Inhibitors of hydrosilylation catalysts

Abstract

A composition comprising the following components: (a) a hydrosilylation catalyst comprising a metal-ligand complex, and (b) an inhibitor of the catalyst, wherein the inhibitor is different from the ligand of the metal-ligand complex and is represented by formula (I): X-CHR-CO-Y (I), wherein X represents -NO2, -S(=O)R, or R c 2R a C-CO-; Y represents 2-furyl, -S(=O)R, -CN, -NO2, or -CR b x R d 3‑x ; R a and R b are independently selected from the group consisting of -O-R, -O-CO-R, -CO-O-R, 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 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.

Description

TECHNICAL FIELD

[0001] The present invention relates to the use of a new inhibitor of hydrosilylation catalysts, to compositions containing the catalyst and the inhibitor, and to methods of performing hydrosilylation reactions using the catalyst and the inhibitor. BACKGROUND

[0002] Organic platinum catalysts such as Karstedt’s catalyst (e.g. an adduct of divinyltetramethyldisiloxane and chloroplatinic acid) are used to catalyse hydrosilylation reactions, for example to obtain cross-linked polydimethylsiloxane (PDMS). Typically, the composition used for the reaction is pre-mixed before the catalyst is applied. The high activity of the platinum catalyst reduces the pot life of the composition. A pot life of a few hours at room temperature is long enough for applications of the composition that are cast or screen printed. However, other applications of the composition require a longer pot life, for example in inkjet printing applications disclosed in Sturgess et al. (“3D Reactive Inkjet Printing of Polydimethylsiloxane”, J. Mater. Chem. C, 2017, 5, 9733-9743) and Mikkonen et al. (“Inkjet- printable polydimethylsiloxanes for fully inkjet-printed multilayer soft electrical applications”; ACS Appl. Mater. Interfaces 2020, 12, 10, 11990-11997). In order to extend the pot life of the composition for inkjet printing, it can be stored refrigerated immediately after it is transferred to the print cartridge. The refrigerated ink can be used for several days. Another method to reduce the viscosity of the inkjet printable composition and thus extend the pot life is to add a solvent. One known solvent is octyl acetate (OA), which is miscible with PDMS and provides a suitable vapour pressure for printing. The addition of OA dilutes the components and thus extends the pot life of the formulation.

[0003] PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In inkjet printable formulations, the content of solvent as viscosity modifier and pot life extender should not be too high. Therefore, the pot life of inkjet printable formulations is limited to at most a few hours. This causes significant practical and technical limitations for applications in inkjet printing. The pot life and viscosity of the formulation are also a problem in applications of the formulation that do not use a solvent in the formulation, for example in a method for producing LEDs that includes a step of dispensing the formulation using a syringe.

[0005] Therefore, the basic problem of the present invention is to provide an effective and reversible inhibitor of hydrosilylation catalysts to extend the pot life of a hydrosilylation reaction mixture. SUMMARY

[0006] The basic problem of the present invention is solved by providing a composition containing an inhibitor for a hydrosilylation catalyst, wherein the inhibition is effective and based on a reversible interaction.

[0007] The present application covers the following points [1] to

[15] .

[0008] [1] A composition containing the following components:

[0009] (a) a hydrosilylation catalyst comprising a metal-ligand complex, and

[0010] (b) an inhibitor for the catalyst, wherein the inhibitor is different from the ligand of the metal-ligand complex and is represented by formula (I):

[0011] X-CHR-CO-Y (I),

[0012] wherein X represents -NO2, -S(=O)R or R c 2R a C-CO-; Y represents 2-furyl, -S(=O)R, -CN, -NO2 or -CR b x R d 3-x ; R a and R b are independently selected from the group consisting of -O-R, -O-CO-R, -CO-O-R, 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 is independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl and -Br; and x is 0 or 1.

[0013] [2] The composition according to [1], wherein the inhibitor (b) is represented by formula (II):

[0014] R c 2R a C-CO-CHR-CO-Y (II), wherein the radicals are defined as in [1].

[0015] [3] The composition according to [1], wherein the inhibitor (b) is represented by formula (III): R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III), wherein the radicals are defined as in [1].

