Polysiloxane coating composition with tin-free catalyst

Abstract

A composition formulated for forming a silicone coating, the composition comprising a first part, a second part, and a catalyst system. The first part includes a reactive silicone resin. The second part includes a silane crosslinker. The catalyst system comprises: (i) a titanium-based compound in combination with a zinc-based compound, bismuth-based compound, and / or aluminum-based compound; (ii) a zirconium-based compound in combination with a zinc-based compound and / or bismuth-based compound; and / or (iii) a bismuth-based compound in combination with an aluminum-based compound.

Description

POLYSILOXANE COATING COMPOSITION WITH TIN-FREE CATALYSTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of United States Provisional Application No. 63 / 730,557, filed December 11, 2024, the entirety of which is incorporated herein by reference.BACKGROUND

[0002] Silicone coating compositions are used in a variety of applications. Such coating compositions can exhibit properties of durability, chemical resistance, UV resistance, anticorrosion, and anti-fouling, and find use in industrial applications, marine applications, infrastructure, commercial and residential buildings, automotive, and aerospace applications, for example.

[0003] A catalyst is typically required to promote effective crosslinking and curing of such polysiloxane coating compositions. The catalyst is commonly an organotin catalyst. Such tin compounds, however, can be toxic to humans and the environment.SUMMARY

[0004] Disclosed herein is a composition formulated for forming a silicone coating, the composition comprising a first part, a second part, and a catalyst system. The first part includes a reactive silicone resin. The second part comprises a silane crosslinker. The catalyst system comprises: (i) a titanium-based compound in combination with a zinc-based compound, bismuth-based compound, and / or aluminum-based compound; (ii) a zirconium-based compound in combination with a zinc-based compound and / or bismuth-based compound; and / or (iii) a bismuth-based compound in combination with an aluminum-based compound.

[0005] The composition can essentially omit or completely omit tin compounds such as tin-based catalysts. The catalyst system can be included in the first part and / or second part.

[0006] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended toidentify key features or essential features of the claimed subject matter, nor is it intended to be used as an indication of the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various features and advantages of this disclosure will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings and the appended claims, all of which form a part of this specification.

[0008] Figure 1 is an example reaction scheme illustrating condensation curing of a composition comprising hydroxyl-terminated polysiloxane oligomers and a tetrafunctional silane crosslinker.DETAILED DESCRIPTIONIntroduction

[0009] Polysiloxane (i.e., silicone) coating compositions find use in industrial applications (e.g., on equipment, machinery, and structures), marine applications (e.g., ships, offshore platforms, and other marine structures), infrastructure (e.g., bridges, overpasses, and other structures), commercial and residential buildings (e.g., floors, indoor and outdoor walls), and automotive and aerospace applications (e.g., on protectable parts including exterior components).

[0010] Promoting timely curing and effective crosslinking of polysiloxane coating compositions typically involves use of a catalyst. One conventional approach has favored the use of a tin-based catalyst, such as dibutylbis(pentane-2,4-dionato-O,O')tin. While such tin- based compounds have been effective as catalysts in polysiloxane coating systems, their use has several drawbacks.

[0011] Tin compounds, particularly organotin compounds such as those conventionally used as catalysts in polysiloxane coating systems, are toxic to humans and the environment. Adverse health effects associated with tin exposure include skin irritation and respiratory problems in the short term, and neurological effects, endocrine disruption, immunotoxicity, and renal / hepatic injury with longer term exposure. In the environment, organotin compounds can accumulate in the food chain and are known to be particularly harmful to marine life.

[0012] Disclosed herein is a coating composition formulated for forming a silicone coating, the composition comprising a first part, a second part, and a catalyst system included in the first part and / or second part. The catalyst system comprises at least two different metal catalysts. For example, the catalyst system can include: (i) a titanium-based compound in combination with a zinc -based compound, bismuth-based compound, and / or aluminum-based compound; (ii) a zirconium-based compound in combination with a zinc -based compound and / or bismuth-based compound; and / or (iii) a bismuth-based compound in combination with an aluminum-based compound. The composition can essentially omit or completely omit tin compounds such as tin-based catalysts.

