Field of the Invention

[0001] The invention pertains to packaging materials for the protection of articles such as steel coils.

Background of the Invention

[0002] Products that are prone to corrosion or damage, such as steel coils, are wrapped to protect them from scratching, abrasion, mechanical damage and moisture penetration during shipping and storage. The packaging material used for this purpose is typically a flexible sheet material in strip form that is wound around the product in an overlapping manner. Such strip products are commonly applied by automated packaging machines, though they can also be applied manually.

[0003] In the prior art, the use of such strip packaging material also requires the use of an outer wrap, commonly a stretch wrap plastic, which is applied over the wound strip material to bond and hold its strips together. Without this outer wrap, the windings of the strip material would be prone to slippage, leaving gaps between the strips that would allow moisture and air to corrode the unprotected surfaces and make the wrapped product susceptible to handling damage. The outer layer helps to prevent this, but involves an additional packaging step and higher material cost.

Summary of Invention

[0004] The invention is a packaging material, suitable for application to a coil of steel or other object, comprising a strip material that bonds or adheres to itself, thus avoiding slippage of the windings of

the strip material and eliminating the need for an outer wrapper as used in the prior art.

[0005] According to one embodiment of the invention, there is provided a strip of packaging material for wrapping an object, the strip being water impermeable and having an upper surface, a lower surface and two longitudinal edges, wherein said lower surface is adapted to releasably bond to said upper surface when the strip is applied to said object in overlapping manner such that a portion of the lower surface is in contact with the upper surface and the lower surface is towards said object.

[0006] According to a further embodiment of the invention, there is provided a strip of packaging material for wrapping an object, the strip being water impermeable and having an upper surface, a lower surface and first and second longitudinal edges, the strip comprising a first bonding band on the upper surface adjacent to the first longitudinal edge and a second bonding band on the lower surface adjacent to the second longitudinal edge, the first and second bands being adapted to releasably bond to each other when the strip is applied to the object in overlapping manner such that the first and second bands are in contact with each other and the lower surface is towards the object.

[0007] According to a further embodiment of the invention, there is provided a strip of packaging material for wrapping an object, the strip being water impermeable and having an upper surface, a lower surface and two longitudinal edges, the strip comprising a bonding band on the upper surface adjacent to one the longitudinal edge, the band being adapted to releasably bond to the lower surface when the strip is applied to the object in overlapping manner such that the band is in contact with the lower surface and the lower surface is towards the object.

[0008] According to further embodiments of the invention, there are provided methods for wrapping an object using a strip of the packaging material of the invention, comprising the step of applying the strip to the object in an overlapping manner such that a portion of the lower surface of the strip is in contact with the upper surface and the lower surface is towards the object.

Brief Description of the Drawings

[0009] Fig. l(a) is a cross-sectional view across the width of a strip of packaging material according to a first embodiment of the invention.

[0010] Fig. l(b) shows an alternative configuration of the embodiment of Fig. l(a).

[0011] Fig. l(c) shows a second alternative configuration of the embodiment of Fig. l(a).

[0012] Fig. l(d) shows a third alternative configuration of the embodiment of Fig 1 (a).

[0013] Fig. l(e) shows a fourth alternative configuration of the embodiment of Fig. l(a).

[0014] Fig. 2(a) is a cross-sectional view across the width of a strip of packaging material according to a second embodiment of the invention.

[0015] Fig. 2(b) is an alternative configuration of the embodiment of

Fig. 2(a).

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[0016] Fig. 3(a) is a cross-sectional view across the width of a strip of packaging material according to a third embodiment of the invention.

[0017] Fig 3(b) is an alternative configuration of the embodiment of Fig. 3(a).

Detailed Description of the Preferred Embodiments

[0018] Corresponding and like parts are referred to in the following description and indicated in the drawings by the same reference characters.

