Room temperature curing adhesive composition having high temperature properties
View Patent ↗Room temperature curing structural adhesive compositions including polyurethane oligomers having multi-methacrylate functionality, cycloalkylmethacrylate, at least one maleimide-functionalized compound and a cure system are disclosed. These compositions exhibit enhanced high temperature properties, including hot strength, heat/humidity strength, and heat aging strength, without compromising initial tensile strength and fixture speeds and still possessing a room temperature cure.
1. A room temperature cure adhesive composition comprising:
a) at least one polyurethane oligomer having (meth)acrylate functionality present in an amount of from about 25% to about 30% by weight of the total composition;
b) a reactive monomer comprising cycloalkyl(meth)acrylate present in an amount of from about 10% to about 50% by weight of the total composition;
c) at least one maleimide-functionalized compound present in an amount of from about 15% to about 30% by weight of the total composition; and
d) a cure system comprising at least one free-radical initiator.
2. The composition of claim 1 , wherein the cycloalkyl(meth)acrylate is selected from the group consisting of cyclohexylmethacrylate, cyclohexylacrylate, isobornyl methacrylate, isobornyl acrylate and combinations thereof.
3. The composition of claim 1 , wherein the reactive monomer is present from about 20% to about 50% by weight of the total composition.
4. The composition of claim 1 , wherein the maleimide-functionalized compound is 4,4′-bis(maleimido)diphenylmethane.
5. The composition of claim 1 , wherein the maleimide-functionalized compound corresponds to the formula
wherein R′ is selected from the group consisting of alkylene, arylene, cycloalkylene, aralkylene, alkarylene and arylalkylarylene.
6. The composition of claim 1 , further including a rubber toughener material.
7. The composition of claim 6 , wherein the rubber toughener is in solution or admixture with the reactive monomer.
8. The composition of claim 1 , wherein the polyurethane oligomer having (meth)acrylate functionality comprises a (meth)acrylate-capped polyurethane.
9. The composition of claim 1 , wherein the polyurethane oligomer having (meth)acrylate functionality is the reaction product of an isocyanate-terminated polyurethane oligomer and an isocyanate-reactive ethylenically unsaturated compound.
10. The composition of claim 9 , wherein the polyurethane oligomer is the reaction product of diisocyanate and an isocyanate-reactive compound having at least two isocyanate reactive functional groups selected from the groups consisting of hydroxy, amino, mercapto, carboxy and combinations thereof.
11. The composition of claim 8 , wherein the (meth)acrylate functionality is selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyethyl vinyl ether, isobornyl acrylate, isobornyl methacrylate, (meth)acrylate ester if a linear, branched or cyclic alcohol of 1 to 22 carbon atoms, acrylamide, methyacrylimide and combinations thereof.
12. The compositions of claim 1 , wherein the cure system further comprises an organic acid and saccharin salt.
13. The composition of claim 1 , wherein the free radical initiator is selected from the group consisting of hydrogen peroxide, alkyl peroxide, alkyl hydroperoxide, aralkyl peroxide, peroxyester and combinations thereof.
14. The composition of claim 1 , further including a hydroquinone stabilizer.
15. The composition of claim 1 , further including an antioxidant.
16. A process for preparing a room temperature curing adhesive composition having high temperature properties when cured, said process comprising:
combining at least one polyurethane oligomer having (meth)acrylate functionality, in amounts of about 25% to about 30% by weight, a reactive monomer comprising cycloalkyl(meth)acrylate present in amounts of about 10% to about 50% by weight; at least one maleimide-functionalized compound present in amounts of about 15% to about 30% by weight, and a cure system comprising at least one peroxide in an amount sufficient to initiate room temperature cure.
17. A method of bonding a first substrate and to a second substrate to form a bonded composite thereof, said method comprising the steps of:
(i) providing a composition comprising:
a) at least one polyurethane oligomer having (meth)acrylate functionality; in amounts of about 25% to about 30% by weight;
b) a reactive monomer comprising cycloalkyl(meth)acrylate present in the amount of about 10 to about 50% by weight;
c) at least one maleimide-functionalized compound present in the amount of about 15% to about 30% by weight; and
d) a cure system comprising at least one peroxide;
(ii) applying said composition to a surface on at least one of said first or second substrates;
(iii) matingly engaging said first and second substrate at said surface; and
(iv) permitting the composition to cure.
18. A process for preparing a room temperature curing adhesive having high temperature properties when cured comprising
b) combining at least one polyurethane oligomer having (meth)acrylate functionality present in an amount of from about 25% to about 30% by weight of the total composition, a reactive monomer comprising cycloalkyl(meth)acrylate in an amount of from about 10% to about 50% by weight of the total composition, a maleimide-functionalized compound present in an amount of from about 15% to about 30% by weight of the total composition and at least one peroxide as a first component;
c) providing a surface activator to produce a second component; and
d) contacting said first and second components to produce said room temperature curing adhesive having high temperature properties.