Photocurable organopolysiloxane resin

Abstract

The present invention relates to a composition comprising a bisacylphosphine photoinitiator as described herein and a polyacrylate functionalized organosiloxane. The composition of the present invention provides homogeneous coatings that achieve acceptable cure depths by UV or LED irradiation.

Description

[0001] Photocurable Organopolysiloxane Resin Background of the Invention The present invention relates to a photocurable polyorganosiloxane resin and a bisacylphosphine oxide photoinitiator. UV or LED initiated curing of polymers is desirable for high throughput processing. Curing is induced by a photoinitiator that is compatible with the polymers; for organopolysiloxane curing systems, however, compatibility is a long-standing and heretofore unsolved problem. Photoinitiators with poor compatibility are undesirable as curing agents because they separate from the silicone matrix during storage, resulting in ineffective cure, undesired haze, and coating defects of the cured product. US 10,597,413 B2 (Tan) describes an acyl phosphine oxide substituted with -CH2-O-Si(OR)3 groups, a typical example of which is the following compound: Although Tan discloses that these standing solubility problem, it is evident that another problem is introduced, namely susceptibility to acid cleavage of the silyl ether bond (CH2-OSi), thereby rendering the photoinitiator incompatible with the silicone matrix. It would therefore be an advantage in the art of photoinitiation in silicone systems to achieve solubility and with maintenance of stability. Summary of the Invention The present invention addresses a need in the art by providing a composition comprising a bisacylphosphine oxide photoinitiator and a polyacrylate functionalized organosiloxane; wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1: where m is 0, 1, 2, or 3; and n is 0, 1 or 2; R1is -phenyl-(R3)n, -C(O)-phenyl-(R2)m, -O-C1-C20-alkyl, or -O(CH2CH2O)x-H, where x is from 1 to 20; each R2is independently C1-C6-alkyl; C1-C6-alkoxy; -OCH2-phenyl; or R2together with an adjacent R2on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R3is independently C1-C6-alkyl or C1-C6-alkoxy; R4is i) –(Si(Me2))p(CH2)q(Si(R52)O)r(X)s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH2CH2or CH(CH3); s is 0 or 1 with the proviso that when s is 0, Y is SiMe2H, and when s is 1, Y is Si(OMe)3; SiMe3; Si(OEt)3; SiMe2OMe; SiMe2OEt; Si(OSiMe3)3; SiMe(OSiMe3)2; SiMe2(OSiMe3); or ; where the dashed line is the point of X; and each R5is independently C1-C6-alkyl or phenyl; or R4is ii) –(Si(Me2))p(CH2)t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either: where the dashed line is the to t. The composition of the present invention addresses a need in the art by providing an organopolysiloxane composition that can be cured by UV or LED to form a haze free, defect free coating.

[0002] Detailed Description of the Invention The present invention is a composition comprising a composition comprising a bisacylphosphine oxide photoinitiator and a polyacrylate functionalized organosiloxane; wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1: I where m is 0, 1, 2, or 3; and n is 0, 1 or 2; R1is -phenyl-(R3)n, -C(O)-phenyl-(R2)m, -O-C1-C20-alkyl, or -O(CH2CH2O)x-H, where x is from 1 to 20; each R2is independently C1-C6-alkyl; C1-C6-alkoxy; -OCH2-phenyl; or R2together with an adjacent R2on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R3is independently C1-C6-alkyl or C1-C6-alkoxy; R4is i) –(Si(Me2))p(CH2)q(Si(R52)O)r(X)s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH2CH2or CH(CH3); s is 0 or 1 with the proviso that when s is 0, Y is SiMe2H, and when s is 1, Y is Si(OMe)3; SiMe3; Si(OEt)3; SiMe2OMe; SiMe2OEt; Si(OSiMe3)3; SiMe(OSiMe3)2; SiMe2(OSiMe3); or ; where the dashed line is the point of attachment from Y to X; and each R5is independently C1-C6-alkyl or phenyl; or R4is ii) –(Si(Me2))p(CH2)t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either: where the dashed line is In one aspect, R1is -C(O)-phenyl-(R2)m. An example of a preferred R1group is represented by the following structure: In one aspect, R4is –(Si(Me2))p(CH2)q Y; in another aspect, each R5is methyl. In one aspect, when p is 0, q is 3 or 4; in p is 1, q is 2; r is from 3 or from 6 or from 10, to 300 or to 200 or to 100 or to 50. The compound of Formula I can be prepared as described in Schemes 1 to 3. Where R1is -C(O)-phenyl-(R2)m, and R4is in the para position of benzene ring, the compound of Formula I can be prepared in accordance with Scheme 1. The reaction conditions for each step are described in the experimental section. Scheme 1 Alternatively, where R1is -C(O)-phenyl-(R2)m, the compound of the present invention can be prepared by reacting the final Intermediate with either compound A or B: O O O H O Si O O Si A B where X is CH2CH2 or Where p is 1, the first compound in Scheme 1 can be prepared by contacting in a first step a dibromobenzene, particularly p-dibromobenzene, with a vinyl dimethylsilyl chloride in the presence of n-butyl lithium to form the following intermediate: where b is from 0 to 10. Where p is 0, the first compound, especially where q′ is 2, can be prepared as described in Li, Y.-L.; Song, D.-P.; Pan, L.; Ma, Z.; Li, Y.-S. Polym. Chem.2019, 10, 6368-6378. Where R1is -O-C1-C20-alkyl, or -O(CH2CH2O)x-H, the compound of Formula I can be prepared in accordance with Scheme 2.

