JP2002155070A - Method for producing low-viscosity liquid acid anhydride and epoxy resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a low-viscosity liquid acid anhydride having liquid stability even at -20 deg.C and giving an epoxy resin cured product of uniform hue, and to provide an epoxy resin composition comprising the liquid acid anhydride and an epoxy resin and giving a cured product of excellent characteristics. SOLUTION: This method for producing a low-viscosity liquid acid anhydride comprises the following process: a 3-methyl-tetrahydrophthalic anhydride/4- methyl-tetrahydrophthalic anhydride mixture synthesized from maleic anhydride and a C5-fraction with the cyclopentadiene content reduced to <=10 wt.% based on the total amount of trans-piperylene, isoprene and cyclopentadiene is heated in the presence/absence of a stereoisomerization catalyst to effect stereoisomerization so that the isomerization percentage for 3-methyl- tetrahydrophthalic anhydride comes to >=70% followed by heating in the presence of a structural isomerization catalyst to effect the isomerization percentage for 4-methyl-tetrahydrophthalic anhydride at 35-60%. The other objective epoxy resin composition comprises the above liquid acid anhydride and an epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a low-viscosity liquid acid anhydride containing a specific methyltetrahydrophthalic anhydride and an epoxy resin composition containing the liquid acid anhydride and an epoxy resin. .

[0002]

2. Description of the Related Art Conventionally, methyltetrahydrophthalic anhydride (hereinafter abbreviated as Me-THPA) is well known as a curing agent for an epoxy resin, and a liquid at room temperature is generally known.

[0003] Such room temperature liquid Me-THPA includes 4-methyltetrahydrophthalic anhydride (hereinafter, referred to as "meth-THPA").
4Me-THPA) is heated in the presence of an acid catalyst such as sulfuric acid, phosphoric acid, BF ₃ complex, AlCl ₃ , cation exchange resin or the like to cause a structural isomerization reaction, thereby obtaining a double bond in a cyclohexene ring. Mixtures of structural isomers with different positions are known (see, for example, US Pat. No. 2,955).
9,599).

Further, by heating 3-methyltetrahydrophthalic anhydride (hereinafter abbreviated as 3Me-THPA) in the presence or absence of a basic catalyst, the position of the double bond in the cyclohexene ring shifts. A stereoisomer mixture obtained by a non-stereoisomerization reaction is known (for example, JP-A-54-22499).

Further, 4Me-THPA and 3Me-TH
A mixture of PA at a specific ratio is structurally isomerized (for example, Japanese Patent Publication No. 45-15495) or stereoisomerized (for example, Japanese Patent Application Laid-Open No. 54-151941) to obtain -15 to-. It is known that an acid anhydride mixture which remains liquid even at 20 ° C. can be obtained.

Further, 4Me-THPA and 3Me-THP
It is also known to obtain a liquid having a melting point of −20 ° C. or lower by stereoisomerizing a mixture obtained by mixing A in a specific ratio, followed by stereoisomerization (for example, JP-A-55-89).
277).

[0007]

SUMMARY OF THE INVENTION The above 3Me-THP
A and 4Me-THPA is usually pre-transformer or C ₅ fraction obtained by decomposing naphtha - after piperylene and isoprene extraction separation can be obtained by the respective Diels-Alder reaction with maleic anhydride. If 3Me-THPA and 4Me-THPA are prepared separately as described above, there is an advantage that the mixing ratio can be freely adjusted, but it is not economical because the extraction and separation of conjugated dienes requires a cost. Transformer C ₅ distillate - be reacted with no maleic anhydride to previous separation piperylene and isoprene, more economically yet energy-saving manner a liquid acid anhydride considered to be produced.

