US2442161A - Method of making gas filled flexible containers - Google Patents

Description

s. BERGSTEIN 2,442,161

METHOD OF MAKING GAS FILLED FLEXIBLE CONTAINERS May 25, 1948.

Filed Oct. 10, 1944 2 Sheets-Sheet 1 .FIG. I

FIG. 2 Y

SHMUEL BERGSTEION I INVENTOR.

May 25, 1948. f "s. BERGSTEIN 2,442,161

METHOD OF MAKING GAS FILLED FLEXIBLE CONTAINERS Filed Oct. 10, 1944 2 Sheets-Sheet 2 FIG. 5

SHMUEL BERG-STEIN 4 INVENTOR.

fatented May 25,

METHOD OF MAKING GAS FILLED FLEXIBLE CONTAINERS Samuel Bergstein, Cincinnati, Ohio Appiication October 10, 1944, Serial No. 557,984

Claims.

My invention has for its principal object the provision of flexible walled packages in which the contents are immersed in-a special atmosphere to be retained about the contents for as long as the package lasts.

Most food products require protection against the loss or gain of moisture, and this problem has been pretty well solved in various ways, as by the provision of moistureproof wrappings, sealed bags, and the like. But many food products additionally require protection from oxidation and other chemical changes producing rancidity, deteriorating taste, or introducing foreign tastes and odors. mersing the goods in a non-reactive atmosphere within the package.

Attempts have been made to provide flexible walled packages containing controlled atmospheres, but these attempts have not been commercially satisfactory. They have followed the procedure of introducing the desired atmosphere along with the contents or of effecting atmospheric exchange prior to the sealing of the package. This was necessary because the ultimate seal at the closures involved cementing together layers of the flexible material of the packages in lapping or face-to-face relationship. The seal was, therefore, essentially an interior seal.

Introducing the desired gas along with the contents or introducing it into the filled but unsealed package can be accomplished; but great difficulty has been encountered in providing dependable gas-tightness in packages where reliance must be placed on an interior seal.

Hence, in commercial practice, products requiring immersion in a non-reactive gas, have had to be packaged in glass or in metal.

I have found that flexible gas containing packages may be provided by a procedure involving a new concept. Briefly, in the practice of my invention, I first enclose the goods in a flexible walled package which, in itself, does not require to be gas-tight. It may be made of gas-tight materials and may be provided with interior seals such as have been mentioned above; but this is not necessary.

The property of gas-tightness is imparted to the closed package by the next step of my process which involves the formation over the whole package of an externally located, tough film of gas-tight substance. There are various ways in which the substance may be applied, but the most convenient way is to immerse the filled and closed package in a bath of sealing substance of thermoplastic character which, when the package is Such protection is best attained by im-' withdrawn from the bath, will form about it an integral, continuous, imperforate and gas-tight skin. Since this skin is relied upon for gas-tightness, it is essential that it be sufficiently tough to withstand the strains of handling and shipment to which the package will be subjected.

The next step of my procedure involves forming one or more openings through the skin and the flexible wall or walls of the container to provide a gas passageway or passageways from the outer air to the interior and contents of the package. This may be done by puncturing the skin and the underlying wall or walls with a suitable instrument, or it may be done by exerting pressure on a preformed weakened portion of the flexible wall of the package so as to form an opening through the wall, and so as to tear or puncture the gas-tight skin at the same time. The introduction of the desired special atmosphere and the expulsion of the contained air may then be accomplished through the opening or openings in a variety of ways. When atmospheric exchange has been effected, the package is then resealed by forming over the opening a closure of sealing substance. The sealing substance must be one capable of forming a gas-tight skin, of bonding to or fusing with the material of the first mentioned gas-tight skin, and having sufficient strength to withstand the strains of handling and equipment.

Where the opening in the sealed package is of relatively large extent, it is within the scope of my invention to provide a support for the skin closure in bridging over the opening. This support may be in the nature of a piece of flexible material disposed over the opening; but the essential seal is formed by the skin itself extending continuously across the opening and bonded to or fused with the first applied skin.

Reference is made to the accompanying drawings wherein I have shown an exemplary con-' tainer and an exemplary mode of treatment for it.

Figure 1 shows a carton blank suitable for forming a scalable package, similar to the carton described and claimed in my co-pending application entitled Cartons for sealing by immersion, Serial No. 538,764, filed June 5, 1944 (now Patent No. 2,412,031), but having an additional feature as hereinafter described.