[0016] [3-1] In a preferred embodiment of any 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 of the above [1] to [3], the ligand of the metal-ligand complex is not a compound belonging to the respective definition of the inhibitor (b). [3-3] In another preferred embodiment of any 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] More preferably, a combination of the features of [3-1] and [3-2]. [3-5] More preferably, a combination of the features of [3-1] and [3-3]. [3-6] More preferably, a combination of the features of [3-2] and [3-3]. [3-7] Most preferably, a combination of the features of [3-1], [3-2] and [3-3].

[0017] [4] The composition according to any of the points [1] to [3-5], comprising the following components:

[0018] (a) a hydrosilylation catalyst comprising platinum (0) and an olefin ligand, and

[0019] (b) an inhibitor represented by formula (I), (II) or (III) as defined in any of the points [1] to [3-5].

[0020] The inhibitor of formula (III) is preferred.

[0021] [5] The composition according to any of the preceding points, wherein -CR a R c 2 and -CR b x R d 3-x at least one of R1, R2and R3is -CF3.

[0022] [6] The composition according to any of the preceding points, comprising the following components: (c) a siloxane having an olefin group and (d) a siloxane containing hydrogen directly bonded to silicon.

[0023] [7] The composition according to any of the preceding points, comprising the following components: (c) a poly siloxane containing a vinyl group and (d) a poly siloxane containing hydrogen directly bonded to silicon.

[0024] [8] The composition according to any of the preceding points, wherein the hydrosilylation catalyst is a complex of platinum (0) and a divinyl-containing disiloxane.

[0025] [9] The composition according to any of the preceding points, wherein the weight ratio of component (b) : ((c) + (d)) is 3 : 100 to 20 : 100.

[0026]

[10] The composition according to any of the preceding points, containing a solvent not defined as component (a) to (d) as component (e).

[0027]

[11] A dual-packaged hydrosilylation system, wherein the first package comprises a siloxane containing silicon-bonded hydrogen directly and the second package comprises the composition of any one of points [1] to [5] and a siloxane having an olefinic group; or wherein the first package comprises the composition of any one of points [1] to [5] and a siloxane containing silicon-bonded hydrogen directly and the second package comprises a siloxane having an olefinic group.

[0028]

[12] A process of hydrosilylation, comprising the steps of:

[0029] (i) providing a reaction system comprising the following components:

[0030] (a) a hydrosilylation catalyst comprising a metal-ligand complex, and

[0031] (b) an inhibitor for the catalyst, wherein the inhibitor is different from the ligand of the metal-ligand complex and is represented by formula (I), (II) or (III):

[0032] X-CHR-CO-Y (I),

[0033] wherein X represents -NO2, -S(=O)R or R c 2R a C-CO-; Y represents 2-furyl, -S(=O)R, -CN, -NO2 or -CR b x R d 3-x ; R a and R b are independently selected from the group consisting of -O-R, -O-CO-R, -CO-O-R, 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 is independently selected from the group consisting of -H, optionally fluorinated C1-C8-alkyl, -F, -Cl and -Br; and x is 0 or 1.

[0034] R c 2R a C-CO-CHR-CO-Y (II),

[0035] wherein the radicals are defined as in relation to formula (1),

[0036] R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III),

[0037] wherein the radicals are defined as in connection with formula (1),

[0038] (c) siloxane having an olefinic group, and

[0039] (d) siloxane containing hydrogen directly bonded to silicon;

[0040] (ii) carrying out a hydrosilylation reaction to crosslink components (c) and (d);

[0041] (iii) at least partially removing the inhibitor from the reaction system.

[0042] The hydrosilylation reaction in step (ii) can be initiated and / or accelerated by step (iii).

[0043] [12-1] In an embodiment of

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

[0044]

[13] A crosslinked product can be obtained by the process of

[12] . [13-1] In an embodiment of the present application, the crosslinked product of

[13] contains the inhibitor which 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. in the composition, is 0.0000001 to 5% by weight, preferably 0.000001 to 1% by weight, more preferably 0.0001 to 1% by weight, and most preferably 0.0001 to 0.1% by weight.

