JPH0565335A - Curing agent for epoxy resin - Google Patents

Abstract

PURPOSE:To obtain the subject agent which can give a cured epoxy resin excellent in heat resistance and mechanical strengths by mixing a specified dicarboxylic anhydride with hexahydrophthalic anhydride. CONSTITUTION:The objective epoxy resin curing agent is obtained by mixing 5-(2,4-dioxotetrahydro-3-furanylmethyl)norbornane-2,3-dicarboxylic anhydride (A) with hexahydrophthalic anhydride (B). When a conventional dibasic acid anhydride such as hexahydrophthalic anhydride is used, the heat resistance of a cured product is insufficient, and when an acid anhydride curing agent such as pyromellitic anhydride is used, the heat resistance of a cured product is excellent, but is difficultly mixable with an epoxy resin because of its high melting point. When the component A is used alone, it is easily handled and can give a cured product of excellent heat resistance, but the cured product is defective in hardness and brittleness. By mixing the component A with the component B, the resulting mixture can give a cured product excellent in heat resistance and mechanical strengths.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an epoxy resin curing agent, and more particularly to an epoxy resin curing agent containing two alicyclic carboxylic acid anhydrides.

[0002]

2. Description of the Related Art The use of alicyclic dicarboxylic acid anhydrides as epoxy resin curing agents is known in the art. For example, hexahydrophthalic anhydride is currently widely used as an epoxy resin curing agent. In addition, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride (Japanese Patent Publication No. 39-14521), norbornane dicarboxylic acid anhydride or methyl norbornane dicarboxylic acid anhydride (Japanese Patent Publication No. 62- No. 47891) is known.

However, these dibasic acid anhydrides including the widely used hexahydrophthalic anhydride have a problem that the heat resistance of the cured product is insufficient.

[0004] In recent years, the demand for heat resistance has increased with the advancement of technology for electronic devices and the like, and acid anhydride type curing agents such as pyromellitic acid anhydride and benzophenonetetracarboxylic acid anhydride have been developed. Was done. However, although the cured product obtained using these has excellent heat resistance, it has a working defect that the curing agent has a high melting point and is difficult to mix with an epoxy resin.

Furthermore, a novel compound, 5- (2,4-dioxotetrahydro-3-furanylmethyl) norbornane-2,3-dicarboxylic acid anhydride, which was previously filed by the present inventors (Japanese Patent Application No. 3-15763). No.) is easy to handle and gives a cured product having excellent heat resistance as an epoxy curing agent, but the cured product has properties of being hard and brittle, and therefore mechanical properties such as bending strength are slightly inferior.

[0006] Therefore, an object of the present invention is to provide an epoxy resin curing agent in which the above-mentioned drawbacks are improved.

[0007]

The present invention provides (A) 5- (2,4-
Dioxotetrahydro-3-furanylmethyl) norbornane-2,3-dicarboxylic anhydride (hereinafter sometimes abbreviated as HMNTC), and (B) hexahydrophthalic anhydride (hereinafter abbreviated as HHPA) The present invention provides an epoxy resin curing agent containing

First, the component (A) will be described. The HMNTC used in the present invention has the following formula (Formula 1):

[0009]

[Chemical 1] It has the structure shown by. This compound is 5- (2,4-
It can be easily prepared by hydrogenating dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic acid anhydride (hereinafter sometimes referred to as MNTC). MNTC is 5-methylene norbornane-
2,3-dicarboxylic anhydride or 1-methylnorbornene
It can be prepared by reacting -2,3-dicarboxylic acid anhydride and / or 5-methylnorbornene-2,3-dicarboxylic acid anhydride with maleic anhydride. One of the raw materials, 5-methylenenorbornane-2,3-dicarboxylic acid anhydride, has extremely high reactivity because it has a double bond at the terminal, and it reacts easily with maleic anhydride to give 5- ( This produces 2,4-dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic acid anhydride. The reaction is presumed to proceed according to the following formula. This is a kind of ene synthesis, and the ene synthesis itself is described, for example, in Japanese Examined Patent Publication No. 51955/1983.

[0010]

[Chemical 2] 5-methylene norbornane-2,3-dicarboxylic acid anhydride is
5-Methylnorbornene-2,3-dicarboxylic acid anhydride and /
Alternatively, it can be prepared by isomerization of 1-methylnorbornene-2,3-dicarboxylic acid anhydride in the presence of an acid catalyst. Here, "isomerization" broadly includes structural isomerization and stereoisomerization, and does not have a narrow meaning such as geometric isomerization or positional isomerization. 5-methylenenorbornane-2,3-dicarboxylic acid anhydride has two types, an endo form and an exo form, and either one may be used. It is also possible to use a mixture of both.