Figure 2 shows the carton of Figure 1 after it has been erected, filled with contents, and both ends thereof closed.

Figure 3 shows the package in Figure ;2 after it hasbeen dipped in a sealing and skin-forming i which has good adhesion to the container walls substance to effect a continuous, enveloping, gastight skin.

Figures 4 and 5 taken together show diagrammatically various steps involved in'one mode of V treating the containers to effect gas exchange 5 therein and in rescaling the containers, as will be described hereinafter.

In Figure 1 is shown a carton in fiat knocked down form constructed according to my said co pending application." This carton has enclosin 10 body walls 1,2, 3, 4 and a glue flap 5, demarked by the usual score lines. The carton, as shown, is provided with seal end flaps, two short flaps 6 and I being articulated to the ends, resp'eic tively, of walls I and 3, an intermediate sass being articulated to each end of the wall 4., and an outer flap 9 being articulated tdeabh'hdhf wall 2. The carton blank is'formed' dfb'oxboard (either proofed or otherwise) and is tubed in the usual fashion by bending it upon two of'it's'score" lines and adhering the'glue flap- 5 to the wall I, either on the inside or outside of the tube'd strnc wra I l e In the carton as shown there may be incorporated in oneor more of the walls, asmall'outout 'or provision for the formation of a gas'bpening. I havesh own a tab l l in the wall 2',"'defined by a line l2 of perforation or cutting, and which maybe folded ona crease line'1'3. i

Figure 2 is the package sh-own in Fig. 1 after it is filled with contentsfand the flaps-at both ends adhesively secured; The short flaps 6 and l are folded first, then flapBjandfinally flap 9, adhesive being applied'betweenthe meeting surfaces.- It is usual-to-ere'ct the carton, close one end of it as described, fill itjand then close the other end. The filled'carton may then be mersed, if desiredf The object of'the-immersion is to apply a uniform', continuous, outer skin 'or coating of gastight type, and continuous over the whole outer surface of the package, whatever' that surface may be. The nature of the sealing medium is of the'utmost importance because gas tightness will depend in important degree uponthecontinuity and the characteristicsof the film so formed by the dipping or immersion operation."

Furthermore, it is to "the skin so formed that fusion is accomplished during the resealing operation. A strong film-formingcharacteristic is essential in the coating substance, so that in simple application operations the formation of a continuous skin is assured. The 'substance must be one capable of forming 'a gas-tight skin. Hence the substance mustitselfbe impervious to atmospheric air and'the desired inert gas or gases, but "the skin formedmust be free of blow.- holes and other imperfections which would permit breathing. The substance is preferably one to which it is applied; andrit must home which, in skin or membrane form, atitemperaturesto which the package will be subjected, is strong, tough and non-brittle, so that it will withstand the strains of handling, storage and shipment. to Other qualities ar frequently desirable such as resistance to Water or moisture, lack of odor or toxicity, lack of'noticeable color, and transparn as wh re e in a bl d ver ri ted surfaces. It should also be low in cost; .70

The various qualities are most conveniently attained in thermoplastic mixtures. l ?araflin, for example, is deficient in many of the required qualities; but paraffin, or mixtures of par'a'ifin and micro-crystalline:waxes, or other way subr n and i n- Fi t Qumran-t ght t e stances can be toughened and improved as to their skin-forming characteristics and rendered permanently non-brittle by the addition-of various natural or artificial resinous substances.

I give as one example of a formula which has been found satisfactory in the production of gastight packages according to this invention, the following:

Per cent Pa a n w 32. 2

50 Micro-crystalline wax (Petrosene B-Socony Vacuum) 'Ester Gum (melting point, 154") 12 This composition is brought to molten form at a temperature preferably 20 to 30 F. above the melting point of the composition itself, and the sealed package as previously described is immersed for a matter of seconds only in the molten composition, and is thereupon withdrawn. Because the dipping is carried out in the molten composition and the 3 package promptly withdrawn, it can be subjected'tdfurther handling and use almost instantly because the composit'ion' sets by cooling and cooling is rapid. Because of the advantage of rapid setting'by cooling, I prefer'to use a thermoplasticcomposition such as the one given above in carrying out my invention. Howevenif desired, other types'of sealing mediums may be used such; 'forexample, as a resin in solution or in emulsion, provided that, after the film so applied has been allowed to set or harden by cooling'or evaporation orotherwise, the package itself is found to be covered with an integrated gas-tight skin or outer coat- Total or repeated partialirnmersions are convenient and-effective ways of forming thegastight skin;'though the application may be made otherwise if desired. The operations may be carried out by machine or by hand. Where'thermm pl'astic substances are" used, their melting" points should not beso high as to impair: the'packa'ge or its"conte'nts; and whre't'he package walls are porous, care shouldbe taken'to form an adequate external skin by avoiding too great penetration'of the skin-forming"substance'into the Walls. The avoidance of excess 'fluidity and excess temperatures 'in the coating "medium is helpful. It is'not without the scope of my inventionto'dip the package a'plurality of times either iii'the same orin'bath's of different substances so to thicken the skin or f orm' a skin of different layers.

