terephthalic acid is one of isomers of phthalic acid, an organic compound with formula p-c6h4(cooh)2, two carboxyl groups in the para position of the benzene. purified terephthalic acid is used principally as a precursor to the pet. nowadays, the demand of pta keep increasing as constantly growing and expanding in polyester industry of the world, pta has replaced dmt to be the main material of polyester fiber synthetic, one of the three major synthetic material.
paraxylene (px), manufactured from aromatic unit, is the raw material of purified terephthalic acid (pta). during the production process, acetic acid is used as the solvent. the oxidation reaction is conducted with catalyst and oxygen, in order to produce crude terephthalic acid (cta). with the process of hydrogenation, the impurity would be removed. after crystallization, separation and drying, crude terephthalic acid (cta) is processed into purified terephthalic acid (pta).
purified terephthalic acid (pta) and ethylene glycol (eg) could directly conduct esterification polycondensation process to produce polyester melt. according to different type of products, it could produce polyester chip, filament and staple fiber, which are used widely in textile industry. if conducting copolymerization with purified isophthalic acid (pia), it could furtherproduce bottle chip, low melting fiber. in addition, purified terephthalic acid (pta) could be used to produce pbt, resins and dotp.
| item | specification | product (typical) |
| acid nmber(mg koh/gm) | 675±2 | 675±2 |
| 4-cba(ppm w/w) | max 25 | max 25 |
| p-toluic acid(ppm w/w) | max 150 | max 150 |
| water(% w/w) | max 0.2 | max 0.15 |
| b*(colour) | max 1.2 | 0.3~1.2 |
| apha colour(2n koh) | max 10 | max 6 |
| aah(ppm w/w) | max 9 | max 6 |
| metals(ppm w/w) | none greater than 1 and in total max 4 |
none greater than 0.5 and in total max 2 |
| median particle size(um) |
- | 115~175 |
isophthalic acid is one of isomers of phthalic acid, also called m-phthalic acid, an organic compound with the formula m-c6h4(cooh)2, two carboxyl groups in the meta position of the benzen. isophthalic acid is an important copolymer material for bottle grade polyester chips, low melting fiber, coating resin.
metaxylene (mx), which produced from aromatic unit, is the raw material of purified isophthalic acid (pia). during the production process, acetic acid is used as the solvent. the oxidation reaction is conducted with catalyst and oxygen, in order to produce crude isophthalic acid (cia). with the process of hydrogenation, the impurity would be removed. after crystallization, separation and drying, crude terephthalic acid (cia) is processed into purified isophthalic acid (pia).
pia has been used widely in chemical industry. if conducting with purified terephthalic acid (pta) during copolymerization, it could produce bottle chip and low melting fiber. adding purified isophthalic acid (pia) into alkyd coating resins, or unsaturated polyester resins, could strengthen the weather resistance. the resins could be used as outdoor products. with the sulfonation reaction, purified isophthalic acid (pia) apply to produce polyester textile dyeing modifier (sipm). after the copolymerization, polyester fiber could be dyed by cationic dyestuff. it is not only used to improve the dyeing properties of polyester textile, but lower the temperature during the dyeing process.
| item | specification | product (typical) |
| purity(wt%) | min 99.8% | min 99.9% |
| acid nmber(mg koh/gm) | 675±2 | 675±2 |
| 3-cba(ppm w/w) | max 25 | max 25 |
| m-toluic acid(ppm w/w) | max 150 | max 150 |
| moistur(wt%) | max 0.15 | max 0.10 |
| b*(colour) | max 1.0 | max 1.0 |
| apha colour(2n koh) | max 15 | max 10 |
| aah(ppm w/w) | max 15 | max 9 |
| metals(ppm w/w) | none greater than 2 and in total max 10 |
none greater than 1.0 and in total max 6 |
| median particle size(um) | - | 120±30 |