Introduction

Isophthalic acid (IPA), also known as 1, 3-phthalic acid, molecular formula C8H604, molecular weight 166.13[1], appearance of white crystalline powder or needle crystal, melting point 345~347 ℃, can sublimate, easily soluble in methanol, ethanol, acetone and glacial acetic acid, slightly soluble in boiling water, insoluble in benzene, toluene and petroleum aldehyde. Phthalic acid has strong heat resistance, hydrolysis resistance and chemical resistance, flammable, low toxicity, skin, eyes, mucous membrane and other soft tissue stimulation, operation should comply with the provisions of toxic and flammable chemicals.

Picture 1 Isophthalic acid powders

Industrial Isophthalic acid is mainly prepared from m-xylene as raw material, acetic acid drill as catalyst, acetaldehyde as promoter, acetic acid as solvent, and liquid phase oxidation at 120 ℃ at about 0.6mpa. Isophthalic acid has the characteristics of general dibasic acid reaction, can happen to salt, dehydration, hydrogenation, halogenation reactions, such as the products are mainly used in the production of coatings, polyester (PET) resin, unsaturated polyester resin (UPR), special fiber, hot melt adhesives, printing ink, dyeing of modified polyester fibers and resin, plasticizer, etc., the development and utilization prospect.

Production of acid modified copolyesters

The copolymerization of terephthalic acid, terephthalic acid and ethylene glycol with mole fraction of 1%~10% is a copolyester polymer, which has good tear strength, impact resistance, melt viscosity and dyeability. The bottle made with copolyester can increase transparency, reduce aldehyde content, improve barrier and shorten processing cycle time. In addition, these acid modified copolyesters can also be used to manufacture a wide range of fiber and film products, such as high resilience aromatic thermobonded polyester fibers, heterothermal shrinkage blended fibers, soft leavened imitation silk, imitation silk.

Production of low melting point polyester

In general, the melting point of polyester produced is about 250℃, and the melting point of polyester produced by 100% terephthalic acid is about 65℃. If 50% terephthalic acid is used in polyester production instead of terephthalic acid, the melting point of copolecster generated is about 120℃. Therefore, according to the requirements of polymer properties, the content of Isophthalic acid can be changed in a wide range to generate polyester with different melting temperatures. Filaments from this type of polyester produce flexible fabrics that feel light, soft and luxurious. In addition to the production of fiber for the manufacture of heat bonded non-textile, but also can be used as filler, increase the volume of non-woven, reduce the weight of the filler, increase the thermal insulation performance. The dyeing performance of microfiber is better than that of pure PET microfiber due to the reduction of crystallization zone.

Production of polyaromatic amide

The m-aryl amide polymer fiber produced from Isophthalic acid is not easy to burn, do not spark, do not melt or do not adhere to the skin and other characteristics, suitable for the manufacture of various types of heat-resistant overalls. Polyaromatic amide fiber materials can also be used for aircraft interior decoration materials, improve flame retardant, increase aircraft safety. In addition, it can also be used as filter bag for hot flue gas, asbestos substitute, dry tape and rubber reinforcement for paper making, high-temperature insulating paper and pipe network for electrodes, engines, transformers and cables, household ironing board and kitchen gloves, etc.

Production of unsaturated resins

By isophthalic acid, butylene crisp acid and ethylene glycol mixture polycondensation of isophthalic acid type unsaturated resin is phthalic acid type unsaturated resin has better hydrolysis stability, higher hardness, higher thermal decomposition temperature and better chemical resistance, suitable for room temperature low pressure molding and extrusion molding, can be used as a resistance to chemical corrosion of equipment and the anticorrosive coating of steel equipment or lining, such as glass Fiber-reinforced plastics and surface gelatinizing layer are especially suitable for winding molding products and heat-resistant products and gelatinizing layer that are used for a long time below 100℃.

They are widely used in construction, pipeline, storage tank, transportation, navigation, electronic appliances and daily consumer goods and other fields. Phthalic acid mixed with high-performance paper materials can be made into good physical properties, low cost flame retardant resin and structural resin, used in the manufacture of elevators, handrails and fishing rods. Anticorrosive terephthalic acid type unsaturated polyester resin is used for repair and replacement of underground storage tanks, gasoline pipelines, public infrastructure, such as roads, highways, Bridges and auxiliary facilities (rain proof, light proof, earthquake proof), docks, breakwaters, water supply systems, waste treatment systems, etc. Compressed-molded resins made from Isophthalic acid are used in the manufacture of automotive parts, industrial parts, microwave ovens, electrical parts, sinks, bathtubs, shower partitions and small boats.

Reference

1 Zhang Sigui. Handbook of Practical Fine Chemicals. Beijing: Chemical Industry Press, 1996: