Patent Application
20120061279
This invention is related to molded plastic containers, and in particular, creating a molded plastic container which also acts as an oxygen barrier to products contained therein.
It is well known in the art that plastic pails and containers are used for the storing of perishable items. The shelf life of perishable items such as foods, medicines and paints are affected by temperature, humidity and most importantly oxidation. In order to improve shelf life, many approaches have been taken including the formation of airtight seals, the use of better plastic materials, the use of plastic and foil seals across the opening of the container below the cap or lid of containers and even the use of labels about the container to prevent or slow down the rate at which the perishable item is exposed to oxygen. These prior art structures have been satisfactory, however, the plastic materials used for molding of containers still allow oxygen to pass there through and conventional labels do not envelope enough of the container surface to form an effective barrier. Therefore, over time, oxygen passes through the walls of injection, thermoformed and blow molded containers.
It is known from the prior art to put oxygen barriers into the interior structure of a laminate and to affix the laminate to the container. It is also known to injection mold an oxygen barrier material, such as a second plastic within the container wall. Although these structures may prove satisfactory, they require complex structures and/or molding techniques. They also require extra materials as the laminate requires extra layers between which to sandwich the oxygen barrier. The molding technique requires molding a cavity to the oxygen barrier material within the container wall, and then molding the second material into the cavity.
Accordingly, a structure and methodology for creating the containers which increases the impermeability of a molded plastic container wall, floor or lid to oxygen without significantly increasing cost, materials or complex is desired.
A container is molded from a plastic. The container has at least a floor and a wall extending therefrom. A film is coated with an oxygen barrier solution and then applied to the molded container. The film may be formed of a multilayer structure including a deposit of nano-particles sprayed on at least one side of the film substrate. The film is applied to the container during an injection molding of the container by an injection mold label process so that when applied, the oxygen barrier material is in direct facing relation with a wall of the container. In a preferred embodiment, the nano-particles are silicate based and the film is corona charge treated.
As is known in the art, and is shown in
During manufacture to create container 10, a shot of plastic, such as polypropylene material by way of non-limiting example, is injection molded to form container 10, and/or lid 22.
Apart from the manufacture of the container itself, a thin film barrier 100 is manufactured. The label may be a multilayer structure. In a preferred embodiment, thin film 100 is applied as an in mold label. In a preferred example, as shown in
Thin film barrier 100 is applied to sidewall 12. A bottom film 14, having a similar structure to film 100 is applied to bottom 18.
In a preferred embodiment, the barrier solution is formed from a nano-silicate solution or a nano-clay formed as an aqueous suspension as known from NanoLok PT MM manufactured by InMat Inc. A porous cylinder is used to dispose the aqueous nano-solution across at least one of the interior surface (facing towards layer 110) of first layer 102 or outer layer 110 of the film 100 by way of nonlimiting example. The barrier solution may also be disposed between layer 102 and 110 and an internally adjacent layer. The thickness of the nano-solution layer 112 is controlled by the diameter of the pores within the cylinder and the internal pressure of the cylinder. Other application methods such as cascade coating may be used. In a preferred embodiment, the thickness of the aqueous solution layer 112 is less than or equal to 3 microns.
In a preferred, nonlimiting example, the first layer 102 and outer layer 110 are formed as plastic films, and more preferably polypropylene. However, first layer 102 may be formed of treated or untreated paper, foil or the like.
The gas barrier layer 106 (preferably an oxygen barrier layer) may be formed from an EVOH. Layer 106 of thin film 100 could be replaced or coupled with PVDC (polyvinylidene chloride), aluminum, PVOH (polyvinyl alcohol), aluminum oxide, silicium oxide, a nano-clay or nano-crystalline cellulose alone or in any combination thereof. The properties of the various layers may enable film 100 to act as a moisture and/or light barrier. Furthermore, when thin film 100 is applied to an outer surface of container 10 such as sidewall 12 and bottom 18 as film 14, in sections 202, 204, thin film 100 may be printed upon with ink to form a label without affecting the use of the barrier's nano-particle layer 112. The film may also be provided on the interior structure of container 10 such as the interior of sidewall 12, floor 18 or lid 22.
