WO2014004139A1 - Curable polysiloxane composition - Google Patents

Abstract

A curable composition comprises (a) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydroxysilyl moieties, the hydroxysilyl moieties optionally being generated in situ by hydrolysis of at least one hydrolyzable moiety; (b) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydrosilyl moieties; and (c) at least one catalyst comprising iron (III) and at least one thermally-displaceable or radiation-displaceable ligand; wherein at least one of the components (a) and (b) has an average reactive silane functionality of at least three.

Description

CURABLE POLYSILOXANE COMPOSITION

STATEMENT OF PRIORITY

This application claims the priority of U.S. Provisional Application No. 61/663815, filed June 25, 2012, the contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to curable compositions comprising reactive silane functionality and, in other aspects, to processes for coating the compositions and articles prepared thereby.

BACKGROUND

Curable polysiloxane compositions have been used to prepare a variety of surface coatings and surface treatments, ranging from encapsulants and release coatings to pressure-sensitive adhesives (PSAs). Some of the curable polysiloxane compositions are moisture-curable (for example, by hydrolysis and subsequent condensation). The moisture for curing is typically obtained from the atmosphere or from a substrate to which the composition has been applied, although it can also be added to the composition (for example, to enable curing in depth or in confinement).

Moisture-curable polysiloxane compositions usually comprise siloxane polymers having groups (for example, alkoxysilyl or acyloxysilyl moieties) that can react in the presence of moisture to form cured (that is, crosslinked) materials. Commonly used catalysts include Bronsted and Lewis acids (including a variety of metal complexes).

Other curable polysiloxane compositions can be cured through various different mechanistic routes including peroxide cure, hydrosilylation, condensation, high energy radiation cure, and photoinitiated radiation cure. For example, two different types of cure chemistries generally have been used to prepare silicone PSAs.

Peroxide cure involves a free radical curing mechanism and has been used to bond non- functional silicone polymers to Q resins. Curing can be performed in a temperature range of about 150-170°C by using, for example, either dibenzoyl peroxide or dichlorobenzoyl peroxide as a radical initiator. Peroxide curing is a two-step process that generally requires the use of a multi-zone oven to remove solvent from a curable composition prior to curing.

Platinum-catalyzed hydrosilylation cure is the other commonly-employed cure chemistry for silicone PSAs. This method involves an addition curing mechanism and has been used to cure compositions comprising vinyl-terminated silicone base polymer(s), vinyl-functionalized Q resin(s), and silane crosslinker(s). Typically, such a curable composition can be cured in a vented, continuous coating oven at temperatures as low as about 80°C (176°F). When coating flexible substrates (for example, polyester or polyolefm films), typical curing speeds have ranged from about 2 minutes at about 100°C (212°F) to about 1 minute at about 125°C (257°F). The foregoing curing methods suffer, however, from various important drawbacks, including a need for use of solvent, a need for relatively high temperatures, and/or a relatively high cost. Although silicone PSAs exhibit many useful properties (for example, performance at high temperatures; resistance to chemicals, moisture, weathering, and ultraviolet (UV) light; adhesion to low energy surfaces; and electrical insulating properties), such curing method drawbacks impede the use of silicone PSAs.

Conventional tin catalysts such as dibutyl tin dilaurate can provide stable curable polysiloxane compositions that can be processed and coated without premature gelation. In addition to typical moisture-curable systems, it has been found that curable compositions comprising dual reactive silane functionality in the form of hydrosilyl and hydroxysilyl groups (dehydrogenatively-curable systems) can be cured by using tin catalysts. The compositions have been widely used for pressure-sensitive adhesive and mold release applications but have sometimes suffered from relatively short pot lives. In addition, the use of tin catalysts is becoming particularly problematic because the organotin compounds generally employed as catalysts are now considered to be toxicologically objectionable.

SUMMARY

Thus, we recognize that there exists an ongoing need for curable polysiloxane compositions that can provide acceptable cure rates without significant processing and storage difficulties (for example, due to premature gelation). Preferably, these compositions will be efficiently processable (for example, without the need for mixing of a two-part system prior to cure or without the need for relatively large quantities of solvent), will employ catalysts that do not generate species requiring removal, and/or will not require heat activation (so as to enable curing at relatively low temperatures and/or the use of heat- sensitive substrates). Ideally, the compositions will employ catalysts that are relatively non-toxic, provide compositions that are relatively stable in solution but relatively fast-curing upon drying, effective in relatively low concentrations, and/or effective under relatively low (or no) moisture conditions.

Briefly, in one aspect, this invention provides a curable polysiloxane composition comprising dual reactive silane functionality. The composition comprises

(a) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydroxysilyl moieties (that is, monovalent moieties comprising a hydroxyl group bonded directly to a silicon atom), the hydroxysilyl moieties optionally being generated in situ by hydrolysis of at least one hydrolyzable moiety;

(b) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydrosilyl moieties (that is, monovalent moieties comprising a hydrogen atom bonded directly to a silicon atom); and

(c) at least one catalyst comprising iron (III) and at least one thermally-displaceable or

radiation-displaceable ligand; wherein at least one of components (a) and (b) has an average reactive silane functionality of at least three (that is, component (a) has at least three hydroxysilyl moieties (on average), component (b) has at least three hydrosilyl moieties (on average), or both).

Components (a) and (b) preferably comprise at least one polyorganosiloxane (more preferably, at least one polyalkylsiloxane (that is, at least one polydialkylsiloxane, polyalkyl(hydro)siloxane, or a combination thereof); most preferably, at least one polymethylsiloxane (that is, at least one

polydimethylsiloxane, polymethyl(hydro)siloxane, or a combination thereof)) having the above-specified reactive silane functionalities, respectively.

Preferably, component (a) is hydroxyl-endblocked, so as to comprise two terminal hydroxysilyl moieties (on average). The catalyst preferably comprises iron (III) and at least one ligand comprising at least one moiety selected from beta-diketonato, halo, and combinations thereof (most preferably, the catalyst is iron (III) 2,4-pentanedionate (also known as iron (III) acetylacetonate)). The composition preferably further comprises at least one solvent (for example, an aprotic organic solvent such as heptanes).

It has been discovered that, unlike at least some other metal complexes including iron (II) complexes (which are ineffective), the above-described iron (III) complexes can effectively catalyze the curing (apparently, by dehydrocondensation) of polysiloxane compositions comprising reactive silane functionality in the form of hydrosilyl and hydroxysilyl moieties. The complexes can provide relatively rapid cure (for example, upon removal of solvent curing can occur within periods of time as short as about 1 or 2 minutes) even at temperatures as low as about 50°C (or lower, if radiation curing is carried out), and can be effective in relatively small amounts (for example, at concentrations as low as about 0.5 or 0.25 weight percent or less, based upon the total weight of components (a), (b), and (c)). Thus, polysiloxane compositions comprising the complexes can be suitable for use in high speed coating and curing operations in an industrial setting. In spite of such effective curability, the compositions can exhibit relatively good storage stability (for example, for a period of weeks in a closed container) and/or relatively long pot life (for example, on the order of 8 hours or more) in a variety of solvents (for example, heptane, methyl ethyl ketone, or a combination thereof), without the need for mixing of a two- part system immediately prior to use.

In surprising contrast with prior art compositions, the complexes can be effective in the curable polysiloxane composition of the invention in the substantial absence of other condensation catalysts and/or in the substantial absence of moisture. The complexes can be used as substitutes for conventional tin catalysts to provide organometallic catalyst- free, curable polysiloxane compositions, without the need for changes in the nature of the polysiloxane components of conventional tin-cured polysiloxane compositions (for example, release coating compositions such as Syl-Of ^M 292 coating composition, available from Dow Corning Corporation, Midland, MI). Unlike the conventional tin catalysts, at least some of the complexes (for example, iron (III) acetylacetonate) are relatively non-toxic (as well as being effective in relatively smaller amounts than tin catalysts) and therefore suitable for use in preparing relatively environmentally friendly or green polysiloxane compositions.

