Dual cure organopolysiloxane composition with shelf-life stability

Abstract

A dual-cured organopolysiloxane composition comprising: (a) a first organopolysiloxane having an average of two or more mercaptoalkyl groups per molecule and being free of alkenyl functional groups; (b) a second organopolysiloxane having an average of one or more alkenyl groups per molecule and having an average of one or more hydrolyzable groups per molecule; (c) a third organopolysiloxane, if present, having at least two alkenyl groups per molecule and being free of alkoxy groups; (d) a bis(xylphosphine oxide) photoinitiator; (e) a carrier liquid, if present; (f) a condensation catalyst; (g) a silane having an average of two or more hydrolyzable groups per molecule; and (h) a free radical scavenger.

Description

Technical Field

[0001] This invention relates to an organopolysiloxane composition capable of UV- and moisture-induced curing. Prior Technology

[0002] Organopolysiloxane systems capable of dual curing (curing via two different mechanisms) are becoming increasingly popular. Specifically, organopolysiloxane systems that undergo both UV curing and moisture curing are suitable for many applications. The UV-curable state of the composition provides rapid initial curing for continuous processing or handling without damaging the coating in areas of the composition exposed to UV light. The moisture curing mechanism is used to cure the composition in areas where exposure is blocked ("dark areas") and to allow the composition to cure more completely over time. One type of UV / moisture dual-curing system uses thiol-olefin chemicals for UV curing. Thiol-olefin curing is superior to (meth)acrylate-based UV curing mechanisms because thiol-olefins are not as sensitive to oxygen as (meth)acrylate materials. Thiol-olefin systems contain thiol-containing organopolysiloxanes that, upon exposure to UV light, react with carbon-carbon double bonds (olefins) in other components of the reaction system, thereby causing chemical crosslinking or curing. Dual curing systems utilizing thiol-olefin chemicals typically include thiol-containing organopolysiloxanes and unsaturated organopolysiloxane reactants.

[0003] Compared to moisture-only curing systems or thiol-ene-only UV-cured silica alkane systems, thiol-ene-based dual UV and moisture curing systems tend to suffer from relatively shorter shelf lives. Shelf life can be assessed relative to when the composition is freshly prepared by determining whether the composition experiences an increase in viscosity and / or a decrease in curing depth after UV curing and / or an increase in the time required to achieve a non-sticky surface after storage.

[0004] WO2020 / 076620 attempts to address the shelf life issue of thiol-olefin-based dual-cured formulations by providing a thiol-olefin dual-cured organopolysiloxane system that requires epoxy compound stabilization.

[0005] A dual-cured polyorganosiloxane system subjected to moisture curing and thiol-olefin UV curing needs to be identified, which achieves storage stability without the need for epoxy compounds. This storage stability is characterized by its ability to be aged for 21 days in a syringe within a vacuum-sealed aluminum bag, in the dark, at 55°C to remove moisture, followed by: (1) Experiencing a viscosity increase of less than twice its initial viscosity, as measured according to ASTM D-1084 using a Brookfield DVII+P viscometer with a conical spindle CPA-52Z at 23 + / -2°C; and (2) When exposed to 2 joules / cm² UVA and UVB radiation, the curing depth is at least 70%, preferably 80% or greater, more preferably 90% or greater, relative to a freshly prepared identical composition, and ideally, a curing depth of at least 8 mm is achieved both before and after aging; and (3) Allow 24 hours or less for the moisture to cure and become non-sticky. Summary of the Invention

[0006] This invention provides a dual-cured polyorganosiloxane system subjected to moisture curing and thiol-olefin UV curing, which exhibits storage stability without the need for epoxy compounds. The storage stability is characterized by its ability to age for 21 days in a vacuum, in darkness, and at 55 degrees Celsius (°C) to remove moisture, followed by: (1) Experiencing a viscosity increase of less than twice its initial viscosity, as measured according to ASTM D-1084 using a Brookfield DVII+P viscometer with a conical spindle CPA-52Z at 23 + / -2°C; and (2) When exposed to 2 joules / cm² UVA and UVB radiation, the cured depth is at least 70%, preferably 80% or greater, more preferably 90% or greater, compared to a freshly prepared identical composition, and a cured depth of at least 8 mm can be achieved both before and after aging; and (3) Allow 24 hours or less for the moisture to cure and become non-sticky.

[0007] Surprisingly, it has been found that including a diacetylphosphine oxide photoinitiator in the dual-cured polyorganosiloxane system enables the dual-cured system to meet the aforementioned requirements for storage stability.

