Double curing composition

Abstract

1. A composition comprising: (a) a polysiloxane resin having the following siloxane units: [RSiO 1 / 2 ], [(OZ) q SiO (4-q) / 2 ], and [(OZ) t R EP SiO (3-t) / 2 ] and [(OZ) d RR EP SiO (2-d) / 2 wherein each R, at each occurrence, is independently selected from hydrocarbyl; EP is an epoxy-functional hydrocarbyl group, and the subscript q, at each occurrence, is a number selected from the range of 0 to 3, the subscript t, at each occurrence, is a number selected from the range of 0 to 2, and the subscript d, at each occurrence, is a number selected from the range of 0 to 1, with the proviso that the average concentration of OZ groups is at least 15 mole percent based on the moles of silicon atoms in said polysiloxane resin; (b) a photoacid generator; (c) a moisture-cure catalyst; and (d) optionally an epoxy-functional diluent.

Description

[Technical Field]

[0001] The present invention relates to dual cure compositions containing epoxy-functionalized polysiloxanes.

[0002] Introduction Light and moisture dual-cure polysiloxane resin compositions are useful, for example, in coating, encapsulation, potting, and adhesive applications where it is difficult to expose all portions of the coating to light, yet rapid cure of the coating is desirable. The light-cure mechanism promotes rapid cure of the composition upon exposure to light. The moisture-cure mechanism serves to cure portions of the composition that are blocked from exposure to light ("shadow areas"). The dual-cure mechanism is valuable in coatings that require complete cure via moisture cure when light cannot access all areas of the coating.

[0003] Dual-cure polysiloxane resin compositions can include (meth)acrylate-based cure systems. However, (meth)acrylate-based systems are oxygen sensitive and inhibited by oxygen, requiring inert conditions during cure, at least at the surface of the composition. Providing the necessary inert atmosphere adds undesirable cost and complexity to the cure process.

[0004] Another dual-cure polysiloxane resin composition relies on a "thiol-ene" reactive system for light-triggered curing. Upon exposure to ultraviolet (UV) and / or visible light, the thiol functional groups react with and add across carbon-carbon unsaturated bonds, such as in vinyl groups. Typically, thiol-ene reactive systems include a photoinitiator for the light-triggered curing reaction.

[0005] Dual-cure polysiloxane resin compositions typically include a multifunctional alkoxysilane crosslinker to achieve rapid moisture cure of the formulation to form a strong coating with acceptable adhesion to the substrate. The multiple alkoxy groups on the silane participate in the moisture cure of the alkoxysilane to form a crosslinked structure that rapidly imparts skin formation on the composition. Generally, it is desirable to achieve a moisture-cure skin within four hours or less after application of the formulation to a substrate when exposed to an atmosphere of at least 60% relative humidity at 23 degrees Celsius (°C). To simplify the formulation of dual-cure polysiloxane resin compositions, it is desirable to identify dual-cure polysiloxane resin compositions that do not require a multifunctional alkoxysilane component to moisture cure to form a skin within four hours of application of the dual-cure polysiloxane resin composition to a substrate when exposed to an atmosphere of at least 60% relative humidity at 23°C.

[0006] Dual-cure polysiloxane resin compositions also typically contain a non-reactive organic solvent. The non-reactive organic solvent reduces the viscosity of the composition, thereby facilitating application of the composition to a substrate. This is important when formulating polysiloxane resins. Polysiloxane resins are typically solids or liquids with very high viscosities (greater than 26 Pascal*seconds (Pa*s)), which makes blending the composition components difficult and applying the composition to a substrate difficult. Unfortunately, the non-reactive organic solvent remains as a contaminant, typically an extractable contaminant, in the polysiloxane resin composition even after curing. Therefore, it would be desirable to identify a dual-cure polysiloxane resin composition that can be applied to a substrate without the need for a non-reactive organic solvent.

[0007] It is desirable to identify a dual-cure polysiloxane resin composition that cures with both light and moisture to form a cured polysiloxane resin composition, but that has a viscosity of 26 Pa*s or less, or does not require a (meth)acrylate-based cure system, a thiol-ene reactive system, an alkoxysilane-based crosslinker, or a non-reactive organic solvent for curing with both UV light and moisture, and that forms a moisture-cured skin within 4 hours of application when exposed to an atmosphere of at least 60% relative humidity at 23°C. Summary of the Invention

[0008] The present invention provides dual-cure polysiloxane resin compositions that are cured by both light and moisture to form a cured polysiloxane resin composition, but do not require (meth)acrylate-based cure systems, thiol-ene reactive systems, alkoxysilane-based crosslinkers, or non-reactive organic solvents for application to a substrate or curing. The present invention provides compositions that undergo UV curing to form tack-free, non-liquid coatings upon 0.5 Joules of UV exposure or greater, form a moisture-cured skin within 4 hours of application when exposed to an atmosphere of at least 60% relative humidity at 23°C, and are capable of achieving an adhesion rating of 3 in the adhesion to glass test described herein.

