprising the following ingredients: (a) a hydrosilylation catalyst comprising a metal-ligand complex; and (b) an inhibitor for said catalyst, said inhibitor being different from said ligand of said metal-ligand complex and having formula (I): X-CHR-CO-Y (I) (Wherein, -X is -NO2, -S(=O)R, or R c 2nd Round a represents C-CO-; Y is 2-furyl, -S(=O)R, -CN, -NO2, or -CR b X R d 3-x represents;R a and R bare independently selected from the group consisting of -OR, -O-CO-R, -CO-OR, 2-furyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and each R d are independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; and x is 0 or 1. [2] The composition according to [1], wherein the inhibitor (b) is represented by formula (II). R c 2nd Round a C-CO-CHR-CO-Y (II) (wherein the groups are as defined in [1]). [3] The composition according to [1], wherein the inhibitor (b) is represented by formula (III). R c 2nd Round a C-CO-CHR-CO-CR b x R d 3-x (III) (wherein the groups are as defined in [1]). [3-1] In a preferred embodiment of any one of the above [1] to [3], the concentration of the inhibitor in the composition is higher than the concentration of the ligand of the metal-ligand complex. [3-2] In another preferred embodiment of any one of the above [1] to [3], the ligand of the metal-ligand complex is not a compound that falls within the definition of the inhibitor (b). [3-3] In another preferred embodiment of any one of the above [1] to [3], the boiling point of the ligand of the metal-ligand complex is higher than the boiling point of the inhibitor (b). [3-4] A combination of the features of [3-1] and [3-2] is more preferred. [3-5] A combination of the features of [3-1] and [3-3] is more preferred. [3-6] A combination of the features of [3-2] and [3-3] is more preferred. [3-7] A combination of the features of [3-1], [3-2], and [3-3] is most preferred. [4] A composition according to any one of points [1] to [3-5], comprising the following components: (a) a hydrosilylation catalyst comprising platinum(0) and an olefinic ligand; and (b) An inhibitor represented by formula (I), (II), or (III) as defined in any one of [1] to [3-5]. Inhibitors of formula (III) are preferred. [5] -CR a R c 2 and -CR b x R d 3-x The composition of any one of the preceding points, wherein at least one of is —CF3. [6] The composition of any one of the preceding points, comprising: (c) a silane (siloxane) having an olefinic group, and (d) a silane (siloxane) containing hydrogen bonded directly to silicon. [7] The composition of any one of the preceding points, comprising: (c) a vinyl-containing polysiloxane; and (d) a polysiloxane containing hydrogen bonded directly to silicon. [8] The composition of any one of the preceding points, wherein the hydrosilylation catalyst is a complex of platinum(0) and a divinyl-containing disiloxane. [9] The composition of any one of the preceding points, wherein the weight ratio of composition (b):((c)+(d)) is from 3:100 to 20:100.

[10] The composition of any one of the preceding points, comprising as composition (e) a solvent not falling within the definition of any of compositions (a) to (d).

[11] Two packages of a hydrosilylation system, the first package containing a silane (siloxane) containing hydrogen directly bonded to silicon, and the second package containing a composition according to any one of points [1] to [5] and a silane (siloxane) containing an olefinic group; or two packages of a hydrosilylation system, the first package containing a composition according to any one of points [1] to [5] and a silane (siloxane) containing hydrogen directly bonded to silicon, and the second package containing a silane (siloxane) containing an olefinic group.