[0008] In the first embodiment, the present invention is a dual-cured organopolysiloxane composition comprising: (a) a first organopolysiloxane having an average of two or more mercaptoalkyl groups per molecule and being free of alkenyl functional groups; (b) a second organopolysiloxane having an average of one or more alkenyl groups per molecule and having an average of one or more hydrolyzable groups per molecule; (c) a third organopolysiloxane, whichever is present, having at least two alkenyl groups per molecule and being free of alkoxy groups; (d) a bis(xylphosphine oxide) photoinitiator; (e) a carrier liquid, whichever is present; (f) a condensation catalyst; (g) a silane having an average of two or more hydrolyzable groups per molecule; and (h) a free radical scavenger.

[0009] The compositions of this invention are suitable for use as dual-cured polyorganosiloxane systems. Simple Explanation of the Diagram

[0010] none Implementation

[0011] Test methods refer to the most recent test method as of the priority date of this document, unless otherwise specified in the test method number. Reference test methods include both the reference testing association and the test method number. The following test method abbreviations and identifiers are used in this document: ASTM refers to ASTM International Methods; END refers to European Norm; DIN refers to the German Institute for Standardization; ISO refers to the International Organization for Standardization; and UL refers to Underwriters Laboratories.

[0012] Products identified by trademarks refer to compositions available under those trademarks as of the priority date herein.

[0013] "Multiple (species)" means two (species) or more (species). "And / or" means "and, or as an alternative." Unless otherwise indicated, all ranges include end values.

[0014] "Liquid" means that it flows freely at 25 degrees Celsius (°C).

[0015] "Polar liquids" refers to liquids that can dissolve polar substances. To avoid any ambiguity, toluene is not considered a polar liquid.

[0016] "Hydrolyzable groups" refer to groups that, when attached to silicon atoms, can form silanols in water. Hydrolyzable groups include alkoxy, hydroxyimino, acetoxy, and amino groups.

[0017] "Organic polysiloxane" is a polysiloxane having at least one organic group bonded to the main chain of the polysiloxane.

[0018] "Polysiloxane" is a polymer comprising multiple siloxane units bonded together to form a siloxane backbone. Unless otherwise specified, the siloxane units may be selected from "M" type siloxane units having the following chemical structures: R' 3SiO 1 / 2; "D" type siloxane units having the following chemical structures: R' 2SiO 2 / 2; "T" type siloxane units having the following chemical structures: R'SiO 3 / 2; and "Q" type siloxane units having the following chemical structures: SiO 4 / 2, wherein R' may be any group in each occurrence, but is typically selected from hydrogen, hydroxyl, alkoxy, mercapto, amino, hydrocarbon, and substituted hydrocarbon groups. In a specific siloxane unit, oxygen atoms with a subscript of "1 / 2" represent oxygen atoms shared with another silicon atom in the siloxane backbone, where the molecule indicates how many shared oxygen atoms are bonded to the silicon atoms of a specific siloxane unit.

[0019] This invention relates to a dual-cured organopolysiloxane composition. "Dual-curing" means that the organopolysiloxane component of the composition can undergo a cross-linking reaction by exposure to ultraviolet (UV) light or moisture. The UV-triggered cross-linking reaction is a "thiol-alkene" reaction between the thiol functional groups of the mercaptoalkyl group and the olefin functional groups. The moisture-triggered cross-linking reaction occurs between hydrolyzable groups on different molecules.

[0020] The dual-cured organopolysiloxane composition comprises a first organopolysiloxane containing an average of 2 or more per molecule, and may contain 3 or more, 4 or more, or even 5 or more, while typically containing 20 or fewer, 15 or fewer, 10 or fewer, 8 or fewer, or even 6 or fewer mercaptoalkyl groups and is free of alkenyl functional groups.

[0021] The first organopolysiloxane is preferably composed of M-type and D-type siloxane units. For example, an ideal first organopolysiloxane is a linear organopolysiloxane having chemical structure (I): (R 1 2R 3SiO 1 / 2) 2(R 1R 2SiO 2 / 2) m(R 1 2SiO 2 / 2) n(I) in: R1, each time it appears, is independently a hydrocarbon group or a substituted hydrocarbon group, having one or more, and may have 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or even 8 or more, while typically having 20 or fewer, 18 or fewer, 16 or fewer, 14 or fewer, 12 or fewer, 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, or even 2 or fewer carbon atoms. Examples of suitable R1 groups include methyl, ethyl, phenyl, and 3,3,3-trifluoropropyl groups. Preferably, R1 is methyl.