[0009] The present invention is the result of the discovery that polysiloxane resins having epoxy functionality and an average of 15 mole percent or more of hydroxyl and / or alkoxyl functionality relative to silicon atoms (collectively referred to herein as "OZ" groups) are surprisingly both fluid enough to have a viscosity of 26 Pascal seconds (Pa*s) or less, such that the polysiloxane resins can be formulated without solvent to form a dual-cure composition that can be easily applied to a substrate, and can be cured by both light and moisture to form a cured polysiloxane resin composition having the described curability and adhesive properties, without the need for an alkoxysilane-based crosslinker or any additional crosslinker.

[0010] In a first aspect, the present invention provides a composition comprising: (a) a polysiloxane resin having the following siloxane units: [RSiO 1 / 2 ], [(OZ) q SiO (4-q) / 2 ], and [(OZ) t R EP SiO (3-t) / 2 ] and [(OZ) d RR EP SiO (2-d) / 2 wherein each R, at each occurrence, is independently selected from hydrocarbyl; EP is an epoxy-functional hydrocarbyl group, and the subscript q, at each occurrence, is a number selected from the range of 0 to 3, the subscript t, at each occurrence, is a number selected from the range of 0 to 2, and the subscript d, at each occurrence, is a number selected from the range of 0 to 1, with the proviso that the average concentration of OZ groups is at least 15 mole percent based on the moles of silicon atoms in the polysiloxane resin; (b) a photoacid generator; (c) a moisture-cure catalyst; and (d) optionally an epoxy-functional diluent.

[0011] In a second aspect, the present invention is a method for forming a cured polysiloxane resin, the method comprising the steps of: (a) providing a composition of the first aspect; (b) exposing the composition to ultraviolet light; and (c) exposing the composition to moisture.

[0012] The compositions of the present invention provide a light / moisture dual cure formulation that requires fewer components than other dual cure formulations, yet produces a cured formulation with desirable adhesion and strength properties. [Brief explanation of the drawings]

[0013] [Figure 1]Figure 2 provides the Si nuclear magnetic resonance (NMR) spectra of Resins A and I, respectively, showing the relative positions of the siloxane units in the resins. The ppm shift values ​​on the x-axis are relative to tetramethylsilane (TMS) and provide general guidance for the absolute position of each unit; the actual position will depend on the groups attached to and around the silicon of the siloxane unit. [Figure 2] Figure 2 provides the Si nuclear magnetic resonance (NMR) spectra of Resins A and I, respectively, showing the relative positions of the siloxane units in the resins. The ppm shift values ​​on the x-axis are relative to tetramethylsilane (TMS) and provide general guidance for the absolute position of each unit; the actual position will depend on the groups attached to and around the silicon of the siloxane unit. DETAILED DESCRIPTION OF THE INVENTION

[0014] Test methods, unless a date is given with the test method number, refer to the test method most recent as of the priority date of this document. Reference to a test method includes both a reference to the testing institute and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International, EN refers to European Norm, DIN refers to Deutsches Institut fuer Normung, and ISO refers to the International Organization for Standardization.

[0015] "Plurality" means two or more. "And / or" means "and, or alternatively." All ranges are inclusive unless otherwise indicated. Products identified by trade names refer to compositions available from suppliers under those trade names as of the priority date of this document, unless otherwise stated herein.

[0016] "Polysiloxane" refers to a polymer containing multiple siloxane bonds. Polysiloxanes are polymers containing SiO 4 / 2 (“Q” type), RSiO 3 / 2 (“T” type), R2SiO 2 / 2 ("D" type) and R3SiO 1 / 2 The D-type unit includes siloxane units selected from those known in the art, such as ("M" type). The subscript on the R group indicates how many R groups are bonded to the silicon atom. The subscript on the oxygen indicates how many oxygens are bonded to silicon atoms that are also bonded to other silicon atoms (i.e., siloxane bonds, "Si-O-Si" bonds, how silicon atoms participate), with the number divided by two because an oxygen is shared with another silicon atom. Thus, a D-type unit includes a silicon atom that is bonded to two R groups and shares two oxygens with other silicon atoms. In general, the R group can be any substituent other than -OSi (i.e., siloxane bonds to silicon). In general, the R group is a hydrocarbyl bonded to the silicon atom via a carbon-silicon bond. However, in the broadest sense of the present invention, the R group can also be a group bonded to a silicon atom with an atom other than carbon, such as sulfur or oxygen. For example, the R group can be selected from a hydroxyl group or an alkoxyl group, collectively referred to as an "OZ" group.

[0017] "MQ resin" is a type of polysiloxane containing M-type and Q-type siloxane units. MQ resins may also contain D-type and / or T-type siloxane units, unless otherwise specified.

[0018] "Hydrocarbyl" is a monovalent radical derived from a substituted or unsubstituted hydrocarbon. A substituted hydrocarbon has one or more hydrogen or carbon atoms replaced with another atom or substituent. As used herein, hydrocarbyl in each occurrence can be either substituted or unsubstituted, corresponding to hydrocarbyl derived from either a substituted or unsubstituted hydrocarbon, respectively.

[0019] An "epoxy group" refers to a functional group that contains an oxygen atom attached by single bonds to two adjacent carbon atoms to form a three-membered ring containing two carbon atoms and one oxygen atom.

