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, and

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 carrier comprising an amino silane or an amino silane capped polymer.

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 , which is a two-part composition in which the free-radically polymerizable monomer component comprises at least one (meth)acrylate monomer which is provided in both parts and the initiator system is provided in one part.

4. A two-part polymerizable adhesive composition according to claim 3 , comprising:

part A) an effective amount of an initiator system and an amino silane or an amino silane capped polymer; and

part B) at least one (meth)acrylate monomer, optionally with one or more of a toughener, acid, filler and thickener.

5. A two-part polymerizable adhesive composition according to claim 3 , comprising:

part A) an effective amount of an initiator system, an amino silane or an amino silane capped polymer, 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.

6. A composition according to claim 1 , wherein three of R 1 -R 4 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.

7. A composition according to claim 1 , wherein three of R 1 -R 4 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.

8. A composition according to claim 1 , wherein each of R 5 -R 8 of the quaternary ammonium ion of formula VII is the same C 1 -C 5 alkyl group.

9. 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.

10. A composition according to claim 1 , wherein the initiator system is used in an amount sufficient to provide 0.01% to 5% by weight of boron in the total composition.

11. A composition according to claim 1 , wherein the amino silane is a member selected from the group consisting of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane and aminoethylaminopropyltriethoxysilane.

12. A composition according to claim 1 , wherein the amino silane is 3-aminopropyl triethoxy silane.

13. A composition according to claim 1 , wherein the amino silane is an amino silane capped polymer.

14. A composition according to claim 13 , wherein the amino silane capped polymer is an amino siloxane selected from the group consisting of monoamino siloxanes, diamino siloxanes and polyamino siloxanes, provided none of the amino siloxanes have pendant functional groups capable of polymerization.

15. A composition according to claim 13 , wherein the amino silane capped polymer is embraced by:

wherein R 18 , R 19 , R 20 and R 21 may be the same or different and are selected from the group consisting of hydrogen, hydroxyl, alkyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy; R 22 and R 23 may be the same or different and are selected from the group consisting of hydrogen, alkyl and aryl; and X is selected from alkylene, alkenylene, arylene, with or without interruption by a heteroatom; urethanes; polyethers; polyesters; polyacrylates;

polyamides; and polyimides.

16. A composition according to claim 14 , wherein the diamino siloxane is embraced by:

wherein R 26 and R 27 may be the same or different and are selected from the group consisting of alkylene, arylene, alkylene oxide, arylene oxide, alkylene esters, arlyene esters, alkylene amides and arylene amides; R 24 and R 25 may be the same or different and are selected from the group consisting of alkyl and aryl; R 22 and R 23 are as defined above and n is 1-1,200.

17. A composition according to claim 1 , wherein the amino silane is a member selected from the group consisting of N-2(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)-3-aminopropyltrimethoxysilane, N-2(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butyliden)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilanehydrochloride, N-vinylbenzyl-N′-aminoethyl-e-aminopropylpolysiloxane, N-(n-butyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and triamino-functional propyltrimethoxysilane.

18. 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.

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

mixing parts A and B of a two part adhesive composition according to claim 3 prior to use in order to initiate polymerization,

applying the mixed adhesive composition to at least one of the substrates,

bringing the substrates together with the composition, and

allowing the composition to cure by completion of the polymerization initiated on mixing of the two parts A and B.

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 bond formed between two substrates by the polymerization product of a composition according to claim 1 .

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

24. 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 .

25. A composition according to claim 1 , which when polymerized to bond together two substrates and exposed for 250 hours under 60° C. and 95% RH the polymerized composition at least maintains bond strength.