[0045]

[14] The use of a compound of the following formula (I) or (II) or (III) as an inhibitor for a hydrosilylation reaction employing a catalyst comprising a metal-ligand complex, wherein the inhibitor is different from the ligand of the metal-ligand complex:

[0046] X-CHR-CO-Y (I),

[0047] wherein X represents -NO2, -S(=O)R or R c 2R a C-CO-; Y represents 2-furyl, -S(=O)R, -CN, -NO2 or - CR bx R d 3-x ;R a and R b The R is independently selected from -OR, -O-CO-R, -CO-OR, 2-furanyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from -H, optionally fluorinated C1-C8. - Alkyl groups, -F, -Cl, and -Br; each R c and each R d The x is independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl and -Br; and x is 0 or 1.

[0048] R c 2R a C-CO-CHR-CO-Y(II),

[0049] Wherein, the group is defined as in formula (I);

[0050] R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III),

[0051] Wherein, the group is defined as in formula (I);

[0052]

[15] According to the use described in

[14] , wherein the hydrosilanization reaction is carried out in an inkjet printing composition or a syringe dispensing composition.

[0053] Advantages of the present invention

[0054] The inhibitor is effective and not highly toxic. Adding small amounts of inhibitor extends the shelf life of the composition or single-component polymer systems containing catalysts, and extends the pot life of two-component polymer systems containing catalysts after mixing.

[0055] This inhibitor can be used in, for example, inkjet printable compositions and is readily applicable to other printing technologies, such as aerosol jetting and screen printing. Therefore, a range of novel and innovative manufacturing possibilities are possible in the fields of 2D and 3D printing. Attached Figure Description

[0056] Figure 1Viscosity of PDMS resin (Sylgard 184; PDMS base: Curing agent = 10:1 wt / wt) with 15 wt% of 1,1,1-trifluoroacetylacetone (TFAA) at 40 °C over a period of 120 minutes (Example 5) is shown. DETAILED DESCRIPTION

[0057] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. For example, a reference to "an" inhibitor or "a" component is a reference to one or more inhibitors or one or more components and includes the possibility of combinations thereof. The term "and / or" includes any and all combinations of one or more of the associated listed items. The verbs "comprise" "include" and "have" and their conjugates, are used to indicate that the object or objects of the verb are not necessarily singular, but can be plural, unless the context clearly dictates otherwise. The phrase "consisting essentially of" means that the composition or method does not include more than the recited elements, but can include one or more additional elements that do not materially affect the basic and novel characteristics of the composition or method. The method steps and processes described herein are not to be construed as necessarily requiring their performance in the particular order in which they are discussed or illustrated, unless specifically identified as an order of performance. As used herein, the term "silicon(oxy)ane" is intended to be equivalent to the term "(poly)silane and / or (poly)siloxane", where "poly" refers to a degree of polymerization of 2 or higher.

[0058] The inhibitors used in the present invention inhibit the activity of catalysts used in hydrosilylation reactions. Hydrosilylation reactions crosslink compounds containing olefinic groups and hydrogen-containing silicon. The groups to be crosslinked can be contained in the same molecule (one-component system) or can be contained in separate molecules (two-component system), for example polymethylhydrogenosiloxane and polymethylvinylsiloxane. The reaction can be induced thermally or by exposure to UV light. The reaction product which is crosslinked, i.e. cured, is referred to herein as a "silicone elastomer". The degree of crosslinking is not limited and can be high, such that the silicone is no longer an elastomeric polymer, but a hard cured polymer.

[0059] An organic platinum catalyst useful in the present application is Karstedt's catalyst (hereinafter simply referred to as "catalyst") as disclosed in U.S. Patent 3,814,730. The catalyst contains platinum in zero oxidation state and without coordinated chloride. In the absence of an inhibitor, the catalyst contains a complex of Pt(O) with olefinic groups. Preferably, the olefinic ligand of the catalyst is an olefinic group of silane and / or siloxane used as a reaction component in the hydrosilylation reaction. More preferably, the olefinic ligand is an olefinic group of polyorganosiloxane, each molecule of which includes at least two olefinic groups directly bonded to silicon atoms. One specific example is polymethyldivinylsiloxane, preferably divinyl-containing disiloxane. The catalyst promotes the hydrosilylation reaction at low temperature and forms a siloxane elastomer by an addition cross-linking reaction between Si-vinyl and Si-H groups.

[0060] The inhibitor used according to the present application or contained in the composition or dual-pack hydrosilylation system of the present application is an inhibitor of formula (I), (II) or (III) and will be simply referred to as "inhibitor" hereinafter. The inhibitor reversibly interacts with the catalyst.

[0061] The composition of the present application contains (a) a hydrosilylation catalyst including a metal-ligand complex and (b) an inhibitor of (I), (II) or (III) catalyst. The metal-ligand complex of component (a) includes a metal and at least one ligand. Thus, the composition of the present application contains at least three components, i.e. a metal, a ligand and an inhibitor. The ligand in the metal-ligand complex of the catalyst is different from the inhibitor of component (b). Preferably, the ligand is not a compound of formula (I), (II) or (III). The catalytic ability of the ligand and the inhibitor in combination with the metal is different. This means that the combination of the metal and the ligand of the metal-ligand complex of component (a) as a hydrosilylation catalyst has a higher activity than the combination of the metal and the inhibitor. Thus, the catalytic activity of the composition containing the metal, the ligand and the inhibitor can be increased by removing the inhibitor and / or adding the ligand, and can be decreased by removing the ligand and / or adding the inhibitor. In this way, the ligand and the inhibitor can be clearly identified and distinguished in the composition. Another difference between the ligand and the inhibitor is the higher boiling point of the ligand. Due to this difference, the inhibitor can be selectively removed by increasing the temperature, and thus the hydrosilylation reaction can be easily accelerated.

[0062] As described below, the structural feature of the inhibitor is the negative inductive effect of the substituent group R a and the optional substituent group R b to R d . Preferably, R a is a halogen atom selected from fluorine, chlorine and bromine. More preferably, R a and R cat least one of which is a halogen atom. Most preferred are compounds wherein R a and R c together represent two or three halogen atoms, and the other radicals represented by R c , R b and R d represent 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.

[0063] The inhibitor is a compound of formula (I), (II) or (III), i.e. a 1,3-diketone (acetylacetone derivative) or a compound similar to a 1,3-diketone. 1,3-diketones, which can tautomerize to an enol conjugated to the other carbonyl group, are usually present mainly in the enol form, and particularly when the product can be further stabilized by a six-membered ring containing a hydrogen bond. For example, the percentage of enol in acetylacetone, 1,1,1-trifluoroacetylacetone (TFAA) and hexafluoroacetylacetone is 85, 97 and 100%, respectively. The 1,3-diketone and the metal can form a metal acetylacetone coordination complex. Hexafluoroacetylacetone and trifluoroacetylacetone form complexes whose structure is generally related to that of conventional acetylacetone, but which are more acidic and more volatile. Thus, they are not only more effective as inhibitors, but also more easily removed by evaporation. Example 3 shows that acetylacetone is ineffective as an inhibitor.

[0064] Without wishing to be bound by theory, the inventors hypothesize that the inhibitor affects the activity of the catalyst in the type used for "allosteric" control. The inhibitor is hypothesized to have the potential to complex the catalytically active metal. The negative inductive effect of substituents such as trifluoro groups makes the Lewis acidity of the inhibitor stronger. Since the complex is not too strong, a chemical equilibrium can be maintained between the complex and the free ligand. Example 4 shows that the inhibition of the catalyst is completely reversible. When the inhibitor is removed from the composition, for example by evaporation, the catalyst returns to its original active form and the crosslinking proceeds normally.

[0065] Amines and other compounds capable of complexing the active metal centers of the catalyst can inhibit crosslinking in a similar manner to the inhibitors used in the present application. However, the inhibition by amines was found to be irreversible or only partially reversible. It is postulated that this is due to the formation of stable complexes between the amine (base) and the metal center (having an acidity). Example 4 shows that the inhibition of the catalyst by primary and secondary amines is irreversible even at temperatures exceeding the boiling point of these amines. For tertiary amines, very limited reversibility was observed, hindering crosslinking, resulting in very soft, incompletely cured silicone elastomers. Furthermore, in the case of tertiary amines, the required curing time is too long for useful practical applications. In addition, most primary, secondary and tertiary amines are highly toxic and produce toxic vapors.