Reference is now made to
In this embodiment, film barrier 600 includes a film substrate 504. In a preferred embodiment, film substrate 504 is polypropylene. A first side of film 504 is coated with an oxygen barrier coating 502. As with the previous embodiments, barrier coating 502 may be a nano-solution such as a nano-silicate solution or a nano-clay formed as an aqueous solution as known from NanoLok PT MM manufactured by InMat Inc. Artwork 506 such as indicia for labeling may be disposed on the opposed side of film substrate 504. Additionally, as is known in the art as shown from the embodiment
The indicia 506 may be provided as a layer of an ultraviolet primer, an ultraviolet ink and an aqueous top coat.
The film barrier 500 is then affixed so that the oxygen barrier layer 502 is placed in facing relationship to what will become wall 12 of a container 10 during an injection mold labeling process (see
To facilitate the structure, in a preferred embodiment, film 504 is formed from a standard polypropylene such as ETH-57 manufactured by Treofan Group which is then corona treated to change the surface tension enabling the nano-silicate barrier coating 502 to better adhere to the polypropylene forming film 504. During the process, by way of nonlimiting example, a 1 mil film is subjected to up to 10,000 W of current as a function of line speed. In one embodiment, 6,000 W is applied to a film being fed at 400 ft/min.
Furthermore, barrier coating 502 may contain adhesion promoters such as the formulation known from NanoLok EXC 1007V-1 to adhere to the polypropylene container during the injection mold labeling process.
In order to maximize the oxygen barrier nature of the present invention, it is preferred to encapsulate, i.e. substantially entirely cover the container with the barrier with any of the films discussed above so that a film covering at the bottom and about the sidewall of the container is desired. However, prior art molding processes resulted in the interference between the bottom film and the side film in the injection mold label formation process.
In accordance with a preferred embodiment of the present invention, a bottom film 204 and a sidewall film 202 are carried by a formed mandrel 300 as shown in
Bottom film 204 also has an area greater than an area of container bottom 10. Side film 202 has a length greater than a length of sidewall 12. In this way, bottom film 204 extends beyond the bottom 18 of container 10 by an overhang portion 204a. Similarly, side film 202 overhangs container wall 12 by an overhang portion 202a. In order to prevent interference between bottom film 204 and wrap around film 202 during the molding process, a bottom surface 302 of mandrel 300 is formed at least in part with a concave shape to arc bottom film 204 to take up any slack and prevent interference between wrap around film 202 and bottom film 204. Each of wrap around film 202 and bottom film 204 are held to mandrel 300 by a vacuum pressure at mandrel 300 and/or a static charge of between 10 and 12 K volts.
In a next step, mandrel 300 with films 202, 204 thereon are inserted into a mold steel cavity 400 (see
As seen in
As seen in
In another embodiment, a single film diper label may be used. A five faced diper label positioned at the bottom of mold 400 and used in an injection mold process would still cover 99.1% of the outer container surface. However, the preferred embodiment is the two label method which covers more than 99.4% of the surface.
Because of the level of static charge, air flow from the mandrel forces the label to the mold and the fact that the mold is made out of steel, when mandrel 300 is inserted into mold cavity 400, the attraction as a result of the static charge plus the air flow, between either of label 202, 204 and mold cavity 400 is greater than the attraction between either of film 202, 204 and mandrel 300. Accordingly, once in sufficient proximity to mold cavity 400, the labels 202, 204 are released from mandrel 300 and are held in place by the respective wall 402 and floor 404 of cavity 400.
As seen in
As can be seen from
It is understood that films 202, 204 may have the structure of film 100. In another embodiment of the invention, a barrier solution is formed in a liquid or gel state. In a preferred embodiment, the solution is a nano-clay formed of an aqueous suspension of nano-dispersed silicate and polyester resin such as NanoLok PT MM manufactured by InMat Inc. The barrier may also be a resin which cures about the container.
The aqueous gel may be applied as discussed above in connection with film 100 to an inner or outer surface of any of sidewall 12 or floor 18 by way of a dipping process, vapor deposition, an aqueous spray, or a fine particulate atomized spray. In a preferred embodiment, container 10 may be heat treated prior to the deposition of the aqueous barrier solution onto a surface of container 10.
Lid 22 may be treated in the same way as the body of the container to enhance the oxygen barrier properties of lid 22.
In an alternative embodiment, the polypropylene stock material may be treated with the aqueous barrier solution prior to injection molding to form container 10. The raw stock of material such as polypropylene material may be dipped in a liquid or gel state of the barrier material, sprayed with the barrier material, or subject to vapor deposition of the barrier material or an atomized version of the solution. In this way, the injection molded lid 22 and/or container 10 are formed with an inherent oxygen barrier.
While this invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention encompassed by the appended claims.
