Package of materials which are subject to undesirable deterioration

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT

TO UNDESIRABLE DETERIORATION

Filed Dec. 28, 1960. 6 Sheets-Sheet 1

<img file="US3131069A_D0001.tif" />

<img file="US3131069A_D0002.tif" />

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT

TO UNDESIRABLE DETERIORATION

Sheets-Sheet 2

Filed Dec. 28, 1960

2! 12

25 84 \'///////////Λ

<img file="US3131069A_D0003.tif" />

<img file="US3131069A_D0004.tif" />

<img file="US3131069A_D0005.tif" />

<img file="US3131069A_D0006.tif" />

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT

TO UNDESIRABLE DETERIORATION

Filed Dec. 28, 1960 6 Sheets-Sheet 3

<img file="US3131069A_D0007.tif" />

<img file="US3131069A_D0008.tif" />

INVENTORS /Rabe-rid. Goiter, _RV Porr&amp;st RHarrirrN

Pout Et. G'rdzdrod,

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT •TO UNDESIRABLE DETERIORATION

Filed Dec. 28, 1960 6 Sheets-Sheet 4

<img file="US3131069A_D0009.tif" />

<img file="US3131069A_D0010.tif" />

<img file="US3131069A_D0011.tif" />

<img file="US3131069A_D0012.tif" />

_DV Fbrr&amp;Dt D Hamrrp, ^B PaidEGruTjcirod-.

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT

TO UNDESIRABLE DETERIORATION

Filed Dec. 28, 1960 6 Sheets-Sheet 5

<img file="US3131069A_D0013.tif" />

<img file="US3131069A_D0014.tif" />

<img file="US3131069A_D0015.tif" />

<img file="US3131069A_D0016.tif" />

<img file="US3131069A_D0017.tif" />

INVENTORS

Robert L. Gotter, _BV Forrest D. Hamm, ^Y Faiot K Grcrzotroct,

<img file="US3131069A_D0018.tif" />

April 28, 1964 r. l. goller etal 3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT

TO UNDESIRABLE DETERIORATION

Filed Dec. 28, 1960 6 Sheets-Sheet 6

<img file="US3131069A_D0019.tif" />

United States Patent Office _Patented

1clLeilltiCl tuOj JL9U*Z

3,131,069

PACKAGE OF MATERIALS WHICH ARE SUBJECT TO UNDESIRABLE DETERIORATION

Robert L. Golier, Forrest D. Hamm, and Paul E. Grindrod, Madison, Wis., assignors to Oscar Mayer &amp; Company, Inc., Chicago, ΙΠ., a corporation of Illinois

Filed Dec. 28, 1960, Ser. No. 79,069

Claims. (Cl. 99—174)

The present invention relates to new and improved packages which are particularly adapted for use in the storing and merchandising of products which are subject to spoilage or other types of undesirable deterioration. More specifically, the present invention is directed to the packaging of meat products and to special packages which exhibit new and improved properties.

It is an object of the invention to provide new and improved packages and methods of forming the same, the packages being particularly adapted for use with food products and the like subject to spoilage and deterioration, although it will be understood that the various packages disclosed are readily adapted for use with other types of products where the presence of their unusual characteristics are considered desirable.

Another object is to provide new and improved packages and methods of forming the same, the packages being espeically adapted for use in the merchandising of meat products, the packages being capable of establishing and maintaining hermetic sealing conditions.

Still another object is to provide new and improved packages capable of being readily opened for access to the porduct enclosed thereby, and further being reclosable to an extent that the product may be continuously protected by the package.

A further object is to provide new and improved forms of packages which make use of at least a semi-rigid base on or in which a product is received, the product being completely covered and sealed by an enclosing film which is peripherally sealed to the base.

Still another object is to form new and improved packages from specially selected materials, especially film materials capable of exhibiting the formability and sealing characteristics of polyvinylidene chloride film, the invention encompassing in its scope the use of supercooled polyvinylidene chloride film or any other film capable of exhibiting the essential characteristics and properties of this film.

