KR20100030469A - Epoxy resin composition for hardening type prepreg - Google Patents

Abstract

PURPOSE: An epoxy resin composition for curable prepreg is provided to be multifunctional, to ensure good solubility, prepreg production workability, high glass transition temperature, good temperature characteristic, and excellent chemical resistance. CONSTITUTION: An epoxy resin composition for curable prepreg is obtained by mixing 100 weight% tetraglycidylmethylenedianiline that is a tetrafunctional epoxy resin, 36 weight% 4,4'-diaminodiphenylsulfone(DDS) that is an aromatic amine-based hardener, and 0.5 weight% boron trifluoride-monoethylene amine that is a curing accelerator.

Description

Epoxy resin composition for hardening type prepreg}

The present invention relates to an epoxy resin composition for a curable prepreg, and more particularly, has excellent polyfunctional and high solubility, and is excellent in prepreg manufacturing workability, high glass transition temperature, excellent high temperature property, and excellent chemical resistance and high temperature. It is to provide epoxy resin composition for 176 ° C (350 ° F) curable prepreg with high mechanical properties and very long pot life at working temperature.

In general, the prepreg material, which is a reinforcing fiber material, is widely used in various industrial fields such as sports equipment, aircraft, boats, etc., which require high strength and strong elasticity.

Thermosetting resins, including epoxy resins, are widely used for such prepregs. Recently, there have been many attempts to use thermoplastic resins such as PEEK (polyether ether ketone). Whatever polymer material is used, it is optimally controlled when prepreg sheets are formed from raw materials, such as sticking to molding molds and tooling tools, and adhesives are adhered to each other, and the fiber layer does not break easily when lamination is wrong. Required properties.

In addition, the epoxy resin must be a latent curative system in order to be used for prepreg, and at room temperature to prevent reactions that degrade tack, drape, and out time at room temperature. While the reaction at the following temperature should be slow, the curing reaction should proceed quickly at a relatively high curing temperature. Most of the latent curing systems in use today do not completely exclude the reaction at room temperature (cure).

Prepreg has the disadvantage that it should be transported and stored at low temperature, and before use, the sealed prepreg should be opened and used after raising to a room temperature. In general, the shelf life of prepreg varies slightly depending on the type and nature of the resin used, but is based on one year when stored at a temperature below -20 ℃.

In addition to epoxy resins, epoxy resin compositions for prepregs having various kinds of curing agents and catalysts (reaction accelerators) as well as fillers suitable for special use conditions have been developed. Many examples of epoxy resins used in prepreg production are known. Resins with various viscosities, number of active reactors (associated with epoxy equivalents), and various structures are used. Small amounts of additives are usually used to control the viscosity of the resin before curing, to improve impact resistance, and to improve other physical properties.

Curing agents used with epoxy compounds include amines, acid anhydrides, and acids. Acid anhydride-based compounds easily break anhydride groups (anhydrides) due to moisture, which initiates the reaction. Since it can also play a role, many aromatic amine compounds are mainly used.

In many cases, it can be seen that an aromatic amine-based compound is used, and the aliphatic amine-based curing agents are rarely used because of their high reactivity with the epoxy group at low temperature and room temperature, and their storage life is very short. Dicyandiamide (DICY) decomposes at 145-154 ° C. to other reactive compounds, including nitrogen, which acts as a curing agent. The curing agent 4,4'-diaminodiphenylsulfone (DDS) [4,4'-diaminodiphenylsulfone (DDS)] is poorly soluble and may not be completely dissolved in the epoxy resin. It exhibits latent curing characteristics. The curing agent is designed to react almost quantitatively with the epoxy group and to adjust the mixing ratio to obtain optimum physical properties in actual use.

In order to complete the curing reaction in a short time, that is, to promote the curing reaction (catalysts) is used. Borontrifluoride (BF ₃ ) [Brontrifluoride (BF ₃ )] forms a complex with monoethylamine (monoethylamine) to exhibit the properties of the latent curing agent. Various other amines may be used and in practice, the epoxy compounds, curing agents, and catalysts may be designed and combined to meet the requirements of the final structural properties, prepreg manufacturing processability, workability, and storage / transportation. Will be decided.

