JP2001302760A - Epoxy resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition which is stable at room temperature, can be primarily cured at a relatively low temperature, e.g. at 70-100 deg.C, in a short time, e.g. within 10 h, exhibits a glass transition temperature of 150 deg.C or higher when secondarily cured at 130 deg.C or higher, and gives a cured item excellent in high-temperature mechanical properties, especially an epoxy resin composition which can be suitably used as a matrix resin for a fiber- reinforced composite material. SOLUTION: This composition mainly comprises (a) 100 pts.wt. epoxy resin containing a trifunctional or higher epoxy resin and (b) 3-40 pts.wt. heat-curing- type latent curing agent activated at 70-100 deg.C and satisfies the requirements (1) to (3): (1) the viscosity increase when left standing at 25 deg.C for 3 weeks after the preparation is not higher than 2 times the viscosity just after the preparation; (2) after the primary curing at 100 deg.C or lower for 10 h or shorter, the degree of curing is 70% or higher or the tensile shear strength (adhesive strength) according to JIS K 6848 and 6850 is 10 MPa or higher; and (3) the glass transition temperature of a cured item obtained by the secondary curing at 130 deg.C or higher is 150 deg.C or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy which can be cured in a short time at a temperature of 100 ° C. or less and then cured at a temperature higher than the primary curing temperature to obtain a cured product having high heat resistance. It relates to a resin composition.

[0002]

2. Description of the Related Art Fiber reinforced composite materials (hereinafter referred to as FRP)
Is widely used in sports and leisure, aircraft, and industrial applications. As a general FRP molding method, there is a method of molding using a molding die. For example, a reinforcing fiber material such as a cloth is attached to a molding die while impregnating the resin, and this is repeated, then cured, and then removed from the mold to obtain a molded product. The impregnated so-called prepreg is attached to the molding die and attached, and this is repeated and then cured, and the hand lay-up method of obtaining the molded product by releasing from the die, or setting the reinforcing fiber material such as cloth in the molding die, Resin transfer molding (RTM) that cures after injecting resin into a mold and removes the mold to obtain a molded product
There is known a method or a method of cutting a reinforcing fiber into short fibers, injecting a molding compound mixed with a resin into a molding die, and curing the molding compound to obtain a molded product.

[0003] Molds of various materials are used. Metal molds are excellent in heat resistance and durability,
The production of the mold requires time and effort and is expensive. On the other hand, resin molds are inferior in heat resistance and durability, but are inexpensive. In order to respond to various needs in recent years, small-quantity multi-product production has been increasing, and in many cases, a resin mold is used.
However, when a resin mold is used, the heat resistance of the mold at high temperatures using the mold is not sufficient because the mold itself has insufficient heat resistance.
There is a problem that it is difficult to mold P and cannot be applied to the molding of a molded article having high heat resistance.

[0004] In the case of producing a FRP mold, a master mold is raised from a real product, and a prepreg or the like is laminated on the master mold and cured to produce an FRP mold. In order to obtain it, it is necessary to mold at a high temperature, and an FRP mold having high heat resistance is required. In order to mold the FRP mold having high heat resistance, the master mold also needs to have heat resistance. As a result, the production of the master mold has required a great deal of cost and labor.

[0005] Therefore, as a method of obtaining an FRP molded product having high heat resistance using a molding die having low heat resistance such as resin, a relatively low temperature (100 ° C. or less) using a molding die having low heat resistance such as resin is used. FR is hardened so that it can be removed from the mold and retains its shape sufficiently. Then, it is removed from the mold and heated and left at a higher temperature for secondary curing to achieve high heat resistance.
Attention has been paid to a method for obtaining a P-shaped product. The same applies to the case where an FRP mold having high heat resistance is manufactured using a master mold having low heat resistance.

[0006] In recent years, the technology of a resin which is relatively stable at room temperature and which cures at a relatively low temperature of 70 to 100 ° C.
Although disclosed in Japanese Patent No. 302412, any of the techniques cures at low temperatures and provides excellent mechanical properties, but does not provide sufficient heat resistance even after secondary curing at high temperatures. On the other hand, a resin giving a cured product having good heat resistance is 100
There is a problem that it takes a long time to cure the resin at a relatively low temperature of not more than ℃ until it can be released from the mold.

