US2506056A - Gastight and gas-filled package and method of making it - Google Patents

Description

May 2, 1950 s. BERGsTElN 2,506,056

GAS-TIGHT AND GAS-FILLED PACKAGE AND METHOD OF MAKING IT 2 Sheets-Sheet 1 Filed Oct. 6, 1945 1N VEN TOR. 5mm/1. fzmsrE/N.

ATTORNEYS.

Fragt 10.

May 2, 1950 s. BERGSTEIN 2,506,056

GAS-TIGHT AND GAS-FILLED PACKAGE AND METHOD oF MAKING 1T Filed Oct. 6. 1945 2 Sheets-Sheet 2 IN I 'EN TOR. 541141151. 5f/565 'rf/N.

ATTORNEYS.

Patented May 2, 1950 zsoaoss i UNITED STATES -PATENT oFFicE GAS-TIGHT AND GAS-FILLED PACKAGE AND METHOD F MAKING IT samuel Burgum, cincinnati, ohm Application october s, 194s, serai Nn. 620,124

(ci. zza-,3.5)

8 Claims. l

My invention relates to packages made of or comprising paperboard which have the attribute of gas-tightness, so as to protect the contents from external gases, or to permit the maintenance of the contents in an atmosphere of protective gas which is prevented from diffusing to the outer air. The packages are preferably of the general type of knock-down or folding paperboard cartons or containers and capable of use as such.

Hitherto the only significantly gas-tight results which have been achieved in packages of this kind, were achieved by subjecting the lled and closed package to an all-over clip in a bath of coating substance capable of forming a gas-tight lm continuously over all external surfaces of the package. For modes of making and gassing such packages, reference is made to my copending application, Serial No. 557,984, iiled October 10, 1944, now Patent No. 2,442,161 and entitled Method of making gas lled flexible containers, and to my copending application, Serial No. 553,374, iiled September 9, 1944, and entitled Method of gassing filled packages.

Good results may be obtained in this way; but the practice of an over-all dip entails certain disadvantages which it is an object of this invention to overcome. For one thing, since paperboard itself readily permits the diiusion of gas, the gas-tight result is wholly dependent upon the continuity and integrity of a lm of coating substance which must be applied thickly in order to assure continuity and integrity, and which is an external nlm of large area, hence peculiarly susceptible to mechanical disruption. 'I'he hnforming coating is a hot-melt substance, the use of which subjects the whole submerged package to a substantial degree of heat. This sometimes has undesirable effects on the contents of the package. Moreover, the heating of the package during dipping produces expansion of contained air or other gas, the consequent expulsion of which tends to blow holes in the coating, thus complicating the problem of producing a continuous and imperforate film. An over-all external, heavy film is also detrimental to the appearance of the package.

It is an object of this invention to provide means and methods whereby equivalent gastightness can be achieved without the need of an all-over dip, which not only avoids these dimculties, but provides economies in operation, as well as in the quantity of coating substance required.

These and other objects which will become apparent as the description proceeds, I accomplish in those structures and procedures of which I shall now describe exemplary embodiments. Reference is made to the drawings, wherein:

Figure 1 is a, diagrammatic showing of a mode of coating and laminating.

Figure 2 is a diagrammatic cross section of a composite board.

Figure 3 is a plan view of a carton blank.

Figure 4 is a partial cross-sectional view of an edge-treated board portion, taken along the line 4-4 of Figure 3.

Figure 5 is a partial plan view of a tubed carton edge-treated as in Figure 4.

Figure 6 is a cross-sectional view of the longitudinal seam in a tubularcarton edge-treated as in Figures 4 and 5, and taken along the line 6--6 of the latter figure.

Figure 'l is a partial plan view of a tubed carton the longitudinal seam of which has been treated in another fashion.

Figure 8 is a cross-sectional view of the longitudinal seam in a tubular carton in which the seam has been treated after formation, and is taken along the line 8-8 of Figure 7.

Figure 9 is a perspective view of a, carton after filling and in the process of being closed.

