In-mold labeled vessel with elongated bottom projection and method for producing same

Abstract: The invention relates to an in-mold labeled vessel (B) with an elongated bottom projection (2) and a method for producing the same, wherein a label (A) for in-mold labeling is constituted into a shape having a bottom portion (a1) and side wall portions (a2). Notches () are formed in folded portions as connections between the bottom portion (a1) and the side wall portions (a2) of the label (A), or the label (A) is formed using material and a thickness thereof which permit breakage of the label (A) at a resin temperature and at an internal mold pressure. The label (A) is loaded into a mold for injection molding, and an injection molding is performed, whereby the molding resin which has been injected flows out through the notches (1) or through broken folded portions into an elongated bottom projection forming recess which is formed in the mold to form the elongated bottom projection (2) integrally with the vessel bottom.

Description: The present invention relates to a method of producing an in-mold labeled vessel with an elongated bottom projection. Heretofore, there have been known a large number of in-mold labeled vessels, but in these conventional vessels, a bottom portion of a label is formed on the vessel bottom and a lower end of a side wall portion of the label, i.e., a bent portion at the connection with the vessel bottom, constitutes, as it is, a part of the vessel bottom, thus resulting in poor looking of the vessel. The above drawback may be overcome by in-mold labeling a vessel with legs. However, it is difficult to make alignment between the lower end of a side face portion of a label and the leg side portion, and wrinkles are easily formed. Further, resin flows onto the label surface. Moreover, since the vessel is formed with legs, a space portion is formed between adjacent legs in plan or side view, and thus the vessel is unsatisfactory in point of stability and outward appearance. An in-mold labelled vessel with an elongated bottom projection and a method of producing the same is known from GB-A-2190620. The label is provided with a series of spaced slits along fold lines linking the base and wall portions thereof. The label is positioned in a mold and material is injected to form the container wall and the base against the label. Additionally, the material flows through the slits in the label to form flanges that project downwardly below the base of the label and define a false bottom of the container. The present invention has been accomplished for overcoming the above-mentioned problems, and it is the object of the invention to provide a simple method of producing an in-mold labeled vessel having an elongated bottom projection integral with the vessel bottom. This object is solved according to the present invention by a method including the features of claim 1. According to the present invention, a label for in-mold labeling is formed into a shape having a bottom portion and said wall portions, folded portions being formed as connections between such bottom portion and side wall portions, the label is loaded into a mold for injection molding and then subjected to injection molding, whereby the label is broken at such bent portions by the temperature or flow pressure (shear pressure) of resin used, allowing the resin to flow into a recess for an elongated bottom projection formed on a cavity side of the mold to form an elongated bottom projection as an integral part. Fig. 1 is a development view of a label; Fig. 2 is a sectional view of a mold for injection molding loaded with the label; Fig. 3 is a sectional view of the mold with a molding resin injection-molded; and Fig. 4 is a partially cut-away perspective view of a vessel. An embodiment of the present invention will be described in detail hereinunder with reference to the accompanying drawings. Label A is formed using an ordinary grade paper, a plastic film, a laminate film, or a material of the same kind as a molding resin used, e.g. a synthetic paper, has a thickness of 60 to 100 microns, and it is cut into a predetermined development form (a two- or four-directional label) so as to be in-molded on the surface of a vessel B. The label A, having a predetermined print thereon, comprises a bottom portion a1 and side wall portions a2 positioned on the bottom and side walls, respectively, of the vessel, and a suitable number of notches 1 are formed in folded portions a3 as connections between the bottom portion a1 and the side wall portions a2 (Fig.1). In the case where the label A is constituted by material of the same kind as a molding resin, e.g. synthetic paper, or when the label has a thickness which causes breakage of the label at a resin temperature and at a flow pressure (shear pressure) of the resin, the notches may sometimes be omitted. The label A having such construction is loaded into a mold C for injection molding, and a molding resin b (Fig.3) is injected into the mold at a melt temperature of 190 - 200°C and an internal pressure of 300 - 600 kg/m 2 . The mold C is for injection molding, having form and construction known in this technical field. It is divided into a core cl side and a cavity c2 side, and the molding resin b for the vessel B is injected into a space c3 formed between c1 and c2. A recess c4 for the formation of an elongated bottom projection is formed circumferentially on the cavity c2 side. The label A is loaded into the space c3 by vacuum suction and brought into abutment with the inner surface of the cavity c2, then the molding resin b is injected into the space. The injection of the resin b may be done from either the cavity side or the core side, but when it is done from the cavity side, a resin inlet hole (not shown) is formed in the bottom portion a1 of the label A. As the molding resin b there is used a soft or hard synthetic resin, e.g. polypropylene (PP), polystyrene (PS), polyester (PET), or polyethylene (PE). Using such molding resin, there can be molded a transparent, translucent or opaque vessel B, and the label A is in-molded on the outer surface of such vessel B. The vessel B is formed by injection molding in which the molding resin b in a molten condition is injected into both the space c3 and the elongated bottom projection forming recess c4 of the injection molding mold C. To its bottom B-1 and peripheral side B-2 there are integrally bonded the bottom portion a1 and side wall portions a2, respectively, of the label A. Further, an elongated bottom projection 2 is formed throughout the whole circumference of the bottom B-1 at a predetermined height by the resin which has been injected into the recess c4 of the mold C. The vessel B has a desired three-dimensional shape such as a polygonal shape, e.g. square, rectangular or hexagonal shape, or a circular or elliptical shape. It may have flat and curved surfaces. The elongated bottom projection 2 may extend on the same plane as the peripheral side B-2, or it may be in a somewhat inside position of the bottom B-1, and the elongated bottom projection forming recess c4 is formed accordingly on the cavity c2 side of the mold C. For forming the elongated bottom projection 2, the molding resin b is injected in a molten condition into the mold C in a loaded state therein of the label A. In the case according to the present invention where the label A is formed using a material of the same kind as the molding resin, e.g. synthetic paper, or when it is formed using material and thickness which permit breakage at a resin temperature and at a flow pressure (shear pressure) of the resin, the folded portions a3 are partially broken by the injection pressure of the molten resin even without forming notches, so that the resin flows into the recess c4 and when solidified the resin in each broken portion serves as an adhesive or the broken portion is filled with the resin. According to the method of the present invention, a label for in-mold labeling is formed to have a bottom portion and side wall portions, and the label is formed using a material of the same kind as the molding resin, e.g. synthetic paper, or it is formed to have a thickness which permits breakage of the label at a resin temperature and at a flow pressure (shear pressure) of the resin, followed by injection molding, with the result that the molding resin flows out into an elongated bottom projection forming recess formed in the mold while breaking the folded portions, thereby forming an elongated bottom projection integrally with the vessel bottom. Therefore, the entire vessel height increases by an amount corresponding to the height of the elongated bottom projection, thus affording a very good outward appearance, and hence the vessel is of great commercial value. Moreover, if the color of the molding resin and that of the label are made alike, the boundary between the label and the elongated bottom projection becomes indistinct, whereby the entire vessel can be seen larger than the actual size thereof and the positioning of the label into a mold can be done more easily than in the conventional construction with legs. There is no fear of wrinkling or flowing of a molding resin onto the label surface. Besides, since an elongated bottom projection is formed throughout the whole circumference without formation of a space portion in the front or side faces, the vessel obtained is stable and its outward appearance is further improved. Moreover, since a molding resin which has been injected into a mold can flow easily into an elongated bottom projection forming recess of the mold when notches are also formed in folded portions, the surface finish is good and there will be no defect of the resin portion. Further, since the label for in-mold labeling is formed using a material of the same kind as a molding resin, e.g. synthetic paper, or it is formed to have a thickness which permits breakage of the label at a resin temperature or at a flow pressure (shear pressure) of the resin, part of each folded portion will be broken by an injection pressure of the resin even without forming the foregoing notches (although the notches may be formed, of course), resulting in that the resin flows through the broken part into the elongated bottom projection forming recess, thus also permitting easy molding.

