Heat-resistant structure of neck of synthetic resin container.

FIELD OF ART

0001This invention relates to a heat resistant construction of a neck of a synthetic resin container used as a packaging container for liquids such as juice, food oil, a seasoning or the like which are required to be heated and filled.

BACKGROUND OF THE ART

0002In thin-wall synthetic resin containers whose body portion and bottom portion are biaxially oriented by orientation blow molding, a neck portion remains as a neck portion of a preform injection or extrusion molded and is in a non-oriented state, which is poor in heat resistance. Therefore, in containers such as bottles formed of polyethylene terephthalate resin, the neck portion is often heat deformed after being heated and filled.

0003In view of the foregoing, as shown in FIGS. 5 and 6, there has been contemplated a neck portion 20 having a three-layer construction in which a thermoplastic resin forming a neck portion 20 of a container is interiorly provided with a heat resistant layer 21 formed of a thermoplastic resin excellent in heat resistance, and the heat resistant layer 21 is surrounded by an inner layer 22 and an outer layer 23 formed of a neck forming resin to provide a heat resistance, as disclosed in the publication JP-A-61259946.

0004However, in the above-described conventional construction, though the heat deformation of a peripheral portion of the neck portion 20 may be prevented by the heat resistant layer 21, a deformation of an open end 24 cannot be prevented. An outer peripheral edge 25 gives rise to a partial strain due to the heat deformation of the open end 24, thus posing a problem that the contents leak after a cap has been sealed, and the like.

0005A bottle neck provided with a resistant layer extending out of the neck portion and forming the uppermost portion of the neck, a thread portion and a ring portion of the neck, is disclosed by the publication JP-U-61 5707.

DISCLOSURE OF THE INVENTION

0006This invention has been achieved to provide a heat resistant construction of a neck portion in which a portion externally of a neck portion including an open end and a support ring are formed of resins having a heat resistance, whereby the heat deformation of the neck portion as well as the open end is difficult to occur, and a container can sufficiently withstand the external force by an integral structure of the neck forming resin and the heat resistant resin.

0007For achieving the aforementioned object, this invention provides a construction of a neck portion having an open end, a thread portion and a support ring in the outer periphery of the neck portion, said neck portion having a multi-layer construction comprising a heat resistant layer formed of a thermoplastic resin excellent in heat resistance as compared with the resin, of the other layers of the construction, wherein said heat resistant layer is exposed outside the neck construction at said open end and at said thread portion, characterized in that said heat resistant layer is extended into in the interior of the said support ring to provide a heat resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

0008FIGS. 1 is a half longitudinal sectional view of an example of a heat resistant construction of a neck portion of a synthetic resin container.

0009FIG. 2 is a longitudinal sectional view partly in an enlarged scale of the neck construction of the fig. 1.

0010FIG. 3 is a longitudinal sectional view in an enlarged scale showing essential parts of another known example of neck construction (see eg. JP-U-62 99506).

0011FIG. 4 is a longitudinal sectional view in an enlarged scale showing essential parts of a neck construction according to the invention.

0012FIG. 5 is a half longitudinal sectional view of a construction of a neck portion of a conventional container.

0013FIG. 6 is a longitudinal sectional view partly in an enlarged scale of prior art.

0014In FIGS. 1 and 2, reference numeral 1 designates a neck portion integrally formed with a thread portion 11 and a support ring 12 in the outer periphery thereof and is formed of a polyethylene terephthalate, within which is provided as a heat resistant layer 2 with a heat resistant resin comprising a polyamide, an ethylene vinyl alcohol copolymer, and an alloy of polyamide or carbonate and polyethylene terephthalate, whereby the neck portion 1 constitutes a three-layer construction consisting of an inner layer 3 and an outer layer 4 formed of said polyethylene terephthalate and said heat resistant layer 2.

0015An open end 5 of the neck portion 1 is formed with a part of the heat resistant resin forming the heat resistant layer 2 exposed to out side the inner and outer layers formed of polyethylene terephthalate, and ends of the inner layer 3 and outer layer 4 are coated with the open end 5 formed of the heat resistant resin.

0016A thickness of this open end 5 can be suitably adjusted when the neck portion 1 is injection molded. Since the open end 5 is molded integral with the heat resistant layer 2, the external force applied to the open end 5 is transmitted to the whole neck portion through the heat resistant layer 2, and the external force is not concentrated on a joined surface 6 between the open end 5 and the inner and outer layers. As a result, even in the case where the open end 5 is formed to be thin in the wall, no peeling or damage due to the external force occur.

0017The open end 5 can be molded by application of a method which comprises first injecting a part of a neck forming resin, and then simultaneously injecting the neck forming resin and a heat resistant layer forming resin.

0018In carrying out this method, it is preferable to use a triple nozzle having an inner layer forming nozzle, a heat resistant layer forming nozzle and an outer layer forming nozzle superposed in a concentric fashion. In the case where only the neck portion 1 is formed into a multi-layer construction, a check valve may be provided on the heat resistant forming nozzle to control an injection amount of the heat resistant forming resins.

0019In molding, a required quantity of the neck forming resins is injected into a cavity simultaneously from two nozzles for forming the inner and outer layers. Next, the heat resistant layer forming resins as well as the neck forming resins are injected from the nozzle. In this case, if the first quantity of injection is large, even if the heat resistant layer forming resins reach a neck opening of a mold, the heat resistant layer forming resins are not exposed from the neck forming resins to assume the state surrounded by the neck forming resins as in the conventional construction shown in FIG. 6, and the open end formed by the heat resistant layer forming resins is not formed.

0020Another example of the prior art shown in FIG. 3 shows a construction of a neck formed of heat resistant resins with an open end 5 and a thread portion 11 outside the neck portion exposed externally from the interior of the neck forming resins. FIG. 4 shows a construction of a neck portion according to the invention in which a heat resistant layer is extended from the thread portion 11 into the support ring 12 to provide a heat resistance from the support ring 12 to the open end 5.

0021Such a construction of a neck portion can be easily obtained by adjusting a quantity of the neck forming resins first injected, an injection speed, an injection pressure, an injection timing and the like so that the heat resistant layer forming resins within the neck forming resins are exposed from the open end 5 to a portion near the thread portion 11.

0022In the construction of a neck portion according to this invention, the neck forming resins interiorly have the heat resistant layer formed of heat resistant resins, and the heat resistant layer forming resins are exposed to or extended to the open end of the neck portion of the container or the outer portions of the open end and neck portion, and in addition, the thread portion and the interior of the support ring. Therefore, not only the peripheral wall portion of the neck portion but the open end are formed into heat resistance, and even if it is put into a bath at 85°C for 10 minutes, no heat deformation occurs in the open end as well as the upper portion of the support ring. In addition, the heat resistant layer and the open end and in addition, the outer portion of the neck portion are integrally formed, and therefore, the neck can sufficiently withstand the external force, and even if the open end, the thread portion and the like are molded of resins different from the neck forming resin, they are not peeled off during the cap seal.

INDUSTRIAL APPLICABILITY

0023In this invention, the outer portion of the neck including the open end of the neck and the open end and in addition the support ring are formed of resins having the heat resistance as described above, and therefore, the heat resistance is enhanced as compared with the case where the neck portion is formed into heat resistance only by the heat resistant layer interiorly formed, and since the article can withstand the external force by the integral structure of the neck forming resin and the heat resistant resin. Therefore, this invention can be used as a heat resistant construction of a neck portion of a packaging container for liquids requiring heating and filling, and molding can be easily carried out by applying a conventional multi-layer injection molding, which is therefore very effective in industry and can be used extensively.