MATRIX RESIN FOR LAMINATES WITH HIGH TRANSPARENCY, LOW YELLOWING AND HIGH GLASS TRANSITION TEMPERATURES

Abstract

The present invention relates to curable resin compositions, to methods for producing cured compositions using said curable resin compositions, and to items, in particular molded parts, produced by means of such method.

Claims

1. A resin composition comprising at least one epoxy resin component at least one curing component and at least one quaternary phosphonium compound.

2. The resin composition according to claim 1, characterized in that the amount of the at least one quaternary phosphonium compound is in the range of from 0.1 to 5 wt. %, based on the total weight of the resin composition.

3. The resin composition according to claim 1, characterized in that the resin composition is substantially free from tertiary amine compounds.

4. The resin composition according to claim 1, characterized in that the at least one quaternary phosphonium compound is trihexyl(tetradecyl)phosphonium chloride.

5. The resin composition according to claim 1, characterized in that the at least one epoxy resin component is an epoxy compound selected from the group consisting of bis-(3,4-epoxycyclohexylmethyl) oxalate, bis-(3,4-epoxycyclohexylmethyl) adipate, bis-(3,4-epoxy-6-methylcyclohexylmethyl) adipate, bis-(3,4-epoxycyclohexylmethyl) pimelate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, bis-(3,4-epoxycyclohexyl) adipate, 3,4-epoxy-1-methylcyclohexylmethyl-3,4-epoxy-1-methylcyclohexane carboxylate, and mixtures thereof.

6. The resin composition according to claim 1, characterized in that the at least one curing component comprises at least one anhydride curing agent.

7. The resin composition according to claim 6, characterized in that the at least one anhydride curing agent is selected from bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid anhydride, bicyclo[2.2.1]methylhept-5-ene-2,3-dicarboxylic acid anhydride, and mixtures thereof.

8. A method for producing a cured composition comprising the steps of: (1) viding a resin composition according to claim 1; and (2) curing the resin composition in order to obtain a cured composition.

9. The method according to claim 8, characterized in that the method is a transfer molding (RTM) method and the resin composition is a reactive injection resin.

10. The method according to claim 8, characterized in that step (1) comprises injecting the resin composition into a die in which fibers or semi-finished fiber products (prewovens/preforms) are placed.

11. The method according to claim 8, characterized in that (a) the resin composition in step (2) is cured at a temperature of between 80° C. and 240° C., for 0.01 to 10 hours; or (b) the resin composition in step (2) is first pre-cured at a temperature of between 70° C. and 150° C., for 0.1 to 3 hours, and is then post-cured at least once in each case at a temperature of between 110° C. and 260° C., in each case for 0.1 to 3 hours.

12. A cured composition obtainable according to a method to claim 8.

13. The cured composition according to claim 12, characterized in that the K1c value of the cured composition is at least 0.9.

14. The cured composition according to claim 12, characterized in that the cured composition has a glass transition temperature T.sub.g 200° C.

15. The cured composition according to claim 12, characterized in that the cured composition is a molded part, in particular a fiber-reinforced molded part.

Description

EXAMPLES

Comparative Example

[0077] Epoxy Resin Component:

[0078] 143.1 g cycloaliphatic epoxy with 30% core-shell structure particles

[0079] 3.2 g multi-functional fatty acid ester (release agent)

[0080] Curing Component:

[0081] 131.1 g mixture of hexahydrophthalic anhydride and methylhexahydrophthalic anhydride

[0082] 2.0 g 1-methylimidazole

[0083] The epoxy resin component and the curing component were homogenized and then poured into a steel mold. The pre-curing took place at 120° C. over a period of 30 minutes. The mixture was then kept at 180° C. for one hour in order to ensure complete cross-linking. In this way, polymer plates approximately 4 mm thick with an area of 20 cm×20 cm were produced.

[0084] The physical properties of the plate produced in this way are clearly summarized in the table below.

TABLE-US-00001 TABLE 1 Physical properties of the comparative example formulation Flexural modulus [MPa] 2,011 Flexural strength [MPa] 98 K1c [MPa*m½] 1.4 Tg DMA tan delta [° C.] 226 Tg DMA E′ onset [° C.] 177 Transparency* 5 Yellowing** 5 *= fully transparent; 10 = non-transparent **= clear, no yellowing; 10 = dark yellow

Example Formulation 1

[0085] Epoxy Resin Component:

[0086] 180.0 g cycloaliphatic epoxy with 30% core-shell structure particles 3.4 g multi-functional fatty acid ester (release agent)

[0087] Curing Component:

[0088] 162.9 g mixture of hexahydrophthalic anhydride and methylhexahydrophthalic anhydride

[0089] 2.3 g trihexyl(tetradecyl)phosphonium chloride

[0090] The epoxy resin component and the curing component were homogenized and then poured into a steel mold. The pre-curing took place at 120° C. over a period of 30 minutes. The mixture was then kept at 180° C. for one hour in order to ensure complete cross-linking. In this way, polymer plates approximately 4 mm thick with an area of 20 cm×20 cm were produced.

[0091] The physical properties of the plate produced in this way are clearly summarized in the table below.

TABLE-US-00002 TABLE 2 Physical properties of example formulation 1 Flexural modulus [MPa] 2,059 Flexural strength [MPa] 94.0 K1c [MPa*m½] 1.4 Tg DMA tan delta [° C.] 217 Tg DMA E′ onset [° C.] 188 Transparency* 1-2 Yellowing** 3 *= fully transparent; 10 = non-transparent **= clear, no yellowing; 10 = dark yellow

Example Formulation 2

[0092] Epoxy Resin Component:

[0093] 142.0 g cycloaliphatic epoxy with 30% core-shell structure particles

[0094] 3.3 g multi-functional fatty acid ester (release agent)

[0095] Curing Component:

[0096] 137.0 g methylhexahydrophthalic anhydride

[0097] 1.9 g trihexyl(tetradecyl)phosphonium chloride

[0098] The epoxy resin component and the curing component were homogenized and then poured into a steel mold. The pre-curing took place at 120° C. over a period of 30 minutes. The mixture was then kept at 180° C. for one hour in order to ensure complete cross-linking. In this way, polymer plates approximately 4 mm thick with an area of 20 cm×20 cm were produced.

[0099] The physical properties of the plate produced in this way are clearly summarized in the table below.

TABLE-US-00003 TABLE 3 Physical properties of example formulation 2 Flexural modulus [MPa] 1,982 Flexural strength [MPa] 83 K1c [MPa*m½] 1.4 Tg DMA tan delta [° C.] 223 Tg DMA E′ onset [° C.] 182 Transparency* 1 Yellowing** 1-2 *= fully transparent; 10 = non-transparent **= clear, no yellowing; 10 = dark yellow

[0100] The direct comparison of the two example formulations 1 and 2 according to the present invention with the formulation of the comparative example shows that the use of a quaternary phosphonium compound instead of an amine catalyst in cycloaliphatic epoxy resin compositions results in cured items which are more transparent and more colorless (i.e., less yellowed). In addition, the cured items have an increased E′ onset glass transition temperature.