Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-28
2003-01-14
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S272000, C528S286000, C528S301000, C528S302000, C528S308000, C528S308600, C525S437000, C524S706000, C524S710000
Reexamination Certificate
active
06506853
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for producing a substantially soluble isophthalic acid in glycol solution, to a process for using the solution in manufacturing a copolymer having repeat units derived from a carbonyl compound, isophthalic acid, and glycol, and to a process for producing the copolymer in the presence of a phosphorus compound.
BACKGROUND OF THE INVENTION
Polyesters are widely used to manufacture textile fibers and bottle resins. The largest volume polyester is polyethylene terephthalate (PET). Polypropylene terephthalate and polybutylene terephthalate are gaining importance. Polyester can be manufactured by combining a glycol such as ethylene glycol and a carbonyl compound such as dimethyl terephthalate (DMT) or terephthalic acid (TPA).
For example, DMT reacts with glycol to form bis-glycolate ester of terephthalate (“monomer”) in the ester exchanger column. The monomer is polymerized by condensation reactions in one or two prepolymerizers and then a final polymerizer or finisher. TPA can be combined with a glycol to form a slurry at 60 to 80° C. followed by injecting the slurry into an esterifier. Linear oligomer with degree of polymerization less than 10 is formed in one or two esterifiers at temperatures from 240° C. to 290° C. The oligomer is then polymerized in one or two prepolymerizers and then in a final polymerizer or finisher at temperatures from 250° C. to 300° C.
Additives such as catalysts, stabilizers, delusterants, and toners are often added to the DMT process before the ester exchanger, in the exchanger, or in the monomer before the prepolymerizer, or to the TPA slurry before the esterifier, in the esterifier, or in the oligomer before the prepolymerizer. Commercial polyester processes commonly use antimony compounds as polycondensation catalyst and phosphorous compounds as stabilizers. See generally, Encyclopedia of Chemical Technology, 4
th
edition, John Wiley, New York, 1994, Volume 10, pages 662-685 and Volume 19, pages 609-653.
Many commercial processes have one common esterification process or one common ester exchange process, which supplies oligomer or monomer to several continuous polymerization (CP) processes. Some of the CP processes produce polyester for fibers, while other CP processes produce polyester for packaging materials or other products. Different polyester products require different additives. In the case where one esterification process or one ester exchange process supplies several CP processes, most additives are added to the oligomer or monomer before the prepolymerizer.
Polyesters are sometimes modified with addition of a co-monomer such as isophthalic acid (IPA). For example, PET for bottle resin contains 1 to 5% IPA and 99 to 95% TPA by mole. A few PET fibers such as low-melt binders contain 10% to 45% IPA, and 90% to 55% TPA by mole, most PET for textile fiber does not contain IPA. Common practice in PET production is to have one common esterification process or ester exchange process to supply oligomer or monomer to two or more CP processes for different products, where some products need co-monomer and some do not. Currently two approaches are practiced for the addition of IPA co-monomer to PET.
One approach is to build a separate continuous esterification process to produce IPA oligomer at 240° C. to 290° C., which is injected to TPA oligomer process or DMT monomer process which is to be used for packaging materials or fibers that require IPA. The injection temperature is normally higher than 240° C. to avoid solidifying of IPA oligomer. In this approach, IPA goes to the products where it is needed. However, the separate esterification process for IPA oligomer is complicated and expensive.
Another approach is to add IPA slurry to TPA slurry or esterifier of the common esterification process. IPA slurry is generally produced by suspending IPA powder or particles in a glycol at 60° C. to 80° C. In this approach, the IPA goes to all the products whether it is desired or undesired.
Japanese Patent No. 11158260 discloses adding IPA slurry and ethylene glycol to TPA oligomer line to make copolymer. A sufficiently high flow rate of IPA slurry is required to avoid settling in the piping or injection nozzle and consequently shutting down the process. Japanese Patent No. 11209465 discloses adding a phosphorus compound to the IPA in ethylene glycol slurry and (PET) oligomer.
Therefore, there is an increasing need to develop a process for producing a substantially soluble IPA in glycol solution, which is less expensive and more flexible to operate than the known processes in manufacturing copolymer containing TPA and IPA.
SUMMARY OF THE INVENTION
A substantially soluble solution comprises isophthalic acid in a first glycol.
A process for producing a substantially soluble isophthalic acid in a first glycol solution comprises combining the isophthalic acid with the first glycol under an effective condition sufficient to substantially esterify the carboxyl group of the isophthalic acid with the glycol.
A process comprises contacting, optionally in the presence of a phosphorus compound and/or a catalyst, either (a) an isophthalic acid or substantially soluble isophthalic acid in a first glycol with a polymerization mixture comprising a carbonyl compound and a second glycol or (b) an isophthalic acid or substantially soluble isophthalic acid in a first glycol with an oligomer derived from a carbonyl compound and a second glycol under a condition effective to produce a copolymer comprising repeat units derived from the carbonyl compound or its ester, isophthalic acid and the first and/or second glycol.
DETAILED DESCRIPTION OF THE INVENTION
The term “substantially” refers to more than trivial and “substantially soluble” can mean that the concentration of insoluble isophthalic acid (IPA) in glycol is lower than 5 g, preferably lower than 2 g, and most preferably lower than 1 g per 100 g of glycol. The weight % of IPA in the solution can be in the range of from about 5% to about 75%, preferably about 5% to about 60%, more preferably 10% to 40%, and most preferably 20% to 35%, based on the total weight equaling 100%. A substantially soluble IPA in glycol solution generally remains soluble, without forming dispersion or gels, at room temperature (about 25° C.).
The preferred first glycol can have 1 to about 10, preferably 1 to about 8, and most preferably 1 to 4 carbon atoms per molecule such as, for example, an alkylene glycol, a polyalkylene glycol, 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 glycol is ethylene glycol for it can be used in the production of a PET copolymer.
The process of the invention can be carried out by combining IPA with a glycol to form a slurry in any suitable vessel, container, or reactor. The slurry can be heated under any suitable condition effective to esterify about 50% to about 100%, preferably about 70% to about 98%, more preferably about 75% to about 95%, and most preferably 80% to 95% of the carboxyl groups in IPA, all mole %. A suitable condition can include a temperature in the range of from about 100° C. to about 250° C., preferably about 140° C. to 220° C., and most preferably 160° C. to 190° C.; a pressure that can accommodate the temperature range; and a period sufficient to substantially solubilize IPA in the glycol, generally about 1 minute to about 5 days, preferably about 10 minutes to about 2 days, and most preferably about 30 minutes to about 4 hours.
Wishing not to be bound by theory, it is believed that during the heating, the carboxyl groups in IPA are partially esterified by glycol, which is completely or substantially dissolved in glycol. This completely dissolved IPA solution can solidify or become gel when the s
Acquah Samuel A.
E. I. du Pont de Nemours and Company
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