MXPA00001972A - Reinforced shrink wrap and method of manufacture - Google Patents

Abstract

A reinforced shrink wrap has been developed for use in all types of environments and products or applications. The shrink wrap is tear resistant and can be prepared to withstand exposure from the sun and corrosive elements. The shrink wrap includes a layer of a shrink film and a layer of polyolefin film. In addition, a reinforcing filamentous grid in an extrusion tie layer is disposed in between the shrink film and a polyolefin film.

Description

REINFORCED ENCOGIBLE ENVELOPE AND MANUFACTURING METHOD Background of the Invention The shrink wrap is used for a multitude of applications, ranging from wrapping agricultural products in supermarkets to covering containers and products for shipping. The manufacture of the shrinkable envelope can be achieved generally by extrusion of resinous materials, whhave been heated to their point of flow or melt from an extrusion die in tubular or flattened form. After a post-extrusion flash cooling, the extrudate is then reheated to its orientation temperature under whit is stretched either uniaxially or biaxially. After being stretched, the film is rapidly cooled for sudden cooling and closure in the oriented molecular configuration. Subsequently, the film can be stored in rolls and used to closely pack a variety of items. When the shrink wrap is in use, the product to be packaged is first housed in the shrink wrap, and the housed product is subjected to elevated temperatures by passing the product through hot air, hot water tunnel, or other methods. This causes the film to shrink around the product to produce a narrow wrap that conforms closely to the contour of the product.

Because the shrink wrap covers the outside of a product, it is subject to cuts, tears and punctures. Accordingly, in order to obtain a shrinkable, durable wrapped product, it is important that the shrinkable wrap have a relatively high tensile strength, puncture resistance and tensile strength, and other mechanical properties. However, most existing shrink films are unitary in nature, ie the entire film is shrinkable. As such, the shrinked film generally has no greater strength than the shrinkable wrapper itself. Although there are some composite, multi-layered shrink wrappers, they may not have sufficient strength or seam integrity to withstand tearing and perforation, thereby resulting in delamination, product exposure, or seam rupture. Accordingly, it would be desirable to develop a method for manufacturing reinforced shrink wrap with improved strength, seam integrity and other desired properties. Apart from the shrink wrap, reinforced plastic films have been developed that are durable, resistant, and puncture-resistant. Plastic films can be reinforced by using a net or mesh that has greater strength than plastic films. In addition to the reinforcement network, an elastomeric tie layer has also been used to secure the reinforcement network between the plastic films.

To manufacture such reinforced plastic films, a lamination-extrusion process has been used. During the rolling-extrusion process, an elastomeric material is extruded from a die to form a tie layer. A reinforcement net can be attached to the tie layer, and the tie layer with the reinforcement net is sandwd between two thermoplastic sheets. The entire assembly is then laminated by passing it through a pair of rollers under a certain nipple pressure. Such reinforced plastic films are said to possess good mechanical properties, such as puncture resistance, tensile strength, and tear resistance. Furthermore, reinforced plastic films have a good resistance to seam separation and peel strength. But these reinforced plastic films are not shrinkable, and thus can not be used as a shrink wrap. Although reinforcement nets with an elastomeric tie layer have been used in the manufacture of plastic films, a shrink wrap reinforced by an elastomeric tie layer manufactured by a lamination-extrusion process has not been available. This is because there is a belief that the processing temperature in a typical lamination-extrusion process may be too high for a shrinkable film that may start to shrink during the rolling process. So, the benefits of using reinforced nets with an elastomeric tie layer in the manufacture of reinforced shrink wrap have not been achieved. For the above reasons, there is a need to explore the possibility of manufacturing a reinforced shrink wrap that incorporates the advantages of using a reinforcement network with an elastomeric tie layer there disposed. Furthermore, it is desirable to develop a method to achieve such a goal in a simple and cost-effective manner. SUMMARY OF THE INVENTION Embodiments of the invention satisfy the above requirement by providing a reinforced shrink wrap and a method of making such a shrink wrap. The reinforced shrinkable envelope can be obtained by the following method: (a) providing two thermoplastic sheets, at least one of the sheets being a shrinkable film; (b) placing a reinforcement network between the two thermoplastic sheets; (c) extruding an elastomeric material at an elevated temperature to form a tie layer between the two sheets wherein the tie layer is in contact with the reinforcing network and the two thermoplastic sheets; (d) laminating the two sheets and the reinforcement net with the tie layer to form a reinforced shrink wrap; and (e) controlling the thickness of the tie layer so that the shrinkable film does not begin to shrink substantially during rolling. After laminating, the reinforcing network is held by the elastomeric tie layer between the two thermoplastic sheets. The reinforced shrinkable envelope, according to an embodiment of the invention, includes: (1) a first layer of thermoplastic material; (2) a second layer of thermoplastic material, at least one layer of the first and second layers including a shrinkable film of highly irradiated polyolefin; (3) a reinforcing network disposed between the first and second layers of thermoplastic material; (4) a tie layer of elastomeric material disposed between the first layer and the second layer, holding the reinforcement net, but allowing the slippage of the reinforcement net in the tie layer upon stress loading of the reinforced laminate. The first layer, the second layer, the reinforcement net and the tie layer are laminated together to form the reinforced shrink wrap. The shrinkable film can be made of linear low density polyethylene, low density polyethylene, or mixtures thereof. The elastomeric tie layer can be characterized as having a lower module than at least one of the other thermoplastic layers. The thermoplastic film may be a multi-layer film of co-extruded layers. The thermoplastic film or a layer of the film may include additives such as ultraviolet stabilizer, flame retardant, static inhibitor, color additive, anti-oxidant, corrosion inhibitor, biocide, or mixtures thereof. The reinforcement network can be a non-woven mesh of nylon, polypropylene or polyester filaments from about 200 to about 800 denier. The tie layer in which the filamentous web is disposed can have a thickness of about 0.75 to about 1.5 mils. Moreover, the reinforced shrink wrap may be composed of multiple layers of thermoplastic with more than one net disposed in a tie layer between the thermoplastic layers.

Among these multiple layers of thermoplastic, at least one thermoplastic layer is a shrinkable film. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic of a manufacturing process of shrinkable wrapper reinforced according to an embodiment of the invention. Figure 2 is an enlarged view, in cross section, of an embodiment of the reinforced shrinkable envelope. Figure 3 is an enlarged cross-sectional view of an alternative embodiment of the reinforced shrinkable wrapper. Figure 4 is an enlarged view, in cross-section, of yet another embodiment of the reinforced shrinkable envelope, showing multiple layers. Figure 5 is an illustration of a pallet of boxes covered by the reinforced shrinkable wrapper according to an embodiment of the invention.

Detailed Description of Ways of Embodiment of the Invention Embodiments of the invention provide a reinforced shrink wrap made by an extrusion-lamination process. The method of manufacturing the reinforced shrink wrap includes the following steps: (a) providing two thermoplastic sheets, at least one of the sheets being a shrinkable film; (b) placing a reinforcement network between the two thermoplastic sheets; (c) extruding an elastomeric material at an elevated temperature to form a tie layer between the two sheets, wherein the tie layer is in contact with the reinforcing network and the two thermoplastic sheets; (d) laminating the two sheets and the reinforcement net with the tie layer to form a reinforced shrink wrap; and (e) controlling the thickness of the tie layer so that the shrinkable film does not begin to shrink during rolling. After laminating, the reinforcing network is held by the elastomeric tie layer between the two thermoplastic sheets. Figure 1 illustrates an extrusion-rolling installation for making the shrinkable wrapper reinforced in accordance with an embodiment of the invention. Referring to Figure 1, two thermoplastic sheets 12 and 15 are provided by rollers 16 and 19, respectively. The sheet 12 is a shrinkable film, while the sheet 15 may or may not be a shrinkable film. A reinforcing network 13 is provided by a roller 20. An extrusion die 14 extrudes a sheet of elastomeric material 11 to fuse it with the reinforcing network 13 which is sandwiched between the two thermoplastic sheets 12 and 15. The extrusion die 14 is heated to a temperature of about 530 to about 630"F. Preferably, the temperature of the die varies from about 550 to about 600" F. The thermoplastic sheets 12 and 15, the tie layer 11 and the reinforcement net 13 are passed through a pressure roller 18 and a cooled roller 17. The layers are sufficiently pressurized to allow adhesion of the outer epidermal layers around of the mooring layer and net while avoiding excessive pressure that can lead to melting and thinning of the layers. The outer sheets 12 and 13 are adhered together by the tie layer 11 with the reinforcement net 13 attached to the tie layer to form the reinforced laminate 21. Because the shrinkable film 12 is used in the lamination process, care must be taken to control the thickness of the tie layer so that the shrinkable film 12 does not begin to shrink during the rolling process. It has been found that when the thickness of the tie layer 11 does not exceed a certain value, the shrinkable film will not begin to shrink during the rolling process. The exact maximum thickness value varies, depending on the process conditions and the type of materials used. One way to reduce the thickness of the tie layer 11 is to increase the line speed and / or reduce the extrusion rate. When the thickness of the tie layer 11 is reduced, less heat is transferred to the shrinkable film 12. As such, the temperature at which the shrinkable film is subjected is likely to be lower. Cooling the cold roll 17 further reduces the temperature of the shrinkable film 12. In this manner, a shrinkable film can be successfully laminated with a reinforcement network, a tie layer, and one or more thermoplastic sheets, without causing substantial shrinkage of the Shrinkable film during the lamination process. In one embodiment, the reinforced shrink wrap includes: (1) a first layer of thermoplastic; (2) a second layer of thermoplastic, at least one layer of the first and second layers including a shrinkable film of highly irradiated polyolefin; (3) a reinforcing network disposed between the first and second thermoplastic layers; (4) a tie layer of elastomeric material disposed between the first layer and the second layer, holding the reinforcement net, but allowing the slippage of the reinforcement net in the tie layer upon tension loading. The first layer, the second layer, the reinforcement net, and the tie layer are laminated together to form the reinforced shrink wrap. The reinforced shrink wrap may be custom-made for its intended use, as will be understood from the following description. The various layers can be modified in thickness and by additives, as needed. For example, for applications with large equipment for embarking on a vessel overseas where there will be exposure to salt spray and other elements, a thicker shrinkable envelope with a corrosion inhibitor would be preferred. If exposure to the sun is expected, an ultraviolet stabilizer would be desirable. Many variations of the invention will be understood by those familiar with the rolling process. Any shrinkable film can be used in embodiments of the invention. Preferably, the shrinkable film layer is highly irradiated polyolefin such as an ethylene-olefin copolymer, including ethylene-vinyl acetate copolymer. The preferred thickness is from about 0.75 to about 1.5 mils (inch) and can be varied based on its intended use and the desired strength of the multi-layered final product. A preferred shrink film is the Cryovac® D-925 film, available from Technical Packaging, a distributor of Cryovac North America, of Duncan, South Carolina, United States. Such a shrinkable film is preferred because it has the desired physical properties. For example, it shrinks fairly uniformly both in the machine direction and in the transverse direction. It is highly cross-linked transversally from an irradiation process and has the following specifications of Table 1.

^^^ Table 1 - Physical Properties of Crvovac® D-925 Film A suitable reinforcement network can be a network of non-woven fibers. The network is typically composed of main filaments running in the direction of the machine and orthogonal filaments running in the transverse direction. Different network constructions can be obtained using varying numbers of fibers in the machine direction and the transverse direction. The filaments preferably must have high strength, low shrinkage upon heating, and be able to withstand the temperature of the plastic being poured, laminated or extruded thereon. Preferably, the filaments used for the construction of this network are made of polyester, nylon or physical blends of polyolefin, aramid, fiberglass and other commonly used filament materials. More preferably, a net made of polyester, nylon or fiberglass is used. In the case of polyester, the type of filament used for the construction of the network is a high tenacity yarn, low shrinkage of about 500 to about 1,500 denier. More preferably, the yarn is of a type from about 840 to about 1,000 denier, such as yarn 787 from Hoechst Celanese, Salisbury, North Carolina, United States. The net or mesh can be manufactured by laying the crossed strands over each other, securing them together by passing them through a bath of a tackifier, commonly polyvinyl alcohol, and then drying, rolling and packing into a core. This process without weaving makes possible the construction of a reinforcing fabric with a low count of filament yarns. The networks commonly used for reinforcement of plastic sheets can vary from a construction of 20 x 20 to l x l ("20 x 20" means 20 filaments per inch in the machine direction and 20 filaments per inch in the transverse direction). Preferably, the construction used varies from 5 x 5 to 1 x l. More preferably, the constructions are 3 x 2 and 2 x l. The reinforcement net is generally held by a tie layer between two external sheets. The net can be attached to or surrounded by the mooring layer. The mooring layer is preferably a material with a lower module than the outer sheets. Certain elastomeric materials with a relatively low modulus include, but are not limited to, butyl rubber, PVC, polyurethane, neoprene and ethylene propylene diene (EDPM). These materials need to be dissolved in water or solvents for processing. In addition, ethylene methylacetate (EMA) and ethylene vinyl acetate (EVA) have a lower modulus than polyethylenes and polypropylenes used for laminates. A group of elastomeric materials suitable for use as a tie layer are polyolefin elastomers manufactured by the co-polymerization of ethylene or propylene with monomers, such as propylene, butene, hexene, octene, methyl acrylate and vinyl acetate, using process technology either gas phase or solution. Some examples of elastomeric materials suitable as a tie layer include those referred to as plastomers (Exxon and Dow) or Catallow resins (Himont). Like elastomers, these polyolefin resins are soft and resilient. On the other hand, they can be processed in the form of free-flowing pearls, just like plastics. The Catallow polypropylene resins are preferably used when the outer epidermal layers are made from polypropylene. The polyethylene plastomer resins are preferably used as polyethylene epidermal films. Table 2 is a comparison of the physical characteristics and properties of LDPE film, LLDPE, which are used as external sheet material, Exact 4044, EMA and EVA. Exact 4044 is an ethylene-based hexene plastomer made by Exxon Chemical.

Table 2 Suitable polyethylene resins are substantially linear olefins within a narrow molecular weight distribution. Preferably, the density of polyethylene resins should vary from about 0.860 to about 0.920 g / cc, and the co-monomer concentration should vary from about 0.860 to about 0.920 g / cc, and the co-monomer concentration It should vary from around 6 to around 20%. More preferably, the density should range from about 0.890 to about 0.910, with a tension modulus (1% secant - D882) in the range of about 5,000 to about 15,000 psi. Table 3 lists physical characteristics and film properties typical of some polyethylene and polypropylene copolymers that can be used in the tie layer.

Table 3 -aft¿ U;; »-« * ..

Some elastomeric materials used as tie layers tend to be unstable when extruded due to their elastic nature. They can be stabilized by adding about 1 to 90% of a stabilizing resin. For example, low density polyethylene (LDPE), such as Chevron PE-1017, is added when a very low density polyethylene is used. Typically, the addition of about 5 to 6% LDPE resin is sufficient to markedly improve the processing performance of these materials. As discussed above, the thickness of the tie layer must be controlled such that the shrinkable film does not begin to shrink substantially during rolling. Moreover, the thickness of the mooring layer is also important for the performance of the product. The mooring layer is preferably about 5 to 25% of the total thickness of the product. More preferably, a tie layer representing about 15 to 25% of the total thickness is used. For example, the thickness of the elastomeric tie layer may be between about 0.75 and 1.5 thousandths (inches), with a preferred thickness of about 1.0 thousandths (inches). Additives can be used in the tie layer to impart specific properties, including but not limited to, ultraviolet stability, flame retardancy, and infrared barriers. Suitable additives may include ultraviolet stabilizers, flame retardants, static inhibitors, color additives, anti-oxidants, corrosion inhibitors, biocides, and mixtures thereof. The outer layer of the shrinkable envelope includes a thermoplastic film, preferably from about 0.75 to about 6 mils. Additional thermoplastic layers can be used as internal layers arranged between the tie layers with or without reinforcement networks. Suitable thermoplastics include, but are not limited to, polyethylenes, polypropylenes, polyvinyl chloride, polyester, and any other polymers capable of being formed into sheets and laminates by means of this extrusion process. Preferably, a physical mixture of linear low density polyethylene (LLDPE) and low density polyethylene is used, because it has good toughness, tear resistance and puncture resistance. The thermoplastic film can have two or more layers.

When the polyolefin film contains more than one layer, each layer can be made of a different polyolefin or mixtures thereof. For example, the layer that will be the outward facing surface of the shrink wrap may be of low density polyethylene, which is suitable for heat sealing and is suitable for making the product covers and also has a good surface appearance. The other layer or layers may be another polyolefin or mixtures. The multilayer film can be prepared by methods such as co-extruded, blown film manufacturing techniques.