An important object of the present invention taken in conjunction with the foregoing objects is to provide packages which utilize a unique seal forming arrangement, this arrangement involving the utilization of a plasticizer interface which functions to seal together or adhere film and base material portions of the package. This important object also involves the utilization of the unique properties of supercooled polyvinylidene chloride film or an equivalent, as well as additionally utilizing other suitable films as a source for the plasticizer interface.

Other objects not specifically set forth will become apparent from the following detailed description of the invention made in conjunction with the accompanying drawings wherein:

FIG. 1 is a plan view of one form of wiener-type product package making use of the principles of the present invention;

FIG. 2 is an elevation of the package of FIG. 1;

FIG. 3 is an enlarged fragmentary section of the package of FIG. 1 taken along line 3—3 therein and illustrating the particular combination of films and materials used in forming the same, it being understood that this view, as in the case of a number of subsequent views to be described, is basically schematic for the purpose of best describing the inventive concepts;

FIG. 4 is a view similar to FIG. 3 illustrating a modification of the package of FIG. 1;

FIG. 5 illustrates still another modification of the package of FIG. 1;

FIG. 6 illustrates still another modification of the package of FIG. 1;

FIG. 7 illustrates a further modification of the package of FIG. 1;

FIG. 8 is a schematic plan view of a special form of bacon-type package which makes use of the principles of the present invention;

FIG. 9 is a cross section of the package of FIG. 8;

FIG. 10 is an enlarged fragmentary section of a portion of the package of FIG. 8 taken generally along line 10—10 therein;

FIG. 11 is an enlarged fragmentary section of a modified form of package related to the type of package shown in FIG. 8;

FIG. 12 is a view similar to FIG. 11 illustrating still another modification of the package of FIG. 8;

FIG. 13 illustrates still a further modification of the package of FIG. 8;

FIG. 14 is a perspective of another basic package structure which incorporates the principles of the present invention;

FIG. 15 is an enlarged fragmentary section of one form of package related to the basic package of FIG. 14;

FIG. 16 is a view similar to FIG. 15 of still a further modification;

FIG. 17 is a substantially enlarged section of a portion of the seal area of the package of FIG. 16;

FIG. 18 is a perspective of another basic package capable of making use of the principles of the present invention;

FIG. 19 is an enlarged plan view of the base member of the package of FIG. 18;

FIG. 20 is a sectional view of the base member of FIG. 19 taken generally along line 20—20 therein; and

FIG. 21 is an enlarged fragmentary section of a portion of the edge seal of the package of FIG. 18 taken generally along line 21—21 therein.

A basic concept of the present invention involves the utilization of the unique properties of polyvinylidene chloride film or its equivalent in its supercooled state. Polyvinylidene chloride, normally in the copolymer form of vinylidene chloride and vinyl chloride, can readily be extruded into film or sheet form of varying thickness. As the hot film is formed at the extruder, the film is in a molten, amorphous state and wiil solidify upon cooling, becoming crystalline after the expiration of a relatively short period of time. To this extent polyvinylidene chloride film is quite similar to a number of known films but it has been found that polyvinylidene chloride film exhibits the unusual characteristics of being susceptible to retention of the amorphous state if the film is subjected to adequate supercooling following formation. The hot amorphous film is immediately passed through a supercooling bath of water or the like in which the temperature of the film is quickly reduced to a much lower and cooler temperature. The temperature of the supercooling bath may vary considerably depending upon film requirements and it has been found that, by way of example only, room temperature or below is quite adequate to make full utilization of the unique properties of the film. With immediate temperature quenching of the film to pass the same into its supercooled state, the film remains amorphous and exhibits substantial formability while in this state. Any very substantial stretching of the film may substantially induce crystallization and complete stretching of supercooled film to form tube-like packages and the like has been practiced. However, with substantial

3,131,069 stretching or forming of the film it has been found that the crystalline structure established by the working becomes oriented.

