GB2281282A - Tearing a polymeric film or bag - Google Patents

Abstract

An article such as a bag 10 made from a polymeric film such as polyethylene includes a second polymeric film in the form of a strip 13 adhered to the first polymeric film. The strip 13 may be made from a mono-oriented polymeric film such as mono-oriented polyethylene in which a tear will propagate in a single, known direction. When the two films are coupled together the tear still tends to propagate in the single direction. Instead of using a tape a laminate may be used, one entire or part layer of which is a mono-oriented polymeric film. A cub or notch may define the start point of the tear line. <IMAGE>

Description

ARTICLES MADE FROM POLYMERIC FILM This invention relates to articles made from polymeric films. Such articles may be bags or envelopes and polymeric films have many advantages over known paper products because they are tough, water resistant and offer greater protection to the bag contents.

However the toughness of the materials often makes the bags difficult to open without using a separate cutting device or a special construction.

One such special construction involves the incorporation into the package of a tear strip which will cut through the package wall when pulled. This however requires special equipment to insert the tear strip and can require significant force to cause the strip to tear through the bag wall.

Another approach has been to weaken the bag wall by cutting through or by crushing the bag wall and providing a pull tab to enable tearing of the wall in a predetermined location. Again special manufacturing equipment is needed and also the bag wall is weakened.

A further known means is to make cuts in the strong layer and then cover the cuts with a heat seal layer. Again specialised equipment is needed in manufacture and points of weakness are introduced into the bag wall. It is also known to provide perforations but, although this requires only a minor modification to existing equipment, it weakens the wall and allows the inside of the bag to become contaminated.

According to a first aspect of the present invention there is provided an article made from polymeric film having at least one portion of a second polymeric film adhered thereto, said second polymeric film being less tear resistant than the first film.

Preferably the or each portion of second polymeric film is in the form of an elongate strip.

In further preferred arrangements the second polymeric film is generally mono-axially oriented whereby a tear will propagate in one known direction, namely the elongate direction of the strip.

The first polymeric film may be chosen from the group comprising polyethylene, polypropylene, and their co-polymers, polyamide and nylon or indeed laminations of any of these. The second polymeric film may be chosen from the group comprising monooriented polyethylene and mono-oriented polypropylene and their co-polymers, mono-oriented polyvinyl chloride, mono-oriented polyvinylidene chloride and mono-oriented polystyrene. Ideally the second polymeric film is in the form of an adhesive tape. It is possible, however, for the first and second polymeric films to be laminated together across their entire area.

In preferred arrangements the article is in the form of a bag, said second polymeric film providing means for opening the bag. The second polymeric film may extend completely along an edge of the bag on both opposed faces of the bag.

Alternatively the second polymeric film may extend only over a fixed distance in a given location so as to produce an opening of a predetermined shape and/or size in a predetermined location.

Such bags can be opened easily, for example by the finger tips. Also it is possible to make such articles on standard bag making machines with little or no modification. Also the integrity of the bag remains until it is opened because the walls of the bag are not weakened by cuts/perforations for example.

According to a second aspect of the present invention there is provided a method of making an article comprising the step of adhering one or more portions of a second polymeric film to a first polymeric film, said second polymeric film being less tear resistant than the first polymeric film.

Embodiments of the invention will now be described in more detail. The description makes reference to the accompanying diagrammatic drawings in which: Figure 1 shows a bag according to the present invention; Figure 2 shows another bag according to the present invention; Figure 3 shows a further bag according to the present invention; and Figure 4 shows a series of bags according to the present invention.

In Figure 1 there is shown a simple rectangular bag 10 having top and bottom closing seams 11,12 and being made from a first polymeric material.

There is also provided a strip 13 which is made from a second polymeric material and which is adhered to the first polymeric material adjacent the top seam 11. A similar strip is provided on the back of the bag, also adjacent the top seam 11.

It has been found that if a polymeric film which will tear easily is adhered to a tear resistant polymeric film then the combined polymeric film will also tear easily. Also, if the polymeric film which is easily torn is mono-axially oriented then any tear will propagate in one known direction, i.e., the mono-axial direction.

Examples of suitable tear resistant films are polyethylene, polypropylene, polyamide and nylon or even laminations of these perhaps even with a barrier material between. Examples of the suitable polymeric films with lower tear resistance are mono-oriented polyethylene and mono-oriented polypropylene and polymers thereof, polyvinyl chloride, polyvinylidene chloride and polystyrene.

Returning to the construction of Figure 1 the main portion of the bag 10 is made from a more tear resistant polymeric film. The strip 13 is made from a mono-axially oriented polymeric film. The strip 13 may be applied to the bag 10 before or after filling.

