CA1181914A

CA1181914A - Plastics material film sheet having a preselected weakened area

Info

Publication number: CA1181914A
Application number: CA000412355A
Authority: CA
Inventors: Brian R. Pike
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-18
Filing date: 1982-09-28
Publication date: 1985-02-05
Also published as: GB2122166A; GB2122166B

Abstract

ABSTRACT

A plastics material film which is formed of two films of the same thermoplastics material which are self heat bonded together a first of the films being relatively thick and having resist material thereon in predetermined patterns, and the other of the films being thin as compared to the one film with the other of the films being bonded to the one film at all areas except for the resist area so as to provide a thermoplastics material film sheet or a predetermined thickness which in selected areas only there are two separate films with these areas defining seal forming areas. The film sheet with the seal forming areas may be readily folded and bonded to define pouches or packages having predetermined weakened seals of a predetermined rupture strength. The resist material, particularly in the case of packages for food products is formed of a food or a food additive.

Description

PLASTICS MATERIAL FILM SHEET HAVING A
_ PRESELECI'ED WE _ NED AREA

This invention relates in general to new and useful i.mpro~ements in the manufacture of packages, and more particularly to a plastic material film sheet par-ticularly adapted to form a package for foods and having a rupturable seal between two compartments throuyh which one of at least two foods passes to permit mixing within the package.
~ This invention generally relates to the maklng : ~ of packages with rupturable seals of the general type ~ 10 disclosed in my prior U.S. patent 3,608,709.
; In the past, it has been necessary to adhesively :~ bond tow~films together with the bond between the films ,.
in certain areas being weaker than in other areas to as to define a preselected weakened area which becomes part of the seal. Not only have such films been difficult to form, but also the strength of the bond surrounding the weakened area has not been sufficiently predictable.
In accoxdance with this invention it is proposed to provid what is truly a single sheet of thermoplastic that has a localized area of resist, which divides the sheet at intermediate portions into two discreet thick-.nesses of the same material and which two discreet thick-nesses cannot be fused togethPr at a later date due to the presence of the resist material. In other words, the resuItant sheet of thermoplastic material that has been formed from two thicknesses of the same material has an integral self bond therein so that for all practical '~

- 2 -purposes, except in the area of the .resist material, is a single thickness material.
In my prior U.S. Patent 3,608,709 the sheet of thermoplastic material was a laminated sheet and the -two layers were not unitarily bonded together such as being fused or welded so as to constitute a single thickness material except in the resist material area. In all instances of my prior U.S. Patent 3,608,709 the two la~ers of the larninat.ed sheet had to be adhesively bonded together. Inasmuch as adhesive bonds have a tendency to peel, certain of the packages failed to open due to the continued separation of the laminated sheet on one or both sides of the resist material.
~ This invention also particularly rela-tes to packages for food wherein two different foods may be packaged in a single package in adjacent compartments separated by a rupturable seal such that when the seal is ruptured, food being transferred from one compartment to the adjacent compartment will actually pass over the resist material. It is therefore an important feature of the invention to form the resist material itself of a food grade material. The resist material itself may be a food or be recognized as being quite compatible as a food additive.
In accordance with this invention, it is pro-posed to provide a first film and to apply to that first film at preselected areas a resist. Thereafter, a second and thinner film is applied to the first ~ilm and integra]ly bonded thereto in all~r~s- except for the area having the resist material thereon~ The first and second films are so self bonded together so as to constitute a single film having a thickness corresponding to the total thickness of the two films and the film having weakened areas which may be utilized in the formation of seals in packages.
The resist material may be suitably applied to 1 ~8~g1~
the first film by means of printlng and the like.
The second film could be a preformed second film which is heat bonded to the first film, or it may be cast in place on the first film and directly bonded thereto as it engages the first sheet. A cast second film has a definite advantage over a preformed second film in that in the normal formation of plastic rnaterial films a tube is e~truded and is then blown and stretched to a much larger diameter. Certain of this stretching takes place at -the orientation temperature and, there-fore, the plastic material becomes oriented and is much stronger than like thickness cast film of the same material. It is also to be understood that when the second film is preformed, it must be drawn from a roll over rollers in tension with a result that a relatively high stress is put on the preformed second film and it must have a much higher strength than tha-t required in the package. Therefore~ a cast film has a positive advantage over a preformed film.
The plastics material film sheet formed in accordance with this invention ma~ be folded and cut to length to form pouches which have either at the ends thereof or in intermediate areas thereof a seal which is aligned with and contained within the perimeter of a weakened area and wherein when opening force is applied, the ~ilm ahving the weakened areas therein will rupture along that weakened area so as to effect an opening of the pouch.
It is to be understood that the plastics material film sheet may also be bonded to other sheets which may be formed of other materials or plastics materials either by heat bonding or by means of a suitable adhesive~ -Further, it is to be understood that the plastics material film sheet is particularly adaptable for use in

