Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-02-08
2001-11-20
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036910, C428S542800, C156S244130, C264S513000, C264S514000, C264S515000
Reexamination Certificate
active
06319574
ABSTRACT:
TECHNICAL FIELD
This invention relates to a multi-layer plastic preform for blow molding a container and also relates to the method for making the preform.
BACKGROUND ART
Plastic blow molding of containers is conventionally performed either by extrusion of a hot plastic parison or by a plastic preform which is usually injection molded from plastic. The hot plastic parison or heated preform is received within a mold cavity whereupon pressurized gas provides the blow molding of the container to the shape of the mold cavity.
With certain resins such as polyethylene terephthalate, the resin has to be treated to increase its intrinsic viscosity in order to have sufficient strength to be extruded as a hot parison capable of being blow molded, such as disclosed by U.S. Pat. No. 4,219,527 Etelman et al. Such processing of the resin increases its cost and hence the resultant cost to the consumer.
While preforms for plastic blow molding are conventionally injection molded from a single resin, there have also been prior multi-layer preforms such as disclosed by U.S. Pat. Nos.: 3,719,735 Valyi; 3,787,157 Valyi; 4,067,944 Valyi; 4,391,861 Nilsson; and 4,646,925 Nohara.
Other prior art involving plastic resins, parison extrusion and preforms is disclosed by U.S. Pat. Nos.: 4,398,642 Okudaira et al.; 4,564,541 Taira et al.; 4,728,549 Shimizu et al.; 4,764,403 Ajmera; 4,816,308 Shimizu et al.; 4,861,630 Mihalich; 4,874,647 Yatsu et al.; 4,994,313 Shimizu et al.; 5,034,177 Niimi et al.; 5,039,780 Hashimoto et al.; 5,115,047 Hashimoto et al.; 5,256,363 Hashimoto et al.; 5,281,387 Collette et al.; 5,286,187 Niimi et al.; 5,380,479 Schrenk et al.; and 5,439,718 Klerks et al.
DISCLOSURE OF INVENTION
One object of the present invention is to provide an improved multi-layer plastic preform for blow molding a container.
In carrying out the above object, a multi-layer plastic preform for blow molding a container is constructed to include an inner layer that is extrusion blow molded from a resin having an intrinsic viscosity greater than 0.90. This inner layer is no greater than 20% by weight of the total weight of the preform. An outer layer of the preform is injection molded around the inner layer from a resin having an intrinsic viscosity that is at least 0.10 less than the intrinsic viscosity of the inner layer. The outer layer is at least 80% by weight of the total weight of the preform. Such a preform can be utilized to provide a blow molded container that has good strength characteristics at its bottom end as a result of the higher strength of the inner layer without having the cost disadvantage associated with containers extrusion blow molded entirely from high viscosity resins.
In the preferred construction of the preform, the inner layer is extrusion blow molded from a resin having an intrinsic viscosity greater than 1.0. The preferred construction of the preform also has the inner layer provided so as to be no greater than 15% by weight of the total weight of the preform. In its preferred construction, the inner layer is extrusion blow molded from a resin having an intrinsic viscosity greater than 1.0 and is also no greater than 15% by weight of the total weight of the preform.
The preferred construction of the preform has the outer layer injection molded from a resin having an intrinsic viscosity that is at least 0.15 less than the intrinsic viscosity of the inner layer. The outer layer is also preferably at least 85% by weight of the total weight of the preform. In the preferred construction, the preform is injection molded from a resin having an intrinsic viscosity that is at least 0.15 less than the intrinsic viscosity of the inner layer and is also at least 85% by weight of the total weight of the preform.
Different constructions are possible with the plastic preform. Specifically, the inner and outer layers can be made of the same type of resin or of different types of resin. The inner and outer layers can both be made of virgin resin, or the inner layer can be made of virgin resin and the outer layer made of post consumer recycled resin. The inner layer preferably defines the entirety of an inner surface of the preform. The outer layer preferably defines the entirety of an exterior surface of the preform. In the preferred construction, the inner layer defines the entirety of an inner surface of the preform and the outer layer defines the entirety of the exterior surface of the preform.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 3719735 (1973-03-01), Valyi
patent: 3787157 (1974-01-01), Valyi
patent: 3869056 (1975-03-01), Valyi
patent: 4067944 (1978-01-01), Valyi
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patent: 4219527 (1980-08-01), Edelman et al.
patent: 4391861 (1983-07-01), Nilsson
patent: 4398642 (1983-08-01), Okudaira et al.
patent: 4535901 (1985-08-01), Okudaira et al.
patent: 4564541 (1986-01-01), Taira et al.
patent: 4646925 (1987-03-01), Nohara
patent: 4728549 (1988-03-01), Shimizu et al.
patent: 4741936 (1988-05-01), Nohara et al.
patent: 4755404 (1988-07-01), Collette
patent: 4764403 (1988-08-01), Ajmera
patent: 4816308 (1989-03-01), Shimizu et al.
patent: 4861630 (1989-08-01), Mihalich
patent: 4874647 (1989-10-01), Yatsu et al.
patent: 4910054 (1990-03-01), Collette et al.
patent: 4980211 (1990-12-01), Kushida et al.
patent: 4991734 (1991-02-01), Nilsson et al.
patent: 4994313 (1991-02-01), Shimizu et al.
patent: 5034177 (1991-07-01), Niimi et al.
patent: 5035931 (1991-07-01), Yamada et al.
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patent: 5286187 (1994-02-01), Niimi et al.
patent: 5302686 (1994-04-01), Tanaka et al.
patent: 5380479 (1995-01-01), Schrenk et al.
patent: 5439718 (1995-08-01), Klerks et al.
patent: 5443766 (1995-08-01), Slat et al.
patent: 5582788 (1996-12-01), Collette et al.
patent: 5656719 (1997-08-01), Stibal et al.
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patent: WO 97/01427 (1997-01-01), None
patent: WO 97/32708 (1997-09-01), None
patent: WO 98/06557 (1998-02-01), None
Brooks & Kushman P.C.
Dye Rena L.
Plastipak Packaging, Inc.
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