Process of manufacturing a curable precursor of a structural adhesive composition
The present disclosure relates to a process of manufacturing curable precursor of a structural adhesive composition. According to another aspect, the present disclosure is directed to method of bonding two parts.
1. A process of manufacturing a curable precursor of a structural adhesive composition, comprising the steps of:
providing an extruder comprising a reaction chamber and an extrusion die;
providing a curable precursor of a structural adhesive composition, comprising:
a cationically self-polymerizable monomer, wherein the cationically self-polymerizable monomer is a polyfunctional compound comprising at least one cyclic amine;
a polymerization initiator of the cationically self-polymerizable monomer which is initiated at a temperature T 1 ;
a curable monomer which is different from the cationically self-polymerizable monomer, wherein the curable monomer which is different from the cationically self-polymerizable monomer comprises at least one functional group selected from the group consisting of epoxy groups; and
a curing initiator of the curable monomer which is initiated at a temperature T 2 and which is different from the polymerization initiator of the cationically self-polymerizable monomer;
incorporating and mixing the curable precursor of the structural adhesive composition in the reaction chamber of the extruder, thereby forming an extrudable composition;
pressing the extrudable composition of the preceding step through the extrusion die, thereby forming an extrudate of the curable precursor of the hybrid structural adhesive composition;
optionally, cooling down the extrudate of preceding step; and
allowing the self-polymerization reaction of the cationically self-polymerizable monomers in the extrudate; and
wherein the polymerization initiator of the cationically self-polymerizable monomer or the cationically self-polymerizable monomer is incorporated and mixed in the curable precursor of the structural adhesive composition immediately prior to the step of pressing the extrudable composition through the extrusion die.
2. A process according to claim 1 , wherein the temperature T 2 is greater than T 1 , and wherein the temperature T 1 at which the polymerization initiator of the cationically self-polymerizable monomer is initiated is insufficient to cause initiation of the curing initiator of the curable monomer.
3. A process according to claim 1 , wherein the cationically self-polymerizable monomers remain substantially unpolymerized before the extrudable composition is pressed through the extrusion die.
4. A process according to claim 1 , wherein the cationically self-polymerizable monomer is an oligomer having a number average molecular weight no greater than 20,000 g/mol.
5. A process according to claim 1 , wherein the cationically self-polymerizable monomer is a polyfunctional compound comprising two cyclic amines.
6. A process according to claim 1 , wherein the cationically self-polymerizable monomer is an aziridino-functional polyether oligomer.
7. A process according to claim 1 , wherein the curable monomer which is different from the cationically self-polymerizable monomer comprises at least one functional group selected from the group consisting of glycidyl groups.
8. A process according to claim 1 , wherein the polymerization initiator of the cationically self-polymerizable monomer is selected from the group consisting of protonating agents, alkylating agents, and any mixtures thereof.
9. A process according to claim 1 , wherein the curing initiator of the curable monomer is selected from the group consisting of primary amines, secondary amines, and any mixtures thereof.
10. A process according to claim 1 , wherein the extrudate comprises:
a polymeric material comprising the self-polymerization reaction product of a polymerizable material comprising a cationically self-polymerizable monomer, wherein the cationically self-polymerizable monomer is a polyfunctional compound comprising at least one cyclic amine;
optionally, some residual polymerization initiator of the cationically self-polymerizable monomer which is initiated at a temperature T 1 ;
a curable monomer which is different from the cationically self-polymerizable monomer, wherein the curable monomer which is different from the cationically self-polymerizable monomer comprises at least one functional group selected from the group consisting of epoxy groups;
a curing initiator of the curable monomer which is initiated at a temperature T 2 and which is different from the polymerization initiator of the cationically self-polymerizable monomer; and
wherein the curable monomers are substantially uncured and are embedded into the polymeric material comprising the self-polymerization reaction product of a polymerizable material comprising a cationically self-polymerizable monomer.
11. A process according to claim 1 , which further comprises the step of shaping the extrudate in the form of a three-dimensional object.
12. A process according to claim 11 , wherein the three-dimensional object has a shape selected from the group consisting of circular, semi-circular, ellipsoidal, square, rectangular, triangular, trapezoidal, polygonal shape, or any combinations thereof.
13. A method of bonding two parts, which comprises the steps of:
applying an extrudate as described in claim 1 to a surface of at least one of the two parts;
joining the two parts so that the extrudate is positioned between the two parts; and
substantially fully curing the extrudate by initiating the curing initiator of the cationically curable monomer, thereby obtaining a structural adhesive composition having a degree of polymeriaztion of at least 95% and bonding the two parts.
14. A method of bonding two parts according to claim 13 , wherein the two parts are metal or composite material parts, and wherein the method is for hem flange bonding of metal or composite material parts.