[0007]

The present invention is stable at room temperature, can be primary-cured at a relatively low temperature (100 ° C. or less) in a short time (within 10 hours), and has heat resistance at a high temperature (130 ° C. or more) with secondary curing. To provide an epoxy resin composition having a high cured product (Tg of 150 ° C. or higher) and excellent mechanical properties at high temperatures, and particularly an epoxy resin which can be used as a matrix resin for a fiber-reinforced composite material. It provides a composition.

[0008]

That is, the gist of the present invention is to provide (a) 100 parts by weight of an epoxy resin containing a trifunctional or higher functional epoxy resin and (b) a heat-curable latent resin activated at 70 to 100 ° C. An epoxy resin composition containing 3 to 40 parts by weight of a curable curing agent as a main component, comprising the following (1) to (3):
Is an epoxy resin composition characterized by satisfying the following conditions. (1) The viscosity increase after standing at 25 ° C. for 3 weeks after preparation is not more than twice that immediately after preparation. (2) In primary curing at a temperature of 100 ° C. or less within 10 hours, the degree of curing is 70% or more or JIS-K-6848, 6
Tensile shear strength (bonding strength) based on 850 is 10 MPa
That is all. (3) The glass transition temperature of the cured product in secondary curing at 130 ° C. or higher is 150 ° C. or higher.

In particular, the epoxy resin containing a trifunctional or higher functional epoxy resin of the component (a) is a novolak type epoxy resin of the structural formula (1) and / or an epoxy resin containing tetraglycidyldiaminodiphenylmethane, and the component (b) Of 7
An epoxy resin composition which is an amine adduct type or microcapsule type latent curing agent as a heat curing type latent curing agent activated at 0 to 100 ° C.

[0010] The epoxy resin composition of the present invention has excellent stability at room temperature, and is cured to such an extent that it can be demolded by primary curing within 10 hours at a temperature of 100 ° C or less. 100 ℃
It is more preferable that the molding temperature be within 5 hours at the following temperature because the molding cycle can be shortened.

[0011] The term "stable at room temperature" means that the viscosity increase of the resin after standing at 25 ° C for 3 weeks after preparation is not more than twice that of immediately after preparation. When the increase in viscosity after standing at 25 ° C. for 3 weeks is 1.5 times or less, the working life is further increased, which is more preferable. The rate of increase in viscosity is derived by the following method.
The viscosity ηi at 40 ° C. of the resin immediately after preparation is measured with a parallel plate at a frequency of 10 radians / sec using DSR-200 manufactured by Rheometrics or an apparatus having equivalent performance. Next, the resin was left in a thermostat at 25 ° C. for 3 weeks,
Thereafter, the viscosity η at 40 ° C. was measured in the same manner, and η / ηi
To determine the viscosity increase ratio.

[0012] Curing to the extent that the mold can be removed by primary curing means that the calorific value of the resin immediately after resin preparation (Ei) and the calorific value of the first-cured resin (E1) are respectively measured by a differential scanning calorimeter (DSC). ), And the degree of curing is calculated by the following equation: Curing degree (%) = (Ei−E1) / Ei × 100. One of the indices is that the curing degree is 70% or more.

[0013] Alternatively, JIS-K-
It can be used as an index that the tensile shear strength (adhesive strength) determined by the method specified in 6848 and 6850 is 10 MPa or more.

As a measurement sample, first, 25 × 100 ×
A 12.5 mm wrap portion of a 1.5 mm aluminum plate (A2024P specified in JIS H4000) is polished with sandpaper (# 240) and degreased with acetone. Next, the resin is uniformly applied to the lap portion, and the lap portions of the aluminum plate treated in the same manner are overlapped. Finally, it is fixed at a pressure of 1 kgf / cm ² , cured first, and then gradually cooled to room temperature.

