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US 4,013,519 AGranted
Recovery method for polyester still bottoms
AssigneeSafetech, Inc.
InventorsBruce Noel Hoppert, Alfred Berghausen, III
Life of this patent
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Abstract
A recovery method by means of which an antimony compound is separated from polyester still bottoms. If desired, the method can be employed so as to recover in usable form, the antimony compound, and the monomers polymerized to produce the polyester.
Claims5
A recovery method for polyester still bottoms which includes polyester materials, antimony compounds, terephthalic acid, and glycols, comprising:
- A. subjecting the still bottoms to an alkaline hydrolysis step, the amount of water in step (A) being about 10 parts by weight of water for each part of terephthalic acid present, said alkali hydrolysis step carried out at a temperature of about 185.degree. to 212.degree. F. and at a pH of between about 8 to 8.5,
- B. acidifying the material from step (A) to a pH of about 6.2 to 6.5 to precipitate a portion of the antimony compounds therefrom,
- C. removing the precipitated antimony compounds and treating the unprecipitated material with activated carbon,
- D. acidifying the unprecipitated material from step (B) at a temperature of about 170.degree. F. to a pH of about 1 to 3 to precipitate terephthalic acid,
- E. removing the precipitated terephthalic acid,
- F. adding a sufficient quantity of sodium thiosulfate to precipitate substantially all of the remaining antimony compounds, the temperature at which the mixture is maintained being about 180.degree. to 212.degree. F.,
- G. removing the precipitated antimony compounds.
4 more elements
Dependencies are inferred from the claim text.