Technical field

[0001 ] The present invention relates generally to a pre stretched plastic stretch film and a method for production thereof.

Background art

[0002] Pre stretched film is used in various industries for instance for packaging of goods. A pre stretch film could be applied either manually or by using an automatic equipment. For example, goods on a pallet may be wrapped with pre stretched film in order to secure the goods on the pallet during transportation.

[0003] Pre stretched film is created by stretching stretch film close to its ultimate breaking point, and then either feed this pre stretched film onto core tubes or onto a transitional roll for creating a coreless pre stretch film. These both types are then shipped or ready for final use. This method implies that the pre stretch film does not require as much stretching energy when finally applied on an item compared to a standard stretch film, in order for the pre stretch film to achieve the same wrapping force as a standard stretch film. This is one of the main reasons why pre- stretched films are popular for packaging goods, and in particular for hand wrap. In fact, in using pre stretched film, hand applications can create the same load stability as machine applications.

[0004] It has been found that the edges of many types of plastic film play a very important role when it comes to the overall strength of the film and the ease of handling thereof. In order to achieve a pre stretched plastic stretch film with reinforcing longitudinal bands in the edges, ordinary plastic stretch film with the outermost portions of the film folded over longitudinally have been fed into pre stretch machinery equipment. However, this causes the overall width of the final product/the pre stretched plastic stretch film to be smaller than the width of the stretch film originally fed into the pre stretch machinery equipment. Furthermore, by using this method it is only the outermost portions of the final product/pre stretch film which is reinforced. Reinforcing other parts of a pre stretch film, instead or in addition to the outermost portions of the film, would definitely add an added advantage as such a pre stretch film would exhibit a significantly higher strength than a film with only reinforced outermost portions.

[0005] Furthermore, many standard pre stretched plastic stretch films are not rigid enough for some application areas.

[0006] Furthermore, by feeding ordinary plastic stretch film with the outermost portions of the film folded over longitudinally into pre stretch machinery equipment, implies that the reinforced areas will be twice as thick as the non-reinforced areas. For some application areas the reinforced areas should preferably exhibit a thickness greater than twice the thickness of the non-reinforced areas, and for some application areas the reinforced areas should exhibit a thickness smaller than twice the thickness of the non-reinforced areas.

[0007] It therefore exists a need for a pre stretched plastic stretch film which does not have the outermost portions of the film folded over longitudinally for reinforcing purposes, which has its outermost portions reinforced and/or other parts reinforced, which is more rigid than standard pre stretched plastic stretch films, and which could exhibit a variable thickness of the reinforced areas compared to the thickness of the non-reinforced areas, i.e. which does not always have reinforced areas twice as thick as the non-reinforced areas.

Summary of invention

[0008] An object of the present invention is thus to accomplish a pre stretched plastic stretch film and a method for production thereof, wherein the pre stretched plastic stretch film does not have the outermost portions of the film folded over longitudinally for reinforcing purposes, has its outermost portions reinforced and/or other parts reinforced, is more rigid than standard pre stretched plastic stretch films, and could exhibit a variable thickness of the reinforced areas compared to the thickness of the non-reinforced areas, i.e. which does not always have reinforced areas twice as thick as the non-reinforced areas. [0009] The inventors searched for a possibility to achieve above mentioned characteristics of a pre stretched plastic stretch film. The possibility to alter a pre stretch machinery for achieving the requested properties was examined, unfortunately with no success.

[0010] The alteration of a pre stretch machinery was also combined with using different types of plastic stretch films in order to achieve the requested properties. These tests were unfortunately also not successful.

[0011 ] In patent application number EP2857183 a method of producing an innovative plastic stretch film and the innovative stretch film itself is presented. The inventors tested to feed the now mentioned innovative stretch film into a pre stretch machinery.