[0015] Further, the epoxy resin composition of the present invention obtains a molded article having high heat resistance by secondary curing. The cured product obtained by secondary curing at a curing temperature of 130 ° C or more has a glass transition temperature of 150. C. or higher. Especially 150 ° C
When the glass transition temperature is 180 ° C. or higher due to the secondary curing at the above (for example, 180 ° C.), it is preferable because the heat resistance is further improved. The time for the secondary curing is not particularly limited,
It is preferably within 10 hours, more preferably within 5 hours.

The glass transition temperature of the cured product is measured by the following method. Using RDA-700 manufactured by Rheometric Co., Ltd. or a viscoelasticity measuring device having the same performance, the storage elastic modulus (G ′) when the temperature is raised stepwise in steps is measured at each temperature. The temperature is raised at a rate of 5 ° C./step. In each step, the temperature is maintained for 1 minute after the temperature is stabilized before measurement. The frequency is measured at 10 radians / second. The logarithmic value of G ′ is plotted against the temperature, and the temperature at the intersection of each tangent of the obtained G ′ curve is defined as the glass transition temperature. (Figure 1
reference)

In the epoxy resin composition of the present invention, an epoxy resin containing a trifunctional or higher functional epoxy resin is used as the component (a). As a result, a molded cured product having excellent heat resistance after the secondary curing can be obtained. In particular, 3 in component (a)
It is more preferable that the epoxy resin having a functionality of not less than 40% by weight, more preferably 60% by weight or more is contained. Examples of such trifunctional or higher functional epoxy resins include tetraglycidyl diaminodiphenylmethane, aminophenol type epoxy resin, aminocresol type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, and epoxy represented by the following structural formula (1). Resins and the like can be exemplified.

[0018]

Embedded image

In the structural formula, n is an integer of 0 or more.

In particular, a novolak type epoxy resin represented by the structural formula (1) and / or an epoxy resin containing tetraglycidyldiaminodiphenylmethane can be suitably used. It may also contain an epoxy resin having less than three functions, such as a bisphenol-type epoxy resin, a hydrogenated bisphenol-type epoxy resin, a biphenol-type epoxy resin, and a naphthalene diol-type epoxy resin. If it is desired to ensure heat resistance as much as possible, even if the epoxy resin has a relatively rigid skeleton structure such as a biphenol-type epoxy resin or a naphthalene diol-type epoxy resin as an epoxy resin having less than three functions, favorable results can be obtained. it can.

For example, bisphenol S having an SO ₂ structure
The use of a pre-reacted product of a type epoxy resin or an aromatic diamine and a bisphenol type epoxy resin is advantageous in that a cured product having relatively high heat resistance and toughness can be obtained.

Examples of the heat-curable latent curing agent which is activated at 70 to 100 ° C. of the component (b) include cyano compounds such as dicyandiamide, cyano compounds and urea compounds such as dichlorophenyldimethylurea and phenyldimethylurea. In addition to the combination system, an amine adduct-type curing agent can be used. As an amine adduct-type curing agent, it is commercially available from Ajinomoto Co. under the trademark "Amicure".
N-23 and MY-24.

Further, a microcapsule type curing agent is mentioned and is commercially available from Asahi Ciba Co., Ltd. under the trademark "NOVACURE". For example, Novacure HX3721 and HX3722 can be given.

[0024] Further, Fujicure FXE- manufactured by Fuji Kasei Kogyo Co., Ltd. has an active hydrogen part and a catalyst part in the molecule.
1000, FXR-1030, ACR Hardener H-3615, H-40 manufactured by AC R Co., Ltd.
70, H-3293, H-3366, H-3849, H
-3670, Cure duct P manufactured by Shikoku Chemicals Co., Ltd.
-0505, Cureazole 2E4MZ-CNS, C11
Z-CNS and C11Z-A can be exemplified.

The amine adduct-type curing agent and the microcapsule-type curing agent are relatively stable at room temperature to about 50 ° C. and hardly react when mixed with the epoxy resin.
It is activated at 0 ° C. to start the reaction, and is particularly preferably used.

