Patent Application
20110281001
The disclosure is directed to food packaging and in particular to food packaging containers that prolong the shelf life of fresh cut fruits and produce.
In the food packaging industry, it is known that fresh cut produce exudes a fair amount of juice and liquid, which collects at the bottom of the package. The produce sitting in such liquid has a shorter shelf life as compared to produce that is above the liquids. Accordingly, separating the fresh cut produce from the liquid will increase the shelf-life of the product.
Apertured plastic films are well known and essentially comprise a planar film with holes in it. The problem with the use of such films in food packaging applications, however, is that the juices can flow equally well through the film in both directions. Thus, as the package is moved, turned, inverted, etc. during storage or transport, the liquid is splashed all over the produce.
Vacuum formed films typically have a plurality of apertures that allow liquids and gases to pass through the film. Such films may be incorporated into disposable personal care products (e.g., feminine hygiene products, diapers, incontinent products, hospital pads, etc.), as agricultural films (e.g., weed block fabrics) and in a variety of other uses.
In the vacuum forming process a film is placed on a rotating screen having a plurality of holes. The film passes over a vacuum chamber as the screen rotates creating a pressure differential on either side of the plastic film. The pressure differential causes the film to rupture at the holes in the screen to form the apertures. The holes in the screen may be in a specific pattern or shape that transfers onto the film in the process.
The vacuum forming process may be practiced using a precursor film that is heated to a softening point prior to being subjected to vacuum (so-called reheat process) or is practiced using a molten sheet of polymer that is cast onto the screen immediately prior to the vacuum (so called direct cast process). In either case, the film is supported by the screen and a vacuum applied to the underside of the perforated screen. Film is pulled by the vacuum until it ruptures. In the process, the film is cooled as it is being pulled, such that the resulting product has a plurality of tapered, funnel-shaped structures with an aperture at the apex of the structure. These apertures in the structures lie in a plane spaced from the base plane of the film. As a result, these films are generally known as “three-dimensional” films in the art.
Many methods and apparatuses for preparing plastic films comprising apertures have been developed, examples include U.S. Pat. Nos. 4,155,693; 4,252,516; 3,709,647; 4,151,240; 4,319,868; 4,388,056; 4,950,511; 4,948,638; 5,614,283; 5,887,543, 5,897,543; 5,718,928; 5,591,510; and 5,562,932; 3,054,148; and 3,814,101, which are all hereby incorporated by reference.
Laminates of three-dimensional films are also known. For example, U.S. Pat. No. 4,995,930 discloses a process in which a film is simultaneously apertured and bonded to a nonwoven web to form an apertured film laminate. Similarly, U.S. Pat. No. 5,698,054 discloses a variety of laminates wherein an apertured film is bonded to another apertured film, a non-apertured (or “flat”) film, and/or a nonwoven web. Both of these patents are incorporated herein by reference in their entirety.
One advantage of three-dimensional films is that the apertures tend to act as a one-way valve in that liquids tend to flow through the films better in one direction versus the other. There is a need for films and laminates that provide improved protection and increased shelf-life of fresh cut produce.
In one embodiment, the disclosure provides a package comprising a first section and a second section separated from one another by a web, the web comprising a three layer laminate wherein the first layer is a three-dimensional apertured film, the second layer is a three-dimensional apertured film, and the third layer is a nonwoven web.
In some embodiments, at least one of the apertured films comprises a plurality of channels extending through the film, wherein the channels are oriented at an angle of greater than 70° with respect to a female side of the film.
A further understanding of the embodiments may be obtained upon reading of the following detailed description with reference to the accompanying drawings and the appended claims.
With reference to
Without the web 18, the produce 16 would be in contact with and, depending on the produce, may be submerged in the juices 20. Fruits and vegetables sitting in juice or other liquids are not appealing to the consumer because they connote a reduced freshness. In addition, produce sitting in juice of other exuded liquid can change texture overt time. Moreover, the juice may contain or result in unwanted growth of undesired microorganisms or mold. Because the juice was released after storing the fruit, the fruit has not been pasteurized or other means have not been provided to prevent the growth of such undesirable microorganisms or molds. Accordingly, maintaining separation between the produce and the juice will increase the shelf-life of the product.
With reference to
Alternatively, the web 18 may be prepared by depositing the nonwoven web 34 onto a forming screen, extruding a molten polymer film onto the nonwoven web, applying the three-dimensional film 30, then subjecting the resulting structure to vacuum to form the three-dimensional film 32 and simultaneously bond the layers together. In yet another process, the web 18 may be constructed by making each three-dimensional film independently, laminating the films together with temperature and pressure, and then laminating the film/film bilaminate to the nonwoven.
The first three-dimensional film 30 comprises a plurality of surface structures 36 in the form of tapered conical shaped structures terminating in an aperture 38. The film 30 has a base plane 40 and a secondary plane 42. The base plane 40 is defined by the land areas 44 between the surface structures 36 and the secondary plane 42 is defined by the plane formed by the apertures 38. As seen in
Similarly, the second three-dimensional film 32 comprises a plurality of surface structures 48 in the form of tapered, conical shaped structures or protuberances. The protuberances 48 terminate in apertures 50. The second film 32, like the first film 30, also has two generally parallel, spaced apart planes 52, 54 which define the loft of the film.