It will be noted in Figure 1 that the side edges of the intermediateflaps 8"'are"cut back slightly (intermediate the end's of the side'ed'gesl asst H}. When the carton is closed as has 'be'en 'de scribed, shallowrecessesare thus left at opposite end edges 6f the car on; between the summed inher'fflaps." These recesses may be filled with the sealingcompoiind wheri thefpackage is dipped, e it r w he ma a i d we e a err ir hs. heed-j hlrlu zl lse wea -goite 1 he sea ns om n ni e ee s l i Yerstrong and forms a protection againstidisruption panes indis ted a 1.4, V V V T re e nat re he esi ewal ed kagedoe-s not form a limitation on my inve se. h n e f taught. Or the'contents may be placed or sealed in one or more bags which in turn are. placed in an outer carton, like that hereinabove described, or otherwise. As hereinafter explained, a carton may-be wrapped prior to dipping. The essential is the provision of a container of flexible, singleor multi-walled character, about which the flexible, integral, gas-tight skin may be formed, which skin .will constitute the outer surface of the package, at least at the time of gas-exchange and rescaling as hereinafter taught.

In the formation of the gas-tight skin on cartons, certain factors must be kept in mind. A perfect and complete seal must be obtained so that the package cannot breathe either through the faces or edges of the boxboard. Boxboard is normally absorptive to the coating; and to the extent that the coating substance strikes into the board it is less effective in producing gas-tightness, since an external, integral film or skin is most effective in this regard. Precautions must be taken to form and maintain the integrity of an outer skin, either by insuring the application of a sufiicient quantity of the coating composition, or by minimizing or preventing absorption.

As to the latter, the viscosity of the coating composition will have an effect. But it is possible to size a filled and closed carton so as to destroy or minimize its absorptivity. Thus a carton may be clipped in or otherwise coated with a cellulosic or resinous composition so as to seal its pores, and afterwards it may be dipped in the coating composition. By way of a single example, a filled and closed carton may be dipped in a solution of polyvinyl alcohol or other vinylite resin, dried, and thereafter coated so as to form a gas-tight skin.

Excellent results are obtained with a carton which is first wrapped in some material that is in itself quite gas-tight-such, for example, as Cel1ophaneand is then dipped as described. A wrapping of this kind not only adds an extra barrier against gas penetration, but provides better mechanical protection in that, if some point of the skin is disrupted the wrapper remains to prevent leakage. Other advantages are also realized. Less difliculty is encountered with blow-holes in the skin produced by the escape of .bubbles of internal gas expanded by heat during the coating step.

The overall cost, in the employment of a wrapper, is frequently less because the decreased amount of coating substance required (due to the lessened absorptivity) offsets, or more than offsets, the cost of the wrapper. As a wrapping material, I may use any flexible, gas-tight film or membrane, for example, Cellophane, cellulose acetate, ethyl cellulose and other non-fibrous films, as well as fibrous ones such as g1a-ssine.- Composite, plied sheet materials including such films, or paper, or metal foils, may also be employed.

The wrapping operation does not require description. It may be performed by hand or by any of the known wrapping machines. The wrap itself does not have to be adhesively secured in such manner as to be gas-tight in itself; but the folds should be well made and held down sufficiently so that a satisfactory skin may be formed when the package is dipped closing any crevices in the wrapper but not permitting penetration of the dipping compound to the interior of the wrap. These requirements are easily met by modern wrapping machines. In Figure 3, I have indicated 9. wrapping in dotted lines at Ma.

The characteristics of the clipping compound can be advantageously varied in accordance with the nature of the surface to which it is to be applied. For a Cellophane-wrapped package, an excellent formula is:

Parts Paraffin, M. P. 135 A mixture of 25 parts of a, high molecular weight hydrocarbon resin such as Vistanex and 75 parts paraffin 15 Vistanex #6 (a low molecular weight resin) 3 Other exemplary formulae are:

The 25-15 Vistanex paraffin mixture mentioned above Ester gum, or of a resin known as Penros and manufactured by Newport Industrial Chemical Company Other dipping compounds, thermoplastic or not, may be employed to form the gas-tight skin pro-- viding they meet the general requirements given. above.