[0019] According to a first embodiment of the invention, shown in

Fig. l(a), the wrapping strip material 10 comprises a lower woven layer 12 (i.e. a scrim) laminated to an upper, non- woven layer 14. The strip has opposed longitudinal edges 11, 13. A bonding coating 18, which may be an adhesive or cohesive or polymeric tackifier coating, is applied to the entire lower (bottom) surface 16 of the woven layer. The coating of layer 18 is selected to have a degree of adhesiveness that provides a suitable degree of adhesion with upper (top) surface 20. The bonding coating 18 is capable of adhering to the surface 20 of the strip material 10, when the strip is applied in an overlapping or partially overlapping manner in packaging a steel coil or other product, but at the same time the coating 18 does not leave any adhesive residue on the product. In use, coating 18 is in contact with the object to be wrapped.

[0020] In some cases, the top surface 20 of the strip 10 will preferably be treated by means of a corona treatment. For example, the cohesion between the coating 18 and the surface 20 can be improved by applying a low tack adhesive to the surface 20. In such case, the surface 20 will be corona treated. Second, where the tack level of the adhesive of the coating 18 is too high, it will stick too firmly to layer 14, preventing

easy unwinding of the roll of strip. A release coating material, such as varnish, is then applied to surface 20 to reduce the degree of cohesion to the coating 18. In such case, upper surface 20 will be corona treated. Third, if it is desired to be able to print on upper surface 20, corona 5 treatment is used to achieve proper ink adhesion.

[0021] The bottom surface 16 of the woven layer 12 may also be treated in a suitable manner, e.g. by a corona treatment, to promote the bonding between the bonding coating 18 and the surface 16 of the strip.

I O

[0022] The bonding coating 18 is preferably tacky in feel, such that it adheres to the top surface 20 of the strip 10 when wound in an overlapping manner, sufficiently to resist lateral forces on and sliding movement of the strip, but the coating readily releases when the strip 10 is unwound to un-

1 5 wrap the product. Optionally, the bonding coating 18 may also have the characteristic of removably adhering to the metal coil or other wrapped product.

[0023] The strip 10 may incorporate corrosion inhibitors, such as 0 volatile corrosion inhibitors. Such corrosion inhibitors may be present in the bonding coating 18 or in the woven layer 12.

[0024] The woven layer 12 is preferably formed of tapes of polyolefin material, such as polyethylene or polypropylene, or fiberglass or 5 polyester strand fibers. The woven layer 12 may also be formed of partially or fully stretchable elastic tapes. The non- woven layer 14 is preferably a film of polyolefin material. Its purpose is principally to maintain the integrity of the woven layer and impart a waterproof outer coating to the wrapping material. The non-woven layer can be bonded to O the woven layer by any conventional method, for example by lamination, heat sealing, adhesives, or by direct extrusion onto the woven layer.

[0025] Optionally, the wrapping material 10 may include one or more additional layers, such as a layer of kraft paper or a second layer of synthetic polymeric material or non-woven material (Spunbond Polypropylene PP). Fig. l(b) illustrates a wrapping material 1OA, an alternative embodiment of the wrapping material of Fig. 1 (a), which incorporates one such additional polyolefin layer 22.

[0026] The strip material 10 may be wound into a roll for use, the roll diameter being preferably in the range of about 9.5 and 11 inches. The width of the strip is preferably in the range of 3 to 24 inches, more preferably 7 to 12 inches. It is a thin, flexible material (in the drawings, the thickness is exaggerated for clarity of illustration).

[0027] Referring next to Fig. l(c), a further alternative configuration of material 10 is strip material 1OB in which layer 14 may be made out of a polyolefin (such as LDPE or LLDPE) and/or an elastomer that may be stretchable and that may include a tackifier. In this configuration, woven layer 12 may also include tapes that are partially or fully stretchable or elastic; these tapes may include a vapor corrosion inhibitor.

[0028] Fig. l(d) shows a further configuration of the strip material,

1OC, in which either polyolefin layer 22 or non- woven layer 14 or both layers may be a polyolefin (such as LDPE or LLDPE) layer that may be stretchable and that includes a tackifier. The non- woven stretchable layers 14 and 22 in Figs. l(c) and (d) can be bonded to the woven layer by any conventional method, for example by lamination, heat sealing, adhesives, or by direct extrusion onto the woven layer.