By avoiding excessive stretching or forming of the supercooled film while maintaining the same in its super- 5 cooled state, it has been found that the film is readily self-adhering even to the extent that a fused-type seal can be obtained when portions of film are contacted. This phenomenon has been used to advantage in the forming of various types of packages. A procedure followed in- 10 volves the insertion of a product between two supercooled films, the combining of the films by evacuation of the product area between the same, and subsequent crystallization of the combined films to remove the unique adherence properties thereof and permit ready handling of 15 the finished package. This procedure results in an economical and efficient package forming operation. The supercooled film is readily formable and can be drawn about a product to conform to the shape thereof without the formation of folds or pleats which would normally 20 establish potential leakage areas. Controlled stretching or forming of the film while in the supercooled state can be practiced without accompanying crystallization of the film to an extent that the supercooled properties thereof are retained in order to make full utilization of the self- 25 sealing characteristics of the film.

In accordance with an important concept of the present invention, it has been found that supercooled polyvinylidene chloride film can be combined with other packaging films through a film plasticizer interface to form a unique 30 hermetic seal. The seal is of a type which can be readily broken by peeling back or otherwise separating one or more of the films sealed together through the interface. The breaking of the seal is very readily obtained without destruction of the packaging film and this film in the area 35 of seal breakage can be recombined for general product protection resealing of the package following removal of a portion of the product therefrom. Basically, the seal comprises and is formed from at least two layers of packaging material adhered to one another through a 40 plasticizer interface, one of the film layers being polyvinylidene chloride film or an equivalent thereof which is adhered to the other layer of packaging material through the interface while in an amorphous or supercooled state, the polyvinylidene chloride film in the finished condition of the package after expiration of a short period of time exhibiting at least substantially random crystal arrangement. It is theorized that supercooled polyvinylidene chloride film exhibits unusual flow and forming properties of a nature which results in the film actually “wetting” almost any surface with which it contacts. This film in its supercooled state exhibits at least a slight tendency to stick to many substances without the substances necessarily being chemically similar. With the present discovery it has been found that this tendency 55 to adhere to many materials can be materially increased by further plasticizing the adhering surface of the film. Such plasticizing may be accomplished in several different ways, namely, by contacting the supercooled film with a plasticized film having available plasticizer on its con- ₆₀tacting surface, by applying a separate layer or coating of plasticizer to a surface to be contacted by the supercooled film, and in certain instances incorporating adequate plasticizer in the supercooled film to improve the tendency of the same to adhere to other materials. The ₆₅seal forming concept described permits efficient and economical cold package forming operations thus completely eliminating the requirement of heated plastic flow in packaging film to form a hermetic seal.

The accompanying drawings illustrate a number of different types of packages which can be advantageously formed by practicing the principles of the present invention. It will be understood that the packages illustrated and the particular materials used, as will be described, are not intended to be all-inclusive but are merely 75 intended to illustrate the basic concepts of the invention. FIGS. 1-3 illustrate a wiener-type package 10 which is formed from the combining of laminated films. For description purposes the package 10 includes a top laminate 11 and a bottom laminate 12 which cooperatively enclose therebetween a plurality of wieners or wienertype products 13, these products being placed in side-byside relation. The laminates 11 and 12 are combined peripherally about the products 13 to form a continuous edge seal. The laminates are also drawn inwardly about the products to conform to the contour thereof. FIG. 1 illustrates the use of a wiener band 14 which is commonly used in grouping a plurality of wieners, but this band need not be incorporated therein if desired. By reason of the laminates 11 and 12 intimately engaging and surrounding the products 13 and conforming to the shape thereof, the package 10 is adequately rigid for efficient handling.