[0020] As used herein, "light" in its broadest sense refers to electromagnetic radiation. Preferably, light as used herein refers to visible light and / or ultraviolet (UV) light.

[0021] "Non-reactive," such as non-reactive organic solvent, means that the material does not react with other components of the composition during UV or moisture cure.

[0022] Resin molecular weights, when determined by gel permeation chromatography (GPC), are reported as weight average molecular weights. Details of the GPC procedure are provided in the Examples section herein.

[0023] Determine the viscosity of the resins and compositions using a Brookfield viscometer (model DV-E) according to the method of ASTM D2196.

[0024] The composition of the present invention comprises a polysiloxane resin, wherein the polysiloxane resin has the following siloxane units: [RSiO 1 / 2 ], [(OZ) q SiO (4-q / 2) ], and [(OZ) t R EP SiO (3-t) / 2 ] and [(OZ) d RR EP SiO (2-d) / 2The polysiloxane resin may comprise or consist of at least one of [(OZ) t R EP SiO (3-t) / 2 ] and [(OZ) d RR EP SiO (2-d) / 2 ] units, or it may contain either one so long as it contains the other.

[0025] In the broadest scope of the present invention, the polysiloxane resin is RSiO 1 / 2 ], [(OZ) q SiO (4-q / 2) ], and [(OZ) t R EP SiO (3-t) / 2 ] and [(OZ) d RR EP SiO (2-d) / 2 For example, the polysiloxane resin may contain siloxane units other than at least one of RSiO 2 / 2 Units (D-type units) and / or R3SiO 3 / 2 (T-type units). Generally, it may be desirable to include D-type units to impart a linear character to the resin, which reduces the hardness of the cured composition as the concentration of D-type units increases. In contrast, one desirable composition of the present invention provides a cured composition having a pencil hardness of 2H or greater. For such hard coatings, it is desirable to keep the concentration of D-type units in the polysiloxane resin to 10 mol% or less, preferably 5 mol% or less, and even more preferably 2 mol% or less, 1 mol% or less, or even 0.5 mol% or less, based on the total moles of siloxane units. The polysiloxane resin need not contain D-type siloxane units to achieve maximum hardness in the cured composition.

[0026] Each R, in each occurrence, is independently selected from hydrocarbyl, preferably unsubstituted hydrocarbyl, and more preferably from the group consisting of methyl, ethyl propyl, butyl, and phenyl.

[0027] R EPis an epoxy-functional hydrocarbyl group. For example, R EP can be a 3,4-epoxycyclohexyl)ethyl group, a 3,4-epoxycylcoheyl)propyl group, a 3-(2,3-epoxypropioxy)propyl group (also known as a 3-glycidyloxypropyl group), a 3,5-epoxybutyl group, a 4,5-epoxypentyl group, or a 5,6-epoxyhexyl group.

[0028] The subscript t, at each occurrence, is a number selected from the range of 0 to 2, the subscript d, at each occurrence, is a number selected from the range of 0 to 1, and the subscript q, at each occurrence, is a number selected from the range of 0 to 3, provided that the average concentration of OZ groups in the polysiloxane resin (the "OZ content") is in the ranges described below.

[0029] OZ, at each occurrence, is independently a hydroxyl group or an alkoxyl group. Desirably, each OZ, at each occurrence, is independently selected from hydroxyl, methoxy, and ethoxy. Desirably, the polysiloxane resin contains methoxy and / or ethoxy groups. The OZ content is 15 mole percent (mol%) or greater, and can be 18 mole% or greater, 20 mole% or greater, 22 mole% or greater, or even 25 mole% or greater, 30 mole% or greater, 40 mole% or greater, 50 mole% or greater, 60 mole% or greater, or 70 mole% or greater. Increasing the OZ content generally increases the resin's fluidity (decreases its viscosity) and increases the rate (reduces the time required) for the composition to moisture cure and form a skin. Increasing the OZ content also tends to increase glass adhesion. Therefore, a higher OZ content is desirable to enhance these characteristics. In some applications, the thermal stability of the resin may be important, and because the thermal stability of the resin tends to decrease with increasing OZ content, an upper limit on the OZ content may be important. It may be desirable for the polysiloxane resin to have a 5% weight loss temperature (by thermal gravimetric analysis (TGA)) greater than 150 degrees Celsius (°C). To achieve such thermal stability, the OZ content is desirably 80 mol% or less, preferably 60 mol% or less, more preferably 50 mol% or less, even more preferably 40 mol% or less, and may be 30 mol% or less, or even 20 mol% or less. For the avoidance of doubt, it is intended that any of these upper limits for OZ content can be combined with any of the lower limits for OZ content set forth above to define a preferred OZ content of the polysiloxane resin. As used herein, OZ content is relative to the moles of silicon atoms in the polysiloxane resin.

