US3122297A

US3122297A - Multi-ply liner bags

Info

Publication number: US3122297A
Application number: US146744A
Authority: US
Inventors: John P Sachs
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1961-10-23
Filing date: 1961-10-23
Publication date: 1964-02-25
Anticipated expiration: 1981-02-25

Description

Feb. 25, 1964 J. P. SACHS 3,122,297

MULTI-PLY LINER BAGS Filed Oct. 23, 1961 3 Sheets-Sheet 1 INVENTOR. JOHN P. SACHS ATTORNEY Feb. 25, 1964 INVENTOR JOHN P. SACHS ATTORNEY Feb. 25, 1964' J. P. sAcHs 3,122,297

MULTI-PLY LINER BAGS Filed Oct. 25, 1961 3 Sheets-Sheet 3 M INVENTOR. ($194K JOHN RSACHS ATTORNEY United rates Patent Oflice 3,l22,2fl? Fatented Feb. 25, 1964 3,122,297 MULTl-PLY LINER BAGS John P. Sachs, La Grange, ill, assignor to Union (Jarbide Corporation, a corporation of New York Filed Get. 23, 1961, Ser. No. 146,744 1t} tilaims. (CL 229-44) This invention relates to a multi-ply thermoplastic film liner bag and the method of forming the same, and furthermore, this invention relates to the use of said multi-ply liner bag in a rigid container for shipping, storing and dispensing such diverse items as milk, fruit juices, syrups and other liquids, as well as ice cream and pasty and pulverulent materials.

In an attempt to overcome the deficiencies of using metal, glass and wax-lined cardboard containers for shipping, storing and dispensing flowable materials, such as milk, plastic film liner bags shaped and supported in a rigid container commonly made of corrugated paper, are being used.

At the dairy, the plastic film liner bag generally having a filling and pouring spout is placed in the corrugated paper container and filled with milk. The container is then distributed, as a package, to restaurants and institutions for dispensing the milk therefrom. At the restaurant, the pouring spout is withdrawn from the package, and the package is set into a conventional refrigerated dispenser unit in an inverted position, and the pouring spout is passed through a (pinch clamp) dispensing valve.

In using such liner bags of plastic film for shipping milk, a high incidence of liner leakage has resulted from efects particularly pinholes in the plastic liner bag, caused by a variety of factors most of which are related to the severity of the conditions in shipping milk in a plastic liner bag, within a rigid container, over rough country roads from the dairy to the user. Pinholes below the liquid level within the plastic liner bag cannot be tolerated because of leakage during shipment. Pinholes at or above the liquid level line within the plastic liner bag are objectionable because when the package is inverted for dispensing, leakage will occur.

The presence of pinholes in the plastic film of the liner bag has been found to primarily result from environmental stress corrosion and flex fatigue of the plastic film, especially where folds in the film existed. Such adverse efiects are related to normal shipping motion which sloshes or moves the milk in and about the bag, thereby producing the physical ellects of Wave vibration and hydraulic hammer that result in the environmental stress corrosion of flex fatigue. The physical effects of wave vibrations and hydraulic hammer have been found to be particularly concentrated in folds in the plastic film of the liner bag, flexing and unflexing said film folds; and this is Where the greatest damage due to environmenta stress corrosion and flex fatigue has occurred.

Also, the lactic acid and butter fat content or" the liquid milk tend to react chemically with the plastic film of the liner bag and cause environmental stress corrosion and flex fatigue in the liner walls, particularly at or above the normal liquid level within the liner bag. In addition, punctures or abrasion in the liner bag from handling and contact with the rigid container, have contributed to the high incidence of pinholes in the liner bags of plastic film.

Furthermore, any slight leakage of the liquid-filled plastic liner bag is accentuated by the absorptive attraction of the supporting corrugated paper walls of the rigid container, and by the hydraulic head of the liquid contents on the pinhole.

Additionally, in using such liner bags for shipping milk or other perishable food products, if the bags are not formed with an essentially sterile interior and maintained in such condition, undesirable flavor, odor and bacterial growth tend to be imparted to said products.

Among the objects of the present invention are to pro vide a novel multi-ply liner bag of flexible thermoplastic lm for flowable materials and especially for milk; to provide such a multi-ply flexible thermoplastic liner bag which is essentially sterile and to a method for forming such a bag; to provide such a multi-ply flexible thermoplastic liner bag which is leakproof; to provide such a multi-ply flexible thermoplastic liner bag which will resist stress corrosion, flex fatigue, puncture and abrasion from shipping movement, prolonged storage in the inverted position, handling and contact with a rigid containe; to provide such a bag which is leakproof and will collapse to void all its contents; to provide such a bag which can be made of a sufliciently inexpensive material that it can be disposed of after one use, and to provide such a bag which can be easily and economically made.

The objects of this invention are accomplished in general, by providing a rigid container with a multi-ply leakproof, flexible, collapsible liner bag having an inner ply of flattened seamless flexible thermoplastic tubular film, preferably interiorly essentially sterile, an outer film ply of flexible thermoplastic sheeting circumscribed about the inner film ply with the longitudinal free edges of the sheeting heat sealed together, thereby forming a tubing concentric with the inner ply, and with the coextensive ends of the inner and outer film plies heat sealed together, said multi-ply bag having an opening therein for communicating with the interior of said seamless tubular inner film ply.

