Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-08-04
2001-10-16
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S272000
Reexamination Certificate
active
06303738
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for controlling color formation in polyesters and co-polymers using a catalyst comprising titanium and phosphorous.
BACKGROUND OF THE INVENTION
Polyesters such as, for example, polyethylene terephthalate and polybutylene terephthalate, generally referred to as “polyalkylene terephthalates”, are a class of important industrial polymers. They are widely used in thermoplastic fibers, films, and molding applications. They are generally 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 or polycondensation. Frequently an organic titanium compound is used as the catalyst of choice for the esterification and/or polycondensation. Certain phosphorus compounds may also be added during or after the esterification and polycondensation steps as catalyst modifiers.
An important group of polyesters are those polymers made with adipic acid and a glycol, or copolymers made with a combination of adipic acid and terephthalic acid, with a glycol such as 1,4-butanediol.
A titanium compound is often used as catalyst for the production of polyester. However, when an organic titanium compound is used as the polycondensation catalyst with adipic acid-containing monomers, the resulting polymer or copolymer is typically intensely colored, generally red. This is probably attributed to a complex formed between the titanium and the adipic acid or adipate ester.
For example, WO 99/28,033 discloses an organometallic compound suitable for use as catalyst for the preparation of an ester comprising the reaction product of an orthoester or condensed orthoester of titanium, zirconium, or aluminum, an alcohol containing at least two hydroxyl groups, an organophosphorous compound containing at least one P—OH group, and a base. It does not disclose or suggest a process useful for preventing formation of color during the polycondensation of adipic acid-based polymers or copolymers. JP 11236,442A discloses a method for producing a polyester consisting of adipic acid and 1,4-butanediol using a titanium compound as condensation catalyst to produce a molten polyester and, adding after the polycondensation step a pentavalent phosphorous compound containing at least one hydroxyl group. Since this method requires the titanium and adipate compounds to be in contact before addition of the phosphorus compound, it is only partially effective in preventing formation of a red color. JP 04080932B discloses preparation of adipic acid copolymers comprising esterification or transesterification of terephthalic acid or its derivative and butanediol in the presence of a titanium compound and, thereafter, polycondensing the resultant reaction product in the presence of a titanium compound and a pentavalent phosphorous compound. JP 60147430 discloses a method of producing a polyester by esterifying terephthalic acid, adipic acid and 1,4-butanediol in the presence of a titanium compound, and then polycondensing the resulting reaction product in the presence of a titanium compound and a pentavalent phosphorus compound. Adding the phosphorus compound as a separate compound before the polycondensation step tends to cause deactivation of the titanium catalyst.
Therefore, there is a need to develop a process for producing polyester, especially an adipic acid-base polyester or copolymer thereof, with little or no discoloration.
SUMMARY OF THE INVENTION
The term “polybutylene adipate” used in the invention is exchangeable with the term “butanediol adipate” or “1,4-butanediol adipate”
The invention provides a process that can be used to produce polyester such as, for example, polyesters of polyalkylene adipate or a copolymer thereof, such as polybutylene adipate or a copolymer thereof. The process comprises contacting, in the presence of a catalyst, at least one carbonyl compound with an alcohol, preferably an alkylene glycol, in which the catalyst comprises a titanium compound and a phosphorus compound, preferably a complex of titanium and mixed alkyl phosphate esters.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, any carbonyl compound, which when combined with an alcohol, can produce an ester or polyester can be used. Generally, such carbonyl compounds include, but are not limited to, acids, esters, amides, acid anhydrides, acid halides, salts of carboxylic acid oligomers or polymers having repeat units derived from an acid, or combinations of two or more thereof. The presently preferred acid is an organic acid such as a carboxylic acid or ester thereof, or salt thereof. The presently preferred process is the polymerization of (1) an acid or ester and (2) an alcohol or glycol for the production of a polyester.
A preferred process for producing an ester or polyester comprises, consists essentially of, or consists of contacting a reaction medium with a composition disclosed above in the first embodiment of the invention. The reaction medium can comprise, consist essentially of, or consist of an alcohol and either (1) an organic acid, a salt thereof, an ester thereof, or combinations thereof or (2) an oligomer having repeat units derived from an organic acid or ester.
The preferred organic acid has the formula of HO
2
CACO
2
H in which A is an alkylene group, an arylene group, alkenylene group, or combinations of two or more thereof. Each A has about 2 to about 30, preferably about 3 to about 25, more preferably about 4 to about 20, and most preferably 4 to 15 carbon atoms per group. Examples of suitable organic acids include, but are not limited to, terephthalic acid, isophthalic acid, napthalic acid, succinic acid, adipic acid, phthalic acid, glutaric acid, acrylic acid, oxalic acid, benzoic acid, maleic acid, propenoic acid, and combinations of two or more thereof. The presently preferred organic acid is adipic acid, phthalic acid, or terephthalic acid because the polyesters produced therefrom have a wide range of industrial applications.
Examples of suitable esters include, but are not limited to, dimethyl adipate, dimethyl phthalate, dimethyl terephthalate, methyl benzoate, dimethyl glutarate, and combinations of two or more thereof.
Any alcohol that can esterify an acid to produce an ester or polyester can be used in the present invention. The presently preferred alcohol has the formula of R(OH)
n
, an alkylene glycol of the formula (HO)
n
A
1
(OH)
n
, or combinations thereof in which each R can be the same or different and is a hydrocarbyl radical having 1 to about 10, preferably 1 to about 8, and most preferably 1 to 5 carbon atoms per radical. The presently preferred R is an alkyl radical, either branched or straight chain. A
1
is an alkylene radical having 2 to about 10, preferably 2 to about 7, and most preferably 2 to 4 carbon atoms per molecule. Each n can be the same or different and is independently a number in the range of from 1 about to about 10, preferably 1 to about 7, and most preferably 1 to 5. Examples of suitable alcohols include, but are not limited to, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, diethylene glycol, triethylene glycol, 2-ethyl hexanol, and combinations of two or more thereof. The presently most preferred alcohol is an alkylene glycol such as 1,4-butanediol.
According to the invention, the catalyst can comprise, consist essentially of, or consist of a titanium compound and a phosphorous compound. The catalyst can further comprise a solvent. Preferably, the catalyst is a reaction product, or complex, of the titanium compound and the phosphorous compound.
The preferred titanium compounds are organic titanium compounds as disclosed in U.S. Pat. No. 6,066, 714, disclosure of which is herein incorporated by reference and is omitted herein for the interest of brevity. The presently preferred titanium compounds are tetraalkyl titanates. The pres
Fortmann Kathy Lynn
Putzig Donald Edward
Boykin Terressa M.
E. I. Du Pont de Nemours and Company
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