US3793135A

US3793135A - Formable barrier packaging material, process therefor and package thereof

Info

Publication number: US3793135A
Authority: US
Inventors: V Monia
Original assignee: Guardian Packaging Corp
Current assignee: Guardian Packaging Corp
Priority date: 1969-04-01
Filing date: 1971-10-06
Publication date: 1974-02-19
Anticipated expiration: 1991-02-19
Also published as: US3809602A; CA956224A

Abstract

A strip of methyl methacrylate styrene polymer is laminated with a coating of a vinyl chloride-vinylidene chloride polymer. This lamination is a transparent semi-rigid, flexible packaging material which can be readily drawn in a mold to form a food containing package. The package can be filled with food product at relatively high temperature, and provides, when sealed, a food preserving package of long shelf life.

Description

United States Patent [1 1 Monia [451 Feb. 19, 1974 FORMABLE BARRIER PACKAGING MATERIAL, PROCESS THEREFOR AND PACKAGE THEREOF [75] Inventor: Victor Monia, Mountain View,

[21] Appl. No.: 187,073

Related U.S. Application Data [63] Continuation-impart of Ser. No. 812,238, April 1,

1969, abandoned.

[52] U.S. Cl 161/165, 161/252, 161/253, 161/254, 161/255, 161/256, 99/171 LP,

[51] Int. Cl B32b 27/32 [58] Field of Search... 161/165, 252, 253, 254, 255, 161/256;117/76 F; 99/171 LP, 171 CT, 171 CP, 171 MP; 206/46 F [56] References Cited UNITED STATES PATENTS 3,717,544 2/1973 Valyl 161/252 3,393,185 7/1968 Keskkula 99/171 LP UX 3,328,196 6/1967 SincOck 117/76 F 3,354,238 l1/1967 Schmitt 260/880 R 3,387,988 6/1968 DeLapp et al 117/76 F 2,990,306 6/1961 Dyer 161/165 2,824,024 2/1958 Chapman 117/76 F 3,222,211 12/1965 Updegrove et al. 117/76 F Primary ExaminerGeorge F. Lesmes Assistant Examiner-E. P. Robinson Attorney, Agent, or Firm,Moore, Zimmerman & Dubb [57] ABSTRACT A strip of methyl gnethacrylate styrene polymer is laminated with a coating of a vinyl chloride-vinylidene chloride polymer. This lamination is a transparent semi-rigid, flexible packaging material which can be readily drawn in a mold to form a food containing package. The package can be filled with food product at relatively high temperature, and provides, when sealed, a food preserving package of long shelf life 5 Claims, 5 Drawing Figures FORMABLE BARRIER PACKAGING MATERIAL, PROCESS THEREFOR AND PACKAGE THEREOF CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of its abandoned parent application Ser. No. 812,238 filed Apr. 1, 1969 for FORMABLE BARRIER PACKAGING MATERIAL, PROCESS THEREFOR AND PACK- AGE THEREOF in the name of Victor Monia.

BACKGROUND OF THE INVENTION This invention relates to a semi-rigid flexible package having barrier characteristics in which a strip or substrate of methyl methacrylate styrene polymer is laminated with a coating of Saran, a trade name for a vinyl chloride-vinylidene chloride polymer, and then drawn to form a food container.

Semi-rigid flexible packages are known. Typically a semi-rigid packaging material is drawn under vacuum or pressure or other mechanical methods to form a container in which a food product is later placed. The container, when filled, is sealed and forms a disposable package which can be discarded when the contained food is consumed. Semi-rigid flexible packages having barrier properties to prevent both the escape of moisture from packaged food and the penetration of spoiling oxygen into the food are known. Heretofore, such packages have been fabricated from materials including one or more laminates of semi-rigid vinyl and other plastics of varying barrier properties. When it has been desired that the package be clear, i.e., transparent, vinyl has been used to produce such packages.

Semi-rigid vinyl is a material having some barrier properties. This vinyl, while capable of being drawn to form a package, suffers serious disadvantages. These disadvantages include the fact that the vinyl only be drawn at relatively slow rates. Moreover, when vinyl is drawn to form semi-rigid flexible packages, it commonly must be retained in, or dwell within a heated ambient for a relatively long interval of time, or the material will elastically return or memory back, wholly or partially, to its original preformed disposition. Finally, vinyl packages can only be filled with food product at relatively low temperatures in the range of 170F., as temperatures in excess of this limit cause the filled package to deform.