In the preferred embodiment of this invention, a rigid container is provided with a multi-ply leakproof, flexible, collapsible liner bag having an inner film ply of flattened seamless flexible thermoplastic tubular film interiorly essentially sterile and a concentric, coextensive outer film ply of centerfolded sheeting circumscribed about said inner ply. The centerfold of the sheeting which forms the outer ply is juxtaposed along one longitudinal edge of the flattened seamless tubular film and the free edges of the sheeting opposite said centerfold are heat sealed together in juxtaposition with the other longitudinal edge of the flattened seamless tubular film. The coextensive ends of the inner and outer plies of flattened seamless tubular film and centerfolded heat sealed sheeting are sealed together by transverse heat seals, and an opening in said multi-ply liner bag communicates with the interior of the inner film ply for the passage of flowable material. Preferably one of the transverse heat seals terminates inwardly from one corner of the film plies, thereby providing an opening or gap for a filling and pouring spout.

The length of the multi-ply thermoplastic liner bag is such as to preferably provide a free board portion to insure filling the flowable material, such as milk, to a precise predetermined volume. Accordingly, after filling the multi-ply liner bag with flowable material, the film walls comprising the free-board portion can be loosely infolded about the normal milk or other product level.

With respect to a method of forming an interiorly essentially sterile multi-ply thermoplastic liner bag of the present invention, the interior of flexible thermoplastic film melt-extruded as seamless tubing is sterile. Accordingly, it is preferred to form the liner bags by forming the inner film ply from a continuous length of such melt-extruded flattened seamless flexible thermoplastic tubular film. The outer concentric film ply of the liner bag is formed with sheeting by center-folding and circumscribing sheeting about said continuous length of flattened seamless tubular film with said center-fold of the sheeting juxta- LE posed along one longitudinal edge of said flattened seamless tubular film, heat sealing the free edges of the sheeting opposite said center fold together in juxtaposition with the other longitudinal edge of said flattened seamless tubular film, transversely heat sealing the concentric inner and outer film plies of seamless tubular film and centerfolded heat-sealed tubular sheeting together across the widths thereof, transversely heat sealing said concentric inner and outer plies together spaced from the other transverse heat seal in such manner so as to preferably leave an opening or gap in one corner of said inner and outer film plies, and transversely severing said concentric inner and outer plies of heat sealed seamless tubular film and sheeting into unit multi-ply bags. A dispensing tube open to the interior or" the inner ply of flattened seamless tubular film and inserted into said opening or gap, is aifixed to said liner bag in such manner that the essentially sterile condition or" the interior of the multi-ply liner bag is maintained.

In an alternate embodiment of this invention the multiply leakproof, flexible, collapsible liner bag comprises a concentric outer ply formed of two edge-sealed sheets of flexible thermoplastic film superimposed about and coextensive with the inner ply of the flattened seamless interiorly essentially sterile flexible thermoplastic tubular film. The longitudinal free edges of the outer ply sheets are coterminous, and are heat sealed together in juxtaposition with the adjacent flattened edges of the inner seamless tubular film ply; and the coextensive ends of the inner and outer plies of flattened seamless tubular film and longitudinally heat sealed sheets are transversely heat sealed together as in the preferred embodiment.

in forming the interiorly essentially sterile multi-ply bag of the alternate embodiment the method set forth for the preferred embodiment can be used, except that the outer concentric film ply is formed by superimposing the two sheets about the continuous length of flattened seamless tubular film and heat sealing the longitudinal free edges of the two sheets in juxtaposition with the adjacent edges of the flattened seamless tubular film.

The nature of the invention and the manner in which it can be practiced will become clear from the detailed description when taken in conjunction with the accompanying drawings forming this specification and wherein:

FIG. 1 is a side elevation of the preferred embodiment of the multi-ply thermoplastic liner bag of the present invention;

FlG. 2 is an enlarged cross-sectional view of the multiply thermoplastic liner bag of FIG. 1 taken along the lines 22 thereof;

PEG. 3 is an enlarged longitudinal sectional view of the multi-ply thermoplastic liner bag of PEG. 1 taken along the lines 3-3 thereof;

FIG. 4 is a pictorial view of a rigid container broken away to show the mnlti-ply thermoplastic liner bag of the present invention filled with a flowable material;

FIG. 5 is a side elevation of the alternate embodiment of the multi-ply thermoplastic liner bag of the present invention;

FIG. 6 is an enlarged cross-sectional view of the multiply liner bag of FIG. 5 taken along the lines 6-6 thereof; and

PEG. 7 is an enlarged longitudinal sectional view of the multi-ply liner bag of FIG. 5 taken along the lines 77 thereof.

Referring to the details of the FIGS. 1-3 there is shown a two-ply, leakproof, flexible collapsible thermoplastic liner bag 10 for a rigid container 12, such as shown in FIG. 4. The inner film ply 14 of the bag 10 is made of flattened flexible seamless thermoplastic tubular film interiorly essentially sterile. The outer film ply 16 of the bag it? is coextensive with the inner ply 14 and is made of center-folded flexible thermoplastic sheeting circumscribed about said inner ply 1 For a five gallon capacity th dimensions of the flattened inner seamless tubular film 4 are typically 0.0015 inch thick, 2 inches in flat width and 23% inches long; and the dimensions of the outer centerfolded sheeting ply are 0.0015 inch thick, 42 inches in width in its unfolded condition, and 23% inches long.

The center-fold 318 of the sheeting forming the circumscribing outer ply 16 is juxtaposed along one longitudinal edge of the flattened inner seamless tubular film ply 14 and the free edges 2%? of the sheeting opposite its centerfold 18 are sealed together by a longitud nal controlled pressure heat seal 21 in juxtaposition with the other longitudinal edge of the flattened inner seamless tubular film ply 14.

