IMPROVEMENTS IN RESIN CURATIVE SYSTEMS

Abstract

There is provided a curative system for epoxy resins comprising an alkyl benzene diamine and an additional aromatic amine. There is also provided the use of an alkyl benzene diamine to enhance the performance of an aromatic amine as a curative for an epoxy resin in an infusion processes for the production of fibre reinforced composites; a curable epoxy resin composition containing a mixture of an epoxy resin and a curative system according to the invention; the use of a composition according to the invention as the curable resin in the production of fibre reinforced composites and/or in the production of fibre reinforced composites by infusion processes; a fibre reinforced composite comprising fibrous reinforcement material and a cured epoxy resin obtainable by curing a curable epoxy resin composition according to the invention, and a process for the production of fibre reinforced composites wherein a fibrous reinforcement material is laid up and a curable epoxy resin composition according to the invention is infused through the fibrous reinforcement material at a temperature of 80 to 130 C. and, once the composition has infused the fibrous reinforcement material, the temperature is raised to 150 to 190 C.

Claims

1. A curative system for epoxy resins comprising an alkyl benzene diamine and an additional aromatic amine.

2. A The curative system according to claim 1 in which the alkyl benzene diamine is a toluene diamine having one or more additional alkyl and/or thioalkyl groups.

3. A The curative system according to claim 2 in which the alkyl benzene diamine is of the formula: ##STR00006## wherein Y is an alkyl groups containing from 1 to 4 carbon atoms, X is hydrogen or an alkyl group containing from 1 to 4 carbon atoms, and R and R are alkyl groups or alkylthio groups, preferably alkyl groups or alkylthio groups containing from 1 to 4 carbon atoms.

4. A The curative system according to claim 3 in which the compound of formula I has the following structure: ##STR00007##

5. A The curative system according to claim 4 in which the compound of formula II has the following structure: ##STR00008##

6. The curative system according to claim 5 in which the alkyl benzene diamine comprises a mixture of compounds of formula I and formula II, wherein the ratio of compounds of formula I to compounds of formula II is 80:20.

7. A The curative system according to claim 6 in which the alkyl benzene diamine comprises a mixture of: ##STR00009## in a ratio of from 80% to 20%.

8. (canceled)

9. The curative system according to claim 7 in which the additional aromatic amine is a 4,4 methylene bis aniline.

10. The curative system according to claim 9 in which the methylene bis aniline has the formula: ##STR00010## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently selected from: hydrogen; C.sub.1 to C.sub.6 alkoxy, preferably C.sub.1 to C.sub.4 alkoxy, where the alkoxy group may be linear or branched, for example methoxy, ethoxy and isopropoxy; C.sub.1 to C.sub.6 alkyl, preferably C.sub.1 to C.sub.4 alkyl, where the alkyl group may be linear or branched and optionally substituted, for example methyl, ethyl, isopropyl and trifluoro methyl; or halogen, for example chlorine; wherein at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is a C.sub.1 to C.sub.6 alkyl group.

11. (canceled)

12. (canceled)

13. The curative system according to claim 10, comprising from 20 to 40% by weight of the curative system of the alkyl benzyl diamine.

14. The curative system according to claim 13 in which a mixture of the alkyl benzene diamine and the additional aromatic amine is liquid at 22 C.

15. (canceled)

16. (canceled)

17. The curable epoxy resin composition containing a mixture of an epoxy resin and a curative system according to claim 1.

18. (canceled)

19. A The curable epoxy resin composition according to claim 17 in which the relative amounts of amine groups provided by the curative system and the epoxy groups provided by the epoxy resin is from 0.8:1.2.

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. The process for the production of fibre reinforced composites wherein a fibrous reinforcement material is laid up and a curable epoxy resin composition according to claim 17 is infused through the fibrous reinforcement material at a temperature of 80 to 130 C. and, once the composition has infused the fibrous reinforcement material, the temperature is raised to 150 to 190 C.

25. (canceled)

Description

EXAMPLE 1

[0056] Mouldings were produced by the resin transfer moulding technique in which twenty four plies of dry unidirectional carbon fibre fabric (UD194 IMA/V800E/ZDO/500MM, available from Hexcel Corporation) were laid up in a mould with a quasi-isotropic layup of [+45/0/-45/90].sub.3s and infused with various resin compositions. The resin compositions comprised the functional epoxy resin commercially available as Araldite MY 721 (N,N,N,N Tetraglycidyl-4-4 methylene bis benzamine) and various amounts of curatives to provide a stoichiometric amount of curative amine groups for the epoxy content of the Araldite MY 721. The resin compositions were injected into the mould at 110 C. and cured by heating the mould to 180 C. by increasing the temperature by 2 C. per minute and then holding the mould at 180 C. for two hours.

[0057] The curatives used were the 4,4 methylene bis aniline available from Lonza as MDEA (4,4 methylene bis (diethyl aniline)), the 4,4 methylene bis aniline available from Lonza as MCDEA (4,4 methylene bis (chlorodiethyl aniline)) and the dimethylthiotoluenediamine isomeric mixture available from Albermarle as Ethacure 300. The amounts of the resins used are shown in Table 1.

TABLE-US-00001 TABLE 1 Composition wt % IDS20 IDS21 IDS22 IDS23 IDS24 MY721 57 58.4 59.7 62.1 63.2 Ethacure 300 0 4.2 8.1 15.1 18.4 MCDEA 21.5 18.7 16.1 11.4 9.2 MDEA 21.5 18.7 16.1 11.4 9.2 Proportion of 0% 10% 20% 40% 50% Ethacure 300 to total curative

[0058] Mouldings 420 mm by 420 mm by 4.5 mm were produced, and the open hole compression strength of the mouldings (OHC) was determined according to AECMA standard pr EN 6036 of December 1995 and the wet glass transition temperature of the mouldings was measured according to the AECMA standard pr En 6032 of November 1995.

