Dual cure adhesive formulations

Abstract

An adhesive composition comprising as principal components, a polymerizable component, an ambient temperature radical polymerization catalyst system and a photoinitiator. The adhesive may optionally comprise an adhesion promoter, a toughener, an epoxy, and a filler material. Further, a two-part reactive adhesive comprising, a first part comprising, (i) at least one free radical-polymerizable monomer, (ii) at least one reducing agent, and (iii) a photoinitiator, and a second part comprising an oxidizing agent that is reactive at ambient temperature with the reducing agent to produce free radicals that are capable of initiating and propagating free radical polymerization.

1 . A radical-cured composition comprising:
 (a) at least one free radical-polymerizable monomer;   (b) an ambient temperature radical initiator system; and,   (c) a photoinitiator.   
     
     
         2 . The composition of  claim 1 , wherein the photoinitiator comprises a phosphine oxide photoinitiator. 
     
     
         3 . The composition of  claim 1 , wherein the photoinitiator comprises an alpha-hydroxyketone. 
     
     
         4 . The composition of  claim 1 , wherein the photoinitiator comprises 2-hydroxy-2-methyl-1-phenyl-1-propanone. 
     
     
         5 . The composition of  claim 1 , wherein the monomer comprises an olefinic monomer. 
     
     
         6 . The composition of  claim 1 , wherein the monomer comprises at least one of tetrahydrofurfuryl methacrylate, methacrylic acid, and methyl methacrylate. 
     
     
         7 . The composition of  claim 1 , wherein the monomer is present in an amount from 20-70 weight percent based on the total amount of the components (a), (b), and (c). 
     
     
         8 . The composition of  claim 1 , wherein the reducing agent comprises a tertiary amine. 
     
     
         9 . The composition of  claim 1 , wherein the reducing agent has a formula (I): 
       
         
           
           
               
               
           
         
         wherein each of R 1  and R 2 , which may be the same or different, is independently selected from the group consisting of linear or branched, saturated or unsaturated, C1-C10 alkyl and linear or branched, saturated or unsaturated, C1-C10 hydroxyalkyl (i.e., alkyl substituted by —OH); 
         each of R 3  and R 4  is independently selected from the group consisting of hydrogen and linear or branched, saturated or unsaturated C1-C10 alkyl; and 
         X is a halogen. 
       
     
     
         10 . The composition according to  claim 1 , wherein the reducing agent is selected from N,N-diisopropanol-p-chloroaniline; N,N-diisopropanol-p-bromoaniline; N,N-diisopropanol-p-bromo-m-methylaniline; N,N-dimethyl-p-chloroaniline; N,N-dimethyl-p-bromoaniline; N,N-diethyl-p-chloroaniline; and N,N-diethyl-p-bromoaniline. 
     
     
         11 . The composition of  claim 1 , wherein the oxidizing agent comprises an organic peroxide. 
     
     
         12 . The composition of  claim 1 , further comprising an adhesion promoter. 
     
     
         13 . The composition of  claim 1 , wherein the adhesion promoter comprises a phosphorous containing adhesion promoter. 
     
     
         14 . The composition of  claim 13 , wherein the adhesion promoter comprises from 0.01 to 20 weight percent based on the total weight of the principle components. 
     
     
         15 . The composition of  claim 1 , further comprising a toughener. 
     
     
         16 . The composition of  claim 15 , wherein the toughener comprises an olefinic-terminated liquid elastomer produced from a hydroxyl-terminated polyalkadiene. 
     
     
         17 . The composition of  claim 15 , wherein the toughener comprises an A-B-A block copolymer wherein the A block is selected from styrene, ring alkylated styrene or a mixture thereof and the B block is an elastomeric segment having a low T g  selected from conjugated diene or ethylene-propylene. 
     
     
         18 . The adhesive composition according to  claim 15 , wherein the toughener is present in an amount of about 1 to 10 weight percent. 
     
     
         19 . The composition of  claim 15 , further comprising an auxiliary toughener present in an amount from about 1 to about 15 weight percent based on the total weight of the principle components. 
     
     
         20 . A two-part, reactive adhesive comprising:
 (a) a first part comprising
 (i) at least one free radical-polymerizable monomer; 
 (ii) at least one reducing agent; and, 
 (iii) a photoinitiator; and, 
   (b) a second part comprising an oxidizing agent that is reactive at ambient temperature with the reducing agent to produce free radicals that are capable of initiating and propagating free radical polymerization.   
     
     
         21 . The two-part reactive adhesive of  claim 20 , wherein (a) further comprises an auxiliary high molecular weight toughener with a M w  greater than about 18,000 or a M n  greater than about 10,000. 
     
     
         22 . The two-part reactive adhesive of  claim 20 , wherein (a) further comprises 0.1 to 20 weight percent of a phosphorous-containing compound having one or more olefinic groups. 
     
     
         23 . A method of bonding together substrates to form an assembly comprising:
 a) contacting a substrate with an adhesive comprising a polymerizable component, an ambient temperature radical catalyst system, and a photoinitiator;   b) joining the substrates by pressing the substrates together until excess adhesive in the bond lines becomes exposed to air;   c) allowing the adhesive to develop partial or full strength by the ambient temperature radical catalyst system; and,   d) subjecting the air-exposed adhesive to activating electromagnetic energy to cure the exposed adhesive portion.   
     
     
         24 . A method for bonding together substrates to form an assembly comprising;
 a) applying an adhesive comprising a polymerizable component, an ambient temperature radical catalyst system, and a photoinitiator between two substrates such that the adhesive contacts both substrates and at least partially fills the area between the substrates and is at least partially exposed to air;   b) allowing the adhesive to at least partially cure through the ambient temperature radical catalyst system   c) illuminating the portion of the adhesive exposed to air with activating electromagnetic energy to cure the exposed adhesive portion through the photoinitiator.   
     
     
         25 . A method of forming a hem flange assembly, comprising the steps of:
 (a) positioning a first panel adjacent to, but not contacting, a second panel such that an edge of the second panel extends beyond an edge of the first panel;   (b) providing an adhesive comprising a polymerizable component, an ambient temperature radical catalyst system, and a photoinitiator between the overlapping portion of the two panels;   (c) folding the non-overlapping portion of the second panel over the edge of the first panel;   (d) applying pressure to the overlapping portion of the panels so that the panels move toward each other to a point where they remain a predetermined distance apart and at least a portion of the adhesive resides in the gap between the first and second panels with a portion of the adhesive exposed to the atmosphere;   (e) allowing the ambient temperature cure to take place; and   (f) curing the exposed portion of adhesive by subjecting the portion of exposed adhesive to electromagnetic energy.   
     
     
         26 . The method of  claim 25 , wherein prior to subjecting the exposed portion of adhesive to electromagnetic energy, the exposed surface of the adhesive is tacky. 
     
     
         27 . The method of  claim 25 , wherein after subjecting the exposed portion of adhesive to electromagnetic energy, the surface is tack-free. 
     
     
         28 . The method of  claim 25 , wherein the adhesive is exposed to electromagnetic energy by means of a robotic arm comprising an electromagnetic energy source. 
     
     
         29 . The method of  claim 25 , wherein the adhesive is dispensed through an applicator tip mounted on a controllable robotic arm.