[0003] Scheme 2 where R is HO-C1-C20-alkyl, or HO(CH2CH2O)x-H. Where R1is -phenyl-(R3)n , the compound of Formula I can be prepared in accordance with Scheme 3. Scheme 3 on the weight of the composition. As used herein, “photoinitiator core” refers to the following fragment of the bisacylphosphine oxide photoinitiator: where q′ is 1 to 10 when p is 0, and q′ is 0 to 10 when p is 1. As used herein, the term “polyacrylate functionalized organosiloxane” refers to an organosiloxane functionalized with two or more acrylate or methacrylate groups displaced from the silicon atom by a divalent hydrocarbyl group, preferably a -CH2- or -CH2CH2CH2- group. An example of a fragment of a polyacrylate functionalized organosiloxane is illustrated in Formula 2: where R6is H or methyl; e is 1 or 3; and the dotted line represents attachment of the fragment to an M unit, a D unit, a T unit, or a Q unit; and c is from 1 to 4.

[0004] where R7is C1-C6alkyl, preferably methyl; and each R8is C1-C6-alkyl, preferably methyl or phenyl. Where moisture curing is desired, the acrylate functionalized organosiloxane advantageously further includes C1-C6-alkoxysilyl groups, preferably two or more methoxysilyl groups. An example of a subclass of such a dual functionalized polymer is illustrated in Formula 3: where include an organopolysiloxane functionalized with C1-C6-alkoxysilyl groups, preferably two or more methoxysilyl groups. Where moisture cure is desired, the composition advantageously comprises a moisture cure catalyst such as a titanium catalyst, and example of which is titanium dioxide acetoacetate complex, commercially available as Tyzor PITA-SM Organic Titanate. The composition of the present invention is capable of undergoing UV cure as well as moisture cure with the inclusion of a single compound with dual Si-alkenyl / Si-alkoxy functionality or a mixture of compounds with Si-alkenyl and Si-alkoxy functionalities. Examples Intermediate Example 1 – Preparation of M′D14M′ Polysiloxane Substituted Photoinitiator A. Preparation of (4-(But-3-en-1-yl)phenyl)dichlorophosphane In a glovebox, a 500 mL round bottom flask was charged with 1-bromo-4-(but-3-en-1- yl)benzene (17.1 g), dry THF (118 mL), and dry diethyl ether (37 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred under N2 and cooled to -78 °C, then n-butyllithium (n-BuLi, 2.5 M in hexane, 34.0 mL) was added dropwise to the mixture. The mixture stirred for 30 min, after which time chlorobis(diethylamino)phosphine (17.9 mL, 85.1 mmol). The mixture stirred for 20 min and was allowed to warm to ambient temperature. The solution was poured into a separatory funnel containing diethyl ether and water. The phases were separated, and the aqueous phase was extracted with a few portions of diethyl ethyl ether. The combined organic fractions were washed with brine, dried over MgSO4 and concentrated in vacuo. The crude oil was transferred to a 1000-mL round bottom flask, which was placed in a glovebox. The oil was dissolved in dry diethyl ether (100 mL). The mixture was stirred and treated with HCl (2.0 M in diethyl ether, 162 mL, 324 mmol, 4.00 equiv) dropwise, and a white solid precipitated. After 2 h, the slurry was filtered and the filtrate was concentrated. A colorless oil was isolated (15.9 g, 84%), which was used in the next step without further purification. B. Preparation of (4-(But-3-en-1-yl)phenyl)phosphane In a glovebox, a 500 mL jar was charged with diethyl ether (100 mL) and LiAlH4 (2.0 M in THF, 19.8 mL, 39.6 mmol, 0.60 eq.). The solution was stirred vigorously, and (4-(but-3-en-1-yl)phenyl)dichlorophosphane (15.4 g, 66.1 mmol, 1.00 eq.) in diethyl ether (65 mL) was added