Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-05-14
2003-04-22
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C528S275000, C528S279000, C528S281000, C528S285000, C528S298000, C528S302000, C528S308000, C528S308600, C264S331110, C264S503000, C264S513000, C428S036920
Reexamination Certificate
active
06551675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a copolyester containing ethylene naphthalate unit (EN) and its application. The present invention discloses a manufacturing method of using 2,6-naphthalenedicarboxylic acid (NDA), purified terephthalic acid (PTA), and ethylene glycol (EG) to proceed with esterification reaction or using dimethyl 2,6-naphthalenedicarboxylate (NDC), dimethyl terephthalate (DMT), EG, and transesterification catalyst to proceed with transesterification reaction or using the PTA process. While the esterification reaction reaches 85~98 percent of esterification ratio, NDC, EG, and transesterification catalyst are added to proceed with transesterification reaction. The monomer obtained from each of previous process is added with polymerization catalyst thereafter to proceed with polycondensation reaction to produce copolyester. The produced copolyester is further polymerized at solid state to increase its viscosity. Then, the copolyester is ejected to be blow-molded so as to produce the one-way bottle which can be pasteurization.
2. Problems to be Solved by the Present Invention
Polyethylene terephthalate (PET) is widely used in food packaging vessel, fiber, film, and transparent sheet at the present time, particularly in food packaging vessel owing to its environmental advantages such as light weight, high transparency and shinning, good air impermeability, and being recyclable. Therefore, it's greatly used to manufacture bottles for carbonic beverage, juice, mineral water. However, PET bottles are recently used to contain those which are sensitive to oxygen such as beer, milk, food product, potato product, which require higher standard for the permeability of carbon dioxide. Especially, a common PET bottle is lack of the capability of preventing the oxygen from getting into the bottle and of preventing the carbon dioxide from permeating out of the bottle while containing beer product. Besides, the common PET bottle can not meet the requirement of pasteurization while filling. Therefore, several prior arts disclose the method of improving the air impermeability of present PET bottle. One of the prior arts is to use di-ester or di-acid compound which contains di-cyclobenzene structure, such as dimethyl 2,6-naphthalenedicarboxylate or 2,6-naphthalenedicarboxylic acid to react with excess ethylene glycol to obtain homopolymer polyethylene naphthalate (PEN) thereby. PEN owns very good glass transition temperature (Tg) up to 120° C. so as to be able to meet the requirement of pasteurizatio. Consequently, PEN bottle has already been used in packaging beer by some brewer. However, PEN has its limitation in application due to higher price. Therefore, PEN bottles are nowadays recycled for many times. Some of the prior arts then blend PEN and PET so as to decrease the cost and also improve the air impermeability and heat durability. Nevertheless, the blending of the two polymers involve the difference of their adaptability. Therefore, an appropriate physical specification should be concerned when they are blended.
The present invention thus discloses a manufacturing method of PET copolymer which contains an appropriate amount of PEN. The copolymer does not have the said problem of adaptability; and the bottle made of the copolymer is suitable for one-way bottle and can meet the requirement of pasteurization.
3. Description of Prior Arts
The prior arts which intend to solve the said problem of adaptability are discussed as follows:
The U.S. Pat. No. 5594092 of Shell corp. discloses a process of combining both PTA process and transesterification reaction to produce either PET copolyester containing PEN or PEN copolyester containing PET. The NDC, EG, and transesterification catalyst react to produce monomer—BHEN which is further added with polymerization catalyst to proceed with polymerization so as to have the molecular weight of BHEN monomer being between 4800 and 24200. Then, the BHEN monomer is injected to the esterification reaction of PET process. Further, through polymerization reaction, the PET/PEN copolyester is produced. This patent claims the PEN component of the copolyester is between 2~5 mole %.
The U.S. Pat. No. 5895807 of Shell corp. discloses a process of combining both PTA process and transesterification reaction to produce either PET copolyester containing PEN or PEN copolyester containing PET. The NDC, EG, and transesterification catalyst react to produce BHEN. While the molecular weight of BHEN is below 400, the BHEN is injected to the esterification reaction of PET process. Further, through polymerization reaction, the PET/PEN copolyester is produced. This patent claims the PEN component of the copolyester is between 1~15 mole %.
The U.S. Pat. No. 6031065 of Wellman corp. discloses a process, wherein the NDC is injected into the first tank of esterification in PTA process. The produced water and methyl alcohol are transformed into carbon dioxide and water by the combustion equipment at the top of distillation tower.
The PEN disclosed by the ROC patent No. 82111169 of the PET Continental Technology corp. of the USA is applied in multi-layer refilled container which differs from the one-way bottle.
The ROC patent No. 85113329 of Japan Mitsui Chemical Corp. discloses a process of combining NDA and EG into PEN homopolymer on condition of existing in water which differs from the PET copolyester containing a little PEN of the present invention.
The naphthalene irregular copolyester disclosed by ROC patent No. 84107601 of the ROC National Science Committee contains two repeat units. The first repeat unit contains the following formula:
The second repeat formula contains the following formula:
The copolyester thereof differs from the PET copolyester containing a little PEN of the present invention.
The Technical Skill Utilized by the Present Invention
One of the practiced examples is to use a relatively less but appropriate amount of NDC or NDA to react with a relatively greater amount of DMT or PTA so as to produce the PET copolyester which contains a less but appropriate amount of PEN. The main body of the copolyester is the ethylene terephthalate unit, the structural formula of which is as follows:
and the structure formula of the ethylene naphthalate unit which is less but appropriate in terms of quantity is as follows:
the bottle made of the said copolyester owns a better air impermeability than the common PET bottle and meets the requirement of hot filling. The air impermeability of the bottle made of the said copolyester may be not so good as that of the bottle made of PEN though, the price of which has the advantage of lower cost. This characteristic contributes to a wide application of the one-way bottle which needs to meet the requirement of pasteurization. In addition, the adaptability between the ethylene terephtahlate unit and ethylene naphthalate unit in the copolyester is good while blended.
The main body of the copolyester in the present invention can be polyethylene terephthalate (PET), or polypropylene terephthalate (PPT), or polybutylene terephthalate (PBT), among which the PET is preferable.
Furthermore, there are two manufacturing methods of PET for the prior art. One is using purified PTA as raw material which goes on esterification reaction with excess EG. While the esterification ratio reaches above 95 percent, the polymerization reaction proceeds so as to obtain PET. This method is called PTA process. The other one is using DMT as raw material which goes on transesterification with excess EG and then goes on polymerization so as to obtain PET. This method is called DMT process. The PTA process has advantages of better skill and lower cost. From technical point of view, the PTA process does not produce methyl alcohol so that the wastewater at the top of distillation tower is relatively easier to treat. In addition, the excess EG required for PTA process is less than that required for DMT process. In addition, the PTA process does not need to use the este
Acquah Samuel A.
Nan Ya Plastics Corporation
Stevens Davis Miller & Mosher LLP
LandOfFree
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