[0013] The disclosed coating composition, upon mixing of the first part and second part and allowing the mixture to cure, forms a coating that exhibits effective drying times without relying on a tin-based catalyst. For example, when the first part and second part of the coating composition are mixed to form a coating, the resulting coating can exhibit a shorter tack-free time (as tested according to ASTM DI 640: Dry to Touch and Handle) as compared to the same coating including only a single metal catalyst (e.g., including only one of the titanium-based compound, zirconium-based compound, bismuth-based compound, zinc -based compound, or aluminum-based compound).

[0014] Figure 1 is an example reaction scheme illustrating condensation curing of a reactive silicone resin and a silane crosslinker. In the example reaction of Figure 1, the reactive silicone resin includes hydroxyl-terminated polysiloxane oligomers and the silane crosslinker includes a tetrafunctional silane crosslinker in the form of a tetraethoxysilane (also known as tetraethyl orthosilicate or TEOS). Other reactive silicone resins and / or silane crosslinkers may additionally or alternatively be utilized, such as described in more detail below. The catalyst system can accelerate the process by which the reactive groups (e.g., the hydroxyl groups of the illustrated reaction) react to form siloxane bonds.

[0015] The coating composition may be formulated as a two-part composition where the polysiloxane oligomers are included in a first part (i.e. , a reactive silicone resin) while the silane crosslinker is included in a second part. The catalyst system can be included in the first part and / or the second part, though it is typically included in the second part. The term “part” may be used synonymously with “container” when used in the context of separate first and second containers for holding the respective first and second parts of the composition.

[0016] The term “alkyl” is inclusive of all constitutional isomers thereof, including branched alkyl groups and unbranched / linear alkyl groups. For example, where an alkyl is propyl, the propyl may be n-propyl or iso-propyl, or where an alkyl is butyl, the butyl may be n-butyl, sec -butyl, iso-butyl, or tert-butyl. An alkyl group can have 1 to 18 carbons, such as 1 to 16 carbons, such as 1 to 14 carbons, such as 1 to 12 carbons, such as 1 to 10 carbons, such as 1 to 8 carbons, such as 1 to 6 carbons, such as 1 to 4 carbons, such as 1 or 2 carbons. An alkyl can be unsubstituted or can be substituted such as wherein any H of the alkyl is replaced by a monovalent radical such as a hydroxyl, an alkoxy (e.g., a Cl to C2 alkoxy), or a halogen.

[0017] The term “cycloalkyl” refers to any alkyl comprising a cyclic moiety such as a cyclopentane or a cyclohexane. A cycloalkyl group can have 3 to 10 carbons, such as 3 to 8 carbons, such as 5 to 6 carbons. The term cycloalkyl is also inclusive of polycyclic alkyl groups such as an adamantly or a dicyclopentanyl group.

[0018] The term “aryl”, as used herein, is inclusive of substituted aryl groups wherein any H of the aryl can be replaced by a monovalent radical such as a hydroxyl, an alkyl (e.g., a Cl to C2 alkyl), or a halogen, and is inclusive of all positional isomers (e.g., ortho, meta, and para isomers) of such substituted aryl groups. An aryl group can include a phenyl group or tolyl group, for example. Aryl groups can be attached to the polysiloxane backbone by a linker chain, such as a C1-C3 linker chain.

[0019] The term “alkoxy” refers to an alkyl group bonded to an oxygen. An alkoxy group has the formula -OR, where R is an alkyl.

[0020] The term “acyloxy” refers to an acyl group (e.g., an acetyl group) bonded to an oxygen atom according to the formula -O-C(=O)-R, where R is any monovalent radical such as H, alkyl, alkoxy, or halogen.

[0021] A “siloxy” group has the formula -O-SiH?. The siloxy can be substituted by replacing one or more H groups with a monovalent radical such as an alkyl or a halogen. For example, a “trialkylsiloxy” group has the formula -O-Si-Rs, where each R is an alkyl.

[0022] When a labelled group has multiple instances and each instance of the group is described as “independently” selected from a list of alternatives, it means that each individual instance can be selected from the recited list of alternatives without requiring, but allowing for, the same selection for each instance. For example, for a compound with mulliple Z groups, the phrase “each Z is independently an alkyl or an aryl” means that all the Z groups can be alkyl, all the Z groups can be aryl, or the Z groups can include any combination of alkyl and arylgroups such as where one or more are alkyl with the remainder being aryl, or where one or more are aryl with the remainder being alkyl.

