JPH0339066B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a novel polycarboxylic acid anhydride useful as a curing agent for epoxy resins, an intermediate for organic synthesis, and the like. More specifically, the present invention relates to an improvement in the method for producing polycarboxylic acids disclosed in JP-A-55-133374. Epoxy resin has the property of becoming a cured product with excellent chemical, mechanical and electrical properties when cured with organic polyamines, organic acid anhydrides, etc., and can be used as paints, adhesives, casting materials, laminate forming materials, etc. Widely used. Acid anhydrides are used as curing agents because they are less toxic than polyamines, produce less heat when curing epoxy resins, provide products with low shrinkage, and provide cured products with excellent electrical properties. Liquid epoxy resins with hardening agents are widely used as insulation impregnating materials and sealing materials for electrical parts. Such acid anhydrides include methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, etc.

[Formula] Acid anhydrides having one group are generally used, but the heat distortion temperature of cured epoxy resins using these acid anhydrides as curing agents is 60 to 130°C, and depending on the application, 150
A heat distortion temperature of ℃ or higher is required. Pyromellitic anhydride, benzophenonetetracarboxylic anhydride, and chlorendic anhydride are known as curing agents that meet this requirement. However, the two polycarboxylic acid anhydrides are solids with melting points of 228°C and 286°C, respectively, and when mixed with liquid epoxy resin, the former has a melting point of 120°C.
The latter requires heating to a high temperature of 170°C or higher, and the latter in particular has a pot life of 5 to 10 minutes, making it impractical. Furthermore, although chlorendic acid anhydride has the advantage of imparting flame retardancy to the cured product, it causes a rash when it comes into contact with the skin, so care must be taken when handling it. In order to improve the shortcomings of these conventional curing agents, the present inventors first prepared a carboxylic acid anhydride represented by the following general formula [] and maleic anhydride from 120 to
A polycarboxylic acid anhydride having a melting point of 80 to 90°C obtained by reacting at 150°C for 15 to 20 hours was proposed (see Japanese Patent Application Laid-open No. 13337/1983). The heat deformation temperature of the epoxy resin cured with this polycarboxylic anhydride is 176°C, making it a tough cured product. However, in the method disclosed in JP-A No. 55-133374, the by-product is 2 shown by the following formula ().
-Carboxy-3,4-dimethyl-7-isopropylidenebicyclo[4.2.0]-oct-3-ene-
8-one occurs in a proportion of about 5-10% by weight and must be separated from the polycarboxylic acid. This by-product is more likely to be produced when an acid such as p-toluenesulfonic acid, boron trifluoride etherate, or aluminum chloride is present than when no acid is present. Heat resistance, tensile strength, impact resistance, etc. of a cured epoxy resin obtained by using a polycarboxylic acid anhydride containing 5 to 10% by weight of the by-product represented by formula () as a curing agent Since the mechanical strength of the polycarboxylic anhydride decreases, it is necessary to separate the by-product from the polycarboxylic anhydride. This by-product has poor compatibility with the product polycarboxylic acid anhydride and precipitates in the reaction product, so separation is carried out after 80 minutes after the completion of the addition reaction of maleic anhydride.
It is carried out by filtering the reaction product at ~100°C. However, the addition of such a step of separating by-products is industrially disadvantageous, and the by-products are
A high content of 10% by weight is also undesirable as it increases the cost of the product. The present inventors have investigated various catalysts and reaction temperature conditions for the reaction between carboxylic acid anhydride and maleic anhydride with the aim of reducing the amount of such by-products generated to 1% by weight or less, but all of them have been found to be satisfactory. I couldn't get any results. Next, in order to suppress the generation of such by-products, various efforts were made based on the idea that it would be possible to isomerize the raw material carboxylic acid anhydride so that the isomerization reaction shown in the previous equation does not occur. A study of isomerization catalysts revealed that carboxylic acid anhydride represented by the general formula () was liquefied using an alkali metal halide as an isomerization catalyst, and even when reacted with maleic anhydride, the carboxylic acid anhydride represented by the general formula () was It has been discovered that the amount of by-products produced can be suppressed to 1% by weight or less, and the present invention has been achieved. That is, the present invention provides general formula () The present invention provides a method for producing a polycarboxylic anhydride by reacting maleic anhydride with a liquid obtained by heating the carboxylic anhydride shown in the following in the presence of an alkali metal halide. In carrying out the present invention, the carboxylic acid anhydride represented by the above general formula () is obtained by thermal isomerization reaction of α-pinene or dimerization reaction of isoprene (Japanese Patent Publication No. 48-30603 , Tokko Akira
No. 50-7565) Alloocimene and maleic anhydride
Obtained by Diels-Alder reaction at a temperature of 70-90°C. In addition, alloocimene represented by the following formula () obtained by thermal isomerization reaction of α-pinene exists in two types of isomers: trans-cis type and trans-trans type, and the general commercial product is Usually, it contains 50-70% trans-cis isomer and 30-50% trans-trans isomer. The anhydrous maleated allooocimene represented by the general formula () obtained by adding maleic anhydride to such allooocimene by the Diels-Alder reaction is usually a mixture of the following two types of isomers, and its melting point is 70 ℃ or above, for example 83
~84°C, and of course is solid at room temperature.