[0022] R2, each time it appears, is independently a mercaptoalkyl group. "Mercaptoalkyl" refers to a -R-SH group, where R is a divalent hydrocarbon, preferably having one or more, more preferably two or more, and may have three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, twelve or more, fourteen or more, sixteen or more, or even eighteen or more carbon atoms, while typically having 20 or fewer, or even eighteen or fewer, sixteen or fewer, fourteen or fewer, twelve or fewer, ten or fewer, eight or fewer, six or fewer, four or fewer, or even two or fewer carbon atoms. The R group may be straight-chain or branched-chain. For example, R2 may be selected from -CH2SH, -CH2CH2SH, -CH2(CH2)2SH, and -CH2(CH2)3SH.

[0023] Each time R3 appears, it is independently selected from the options of R1 and R2.

[0024] The average value of the subscript m is 2 or greater, and can be 3 or greater, 4 or greater, 5 or greater, 10 or greater, 20 or greater, 30 or greater, 40 or greater, 50 or greater, 60 or greater, 70 or greater, 80 or greater, 90 or greater, 100 or greater, 200 or greater, 300 or greater, 400 or greater, or even 500 or greater, while usually 1000 or less, 750 or less, 500 or less, 250 or less, 100 or less, 75 or less, 50 or less, 20 or less, 15 or less, 10 or less, 8 or less, or even 6 or less.

[0025] The average value of the subscript n is zero or greater, one or greater, and can be 5 or greater, 10 or greater, 15 or greater, 20 or greater, 25 or greater, 30 or greater, 35 or greater, 40 or greater, 43 or greater, 45 or greater, even 50 or greater, 100 or greater, 200 or greater, 300 or greater, 400 or greater, even 500 or greater, while usually 1000 or less, 750 or less, 500 or less, 250 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, even 45 or less.

[0026] A desirable first organopolysiloxane has the chemical structure of formula (I), wherein R1 is methyl, R2 is -CH2(CH2)2SH and the average value of m is 5 and the average value of n is 43.

[0027] Ideally, the first organopolysiloxane is present at a concentration sufficient to provide a molar ratio of 0.3 or greater for the mercaptoalkyl group from the first organopolysiloxane and the alkenyl group from the second organopolysiloxane and (if present) the third organopolysiloxane, and this molar ratio may be 0.5 or greater, 1.0 or greater, 1.5 or greater, 2.0 or greater, 2.5 or greater, 3.0 or greater, 3.5 or greater, 4.0 or greater, or even 4.5 or greater, while typically being 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, 2.5 or less, 2.0 or less, 1.5 or less, or even 1.0 or less. The molar ratio of mercaptoalkyl to alkenyl groups in the components and formulations used to prepare the composition is determined. If the formulation is unknown, the molar ratio of mercaptoalkyl to alkenyl groups is determined using infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy.

[0028] The compositions of the present invention also comprise a second organopolysiloxane. Each molecule of the second organopolysiloxane contains one or more alkenyl groups on average, and may contain 2 or more, 3 or more, 4 or more, 5 or more, even 6 or more, and typically contains 20 or fewer, 15 or fewer, 10 or fewer, even 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer alkenyl groups. The average number of alkenyl groups per molecule is determined by the material used as the second organopolysiloxane in preparing the composition. If the formulation is unknown, the average number of alkenyl groups per molecule is determined using NMR spectroscopy. The alkenyl group is preferably a terminal alkenyl group, meaning that the carbon-carbon double bond (C=C) of the alkenyl group includes the terminal carbon of the alkenyl group. Preferably, the alkenyl group is a vinyl group.

[0029] The second organopolysiloxane also contains one or more, and may contain 2 or more, 3 or more, 4 or more, 5 or more, or even 6 or more, and typically contains 20 or fewer, 15 or fewer, 10 or fewer, or even 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer hydrolyzable groups per molecule. The average number of hydrolyzable groups per molecule is determined by the material used as the second organopolysiloxane in the preparation of the composition. If the formulation is unknown, the average number of hydrolyzable groups per molecule is determined by NMR spectroscopy. The hydrolyzable group is preferably an alkoxy group, preferably an alkoxy group having the following chemical structure: -OR 3, wherein R 3 is an alkyl group having one or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or even 8 or more, and typically having 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, or even 2 or fewer carbon atoms. Preferably, the alkoxy group is selected from methoxy, ethoxy, and propoxy, and more preferably, the alkoxy group is methoxy. Preferably, the hydrolyzable group is bonded to the silicon atoms of the M-type and / or D-type siloxane units in the second organopolysiloxane.