Referring specifically to FIG. 3, the top laminate 11 is formed from combined films 15 of polyvinylidene chloride and 16 of polyvinyl chloride. The bottom laminate 12 is formed from combined films 17 of polyvinylidene chloride, 18 of polyvinyl chloride, and 19 of polyvinylidene chloride. In the forming of this package the polyvinylidene chloride film layer 19 is applied thereto in its supercooled state and functions to form the peripheral edge seal with the polyvinyl chloride film layer 16 of the top laminate when the same are combined. The polyvinyl chloride film layer 16 is highly plasticized to provide for the presence of plasticizer on the surface thereof for contact by the supercooled polyvinylidene chloride film 19. Plasticized polyvinyl chloride film may contain from 20 to 30% plasticizer and with this amount of plasticizer incorporated therein, in a micro-film of the plasticizer is established on the film surface. A suitable plasticizer may be used such as the commercially available and widely used “Santicizer 141” which is basically 2-ethylhexyldiphenyl phosphate. Other suitable plasticizers are dibutyl sebacate, diisobutyl adipate, “Citroflex A-4” (acetyl tributyl citrate) and “Santicizer E-15” (ethyl phthalyl ethyl glycolate).

In forming the package 10 there is adequate adherence between the various films which are combined to form the top and bottom laminates. The combined films of these laminates each contribute certain characteristics which provide for an overall package of adquate flexibility, toughness and oxygen impermeability. The flexibility aids in the forming of the package and further prevents subsequent package breakage as a result of handling. The toughness, of course, particularly aids in maintaining the package in good condition during handling. The unique supercooled properties of the polyvinylidene chloride layer 19 provides for combining of this layer with the plasticized polyvinyl chloride layer 16 in such a manner that a hermetic seal is formed. Furthermore, this seal is peelable and the top and bottom laminates can be separated along the seal area for access into the package. Separation of the laminates does not result in the loss of adequate sealing properties to prevent resealing of the package although upon resealing the package is no longer hermetic. Any suitable means, such as a tab of the type to be described, may be used in the seal area to permit ready separation of the top and bottom laminates for access into the package.

The films used in forming the laminates 11 and 12 of the package 10 may be varied considerably. By way of example, polyethylene film may be substituted for the polyvinyl chloride film in laminate 12. Soluble polyvinylidene chloride may be used as a substitute for the outer films 15 and 17. This material is in the form of a lacquer with the copolymers of vinyl and vinylidene chloride being dissolved in selected solvents such as tetrahydrofuran, cyclohexanone, cyclopentatone, 1,4-dioxane, isophrone and o-dichlorobenzene. By substituting an acrylonitrile monomer for the vinyl chloride monomer in polymeriza3,131,069 ⁵ tion with vinylidene chloride, a copolymer is produced which is soluble in common lacquer solvents such as acetone, methyl ethyl ketone and toluene. The soluble materials may be applied as coatings to any other materials such as polyethylene, polyvinyl chloride, paper and cellophane in very thin coatings such as between Mo and Mo of a mil. Such a coating improves the oxygen barrier properties of the materials rather substantially. For example, polyethylene film which is normally rather porous to oxygen will exhibit a markedly improved oxygen impermeability when coated with soluble polyvinylidene chloride or suitable polymeric materials of the type described. The soluble materials are applied in solution and the solvent is evaporated leaving a dry flexible film.

A modification of a wiener-type package is shown in FIG. 4. This package 20 is formed from a top laminate of supercooled polyvinylidene chloride film 21, plasticized polyvinyl chloride film 22, and supercooled polyvinylidene chloride film 23. The bottom laminate is formed from plasticized polyvinyl chloride film 24 and supercooled polyvinylidene chloride film 25. The films 23 and 24 are hermetically sealed to one another through a plasticizer interface 26. The films 21 and 25 may preferably be oxygen barrier polyvinylidene chloride having a composition of approximately 85% vinylidene chloride and 15% vinyl chloride. These films function to efficiently protect the package from oxygen permeability and the films are adequately fat resistant and flexible. By way of example only, each of these films may be approximately 1 mil thick. The plasticized polyvinyl chloride film 24 may supply the plasticizer interface but if other films such as polystyrene or polyvinyl butyral are used, the plasticizer interface 26 is supplied in the form of a separately applied coating. The plasticized polyvinyl chloride films 22 and 24 may be from Vi to 1 mil in thickness.