The curable polysiloxane composition of the invention can be cured to provide crosslinked networks having properties that can be tailored to the requirements of various different applications (for example, by varying the natures, relative amounts, and/or degrees of reactive silane functionality of starting components (a) and/or (b)). Thus, the curable polysiloxane composition can be used to provide coatings having a variety of surface properties for use in numerous coating applications (for example, use as encapsulants or sealants, pressure-sensitive adhesives (with the addition of tackifying resin to the composition), release coatings for pressure-sensitive adhesives, protective coatings, water- and/or oil- repellent coatings or surface treatments, and the like). The curable polysiloxane composition of the invention can be particularly useful in relatively sensitive applications requiring careful and/or tailored control of surface properties (for example, release coating applications and/or pressure-sensitive adhesive applications), as the iron (III) catalysts do not appear to produce species requiring removal.

In view of the foregoing, at least some embodiments of the curable polysiloxane composition of the invention meet the above-described, ongoing need for curable compositions that can provide acceptable cure rates without significant processing and storage difficulties (for example, being relatively stable in solution but relatively fast-curing upon drying), while also being efficiently processable (for example, without the need for mixing of a two-part system prior to cure, for moisture, and/or for contaminant removal). At least some embodiments of the curable polysiloxane composition also employ catalysts that are relatively non-toxic, while being effective in relatively low concentrations and/or under relatively low (or no) moisture conditions.

In another aspect, this invention also provides a coating process comprising

(a) providing the above-described curable polysiloxane composition of the invention;

(b) providing at least one substrate having at least one major surface;

(c) applying the curable polysiloxane composition to at least a portion of at least one major surface of the substrate; and

(d) allowing or inducing the curable polysiloxane composition to cure to form a coating.

In yet another aspect, this invention provides an article comprising at least one substrate having at least one major surface, the substrate bearing, on at least a portion of at least one major surface, a coating prepared by the above-described coating process.

DETAILED DESCRIPTION

In the following detailed description, various sets of numerical ranges (for example, of the number of carbon atoms in a particular moiety, of the amount of a particular component, or the like) are described, and, within each set, any lower limit of a range can be paired with any upper limit of a range. Such numerical ranges also are meant to include all numbers subsumed within the range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, and so forth). As used herein, the term and/or means one or all of the listed elements or a combination of any two or more of the listed elements.

The words preferred and preferably refer to embodiments of the invention that may afford certain benefits under certain circumstances. Other embodiments may also be preferred, however, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

The term comprises and variations thereof do not have a limiting meaning where these terms appear in the description and claims.

As used herein, a, an, the, at least one, and one or more are used interchangeably.

The above Summary of the Invention section is not intended to describe every embodiment or every implementation of the invention. The detailed description that follows more particularly describes illustrative embodiments. Throughout the detailed description, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, a recited list serves only as a representative group and should not be interpreted as being an exclusive list.

Definitions

As used in this patent application:

catenated heteroatom means an atom other than carbon (for example, oxygen, nitrogen, or sulfur) that replaces one or more carbon atoms in a carbon chain (for example, so as to form a carbon- heteroatom-carbon chain or a carbon- heteroatom-heteroatom-carbon chain);

cure means conversion to a crosslinked polymer network (for example, through catalysis);

fluoro- (for example, in reference to a group or moiety, such as in the case of fluoroalkylene or fluoroalkyl or fluorocarbon) or fluorinated means only partially fluorinated such that there is at least one carbon-bonded hydrogen atom;

fluorochemical means fluorinated or perfluorinated;

halo means a monovalent group or moiety of formula -X, where X is a halogen atom selected from fluorine, chlorine, bromine, iodine, and combinations thereof (preferably, selected from chlorine, bromine, and combinations thereof; more preferably, chlorine);

heteroorganic means an organic group or moiety (for example, an alkyl or alkylene group) containing at least one heteroatom (preferably, at least one catenated heteroatom);

hydrosilyl refers to a monovalent moiety or group comprising a silicon atom directly bonded to a hydrogen atom (for example, the hydrosilyl moiety can be of formula -Si(R)3__p(H)_p , where p is an integer of 1, 2, or 3 and R is a hydrolyzable or non-hydro lyzable group (preferably, non-hydro lyzable) such as alkyl or aryl);

hydroxysilyl refers to a monovalent moiety or group comprising a silicon atom directly bonded to a hydroxyl group (for example, the hydroxysilyl moiety can be of formula -Si(R)3__p(OH)_p where p is an integer of 1, 2, or 3 and R is a hydrolyzable or non-hydro lyzable group (preferably, non-hydro lyzable) such as alkyl or aryl);

oligomer means a molecule that comprises at least two repeat units and that has a molecular weight less than its entanglement molecular weight; such a molecule, unlike a polymer, exhibits a significant change in properties upon the removal or addition of a single repeat unit;

oxy means a divalent group or moiety of formula -0-; and

perfluoro- (for example, in reference to a group or moiety, such as in the case of

perfluoroalkylene or perfluoroalkyl or perfluorocarbon) or perfluorinated means completely fluorinated such that, except as may be otherwise indicated, there are no carbon-bonded hydrogen atoms replaceable with fluorine.

Component (a)

Polysiloxanes suitable for use as component (a) of the curable polysiloxane composition of the invention include polyorganosiloxanes, fluorinated polyorganosiloxanes, and combinations thereof (preferably, polyorganosiloxanes; more preferably, polydialkylsiloxanes) comprising reactive silane functionality comprising at least two hydroxysilyl moieties (that is, monovalent moieties comprising a hydroxyl group bonded directly to a silicon atom). The hydroxysilyl moieties optionally can be generated in situ by hydrolysis of at least one hydrolyzable moiety (preferably, at least one hydrosilyl moiety). The polysiloxanes can be oligomers, polymers, or a combination thereof. Preferably, the polysiloxanes are polymers, which can be linear, branched, or cyclic. Useful polymers include those that have random, alternating, block, or graft structures, or a combination thereof.

The molecular weight and the reactive silane functionality of component (a) (including the number and nature of the hydroxysilyl moieties) of the polysiloxanes can vary widely, depending upon, for example, the molecular weight and the reactive silane functionality of component (b) and the properties desired for the curable and/or cured composition. At least one of components (a) and (b) has an average reactive silane functionality of at least three, however (that is, component (a) has at least three hydroxysilyl moieties (on average), component (b) has at least three hydrosilyl moieties (on average), or both), so as to enable the formation of a crosslinked network.

Preferably, the polyorganosiloxanes, fluorinated polyorganosiloxanes, and combinations thereof used for component (a) are hydroxyl-endblocked, so as to comprise two terminal hydroxysilyl moieties (on average). The polysiloxanes preferably have a weight average molecular weight of about 150 to about 1,000,000 (more preferably, about 1,000 to about 1,000,000).

A preferred class of useful polysiloxanes includes those that can be represented by the following general formula:

(OH)_p-Si(R')₃-_p-[G-Si (R')₂]rO-[(R')₂SiO]_q [Si(R')₂-G]_t-Si(R')3-_P-(OH)_p (I) wherein each p is independently an integer of 1, 2, or 3 (preferably, 1); each G is independently a divalent linking group; each R' is independently selected from alkyl, alkenyl, fluoroalkyl, aryl, fluoroaryl, cycloalkyl, fluorocycloalkyl, heteroalkyl, heterofluoroalkyl, heteroaryl, heterofluoroaryl, heterocycloalkyl, heterofluorocycloalkyl, and combinations thereof; q is an integer of 0 to about 50,000 (preferably, about 20 to about 15,000; more preferably, about 100 to about 15,000); and each t is independently an integer of 0 or 1 (preferably, 0). Preferably, each R' is independently selected from alkyl (preferably, having 1 to about 8 carbon atoms), fluoroalkyl (preferably, having 3 to about 8 carbon atoms; more preferably, RfC2H4-, wherein Rf is a fluorinated or perfluorinated alkyl group having 1 to about 6 carbon atoms (preferably, 1 to about 6 carbon atoms)), aryl, and combinations thereof (with alkyl being most preferred). More preferably, each R' is independently selected from methyl, C₄F₉C₂H₄-, C₆F₁₃C₂H₄-, CF₃C₂H₄-, phenyl, C₆H₅C₂H₄-, and combinations thereof (even more preferably, methyl, CF₃C₂H₄-, phenyl, C₄F₉C₂H₄-, and combinations thereof; most preferably, methyl). Each divalent linking group, G, is preferably independently selected from oxy, alkylene, arylene, heteroalkylene, heteroarylene, cycloalkylene, heterocycloalkylene, and combinations thereof (more preferably, selected from oxy, alkylene, arylene, and combinations thereof). Heteroatoms (in G and/or R') can include oxygen, sulfur, nitrogen, phosphorus, and combinations thereof (preferably, oxygen, sulfur, and combinations thereof; more preferably, oxygen). G can contain fluorine, provided that it is separated from silicon by at least two carbon atoms.