[0066] The inhibitors can have a boiling point below 120°C. For example, the boiling points of TFAA and hexafluoroacetylacetone are 105-107°C and 70-71°C, respectively. In comparison, the boiling points of acetylacetone and OA are 140°C and 211°C, respectively. Reactions catalyzed by, for example, organoplatinum catalysts can be accelerated by evaporation of the inhibitor at elevated temperatures and / or reduced pressures.

[0067] The organoplatinum catalyst is preferably used in an amount of at least 0.1 ppm platinum metal and more preferably 1 to 50 ppm platinum metal relative to 100 parts of the compound containing an olefinic group. The amount of hydrogen-containing crosslinking agent used is preferably 1 to 50 parts and more preferably 1 to 25 parts relative to 100 parts of the compound containing an olefinic group.

[0068] The amount of inhibitor compound added to the composition will vary depending on the particular application of the composition. Preferably, the concentration of the inhibitor in the composition is higher than the concentration of the ligand of the metal-ligand complex, or the concentration of the inhibitor in the composition is higher than the concentration of the metal of the metal-ligand complex. More preferably, the concentration of the inhibitor can be 5 times or more or 10 times or more or 100 times or more higher than the concentration of the metal of the metal-ligand complex. The higher the level of inhibitor present, the longer the storage stability of the composition for one-component systems, and the longer the pot life of the composition if it is a two-component system. For most applications, the concentration of the inhibitor can be 0.01 to 200 parts by weight, preferably 0.01 to 10 parts by weight, relative to 100 parts by weight of the base olefin-containing compound.

[0069] The composition of the present application can contain a one-component polymer system including the catalyst and the inhibitor, or the composition can contain the catalyst, the inhibitor and one component of a two-component polymer system, such as the vinyl component of a PDMS system. In both cases, 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.

[0070] In the dual-package hydrosilylation system of the present invention, the reactive components of the two-component polymer system are packaged separately. This means that the alkenyl-containing polymer, such as a vinyl-containing polymer, is packaged separately from the hydride crosslinker. The inhibitor can be packaged with the alkenyl-containing compound, or it can be packaged with the hydride crosslinker. The catalyst is preferably compounded or mixed with the alkenyl-containing polymer. In most cases, it is preferred to mix the inhibitor with the catalyst in the alkenyl-containing compound.

[0071] The composition can also be a one-package system, that is, where all of the ingredients are mixed together and the composition is utilized by simply heating at elevated temperature to produce a cured silicone elastomer by evaporation of the inhibitor. In the case of a one-package system, the amount of inhibitor can be greater than 15 parts per 100 parts of alkenyl-containing compound to extend the shelf life of the composition.

[0072] The alkenyl-containing compound, such as a vinyl-containing polysiloxane, preferably has a low viscosity and serves as a diluent and reinforcing agent for the final cure of the elastomer. The alkenyl-containing compound can be a polymer or a blend of alkenyl-containing polymers, and more specifically a blend of alkenyl-containing polymers with other alkenyl-containing polymers having olefinic units, such as vinyl units, both at terminal positions and internal positions in the polymer chain, such as a polysiloxane chain. The hydrogen-containing crosslinker can be any of those commonly used in hydrosilylation reactions to form silicone elastomers, and can be a hydrogen-containing polysiloxane having a viscosity of preferably 1 to 10,000 mPa-s at 25°C. In addition, various other additives can be added to the composition, such as fillers and pigments, heat aging additives, and other types of additional ingredients commonly associated with the manufacture of such compositions.

[0073] The vinyl-containing polysiloxane preferably contains 0.01 to 1 mole percent of vinyl groups. Preferably, the polymer is linear, and preferably the vinyl groups are at terminal positions in the linear polymer chain. However, the vinyl groups can be at any portion of the polymer chain. The polymer can be a single polymer species, or it can be a blend of vinyl-containing polymer materials. Other substituents in addition to the vinyl groups can be any monovalent hydrocarbon group or halogenated monovalent hydrocarbon group, preferably of no more than 10 carbon atoms. Most preferably, the substituents bonded to the silicon are selected from the group consisting of lower alkyl groups of 1 to 8 carbon atoms, vinyl groups, and phenyl groups. The most preferred polymer species within the range of vinyl-containing polymers is a strictly linear polymer having terminal units of vinyl radicals.

