Easy opening shrink wrapper for product bundle

Abstract

A product bundle plastic film shrink wrapper and method of forming same is described. The shrink wrapper comprises a plastic film having shrink properties and formed from a blend having from about 5% to 10% polybutene-1. The plastic film forms a wrapper for the bundle by being shrunk wrapped about the bundle with a lap seal formed by overlapped film end portions of the film in a section of the wrapper. The polybutene-1 provides for the lap seal to have a shear force sufficient to hold the product bundle together and low peel force to permit separation of the overlapped film portion by sliding fingers of a user's hand in an unsealed gap of the lap seal and sliding the fingers along the lap seal whereby to easily remove the wrapper from the product bundle.

Description

TECHNICAL FIELD

The present invention relates to a product bundle plastic film shrink wrapper having a lap seal providing a means to easily remove the shrink wrap from the product bundle. The present invention also relates to the method of forming a shrink wrap about a product bundle with the easy opening lap seal feature.

BACKGROUND ART

Roofing shingles have been packaged in the past with a paper outer wrap and more recently the bundles have been secured together by a plastic outer wrap which is shrunk about the bundle. A typical example of such wrappers and its method of manufacture is described and illustrated in US Patent application 2006/0032194 A1 published on Feb. 16, 2006. Another example of shingle bundle wrappers is described in U.S. Pat. No. 5,027,946. A major problem with shrink wrap bundles of all sorts is that it is difficult to remove the plastic film shrink wrapper from the bundle as the film is under tension and there is usually no protruding portions to the shrink wrap that one can grasp to tear the shrink wrapper from the bundle. Also, the tension in the plastic wrap makes it difficult to grasp and the removal of the wrap is usually time consuming and often requiring a cutting instrument such as a knife or scissors to provide access thereto for its removal.

When wrapping a product bundle, such as asphalt roofing shingles with such shrink wrapper, there is afforded improvements over the conventional paper wrappers in that the tension in the film maintains the bundle intact particularly if it is dropped during transport. It also provides a waterproof seal for the bundle. However, the fact that the wrapper is difficult to remove results in a disadvantage which sometimes outweighs the advantages provided thereby. There is therefore a need to provide a means to open a plastic film shrink wrap product bundle which substantially overcomes the above-mentioned disadvantages of the prior art while maintaining the advantages of plastic film shrink wrappers.

SUMMARY OF THE INVENTION

It is therefore a feature of the present invention to provide a product bundle plastic film shrink wrapper which is easy to open and which substantially overcomes the above-mentioned disadvantages of the prior art.

Another feature of the present invention is to provide a product bundle plastic film shrink wrapper which is provided with a lap seal having an unsealed gap therein to permit for the insertion of a separation means which can be moved along and between a lap seal to break the seal and easily remove the shrink wrapper.

A further feature of the present invention is to provide such an unsealed gap in the lap seal which permits one or more fingers of a person's hand to be inserted therein and moved along the lap seal to separate the lap seal permitting the removal of the shrink wrapper.

Another feature of the present invention is to provide a method of forming a shrink wrapper about a product bundle with an overlap seal having means which permits the separation of the lap seal to easily remove the shrink wrapper.

According to the above features, from a broad aspect, the present invention provides a product bundle plastic film shrink wrapper which comprises a plastic film having shrink properties and formed from a blend having from about 5% to 10% polybutene-1. The plastic film forms a wrapper for the bundle by being shrunk wrapped about the bundle with a lap seal formed by overlapped film end portions of the film in a section of the wrapper. The polybutene-1 provides for the lap seal to have a shear force sufficient to hold the product bundle together and a low peel force to permit separation of the overlapped film portion by sliding a separation means between the overlapped film portions to separate the lap seal whereby to easily remove the wrapper from the product bundle.

According to a further broad aspect of the present invention there is provided a method of forming a plastic film shrink wrap about a product bundle. The method comprises wrapping the product bundle with a plastic film having shrink properties and formed from a blend having therein from about 5% to 10% polybutene-1. The film has overlapped film portions on an underside thereof. The wrapped bundle is then subjected to a heat source to shrink the polymer film about the product bundle. The overlapped film portions of the film forms a lap seal when subjected to heat. The blend creates a lap seal having a shear force sufficient to hold the product bundle together and a low peel force to permit separation of the lap seal by sliding a separation means between the overlapped film portions whereby to easily remove the shrink wrap from the product bundle.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view showing a product bundle, herein an asphalt shingle bundle which is shrink wrapped with a plastic film which forms a longitudinal lap seal along at least a portion of a face of the bundle;

FIG. 2 is a fragmented perspective view showing how the lap seal is separated whereby to remove the shrink film wrapper from the bundle;

FIG. 3 is an enlarged plan view showing the unsealed gap formed in the longitudinal lap seal;

FIG. 4A to 4C are sequence illustrations, in perspective, showing how the plastic film sheet is wrapped around the bundle prior to being subjected to heat treatment; and