Low viscosity resin is used because it lowers the viscosity of the entire resin system, facilitates the preparation of prepreg, and improves the fluidity of the resin during curing.In order to control the crosslinking density of aromatic epoxy resins with different epoxy functional groups use. The shape or amount of epoxy compound can be changed to improve processing and handling characteristics and to meet the properties of moldings.

Fiber-reinforced composite materials have been applied to various structures not only for general industrial structures but also for aerospace industries by replacing existing metal products based on excellent physical properties, and the demand is expected to increase rapidly. In addition, carbon fiber and prepreg materials based on carbon fibers are also a time when companies that require these materials are experiencing great difficulties due to the surge in world demand.

The importance of carbon fiber-reinforced epoxy resin composites used for primary structures compared to the existing technology for manufacturing secondary structure composites for aviation using 121 ℃ (250 ℉) epoxy resins, and the development of advanced materials In order to improve the storage at low temperature, high temperature 176 ℃ (350 ℉) epoxy and high heat-resisting resin and prepreg based on this require more technology for securing resin composition for high temperature curing and developing resin compounding technology. It's happening.

Therefore, the present inventors have excellent multi-functionality and high solubility, and are excellent in prepreg manufacturing workability, high glass transition temperature, excellent high temperature property, excellent chemical resistance, high mechanical properties at high temperature, and show very long pot life at working temperature. The present invention has been completed by researching and developing the present invention to provide an epoxy resin composition for a 176 ° C. (350 ° F.) curable prepreg with a resin composition that is easy to manufacture a large composite structure.

In the present invention, tetraglycidyl methylene dianiline (tetraglycidylmethylenedianiline), a tetrafunctional epoxy resin, and 4,4'-diaminodiphenyl sulfone (DIES), which is an aromatic amine curing agent. '-diaminodiphenylsulfone (DDS)], a curing accelerator is a boron trifluoride-amine monoethylenically _{(BF 3 -MEA) [BoronTrifluoride- monoethylene} amine (BF 3 -MEA)] of methyl ethyl ketone to a resin composition combining [Em MEK] Carbon fiber-reinforced epoxy resin composites used in primary structures by mixing them in solution and applying them to the resin formulation of 176 ° C (350 ° F) epoxy high heat-resistant resins. Made it possible.

According to the epoxy resin composition for curing prepreg in the present invention, it is polyfunctional and has good solubility and is excellent in prepreg manufacturing workability.

It has high glass transition temperature, excellent high temperature property, excellent chemical resistance, high mechanical properties at high temperature, and very long pot life at working temperature, making it easy to manufacture large composite structures.

The present invention relates to tetraglycidyl methylenedianiline (tetraglycidylmethylenedianiline), which is an epoxy resin having a tetrafunctionality represented by the general formula (I), and an aromatic amine curing agent represented by the general formula (II) in the epoxy resin composition. '-Diaminodiphenylsulfone (dies) [4,4'-diaminodiphenylsulfone (DDS)], and a boron trifluoride-monoethylene amine (BF ₃ -MEA), a curing accelerator represented by the formula (III) [BoronTrifluoride -Monoethylene Amine (BF ₃ -MEA)] was mixed in a weight ratio of 100/36 / 0.5% by weight to form a resin composition, and the methyl ethyl ketone (MEK) solution was added for 30 to 200% by weight for its use. do.

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Hereinafter, the present invention will be described in detail.

The present invention relates to tetraglycidyl methylenedianiline, which is an epoxy resin having the tetrafunctionality of the above formula, and 4,4'-diaminodiphenylsulfone (dies) [4,4'-], which is an aromatic amine curing agent. diaminodiphenylsulfone (DDS)], a curing accelerator and a boron trifluoride-amine monoethylenically contribute to fiber-reinforced and contains a _{(BF 3 -MEA) [BoronTrifluoride- monoethylene} amine (BF 3 -MEA)] developed an epoxy resin, or 121 ℃ ( Epoxy resin composition for prepreg with improved product development and improved storage properties at low temperatures compared to 250 ° F.).