【formula】

[Formula] To isomerize this anhydrous maleated alloocimene, 0.01
-5.0% by weight, preferably 0.5-3% by weight of alkali metal halogen is blended and heated at 100-250°C, preferably 120-220°C for 10 minutes to 10 hours, preferably
This is carried out by heating for 0.5 to 3 hours (see JP-A-55-115880). The alkali metal halides used include alkali metal bromide salts such as lithium bromide, sodium bromide, potassium bromide, rubidium bromide and cesium bromide, alkali metal chloride salts such as lithium chloride and rubidium chloride, sodium iodide, Examples include alkali metal iodide salts such as lithium iodide and potassium iodide, and lithium fluoride. Among these, sodium iodide and lithium bromide are preferred because they are easily available and require a short isomerization time. In addition to alkali metal halides, amines such as aminoethanol and triethylenetetramine, organic phosphorus compounds such as triethylphosphine and methyltriphenylphosphonium chloride, and thiocyanates (PCT/JP79) can be used as isomerization catalysts for anhydrous maleated allocimene. /0049), aluminum chloride, and acids such as p-toluenesulfonic acid. However, when amines, organic phosphorous compounds, thiocyanates, etc. are used as isomerization catalysts, the amount of byproducts can be suppressed to 3 to 5% by weight, but this suppression amount is still not economically sufficient. No, no. Furthermore, when an acid catalyst is used, there is an increased chance of formation of by-products represented by the general formula (), which is undesirable (see Japanese Patent Application Laid-open No. 39041/1983). The alkali metal halide may be added directly to the heated and melted carboxylic acid anhydride represented by the formula () (anhydrous maleated allocimene) as a solid, or the alkali metal halide may be dissolved in a solvent such as water or acetone. It may also be added. This isomerization reaction is completed when the carboxylic acid anhydride becomes liquid at room temperature (20 to 30°C). In order to suppress the by-products represented by formula (), it is presumed that it is not necessary to carry out the process until it becomes liquid. Easily mixes with maleic acid (melting point 52.8°C). This isomerization reaction produces isomers of the following formulas () and (), and further double bond isomerization reactions occur, and several types of geometric and structural isomers coexist in the processed product. It is assumed that this causes the freezing point to lower and liquefy.

