Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-12-09
2001-11-13
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S275000, C528S277000, C528S280000, C528S281000, C528S282000, C528S283000, C528S286000, C524S706000, C524S710000, C524S783000, C524S784000, C524S786000
Reexamination Certificate
active
06316584
ABSTRACT:
BACKGROUND OF THE INVENTION
Independent of their constitution, which can cover a number of possible variations from aliphatic to fully aromatic, polyesters and copolyesters are generally produced in a two-stage process. In the first stage, the esters to undergo polycondensation, or a polyester precondensate comprising a mixture of oligoesters and having an average relative molecular weight of normally 100-2,000 depending on the molar ratio of the starting compounds, are produced by transesterification of dicarboxylic acid esters or esterification of dicarboxylic acids with an excess of dialcohols. If a branching modification is desired, limited amounts of higher-functional starting components such as glycerin, pentaerythritol, or trimellitic acid can also be employed. Equivalent process methods for the first stage are the conversion of dicarboxylic acid chlorides with diols, the attachment of ethylene oxide to dicarboxylic acids, the esterification of an anhydride with a dialcohol, the conversion of anhydrides with epoxides, and the conversion of dicarboxylic acids or dicarboxylic acid esters with the diacetate of a diol. The second reaction stage is the actual polycondensation, in which the desired high molecular weight of the polyesters and copolyesters must be attained through splitting off alcohol and/or water. In addition to applying a vacuum, introducing an inert gas, and increasing the reaction temperature, polycondensation is accelerated in particular by specific polycondensation catalysts.
For the production of film and fiber-forming polyesters, a legion of polycondensation catalysts have been proposed to accelerate the polycondensation reaction. Since the great majority of the compounds cited in numerous patents have an insufficient catalytic activity or other disadvantages, compounds containing Sb have found almost exclusive use as polycondensation catalysts in the art. Unfortunately, this catalyst has recently encountered criticism on environmental grounds, so that a replacement generally appears to be desirable.
Attempts are constantly being made to supply catalysts to replace Sb
2
O
3
. In particular, alkoxy titanates, especially tetrabutyl titanate, have been proposed, whereby these compounds are used either for transesterification only (JA-PS 74 11 474), transesterification and polycondensation (JA-OS 77 86 496), or polycondensation only (JA-OS 80 23 136), since they are catalytically active in both stages. Since the use of titanium compounds causes discoloration of the polycondensed polyesters, JA-OS 78 106 792 requires pretreatment of titanium compounds with various organic substances, e.g., amines, or they must be combined with other polycondensation catalysts, in particular with Sb
2
O
3
(JA-OS 78 109 597).
DE P 947 517 teaches that metallic oxides such as zinc oxide, boron trioxide, lead oxide, and titanium dioxide can be used as polycondensation catalysts for producing polyethylene terephthalate. The polycondensation time with these metallic oxides, however, is inordinately long, from 7-14 hours in the examples given in that publication. For this reason, BE P 619 210 uses Sb
2
O
3
(see example 1) as a polycondensation catalyst to supplement TiO
2
for producing the polyesters described therein, which dramatically increases the speed of the polycondensation process. Given these circumstances, it of course became practical to work only with Sb
2
O
3
or titanium tetrabutylate as a polycondensation catalyst (see the additional examples of BE P 619 210).
DE-A1 44 00 300 and DE-A1 44 43 648 disclose TiO
2
/SiO
2
and TiO
2
ZrO
2
coprecipitates as polycondensation catalysts.
SUMMARY OF THE INVENTION
The present invention responds to the task of providing additional novel polycondensation catalysts for the general synthesis of polyesters and copolyesters as replacements for Sb
2
O
3
, whereby the catalysts are distinguished in particular by a higher catalytic activity than that demonstrated by Sb
2
O
3
, TiO
2
, or titanium tetrabutylate in the same respective concentration.