[0023] Further, unless specified otherwise, a statement describing multiple groups as having the same genus type (e.g., “each R is an alkyl”) will be understood to allow for, but not require, different combinations of species within that genus (e.g., one or more R groups can be methyl, and one or more R groups can be ethyl).Reactive Silicone Resin

[0024] The reactive silicone resin can comprise multiple hydrolysable groups (e.g., at least two per oligomer molecule). The hydrolysable groups can include an alkoxy (e.g., methoxy, ethoxy, and / or propoxy), acyloxy (e.g., acetoxy), siloxy (e.g., trialkylsiloxy such as trimethylsiloxy), halogen (e.g., chloro), oxime comprising an O bonded to an Si of the polysiloxane chain, and / or a hydroxyl. Other side groups can include branched or linear / unbranched alkyl (e.g., C1-C8 alkyl), cycloalkyl (e.g., C3-C10 cycloalkyl), and / or aryl (e.g., phenyl).

[0025] The reactive silicone resin can include hydroxyl-functional polysiloxane oligomers of the formula:where each Ri is independently C1-C6 alkyl (e.g., such as methyl) or aryl (e.g., such as phenyl), and n is selected to give a number average molecular weight (Mw) in the range of 100-100,000 g / mol, or in the range of 200 to 14,000 g / mol, or in the range of 400 to 12,000 g / mol, or in the range of 500 to 10,000 g / mol, or within a range with endpoints selected from any combination of the foregoing values, as determined using gel permeation chromatography (GPC) such as according to ASTM D5296-19. A composition that includes a reactive silicone resin with molecular weight that is too low can result in a coating that is more brittle than desired. A composition that includes a silicone resin with molecular weight that is too high can result in a coating that is more viscous than desired.

[0026] The reactive silicone resin can be included in the coating composition at 25 wt. % to 75 wt. %, such as 35 wt. % to 65 wt. %, such as 40 wt. % to 60 wt. %, or included within a range using any two of the foregoing values as endpoints, based on total weight of the composition (i.e., based on both the first and second parts combined when formulated as a two- part composition).

[0027] A base formulation suitable for use as the first part of the disclosed composition is the resin / base portion of the two-part composition sold under the trade name SIGMAGLIDE® 2390 (available from PPG Industries Ohio, Inc.).Silane Crosslinker

[0028] The silane crosslinker can include two to four reactive groups. In this context, reactive groups of the silane crosslinker refer to groups that are reactive toward the silicone resin. The reactive groups can include alkoxy, oxime, acyloxy, and / or hydroxycarboxylate groups.

[0029] The silane crosslinker can include the formula:(R1)4.y- Si - (OR2)ywhere y equals 2 to 4, and R1and R2are independently alkyl (e.g., methyl), alkenyl (e.g., vinyl), aryl (e.g., phenyl), acyl (e.g., acetyl), or cycloalkyl groups. R1and R2can independently have 1 to 12 carbon atoms, or 1 to 6 carbon atoms (at least 6 for aryl groups and at least 3 for cycloalkyl groups), for example.

[0030] Examples of silane crosslinkers comprising an alkoxy functional group include tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. Examples of silane crosslinkers including an acyloxy functional group, such as an acetoxy functional group, include methyltri acetoxysilane, ethyltriacetoxysilane, propyltriacetoxysilane, and vinyltriacetoxysilane. Examples of silane crosslinkers including a hydroxycarboxylate group include those that comprise a lactato group and / or lactato ester group, such as vinyltris(ethyl lactato)silane and methyltris(ethyl lactato)silane.

[0031] The silane crosslinker can be included at 4 wt. % to 12 wt. %, such as 6 wt. % to 10 wt. %, or included within a range using any two of the foregoing values as endpoints, based ontotal weight of the composition (i.e., based on both the first and second parts combined when formulated as a two-part composition).Catalyst System

[0032] The catalyst system can comprise at least two different metal catalysts. For example, the catalyst system can include: (i) a titanium-based compound in combination with a zinc-based compound, bismuth-based compound, and / or aluminum-based compound; (ii) a zirconium-based compound in combination with a zinc -based compound and / or bismuth-based compound; and / or (iii) a bismuth-based compound in combination with an aluminum-based compound. The composition can essentially omit or completely omit tin compounds such as tin-based catalysts.