[12] A hydrosilylation process comprising the steps of: (i) providing a reaction system comprising the following composition: (a) a hydrosilylation catalyst comprising a metal-ligand complex; and (b) an inhibitor for said catalyst, said inhibitor being different from said ligand of said metal-ligand complex and having formula (I), (II), or (III). X-CHR-CO-Y (I) (Wherein, -X is -NO2, -S(=O)R, or R c 2nd Round a represents C-CO-; Y is 2-furyl, -S(=O)R, -CN, -NO2, or -CR b X R d 3-x represents;R a and R b are independently selected from the group consisting of -OR, -O-CO-R, -CO-OR, 2-furyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and each R d are independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; and x is 0 or 1. R c 2nd Round a C-CO-CHR-CO-Y (II) wherein the groups are as defined in relation to formula (I). R c 2nd Round a C-CO-CHR-CO-CR b x R d 3-x (III) wherein the groups are as defined in relation to formula (I). (c) silanes (siloxanes) containing olefinic groups, and (d) Silanes (siloxanes) containing hydrogen directly bonded to silicon. (ii) carrying out a hydrosilylation reaction to crosslink composition (C) and composition (d); (iii) at least partially removing the inhibitor from the reaction system. The hydrosilylation reaction in step (ii) may be initiated and / or accelerated by step (iii). [12-1] In an embodiment of

[12] , the inhibitor is not completely removed from the reaction system in step (iii).

[13] A crosslinked product obtained by the method described in

[12] . [13-1] In one embodiment of the present invention, the crosslinked product of

[13] contains the inhibitor that is not completely removed in step (iii) of the process of

[12] or [12-1]. In other words, [13-1] relates to a composition containing the crosslinked product and the inhibitor. [13-2] In a preferred embodiment of [13-1], the concentration of the inhibitor in the crosslinked product, i.e., the composition, is 0.0000001 wt% to 5 wt%, preferably 0.000001 wt% to 1 wt%, more preferably 0.0001 wt% to 1 wt%, and most preferably 0.0001 wt% to 0.1 wt%.

[14] 1. Use of a compound of formula (I), (II) or (III) below as an inhibitor of a hydrosilylation reaction using a catalyst comprising a metal-ligand complex. wherein said compound is different from said ligand of said metal-ligand complex in that: X-CHR-CO-Y (I) (Wherein, -X is -NO2, -S(=O)R, or R c 2nd Round a represents C-CO-; Y is 2-furyl, -S(=O)R, -CN, -NO2, or -CR b X R d 3-x represents;R a and R b are independently selected from the group consisting of -OR, -O-CO-R, -CO-OR, 2-furyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and each R d are independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; and x is 0 or 1. R c 2nd Round a C-CO-CHR-CO-Y (II) wherein the groups are as defined for formula (I). R c 2nd Round a C-CO-CHR-CO-CR b x R d 3-x (III) wherein the groups are as defined for formula (I).

[15] 14. The use according to claim 13, wherein the hydrosilylation reaction is carried out in an inkjet printed composition or in a syringe-administered composition. [Effects of the Invention]

[0006] The inhibitors are effective and not acutely toxic. The addition of small amounts of inhibitors extends the shelf life of the composition or one-component polymer systems containing the catalyst, and extends the pot life of two-component polymer systems containing the catalyst after the components are mixed.

[0007] The inhibitors can be used, for example, in inkjet printable compositions and can be easily adapted to other printing techniques such as aerosol jet and screen printing, thus enabling a range of novel and innovative manufacturing possibilities in the fields of 2D and 3D printing. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows the viscosity of a PDMS resin (Sylgard 184; PDMS base:curing agent = 10:1 wt / wt) over a 120 minute period at 40° C. compared to the same resin containing 15 wt % 1,1,1-trifluoroacetylacetone (TFAA) (Example 5). DETAILED DESCRIPTION OF THE INVENTION

[0009] As used herein, the singular forms "a," "an," and "the" may be intended to include the plural unless the context clearly dictates otherwise. For example, structural elements and components are generally described in the singular, such as "an" inhibitor or "containing a" component. Such singular combinations mean containing two or more of the indicated components or structural elements, unless otherwise indicated. The term "and / or" includes any and all combinations of one or more of the associated listed items. The verbs "contain," "comprise," and "have" are inclusive and thus specify the presence of stated features, steps, elements, or components, or combinations thereof, but do not exclude the presence or addition of one or more other features, steps, elements, components, or groups or combinations thereof. The steps and processes of the methods described herein should not be construed as necessarily requiring their performance in the particular order described or illustrated, unless specifically stated as such an order of performance. As used herein, the term "silane(oxane)" is intended to be equivalent to the terms "(poly)silane and / or (poly)siloxane," where "poly" refers to a degree of polymerization of 2 or greater.