Figure l0 is a perspective view of a completed, gassed package.

Figure 11 is a perspective View of a carton showing the result of a treatment of the longitudinal seam after the carton is erected..

Figure 12 is a plan View of a, tubed carton i1- lustrating yet another mode of treating the 1ongitudinal seam.

Figure 13 is a perspective view of a carton showing a similar treatment applied after the carton has been squared up.

Figure 14 is an elevational View with lparts in section of a board-edge treating mechanism.

Figure 15 is a cross-section thereof taken along the line I5-I5 of Figure 14.

Figure 16 is a perspective View, with a part in.

section, showing the result of an edge treatment. Figure 1'7 is a diagrammatic representation of 3 apparatus which may be used in longitudinal seam formation.

Figure 18 is a section taken along the line lag- I8 of Figure 17.

Figure 19 'is a cross-sectional view of'a completed seam formed as in Figure 17.

It is possible, by plying a gas-proof web to a layer of paperboard, to make a composite which is resistant to the passage of gas. But this by no means solves the problem of providing a gasproof package. Paperboard is itself pervious to the passage of gas throughout its body in all directions. Hence, in all seams and closures gas can escape, or diffusion of gas can take place, through the free edges of the paperboard. Hitherto there was no solution for this problem excepting the all-over dip mentioned above, which not only entails the diiculties set forth, but renders the use of a gas-tight body ply substantially nugatory.

The present invention is based on the concepts that if a web of paperboard or other material from which a knock-down carton is formed can be made or treated so as to be gas-tight in the direction of its thickness (i. e. so that as a membrane it will not permit the passage or diffusion of gas) and if a carton can be formed of it and can be treated as to the longitudinal seam in such manner that the assembly of body walls will form a gas-tight, tubular structure, then the end closures may be rendered gas-tight by dipping the end portions only. Thus the whole package need not be subjected to the heat of a bath of molten coating substance, a substantial saving of coating substance may be effected, and a neater vand more attractive package Will be obtained.

Such a package will not loe dependent upon an all-over gas-tight lm for its operation.

The problems involved are complicated and are divisible into various sections or groups.

First is the problem of providing a web which shall have the` required gas-tightness transversely, or as a membrane, and'shall be adaptable to the required manipulations and use.

The art has not yet produced a paperboard which per se is gas-tight. Nor is it feasible in the present state of the art to impregnate boxboard or paperboard in bulk to impart gas-tightness toit. Some materials, such as certain waxes can be driven into paperboard, and impregnation may be attained by the use of solvent solutions. But the fibrous nature of the paperboard makes it exceedingly diicult to obtain a dependable result over any large surface area. The evaporation of solvent from solutions tends to leave the residue in a porous condition. Most waxes having sharp melting points, and hence freely enough liquid to have good saturating characteristics, tend to be brittle at normal temperatures; and in general, impregnants in paperboard do not remain in continuous and imperforate association with the bers when the paperboard is handled, scored, bent, or folded.

The employment of surface coating as a membranous gas-proofing for paperboard webs likewise presents difficulty. If a tough and relatively hard coating is employed it is likely to split or rupture upon scoring and folding, whereas if a softer substance is used it is likely not only to foul the scoring and cutting rules or the make- Y ready (dependingupon the side of the board upon asoaoue my invention, I laminate a gas-proof web or composite to boxboard or paperboard, producing a laminated product which may be scored, folded and otherwise handled as paperboard is handled, and without loss of its gas-proofness. A suitable product or stock may be made in various ways. A web or film of gas-tight material in sheet form may be laminated to boxboard with a suitable adhesive. For example, glassine laminated to boxboard by means of rubber derived from latex as in my Patent No. 1,987,225. Or glassine may be laminated to boxboard with rubbcry or resinous substances derived from latices, emulsions or dispersions, such, for example, as the dispersion of synthetic rubber obtainable under the trade name Dispersite 1760-A." Or a suitable web may be laminated to boxboard by means of a thermoplastic or hot-melt substance. To the extent that the laminant adhesive forms in itself an imperforate and gas-tight coating, gas-tightness of the web or lm becomes less important, so that I do not intend to confine myself to the use of gas-tight webs. The laminant adhesive must in any event be one which will be non-brittle under all conditions of use, and at the same time one which can withstand the strains of scoring and bending.