Attempts to remedy these deficiencies of vinyl have been made. These attempts have included fabricating laminates of vinyl with intermediate layers of Saran and exterior layers of polyethylene. The resulting packaging material, however, having improved flexibility and barrier characteristics, still maintains many of the basic deficiencies of vinyl. These dificiencies include the relatively slow rates at which vinyl can be drawn and the relatively low temperature at which the food product can be placed into the container withoutthe formed package becoming deformed. Moreover, the laminates of vinyl often do not have the clarity of vinyl, per se.

SUMMARY OF THE INVENTION An object of this invention is to set forth a flexible and semi-rigid package laminate which can be drawn into a food containing package having improved barrier properties. Accordingly, a strip or substrate of methyl methacrylate styrene polymer has Saran laminated thereto. The substrate imparts rigidity to the formed package while the Saran layer produces a barrier providing improved shelf life of the package when formed.

A further object of this invention is to provide a package laminate which can be rapidly drawn without excessive dwell in a heated ambient. The total time necessary to form a food containing package can be up to 30 percent less than that necessary for the forming of vinyl laminates.

A still further object of this invention is to provide a package having an inside Saran coating or lamination which gives improved shelf life to packaged products by preventing water loss, oxygen penetration, and grease and oil loss through the package wall.

An advantage of the package of this invention is that it can be filled with food product at temperatures in the range of F. without the danger of package deformation. Further, it has been found that food product contained within the package can be cooked to temperatures approaching the range of 185F. without package deformation, a result not possible with vinyl laminated packages.

Other objects, features and advantages of the present invention will become apparent as the following specification progresses, reference being had to the accompanying drawing for a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the accompanying two sheets of drawings;

FIG. 1 is a schematic diagram illustrating the process by which the laminate of this invention is made;

FIG. 2 is a diagram of the coating station for applying the layers of adhesive and Saran, respectively;

FIG. 3 is a schematic diagram illustrating the laminated material of this invention prior to forming into a package;

FIG. 4 is a schematic diagram of laminated material during forming of a package; and

FIG. 5 is a schematic diagram of the laminated material after forming into a package.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2, a schematic illustration of the disclosed process for making the laminated strip is illustrated. An advancing strip A of the substrate methyl methacrylate styrene polymer is shown being fed from a convolute roll 14. The strip winds under idler rolls 16 and passes through a first coating station B which applies a layer of adhesive to the strip. After receiving the adhesive, the strip advances through idler rollers 17 and through an oven D1 which drys the adhesive on the strip. After passing through the oven DI, the advancing strip is fed through idler rolls 18 to a second coating station C where a coating of Saran is applied. The laminate then passes through to idler rolls 19 and through an oven D2 which dries the Saran on the adhesive. The laminated strip A is finally wound in a convolute roll about a rewind core 20.

With reference to FIGS. 3, 4, and 5, the fabrication of a semi-rigid flexible package from the Saran laminated methyl methacrylate styrene. polymer is illustrated. The laminated strip A is passed directly over a mold F with the Saran laminate facing away from the mold surface. Mold F has concavities conforming to the outside dimension of the formed container. The strip is placed on the mold F and heated to a temperature in the range of approximately 300-350F. and drawn under pressure (here shown as a vacuum) interior of the female concavities of the mold. The vacuum drawn through holes G in mold F pulls the laminated strip A down and into the molding surfaces when the temperature of the strip exceeds its thermoplastic state and rapidly imparts concavities to the strip. When the strip is separated from the mold by release of the vacuum, it has the concavities formed therein. These concavities can subsequently by filled with food, sealed and distributed in a package which provides the contained food product with a long shelf life.

The methyl methacrylate styrene polymer substrate normally has a thickness in the range of 0.006 inches to 0.060 inches, a thickness of 0.012 to 0.040 inches being preferred. Although this base film can be made a selected color by the suitable addition of coloring agents, its natural transparency make it quite suitable for combination with the Saran in forming a transparent package.

A suitable adhesive applied at firstcoating station B is usually applied in an even and uniform coating in the range of 0.1 to 3, dry pounds per ream of passing strip A, a coating of 2 dry pounds per ream being preferred. A ream as commonly used in the trade to which this invention relates and as used herein means 3,000 square feet.