[0010] The inhibitors used in the present invention suppress the activity of the catalyst used in the hydrosilylation reaction. The hydrosilylation reaction crosslinks silicon compounds containing olefinic groups with silicon compounds containing hydrogen. The crosslinked groups may be contained in the same molecule (one-component system) or in separate molecules (two-component system), such as polymethylhydrosiloxane and polymethylvinylsiloxane. The reaction may be induced thermally or by exposure to UV light. The crosslinked, or cured, reaction product is referred to herein as a "silicone elastomer." The degree of crosslinking is not limited and may be so high that the silicone is no longer an elastomeric polymer but a cured polymer.

[0011] An organoplatinum catalyst that can be used in the present invention is the Karstedt catalyst (hereinafter simply referred to as the "catalyst") disclosed in U.S. Pat. No. 3,814,730. The catalyst contains platinum in the zero oxidation state, free of coordinated chloride. The catalyst comprises a complex of platinum(0) with an olefinic group in the absence of an inhibitor. Preferably, the olefinic ligand of the catalyst is the olefinic group of a silane and / or siloxane used as a reactant in the hydrosilylation reaction. More preferably, the olefinic ligand is the olefinic group of a polyorganosiloxane, containing at least two olefinic groups directly bonded to silicon atoms per molecule. A specific example is polymethyldivinylsiloxane, preferably a divinyl-containing disiloxane. This catalyst promotes low-temperature hydrosilylation reactions, forming silicone elastomers through an addition crosslinking reaction between Si-vinyl groups and Si-H groups.

[0012] The inhibitor used in accordance with the present invention or included in the compositions or two-package hydrosilylation systems of the present invention is an inhibitor of formula (I), (II), or (III), and may hereinafter be referred to simply as the "inhibitor." The inhibitor interacts reversibly with the catalyst.

[0013] The composition of the present invention comprises (a) a hydrosilylation catalyst comprising a metal-ligand complex and (b) a catalyst inhibitor of formula I, (II), or (III). The metal-ligand complex of component (a) comprises a metal and at least one ligand. Thus, the composition of the present invention comprises at least three components: a metal, a ligand, and an inhibitor. The ligand of the catalyst metal-ligand complex is different from the inhibitor of component (b). Preferably, the ligand is not a compound of formula I, (II), or (III). The ligand and inhibitor have different catalytic abilities when combined with the metal. This means that a composition of metal and ligand capable of forming the metal-ligand complex of component (a) has higher hydrosilylation catalytic activity than a composition of metal and inhibitor. Therefore, the catalytic activity of a composition comprising a metal, a ligand, and an inhibitor can be increased by removing the inhibitor and / or adding a ligand, or decreased by removing the ligand and / or adding an inhibitor. In this way, the ligands and inhibitors can be clearly identified and distinguished in the composition. Another difference between the ligands and inhibitors is that the ligands have a higher boiling point. This difference allows the inhibitors to be selectively removed by increasing the temperature, thus facilitating the acceleration of the hydrosilylation reaction.

[0014] As explained below, the structural features of the inhibitors are determined by the substituent R a and optionally a substituent R b From R d The negative inductive effect of R a is a halogen atom selected from fluoro, chloro and bromo. More preferably, R a , and R C At least one of R is a halogen atom. a and R C together represent two or three halogen atoms, and R C , R b , and R drepresents hydrogen. Particularly preferred compounds are HF2C-CO-CH2-CO-CH3, F3C-CO-CH2-CO-CH3, HF2C-CO-CH2-CO-CF3, F3C-CO-CH2-CO-CF3, Cl3C-CO-CH2-CO-CH3, and Cl3C-CO-CH2-CO-CCl3.