Boxboard stocks suitable for my purpose may be made in bulk by laminating procedures, and may be wound into rolls or cut immediately into sheets of sizes suitable for the formation of cartons.

Before proceeding to a description of a particular preferred boxboard stock, I point out that in the practice of my invention it is necessary that the gas-proof web, lm or composite be laminated to the outside surface of the boxboard, i. e. that surface which is to form the external surface of the carton.

As already indicated, the topmost layer of my structure, which I sihall hereinafter refer to as the web, is preferably formed of a material highly resistant to the passage of gas as well as durable and flexible in character. The so-called glassine of commerce, which is a felted web formed yof highly hydrated paper stock, is excellent for the purpose. Certain non-fibrous substances which have high resistance to the passage of gas may likewise be employed, and iilms of ethyl cellulose or cellulose acetate `are exemplary in this connection. Composite structures Ior laminates may likewise be employed, as for example, a metal foil and glassine laminate disclosed ln my copending application entitled Foil-laminated sheeting and method of making it, Serial No. 619,854, filed October 2, 1945, now abandoned. My invention is not, however, confined to the use of Webs which are in themselves gas-tight, for the reason that the layer of laminating adhesive (hereinafter referred to as the skin), may itself be an imperforate nlm of gas-tight substance underlying the web and lo-` cated between it and the paperboard. Hence, I may even employ ordinary papers which are not themselves gas resisting for the web, providing precautions are taken so that the end closures formed by dipping penetrate the papers and seal in la gas-tight fashion with the skin.

Best results are obtained with a web which is gas-resistant in itself, the skin serving to adhere the web to the boxboard, to supply moisture and vapor resistance to a web which may not have these qualities in itself,` and to enhance the gas-proofness.

The adhesive substance which forms the skin maybeprodueedlnvariouswaysofvarylng formulae, as has already been indicated. It should have strong film forming characteristics such as to promote the easy production oi' an imperforate 'and integral layer or skin. It should be strongly 'adhesive to the paperboard and to the external web. At all temperatures which the package is to encounter in normal handling, storage and shipment, at least until' it is brought into the hands of the ultimate consumer, the skin should remain pliable, tough and non-brittle. The skin should be compatible with the dipping substance for covering the ends of the carton, hereinafter to be described. I prefer a laminant which remains pliable when cold, although preferably also devoid of cold flow. Of the available skin substances. I prefer those which are thermoplastic, and may be applied as hot-melts.

The desirable qualities for the skin are easily secured in compositions containing waxes and various resinous substances. By way of a single example and without limitation, an entirely satisfactory formula is as follows:

100 parts paraln of 135 F. melting point,

parts of a mixture (milled together of 25 parts of a medium molecular Weight polybutene such as the one sold under the trade name Vistanex and 75 parts parafn wax),

3 parts of a low molecular weight polybutene.

By a medium molecular Weight resin I mean one having a molecular weight of 80,000 to 100,000, the low molecular weight substance being appreciably below this range.

Another very suitable formula is as follows:

95 parts medium microcrystalline wax, melting point 160 to 165 F.,

25 parts polybutene of medium molecular weight as above,

10 parts Vistac #1, a synthetic hydrocarbon polymer in the form of a viscous liquid acting as a plasticizer.

All parts in the above formulae are by weight.

Other suitable compounds, by way of further example, may be made from mixtures of parain wax, microcrystalline wax, or both, and other resinous substances such, for example, as ester gum. Many -other available resins are compatible with and contribute the required characteristics to waxes or waxy compositions.