However, during the C ₅ fraction contained in large amount in addition to cyclopentadiene these conjugated dienes, to react with maleic anhydride endomethylene tetrahydrophthalic anhydride by-product in Me-THPA mixture It is expected to reduce purity and before reacting with maleic anhydride,
It is necessary to reduce the amount of cyclopentadiene in the C ₅ cut as much as possible. Trans content of cyclopentadiene - piperylene, C ₅ which is reduced to 10% by weight or less based on the total amount of isoprene and cyclopentadiene
When the fraction and maleic anhydride were reacted, 3Me-T
The weight ratio of HPA / 4Me-THPA is 25/75 to 35
/ 65, a Me-THPA mixture having an endmethylenetetrahydrophthalic anhydride content of 10% by weight or less was obtained.

When the thus prepared Me-THPA mixture was subjected to structural isomerization, a stable liquid was obtained at -20 ° C. for 15 days or more, but the viscosity was relatively high (25 ° C.).
And 62.8 mPa · s). When this Me-THPA mixture was stereoisomerized, it had a low viscosity (39.25 at 25 ° C.).
Although a liquid material of 7 mPa · s) was obtained, the stability of the liquid was inferior, and crystals were deposited when left in a constant temperature bath at −20 ° C. for several hours.

[0010] Similarly, when the product is structurally isomerized and then stereoisomerized, a liquid material having a low viscosity (37.3 mPa · s at 25 ° C) and free from crystals even when left at -20 ° C for -15 days is obtained. However, this isomerized product was still yellow-brown even after distillation, and there was a problem in that when the epoxy resin cured product was cut, the central part was colored red to brown, and the hue of the cured product became uneven. Was.

According to the present invention, the content of cyclopentadiene is reduced to 10% by weight or less based on the total amount of trans-piperylene, isoprene and cyclopentadiene.
3Me-THPA synthesized from ₅ fractions and maleic anhydride
/ 4Me-THPA weight ratio of 25/75 to 35/65
Low viscosity (50 mPa at 25 ° C.) by performing a specific isomerization on a 3Me-THPA mixture having a content of endmethylenetetrahydrophthalic anhydride of 10% by weight or less.
S or less) and a method for producing a liquid acid anhydride having liquid stability even at −20 ° C. and uniform hue of a cured epoxy resin. The present invention also provides an epoxy resin composition comprising the liquid acid anhydride and an epoxy resin, which has a low viscosity and excellent properties of a cured product.

[0012]

The present inventors have SUMMARY OF THE INVENTION, the content of intense research results of extensive, endomethylene tetrahydrophthalic anhydride synthesized from C ₅ fraction and maleic anhydride to solve the aforementioned problems Is less than 10% by weight of Me-T
The inventors have found that the problem can be solved by subjecting the HPA mixture to stereoisomerization and then to structural isomerization, thereby completing the present invention.
That is, the present invention, trans content of cyclopentadiene - piperylene, C ₅ which is reduced to 10% by weight or less based on the total amount of isoprene and cyclopentadiene
3Me-THPA synthesized from the fraction and maleic anhydride /
The weight ratio of 4Me-THPA is 25/75 to 35/65.
And heating the Me-THPA mixture having an endmethylenetetrahydrophthalic anhydride content of 10% by weight or less in the presence or absence of a stereoisomerization catalyst to obtain 3Me-THP.
After stereoisomerization so that the isomerization ratio of A is 70% or more,
The present invention relates to a method for producing a low-viscosity liquid acid anhydride in which the isomerization rate of 4Me-THPA is 35 to 60% by heating in the presence of a structural isomerization catalyst. The present invention also relates to an epoxy resin composition containing the liquid acid anhydride and an epoxy resin.

[0013]

In DETAILED DESCRIPTION OF THE INVENTION The present invention, it is essential to react directly with maleic anhydride without separating previously conjugated diene naphtha from C ₅ fraction obtained by thermal decomposition as described above. Generally, the C5 fraction contains ₅ to 8% by weight of trans-piperylene, 12 to 15% by weight of isoprene, and 16 to 20% by weight of cyclopentadiene as another conjugated diene. Cyclopentadiene reacts with maleic anhydride to produce endomethylenetetrahydrophthalic anhydride. Therefore, lowering the purity of Me-THPA if not previously reduced content of cyclopentadiene prior to reacting the C ₅ fraction and maleic anhydride, occurs disadvantages such as increasing the viscosity and freezing point.