In some embodiments, the thermoplastic layers include color additives and may have a printed message on any layer, if desired. Other additives that may be used include stabilizers for ultraviolet light, anti-oxidants and corrosion inhibitors. Also, static inhibitors, flame retardants and biocides compatible with polyolefins can be incorporated into or coated on the film layer. The various additives can be combined and included in more than one layer of polyolefin or different additives or their combinations can be included in more than one layer. In the shrink wrapping laminate with multiple polyolefin layers, additives or combinations thereof can be included in one or more of the layers. In one embodiment, the external thermoplastic layer includes an ultraviolet stabilizer as an additive in a mixture of low density polyethylene and linear low density polyethylene. A commercially available ultraviolet stabilizer is Chimassorb 944®, of Geigy, of a family of hindered amines. The stabilizer is prepared in a polyethylene concentrated form and physically mixed with polyolefin before preparing the film. In another embodiment, the thermoplastic layer has an anticorrosive additive in linear low density polyethylene. A preferred corrosion inhibitor is the anti-corrosive additive PA4733, manufactured by Northern Instruments Corporation.

The following examples illustrate some embodiments of the invention. They are merely exemplary and are not limiting of the invention, as it is otherwise described herein. It should be understood that all numerical values are approximate. Example 1 Figure 2 is a cross-section of an embodiment of a three layer reinforced shrink wrap. The reinforced shrinkable envelope 30 includes a shrinkable film 31, a polyethylene sheet 32, a reinforcement network shown as 36a, 36b, and 36c in a tie layer 34. The layer 31 is a shrinkable polyethylene film, highly irradiated. The shrinkable film is a Cryovac® D-925 film, with a thickness of about 0.75 mils (inch). The layer 34 is the elastomeric tie layer. It includes about 70% LDPE (ie, PE-1017, from Chevron), about 25% VLDPE (ie Exxon Exact 4044), and about 5% ultraviolet inhibitor (ie, Chimas -sorb 944®, by Geigy). A cross-section of the reinforcing filamentary network 36a, 36b, and 36c, is shown in layer 34. The preferred multi-filament nylon or polyester yarn is a non-woven mesh of 2.67 x 2.67 (about 0.05"). 500 denier). The layer 32 is a sheet of LDLBPE having a thickness of about 2 mils (inch). The following Table 4 includes the properties of the reinforced shrink wrap of Figure 2 with ASTM tests used to measure the properties.

E Temple 2 Figure 3 shows the cross section of another embodiment of the reinforced shrink wrap. The reinforced shrink wrap 40 includes layers 41, 42 and 44. The layer 41 is a shrinkable film, and the layer 44 is an elastomeric tie layer. A reinforcement network is attached to the tie layer 44 with the cross section of the net shown at 46a, 46b, and 46c. The layer 42 is a thermoplastic layer composed of a co-extruded film of three layers. The layers are designated 42a, 42b and 42c, respectively. In one embodiment, the middle layer 42c is about 50 to 70% of the total thickness. The multilayer film can be made by co-extrusion and other processes used in the production of films. The multilayer film layer allows the preparation of a single film with varied characteristics for each layer. For example, an additive that may be more effective on an external surface, such as a corrosion inhibitor, may be added to the outer layer material prior to manufacture, such that only one layer contains the additive. Similarly, the polyolefin content can be varied for each layer so that the outer layer has a polyolefin content with better surface characteristics and the inner layer is formulated for strength and durability characteristics. Of course, it should be recognized that any number of layers can be used to obtain the desired properties and performance.

Example 3 Figure 4 shows an embodiment of a reinforced shrink wrap, multi-layered 50. Layers 54, 51 and 55 may be a thermoplastic or shrinkable film, as long as there is a shrinkable film layer. Layers 52 and 53 are elastomeric tie layers with network 57a and 57b, and network 56a, 56b and 56c disposed in layers 52 and 53, respectively. Figure 4 is an example of a shrinkable wrap with double tie layers with reinforcement nets. Other embodiments with more than two tie layers and netting and multiple layers of shrinkable film can be made according to the desired product properties for the intended purpose. Table 5 lists some of the physical properties of a five-layer shrink wrap, measured by ASTM methods.