Preferred polysiloxanes include hydroxyl-endblocked polydimethylsiloxane homopolymer, as well as hydroxyl-endblocked copolymers comprising dimethylsiloxane units and up to about 40 or 50 mole percent of other units selected from dialkylsiloxane units, (alkyl)(methyl)siloxane units, and (alkyl) (phenyl) siloxane units wherein each alkyl group is independently selected from alkyl groups having two to about 8 carbon atoms (for example, hexyl), di(fluoroalkyl)siloxane units,

(fluoroalkyl)(methyl)siloxane units, and (fluoroalkyl)(phenyl)siloxane units wherein each fluoroalkyl group is independently selected from fluoroalkyl groups having 3 to about 8 carbon atoms (for example, trifluoropropyl or nonafluorohexyl), diphenylsiloxane units, and combinations thereof.

The polysiloxanes useful as component (a) can be used in the curable composition of the invention singly or in the form of mixtures of different polysiloxanes. Sometimes mixtures can be preferred. A preferred composition for use as component (a) comprises a mixture of (1) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof (preferably, at least one polyorganosiloxane) having a weight average molecular weight in the range of about 300,000 to about 1,000,000 (more preferably, about 400,000 to about 900,000; most preferably, about 500,000 to about 700,000) and (2) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof (preferably, at least one polyorganosiloxane) having a weight average molecular weight in the range of about 150 to about 150,000 (more preferably, about 10,000 to about 120,000; most preferably, about 10,000 to about 15,000). The relative amounts of component (1) and component (2) and their molecular weights can be selected for release applications according to the nature of the adhesive (or other material) to be utilized and the level of release desired.

For example, for mold release applications, the weight ratio of the former polysiloxane to the latter polysiloxane can range from about 3 : 1 to about 19: 1 (preferably, about 4: 1 to about 9: 1 ; more preferably, about 6: 1). For pressure sensitive adhesive (PSA) release applications, the weight ratio of the former polysiloxane to the latter polysiloxane can range, for example, from about 2: 1 to about 1 : 10 (preferably, about 1 : 1 to about 1 :6; more preferably, about 1 :2 to about 1 :4).

The polysiloxanes suitable for use as component (a) can be prepared by known synthetic methods and many are commercially available. For example, the hydroxysilyl-functional components of Syl- OffT^M 292 coating composition (available from Dow Corning Corporation, Midland, MI) are preferred polysiloxanes, and other useful polysiloxanes of varying molecular weight can be obtained from Gelest, Inc., Morrisville, PA (see, for example, the polysiloxanes described in Silicon Compounds: Silanes and Silicones, Second Edition, edited by B. Arkles and G. Larson, Gelest, Inc. (2008)).

Component (b)

Polysiloxanes suitable for use as crosslinker component (b) of the curable composition of the invention include polyorganosiloxanes, fluorinated polyorganosiloxanes, and combinations thereof (preferably, polyorganosiloxanes; more preferably, polyalkyl(hydro)siloxanes) comprising reactive silane functionality comprising at least two hydrosilyl moieties (that is, monovalent moieties comprising a hydrogen atom bonded directly to a silicon atom). The polysiloxanes can be small molecules, oligomers, polymers, or a combination thereof. Preferably, the polysiloxanes are polymers. The polysiloxanes can be linear, branched, or cyclic. Useful polymers include those that have random, alternating, block, or graft structures, or a combination thereof.

The molecular weight and the reactive silane functionality of component (b) (including the number and nature of the hydrosilyl moieties) can vary widely, depending upon, for example, the molecular weight and the reactive silane functionality of component (a) and the properties desired for the curable and/or cured composition. Preferably, component (b) has an average reactive silane functionality of at least three (so as to enable the formation of a crosslinked network when component (a) is hydroxyl- endblocked). The polysiloxanes preferably have a weight average molecular weight of about 100 to about 100,000.

A preferred class of polysiloxanes includes those that can be represented by the following general formula:

R'₂R"SiO(R'₂ SiO)_r(HR'SiO)_s SiR"R'₂ (II)

wherein R' is as defined above for Formula (I); each R" is independently hydrogen (hydro) or R'; r is an integer of 0 to about 150 (preferably, 0 to about 100; more preferably, 0 to about 20); and s is an integer of 2 to about 150 (preferably, about 5 to about 100; more preferably, about 20 to about 80). Most preferably, both R" and R' are methyl, r is 0, and/or s is about 40.

Preferred hydride- functional polysiloxanes include those comprising polymethyl(hydro)siloxane homopolymer, as well as those comprising copolymer(s) comprising methyl(hydro)siloxane units and up to about 40 or 50 mole percent of other units selected from dialkylsiloxane units, (alkyl)(methyl)siloxane units, and (alkyl)(phenyl)siloxane units wherein each alkyl group is independently selected from alkyl groups having two to about 8 carbon atoms (for example, hexyl), di(fluoroalkyl)siloxane units, (fluoroalkyl)(methyl)siloxane units, and (fluoroalkyl)(phenyl)siloxane units wherein each fluoroalkyl group is independently selected from fluoroalkyl groups having 3 to about 8 carbon atoms (for example, trifluoropropyl or nonafluorohexyl), diphenylsiloxane units, and combinations thereof. Although homopolymer is often preferred, copolymers can be preferred for some applications.

The polysiloxanes useful as component (b) can be used in the curable composition of the invention singly or in the form of mixtures of different polysiloxanes. The polysiloxanes can be prepared by known synthetic methods and many are commercially available. For example, Syl-Of ^M Q2-7560 crosslinker, Syl-Off™ 7678 crosslinker, and the hydrosilyl-functional component (for example, Syl-Off™ 7048 crosslinker) of Syl-Off™ 292 and Syl-Of ^M 294 coating compositions (all available from Dow Corning Corporation, Midland, MI) are preferred polysiloxanes, and other useful polysiloxane crosslinkers of varying molecular weight can be obtained from Gelest, Inc., Morrisville, PA (see, for example, the polysiloxanes described in Silicon Compounds: Silanes and Silicones, Second Edition, edited by B. Arkles and G. Larson, Gelest, Inc. (2008)).

Component (c)

Catalysts suitable for use as component (c) of the curable composition of the invention include those comprising iron (III) and at least one thermally-displaceable or radiation-displaceable ligand. Such a displaceable ligand is one that, when associated with iron (III) inhibits its ability to catalyze the curing of components (a) and (b), but, when exposed to heat or to actinic radiation, is either displaced or otherwise modified such that the iron (III) becomes available to catalyze the curing reaction. Suitable forms of actinic radiation include photochemically active radiation and particle beams, including, but not limited to, accelerated particles (for example, electron beams); and electromagnetic radiation (for example, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma-rays).

Preferably, the ligand(s) are thermally-displaceable upon exposure to temperatures of about 50°C to about 150°C (more preferably, about 80°C to about 130°C), or are radiation-displaceable upon exposure to actinic radiation having a wavelength of about 200 nanometers to about 800 nanometers (more preferably, about 200 nanometers to about 400 nanometers).

Useful ligands include those that comprise at least one moiety selected from beta-diketonato (β- diketonato), eta-bonded cyclopentadienyl (η-cyclopentadienyl), sigma-bonded aryl (σ-aryl), halo, and combinations thereof. Preferably, the ligands comprise at least one moiety selected from beta-diketonato, halo, and combinations thereof (more preferably, at least one moiety selected from beta-diketonato and combinations thereof). Suitable beta-diketonato moieties include 2,4-pentanedionato, 2,4-hexanedionato, 2,4-heptanedionato, 3,5-heptanedionato, 1 -phenyl- 1 ,3-heptanedionato, 1 ,3-diphenyl- 1 ,3-propanedionato, and combinations thereof; and suitable halo moieties include chloro, bromo, and combinations thereof.

