KR20200079994A - Toughened Cycloaliphatic Epoxy Resin Curing Composition and Process for its Preparation - Google Patents

Abstract

The present invention relates to a curing composition of a cycloaliphatic-based epoxy resin, an epoxy resin modified with nanosilica, a curing agent and a curing accelerator. According to the present invention, the composition is formed by curing the mixture of two cycloaliphatic-based epoxy resins, the epoxy resin modified with nanosilica, the curing agent and the curing accelerator, having the viscosity of 100 to 500 cps at room temperature, in which the viscosity of the mixture is 5 to 30 cps at 120°C, the tensile strength after curing is 50MPa or more, the fracture toughness is 1.3 MPa·m^1/2, and a glass transition temperature is 230°C or higher based on a maximum value of DMA loss modulus. Accordingly, the present invention uses a cycloaliphatic-based epoxy resin and a cycloaliphatic modified epoxy resin modified with nanosilica, thereby obtaining high heat resistance, high toughness properties, and high heat resistance with a glass transition temperature of 230°C or higher while providing excellent processability with a lower viscosity than conventional resins for resin transfer molding.

Description

Toughened Cycloaliphatic Epoxy Resin Curing Composition and Process for its Preparation

The present invention relates to a toughened cycloaliphatic epoxy resin curing composition and a method for manufacturing the same, more specifically, low viscosity, excellent workability, excellent fracture toughness, high glass transition temperature, high heat resistance, high toughness properties It relates to an epoxy resin cured composition having a and a method for producing the same.

Epoxy resins are widely used in the composite material field because they have excellent thermal properties and excellent mechanical properties. The epoxy resin generally used is a bisphenol A type resin, but even if it uses a curing agent that has high heat resistance, most of them have a heat resistance of 200°C or less, so they do not fit the purpose of the study and use resins with excellent heat resistance. This is necessary.

In general, epoxy resins having high heat resistance include novolac-based epoxy resins, cycloaliphatic epoxy resins, and glycidylamine-type epoxy resins.

Of these, the cycloaliphatic epoxy resin is a type of epoxy that produces cycloaliphatic acid anhydrides such as hexahydrophthalic anhydride and methyl hexahydrophthalic anhydride through reaction with epichlorohydrin. It is commercialized and sold.

Glycidylamine type epoxy resins include diglycidyl aniline type, diglycidyl toluidine type, tetraglycidyl dimethyldiaminomethane type, tetraglycidyl diaminodiphenyl sulfone type, triglycidyl aminophenol type, And metatriglycidyl aminophenol type.

However, cycloaliphatic epoxy resins and glycidylamine-type epoxy resins have excellent heat resistance, but are often difficult to use because of their low toughness. Therefore, in order to solve this, a reactive rubber, a thermoplastic resin, an acrylic core cell, a block copolymer, etc. are modified and used, but the viscosity is greatly increased, so there are restrictions on use in processes requiring low viscosity such as resin transfer molding.

Resin transfer molding is a method of molding a product by curing and then injecting (impregnating) a resin by applying heat and pressure while maintaining a vacuum in a mold of a desired shape. The resin transfer molding method has a wider range of use than other molding methods, the equipment and equipment cost is low, and it is possible to easily mold large parts of complex shapes, and improve the mechanical properties of the product by controlling the amount and direction of the reinforcement. It is a molding method that has properties such as making it possible. Due to these advantages, it is widely applied to the aerospace field, where there are not many production units and high quality properties are required.

In general, an epoxy resin of bisphenol A type is mainly used as an epoxy resin that can be applied to resin transfer molding, and an acid anhydride, particularly methyl hexahydrophthalic anhydride, nadic methyl anhydride, hexahydro as a curing agent Talic anhydride and the like are frequently used, and amine curing agents include 4,4-methylenediamine (MDA), diethyltoluenediamine (DETDA), metaphenylene diamine, paraphenylene diamine, and isoprondiamine (IPDA), Metaxylenediamine (MXDA) and polyetheramines are frequently used.