[0030] 29 Si nuclear magnetic resonance spectroscopy ( 29 The OZ content of the samples was determined using Si NMR. 29Si NMR was performed. Chemical shifts were referenced to internal solvent resonances and reported relative to tetramethylsilane. Each siloxane unit in the resin appears at a unique location. Integrating under the peak area allows for calculation of the concentration of OZ groups relative to the silicon atom. Figures 1 and 2 show the general location of each siloxane unit relative to each other, with the x-axis ppm values ​​relative to tetramethylsilane (TMS), for two polysiloxane resins used in the examples herein. 29 The Si NMR spectrum is shown, with the peaks labeled with respect to the siloxane units to which they correspond: M=R3SiO 1 / 2 D1=R2(OZ)SiO 1 / 2 D2=R2SiO 2 / 2 T1=R(OZ)2SiO 1 / 2 T2 = R(OZ)SiO 2 / 2 T3=RSiO3 / 2 Q1=(OZ)3SiO 1 / 2 Q2=(OZ)2SiO 2 / 2 Q3=(OZ)SiO 3 / 2 Q4=SiO 4 / 2 Determine the OZ content relative to silicon atoms as mole % using the following formula, where the label for each peak in the formula corresponds to the integrated area under the peak corresponding to that label.

number

[0031] Surprisingly, it has been discovered that this resin has a viscosity of 26 Pa*s or less when the OZ content is 15 mol% or more relative to the polysiloxane. Polysiloxane resins typically contain less than 15 mol% OZ and tend to be solid. Solid and highly viscous (greater than 26 Pa*s) polysiloxane resins generally require mixing with a solvent, typically an organic solvent, to form a liquid in order to formulate into a composition that can be applied as a liquid. The polysiloxane resins of the present invention do not require mixing with a solvent to form a liquid in order to formulate or form a composition that can be applied as a liquid. In fact, the compositions of the present invention may be free of solvents, particularly non-reactive solvents, and at the same time, may be liquid. Desirably, the compositions of the present invention are free of organic solvents, and preferably completely free of solvents.

[0032] Polysiloxane resins can be synthesized from epoxy-functional alkoxysilanes and silanol-functional resins using base-catalyzed reactions. Examples of such reactions are described in the Examples section below.

[0033] Desirably, the composition contains less than 5 weight percent (wt%), and can contain 4 wt% or less, 3 wt% or less, 2 wt% or less, or even 1 wt% or less of alkoxy-functional silicon-containing components other than the polysiloxane resin, where wt% is based on the weight of the composition. The composition may be free of alkoxy-functional silicon-containing components other than the polysiloxane resin.

[0034] The compositions of the present invention further include a photoacid generator (PAG). The PAG becomes acidic upon exposure to light and therefore acts as a photoinitiator for the acid-catalyzed reaction. The composition requires a PAG to achieve rapid UV cure of the composition, i.e., a composition that is tack-free to the touch (and not liquid) upon exposure to 0.5 joules of UV radiation. PAGS typically become acidic by dissociating to form a strong acid or by dissociating a proton upon exposure to light. One common type of PAG includes triphenylsulfonium salts. Examples of PAGs include bis(4-dodecylphenyl)iodonium hexafluoroantimonate, (p-dodecylphenyl)(p-methylphenyl)iodonium hexafluoroantimonate, (p-isopropylphenyl)(p-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium nitrate, diphenyliodonium hexafluorophosphate, (4-fluorophenyl)diphenylsulfonium triflate, N-hydroxynaphthalimide triflate, (4-iodophenyl)diphenylsulfonium triflate, N-hydroxynaphthalimide triflate, and (4-iodophenyl)diphenylsulfonium triflate.

[0033] Examples of the compounds include (4-tert-butylphenyl)diphenylsulfonium triflate, (4-methoxyphenyl)diphenylsulfonium triflate, (4-phenoxyphenyl)diphenylsulfonium triflate, triarylsulfonium hexafluorophosphate, triphenylsulfonium perfluoro-1-butanesulfanate, triphenylsulfonium triflate, tris(4-tert-butylphenyl)sulfonium perflurro-1-butanesulfonate, bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate, and bis(4-tert-butylphenyl)iodonium p-toluenesulfonate.

[0035] The PAG is typically present in the composition at a concentration of 0.1 weight percent (wt%) or more, 0.25 wt% or more, 0.5 wt% or more, 0.75 wt% or more, 1.0 wt% or more, or even 1.5 wt% or more, and at the same time, typically 3.0 wt% or less, 2.5 wt% or less, 2.0 wt% or less, 1.5 wt% or less, and may be 1.0 wt% or less, or even 0.75 wt% or less, by weight of the composition.

[0036] The composition further includes a moisture-cure catalyst. The moisture-cure catalyst increases the rate at which the alkoxysilyl groups on the polyorganosiloxane react with moisture and cure. Suitable moisture-cure catalysts include any one or combination of two or more organometallic catalysts selected from the group consisting of titanium compounds, tin compounds, and zirconium compounds. Desirably, the moisture-cure catalyst is a titanium-based catalyst, a tin-based catalyst, or a combination thereof. Examples of suitable titanium compounds include tetraisopropyl orthotitanate, titanium diisopropoxide bis(ethylacetoacetate), tetraisopropyl titanate tetrabutoxyorthotitanate, di(isopropoxy)bis(ethylacetoacetate)titanium, di(isopropoxy)bis(methylacetoacetate)titanium, and NS di(isopropoxy)bis(acetylacetonate)titanium. Examples of suitable tin compounds include dibutyltin dilaurate and dibutyltin dioctoate. Examples of suitable zirconium compounds include tetra(isopropoxy)zirconium, tetra(n-butoxy)zirconium, tetra(t-butoxy)zirconium, di(isopropoxy)bis(ethylacetoacetate)zirconium, di(isopropoxy)bis(methylacetoacetate)zirconium, and di(isopropoxy)bis(acetylacetonate)zirconium.