[0074] One example of a two-component silicone elastomer system is Polytek 71 - Silliglass, which contains a hydrogenated silicone and a portion of the PDMS A containing vinyl silicone, as well as a portion of the PDMS B containing vinyl silicone and a catalyst (Sturgess et al.). The inhibitors used in the present invention can be added to any of the components corresponding to the PDMS A or PDMS B disclosed by Sturgess et al.

[0075] Another example of a two-component silicone elastomer system is 184, which contains a polymeric base and a curing agent that crosslinks with the polymeric matrix. The resulting composite formed is a polydimethylsiloxane (PDMS) having a tensile strength (UTS) of about 5.2 MPa at room temperature and a Shore hardness of about 44. At higher curing temperatures, the tensile strength, hardness, and Young's modulus (E) increase. The pot life at 25 °C is 1.5 hours and is defined as the time required for the viscosity to double after mixing of the base and the curing agent. The initial viscosity of the mixture is 3500 Pa-s. The curing time depends on the temperature and is 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 inhibited for a long time. Thus, the pot life of the composition can be extended.

[0076] By raising the temperature to or above the boiling point of the inhibitor, the inhibitor cannot be completely removed from the hydrosilylation reaction system. 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. Thus, the reaction product prepared by using the inhibitor of the present invention is different from the reaction product prepared without using such an inhibitor. In other words, the crosslinking product according to the present invention is different from the product of the prior art.

[0077] GC-MS is a very sensitive method and concentrations in the ppb (parts per billion) range, i.e. concentrations as low as 0.0000001 wt% or even lower, are easily detected.

[0078] The inhibitor is present in the reaction system in diluted form. The interaction with the diluent (e.g. solvent) has the effect that the inhibitor cannot be completely removed by raising the temperature to the boiling point of the inhibitor. The inventors could demonstrate in experiments that a solution containing 5 wt% of TFAA having a boiling point of 107 °C still contained a significant amount of TFAA after heating at 120 °C for a longer time, e.g. 1 hour.

[0079] The hydrosilylation system comprises the raw materials for polymerization, the catalyst and the inhibitor. The inhibitor and other components of the reaction system physically interact. In particular, it can be assumed that the inhibitor is able to form a complex with the metal of the catalyst. For this reason, it is not possible to completely remove the inhibitor by heating and, when typical reaction conditions are employed, a residual amount of inhibitor is always contained in the reaction product. This residual amount can be detected by methods such as GC-MS. If desired, the low-molecular inhibitor can be extracted from the high-molecular polymerization product before performing the CG-MS. Silicone elastomer systems such as PDMS can be used as a mold resin in soft lithography for various applications such as microfluidics, microelectromechanical systems (MEMS) and other flexible electronics. It also forms a hydrophobic PDMS film that can be used as a moisture barrier in photovoltaic cells. Furthermore, due to its low cost, ease of fabrication, flexibility and optical transparency, PDMS is an alternative material for prototyping in a variety of research and development fields.

[0080] One possible use of PDMS is inkjet printing. The use of PDMS systems in inkjet printing, materials and methods and the application of inkjet printed PDMS systems are described in detail by Mikkonen et al. and Sturgess et al.

[0081] The use in inkjet printing requires the addition of a solvent to reduce the viscosity. On the other hand, the solvent should have a low boiling point to be removable 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. The solvent does not belong to the definition of any of components (a) to (d). In particular, the solvent does not contain the metal of the catalyst, it is not a compound of formula (I), (II) or (III) and it 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.

[0082] Mikkonen et al. disclose the use of OA as a solvent. Since the two components of Sylgard 184 are mixed before printing, the cartridge temperature must be kept as low as possible, thereby hindering the crosslinking of the PDMS components. The 1 :2 PDMS-OA solution viscosity is too high, requiring the cartridge to be heated to a temperature above 35 °C. However, heating accelerates the crosslinking. Both the 1 :3 and 1 :4 PDMS-OA solutions can be printed without heating the cartridge to above 30 °C. To maximize the PDMS content of the ink, the 1 :3 PDMS-OA solution is used.

