Photocurable adhesion-promoting compositions and methods of use

Abstract

Photocurable adhesion-promoting compositions containing organic titanates and/or organic zirconates and partially reacted alkoxysilanes and the use of the photocurable adhesion-promoting compositions to provide adhesion between metal substrates and an overlying radiation-cured sealant are disclosed.

1 . A photocurable adhesion-promoting precursor composition comprising:
 an amine-functional alkoxysilane;   an alkenyl-functional alkoxysilane;   a photoinitiator; and   an organic solvent.   
     
     
         2 . The precursor composition of  claim 1 , wherein the precursor composition comprises:
 from 1 wt % to 30 wt % of the amine-functional alkoxysilane;   from 1 wt % to 30 wt % of the alkenyl-functional alkoxysilane;   from 0.1 wt % to 20 wt % of the photoinitiator; and   from 30 wt % to 95 wt % of the organic solvent;   wherein wt % is based on the total weight of the photocurable adhesion-promoting precursor composition.   
     
     
         3 . The precursor composition of  claim 1 , further comprising:
 a mercapto-functional alkoxysilane; and   an organic titanate and/or an organic zirconate.   
     
     
         4 . The precursor composition of  claim 3 , wherein,
 the mercapto-functional alkoxysilane comprises a γ-mercapto-functional alkoxysilane; and   the organic titanate and/or organic zirconate comprises an organic titanate.   
     
     
         5 . (canceled) 
     
     
         6 . The precursor composition of  claim 3 , wherein the precursor composition comprises:
 from 1 wt % to 15 wt % of the amine-functional alkoxysilane;   from 1 wt % to 17 wt % of the alkenyl-functional alkoxysilane;   from 0.1 wt % to 4.5 wt % of a mercapto-functional alkoxysilane;   from 0.5 wt % to 6.0 wt % of an organic titanate, an organic zirconate, or a combination thereof;   from 0.1 wt % to 3.0 wt % of the photoinitiator;   from 65 wt % to 98 wt % of the organic solvent; and   from 0.1 wt % to 9 wt % of water,   wherein wt % is based on the total weight of the photocurable adhesion-promoting precursor composition.   
     
     
         7 . (canceled) 
     
     
         8 . The precursor composition of  claim 1 , wherein the amine-functional alkoxysilane comprises:
 from 65 wt % to 85 wt % of an y-amine-functional alkoxysilane; and   from 15 wt % to 35 wt % of a secondary amine-functional alkoxysilane,   wherein wt % is based on the total weight of the amine-functional alkoxysilane in the photocurable adhesion-promoting precursor composition.   
     
     
         9 . (canceled) 
     
     
         10 . The precursor composition of  claim 1 , wherein the precursor composition is substantially free of an acid capable of catalyzing hydrolysis of the alkoxysilanes. 
     
     
         11 . The precursor composition of  claim 1 , wherein the precursor composition comprises an acid, a base, or a combination thereof. 
     
     
         12 . The precursor composition of  claim 11 , wherein the acid or base is selected from acetic acid, hydrochloric acid, diphenylguanidine, 1,5-diazabicyclo[4.3.0]non-5-ene, and 1,8-diazabicyclo(5.4.0)undec-7-ene. 
     
     
         13 . The precursor composition of  claim 1 , wherein the precursor composition comprises:
 from 3 wt % to 13 wt % of a monoamine-functional trialkoxysilane;   from 3 wt % to 13 wt % of an alkenyl-functional alkoxysilane;   from 1 wt % to 4 wt % of a triamine-functional trialkoxysilane;   from 50 wt % to 70 wt % of an organic solvent;   from 1 wt % to 7 wt % of an organic titanate and/or organic zirconate;   from 1 wt % to 4 wt % of a thiol-functional trialkoxysilane;   from 1 wt % to 7 wt % of an alkenyl-functional tris-ketoximinosilane;   from 2 t% to 8 wt % water;   from 0.5 wt % to 3.5 wt % of a photoinitiator; and   from 1 wt % to 7 wt % of a photosensitizer and/or co-initiator,   wherein wt % is based on the total weight of the precursor composition.   
     
     
         14 . A photocurable adhesion-promoting composition, comprising the product of heating the photocurable adhesion-promoting precursor composition of  claim 1  at temperature from 40° C. to 100° C. for from 20 hours to 200 hours. 
     
     
         15 . The adhesion-promoting composition of  claim 14 , wherein the photocurable adhesion-promoting composition has substantially the Si-NMR spectrum of  FIG.  1   . 
     
     
         16 - 17 . (canceled) 
     
     
         18 . A photocurable adhesion-promoting layer derived from the photocurable adhesion-promoting composition of  claim 14 . 
     
     
         19 . The adhesion promoting layer of  claim 18 , wherein,
 the photocurable adhesion-promoting layer comprises the photocurable adhesion-promoting composition after drying; and   the photocurable adhesion-promoting layer comprises:
 from 20 wt % to 40 wt % of the amine-functional alkoxysilane; 
 from 25 wt % to 45 wt % of the alkenyl-functional alkoxysilane; 
 from 2.5 wt % to 12.5 wt % of the mercapto-functional alkoxysilane; 
 from 7.5 wt % to 17.5 wt % of the organic titanate and/or organic zirconate; and 
 from 2.0 wt % to 8.0 wt % of the photoinitiator; 
 wherein wt % is based on the total weight of the dried adhesion-promoting layer. 
   
     
     
         20 . A multilayer system comprising:
 (a) the photocurable adhesion-promoting layer of  claim 18 ; and   (b) a polymer layer overlying the photocurable adhesion-promoting layer, wherein the polymer layer is derived from a radiation-curable composition.   
     
     
         21 . The multilayer system of  claim 20 , wherein the radiation-curable composition comprises a UV-curable composition. 
     
     
         22 . The multilayer system of  claim 20 , wherein,
 the polymer layer comprises a reaction product of reactants comprising:   a thiol-terminated sulfur-containing prepolymer; and   a curing agent reactive with the thiol-terminated sulfur-containing prepolymer, wherein the curing agent comprises a polyalkenyl, a polyalkynyl, or a combination thereof.   
     
     
         23 . The multilayer system of  claim 20 , wherein,
 the multilayer system overlies a metal substrate; and   the multilayer system, when cured, exhibits greater than 20 pli peel (3502 N/m) strength and 100% cohesive failure is determined according to Draft Specification G9-16AA after curing for at least 1 week at 25° C./50% RH.   
     
     
         24 . A vehicle comprising the multilayer system of  claim 20 . 
     
     
         25 . The vehicle of  claim 24 , wherein the vehicle is an aerospace vehicle.