The bottom end 22 of the coextensive inner and

outer film plies

14, 16 is sealed together with a transverse controlled pressure heat seal 24 extending across the width of the multi-ply liner bag 10. The top end 26 of the coextensive inner and

outer film plies

14, 16 is sealed together with a transerse controlled pressure heat seal 28 leaving a inch gap between one corner 3% or" the top end film plies l4, l6 and the terminus of the heat seal 28, to provide a flattened opening or gap 32 communicating with interior of the inner film ply Such opening 32 is provided adjacent the center-fold 18 of the sheeting 16 for the insertion of a filling and pouring spout E4 in the form of a V inch diameter by 8 inch long rubber tube closed at its outer end 3:5 by a plug (not shown). The filling and pouring tube or spout 34 is inserted into the opening 32 in an essentially sterile manner and the bag inner and

outer film plies

14, 16 of the corner 3% are gathered about the rubber tube 34 into overlapped spiralled folds 38 and fastened to the rubber tube 34 by a conventional twist wire fastener lil.

To insure filling the multi-ply liner bag it with flowable material, such as milk, to a prior predetermined volume such as 5 gallons, the length of the multi-ply thermoplastic liner bag it? is such as to preferably provide a free board portion 41, such as about /2 inch. Accordingly, after filling the multi-ply liner bag it? with flowable material, the film walls comprising the free board portion 41 can be loosely infolded at the normal milk level as shown in FIG. 4.

Referring to FTGS. 5-7 wherein like reference numerals are used to designate like elements shown in FIGS. 1-3, except that a prime is used after the numeral, a two-ply, leakproof flexible collapsible thermoplastic liner bag 10 is shown including an inner ply 14 of flattened, essentia ly interiorly sterile seamless flexible thermo plastic tubular film, and a concentric outer ply 16' of two flexible

thermoplastic sheets

17, 19 superimposed about and coextensive with the inner ply '14-.

The inner flattened seamless tubular film ply 14' is centrally positioned within the two sheets 17, i=9. The longitudinal free edges 20' of the sheets 17, .19 are coter minous and are heat sealed 21' together in juxtaposition: with the adjacent edges of fla te ed seamless tubular film.

The bottom and top ends 22', 26 of the multi-ply liner bag It) are heat sealed with transverse heat seals 24, 8." in the same manner as described and illustrated for multi ply liner bag 1d of FIGS. 13. The top end heat seal 28 terminates inwardly from the corner 30' to provide a flat tened opening 32 in the liner bag it? for the filling and pouring spout 34, in the form of a tube, about which the film plies 14, 16' are gathered into the overlapped spiralled folds 38' and fastened thereto by the conven' tional twist wire fastener 45?.

As in FIGS. 1-3, the length of the multi-ply liner bag 10' of concentric tubular film plies 14, 16' is such so as to provide the free board portion 4-1 which can be loosely infolded to the normal milk level.

Typically, for a five gallon capacity multi-ply liner bag 1d, the inner ply 14 of flattened seamless tubular film is 0.0015 inch thick, 20 inches in flat width and 23% inches long, while each sheet of the outer ply i6 is 0.0015 inch thick, 21 inches wide, and 23% inches long.

In a multi-ply thermoplastic liner bag of the present invention, any slight leakage of liquid through pinholes of the inner ply is kept to a minimum because the outer ply of film serves as a barrier to isolate the pinhole from the absorptive effect of a rigid container, and the hydraulic head of the liquid contents serves in a self-sealing capacity to press and block the film adjacent the pinhole against the outer film ply to equalize the hydraulic pressure gradient through the pinhole.

The high incidence of liner leakage resulting from defects and particularly pinholes is also avoided by preferably providing the rigid container with a multi-ply liner bag comprising an inner ply of flexible thermoplastic film and preferably polyolefin film resistant to environmental stress corrosion and flex fatigue, especially in the film folds, and an outer ply of flexible thermoplastic film and preferably polyolefin film resistant to abrasion and puncture; particularly caused by handling and contact with a rigid container.

Multi-ply liner bags of polyolefin film plies having inner and outer film plies with the particular properties herein described, are admirably suited for containing flowable materials and particularly perishable materials, such as milk. Among the reasons the multi-ply liner bags of the invention are admirably suited for the described purposes is that the physical elfects in normal usage of wave vibration and hydraulic hammer on the inner film ply do not result n adverse film defects due to environmental stress corrosion and flex fatigue. This is particularly true in any folds in the multi-ply liner bag, such as the infolded

free board portion

41 or 41 of bag or 10, respectively, even with the flexing and unfiexing of said folds incurred during normal shipping movement. Secondly, the inner film ply is not adversely affected because of contact with the lactic acid and butter fat content of the liquid milk. Thirdly the outer ply of the multi-ply bag resists punctures or abrasion, particularly resulting from handling of the bag, and contact of said bag with the rigid container. Fourthly, the interior of thermoplastic film mel-extruded into seamless tubing, such as by the blown-tube method described in U.S. Patent 2,461,975, is essentially sterile and does not impart undesirable flavor, odor and bacterial growth to the product.

Moreover, multi-ply polyolefin liner bags having the aforedescribed properties, are admirably suited for containing flowable materials, such as milk, because they are heat scalable to prevent leakage thereof. In addition, a multi-ply liner bag of such polyolefin film plies is flexible and will collapse to void all its contents and is a sufiiciently inexpensive material that it can be disposed of after one use.

Of particular preference for a liner bag for the shipping and dispensing of milk in a rigid container, is a multiply construction comprising in combination, an inner ply of polyethylene seamless tubular film that has a high tensile strength and flex modulus and is interiorly essentially sterile, and an outer ply of a polyethylene film that has a relatively high tear strength and elongation to break and a low coeflicient of friction and is non-conjoint and non-laminated to the inner ply. A multi-ply liner bag having such an inner ply is resistant to environmental stress corrosion and flex fatigue and does not impart undesirable flavor, odor and bacterial growth to the products contained therein. Additionally, a multi-ply liner bag having such an outer ply is resistant to puncture and abrasion.