Representative examples of useful catalysts include the following:

sigma-bonded aryl complexes of iron (III), including those of the formula COD-M-(Aryl)₂, wherein COD is a cyclooctadienyl group, M is iron (III), and Aryl is a sigma-bonded aryl moiety that is unsubstituted or substituted (for example, a phenyl group optionally substituted with one or more of alkyl, alkoxy, halogen, perfluoroalkyl, and perfluoroalkoxy);

η-cyclopentadienyl complexes of iron (III), including those of the formula CpFe³⁺(R^b)3, wherein Cp represents a cyclopentadienyl moiety that is eta-bonded to iron (III), and each R^b group is, independently, a saturated aliphatic group having from one to about eighteen carbon atoms and sigma bonded to iron (III) (for example, trialkyl(cyclopentadienyl)iron (III) complexes), as well as complexes in which the cyclopentadienyl moiety is substituted with a Ci to C4 hydrocarbon (for example,

trimethyl(methylcyclopentadienyl)iron (III));

beta-diketonato complexes of iron (III), including those derived from beta-diketones of the formula R¹COCHR²COR³, wherein R¹ is a substituted or unsubstituted, linear, cyclic, or branched C₁-C30 hydrocarbon-based radical (aliphatic, alicyclic, or aromatic; preferably, aliphatic or aromatic; more preferably, aliphatic); R² is hydrogen or a hydrocarbon-based (preferably, aliphatic; more preferably, alkyl) radical (preferably, having no more than 4 carbon atoms); R³ is a substituted or unsubstituted, linear, cyclic, or branched C₁-C30 hydrocarbon-based radical (aliphatic, alicyclic, or aromatic; preferably, aliphatic or aromatic; more preferably, aliphatic), or an -OR⁴ radical, wherein R⁴ is a substituted or unsubstituted, linear, cyclic, or branched C₁-C30 hydrocarbon-based radical (preferably, aliphatic or alicyclic; more preferably, aliphatic); wherein R¹ and R² optionally can be bonded together to form a ring; and wherein R² and R⁴ optionally can be bonded together to form a ring;

halo complexes of iron (III); and the like; and combinations thereof.

Preferred catalysts include iron (III) 2,4-pentanedionate, iron (III) 2,4-hexanedionate, iron (III) 2,4-heptanedionate, iron (III) 3,5-heptanedionate, iron (III) 1 -phenyl- 1, 3 -heptanedionate, iron (III) 1,3- diphenyl- l,3-propanedionate, iron (III) chloride, iron (III) bromide, and combinations thereof. More preferred catalysts include iron (III) 2,4-pentanedionate, iron (III) 2-ethylhexanoate, iron (III) chloride, iron (III) bromide, and combinations thereof (even more preferably, iron (III) 2,4-pentanedionate, iron (III) 2-ethylhexanoate, and combinations thereof; most preferably, iron (III) 2,4-pentanedionate).

Preparation of Curable Composition

The curable composition of the invention can be prepared by combining components (a), (b), and (c) in essentially any order (preferably, with agitation or stirring). Preferably, components (a) and (b) are combined initially, followed by addition of component (c). The composition can be maintained as a relatively shelf-stable, 2-part system (for example, by keeping component (c) separate from the other two components), if desired, but a 1-part system (comprising all three components) can also be stable for periods of up to, for example, about two weeks in dry solvent (a relatively long pot life), prior to coating or other application of the composition. Preferably, the composition consists essentially of components (a), (b), and (c) (that is, the composition can contain other components that do not change its basic nature, including conventional additives (for example, release modifiers or tackifiers such as silicate resins, including MQ, Q, T, and MT silicate resins, and the like; adhesion promoters such as trialkoxysilanes; and polysiloxane components (for example, polydimethylsiloxane) having no reactive silane functionality), but the composition preferably contains no alkoxysilyl-containing components other than minor amounts of alkoxy- functional silanes (more preferably, the composition contains no alkoxysilyl- containing components)).

The relative amounts of components (a) and (b) (and the amount of component (c)) can vary widely, depending upon the nature of the components and the desired properties of the curable and/or cured composition. Although stoichiometry prescribes a 1 : 1 molar ratio of reactive silane functionality (for example, one mole of hydrosilyl moieties for every mole of hydroxysilyl moieties), in practice it can be useful to have a deficiency or an excess of hydrosilyl functionality (for example, this can be useful when cure inhibitors are present). Molar ratios (of hydrosilyl moieties to hydroxysilyl moieties) up to, for example, about 8: 1 or about 13: 1 or even as high as about 35: 1 can be useful. Component (c) (the catalyst(s)) can be present in the curable composition in amounts ranging from about 0.1 to about 10 weight percent (preferably, from about 0.1 to about 5 weight percent; more preferably, from about 0.5 to about 2 weight percent; most preferably, from about 1 to about 2 weight percent), based upon the total weight of components (a), (b), and (c).

Preferably, the curable composition comprises at least one solvent or diluent to aid in storage stability, mixing, and/or coating, particularly when components (a) and (b) are polymeric. Suitable solvents for use in the curable composition of the invention include aprotic solvents such as aromatic solvents (for example, xylene, toluene, 1 ,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and the like, and mixtures thereof), ketones (for example, methyl ethyl ketone (MEK), cyclohexanone, and the like, and mixtures thereof), alkyl esters (for example, ethyl acetate, butyl acetate, and the like, and mixtures thereof), alkanes (for example, heptane, isoparaffinic hydrocarbons, and the like, and mixtures thereof), haloalkanes (which can aid in catalyst solubility; for example, dichloromethane and the like and mixtures thereof), ethers (for example, ?-butyl methyl ether, tetrahydrofuran (THF), and the like, and mixtures thereof), and the like, and mixtures thereof. Preferred solvents include aromatic solvents, alkanes, haloalkanes, ketones, and mixtures thereof; with xylene, heptane, methyl ethyl ketone, dichloromethane, and mixtures thereof being more preferred and heptane, methyl ethyl ketone, dichloromethane, and mixtures thereof most preferred.

Minor amounts of optional components can be added to the curable composition to impart particular desired properties for particular curing methods or uses. Useful compositions can comprise conventional additives such as, for example, catalysts (including conventional condensation catalysts such as tin catalysts, which can be added as co-catalysts if desired), initiators, emulsifiers (including surfactants), stabilizers, anti-oxidants, flame retardants, adhesion promoters, release modifiers (for example, silicate MQ resin), colorants, thickeners (for example, carboxy methyl cellulose (CMC), polyvinylacrylamide, polypropylene oxide, polyethylene oxide/polypropylene oxide copolymers, polyalkenols), metal oxide nanoparticles (for example, silica nanoparticles including hydrophobic silica nanoparticles), and the like, and mixtures thereof. When used to prepare pressure-sensitive adhesives, the curable composition can further comprise at least one tackifying resin (for example, at least one hydroxyl-functional, hydro-functional, or vinyl- functional polyorganosiloxane resin). A wide variety of polyorganosiloxane resins can be suitable.

Particularly suitable polyorganosiloxane resins include MQ silicate resins, Q silicate resins, T silicate resins, and the like, and combinations thereof (preferably, MQ silicate resins, Q silicate resins, and combinations thereof).