[0037] Typically, the concentration of the moisture-curing catalyst is 0.1 wt. % or more, 0.5 wt. % or more, 1 wt. % or more, 2 wt. % or more, and even 3 wt. % or more, based on the weight of the composition, and at the same time, is generally 3 wt. % or less, 2 wt. % or less, or even 1 wt. % or less.

[0038] The composition may optionally include an epoxy-functional diluent ("reactive diluent"). Epoxy-functional diluents can be useful for reducing the viscosity of the composition. However, the epoxy functionality allows the diluent to participate in the curing of the composition, thereby bonding to the cured resin rather than remaining as an extractable component like a non-reactive solvent. The epoxy-functional diluent can have an average of one or more epoxy functional groups per molecule, preferably two or more. Examples of suitable epoxy-functional diluents include any one or combination of two or more selected from the group consisting of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, resorcinol diglycidyl ether, dichloropentadiene dioxide, and neopentyl glycol diglycidyl ether. Reactive diluents are typically present in concentrations of less than 30% by weight, more typically 15% by weight or less, based on the weight of the composition.

[0039] The composition may further comprise any one or any combination of two or more additional components, including pigments, colorants, conductive fillers (such as metal powders and flakes), insulating fillers, adhesion promoters, and dispersing aids.

[0040] The composition of the present invention is particularly advantageous because the polysiloxane resin is a liquid having a viscosity of 26 Pa*s or less, and therefore the composition itself is liquid without requiring any additional components (particularly liquid components) other than the polysiloxane resin, photoacid generator, moisture-curing catalyst, and reactive diluent. The composition may contain less than 30% by weight, preferably 20% by weight or less, 10% by weight or less, 5% by weight or less, or 1% by weight or less of liquid components other than the polysiloxane resin, photoacid generator, moisture-curing catalyst, and reactive diluent, or may even be free of these, and at the same time, the composition itself may be liquid.

[0041] The composition may be free of silanes and / or polysilanes having multiple OZ groups per molecule, or may be completely free of silane and / or polysilane molecules. While any or all of the composition options described herein may be combined in some fashion, one particularly desirable composition is free of silanes or polysilanes having multiple hydroxyl or alkoxy groups per molecule, free of organic solvents, or free of both silanes or polysilanes having multiple hydroxyl or alkoxy groups per molecule and free of organic solvents. Even when the composition is free of silanes and / or polysilanes having multiple OZ groups, it can still moisture cure to form a skin within 4 hours in an atmosphere of at least 60% relative humidity at 23°C.

[0042] The compositions of the present invention are useful as dual-cure compositions that can be cured by exposure to light and / or moisture to form a cured polysiloxane resin. Advantageously, the compositions can be cured by both light and moisture, allowing the exposed portions of the composition to be rapidly cured by light and the unexposed portions of the composition to be further cured by moisture. The compositions are particularly useful as curable coating fillers.

[0043] The method of dual curing the composition of the present invention to form a cured polysiloxane resin involves providing a composition, then exposing the composition to light, typically ultraviolet light, and exposing the composition to moisture. The order in which the composition is exposed to light and moisture is not important, and can actually occur simultaneously. Typically, the composition is first exposed to light, and then moisture-cured.

[0044] Desirably, the method for forming a cured polysiloxane resin from the composition of the present invention further comprises applying the composition to a substrate before exposing the composition to light. A beneficial aspect of the present invention is that the composition is a liquid and can be applied as a liquid without the need for a solvent or liquid component other than the polysiloxane resin. This makes the composition easy to apply and allows the composition to be solvent-free, without the need for solvent removal after application to the substrate. Thus, the cured composition can be applied as a liquid and cured into a cured polysiloxane resin, and does not contain extractable liquid components in the coating, without the need to remove anything from the cured composition. [Example]

[0045] Characterization of epoxy-functionalized resins Determine resin viscosity using a Brookfield viscometer (Model DV-E) according to the method of ASTM D2196.

[0046] Resins are characterized for thermal stability using thermogravimetric analysis (TGA) on a TA Instruments Q50 device. A 14-20 milligram resin sample is placed in a platinum pan and heated using the following profile: 23°C to 900°C at 10°C / min under a 60 ml / min nitrogen purge (with a 40 ml / min nitrogen purge remaining). The temperature at which the sample loses 5% of its weight, i.e., the 5% weight loss temperature, is determined.