[0015] The inhibitors are compounds of formula (I), (II), or (III), i.e., 1,3-diketones (acetylacetone derivatives) or compounds similar to 1,3-diketones. 1,3-diketones, which can tautomerize to enols conjugated to other carbonyls, typically exist primarily in the enol form, especially when the product can be further stabilized by a six-membered ring containing hydrogen bonds. For example, the enol percentages of acetylacetone, 1,1,1-trifluoroacetylacetone (TFAA), and hexafluoroacetylacetone are 85, 97, and 100%, respectively. 1,3-diketones and metals can form metal-acetylacetonate coordination complexes. Hexafluoroacetylacetonate and trifluoroacetylacetonate form complexes that are often structurally related to regular acetylacetonate, but are Lewis acidic and highly volatile. Therefore, they are not only more effective as inhibitors but also more easily removed by evaporation. Example 3 demonstrates that acetylacetone is not an effective inhibitor.

[0016] Without wishing to be bound by theory, the inventors hypothesize that inhibitors affect the activity of the catalysts they are used in through a type of "allosteric" control. It is believed that inhibitors may complex the active metal of the catalyst. The negative inductive effect of substituents such as trifluoro groups makes the inhibitor more Lewis acidic. Because the complex is not very strong, a chemical equilibrium can be maintained between the complex and the free ligand. Example 4 demonstrates that catalyst inhibition is completely reversible. When the inhibitor is removed from the composition, e.g., by evaporation, the catalyst reverts to its original active form, and crosslinking proceeds normally.

[0017] Amines and other compounds capable of complexing the active metal center of the catalyst can inhibit crosslinking in a manner similar to the inhibitors used in this invention. However, inhibition by amines has been found to be irreversible or only partially reversible. This is believed to be due to the formation of stable complexes between the amine (basic) and the metal center (acidic in nature). Example 4 demonstrates that inhibition of the catalyst by primary and secondary amines is irreversible even at temperatures above the boiling points of these amines. In the case of tertiary amines, very limited reversibility is observed, preventing crosslinking and resulting in very soft, incompletely cured silicone elastomers. Furthermore, in the case of tertiary amines, the required cure time is too long for useful practical applications. Furthermore, most primary, secondary, and tertiary amines are acutely toxic and produce toxic vapors.

[0018] The boiling points of the inhibitor may be below 120 °C. For example, the boiling points of TFAA and hexafluoroacetylacetone are 105–107 °C and 70–71 °C, respectively. By comparison, the boiling points of acetylacetone and OA are 140 °C and 211 °C, respectively. For example, reactions catalyzed by organoplatinum catalysts can be accelerated by removing the inhibitor by evaporation at elevated temperatures and / or reduced pressure.

[0019] The organoplatinum catalyst is preferably utilized in an amount of at least 0.1 ppm of platinum metal, more preferably 1 to 50 ppm of platinum metal, per 100 parts of olefin group-containing compound. The hydrogen-containing crosslinker is preferably utilized in an amount of 1 to 50 parts, more preferably 1 to 25 parts, per 100 parts of olefin group-containing compound.

[0020] The amount of inhibitor compound added to the composition will vary depending on the specific application of the composition. Preferably, the concentration of inhibitor in the composition is greater than the concentration of the ligand in the metal-ligand complex, or greater than the concentration of the metal in the metal-ligand complex. More preferably, the concentration of inhibitor may be 5 times or more, 10 times or more, or 100 times or more greater than the concentration of the metal in the metal-ligand complex. The higher the level of inhibitor present, the longer the shelf life of the composition will be for one-component systems, and for two-component systems, the longer the composition will have a pot life. For most applications, the concentration of inhibitor may be 0.01 to 200 parts by weight, preferably 0.01 to 10 parts by weight, per 100 parts of base olefinic-containing compound.