1-Methylnorbornene-2,3-dicarboxylic acid anhydride and 5-methylnorbornene-2,3-dicarboxylic acid anhydride (hereinafter sometimes abbreviated as 1-MeNA and 5-MeNA, respectively) are known. Is. Each of these two acid anhydrides has two stereoisomers, an endo isomer and an exo isomer, and either of them can be used. 5-MeNA and 1-MeNA, which are raw materials, can be produced, for example, as follows. That is, 1-methylcyclopentadiene (abbreviated as 1-MeCPD) and 2-
Methylcyclopentadiene (abbreviated as 2-MeCPD)
When reacted with maleic anhydride (Diels-Alder reaction), the endo form of 1-MeNA from 2-MeCPD becomes 2-
5-MeNA endo form is produced from MeCPD. 1-M
eCPD and 2-MeCPD are usually obtained as a mixture of the two, and it is not necessary to separate the two for the purposes here. The mixture of 1-MeNA and 5-MeNA thus obtained was subjected to the isomerization described below to obtain the en
The do-form produces an exo-form of 5-methylenenorbornane-2,3-dicarboxylic acid anhydride via the 5-MeNA exo-form, while the 5-MeNA endo-form directly produces 5-methylene. The endo form of norbornane-2,3-dicarboxylic acid anhydride is produced. In addition, some 5-MeNA endo-forms have 5-MeNA e
The exo form of 5-methylenenorbornane-2,3-dicarboxylic acid anhydride is produced via the xo form. In addition, 1-MeNA endo
When the body is heated in the absence of acid as described below, 5-MeNA
It isomerizes to the exo form, but does not further isomerize to the exo form of 5-methylenenorbornane-2,3-dicarboxylic acid anhydride. Methylnorbornene-2,3-dicarboxylic acid anhydride is generally commercially available, and it is also possible to use this one.

The isomerization reaction is carried out by using 5-methylnorbornene-2,3
It can be carried out by heating the dicarboxylic acid anhydride and / or 1-methylnorbornene-2,3-dicarboxylic acid anhydride in the presence of an acid. The acid used for the isomerization reaction is not particularly limited, and various known acids can be used. Examples include Bronsted acids such as aromatic sulfonic acids such as benzenesulfonic acid, paratoluenesulfonic acid and paraxylene-2-sulfonic acid, mineral acids such as sulfuric acid and hydrochloric acid, heteropolyacids such as molybdic acid, and carboxylic acids such as maleic acid. Examples of the acid include Lewis acids other than the above, such as aluminum chloride and boron fluoride. Further, since an acid anhydride such as maleic anhydride can react with water to generate an acid, the isomerization reaction may proceed even if an acid anhydride is used instead of the acid. Bronsted acid is preferably used. The amount of acid used is methylnorbornene-2,3-
About 0.01 to 5% by weight, especially about about 5% by weight of dicarboxylic acid anhydride
It is preferably 0.02 to 3% by weight. The temperature during heating is preferably about 120 to 250 ° C, especially about 150 to 230 ° C. The isomerization reaction by heating can be carried out batchwise or continuously. In the case of a batch system, the reaction time is preferably about 30 minutes to 10 hours, particularly about 1 to 5 hours.

The reaction between 5-methylenenorbornane-2,3-dicarboxylic acid anhydride and maleic anhydride is carried out by adding 0.5 to 5
Charged at a double molar ratio, preferably about 2 at about 160-220 ° C.
It is performed by heating and stirring for -24 hours. This reaction may be carried out in the presence of any catalyst. As a catalyst,
Lewis acids such as aluminum chloride and boron fluoride are preferable, but not limited thereto. The reaction does not require the use of a solvent, but it can be carried out in any solvent. Preferred solvents include chlorobenzene, xylene, mesitylene, triethylbenzene and the like.

In the above, 1-methylnorbornene-2,3-dicarboxylic acid anhydride and / or 5-methylnorbornene-
Isomerization of 2,3-dicarboxylic anhydride to give 5 as an intermediate
-Methylene norbornane-2,3-dicarboxylic acid anhydride was made once and then MNTC was made by ene synthesis. However, this isomerization and ene synthesis may be performed as one operation. That is, 1-methylnorbornene
Isomerization and ene synthesis occur sequentially by heating -2,3-dicarboxylic acid anhydride and / or 5-methylnorbornene-2,3-dicarboxylic acid anhydride in the presence of maleic anhydride.