Several primers or adhesives are known and can be used to effect the desired adhesion between the substrate and the Saran. An adhesive sold under the trademark HERMETITE H1037, a product of the Hermetite Adhesive Company is one such product. It comprises a mixture consisting essentially of about 68 percent by weight of acryloid resin including methyl acrylate and methyl alkyl acrylates with alkyl denoting the groups ethyl, propyl and butyl, such methyl alkyl acrylates being commercially available and sold under the trade name ACRYLOID 8-66 by the Rohm and Haas Company; about 10 percent of FDA approved glycolate; and about 22 percent of a polymer consisting essentially of vinyl chloride and vinyl acetate terpolym'er; all suspended in a liquid vehicle comprising principally methyl ethyl ketone. It has been found that this adhesive provides the anchoring qualities between the substrate and Saran necessary for the finished material to withstand the package forming operation. Moreover, the strong adhesion of the Saran to the substrate resulting'from this adhesive does notdegrade over the period of time required for packages of most food products of interest. The adhesive, when cured, is clear and does not detract from the transparency of the finished material.

It is to be noted that the adhesive chosen should have a solvent which will not emanatefrom the finally produced laminate when it is formed into a food containing package. If the solvent of the adhesive is not completely dried and removed from the laminated strip A, it will evaporate into the formed food containing package imparting an undesired taste and conceivably could be injurous when consumed with the food.

Adhesives sold under the trade names ACCOBOND 1094, a product of the American Cyanamid Co. and ADCOATE 102A, a product of Morton Chemical Co., Inc., have also been found sufficient to effect the desired bonding, and solvent releaseproperties suitable for use with this invention.

Typically, the Saran coating is applied at second coating station C so as to be in a concentration in the range of 2 pounds to 25 pounds as dried per ream of strip A, a coating of 5 to 8 pounds per ream being preferred. This Saran is typically a water emulsion in which the water diluent comprises approximately 50 percent by weight of the liquid mixture. Alternatively, lacquer solutions of Saran can be used. The Saran imparts to the pervious strip a barrier laminate which typically arrests the passage of moisture out of the contained food product and prevents the penetration of spoiling oxygen through the formed package into the contained food product.

Coating stations B and C are similar in that they both apply laminates to the passing strip A in liquid form. Coating station B illustrated in FIG. 2 is sufficient to describe both functions. Typically, the coating station comprises a container 22 for confining a bath 24 of either adhesive (as in the case of FIG. 2) or Saran (as in the case of station C). An applicator roller 26 is rotatably mounted about an axis 27 relative to the bath 24 so that the lower portion of the applicator roller is immersed and the upper portion of the applicator roller contacts the passing web. Typically the applicator roller is rotated so as to parallel at its upward surface the movement of the passing strip A and transports the liquid from bath 24 to strip A to apply a coating thereto.

Strip A, shown passing from right to left across coating station C in FIG. 2, passes over first tension roller 31. Thereafter strip A passes into contact with the outside surface of applicator roll 26 where the coating, here shown as adhesive, is applied by applicator roller 26. Web A then is contacted between a second idler roller 32 on the non-coated side and a metering rod 34 on the coated side. Metering rod 34, a standard item of manufacture, functions to remove-the excess coated material from the passing strip A leaving only a uniform coating of the desired thickness thereon.

After passing through adhesive coating station B, the web passes upwardly and through oven D1 in an arcuate path defined by idler 17. The strip A is reversed in its path so that idler rollers 17 contact the uncoated side of the strip and the freshly coated adhesive is exposed to the oven D1.

Oven Dl, commonly of a length in the range of 12feet-1'4feet, is heated to a temperature of approximately 300F. This element, having an arcuate shape complementary to the arcuate path of the web thereunder, exposes its heated surface approximately 1 inch from the passing web. The web, advancing at a speed range between feet and feet per minute, is dried so as to remove substantially all of the solvent contained in the liquid adhesive coating from the adhesive coating. The adhesive when exiting oven element D1 on strip A is a flexible and solid laminate.

After passing through oven DI, the web is then guided by idler rolls 18 to coating station C. At station C the web receives its desired uniform coating of Saran.