[0030] The second organopolysiloxane may comprise any combination of M-type, D-type, T-type, and Q-type siloxane units. The second organopolysiloxane preferably has a chemical structure (II): (SiO 4 / 2) x(R a 2SiO 2 / 2) y(R aBSiO 2 / 2) y '(R a 2BSiO 1 / 2) z(II) in: Ra is independently selected from alkyl and aryl groups each time it appears; B is independently selected from alkenyl and alkoxy groups and alkoxy-containing groups each time it appears, so as to achieve an average of one or more alkenyl groups and one or more alkoxy groups per molecule; On average, x is 0 or greater and simultaneously 10 or less; On average, the sum of y and y' is 20 or greater, and 1000 or less; and On average, z has a value of 2 or greater and is simultaneously 20 or less. A suitable second organopolysiloxane has the average chemical structure of chemical structure (III): Si[O-((CH 3) 2SiO) a-Si(CH 3) 2-CH=CH 2] 2[O-[Si(CH 3) 2O] b-Si(CH 3) 2-CH 2CH 2-Si(CH 3) 2-O-Si(CH 3) 2-CH 2CH 2-Si(OCH 3) 3] 2(III) The subscripts a and b are independently values ​​of 10 or greater, 15 or greater, 20 or greater, 25 or greater, 30 or greater, 45 or greater, 60 or greater, 100 or greater, or even 500 or greater, while simultaneously being values ​​of 200 or less, 100 or less, 50 or less, 45 or less, 40 or less, 35 or less, or even 30 or less.

[0031] The compositions of the present invention may further comprise a third organopolysiloxane. Each molecule of the third organopolysiloxane has 2 or more, 3 or more, 4 or more, 5 or more, or even 6 or more, and typically contains 20 or fewer, 15 or fewer, 10 or fewer, or even 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer alkenyl groups. The average number of alkenyl groups in each molecule is determined by the material used as the third organopolysiloxane in preparing the composition. If the formulation is unknown, the average number of alkenyl groups in each molecule is determined using NMR spectroscopy. The alkenyl groups are preferably terminal alkenyl groups. Preferably, the alkenyl groups are vinyl groups. The third organopolysiloxane is preferably composed of M-type and D-type siloxane units. Examples of suitable third organopolysiloxanes have the chemical structure (IV): (CH 3) 2ViSiO-[(CH 3) 2SiO] d-Si(CH 3) 2Vi (IV) Wherein "Vi" refers to vinyl and the subscript d usually has a value of 100 or greater, 150 or greater, 200 or greater, 250 or greater, 300 or greater, 350 or greater, 400 or greater, 450 or greater, 500 or greater, 550 or greater, 600 or greater, 650 or greater, 700 or greater, or even 750 or greater or 760 or greater, while usually having a value of 1000 or less, 950 or less, 900 or less, 850 or less or even 800 or less, or 775 or less.

[0032] The third organopolysiloxane may be present in the composition at a concentration of zero wt% or greater, 10 wt% or greater, 20 wt% or greater, 30 wt% or greater, 40 wt% or greater, 50 wt% or greater, 60 wt% or greater, or even 70 wt% or greater, while typically present at a concentration of 80 wt% or less, and may be present at a concentration of 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, 20 wt% or less, or even 10 wt% or less, where wt% is relative to the combined weight of the second and third organopolysiloxanes.

[0033] The compositions of the present invention further comprise a bis(acrylphosphine oxide) photoinitiator. The present invention has surprisingly and unexpectedly discovered that using a bis(acrylphosphine oxide) as a photoinitiator results in greater storage stability compared to similar compositions that do not contain a bis(acrylphosphine oxide) photoinitiator. Examples of suitable bis(acrylphosphine oxide) photoinitiators include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and bis(2,4,4-trimethylpentyl)phenylphosphine oxide.

[0034] Bis(hydroxyphosphine) oxide may be the sole photoinitiator in the composition or additional photoinitiators may be present. Examples of additional photoinitiators include those selected from hydroxyacetophenone, aminoacetophenone, phosphine oxide, benzophenone, substituted benzophenone, and 9-oxosulfuron. Any combination of one or more of the above. Particularly desired additional photoinitiators include 2-hydroxy-2-methyl-1-phenyl-1-propanone, ethyl (2,4,6-trimethylbenzoyl)phenylphosphonite; 2,2-dimethoxy-1,2-diphenylethyl-1-one; 2,2-diethoxyacetophenone; and 1-hydroxy-cyclohexyl-phenyl-one. Particularly desired additional photoinitiators are liquid photoinitiators. Liquid photoinitiators can be used as a carrier liquid for the composition. Examples of suitable liquid photoinitiators include 2-hydroxy-2-methylphenylpropanone, ethyl (2,4,6-trimethylbenzoyl)phenylphosphonite, and 2,2-diethoxyacetophenone.

