US3596828A

US3596828A - Flexible pouches and bags

Info

Publication number: US3596828A
Application number: US857096A
Authority: US
Inventors: Norman Foster; Kenneth George Tee; David Edward Conway; Ernest Stonehouse
Original assignee: British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1968-10-16
Filing date: 1969-09-11
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: DE1949723C2; NL6915436A; GB1254444A; CA935790A; DE1949723A1

Abstract

A flexible pouch, such as a tobacco pouch, comprises two layers of heat-sealable thermoplastic plastics materials adherent to opposite surfaces of a layer of metal foil. The materials of the said two layers have limited compatibility with each other and the pouch is sealed, where it will require to be opened, at a line of contact between surfaces of different layers of the plastics materials. Thus a peelable seal can be so formed between the backwall of the pouch and an inwardly folded portion at the marginal edge of the front wall thereof and/or between the front wall of the pouch and a flap folded over the said front wall.

Description

United States Patent inventors Norman Foster Hampshire; Kenneth George Tee, Hampshire; David Edward Conway, Hampshire; Ernest Stonehouae, Somerset, all of, England Appl. No, 857,096 Filed Sept. 1 l, 1969 Patented Aug. 3, 1971 Assignee British-American Tobacco Company,

. Limited London, England Priority Oct. 16, 1968 Great Britain 49027/68 FLEXIBLE POUCHES AND BAGS 6 Claims, 8 Drawing Figs.

0.8. 229/62, 229/55, 229/68, 206/41 F lat. 865d 33/22 229/48 T,

Field of Search 62, 55, 68, 3.5 MP; 206/41 F [56] References Cited UNITED STATES PATENTS 2,715,089 8/1955 Michener et a]. 229/3.5 UX 3,332,603 7/1967 Kamins et a]. 229/55 X Primary Examiner- -David M. Bockenek Attorney-Kane, Dalsimer, Kane, Sullivan and Smith ABSTRACT: A flexible pouch, such as a tobacco pouch, comlayers of the plastics materials. Thus a peelableseal can be so formed between the backwall of the pouch and an inwardly folded portion at the marginal edge of the front wall thereof and/or between the front wall of the pouch and a flap folded over the said front wall.

8 v 8 G 6 I 2 F QJ I I m m D ill 3 CI F A B A Ru A lllll I! H 2 M 03 1 G n H Mu W E m D lullll D nld E El E F A D C U E ll W .l H A P FLEXIBLE roucnss AND BAGS This invention concerns improvementsrelating to flexible pouches and like bags, hereinafter referred to as pouches. It is ble with advantage to pouches for other purposes, for example v particularly concemedwith tobacco pouches, but is applicafor containing food products such as potato crisps, roasted metal foil, the materials of the said two layers having limited compatibility with each other,"and the pouch being sealed, where it will require to be opened, at a line or lines of contact between surfaces of different layers of the plastics materials.

By limited compatibility is meant compatibility such that seals produced between surfaces of the two materials on melting the said surfaces under predetermined conditionsoftempera-- ture, time, and pressure are, although hermetic, capable'of being peeled open.

The plastics layers, which may be of basically the same com position, for example different types'of polyethylene, or of dif' ferent compositions, for example an inner layer of a low-melt'- ing copolymer of ethylene vinyl acetate and an outer layer of a low-density polyethylene on the one hand and a low or medi 1 um-density, higher melting, polyethylene on the other hand,

preferably comprise an outer layer of harder,'higher melting 1 poinnmaterialand an inner layer-of softer, lower melting point, material.

The layers may be produced as a triple laminate or one the plastics layers may be coextruded with the metal foil and theother subsequently laminated onto the foil. If the outerlayer is thus laminated, it may additionally serve to protect printed matter applied to the foil.

One manner of carrying the invention into effect, as-applied to a tobacco pouch, will now'be more fully'described byway of example, and with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of ablank,

FIGS. 2 to 4 are comparable views illustrating successive folding stages, and I FIGS. 5 to 8 are diagrammatic side views of the blank at stages corresponding to those of FIGS. 1 to 4, the thickness of its layers being shown greatly exaggerated.

In this example, the pouch is to be made from a single rectangular blank A B C D (FIGJ) of a flexible sheet"(FIG.

