Methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) is a new type of liquid organic acid anhydride epoxy resin curing agent with excellent performance. Because the anhydride curing agent has better heat resistance and chemical stability than the amine curing agent, and can maintain excellent physical and electrical properties at higher temperatures, in recent years, it has been insulated with the motor, electronics and electrical industries. The continuous improvement of structural reliability requirements has led to the rapid development of the application of such curing agents.
Methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) is a high performance product of anhydride curing agent. Its performance characteristics include high purity, light color, low viscosity, low volatility, low toxicity, low heating loss, stable performance, long pot life, and freezing point. Long-term storage at low and room temperature. Methyl hexahydrophthalic anhydride is obtained by catalytic hydrogenation of methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA). Its properties are as follows: light color, colorless transparent body, epoxy cured product white color; good heat resistance, especially at 150 ° C The epoxy cured product has excellent mechanical and electrical properties, good weather resistance, is not affected by light and heat, and has good moisture resistance; high reactivity, rapid curing, and short gel time.
This product is widely used in epoxy potting materials, casting materials, bonding, lamination, impregnation, molding and winding processes, as well as insulation bushings, oil pipelines, fishing machinery and so on. For example: casting and filling electronic components, large dry-type transformers, high-voltage switches, capacitors, current and voltage transformers, large and micro motors, line output transformers, large resin insulators, etc. It is understood that the epoxy resin curing agent used in the manufacture of wind power blades and hubs is mainly an acid anhydride curing agent such as methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) or methyl hexahydrophthalic anhydride.
II. the raw materials
Isoprene, a volatile liquid with a boiling point of less than 45 ° C, is heavier than air, is a flammable and explosive substance, and is explosive with air. The upper limit point (weight ratio) is 8.9% and the lower limit is 2.0%. When isoprene is in contact with air, it is easy to produce potentially dangerous peroxides. Therefore, inert gas protection should be added during handling, storage and transportation. Industrially, isoprene is mainly derived from the cracked C5 fraction of by-products of ethylene plants.
Maleic anhydride, also known as maleic anhydride, white crystal, flammable, sublimation, soluble in water, hydrolyzed to maleic acid, soluble in acetone, chloroform and benzene, soluble in ethanol to form ester. This product is toxic, strongly irritating to the skin and mucous membranes, and can cause chemical burning. The main technical conditions are ≥99.5 % and the melting point range is 52-53 °C.
The main raw material consumption: 1t methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) consumes 0.8t of maleic anhydride; the theoretical unit consumption of isoprene is 0.4t.
The industrial synthesis of methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) is obtained by synthesizing maleic anhydride and isoprene through the synthesis of diene and then isomerizing.
1) Synthesis of diene: The raw material maleic anhydride and isoprene are pretreated and then introduced into the reaction vessel, and under the action of the catalyst, the chemical reaction is carried out under normal pressure, and the reaction is completed to obtain the primary product of the commercial methyltetrahydrogen product.
2) Isomerization: The product synthesized by diene is vacuum-introduced into the isomeric kettle for isomerization, and the product is purified to obtain methyltetrahydrophthalic anhydride.
3) Main reaction conditions
Diene synthesis: operating pressure is normal pressure, operating temperature 120°C;
Isomerization: operating pressure is normal pressure, operating temperature is 120°C;
Refining: The operating pressure is normal pressure and the operating temperature is 160°C.
(Methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) hydrogenation can produce methyl hexahydrophthalic anhydride, hydrogenation operation pressure 4-7Mpa, operating temperature 110 ° C;).
IV. the market
Methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) is used as an epoxy resin curing agent, solvent-free paint, laminate, adhesive, etc. It has long-term coexistence at room temperature, low freezing point and low toxicity. It is widely used in the electronic and electrical industry, such as: dry Transformers, insulators, insulating basins, insulating sleeves, insulating varnishes, high voltage switches, transformers, line output transformers, power and household capacitors, oil pipelines, etc. In addition to being used in the above fields, methyl hexahydrophthalic anhydride is particularly suitable for outdoor use, such as outdoor transformers, light-emitting diodes, and oil rafts. At present, domestic manufacturers of methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) are mainly concentrated in Shanghai, Jiaxing, Wuxi, Nantong, etc. The actual annual production capacity is about 50,000 tons.
In recent years, due to the rapid development of automatic molding technology for epoxy insulation products, new insulation materials using these products as raw materials have replaced traditional materials such as bakelite, SMC, porcelain, etc., and there is a great deal of epoxy insulation materials. Trends, market demand is growing.
With the rapid development of the electronic and electrical industry in China's four pillar industries and the transfer of such product manufacturing centers to China, the application of epoxy resin in China will be greatly increased, and the anhydride curing in this field will be applied. The agent will also grow at the same time. According to experts' estimates, by 2015, China's acid anhydride curing agent for the electrical and electronic industry can reach 200,000 tons, of which only 40,000 tons can be used for dry-type transformers. The main varieties are methyl tetrahydrophthalic anhydride (MTHPA, MeTHPA) and methyl. Hexahydrophthalic anhydride. In particular, with the vigorous development of China's wind power industry, the demand for composite materials such as resins and coatings is increasing correspondingly for wind turbine components, which has found a new growth point for the market application of acid anhydride curing agents.