After receiving its coating of Saran, the web passes up wardly to idler rolls 19 again tracing an arcuate path under an over D2. i

Oven D2 is a 22 foot long heater apparatus divided into. two 11

foot sections

36 and 38. First section 36,

spaced above the passing web at an interval of approximately 1, inch is heated to a temperature of approximately 400F. Second section 38, spaced a'similar interval above the passing web, is heated to a temperature of 340F. The reduction in temperature between first stage 36 and second stage 38 affects on the passing and drying Saran lamination a gradual reduction in temperature so that when the finally processed web is wound and received about rewind core E, no sticking or blocking of the Saran occurs.

It will be noted that virtually any apparatus for coating strip A with either the adhesive or Saran emulsion is sufficient in the practice of this invention.

Typically, once the laminated packaging material is manufactured, it is transported in a convolute wind to the location where the packages are subsequently formed. Such formation, is illustrated in FIGS. 3, 4 and 5.

As a first step in package formation, the laminated strip A is typically removed from its convolute wind and placed in a planar disposition by apparatus not shown. Typically, the web is advanced in uniform increments coextensive with an overlying mold F.

Mold F as shown in FIGS. 3, 4 and 5 has a heated body maintained at a temperature in the range of 300-350F.. (by apparatus not shown). The mold includes a plurality of concavities 44, which concavities have an inside dimension equal to the desired outside bottom dimension of the finished container. As shown in the illustrated FIGS. 4 and 5, the concavities 44 are typically orientated in longitudinal columns with transverse rows so that a plurality of containers (here shown being 12 in number) can be formed simultaneously.

Concavities 44 of mold F are each given a depth and width so that strip A will not be drawn beyond a point where the Saran maintains its continuity and is not ruptured. A draw ratio area to area in the range of two to one is preferred. Drawing beyond this limit can cause loss of barrier in the formed package.

Extending between the bottom surface 46 of each mold and connected to suction apparatus (not shown) there are a plurality of holes G. Holes G function to draw a vacuum on strip A so as to deform those portions of the strip overlying concavities 44 downwardly into the mold for forming containers.

Strip A, as shown in FIG. 3, is first placed in overlying relation to mold F, where heat is imparted to the strip by conventional apparatus not shown. Sufficient heat is applied to raise the temperature of the strip beyond its thermoplastic point. As shown in FIG. 4, a vacuum is drawn through holes G in the bottom of the mold. This vacuum causes the heated laminant to be pulled downwardly into the mold so that the desired food containing concavities are formed in strip A. When the vacuum is released, the formed strip is removed as shown in FIG. 5.

In the forming of the food containing packaging, pressure (herein shown as a vacuum) is applied to the mold for a period of time just long enough to cause the food concavity to be formed. Once the concavity is formed, the pressure is released, and the strip removed from the mold with the concavities permanently formed therein.

The vacuum fonning herein illustrated is exemplary only. Virtually any known type of forming can be used. Such forming methods can include forming with either heated or non-heated molds, drape forming or other known methods of producing the desired concavities.

Utility of. the joined food containing packages is believed apparent. Typically, the formed packages are moved to another station (not shown) where they are filled with product, and to a third station where they are remotely sealed (also not shown).

Many processes of forming include the step of filling the formed package within the mold. It will be understood that this disclosure is intended to cover such simultaneous forming steps.

In the formation of the molded package it is desirable that the Saran laminate on the formed package be on the inside and exposed to the contained food. If the laminate is on the outside of the package, physical abrasion can sometimes cause removal of portions of the Saran. When such portions are removed, the pervious strip is exposed and the shelf life characteristic of the packaged food product is adversely affected.

EXAMPLE I In one formation of the laminated packaging material, the methyl methacrylate styrene polymer sheet is a 15 mil thick sheet obtained from Baum Chemical Corp. of El Segundo,'Calif., which sheet is formed by extruding the methyl methacrylate styrene polymer resin sold by American Cyanamid Co. under the designation XT polymer" and described in US. Pat. No. 3,354,238. The Saran is obtained and applied to the styrene polymer as an emulsion sold by the W. R. Grace Co., a division of Dewey and Almy, Boston, Massachusetts, under the designation Daran 220. The adhesive used is the previously identified Hermetite l-I-1037.

The substrate is passed through the coating station labelled B in the drawing where 2 pounds by weight per ream (3,000 sq.ft) of the adhesive is metered by a Myer rod uniformly on its surface. The solvent in the adhesive is'dried from the substrate by passing the coated sheet through theoven labeled D in the drawing, to leave a coating of the adhesive having a thickness of about 1/6 mil on the average.