MQ silicate resins (or MQ resins as they are often called) are copolymeric silicate resins having R^a ₃SiOi_/2 (M) units and Si0_4/2 (Q) units, where each R^a is independently a hydroxyl group, hydrogen, a vinyl group, or a monovalent organic group. Suitable R^a groups include alkyl groups, aryl groups, alkenyl groups, as well as halogenated versions of these groups. Such resins are described in, for example, Encyclopedia of Polymer Science and Engineering, vol. 15, John Wiley & Sons, New York, (1989), pp. 265 to 270, and in U.S. Patent Nos. 2,676,182; 3,627,851 ; 3,772,247; and 5,248,739. MQ silicate resins having functional groups are described in U.S. Patent No. 4,774,310 (silyl hydride groups), U.S. Patent No. 5,262,558 (vinyl and trifluoropropyl groups), and U.S. Patent No. 4,707,531 (silyl hydride and vinyl groups). Additional examples are included in U.S. Patent No. 5,726,256 and U.S. Patent No. 5,861,472. Exemplary M groups include Me₃SiOi_/2, Me₂ViSiOi_/2, Me₂PhSiOi_/2, and

Ph₂MeSiOi_/2, wherein Me is methyl, Vi is vinyl, and Ph is phenyl. The above-described resins are generally prepared in solvent.

Suitable MQ resins include those having a molar ratio of M to Q units of 0.5 to 1.5 M units per Q unit (M/Q ratio). In some embodiments, the M/Q ratio can be 0.6 to 1.2. Q resins comprise only SiO/_t/2 (Q) units, and T resins comprise only SiOi_.5 (T) units.

The tackifying resin can comprise a single resin or a mixture of resins. If more than one resin is present, the resins can vary in composition, molecular weight, substituent groups, or some combination of these attributes.

The tackifying resin can have a number average molecular weight ranging from about 1,500 to about 15,000. In some embodiments, the number average molecular weight can range from about 3,000 to about 7,500, or even from about 3,500 to about 6,500, as measured by gel permeation chromatography.

Commercially available silicate resins include SR-545 MQ resin in toluene, available from General Electric Co., Silicone Resins Division, Waterford, N.Y.; MQOH resins, which are MQ resins in toluene, available from PCR, Inc., Gainesville, FL; MQR-32-2 MQD resins in toluene, available from Shin-Etsu Silicones of America, Inc., Torrance, CA; PC-403 hydride functional MQ resin in toluene, available from Rhone-Poulenc, Latex and Specialty Polymers, Rock Hill, SC; and SQT-221 silanol- trimethylsilyl modified Q resin in toluene, available from Gelest, Inc., Morrisville, PA. Such resins are generally supplied in organic solvent and can be used in the curable composition of the invention as received. If desired, however, these solutions of silicate resin can be dried by any number of techniques known in the art (for example, spray drying, oven drying, steam separation, and the like) to provide a silicate resin with 100 percent non-volatile content for use in the curable composition. If desired, the curable composition can be prepared in the form of an emulsion (for example, by using water as a diluent). Useful emulsifiers (also known as emulgents) include surface active substances or surfactants. Silicone emulsions often contain water, silicone oil, stabilizing surfactants, preservatives, and other additives for viscosity stabilization and freeze -thaw stability.

The curable composition of the invention can be prepared in the form of an emulsion by any of a variety of known or hereafter-developed mechanical or chemical emulsification techniques. Some suitable emulsions are also commercially available (for example, Syl-Off™ 1181 aqueous emulsion coating composition, available from Dow Corning Corporation, Midland, MI) and can be used in combination with catalyst (component (c)). Useful emulsification techniques include those described, for example, in European Patent Applications Nos. 0 268 982 (Toray Silicone Company, Ltd.), 0 459 500 (Dow Corning Corporation), and 0 698 633 (Dow Corning Corporation), the descriptions of the techniques being incorporated herein by reference.

A particularly useful technique for producing silicone in water emulsions is that described in U.S. Patent No. 6,013,682 (Dalle et al.), the technique description being incorporated herein by reference. This technique provides emulsions in which silicones polymerize by chain extension at the interior of silicone droplets suspended in water. U.S. Patent No. 5, 229, 212 (Reed) describes another useful technique in which a high molecular weight, water-soluble or water-dispersible polymeric thickening agent (such as polyethylene oxide) is utilized, the description of the technique being incorporated herein by reference.

Suitable emulsifiers for use in the curable composition of the invention include non-ionic (including polymeric non-ionic surfactants (for example, alkylpolysaccharide)), cationic, anionic, and amphoteric surfactants, and the like, and combinations thereof. The surfactants can be used individually or in combination. Although essentially any type of surfactant can be used, non-ionic surfactants can be preferred.

Useful non- ionic surfactants include those that are rendered hydrophilic by the presence of a polyethylene glycol chain (obtained by the polycondensation of ethylene oxide). Such non-ionic surfactants are termed polyethoxylated non-ionics. Other examples of useful non-ionic surfactants include polyalkenols (also known as polyvinyl alcohols), polyoxyalkylene alkyl ethers, polyoxyalkylene sorbitan alkyl esters, polyoxyalkylene alkyl esters, polyoxyalkylene alkylphenol ethers, polyethylene glycols, polypropylene glycols, diethylene glycols, polyethylene oxide -polypropylene oxide block copolymers, ethoxylated or sulfonated resins, carboxymethyl cellulose and other polysaccharide derivatives, polyacrylates, xanthane, and the like, and combinations thereof. Preferred non-ionic surfactants include polymeric non-ionic surfactants and combinations thereof (more preferably, polyalkenols and combinations thereof).

Examples of useful cationic surfactants include quaternary ammonium hydroxides (for example, tetramethylammonium hydroxide, octyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octyldimethylbenzylammonium hydroxide, decyldimethylbenzyl ammonium hydroxide, didodecyldimethylbenzyl ammonium hydroxide, dioctadecyldimethylammonium hydroxide, tallow trimethylammonium hydroxide,

cocotrimethylammonium hydroxide, and the like, and combinations thereof), corresponding salts of the quaternary ammonium hydroxides, fatty acid amines and amides and their derivatives, salts of the fatty acid amines and amides (including aliphatic fatty amines and amides) and their derivatives, homologs of aromatic amines having fatty chains, fatty amides derived from aliphatic diamines, fatty amides derived from disubstituted amines, derivatives of ethylene diamine, amide derivatives of amino alcohols, amine salts of long-chain fatty acids, quaternary ammonium bases derived from fatty amides of disubstituted diamines, quaternary ammonium bases of benzimidazo lines, basic compounds of pyridinium and its derivatives, sulfonium compounds, quaternary ammonium compounds of betaine, urethanes of ethylene diamine, polyethylene diamines, polypropanolpolyethanol amines, and the like, and combinations thereof.

Examples of useful anionic surfactants include alkylbenzene sulfonates (detergents), fatty acids (soaps), alkyl sulfates such as lauryl sulfate (foaming agents), di-alkyl sulfosuccinates (wetting agents), lignosulfonates (dispersants), and the like, and combinations thereof. Other useful anionic surfactants include those described in U.S. Patent No. 6, 013,682 (Dalle et al.), the descriptions thereof being incorporated herein by reference.

Another class of useful surfactants is that of amphoteric or zwitterionic surfactants, which include single surfactant molecules that exhibit both anionic and cationic dissociations. Examples of useful amphoteric surfactants include betaines, sulfobetaines, natural substances such as aminoacids and phospholipids, and the like, and combinations thereof.

The amount of surfactant that can be included in the curable composition of the invention will vary (for example, depending upon the nature of the surfactant(s)). Amounts of surfactant in the range of about 0.01 to about 35 weight percent (based upon the total weight of the curable composition), however, can often be useful (with amounts in the range of about 0.1 to about 20 weight percent being preferred, and amounts in the range of about 0.5 to about 5 or 10 weight percent being more preferred). The total amount of water that can be included in the curable composition to form an aqueous emulsion can also vary but generally can be in the range of about 20 to about 95 weight percent (based upon the total weight of the curable composition).

If desired, the catalyst (component (c)) can be pre-emulsified (for example, by addition of catalyst to an aqueous solution of surfactant and/or thickening agent, followed by shaking or agitation of the resulting mixture) prior to its combination with the other components of the curable composition.

Use and Curing of Curable Composition

The curable composition of the invention can be used in various different applications. For example, the composition(s) can be used as encapsulants or sealants, pressure-sensitive adhesives, release coatings, surface treatments, hardcoats, and the like. When used as fluorinated surface treatments, a degree of hydrophobicity and/or oleophobicity can be imparted to a variety of substrates (for example, for surface protection or to enhance ease of cleaning). The curable composition of the invention (or, alternatively, its components) can be applied to at least a portion of at least one major surface of a substrate (for example, a sheet, a fiber, or a shaped object) by essentially any known or hereafter-developed application method, so as to form a variety of different coated articles. The composition can be applied in essentially any manner (and with essentially any thickness) that can form a useful coating.