[0059] The results of the tests are shown in Table 2.

TABLE-US-00002 TABLE 2 Proportion of Ethacure to OHC Tg wet Composition total curative (MPa) Tg dry ( C.) ( C.) IDS20 0% 267 185 162 IDS21 10% 291 186 163 IDS22 20% 307 186 162 IDS23 40% 303 200 171 IDS24 50% 305 204 173

[0060] As shown in Table 2, the combination of 20 wt % of an alkyl benzene diamine and 80 wt % of additional aromatic amine curative provides clear improvements in open hole compression performance compared to the use of 100 wt % of the aromatic curative. Similar advantages are also provided by the use of combinations of 40 wt % alkyl benzene diamine and 60 wt % additional aromatic amine curative and 50 wt % alkyl benzene diamine and 50 wt % additional aromatic amine curative. In addition, there is no significant decrease in either wet or dry Tg values associated with the use of the alkyl benzene diamine, and increases are provided at some concentrations.

EXAMPLE 2

[0061] The procedure of Example 1 was repeated but the mixture of MDEA and MCDEA was replaced by 4,4 methylene (methyl ethyl aniline)-(chlorodiethyl aniline) (M-MEACDEA), used in the proportions shown in Table 3.

TABLE-US-00003 TABLE 3 Composition wt % IDS25 IDS26 IDS27 IDS28 IDS29 MY721 57.7 59 60.2 62.5 63.5 Ethacure 300 0 4.1 8 15 18.3 M-MEACDEA 42.3 36.9 31.9 22.5 18.3 Proportion of 0% 10% 20% 40% 50% Ethacure 300 to total curative

[0062] Mouldings were produced and tested as in Example 1, and the results are shown in Table 4.

TABLE-US-00004 TABLE 4 Proportion of Ethacure to OHC Tg wet Composition total curative (MPa) Tg dry ( C.) ( C.) IDS25 0% 283 209 181 IDS26 10% 286 212 189 IDS27 20% 302 208 190 IDS28 40% 297 208 190 IDS29 50% 291 214 190

[0063] As shown in Table 4, the combination of 20 wt % of an alkyl benzene diamine and 80 wt % of additional aromatic amine curative provides clear improvements in open hole compression performance compared to the use of 100 wt % of the aromatic curative. Similar advantages are also provided by the use of combinations of 40 wt % alkyl benzene diamine and 60 wt % additional aromatic amine curative and 50 wt % alkyl benzene diamine and 50 wt % additional aromatic amine curative. In addition, there is no significant decrease in either wet or dry Tg values associated with the use of the alkyl benzene diamine, and increases are provided at some concentrations.

EXAMPLE 3

[0064] A resin composition was prepared comprising a mixture of 39.19 wt % of the multifunctional epoxy resin N, N, N, N, N tetra glycidyl-4-4methylene bis benzamine, commercially available as Araldite MY 9655 from Huntsman Advanced Materials (UK) Limited; 21.09 wt % of the multifunctional epoxy resin N,N,N,N-tetraglycidyl-3,3-diethyl-4,4-methylene bis benzamine, commercially available as Araldite MY 722 from Huntsman Advanced Materials (UK) Limited; 36.72 wt % of a curative system, and 3 wt % of acrylic core shell toughening particles, commercially available as XT100 from Arkema. The curative system comprised 7.35 wt % (by weight of the total composition) of an alkyl benzene diamine, in the form of the dimethylthiotoluenediamine isomeric mixture available from Albermarle as Ethacure 300, and 29.37 wt % (by weight of the total composition) of an additional aromatic amine, in the form of 4,4 methylene (methyl ethyl aniline)-(chlorodiethyl aniline) (M-MEACDEA). The alkyl benzyl diamine comprised 20 wt % of the curative system and the additional aromatic amine comprised 80 wt % of the curative system.

[0065] The resin of Example 3 was used to prepare test laminates as set out in Example 1, except that the reinforcement used was in the form of UD210 IMA/V800E/ZD4/6.35 mm. The laminates were tested as set out in Example 1, and the open hole compression performance was found to be good (302 MPa) with no significant impact on either dry or wet Tg (dry Tg 192 C., wet Tg 178 C.).

EXAMPLE 4

[0066] A resin composition was prepared comprising a mixture of 38 wt % of functional epoxy resin N,N,N,N Tetraglycidyl-4-4 methylene bis benzamine, commercially available as Araldite MY 721 from Huntsman Advanced Materials (UK) Limited; 21 wt % of the multifunctional epoxy resin N,N,N,N-tetraglycidyl-3,3-diethyl-4,4-methylene bis benzamine, commercially available as Araldite MY 722 from Huntsman Advanced Materials (UK) Limited; 38 wt % of a curative system, and 3 wt % of acrylic core shell toughening particles, commercially available as XT100 from Arkema. The curative system comprised 4 wt % (by weight of the total composition) of an alkyl benzene diamine, in the form of the diethyltoluenediamine isomeric mixture available from Albermarle as Ethacure 100, and 24 wt % (by weight of the total composition) of an additional aromatic amine, in the form of 4,4 methylene (methyl ethyl aniline)-(chlorodiethyl aniline) (M-MEACDEA). The alkyl benzyl diamine comprised 10.5 wt % of the curative system and the additional aromatic amine comprised 89.5 wt % of the curative system.

[0067] The resin of Example 4 was used to prepare test laminates as set out in Example 3 using the reinforcement material listed therein. The laminates were tested as set out in Example 1, and the open hole compression performance was found to be good (295 MPa) with no significant impact on either dry or wet Tg (dry Tg 198 C., wet Tg 175 C.).