Referring to Figure l, I have shown a web I of suitable substance, e. g. glassine, vbeing unwound from a roll 2 and passed over and in contact with one or more coating rolls 3 turning in a bath 5 of the molten thermoplastic adhesive. By such means a coating of the required thickness is applied to the web I, whereupon the coated surface of the web may be drawn over a heated smoothing bar 'l which unifles the coating and insures an imperforate skin. The coated glassine or other web may then be cornbined with paperboard 9 being withdrawn from a roll I0, the two materials being passed concurrently through combining rolls Il and l2, one or both of which may be heated. The thermoplastic adhesive, reactivated at this point, joins the web I to the paperboard 9 with complete surface conformity. The laminated product I3 may be cut apart into sheets as desired by the usual fly knife arrangement I4, the sheets being stacked vas at I 6. If desired, the laminant may be applied to the paperboard instead of to the glassine or other web.

Figure 2 is representative of a cross-section scoring, preceded by printing, if desired. The

thermoplastic substance of the above formulae are clear and transparent in thin layers while the glassineis suiciently translucent so that printing upon the boxboard 9 will show through the covering very well. The glassine or other web may, however, be printed before or after the sheets are formed, or either the paperboard 9 or the web I or both may be printed prior to the laminating. As already pointed out, the skin and web must be aillxed to the outer surface of the paperboard, i. e. that face of the paperboard which is to form the outside of the carton. Another web and skin may, if desired, be laminated to the inside face of the paperboard but this is not necessary and normally presents no advantage as respects gas-tightness, though it may be desirable for other purposes. The combined weights or thicknesses of the web I, the skin Il and the paperboard 9 will be chosen to give a laminated product of the desired over-all weight or caliper.

I have found that such a laminated product may be cut and scored by the usual means and in the usual way current in the carton art without loss of its gas-proof character. The web should be thin but tough and strong, the paperboard appreciably thicker than the web, and the coating or skin should have the characteristics set forth above. Since the web covers the skin, there is no tendency to foul the cutting knives or make-ready. An external skin over the web is not required nor ordinarily desirable, although it does not constitute a departure from the principles of this invention.

Nor is the invention limited to the kind, style or dimensions of the cartons produced from the laminated stock made as described. For ordinary purposes, however, a carton of the usual seal end form is desirable. In Figure 3 I have shown an exemplary blank having body walls I8, I9, 20 and 2| and a glue flap 22 in articulation in the order named. In this gure dot and dash lines represent lines of score. Seal end aps 23, 24, 25 and 26 are articulated respectively to one end of the body Walls, their primed counterparts being articulated to the other. A carton blank so formed may be tubed by the use of common carton tubing machinery, by being bent on a pair of intermediate score lines with a union of the glue flap 22 to the free edge of wall Il by means of an adhesive indicated at 21. i

Two additional features are of importance and value in cartons designed for the purpose of this invention, but are not limitations upon the invention otherwise than as set forth in the appended claims. As shown in Figure 3, the naps 25 and 25' are preferably cut back slightly along their lateral edges excepting at the ends of these edges, as shown at 28. These flaps are the ones which will immediately underlie the last folded flaps 23 and 23' in the closed carton. As described in my copending application Serial No. 538,764, filed June 5, 1944, now Patent No. 2,412,031, and entitled Cartons for sealing by immersion, the cutting back ,of the lateral edges of the underlying flaps permits a coating of proong substance applied by dipping or the like to form a more dependable seal at a carton closure.

Also where the cartons are to be gassed by certain processes as hereinafter set forth, I prefer to form in the carton walls means permitting the more ready insertion of a gassing nozzle or needle. These means may be actual perforations; but I prefer to form them as tiny depressible tabs demarked partially by a cut line as indicated at 28 in Figure 3. There may be one, two or more of these means as required by any particular gassing procedure.

The use of a gas-proof adhesive 21 is indicated in some forms of my invention, though in others ordinary adhesives may be employed. Where a gas-proof adhesive is required, I prefer to employ a thermoplastic substance which may be applied molten to the glue iiap 22. The parts are either brought together before the adhesive has set or the adhesive coating is reactivated (preferably by radiant heat) at the time of folding and pressing the parts together.

