Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1997-06-19
1999-05-18
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528274, 528283, 528285, 528308, 5283086, 524745, 524783, C08G63/78
Patent
active
059051361
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a class of catalyzers to be used in the stage of polycondensation during the synthesis of poly(ethylene terephtalate). Poly(ethylene terephtalate) (PET) is a thermoplastic polyester used in the production of textile fibers, containers and films for food use, supports for magnetic tapes and photographic films. It is industrially compounded through a multi stage synthesis of ethylene glycol and terephtalic acid or dimethyl terephtalate, in the presence of the proper catalyzers.
PET is synthesized in two stages.
During the first stage (scheme 1), dimethyl terephtalate (DMT) reacts in the presence of alchoolysis catalyzers in order to give an oligomeric mixrure the main component of which is bi-(hydroxyethyl)terephtalate (BHET).
Due to improvements in the purification of terephtalic acid and because it costs less than DMT, in recently perfectioned processes, terephtalic acid instead of ester is used as raw material. In such case the reaction of the first stage (scheme 2) is an esterification (the result also in this case is BHET). BHET obtained in either of the ways explained is transformed in poly(ethylene terephtalate). ##STR1##
The optimum characteristics of a polycondensation catalyzer are: high activity, absence of secondary reactions which could give formations, for example of acetaldehyde or unwanted coloured generations in the final material, atoxicity, particularly for the food applications of PET.
Patent literature describes a huge variety of inorganic, organic and organometal compounds that are efficient in catalyzing the polycondensation reaction. Since the discovery of PET catalyzers consisting of antimonium compounds are described, especially oxide, acetate, alcoholates. It is known however, that in order to obtain sufficiently fast reaction kinetics it is fundamental to use such compounds in quantities so that at the end of the reaction PET contains 200-300 ppm of metal. Which is undesirable for polymer applications to food containers.
Titanium compounds have a very high activity, though they cause the formation of a yellow colouring in the final material due to the formation of acethaldheyde and of degradation products (J. M. Besnoin and K. Y. Choi, J. Macromol. Sci., Rev. Macromol. Chem. Phys., C29, 55 (1989)). Mixtures of titanium compounds with other metallic derivatives such as cobalt, manganese and magnesium, nickel, zinc, lanthanum, stannum and others are described. Germanium compounds represent another considerable class of polycondensation catalyzers. The weakness of germanium compounds consists in the incredibly high cost and a higher toxicity than antimonium. Combinations of titanium and germanium are reported in several patents. Another metal that gives derivatives provided with catalytic activity is stannum, though they have a quite reduced activity, and they also cause the polymer's dark-yellow colouring.
The protonic acids have a moderate catalytic activity, and cause the di- and trimerization of ethylene glycol, which remains in the chain of the final polymer drastically lowering its fusion temperature until making it completely amorphous, and reducing its thermic and hydrolytic stability. The compounds described are sulfuric acid and acids, esters, anhydrides, amides and sulfonic amides.
None of these systems presents the above described characteristics in the same time (high activity, atoxicity and absence of secondary reactions).
We have by now surprisingly overcome these problems carrying out the polycondensation in the polyethylene terephtalate synthesis through a catalyzer which is formed by a mixture or derivatives of: metallic and non metallic elements, titanium, sulfonic acid.
According to this, the purpose of this invention is a composition able to catalyze the polycondensation of bi(2-hydroxyetil) terephtalate or its homologous oligomers, constituted by the derivatives of elements belonging to the following groups: IVA, VA. The composition is also characterized by the fact that it contains: stands for an organic radical that can be linear or ram
REFERENCES:
patent: 4447595 (1984-05-01), Smith et al.
Pelosini Luigi
Po Riccardo
Acquah Samuel A.
Inca International S.p.A.
Montefibre S.p.A.
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