C_Five Cyclopentadiene content in the fraction
To decrease, C_Five Heat the fraction and add cyclopentadie
Is converted to dicyclopentadiene, and the difference in boiling points is utilized.
Known techniques such as removal of generated dicyclopentadiene
Surgery can be used. At this time, C _Five Adjust the heating conditions of the fraction
By adjusting the content of cyclopentadiene
You.

By the way, it takes a long time at a high temperature to reduce the content of cyclopentadiene to substantially zero, which is not preferable from the viewpoint of energy saving and economical efficiency. In addition, trans-piperylene and isoprene may be heated at a high temperature for a long time. Such active ingredients are not preferable because they form a dimer together with cyclopentadiene, resulting in loss of the active ingredient. We have:
The end-methylenetetrahydrophthalic anhydride content in the Me-THPA mixture and the properties of the epoxy cured product were examined. Even when the endmethylenetetrahydrophthalic anhydride content was 10% by weight or less, heat resistance, mechanical and electrical properties were large. Confirmed that there is no effect.

[0016] The C ₅ fraction was heated under a mild condition, the content of cyclopentadiene trans - piperylene, the total amount of the isoprene and cyclopentadiene, about 10
It is adjusted to not more than weight%. The present invention relates to the above Me-TH
It is intended to provide a method for producing a liquid acid anhydride having a low viscosity by performing a specific isomerization on a PA mixture, having a liquid stability even at -20 ° C, and a uniform hue of a cured epoxy resin. .

[0017] 3Me-THPA / 4Me-THPA weight ratio of the transformer in C ₅ fraction - piperylene / determined by the content ratio of isoprene, using the normal C ₅ fraction, 3Me-THPA / 4Me-THPA Is within the above range. 3Me-THPA / 4Me-THPA
To the weight ratio of the range is trans C ₅ fraction - or adding piperylene or isoprene, the resulting Me
-3Me-THPA or 4Me-THP in THPA mixture
Although it is necessary to add A, such an operation is not necessary for practicing the present invention because the economic efficiency is impaired.

As the content of endmethylenetetrahydrophthalic anhydride in the Me-THPA mixture increases, the viscosity increases. When the content exceeds 10% by weight, the viscosity of the liquid acid anhydride becomes 50 mPa · s or more at 25 ° C. A low viscosity product cannot be obtained. 50 mPa · s at 25 ° C. in the present invention
The following low-viscosity liquid acid anhydrides are produced as follows.

That is, the above-mentioned Me-THPA mixture is first heated in the presence or absence of a stereoisomer catalyst to obtain a stereoisomer mixture, and then heated in the presence of a structural isomerization catalyst. If this order is reversed, a liquid acid anhydride that achieves the object of the present invention cannot be obtained.

The present invention relates to a method for preparing 3Me-THP
It is essential to adjust the isomerization ratio of A to be 70% or more. The stereoisomerization rate of 3Me-THPA was determined by analyzing the content of the cis-form and the trans-form by gas chromatography. {Trans-form / (cis-form + trans-form)} ×
It is determined by calculating 100.

When the isomerization ratio of 3Me-THPA is less than 70%, the viscosity of the obtained liquid anhydride increases and the liquid stability at -20 ° C deteriorates, which is not desirable. Cannot be obtained so as to achieve a low viscosity liquid acid anhydride.

As the stereoisomerization catalyst, a basic catalyst is used. For example, hydroxides, oxides, alcoholates, phenolates and the like of alkali metals such as sodium, potassium and lithium, tertiary amines such as N, N-dibutylaniline, N, N-diethylaniline and dimethylaminoethanol, and triethylbenzylammonium There are quaternary ammonium salts such as chloride and zeolites. The stereoisomerization is performed by adding 0.05 to 5% by weight of a stereoisomerization catalyst to the Me-THPA mixture,
It is preferable to heat for 20 to 20 hours, especially 150 to
It is preferable to heat at 200 ° C. for 2 to 10 hours.