To obtain a multi-ply liner bag with the necessary combination of properties herein described, it is preferred to have an inner ply made of a high molecular Weight film-forming polyethylene resin having an intrinsic viscosity of at least about 1.0 and preferably of about 1.0 to 2.5 and optimumly about 1.3 to 2.0; a melt index of less than about 2.0 and preferably less than about 0.20 and optimurnly about 0.05 to 0.10; a density of not greater than 0.935 and preferably less than 0.925 and formed into tubular film such as by the blown-tube method described in U.S. Patent 2,461,975. In such a construction, a multi-ply liner bag is preferred wherein the outer ply is made of film-forming polyethylene resin having an intrinsic viscosity of at least about 0.6 and optimumly greater than about 1.0; a melt index of less than about 10.0 and preferably less than about 2.0; a density of preferably not more than .935; and which when formed into film, is resistant to puncture and abrasion and has a low coefiicient of friction.

Surprisingly, multi-ply liner bags and particularly multi-ply liner bags comprising, in combination an inner ply made of the polyethylene, herein described and thereafter formed by the blown-tube method and an outer ply made of the polyethylene herein described, have been found to avoid the high incidence of defects which produce the undesired leakage to a significantly greater extent than single ply film liner bags.

This is clearly shown by a shipping and storage test for leaks that shows good agreement With actual shipping conditions of milk in trucks operated over country roads, followed by a storage period. This simulated shipping-storage test is conducted by filling the liner in the rigid container with 45 F. tap water, closing it off and placing it on a platform which is vertically oscillated a distance of one inch at 300 vibrations per minute in a succession of three minute vibration cycles and thereafter subjecting it to a 480 minute storage period. Each cycle was considered to be the equivalent of miles of truck shipping over country roads.

The following tables show the results of such leakage for liner bags made of multi-ply bags of the present invention as compared to single ply bags employing the same films.

Table 1 sets forth the polyethylene resin properties of the films used to form the bags. Table II sets forth the percentage of bags surviving such a vibration and storage test. Table III sets forth suitable film properties for the inner and outer film plies of the multi-ply liner bag of the present invention.

TABLE I Properties of Resins From Which Polyethylene Films are Formed Polyethylene Intrinsic Melt Density Resin Viscosity Index A -l 1.3 0.097 .920 B 0. 8 1. 60 919 TABLE H Liquid-Filled Liner Bags Surviving Vibration-Storage Test 1 EXAMPLE OF TWO-FLY BAGS OF THIS INVENTION Type of Liner Bags Percent of Liner Bags With No Leaks Test Polyethy- Film Ply Thickness 12 Minutes 480 lene Resm (inches) Vibration Minutes Storage A Two ply: 2

.0015 inner ply 1 {B .0o1 outer ply l 100 01 s3 s3 CONTROL BAGS 4 A .003 single ply 16 16 5 B .003 single ply 20 20 1 Vibration test above described.

2 Two-ply bags of construction herein described and shown in Figs. 4-6. 2 made from seamless tubing such as described in U.S. Patent ,4 Fbur three minute vibration cycles.

TABLE 111 Physical Properties of Polyethylene Film Formed by the Blown Tube Method Film Impact Polyethylene Tbick- Tensile Strength Flex Modulus Elongation To Break (1n. Coeft. Of

Resin ness (p.s.i.) (p.s.i.) (Percent) lb./1nil) Friction (inches) M.D. T.D. M.D. T.D. M.D. T.D.

A .0014 2 4,300 2 4, 400 2 27,100 2 32, 000 660 1,160 24. 7 46 B .0015 2, 620 2, 360 15, 100 17, 900 862 3 l 130 8. 9 .35

1 Blown tube method, such as described in U.S. Patent 2,461,975 wherein the blow ratio was 12 transverse direction to 4 machine direction.

2 Desirable tensile strength, flex modulus for inner film ply of present invention. 3 Desirable elongation to break and coefiicient of friction for outer film ply or present invention.

4 M.D. (Machine Direction), T.D. (Transverse Direction).

The test methods determining the values and units for such values set forth herein and particularly in Tables I and III are:

Tensile strength (in pounds per square inch) as measured by test procedure ASTM D882-56T Flex modulus at 1% elongation (in pounds per square inch) as measured by test procedure ASTM D1530- 5ST Elongation to break (in percent) as measured by test procedure ASTM D882-56T modified to be conducted at 135 C.

Impact (inch pounds per mil) at room temperature as measured by a 2.3 pound steel ball dropped 2.58 feet, (Modern Packaging, p. 150, June 1054).

COClfiClfillt of friction (film-to-filrn) is the numerical result of dividing the force in grams required to slide 4.5 square inches of film of the same composition at a rate of 24 inches per minute and under a Weight load of 240 grams in sliding contact, by 240.

Intrinsic viscosity (in deliciters per gram) as measured by test procedure ASTM D160158T Melt index (flow in grams per minutes) as measured by test procedure ASTM D1238-52T Density (in grams per cubic centimeter) in a gradient column made up of water, methanol, and sodium acetate at 25 C.

It will be noted from the above Table II that the percent of liquid-filled liner bags surviving the vibration tests increased markedly as the construction was changed from a single ply bag of 3 mil thickness of tests 4 and 5 to an equivalent multi-ply construction of two plies each of 1 mil thickness. Furthermore, it is to be noted that the multi-ply combination of two similar films, made from the same resin, was not as eilective in surviving the vibration test as the multi-ply construction using film A as an inner ply and film B as an outer ply.