After the above reaction, the product is preferably subjected to a purification treatment. Purification may be carried out by removing unreacted raw materials by simple distillation or the like, and then recrystallizing the obtained crude product. Examples of the recrystallization solvent include, but are not limited to, acetic anhydride and a ketone solvent such as methyl isobutyl ketone.

5- (2,4-dioxotetrahydro-3-furanylmethyl) -5-norbornene obtained as described above
By hydrogenating 2,3-dicarboxylic acid anhydride (MNTC), the HMNTC used in the present invention can be obtained.

The hydrogenation method is not particularly limited, and various known methods can be used. Examples thereof include, but are not limited to, a method of performing catalytic hydrogenation on MNTC, and a method of causing a combination of hydrogen iodide and red phosphorus or sodium and alcohol to act. The preferred method is hydrogenation by catalytic hydrogenation. Catalytic hydrogenation is usually
The MNTC is carried out by contacting with hydrogen while heating, preferably in the presence of a hydrogenation catalyst. Preferred catalysts include, but are not limited to, palladium, cobalt, nickel, platinum and the like. A carrier may be used in combination. The heating temperature is preferably about 80 to 300 ° C, more preferably about 120 to 250 ° C. The hydrogen pressure during the hydrogenation reaction is preferably about 10 to 150 kg / cm ² G. The reaction time is preferably 1 to 10 hours, more preferably 2 to 6 hours. No solvent is required for the hydrogenation reaction, but the reaction raw materials and products are solid at room temperature,
In addition, a solvent such as tetrahydrofuran may be used in order to smoothly proceed the hydrogenation reaction.

The MNT obtained by the above-mentioned synthesis method
It is also possible to subject C to hydrotreating without isolation or after a simple purification operation to give HMNTC.

After the above reaction, the product may be subjected to a purification treatment. The purification treatment can be performed, for example, by recrystallization using a solvent such as methyl isobutyl ketone.

HMNTC can be identified by measuring means such as IR and NMR. For example, the IR of the compound
, Peaks due to C═O stretching of the carboxylic acid anhydride are observed at 1770 to 1780 cm ⁻¹ and 1850 cm ⁻¹ . Further, in ¹ H-NMR, four −
CH ₂ - due to peak 8H min (starting material 5- (2,4
6H min for dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic anhydride, 4H min for 5-methylenenorbornane-2,3-dicarboxylic anhydride, 1-
Or 5-methylnorbornene-2,3-dicarboxylic acid anhydride is observed only for 2H), but the peak 6H due to six> CH- at δ 2.0 to 3.6 (5- (2,
4-dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic anhydride for 5H, 5-methylenenorbornane-2,3-dicarboxylic anhydride and 5-methylnorbornene-2,3- 4H for dicarboxylic acid anhydride, 1-
3H for methylnorbornene-2,3-dicarboxylic anhydride
Only minutes are observed). On the other hand, a peak at δ 5.5 to 5.6 due to = CH- of the norbornene ring (5- (2,4-dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic acid anhydride and 1-H for 5-methylnorbornene-2,3-dicarboxylic anhydride
, 1-methylnorbornene-2,3-dicarboxylic anhydride is observed for 2H), vinylidene peak (starting material 5-methylenenorbornane-2,3-dicarboxylic anhydride is observed for 2H) And a peak of a methyl group (observed for 3H in 1- or 5-methylnorbornene-2,3-dicarboxylic acid anhydride as a starting material) is not observed.

Next, the component (B) hexahydrophthalic anhydride itself is known. Hexahydrophthalic anhydride is
Also called cyclohexane-1,2-dicarboxylic acid anhydride,
The manufacturing method is known. Hexahydrophthalic anhydride is commercially available, and those commercially available products can also be used.

The preferable mixing ratio of (A) and (B) in the epoxy resin curing agent of the present invention is (B) 5 to 95 parts by weight, more preferably 95 to 5 parts by weight of (A). Is
(A) 80 to 5 parts by weight, (B) 20 to 95 parts by weight. (A)
If it is less than 5 parts by weight, the heat resistance of the cured product will not be improved so much, and if it exceeds 95 parts by weight, the heat resistance will be high but the mechanical strength will decrease.

The epoxy resin curing agent of the present invention comprises the component (A)
It can be produced by mixing and (B). For example, a method of heating and melt mixing, or mixing by dry blending can be used. Further, the components (A) and (B) may be separately added to the epoxy resin and mixed.