The use of gas-proof adhesive 21, however, does not solve the problem of producing a gastight longitudinal body seam in the carton. The

material of the carton is gas-proof as a membrane; but in any longitudinal seam (whether the glue flap be lapped inside or outside the adjacent body wall) a gas exchange can occur by infiltration and diffusion through the body of the paperboard itself. This would be true in a lapped seam even if both surfaces of the boxboard were faced with a gas-tight web and skin. Steps therefore have to be taken to prevent such gas passage.

One way of accomplishing this is to treat the carton in blank for-m as to a longitudinal edge portion. This will be the portion which is to lap an underlying portion in the seam. Thus where the glue iiap is to be adhered to the under side of the opposite body wall, as is preferred in box manufacture, I treat the edge portion of the said opposite body wall. Either in a separate treatment of the blanks or in an operation performed in the tubing machine as the blanks are moved along, I have found that I can apply to the free edge of the body wall I8 a deposit of ma terial indicated at (see Figures 3, 4 and 6). This deposit has been represented as located on a portion of the inner face of the wall I8 but covering also the edge portion thereof as at 30a and merging with the coating or skin I1 lying on the outer surface of the board. It may or may not overlie the web I, depen-ding upon the mode of its application.

It is not a limitation on my invention as to how far, if at all, the deposit 30 penetrates the body of the paperboard layer 9. It may be entirely superficial or it may penetrate the board to a very substantial extent. Were it possible to drive it entirely into the board, this would not be objectionable so long as the function hereinafte-r set forth is performed. The deposit may be a deposit of substance similar to or the same as the substance of the skin I1, or it may be a modified material, for example ethyl cellulose. It should bond strongly with the paperboard and make a gas-tight connection with the skin I1 and preferably also the web I.

An edge coating such as that illustrated in Figure 4 may be made by passing the edge of the board along an adhesive applying means such as the surface of a roll while moving it also slightly in the transverse direction so as to be sure of covering the edge portion of the flap I8 as at 38a. A more convenient apparatus for the purpose is illustrated in Figures 14 and 15 where I have shown a lower coating roll 3| turning In a pan 32 of suitable adhesive. A spring pressed upper coating roll Is indicated at 33. The lower roll at least will be driven and the edge portion of the blank as indicated at I8 will be passed between the rolls. The lower roll may be relied upon to transfer coating substance to the upper roll between the passage of blanks, or means including a pan of coating substance 34 and transfer rolls 35 and`3Ii may be used to apply adhesive directly to the upper roll 33.

The result of the use of this form of apparatus ls the complete covering of a marginal portion of the blank with coating substance so that the coating substance is deposited on both surfaces of the marginal portion of the blank and bridges over and around the edge portion as clearly indicated in Figure 16. The coating will also be joined or merged around the edge of any end portion of the blank permitted to pass between the rolls as shown at 30h. Hence it may be employed for treating the glue flap 22 in types of construction in which the glue flap is adhered outside the body wall to which it is attached. If it be desired to apply the coating to a marginal portion of the wall I8 only without applying it to the flaps 23 and 23', it is possible either to separate the rolls 3| and 33 during the passage of the end flaps between them or else to make these rolls in the form of timed spotting rolls with configured surfaces which will contact only the desired portion of the blank.

A longitudinal glue seam in a carton is illustrated in Figure 6 where the plied structure comprising the boxboard 9, the skin I1 and the web I forming a part of wall I8 of the carton laps a similar structure forming the glue flap 22, and is adhered thereto by the gas-proof adhesive 21 while the deposit 30 forms, as illustrated, a gastight bridge or connection between the skin I1 and web I of the wall I8 and their counterparts in the glue flap 22.

Yet another mode of accomplishing a gastight longitudinal seam in the carton is illustrated in Figures '1 and 8. Here the carton is rst tubed, the adhesive union of the wall I8 and the glue fiap 22 being accomplished by a generous application of the adhesive 21 so that it comes out to the edge of the seam. After the seam has been formed in this way a deposit of sealing substance 31 is run along the seam edge in such a way as to bridge the gap between the adhesive 21 and the skin I1 and web I of the wall I8. Preferably the deposit 31 is so produced as also to contact and bond to the web portion of the glue flap 22.