[0021] The compositions of the present invention may comprise a one-component polymer system containing a catalyst and an inhibitor, or may comprise a catalyst, an inhibitor, and one component of a two-component polymer system, such as the vinyl component of a PDMS system. In either case, the inhibitor extends the shelf life of the composition. After mixing the components of a two-component polymer system, such as a PDMS system, the inhibitor extends the pot life of the system.

[0022] In the two-package hydrosilylation system of the present invention, the reactants of the two-component polymer system are placed in separate containers. This means that the olefin-containing polymer, such as the vinyl-containing polymer, is placed in a container separate from the hydride crosslinker. The inhibitor can be placed in the container with the olefin-containing compound or with the hydride crosslinker. The catalyst is preferably blended or mixed with the olefin-containing polymer. In most cases, it is preferred to mix the inhibitor with the catalyst in the olefin-containing compound.

[0023] The composition can also be a one-package system, i.e., all components are mixed together and the composition is utilized simply by heating at elevated temperature to produce a cured silicone elastomer by evaporating the inhibitor. For one-package systems, the amount of inhibitor can be greater than 15 parts per 100 parts of olefin-containing compound to extend the shelf life of the composition.

[0024] The olefin-containing compound, such as a vinyl-containing polysiloxane, preferably has a low viscosity and serves as both a diluent and a toughening agent for the final cure of the elastomer. The olefin-containing compound can be a polymer or a mixture of olefin-containing polymers, more specifically, a mixture of an olefin-containing polymer with another olefin-containing polymer having olefin units, such as vinyl units, at both terminal and internal positions in the polymer chain, e.g., the polysiloxane chain. The hydrogen-containing crosslinker can be any of those typically utilized in hydrosilylation reactions to form silicone elastomers, preferably a hydrogen-containing polysiloxane with a viscosity of 1 to 10,000 mPa·s at 25°C. Additionally, various other additives can be added to the composition, such as fillers and pigments, heat-aging additives, and other types of additional ingredients typically associated with the preparation of such compositions.

[0025] Vinyl-containing polysiloxanes preferably contain 0.01 to 1 mole percent vinyl. Preferably, the polymer is linear, with the vinyl preferably at the terminal position of the linear polymer chain. However, the vinyl group can be present anywhere along the polymer chain. The polymer can be a single polymer species or a blend of vinyl-containing polymeric materials. The other substituents, in addition to the vinyl radical, can be any monovalent hydrocarbon radical or halogenated monovalent hydrocarbon radical, preferably not exceeding 10 carbon atoms. Most preferably, the silicon-bonded substituents are selected from lower alkyl radicals of 1 to 8 carbon atoms, vinyl radicals, and phenyl radicals. Within the vinyl-containing polymer range, the most preferred polymer species are strictly linear polymers with vinyl radical-terminated units.

[0026] An example of a two-part silicone elastomer system is Polytek PlatSil® 71-Silliglass (Sturgess et al.), where PDMS A contains a silicone hydride and a vinyl-containing silicone moiety, and PDMS B contains a vinyl-containing silicone moiety and a catalyst. The inhibitors used in the present invention can be added to any of the corresponding components of PDMS A or PDMS B disclosed in Sturgess et al.

[0027] Another example of a two-component silicone elastomer system is SYLGARD® 184, which contains a polymer base and a curing agent that crosslinks with the polymer matrix. The resulting composite is a polydimethylsiloxane (PDMS) with a tensile strength (UTS) of approximately 5.2 MPa and a Shore hardness of approximately 44 at room temperature. Tensile strength, hardness, and Young's modulus (E) increase with increasing curing temperature. The pot life is 1.5 hours at 25°C, defined as the time required for the viscosity to double after mixing the base and curing agent. The initial viscosity of the mixture is 3500 Pa·s. The curing time varies depending on the temperature: 48 hours at 25°C, 35 minutes at 100°C, 20 minutes at 125°C, and 10 minutes at 150°C. As shown in Example 5, the increase in viscosity can be suppressed over a long period of time. Therefore, the pot life of the composition can be extended.