The sheet is then passed through coating station B where the Saran emulsion is applied to it. Sufficient emulsion is applied to the adhesively coated side of the substrate by Myer rod to leave a uniform coating of 8 pounds dry weight per ream of Saran on the substrate after the emulsifier is removed by passage of the material through oven D2. The resulting thickness of the Saran laminate is approximately l/3 mil.

The adhesion of the Saran to the substrate for the above example was tested and found to surpass the tensile strength of the laminate material. That is, structural failure of the substrate occurred before the bond between the Saran and substrate could be caused to separate. The barrier properties of the finished material to oxygen were also determined by the techniques commonly used in the art. It was found that under room conditions (1 atmosphere of pressure at 72F. .and 50 percent relative humidity) only 0.5lcc of oxygen passed through 100 square inches of the material in a 24 hour period. Similarly, only 0.30 gms of water from a 100F. percent relative humidity air atmosphere at 1 atmosphere of pressure passed through square inches of the laminated material in 24 hours. It was further found that the material retained these barrier property values after it was formed into food molds as EXAMPLE II In another formation of laminated packaging material of the invention, the materials and conditions of making the laminations is the same as that set forth in Example I, except that the adhesive is that sold by Morton Chemical Co., a division of Morton International, 110 Wacker Dr., Chicago, 111., under the designation ADCOATE 102A. This adhesive is used in the same proportions as the HERMETITE H-l037. I

The barrier properties of the resulting material are the same as those set forth above. And although the bond obtained with this adhesive is not as exceptional as that obtained with the HERMETITE 1037, it is quite acceptable.

I claim:

1. A molded generally cup-shaped packaging article for holding spoilable eatables and being formed from a flexible semi-rigid laminated packaging material comprising: a first lamina of methyl methacrylate styrene polymer having a thickness of 0.006 inches to 0.060 inches; a second lamina of a vinyl chloride-vinylidene chloride polymer and a third lamina of adhesive between said first and second laminae for bonding all of said laminae together; said adhesive being a deposited mixture of about 68 percent by weight of acryloid resins, 10 percent glycolate and 22 percent of a copolymer consisting essentially of vinyl chlorideand vinyl acetate suspended at the time of deposition in a liquid solvent.

2. The article of claim 1 wherein said first lamina has a thickness of 0.012 to 0.040 inches, and said second lamina has a thickness of 2 to 25 pounds per ream of laminate.

3. The article of claim 1 wherein said first lamina is on the outside exposed surface of and said second lamina is on the inside exposed surface of the cup-shaped article.

4. A flexible semi-rigid laminated packaging material comprising: a first lamina of material of methyl methacrylate styrene polymer having a thickness of 0.006 inches to 0.060 inches; a second lamina of vinyl chloride-vinylidene chloride polymer; and a third lamina of adhesive bonding said first and second laminae together, said adhesive being obtained by depositing onto said first laminae a mixture of about 68 percent by weight of acryloid resins, 10 percent glycolate and22 percent of a polymer consisting essentially of vinyl chloride and vinyl acetate suspended at the time of the deposition in a liquid vehicle comprising methyl ethyl ketone.

5. The packaging material of claim '4 wherein said first lamina has a thickness of 0.012 to 0.040 inches and said second lamina has a thickness of 2 to 25 pounds per ream of laminate.

Claims

2. The article of claim 1 wherein said first lamina has a thickness of 0.012 to 0.040 inches, and said second lamina has a thickness of 2 to 25 pounds per ream of laminate.
3. The article of claim 1 wherein said first lamina is on the outside exposed surface of and said second lamina is on the inside exposed surface of the cup-shaped article.
4. A flexible semi-rigid laminated packaging material comprising: a first lamina of material of methyl methacrylate styrene polymer having a thickness of 0.006 inches to 0.060 inches; a secoNd lamina of vinyl chloride-vinylidene chloride polymer; and a third lamina of adhesive bonding said first and second laminae together, said adhesive being obtained by depositing onto said first laminae a mixture of about 68 percent by weight of acryloid resins, 10 percent glycolate and 22 percent of a polymer consisting essentially of vinyl chloride and vinyl acetate suspended at the time of the deposition in a liquid vehicle comprising methyl ethyl ketone.
5. The packaging material of claim 4 wherein said first lamina has a thickness of 0.012 to 0.040 inches and said second lamina has a thickness of 2 to 25 pounds per ream of laminate.