The deposit 31 may be applied in various ways which may be extruded while molten or plastic from a nozzle and smoothed into position in any suitable way by means following the nozzle as respects the path of travel of the blank. Or the deposit may be made in this fashion or by any other suitable means. e. g. a coating disk, and then it may be resotened or liquefied in place by radiant heat applied thereto. When using this mode of forming a longitudinal gas-tight seam, it is well so to proportion the carton parts that the deposit 31 will not cover the score line by which the glue flap 22 is articulated to the wall 2I.

It is also within the scope of my invention to apply a coating or deposit of sealing substance over the edge of a longitudinal seam in a carton after the carton has been erected or after it has been filled and closed. In Figure 11 I have indicated a deposit 31a covering the edge of the longitudinal seam in an erected and closed carton. Such a deposit may be applied by means of a grooved coating roller, or in other ways; and may extend onto two contiguous` walls of the carton covering the corner portion containing the edge of the longitudinalseam.

Deposits 3D and 37. such as have been described, are not fragile and do not appreciably lessen the appearance factor in my cartons. It is, however, within the scope of this invention to cover any such deposit with an external strip of web material which inthis event will preferably be adhesively joined also to adjacent portions of the web I.

It is possible also to employ over a longitudinal seam in a carton a covering strip of gas-tight substance making a gas-tight juncture with the web at each side of the longitudinal seam. In Figure l2 I have illustrated a tubed carton having a longitudnal seam at the juncture of body walls I8 and 2|. A coverng strip of material 38 is shown as being applied to these walls so as to cover the juncture between them. This material may be a coated produ-ct comprising a web and a skin similar to the web and skin laminated to the boxboard in the carton itself and it may be applied under heat and pressure where the skin is of thermoplastic substance capable of bonding in a gas-tight manner with the web on the body walls of the carton.

In Figure 13 I have illustrated how the same effect may be accomplished by applying a strip of material 39 across the longitudinal seam and onto the body walls I8 and 2I in an erected, lled and closed carton.

There are various other Ways in which a longitudinal seam in a' carton may be treated so as to be rendered gas-tight. One of these is a modiiication of a, procedure shown in my Patent No. 1,980,180, dated November 13, 1934, and is illustrated in Figures 17, 18 and 19. Here the carton blank has been formed as described above from the boxboard laminate and comprises the same parts. The gluev tab 22 of the carton, however, has been provided with a longitudinally extending line of cut 40 which severs the boxboard itself down to the skin I'I without severing the external web I.

As an incident to the operation of tubing this carton as indicated in Figure 17, the blank is moved along in the direction of the arrows and a guide or sweep 4I is employed to bend downwardly that part of the glue tab 22 lying beyond the cut 49. The result of this is to separate the boxboard portions from each other and expose the skin I'I, as it were, in a groove on theinner or boxboard side of the laminate. While the outer portion of the glue tab is still bent downwardly adhesive is applied to it as by a wheel 42 in such fashion as to coat the exposed edges of the boxboard in the cut 49 and merge with the skin Il in a gas-tight fashion. The adhesive is indicated at 43 and it will be noted that it is also applied so as to coat adjacent inner face portions of the glue tab.

In the further movement of the container blank it is folded over upon two longitudinal score lines for tubing by sweeps 44 and 45 or their equivalent, and in such a way that the glue tab 22 lies outside the wall I8 to which it will be pressed and adhesively secured by means not shown. The result is a seam as illustrated in Figure 19 where the glue tab 22 is joined externally to the wall IB by adhesive 43 which not only isbonded in a gas-tight fashion to the web I lacing the wall I8 but also is bonded as at 4E to the skin on the overlying web I of the glue tab. By this procedure, if it is accurately performed, a gastight longitudinal seam is effected in the carton with the advantage that external applications of coating substance or of strip material are avoided. A seal will be effected between the cap-like closures formed by end-dipping and the afore-mentioned seam at the ends of the glue tab.