I have now produced, in any of the ways taught, a completely sealed and gas-tight, filled package but the atmosphere in it is air. In a continuation of my process I now effect an exchange of the air for some controlled atmosphere, for example, an inert gas.

. An ensuing step in my process is the disrupting or puncturing of the outer skin or coating and the container wall or walls, at one or more relatively small predetermined areas. This may be done mechanically. In Figure 4, as one exemplary showing, the puncturing or rupturing of the outer film is carried out on a group of packages side by side through the use of an overhead frame bearing fingers or puncturing means which, when the frame is lowered with respect to the packages, actually perforate .or puncture the skin and con tainer walls, or register with the tabs II on the cartons, depressing them, and in either case effecting a gas passageway into the interior of the packages.

In this punctured condition the containers are subjected to conditions producing atmospheric exchange. One way of accomplishing this object is to subject the packages first to vacuum to withdraw the atmosphere within them, and afters ward to the desired gas under atmospheric pres sure. The vacuumizing and introduction of the gas may be done in a chamber in which the car tons are placed for the purpose. The effecting ofa gas opening in the containers and the reseal ing of them after gassing may also be accomplished in the same chamber; but may be accomplished elsewhere.

In Figures 4 and 5 I have shown one form of apparatus which may be used. An assembly of the filled and sealed cartons I6 is shown restin v on a tray or pan l! on a work table Hi. In line with this work table is a chamber l8 having re movable end closures l9 and 2!]. When the closure I9 is removed, the assembly of cartons on its tray may be slid into the chamber and accurately positioned therein, whereupon the closure I9 may be replaced.

The chamber I1 is provided with a connection 2!, valved as at 22, to a vacuum pump or vacuum cylinder, not shown; ..It.1has'al'so.a.. connection 23,1valvedasat Zhtoa source, not shown, of the desired g'as. to be substitutedin the carton.

. Anoverheadbar 2-5is.mountecl in the chamber.-

23v are subsequently raised, the tabs will spring back substantially in the plane of the, carton walls in Which' they are formed. 01' thepins'n may be puncturing points arranged to form one or more small holes through the skin and walls of each container.

With the cartons in the airtightchamber Hi,

the vacuum. pump connected to conduit- 2l is first.

utilized, the valve 22 being. turned to open position, to pull a substantialvacuum whereby to exhaust the cartons. Then the valve 22 is closed, the valve 2-4 opened, and a supply. of CO2 or. other desired gas is released into the chamber until the pressurev in :the chamber has beenraised to atmospheric pressure. By this process, through the openings above described, the air is withdrawn from th packages in the chamber, andissubs'equentlyireplaced withthe desired, other gas.

The. group of gassedpackages is nowwithdr'awn from the" chamber on its. tray l1 onto a Work.

table 29, the closure 20. of the chamber bein first opened. As shown in Figure the cartonsmay be. passed along a table. 39, then-separated by a device 31!. and delivered to acojnveyor 32in spaced relation. The gas openings will now be sealedas hereinafter described.

The means for efiecting gas exchange need-not be those specifically above. described. For exam.-

ple, as set forth in my copendingapplication en:

titled Method of gassing, filledpackages, Serial No. 553,374, filed September 9, 1944. Imay dis-- pense. entirely with a vacuum-pressurev chamber, and instead puncture the skin and the carton walls. with hollow. needles, blowing in thedesired gas through one and permitting. the. escape of airthrough the other. Or I may employ a single.

needle with means for slightly enlarging the. hole,

it makes, blow in the gas through the hollow needle, and permit escapeoi the air about the outside of the needle. Proper placement of the needle orifice or orifices will insurerapid-and efiicient gas exchange. I