Useful application methods include coating methods such as dip coating, spin coating, spray coating, wiping, roll coating, wire coating, and the like, and combinations thereof. The composition can be applied in neat form or in the form of solvent solutions (for example, in solvents such as alkyl esters, ketones, alkanes, haloalkanes, aromatics, and the like, and mixtures thereof) or emulsions. When solvent is used, useful concentrations of the composition can vary over a wide range (for example, from about 1 to about 90 weight percent), depending upon the viscosity of the composition, the application method utilized, the nature of the substrate, and the desired properties.

Substrates suitable for use in preparing the coated articles include those having at least one surface comprising a material that is solid and preferably substantially inert to any coating or application solvent that is used. Preferably, the curable composition can adhere to the substrate surface through chemical interactions, physical interactions, or a combination thereof (more preferably, a combination thereof).

Suitable substrates can comprise a single material or a combination of different materials and can be homogeneous or heterogeneous in nature. Useful heterogeneous substrates include coated substrates comprising a coating of a material (for example, a metal or a primer) borne on a physical support (for example, a polymeric film).

Useful substrates include those that comprise wood, glass, minerals (for example, both man-made ceramics such as concrete and naturally-occurring stones such as marble and the like), polymers (for example, polycarbonate, polyester, polyacrylate, and the like) including multi-layer polymeric films, metals (for example, copper, silver, gold, aluminum, iron, stainless steel, nickel, zinc, and the like), metal alloys, metal compounds (for example, metal oxides and the like), leather, parchment, paper, textiles, painted surfaces, and combinations thereof. Preferred substrates include glass, minerals, wood, metals, metal alloys, metal compounds, polymers, paper, and combinations thereof (more preferably, metals, metal alloys, metal compounds, polymers, paper, and combinations thereof).

Preferred substrates include those used for pressure-sensitive adhesive (PSA) products. For example, the curable composition can be applied to suitable flexible or inflexible backing materials and then cured. Useful flexible backing materials include paper, Kraft paper, polyolefin-coated paper, plastic films (for example, poly(propylene), poly(ethylene), poly(vinyl chloride), polyester (including poly(ethylene terephthalate), polyamide, cellulose acetate, and ethyl cellulose), and the like, and combinations thereof, although essentially any surface requiring release toward adhesives can be utilized. Backings can thus also be of woven fabric formed of threads of synthetic or natural materials such as cotton, nylon, rayon, glass, or ceramic material, or they can be of nonwoven fabric such as air-laid webs of natural or synthetic fibers or blends of these. In addition, suitable backings can be formed of metal, metallized polymeric film, or ceramic sheet material. Primers (including surface treatments such as corona treatment) can be utilized, but they are not always necessary.

The curable composition of the invention can provide coatings (pressure-sensitive adhesive coatings and release coatings) that are suitable for use in the manufacture of PSA-coated labels and tapes. The specific level of adhesion or release provided upon curing can be controllably varied through variation in, for example, the weight percentage and molecular weight of component (a) of the composition, and/or through the addition of tackifiers or release modifiers (for example, silicate MQ resin), which also can be varied in nature and/or amount.

The curable composition can be cured by concentration (for example, by allowing solvent evaporation). The preferred curing conditions will vary, depending upon the particular application and its accompanying requirements and conditions. Moisture can be present but generally is not necessary. Cure generally can be effected at temperatures ranging from room temperature (for example, about 20-23°C) up to about 150°C or more (preferably, temperatures of about 50°C to about 140°C; more preferably, about 65°C to about 135°C; most preferably, about 80°C to about 130°C). Curing times can range from a few minutes (for example, at about 100°C) to hours (for example, under low catalyst conditions or when thermally curing at room temperature). Radiation curing can be utilized, if desired.

Release coatings obtained via cure of the curable composition of the invention generally contain little or no free silicone to adversely affect the tack and peel properties of PSAs that come in contact with them. The curable composition of the invention can cure relatively rapidly to provide relatively firmly anchored, highly crosslinked, solvent-resistant, tack- free coatings, which can be used with a broad range of PSA types (for example, acrylates, tackified natural rubbers, and tackified synthetic elastomers).

Articles in the form of PSA laminates (for example, comprising a layer of PSA borne on a release liner) can be prepared by placing a PSA layer in contact with the release coating through dry lamination, wet solution casting, or even by application of a photopolymerizable composition to the release coating, followed by irradiation to effect photopolymerization (for example, as described in U.S. Patent No.

4,181 ,752 (Martens et al.), the description of which is incorporated herein by reference). Such articles can exhibit relatively good storage stability (as evidenced, for example, by the results of room

temperature and/or heat accelerated aging tests to evaluate any change in the level of release (peel force) from the release coating and/or in the subsequent level of adhesion to a desired substrate).

EXAMPLES

Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. Materials

Unless otherwise noted, all parts, percentages, ratios, etc., in the examples and in the remainder of the specification are by weight. Unless otherwise noted, all chemicals were obtained from, or are available from, chemical suppliers such as Sigma-Aldrich Chemical Company, St. Louis, MO.

SYL-OFF 292 is a 30 weight percent solids dispersion of a blend of reactive hydroxysilyl- functional siloxane polymer(s) (said to comprise hydroxyl-terminated polydimethylsiloxane) and hydrosilyl-functional polysiloxane crosslinker (said to comprise poly(methyl)(hydrogen)siloxane) in xylene (a premium release coating composition obtained from Dow Corning Corporation, Midland, MI, under the trade designation Syl-Off™ 292).

SYL-OFF 7048 is a 100 weight percent solids hydrosilyl-functional polysiloxane crosslinker (said to comprise methylhydrogen cyclosiloxane, obtained from Dow Corning Corporation, Midland, MI, under the trade designation Syl-Of ^M 7048).

SYL-OFF 7678 is a 100 weight percent solids hydrosilyl-functional polysiloxane crosslinker (said to comprise dimethyl, methylhydrogen siloxane, obtained from Dow Corning Corporation, Midland, MI, under the trade designation Syl-Of ^M 7678).

POLYMER 3-0134 is a hydroxyl-endblocked organosiloxane, obtained from Dow Corning Corporation, Midland, MI, under trade designation DOW CORNING™ 3-0134 POLYMER 50000 cST.

POLYMER 3-0135 is a hydroxyl-endblocked polyorganosiloxane, obtained from Dow Corning Corporation, Midland, MI, under the trade designation DOW CORNING™ 3-0135 POLYMER.

DMS-S51 is hydroxyl-endblocked polydimethylsiloxanes, obtained from Gelest, Inc.,

Morrisville, PA, under the trade designation DMS-S51.

DMS-S21 is hydroxyl-endblocked polydimethylsiloxanes, obtained from Gelest, Inc.,

Morrisville, PA, under the trade designation DMS-S21.

SS-4191A is a 29 weight percent solids dispersion of hydroxyl-endblocked polydimethylsiloxane gum in toluene, obtained from Momentive Performance Materials, Columbus, OH, under the trade designation SS-4191 A.

SQT-221 is a silanol-trimethylsilyl-modified 60 weight percent Q-resin in toluene, obtained from Gelest, Inc., Morrisville, PA, under the trade designation SQT-221.

AEROSIL R805 is a fumed hydrophobic silica nanoparticle powder obtained from Evonik- Degussa Corp., Piscataway, NJ, under the trade designation AEROSIL™ R805.

Iron (III) tris(acetylacetonate), Fe(acac)3, alternatively known as iron (III)-2,4-pentanedionate, or tris(pentane-2,4-dionato-0,0) iron (III), was purchased from Sigma-Aldrich Chemical Company, St. Louis. MO, and was used as a 10 weight percent solution in dichloromethane.

