Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1995-08-28
2004-09-07
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S280000, C528S301000, C528S302000, C528S307000, C528S308000, C528S308600, C528S286000, C524S081000
Reexamination Certificate
active
06787630
ABSTRACT:
The present invention relates to a process for the preparation of heat-stable, antimony-free polyesters of neutral color using a titanium polycondensation catalyst, which is very easily reproducible and has a very high rate of polycondensation, even with very small additions of the titanium polycondensation catalyst, and in which a considerable reduction in thermal degradation and uncontrolled crosslinking of the polyester formed results, and to the products which can be prepared by this process, which are distinguished by outstanding clarity and color neutrality.
Polyesters have acquired very great importance in very many fields of use. In particular, saturated polyesters are widely used for the production of fiber materials, and also of other types of shaped articles, such as, for example, drinks bottles. For problem-free processability of these polyesters by extrusion processes and for the further use of the extrudates, for example in the textile industry or drinks industry, very high requirements are imposed on the quality of the polyesters. In particular, it is required that the processing and use properties of polyester types employed for a particular processing operation are always the same within very narrow limits. For processing by extrusion processes, for example by melt spinning, it is of prime importance that they have a constantly uniform molecular weight and a constantly reproducible molecular weight distribution, are free from gel fractions and as far as possible do not tend toward yellowing or toward thermal degradation. For further processing, as far as possible no catalyst metals should dissolve out of the fiber material during dyeing processes, since these must be removed from the dyehouse waste water and disposed of by expensive purification operations.
There should also be no difficulties caused by troublesome constituents in the disposal or re-use (recycling) of the used polyester products.
Polyesters are usually prepared by esterification of aromatic dicarboxylic acids or transesterification of lower aliphatic esters of aromatic dicarboxylic acids with aliphatic diols and subsequent polycondensation until the molecular weight required for the planned use is achieved.
A possible transesterification is carried out in the presence of transesterification catalysts which, after the transesterification has ended, must be deactivated by addition of complexing agents. Complexing agents which are usually employed are phosphoric acid, phosphorous acid and/or phosphonic acids or derivatives thereof. After the esterification or the transesterification, the polycondensation is carried out to give the desired molecular weight, this also being carried out in the presence of a suitable catalyst. Antimony compounds, usually antimony trioxide, have become accepted as the polycondensation catalyst on a large industrial scale. Some of the antimony compound here may be reduced to antimony metal by reducing agents, which leads to a graying of the polyester.
This results in a lack of clarity and a non-neutral color shade.
Furthermore, the relatively high content of antimony compounds in the polyesters is regarded as a disadvantage since it makes the preparation more expensive. In addition, th re is the possibility of antimony compounds being liberated during further processing operations, for example during dyeing. The relatively high content of antimony compounds leads to an influence on spinning properties, in addition to the formation of antimony deposits.
Proposals have therefore already been made to eliminate the disadvantages of the preparation process described.
It is thus known to improve the color shade of the polyesters by addition of cobalt compounds and/or optical brighteners. It is furthermore known to employ titanium compounds, instead of antimony compounds, as the polycondensation catalyst.
Various publications, for example U.S. Pat. No. 3,962,189, JP-PS-28006 (1979), JP-PS-123311 (1976), JP-PS-43564 (1979), JP-PS-111985 (1980) or JP-PS-280048 (1989), disclose a process for the preparation of polyesters in which, in order to improve the color shade of the polyester, a cobalt compound which—like the transesterification catalyst—must be complexed before the start of the polycondensation is added, and in which the polycondensation is carried out in the presence of a titanium compound.
According to these publications, the amount of complexing agent employed for complexing the added cobalt is said to be in the range from 0.5 to 7.5 mol per mole of cobalt compound.
The P/Co ratio used is thus 0.5 to 1.5 in JP Patent 28006, 0.7 to 3 in JP Patent 111985 and 0.5 to 7.5 [mol/mol] in JP Patent 280048.
This known process has the considerable advantage that all the disadvantages associated with the use of antimony compounds are eliminated and that it can thus actually be possible to produce clear polyesters of neutral color which are suitable for demanding processing operations and uses.
However, a disadvantage of this known process is that its reproducibility leaves something to be desired. Thus, occasionally the desired products are not obtained, but instead disturbances occur in the polycondensation reaction, the molecular weights required are not reached, and if it is considered necessary to prolong the polycondensation time, then yellowing of the polyester, the formation of gel fractions owing to uncontrolled crosslinking and heat sensitivity of the products occur, considerably impairing further processing.
The advantages which the process offers per se therefore cannot always be realized.
It has now been found that it is possible, surprisingly, to prepare heat-stable, antimony-free polyesters of neutral color in a manner which is always reproducible by esterification of aromatic dicarboxylic acids or transesterification of lower aliphatic esters of aromatic dicarboxylic acids with aliphatic diols and subsequent polycondensation, if
a possible transesterification is carried out in the presence of 20 to 120 ppm, based on the catalyst metal, of a transesterification catalyst, preferably manganese in the form of a manganese compound, then, after the esterification or transesterification has ended,
phosphoric acid, phosphorous acid and/or phosphonic acids or a derivative thereof are added to the esterification or transesterification batch as a complexing agent in an amount which is 100% of the amount equivalent to the transesterification catalyst employed and up to 99% of the amount equivalent to the cobalt to be employed,
0 to 80 ppm of cobalt in the form of a cobalt compound are added to the batch,
and the polycondensation is carried out without the addition of antimony, in the presence of 1 to 10 ppm of titanium, which is added in the form of a titanium compound, and if appropriate in the presence of up to 1000 ppm of organic compounds which donate crosslinking structural groups
and if appropriate up to 50 ppm of an optical brightener.
Suitable transesterification catalysts are known from the literature. For example, compounds of metals of groups Ia (for example Li, Na, K), IIa (for example Mg, Ca) and VIIa (for example Mn) of the Periodic Table, in particular those which have a certain solubility in the transesterification batch, such as, for example, salts of organic acids, are suitable for the process according to the invention. Preferred compounds are salts of group VIIa, in particular of manganese, with lower aliphatic carboxylic acids, in particular acetic acid.
A preferred embodiment of the process according to the invention therefore comprises carrying out a possible transesterification in the presence of 20 to 120 ppm of manganese (calculated as the metal) in the form of a manganese compound, in particular manganese acetate.
The cobalt compound added to improve the color shade of the polyester is expediently likewise a salt of cobalt with an organic acid, for example with acetic acid or adipic acid.
The minimum amount of cobalt compound depends on the extent of the color shift necessary in an individual case to achieve a neutral color shade. If optic
Dominguez De Walter Ligia
Klein Peter
Moore Banks Bryan
Acquah Samuel A.
Arteva North America S.A.R.L.
Clements Gregory N.
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