'5) comprising a layer 1 of a low-melting point polyethylene-' based material laminated to one surface of a sheet '2 of softtempered aluminum foil and a layer 30f a'higher meltingpoint' polyethylene material laminated to the other surface of the aluminum foil. The low-melting point material maybe, for ex ample, a copolymer of ethylene and vinyl acetate which -has:a density of 0.940-0.945 g./cc. and melting range of I00" 105C. The higher melting point material forexample, an

ethylene homopolymer with a density within the range off 0.920 and 0.960 :g./cc. and a melting range of 105-125C.

folds,on the line E F to the'condition'shown in FIGS. 4 and 8 and is heat-sealed'alon'gand withinthe rectangle C D E F (FIG. 4), the nearer edge of the'sal parallel'to the line E F I being at-'a'distance,-say one-eighth inc'h, from the line E This sealis formed under conditions of temperature and pressure, namely I80 C. and 9 poundsp'er square inch, such that strippable seals' are formed between the unlike'layers 1 and 3 in the area of said rectangle C D E F at 4 and 5 (F IG. 8). These seals can'be produced in one operation if heat is applied simultaneously fromboth'sides of the'pouch over the said area. A permanent seal is formed between the like layers 1 at 6 (FIG. 8) in the area of the saidrectangle. When access to the tobacco is required, the flap is opened and pulled firmly away from the body of the pouch to'pe'elth'e' transverse seals at 4 and 5. The permanent side-edg-seals produced from D to H and C to G as described above at the stage of FIG. 3 remain unafiected, as does also thepermanent seal at 6. Access is thus simple and convenient. After as much of the tobacco as is required has been removed, the pouch can be closed by simply folding it. Normal pouch protection continues to be given to the tobacco.

Pouches produced in the aforesaid manner have been stored for varying periods of time under a range of climatic conditions and the quality of the tobacco assessed. Under storage, at a temperature of 38 C. and 90 percent relative hu midity,'the tobacco gained 1 percentmoisture in about200 days, which shows that the seals provided adequate protection against moisture pickup by the tobacco. In addition, due to the substantially hermetic sealing, not only did the pouches protect the tobacco against moisture changes under adverse climatic conditions and against contamination from outside, but ioss of aromatic constituents from the tobacco was prevented.

Testing of samples cut from the pouches showed that the permanent seals had an average tensile'strength of 800 gJcm. of sealed'area and that the trippable seals an average tensile strength of I g./cm. of sealed area.

The resultant pouch is of a conventional rectangular pouch .shape',i.e. with a rear wall 8 (FIG. 8) of thefull height of the pouch, a slightly shorter'front wall 9 and a front flap 10 integral with the rear wall and overlapping rather more than the upperhalf of the front wall. The tobacco is contained in the space,'indicated at ll, between the front and rear walls. The front wall has aninwardly folded short portion 12 at its upper edge'permanently-sealed back'at 6 onto the inside of the said wall. There are peelable seals at '4 and 5 at about the same level. 'The'seals 4 and '5 are adequate to prevent escape of moisture and aroma from the tobacco and contamination or deterioration thereof by outside influences, but capable of being readily peeled open without either destroying the coniinuity of the pla'stics'layers or films or detaching them from themetalfoil. The above-described seals'from Dto'I-I and C to 'G form side seams between the insides of the front and rear walls, which are permanent except where the inwardly folded portion '12 intervenes. This arrangement has the advantage that an opening the pouch,-after breaking the seal 4 between theflap 10 and front wall 9tand lifting the flap, the wall 9 and edge portion '12 can 'bepressedoutwardly away from the The material of the layer 1, which is to become'the inner layer charge of tobacco, so as to rupture the side seams for the of the pouch, is such that it will iheat-seal'to itself to 'form a layer 1 visible is a rectangle of the area AB F E-inFIG. BJHeat seals are then formed along the side edges E H and F G (FIG;

height of the said-edgeportion 12 and provide'a convenient po'int of attack for breaking the inner seal at 5 between the zedgepor'tion 12 of thefront wall and the rear wall '8.

The-thicknesses of the

layers

1, 2, and 3 will depend on the 'totalathickness required for the laminated pouch material in aordento secure-desired physicaland/or mechanical properties. Suitably the thicknesses of the layers'in thousandths of an inch :rna'y be as follows: Inner layer 1 from l to 3 thou., foil 2 from 0:5 to .l.2 thou. and outer layer at least I thou.