FIG. 4D is an end view showing the product bundle being subjected to heat to shrink wrap the plastic film sheet thereabout.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1 there is shown generally at 10 a product bundle shrink wrapped with a film formed in accordance with the invention. As herein shown the product bundle is comprised of a plurality of asphalt roofing shingles 11 stacked one on top of the other to form a substantially rectangular bundle. A plastic film shrink wrapper 12 is secured about the bundle with the wrapper having a longitudinal lap seal 13 formed at least along the longitudinal axis of the bundle and herein along a longitudinal face 14 thereof. The lap seal is formed by overlapping end portions of a plastic film sheet prior to the sheet being shrunk wrapped about the bundle. Accordingly, the asphalt shingle bundle is rigidly retained in its bundle form by the plastic film shrink wrapper 12 and seals the bundle from the elements.

The plastic film wrapper is formed from a plastic film having shrink properties and blended with from about 5% to 10% polybutene-1. The plastic film may be LDPE (Low Density Polyethylene), and LLDPE (Linear Low Density Polyethylene) whereby the lap seal 13 becomes an easy to open seal as the polybutene-1 and the polyethylene are incompatible thus resulting in an easy to open seal. The film can be extruded as a mono or multi-layer film. If a multi-layer film is produced, the polybutene-1 can be added in all layers or in one of the outer skin layers. As herein illustrated, the polybutene-1 is blended solely in the inner layer, for purposes of economics. It has been found that by adding the polybutene-1 the lap seal 13 provides a good shear force to hold a packaged bundle together but a low peel force to peel it open easily.

Measurements and testing of a product bundle formed with the plastic film blend as above described show that the shear force of the overlapped seal, formed as a 1″ wide seal, to be 6 lbs. Regular film has over 6 lbs of shear force and can have a thickness ranging from 1.75 mil to 3 mil and may be a blown film or cast film. The peel force of the lap seal was also tested and measured at 1.6 lbs making it easy to open as compared to a regular shrink film which has over 6 lbs peel force and tests have demonstrated that such films deform and tear easily.

In order to facilitate the separation of the longitudinal lap seal 13 there is provided an unsealed gap 15 at a convenient location along the lap seal 13. This unsealed gap provides for the insertion of a separation means which may be constituted by several elements and as shown in FIG. 2 it is constituted by a user person inserting two or three fingers 16′ of his hand 16 into the unsealed gap 15 and sliding the fingers along the longer side of the lap seal in the direction of arrow 17 or on both sides of the gap as also indicated by arrow 18 whereby to break or separate the longitudinal seal providing for the wrapper to be easily removed. Accordingly no special tools are required to remove the shrink wrapper such as a utility knife which is now used in the trade and which also marks and damages the shrunk wrapped product which may be a bundle of plastic water bottles, oil cans or other beverage products which may be in cardboard containers, etc.

As shown in FIG. 2 the plastic film wrapper 12 may be formed by a film which is printed with a color, whereby to render the film opaque, and in such a wrapper it may be convenient to provide a window area 19 which is maintained clear whereby to view the product wrapped therein and as herein shown the colored texture 20 of the asphalt shingles 11. Printed matter 21 may also be provided on the shrink wrapper either by printing the film prior to packaging or after packaging. Printed matter may also be provided adjacent the unsealed gap 15 as shown in FIG. 3 whereby to provide instructions pertaining to this unsealed gap to permit easy separation of the lap seal 13 and the removal of the shrink wrapper.

With reference now to FIGS. 4A to 4D there will be described how the plastic film shrink wrapper is formed about a product bundle such as the asphalt shingle bundle 11 as herein illustrated. Firstly, a plastic film formed from a blend as previously described is provided in a rectangular sheet form, as shown at 25, and dimensioned to overlap the ends 11′ of the bundle and sufficiently wide whereby when wrapped and shrunk about the bundle as shown by arrows 26 and 27 forms a lap seal 13. The unsealed gap 15 is formed by a strip of release varnish 28 (which usually contains silicone or wax) being applied at a predetermined position on the sheet 25. The varnish strip 28 may be about 2 to 3 inches wide. The lap seal 13 is herein shown as extending longitudinally of the bundle. The release varnish prevents the overlapped film sheet from adhering in the varnish area of the lap seal thus providing the unsealed gap 15. Once the bundle is wrapped as shown in FIG. 4C it is then inverted whereby the lap seal 13 is disposed under the bundle which can then be conveyed through a heat tunnel or other heat source environment to apply heat to the bundle, such as illustrated by the radiant lines 29, all about the bundle 11. As herein shown the longitudinal seal also extending to end wall portions 13′ of the bundle.