[0012] Prior testing a stretch film according to the above mentioned patent application specifically into a pre stretch machinery, the inventors did not know if the stretch film would result in a final product/pre stretched plastic stretch film where the reinforcing longitudinal bands and the rest of the film would maintain the same thickness ratio versus each other as in the original stretch film fed into the pre stretch machinery. However, the thickness ratio between the reinforcing longitudinal bands and the rest of the film in the final product/pre stretched plastic stretch film proved to be the same as the thickness ratio between the reinforcing longitudinal bands and the rest of the film in the original stretch film fed into the pre stretch machinery. Thus the requested technical result was eventually achieved.

[0013] The reason why mentioned thickness ratios for the reinforced areas of the pre stretched plastic stretch film compared to the non-reinforced areas of the pre stretched plastic stretch film can be achieved is due to the very specific characteristics of the above mentioned innovative stretch film in combination with how a pre stretch machinery equipment processes the innovative stretch film. The result is described in the following text.

[0014] According to one aspect, the invention concerns a method for creating a pre stretched plastic stretch film, comprising the step of feeding a plastic stretch film from an off-line roller to a first roller of a pre stretch machinery equipment comprising the first roller for receiving the fed plastic stretch film and a second roller. The plastic stretch film comprises a reinforced longitudinal band having a thickness thicker than a main portion of the plastic stretch film. The reinforced longitudinal band is integral with the main portion of the plastic stretch film in a single ply. The method further comprises the step of feeding the plastic stretch film from the first roller to the second roller. The circumferential velocity of the second roller is greater than the circumferential velocity of the first roller thereby pre stretching the plastic stretch film in the pre stretch machinery equipment. The pre stretching is conducted so that a pre stretched plastic stretch film is formed comprising a final reinforced longitudinal band formed from the reinforced longitudinal band, and the pre stretched plastic stretch film comprising a final main portion formed from the main portion. The final reinforced longitudinal band is thicker than the final main portion. The final reinforced longitudinal band is integral with the final main portion of the pre stretched plastic stretch film in a single ply.

[0015] An advantage with the solution is that it permits the created pre stretch plastic stretch film to: be reinforced thanks to the final reinforced longitudinal band by having its outermost portions reinforced and/or other parts reinforced, not have the outermost portions folded over longitudinally for reinforcing purposes, be more rigid than standard pre stretched plastic stretch films, exhibit a variable thickness of the final reinforced longitudinal band compared to the thickness of the non- reinforced areas, i.e. the final reinforced longitudinal band does not always have a thickness twice as thick as the non-reinforced areas. A further advantage is that the described pre stretched plastic stretch film could comprise non-reinforced areas having a smaller thickness compared to standard pre stretched plastic stretch film, resulting in less material used and consequently being less costly to manufacture and less environmentally unfriendly.

[0016] The above method may be configured according to different optional embodiments. For example, the method may comprise the step of feeding the created pre stretched plastic stretch film from the second roller onto a core tube for creating a pre stretched plastic stretch film applied on a core tube. [0017] An advantage with the method, by feeding the created pre stretched plastic stretch film from the second roller onto a core tube for creating a pre stretched plastic stretch film applied on a core tube, is that the final product can easily be removed from the pre stretch machinery equipment and moved/shipped to the site where the pre stretched plastic stretch film is to be used.

[0018] According to an embodiment of the invention, the method may comprise the step of feeding the created pre stretched plastic stretch film from the second roller onto a transitional roller for creating a coreless pre stretched plastic stretch film. The coreless pre stretched plastic stretch film is subsequently removed from the transitional roller.

[0019] An advantage with the method, by feeding the created pre stretched plastic stretch film from the second roller onto a transitional roller for creating a coreless pre stretched plastic stretch film, wherein the coreless pre stretched plastic stretch film is subsequently removed from the transitional roller, is that the final product can easily be removed from the pre stretch machinery equipment and moved/shipped to the site where the pre stretched plastic stretch film is to be used. An additional advantage with the method is that without a core the weight is decreased, which implies that the final product requires less material and less energy/fuel in order to be transferred to its final destination. This results in financial and environmental benefits.

[0020] According to an embodiment of the invention, the method may be preceded by the step of adhering the plastic stretch film onto the first roller and further onto the second roller permitting the plastic stretch film to be fed through the pre stretch machinery equipment.