The present invention is tetraglycidyl methylene dianiline, which is an epoxy resin having a tetrafunctional epoxy group represented by the above formula (I), and 4,4'-diamino, which is an aromatic amine curing agent represented by the above formula (II). Diphenylsulfone (dies) [4,4'-diaminodiphenylsulfone (DDS)] and boron trifluoride-monoethylene amine (BF ₃ -MEA), a curing accelerator represented by the formula (III) [BoronTrifluoride- Monoethylene Amine ( BF ₃ -MEA)] ratio of composition, that is, the viscosity of the resin solution having a weight ratio of 100/36 / 0.5 / 30% by weight of epoxy / DDS / BF ₃ -MEA / MEK, was suitable for coating. It was also observed that the viscosity increase was not so large even when left in an oven at 80 ° C. for 2 days.

1 is a graph showing the viscosity change with temperature and time of the curable epoxy resin composition for prepreg provided in the present invention.

As can be seen in Figure 1 it can be seen that this resin composition has a very low rate of viscosity increase over time.

In addition, in the case of a filament winding resin using a bifunctional diglycidyl ether bispenol-A (DGEBA) -based epoxy resin, it takes about twice the initial viscosity, that is, pot life. The resin composition was found to be very responsive when left at a relatively low temperature compared to the average of 10-12 hours. In addition, the higher the temperature left, the greater the increase in viscosity, which is a general tendency of thermosetting resin composition to undergo crosslinking by thermosetting reaction.

Table 1 shows the viscosity change over time at this temperature by the Brookfield and Gardner method to confirm the shelf life at 25 ℃ and 50 ℃.

Viscometer 25 ℃ storage (cps) 50 ℃ storage (cps) Brook field # 2, 60 rpm, 1min Initial: 153 Initial: 102 6hr elapsed: 170 After 3hr: 107 20hr elapsed: 199 After 6hr: 124 Elapsed 30hr: 198 11hr Elapsed: 155   Elapsed 76hr: 213  Elapsed 45hr: 169  After 6 days: 236 2 days elapsed: 187  After 7 days: 247 9 days pass: 369 After 13 days: 272 10 days elapsed: 380 After 14 days: 279 Elapsed 12 days: 402 After 23 days: 270 20 days pass: 510 25 days passed: 320     Elapsed 26 days: 620 After 28 days: 327     Elapsed 28 days: 680 Elapsed 36 days: 387      30 days elapsed: 710 Gardner (25 ℃) Initial: G-H      Initial: G + Day 1: H-    Day 1: H-I Day 2: H +    Day 2 elapsed: J Day 3: H +    Day 5: K-L After 20 days: K-L   10 days elapsed: O- 25 days pass: L- 20 days pass: P     30 days elapsed: M 30 days elapsed: More than T +

As a result of the analysis of Table 1, the epoxy resin composition for high temperature curing has a very good storage stability at relatively low temperature as a whole, and in view of these characteristics, workability and prepreg storage stability are also very high. It can be seen that it is excellent.

Hereinafter, an embodiment of the present invention will be described.

Experimental Example

In order to understand the curing pattern and characteristics of the cured epoxy / DDS resin composition, the resin specimens were prepared with the composition and curing cycle as variables.

At this time, the mixing ratio of each composition in the epoxy / DDS / BF ₃ -MEA was 100/36 / 0.5% by weight and used an open aluminum mold having a diameter of 10cm. Details of resin specimen preparation are as follows.