Table III shows that films, such as polyethylene film type A, characterized by high tensile strength and flex modulus and employed as an inner ply of a multi-ply liner bag, in combination with films such as polyethylene film type B, characterized by high resistance to percent elongation to break and a 10W coefficient of friction and employed as an outer ply of a multi-ply liner bag, provided a multi-ply liner bag wherein no bags failed due to leakage when subjected to a vibration test simulating actual shipping conditions.

Table 1 shows the intrinsic viscosity, melt and density characteristics of the film-forming resins for a preferred embodiment of multi-ply liner bag. An important physical characteristic of film-forming polyolefin resins, such as used in the preferred embodiment, is the intrinsic viscosity. Polyethylene film A is preferably made for a film-forming resin that has an intrinsic viscosity of at least about 1.0, characteristic of a resin that has a high molecular weight and properties ideally suited for an inner ply of a multi-ply liner bag. Film B is preferably made from a film-forming resin that has an intrinsic viscosity of at east abo t 0.6 and a density not to exceed 9.935, and properties suited for an outer ply of a multi-ply liner bag.

While it is preferred to form the inner and outer plies of the multi-ply bags with polyethylene film herein described, other polyolefin films including polyethylene copolymers, polypropylene, copolymers of ethylene and propylene, and mixtures of polyethylene and polypropylene, as well as mixtures of such polyolefins and other film-forming polymers which have the aforedescribed properties, can be used. Desirably, the inner film ply of the multi-ply liner bag is made of film-forming polyolefin resins having an intrinsic viscosity of at least about 1.0 and the outer film ply is made of film-forming polyolefin resins having an intrinsic viscosity of at least about 0.6. Flexible thermoplastic films ha dug a flex modulus of at least about 25,000 pounds per square inch in the longitudinal and transverse directions can also be used for the inner ply of the multi-ply liner bags. Furthermore, flexible thermoplastic materials having a coefi'lcien: of friction of less than about 0.40 can be used for the outer ply.

The size of the liner bag can vary, depending on the amount of fiowable material to be handle lne liner bag 10 or ill herein described and illustrated in the drawings has a five-gallon capacity. Liner bags having a three-gallon, ten-gallon capacity, etc. can also be used.

The number of plies for any given liner bag will depend on among other things, th weight, vol me and type of material to be contained in the bag, and the shipping conditions likely to be encountered. For example, the five-gallon, two-ply polyethylene liner bag 10 or ill herein described and illustr ed is ideally suited for use in combination with the rigid container 12 for shipping milk over rough country roads and storing it for long periods of time. Where more than two plies are desired, the intermediate plyfics) can be madeof fihn which is resistant to environmental stress corrosion and flex fatigue.

Depending upon the number of plies used, individual ply thickness need only be /2, /3 or A as thick as a single ply liner. Moreover, multi-ply liner bags have been found to be stronger and more flexible than single bags of the same total Weight or" material.

Each ply of film of the liner bag It? is self-supportin Films having a thickness to provide the required durability, typically of .0610 to 0.0030 inch or more, have been found satisfactory for such usage.

With respect to forming the essentially sterile multiply thermoplastic liner bag, the interior of melt-extruded flexible, thermoplastic seamless tubular film, such as that formed by the blown-tube method described in US. Fat en't 2,461,975, is sterile.

Accordingly, one method of fabricating the liner bags 10 of FIGS. 1-3 is by forming the inner film ply 14 from a continuous length of such melt-extruded flattened seam ess tubular film, and forming the outer concentric film ply 16 by center-folding and circumscribing sheeting about said continuous length of flattened seamless tubular film with the sheeting center-fold 13 in juxtaposition with one side of said flattened seamless tubular film, and heat sealing the free edges 2% of the sheeting 16 together in juxtaposition with the other side of the flattened seamess tubular film. The bottom end 22 of the multi-ply liner bag 1t is formed by transversely heat sealing the inner and

outer plies

14, 16 of flattened seamless tubular film and center-folded heat sealed, tubular sheeting, toget er across the width of said bag 16). The top end 2-5 of multi-ply liner bag 11 is formed by transversely heat sealing said inner and

outer plies

14, 16 together, spaced from the heat seal of the bottom end 22, in such manner so as to leave a gap 32 in the corner 38 adjacent the sheeting center-folded 1S. Thereafter, the thusly heat sealed film plies 14, 16 can be cut into unit bags 1t"; and the filling and dispensing spout can be inserted in the gap 32 and open to the interior of the inner film ply 14, to maintain the essentially sterile interior of the inner film ply such as by inserting the rubber tube 34 in'the gap 32, gathering the film plies 14, 16 into overlapped spiralled leak-proof folds about the tube 34, and fastening the twisted fold of film plies 14, 16 such as by a conventional twist wire 43.

A production operation for the fabrication of liner bags for milk shipping containers made according to the described method is regularly tested for sterility of the liner bag interior. This test is conducted by the procedure described in the Standard Methods for the Ex amination of Dairy Products, 11th Edition, 1960, published by the American Public Health Association, Inc. The allowable total bacterial colony count is stated in the regulation to be 18,906 for a five-gallon size of milk container.