[0035] Based on the weight of the composition, the combination of bis(hydroxyl) phosphine oxide photoinitiator with any additional photoinitiator is preferably present at a concentration of 0.01 wt% or greater, 0.1 wt% or greater, 0.5 wt% or greater, 1.0 wt% or greater, 2.0 wt% or greater, 3.0 wt% or greater, or even 4.0 wt% or greater, while typically at a concentration of 5.0 wt% or less and may be at a concentration of 4.0 wt% or less, 3.0 wt% or less, 2.0 wt% or less, or even 1.0 wt% or less. The bis(hydroxyphosphine) oxide is preferably 5 wt% or more, 10 wt% or more, 20 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or even 90 wt% or more, and simultaneously 100 wt% or less, and may be 90 wt% or less, 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, or even 20 wt% or less, of the total weight of the photoinitiator in the composition.

[0036] The composition may include a carrier liquid, if applicable. The carrier liquid is desirable because it allows for compatibility of the bis(phosphine oxide) with the organopolysiloxane component of the composition, thereby enabling the formation of a homogeneous composition. Generally, when preparing the compositions of the present invention, the bis(phosphine oxide) photoinitiator is mixed with the carrier liquid, and then with the organopolysiloxane component. The carrier liquid may be or may contain a liquid photoinitiator. Examples of liquid photoinitiators that may serve as carrier liquids include 2-hydroxy-2-methylphenylacetone, ethyl (2,4,6-trimethylbenzoyl)phenylphosphonite, and 2,2-diethoxyacetophenone. Similarly, the carrier liquid may contain or consist of one or more liquids that are not photoinitiators, such as silanes, including methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, and phenylmethyldimethoxysilane. The carrier liquid may contain or consist of one or more nonpolar organic liquids (such as toluene).

[0037] The carrier liquid is present in the composition at a concentration of 0 wt% or greater, based on the weight of the composition, and may be present at concentrations of 0.005 wt% or greater, 0.01 wt% or greater, 0.05 wt% or greater, 0.10 wt% or greater, 0.25 wt% or greater, 0.50 wt% or greater, 0.75 wt% or greater, 1.0 wt% or greater, 1.5 wt% or greater, 2.0 wt% or greater, 2.5 wt% or greater, 3.0 wt% or greater, 3.5 wt% or greater, 4.0 wt% or greater, or even 4.5 wt% or greater, while typically present at concentrations of 5.0 wt% or less, 4.5 wt% or less, 4.0 wt% or less, 3.5 wt% or less, 3.0 wt% or less, 2.5 wt% or less, 2.0 wt% or less, 1.5 wt% or less, and so on. It is present at concentrations of wt% or less, 1.0 wt% or less, 0.50 wt% or less, 0.25 wt% or less, 1.0 wt% or less, 0.05 wt% or less, or even 0.01 wt% or less.

[0038] The composition contains a condensation catalyst. The condensation catalyst is typically a titanate, tin, or zirconium-based catalyst. Examples of suitable condensation catalysts include any combination of one or more condensation catalysts selected from the group consisting of: tetraisopropyl titanate, titanium n-butoxide (IV), titanium tributoxide (IV), titanium (IV), di(isopropoxy)bis(ethylacetate)titanium, tetra(trimethylsilyloxy)titanium; di(isopropoxy)bis(methylacetate)titanium, zirconium isopropoxide (IV), zirconium n-butoxide (IV), zirconium tributoxide (IV), di(isopropoxy)bis(ethylacetate)zirconium, di(isopropoxy)bis(methylacetate)zirconium, di(isopropoxy)bis(acetylacetonate)zirconium, di(isopropoxy)bis(acetylacetonate), dimethyltin dineodecanate, dibutyltin dilaurate, dibutyltin dioctanoate, and stannous octanoate.

[0039] Typically, the concentration of the condensation catalyst relative to the weight of the composition is 0.01 wt% or greater, 0.05 wt% or greater, 0.1 wt% or greater, 0.5 wt% or greater, 1.0 wt% or greater, 1.5 wt% or greater, 2.0 wt% or greater and even 3.0 wt% or greater, while usually 5.0 wt% or less, 4.0 wt% or less, 3.0 wt% or less, 2.0 wt% or less or even 1.0 wt% or less.

[0040] The composition comprises a silane having an average of two or more hydrolyzable groups per molecule. The silane acts as a crosslinking agent. It may also act as a carrier liquid and / or a reactant diluent. The hydrolyzable groups are preferably alkoxy groups, more preferably alkoxy groups selected from the group consisting of: methoxy, ethoxy, propoxy, and butoxy. The silane may be dialkoxysilane, trialkoxysilane, or a combination of dialkoxysilane and trialkoxysilane. Most preferably, the silane is a trialkoxysilane.