[0033] The disclosed coating composition, upon mixing of the first part and second part and allowing the mixture to cure, forms a coating that exhibits effective drying times without relying on a tin-based catalyst. For example, when the first part and second part of the coating composition are mixed to form a coating, the resulting coating can exhibit a shorter tack-free time (as tested according to ASTM D1640: Dry to Touch and Handle) as compared to the same coating including only a single metal catalyst (e.g., including only one of the titanium-based compound, zirconium-based compound, bismuth-based compound, zinc -based compound, or aluminum-based compound).

[0034] The titanium-based compound can include an alkyl titanate, such as a tetra C1-C8 alkyl titanate, such as a tetra propyl titanate, tetra butyl titanate, and / or tetra 2-ethylhexyl titanate.

[0035] The zirconium-based compound can include an alkyl zirconate, such as a tetra Cl- C8 alkyl zirconate, such as a tetra propyl zirconate, tetra butyl zirconate, and / or tetra 2- ethylhexyl zirconate.

[0036] The zirconates and / or titanates of the coating composition can be according to the formula:where M is zirconium or titanium, and each R is independently a C1-C8 alkyl. The alkyl may be branched or unbranched / linear. For example, where R is propyl, the propyl may be n-propyl or iso-propyl, or where R is butyl, the butyl may be n-butyl, sec -butyl, iso-butyl, or tert-butyl, or where R is a C8 alkyl, the C8 alkyl may be a branched ethylhexyl group, such as a 2- cthylhcxyl group.

[0037] As in the ail, the term alkyl zirconate is used synonymously herein with the terms zirconium alkoxide and alkoxy zirconium. Similarly, the term alkyl titanate is used synonymously herein with the terms titanium alkoxide and alkoxy titanium. Accordingly, a tetra alkyl zirconate is equivalent to a zirconium (IV) alkoxide and to a tetra alkoxy zirconium, and a tetra alkyl titanate is equivalent to a titanium (IV) alkoxide and a tetra alkoxy titanium.

[0038] Suitable titanium-based catalysts include those sold under the trade names TYZOR 9000, TYZOR TNBT, TYZOR TOT, and TYTAN TNBT. Suitable zirconium-based catalysts include those sold under the trade names TYTAN TNBZ and TYTAN TNPZ.

[0039] The bismuth-based compound can include a bismuth carboxylate. The zinc -based compound can include a zinc carboxylate. When a zinc carboxylate and / or bismuth carboxylate are included, the carboxylate of the zinc carboxylate and / or bismuth carboxylate can comprise (i) a Cl -Cl 7 alkyl carboxylate (where the alkyl can be branched or unbranched / linear), such as an acetate, octoate (e.g., a linear octoate and / or an ethylhexanoate, such as a 2- ethylhexanoate), neodecanoate, stearate, and / or linoleate; and / or (ii) an aromatic carboxylate, such as a benzoate and / or naphthenate.

[0040] The catalyst system can essentially omit or completely omit zirconium and / or titanium catalysts that are in the form of octoates, neodecanoates, or naphthenates. Moreover, while some examples include zinc and / or bismuth catalysts that are in the form of octoates, neodecanoates, or naphthenates, other examples can essentially omit or completely omit zinc and / or bismuth catalysts that are in the form of octoates, neodecanoates, or naphthenates.

[0041] Suitable zinc -based compounds are sold under the trade names K-KAT XK 661, K- KAT XK-614, and K-KAT 670 (King Industries, Norwalk, Conn.). Although the formulations of these products are not provided by the manufacturer, they are understood to include zinc carboxylates (in the form of octoates, neodecanoates, or naphthenates), blended with amine compounds such as those disclosed herein.