FIG. 5 illustrates a similar type package 27 including a rigid or at least substantially rigid base member 23. By way of example, the base 28 may be formed from 10 mil thick polyvinyl chloride sheeting. This type of vinyl sheeting is known and is generally referred to as calendered food-approved sheeting. The coating of plasticizer 29 is applied to the flange portion of the base 28 (which may have indentations if desired) and a top film laminate of a combined layer of oxygen barrier supercooled polyvinylidene chloride 30 and flexible supercooled polyvinylidene chloride 31 completes the package. A suitable flexible film of supercooled polyvinylidene chloride may be prepared from a coplymer of 68% vinylidene chloride and 32% vinyl chloride. Also, by way of example, oxygen barrier polyvinylidene chloride film may have a composition of approximately 90% vinylidene chloride and 10% vinyl chloride. The combined film layers 30 and 31 will become fused together during combination and the laminate functions as a single film although the individual properties of each layer are advantageously retained. By way of example only, the layer 30 may have a thickness of about 1 mil whereas the layer 31 may have a thickness of from 2 to 3 mils.

The package 32 of FIG. 6 is at least semi-rigid _ by reason of the use of a relatively thick base 33 of rigid polyvinyl chloride or high strength polystyrene. Here again, the base 33 may have a thickness of about 10 mils. A coating 34 may be applied to the top surface of the base 33 throughout its entirety to adhere thereto a. film 35 of crystalline polyvinylidene chloride having oriented crystal arrangement (i.e. not supercooled) or supercooled polyvinylidene chloride which functions as an. oxygen barrier. In this instance where supercooled film is used there should be adequate time permitted for sufficient crystallization inducement to prevent formation of a fused seal and form a peelable seal. The coating 34 may be of any suitable adhering material such as a plasticizer or an adhesive. A coating 36 of plasticizer is applied to the flange edge portion of the barrier film 35 and adheres thereto a top surface laminate formed from combined supercooled polyvinylidene chloride films 37 and 38. The plasticizer coating 36 defines the seal area and the top laminate may be readily peeled from the base structure for access into the package. The thickness of the film 5 layers 37 and 38 may be on the same order as previously described in connection with the package 27 of FIG. 5.

The package 39 of FIG. 7 is slightly different in construction in that the rigid plastic base 40 thereof has applied to the outer bottom surface, as viewed, an oxygen 10 barrier film 41. This film is adhered to the base 40 by a plasticizer or adhesive coating 42. The flange seal surface of the base 40 has applied thereto a thin coating of plasticizer 43 which adheres thereto a top laminate of polyvinylidene chloride films 44 and 45.

In considering the various types of packages described above, it will be understood that the plasticizer sealing interface may be supplied either from a film layer itself or actually applied to a seal-defining surface portion of a package. In either case the plasticizer film will pref20 erably be very thin although the film layer as illustrated is greatly enlarged out of proportion merely to establish its location in a diagrammatic or schematic manner. Preferably, the plasticizer film may be only a few molecules thick, such as the thickness of a soap bubble about 25 to burst and thus actually exhibiting Newtonian rings.

Where the plasticizer is actually applied as a coating, the same is readily mixed with a suitable volatile solvent of the type described above for ease of application, the solvent eventually leaving the plasticizer in the form of 30 a continuous coating. However, the plasticizer by its nature need not be applied in solvated form. Supercooled polyvinylidene chloride film upon contacting the plasticizer interface is so completely and unusually formable that it will flow into intimate adhering contact and 35 provide a smooth, wrinkle-free seal area. The package will not warp appreciably and only a very low pressure need be applied to form the seal.