[0041] Silanes preferably have the following structures: R 3 fSi(OR 3) 4-f The subscript f is i, ii, or tri (preferably i or ii, most preferably i), and R 3 is independently selected from the group consisting of methyl, ethyl, propyl, and butyl each time it appears. Examples of suitable silane compounds include any one or more combinations selected from methyltrimethoxysilane, ethyltriethoxysilane, and dimethyldimethoxysilane.

[0042] Based on the weight of the composition, the compositions of the present invention may contain 0.05 wt% or more, 0.5 wt% or more, 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, or even 10 wt% or more, while typically containing 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, 16 wt% or less, 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, or 10 wt% or less of an alkoxysilane compound.

[0043] The composition further comprises a free radical scavenger (inhibitor) to inhibit free radical reactions during storage, thereby contributing to increased storage stability of the composition. Examples of suitable free radical scavengers include any one or more combinations of butylated hydroxytoluene (BHT), 4-methoxyphenol and tributylhydroquinone, 6-tributyl-2,4-xylenol, 2-tributyl-1,4-benzoquinone, 4-tributylcatechol, 2,6-bis-tributylphenol and N-nitroso-N-phenylhydroxyaminoaluminum salt. The free radical scavenger is typically present at concentrations of 0.001 wt% or greater, 0.005 wt% or greater, 0.01 wt% or greater, 0.05 wt% or greater, 0.10 wt% or greater, 0.50 wt% or greater, 1.0 wt% or greater, or even 1.5 wt% or greater, based on the weight of the composition, while also typically present at concentrations of 2.0 wt% or less, 1.5 wt% or less, 1.0 wt% or less, or even 0.5 wt% or less.

[0044] The composition may include additional components, such as fillers. Examples of suitable fillers include silica, such as fumigated silica and quartz. The filler may be present at concentrations of 0 wt% or greater, 1 wt% or greater, 5 wt% or greater, 10 wt% or greater, 15 wt% or greater, or even 20 wt% or greater relative to the weight of the composition, while typically present at concentrations of 30 wt% or less, 20 wt% or less, 10 wt% or less, or even 5 wt% or less.

[0045] Example Table 1 lists the components used in the following examples. Table 1 [Material] [describe] [source] First organopolysiloxane The dimethylsiloxane methyl (3-mercaptopropyl)siloxane copolymer has the following chemical structure: (R 2R"SiO 1 / 2) 2(RR'SiO 2 / 2) m(R 2SiO 2 / 2) n Where R = R" = methyl, R' = HS(CH 2) 2CH 2-, and on average, n = 43 and m = 5. Prepared according to the procedure taught in US4780486a Second organopolysiloxane Vinyl and alkoxysilyl functionalized dimethyl polysiloxanes have the following chemical structures: Si[O-(Si (CH 3) 2O) 30-Si(CH 3) 2-CH=CH 2] 2[O-[Si(CH 3) 2O] 30-Si(CH 3) 2-CH 2CH 2- Si(CH 3) 2-O- Si(CH 3) 2-CH 2CH 2-Si(OCH 3) 3] 2 Prepared according to the instructions in WO2020 / 076620A1. Third organopolysiloxane Vinyl-functional dimethyl polysiloxane has the following chemical structure: (CH 3) 2ViSiO-[(CH 3) 2SiO] 766-Si(CH 3) 2Vi Purchased from Dow Chemical Company under the trade name XIAMETER™ RBL-2198. Photoinitiator 1 (Liquid photoinitiator) 2-Hydroxy-2-methylphenylacetone Purchased under the trade name OMNIRAD™ 1173 from IGM Resins. Photoinitiator 2 (monopropylphosphine oxide) 2,4,6-Trimethylbenzoyl di-phenylphosphonite Purchased from IGM Resin under the trade name OMNIRAD TPO-L Photoinitiator 3 2,2-Dimethoxy-1,2-diphenylethyl-1-one Purchased from IGM Resin under the brand name OMNIRAD™ BDK Photoinitiator 4 (bis(acrylphosphine oxide)) Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide Purchased from IGM Resin under the trade name OMNIRAD™ 819 Carrier fluid 1 Toluene Sigma-Aldrich Condensation catalyst 1 A complex of titanium acetyl ethyl acetate mixed with methyl-trimethoxysilane. Obtained from Dorf Ketal under the product name TYZOR™ PITA-SM. Condensation catalyst 2 Tetra-tertiary butyl titanate Sigma Aldridge Condensation catalyst 3 4-(trimethylsilyloxy)titanium Gelest silane Methyltrimethoxysilane Sigma Aldridge Free radical scavengers Butylated hydroxytoluene (BHT) Sigma Aldridge filler Smoky silicon dioxide treated with hexamethyldisilazane. The TS-530 is available from Cabot. IRGACURE is a trademark of BASF SE company. OMNIRAD is a trademark of IGM Group BV. XIAMETER is a trademark of Dow Corning Corporation. TYZOR is a trademark of DuPont.

