Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-08-14
2002-08-20
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S274000, C528S277000, C528S280000, C528S281000, C528S282000, C528S285000, C528S286000, C528S301000, C528S302000, C528S308000, C528S308600, C524S081000, C524S780000, C524S783000, C524S785000, C524S786000, C524S789000
Reexamination Certificate
active
06437088
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for producing a polyester. More specifically, this invention relates to a process for polymerizing a carbonyl compound and a glycol in the presence of a coated titanium dioxide and a titanium catalyst composition.
BACKGROUND OF THE INVENTION
Polyesters such as, for example, polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate, generally referred to as “polyalkylene terephthalates,” are a class of important industrial polymers. They are widely used in fibers, films, and molding applications.
There are several known methods for producing polyester. In one method, polyester is produced by transesterification of an ester, such as dimethyl terephthalate, (DMT) with a glycol followed by polycondensation. In another known process, an acid such as terephthalic acid (TPA) is directly esterified with a glycol followed by polycondensation. A catalyst is typically used to catalyze the esterification, transesterification, and/or polycondensation reactions.
Antimony is often used as a catalyst for the polymerization and/or polycondensation reactions. Unfortunately, antimony-based catalysts suffer from several shortcomings. Antimony forms insoluble antimony complexes that plug fiber spinnerets. As a result, during fiber spinning, frequent shutdowns are necessary to wipe the spinnerets clean of precipitated antimony compounds. In addition, there are increased environmental and regulatory controls, especially in food contact applications, due to the toxic characteristics of antimony-based catalysts.
Titanium catalysts, which are less toxic than antimony-based catalysts, have been studied extensively for use as catalysts in these esterification, transesterification, and polycondensation reactions. Titanium catalysts reduce the amount of inorganic solids in polyester formed using antimony-based catalysts, thereby reducing pack pressure in spinning and haziness in the bottle resin. Titanium catalysts also reduce spinning breaks and improve the yield in fiber spinning.
During the production of polyester, uncoated titanium dioxide (TiO
2
) has been widely used as a delusterant. It has been found, however, that uncoated titanium dioxide deactivates the titanium catalyst. As a result of this deactivation, it becomes necessary to dramatically increase the amount of titanium catalyst to achieve the same degree of polymerization as the amount of titanium catalyst used without a titanium dioxide delusterant.
There is a need for a new process for producing polyester wherein the degree of deactivation of the titanium catalyst caused by titanium dioxide is reduced or eliminated.
SUMMARY OF THE INVENTION
The present invention provides a process for producing a polyester, wherein deactivation of the titanium catalyst by a titanium dioxide is reduced or eliminated.
The present invention provides a process for producing a polyester. The process comprises polymerizing a polymerization mixture comprising (i) a carbonyl compound or an oligomer of a carbonyl compound and (ii) a glycol, in the presence of a titanium catalyst composition, to produce the polyester, wherein a coated titanium dioxide comprising a titanium dioxide and a coat is added before or during the polymerizing.
The coat of the coated titanium dioxide can comprise an aluminum compound, a silicon compound, a manganese compound, a phosphorous compound, an antimony compound, a cobalt compound, an organic compound, or a combination thereof. In one embodiment, the coat comprises at least one of an aluminum oxide, a silicon oxide, a potassium oxide, an antimony oxide, or a manganese oxide. In another embodiment, the coat comprises polyethylene oxide, trimethylolpropane, polyvinylpyrrolidone, polyvinyl alcohol, or a combination of two or more thereof.
In one embodiment, the titanium dioxide is 70 to 99.5% by weight of the coated titanium dioxide. In another embodiment, the coat is 0.5 to 30% by weight of the coated titanium dioxide.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides a process for producing a polyester which comprises polymerizing a polymerization mixture comprising (i) a carbonyl compound or an oligomer of said carbonyl compound and (ii) a glycol, in the presence of a titanium catalyst composition, to produce said polyester. In the process of the invention, a coated titanium dioxide comprising titanium dioxide and a coat is added before or during the polymerizing.
The coated titanium dioxide of the invention comprises a coat and titanium dioxide. The titanium dioxide can be anatase or rutile, and is partially or completely coated with the coat. The coat is made of an organic and/or an inorganic material. Suitable coating materials include, but are not limited to, an aluminum compound, a silicon compound, a manganese compound, a phosphorous compound, an antimony compound, a cobalt compound, an organic compound such as polyethylene oxide and/or trimethylolpropane, and combinations of two or more thereof. Preferably, the coat is 0.5 to 30% by weight of the coated titanium dioxide, more preferably 2 to 20% by weight, and most preferably 3 to 10% by weight.
Examples of coating compounds include, but are not limited to, an aluminum oxide, a silicon oxide, a potassium oxide, an antimony oxide, a manganese oxide, polyethylene oxide, and trimethylolpropane. The coat of the coated titanium dioxide is 0.5% to 30% by weight of the coated titanium dioxide.
In one embodiment, the coat of the coated titanium dioxide comprises one or more of the following, such that the coat of the coated titanium dioxide is 0.5% to 30% by weight of the coated titanium dioxide: (i) 0.01% to 10% Al
2
O
3
, preferably 0.01% to 5%; (ii) 0.01 to 20% SiO
2
, preferably 0.01 to 10%; (iii) 0.01 to 2% P
2
O
5
, preferably 0.01 to 1%; (iv) 0.01 to 1% Sb
2
O
3
; (v) 0.01 to 1% MnO; (vi) 0.01 to 20% of an organic compound such as polyethylene oxide or trimethylolpropane, preferably 0.01 to 5%.
The coated titanium dioxide can be in the form of a slurry that comprises coated titanium dioxide in a glycol and/or water. The concentration of coated titanium dioxide in the slurry can be 1 to 80%, preferably 10 to 60%, most preferably 20 to 30% by weight.
In one embodiment, the coated titanium dioxide slurry includes a glycol having 1 to 10, preferably 1 to 8, and most preferably 1 to 4 carbon atoms per molecule, such as an alkylene glycol, a polyalkylene glycol, an alkoxylated glycol, or combinations thereof. Examples of suitable glycols include, but are not limited to, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol and combinations of two or more thereof. The most preferred glycols are ethylene glycol, 1,3-propanediol, and butylene glycol, which can be used in the production of commercially important polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate.
The slurry of coated titanium dioxide can be prepared using techniques well known to those skilled in the art. The slurry can be prepared in any suitable vessel or container by techniques well known to those skilled in the art, such as wet milling, sand milling, pearl milling, ball milling, colloid milling, homogenization, centrifugation, agitation, filtration, and combinations of two or more thereof.
Optionally, the coated titanium dioxide slurry can further include a dispersing agent. The coated titanium dioxide can be mixed in the presence of a dispersing agent, such as potassium tripolyphosphate, potassium pyrophosphate, polyvinylpyrrolidone, and/or polyvinyl alcohol, with a glycol to form a slurry.
Examples of suitable dispersing compounds include, but are not limited to, a polyphosphoric acid or a salt thereof, a phosphonate ester, a pyrophosphoric acid or salt thereof, a pyrophosphorous acid or salt thereof, polyvinylpyrrolidone, polyvinyl alcohol, and combinations of two or more thereof. The polyphosphoric acid
Acquah Samuel A.
E. I. du Pont de Nemours and Company
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