In the method of forming the packages of the type described, a product is placed on the selected base material 4Q with this material providing a continuous peripheral edge portion which projects beyond the product. The top surface of the edge portion is supplied with a thin film of plasticizer either by reason of the particular film used in forming the base or by application of a separate plasticizer coating. The top film is then brought down over the product to confine the same and the peripheral portion of the top film adheres to the base material through the plasticizer interface. The packaging material used in forming the package may be confined in a package form₅₀ ing die and the area about the product between the base material and covering film may be evacuated. In following this procedure, oxygen is withdrawn from the interior of the package to aid in extending the shelf-life of the product and evacuation results in the drawing down of 55 the top film, as well as the drawing up of the bottom film if the same is flexible, and automatic forming of the seal. Not only do the films engage in the seal area to completely define the finished seal but the flexible and formable packaging film conforms to the contour of the 00 product enclosed thereby in a manner previously described. By using supercooled polyvinylidene chloride film, a readily formable cold seal is obtained and the packaging operation is greatly simplified. By way of example only, a seal of the type described may be formed 05 with less than 15 p.s.i. where package vacuumization procedures are followed.

FIGS. 8 and 9 illustrate a package prepared in accordance with the principles of the present invention and particularly adapted for use with a bacon product. The 70 package 46 comprises a base board or member 47 which has mounted centrally thereon a product board or member 48 having in turn the bacon product 49 mounted thereon. The bacon product is in the form of a plurality of stacked bacon slices which extend along the product 75 board 48 in an inclined position. The package is com

3,131,069 pleted by a top film 50 which completely covers the product 49, extends downwardly along the edges thereof in intimate contact, extends over the product board 48 and into sealed engagement with the exposed peripheral top surface of the base board 47. Referring to FIGS. 8 and 10, a comer portion of the base board 47 carries a triangular insert 51 placed on the top thereof and formed from material which is not adherent to the covering film 50. A corner of the film extends over the insert 51 and is not adhered thereto. In this manner, a corner of the film may be readily lifted and grasped for subsequent peeling of the film from the surface of the base board 47 to which it is adhered for access into the package.

FIG. 11 illustrates a particular form of bacon package 52. This package is formed from a base board 53 of any suitable relatively rigid material such as bleached kraft paperboard which may have a thickness of from 0.01 to 0.020 of an inch. The bottom surface of the base board 53 may be provided with a coating 54 of microcrystalline paraffin wax for protection and at least partial sealing of the base board 53. The top surface of the base board 53 has applied thereto a continuous suitable coating 55 of adhesive or glue to adhere thereto an oxygen barrier material such as aluminum foil 56. Placed on top of the foil 56 is a lacquer coating 57 of polyvinyl chloride. By way of example, the aluminum foil 56 may have a thickness of about 0.00035 of an inch and the lacquer 57 may be applied to the extent of 1 pound per 1000 square feet.

A product board 58 is received on top of the lacquer coating 57 and has the bacon product 59 supported thereon. The product board 58 may be formed from waxed paperboard having a thickness of from about 0.0015 to 0.007 of an inch. The top film may be in the form of a laminate including oxygen barrier supercooled polyvinylidene chloride film 60 fused with flexible supercooled polyvinylidene chloride film 61. The film 60 may be 1 mil thick whereas the film 61 may be from 2 to 3 mils thick. The seal between the top film and the combined structure of the base board is obtained through a plasticizer interface 62. This interface is applied to the base board structure on the top surface thereof surrounding the product board 58 and the formability of the supercooled polyvinylidene chloride top film permits ready conformation thereof to the peripheral edge portion of the product board 58 and the peripheral edge portion of the base board.

FIG. 12 illustrates a modified package 63 the construction of which includes a base board member 64 formed from 0.012 to 0.020 of an inch thick bleached kraft paperboard. The bottom surface of the board 64 has applied thereto a suitable wax coating 65. The top surface of the board 64 has applied thereto a clay coating 66 of known type. The board structure described is commercially available, the coating 66 constituting a resinous clay coating to which supercooled polyvinylidene chloride will adhere although not necessarily form a hermetic seal.