[0046] [program] [] [, aging , ] [, . To age the samples, they were encapsulated in 30 mL EFD syringes and degassed by centrifuging the samples in the syringe and then pushing the plunger to expel air. The syringes were then sealed in vacuum-sealed aluminum bags to remove moisture and light. The bags containing the samples were placed in a preheated oven at 55°C for 21 days.

[0047] [, UV , ] [, Curing depth measurement.The UV curing depth of the samples was determined as follows: A 2.54 mm diameter × 20 mm depth cavity was filled in a polytetrafluoroethylene (PTFE) block with the sample. The sample was then exposed to UVA and UVB light using a mercury lamp and a Colight UV device at an exposure dose of 300 mW / cm² and a dose of 2 joules / cm². The sample material was removed from the PTFE block, uncured sample was wiped off, and the thickness of the solidified sample was then measured using a ruler to determine the curing depth.

[0048] [, achieve , ] [, " , ] [, Non-sticky , ] [, ” , ] [, Moisture curing time A 1.27 mm (50 mm) thick film of the sample was drawn onto an FR4 plate. The film was moisture-cured by placing it in a dark chamber at 22°C and 35–42% relative humidity until the surface was non-sticky. The non-stickiness of the surface was assessed by sliding a finger covered with an acrylonitrile glove across the sample. The sample was considered non-sticky when no sample transferred to the acrylonitrile glove after sliding across the surface.

[0049] [, Viscosity Measurement , ] [, . According to ASTM D-1084, the viscosity of a sample composition was determined using a Brookfield cone-plate viscometer (model HBDVII+P) with a cone spindle CPA-52Z at 23 + / -2°C. The viscosity of organopolysiloxanes was determined using a Brookfield DV1 viscometer at 23 + / -2°C according to ASTM D-1084.

[0050] [] [Sample Preparation] [] Samples were prepared using the components identified in Table 2. The first, second, and third organopolysiloxanes and the filler were combined in a 100 mL dental cup. The mixture was stirred for 20 seconds at 1000 rpm using a dental laboratory mixer, followed by stirring at 2000 rpm for 45 seconds to form an initial mixture. The silanes and free radical scavenger were premixed separately and added to the initial mixture, then stirred at 2000 rpm for 30 seconds. The photoinitiator (if used, premixed with the carrier liquid) and condensation catalyst were added, and the mixture was stirred at 2000 rpm for 30 seconds. The sample was encapsulated in a 30 mL EFD syringe and degassed by centrifuging the sample in the syringe and then pushing the plunger to expel air. This sample at the preparation point was used to characterize "fresh" samples. To characterize "aged" samples, the syringe was vacuum-sealed in an aluminum bag and aged as described in the "aging" procedure above.

[0051] The formulations and characterization results of the samples are listed in Table 2. The amounts of each component in the formulations are reported in grams. Comparative examples (Comp Ex) and examples (Exs) are described.

[0052] [result] [] The results in Table 2 show that the composition achieved the three-fold target only in the presence of a bis(hydroxyl)phosphine oxide photoinitiator: (1) Experiencing a viscosity increase of less than twice its initial viscosity, as measured according to ASTM D-1084 using a Brookfield DVII+P viscometer with a conical spindle CPA-52Z at 23 ± 2 °C; and (2) When exposed to 2 joules / cm² UVA and UVB radiation, the cured depth reaches at least 70%, preferably 80% or greater, more preferably 90% or greater, compared to a freshly prepared identical composition, and even achieves a cured depth of at least 8 mm before and after aging; and (3) Allow 24 hours or less for the moisture to cure and become non-sticky.