Example 2 Figure 3 shows the cross section of another embodiment of the reinforced shrink wrap. The reinforced shrink wrap 40 includes layers 41, 42 and 44. The layer 41 is a shrinkable film, and the layer 44 is an elastomeric tie layer. A reinforcement network is attached to the tie layer 44 with the cross section of the net shown at 46a, 46b and 46c. The layer 42 is a thermoplastic layer composed of a co-extruded film of three layers. The layers are designated 42a, 42b and 42c, respectively. In one embodiment, the middle layer 42c is about 50 to 70% of the total thickness. The multilayer film can be made by coextrusion and other processes used in film production. The multilayer film layer allows the preparation of a single film with varied characteristics for each layer. For example, an additive that may be more effective on an external surface, such as a corrosion inhibitor, may be added to the outer layer material prior to manufacture such that only one layer contains the additive. Similarly, the polyolefin content can be varied for each layer so that the outer layer has a polyolefin content with better surface characteristics and the inner layer is formulated to have strength and durability characteristics. Of course, it should be recognized that any number of layers can be used to obtain the desired properties and performance.

Example 3 Figure 4 shows an embodiment of the multi-layer, reinforced shrinkable wrap 50. The layers 54, 51 and 55 may be a thermoplastic or shrinkable film as long as there is a shrinkable film layer. Layers 52 and 53 are elastomeric tie layers with network 57a and 57b and network 56a, 56b and 56c disposed in layers 52 and 53, respectively. Figure 4 is an example of a shrinkable wrap with double tie layers with reinforcement nets. Other embodiments with more than two tie layers and net and multiple layers of shrinkable film can be made according to the desired product properties for the intended purpose. Table 5 lists some physical properties of a shrink wrap of five layers measured by ASTM methods. It is noted that the 5-ply shrinkable wrapper tested according to the ASTM methods had a construction shown in Fig. 4. Both plies 54 and 55 were LDLBPE sheets with a thickness of about 2 mils. Layer 51 was a shrinkable film (Cryovac® D-925) with a thickness of about 0.75 mils (inch). Layers 52 and 53 were elastomeric tie layers. Each tie layer included about 70% LDPE (ie, Chevron PE-1017), about 25% VLDPE (ie Exxon Exact 4044), and about 5% ultraviolet inhibitor (ie. , Chimas-sorb 944® by Geigy). Transverse sections of a reinforcing filamentary network 56a, 56b, and 56c in layer 53 and another reinforcing filamentary network 57a and 57b in layer 52 are shown in Figure 4. The reinforcing network was a nylon or polyester yarn of multiple filaments of a nonwoven mesh of 2.67 x 2.67 (about 500 denier). Example 4 Figure 5 is an example of a pallet of boxes covered by the reinforced shrinkable wrapper according to an embodiment of the invention. Covers for products, boxes or packaging can be made by any method of cost and joining for large equipment and machinery. Large decks can be constructed by joining rolls of shrinkable film reinforced with stitched seams, heat seal, hot melt adhesive, radio or ultrasonic waves, or any other sewing or joining method available, appropriate for the material. The reinforced shrink wrap may also be used for small items, and is not intended to limit in any way the size or shape of the cover that can be made and used. In use, the reinforced shrink wrap is placed around the package or product, and applies heat using hot air guns, ovens or any other means, to shrink it. The shrinkable film deforms and conforms to the shape and size of the coated article, and the outer layers of the shrinkable wrapper are also deformed to provide a sturdy, reinforced, tight cover for the article. The shrink wrap is resistant to burning through when localized heat is used to shrink the cover. It has a minimum shrinkage of around 4.5%. As demonstrated above, the embodiments of the invention combine some or all of the advantages of a reinforced plastic film with the benefits of a shrinkable wrap. The invention combines the advantages of these two different materials and produces a laminate that is flexible, heat-sealable throughout the material, and exhibits fiber slippage for improved tear strength and good outdoor performance. Furthermore, using a polyolefin extrusion lanyard provides a product with improved properties over those laminated with adhesives. The elastomeric tie layer can also increase the flexibility and appearance of the finished product. The reinforcement network minimizes tears and tears and prevents perforations from spreading. Still, the reinforced shrink wrap is deformed to fit the product or container in the same or similar manner as the conventional shrink wrap. The resulting reinforced shrink wrap has good tension and perforation properties, but it's also a layered, soft film. The puncture resistance and the integrity of the seam have been improved. Moreover, the reinforced shrink wrap is resistant to burning through, located, during the heating step used to shrink the wrap around the product. As such, the reinforced shrink wrap may be superior to the conventional, non-reinforced product for packing, handling, shipping and storing articles. It can be used to cover all sizes of products and containers and is specially adapted for large equipment covers. Particularly, the reinforced shrink wrap is suitable to protect cargo and equipment exposed to harsh environments. In addition to the reinforced shrink wrap, the embodiments of the invention also provide a simple and cost effective method for manufacturing the reinforced shrink wrap. Although the invention has been described with respect to a limited number of embodiments, modifications and variations thereof exist. For example, any sheets or thermoplastic films can be used to manufacture the reinforced shrink wrap. Further, reinforcement can be effected by using any net or mesh that has greater strength than thermoplastic sheets. Although an extrusion-lamination method is used to make the shrink wrap reinforced, other lamination methods, such as lamination with adhesives, can also be employed. Additionally, any shrinkable film can be used in embodiments of the invention. The shrinkage can be effected by a variety of methods, including but not limited to, heat, light, ultrasound and so on. It should be recognized that the order of the steps for putting the invention into practice is not limited to the way described. Any order that achieves the objectives and results of the invention can be put into practice. The appended claims are intended to cover all those modifications and variations that fall within the scope of the invention.