3 ~ 4 forming pouches for receiving medical disposables andmay employ the conventional chevron seal configuration.
In addition, the film sheet may he utilized in the sealing of jars and the like wherein the weakened area is annular and the film sheet is secured to the container lip in alignment with the weakened area so that the lid formed by the film sheet may be torn off all except for the thin narrow part which forms part of the seal with the container.
Another use of the film sheet is as a removable seal for cartons and the like and as such may also function as a label.
It is particularly pointed out here that the resist material incorporated in the film sheet must have the proposed of preventlng bonding together of the film sheet in the weakened area during the formation of a heat seal.
With the above, and other objects in view that will herinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings.
IN THE D~AWINGS:
Figure l is a schematic view showing the manner in which the film sheet of this invention may ~e formed utilizing two prior formed films.
Figure 2 is a schematic view similar to Figure l and shows the film sheet being formed with the thinner film being cast in place as an extrudate.
Figure 3 is an enlarged fragmentary sectional view taken along the line 3-3 of Figure 2 and shows the cross section of the film sheet.
Figure 4 is a schematic view showing the manner in which the film sheet may be transversely folded to form a tube which may be severed at intervals to form pouches.

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Figure 5 is a plan view of a pouch which is formed with the tube material of Figure 4.
Figure 6 is an enlarged fragmentary sectional view taken along the line ~-6 of Figure 1 ancl shows -the seal area of the pouch.
Fiyure 7 is an enlarged ~ragmentary sectional view similar to Figure 6 and shows the ruptured seal.
Figure 8 J.S a fragmentary sec-tional view similar to Figure 6 and shows the fiLm sheet secured to another sheet of different material in the formation of a pouch.
Figure 9 is a schematic fragmentary p:lan v;ew of the film sheet utilized in forming a pouch for medical ; disposables wherein the seal is a chevron seal.
Figure 10 is a schematic plan view with parts broken away in section showing the film sheet utilized as a removable lid for a container such as a jar.
Figure 11 is a 'ragmentary sectional view showing a carton or thelike wherein end of flaps are held together by a seal ~ormed of the film sheet and wherein the seal may be in the form of a label.
~ eferring now to the drawings in detail, reference is first made to Figure 3 wherein there is il-lustrated a plastics material film sheet having a preselected weakened area therein formed in accordance with this invention. The plastics material sheet is generally identified by the numeral 10 and has a weakened area 11 defined by an internal resist layer 12. The material of the resist layer 12 may be a food or be recognized as being compatible as a food additive as will be discussed hereinafter.
The film sheet 10 may be formed in several manners including those shown in Figures 1 and 2. With particular reference to Figure 1, a previously formed thermoplastic film sheet 13 has the resist material 12 printed thereon by means of a suitable printing device 14.

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Then a second previousl.y formed thermoplasti.c film sheet 15, which is of the same material as the sheet 13 or a different material which will directly fuse to the material of sheet 13, is applied to that surface of the film sheet 13 having the resist material 12 printed thereon by passing the two film sheets through suitable : heaters 16, 17 and then through a nip defined by two rollers 18. The film sheets 13, 15 t:hus become integrally bonded together with the resist material 12 entrapped therein as shown. It is to be understood that the film sheet 10 becomes inteyral except the weakened areas where the resist material 12 is located.
Referring now to Figure 2, it will be seen that the film sheet 10 may be formed in a slightly dif-ferent manner. The separate fi~n sheet 13 is providedand the resist material 12 is applied utilizing a printing mechanism 14 in the manner illustrated in Figure 1. Then a second film sheet 20 is extruded from a film extruder 21 as a cast extrudate at a sufficient tempera-ture wherein the film sheet 20 becomes integrally bonded ~ to the film sheet 13. As previously described, the : second film sheet 20, when it is in the form of a cast extrudate, will be much weaker than the film 15 and, therefore, rupture of a seal may be controlle~ to be at a much lower force.
It is to be understood that the plasticsmaterial from which the film sheets 13, 15 and 20 are formed must be conventional thermop]astics whlch are self bondingO More particularly, they must be self bonding at the elevated temperature at which thermo-plastic material is cast so that with particular reference to the embodiment of Figure 2, the cast film 20 will self bond to the film 13 to result in, for all practical purposes, a single laye.r sheet as is shown in Figure 3.
The preferred thermoplastics include poly~thylene, . 9 .~ ~

