Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1996-12-09
1998-11-03
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528274, 5283082, 5283084, 5283085, 5283086, 528499, 528502, 528503, 524714, 524765, 524773, C08G 6378
Patent
active
058309810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE TECHNIQUE
The present invention relates to a process for producing a polyethylene terephthalate to be used for molding various products including bottles, films and sheets and, in particular, to a process for producing such a polyethylene terephthalate as to cause metal mold staining upon the molding to occur difficultly.
BACKGROUND OF THE TECHNIQUE
For the material of the containers for, such as condiments, vegetable oils, drinks, cosmetics and detergents, various resins have hitherto been employed in accordance with each specific contents charged therein and with the purpose of the use thereof.
Among them, polyethylene terephthalate is particularly suitable as the material of containers to be charged with drinks, such as juices, refrigerants and carbonate drinks, since it is superior in the mechanical strength, heat resistance, transparency and gas-barriering property.
The polyethylene terephthalate can be obtained by esterifying dicarboxylic acids including mainly terephthalic acid or ester-forming derivatives of such acids with glycols including mainly ethylene glycol or with ester-forming derivatives of such glycols and subjecting the resulting esters to a liquid phase polycondensation and, then, to a solid phase polycondensation. In general, such polyethylene terephthalate is supplied to a molding machine, such as an injection molding machine, to shape it into a preform for a hollow molded article, whereupon the preform is placed in a metal mold to subject it to an expansion blow molding or, further, to a heat treatment (heat setting) to form into a hollow molded container.
Conventional polyethylene terephthalates obtained by the production process described above contain oligomers, such as cyclic trimer etc., which cause staining of the metal mold by adhering on, for example, the inner surface of the metal mold for blow molding, the gas exhaustion outlet and vent pipe, or on the vent portion of the metal mold of injection molding machine mentioned above.
Such a metal mold staining may cause a rough surface or a whitening of the resulting bottles. When whitening of bottles occurs, such bottles must be discarded. Therefore, such metal mold staining must be removed at frequent intervals upon molding bottles using a hitherto known polyethylene terephthalate, whereby a large problem is brought about in that the bottle productivity decreases considerably.
The principal cause for the occurrence of metal mold staining upon molding is due to an increase in the total amount of the oligomers, such as cyclic trimer etc., resulting from the formation of large amount of such oligomers during the molding with a polyethylene terephthalate. In order to prevent this, a measure has been proposed for markedly suppressing the increase of total amount of oligomers, such as cyclic trimer etc., during the molding, by causing the polyethylene terephthalate resulting from the solid phase polycondensation to contact with water (Japanese Patent Kokai No. 47830/1991).
In conventional processes for producing polyethylene terephthalate, a polycondensation catalyst, such as germanium dioxide or the like, is employed, which is difficultly soluble in the reaction system and, hence, has been customed to be added to the reaction system after having been dissolved using an alkaline solubilizing agent, such as tetraethylammonium hydroxide (EAH).
The inventors carried out sound research as to polyethylene terephthalates and to the process for their production, in order to obtain such a polyethylene terephthalate in which the amount of oligomers formed during the molding is further decreased and the metal mold staining occurs difficultly, whereby it was discovered that the lower the amount of the alkaline solubilizing agent for dissolving the polycondensation catalyst, the more was the increase in the total amount of oligomers, such as cyclic trimer, in the resulting polyethylene terephthalate upon the molding able to be suppressed, whereupon the present invention was led to completion.
An object of the present invention
REFERENCES:
patent: 5241046 (1993-08-01), Shiraki et al.
Koreishi Hiroshi
Miura Kimiyoshi
Tanaka Yasuhiro
Acquah Samuel A.
Mitsui Petrochemical Industries Ltd.
LandOfFree
Process for producing polyethylene terephthalate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing polyethylene terephthalate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing polyethylene terephthalate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-690059