C-1: Epoxy / DDS [80 ° C. (12h) + 120 ° C. (2h) + 175 ° C. (4h)]

C-2: Epoxy / DDS / BF ₃ -MEA [80 ° C. (12h) + 120 ° C. (2h) + 175 ° C. (4h)]

C-3: Epoxy / DDS / BF ₃ -MEA [80 ° C. (4h) + 120 ° C. (2h) + 155 ° C. (4h)]

C-4: Epoxy / DDS / BF ₃ -MEA [80 ° C. (4h) + 120 ° C. (2h) + 155 ° C. (24h)]

C-5: Epoxy / DDS / BF ₃ -MEA [80 ° C. (4 h) +120 (40 h)

Experimental results C-1 and C-2 correspond to the case of curing at a relatively high temperature of 175 ℃ according to the recommended curing cycle, the difference is the use of a curing accelerator. In this case, the longer exposure time at 80 ° C was to qualitatively confirm the complete removal of MEK used as a solvent and the viscous behavior of exposure at 80 ° C. In both cases, the gelation progressed somewhat after 12 hours of exposure at 80 ° C., although it was fluid in the oven but slightly fluid at room temperature. In addition, the resin after exposure at 120 ° C. for 2 hours had some fluidity in the oven, but was a pale yellow, brittle solid at room temperature. There was little effect of the use of BF ₃ -MEA as a curing accelerator. After 4 hours of exposure at 17 ° C for the final curing, the specimens were obtained in both cases with a clear, yellow-free visual defect.

In addition, the state of the resin composition combined with a general difunctional epoxy resin and an aromatic amine curing agent was cured at a final curing temperature of 155 ° C., which is frequently used as a cycle for cure.

4 hours at 155 ° C. and 24 hours at 155 ° C. for C-3. As a result, in both cases a specimen was obtained that appeared to be hardened normally with the naked eye. In addition, C-5 corresponds to a case where the final curing temperature is set at a relatively low temperature of 120 ° C. and then cured in an oven for 40 hours. In this case as well, a light yellow specimen was obtained in which no defect could be observed by the naked eye. The thermal and basic properties of these specimens were tested and some of the experimental procedures are described below, and the results of C-2 are shown in Table 2.

Table 2 shows the evaluation items for C-2 (Epoxy ⁽¹⁾ / DDS ⁽²⁾ / BF ₃ -MEA ⁽³⁾ [80 ° C (12h) + 120 ° C (2h) + 175 ° C (4h)]) And the evaluation results.

     Evaluation item unit Result Assessment Methods Resin void content %  2.25 ASTM D2734 2. Tensile Strength MPa 67.3  ISO 527 3. Tensile modulus of elasticity GPa  2.53 ISO 527 4. Flexural Strength (r.t / 121 ℃) MPa  120.3 58.8  ISO 178 5. Flexural modulus of elasticity (r.t / 121 ℃) GPa 3.15 1.92   ISO 178 6. Resin Density g / cm ㅃ 1.20 Density measurement 7. Glass transition temperature (thermal characteristic)  % 181.5 HDT (ASTM D648) 8. Shrinkage % 0.38 Precision measurement

(week)

(1): EPIKOTE ^™ Resin 497 (manufactured by Hexion) was used as tetraglycidyl methylenedianiline, a tetrafunctional epoxy resin.

(2): EPIKURE ^TM Curing Agent 962 (manufactured by Hexion) was used as an aromatic amine curing agent, 4,4'-diaminodiphenylsulfone (DDS) [4,4'-diaminodiphenylsulfone (DDS)].

(3): BF ₃ -MEA (Hexion) was used as a boron trifluoride-monoethylene amine as a curing accelerator.

Although the technical spirit of the present invention has been described with reference to specific embodiments as described above, the protection scope of the present invention is not necessarily limited to these embodiments, and a simple design change within a range that does not change the technical gist of the present invention. In the case of substitution of common means, the scope of the present invention is clearly clarified.

1 is a graph showing the viscosity change with temperature and time of the curable epoxy resin composition for prepreg provided in the present invention

Claims (1)

In the epoxy resin composition, With respect to 100 weight% of tetraglycidyl methylene dianiline which is an epoxy resin which has a tetrafunctional by weight ratio, 36 weight% of 4,4'-diaminodiphenylsulfone (DDS) which is an aromatic amine hardening | curing agent,  An epoxy resin composition for a curable prepreg, wherein 0.5 wt% of boron trifluoride-monoethyleneamine is used as a curing accelerator.

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