Claims (31)

1. REVINDICATION 1. A reinforced shrink wrap, comprising: a first layer of thermoplastic; a second layer of thermoplastic; at least one layer of said first and second layers comprising a shrinkable film of highly irradiated polyolefin; a reinforcement network disposed between the first and second thermoplastic layers; and a tie layer of elastomeric material disposed between the first layer and the second layer that holds the reinforcement net but allows the slippage of the reinforcement network in the tie layer when stress load occurs, where the first layer, the second layer layer, reinforcement net and tie layer are laminated together to form the reinforced shrink wrap.
2. 2. A reinforced shrinkable wrapper of claim 1, wherein the highly irradiated polyolefin shrinkable film is polyethylene.
3. 3. A reinforced shrink wrap of claim 1, wherein the reinforcing network is a non-woven mesh.
4. A reinforced shrinkable wrapper of claim 3, wherein the reinforcing network material is selected from the group consisting of nylon filaments and polyester filaments of from about 200 to about 800 denier.
5. 5. A reinforced shrinkable wrapper of claim 1, wherein the elastomeric tie layer has a lower modulus than at least one of the thermoplastic layers.
6. 6. A reinforced shrinkable wrapper of claim 1, wherein at least one of said thermoplastic layers includes multiple layers of thermoplastic.
7. 7. A reinforced shrinkable wrapper of claim 1, wherein the tie layer is from about 0.75 to about 1.5 thousandths of an inch thick.
8. 8. A reinforced shrink wrap of claim 1, wherein the first and second thermoplastic layers are from about 0.75 to about 6 mils.
9. 9. A reinforced shrinkable wrapper of claim 1, wherein at least one of the thermoplastic layers includes an additive selected from the group consisting of ultraviolet stabilizer, flame retardant, static inhibitor, color additive, anti-oxidant, corrosion inhibitor. , biocide, and their mixtures.
10. 10. A reinforced shrinkable wrapper of claim 1, wherein the tie layer includes an additive selected from the group consisting of ultraviolet stabilizer, flame retardant, static inhibitor, color additive, anti-oxidant, corrosion inhibitor. , biocide, and their mixtures.
11. 11. A reinforced shrinkable wrapper of claim 6, wherein at least one layer of thermoplastic contains an additive selected from the group consisting of ultraviolet stabilizer, flame retardant, static inhibitor, color additive, anti-oxidant, inhibitor. of corrosion, biocide, and their mixtures.
12. 12. A reinforced shrink wrap of claim 2, wherein the polyethylene is selected from the group consisting of linear low density polyethylene, low density polyethylene, and mixtures thereof.
13. A product cover made of the reinforced shrink wrap of claim 1.
14. 14. A reinforced shrink wrap, comprising: a layer of highly irradiated polyethylene shrinkable film, selected from the group consisting of linear low density polyethylene, polyethylene of low density, and their mixtures, of between about 0.75 and about 1.5 thousandths of an inch thick; a layer of thermoplastic; an elastomeric tie layer laminated between the thermoplastic layer and the shrinkable film layer; a thread selected from the group consisting of nylon and polyester in a network pattern of mutual crosses, arranged in the elastomeric tie layer, the tie layer holding the thread but allowing slippage of the thread in the tie layer when stress load occurs .
15. 15. A reinforced shrink wrap, multi-layered, comprising: at least three layers of thermoplastic; at least one of the layers of thermoplastic is a shrinkable film of polyolefin highly irradiated; and at least two tie layers of elastomeric material, arranged alternately between the thermoplastic layers, each one holding a reinforcement net but allowing the slippage of the reinforcement net in the tie layer when tension loading occurs, where the layers of thermoplastic , the tie layers with the net are laminated together to form the reinforced, multi-layered shrink wrap.
16. 16. A reinforced shrinkable, multi-layer wrapping of claim 15, wherein the highly irradiated polyolefin shrinkable film is polyethylene.
