Claims
- 1. Polybutylene terephthalates having an intrinsic viscosity (determined at 25.degree. C. on a 0.5% by weight solution in a 1:1 by weight mixture of phenol and tetrachloroethane) of from 0.2 to 1.4 dl/g, a molecular non-uniformity of below 1.10, and a carboxyl group content equal to or below 0.07% by weight, based on the polybutylene terephthalate, determined at an intrinsic viscosity of 1.0 dl/g.
- 2. Polybutylene terephthalates according to claim 1, characterized in that they have a carboxyl group content equal to or below 0.05% by weight, based on the polybutylene terephthalate, determined at an intrinsic viscosity of 1.0 dl/g.
- 3. A continuous process for the production of polybutylene terephthalate which comprises transporting a molten reaction mixture of terephthalic acid mono- and/or bis-(hydroxybutyl) ester or low viscosity polybutylene terephthalate at 160.degree. to 300.degree. C., together with a heated inert gas, in a diphasic annular stream through an externally heated spiral reaction tube (of substantially constant pitch) having a diameter of from 3 to 100 mm and a diameter/length ratio of from 1:400 to 1:2000 by the maintenance of a pressure difference between the beginning and end of the reaction tube, under conditions such that the absolute pressure, determined at the point of entry of the reaction mixture into the tube, is from 1 to 100 bar and the viscosity of the annular stream is from 1 to 10,000 poises (determined at the reaction temperature), and a circular stream between the surface of the melt and the wall of the tube is produced by the curvature of the tube and a stream of gas flowing at a velocity of from 20 to 300 m/sec to accelerate the transport of material between the melt and the inert gas, whereby reaction takes place in the liquid phase and/or at the melt/gas interface.
- 4. A process as claimed in claim 3, wherein the reaction tube diameter is from 40 to 50 mm.
- 5. A process as claimed in claim 3, wherein the absolute pressure at the point of entry of the reaction mixture into the tube is from 1 to 30 bar.
- 6. Polybutylene terephthalates obtainable by a process as claimed in claim 3.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2719969 |
May 1977 |
DEX |
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2734924 |
Aug 1977 |
DEX |
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Parent Case Info
This application is a continuation-in-part-application of our application Ser. No. 829,384, filed Aug. 31, 1977, now abandoned.
US Referenced Citations (6)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
829384 |
Aug 1977 |
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