Claims: A method of producing an in-mold labelled vessel with an elongated bottom projection (2) including the steps of constituting a label (A) for in-mold labelling into a shape having a bottom portion (a1) and side wall portions (a2), loading the label (A) into a mold (C) for injection molding, and performing an injection molding to break portions of the label (A) in the vicinity of or at folded portions (a3) between said bottom portion (a1) and said side wall portions (a2) and over a recess (c4) of the mold (C) for the formation of the elongated bottom projection (2) at a molding resin temperature and at a flow pressure (shear pressure) of the resin to allow the molding resin to flow out to form the elongated bottom projection (2), while allowing the broken portions to be connected with the resin. A method according to claim 1, characterized in that the folded portions (a3) are also formed with notches (1).

Inventors: HIRATA MASANORI, KATAYAMA KEN, MAEKAWA KOHJI, MIZUKOSHI KOUBU, HIRATA, MASANORI, KATAYAMA, KEN, MAEKAWA, KOHJI, MIZUKOSHI, KOUBU
Applicants: NIPPLA CO LTD, SNOW BRAND MILK PROD CO LTD, NIPPLA CO., LTD., SNOW BRAND MILK PRODUCTS CO., LTD.
Application year: 1991
Main classification: B29C45
IPC codes: B65D25, B29C45, B29L22, B65D1, B29D99