[0083] As shown in Figure 1 The inhibitor used in the present invention not only inhibits the increase in viscosity over time, but also has the effect of reducing the viscosity at the start. Thus, the inhibitor can at least partially replace component (e) as a solvent for adjusting the viscosity of the composition for inkjet printing.

[0084] Examples

[0085] In the following examples, the ratio of components is a weight ratio, and the percentages are weight percentages. The PDMS used in the examples is 184 A pre-mix of two components (PDMS base: curing agent = 10:1). 1,1,1- trifluoroacetylacetone (TFAA) was used as inhibitor.

[0086] Example 1

[0087] The PDMS was diluted with OA in a 1:2 ratio, as described by Mikkonen et al. In addition, TFAA was added at different concentrations:

[0088] PDMS + OA (1:2) + TFAA (1.5% - 90% relative to PDMS)

[0089] The containers were sealed and stored at 80°C for 48 hours. As a result, concentrations up to 6% (relative to PDMS) were successful in curing, while concentrations at 15% (relative to PDMS) or higher were successful in inhibiting curing.

[0090] Example 2

[0091] The PDMS was diluted with OA (1:2), as described in Example 1. Intermediate concentrations (6%, 9%, and 12%, each relative to PDMS) were included, indicating that the minimum concentration for inhibiting curing was between 9% and 12%.

[0092] Example 3

[0093] The PDMS was diluted with OA (1:2), as described in Example 1, and acetylacetone was added at different concentrations:

[0094] PDMS + OA (1:2) + acetylacetone (3% - 30% relative to PDMS)

[0095] Acetylacetone proved to be ineffective at any of the concentrations used.

[0096] Example 4

[0097] In preliminary experiments, propylamine, pyrrolidine, and triethylamine, which are examples of primary, secondary, and tertiary amines, respectively, were tested at a concentration of 15% each, and they all successfully inhibited crosslinking.

[0098] Next, the reversibility of the successful inhibition was tested. The open containers were placed in an oven at 60 °C for 24 hours to evaporate the additive. Reversibility was observed for all TFAA mixtures, i.e. crosslinking occurred upon evaporation of TFAA. Higher concentrations of TFAA resulted in softer surfaces, indicating that the elastomer was not fully cured. In contrast, no reversibility was observed for propylamine, pyrrolidine and triethylamine. Crosslinking was hindered and the material remained liquid.

[0099] Next, higher temperatures and vacuum were used to accelerate evaporation of the additive and show potential reversibility of the inhibition. 72 hours at 80 °C and 100 mbar showed that for higher TFAA concentrations, the inhibition was also fully reversible. For propylamine and pyrrolidine, the experiments showed that the reaction was fully irreversible and the material remained liquid. For triethylamine, very limited reversibility was observed, hindering crosslinking, resulting in a very "sticky", not fully cured elastomer.

[0100] Example 5

[0101] In a prolonged rheology measurement, non-diluted PDMS was compared to non-diluted PDMS with TFAA (15%) showing the progress of crosslinking over time. Figure 1 Viscosity of PDMS with the same resin using 15% TFAA at 40 °C over 120 minutes is shown.

Claims

1. A composition comprising the following components: (a) Hydrosilylation catalysts comprising metal-ligand complexes, and (b) The inhibitor of the catalyst, wherein, The inhibitor is different from the ligand of the metal-ligand complex and is represented by formula (I): X-CHR-CO-Y (I), Where -X represents -NO2, -S(=O)R, or R c 2R a C-CO-; Y represents 2-furanyl, -S(=O)R, -CN, -NO2, or -CR b x R d 3-x ;R a and R b The R is independently selected from -OR, -O-CO-R, -CO-OR, 2-furanyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and R d The x is independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl and -Br; and x is 0 or 1.

2. The composition according to claim 1, wherein, The inhibitor (b) is represented by formula (II): R c 2R a C-CO-CHR-CO-Y (II), The groups therein are as defined in claim 1.

3. The composition according to claim 1, wherein, The inhibitor (b) is represented by formula (III): R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III), The groups therein are as defined in claim 1.