[0028] The inhibitor cannot be completely removed from the hydrosilylation reaction system by raising the temperature above the boiling point of the inhibitor. As a result, the reaction product of the hydrosilylation reaction inevitably contains a detectable amount of the inhibitor, which can be quantitatively detected by methods such as GC-MS. Therefore, the reaction product prepared using the inhibitor of the present invention is different from the reaction product not prepared using such an inhibitor. In other words, the crosslinked product of the present invention is different from the product of the prior art.

[0029] GC-MS is a highly sensitive method, easily detecting concentrations in the ppb (parts per billion) range, i.e., concentrations below 0.0000001 wt%.

[0030] The inhibitor is present in the reaction system in a diluted form. Interaction with the diluent, e.g., solvent, can prevent complete removal of the inhibitor, even when the temperature is raised to the inhibitor's boiling point. In experiments, the inventors were able to demonstrate that a solution containing 5 wt. % TFAA, which has a boiling point of 107°C, still contains significant amounts of TFAA even after heating at 120°C for a longer period (e.g., 1 hour).

[0031] A hydrosilylation system contains polymerization precursors, catalysts, and inhibitors. The inhibitors physically interact with the other components of the reaction system. In particular, it is speculated that the inhibitor can form complexes with the catalyst metal. For this reason, it is impossible to completely remove the inhibitor by heating. Under normal reaction conditions, residual amounts of inhibitors are always present in the reaction product. This residual amount can be detected by methods such as GC-MS. If necessary, small molecule inhibitors can be extracted from the polymer polymerization product before GC-MS. Silicone elastomer systems such as PDMS can be used as stamping resins for soft lithography in various applications, such as microfluidics, microelectromechanical systems (MEMS), and other flexible electronic devices. They also form hydrophobic PDMS films that can be used as water membranes in solar cells. Furthermore, its low cost, easy fabrication, flexibility, and optical transparency make PDMS an ideal material for prototyping in a variety of research and development fields.

[0032] A possible use of PDMS is inkjet printing. The use of PDMS systems in inkjet printing, materials and methods, and applications of inkjet-printed PDMS systems are disclosed in detail in Mikkonen et al. and Sturgess et al.

[0033] For use in inkjet printing, a solvent must be added to reduce viscosity. Meanwhile, the solvent must have a low boiling point so that it can be removed after printing. In the present invention, the solvent (component (e)) has a molecular weight of less than 250 g / mol and a boiling point of less than 250°C. Solvents are not included in the definition of any of components (a) to (d). In particular, the solvent does not contain a catalytic metal, is not a compound of formula (I), (II), or (III), and is not a silane or siloxane. Examples of suitable solvents are organic solvents such as octyl acetate (OA), n-butyl acetate, or isobutyl acetate, or acetylacetone.

[0034] Mikkonen et al. disclose the use of OA as a solvent. Because the two components of Sylgard 184 were mixed before printing, the cartridge temperature had to be kept as low as possible, preventing cross-linking of the PDMS component. The 1:2 PDMS-OA solution was too viscous, requiring the cartridge to be heated to temperatures above 35 °C. However, heating accelerates cross-linking. Both the 1:3 and 1:4 PDMS-OA solutions could be printed without heating the cartridge above 30 °C. The 1:3 PDMS-OA solution was used to maximize the PDMS content of the ink.