Among them, the most used system for increasing the heat resistance in the aerospace field uses bisphenol A-type epoxy resin having an epoxy equivalent of 180 to 190 g/eq and methylene dianiline, and the glass transition temperature of this cured product is approximately 160 to 180℃. , Tensile strength is in the range of 40 ~ 70MPa.

The resin transfer molding method involves placing a fiber mat or preform in a mold and injecting a resin to mold it at a constant temperature, which is inevitably affected by the viscosity of the material. Therefore, the viscosity of the mixture of the epoxy resin and the curing agent at room temperature is low, and an epoxy resin system having a viscosity that can penetrate into the fiber is used, or the epoxy resin and the curing agent are pre-heated to artificially increase the injection temperature to enable resin transfer molding. For this, it is most preferable to maintain the viscosity of the epoxy resin and the cured product below 100 cps.

In general, as a curing agent that can be used with a cycloaliphatic epoxy resin to exhibit high heat resistance, resin transfer molding is performed with liquid curing agents such as methylnadic anhydride and hydrogenated methylnadic anhydride. It is desirable to harden it by raising the temperature.

However, since the cured product by the cycloaliphatic epoxy resin and the acid anhydride curing agent is very vulnerable to impact, various reactive rubbers (CTBN, ATBN, etc.), copolymers (ABS Block Copolymer), and acrylic core cells are generally used to improve toughness. Mixing, reacting, etc. improves the physical properties, but when the toughening agents are mixed with an epoxy resin, the viscosity rises excessively and the glass transition temperature falls.

(Patent Document 1) KR10-1462449 B1 (2014.11.11.)

The problem to be solved by the present invention is to use an epoxy resin having a low viscosity and high heat resistance, and at the same time mixing a toughening agent that does not damage the heat resistance while having a low viscosity with an epoxy resin to facilitate molding while providing high heat resistance and high toughness. To provide a low-viscosity cycloaliphatic epoxy resin curing composition capable of resin transfer molding.

The objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention is to achieve the above object, the cycloaliphatic epoxy resin cured composition according to a preferred embodiment of the present invention is a cycloaliphatic epoxy resin having a structural formula of Formula 1 or Formula 2 As a topical agent, cycloaliphatic epoxy resin modified with silica nanoparticles, curing agent is methylnadic anhydride curing agent having the structure of Chemical Formula 3, and 2-ethyl curing curing agent having the structure of Chemical Formula 4 below. It is prepared by mixing/curing -4-methylimidazole.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

According to a preferred embodiment, the curing composition is based on 100 parts by weight of the epoxy resin, methylnadic acid anhydride having the formula (3), 90 to 110 parts by weight, and cycloaliphatic epoxy resin reinforced with nanosilica having an average particle size of 20 nm. Mix 40 parts by weight.

According to a preferred embodiment, the curing composition has a viscosity of 1 to 50 cps at 100°C, which is the resin injection temperature, and after curing by heating at 160 to 200°C for 1 to 3 hours, the tensile strength is 50 Pa or more and the fracture toughness is Is 1.3MPa·m ^1/2 or more, and the glass transition temperature based on the maximum DMA loss modulus is 230°C or more.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

According to a preferred embodiment of the present invention, the curing step is a step of filling a composition for mixing the epoxy resin and the curing agent in a resin molding apparatus at room temperature ~ 100 ℃, heating to 160 ~ 200 ℃, and 160 ~ And heating at 200° C. for 1 hour to 3 hours to cure.