Ferric chloride (FeCl₃), ferric bromide (FeBr₃), ferrous chloride (FeCl₂), ferrous bromide (FeBr₃), and iron (II) acetate were purchased from Sigma-Aldrich Chemical Company, St. Louis. MO, and were used as 10 weight percent solutions in dichloromethane. Iron (0) powder and iron (III) 2-ethylhexanoate were purchased from Sigma-Aldrich Chemical Company, St. Louis. MO, and were used as such.

Method for Peel Adhesion Measurements

Peel adhesion (of samples prepared according to the Examples and Comparative Examples described below) was measured with an IMASS SP-2000 peel tester (obtained from IMASS, Inc., Accord, MA) using 0.5 inch by 5 inch (about 1.25 centimeter (cm) by 12.7 cm) samples. The samples were applied to a clean thermoplastic plastic olefin (TPO) panel using four total passes of a 2 kg-rubber roller. Prior to testing, the samples were allowed to dwell for 20 minutes at room temperature and 50 percent relative humidity. The panel was then mounted on the IMASS SP-2000 peel tester, and the samples were pulled off of the panel at a 90 degree angle at a speed of 30.48 cm/minute. Peel force was measured in units of ounces per inch (oz/inch), was used to calculate the average peel force for a minimum of three samples, and was then converted to Newtons per decimeter (N/dm).

Example 1

A pressure-sensitive adhesive (PSA) formulation was prepared by mixing the following components: POLYMER 3-0135 (19 g), SQT-221 (38 g), SYL-OFF 7048 (2.0 g), and Fe(acac)₃ (2 weight percent with respect to total solids). The resulting PSA formulation was coated on a 2-mil (0.058 millimeter (mm)) thick polyester terephthalate (PET) film (obtained from Mitsubishi Polyester Film, Greer, SC, under the trade designation Hostaphan™ 3SAB, referred to hereinafter as 3SAB PET film, which has one side chemically treated or primed to improve the adhesion of silicone coatings) using a knife coater to provide a dry coating having a thickness of 2-3 mil (0.058-0.076 mm). The coated PET film was placed in a forced air drying oven maintained at 1 10°C (for 2 minutes) to cure the PSA formulation to form a bodied silicone PSA. After curing, the coated PET films were cut into samples for measuring peel adhesion according to the method described above. The average peel force of the resulting samples was about 25.17 N/dm (23 oz/in).

Example 2

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: SS-4191A (65 g), SQT-221 (38 g), SYL- OFF 7048 (2.0 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 27.25 N/dm (25 oz/in).

Example 3

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: DMS-S51 (19 g), SQT-221 (38 g), SYL- OFF 7048 (2.0 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 23.98 N/dm (22 oz/in). Example 4

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: POLYMER 3-0134 (19 g), SQT-221 (38 g), SYL-OFF 7048 (2.0 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 21.80 N/dm (20 oz/in).

Example 5

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: POLYMER 3-0135 (19 g), SQT-221 (38 g), SYL-OFF 7678 (2.5 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 22.89 N/dm (21 oz/in).

Example 6

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: SS-4191A (65 g), SQT-221 (38 g), SYL- OFF 7678 (2.5 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 28.34 N/dm (26 oz/in).

Example 7

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: DMS-S51 (19 g), SQT-221 (38 g), SYL- OFF 7678 (2.0 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 25.07 N/dm (23 oz/in).

Example 8

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: POLYMER 3-0134 (19 g), SQT-221 (38 g), SYL-OFF 7678 (2.0 g), and Fe(acac)3 (2 weight percent with respect to total solids). The average peel force of the resulting samples was about 22.89 N/dm (21 oz/in).

Example 9

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: DMS-S51 (19 g), SQT-221 (38 g), SYL- OFF 7678 (2.0 g), and Fe(acac)3 (1 weight percent with respect to total solids). The average peel force of the resulting samples was about 22.89 N/dm (21 oz/in).

Example 10

Samples were prepared in essentially the same manner as in Example 1, except that the PSA formulation was prepared by mixing the following components: SS-4191A (65 g), SQT-221 (38 g), SYL- OFF 7678 (2.5 g), and Fe(acac)3 (1 weight percent with respect to total solids). The average peel force of the resulting samples was about 19.62 N/dm (18 oz/in). Example 11

A coating formulation was prepared by mixing POLYMER 3-0134 (8.5 g), SYL-OFF 7678 (1.5 g), and Fe(acac)3 (2 weight percent with respect to total solids). A small amount of the formulation was spread on a glass substrate (borosilicate glass microscope slides about 15 cm by 4.5 cm in dimension, obtained from VWR International, Radnor, PA) with a wooden tongue-depressor and cured in a forced air drying oven maintained at 1 10°C (2-5 minutes) to form a crosslinked or hardened solid.

Example 12

Example 12 was prepared and cured in essentially the same manner as Example 1 1, except that the coating formulation was prepared by mixing POLYMER 3-0134 (8.5 g), SYL-OFF 7048 (1.5 g), and Fe(acac)3 (1 weight percent with respect to total solids). Curing of the formulation resulted in the formation of a crosslinked or hardened solid.

Example 13

Example 13 was prepared in essentially the same manner as Example 11 , except that the coating formulation was prepared by mixing POLYMER 3-0134 (8.5 g), SYL-OFF 7048 (1.5 g), and FeCl₃ (2 weight percent with respect to total solids), and the curing was carried out at 120°C (2 hours). Curing of the formulation resulted in the formation of a crosslinked or hardened solid.

Example 14

Example 14 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0134 (8.5 g), SYL-OFF 7048 (1.5 g), and FeBr₃ (2 weight percent with respect to total solids). Curing of the formulation resulted in the formation of a crosslinked or hardened solid.

Example 15

Example 15 was prepared in essentially the same manner as Example 11 , except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and iron (III) ethyl 2-hexanoate (2 weight percent with respect to total solids), and the curing was carried out at 1 10°C (30 minutes). Curing of the formulation resulted in the formation of a crosslinked or hardened solid.

Example 16

Example 16 was prepared in essentially the same manner as Example 11 , except that the coating formulation was prepared by mixing POLYMER 3-0134 (8.5 g), SYL-OFF 7048 (1.5 g), AEROSIL R805 (0.3 g), and Fe(acac)3 (2 weight percent with respect to total solids). Curing of the formulation resulted in the formation of a crosslinked or hardened solid.

Example 17

A pressure-sensitive adhesive (PSA) formulation was prepared by mixing the following components: POLYMER 3-0135 (19 g), SQT-221 (38 g), SYL-OFF 7048 (2.0 g), and Fe(acac)₃ (2 weight percent with respect to total solids). The resulting formulation was coated on 3 SAB PET film using a knife coater to provide a dry coating thickness of 2-3 mils (0.058-0.076 mm). The coated film was dried at 70°C for 2-minutes and then cured by passing it twice under ultraviolet (UV) irradiation from a LIGHT HAMMER™ 6 UV-chamber (obtained from Fusion UV Systems, Inc. Gaithersburg, Maryland, under the trade designation LIGHT HAMMER™ 6) equipped with an H-bulb (located 5.3 cm above the coated film) at a speed of 1 1 meters/minute. After curing, the coated film was cut into samples for measuring peel adhesion according to the method described above. The average peel force of the resulting samples was about 22.89 N/dm (21 oz/in).

Example 18

Samples were prepared in essentially the same manner as in Example 17, except that the PSA formulation was prepared by mixing the following components: DMS-S51 (19 g), SQT-221 (38 g), SYL- OFF 7678 (2.5 g), and Fe(acac)3 (1 weight percent with respect to total solids). The average peel force of the resulting samples was about 20.71 N/dm (19 oz/in).

Example 19

SYL-OFF 292 (3.0 g) was diluted with 12 g heptanes, followed by the addition of Fe(acac)3 (2 weight percent with respect to total solids). The resulting formulation was coated on one side of a 58# corona-treated, polyethylene-coated Kraft paper (PCK, 156 grams per square meter weight, available from International Converter, Kaukauna, WI) with a # 5 Mayer bar. The coated layer was cured at 1 10°C for 3 minutes in an oven equipped with solvent exhaust. The resulting cured release liner coating showed no smear upon rubbing.

