Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Patent
1990-12-03
1994-07-19
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
250223B, 209578, G01N 2190
Patent
active
053311671
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of inspecting a heat-resistant multilayer container made of synthetic resin, capable of evaluating the quality of a product of a heat-resistant multilayer container on the basis of a non-destructive technology and to an apparatus to be utilized for the method.
BACKGROUND ART
Marketing of containers made of synthetic resin, particularly of PET (Polyethylene Terephthalate), has been widely developed mainly regarding large sized containers for soft drinks. Recently, usage of a heat resistant container has been required and, hence, much study and development has been carried out.
Synthetic resin containers of the heat-resistant multilayer type are generally composed of a mouth portion with which a lid is screw engaged, and a shell portion continuous to the lower end of the mouth portion. Such containers are manufactured by forming a parison formed of a main resin and a heat-resistant resin and forming a shell portion by holding a mouth portion of the parison and by performing a drawing blow process.
The formation of the heat resistant container involves such problems as degradation of the heat resistant deformability, chemical resistance and strength of the mouth portion because the mouth portion is not drawn and maintained as it is injected. In order to obviate these problems, conventional art provides such methods as (a) a method in which the mouth portion is heat crystallized, (b) a method in which the mouth portion is formed by two-color formation of the heat-resistant resin and (c) a method in which the mouth portion is formed by preliminarily forming an outer periphery of the mouth portion with the heat-resistant resin and carrying out insertion formation in the preliminarily formed product.
However, the mouth portion formed by the method (a) involves faults such that diameters of a screw thread and a screw root thread of the mouth portion as well as the size thereof are not stably formed because of shape deformation during the heat crystallization process of the mouth portion, the sealing performance thereof is degraded because of the deformation of a top surface of a seal portion, and this method also is not applicable in a case where a totally transparent container is required, because of the opacity due to the crystallization. Furthermore, a crystallizing process is additionally needed, resulting in less productivity of products and an increased cost.
The mouth portion formed by the method (b) has an insufficient layer-to-layer adhesive strength between the main resin and the heat-resistant resin and, in addition, requires a plurality of molding devices for the manufacturing thereof, involving complicated processes and, hence, resulting in cost respectively.
The mouth portion formed by the method (c) has also insufficient layer-to-layer adhesive strength between the main resin and the heat-resistant resin and also requires a plurality of molding devices. An insert device is further needed, thus also involving complicated processes and cost respectively.
There has been proposed a further method for eliminating the defects described above in which the main and heat resistant resins are co-injected from the lower portion to thereby form a parison and the parison is thereafter subjected to drawing blow formation to form a heat-resistant multilayer container. In such a parison formation method, it is required to utilize a hot runner for uniformly co-injecting the molten resin of the main and heat-resistant resins in accordance with the predetermined timing and injection quantity. The applicant of the present invention has developed a co-injection molding machine provided with a hot runner in which a hot runner portion, except a hot-runner branching point and a portion near that point, is composed of a pair of molten resin flow passages extending mutually closely and having the same cross sections and there is provided an area which combines two resin flows to the branching point (Japanese Patent Laid-open Publication No. 61-252977).
It is requi
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Hoshino Masaru
Yamada Tsutoo
Dai Nippon Insatsu Kabushiki Kaisha
Dunn Drew A.
Fields Carolyn E.
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