As described above, in the cycloaliphatic epoxy resin curing composition of the present invention, a subject having the structure of Formula 1 or Formula 2, which is a hexahydrophthalic acid anhydride or methyl hexahydrophthalic acid anhydride having a low viscosity, is used in the epoxy resin. The epoxy resin cured composition of the present invention has the advantage of excellent workability as a low viscosity at room temperature, and applies a curing agent mixed with methylnadic acid anhydride (NMA) having the structure of Formula 3 having high heat resistance properties to the conventional resin transfer molding resin It has the advantage of being able to have high heat resistance with a glass transition temperature of 230°C or higher while having excellent workability at a lower viscosity. Therefore, it is effective to use an acid anhydride curing agent having a low viscosity and excellent heat resistance at the same time as the use of an epoxy resin having a low viscosity and high heat resistance. In addition, by improving the brittleness of the epoxy resin with an average of about 20 nanometers of nano-silica, there is an advantage that it is possible to implement toughening without significantly increasing the viscosity.

1 is a graph showing DMA results according to a formulation for explaining the heat resistance of Example 1 of the present invention.
2 is a graph showing DMA results according to a formulation for explaining the heat resistance of Example 2 of the present invention.
3 is a graph showing DMA results according to a formulation for explaining the heat resistance of Comparative Example 1 of the present invention.
4 is a graph showing DMA results according to a formulation for explaining the heat resistance of Comparative Example 2 of the present invention.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims.

The terminology used herein is for describing the embodiments, and is not intended to limit the present invention. In the present specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other components other than the components mentioned.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains. In addition, terms defined in the commonly used dictionary are not ideally or excessively interpreted unless specifically defined.

Advantages and features of the present invention according to the present embodiment, and a method of achieving them will be clarified by referring to embodiments described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The cycloaliphatic epoxy resin curing composition according to an embodiment of the present invention includes a cycloaliphatic epoxy resin having a chemical structural formula of Formula 1 or Formula 2, an acid anhydride curing agent of Formula 3, a curing accelerator of Formula 4, and an average of 20 nm. It is formed by mixing and curing a mixture of cycloaliphatic epoxy resins containing 20 to 50% of nanosilica.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

The curing composition is mixed with 95 to 105 parts by weight of a methylnadic acid anhydride curing agent having the structure of Formula 3 with respect to 100 parts by weight of the epoxy resin. In addition, 10 to 40% of the cycloaliphatic epoxy resin containing 20 to 50% of the average particle is mixed, and 0.2 to 2 parts by weight of the curing accelerator of Chemical Formula 4 is mixed.

Preferably, the curing composition is a cycloaliphatic epoxy resin is provided with a hexahydrophthalic anhydride epoxy resin having an epoxy equivalent of 164 g/eq, and the curing agent is methylnadic acid anhydride and the acid anhydride equivalent is 178 g/eq. In addition, 20 parts by weight of cycloaliphatic (NANOPOX F 631 manufactured by EVONIK) mixed with 40% of nano-silica as a toughening agent, and the mixed viscosity at room temperature of the entire mixture thereof may be prepared as a liquid, low-conductivity mixture of 100-500 cps. Can.

The curing composition is capable of being injected at room temperature, the viscosity is 1-50 cps at a resin injection process temperature of 100° C., the tensile strength after curing is 50 MPa, the fracture toughness strength is 1.3 MPa·m ^1/2 or more, and the DMA device It is characterized in that the glass transition temperature based on the maximum loss modulus by 230°C or higher.

A method for producing a cycloaliphatic epoxy resin curing composition will be described in detail.

First, 100 parts by weight of a cycloaliphatic epoxy resin having the structural formula of Chemical Formula 1 or Chemical Formula 2, and 90 to 130 parts by weight of a methylnadic acid anhydride curing agent having the structure of Chemical Formula 3 are mixed. As the subject, a cycloaliphatic epoxy resin having the structural formula of Formula 1 or Formula 2 is optionally used, and it is also within the scope of the present invention to be used in combination. The main cycloaliphatic epoxy resin curing composition has a low viscosity and excellent workability. Then, 20 parts by weight of a cycloaliphatic resin (NANOPOF F631 manufactured by Evonik) mixed with nanosilica of 40% in size of 40% as a toughening agent was mixed, and 2-ethyl-4-methylimidazole (2E4MZ) was used as a curing accelerator. Mix.