The isomerization in the absence of a stereoisomerization catalyst is preferably carried out at 150 to 250 ° C. for 1 to 20 hours, particularly preferably at 180 to 230 ° C. for 3 to 10 hours.

The stereoisomer obtained by heating in the presence or absence of the stereoisomerization catalyst can be obtained by separating the stereoisomerization catalyst or high-molecular-weight by-product by distillation or without separating it, Subjected to heating in the presence of 4
It is essential to control the structural isomerization ratio of Me-THPA to be 35 to 60%.

The structural isomers of 4Me-THPA include:
4Me-Δ ⁴ -THPA, 4Me
^{-Δ 3 -THPA, 4Me-Δ 2} -THPA and 4M
Although there is e-Δ ¹ -THPA, in the present invention, 4Me-Δ ²
-The total amount of THPA and 4Me-Δ ¹ -THPA is 0.5
% Is preferable, and those containing none of them are particularly preferable.

The isomerization rate of 4Me-THPA in the present invention, 4Me-Δ ⁴ -TH by gas chromatography
The content of PA and 4Me-Δ ³ -THPA was analyzed, and
Me−Δ ³ −THPA / (4Me−Δ ⁴ −THPA + 4
(Me−Δ ³ −THPA)｝ × 100.

When the isomerization ratio of 4Me-THPA is less than 35%, the obtained liquid anhydride has a low viscosity,
Poor liquid stability at -20 ° C. Also, 4Me-THP
When the isomerization ratio of A exceeds 60%, the viscosity of the obtained liquid acid anhydride increases.

Therefore, the object of the present invention is 50 mPa
In order to obtain a liquid acid anhydride having a low viscosity of s or less, exhibiting liquid stability at -20 ° C, and having a uniform hue of a cured product,
It is necessary to control the isomerization ratio of 4Me-THPA in the range of 35 to 60%.

As the structural isomerization catalyst, for example, sulfuric acid, phosphoric acid, polyphosphoric acid, paratoluenesulfonic acid, BF _3.
Etherate, BF ₃ phenolate, AlCl ₃ , T
An acidic catalyst such as iCl ₄ , ZnCl _{4 or} a cation exchange resin is used.

The amount of these structural isomerization catalysts added was Me
The amount is preferably 0.05 to 5% by weight based on the -THPA mixture, but the amount is appropriately adjusted so that the isomerization ratio of 4Me-THPA becomes 35 to 60%.

The heating conditions are 100 to 250 ° C. and 0.1.
The heating is preferably performed for 5 to 20 hours, but the isomerization ratio of 4Me-THPA is 35 as in the case of the amount of the structural isomerization catalyst.
The conditions are appropriately adjusted so as to be ６０60%.

The acid anhydride mixture obtained by heating in the presence of the structural isomerization catalyst is heated to a desired low-viscosity liquid acid anhydride by removing the catalyst and high-molecular-weight by-products by distillation or the like. Is obtained.

The low-viscosity liquid acid anhydride obtained according to the present invention is useful as a curing agent for an epoxy resin. When mixed with an epoxy resin, an epoxy resin composition having a low viscosity and excellent properties of a cured product can be obtained. Can be

The epoxy resin is a compound having two or more epoxy groups in the molecule. Examples thereof include those obtained by reacting a polyhydric alcohol such as bisphenol A with epichlorohydrin, and a polyhydric alcohol such as 1,4-butadiol. Those obtained by reacting with epichlorohydrin, phthalic acid, polyglycidyl esters of polybasic acids such as hexahydrophthalic acid, N-glycidyl derivatives of compounds having an amine, amide or heterocyclic nitrogen base,
(3 ', 4'-epoxycyclohexylmethyl) -3,4
Alicyclic epoxy resins such as epoxycyclohexanecarboxylate;

In the present invention, the epoxy resin and the low-viscosity liquid acid anhydride obtained by the above-mentioned production method are mixed at an appropriate ratio, and the amount of the acid anhydride group is 0.8 to 1 equivalent of the epoxy group. It is preferable to mix them so as to have an equivalent of 1 to 1 equivalent.