The strip 13 can be in the form of an adhesive tape which is applied to the bag 10 or as a plain strip with adhesive being applied separately. Also the strip 13 could be located internally or externally with, preferably in both cases, an indication to tear along the strip.

In Figure 1 the strip is such that the entire top seam 11 is removed. In Figure 2 however the strip is provided so as to open only a corner of the bag 10.

Such an arrangement may be more convenient for certain items such as frozen peas.

In another arrangement which is not shown a strip of tearable polymeric film could be located so as to create a simple opening in one face of the bag.

In practical examples, bags of low density polyethylene film about 30 microns thick have had strips of adhesive tape sold under the Registered Trademark SELLOTAPE applied to them. Satisfactory results were obtained although the adhesive tape is not truly mono-axially oriented.

Another application of the idea is shown in Figure 3. The bag 10 has a foldover flap 14 which is sealed to the bag using adhesive line 15. A second adhesive line 16 is provided parallel to the first line 15 with the strip 13 disposed between them. In this particular situation the second adhesive line is covered by a release strip (not shown).

Goods, such as for mail order companies, can be sent in the package and to open the package a tear is made along the strip 13. To return goods in the same package the release strip is removed from the second adhesive line 16 which can then be used to attach the flap 14 to the bag 10.

In figure 4 there is shown a series of bags 10a to 10d. The strip 13 is applied front and back in the form of a label area which spans the area to be cut to separate the individual bags. By having the strips 13 overlap it can be guaranteed that the strip 13 coincides with the edge of the first polymeric material. This is clearly shown with bag 10d. Such a construction may be ideal for "form-fill-seal" bags for e.g. frozen foods, confectionery, snack foods.

Whilst much of the above description has involved the use of the strip in opening bags, it will be appreciated that the strip can be used in other applications where a tough polymeric film needs to be torn.

Also, it may sometimes be desirable to form during production a small starting tear or notch in the leading edge of the portion of the bag to be torn.

Such a formation may be particularly useful when the strip 13 is a less well mono-oriented polymeric film.

The tear need only be lmm long but could be longer or shorter. In most applications, however, it is important that the tear does not extend into the sealed portion of the bag. For example it may be formed in the skirt portion of a "skirt weld" used to seal the bag.

Although the above description relates only to a strip of mono-oriented film applied to a more tearresistant film, it is also possible to make articles out of a laminated film comprising mono-oriented film on one side and a tear-resistant film on the other.

Again a starting notch or tear could be provided to assist opening in the correct location. The orientation of the mono-oriented film in the end product could be such that an angled tear is produced in a bag for example whereby the corner of the bag can be removed.

Claims (14)

1. An article made from polymeric film having at least one portion of a second polymeric film adhered thereto, said second polymeric film being less tear resistant than the first film.

2. An article as claimed in claim 1 wherein the or each portion of second polymeric film is in the form of an elongate strip.

3. An article as claimed in claim 1 wherein the first and second polymeric films are laminated together substantially across their entire area.

4. An article as claimed in any one of claims 1 to 3 wherein the second polymeric film is generally mono-axially oriented whereby a tear will propagate in one known direction.

5. An article as claimed in claim 4 wherein the first polymeric film is chosen from the group comprising polyethylene, polypropylene, and their co-polymers polyamide and nylon or laminations of any of these.

6. An article as claimed in claim 4 or claim 5 wherein the second polymeric film is chosen from the group comprising mono-oriented polyethylene and mono-oriented polypropylene and their co polymers, mono-oriented polyvinyl chloride, mono-oriented polyvinylidene chloride and mono oriented polystyrene.

7. An article as claimed in claim 6 wherein the second polymeric film is in the form of an adhesive tape.

8. An article as claimed in any one of claims 1 to 7 wherein the article is a bag and the second polymeric film constitutes means for opening the bag.

9. An article as claimed in claim 8 wherein the second polymeric film extends completely along an edge of the bag on both opposed faces of the bag.

10. An article as claimed in claim 8 wherein the second polymeric film may extend only over a fixed distance in a given location so as to produce an opening of a predetermined shape and/or size in a predetermined location.

11. An article as claimed in any one of claims 1 to 10 wherein a small cut or notch is provided in the article in the portion of superimposed first and second polymeric films.

12. A method of making an article comprising the step of adhering one or more portions of a second polymeric film to a first polymeric film, said second polymeric film being less tear resistant than the first polymeric film.

13. A method as claimed in claim 12 wherein the second polymeric film is in the form of an adhesive strip which is applied to the first polymeric film.

14. A method as claimed in claim 12 wherein the two films are in the form of sheets laminated together.