The epoxy resin which can be cured using the epoxy resin curing agent of the present invention is a compound having two or more epoxy groups in the molecule, for example, polyhydric phenol such as bisphenol A or 1,4-butanediol. Compounds such as polyglycidyl ethers of polyhydric alcohols such as phthalic acid, polyglycidyl esters such as hexahydrophthalic acid, amines, amides and compounds with heterocyclic nitrogen bases N-
Glycidyl derivatives, alicyclic epoxy resins, phenol novolac epoxy resins, orthocresol novolac epoxy resins, and the like.

The curing agent is preferably blended so that the acid anhydride group is 0.3 to 1.5 mol, and particularly 0.7 to 1.2 mol, relative to 1 equivalent of the epoxy group of the above epoxy resin. Is preferred.

The above-mentioned curing agent and epoxy resin can be mixed by an appropriate means and cured at preferably 50 to 200 ° C. For example, at 80-120 ℃ for 1-3 hours, then 150-180
It is particularly preferred that it be cured at 10 ° C for 10 to 20 hours.

Further, the epoxy resin composition containing the epoxy resin curing agent of the present invention can be cured as it is, but the curing of tertiary amine, tertiary amine salt, quaternary ammonium salt, imidazole, metal salt, etc. It is preferable to use an accelerator together because the curing time can be shortened.

The epoxy resin curing composition of the present invention comprises, in addition to the above-mentioned components, conventional additives such as asphalt, quartz powder, mica, glass fiber, fibrin, talc, clay, kaolin, bentonite, calcium carbonate, Fillers such as hydrated alumina or metal powder such as aluminum, dyes or pigments, molding lubricants, flame retardants (antimony trioxide, red phosphorus, etc.), organic solvents (eg xylene, toluene,
Methyl ethyl ketone, methyl isobutyl ketone, etc.) and the like.

The epoxy resin-cured composition of the present invention can be used as a material for heat-resistant casting or molding, varnish for coating, lamination or impregnation.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0031]

EXAMPLES In the following examples,% and parts mean% by weight and parts by weight, respectively.

[0032]

[Reference Example 1] equipped with a reflux condenser, a thermometer, and a stirrer
In a 500 ml four-necked flask, 300 g of endo-methylnorbornene-2,3-dicarboxylic acid anhydride (consisting of 58.5% 1-methyl and 41.5% 5-methyl) and 0.15 g paratoluenesulfonic acid were added. Was introduced and the reaction was carried out by stirring at 180 ° C. for 3 hours. Simple distillation yielded 287 g of a pale yellow, transparent liquid, which was separated from the catalyst and by-products which were heavies.
When the composition of this liquid was analyzed by gas chromatography, 8.8% endo-5-methylenenorbornane-2,3-dicarboxylic acid anhydride, 63.5% exo-5-methylenenorbornane-2,3-dicarboxylic acid anhydride, And unreacted methylnorbornene-2,3-dicarboxylic acid anhydride 27.7%. The structure of the product was identified by infrared absorption spectrum (IR), ¹ H-NMR and the like. For example, in the IR of the compound, 1770 to 1780 cm ^-1 and 1850 cm
A peak due to C = O stretching of the carboxylic acid anhydride was observed at ^-1 . In ¹ H-NMR, δ 4.8-5.
2 due to H ₂ C = C <(this peak is not observed in the starting material methylnorbornene-2,3-dicarboxylic acid anhydride) at δ 1.8 due to —CH ₂ — (2H for starting material) is 2.8-3.6
A peak due to the proton bonded to the tertiary carbon atom of the norbornane ring was observed at. = CH of norbornene ring
No peak due to − was observed.

Then, in a 1000 ml four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, 270 g of the pale yellow transparent liquid obtained above and 294 g of maleic anhydride were placed, and 1
The mixture was stirred at 80 ° C for 6 hours. Next, simple distillation is performed under a pressure of 5 mmHg until the kettle temperature reaches 180 ° C, and unreacted 5-methylenenorbornane-2,3-dicarboxylic acid anhydride and methylnorbornene-2,3-dicarboxylic acid anhydride are reacted. And maleic anhydride was removed, 126 g of product was obtained.

