GB2122166A - Selectively weakened plastics sheet - Google Patents

Abstract

A plastics material film is formed of two films of the same thermoplastics material which are self heat bonded together, one of the films being relatively thick and having resist material 12 thereon in predetermined patterns, and the other 11 film being bonded to the one film at all areas except for the resist area so as to provide a thermoplastics material film sheet of a predetermined thickness which in selected areas only forms 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. The weakened seals may be used in opening packages or for providing communication between separate compartments of a package. <IMAGE>

Description

SPECIFICATION Selectively weakened plastics sheet This invention relates in general to new and useful improvements in the manufacture of packages, and more particularly to a plastics material film sheet particularly adapted to form a package for foods and having a rupturable seal between two compartments through which one of at least two foods passes to permit mixing within the package.

This invention generally relates to the making of packages with rupturable seals of the general type disclosed in prior U.S. patent 3,608,709.

In the past, it has been necessary to adhesively bond two films together with the bond between the films in certain areas being weaker than in other areas 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 accordance with this invention it is proposed to provide 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 thicknesses of the same material and which two discreet thicknesses cannot be fused together at a later date due to the presence of the resist material. In other words, the resultant 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 purposes, except in the area of the resist material, is a single thickness material.

In 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 prior U.S. Patent 3,608,709 the two layers of the laminated 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 relates 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 proposed 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 film and integrally bonded thereto in all areas 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 the first film by means of printing 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 material films a tube is extruded and is then blown and stretched to a much larger diameter. Certain of this stretching takes place at the orientation temperature and, therefore, 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 that 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 may 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 film having 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 forming pouches for receiving medical disposables and may employ the conventional chevron seal configuration.

In addition, the film sheet may be 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 may have the proposed of preventing 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 hereinafter 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 Drawings: Figure 1 is a schematic view showing the manner in which the film sheet of this invention may be formed utilizing two prior formed films.

Figure 2 is a schematic view similar to Figure 1 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.

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 6-6 of Figure 1 and shows the seal area of the pouch.

Figure 7 is an enlarged fragmentary sectional view similar to Figure 6 and shows the ruptured seal.

Figure 8 is a fragmentary sectional 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 plan view 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 fragmentary sectional view showing a carton or the like wherein end of flaps are held together by a seal formed of the film sheet and wherein the seal may be in the form of a label.

Referring now to the drawings in detail, reference is first made to Figure 3 wherein there is illustrated 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 1 3 has the resist material 12 printed thereon by means of a suitable printing device 14. Then a second previously formed thermoplastic film sheet 1 5, which is of the same material as the sheet 1 3 or a different material which will directly fuse to the material of sheet 1 3, 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 1 6, 1 7 and then through a nip defined by two rollers 18. The film sheets 13, 1 5 thus become integrally bonded together with the resist material 12 entrapped therein as shown.

It is to be understood that the film sheet 10 becomes integral 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 different manner. The separate film sheet 1 3 is provided and the resist material 1 2 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 temperature wherein the film sheet 20 becomes integrally bonded to the film sheet 1 3. 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 1 5 and therefore, rupture of a seal may be controlled to be at a much lower force.

It is to be understood that the plastics material from which the film sheets 13, 15 and 20 are formed must be conventional thermoplastics which are self bonding. More particularly, they must be self bonding at the elevated temperature at which thermoplastic material is cast so that with particular reference to the embodiment of Figure 2, the cast film 20 will self bond to the film 1 3 to result in, for all practical purposes, a single layer sheet as shown in Figure 3. The preferred thermoplastics include polyethylene, ionomer resisns, and polyvinylchloride. Polyethylene is particularly advantageous in view of its casting temperature of 61 0-6400F while the ionomer resins have a casting temperature of 580-6000F.