[0053] This result applies to various titanate catalysts. It also applies when using a nonpolar carrier liquid (toluene) or a liquid photoinitiator (photoinitiator 1) as the carrier liquid. Further data confirms that the photoinitiator must be a bis(acrylphosphine) oxide, and similar results were not obtained with a mono(acrylphosphine) oxide photoinitiator (photoinitiator 2), see, for example, Comparative Examples B and E. Table 2 [Components] [Comparison Example A] [Compare Example B] [Comparison Example C] [Example 1] [Example 2] [Comparison Example D] [Comparison Example E] [Example 3] [Example 4] [Comparison Example F] [Example 5] First organopolysiloxane 7.05 7.05 7.05 7.05 7.05 7.05 7.05 7.05 7.05 7.05 7.05 Second organopolysiloxane 28.40 28.40 28.40 28.40 28.40 28.40 28.40 28.40 28.40 28.40 28.40 Third organopolysiloxane 40.66 40.66 40.66 40.66 40.66 40.66 40.66 40.66 40.66 40.66 40.66 Photoinitiator 1 1.03 0.76 1.03 0.76 1.03 0.76 Photoinitiator 2 1.03 1.03 Photoinitiator 3 1.03 Photoinitiator 4 1.03 0.27 1.03 0.27 0.27 Carrier fluid 1 2.5 Condensation catalyst 1 0.10 0.10 0.10 0.10 0.10 Condensation catalyst 2 0.10 0.10 0.10 0.10 Condensation catalyst 3 0.10 0.10 silane 3.74 3.74 3.74 3.74 3.74 3.74 3.74 3.74 3.74 3.74 3.74 Free radical scavengers 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 filler 17.43 17.43 17.43 17.43 17.43 17.43 17.43 17.43 17.43 17.43 17.43 [Evaluate] viscosity (Pascal*second) New system 48.42 56.36 43.66 45.24 49.21 43.66 62.71 42.07 53.98 42.07 45.24 aging 174.6 57.94 132.60 53.98 75.41 184.90 50.01 50.01 63.50 147.60 56.36 Curing depth (mm) New system 2 10 3 12 9 5 10 17 16 3 16 aging 2 6 3 12 9 3 1 16 13 2.5 15 Time to achieve non-sticky moisture curing (in hours) New system 5-8 5-8 5-8 5-8 5-8 5-8 5-8 5-8 5-8 5 5-8 aging 3-5 5-8 3-5 5-8 5-8 3-5 5-8 5-8 5-8 3-5 5-8

[0054] none

Claims

1. A dual-curing organopolysiloxane composition comprising: a. a first organopolysiloxane, wherein each molecule contains two or more mercaptoalkyl groups and is free of alkenyl functional groups; b. a second organopolysiloxane, wherein each molecule contains one or more alkenyl groups and one or more hydrolyzable groups; c. a third organopolysiloxane, wherein each molecule has at least two alkenyl groups and is free of alkoxy groups; d. a bis(hydroxyl) phosphine oxide photoinitiator; e. a carrier liquid, wherein the composition is present; f. a condensation catalyst; g. a silane having two or more hydrolyzable groups per molecule; and h. a free radical scavenger, wherein the concentration is in the range of 0.001 to 2% by weight relative to the weight of the composition, wherein the first organopolysiloxane has the general chemical formula: (R12 R3SiO1 / 2)2(R1R2SiO2 / 2)m(R12SiO2 / 2)n where: R1, each time it appears, is independently a hydrocarbon group or a substituted hydrocarbon group having 1 to 20 carbon atoms; R2, each time it appears, is independently a mercaptoalkyl group; R3, each time it appears, is independently selected from the option of R1; the average value of the subscript m is in the range of 2 to 1000; and the average value of the subscript n is in the range of 0 to 1000.

2. The composition of claim 1, wherein the composition further comprises a liquid photoinitiator.

3. The composition of claim 1 or 2, wherein the first organopolysiloxane is free of alkoxy functional groups.

4. The composition of claim 1 or 2, wherein the concentration of the first organopolysiloxane is sufficient such that the mercaptoalkyl group from the first organopolysiloxane and the alkenyl group from the second organopolysiloxane and, if present, the third organopolysiloxane achieve a molar ratio of 0.3 or greater and 5.0 or less.

5. The composition of claim 1 or 2, wherein the concentration of the third organopolysiloxane is 0% by weight or greater than the combined weight of the second and third organopolysiloxanes, and simultaneously 80% by weight or less.

6. The composition of claim 1 or 2, wherein the concentration of the bis(hydroxyl) phosphine oxide photoinitiator and the liquid photoinitiator present therein is 0.01% by weight or greater and 5% by weight or less relative to the weight of the composition.

7. The composition of claim 1 or 2, wherein the concentration of the condensation catalyst is 0.01% by weight or greater and 5% by weight or less relative to the weight of the composition.

8. The composition of claim 1 or 2, wherein the bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide photoinitiator is bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

9. The composition of claim 1 or 2, wherein the second organopolysiloxane has the following structure: (SiO4 / 2)x(Ra2SiO2 / 2)y(RaBSiO2 / 2)y'(Ra2BSiO1 / 2)z where: Ra is independently selected from alkyl and aryl in each occurrence; B is independently selected from alkenyl and alkoxy and alkoxy-containing groups in each occurrence, so as to achieve an average of one or more alkenyl and one or more alkoxy groups per molecule; on average, x is 0 or greater and simultaneously 10 or less; on average, the sum of y and y' is 20 or greater and simultaneously 1000 or less; and on average, z has a value of 2 or greater and simultaneously 20 or less.