Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-11-13
2004-04-06
Moy, Joseph M. (Department: 3727)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C220S062220
Reexamination Certificate
active
06716500
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a container with a flange obtained by heat-molding a sheet provided with a thermoplastic polyester layer, and to a method of producing the same. More specifically, the invention relates to a polyester container with a flange having improved impact resistance and heat resistance in the lower part of the barrel thereof and having superior transparency.
BACKGROUND ART
Thermoplastic polyesters such as polyethylene terephthalate and the like have excellent impact resistance, heat resistance and transparency as well as a certain degree of gas barrier property, and have been widely used for producing a variety of kinds of packaging containers.
Such packaging containers can be represented by a container with a flange obtained by molding a stretched or unstretched thermoplastic polyester sheet.
Japanese Unexamined Patent Publication (Kokai) No. 53852/1984 discloses a method of producing a transparent container by monoaxially stretching a thermoplastic resin sheet while maintaining the reduction ratio of the width of the sheet to be not larger than 10% and heat-molding the thus obtained monoaxially oriented sheet (prior art 1).
Japanese Examined Patent Publication (Kokoku) No. 27850/1989 discloses a method of heat-molding a polyester sheet by molding a biaxially stretched polyester sheet having a crystallinity of not larger than 30% and an index of surface orientation of from 0.02 to 0.15 by utilizing the compressed air along a mold heated at a temperature which is not higher than the crystallizing temperature (Tc° C.) of the polyester but is not lower than (Tc−70)° C., heat-treating the obtained molded article by bringing it into contact with the heated mold, fitting a cooling mold to the heating mold, the cooling mold having a shape nearly corresponding to the heating mold, forcibly transferring the molded article toward the cooling mold side from the heated mold side by blowing the compressed air, and cooling the molded article upon contact with the cooling mold (prior art 2).
Japanese Examined Patent Publication (Kokoku) No. 36534/1992 discloses a polyester container having a heat-adhering portion that can be thermally adhered to the closure member, the container being obtained by molding a polyester sheet containing a polyethylene terephthalate as a chief constituent component, the heat-adhering portion having a crystallinity of smaller than 20%, and the bottom portion and(or) the side portion of the container having the crystallinity of not smaller than 20%, the container being useful as an ovenable tray (prior art 3).
Japanese Patent No. 2947486 discloses a method of producing a biaxially stretched thermoplastic product by forming a biaxially stretched intermediate product by blow-molding a sheet-like thermoplastic material in a tube at a stretching temperature while preventing the material from adhering to the top of the side walls, placing the intermediate product on a male mold of a preset size and a texture, heating the intermediate product and the mold at a temperature higher than the temperature for stretching the thermoplastic material so that the intermediate product is thermally shrunk on the surface of the mold, cooling the intermediate product that is thermally shrunk, and taking the thermally shrunk intermediate product out of the mold (prior art 4).
The prior art 1 uses a monoaxially stretched sheet as the sheet for molding. This molding method may be capable of improving the transparency of the container but still leaves room for improvement concerning the heat resistance of the container.
The prior art 2 uses a biaxially stretched sheet as the sheet for molding. This molding method may be capable of improving the heat resistance of the container but is not still satisfactory concerning the impact resistance of the container.
These prior arts 1 and 2 use a sheet that has been stretched in advance as the sheet to be molded and, hence, require a particular stretching step and, hence, an additional cost. It is therefore desired to use an unstretched sheet and to impart, in a step of forming the container, the molecular orientation that is desired from the standpoint of imparting the container properties. It is further desired that the properties such as heat resistance, impact resistance and transparency are imparted in the steps of molding the container without requiring any particular step.
According to the prior art 3, an amorphous polyester sheet that is heated and plasticized is formed into a tray by using a metal mold maintained at a crystallizing temperature in order to heat-crystallize the bottom portion and/or the side portion. However, there is no disclosure concerning molecularly orienting the side portion by stretching, and it is considered that the container that is obtained is still insufficient with respect to impact resistance and transparency.
The prior art 4 is to produce a final container by preparing a biaxially stretched intermediate product by the blow-molding and by heat-shrinking the intermediate product on the male mold. This method, however, requires both heating for heat-shrinking the intermediate product on the male mold and cooling for shaping the heat-shrunk intermediate product and for taking it out. Therefore, this method is not still satisfactory from the standpoint of thermal economy, extended periods of time occupying the molds and low productivity.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a container with a flange exhibiting excellent heat resistance and impact resistance in the lower part of the barrel portion and excellent transparency in the container wall despite it is obtained by molding an amorphous polyester sheet, and a method of producing the same.
Another object of the present invention is to provide a heat-resistant thermoplastic resin container having a novel profile of crystallinities in that the side wall portion of the container comprises oriented crystals, and the outer surface of the side wall has a crystallinity larger than that of the inner surface of the side wall, and a method of producing the same.
A further object of the present invention is to provide a method of producing a thermoplastic resin container, having split functions of effecting the heat-set by a female mold and effecting the cooling by a plug, shortening the time for occupying the mold and enhancing the productivity.
A still further object of the present invention is to provide a sheet-molded container having excellent heat resistance, impact resistance and transparency not only in the side wall of the container but also in the central portion on the bottom of the container despite the container is obtained by molding an unoriented or amorphous thermoplastic polyester sheet, and a method of producing the same.
According to the present invention, there is provided an impact resistant container obtained by heat-molding a sheet provided with a thermoplastic polyester layer comprising chiefly an ethylene terephthalate unit, and having a flange portion, a barrel portion and a closed bottom portion, the wall of the lower part of the barrel portion being oriented and crystallized so as to possess a crystallinity of not smaller than 15% as measured by the density method, and the wall of the barrel portion being oriented to satisfy the following formulas (1), (2) and (3),
Iu
(−110)/
Iu
(010)≦1.02 (1)
IL
(−110)/
IL
(010)≦0.89 (2)
and
(
Iu
(−110)/
Iu
(010))−(
IL
(−110)/
IL
(010))≧0.13 (3)
wherein Iu(−110) is a diffraction intensity of the surface having an index of a plane of (−110) in the upper part of the wall of the barrel portion of when an X-ray is incident on the wall surface of the container perpendicularly thereto and when the axial direction of the container is regarded to be a perpendicular of the optical coordinate, Iu(010) is a diffraction intensity of the surface having an index of a plane of (010) in the upper part of the wall of the barrel portion of when an
Iwasaki Tsutomu
Kogure Masahito
Oda Yasuhiro
Otsuki Masahiko
Moy Joseph M.
Toyo Seikan Kaisha Ltd.
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