[0042] Suitable bismuth-based compounds are sold under the trade names COSCAT 83 (Palmer Holland), BORCHI KAT 21 (Borchers Americas Inc., Westlake, OH), K-KAT XC-B221, K-KAT 651, and K-KAT 348 (King Industries, Norwalk, Conn.). These products are understood to be bismuth carboxylates in the form of octoates, neodecanoates, or naphthenates. COSCAT 83, for example, is reported to be a bismuth trineodecanoate.

[0043] The aluminum-based compound can include a tri(Cl-C12)alkyl aluminum and / or aluminum tri(Cl -C4)alkoxide, such as aluminum tri-sec-butoxide. The aluminum-based compound can additionally or alternatively include triisobutyl aluminum, trimethyl aluminum, triethyl aluminum, triisopropyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum, and / or tri-n-dodecyl aluminum, for example.

[0044] The catalyst system can optionally further include an amine compound. Amine compounds known in the art as useful catalysts in polysiloxane systems include, for example, tertiary amines such as DABCO and / or trialkylamines, aliphatic polyamines such as triethylenetetramine and / or diethylenetriamine, heterocyclic amines such as imidazole and / or diazabicyclo compounds, alkanolamines such as di- or tri-methanolamine and di- or triethanolamine, guanidine compounds, and combinations thereof. For example, the diazobicyclo compound can include l,8-Diazabicyclo[5.4.0]undec-7-ene (more commonly referred to as “DBU”) and / or l,5-Diazabicyclo[4.3.0]non-5-ene (more commonly referred to as “DBN”). The guanidine compound can include a tetra alkylguanidine, such as a tetra methylguanidine.

[0045] The coating composition may include the catalyst system at 1 wt. % to 5 wt. %, or 1.5 wt. % to 4 wt. %, or may include it within a range using any two of the foregoing values as endpoints, based on total weight of the composition (i.e., based on both the first and second parts combined when formulated as a two-part composition).

[0046] The catalyst system can include a titanium-based compound in combination with a zinc -based compound, and the weight ratio of the titanium-based compound to the zinc -based compound can be greater than 2.3:1, such as 2.5:1 to 6:1, such as 3:1 to 5:1, such as 4:1, or can be within a range using any combination of the foregoing values as endpoints. The catalyst system can include a bismuth-based compound in combination with an aluminum-based compound, and the weight ratio of the bismuth-based compound to the aluminum-based compound can be greater than 2.3:1, such as 2.5:1 to 6:1, such as 3:1 to 5:1, such as 4:1, or can be within a range using any combination of the foregoing values as endpoints. The catalyst system can include a zirconium-based compound in combination with a bismuth-based compound, and the weight ratio of the zirconium-based compound to the bismuth-based compound can be 1.25: 1 to 5:1, such as 1.5: 1 to 4:1, or can be within a range using anycombination of the foregoing values as endpoints. The catalyst system can include a titanium- based compound in combination with a bismuth-based compound, and the weight ratio of the titanium-based compound to the bismuth-based compound can be 0.5 : 1 to 4: 1 , such as 0.5 : 1 to 2:1, or can be within a range using any combination of the foregoing values as endpoints. The catalyst system can include titanium-based compound in combination with an aluminum-based compound, and the weight ratio of the titanium-based compound to the aluminum-based compound can be 0.5: 1 to 4:1, such as 0.5:1 to 2: 1, or can be within a range using any combination of the foregoing values as endpoints. The catalyst system can include a zirconium- based compound in combination with a zinc-based compound, and the weight ratio of the zirconium-based compound to the zinc -based compound can be 1 :1 to 1:5, such as 1:2 to 1:4. Results have demonstrated that weight ratios of different metal catalyst components within the foregoing ranges can promote effective drying times.Other Coating Composition Components

[0047] The coating composition can include other components including, for example, pigments, water, rheological modifiers, plasticizers, antifoam agents, thixotropic agents, potlife extenders, anti-settling agents, diluents, UV light stabilizers, air release agents, dispersing aids, biocides, and / or other coating composition components as known in the art.