Supported on the top surface of the base board is a layer of barrier material 67 which need not be fixed to the clay coating 66 of the base board. This barrier may be formed from oriented polyvinylidene chloride film, such as having a thickness of 50 gauge, or paper mounted aluminum foil lacquered on the aluminum side with polyvinyl chloride at a rate of approximately 1 pound per 1,000 square feet. Where aluminum foil is used the thickness may be approximately 0.00035 of an inch.

A product board 68 is placed on top of the barrier board or layer 67 and receives the bacon product 69 thereon. The product board 68 may be waxed paperboard having a thickness ranging from about 0.0015 to 0.007 of an inch.

The top film drawn down over the product constitutes a laminate of supercooled polyvinylidene chloride films ⁸ having an outer oxygen barrier film 70 and an inner flexible film 71. A coating of plasticizer 72 is applied to the top peripheral surface of the barrier board 67 and the film laminate is adhered through the plasticizer in5 terface to the base structure of the package to form the peelable hermetic seal.

The package 73 of FIG. 13 is formed from a base board 74 of bleached kraft paperboard having a thickness of about 0.015 of an inch. The bottom surface 10 of this board is provided with an inner coating 75 of adhesive or glue which adheres to the board a layer 76 of aluminum foil. The layer 76 may also be formed from oriented polyvinylidene chloride film.

It will be noted that the top surface of the board 74 15 is not covered with an oxygen barrier material. The inside of the package may be protected from oxygen permeation through the board 74 by impregnating at least the outer edge portion of the board 74 with a plastic material such as polystyrene, vinyl lacquer or 20 other suitable material. The impregnation is carried out to an extent that the board in this area is impermeable to oxygen thus preventing air from diffusing through the edge of the board and discoloring the bacon. Furthermore, lacquer impregnation should be adequate to pro25 vide a surface coating for seal formation as is described below.

The base board 74 carries on the top thereof a product board 77 of waxed paperboard or the like of the type previously described. The top film is a laminate of 30 supercooled polyvinylidene chloride having an outer oxygen barrier film layer 78 and an inner flexible film layer 79. The hermetic seal is obtained through a plasticizer coating 80 applied to the lacquer coated top surface edge portion of the board 74. Here again, a suitable 35 product 81 such as bacon or the like is enclosed in the package.

FIGS. 14-17 deal with another type of package which is well known under the name “Slice-Pak.” The basic type of package under consideration is disclosed in U.S. 40 Patent No. 2,200,200 with the exception that the package of the present invention makes advantageous use of the seal forming properties of supercooled polyvinylidene chloride film in combination with a plasticizer to eliminate the use of a rim-like clamping member to seal the 45 package. The package 82 of FIG. 14 is formed from a base board 83 of relatively rigid material which has sealed thereto a film 84 which includes supercooled polyvinylidene chloride film and which encloses a suitable product 85 such as stacked slices of bologna mounted 50 centrally on the base board 83.

FIG. 15 illustrates a particular form of package 86 including a base board 87 formed from any suitable adequately rigid material. The base board may be formed from metal, bleached kraft paperboard of the 55 type previously described, or substantially rigid plastic material of the type previously described. A layer of aluminum foil 88 or any other suitable oxygen barrier material is suitably applied to the top surface of the base board 87. In the event that the base board 87 is 60 adequately oxygen impermeable, such as with the use of metal, suitable plastics, or the like, the barrier layer 88 may be eliminated. Applied to the top surface of the layer 88 is a film 89 of polyvinyl chloride. A product 90 in the form of stacked slices is received on the 65 film 89. The covering film is formed from a laminate of supercooled polyvinylidene chloride film 91 having on the outer surface thereof a film 92 of polyvinyl chloride or other suitable materials such as polyethylene. The outer film layer 93 may be formed from oxygen 70 barrier supercooled polyvinylidene chloride or from soluble polyvinylidene chloride lacquer of the type previously described. The package seal is formed between the film layer 91 and the film 89. The polyvinyl chloride of the film 89 is adequately plasticized to prepare the surface 75 to which the supercooled polyvinylidene chloride film

3,131,069 will readily adhere. In a package of the type described, the plasticizer used obviously must be fully acceptable for films in contact with food as the product 90 rests on the film 89.