A curing accelerator can be added to the epoxy resin composition according to the present invention. As the curing accelerator, 2-ethyl-4-methylimidazole, cyanoethyl-2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-methylimidazole, 1,2-dimethylimidazole, benzyldimethylamine Tertiary amines such as N, N-dimethylaniline, tris (dimethylaminomethyl) phenol and 1,8-diazabicyclo [5.4.0] undecene-7; 2-ethylhexanoate of such tertiary amine Tertiary amine salts such as, phenol salts, oleates, formates, acetates,
Examples include quaternary ammonium salts such as tetramethylammonium chloride and benzyltriethylammonium chloride, and metal salts such as metal acetylacetone complex salts such as tin octylate, zinc octylate, sodium methoxide, cobalt, and nickel.

The curing accelerator is
It is preferably used in an amount of 0.1 to 8% by weight, particularly 0.3% by weight.
It is preferable to use 5% by weight. To the epoxy resin composition according to the present invention, a reactive diluent, a plasticizer, a filler, a dye, a flame retardant, a silane coupling agent, an anti-settling agent, and the like can be appropriately added.

[0038]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following, parts and% mean parts by weight and% by weight, respectively, unless otherwise specified. The isomerization ratio was determined by gas chromatography analysis as described above. Hue was by Gardner. The viscosity is 25 ° C using an E-type viscometer.
Was measured. The liquid stability at low temperature is as follows. A liquid acid anhydride is placed in a test tube having a diameter of 10 mm and a height of 10 cm for about 8 minutes, and then sealed, and then left in a constant temperature bath set at -20 ° C.
The number of days until crystals began to precipitate was determined. The hue uniformity of the cured product was evaluated as follows. 80 parts of epoxy resin (Epicoat 828, Yuka Shell Epoxy Co., Ltd., trade name), 20 parts of brominated epoxy resin (BROC, Nippon Kayaku Co., Ltd., trade name), 5 parts of titanium white and 5 parts of Erosil (Nippon Aerosil) A) was prepared by mixing 3 parts of each of the above products in a mortar. 100 parts of the above acid anhydride and cyanoethyl-2-ethyl-4-methylimidazole (2E4
MZ-CN, Shikoku Chemicals, trade name, curing accelerator) 2
Part of the mixture is referred to as liquid B. 108 parts of solution A and 60 parts of solution B are mixed to obtain an epoxy resin composition.
Weigh 0 g. After curing by heating at 80 ° C. for 3 hours and then at 105 ° C. for 3 hours, the cured product was taken out of the pudding cup, cut in half, and the hue of the cross section was visually observed. The whole was evaluated to be white or pale yellow and exhibiting a uniform hue as ○, and those exhibiting a reddish central portion, pale yellow around the periphery and exhibiting a non-uniform hue were evaluated as x. The measuring method of the heat distortion temperature of the cured product was based on ASTM: D648.

Example 1 Cyclopentadiene 18.6
%, Isoprene 14.2% and trans - After 12 hours of heating the reaction process the C ₅ fraction at 110 ° C. containing piperylene 6.4%, fraction until a boiling point of 80 ° C. performs atmospheric distillation at 90 ° C. (hereinafter C ₅ abbreviated -D fraction) were collected. This C ₅ -D
The fraction was cyclopentadiene 1.1%, isoprene 17.
It contained 1% and trans-piperylene 7.6%.