[0048] The first part and / or the second part may include a suitable solvent. Suitable solvents can include petroleum solvents such as cyclohexane, toluene, xylene, naphtha, or combinations thereof. The solvent can additionally or alternatively include ketones and / or ketone esters, such as 2,4-pentanedione and ethyl acetoacetate.Additional Terms & Definitions

[0049] While certain aspects of the present disclosure have been described in detail, with reference to specific components and / or features, the descriptions are illustrative and are not to be construed as limiting the scope of the claimed coating composition or related methods.

[0050] Furthermore, it should be understood that for any given component of a described example, any of the possible alternatives listed for that component may generally be used individually or in combination with one another, unless implicitly or explicitly stated otherwise. The various features of a given example can be combined with and / or incorporated into other examples disclosed herein. Thus, disclosure of certain features relative to a specificexample should not be construed as limiting application or inclusion of said features to the specific example. Rather, it will be appreciated that other examples can also include such features.

[0051] Any headings and subheadings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims.

[0052] Any standard testing method discussed herein (e.g., ASTM) will be understood to refer to the most recent version of the testing method available at the time of filing of this disclosure, unless specified otherwise.

[0053] It will also be noted that, as used in this specification and the appended claims, the singular forms “a," “an” and “the” do not exclude plural referents unless the context clearly dictates otherwise. Thus, for example, an embodiment referencing a singular referent may also include two or more such referents.

[0054] The examples disclosed herein should be understood as comprising / including disclosed components, and may therefore include additional components not specifically described. Optionally, the examples disclosed herein are essentially free or completely free of components that are not specifically described. That is, non-disclosed components may optionally be completely omitted or essentially omitted from the disclosed examples. For example, resins, crosslinking agents, and catalyst compounds not specifically disclosed herein may optionally be completely omitted or essentially omitted from the disclosed coating composition.

[0055] A composition that “essentially omits” or is “essentially free of’ a component may include trace amounts and / or non-functional amounts of the component. For example, an “essentially omitted” component may be included in an amount no more than 1%, no more than 0.1%, no more than 0.05%, no more than 0.01%, or no more than 0.005% by total weight of the composition.

[0056] A composition that “completely omits” or is “completely free of’ a component does not include a detectable amount of the component (i.e., does not include an amount above any inherent background signal associated with the testing instrument) when analyzed using standard coating composition analysis techniques such as, for example, chromatographic techniques (e.g., thin-layer chromatography (TLC), gas chromatography (GC), liquid chromatography (LC)), or spectroscopy techniques (e.g., Fourier transform infrared (FTIR) spectroscopy).EXAMPLES

[0057] A series of two-part coating compositions were prepared using the components listed in Table 1.Table 1: Components used in Example Compositions

[0058] The polysiloxane mixture forming “Part A” was the base pack portion of the two- part composition sold under the trade name SIGMAGLIDE® 2390 (available from PPG Industries, Ohio, Inc.), which lists the ingredients as shown in Table 2. Variations within the listed ranges are not expected to affect the test results so long as amounts are held substantially consistent across compared examples, as was the case with the presently disclosed examples.Table 2: Components of Base / Resin Mixture used as “Part A ”

[0059] The zinc complex sold under the trade name K-KAT 670 (King Industries, Norwalk, Conn.) is not characterized by the manufacturer, but functions in testing similar to zinc complexes in which zinc is complexed with common carboxylates such as octoates,neodecanoates, and / or naphthenates in a blend with common amine catalysts such as alkylamines and is therefore treated as such for purposes of these examples. The bismuth carboxylate complex sold under the trade name COSCAT 83 is reported to be a bismuth trineodecanoate.

[0060] Comparative example formulations using a single metal catalyst were prepared as shown in Table 3. All component values represent wt. % based on total weight of the composition. Catalyst amounts were increased until a tack- free time of less than 120 minutes was achieved. Xylene was used as the default solvent for the Part B component, except for a subset of Examples where gelling occurred immediately upon mixing with the xylene, in which case ethyl acetoacetate was selected. Other than the pre-application gelling that occurred in some formulations, the difference in solvent did not measurably affect the drying time results.Table 3: Single Catalyst Formulations

[0061] The Examples were subjected to modified drying tests according to ASTM DI 640: Dry to Touch and Handle. This method was slightly modified because silicone coatings form soft films. In these tests, a cotton ball of diameter approx. 3 cm is dropped from an altitude of 20 cm. After 10 seconds, the cotton ball is blown away in a horizontal direction. Tack-free conditionis reached when the film surface has cured so that the film does not adhere to very light objects placed on it. In the modified drying tests according to ASTM DI 640, the tack-free condition is reached when the dropped cotton no longer leaves fibers left after the cotton is dropped on the coating surface and blown away. Testing was conducted at room temperature (75° F / 23.9° C) and 40% to 44% relative humidity.