FIGS. 16 and 17 deal with a somewhat simplified package structure enclosing a stacked product 95. The package comprises a suitable adequately rigid base board 96 which has applied thereto a layer 97 of oxygen barrier material. This particular layer may be formed from oriented polyvinylidene chloride, supercooled polyvinylidene chloride, polyvinylidene chloride lacquers, polyvinyl chloride lacquer or plasticized polyvinyl chloride. A coating of plasticizer 98 is carried on the outer peripheral top surface of the barrier material 97 and a top film including supercooled polyvinylidene chloride 99 is drawn down over the product and into hermetically sealed engagement with the base of the package through the plasticizer interface. As identified by the broken lines in the covering film 99, this film may be formed from a suitable laminate of any suitable type previously described. The plasticizer coating 98 may be supplied from the film layer 97 if the same is (suitable for this purpose. The plasticizer may also be in the form of a mixture of plasticizer and mineral oil wherein a light mineral oil is used having a viscosity in the range of about 50 to 130 Saybolt. Mineral oil may be used to an extent to attenuate the plasticizer while retaining its ability to produce the desired degree of adhesion.

Another type of rigid base package 100 is illustrated in FIGS. 18-21. The package includes a cup-like, relatively rigid base 101 provided with an outwardly projecting and peripherally continuous sealing flange 102 extending along the top thereof. The base 101 is provided with upstanding side wall portions 103, an oppositely positioned pair of which are of decreasing height toward one end of the base. A product 104 such as sliced bacon is received in the tray-like base 101 and a packaging film 105 is drawn down over the projecting portions of the product 104 and is in sealed engagement with the top surface of the flange 102.

The base 101 as best illustrated in FIGS. 19 and 20 is formed with a bottom which preferably is provided with a reinforcing groove-like rib area 106 formed therein during molding of the base. An end wall 103 shown at the bottom portion of FIG. 19 and at the right hand portion of FIG. 20 is angled but is of rather substantial height. The side walls joining the high end wall slope downwardly with decreasing height toward the opposite end of the base. The continuous top edge peripheral flange 102 may also be angled to conform with the slope of the side walls as illustrated. The base 101 may be formed from any suitable material such as rigid moldable plastic, or metal capable of forming by stamping. Rigid polyvinyl chloride subjected to heat forming may be used in the preparation of the base 101.

The film 105 may be any suitable film capable of being sealed to the flange 102. Heat sealing may be used if desired. FIG. 21 illustrates the film 105 as being formed from laminated film layers 107 and 108. The layer 107 may be an oxygen barrier supercooled polyvinylidene chloride film and the layer 108 may be a flexible supercooled polyvinylidene chloride film. The top surface of the flange 102 may have applied thereto a coating 109 of plasticizer to provide an interface through which the film 105 is hermetically sealed to the base 101. The package illustrated is quite strong and very adequately displays the product disclosed therein. While the base 101 illustrated is provided with a special shape, it will be appreciated that this base could be of cup or pan shape with the product fully received therein or just slightly projecting above the top surface thereof and the packaging film being drawn over the project and sealed with the integral flange of the base.

By disclosing a rather substantial number of packages, it is not intended to convey the impression that the invention is limited to these packages. Obviously, many different types of packages may be formed while utilizing the principles of the present invention. The number of packages disclosed is illustrative of the wide scope of application of the principles of the present invention. The principle of utilizing a plasticizer activated interface in forming a seal between supercooled polyvinylidene chloride film and another suitable material extends to its utilization with materials which may exhibit a marked difference in chemical structure upon comparison with polyvinylidene chloride. Thus the invention will apply to the use of essentially amorphous polyvinylidene chloride film or an equivalent thereof with any other material capable of exhibiting adequate compatibility and adherence properties by the preparation of the seal forming surface through the use of plasticizers.

Obviously certain modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.