【formula】

[Formula] In the isomerization reaction, the isomerization catalyst is supported on a carrier such as pumice, activated carbon, diatomaceous earth, silica gel, molecular sieve, etc., and the vapor of anhydrous maleated allocimene is introduced into a column packed with this supported catalyst. It is possible to carry out continuous heat treatment by passing at a predetermined reaction temperature, but in such a case,
Heat treatment is performed at a high temperature of 250°C for a short time of 10 to 30 minutes. The product liquefied in this way is purified by distillation, or treated with activated carbon, addition of superimposing agents such as diatomaceous earth, and further treated with an appropriate dehydrating agent to remove water. Then, it is purified by distillation and used as a raw material for the production of the next polycarboxylic acid anhydride. However, such purification is usually not necessary, and even if the catalyst remains in the liquid, it does not pose a problem in the production of polycarboxylic acid anhydride. Therefore, it is economically advantageous to omit such a purification step. To produce polycarboxylic acid anhydride by addition-reacting maleic anhydride to this liquefied product, JP-A-55
-Conducted according to the description in Publication No. 133374. Specifically, this purpose can be easily achieved by heating and stirring both in the presence of a suitable solvent or in the absence of a solvent for a certain period of time or longer. If the heating temperature in the addition reaction is too low, the reaction will be slow, and if it is too high, side reactions will occur, both of which are inappropriate. Usually 120-250
Temperatures of 140-200°C are advantageously used. Although the reaction time is not particularly limited, it is desirable to carry out the reaction for a relatively long time, and a practical time is usually about 3 to 50 hours, preferably about 5 to 20 hours. The reaction solvent is not necessarily required as described above, but when used, a solvent inert to the raw materials carboxylic anhydride and maleic anhydride, such as benzene, toluene, dioxane, etc., is used. The amount of maleic anhydride charged per mole of the liquefied product is at least an equimolar amount, preferably 1.05 to 5 times the molar amount. The production of this polycarboxylic acid anhydride does not necessarily require a catalyst, but organic acids (e.g. p-toluenesulfonic acid), zinc chloride,
There is no problem in carrying out the reaction by adding a catalyst such as an organic peroxide to the reaction system. In this addition reaction, it is desirable to replace the inside of the reaction vessel with an inert gas such as nitrogen gas.
It is also preferable to carry out the reaction by adding a phenolic antioxidant, such as 2,6-di-(t-butyl)-p-cresol, to the reaction system, since this yields a good product. After the reaction is completed, the solvent and unreacted substances are removed from the reaction mixture to obtain polycarboxylic acid anhydride, which is usually colored brown. This product can also be decolorized and purified by operations such as washing and reprecipitation. The polycarboxylic acid anhydride obtained by this addition reaction is a mixture containing the following isomers, and its melting point is 50 to 90°C. The mixing ratio of these polycarboxylic acid anhydrides is thought to vary depending on the reaction conditions, but the component ratio cannot be confirmed because separation is difficult. In this addition reaction, the proportion of by-products represented by the general formula () produced is 1% by weight or less. This polycarboxylic acid anhydride is solid at room temperature and is an excellent curing agent for epoxy resins, and can also be used as a raw material for producing glycidyl esters of polycarboxylic acids. The amount of polycarboxylic anhydride used as a hardening agent for 100 parts by weight of epoxy resin is 50 to 100 parts by weight.
parts by weight, preferably 70 to 95 parts by weight. Next, the present invention will be explained in more detail with reference to Examples and Reference Examples. Parts in these examples indicate parts by weight. Example of manufacturing maleic anhydride alloocimene 686 g (7.0 mol) of maleic anhydride was placed in a 3-capacity four-necked flask equipped with a stirrer, thermometer, condenser, dropping funnel, and nitrogen introduction tube, and 100 c.c. of benzene was added. added. While stirring at room temperature, 1000 g (7.35 mol) of alloocymene (manufactured by Yasushi Oil Industries Co., Ltd.) was gradually added dropwise. Since the temperature rose due to the heat of reaction, the reaction temperature was maintained at 70-80°C by cooling with a water bath. After about an hour, I finished instilling the alloocimene. Further, in order to complete the reaction, the mixture was stirred at 70 to 80°C for about 1 hour. The reaction solution was red when alloocimene was added dropwise, and turned light brown as the reaction was completed. After the reaction was completed, excess alloocimene and the solvent benzene were removed by suction using an aspirator at a temperature below 100°C (degree of vacuum: 20 mmHg). The anhydrous maleated allocimene () produced had a melting point of 75-80°C. Liquefaction Treatment Example 1 60 g of anhydrous maleated allocimene () obtained in Production Example 1 above was placed in a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, and heated to about 100°C. and dissolved. 1.8 g of sodium iodide was added to this, and the mixture was stirred at 200°C for 2 hours. Sodium iodide was not completely dissolved and was finely dispersed. After the reaction was completed, 50 c.c. of methyl isobutyl ketone was added, and the mixture was washed with 50 c.c. of 10% sodium thiosulfate aqueous solution.