Example 20

A formulation was prepared by mixing DMS-S21 (15 g), SYL-OFF 7048 (5 g), and Fe(acac)₃ (2 weight percent with respect to total solids) in a 50 mL round bottom flask. The resulting mixture was stirred vigorously at 1 10°C, resulting in the formation of gas that was collected in a test tube. The test tube was inverted, and a glowing wood splint was brought to the end of the test tube, resulting in an explosion that sounded like a highly-pitched pop. The positive pop test was consistent with, and provided support for, a conclusion that the gas was hydrogen and that the condensation reaction mechanism was dehydrogenative coupling between silanol (Si-OH) and silane (Si-H), leading to the formation of Si-O-Si bonds and hydrogen gas.

Comparative Example 1

Comparative Example 1 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and iron (II) oxide powder (2 weight percent with respect to solids). No solid formation or hardening was observed after 2 hours at 120°C.

Comparative Example 2

Comparative Example 2 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and FeC12 (2 weight percent with respect to total solids). No solid formation or hardening was observed after 2 hours at 120°C.

Comparative Example 3

Comparative Example 3 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and FeBr2 (2 weight percent with respect to total solids). No solid formation or hardening was observed after 2 hours at 120°C.

Comparative Example 4

Comparative Example 4 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and iron(II) acetate (2 weight percent with respect to total solids). No solid formation or hardening was observed after 2 hours at 120°C.

Comparative Example 5

Comparative Example 5 was prepared in essentially the same manner as Example 13, except that the coating formulation was prepared by mixing POLYMER 3-0135 (8.5 g), SYL-OFF 7048 (1.5 g), and iron (0) powder (2 weight percent with respect to solids). No solid formation or hardening was observed after 2 hours at 120°C.

The referenced descriptions contained in the patents, patent documents, and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. Various unforeseeable modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only, with the scope of the invention intended to be limited only by the claims set forth herein as follows.

Claims

WE CLAIM:

1. A curable composition comprising

(a) at least one polyorganosiloxane, fluormated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydroxysilyl moieties, said hydroxysilyl moieties optionally being generated in situ by hydrolysis of at least one hydrolyzable moiety;

(b) at least one polyorganosiloxane, fluormated polyorganosiloxane, or combination thereof comprising reactive silane functionality comprising at least two hydrosilyl moieties; and

(c) at least one catalyst comprising iron(III) and at least one thermally-displaceable or

radiation-displaceable ligand;

wherein at least one of said components (a) and (b) has an average reactive silane functionality of at least three.

2. The composition of Claim 1, wherein said components (a) and (b) each comprise at least one polyorganosiloxane.

3. The composition of Claim 2 or Claim 1, wherein said polyorganosiloxane comprises

polymethylsiloxane.

4. The composition of Claim 1 or any other of the preceding claims, wherein said component (a) is hydroxyl-endblocked.

5. The composition of Claim 1 or any other of the preceding claims, wherein said component (a) is selected from polysiloxanes that are represented by the following general formula:

(OH)_p-Si(R')3-p-[G-Si (R')₂]rO-[(R')₂SiO]_q [Si(R')₂-G]_t-Si(R')3-_P-(OH)_p (I) wherein each p is independently an integer of 1, 2, or 3; each G is independently a divalent linking group; each R' is independently selected from alkyl, alkenyl, fluoroalkyl, aryl, fluoroaryl, cycloalkyl, fluorocycloalkyl, heteroalkyl, heterofluoroalkyl, heteroaryl, heterofluoroaryl, heterocycloalkyl, heterofluorocycloalkyl, and combinations thereof; q is an integer of 0 to 50,000; and each t is independently an integer of 0 or 1.

6. The composition of Claim 5, wherein each said G is independently selected from oxy, alkylene, arylene, heteroalkylene, heteroarylene, cycloalkylene, heterocycloalkylene, and combinations thereof; each said R' is independently selected from alkyl, fluoroalkyl, aryl, and combinations thereof; said q is an integer of 20 to 15,000; and/or said t is an integer of 0.

7. The composition of Claim 6, wherein each said R' is independently selected from methyl,

C₄F₉C₂H₄-, C₆F₁₃C₂H₄-, phenyl, CF₃C₂H₄-, C₆H₅C₂H₄-, and combinations thereof.

8. The composition of Claim 1 or any other of the preceding claims, wherein said component (a) comprises a mixture of (1) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof having a weight average molecular weight in the range of 300,000 to 1,000,000 and (2) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof having a weight average molecular weight in the range of about 150 to about 150,000.

9. The composition of Claim 1 or any other of the preceding claims, wherein said component (b) has an average reactive silane functionality of at least three.

10. The composition of Claim 1 or any other of the preceding claims, wherein said component (b) is selected from polysiloxanes that are represented by the following general formula:

R'₂R"SiO(R'₂ SiO)_r(HR'SiO)_s SiR"R'₂ (II)

wherein each R' is independently selected from alkyl, alkenyl, fluoroalkyl, aryl, fluoroaryl, cycloalkyl, fluorocycloalkyl, heteroalkyl, heterofluoroalkyl, heteroaryl, heterofluoroaryl, heterocycloalkyl, heterofluorocycloalkyl, and combinations thereof; each R' ' is independently hydrogen or R'; r is an integer of 0 to 150; and s is an integer of 2 to 150.

1 1. The composition of Claim 10, wherein each said R' is independently selected from alkyl,

fluoroalkyl, aryl, and combinations thereof.

12. The composition of Claim 1 1, wherein each said R' is independently selected from methyl, C₄F₉C₂H₄-, C₆F₁₃C₂H₄-, phenyl, CF₃C₂H₄-, C₆H₅C₂H₄-, and combinations thereof.

13. The composition of Claim 10, wherein said R' and said R" are methyl; said r is an integer of 0; and/or said s is an integer of 40.

14. The composition of Claim 1 or any other of the preceding claims, wherein said ligand is

thermally-displaceable upon exposure to temperatures of 50°C to 150°C.

15. The composition of Claim 1 or any other of the preceding claims, wherein said ligand is

radiation-displaceable upon exposure to actinic radiation having a wavelength of 200 to 800 nanometers.

16. The composition of Claim 1 or any other of the preceding claims, wherein said ligand comprises at least one moiety selected from beta-diketonato, eta-bonded cyclopentadienyl, sigma-bonded aryl, halo, and combinations thereof.

17. The composition of Claim 16, wherein said ligand comprises at least one moiety selected from beta-diketonato, halo, and combinations thereof.

18. The composition of Claim 16 or Claim 17, wherein said beta-diketonato moiety is selected from 2,4-pentanedionato, 2,4-hexanedionato, 2,4-heptanedionato, 3,5-heptanedionato, 1 -phenyl- 1,3- heptanedionato, l,3-diphenyl-l,3-propanedionato, and combinations thereof; and/or wherein said halo moiety is selected from chloro, bromo, and combinations thereof.

19. The composition of Claim 1 or any other of the preceding claims, wherein said catalyst is selected from iron (III) 2,4-pentanedionate, iron (III) 2-ethylhexanoate, iron (III) chloride, iron (III) bromide, and combinations thereof.

20. The composition of Claim 1 or any other of the preceding claims, wherein said composition further comprises at least one tackifying resin; and/or wherein said composition further comprises silica nanoparticles.

21. The composition of Claim 1 or any other of the preceding claims, wherein said composition has been cured.

22. A curable composition comprising

(a) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof that is hydroxyl-endblocked;

(b) at least one polyorganosiloxane, fluorinated polyorganosiloxane, or combination thereof comprising at least three hydrosilyl moieties; and

(c) at least one catalyst comprising iron(III) and at least one ligand comprising at least one moiety selected from beta-diketonato, halo, and combinations thereof.

23. A coating process comprising

(a) providing the curable polysiloxane composition of Claim 1 or any other of the preceding claims;

(b) providing at least one substrate having at least one major surface;

(c) applying said curable polysiloxane composition to at least a portion of at least one said major surface of said substrate; and

(d) inducing said curable polysiloxane composition to cure to form a coating by exposing said curable polysiloxane composition to heat or radiation.

24. An article comprising at least one substrate having at least one major surface, said substrate bearing, on at least a portion of at least one said major surface, a coating prepared by the coating process of Claim 23.