After mixing the epoxy main material and the curing agent, it is a step of curing.

The curing step is cured by heating at a temperature of about 160 to 200°C for about 1 hour to 3 hours. Preferably, curing conditions of about 180° C. for 2 hours are preferred.

More specifically, in the curing step, a composition in which the epoxy resin and the curing agent are mixed is filled in a resin molding apparatus at 100° C., heated to 160 to 200° C., and 1 to 3 hours at 160 to 200° C. During heating, it hardens. Preferably, the resin molding apparatus is filled at 100° C., heated to 180° C., and cured for 2 hours at about 180° C. is preferred.

Table 1 is a chart showing the manufacturing conditions and physical properties of the cycloaliphatic epoxy resin curing composition according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 of the present invention as a table.

Example 1

Example 2
Comparative Example 1 Comparative Example 2 Hydrophthalic anhydride epoxy resin
(ES-602, Kukdo Finechem) 100 100 Methylhydrophthalic anhydride epoxy resin
(ES-604, Kukdo Finechem) 100 Nanosilica cycloaliphatic epoxy (NANOPOX F 631, Evonik) 20 20 Bisphenol A-based epoxy resin (KFR-502, Kukdo Chemical) 100 Methylnadic acid anhydride (NMA) 100 100 100 90 2-ethyl-4-methylimidazole (2E4MZ, BASF) 0.5 0.5 0.5 0.5 Mixing viscosity at 25°C (cps) 230 275 152 409 Tensile strength (MPa) 52 53 42 61 Glass transition temperature
(℃, based on maximum DMA loss modulus) 241.5 231.6 259.6 155.7 Fracture toughness strength (K _IC , MPa·m ^1/2 ) 1.30 1.32 0.75 1.09

As shown in Table 1, the main hexahydrophthalic acid anhydride epoxy resin was ES-602 of Kukdo Finechem, equivalent to 165, and the equivalent of methyl hexahydrophthalic anhydride epoxy resin was ES-604 of Kukdo Finechem. This product has an epoxy equivalent of 175 g/eq.

When the toughening agent was not mixed as a comparative example, and the bisphenol A-type epoxy resin, which is the most commonly used epoxy resin, was applied, it was compared with the examples of the present invention.

[ Example One]

20 g of hexahydrophthalic anhydride epoxy resin (ES-602, Kukdo Chemical) in a 500 mL flask and 20 g of cycloaliphatic epoxy resin (NANOPOX F 631, Evonik) mixed with nanosilica is preheated to 60° C., and 100 weight of MNA Part is added in an equivalent ratio of 1:1, and 0.5 parts by weight of 2E4MZ is added as a curing accelerator to maintain the temperature at 60°C. The mixture was mixed using a rotary stirrer for about 10 minutes at a predetermined time. The viscosity of this mixture was 230 cps at room temperature.

The cycloaliphatic epoxy resin curing composition according to the present embodiment may be formed by being injected into a pre-prepared mold preheated to 100°C and heating it to 180°C, followed by curing at 180°C for 2 hours.

For example, a mold made of 200 mm×200 mm size is preheated to 100° C. using a silicone rubber on a glass plate, and then the mixture is injected, then cured at 180° C. for 2 hours, and cooled to room temperature. Tensile strength specimens and glass transition temperature measurement specimens were processed and tested as plate-shaped specimens made by demoulding.

As a result, a tensile strength of 52 MPa, a glass transition temperature of 241.15°C based on the maximum value of the DMA loss modulus, and a fracture toughness strength of 1.3 MPa·m ^1/2 are high, while the tensile strength is relatively excellent, and a resin composition having excellent fracture toughness strength can be obtained. there was.