Films 30, 32 may be made by the same or different processes, if desired. In a preferred embodiment, the films are made in a direct cast vacuum forming process, as described above. In the alternative, the films may be made by a reheat process or by a hydroforming process. In the hydroforming process, which is known in the art, a precursor film is heated to above the softening point but below the melting point of the film, placed on a perforated screen as in the vacuum forming processes, and then subjected to high pressure water streams which force the film material into the perforations in the screen to aperture and crystallize the film.
In the embodiment depicted in
Each of the films 30, 32 are made of thermoplastic resins. Most preferably, the films are made of polyolefin resins, such as polyethylene, polypropylene, low density polyethylene, high density polyethylene, or blends thereof. Use of polypropylene resin (up to about 30% by weight), particularly in the second three-dimensional film 32, may be advantageous to promote bonding with the nonwoven web as taught in EP 0930861. Other suitable thermoplastic resins and blends are known in the apertured film art.
The nonwoven web 34 may be of any standard construction known in the art. As is known in the art, nonwoven webs are fibrous webs comprised of polymeric fibers arranged in a random or non-repeating pattern. For most of the nonwoven webs, the fibers are formed into a coherent web by any one or more of a variety of processes, such as spunbonding, meltblowing, bonded carded web processes, hyrdoentangling, etc., and/or by bonding the fibers together at the points at which one fiber touches another fiber or crosses over itself. The fibers used to make the webs may be a single component or a bi-component fiber as is known in the art and furthermore may be continuous or staple fibers. Mixtures of different fibers may also be used for the fibrous nonwoven fabric webs.
The nonwoven web 34 can be produced from any fiber-forming thermoplastic polymers including polyolefins, polyamides, polyesters, polyvinyl chloride, polyvinyl acetate and copolymers and blends thereof, as well as thermoplastic elastomers. Examples of specific polyolefins, polyamides, polyesters, polyvinyl chloride, and copolymers and blends thereof are illustrated above in conjunction with the polymers suitable for the film layer. Suitable thermoplastic elastomers for the fibrous layer include tri- and tetra-block styrenic block copolymers, polyamide and polyester based elastomers, and the like.
The thermoplastic fibers can be made from a variety of thermoplastic polymers, including polyolefins such as polyethylene and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyamides, copolyamides, polystyrenes, polyurethanes and copolymers of any of the foregoing such as vinyl chloride/vinyl acetate, and the like. Suitable thermoplastic fibers can be made from a single polymer (monocomponent fibers), or can be made from more than one polymer (e.g., bicomponent fibers). For example, “bicomponent fibers” can refer to thermoplastic fibers that comprise a core fiber made from one polymer that is encased within a thermoplastic sheath made from a different polymer. The polymer comprising the sheath often melts at a different, typically lower, temperature than the polymer comprising the core. As a result, these bicomponent fibers provide thermal bonding due to melting of the sheath polymer, while retaining the desirable strength characteristics of the core polymer.
Bicomponent fibers can include sheath/core fibers having the following polymer combinations: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, poly-ethylene/polyester, polypropylene/polyester, copolyester/polyester, and the like. The bicomponent fibers can be concentric or eccentric, referring to whether the sheath has a thickness that is even, or uneven, through the cross-sectional area of the bicomponent fiber. Eccentric bicomponent fibers can be desirable in providing more compressive strength at lower fiber thicknesses.
In the case of thermoplastic fibers for carded nonwoven fabrics, their length can vary depending upon the particular melt point and other properties desired for these fibers. Typically, these thermoplastic fibers have a length from about 0.3 to about 7.5 cm long, preferably from about 0.4 to about 3.0 cm long. The properties, including melt point, of these thermoplastic fibers can also be adjusted by varying the diameter (caliper) of the fibers. The diameter of these thermoplastic fibers is typically defined in terms of either denier (grams per 9000 meters) or decitex (grams per 10,000 meters). Depending on the specific arrangement within the structure, suitable thermoplastic fibers can have a decitex in the range from well below 1 decitex, such as 0.4 decitex, up to about 20 decitex.
Term “meltblown fibers” refers to fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g., air) stream that attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to a microfiber diameter. The term “microfibers” refers to small diameter fibers having an average diameter not greater than about 100 microns. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers.
The term “spunbonded fibers” refers to small diameter fibers that are formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing or other well-known spunbonding mechanisms.
The nonwoven webs may also be subjected to standard finishing techniques. In a preferred embodiment, the nonwoven web is a fully calendered web.
As seen in
In the embodiment of
Although not shown in the figures, the protuberances in both films may be angled as in film 60 in
The size and shape of the protrusions and apertures in the films is of no critical importance to the disclosure. Numerous shapes of apertures are known from the prior art, including circular, pentagonal, elliptical, boat shaped, oblong, ‘cat eye” and others, any of which may be used to advantage. Larger diameter apertures provide less resistance to fluid flow and therefore enable better drainage of liquids away from the produce. However, larger apertures also are less resistant to preventing the liquids from flowing back into contact with the produce. This can be addressed by using angled protrusions as in
A 30 g/m2 slanted cone film (as seen in
A 30 g/m2 slanted cone film (as seen in
A 30 g/slanted cone film (as seen in
In each of the Examples, the nonwoven web was placed on the plane defined by the apertures at the end of the protuberances of the films, as illustrated in the Figures. The laminates were then tested by pouring 60 ml of water over the laminate and recording the time required for the water to pass through the laminate. This test was repeated for the opposite side of the laminate to determine if there was a difference in the fluid flow rate. Multiple tests were run on each sample. The average times for each sample are reported in Table 1.
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