[0021] An advantage with the method, by preceding the method by adhering the plastic stretch film onto the first roller and further onto the second roller, is that it permits the plastic stretch film to be fed through the pre stretch machinery equipment. Otherwise the plastic stretch film could slip on the first and the second roller, resulting in the machinery and the method to malfunction. [0022] According to an embodiment of the invention, the reinforced longitudinal band of the plastic stretch film may have a thickness which is 3μηι - 50μηι thicker than the main portion.

[0023] An advantage with the method, wherein the reinforced longitudinal band having a thickness which is 3μηπ - 50μηη thicker than the main portion, is that the thickness of the reinforced longitudinal band can vary within a rather large interval. This will result in various advantages for the final product when the plastic stretch film has been fed through the pre stretch machinery equipment.

[0024] According to an embodiment of the invention, the thickness of the final reinforced longitudinal band may be 3pm-50pm thicker than the final main portion.

[0025] An advantage, in that the thickness of the final reinforced longitudinal band is 3pm-50pm thicker than the final main portion, is that the thickness of the final reinforced longitudinal band can vary within a rather large interval. Another advantage is that the final reinforced longitudinal band exhibits a variable thickness compared to the thickness of the non-reinforced areas, i.e. the final reinforced longitudinal band does not always have a thickness twice as thick as the non-reinforced areas. A further advantage is that the described pre stretched plastic stretch film could comprise non-reinforced areas having a smaller thickness compared to standard pre stretched plastic stretch film, resulting in less material used and consequently being less costly to manufacture and less environmentally unfriendly.

[0026] According to an embodiment of the invention, the thickness of the final reinforced longitudinal band is 3pm-25pm thicker than the final main portion.

[0027] An advantage, in that the thickness of the final reinforced longitudinal band is 3μιτι-25μιη thicker than the final main portion, the thickness of the final reinforced longitudinal band can vary within an interval suitable for many

application areas. Another advantage is that the final reinforced longitudinal band exhibits a variable thickness compared to the thickness of the non-reinforced areas, i.e. the final reinforced longitudinal band does not always have a thickness twice as thick as the non-reinforced areas. A further advantage is that the described pre stretched plastic stretch film could comprise non-reinforced areas having a smaller thickness compared to standard pre stretched plastic stretch film, resulting in less material used and consequently being less costly to manufacture and less environmentally unfriendly.

[0028] According to an embodiment of the invention, the final reinforced longitudinal band forms a reinforced edge of the pre stretched plastic stretch film.

[0029] An advantage, in that the final reinforced longitudinal band forms a reinforced edge of the pre stretched plastic stretch film, is that such a reinforced edge protects the rest of the pre stretched plastic stretch film from easily being torn.

[0030] According to an embodiment of the invention, the pre stretched plastic stretch film created may be used for wrapping pallets.

[0031] An advantage, in that the pre stretched plastic stretch film may be used for packaging agricultural produce, is that the wrapping will be more economical, more environmentally friendly and at the same time stronger than standard pre stretched plastic stretch film.

[0032] According to an embodiment of the invention, the pre stretched plastic stretch film created may be used for packaging agricultural produce.

[0033] An advantage, in that the pre stretched plastic stretch film may be used for wrapping pallets, is that the wrapping will be more economical, more

environmentally friendly and at the same time stronger than standard pre stretched plastic stretch film.

[0034] A suitable pre stretch machinery for achieving the requested technical result can also comprise more than two rollers having different circumferential velocities. The pre stretch machinery can for instance pre stretch the plastic stretch film by feeding the film via a first, a second and a third roller, all having different circumferential velocities. [0035] In physics, the circumferential velocity of a rotating body is defined as the rate of change of circumferential displacement, and is a vector quantity that specifies the circumferential velocity of an object and the axis about which the object is rotating. This speed can be measured in the SI unit of circumferential velocity, radians per second, or in terms of degrees per second, degrees per hour, etc. The direction of the circumferential velocity vector is perpendicular to the plane of rotation, in a direction that is usually specified by the right-hand rule.