[0047] Molecular weights for the resins were determined using gel permeation chromatography using a Waters 2695 Separation Module equipped with a vacuum degasser and a Waters 410 differential refractive index detector. Two (300 mm x 7.5 mm) Polymer Laboratories PLgel 5-micrometer Mixed-C columns (molecular weight separation range 200–2,000,000) were used, preceded by PLgel 5-micrometer guard columns (50 mm x 7.5 mm). The column and detector were maintained at 35°C, and the eluent was tetrahydrofuran (THF) flowing at 1.0 mL / min. Samples were prepared in THF at approximately 0.5% volume, solvated for 3 hours with occasional shaking, and filtered through a 0.45-micrometer polytetrafluoroethylene syringe filter before analysis. A 100-microliter sample was injected for analysis, and data was collected for 25 minutes. Data were collected and analyzed using ThermoLabsystems Atlas chromatography software and Polymer Laboratories Cirrus GPC software. Average molecular weights were measured against a calibration curve (third order) generated suing polystyrene standards spanning the molecular weight range of 580 to 2,300,000.

[0048] Synthesis of epoxy-functionalized resins Resin A-MT CHEp Q resin In a three liter (3-L) flask equipped with a magnetic stir bar, add 800 grams (g) of toluene, ((CH)SiO 1 / 2 ) 43.2 (HOSiO 3 / 2 ) 11.5 (SiO 4 / 2 ) 45.3Add 500 g of polysiloxane resin powder (commercially available as DOWSIL™ MQ-1600, DOWSIL is a trademark of The Dow Chemical Company) having an average composition of 337 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (available from Gelest, Inc. and Sigma-Aldrich) and 0.82 g of potassium hydroxide. Stir and heat under nitrogen at reflux (70°C internal reaction temperature). Monitor the reaction mixture for the presence of silane by gas chromatography. Once the silane is consumed (approximately 4 hours), cool the reaction mixture to 23°C, then add 4.1 g of acetic acid. Stir the reaction mixture for 1 hour. Filter the reaction mixture through a 1 micron filter to obtain a clear fluid. Remove volatiles using a roto-vap to obtain a clear liquid resin. 29 Analysis by Si NMR shows that the resin has an average concentration of each siloxane unit relative to total siloxane units as follows: 31.68 mol% M, 1.56 mol% T1, 5.05 mol% T2, 10.10 mol% T3, 0.43 mol% Q1, 3.44 mol% Q2, 15.71 mol% Q3, 31.89 mol% Q4. The R groups on the T1, T2, and T3 units are "T CHEp The reaction characteristics and resin characteristics are included in Table 1.

[0049] Resins B to G: MT with various levels of OZ and molecular weight CHEp Q. To a three-liter (3-L) flask equipped with a magnetic stir bar, add 800 grams (g) of toluene, 500 g of the polysiloxane resin powder used in making Resin A, 337 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 0.82 g of potassium hydroxide. Stir and reflux under nitrogen until all of the silane is consumed (internal temperature of 70 °C), as determined by gas chromatography. Add 12.3 g of water to 20 g of methanol. Attach a Dean-Stark head to the flask. Stir and heat the mixture, collecting volatiles in the Dean-Stark trap. Replace the collected volatile volume with toluene and continue heating to the internal temperature and reaction time listed in Table 1. Cool the reaction mixture to 23 °C and neutralize with acetic acid. Filter the reaction mixture through a 1-micron filter to obtain a clear liquid. Remove the volatiles from the liquid using a roto-vap to obtain the resulting liquid resin. 29 Si NMR and 13 Analyze by C NMR (reveals the presence of epoxy) and for thermal stability. The internal reaction temperatures and reaction times are in Table 1, along with the resulting resin characteristics.

[0050] Resin H:MT Ep Q To a 3-liter flask equipped with a magnetic stir bar, add 800 grams of toluene and 500 grams of the polysiloxane resin powder used to make Resin A. Add 325 grams of (3-glycidoxypropyl)trimethoxysilane and 0.82 g of potassium hydroxide, and stir the mixture at 100°C under nitrogen while monitoring the reaction mixture using gas chromatography. After 5 hours, cool the reaction to 23°C, add 4.1 g of acetic acid, and stir for 1 hour. Filter the solution through a 1-micrometer filter to obtain a clear liquid. Use a roto-vap to remove the volatiles that form a clear liquid, yielding a clear liquid resin (Resin H). 29 Si NMR and 13 Analyzed by C NMR and for thermal stability 13C NMR shows that the epoxy ring is intact. 29 Si NMR shows that the resin has an average concentration of each siloxane unit relative to total siloxane units as follows: 31.42 mol% M, 1.40 mol% T1, 4.63 mol% T2, 10.56 mol% T3, 0.21 mol% Q1, 3.44 mol% Q2, 14.76 mol% Q3, 33.59 mol% Q4. The R groups on the T1, T2, and T3 units are "T Ep " units together. The reaction characteristics and resin characteristics are included in Table 1.