[0035] As shown in Figure 1, the suppressor used in the present invention not only inhibits the increase in viscosity over time, but also acts to initially reduce the viscosity. Thus, the suppressor can at least partially replace component (e) in its function as a solvent used to adjust the viscosity of the composition for use in inkjet printing. [Example]

[0036] In the following examples, the ratios of components are by weight, and % is by weight. The PDMS used in the examples was a premix of the two components of SYLGARD® 184 (PDMS base:hardener = 10:1). 1,1,1-trifluoroacetylacetone (TFAA) was used as an inhibitor. Example 1

[0037] PDMS was diluted with OA in a 1:2 ratio as disclosed in Mikkonen et al.. Furthermore, TFAA was added at different concentrations.

[0038] PDMS + OA (1:2) + TFAA (1.5% to 90% relative to PDMS)

[0039] The container was sealed and stored at 80°C for 48 hours. As a result, concentrations up to 6% (relative to PDMS) cured normally, but curing was inhibited at concentrations above 15% (relative to PDMS). Example 2

[0040] PDMS was diluted with OA (1:2) as described in Example 1. Intermediate concentrations (6%, 9%, and 12%, respectively, relative to PDMS) were included, indicating that the minimum concentration that inhibited curing was between 9% and 12%. Example 3

[0041] As described in Example 1, PDMS was diluted with OA (1:2) and acetylacetone was added at different concentrations.

[0042] PDMS + OA (1:2) + acetylacetone (3% to 30% relative to PDMS)

[0043] Acetylacetone was found to be ineffective at any of the concentrations used. Example 4

[0044] In preliminary experiments, propylamine, pyrrolidine, and triethylamine were tested as examples of primary, secondary, and tertiary amines, respectively, at concentrations of 15%, and all were successful in inhibiting crosslinking.

[0045] The reversibility of successful inhibition was then tested. The open containers were placed in a 60°C oven for 24 hours to evaporate the additive. Reversibility was observed for all TFAA mixtures; that is, crosslinking occurred upon evaporation of the TFAA. Higher concentrations of TFAA resulted in a softer surface, indicating that the elastomer was not fully cured. Conversely, reversibility was not observed with propylamine, pyrrolidine, or triethylamine; crosslinking was prevented and the material remained liquid.

[0046] Higher temperatures and vacuums were then used to accelerate evaporation of the additive and demonstrate the potential reversibility of the inhibition. 72 hours at 80 °C and 100 mbar demonstrated that the inhibition was fully reversible, even at high TFAA concentrations. In the case of propylamine and pyrrolidine, the experiment demonstrated a completely irreversible reaction, and the material remained liquid. In the case of triethylamine, very limited reversibility was observed, which prevented crosslinking and resulted in a very "sticky" elastomer that was not fully cured. Example 5

[0047] Long-term rheological measurements compared neat PDMS with neat PDMS containing TFAA (15%) to demonstrate the progression of crosslinking over time. Figure 1 shows the viscosity of PDMS and the same resin containing 15% TFAA at 40°C over 120 minutes.

Claims

1. A composition comprising the following ingredients: (a) a hydrosilylation catalyst which is a complex of platinum(0) and a divinyl-containing disiloxane; (b) an inhibitor for the catalyst, said inhibitor being different from the ligand of said complex and having the formula (III): R c 2 R a C-CO-CHR-CO-CR b x R d 3-x...(III) (In the formula, R ａ and R ｂ is -O-R, -O-CO-R, -CO-O-R, 2-furyl, -S(=O)R, -CN, -NO ２ , —F, —Cl, and —Br; each R is independently selected from the group consisting of —H, optionally fluorinated C １ -C ８ -alkyl, -F, -Cl, and -Br; ｃ and each R ｄ is —H, optionally fluorinated C １ -C ８ -alkyl, -F, -Cl, and -Br; and x is 0 or 1. (c) a vinyl-containing polysiloxane, and (d) Polysiloxanes containing hydrogen bonded directly to silicon.

2. The weight ratio of components (b):((c)+(d)) is 3:100 to 20:

100. The composition of claim 1.

3. Component (e) contains a solvent that does not fall into any of the definitions of components (a) to (d), The composition of claim 1.

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