EXAMPLE

A 5 layer, multilayer film was formed in accordance with the present invention with the following characteristics

	Layer
	ratio (%)	Resin Blend
Inner Layer	36	LLDPE: 39% + LDPE: 45% + polybutene-
		1: 8% + UVI: 4.5% + color
		M/B: 3.5%
Inner tie layer	10	LLDPE: 62% + LDPE: 30% + UVI:
		4.5% + color M/B: 3.5%
Core	8	LDPE: 95.5% + UVI: 4.5%
Outer tie layer	10	Same as inner tie layer
Outer layer	36	LLDPE: 47% + LDPE: 45% + UVI:
		4.5% + color M/B: 3.5%

The multilayer film can easily be run as mono, co-ex, or 3-layer.

It is within the ambit of the present invention to cover any obvious modifications of the preferred embodiment described herein, provided such modifications fall within the scope of the appended claims.

Claims

1. A product bundle plastic film shrink wrapper comprising a plastic film having shrink properties and formed from a blend having from about 5% to 10% polybutene-1, said plastic film forming a wrapper for said bundle by being shrunk wrapped about said bundle with a lap seal formed by overlapped film end portions of said plastic film in a section of said wrapper, said polybutene-1 providing for said lap seal to have a shear force sufficient to hold the product bundle together and sufficient to permit separation of said overlapped film portion by sliding a separation means between said overlapped film end portions to separate said lap seal whereby to easily remove said wrapper from said product bundle.

2. A product bundle plastic film wrapper as claimed in claim 1 wherein said lap seal is further provided with an unsealed gap to provide for the insertion of said separation means.

3. A product bundle plastic film wrapper as claimed in claim 2 wherein said separation means is constituted by the fingers of a person's hand to be inserted in said gap and slid along said lap seal to separate said seal of said overlapped film end portion.

4. A product bundle plastic film wrapper as claimed in claim 2 wherein said unsealed gap is formed by a release varnish disposed over said plastic film and extending transversely of said overlapped film end portions.

5. A product bundle plastic film wrapper as claimed in claim 1 wherein said product bundle is a bundle of asphalt shingles.

6. A product bundle plastic film wrapper as claimed in claim 1 wherein said plastic film is a multi-layered blend of LDPE (Low Density Polyethylene), LLDPE (Linear Low Density Polyethylene) and said polybutene-1 as an inner layer.

7. A product bundle plastic film wrapper as claimed in claim 1 wherein said plastic film is a mono layer of polyethylene blended with said polybutene-1.

8. A product bundle plastic film wrapper as claimed in claim 1 wherein said plastic film has a thickness of from about 1.75 mil to about 3 mil.

9. A product bundle plastic film wrapper as claimed in claim 1 wherein said lap seal has a low peel force of less than 6 lbs for a one inch wide lap seal and preferably 1.6 lbs.

10. A product bundle plastic film wrapper as claimed in claim 4 wherein said release varnish is disposed over said plastic film of one of said overlapped film portions in the area of said lap seal to prevent sealing of said lap seal in the area of said varnish.

11. A product bundle plastic film wrapper as claimed in claim 4 wherein said unsealed gap is 2 to 3 inches wide.

12. A product bundle plastic film wrapper as claimed in claim 1 wherein said plastic film is a clear plastic film having printed matter thereon and a clear window area for product viewing.

13. A method of forming a plastic film shrink wrap about a product bundle comprising the steps of:

i) wrapping said product bundle with a plastic film having shrink properties and formed from a blend having therein from about 5% to 10% polybutene-1, said film having overlapped film end portions on an underside thereof;

ii) subjecting said wrapped bundle to a heat environment to shrink said plastic film about said product bundle, said overlapped film end portions of said film forming a lap seal when subjected to said heat environment, said polybutene-1 in said blend creating said lap seal to have a shear force sufficient to hold said product bundle together and a low peel force to permit separation of said lap seal by sliding a separation means between said overlapped film end portions whereby to separate said lap seal to easily remove said shrink wrap from said product bundle.

14. A method as claimed in claim 13 wherein there is further provided the step of applying a strip of a release substance coating across one of said overlapped film end portions prior to step (ii) to form an unsealed gap in said lap seal to provide for the insertion of said separation means in said gap and to slide same along said lap seal to separate said overlapped film end portions or a section thereof.

15. A method as claimed in claim 14 wherein said separation means is constituted by the fingers of a person's hand inserted into said unsealed gap and slid along said lap seal to separate said overlapped film end portions, said product bundle being a rectangular asphalt shingles bundle, said lap seal extending longitudinally on an underside of said bundle.

16. A method as claimed in claim 14 wherein said plastic film is a clear plastic film, and wherein there is further provided the step of printing a color and/or matter on said clear plastic film while leaving a clear film window area for product viewing.

17. A method as claimed in claim 13 wherein said plastic film is a mono layer or multilayer blown film or cast film formed from a blend of LDPE (Low Density Polyethylene) and LLDPE (Linear Low Density Polyethylene) and a polybutene-1 polymer on an inner surface thereof to cause said lap seal to form an easy-to-open seal when subjected to said step (ii).