Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-12-22
2001-07-10
Acquah, Samuel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S275000, C528S285000, C528S308100, C528S308300, C502S103000, C502S113000, C502S118000, C502S161000, C502S170000
Reexamination Certificate
active
06258925
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for manufacturing polyesters, in particular, to using a titanyl oxalate, such as lithium titanyl oxalate, as the catalyst for such reaction in combination with a catalyst enhancer such as a metallic oxalate like lithium oxalate to provide fast reactions with improved properties such as reduced acetaldehyde content and good color properties for the resulting polyester at substantially reduced catalyst levels. A synergistic relationship has been discovered between titanyl oxalate catalyst and the catalyst enhancer. A synergistic relationship has also been discovered between the titanyl oxalate catalyst, catalyst enhancer and a metallic cocatalyst such as antimony oxide or antimony triacetate.
DESCRIPTION OF THE PRIOR ART
Polycondensation reactions that produce polyesters require an extremely long period of time that is significantly reduced by a suitable catalyst. Various types of catalysts are used to shorten the reaction time. For example, antimony trioxide antimony triacetate and antimony trisglycoxide are generally used as polycondensation catalysts.
Titanyl oxalate compounds have been suggested as catalysts for polycondensation reactions to produce polyesters. However, titanyl oxalate catalysts when used as polycondensation catalysts for polyesters have caused color problems in the resulting polyester.
Polyesters are obtained by esterification, ester interchange or polycondensation of dibasic acids such as terephthalic acid and isophthalic acid or esters thereof, functional derivatives of acid chlorides and glycols such as ethylene glycol and tetramethylene glycol or oxides thereof and functional derivatives of carbonic acid derivatives. In this case, a single polyester is obtained when one dibasic acid component and glycol component is used. Mixed copolyesters can be obtained when at least two or more types of dibasic acid component and glycol component are mixed, esterified or subjected to ester interchange and then subjected to polycondensation. When a single polyester or two or more initial polycondensates of a mixed copolyester are subjected to polycondensation, an ordered polyester is obtained. In this invention, the term polyester is a general designation for these three types.
Prior literature has disclosed titanyl oxalate compounds for use as polycondensation catalysts for polyesters. The titanyl oxalate compounds disclosed include potassium titanyl oxalate, ammonium titanyl oxalate, lithium titanyl oxalate, sodium titanyl oxalate, calcium titanyl oxalate, strontium titanyl oxalate, barium titanyl oxalate, zinc titanyl oxalate and lead titanyl titanate. However, based upon the examples in such literature references, only potassium and ammonium titanyl oxalate have actually been used to catalyze the polyester forming reaction. See for example Japanese Patent Publication 42-13030, published on Jul. 25, 1967. European Patent application EP 0699700 A2 published Mar. 6, 1996 assigned to Hoechst and entitled “Process for production of Thermostable, Color-neutral, Antimony-Free Polyester and Products Manufactured From It” discloses the use as polycondensation catalyst, however only potassium titanyl oxalate and titanium isopropylate were used for such a catalyst, and, while improved color and antimony free polyester are disclosed, cobalt or optical brighteners were also employed. Other patents have disclosed potassium titanyl oxalate as a polycondensation catalyst for making polyester such as U.S. Pat. No. 4,245,086, inventor Keiichi Uno et al., Japanese Patent JP 06128464, Inventor Ishida, M. et al. U.S. Pat. No. 3,957,886, entitled “Process of Producing Polyester Resin” of Hideo, M. et al, at column 3, line 59 to column 4, line 10, contains a disclosure of titanyl oxalate catalysts for polyesters including a listing of many types of titanyl oxalate catalyst. However, only potassium titanyl oxalate and ammonium titanyl oxalate were used in the examples and lithium titanyl oxalate was not even listed among their preferred titanyl oxalate catalysts.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery that nontitanyl oxalates can enhance the catalytic functionality of titanyl oxalate catalysts. This invention provides a novel catalytic composition containing a titanyl oxalate catalyst and a metallic oxalate catalyst enhancer and optionally containing a metallic cocatalyst such as an antimony based catalyst. A synergistic relationship has been discovered between titanyl oxalate catalyst and the catalyst enhancer. A synergistic relationship has also been discovered between the titanyl oxalate catalyst, catalyst enhancer and a metallic cocatalyst such as antimony oxide or antimony triacetate. Also provided is an improved process of producing polyester by the polycondensation of polyester forming reactants in the presence of a catalytically effective amount of a polycondensation catalyst, wherein the improvement comprises utilizing, as the polycondensation catalyst, the novel catalyst composition containing a titanyl oxalate such as lithium titanyl oxalate and a catalyst enhancer such as a nontitanyl metallic oxalate like lithium oxalate and optionally containing a metallic catalyst such as antimony oxide or antimony triacetate. The improved process produces an improved polyester having lower acetaldehyde numbers and good color. The titanyl oxalate/catalyst enhancer composition can be used as a polycondensation catalyst in combination with other catalysts to achieve synergistic catalytic activity. Preferred is a combination of lithium titanyl oxalate, Li
2
TiO(C
2
O
4
)
2
, lithium oxalate, Li
2
(C
2
O
4
)
2
with antimony oxide or antimony triacetate.
DETAILED DESCRIPTION OF THE INVENTION
The production of polyester by polycondensation of polyester forming reactants is well known to those skilled in the polyester art. A conventional catalyst for the reaction is antimony oxide. The present invention is based upon the discovery of a synergistic relationship between titanyl oxalate catalysts and metallic oxalate catalyst enhancer (e.g. lithium oxalate) is surprisingly superior in catalyst performance for polycondensation reactions by producing polyesters of superior color (white) in comparison to other titanyl oxalate catalysts. The need for an antimony containing catalyst can thereby be eliminated, and an antimony free polyester can thereby be produced with lithium titanyl oxalate as the catalyst. Such advantages provided by using lithium titanyl oxalate are retained when lithium titanyl oxalate is used in combination with other polycondensation catalysts for producing polyester as long as lithium titanyl oxalate comprises at least 1 parts per million (preferably 1 to 20) based on the weight of titanium in the reaction mixture. Included within the meaning of the term “lithium titanyl oxalate” as used herein are di lithium titanyl oxalate [Li
2
TiO(C
2
O
4
)
2
] and mono lithium titanyl oxalate wherein one of the lithiums of di lithium titanyl oxalate is replaced with another alkaline metal such as potassium (e.g., LiKTiO(C
2
O
4
)
2
) and such compounds with or without water of hydration. Lithium titanyl oxalate catalysts can be combined with antimony catalyst to achieve the benefits of both catalysts when elimination of antimony is not a requirement for the resulting catalyzed product.
In addition to enhancing the catalytic effect of titanyl oxalates for catalyzing polycondensation reactions, the metallic oxalates can enhance the catalytic effectiveness of titanyl oxalates for catalyzing esterification and transesterification reactions when used in catalytically effective amounts with reactants known to participate in esterification or transesterification reactions. A catalytically effective amount is suitable. Preferred is about 3 parts of titanyl oxalate based on the weight of titanium per million parts of esterification or transesterification reaction mixture.
Reactants for forming polyesters via a polycondensation reaction are well known to those skilled in the art and disclosed
Dowling Conor M.
Seshadri Sri R.
Acquah Samuel
ATOFINA Chemicals, Inc.
DeBenedictis Nicholas J.
Marcus Stanley A.
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