Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-06-29
2000-06-13
Nazario-Gonzalez, Porfirio
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562486, 4221841, C07C 5100, C07C 5142
Patent
active
060751630
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a process for manufacturing terephthalic acid and more particularly, to a process for manufacturing the highly purified terephthalic acid in a high recovery rate, in accordance with the practice of this invention comprising the following procedures: polyethylene terephthalate (hereinafter referred to as "PET") scrap is hydrolyzed with an akaline aqueous solution to give the slurry of terephthalic acid alkali metal/earth metal salt, then the particle of terephthalic acid formed from acid-neutralization is enlarged to recover the highly purified terephthalic acid.
The PET waste scrap materials, which are discharged after using them from the end-users, refer to polyester scrap textiles, PET scrap bottles, PET scrap containers, polyethylene terephthalate scrap chips generated in the polymerization process of PET, or polyester scrap yarns generated from the process of manufacturing polyester fibers yarns and textiles. The need for the reutilization of the PET scrap, being incessantly discharged by one's daily life or in the manufacturing process, has created a great issue in the viewpoint of reducing production costs and abating environmental problems. Recently, various processes have been proposed for the recovery of terephthalic acid from the PET scrap but they arenot efficient and economical.
The conventional processes of manufacturing and recovering terephthalic acid are as follows, using the PET scrap:
In U.S. Pat. Nos. 3,120,561 and 4,578,502, PET was hydrolyzed at high temperature and pressure, cooled rapidly and crystallized to recover the precipitated terephthalic acid.
In U.S. Pat. No. 3,884,850, bis(hydroxyethyl) terephthalate was employed as a solvent to recover terephthalic acid from PET.
In U.K Pat. No. 2,123,403 and Japanese Patent Unexamined Publication No. 3-16,328, PET was hydrolyzed with a solvent such as water in the presence of decoloring carbon at 200 to 300.degree. C., then cooled under reduced pressure to recover terephthalic acid.
In U.S. Pat. No. 3,952,053, two methods related the recovery of terephthalic acid from PET as follows: a) through the hydrolysis with sulfuric acid, the obtained mixing solution consisting of terephthalic acid and sulfuric acid was precipitated by water to recover terephthalic acid, or b) PET was placed in an aqueous solution of sodium hydroxide to precipitate unsoluble materials for removal and sulfuric acid was added to precipitate terephthalic acid. Then, ethylene glycol was extracted with organic solvent and distilled after the recovery of terephthalic acid.
In U.S. Pat. No. 4,355,175, PET was hydrolyzed by acid, diluted with cold water and filtered immediately. The resulting solution was dissolved in alkali hydroxide solution to precipitate impurities for removal and added with sulfuric acid to precipitate terephthalic acid. Then, the solution was filtered, washed with water and dried to recover terephthalic acid.
In U.S. Pat. No. 3,544,622, PET was reacted by saponification with sodium hydroxide solution at 150.degree. C. in the presence of ethylene glycol, to prepare disodium terephthalate. Then, the resulting solution was filtered, washed with ethylene glycol or aqueous solution of disodium terephthalate at over 90.degree. C. and dissolved in water. Activated charcoal was added to the solution at 90.degree. C., agitated and neutralized with sulfuric acid. Then, terephthalic acid was filtered and washed with water to recover terephthalic acid.
In European Patent No. 497,662, PET was reacted with alkali metal/earth metal hydroxide at atmospheric pressure and 140 to 180.degree. C., to prepare terephthalic acid alkali metal/earth metal salt. This material was dissolved in water to extract impurities with C.sub.3 to C.sub.8, alcohols, then neutralized with acid and followed by filtration to recover terephthalic acid.
In European Patent No. 597,751, PET was reacted with sodium hydroxide in the presence of a mixing extruder without the addition of solvent and then, the obtained d
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patent: 4542239 (1985-09-01), Lamparter et al.
patent: 4578502 (1986-03-01), Cudmore
patent: 5395858 (1995-03-01), Schwartz et al.
Japanese Patent Unexamined Publication No. 03-16328, dated Jan. 24, 1991.
Bae Dongmok
Roh Hang-Duk
Nazario-Gonzalez Porfirio
Sunkyong Industries Co., Ltd.
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