Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-04-15
2001-07-03
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S176000, C528S272000
Reexamination Certificate
active
06255441
ABSTRACT:
FIELD OF INVENTION
This invention relates to a catalyst composition comprising a titanium compound, to a process for producing the composition, and to a process for using the composition in, for example, esterification, transesterification, or polymerization of a carbonyl compound.
BACKGROUND OF THE INVENTION
Polyesters such as, for example, polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), generally referred to as “polyalkylene terephthalates”, are a class of important industrial polymers. They are widely used in thermoplastic fibers, films, and molding applications.
Polyalkylene terephthalates can be produced by transesterification of a dialkyl terephthalate ester with a glycol or by direct esterification of terephthalic acid with the selected glycol followed by polycondensation. A catalyst is used to catalyze the esterification, transesterification or polycondensation.
Many commercial processes use manganese or zinc salts as the catalyst for the transesterification step. Antimony, in the form of a glycol solution of antimony oxide, typically is used as the polycondensation catalyst in either the transesterification or direct esterification process outlined above. However, antimony forms insoluble antimony complexes that plugs fiber spinnerets. Furthermore, the use of antimony catalysts is generally regarded as less environmentally friendly, heavy metal related issues may come up in food contact applications.
Organic titanates, such as tetraisopropyl and tetra n-butyl titanates, are known to be effective polycondensation catalysts for preparing polyalkylene terephthalates in general, and frequently are the catalyst of choice. However, organic titanates are not generally used in producing PET because residual titanate tends to react with trace impurities, such as aldehydes, formed during the polycondensation and processing of PET thereby generating undesirable yellow discoloration. Additionally, many organic titanate catalysts are also substantially insoluble in a polymerization mixture thereby creating a non-uniform distribution of catalyst in the mixture.
Therefore, there is an increasing need for the development of a new catalyst that is substantially soluble, efficient, and produces a polymer with reduced color.
An advantage of the present invention catalyst composition is that, when used in producing a particular polyalkylene terephthalate, it has a high reactivity and the polymer produced therefrom has improved optical properties (e.g., less undesirable color) compared to polymer produced using previously known organic titanate catalysts. Other advantages will become more apparent as the invention is more fully disclosed hereinbelow.
SUMMARY OF THE INVENTION
According to a first embodiment of the present invention, a catalyst composition, which can be used as an esterification or transesterification catalyst, or as a polycondensation catalyst to produce polyalkylene terephthalates, is provided. The composition comprises an organic titanium compound, a solubility promoter, and a phosphorus source. The composition can further comprise a sulfonic acid, and optionally a cocatalyst in which the solubility promoter is selected from the group consisting of ortho silicates, ortho zirconates, and combinations thereof.
According to a second embodiment of the present invention a process for the production of a catalyst composition is provided. The process comprises combining a solvent, an organic titanium compound, a phosphorus source, a solubility promoter, and optionally a sulfonic acid, a cocatalyst, or combinations thereof in which the solubility promoter is selected from the group consisting of ortho silicates, ortho zirconates, and combinations thereof.
According to a third embodiment of the present invention, a process which can be used in, for example, the production of an ester or polyester is provided. The process comprises contacting, in the presence of a catalyst composition, a carbonyl compound with an alcohol. The catalyst composition is the same as that disclosed above.
DETAILED DESCRIPTION OF THE INVENTION
According to the first embodiment of the present invention, a catalyst composition is provided. The composition can comprise an organic titanium compound, a solubility promoter, a phosphorus source, and optionally a sulfonic acid, a cocatalyst, or combinations thereof. The composition can also consist essentially or consist of an organic titanium compound, a solubility promoter, a phosphorus source, and a sulfonic acid. The solubility promoter can be selected from the group consisting of ortho silicates, ortho zirconates, and combinations thereof and the cocatalyst can be selected from the group consisting of a cobalt/aluminum catalyst as described in U.S. Pat. No. 5,674,801, an antimony compound, and combinations thereof.
The catalyst composition of this invention is substantially soluble in a solvent. The term “substantially” means more than trivial. It is preferred that the composition be completely soluble in the solvent. However, a substantial portion of the composition can also be suspended or dispersed in the solvent. According to the present invention, the presently preferred titanium compounds are organic titanium compounds. Titanium tetrahydrocarbyloxides are presently most preferred organic titanium compounds because they are readily available and effective. Examples of suitable titanium tetrahydrocarbyloxide compounds include those expressed by the general formula Ti(OR)
4
where each R is independently selected from the group consisting of an alkyl radical, a cycloalkyl radical, an aralkyl hydrocarbon radical, and combinations of two or more thereof. Each radical can contain from 1 to about 30, preferably 2 to about 18, and most preferably 2 to 12 carbon atoms per radical and each R can be the same or different. Titanium tetrahydrocarbyloxides in which the hydrocarbyl group contains from 2 to about 12 carbon atoms per radical and which is a linear or branched alkyl radical are most preferred because they are relatively inexpensive, more readily available, and effective in forming the solution. Suitable titanium tetrahydrocarbyloxides include, but are not limited to, titanium tetraethoxide, titanium propoxide, titanium isopropoxide, titanium tetra-n-butoxide, titanium tetrahexoxide, titanium tetra 2-ethylhexoxide, titanium tetraoctoxide, and combinations of any two or more thereof.
The presence of a halide, or of other active substituent, in the R group generally is avoided since such substituents can interfere with catalytic reactions or form undesired by-products, which can contaminate the polymer when the titanium compound is used for producing a polymer. Presently it is also preferred that the each R group is identical to facilitate synthesis of the organic titanate. In some cases two or more R groups can be from a common compound chemically bonded together other than at the titanium atom (i.e., multidentate ligands such as triethanolamine, citric acid, lactic acid, malic acid, tartaric acid, hydroxyglycine, a salt of the acid, and combinations of two or more thereof).
The titanium tetrahydrocarbyloxides suitable for use in the present invention can also be produced by, for example, mixing titanium tetrachloride and an alcohol in the presence of a base, such as ammonia, to form the tetraalkyl titanate. The alcohol typically is ethanol, n-propanol, isopropanol, n-butanol, or isobutanol. Methanol generally is not employed because the resulting tetramethyl titanate is insoluble in the reaction mixture, complicating its isolation. Tetraalkyl titanates thus produced can be recovered by first removing by-product ammonium chloride by any means known to one skilled in the art such as filtration followed by distilling the tetraalkyl titanate from the reaction mixture. This process can be carried out at a temperature in the range of from about 0 to about 150° C. Titanates having longer alkyl groups can also be produced by transesterification of those having R groups up to C
4
with alcohols having more than 4 carbon atoms per molecule.
Do Hiep Quang
Jaeger Hermann Ludwig
McBride Edward Francis
Putzig Donald Edward
Schulte Heiner
Boykin Terressa M.
E. I. Du Pont de Nemours and Company
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