After washing with water, the aqueous layer was removed, and the oil layer was dehydrated by adding sodium sulfate as a dehydrating agent, followed by simple distillation at a reduced pressure of 0.5 mmHg.
56 g of pale yellow liquid anhydrous maleated alloocimene (yield: 93
%) was obtained. Example 2 60 g of anhydrous maleated allocimene () obtained in Production Example 1 above was placed in a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube, and heated to about 100°C to dissolve it. Add 0.06g of lithium bromide monohydrate to this,
The mixture was stirred at 200°C for 2 hours. Sodium bromide was not completely dissolved and was finely dispersed. After the reaction was completed, simple distillation was carried out at a reduced pressure of 0.9 mmHg.
55 g of pale yellow liquid anhydrous maleated alloocimene (yield 92
%) was obtained. This liquid anhydrous maleated alloocimene was heated at 5°C.
It was left in a refrigerator at -20°C, in a freezer at -20°C, and at 25°C for more than 2 months, but it did not crystallize.
Its viscosity (E-type viscometer) was 176 cps at 25°C. Example 1 500 parts of the liquid anhydrous maleated allocimene () obtained in Production Example 1 above and 314 parts of maleic anhydride (charged molar ratio = 1:1.5) were reacted using a stirrer, a reflux device, and a thermometer. The mixture was charged into a container and stirred at 180° C. for 6 hours while sufficiently purging the inside of the container with nitrogen gas. After the reaction, unreacted substances were removed by vacuum distillation, and a light brown reaction product was obtained with a yield of 95% (760 parts). When this reaction product was analyzed by liquid chromatography, it was separated into two layers, one layer being the by-product 2-carboxy-3,4-dimethyl-7-isopropylidenebicyclo[4.2.0]-octo- It was confirmed by infrared absorption spectrum analysis that it was 3-en-8one (content 0.5% or less) and that the other layer was polycarboxylic anhydride. 750 parts of this product was washed with 100 parts of acetic anhydride to remove byproducts, and then dried under reduced pressure to obtain a polycarboxylic anhydride having the following physical properties. Melting point: 80-90°C Acid anhydride equivalent: 163 g/acid anhydride/mole Example 2 46.8 parts of liquid anhydrous maleated allocimene () obtained in Production Example 2, 58.8 parts of maleic anhydride (molar ratio of charging = 1:3) A polycarboxylic acid was produced in the same manner as in Example 1 except that the following was used. 96 parts of the obtained product (yield 96%) contained 0.05% or less of a by-product represented by the general formula (). The polycarboxylic acid obtained by washing this product with acetic anhydride and drying under reduced pressure was as follows. Melting point: 75-80°C Acid anhydride equivalent: 176 g/anhydride/mole Comparative Example 1 In Example 1, the solid anhydrous maleated allocimene () obtained in Example 1 was used instead of the liquid anhydrous maleated allocimene (). 701 parts of polycarboxylic anhydride (yield 88%) was prepared in the same manner except that
Obtained. At this time, about 7% of the by-product represented by the general formula () was separately precipitated. The polycarboxylic anhydride obtained by washing the product with acetic anhydride and drying under reduced pressure had the following properties. Melting point: 85-95°C Acid anhydride equivalent: 177 g/1 mole of acid anhydride Example 3 In Example 1, p-toluenesulfonic acid 25
The melting point was 80-90 in the same manner except that the reaction temperature was 120°C and the reaction time was 4 hours.
760 parts (yield 95%) of polycarboxylic acid anhydride having an acid anhydride equivalent of 160 g/1 mol of acid anhydride was obtained. The amount of the compound represented by the general formula () produced as a by-product in this reaction was 0.5% or less. Comparative Example 2 The addition reaction was carried out in the same manner as in Example 3, except that solid anhydrous maleated allocimene was used instead of the liquid maleated anhydride allocimene (2012) to obtain 710 parts of polycarboxylic anhydride (yield: 89%). Obtained. The amount of the compound represented by the general formula () produced as a by-product at this time was approximately 49 parts (yield: 7%). Production example of cured product Application example 40 parts of diglycidyl ether of bisphenol A "Epicote 828" (trade name manufactured by Yuka Ciel Epoxy Chemical Co., Ltd.), 36 parts of the polycarboxylic acid anhydride obtained in Example 1, and as a curing accelerator. N, N-
When a mixture containing 0.5 part of dimethylbenzylamine was heated and cured in a mold at 120°C for 2 hours and then at 200°C for 4 hours, a brown cured product was obtained. The physical properties of this cured product are shown below. Heat distortion temperature 210℃ Tensile strength 9.2Kg/mm ² Tensile elongation 1.8% Izotsu impact strength (notched) 0.8Kg・
cm/cm ² Applied Comparative Example The same application as above except that the polycarboxylic anhydride obtained in Comparative Example 1 containing 7% of the by-product was used instead of the polycarboxylic anhydride obtained in Example 1. A cured product having the following physical properties was obtained in the same manner as in the example. Heat distortion temperature 180℃ Tensile strength 8.5Kg/mm ² Tensile elongation 1.5% Izotsu impact strength (notched) 0.6Kg・
cm/ ^cm2

Claims (1)

[Scope of Claims] 1 Polycarboxylic anhydride is obtained by reacting maleic anhydride with a liquid obtained by heat-treating a carboxylic anhydride represented by the following general formula () in the presence of an alkali metal halide. How to manufacture. 2. The method according to claim 1, wherein the alkali metal halide is sodium iodide.