500 parts of this C ₅ -D fraction, 143 parts of maleic anhydride and 0.3 part of hydroquinone were charged into a pressure-resistant autoclave and reacted at 100 ° C. for 5 hours. After completion of the reaction, normal pressure distillation was performed at 90 ° C. to remove unreacted low boiling components. After removing low-boiling components at 90 ° C. under a reduced pressure of 4 kPa, 233 parts of a Me-THPA mixture containing 4.3% of endmethylenetetrahydrophthalic anhydride at a weight ratio of 3Me-THPA / 4Me-THPA of 31/69. I got

200 g of this Me-THPA mixture and dimethylaminoethanol (Wako Pure Chemical Industries, first grade reagent)
Take 16 g into a 200 mL four-necked flask,
For 2 hours. The reaction solution was mixed with polyphosphoric acid-10.
0.90 g (Nippon Chemical Industry Co., Ltd., trade name; hereinafter, abbreviated as polyphosphoric acid) was added, and the mixture was further heated and stirred at 170 ° C. for 2 hours. Thereafter, vacuum distillation is performed, and 104 at 133 Pa.
Room temperature low viscosity liquid acid anhydride having a boiling point of ~ 108 ° C 1
84 g were obtained. Table 1 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

Example 2 Cyclopentadiene 17.3
%, Isoprene 13.9% and trans - at piperylene 110 ° C. The C ₅ fraction containing 5.7% after 10 hours of heating the reaction process, the boiling point performs atmospheric distillation at 90 ° C. was collected fraction to 80 ° C. . The C during ₅ -D fraction cyclopentadiene 2.2%, isoprene 16.4% and trans - contained piperylene 6.6%. The C ₅ -D fraction 50
The same processing as in Example 1 was performed except that 0 parts were used, and 3M
The weight ratio of e-THPA / 4Me-THPA is 29/71.
8.8% of endmethylenetetrahydrophthalic anhydride with
235 parts of a Me-THPA mixture were obtained. This M
200 g of the e-THPA mixture and 0.16 g of dimethylaminoethanol were placed in a 200 mL four-necked flask, and 1
The mixture was heated and stirred at 70 ° C. for 2 hours. 0.80 g of polyphosphoric acid was added to the reaction solution, and the mixture was further heated and stirred at 170 ° C. for 2 hours. Thereafter, vacuum distillation is performed, and 104 to 104 at 133 Pa.
186 g of low-viscosity liquid acid anhydride at room temperature with a boiling point of 8 ° C
I got Table 1 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

Example 3 Cyclopentadiene 18.9
Collected at piperylene 110 ° C. The C ₅ fraction containing 7.3% after 10 hours of heating the reaction process, the boiling point performs atmospheric distillation at 90 ° C. is a fraction of up to 80 ° C. -%, isoprene 13.9% and trans Was. The C ₅ -D fraction 2.0% cyclopentadiene, isoprene 16.7% and trans - contained piperylene 8.7%. The C ₅ -D fraction 50
The same processing as in Example 1 was performed except that 0 parts were used, and 3M
An e-THPA / 4 Me-THPA ratio of 35/65 yielded 235 parts of a Me-THPA mixture containing 7.3% endomethylenetetrahydrophthalic anhydride. This Me-
200 g of the THPA mixture and 0.16 g of dimethylaminoethanol were placed in a 200 mL four-necked flask,
The mixture was heated and stirred at 0 ° C. for 2 hours. 0.90 g of polyphosphoric acid was added to this reaction solution, and the mixture was further heated and stirred at 170 ° C. for 3 hours. Thereafter, vacuum distillation is performed, and 104 to 104 at 133 Pa.
182 g of low viscosity liquid acid anhydride at room temperature with a boiling point of 8 ° C
I got Table 1 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

Example 4 Me-T used in Example 2
200 g of the HPA mixture was subjected to isomerization and distillation under reduced pressure under the same conditions as in Example 1 to obtain 186 g of a low-viscosity liquid acid anhydride at room temperature.
I got Table 1 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

[0045]

[Table 1]