3). The seals, between unlike layers land 3, from E'to'D and The'temperatures to be used for the heatsealing will depend from F to C are peelable and the seals between :like layers 1! from D to H and C to G are pennanent. At this stage,-=t'he pouch is filled with a required quantity of tobaccoJ-What is to become the flap of the pouch, i.e.,the rectangle-A B'F E-in' FIG. 3-is'folded, in the opposite direction to the'twoprevious layer 1 to the aluminum sheet 2. For the peelable seals, the

upon the thicknesses of thellayers-and the compositions of the :rnaterials-Forthe permanent heat seals, the sealing conditions should be such that the bond strength'in the seal is greater ,than the' bond strength of the inner, low-melting, polyethylene sealing conditions should be such that the bond strength of the layer 1 to the higher melting polyethylene layer 3 is less than the bond strength of both of the layers 1 and 3 to the alu minum sheet 2. Simple seals between two layers only can be produced by jaws heated to between H and 150 C., preferably 120 C., in the case of a permanent seal. The temperatures required for obtaining a peelable seal, i.e. to seal through a number of layers giving one permanent and two peelable seals, are l64208 C., preferably 182 C. The temperatures can be readily determined in any particular case;

, of a softer material than the outer layer 3. This, however, is

not essential. Furthermore, a pouch could be produced from the same materials and in the same manner as has been described above, but with the layer of higher melting point-on the inside. The strength of the seal at 6 would be weak or nonexistent. Although generally undesirable, this may may be advantageous in some cases.

If desired, a tear strip, for instance in the form of a natural or synthetic thread or film, may be included at one or both of the peelable seals 4 and 5. It may be incorporated in one or other of the layers 1 and 3. A tape serving for closure or convenience of manipulation may be provided at the free edge of the flap 10. I

We claim:

1. A flexible pouch comprising two layers of heat-scalable thermoplastics materials adherent to opposite sides of a layer of metal foil, the materials of said two layers having differing melting points and having limited compatibility with each other, the said pouch being sealedalong zones along its lateral edges in which one of the said two layers are in face to face contact with each other to form a permanent seal along said zone and said pouch having a peelable sealed access opening, the peelable seal being formed by contacting both of said two layers thereby forming a bond which is peelable and of less strength than the bond formed" by the zones along the lateral edges of the pouch.

2. A pouch as claimed in claim 1, wherein a peelable" seal between materials of limited compatibility is formed between the .backwall of the pouch and an inwardly folded portion at the marginal edge of the front wall thereof.

3. A pouch as claimed in claim 1, wherein a peelable seal between materials of limited compatibility is formed between the front wall of the pouch and a flap folded over the said front wall.

4. A pouch as claimed in claim 1, wherein the metal foil is of aluminum, the inner layer is of a low-melting polyethylene material and the outer layer of a higher melting polyethylene material.

5. A pouch as claimed in claim 1, wherein the inner and outerlayers are of plastics materials of basically different composition.

6. A flexible pouch comprising two layers of heat-sealable thermoplastic plastics materials adherent to opposite surfaces of a layer of metal foil, the materials of the said two layers having different melting points and the pouch having an access opening which is hermetically sealed along at least one line of contact between opposite surfaces of said two layers of heatscalable thermoplastics materials whereby said hermetic seal is readily peelable.

Claims

1. A flexible pouch comprising two layers of heat-sealable thermoplastics materials adherent to opposite sides of a layer of metal foil, the materials of said two layers having differing melting points and having limited compatibility with each other, the said pouch being sealed along zones along its lateral edges in which one of the said two layers are in face to face contact with each other to form a permanent seal along said zone and said pouch having a peelable sealed acCess opening, the peelable seal being formed by contacting both of said two layers thereby forming a bond which is peelable and of less strength than the bond formed by the zones along the lateral edges of the pouch.

2. A pouch as claimed in claim 1, wherein a peelable seal between materials of limited compatibility is formed between the backwall of the pouch and an inwardly folded portion at the marginal edge of the front wall thereof.

5. A pouch as claimed in claim 1, wherein the inner and outer layers are of plastics materials of basically different composition.

6. A flexible pouch comprising two layers of heat-sealable thermoplastic plastics materials adherent to opposite surfaces of a layer of metal foil, the materials of the said two layers having different melting points and the pouch having an access opening which is hermetically sealed along at least one line of contact between opposite surfaces of said two layers of heat-sealable thermoplastics materials whereby said hermetic seal is readily peelable.