[0051] Resin I:MD Ep Q To a 100 ml flask equipped with a magnetic stir bar, add 25 grams of toluene and 14.7 grams of the polysiloxane resin powder used in making Resin A. 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane and 0.16 grams of potassium hydroxide are added. The mixture is stirred and heated under nitrogen at reflux (70°C internal reaction temperature) while monitoring the reaction mixture by gas chromatography. After 8 hours, the mixture is cooled to 50°C, 0.2 grams of acetic acid is added, and it is stirred for 1 hour as it cools to 23°C. The solution is filtered through a 1 micrometer filter to obtain a clear liquid. The volatiles that form a clear liquid are removed by roto-vap to obtain a clear liquid resin (Resin I). 29 Si NMR and 13 Analyzed by C NMR and for thermal stability 13 C NMR shows that the epoxy ring is intact. 29 Si NMR shows that the polysiloxane resin powder has an average concentration of each siloxane unit relative to total siloxane units as follows: 36.3 mol% M, 5.28 mol% D1, 7.53 mol% D2, 0.00 mol% Q1, 1.62 mol% Q2, 8.10 mol% Q3, 41.18 mol% Q4. The R groups on the D1 and D2 units are "D Ep " to form a unit together Epoxycyclohexylethyl The reaction characteristics and resin characteristics are included in Table 1.

[0052] Resins J-M: MT with various levels of OZ and molecular weight CHEp Q. Prepare Resins J-M using the following procedure and by selecting the type and amount of epoxy-functional silane reactants as follows: Resin J (646.6 g of 3-glycidoxypropyl)trimethoxysilane), Resin K (977.5 g of 2-(3,4-epoxycyclohexl)ethylmethyldimethoxysilane), Resin L (811.8 g of 3-glycidoxypropyl)trimethoxysilane), Resin M (846.3 g of 2-(3,4-epoxycyclohexl)ethylmethyldimethoxysilane).

[0053] To a 3-liter flask equipped with a magnetic stir bar, add 800 grams of toluene and 500 grams of the polysiloxane resin powder used in making Resin A. Add the epoxy-functional silane for the desired resin, as described above, and 1.15 g of potassium hydroxide. Stir the mixture at reflux (approximately 70°C) while monitoring the progress of the reaction using gas chromatography. After the silane is completely consumed (approximately 3 hours), cool the mixture to 23°C, add 5.8 grams of acetic acid, and stir for 1 hour. Filter the mixture through a 1-micrometer filter to obtain a clear liquid. Remove volatiles from the clear liquid using a roto-vap. 29 Si NMR and 13 Analyzed by C NMR and for thermal stability 13 C NMR shows that the epoxy ring is intact. 29 Si NMR shows that the resins have an average concentration of each siloxane unit relative to total siloxane units as follows: The R group on the T unit is glycidoxypropyl for resins J and L, and 2-(3,4-epoxycyclohexyl)ethyl for resins K and M. Reaction and resin characteristics are included in Table 1.

[0054] The data reveal that increasing the OZ content of the same epoxy functionality results in a lower viscosity resin and a lower 5% weight loss temperature (reduced thermal stability). This is most easily seen in the series of resins A-G, which all have the same epoxy functionality. [Table 1] 1 The mole % M, Q and epoxy functionalized siloxane units are based on the total moles of siloxane units. 2 Mole % OZ is relative to moles of silicon atoms.

[0055] dual curable composition Preparation of Dual Cure Compositions Table 3 contains formulation information for each of the sample compositions. 100 gram samples of the compositions are prepared by combining the specified weight percent of epoxy-functional resin, PAG, moisture-cure catalyst, and reactive diluent together in an amber dental mixer cup. The combination of ingredients is mixed in the dental mixer to form a well-blended composition. For each sample, proceed with the UV-cure and moisture-cure steps below.

[0056] The epoxy-functionalized resin is selected from those described above. The other components are selected from those in Table 2. [Table 2] [Table 3] 1 "Not Applicable (0)" means that the ingredient was not included in the formulation.

[0057] Characterization of dual-cure compositions The following characterization methods are used to characterize the samples. Table 4 contains the results of these characterizations.

[0058] Ultraviolet (UV) curing. The composition is coated onto a glass substrate using a drawdown bar for a 250 micrometer thick coating. Immediately cure under UV radiation (0.15 Joules dose broadband) at 23°C using a Fusion Systems Corporation instrument model 31983-E. The sample is exposed to 0.5 Joules of UV radiation. After exposure, if the sample is liquid or tacky to the touch, the sample is a "fail." If the sample is non-liquid and non-tacky to the touch, the sample is a "pass."

[0059] Moisture Cure. Immediately after UV curing, or if no UV curing is performed, moisture cure the sample by placing the coated glass substrate in an environment of 23°C and 60% relative humidity on a coating prepared for UV coating but not UV cured. Record the time it takes for the sample to form a skin ("skin cure time"). To be acceptable or "pass," the sample must have a skin cure time of 4 hours or less.

[0060] Viscosity of the Composition: Determine the viscosity of the composition using a Brookfield viscometer (Model DV-E) according to the method of ASTM D2196.

[0061] Pencil Hardness. Measure pencil hardness according to ASTM D3363-05. Measure pencil hardness on the specimen 6 days after moisture curing, or 1 hour after UV curing if the specimen was not moisture cured. A pencil hardness of 2H or greater is required to pass.