[0036] Furthermore, in order for two or more different rollers having different circumferential velocities all rollers could be connected to the same motor providing the same rotational speed to the rollers. Furthermore, if the diameters of these rollers are different, different circumferential velocities of the different rollers can be achieved.

[0037] A plastic stretch film could have more than one reinforced longitudinal band and consequently the created pre stretched plastic stretch film could have more than one final reinforced longitudinal band.

[0038] Different final reinforced longitudinal bands within the same pre stretched plastic stretch film could furthermore have different thicknesses compared to each other.

[0039] The final main portion may be as thin as 5pm, or slightly thinner. This implies that the final reinforced longitudinal band may be as thin as 8pm, or slightly thinner.

[0040] Said off-line roller is, prior being connected to and for having its content fed into, the here described machinery for creating a pre stretched plastic stretch film, an independent roller comprising the innovative plastic stretch film resulting from the method described in patent application number EP2857183. The off-line roller is thus constituting an independent storage in between the first machinery, i.e. the plastic stretch film machinery, and the second machinery, i.e. the pre stretch plastic stretch film machinery. Brief description of drawings

[0041] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[0042] Fig. 1 shows a plastic stretch film in a view from above.

[0043] Fig. 2 shows a pre stretched plastic stretch film in a view from above.

[0044] Fig. 3 shows a pre stretched plastic stretch film in a cross sectional front view.

[0045] Fig. 4. a shows a pre stretch machinery equipment in a cross sectional side view.

[0046] Fig. 4.b shows a cross sectional side view of a sub part of a pre stretch machinery equipment and a core tube with a pre stretched plastic stretch film applied on the core tube.

[0047] Fig. 4.c shows a cross sectional side view of a sub part of a pre stretch machinery equipment and a transitional roller with a coreless pre stretched plastic stretch film applied on the transitional roller.

Description of embodiments

[0048] In the following, a detailed description of a pre stretched plastic stretch film and a method for production thereof is provided.

[0049] Fig. 1 shows a plastic stretch film 2 according to an embodiment of the invention, made up of several reinforced longitudinal bands 6 integral with the main portion 7 of the plastic stretch film 2 in a single ply.

[0050] Fig. 2 shows a pre stretched plastic stretch film 1 according to an embodiment of the invention, made up of several final reinforced longitudinal bands 8 integral with the final main portion 9 of the pre stretched plastic stretch film 1 in a single ply. [0051] Fig. 3 shows a pre stretched plastic stretch film 1 according to an embodiment of the invention, made up of several final reinforced longitudinal bands 8 integral with the final main portion 9 of the pre stretched plastic stretch film 1 in a single ply. The final reinforced longitudinal band 8 is thicker than the final main portion 9. The final reinforced longitudinal bands 8 form reinforced edges 14 of the pre stretched plastic stretch film 1.

[0052] Fig. 4. a shows a pre stretch machinery equipment 4 comprising a first roller 3 for receiving a plastic stretch film 2 from an off-line roller 20 and a second roller 5. The plastic stretch film 2 is fed from an off-line roller 20 to the first roller 3 and further to the second roller 5. The circumferential velocity of the second roller 5 is greater than the circumferential velocity of the first roller 3 thereby pre stretching the plastic stretch film 2 in the pre stretch machinery equipment 4. The pre stretching is conducted so that a pre stretched plastic stretch film 1 is formed.

[0053] Fig. 4.b shows a sub part of a pre stretch machinery equipment 4. The created pre stretched plastic stretch film 1 is fed onto a core tube 10 for creating a pre stretched plastic stretch film applied on a core tube 1 1.

[0054] Fig. 4.c. shows a sub part of a pre stretch machinery equipment 4. The created pre stretched plastic stretch film 1 is fed onto a transitional roller 12 for creating a coreless pre stretched plastic stretch film 13. The coreless pre stretched plastic stretch film 13 can subsequently be removed from the transitional roller 12.