to the solution dropwise over 10 min. The mixture stirred for 30 min before solid Glauber Salt (25.5 g, 79.3 mmol, 1.20 eq.) was cautiously added. The mixture stirred for 60 min, and the liquid was decanted and filtered through a 0.45 µm syringe filter and concentrated to give a colorless oil (9.73 g, 90%), which was used in the next step without further purification. C. Preparation of ((4-(But-3-en-1-yl)phenyl)phosphoryl)bis(mesitylmethanone) In a glovebox, a solution of Preparation of (4-(But-3-en-1-yl)phenyl)phosphane (9.73 g, 59.3 mmol, 1.00 eq.) in dry THF (300 mL) was treated with sodium tert-butoxide (NatOBu, 11.4 g, 118 mmol, 2.00 eq.), then 2,4,6-trimethylbenzoyl chloride (19.8 mL, 118 mmol, 2.00 eq.) was added dropwise to the mixture. The mixture was stirred overnight. Crude31P NMR spectroscopic analysis indicated that the phosphine was partially consumed. An additional amount of NatOBu (3.99 g) and the benzoyl chloride (6.9 mL) were added to the reaction mixture. After 5 h, the mixture was filtered to remove sodium chloride, and the filtrate was removed from the glovebox and concentrated in vacuo. The crude residue was dissolved in dichloromethane (200 mL), and the solution was treated with hydrogen peroxide (6.0 mL 30 wt.%). The mixture was stirred overnight at ambient temperature, then treated with aqueous sodium bisulfite solution (100 mL) and stirred until the organic phase was negative to a peroxide strip test. Phases were separated and concentrated with celite for chromatography on silica gel (0 to 50% EtOAc in hexane). A yellow oil (13 g) that contained product and some other impurities was isolated. A second column purification was performed, whereupon Intermediate Example 3 (11.3 g) was isolated as a yellow oil. D. Preparation of M′D14M′ Polysiloxane Substituted Photoinitiator Preparation of ((4-(But-3-en-1-yl)phenyl)phosphoryl)bis(mesitylmethanone) (0.07 g) was mixed with dry hexane (3.0 mL) and M′D14M′ Polysiloxane (0.99 g) in a glovebox. The mixture was stirred at 50 °C until the solids dissolved. Karstedt’s Catalyst (2 wt% Pt in xylene, 0.03 mL) was added and the mixture was stirred overnight. Consumption of the alkene was monitored by1H NMR spectroscopy, and additional portions of Karstedt’s Catalyst were added until <5% of the alkene remained. Vinyl trimethoxysilane was added to react with remaining Si-H groups. Volatiles were removed by vacuum pump, leaving an amber oil. A mixture of the following products was identified and calculated to comprise 4.0 wt% photoinitiator.

[0005] Intermediate Example 2 – Preparation of a M′D14M′ Polysiloxane Substituted Photoinitiator A. Preparation of (4-Bromophenyl)dimethyl(vinyl)silane A 1000-mL 3-neck round bottom flask equipped with an addition funnel was charged with dry THF (425 mL) and 1,4-dibromobenzene (20.0 g, 84.8 mmol, 1.00 eq.) under a blanket of N2. The mixture was stirred at cooled to -78 °C. An n-BuLi solution (2.5 M in hexane, 35.6 mL, 89.0 mmol, 1.05 eq.) was added dropwise to the dibromobenzene solution over 25 min. Stirring was continued for another 50 min after the completion of addition of the n-BuLi solution. Chlorodimethylvinylsilane (12.9 mL, 93.3 mmol, 1.10 equiv) was added dropwise to the reaction mixture with stirring. The mixture was gradually warmed to room temperature over 1 h, after which time the mixture was quenched with aqueous ammonium chloride. Product was extracted with several portions of ethyl acetate. Combined organic fractions were dried over sodium sulfate and concentrated. The crude oil was purified in vacuo (450 mTorr, 52-60 °C) to give (4-bromophenyl)dimethyl(vinyl)silane (18.75 g) as a colorless oil.