1 is a graph showing DMA results according to a formulation for explaining the heat resistance of Example 1 of the present invention.

DMA means an analysis method for measuring elastic modulus and energy loss according to temperature or frequency by applying oscillating force or deformation to a polymer specimen, and the glass transition temperature based on the maximum value of DMA loss modulus according to Example 1 by the graph of FIG. 1 It was confirmed that it was 241.15°C.

[ Example 2]

Methyl hexahydrophthalic anhydride epoxy resin (ES-604, Kukdo Chemical) was charged with 20 g of cycloaliphatic epoxy resin (NANOPOX F 631, Evonik) in which 100 g and nanosilica were mixed in a 500 mL flask, preheated to 60° C., and MNA 100 Weight parts are added in an equivalent ratio of 1:1, and 0.5 parts by weight of 2E4MZ is added as a curing accelerator to maintain the temperature at 60°C. The mixture was mixed using a rotary stirrer for about 10 minutes at a predetermined time. The viscosity of this mixture was 275 cps at room temperature.

The cycloaliphatic epoxy resin curing composition according to the present embodiment may be formed by being injected into a pre-prepared mold preheated to 100°C and heating it to 180°C, followed by curing at 180°C for 2 hours.

For example, a mold made of 200 mm ㅧ 200 mm size is preheated to 100° C. using silicone rubber on a glass plate, and then the mixture is injected, and then cured at 180° C. for 2 hours, and cooled to room temperature. Tensile strength specimens and glass transition temperature measurement specimens were processed and tested as plate-shaped specimens made by demoulding.

As a result, a tensile strength of 53 MPa, a fracture toughness strength of 1.3 MPa·m ^1/2 , and a maximum DMA loss modulus, a glass transition temperature of 231.6° C., is high heat resistant, relatively excellent in tensile strength, and a resin composition excellent in fracture toughness strength can be obtained. there was.

2 is a graph showing DMA results according to a formulation for explaining the heat resistance of Example 2 of the present invention.

DMA means an analysis method for measuring elastic modulus and energy loss according to temperature or frequency by applying oscillating force or deformation to a polymer specimen, and the glass transition temperature based on the maximum value of the DMA loss modulus according to Example 1 by the graph of FIG. 2 It was confirmed that it was 222.15°C.

[ Comparative example One]

The hexahydrophthalic anhydride epoxy resin (ES-602, Kukdo Chemical) is pre-heated to 60°C after quantifying 100 g in a 500 mL flask, and 100 parts by weight of MNA is added in an equivalent ratio of 1: 1, and 0.5 parts by weight of 2E4MZ is added as a curing accelerator. Maintain at 60°C. The mixture was mixed using a rotary stirrer for about 10 minutes at a predetermined time. The viscosity of this mixture was 152 cps at room temperature.

The cycloaliphatic epoxy resin curing composition according to the present embodiment may be formed by being injected into a pre-prepared mold preheated to 100°C and heating it to 180°C, followed by curing at 180°C for 2 hours.

For example, a mold made of 200 mm×200 mm size is preheated to 100° C. using a silicone rubber on a glass plate, and then the mixture is injected, then cured at 180° C. for 2 hours, and cooled to room temperature. Tensile strength specimens and glass transition temperature measurement specimens were processed and tested as plate-shaped specimens made by demoulding.

As a result, a tensile strength of 42 MPa, a fracture toughness strength of 0.75 MPa·m ^1/2 , and a DMA loss modulus based on the maximum glass transition temperature of 259.6° C. were very high heat resistance, but a tensile strength and a fracture toughness strength were obtained.

3 is a graph showing DMA results according to a formulation for explaining the heat resistance of Comparative Example 1 of the present invention.

DMA refers to an analysis method that measures elastic modulus and energy loss according to temperature or frequency by applying vibrating force or deformation to a polymer specimen, and the glass transition temperature based on the maximum value of DMA loss modulus according to Comparative Example 1 by the graph of FIG. 3 It was confirmed that it was 259.6°C.