ionomer resins, and polyvinylchloride. Polyethylene is particularly advantageous in view of its cas-tin~
temperature of 610 - 640F while the ionomer resins have a casting temperature of 580 600F.
It is to be understood that due to the hiyh temperature of the cast film and the fact that the cast film, as well as ~:he heated film 15 are at such a hi~h temperature to permit self heat bonding, the surEaces of the two films in the area of the resist material 12, as well as the resis-t material, are hea-ted to a sterilization -temperature and -thus are sterile~
~ccordingly, when the film 15 or the film 20 is ruptured in the opening of a package in the manner described hereinafter, the exposed external surfaces will be sterile.
It has been found that exceptional results have been obtained with hydroxypropyl methyl cellulose USP 3CPS. This material is sold by the siddle Sawyer Corporation of New ~ork. The chief characteristics of this material are its recognition as a food addi-tive by the Food and Drug Administration and the fact tha-t it complies with all USP specifications. Further, it can be given a Certificate of Certification for Kosher food applications.
The above described food additive has the capability of being put into suspension with just water, or with alcohol. As such, it can form a thick viscous liquid which can be diluted on the printing machinery with the further addition of water, allowing the pressman to adjust the viscosity as needed for the particulax application. Since this material can be put into suspension both in water and in alcohol, and in other food-based products, and as itself is recognized as a food additive, it forms a resist which is entirely edible and could not possibly con-taminate ~ood products.

1.~8~gl~
Other materials that are s~itable for use as a resist and which would be acceptable for use with food products are: methyl cellulose hydroxypropyl methyl cellulose phthalate, hydroxypropyl cellulose, ethyl cellulose, microcrystaline cellulose, sugar, pharamaceutical grade shellac, pharmaceutical grade waxes, carboxy methyl cellulose, zein, cross-linked polyvinyl pyrrolidone, polyvinyl acetyle phthalate, cellulose acetate phtyalate, acrylic polymers and products relating to the foregoiny.
It is also pointed out here that in the formation of a typical pouch, the sheet film 10 would have a thick-ness on the order of 0.005 inch with the thicker film 13 having a thic~ness on the order of 0.004 inch and the thinner film having a thickness on the order of 0.001 inch~
~ n the formation of a typical pouch utilizing the film sheet 10, the film sheet 10 is of a predetermined width to form a pouch, or multiples thereof. The width of the resist material 12 is substantially equal to the intended width of the pouch.
The film sheet 10 is reversely folded upon itself in the manner shown in Figure 4 and the remote edges thereof are heat sealed together as at 22. The sealed areas may be folded flat. The ne, result is a tube 23.
The tube 23 may then be provided with transverse seals 24, at intervals, and then cut, as shown in Figure 5. ~fter the resultant pouch, generally identified by the numeral 25, has been formed, a suitable product may be placed therein after which the opposite end of the pouch 25 is closed by a further seal which is aligned with and totally within the weakened area 11 defined by the resist material 12.
In Figure 6, there is illustrated a typical cross section through the pouch. It will be seen that 3 ;~
the heat seal 26 is between the two walls 27, 28 of the pouch and that the walls 27, 28 have free end portions 30, 31 which facilitate the opening of the pouch. As is shown in Figure 7, when the free end portions 30, 31 are pulled apart, the wall 27 will rupture in the area defined by the weakened portion 11 with that part of the weakened portion 11 defined by the thinner of the original film sheets becoming detached and remai.ning fused to the wall 28.
It is to be understood that the illustrated pouch 25 is only one of the numerous usages to which a film sheet, such as the fil.m sheet ].0, may be placed.
Refe:rring now to Figure 8, it will be seen that the film sheet 10 is illustrated in the formation of a ; 15 pouch 35 by bondi.ng it to another sheet materal, generally identified by the numeral 36. It is to be understood that the sheet material 36 could be in the form of paper, paper film laminates, film metal foil laminates, etc. In the illustrated embodiment, the other sheet 36 is shown as a laminate including an inner layer 37 and an outer layer 38 with the inner layer being sealed to the weakened area 11 of the film sheet 10 by a seal 40 which may either be an adhesive seal or a heat bonded seal.
In Figure 9, there is schematica]ly illustrated a conventional type of pouch, generally identified by the numeral 41 which may be utilized for storing and shipping medical disposables. The pouch 41 is provided with.a chevron seal, generally identified by the numeral 42. In accordance with this invention, at least one layer of the pouch 41 is in the form of the film sheet 10 while the other layer may be in the form of a sheet, such as the aforedescribed sheet 3~. The weakened area 11 of the :Eilm sheet 10 is illustrated as being of a chevron configuration and has centered therein a suitable bond 43.