I have shown diagrammatically at 3.3 a. reservoir includingmeans to apply a thermoplastic sealing substance to the gas openingsl With heavier-than-air gases th rescaling, is conveniently done outside the chamber 3,. as

shown, but it may be accomplished within the. chamber if desired. As to the. rescaling, the-es:-

sentials are that the gas opening aboutthe tab I l be closed by a suificiently strong skin of gastight substance, sufiiciently adherent to. the .cartonwalls or to-the sealing substance thereon. The resealingmay be accomplished in several Ways, the essential attribute being what might be termed skin repair. Where the-opening or openings formed in the preformed skin" and: the carton wall are small, a simple application of skin iorming substance as might be done by redipping, by wiping on a layer of thermoplastic substance in; adhesive form, or bydepositing a mi tSS.:O. ..Sea ling substance over the opening; may be allqthat isreages.-

quiredi I The-ability oi-afiliniorming .substanceatd. bridge yatgapzini thepreformed; skin. andzthe con.-

tai-nerwall; depends upon a, numberof factors;

ing substance over that/insucnaway asto rev.

generate the integrity; ofthe enveloping skin upon. the package.

While I. have described my: invention .in. certain exemplary embodiments, itis applicableto flexible: walled packages having, when-filled. with'cone tents, sufficientr. abilityv to... retain .their shapes. to.

permit-the treatmentssetforth herein. It will be.

clearhow my. invention may; be applieditosealcd bags of single and plural .walled: types. Such bags,

treated substantially hereinabove described,"

may in. themselves. constitute. completed pack A bagmaybe filled with; contents, closed, provided with the. exterior integral gas tight skin, as. Ihave taught, and then included within a-carton; and'the presence of the: outer. carton will :not interfere with-the practice. of:my.invention pro: viding. by meanscof a suitable large aperture, it exposes .suflicientof the; surface of' the. bagv and. the skin thereonto permitithe-formation of gas. openings and the subsequent sealingthereof. by skin repair.

Products to be packaged may merely be en closed in a wrapping. andthe inethodiofimy: invention carried out thereon as will be clear. Any of the packages of myinventionmay be. subsequently enclosed in outer. cartons, wrappings or the: like, as may be desired. Reliance for gas-. tightness is uponthe integral continuousgastightskin which Ihave described, and which is.

I have achieved a very simple. and inexpensive process and package which providesthe desired retention of inert'atmospheres over. a long period'of time, to make a low cost'package for foodstuffs and the like which ofiers a protection of inert. atmospheres comparable. to. vacuum gassed metal cans. 7

Modifications .may be made: in my invention. withoutdeparting fromthespiritof'it. Having thus described my invention, what-I claim as new and desire to secure by LettersPa-tent is:

Iclaim: 1. A method-of packaging which includes en- 7 closingaproduct tobe packaged along with air ina flexibleewalled"enclosure to form va. package, forming; overall external surfaces of said-Package, a continuous; imperforategas-tight covering so as to render said. package-gas tig'ht, puncturing.

tight covering for such opening joined in a gastight fashion with said first mentioned covering.

2. A method of packaging which includes providing a closed flexible package with contents therein, immersing in and withdrawing said package from a fluid which when set provides an integral gas-tight skin over the whole outer sur face thereof, effecting an interchange opening through said skin and a wall of said container, removing from said package the internal atmosphere and replacing said atmosphere with another gas through said opening, and thereafter re-sealing said opening with a gas-tight covering, the said fluid being a thermoplastic sealing substance in molten condition, and the resealing being accomplished by positioning over said opening a flexible bridging member and forming over said bridging member a gas-tight skin integrally bonded with said first mentioned skin.

3. A method of packing products in controlled atmospheres, which comprises completely enclosing said products in a flexible-walled package, applying a sealing substance externally to the walls of said package to form a continuous, gas-tight skin thereabout, locating said package in a casing, puncturing said skin and a flexible wall of said package to form a gas opening, evacuating the casing, admitting a desired gas into the casing to restore atmospheric pressure and effect atmospheric exchange within the package, withdrawing the package from the casing, all without submitting the walls of the package to unequal Number internal and external pressures, and rescaling said opening with a gas-tight skin covering said opening and integrally bonded to said first mentioned skin.

4. The process claimed in claim 1 wherein said enclosure comprises a paperboard carton and which includes the step of first wrapping said carton with a flexible substance, over which said continuous, imperforate gas-tight covering is formed.

5. The method claimed in claim 1 including the step of wrapping the said package in a nonfibrous web, resistant in itself to the passage of gas, over which the gas-tight covering is formed, and thereafter puncturing said wrapping along with said covering and flexible wall.

SAMUEL BERGSTEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Crocker Oct. 11, 1881 Dula May 19, 1925 McCrystal June 14, 1927 Eckstein Nov. 27, 1928 Berch Nov. 8, 1938 Waters Apr. 28, 1942 Royal Aug. 4, 1942

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