Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-06-15
2002-02-26
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S285000, C528S286000, C528S302000, C528S307000, C528S308100, C528S308600, C528S501000, C524S706000, C524S780000, C524S783000
Reexamination Certificate
active
06350851
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyester production method and to polyester production raw materials. More specifically, it relates to a method of producing a polyester by using deionized high-purity bis-&bgr;-hydroxyethyl terephthalate containing cations and anions in a total weight of not more than 50 ppm as part of a raw material for the production of a polyester.
PRIOR ART
In the knowledge that a polyester, especially a polyester essentially composed of polyethylene terephthalate exhibits performance well adapted to various application purposes, the polyester has been widely used in fibers, films and resins. In recent years, it has been used in a wider variety of fields. Various industrial methods for producing a polyester have been proposed. Out of these, a method in which polyethylene terephthalate is obtained by polycondensing a reaction product obtained by directly esterifying terephthalic acid and ethylene glycol or carrying out an ester exchange reaction between a lower alkyl ester of terephthalic acid, for example, dimethyl terephthalate and ethylene glycol at a high temperature under high vacuum is widely put to practical use currently.
As the polyester is used for various purposes as described above, higher quality is required of the polyester for the purposes in terms of various items. Since the polyester is basically produced by highly polymerizing an esterified product or ester exchange reaction product at a high temperature under high vacuum in the presence of various metal compounds as a polymerization catalyst by maintaining it in a molten state for a long time, it is not easy to satisfy all the requirements. Under the situation, it is important not only to obtain higher quality polyester raw materials but also to bring out the function of a polymerization catalyst to the full extent. The present inventors have found that a polyester raw material from which cations and anions generally existent therein have been removed satisfies requirements for higher quality and proposed separately. The present inventors conducted further studies on a polymerization method when the specific polyester raw material is used and accomplished the present invention.
SUMMARY OF THE INVENTION
That is, it is an object of the present invention to provide a method of producing a polyester from high-purity bis-&bgr;-hydroxyethyl terephthalate containing cations and anions in trace amounts.
It is another object of the present invention to provide a novel method of producing a polyester from the above high-purity bis-&bgr;-hydroxyethyl terephthalate based on a surprising fact discovered by the present inventors that polycondensation does not proceed at a substantial speed even when a polymerization catalyst such as antimony trioxide is added to the above high-purity bis-&bgr;-hydroxyethyl terephthalate and heated under reduced pressure.
It is still another object of the present invention to provide an industrially advantageous method of producing a copolymerization polyester containing a polyethylene terephthalate or ethylene terephthalate polymerization unit from the above high-purity bis-&bgr;-hydroxyethyl terephthalate.
It is a further object of the present invention to provide a method of producing a polyester by using the above high-purity bis-&bgr;-hydroxyethyl terephthalate as at least part of a raw material for the production of a polyester.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, the above objects and advantages of the present invention are attained by a method for producing a polyester comprising the steps of:
(1) providing polyester production raw materials including bis-&bgr;-hydroxyethyl terephthalate containing cations and anions in a total weight of not more than 50 ppm, ethylene glycol and at least one polymerization catalyst selected from the group consisting of antimony trioxide and germanium dioxide;
(2) heating the polyester production raw materials without distilling off ethylene glycol; and
(3) polycondensing the raw materials by heating under reduced pressure while distilling off ethylene glycol.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The bis-&bgr;-hydroxyethyl terephthalate prepared in the step (1) of the present invention contains cations and anions in a total weight of not more than 50 ppm. The bis-&bgr;-hydroxyethyl terephthalate used in the present invention embraces not only what contains both anions and cations but also what contains only anions or cations if the total weight of cations and anions is not more than 50 ppm. The bis-&bgr;-hydroxyethyl terephthalate used in the present invention may be called “deionized bis-&bgr;-hydroxyethyl terephthalate”. The cations as used herein are those of (I) Na, Mg, Ca, Fe, Co, Zn, Ti, Sn, Sb, Ge and P, and the anions are those of (II) halogen, NO
2
, NO
3
, PO
4
and SO
4
.
According to the results of studies conducted by the present inventors, a polyester obtained from the deionized bis-&bgr;-hydroxyethyl terephthalate has high quality.
According to the results of studies conducted by the present inventors, it has been found that it is practical to substantially decationize and deanionize a solution containing ethylene glycol as the main solvent and bis-&bgr;-hydroxyethyl terephthalate as the main solute using an ion exchanger, especially an ion exchange resin, in order to prepare deionized bis-&bgr;-hydroxyethyl terephthalate used in the present invention. An example of the ion exchange resin for decationization suitable for the embodiment above is an Amberlite cation exchange resin (of Organo Co., Ltd.) and an example of the ion exchange resin for deanionization suitable for the embodiment above is an Amberlite anion exchange resin (of Organo Co., Ltd.). The step in which this ion exchange resin is used can be carried out by using a conventionally known method. Especially when decationization and deanionization operations are to be carried out, it is preferred to select a temperature at which bis-&bgr;-hydroxyethyl terephthalate does not separate out in a solution containing ethylene glycol as the main solvent and bis-&bgr;-hydroxyethyl terephthalate as the main solute and the ion exchange resin can be stably used and the concentration of bis-&bgr;-hydroxyethyl terephthalate in the solution. A decolorization step can be added before or after this step, whereby the total content of cations and anions can be reduced to 50 ppm or less and bis-&bgr;-hydroxyethyl terephthalate having excellent whiteness can be obtained advantageously. It is preferred to carry out the decolorization step by passing through a decolorizing material such as activated carbon in the same manner as the decationization and deanionization operations.
According to the results of studies conducted by the present inventors, it has been found for the first time that when the deionized bis-&bgr;-hydroxyethyl terephthalate is used as at least part of a raw material for the production of a polyester, particularly the thermal stability of the obtained polyester when it is to be put to practical use as a fiber, film or molded product such as a bottle becomes high, making molding easy. Further, when polyester molded products are to be depolymerized, substantially restored to the stage of bis-&bgr;-hydroxyethyl terephthalate and used as a raw material for the production of a polyester, a high-quality polyester can be practically produced by using the above deionized bis-&bgr;-hydroxyethyl terephthalate in the method of the present invention. Stated more specifically, a depolymerized product obtained by depolymerizing polyester molded products using ethylene glycol can be obtained as a solution containing ethylene glycol as the main solvent as described above. Deionized bis-&bgr;-hydroxyethyl terephthalate specified by the present invention can be used again as a raw material for the production of a high-quality polyester by subjecting the solution to the step of removing cations and anions or the decolorizing step a
Inada Shuji
Sato Kikuchi
Acquah Samuel A.
AIES Co., Ltd.
Anderson Kill & Olick
Lieberstein Eugene
Meller Michael
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