[0006] B. Preparation of ((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone) In a glovebox, a 250-mL round bottom flask was charged with (4-Bromophenyl)dimethyl(vinyl)silane (4.31 g, 17.9 mmol, 1.00 eq.), dry THF (26 mL), and dry diethyl ether (8 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred under nitrogen and cooled to -78 °C. whereupon n-BuLi (2.5 M in hexane, 7.51 mL, 18.8 mmol, 1.05 eq.) was added dropwise. The mixture stirred for 30 min, after which time chlorobis(diisopropylamino)phosphine (5.01 g, 18.8 mmol, 1.05 eq.) was added as a solid. The mixture was stirred and allowed to warm to ambient temperature over 2 h. The solution was poured into a separatory funnel containing diethyl ether and water. The phases were separated, and the aqueous phase was extracted with a few portions of diethyl ethyl ether. The combined organic fractions were washed with brine, dried with MgSO4and concentrated by rotary evaporation. The crude oil was transferred to a 250-mL round bottom flask, which was placed in a glovebox. The oil was dissolved in dry diethyl ether (20 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred and cooled to 0 °C under N2. HCl (2.0 M in diethyl ether, 35.7 mL, 71.5 mmol, 4.00 eq.) was then added dropwise and a white solid precipitated. After continued stirring for 2 h, the slurry was filtered and the filtrate concentrated. The crude residue was mixed with diethyl ether and hexane and filtered again. The filtrate was concentrated to give a colorless oil (4.59 g). The crude material was used in the next step without further purification. In a glovebox, a 150-mL jar was charged under vigorous stirring with diethyl ether (44 mL) and LiAlH4 (2.0 M in THF, 5.23 mL, 10.5 mmol, 0.60 eq.). The crude material from the previous step (4.59 g, 17.4 mmol, 1.00 equiv) was added to the LiAlH4solution dropwise over 5 min. The mixture stirred for 30 min, after which time solid Glauber Salt (6.74 g, 20.9 mmol, 1.20 eq.) was cautiously added. Stirring continued for 14 h, after which time the solution was filtered and the filtrate concentrated to give 2.71 g of crude product as a colorless oil. The crude material was used in the next step without further purification. A solution of the crude material from the previous step (2.71 g) in dry THF (70 mL) was treated with dry NatOBu (2.68 g, 27.9 mmol, 2.00 eq.), followed by dropwise addition of 2,4,6-trimethylbenzoyl chloride (4.65 mL, 27.9 mmol, 2.00 eq.). The mixture stirred for 3 h and the mixture was then filtered to remove sodium chloride. The filtrate was removed from the glovebox and concentrated in vacuo. The crude residue was dissolved in dichloromethane (50 mL), and the solution was treated with hydrogen peroxide (1.4 mL, 30 wt.%). The mixture was stirred overnight at ambient temperature, then treated with aqueous sodium bisulfite solution (30 mL). Phases were separated and the organic phase was concentrated in the presence of silica gel to facilitate liquid chromatography on silica gel (0 to 50% EtOAc in hexane). ((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone) (1.98 g) was isolated as a yellow oil that solidified upon standing. C. Preparation of a M′D14M′ Polysiloxane Substituted Photoinitiator ((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone) (0.10 g) was mixed with dry toluene (1.5 mL) and M′D14M′ Polysiloxane (0.24 g) in a glovebox. The mixture was stirred at 80 °C until the solids dissolved. Karstedt’s Catalyst (2 wt% Pt in xylene, 0.012 mL) was added to the mixture and stirring was continued for 1 h. Consumption of the alkene was monitored by1H NMR spectroscopy, and additional portions of Karstedt’s Catalyst were added until <5% of the alkene remained. Vinyl trimethoxysilane was added to react with remaining Si-H groups. Volatiles were remove in vacuo leaving an amber oil. A mixture of the following products was identified and calculated to comprise 30.0 wt% photoinitiator.