The addition amount of these latent curing agents is suitably from 3 to 40 parts by weight based on 100 parts by weight of the epoxy resin of the component (a), and if less than 3 parts by weight, the primary curing is insufficient. When the amount exceeds 40 parts by weight, the stability of the resin at room temperature decreases, which is not preferable.

These latent curing agents may be used alone,
Alternatively, these latent curing agents may be used in combination with a urea compound, a cyano compound, a dihydrazide compound, an acid anhydride, or the like. Particularly, an aromatic urea compound is preferable, and a compound represented by the following structural formula (2) is preferable.

[0028]

Embedded image

X1 and X2 represent H or Cl, which may be the same or different.

[0030] Additives can be added to the epoxy resin composition of the present invention as long as the properties of the present invention are not impaired. For example, it is preferable to dissolve and add a thermoplastic resin, since the effects of suppressing the stickiness of the resin, adjusting the tack of the prepreg to an appropriate level, and suppressing the secular change of the tack are obtained. Examples of such a thermoplastic resin include a phenoxy resin, polyvinyl formal, and polyether sulfone.

[0031] For the purpose of improving the toughness of the cured product, a fine particle or short fiber thermoplastic resin or a rubber component may be added.
Polyamide, polyimide, polyurethane,
Examples thereof include thermoplastic resins such as polyethersulfone, rubber components such as acrylic rubber, butadiene rubber, and butyl rubber, and molecular terminal modified products thereof. Furthermore, fine particles of an inorganic component such as talc, silica, metal such as steel, etc. may be added for the purpose of improving the rigidity of the cured product.

The use of the epoxy resin composition of the present invention includes:
There is no particular limitation, and it can be used anywhere as long as the properties of the present epoxy resin composition can be utilized. However, it can be suitably used as a matrix resin for a fiber-reinforced composite material. In this case, the reinforcing fibers are not particularly limited, and all fibers generally used as reinforcing fibers of fiber-reinforced composite materials, such as carbon fibers, glass fibers, high-strength organic fibers, metal fibers, and inorganic fibers, can be used.

Particularly, in the epoxy resin composition of the present invention, 60
700Pa · sec when viscosity at 10 ℃ is 10Pa · sec or more
When the value is equal to or less than c, it can be suitably used as a so-called prepreg matrix resin in which reinforcing fibers are impregnated with a matrix resin to form a sheet.

If the viscosity at 60 ° C. is less than 10 Pa · sec, the prepreg is undesirably too tacky and sticky. On the other hand, the viscosity at 60 ° C. is 700 Pa · se
If it exceeds c, the drape property of the prepreg is poor,
It is not preferable because it is too hard. As a matrix resin for prepreg, the viscosity at 60 ° C. is 30 Pa · sec.
More preferably, the pressure is in the range of 500 Pa · sec or less. The method for measuring the viscosity is as described above, except that the measurement temperature is 60 ° C.

Further, if the film is formed into a film and the resin flow is set to a small value, or if a glass cloth or the like is impregnated with a resin, it can be used as a sheet-like adhesive. Furthermore, a microballoon or a foaming agent may be added as an additive to use as a lightweight auxiliary material.

[0036]

The present invention will be described in more detail with reference to the following examples. Abbreviations of compounds in Examples and Comparative Examples are as follows.