Comparative Example 1 Me-T used in Example 2
200 g of HPA mixture and 0.1 g of dimethylaminoethanol.
Take 16 g into a 200 mL four-necked flask,
For 2 hours. To this reaction solution, polyphosphoric acid 0.7
0 g was added, and the mixture was further heated and stirred at 170 ° C. for 2 hours. Thereafter, vacuum distillation was performed to obtain 185 g of a low-viscosity liquid acid anhydride at room temperature having a boiling point of 104 to 108 ° C. at 133 Pa. Table 2 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

Comparative Example 2 Me-T used in Example 2
200 g of HPA mixture and 0.1 g of dimethylaminoethanol.
Take 16 g into a 200 mL four-necked flask,
For 2 hours. To this reaction solution was added polyphosphoric acid 1.1.
0 g was added, and the mixture was further heated and stirred at 170 ° C. for 2 hours. Thereafter, vacuum distillation was performed to obtain 184 g of a liquid acid anhydride at room temperature having a boiling point of 104 to 108 ° C. at 133 Pa. Me
Table 2 shows the isomerization conditions of the -THPA mixture and the properties of the isomerate.
Shown in

Comparative Example 3 The C ₅ fraction used in Example 1 was heat-treated at 110 ° C. for 8 hours, and then subjected to atmospheric distillation at 90 ° C. to collect a fraction up to a boiling point of 80 ° C. 2.9% of cyclopentadiene and 16.9 of isoprene were contained in the C ₅ -D fraction.
% And trans-piperylene 7.5%. 500 parts of this C ₅ -D fraction and 143 maleic anhydride
And 0.3 part of hydroquinone were charged into a pressure-resistant autoclave and reacted at 100 ° C. for 5 hours. 90 ° C after completion of the reaction
At room temperature to remove unreacted low-boiling components. After removing low-boiling components at 90 ° C. under reduced pressure of 4 kPa,
The weight ratio of Me-THPA / 4Me-THPA is 31/6
9. In 9, the endmethylenetetrahydrophthalic anhydride was added.
235 parts of a Me-THPA mixture containing 2% were obtained. This Me-THPA mixture was isomerized and distilled under reduced pressure under the same conditions as in Example 1 to obtain 185 g of a liquid acid anhydride at room temperature. Table 2 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerate.

Comparative Example 4 Me-T used in Example 2
200 g of the HPA mixture and 69 g of 4-methyl Δ ⁴ -tetrahydrophthalic anhydride (Tokyo Kasei, reagent) were heated and mixed at 80 ° C. This Me-THPA mixture is 3Me-TH
The weight ratio of PA / 4Me-THPA was 21/79 and contained 6.5% of endomethylenetetrahydrophthalic anhydride. 200 g of this Me-THPA mixture was isomerized and distilled under reduced pressure under the same conditions as in Example 1 to obtain 185 g of a liquid acid anhydride at room temperature. Table 2 shows the isomerization conditions of the Me-THPA mixture and the properties of the isomerized product.

[0050]

[Table 2]

Comparative Example 5 Me-T used in Example 2
200 g of HPA mixture and 0.1 g of dimethylaminoethanol.
Take 16 g into a 200 mL four-necked flask,
For 2 hours. Thereafter, distillation under reduced pressure was performed, and 133
183 g of a low-viscosity liquid acid anhydride at room temperature having a boiling point of 104 to 108 ° C in Pa was obtained. Table 3 shows the isomerization conditions and properties of the isomerized product.

Comparative Example 6 Me-T used in Example 2
200 g of HPA mixture and 0.40 g of polyphosphoric acid
The mixture was placed in a mL four-necked flask, and heated and stirred at 170 ° C. for 4 hours. Thereafter, distillation under reduced pressure was performed, and
193 g of a liquid acid anhydride at room temperature with a boiling point of 108 ° C. were obtained. Table 3 shows the isomerization conditions and the properties of the isomerized product.

