Liquid monobenzoxazine based resin system

1. A liquid resin system comprising:

(a) a liquid monobenzoxazine monomer of the formula (I)

wherein R is allyl, unsubstituted or substituted phenyl, unsubstituted or substituted C 1 -C 8 alkyl group, or unsubstituted or substituted C 3 -C 8 cycloalkyl group; and

(b) at least one non-glycidyl epoxy compound,

wherein the weight ratio of component (a) to component (b) is in a range of about 45:55 to about 55:45 and upon curing provides a cured solid article having a glass transition temperature greater than 160° C.

2. The liquid resin system according to claim 1 wherein R is phenyl.

3. The liquid resin system according to claim 1 wherein the non-glycidyl epoxy compound is a cycloaliphatic epoxy compound.

4. The liquid resin system according to claim 3 , wherein the cycloaliphatic epoxy compound is selected from 3′,4′-epoxycyclohexyl-methyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexyloxirane, 2-(3′,4′-epoxycyclohexyl) -5,1″-spiro-3″,4″-epoxycyclohexane-1,3-dioxane, vinyl cyclohexene monoxide, 3,4-epoxycyclohexanecarboxylate methyl ester and bis(3,4-epoxycyclohexylmethyl)adipate.

5. The liquid resin system according to claim 1 , wherein the weight ratio of component (a) to component (b) is in a range of about 50:50.

6. The liquid resin system according to claim 1 , wherein the viscosity of the liquid resin system is less than 500 cps at room temperature.

7. A method for producing a flame retarded composite article in a resin transfer molding system comprising: a) introducing a fiber preform comprising reinforcement fibers into a mold; b) injecting a thermosetting resin matrix comprising the liquid resin system according to claim 1 into the mold, c) allowing the thermosetting resin matrix to impregnate the fiber preform; and d) heating the resin impregnated preform at a temperature of at least 90° C. for a period of time to produce an at least a partially cured solid article; and e) optionally subjecting the partially cured solid article to post curing operations to produce the flame retarded composite article.

8. A method for forming a flame retarded composite article in a vacuum assisted resin transfer molding system comprising a) introducing a fiber preform comprising reinforcement fibers into a mold; b) injecting a thermosetting resin matrix comprising the liquid resin system according to claim 1 into the mold; c) reducing the pressure within the mold; d) maintaining the mold at about the reduced pressure; e) allowing the thermosetting resin matrix to impregnate the fiber preform; and f) heating the resin impregnated preform at a temperature of at least about 90° C. for a period of time to produce an at least a partially cured solid article; and e) optionally subjecting the at least partially cured solid article to post curing operations to produce the flame retarded composite article.

9. A process for preparing a flame retarded composite article comprising thermally curing a thermosetting resin mixture comprising the liquid resin system according to claim 1 at a temperature above about 90° C.

10. A flame retarded composite article prepared according to the process of claim 9 .

11. A thermosetting resin matrix comprising at least 30% by weight, based on the total weight of the thermosetting resin matrix, of the liquid resin system according to claim 1 and at least one of a solvent, a catalyst, a flame retardant, and/or fillers.

12. A liquid resin system comprising:

(a) a liquid monobenzoxazine monomer obtained by the reaction of a monohydric phenol compound, an aldehyde and a primary amine wherein the molar ratio of monohydric phenol compound to aldehyde is from about 1:2.2 to about 1:2.35 and the molar ratio of monohydric phenol compound to primary amine is from about 1:1;

(b) at least one non-glycidyl epoxy compound wherein the weight ratio of component (a) to component (b) is in a range of about 45:55 to about 55:45 and upon curing provides a cured solid article having a glass transition temperature greater than 160° C.

13. The liquid resin system according to claim 12 , wherein the monohydric phenol compound is phenol, m- and p-cresol, m- and p-ethylphenol, m- and p-isopropylphenol, m- and p-methoxyphenol, m- and p-ethoxyphenol, m- and p-isopropyloxyphenol, m- and p-chlorophenol, 1- and 2-naphthol or a mixture thereof.

14. The liquid resin system according to claim 13 , wherein the primary amine is an amine of the formula R a NH 2 , wherein R a is allyl, unsubstituted or substituted phenyl, unsubstituted or substituted C 1 -C 8 alkyl or unsubstituted or substituted C 3 -C 8 cycloalkyl.

15. The liquid resin system according to claim 12 , wherein the reaction is carried out in the presence of an organic solvent.

16. The liquid resin system according to claim 15 , wherein the organic solvent is toluene, xylene, dioxane, methyl-isobutylketone, isopropanol, sec-butanol or amyl alcohol.