17. 17. A reinforced, multi-layer shrink wrap of claim 15, wherein the reinforcing network is a non-woven mesh.
18. 18. A reinforced, multi-layer shrink wrap of claim 15, wherein the reinforcement network is selected from the group consisting of nylon filaments and polyester filaments of from about 200 to about 800 denier.
19. 19. A reinforced, multi-layer shrink wrap of claim 15, wherein the elastomeric tie layers have a lower modulus than at least one of the thermoplastic layers.
20. 20. A reinforced, multi-layer shrink wrap of claim 15, wherein at least one of said thermoplastic layers includes multiple thermoplastic layers.
21. 21. A reinforced, multi-layer shrink wrap of claim 15, wherein each of the tie layers is from about 0.75 to about 1.5 mils in thickness.
22. 22. A reinforced, multi-layer shrink wrap of claim 15, wherein the thermoplastic layers are from about 0.75 to about 6 mils in thickness.
23. 23. A reinforced, multi-layer shrink wrap of claim 15, wherein at least one of the thermoplastic layers contains an additive selected from the group consisting of ultraviolet stabilizer, flame retardant, static inhibitor, color additive, anti -oxidant, corrosion inhibitor, biocide, and their mixtures.
24. 24. A product cover made of the multi-layer reinforced shrink wrap of claim 15.
25. 25. A method of making a shrinkable reinforced wrap, comprising: providing a thermoplastic sheet and a shrinkable film; placing a reinforcement network on the thermoplastic sheet; forming a tie layer of elastomeric material between the thermoplastic sheet and the shrinkable film; laminating the thermoplastic sheet, the shrinkable film, and the tie layer, with the reinforcement net, to form a reinforced shrink wrap, whereby the reinforcement net is held by the elastomer tie layer between the thermoplastic sheet and the film shrinkable, and the reinforcing network being disposed via the elastomeric tie layer; and winding the shrinkable film layer on a cold roll during the rolling step.
26. 26. A method of making the shrinkable shrink wrap of claim 25, further comprising heating the elastomeric material and applying it by extrusion coating to the thermoplastic sheet.
27. 27. A reinforced shrink wrap, obtained by the method comprising: providing two sheets of thermoplastic, at least one of the sheets being a shrinkable film; place a reinforcement network between the two thermoplastic sheets; extruding an elastomeric material at an elevated temperature to form a tie layer between the two sheets, the tie layer being in contact with the reinforcing network and the two thermoplastic sheets; laminating the two sheets and the reinforcement net with the tie layer, to form a reinforced shrink wrap; and controlling the thickness of the tie layer so that the shrinkable film does not start to shrink substantially during rolling, where the reinforcing network is held by the tie elastomer layer between two thermoplastic sheets after lamination.
28. 28. The reinforced shrink wrap of claim 27, wherein the shrinkable film is highly irradiated polyethylene.
29. 29. The reinforced shrink wrap of claim 27, wherein the reinforcing network is a non-woven mesh.
30. 30. The reinforced shrink wrap of claim 27, wherein the elastomeric layer has a lower modulus than at least one of the thermoplastic layers.
31. 31. A method of using a reinforced shrink wrap, comprising: providing a product to be wrapped; place a reinforced shrink wrap on the product, the reinforced shrink wrap including: a first layer of thermoplastic; a second thermoplastic layer, at least one layer of said first and second layers comprising a shrinkable film of highly irradiated polyolefin; a reinforcement network disposed between the first and second thermoplastic layers; and a tie layer of elastomeric material disposed between the first layer and the second layer that holds the reinforcement net but allows the slippage of the reinforcement network in the tie layer when stress load occurs, where the first layer, the second layer layer, reinforcement net and tie layer are laminated together to form the reinforced shrink wrap; and making the reinforced shrink wrap shrink around the product.