Cartons formed in any of the ways set forth above are folding cartons in knock-down form capable of being shipped as such to the carton user and squared up. filled and closed by him in the usual fashion and with the usual apparatus for that purpose. The carton user will normally erect the tubular body and fold and adhesively secure the flaps on one end. This end may then be dipped, if desired, or the carton may first be filled, closed on the remaining open end and dipped on both ends. The adhesive used in securing the cloture flaps may be any suitable one, not requiring gas-tight characteristics. The use of a gas-tight thermoplastic is, however, within the scope of my invention.

The dipping may be done by any suitable means or by hand. In forming a completely gas-tight package with the structure thus far described, I dip only the end portions of the carton, forming as indicated in a somewhat exaggerated way at 4l and 48 in Figure 10 cap-like lms or skins of thermoplastic adhesive substance covering the entire ends of the carton and joined in a gas-tight fashion to the web I and to any portions of the skin I1 which may be exposed at the corners of `same as the substance used for the skin I'I; but

I prefer to employ a material capable of producing a harder, tougher skin, non-tacky as to surface but capable of retaining its pliability throughout the entire expected range of temperatures to be encountered by the package as set forth alcove.

Again without limitation, since this formula is exemplary only, I have used with excellent effect a composition of matter consisting of the following:

40 parts paraillne having a melting point of 40 parts of a material sold by Monsanto Chemical Company under the trade name Aroclor 5460, which is understood to be a chlorinated tri-phenyl.

20 parts of a milled mixture" made of '75 parts paraiin wax and 25 parts medium molecular weight polybutene as defined above.

'Ihis milled mixture is obtainable on the market under the trade name Tervan. 'I'he composition above is substantially water white in color or very slightly yellow and is capable of forming thin, tough films of excellent gas-tightness and very neat appearance.

The manner in which special atmospheres are introduced into my packages does not form a. limitation upon this invention. A heavier than air atmosphere may be introduced into the package along with the contents and the package may be rendered gas-tight by end dipping rapidly enough to minimize diiusion and loss of the special atmosphere. It is, however, preferred to effect atmospheric exchange by methods taught in my copending applications referred to hereinabove. In each of these methods, after the formation of a gas-tight package, the package walls are perforated. In the first method the packages, introduced into a closed chamber are iirst vacuumized and then lled with the desired special atmosphere. In the second method a hollow needle is introduced into the package and the initial 4air is displaced by blowing the special atmosphere into the package through the hollow needle, there being an exit for the contained air preferably located as far as possible within the coniines of the package from the point of introduction of the special atmosphere, i. e. the end of the needle. In both processes the walls of the package are not subjected to appreciable differences between internal and external atmospheric pressures.

In the cartons of the present invention, periorations may be made by punching inwardly the tiny tab or tabs demarked by the lines of weakening 29, or by inserting gassing or exit nozzles through them, without danger of tearing the carton walls. In both processes as soon as atmospheric exchange has been effected, the opening or openings formed in the package walls are sealed. This may be done by depositing over the' opening or openings masses of a thermoplastic sealing composition or by closing the openings with a patch 48 (Figure 10) comprising a web bearing a lm or skin of gas-tight thermoplastic.

Whereas in the packages described in those cases there was an external, over-all coating of gas-tight character to which the perforation closures just mentioned were caused to adhere and withY which the closure composition was caused to merge, in my present packages similar closure means are bonded by means of the gas-tight thermoplastic to the external web l and its skin l1 to the extent that that skin is exposed.

