PROCESS FOR MANUFACTURING DRAW BLOW-MOLDED BOTTLES OF SATURATED POLYESTER

Abstract: Process for manufacturing draw blow-molded bottles of saturated polyester, which involves the treatment of strengthening the neck of a bottle. In molding according to draw blowing using beads (1), the treatment of strength­ ening the bottle neck is conducted by effecting injection introduction of saturated polyester into metal mold (2) through inlet (3) provided on the side of bottle neck (1a) as well as through ordinary inlet (4) provided on the bottle bottom side so as to cause the molten material to run along the inside surface of the metal mold, thereby to impart centrifugal force and realize molecular orientation.

Description: SPECIFICATION PROCESS FOR PRODUCING SATURATED POLYESTER BOTTLES BY ORIENTATION BLOW MOLDING Technical Field: The present invention relates to an improved process for producing saturated polyester bottles with a reinforced neck by orientation blow molding. Background Art: Recently, saturated polyester bottles produced by orientation blow molding are attracting attention because of their advantages such as excellent gas barrier properties, glass-like clarity, shatter resistance, and non-toxicity. These characteristics which are attributable to the orientation of molecules do not manifest themselves in the bottle necks which do not undergo orientation. Therefore, the bottle necks sometimes give rise to whitening or crazing when attacked by alcohols, esters, etc. contained in high concentrations in the contents of bottles. To eliminate this drawback, a process has been developed in which the part of bottle neck is annealed before the parison is blow molded, immediately after the parison has been blow molded, or after the blow molded bottle has been cooled. This annealing is based on the principle that when subjected to slow cooling, saturated polyesters, even though unoriented, whiten, forming crystals (spherulites), and become chemically stable against the attack of alcohols etc. Annealing, however, requires additional heating and cooling cycles that slow down the entire process. Disclosure of Invention: It is the object of this invention to provide a new process which is free from the above-mentioned drawbacks. The process of this invention is based on the principle that if injection into a mold is performed in such a manner that a saturated polyester is subjected to a centrifugal force, the orientation of molecules takes place and the saturated polyester exhibits improved properties which are obtained normally by orientation. According to the process of this invention, the parison is made by injecting a molten resin from the bottom and, simultaneously, by injecting a molten resin from the side of the bottle neck in such a manner that the injected molten resin circulates vigorously to give centrif ugal force to resin molecules. The molten resin filled in the neck part of the parison circulates vigorously in the mold, generating a centrifugal force which orients resin molecules. The bottle formed from this parison by orientation blow molding exhibits outstanding properties attributable to molecular orientation of the whole bottle. In the process of this invention, no additional step is required after parison molding. Brief Description of Drawings: Fig. 1 is an elevation half in section of the parison as formed in the mold. Fig. 2 is a sectional view taken in the direction of the arrows along line II-II of Fig. 1. Best Mode for Carrying Out the Invention: An embodiment of the present invention will be described with reference to the accompanying drawings, in which a mold 2 for molding a parison 1 is provided with a first inlet 3 through which molten resin enters the neck la of the parison and a second inlet 4 through which molten resin enters the bottom lb of the parison. The first inlet 3 is for a saturated polyester of high intrinsic-viscosity number which is resistant to whitening and crazing, and the second inlet is for a saturated polyester of low intrinsic-viscosity number which is good in moldability. Adequate adjustment is made so that the molten resin from the inlet 3 fills the neck la and the molten resin from the inlet 4 fills the body lc and the bottom lb. The parison 1 thus formed has the neck la in which resin molecules are oriented due to the centrifugal force generated during injection, and therefore, no additional steps are required to bring about orientation in the neck. Description of Symbols: 1 ... Parison la ... Neck lb ... Bottom lc ... Body 2 ... Mold 3 ... Inlet 4 ... Inlet

Claims: Claim: A process for producing a saturated polyester bottle by orientation blow molding which comprises preparing a parison by injecting a molten resin into the mold of neck part in such a manner that the injected molten resin circulates vigorously in the cavity, in addition to injecting a molten resin into the mold of bottom and body parts in the conventional manner, and subsequently subjecting thus prepared parison to orientation blow molding.

Inventors: ITAKURA, TAKESHI
Applicants: YOSHINO KOGYOSHO CO., LTD.
Application year: 1981
Main classification: B29D23
IPC codes: B29C45, B29C49