Assembled liner bags made by the described method are regularly tested on a production basis of. one test bag per 500 per operator. Ninety-five percent of bags tested are sterile. Five percent of the liner bags are showing a total count of never more than 2 colonies per plate, or a total of 100. Thus, it is seen that this method is a distin t and useful advance in the art of making shipping containers for milk.

in forming an interiorly essentially sterile multi-ply liner bag 1t) of FIGS. -7, a continuous length of interiorly essentially sterile flattened seamless tubular film is also used as the inner ply 14' while the outer concentric ply 16 is formed by superimposing two she is 1'7, 19 about the continuous length of flattened seamless tubular film, heat sealing the longitudinal edges 25.? of the

sheets

17, 19 together in juxtaposition with the adjacent edges of the flattened seamless tubular film. Thereafter, the inner and

outer plies

14, 16 can be transversely heat sealed film plies 14', 16', cut into unit bags 16 with the tube 34' inserted into and fastened to tie multi-ply bag as hereinbeiore described for the rnultl-ply bag 1% of FIGS. 13.

The heat seals in the multi-ply inner bags herein described can be formed by well-known techniques, such as by a rotating heated sealing wheel cooperating with a resilient surface for the longitudinal heat seals and by an intermittently operated heated bar or impulse sealing bar for the transverse heat seals.

In using the multi-ply liner bags 10 for milk, a liner bag 10 is placed in a rigid container, such as the paperboard container 12 shown in FIG. 7. The multi-ply bag 1% is that shown in FIGS. 1-3 but it is to be understood that the liner bag 16 of FIGS. 5-7 can be used instead. The plug (not shown) in the tube or spout 34 is removed and after drawing a vacuum on the liner bag 16, it is filled with a measured amount of milk in place in the container 12. The spout 34 is then closed otf again such as by another plug and pulled through a hole 42 in one of the first folded flaps 44 of the container 12. The freeid board portion 41 of the liner bag 19 is thereafter loosely folded about the normal milk level. The spout 34 is then laid fiat upon the first fold flaps 44 and held in place by the second fold flaps 46 of the container 10 when they are pasted down over the first fold flaps 44.

The milk containing container 12 is delivered to dairy customers, such as restaurants and institutions. The tube or spout 34 is then Withdrawn by removing tabs 48 from the second fold flaps 46, the container 12 is inverted and placed into a refrigerated dispenser unit, and the tube 34 threaded through a pinch valve (not shown). The plug in the tube 34 is removed and the dispensing of the milk from the container 12 is commenced.

In place of the milk, the multi-ply liner bag of the present invention can also be used for shipping, storing and dispensing other flowable materials, including fruit juices, syrups, and other liquids, as well as ice cream and pastry and pulverulent materials, such as pudding, jellies, cake mixes, etc.

It will be obvious to those skilled in the art that various changes and modifications may be made in the foregoing description without departing from the spirit and nature of the present invention.

What is claimed is:

1. A flexible, leakproof, collapsible, multiply liner bag for perishable material such as milk and the like, comprising an inner ply of flattened seamless tubular polyolefin film interiorly essentially sterile, and a concentric coextensive outer ply of center-folded polyolefin sheeting circumscribed about said inner ply, said center-fold of the sheeting being juxtaposed along one flattened edge of said seamless tubular inner film ply with the free edges of the sheeting opposite said center-fold heat sealed in juxtaposition with the other flattened edge of said inner seamless tubular film ply, one end of the coextensive inner and outer plies transversely heat sealed together across the width of the multi-ply liner bag and the other end of the coextensive inner and outer film plies transversely heat sealed together so as to leave a gap in one corner of said multi-ply liner bag other end, and a spout open to the interior of said seamless tubular inner film ply and in said gap, thereby providing a leakproot heat sealed multi-ply liner bag, the inner polyolefin film ply being characterized by being resistant to environmental stress corrosion and flex fatigue, and the outer polyolefin film ply being characterized by being resistant to puncture and abrasion.

2. A flexible, leakproof, collapsible, multi-ply liner bag for perishable material such as milk and the like, comprising an inner ply of flattened seamless tubular polyethylene film interiorly essentially sterile, and a concentric coextensive outer ply of center-folded polyethylene sheeting circumscribed about said inner ply, said centerfold of the sheeting being juxtaposed along one flattened edge of said seamless tubular inner film ply with the free edges of the sheeting opposite said center-fold heat sealed in juxtaposition with the other flattened edge of said inner seamless tubular film ply, one end of the coextensive inner and outer plies transversely heat sealed together across the Width of the multi-ply liner bag and the other end or" the coextensive inner and outer film plies transversely heat sealed together so as to leave a gap in one corner of said multi-ply liner bag other end, and a spout open to the interior of said seamless tubular inner film ply and in said gap, thereby providing a leakproof heat sealed multi-ply liner bag, the inner polyethylene film ply comprises a filmforming polyethylene resin having an intrinsic viscosity of at least about 1.0 and a density of not greater than 0.935 and is being characterized by being resistant to environmental stress corrosion and flex fatigue, and the outer polyethylene film ply comprises a film-forming polyethylene resin having an intrinsic viscosity of at least about 0.6 and a density of not more than 0.935 being characterized by being resistant to puncture and abrasion.

3. In combination with a rigid container, a flexible, leakproof, collapsible liner bag within said container for holding, shipping and dispensing a llov/able material having an inner ply of flattened seam ess tubular polyolefin film interiorly essentially s eriie and a concentric, coextensive outer ply of center-folded polyolefin sheeting circumsc ibed about said inner ply, said center-fold of the sheeting being juxtaposed along one flattened edge of said inner seamless tubmar film ply With the free edges of the sheeting opposite said center-fold heat sealed in juxtaposition with the other flattened edge of said inner seamless tubular film ply, one end of the coextensive inner and outer plies transversely heat sealed together across the width of the multi-ply liner bag and the other end of the coextensive inner and outer plies transversely heat sealed together so as to leave a gap in one corner of said multi-ply liner bag other end, and a spout open to the interior of said sea .rless tubular inner film ply and in said gap, thereby providing a leakproof heat sealed muiti-ply liner bag, said rnulti-ply liner bag being of such length so as to provide a freeooard portion to insure filling the flowable material to a precise predetermined volume, thereby effecting a normal material level within said multi-ply liner bag below the upper end thereof and with said freeboard portion being loosely infolded to said normal material level, the inner ply of said multi-ply liner bag comprising a polyolefin film characterized by being resistant to environmental stress corrosion and flex fatigue primarily due to shipping motion Which causes the flowable material to "move in and about the film folds of the infolded freeboard portion, thereby flexing and unfiexing the folds therein, and the outer ply of said multiply liner bag comprising a polyolefin film characterized by being resistant to puncture and abrasion caused by handling and contact with the rigid container.