[0062] Additional example formulations including bimetallic catalyst systems were prepared as shown in Table 4. All component values represent wt. % based on total weight of the composition. As with the formulations of Table 3, catalyst amounts were increased until a tack-free time of less than 120 minutes was achieved. Testing was carried out in the same manner as with the formulations of Table 3.Table 4: Bimetallic Catalyst Formulations

[0063] Several of the bimetallic catalyst formulations exhibited (i) a faster tack-free time and / or (ii) lower amount of catalyst, as compared to the corresponding single catalyst formulations of Table 3. Table 5 shows such formulations grouped with their corresponding single catalyst formulations.Table 5: Bimetallic Catalyst Formulations Compared to Single Catalyst Formulations

[0064] Example 11 included a catalyst with both a titanium-based compound and a zinc- based compound. Additional example formulations were prepared with variable weight ratios of the titanium-based compound to the zinc-based compound, as shown in Table 6 A. The results indicate that a weight ratio of the titanium-based compound to the zinc-based compound greater than 2.3:1 can promote effective drying times. For example, the weight ratio of the titanium-based compound to the zinc-based compound can be 2.5:1 to 6: 1, such as 3:1 to 5:1, such as 4: 1 .Table 6A: Bimetallic Catalyst Formulations with Variable Ratios ofTi to Zn* “Tacky” means that composition remained tacky after 24 hours

[0065] Example 12 included a catalyst with both a bismuth-based compound and an aluminum-based compound. Additional example formulations were prepared with variable weight ratios of the bismuth-based compound to the aluminum-based compound, as shown in Table 6B. The results indicate that a weight ratio of the bismuth-based compound to the aluminum-based compound greater than 2.3:1 can provide effective drying times. For example, the weight ratio of the bismuth-based compound to the aluminum-based compound can be 2.5 : 1 to 6: 1, such as 3:1 to 5: 1, such as 4: 1.Table 6B: Bimetallic Catalyst Formulations with Variable Ratios of Bi to Al* “Tacky” means that composition remained tacky after 24 hours

[0066] Example 10 included a catalyst with both a zirconium-based compound and a bismuth-based compound. Additional example formulations were prepared with variable weight ratios of the zirconium-based compound to the bismuth-based compound, as shown in Table 6C. The results indicate that a weight ratio of the zirconium-based compound to the bismuth-based compound greater than 1 : 1 can provide effective drying times. For example, theweight ratio of the zirconium-based compound to the zinc -based compound can be 1.25:1 to 5: 1, such as 1.5: 1 to 4:1.Table 6C: Bimetallic Catalyst Formulations with Variable Ratios of Zr to Bi* “Tacky” means that composition remained tacky after 24 hours

Claims

CLAIMS1. A composition formulated for forming a silicone coating, the composition comprising: a first part comprising a reactive silicone resin; a second part comprising a silane crosslinker; and a catalyst system comprising(i) a titanium-based compound in combination with a zinc-based compound, bismuth-based compound, and / or aluminum-based compound;(ii) a zirconium-based compound in combination with a zinc-based compound and / or bismuth-based compound; and / or(iii) a bismuth-based compound in combination with an aluminum-based compound.

2. The composition of claim 1, wherein the composition essentially omits or completely omits tin compounds.

3. The composition of any preceding claim, wherein the titanium-based compound comprises an alkyl titanate, such as a tetra C1-C8 alkyl titanate, such as a tetra propyl titanate, tetra butyl titanate, and / or 2-ethylhexyl titanate.

4. The composition of any preceding claim, wherein the zirconium-based compound comprises an alkyl zirconate, such as a tetra C1-C8 alkyl zirconate, such as a tetra propyl zirconate, tetra butyl zirconate, and / or 2-ethylhexyl zirconate.