Ep604: Tetraglycidyl diaminodiphenylmethane “Epicoat 604” manufactured by Yuka Shell Co., Ltd. Tactix742: Solid trifunctional epoxy resin “TACTIX742” manufactured by Dow Chemical Company n = n in structural formula (1)
Epoxy resin Ep1032: Epoxy shell resin, special novolak type epoxy resin "Epicoat 1032S50" Epoxy resin of structural formula (1) N740: Dainippon Ink Co., Ltd., phenol novolak type epoxy resin "Epiclon N-740" Ep828 : Yuka Shell Co., Ltd., liquid bisphenol A type epoxy resin "Epicoat 828" Ep1001: Yuka Shell Co., semi-solid bisphenol A type epoxy resin "Epicoat 1001" EXA1514: Dainippon Ink Co., Ltd., bisphenol S
Type epoxy resin "Epiclon EXA-1514" HX3722: manufactured by Asahi Ciba, latent curing agent "NOVACURE HX3722" FXE1000: manufactured by Fuji Chemical Co., Ltd., latent curing agent "Fujicure FXE-1000" PN23: manufactured by Ajinomoto, latent curing Agent "Amicure P"
N-23 "Dicy: Yuka Shell Co., Ltd., dicyandiamide" Dic
y7 "PDMU: manufactured by BTR Japan, phenyldimethylurea" Omicure 94 "PES: manufactured by Sumitomo Chemical Co., Ltd., polyether sulfone" Sumika Excel PES 3600P "DDS: manufactured by Wakayama Seika Co., Ltd., diaminodiphenyl sulfone" Seika Cure S " Aerosil 300: Nippon Aerosil Co., Ltd., "Aerosil 300" BF3MEA: Hashimoto Chemical Industries, Ltd. Boron trifluoride monomethylamine

Examples 1 to 11 The components (a) having the compositions shown in Tables 1 and 2 (the numerical values are parts by weight) were first uniformly mixed at 150 ° C. If there was an additive such as a thermoplastic resin, it was added at this time and dissolved or mixed. Next 50-60
After cooling to ℃, component (b) was added and mixed uniformly to prepare the epoxy resin composition of the present invention. The stability of the resin composition was evaluated by the method described above.

After the resin composition was heated to 60 ° C. and evacuated, it was cast on a glass plate having a thickness of 2 mm and subjected to a mold release treatment, sandwiched between glass plates subjected to the same treatment, and subjected to primary curing conditions. Cured. The degree of curing after the primary curing was measured by the method described above.
On the other hand, tensile shear strength (adhesion strength) of resin after primary curing
Was measured by the method described above.

Further, the composition was cured in a hot air oven in a free stand under each of the secondary curing conditions, and then the glass transition temperature was measured by the method described above. Furthermore, the value of G ′ at a high temperature (150 ° C., 180 ° C.) was determined as a standard for expressing resin properties at a high temperature. This is a measure of the development of physical properties at a high temperature when a composite material is formed.

(Comparative Example 1) Ep 60 at 130 ° C with the composition shown in Table 3.
Dissolve and mix DDS into 4, immediately reduce the temperature to 70 ° C,
BF3MEA was dissolved and mixed to prepare a resin composition. The present resin composition was stable at room temperature and had good heat resistance at a glass transition temperature of 205 ° C. when cured at 180 ° C. for 2 hours. However, in primary curing at 100 ° C. × 10 hours,
Poor curing.

(Comparative Example 2) Ep828, Ep1
001 was uniformly mixed at 120 ° C. Then, at 60 ° C, H
X3722 and PDMU were mixed to obtain a resin composition. In the same manner as in Example 1, the resin and the resin plate were evaluated. Table 3 shows the evaluation results. After the secondary curing, it did not have sufficient heat resistance.

(Comparative Example 3) Ep1032, Ep10
828 and Ep1001 were uniformly mixed at 120 ° C. Thereafter, PDMU and Dicy were added at 70 ° C. and dispersed and mixed. In the same manner as in Example 1, the resin and the resin plate were evaluated. Table 3 shows the evaluation results. After the secondary curing, it did not have sufficient heat resistance.

Examples 12 and 13 Resin compositions were prepared in the same manner as in Examples 2 and 5. The resin viscosities at 60 ° C. were 80 Pa · sec and 40 Pa · sec, respectively. These resin compositions were uniformly applied on release paper at 60 ° C. to prepare resin films having a basis weight of 80 g / m ² . Next, on a resin film, carbon fiber TR50S-12L manufactured by Mitsubishi Rayon Co., Ltd. is aligned and arranged in one direction so that the carbon fiber weight is 150 g / m ^2, and the resin is further heated and pressed to apply the carbon fiber to the carbon fiber. To obtain unidirectional prepregs. These prepregs had good tack and drape properties.