4. in combination with a rigid container, at flexible, leakproof, collapsible liner bag Within said container for holding, shipping and dispensing milk having an inner ply of flattened seamless tubular polyethylene film interiorly essentially sterile and a concentric, coextensive outer ply of center-folded polyethylene sheeting circumscribed about said inner ply, said center-fold of the sheeting being juxtaposed along one flattened edge of said inner seamless tubular film ply with the free edges of the sheeting opposite said center-fold heat sealed in juxtaposition with the other flattened edge of said inner seamless tubular film ply, one end of the coextensive inner and outer plies transversely heat sealed together across the Width of the multi-ply liner bag and the other end of the coextensive inner and outer plies transversely heat sealed together so as to leave a gap in one corner of said multi-ply liner bag other end, and a spout open to the interior of said seamless tubular inner film ply and in said gap, thereby providing a lealcproof heat sealed multi-ply liner bag, said lti-ply liner bag being of such length so as to provide a freeboard portion to insure filling the fiowable material t being loosely info ded to said normal material level, the inner polyethylene film ply of said multi-ply liner bag comprising a film-forming polyethylene resin having an intrinsic of at least about 1.0 and a density of not greater than 0.935 and characterized by being resistant to environmental stress corrosion and flex fatigue primarily due to shipping motion which causes the fiowable material to move in and about the film folds of the intolded freeboard portion, thereby flexing and unflexing the folds therein, and the outer polyethylene film ply of said multiply liner bag comprising a film-forming polyethylene resin having an intrinsic viscosity of at least about 0.6 and a density of not more than 0.935 characte ized by being resistant to puncture and abrasion caused by handling and contact with the rigid container.

5. in a continuous method of forming a mnlti-ply liner bag of fiexiole, lealcproof, collapsible film comprising forming an inner film ply from a continuous length of melt-extruded flattened seamless flexible thermoplastic tubular film interiorly essentially sterile, forming an outer concentric film ply by center-folding and circumscribing flexible thermoplastic sheeting about said seamless tubular film with said center-fold of the sheeting juxtaposed along one flattened edge of said seamless tubular film, heat scaling the free edges of the sheeting opposite said centerfold together in juxtaposition with the other flattened edge of aid seamless tubular film, transversely heat sealing the concentric inner and outer film plies of flattened seamless tubular film and center-folded heat sealed sheeting together across the Widths thereof, and transversely heat sealing said concentric inner and outer plies together spawd from the other transverse heat seal in such manner so as to leave a gap in one corner of said inner and outer film plies, transversely severing said concentric plies of heat sealed seamless tubular film and sheeting into unit multiply liner bags, and aflixing a spout to said multi-ply liner bag so as to be open to the interior of the inner ply of seamless tubular film and in said gap and rnm'ntain the essentially sterile interior of the seamless tubular film,

to form a leakproof multily liner bag interiorly $88611.

tubular film with said center-fold of the sheeting juxtaposed along one flattened edge of said seamless tubular film, heat sealing the free edges of the sheeting opposite said center-fold together in juxtaposition with the other flattened edge of said seamless tubular film, transversely heat sealing the concentric inner and outer film plies of flattened seamless tubular film and center-folded heat sealed sheeting together across the width thereof, and transversely heat sealing said concentric inner and outer plies together spaced from the other transverse heat seal in such manner so as to leave a gap in one corner of said inner and outer film plies, transversely severing said concentric plies of heat sealed seamless tubular film and sheeting into unit multi-ply liner bags, and aflixing a spout to said multi-ply liner bag so as to be open to the interior of the inner ply of seamless tubular film and in said gap and maintain the essentially sterile interior of the seamless tubular film, to form a leakproof multi-ply liner bag interiorly essentially sterile.

7. A flexible, lealcproof, collapsible, multi-ply liner bag for perishable material such as milk and the like, and having an inner ply of flattened seamless polyethylene film resistant to environmental stress corrosion, flex fatigue and interioriy essentially sterile, and comprising a filmforming polyethylene resin having an intrinsic of at least about 1.0 and a density of not more than 0.935; and a concentric, coextensive ply of two sheets of polyethylene film resistant to abrasion and puncture and comprising a polyethylene resin having an intrinsic of at least about 0.6 and a density of not greater than 0.935, said two polyethylene sheets superimposed about the inner film ply with the free edges of said two sheets heat sealed together in juxtaposition with the adjacent edges of said inner flat-- 13 ply and in said gap, thereby providing a leakproof heat sealed multi-ply liner bag.