1 9 ~

Referring now to Figure 10, it will be seen that the film sheet 10 may be utilized as a lid or other type of cover for containers~ ~ conventional. jar 44 having a sealing lip 45 is il]ustrated. The lid, which is identified by the numeral 46, is suitably bonded to the - lip 45 by way of a seal 47, which may be an adhesive bond or a fusi.on bond and which is aligned with the resist 12 which is illustrated of a circular configurat.ion. The lid ~6 is provided with a suitable tab 48 to facilitate the progressive tearing of the lid material in alignment with the bond 47 in the same manner as is shown in Fi.gure,7.
In Figure 11, there is illustrated a conventi.onal type of carton, generally identified by the numeral 50.
The carton 50 has walls 51, 52 and 53 with the wall 52 having an inner closure flap 54 and the walls 51 and 53 having. outer closure flaps 55 and 56, respectively. A
closure element, generally identified by the numeral 57, is suitably bonded to the flaps 55 and 56 as at 58 in alignment-with-the resist material 12 so that the closrue element 57 may be readily removed.
It is also pointed out here that the closure element 57 may also be in the form of a suitable label or may merely function as a store seal, particularly if the carton 50 contains other containers or packages.
At this time it is particularly pointed out that the sheet film 10 is adapted to be secured to other materials either by way of an adhesive bond or by way of a heat bond or fusion bond. It is to be understood that ~he net result of the bonding of the two layers of the sheet film 10 is an integral single thickness material as opposed to a laminted material. It is further to be understood that the resist material 12 is of a nature and of a thickness so as to prevent self-adhesion of the film sheet 10 in the weakened area 11 during the formation of a fusion bond.

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It is also pointed out that the same film 10, and the resultant seals may be used i.n a multiple cornpartment package of the type disclosed in my prior U.S. Patent No. 3,608~709.
It will be readily apparent that inasmuch as the resist in each instance is a product which is com-patible with food and is either a food or a food addi-tive and the resist and exposible f.ilm sur~aces are sterile, when food is packed in a package formed in accordance with this invention and the package is either opened to communicate two compartments or to dispense a product by the rupture of the film to expose the resist, the food may freely flow over the resist material without dange of contamination.
Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

The embodiments of the invention, in which an exclusive property or privilege is claimed, are defined as follows:-

1. A thermoplastics material film sheet particular adapted to form a package having a rupturable seal, said sheet having an intended seal forming area, said film sheet being formed solely of at least two films of the same thermoplastic material self heat bonded to-gether so as to be of a unitary construction except in said intended seal forming area and an internal resist material within said sheet generally in alignment with said seal forming area, said resist material reducing the effective thickness of said sheet in said seal forming area and defining a preselected weakened area having two surface portions and wherein rupture of one surface portion only may be effected, said sheet otherwise being rupturable only throughout its entire thickness.

2. The sheet of claim 1 wherein said resist material has the caracteristics of preventing self-bonding of said sheet in said weakened area during the formation of a fusion seal in said intended seal forming area.

3. The sheet of claim 1 wherein one of said films is materially thinner than the other, and said thinner film has said seal forming area and defines the effective strength of a resultant seal.

4. The sheet of claim 3 wherein the thickness of the thicker of said films is on the order of 0.004 inch and the thickness of the thinner of said films is on the order of 0.001 inch.

5. The sheet of claim 1 wherein said weakened area extends completely around said intended seal forming area to form a complete path of weakness around said seal forming area.

6. The sheet of claim 1 wherein said resist material is selectively in the form of a food or a food additive.

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7. The sheet of claim 1 wherein said resist material is hydroxypropyl methyl cellulose USP 3 CPS.

8. The sheet of claim 1 wherein said sheet being folded upon itself with a portion of the sheet remote from said seal forming area bonded to said seal forming area and forming a rupturable seal therewith.

9. The sheet of claim 8 wherein other edges of said sheet are bonded together to form a sealed pouch.

10. The sheet of claim 3 wherein said thinner film is a cast film directly cast on the thicker film and self heat bonded to said thicker film.

11. The sheet of claim 3 wherein said resist and the surfaces of said film on opposite sides of said resist are heat sterile.

12. A single material thermoplastics material film sheet particularly adapted to form a package having a rupturable seal, said sheet having an intended seal forming area, and an internal resist material within said sheet generally in alignment with said seal forming area, said sheet except in the area of said resist material being of a unitary construction, said resist material reducing the effective thickness of said sheet in said seal forming area and defining a preselected weakened area, said weakened area extending completely around said intended seal forming area to form a complete path of weakness around said seal forming area, said sheet being folded upon itself with a portion of the sheet remote from said seal forming area bonded to said seal forming area and forming a unitary seal therewith entirely within the confines of said weakened area.