[0045] These prepregs were left at 25 ° C for 3 weeks,
The change with time of tack and drape of the prepreg was evaluated by touch. Tack after leaving for 3 weeks. There was little change in the drapability, and it had a good life.

[0046] These prepregs were laminated in 14 plies in one direction and primary cured by vacuum bag molding. The temperature condition of the primary curing is as follows.
It was left at 0 ° C. for 4 hours. After the primary curing, the formed plate was sufficiently cured to such an extent that the mold could be released sufficiently and no cracks would occur when cut with a diamond wet cutter.
G ′ was measured to determine the glass transition temperature, which was 115 ° C. and 102 ° C., respectively. The primary molded plate was further left in a hot air oven (free stand) to perform secondary curing. The temperature condition for the secondary curing is 3 from room temperature to 180 ° C.
Temperature, maintain at 180 ° C for 4 hours, and further to room temperature for 3 hours.
The cooling conditions were set over time. When the obtained cured molded plate having a thickness of about 2 mm was subjected to ultrasonic inspection, almost no voids were found in the former and some voids were found in the latter, but these prepregs had good moldability. I understood. Cut out the specimen from the hardened plate and G '
Was measured and the glass transition temperature was 185 ° C. and 186 ° C., respectively. ASTM D 2344
Room temperature (23 ° C), 100 ° C, 160 ° C, 18
The interlayer shear strength was measured at 0 ° C. Table 4 shows the results.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

The epoxy resin composition of the present invention is stable at room temperature and relatively low in temperature of 100 ° C. or less (70 to 100 ° C.).
℃) in a short time (within 10 hours)
A cured product obtained by secondary curing at a high temperature (130 ° C. or higher) higher than the secondary curing temperature has a high glass transition temperature (150 ° C. or higher) and further has excellent mechanical properties at a higher temperature. In particular, it can be suitably used as a matrix resin of a fiber-reinforced composite material in applications requiring heat resistance.

[Procedure amendment]

[Submission date] May 29, 2000 (2005.2
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the relationship between temperature and storage modulus.

[Explanation of Signs] G ‘: Storage elastic modulus

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumi Mitani 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Inside the Product Development Laboratory of Mitsubishi Rayon Co., Ltd. (72) Inventor Takumi Wakabayashi 4-Chome Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture No. 1-60 F term in Mitsubishi Rayon Co., Ltd. Product Development Laboratory (reference) 4J036 AD07 AD08 AD21 AF06 AF08 AF15 AF36 AH07 AH09 DA10 DC18 DC25 DC31 FA05 FB03 FB10 FB13 FB14 FB15 HA07 JA06 JA11

Claims (4)

[Claims] The main components are (a) 100 parts by weight of an epoxy resin containing a trifunctional or higher epoxy resin, and (b) 3 to 40 parts by weight of a heat-curable latent curing agent activated at 70 to 100 ° C. An epoxy resin composition comprising the following (1)
An epoxy resin composition characterized by satisfying (3) to (3). (1) The viscosity increase after standing at 25 ° C. for 3 weeks after preparation is not more than twice that immediately after preparation. (2) In primary curing at a temperature of 100 ° C. or less within 10 hours, the degree of curing is 70% or more or JIS-K-6848, 6
Tensile shear strength (bonding strength) based on 850 is 10 MPa
That is all. (3) The glass transition temperature of the cured product in secondary curing at 130 ° C. or higher is 150 ° C. or higher. 2. The epoxy resin containing a trifunctional or higher functional epoxy resin as the component (a) is a novolak epoxy resin of the following structural formula (1) and / or an epoxy resin containing tetraglycidyldiaminodiphenylmethane. The epoxy resin composition according to claim 1, 3. The latent curing agent of component (b) is an amine adduct-type latent curing agent.
The epoxy resin composition according to the above. 4. The epoxy resin composition according to claim 1, wherein the latent curing agent of the component (b) is a microcapsule-type latent curing agent. Embedded image In the structural formula, n is an integer of 0 or more.