The subject of the invention is a process for producing polyesters and copolyesters via polycondensation of polyester-forming starting components, whereby in a first reaction stage esters or oligoesters are produced that in a second reaction stage are polycondensed in the presence of titanium catalysts, the process being characterized by using coprecipitates, individually or in a mixture, as polycondensation catalysts in the polycondensation stage for polycondensing the esters or oligoesters, the coprecipitates being prepared by simultaneous hydrolytic precipitation of a titanium compound and a compound of a metal selected from the groups IA, IIA, VIIIA, IB, IIB, IIIB, or IVB, whereby the titanium and metallic compounds are, independently of one another, an alkylate, alcoholate, or carboxylate of titanium or the metal, respectively, and the molar ratio of the titanium compound to the metallic compound is ≧50:50 mol/mol.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Metals preferred as metallic compounds are sodium, potassium, magnesium, calcium, iron, cobalt, copper, zinc, aluminum, germanium, and tin.
The preferred molar ratio of the titanium compound to the metallic compound is ≧80:20 mol/mol.
The alkylate, alcoholate, or carboxylate group of titanium or the metal, respectively, is for example a compound with 1 to 6 C atoms, whereby the butyl group is especially preferred as the alkylate; the methylate, ethylate, or i-propylate group as the alcoholate; and the acetate or oxalate group as the carboxylate.
A particular high catalytic activity is exhibited by coprecipitates of the invention derived from titanium(IV) tetraisopropylate and tin(IV) dioxalate in a molar ratio of 90:10 mol/mol.
In general, the coprecipitates of the invention have a water content of 0 to 15% by weight, determined by Karl Fischer titration and referred to the hydrated coprecipitate. In the case of water content exceeding 15% by weight, the shelf life decreases, because these catalysts exhibit considerably reduced activity after storage.
Due to the fact that TiO
2
represents a poor polycondensation catalyst for the synthesis of polyesters (see comparative examples 3a and 3b), it is surprising that the coprecipitates of the invention are at all highly effective polycondensation catalysts, in particular for the production of filament-forming high-molecular polyesters and copolyesters, and moreover in the very small quantities that are preferred.
The production of the coprecipitates of the invention from alcoholates is in principle already known (see for example B. E. Yoldes, J. Non-Cryst. Solids, 38 and 39, 81 (1980); E. A. Barringer, H. K. Bowen, J.Am.Ceram. Soc., 65 C 199 (1982); E. A. Barringer, Ph.D. Thesis, MIT (1982); B. Fegley jr., E. A. Barringer, H. K. Bowen, J.Am.Ceram. Soc., 67 C 113 (1984)). The starting metallic alkoxides have the formula M(OR)
m
, where M is Ti and a metal selected from the groups IA, IIA, VIIIA, IB, IIB, IIIB, and IVB, depending on the desired coprecipitate, and m is the most stable oxidation state of the metal. The alkoxides are subjected to hydrolysis, whereby a network is formed as a result of polymerization reactions.
Alcohols suited for preparing metal alkoxides according to methods known per se are, for example, monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butanol, isobutyl alcohol, n-amyl alcohol, 3-methyl-1-butanol, n-hexanol, 2-hexanol, 2-heptanol, n-octanol, and n-decanol, which can be used individually or as mixtures. However, polyhydric alcohols, possibly as a mixture with monohydric alcohols, can also be used, such as ethylene glycol, 1,2-propane diol, 1,4-butane diol, 1,6-hexane diol, 1,10-decane diol, glycerin, trimethylol propane, and pentaerythritol.
In an analogous manner, the coprecipitates can be produced from alkylates such as butylates or from carboxylates such as acetates or oxalates.
The hydrolysis of the organometallic compounds, such as of titanium tetraisopropylate and Sn(IV) dioxalate, can be perfor
Martl Michael Gerd
Seidel Ulf
Acquah Samuel A.
Akzo Nobel nv
Oliff & Berridg,e PLC
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