The structure of this compound was identified by infrared absorption spectrum (IR) and ¹ H-NMR. For example, in the IR of the compound, 1770 to 1780 cm ^-1 and 1850
A peak due to C = O stretching of the carboxylic acid anhydride was observed at cm ^-1 . In ¹ H-NMR, δ 1.8-
Peak of 6H due to three —CH ₂ — in 2.2 (2H for 1- or 5-methylnorbornene-2,3-dicarboxylic anhydride as starting material, 5-methylenenorbornane-2,3-dicarboxylic anhydride Only 4H is observed in the object), but δ
Peaks of 5H due to five> CH- in 2.8 to 3.6 (4H minutes for 5-methylenenorbornane-2,3-dicarboxylic anhydride and 5-methylnorbornene-2,3-dicarboxylic anhydride as starting materials, 1-Methylnorbornene-2,3-dicarboxylic anhydride is observed only for 3H), and a peak of 1H due to = CH- of norbornene ring is observed at δ 5.5 to 5.6, while the peak of methyl group is observed. (The starting material 1- or 5-methylnorbornene-2,3-dicarboxylic anhydride is observed for 3H) and the vinylidene peak (starting material 5-methylenenorbornane-2,3-dicarboxylic anhydride is 2H). Minute observed) was not observed. From these, it was found that the product was 5- (2,4-dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic acid anhydride.

120 g of the product obtained above, 2.4 g of palladium catalyst are placed in a 500 ml autoclave equipped with a stirrer.
(5 wt% metal palladium was supported) and 120 g of tetrahydrofuran as a solvent were charged, and the inside of the autoclave was replaced with hydrogen. Then, the autoclave was heated to 120 ° C. under a hydrogen pressure of 80 kg / cm ² G and hydrogen was stirred for 4 hours. An addition reaction was performed. After the reaction is completed, the catalyst is removed by vacuum filtration, and then the mixture is gradually heated at normal pressure to 150 to 170 ° C (becomes solid unless heated), and then distilled at normal pressure. Tetrahydrofuran, which is a solvent, was completely distilled off under reduced pressure to obtain 112 g.
The product was obtained. The results of analysis of this product are shown in Table 1.

[0036]

[Table 1]

* Δ (unit: ppm), and the values in parentheses represent the area intensity in terms of the number of corresponding protons. From the above, the product of the present example is 5- (2,4-dioxotetrahydro-3-furanylmethyl). ) Norbornane-2,3-dicarboxylic acid anhydride was found. The iodine value of the product 5- (2,4-dioxotetrahydro-3-furanylmethyl) -5-norbornene-2,3-dicarboxylic acid anhydride before hydrogenation was 88.2. The reduction of iodine value in the product after hydrogenation to 2.6 supports the above conclusion.

[0038]

Example 1 Final product obtained in Reference Example (HMN
TC) 30 parts, and HHPA (trade name; RIKACID HH,
70 parts by Shin Nippon Rika Co., Ltd., 100% purity, 120
The epoxy resin curing agent was manufactured by placing in an oven at ℃ and heating and mixing to make it uniform.

Next, an epoxy resin (trade name; Epicoat)
828, made by Yuka Shell Co., Ltd.) 100 parts and 77 parts of the epoxy resin curing agent obtained above are mixed at 110 ° C. and then cooled to 80 ° C., and 2-ethyl-4-methylimidazole as a curing accelerator. 0.5 part (manufactured by Shikoku Kasei Co., Ltd.) was added and stirred to homogenize. This compound was cured at 100 ° C. for 2 hours and then at 170 ° C. for 15 hours to obtain a cured product.
The heat distortion temperature (HDT) and bending strength of this cured product were measured according to JIS K6911. The results are shown in Table 2.

[0040]

Examples 2 to 4 and Comparative Examples 1 and 2 Compounds were prepared in the same manner as in Example 1 except that the composition and amount of the epoxy resin curing agent were as shown in Table 2, and the curing reaction was carried out under the same conditions. It was The heat distortion temperature (HDT) and bending strength of the obtained cured product were measured in the same manner as in Example 1. The results are shown in Table 2.

[0041]

[Table 2]

From Table 2, the epoxy resin curing agents of Examples 1 to 4 containing both HMNTC and HHPA were HHPA.
It can be seen that the heat resistance is improved as compared with Comparative Example 1 in which HMNT was used alone, and the mechanical strength was improved as compared with Comparative Example 2 in which HMNTC was used alone.

[0043]

The heat resistance and mechanical strength of the cured product using the epoxy resin curing agent of the present invention are excellent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiro Ueno 1-3-1, Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Tonen Research Institute

Claims (2)

[Claims] 1. (A) 5- (2,4-dioxotetrahydro-3-
Furanylmethyl) norbornane-2,3-dicarboxylic acid anhydride, and (B) hexahydrophthalic anhydride as an epoxy resin curing agent. 2. The epoxy resin curing agent according to claim 1, which comprises (A) and (B) in a weight ratio of 5:95 to 95: 5.