[0007] Example 1 – Preparation of a Dual Curable Organopolysiloxane Composition A UV curable organopolysiloxane composition was prepared by blending the compound of Formula 3 (10 pbw, d = 120) with the bisacylphosphine oxide photoinitiator of Intermediate Examples 1 or 2 (0.1 pbw). The blend was mixed at 1000 rpm for 20 s, and then at 2000 rpm for 45 s. The sample was then packaged in three 30-mL syringes and deaired, then vacuum sealed in an aluminum bag to avoid moisture and light. Comparative Example 1 – Preparation of a Dual Curable Organopolysiloxane Composition The preparation described in Example 1 was carried out in substantially the same way except that Irgacure 819 bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide photoinitiator (0.1 pbw, Irgacure 819) was used. LED Cure Procedure The samples were cured using Uvitron Skyray 800 LED Flood Curing System with a 365-nm LED with an intensity of 500 mW / cm2and an irradiation dosage of 10 J / cm2. LED Cure Depth Measurement Formulations were filled into a Teflon block with wells having diameters of 25 mm and depths of 20 mm. The coating was exposed to LED irradiation. The samples were removed from the wells and uncured material was removed with a tissue so that cure depth could be measured with a ruler. Table 1 illustrates the formulation appearance, the coating appearance, and the cure depth of the samples cured by LED irradiation. A cure depth of >3 mm was considered acceptable. Table 1 – Cure Depth and Appearance for LED Irradiated Formulations Property Comp. Ex 1 Ex.1 Ex.2 Formulation Appearance Precipitate Emulsion Emulsion us The d on gave homo genous formulations and coatings and acceptable cure depth for LED irradiations. In contrast, the composition containing Irgacure 819 photoinitiator was inhomogeneous and gave an inhomogeneous coating.

Claims

Claims:

1. A composition comprising a bisacylphosphine oxide photoinitiator and a polyacrylate functionalized organosiloxane; wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1:where m is 0, 1, 2, or 3; and n is 0, 1 or 2; R1is -phenyl-(R3)n, -C(O)-phenyl-(R2)m, -O-C1-C20-alkyl, or -O(CH2CH2O)x-H, where x is from 1 to 20; each R2is independently C1-C6-alkyl; C1-C6-alkoxy; -OCH2-phenyl; or R2together with an adjacent R2on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R3is independently C1-C6-alkyl or C1-C6-alkoxy; R4is i) –(Si(Me2))p(CH2)q(Si(R52)O)r(X)s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH2CH2or CH(CH3); s is 0 or 1 with the proviso that when s is 0, Y is SiMe2H, and when s is 1, Y is Si(OMe)3; SiMe3; Si(OEt)3; SiMe2OMe; SiMe2OEt; Si(OSiMe3)3; SiMe(OSiMe3)2; SiMe2(OSiMe3); or; where the dashed line is the point of attachment from Y to X; and each R5is independently C1-C6-alkyl or phenyl; or R4is ii) –(Si(Me2))p(CH2)t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either: where the dashed line is the2. The composition of Claim 1 where the polyacrylate functionalized organosiloxane comprises a fragment represented by Formula 2:where e is 1 or 3; R6is H or methyl; and the dotted line represents attachment of the fragment to a silicon atom attached to an M unit or a D unit or a T unit, or a Q unit; and c is from 1 to 4.

3. The composition of Claim 2 wherein z is 1; R1is -C(O)-phenyl-(R2)m; each R2is methyl, each m is 3, each n is 0, and R4is –(Si(Me2))p(CH2)q(Si(R52)O)r(X)s-Y, where each R5is methyl, X is CH2CH2, r is 10 to 200; q is 3 when p is 0, q is 2 when p is 1; and Y is Si(OMe)3orwhere the dashed line is the point of attachment from to the CH2CH2 group.

4. The composition of Claim 2 wherein z is 1; R1is -C(O)-phenyl-(R2)m; each R2is methyl, each m is 3, each n is 0, and R4is –(Si(Me2))p(CH2)t-Z.

5. The composition of any of Claims 1 to 4 wherein the polyacrylate functionalized organosiloxane is further functionalized with at least two C1-C6-alkoxysilyl group.

6. The composition of Claim 5 wherein the polyacrylate functionalized organosiloxane is represented by the following formula: where d7. The composition of any of Claims 1 to 4 which further comprises an organopolysiloxane functionalized at least two C1-C6-alkoxysilyl groups.

8. The composition of Claim 1 wherein the bisacylphosphine oxide photoinitiator is selected from the group consisting ofwhere r is from 6 to 50.

9. The composition of Claim 1 wherein the bisacylphosphine oxide photoinitiator is selected from the group consisting ofwhere r is from 6 to 50.

10. A method comprising the steps of a) applying to a substrate the composition of any of Claims 1-9; then b) curing the composition by UV or LED curing.

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