It is to be understood that due to the high temperature of the cast film and the fact that the cast film, as well as the heated film 1 5 are at such a high temperature to permit self heat bonding, the surfaces of the two films in the area of the resist material 12, as well as the resist material, are heated to a sterilization temperature and thus are sterile. Accordingly, when the film 1 5 or the film 20 is ruptured in the opening of the package in the manner described hereinafter, the exposed external surfaces will be sterile.

It has been found that exceptional results have been obtained with a food additive, hydroxypropyl methyl cellulose USP 3 CPS. This material is sold by the Biddle Sawyer Corporation of New York under the trade name of "Pharmacot 603". The chief characteristics of "Pharmacot 603" are its recognition as a food additive by the Food and Drug Adminstration and the fact that it complies with all USP specifications. Further, it can be given a Certificate of Certification for Kosher food applications.

"Pharmacot 603" 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 need for the particular application. Since "Pharmacot 603" 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 contaminate food products.

Other materials that are suitable for use as a resist and which would be acceptable for use with food products are: methyl cellulose hydroxpropyl methyl cellulose phthalate, hydroxypropyl cellulose, ethyl cellulose, microcrystaline cellulose, sugar, pharmaceutical grade shellac, pharmaceutical grade waxes, carboxy methyl cellulose, zein, cross-linked polyvinyl pyrrolidone, polyvinyl acetyle phthalate, ceullulose acetate phthalate, acrylic polymers and products relating to the foregoing.

It is also pointed out here that in the formation of a typical pouch, the sheet film 10 would have a thickness on the order of 0.005 inch with the thicker film 1 3 having a thickness on the order of 0.004 inch and the thinner film having a thickness on the order of 0.001 inch.

In 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 net 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. After 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 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 remaining 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 film sheet 10, may be placed.

Referring now to Figure 8, it will be seen that the film sheet 10 is illustrtated in the formation of a pouch 35 by bonding it to another sheet material, 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 schematically 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 36. Th,e weakened area 11 of the film sheet 10 is illustrated as being of a chevron configuration and has centered therein a suitable bond 43.

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. A conventional jar 44 having a seaiing lip 45 is illustrated. 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 fusion bond and which is aligned with the resist 12 which is illustrated of a circular configuration. The lid 46 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 Figure 7.

In Figure 11 , there is illustrated a conventional 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 1 2 so that the closure 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 lable 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 the net result of the bonding of the two layers of the sheet film 10 is an integral single thickness material as opposed to a laminated material. It is further to be understood that the resist material 1 2 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.

It is also pointed out that the same film 10, and the resultant seals may be used in a multiple compartment 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 compatible with food and is either a food or a food additive and the resist and exposible film surfaces 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 damage 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 (13)

1. A thermoplastics material film sheet for forming a package having a rupturable seal, said sheet having an intended seal-forming area, said film sheet being formed of at least two films of the same thermoplastics material self heat bonded together 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. A sheet as claimed in claim 1 wherein said resist material has the characteristics 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. A sheet as claimed in claim 1 or 2 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. A sheet as claimed in claim 3 wherein said thinner film is a cast film directly cast on the thicker film and self heat bonded to said thicker film.

5. A sheet as claimed in claim 3 or 4 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.

6. A sheet as claimed in any of claims 1 to 5 wherein said weakened area extends completely around said intended seal forming area to form a complete path of weakness around said seal forming area.

7. A sheet as claimed in any of claims 1 to 6 wherein said resist material is selectively in the form of a food or a food additive.

8. A sheet as claimed in any of claims 1 to 7 wherein said resist material is hydroxypropyl methyl ceullulose USP 3 CPS.

9. A sheet as claimed in any of claims 1 to 8 wherein said sheet is 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.

10. A sheet as claimed in claim 9 wherein other edges of said sheet are bonded together to form a sealed pouch.

11. A sheet as claimed in any of claims 1 to 10 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 for forming 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 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.

13. A thermoplastics material film sheet for forming a package having a rupturable seal, substantially as hereinbefore described with reference to the accompanying drawings.