4. The composition according to any one of claims 1-3, comprising the following components: (a) A hydrogenation silylation catalyst comprising platinum (0) and olefin ligands, and (b) An inhibitor represented by formula (I), (II) or (III) as defined in the preceding claims.

5. The composition according to any one of claims 1-3, wherein, -CR a R c 2 and -CR b x R d 3-x At least one of them is -CF3.

6. The composition according to any one of claims 1-3, comprising the following components: (c) a silane, siloxane, polysilane or polysiloxane having an olefinic group and (d) a silane, siloxane, polysilane or polysiloxane containing hydrogen directly bonded to silicon.

7. The composition according to any one of claims 1-3, comprising the following components: (c) a vinyl-containing polysiloxane and (d) a polysiloxane containing hydrogen directly bonded to silicon.

8. The composition according to any one of claims 1-3, wherein, The hydrogenation silylation catalyst is a complex of platinum (0) and a divinyl disiloxane.

9. The composition according to any one of claims 1-3, wherein, The weight ratio of component (b):((c)+(d)) is 3:100 to 20:

100.

10. The composition according to any one of claims 1-3, comprising a solvent not defined in any one of components (a) to (d) as component (e).

11. A dual-packaged hydrogenated silanization system, wherein, The first package comprises a silane, siloxane, polysilane, or polysiloxane containing hydrogen directly bonded to silicon, and the second package comprises a composition of any one of claims 1 to 5 and a silane, siloxane, polysilane, or polysiloxane having an olefinic group; or wherein the first package comprises a composition of any one of claims 1 to 5 and a silane, siloxane, polysilane, or polysiloxane containing hydrogen directly bonded to silicon, and the second package comprises a silane, siloxane, polysilane, or polysiloxane having an olefinic group.

12. A method for hydrosilylation, comprising the following steps: (i) Provide a reaction system containing the following components: (a) Hydrosilylation catalysts comprising metal-ligand complexes, and (b) An inhibitor of the catalyst, wherein the inhibitor is different from the ligand of the metal-ligand complex and is represented by formula (I), (II) or (III): X-CHR-CO-Y (I), Where -X represents -NO2, -S(=O)R, or R c 2R a C-CO-; Y represents 2-furanyl, -S(=O)R, -CN, -NO2, or -CR b x R d 3-x ;R a and R b Independently selected from -OR, -O-CO-R, -CO-OR, 2-furanyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and each R d Independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; and x is 0 or 1; R c 2R a C-CO-CHR-CO-Y (II), The groups therein are defined in relation to formula (1), R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III), The groups therein are defined in relation to formula (1), (c) silanes, siloxanes, polysilanes, or polysiloxanes having olefin groups, and (d) Silanes, siloxanes, polysilanes or polysiloxanes containing hydrogen that is directly bonded to silicon; (ii) Perform a hydrosilylation reaction to crosslink components (c) and (d); (iii) Remove at least part of the inhibitor from the reaction system.

13. A crosslinked product that can be obtained by the method of claim 12.

14. Use of compounds of formula (I), (II), or (III) as inhibitors of hydrosilylation reactions, wherein the hydrosilylation reaction uses a catalyst comprising a metal-ligand complex, wherein, The compounds of formula (I), (II), or (III) are different from the ligands of the metal-ligand complexes described above: X-CHR-CO-Y (I), Where -X represents -NO2, -S(=O)R, or R c 2R a C-CO-; Y represents 2-furanyl, -S(=O)R, -CN, -NO2, or -CR b x R d 3-x ;R a and R b The R is independently selected from -OR, -O-CO-R, -CO-OR, 2-furanyl, -S(=O)R, -CN, -NO2, -F, -Cl, and -Br; each R is independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; each R c and each R d Independently selected from -H, optionally fluorinated C1-C8-alkyl, -F, -Cl, and -Br; and x is 0 or 1; R c 2R a C-CO-CHR-CO-Y (II), The groups therein are defined as those in formula (I); R c 2R a C-CO-CHR-CO-CR b x R d 3-x (III), The groups therein are defined as in formula (I).

15. The use according to claim 14, wherein, The hydrogenation silanization reaction is carried out in an inkjet printing composition or a composition dispensed by a syringe.

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