[ Comparative Example 2 ]

Bisphenol-based epoxy resin (KFR-503, Kukdo Chemical) is pre-heated to 60°C after quantifying 100 g in a 500 mL flask, 100 parts by weight of MNA is added at a ratio of 1 to 1, and 0.5 parts by weight of 2E4MZ as a curing accelerator is added to 60°C. Keep it with. The mixture was mixed using a rotary stirrer for about 10 minutes at a predetermined time. The viscosity of this mixture was 230 cps at room temperature.

The cycloaliphatic epoxy resin curing composition according to the present embodiment may be formed by being injected into a pre-prepared mold preheated to 100°C and heating it to 180°C, followed by curing at 180°C for 2 hours.

For example, a mold made of 200 mm×200 mm size is preheated to 100° C. using a silicone rubber on a glass plate, and then the mixture is injected, then cured at 180° C. for 2 hours, and cooled to room temperature. As a plate-shaped specimen made by demoulding, a tensile strength specimen and a glass transition temperature measuring specimen based on the maximum value of DMA loss modulus were processed and tested.

As a result, the tensile strength is 62MPa, the fracture toughness strength is 1.09MPa·m ^1/2 , and the DMA loss modulus is based on the maximum glass transition temperature of 160.05℃, which is relatively excellent in tensile strength and excellent fracture toughness strength, but the heat resistance is greatly reduced. Was able to get

4 is a graph showing DMA results according to a formulation for explaining the heat resistance of Comparative Example 2 of the present invention.

DMA refers to an analysis method that measures elastic modulus and energy loss according to temperature or frequency by applying oscillating force or deformation to a polymer specimen, and the glass transition temperature based on the maximum value of the DMA loss modulus according to Comparative Example 2 by the graph of FIG. It was confirmed that it was 155.7°C.

Claims (6)

In the cycloaliphatic epoxy resin curing composition,
The subject is a cycloaliphatic epoxy resin having a structural formula of Formula 1 or Formula 2 below, a cycloaliphatic epoxy resin in which 20 nm nanosilica is mixed as a strengthening agent, and a curing agent is methyl having the structure of Formula 3 below. Epoxy resin curing composition characterized by mixing/curing nadic acid anhydride with 2-ethyl-4-methylimidazole as a curing accelerator.
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

According to claim 1,
The curing composition is an epoxy resin composition characterized by improving the fracture toughness strength by mixing 20 parts by weight of 20nm silica-modified epoxy resin with respect to 100 parts by weight of the epoxy resin The curing composition of claim 1, wherein the curing composition has a viscosity of 1 to 20 cps at a resin injection temperature of 100°C, a tensile strength of 50 MPa or more after curing, and a fracture toughness strength of 1.3 MPa·m ^1/2 or more. Epoxy resin curing composition, characterized in that. In the method for producing a cycloaliphatic epoxy resin curing composition,
Methylnadic acid anhydride having formula (4) as a curing agent, 10 to 50 parts by weight of epoxy resin modified with nano-silica at 20 parts by weight of 100 parts by weight of cycloaliphatic epoxy resin having the structural formula (1) or (2) Mixing 95 to 105 parts by weight; And
Method for producing an epoxy resin curing composition comprising a; curing by heating for 1 hour to 3 hours at 160 ~ 200 ℃.
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

The method of claim 4,
The curing agent is a method of producing an epoxy resin curing composition, characterized in that present in the liquid phase of 100 ~ 500cps at room temperature. The method of claim 4,
The curing step
Filling a composition in which the epoxy resin and the curing agent are mixed in a resin molding apparatus at 120 ℃,
Method for producing an epoxy resin curing composition comprising the step of heating to 160 ~ 200 ℃ and curing for 1 hour ~ 3 hours at 160 ~ 200 ℃ furnace.

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