5. The composition of any preceding claim, wherein the bismuth-based compound comprises a bismuth carboxylate, and wherein the carboxylate comprises: a Cl -Cl 7 alkyl carboxylate, such as an acetate, octoate, neodecanoate, stearate, and / or linoleate; and / or an aromatic carboxylate, such as a benzoate and / or naphthenate.

6. The composition of any preceding claim, wherein the zinc-based compound comprises a zinc carboxylate, and wherein the carboxylate comprises: a Cl -Cl 7 alkyl carboxylate, such as an acetate, octoate, neodecanoate, stearate, and / or linoleate: and / or an aromatic carboxylate, such as a benzoate and / or naphthenate.

7. The composition of any preceding claim, wherein the aluminum-based compound comprises a tri(Cl-C12)alkyl aluminum and / or aluminum tri(Cl-C4)alkoxide, such as aluminum tri-sec-butoxide.

8. The composition of any preceding claim, wherein the reactive silicone resin comprises a hydroxyl functional silicone resin.

9. The composition of claim 8, wherein the reactive silicone resin comprises reactive polysiloxane oligomers of the formula:wherein each Ri is independently C 1 -C6 alkyl or aryl, and n is selected to give a number average molecular weight in the range of 100-100,000 g / mol.

10. The composition of any preceding claim, wherein the silane crosslinker comprises two to four reactive groups, wherein the reactive groups include alkoxy, oxime, acyloxy, and / or hydroxycarboxylate groups, such as wherein the silane crosslinker comprises tetraethoxysilane.

11. The composition of any preceding claim, wherein the catalyst system is included in the second part of the composition.

12. The composition of any preceding claim, wherein: the reactive silicone resin is included at 25 wt. % to 75 wt. %, such as 35 wt. % to 65 wt. %, such as 40 wt. % to 60 wt. %, based on total weight of the composition; the silane crosslinkcr is included at 4 wt. % to 12 wt. %, such as 6 wt. % to 10 wt. %, based on total weight of the composition; and / or the catalyst system is included at 1 wt. % to 5 wt. %, such as 1.5 wt. % to 4 wt. %, based on total weight of the composition.

13. The composition of any preceding claim, wherein the catalyst system comprises a titanium-based compound in combination with a zinc-based compound, and wherein a weight ratio of the titanium-based compound to the zinc-based compound is greater than 2.3: 1, such as 2.5:1 to 6: 1, such as 3:1 to 5:1.

14. The composition of any preceding claim, wherein the catalyst system comprises a titanium-based compound in combination with a bismuth-based compound, and wherein a weight ratio of the titanium-based compound to the bismuth-based compound is 0.5:1 to 4:1.

15. The composition of any preceding claim, wherein the catalyst system comprises a titanium-based compound in combination with an aluminum-based compound, and wherein a weight ratio of the titanium-based compound to the aluminum-based compound is 0.5 : 1 to 4: 1.

16. The composition of any preceding claim, wherein the catalyst system comprises a zirconium-based compound in combination with a zinc -based compound, and wherein a weight ratio of the zirconium-based compound to the zinc -based compound is 1: 1 to 1 :5, such as 1 :2 to 1:4.

17. The composition of any preceding claim, wherein the catalyst system comprises a zirconium-based compound in combination with a bismuth-based compound, and wherein a weight ratio of the zirconium-based compound to the bismuth-based compound is 1.25:1 to 5:1, such as 1.5: 1 to 4: 1.

18. The composition of any preceding claim, wherein the catalyst system comprises a bismuth-based compound in combination with an aluminum-based compound, and wherein a weight ratio of the bismuth-based compound to the aluminum-based compound is greater than 2.3:1, such as 2.5:1 to 6: 1, such as 3:1 to 5:1.

19. The composition of any preceding claim, wherein when the first part and the second part are mixed to form a coating, the resulting coating exhibits shorter tack-free time, as tested according to ASTM DI 640: Dry to Touch and Handle, as compared to the same coating including only one of the titanium-based compound, zirconium-based compound, bismuth- based compound, zinc-based compound, or aluminum-based compound.

20. A coating composition formed by mixing the first part and the second part of the composition of any preceding claim.

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