[0029] In the embodiments of Figs. l(c) and l(d), the polyolefin layers 22 and 14 have the property to adhere to the top surface 20 of the

strip when wound in an overlapping manner, sufficiently to resist lateral forces on a sliding movement of the strip, but they are readily removed when the strip is unwound to un-wrap the product. Optionally, the tacky layer 22 may also have the characteristics of removably adhering to the metal coil or other wrapped product. The tacky layer 22 may also include a volatile corrosion inhibitor.

[0030] Also on materials 1OB or 1OC layers 14 and 22 have the additional function of sealing the overlap of strip layers during material application.

[0031] Figure l(e) shows a further configuration of the strip, in which strip material 1OD includes layers 14 and 22 bonded to woven layer 12 by bonding layers 17 and 19 respectively. The bonding agent of layers 17, 19 has a different elongation rate than layers 14 and 22. Layers 14 and 22 are more stretchable than layers 17 and 19. This difference allows layers 14 and 22 to move independently from each other and from layer 12 during the packaging application, enhancing the packaging sealability and ability to protect the wrapped material. This independent movement of the layers may be achieved by either fracturing of the bonding agent or its complete separation from layers 12, 14 and 22. The bonding agent may be a polyolefin layer acting as a laminating agent.

[0032] Though it is preferably multilayered, and described as being multilayered, it will be understood that the strip packaging material of the invention can comprise a single layer, so long as the single layer has the required properties of mechanical strength and impermeability.

[0033] According to a second general embodiment of the invention, shown in Fig. 2(a) and (b), the wrapping strip material has bonding bands rather than having a bottom coating on the entire bottom surface of the

stip. The strip 1OE, shown in Fig. 2(a), comprises a non- woven layer 14 and a woven layer 12 as described above in respect of the packaging strip 10. A band 30 comprising a bonding coating extends along one longitudinal edge 13 on the upper surface 20 of the strip and a second bonding coating band 32 extends along the other longitudinal edge 11 on the lower surface 16 of the strip. The bands 30, 32 are preferably about two to three inches wide for a strip that is about 10 inches wide. The coating material comprising bands 30, 32 preferably comprises an adhesive, cohesive or polymeric tackifier coating, i.e. a material that adheres only to itself.

[0034] The strip 1OF, shown in Fig. 2(b) is essentially the same as that of Fig. 2(a), except that it includes a second non- woven layer 22 as the bottom layer, bonded to the woven layer 12. The layer 22 may be a layer of synthetic polymeric material or kraft paper, as described above. When the strip material 1OE, 1OF is used to wrap a product, it is applied in an overlapping manner such that longitudinal edge 13 is the leading edge and band 30 is overlapped by band 32 of the next winding of the strip, so that a bond is formed between the two bands 30, 32.

[0035] According to a third general embodiment of the invention, shown in Figs. 3(a) and 3(b), the wrapping strip materials 1OG and 1OH are essentially the same as described above for strip material 1OE and 1OF respectively, except that, instead of a top and a bottom bonding band 30, 32, there is provided a single bonding band 40 along one longitudinal edge 13 on the upper surface 20 of the strip. The bottom surface of the strip is treated, e.g. by a corona treatment, in order to provide for adequate bonding between the band 40 and the bottom surface.

[0036] Longitudinal edge 13 is intended to be the leading edge as strips 1OG and 1OH are applied to a metal coil or other object. The strip is

applied in an overlapping manner such that a portion of bottom surface 16 (Fig. 3(a)) or 24 (Fig. 3(b)) of a successive winding of the strip overlaps band 40, forming a bond. Band 40 may have adhesive properties the same as those described above with respect to the coating 18 of packaging strip 10.

[0037] If the tack level of the coating 18 is too high, blocking of the roll of strip 1OG, 1OH is caused during unwinding. To avoid this, a release coating material such as varnish can be applied to the bottom surface of the strip.

[0038] The wrapping strip materials of the invention can be applied manually, but they are preferably applied automatically by a machine whereby the strip of packaging material passes through the eye of the coil (i.e. the opening inside the donut-shaped coil), circles around the outer side of the coil and passes through again, and repeats this motion. As the packaging material is circling through and outside of the coil, the coil itself is slowly turned about its axis, allowing for the circular motion of the packaging material to cause an overlap on itself and eventually cover the entire exposed surfaces of the coil.

[0039] As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof, which is defined by the following claims.