[0062] Adhesion to Glass. Adhesion strength to glass is measured using a cross-hatch adhesion test on samples that are both UV-cured and moisture-cured at 23°C for 6 days at 60% relative humidity according to ASTM method D3359 using a Gardco PA-2000 adhesion test kit. Poor adhesion (rating 1) means that more than 50% of the coating has been removed from the coated area. Fair adhesion (rating 2) means that more than 5-50% of the coating has been removed from the coated area. Good adhesion (rating 3) means that more than less than 5% of the coated area has been removed. [Table 4]

[0063] Catalyst Requirement. Samples 1-6 demonstrate the need for both a PAG and a moisture-cure catalyst in the compositions of the present invention. Samples 2 and 5 demonstrate poor adhesion to glass, failing to form a skin within six days, let alone the desired four hours, when a moisture-cure catalyst is not present. Samples 3 and 6 demonstrate that when a PAG is not present in the composition, the composition fails the UV-cure test. Samples 1 and 4 demonstrate that the same composition containing both a PAG and a moisture-cure catalyst passes the UV-cure test, has a skin-cure time of less than four hours, and achieves good adhesion to glass. Samples 1-3 demonstrate this performance in the absence of a reactive diluent, while Samples 4-6 demonstrate these results in the presence of a reactive diluent.

[0064] Effect of OZ Content. Samples 1, 4, and 7-12 demonstrate the effect of OZ content in compositions with and without reactive diluents. As a general trend, the samples demonstrate that decreasing OZ content results in higher viscosity compositions and longer skin cure times. The data also demonstrate that when the OZ content is less than 15 mol%, the composition has a viscosity greater than 26 Pa*s and a skin cure time greater than 4 hours; and when the OZ content is 15 mol% or greater, the composition has a viscosity of 26 Pa*s or less and a skin cure time of 4 hours or less. Samples 1 and 7-10 demonstrate these observations for compositions without reactive diluents, while Samples 8, 11, and 12 demonstrate these observations for compositions containing reactive diluents.

[0065] Different Epoxy Functionalities, PAGs, and Moisture Cure Catalysts. Samples 13-24 show compositional performance consistent with previous observations using different epoxy functionalities, different PAGs, and different moisture cure catalysts on various epoxy-functionalized resins.

Claims

1. 1. A composition comprising: (a) a polysiloxane resin having the following siloxane units: (i)[R ３ SiO １／２ ]、 (ii) [(OZ) ｑ SiO （４－ｑ）／２ ],and (iii) [(OZ) ｔ R ＥＰ SiO （３－ｔ）／２ ] and [(OZ) ｄ R.R. ＥＰ SiO （２－ｄ）／２ ] at least one of wherein each R, at each occurrence, is independently selected from hydrocarbyl; R ＥＰ is an epoxy-functional hydrocarbyl group, subscript q, in each occurrence, is a number selected from the range of 0 to 3, subscript t, in each occurrence, is a number selected from the range of 0 to 2, and subscript d, in each occurrence, is a number selected from the range of 0 to 1, with the proviso that the OZ groups are hydroxyl and / or alkoxyl functional groups and the average concentration of OZ groups is at least 15 mole percent based on the moles of silicon atoms in said polysiloxane resin; (b) a photoacid generator; and (c) a moisture-curing catalyst; (d) optionally, an epoxy-functional diluent.

2. 10. The composition of claim 1, wherein the composition contains less than 30% by weight of liquid components other than (a), (b), and (c), based on the weight of the composition.

3. 3. The composition of claim 1 or 2, wherein the composition contains less than 5 weight percent, based on the weight of the composition, of alkoxy-functional silicon-containing species other than the polysiloxane resin component (a).

4. The composition of any one of claims 1 to 3, wherein the polysiloxane resin comprises at least 15 mole percent, relative to resin silicon atoms, of alkoxy groups selected from the group consisting of methoxy, ethoxy, and combinations thereof.

5. The R is a substituted hydrocarbyl group having an epoxy functional group. ＥＰ The composition of any one of claims 1 to 4, wherein the group is selected from the group consisting of 3-glycidoxypropyl groups, 2-(3,4-epoxycyclohexyl)ethyl groups, and combinations thereof.

6. The composition of any one of claims 1 to 5, wherein the photoacid generator is present in a concentration ranging from 0.1 to 3.0 weight percent of the composition.

7. The composition according to any one of claims 1 to 6, wherein the composition does not contain a silane or polysilane having multiple hydroxyl groups or alkoxy groups on a single molecule, or does not contain an organic solvent, or does not contain both a silane or polysilane having multiple hydroxyl groups or alkoxy groups on a single molecule and an organic solvent.

8. The composition of any one of claims 1 to 7, wherein the polysiloxane resin contains no more than 10 mole percent D-type siloxane units, based on the total moles of siloxane units.

9. 1. A method for forming a cured polysiloxane resin, comprising: (a) providing a composition according to any one of claims 1 to 8; (b) exposing the composition to ultraviolet light; (c) exposing the composition to moisture.

10. 10. The method of claim 9, further comprising applying the composition onto a substrate prior to step (b).

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