Adhesive bonding systems having adherence to low energy surfaces

1. A polymerizable composition for bonding a low surface energy substrate to a similar or different substrate, comprising:

a) at least one free-radically polymerizable monomer component,

b) an effective amount of an initiator system for initiating polymerization of the free-radically polymerizable monomer, said initiator system comprising:

alkylated borohydride or tetraalkyl borane metal or ammonium salts comprising formula VI below:

wherein R 10 is C 1 -C 10 alkyl,

R 11 and R 12 , which may be the same or different, are selected from the group consisting of H, D, C 1 -C 10 alkyl, C 3 -C 10 cycloalkyl, phenyl, phenyl-substituted C 1 -C 10 alkyl and phenyl-substituted C 3 -C 10 cycloalkyl, provided that any two of R 10 -R 12 may optionally be part of a carbocyclic ring,

R 13 is H, D or C 1 -C 10 alkyl, and

M + is a metal ion or a quaternary ammonium ion comprising formula VII below

wherein R 14 -R 17 , which may be the same or different, are selected from the group consisting of C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 3 -C 10 cycloalkyl, aryl, C 1 -C 10 alkylaryl, aryl C 1 -C 10 alkyl and aryl C 1 -C 10 cycloalkyl, provided that any two of R 14 -R 17 may be part of an optionally unsaturated carbocyclic ring; and

c) a polymerizable siloxane reactive with the free-radically polymerizable monomer component.

2. A composition according to claim 1 , which is a two-part composition in which the free-radically polymerizable monomer component is provided in one part and the initiator system is provided in the other part.

3. A composition according to claim 1 , wherein three of R 10 -R 13 of the alkylated borohydride of formula VI are the same C 1 -C 10 alkyl group and one of R 1 -R 4 is phenyl or phenyl-substituted C 1 -C 10 alkyl.

4. A composition according to claim 1 , wherein three of R 10 -R 13 of the alkylated borohydride of formula VI are the same C 2 -C 4 alkyl group and one of R 1 -R 4 is phenyl.

5. A composition according to claim 1 , wherein each of R 14 -R 17 of the quaternary ammonium ion of formula VII is the same C 1 -C 5 alkyl group.

6. A composition according to claim 1 , wherein the initiator system comprises:

wherein

R 10 -R 12 are each the same C 1 -C 6 alkyl group,

R 13 is phenyl;

R 14 -R 17 are each the same C 1 -C 6 alkyl group.

7. A composition according to claim 1 , wherein the polymerizable siloxane is represented by (R 3 SiO 1/2 ) w (R 2 SiO 2/2 ) x (RSiO 3/2 ) y (SiO 4/2 ) z , wherein a portion of the total R content includes (meth)acrylate functionality.

8. A composition according to claim 1 , wherein the polymerizable siloxane is a composition made from (a) a silicon fluid formed as the reaction product of a first silane having at least one hydrolyzable functional group, and a second silane having a (meth)acrylic functional group and at least one hydrolyzable functional group; (b) a (meth)acrylate monomer; and (c) polymerization initiator.

9. A composition according to claim 1 , wherein the polymerizable siloxane is a member selected from the group consisting of

10. A composition according to claim 1 further comprising a cure indicator.

11. A composition according to claim 1 , wherein the polymerizable siloxane comprises a silicone fluid formed as the reaction product of a first silane having at least one hydrolyzable functional group, and a second silane having a (meth)acrylic functional group and at least one hydrolyzable functional group.

12. A composition according to claim 1 , wherein the polymerizable siloxane is formed from (i) at least one silane within the formula R 1 m R 2 p Si(X) 4−(m+p) A, wherein R 1 is a (meth)acrylate functional group or a hydrolyzable group, and R 2 is the same or different and is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C 1-12 alkyl, C 6-12 aryl, C 7-18 alkylaryl, and a hydrolyzable group, X is a hydrolyzable group, m is an integer from 1 to 3, and m+p is an integer from 1 to 3; (ii) at least one silane within the formula R 3 q Si(X) 4−q B, wherein R 3 is the same as or different from R 2 above and is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C 1-12 alkyl, C 6-12 aryl, and C 7-18 alkylaryl, and q is an integer from 1 to 3, reacted with at least another silane within the formula of R 4 r R 5 s Si(X) 4−(r+s) C, wherein R 4 and R 5 is the same or different and is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C 1-12 alkyl, C 6-12 aryl, C 7-18 alkylaryl, r is an integer from 1 to 3, and r+s is an integer from 1 to 3, provided the silicone resin formed contains at least some hydrolyzable group, X; and combinations thereof.

13. A composition according to claim 1 , wherein the polymerizable siloxane is selected from compounds within formula V below:

wherein R 6 , R 7 , R 8 and R 9 are the same or different and are selected from the group consisting of alkyl, alkenyl, aryl, and (meth)acryl, provided that at least one of R 6 , R 7 , R 8 and R 9 is (meth)acryl, having up to 10 carbon atoms (C 1-10 ), or substituted versions thereof; R 10 is alkyl having up to 10 carbon atoms; n is an integer between about 100 and 1,200; a is 1 or 2; b is 0, 1 or 2; and a+b is 1, 2 or 3.

14. A composition according to claim 1 , wherein the polymerizable siloxane is represented by the formula VI below:

wherein R 6 and R 7 are the same or different and are selected from the group consisting of alkyl, alkenyl, aryl, and (meth)acryl, provided that at least one of R 6 R 7 is (meth)acryl, having up to 10 carbon atoms (C 1-10 ), or substituted versions thereof, MA is (meth)acrylate and c is 0, 1 or 2.

15. A composition according to claim 1 , wherein the polymerizable siloxane is a structure represented by (R 3 SiO 1/2 ) w (R 2 SiO 2/2 ) x (RSiO 3/2 ) y (SiO 4/2 ) z , wherein w+x+y+z=1 and a portion of the total R content includes (meth)acrylate functionality.

16. A composition according to claim 1 , wherein the polymerizable siloxane is a member selected from the group consisting of acryloxy terminated ethyleneoxide-dimethylsiloxane-ethyleneoxide ABA block copolymer and and methacryloxypropyl terminated polydimethylsiloxane.

17. A composition according to claim 1 , wherein the polymerizable siloxane is present in the range from about 2% to about 50% by weight of the total composition.

18. A composition according to claim 1 , wherein the polymerizable siloxane is present in the range from about 2% to about 30% by weight of the total composition.

19. A composite article comprising a first substrate and a second substrate bonded to the first substrate by an acrylic adhesive, wherein the acrylic adhesive comprises the polymerization product of a composition according to claim 1 .

20. A cured adhesive composition comprising the polymerization product of a composition according to claim 1 .

21. A bonded article comprising two substrates bonded by the polymerization product of a composition according to claim 1 .

22. A two-part polymerizable adhesive composition according to claim 1 , comprising:

part A) an effective amount of an initiator system, a polymerizable siloxane, and at least one (meth)acrylate monomer, optionally with one or more of a toughener, filler and thickener, but without any compound that is reactive with the initiator system to free an alkylated borohydride or tetraalkyl borane metal or ammonium salt therefrom; and

part B) at least one (meth)acrylate monomer together with a compound reactive with an initiator system to free an alkylated borohydride or tetraalkyl borane metal or ammonium salt therefrom and optionally with one or more of a toughener, filler and thickener.

23. A method for bonding together substrates, at least one of which is constructed of a low surface energy material, the steps of which comprise:

applying a composition according to claim 1 to at least one of the substrates,

bringing the substrates together with the composition, and

allowing the composition to cure.