Epoxy adhesive compositions comprising an adhesion promoter
Curable adhesive compositions comprising vi. a curable epoxy resin vii. an amine curing agent, viii. a polymeric toughening agent, ix. a filler and x. a phosphoric acid ester according to the formula as an adhesion promoter, wherein R represents an aliphatic or aromatic residue that contains one or more carboxylic acid ester units and/or one or more urethane units and that further contains at least one ether group and n represents an integer of 1 or 2, methods of making them, bonded articles and methods for bonding.
1. A method for bonding a first substrate to a second substrate comprising
(i) applying to at least a part of the first substrate a curable epoxy adhesive composition comprising
vi. a curable epoxy resin
vii. an amine curing agent,
viii a polymeric toughening agent,
ix. a filler material and
x. a phosphoric acid ester according to the formula
wherein R represents an aliphatic or aromatic residue containing at least one ether group,
wherein R further contains one or more carboxylic acid ester units and/or one or more urethane units, and wherein n represents an integer of 1 or 2;
(ii) applying the second substrate to the part of the first substrate where the curable composition is applied,
(iv) subjecting the curable epoxy adhesive composition to curing, wherein the first and second substrate are selected independently from each other from aluminium, steel and a resin-based composite material.
2. The method according to claim 1 wherein the curing is carried out at room temperature.
3. The method according to claim 1 wherein the group R of the phosphoric acid ester has a molecular weight between 200 and 10,000.
4. The method according to claim 1 wherein the curable epoxy resin comprises one or more aromatic glycidyl ether units.
5. The method according to claim 1 wherein the curable epoxy resin has a molecular weight of from 150 to 4,000 g/mole.
6. The method according to claim 1 wherein the curable epoxy resin has a functionality of from 1 to 3.8.
7. The method according to claim 1 wherein the curable epoxy adhesive composition further comprises glass particles.
8. The method according to claim 1 wherein the amine curing agent comprises a polyamido amine.
9. The method according to claim 1 wherein the polymer toughening agent comprises a core shell polymer.
10. The method according to claim 1 wherein the polymeric toughening agent comprises a liquid polymer comprising repeating units derived from butadiene.
11. The method according to claim 1 wherein the curable epoxy adhesive composition further comprises at least one phosphorous-containing material comprising encapsulated elemental red phosphorous, melamine phosphate, dimelamine phosphate, pyrophosphate or an inorganic phosphinate.