By the described means I am enabled to produce dependable gas-tight and gassed packages,

capable of retaining their special atmospheres over long periods of use and for sufficient lengths of time to meet the requirements of the ordinary commercial distribution of products requiring such protection. The practice of my invention does not exclude differences in external and internal pressures, but in actual practice the internal and external pressures as respects my packages are preferably the same or substantially the same at normal or room temperatures. The flexibility of the walls of my packages takes care oi differences in pressure naturally occurring due to barometric and temperature changes unless these -be excessive. In packages which have been perforated and gassed by atmospheric exchange in the ways set forth above, closures for the perforations embodying webs and adhesives soft enough to be self-sealing may be arranged to afford relief from excessive internal pressures if desired, though this is not necessary in ordinary practice.

Modifications may be made in my invention without departing from the spirit of it. Having described my invention in certain exemplary embodiments, what I claim as new and desire to secure by Letters Patent is:

1. A moisture, vapor and gas-tight package of iiexible materials and comprising a tubed paperboard carton formed from a blank consisting of body walls in articulation and closure ilaps at the ends of body walls, means for rendering the body formed by such tubed body walls gastight comprising a skin of exible gas-proof composition and an overlying protective web joined to said body walls by said skin and tubed therewith with a gas-tight longitudinal seam, said carton being in closed condition, and end closure means overlying said closure flaps and comprising an imperforate skin of ilexible gas-proof composition bonded in a gas-tight manner to said web peripherally of the carton ends, said closure means being spaced from each other, and said means for rendering the said body gas-tight bridging the gap between said closure means and coacting therewith to impart moisture, vapor and gas-tightness to said package.

2. The structure claimed in claim 1 in which said longitudinal seam includes a deposit of gasproof composition connecting lapped portions of said web and first mentioned skin about an otherwise free edge of paperboard of said carton.

3. The structure claimed in claim 1 in which seid longitudinal seam includes a member comprising a skin and web bridging the gap between lapped portions of said iirst mentioned skin and web about an otherwise free edge of the paperboard of said carton.

4. A process of making a, moisture, vapor and gas-tight package of ilexible materials which comprises providing a paperboard carton blank having body walls in articulation and closure flaps, applying to the entire surface of the blank which will constitute the exterior of the carton, a means for rendering said body walls gas-tight, said means comprising a skin of exible gasproof composition and an overlying protective web joined to said body walls and aps in said blank, concurrently tubing said carton blank and forming in said blank, skin and web a longitudinal gas-tight seam, filling said carton and closing said carton flaps and applying end closure means therefor comprising each an imperforate skin of nexible gas-proof composition covering the end of said carton, and bonding said skin in a gas-tight manner to said first mentioned skin and web peripherally of the ends of said carton, said closure means being spaced by the carton body and said means for rendering the said body gas-tight bridging the gap between said end closure means and coacting therewith to impart moisture, vapor and gas-tightness to said package.

5. The process claimed in claim 4 including the steps of joining said rst mentioned skin and web to paperboard and forming said carton' by concurrently cutting and scoring said paperboard, said skin and said web.

6. The process claimed in claim 4 including the steps of depositing at said longitudinal seam a mass of gas-tight composition bridging the gap between lapped portions of said irst mentioned skin and web around an otherwise free edge of said paperboard.

7. The process claimed in claim 4 including the step of covering said longitudinal seam with a member comprising a skin and web joining lapping portions of said rst mentioned skin and web about an otherwise free edge of said paperboard.

8. The process claimed in claim 4 in which said end closure means are provided by dipping 13 ends only of said package in a heat molten, thermoplastic, gas-proof composition whereby to form at said ends cap-like closures having a body portion lying transverse to the body Walls of said carton and additional portions lapping ends of 5 said body walls. Y

SAMUEL BERGSTEIN.

REFERENCES CITED UNITED STATES PATENTS Name Date Jenkins June 22, 1909 u Number Number 14 Name Date Eckstein Nov. 27, 1928 Wesselman June 2, 1936 Howard July 21, 1936 Magill June 29, 1937 Wesselman Dec. 13, 1938 Swan, 3d June 20, 1939 Waters Dec. 3, 1940 Waters Aug. 12, 1941 Kienlen Oct. 21, 1941 Berch Dec. 2:3, 1941 Waters June 5, 1945 Glmllan July 31, 1945

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