8. In combination With a ri id container, a flexible leakproof, collapsible liner bag within said container for holding, shipping and dispensing milk having an inner ply of flattened seamless tubular polyethylene film and a concentric, coextensive outer ply of two polyethylene sheets superimposed about said inner ply with the longitudinal free edges of said two sheets heat sealed together in juxtaposition to the adjacent edges of the inner flattened seamless tubular film ply, one end of the coextensive inner and outer plies transversely heat sealed together across the width of the multi-ply liner bag, and the other end of the coextensive inner and outer plies transversely heat sealed together so as to leave a gap in one corner of said multi-ply liner bag other end, and a spout open to the interior of said seamless tubular inner film ply and in said gap, thereby providing a leakproof heat sealed multiply liner bag, said multi-ply liner bag being of such length so as to provide a freeboard portion to insure filling the flowable material to a precise predetermined volume, thereby effecting a normal material level within said multiply liner bag below the upper end thereof and with said freeboard portion being loosely infolded to said normal material level, the inner polyethylene film ply of said multi-ply liner bag comprising a film-forming polyethylene resin having an intrinsic viscosity of at least about 1.0 and a density of not greater than 0.935 and characterized by being interiorly essentially streile and resistant to environmental stress corrosion and flex fatigue primarily due to shipping motion which causes the flowable material to move in and about the film folds of the ill-folded freeboard portion, thereby flexing and unflexing the folds therein, and the outer polyethylene film ply of said multiply liner bag comprising a film-forming polyethylene resin having an intrinsic viscosity of at least about 0.6 and a density not greater than 0.935 and characterized by being resistant to puncture and abrasion caused by handling and contact with the rigid container.

9. In a continuous method of forming a multi-ply liner bag of flexible, leakproof, collapsible film comprising forming an inner film ply from a continuous length of melt-extruded flattened, seamless flexible thermoplastic tubular film interiorly essentially sterile, forming an outer concentric film ply by superimposing two sheets of flexible thermoplastic film about said seamless tubular film, heat sealing the longitudinal free edges of the two sheets together in juxtaposition with the adjacent edge of the inner flattened seamless tubular film ply, transversely heat sealing the concentric inner and outer film plies of flattened seamless tubular film and longitudinal heat sealed sheets together across the widths thereof, and transversely heat sealing said concentric inner and outer plies together spaced from the other transverse heat seal in such manner so as to leave a gap in one corner of said inner and outer film plies, transversely severing said concentric plies of heat sealed seamless tubular film and sheeting into unit multi-ply liner bags, and afiixing a spout to said multi-ply liner bag so as to be open to the interior of the inner ply of seamless tubular film and in said gap and maintain the essentially interior of the seamless tubular film, to form a leakproof mnlti-ply liner bag interiorly essentially sterile.

10. The method according to claim 9 wherein the multi-ply liner bag is used for milk; and wherein the inner ply of flattened seamless flexible thermoplastic tubular film interiorly essentially sterile comprises a film-forming polyethylene resin having an intrinsic viscosity of at least 1.0 and a density of not greater than 0.935 and is resistant to environmental stress corrosion and flex fatigue, and the outer ply of two flexible thermoplastic sheets comprises a film-forming polyethylene resin having an intrinsic viscosity of at least about 0.6 and a density of not greater than 0.935.

References Cited in the file of this patent UNITED STATES PATENTS 2,554,157 Snyder May 22, 1951 2,898,027 Scholle Aug. 4, 1959 2,973,119 Parker Feb. 28, 1961 FOREIGN PATENTS 66,747 Denmark May 3, 1948 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,122,297 February 25, we l John P., Sachs It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2 line l5 for "containe" read container column 6; line 7, for ".935" read 0935 column 7, line 32, for June 1054" read June 1954 line 38 for "deliciters read deciliters column 8 line 66 for "@0010" read 0.0010 column 12 lines 60 and 64, for "intrinsic of", each occurrence, read intrinsic viscosity of column 14, line 19, for "essentially interior" read essentially sterile interior Signed and sealed this 14th day of July 19640 (SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting officer Commissioner of Patents

Claims

1. A FLEXIBLE, LEAKPROOF, COLLAPSIBLE, MULTI-PLY LINER BAG FOR PERISHABLE MATERIAL SUCH AS MILK AND THE LIKE, COMPRISING AN INNER PLY OF FLATTENED SEAMLESS TUBULAR POLYOLEFIN FILM INTERIORLY ESSENTIALLY STERILE, AND A CONCENTRIC COEXTENSIVE OUTER PLY OF CENTER-FOLDED POLYOLEFIN SHEETING CIRCUMSCRIBED ABOUT SAID INNER PLY, SAID CENTER-FOLD OF THE SHEETING BEING JUXTAPOSED ALONG ONE FLATTENED EDGE OF SAID SEAMLESS TUBULAR INNER FILM PLY WITH THE FREE EDGES OF THE SHEETING OPPOSITE SAID CENTER-FOLD HEAT SEALED IN JUXTAPOSITION WITH THE OTHER FLATTENED EDGE OF SAID INNER SEAMLESS TUBULAR FILM PLY, ONE END OF THE COEXTENSIVE INNER AND OUTER PLIES TRANSVERSELY HEAT SEALED TOGETHER ACROSS THE WIDTH OF THE MULTI-PLLY LINER BAG AND THE OTHER END OF THE COEXTENSIVE INNER AND OUTER FILM FLIES TRANSVERSELY HEAT SEALED TOGETHER SO AS TO LEAVE A GAP IN ONE CORNER OF SAID MULTI-PLY LINER BAG OTHER END, AND A SPOUT OPEN TO THE INTERIOR OF SAID SEAMLESS TUBULAR INNER FILM PLY AND IN SAID GAP, THEREBY PROVIDING A LEAKPROOF HEAT SEALED MULTI-PLY LINER BAG, THE INNER POLYOLEFIN FILM PLY BEING CHARACTERIZED BY BEING RESISTANT TO ENVIRONMENTAL STRESS CORROSION AND FLEX FATIGUE, AND THE OUTER POLYOLEFIN FILM PLY BEING CHARACTERIZED BY BEING RESISTANT TO PUNCTURE AND ABRASION.