[Comparative Example 7] Me-T used in Example 3
200 g of HPA mixture and 0.40 g of polyphosphoric acid
The mixture was placed in a mL four-necked flask, and heated and stirred at 170 ° C. for 2 hours. To this reaction solution, add dimethylaminoethanol 0.8
4 g was added, and the mixture was further heated and stirred at 170 ° C. for 2 hours. Thereafter, vacuum distillation was carried out to obtain 185 g of a low-viscosity liquid acid anhydride having a boiling point of 104 to 108 ° C. at 133 Pa at room temperature. Table 3 shows the isomerization conditions and properties of the isomerized product.

[0054]

[Table 3]

Example 5 100 parts of Epicoat 828 (trade name of Yuka Shell Epoxy Co., Ltd., epoxy resin), 85 parts of the liquid acid anhydride obtained in Example 2, and DMP-30 (ROHM) as a curing accelerator 1 part of 2,4,6-tris (dimethylaminomethyl) phenol (trade name of Andhaas Co., Ltd.) was mixed until uniform. The viscosity at 25 ° C. of this formulation was 670 mPa · s.
The formulation is then left at 120 ° C. for 5 hours and 150 ° C. for 1 hour.
Cured for 5 hours. The heat-deformation temperature of the obtained cured product is 13
At 2 ° C., the bending strength was 132 MPa.

Comparative Example 8 A compound and a cured product were produced in the same manner as in Example 5 except that the liquid acid anhydride obtained in Comparative Example 5 was used. The viscosity of this formulation at 25 ° C. is 55
It was 0 mPa · s. The heat distortion temperature of the cured product is 1
At 24 ° C., the bending strength was 126 MPa. Comparative Example 9 A blend and a cured product were produced in the same manner as in Example 5, except that the liquid acid anhydride obtained in Comparative Example 6 was used.
The viscosity at 25 ° C. of this formulation is 1080 mPa ·
s. The heat distortion temperature of the cured product was 134 ° C., and the bending strength was 128 MPa. Comparative Example 10 A blend and a cured product were produced in the same manner as in Example 5, except that the liquid acid anhydride obtained in Comparative Example 7 was used. The viscosity at 25 ° C. of this formulation is 830 mPa
-It was s. The heat distortion temperature of the cured product is 128 ° C.
The bending strength was 128 MPa.

[0057]

According to the present invention, the low-viscosity liquid acid anhydride of the present invention comprises C ₅
Fraction previously transformer or - piperylene and isoprene not isolated, is obtained by reacting a direct C ₅ fraction and maleic anhydride, C ₅ fraction used is not completely necessary to remove the cyclopentadiene, low Viscosity (5 at 25 ° C)
(0 mPa · s or less), a liquid acid anhydride having liquid stability even at −20 ° C. can be produced more economically and more energy-saving than before. In addition, the epoxy resin composition of the present invention has low viscosity and is excellent in workability such as casting and impregnation, and the epoxy resin composition of the present invention allows the curing reaction to proceed uniformly so that the hue of the cured product is uniform. And a cured product having excellent heat resistance and mechanical strength can be obtained.

Claims (2)

[Claims] 1. A trans content of cyclopentadiene - piperylene, isoprene and was synthesized from C ₅ fraction and maleic anhydride was reduced to 10% by weight or less based on the total weight of cyclopentadiene 3-methyl tetrahydrophthalic anhydride A methyltetrahydrophthalic anhydride mixture having an acid / 4-methyltetrahydrophthalic anhydride weight ratio of 25/75 to 35/65 and an endmethylenetetrahydrophthalic anhydride content of 10% by weight or less is prepared in the presence of a stereoisomerization catalyst. Alternatively, it is heated in the absence of steric isomerization so that the isomerization ratio of 3-methyltetrahydrophthalic anhydride becomes 70% or more, and then heated in the presence of a structural isomerization catalyst to heat 4-methyltetrahydrophthalic anhydride. 35-60% isomerization rate
A method for producing a low-viscosity liquid acid anhydride, comprising: 2. An epoxy resin composition comprising the liquid acid anhydride according to claim 1 and an epoxy resin.