FLAME RETARDANT COMPOSITION
A curable epoxy resin composition comprising at least one oxazolidone-modified epoxy resin which is the reaction product of an epoxy resin and an isocyanate, at least one maleimide, at least one cyanate ester, and optionally at least one non-oxazolidone containing epoxy resin, wherein at least one component of the composition comprises halogen or phosphorous to provide flame retardancy to the cured composition, a method of making the composition and methods of making a prepreg and an electrical laminate using the composition.
1 . A curable epoxy resin composition comprising:
(a) at least one oxazolidone-modified epoxy resin which is the reaction product of an epoxy resin and an isocyanate;
(b) at least one maleimide;
(c) at least one cyanate ester; and optionally
(d) at least one non-oxazolidone containing epoxy resin,
wherein at least one component of the composition comprises halogen or phosphorous to provide flame retardancy to the cured composition.
2 . A composition as claimed in claim 1 additionally comprising a catalyst.
3 . A composition as claimed in claim 1 additionally comprising a solvent.
4 . A composition as claimed in claim 1 additionally comprising a vinyl ester.
5 . A composition as claimed in claim 1 , wherein the oxazolidone-modified epoxy resin is present in an amount of from 15 to 50% by weight of the composition.
6 . A composition as claimed in claim 1 , wherein the cyanate ester is present in an amount of from 10 to 40% by weight of the composition.
7 . A composition as claimed in claim 1 , wherein the cyanate ester comprises triazine rings.
8 . A composition as claimed in claim 1 , wherein the maleimide is present in an amount of from 5 to 30% by weight of the composition.
9 . A composition as claimed in claim 8 , wherein the maleimide is a bismaleimide.
10 . A composition as claimed in claim 3 , wherein the solvent is present in an amount of from 10 to 40% by weight.
11 . A composition as claimed in claim 1 , wherein the non-oxazolidone containing epoxy resin is present in an amount of from 10 to 40% by weight.
12 . A composition as claimed in claim 4 , wherein the vinyl ester is present in an amount of from 5 to 30% by weight.
13 . A curable epoxy resin composition comprising:
(a) from 15 to 50% by weight of at least one oxazolidone-modified epoxy resin which is the reaction product of an epoxy resin and an isocyanate;
(b) from 5 to 30% by weight of at least one maleimide;
(c) from 10 to 40% by weight of at least one cyanate ester;
(d) from 10 to 40% by weight of at least one non-oxazolidone containing epoxy resin,
(e) at least one catalyst; and
(f) from 10 to 45% by weight of at least one solvent,
wherein at least one component of the composition comprises halogen or phosphorous to provide flame retardancy to the cured composition.
14 . A composition as claimed in claim 1 , wherein the composition has a glass transition temperature of at least 170° C. when measured by Differential Scanning Calorimetry (DSC).
15 . A composition as claimed in any one of the preceding claims, wherein the composition has a flame retardancy of at least V-1 of the UL94 test.
16 . An electrical laminate comprising the composition of claim 1 , wherein the laminate has an energy of delamination on impact of greater than 3J.
17 . An electrical laminate comprising the composition of claim 1 , wherein the laminate has an energy of delamination on impact of greater than 5J.
18 . A method of making a curable epoxy resin composition comprising the step of:
mixing at least one oxazolidone-modified epoxy resin, which is the reaction produce of an epoxy resin and an isocyanate, with at least one maleimide and at least one cyanate ester to form a curable epoxy resin composition,
wherein at least one component of the composition comprises halogen or phosphorous to provide flame retardancy to the cured composition.
19 . A method of making a prepreg comprising the steps of:
impregnating a reinforcing web with the composition of claims 1 to form a prepreg.
20 . A method of making an electrical laminate comprising the steps of:
heating the prepreg of claim 19 to a temperature sufficient to partially react the epoxy component of the composition with the maleimide and/or the cyanate ester;
laminating one or more layers of the prepreg with an electrically conductive material; and
heating the so formed laminate at elevated pressure and elevated temperature to form an electrical laminate.
21 . The composition of claim 1 , wherein the oxazolidone-modified epoxy resin comprises halogen or phosphorous to provide flame retardancy.
22 . The composition of claim 1 , wherein the non-oxazolidone containing epoxy resin comprises halogen or phosphorus to provide flame retardancy.
23 . The composition of claim 22 , wherein the oxazolidone-modified epoxy resin is substantially free of halogen or phosphorous.