MX2008007476A - Slip-cling stretch film. - Google Patents

Abstract

A multilayer stretch film having a high slip surface and an aggressive cling surface for wrapping items or loads for ease of transport is disclosed. In one embodiment, there is disclosed a multilayer film comprises a first surface having a coefficient of friction at least less than about 0.9, comprising at least polypropylene and high density polyethylene, a second surface having a cling force to the first surface at least greater than about 5 g/in, comprising at least ethylene methyl acrylate copolymer and a tackifier resin, and a core layer, positioned between the first surface and the second surface, comprising at least linear low density polyethylene or its blend.

Description

SLIDING-ADHERENT ELASTIC FILM Field of the Invention The embodiments of the present invention generally relate to a multi-layer elastic film. More specifically, the embodiments of the present invention relate to a multi-layer elastic film having a high slip surface and an aggressive adhesive surface for wrapping articles or loads for ease of transportation.

BACKGROUND OF THE INVENTION The use of thermoplastic elastic wrapping films for the overwrapping of merchandise, and in particular, large rolls of paper or carpet, is a commercially significant application of polymeric film. The monolayer elastic wrapping films have identical surfaces on both sides, while the multilayer elastic films can have a non-sticky surface and an adherent surface. The non-stick surface usually does not adhere on its own and prevents the merging of wrapped goods from sticking together. The adherent surface makes it possible for the film to stick on its own to prevent unfolding during transport. However, when REF. : 193238 the non-adherent surface decreases in coefficient of friction, the adherent surface must increase its adhesive aggressiveness to make it possible for the film to stick on its own when it is wrapped around goods. Accordingly, there is a need for an improved slip-adherent film having a high slip surface and an aggressive sticky surface.

Brief Description of the Invention The embodiments of the present invention relate to a multi-layer elastic film having a high slip surface and an aggressive adhesive surface for wrapping articles or loads for ease of transportation. In one embodiment, a multilayer film comprises a sliding layer comprising at least a mixture of polypropylene and high density polyethylene, an adherent layer comprising at least one styrenic blocking copolymer, and an intermediate layer comprising at least polyethylene resin. of low linear density or its mixture. In another embodiment of the present invention, a multi-layer film comprises a first surface having a coefficient of friction of at least about 0.9, comprising at least polypropylene and high density polyethylene, a second surface having a strength adhering to the first surface of at least greater than about 5 g / inch (1.96g / cm), comprising at least one copolymer of styrenic block, and a core layer, placed between the first surface and the second surface, comprising at least linear low density polyethylene resin.

BRIEF DESCRIPTION OF THE DRAWINGS In this way the manner in which the features cited above of the present invention can be understood in detail, a more particular description of the embodiments of the present invention, briefly summarized above, can be taken by reference to a modality, which is illustrated in the attached figure. It will be noted, however, that the appended figure illustrates only a typical modality of embodiments encompassed within the scope of the present invention, and, therefore, will not be considered limiting, the present invention may admit other equally effective modalities, wherein: Figure 1 represents a cross-sectional view of a film in accordance with an embodiment of the present invention. The headings used here are for organizational purposes only and are not intended to be used to limit the scope of the description or claims. As used throughout this application, the word "may" is used in a permissive sense (that is, it means that it has the potential for), rather than the mandatory sense (ie, it means that it must). Similarly, the words "include", "including", and "includes" mean including but not limited to this. To facilitate understanding, similar reference numbers have been used, where possible, to designate similar elements common to the figure.

Detailed Description of the Invention Figure 1 depicts a cross-sectional view of a film in accordance with an embodiment of the present invention. The film 100 generally comprises a sliding layer 102, an adherent layer 104, and at least one intermediate layer 106 (also referred to herein as a "core" layer) positioned between the two surface layers. Slip layer 102 comprises between about 5% by weight and about 20% by weight of film 100. Adherent layer 104 comprises between about 3% by weight and about 20% by weight of film 100. In many embodiments, the rest of the film 100 is the intermediate layer 106.

The sliding layer 102 generally comprises a polymer composition that produces a low coefficient of friction. The coefficient of friction of the sliding layer 102 is at least less than about 0.9. In one embodiment, the coefficient of friction of the sliding layer 102 is approximately 0.5. The sliding layer 102 generally comprises a composition of polypropylene (PP) and high density polyethylene (HDPE). The PP can be provided in a range of about 60% by weight to about 99% by weight, and the remainder of the composition comprises HDPE. In one embodiment, the PP is provided in about 80% by weight and the HDPE is provided in about 20% by weight of the sliding layer 102. In another embodiment, the PP is provided in about 75% to about-95% by weight , the HDPE is provided at about 5% to about 25% by weight, and the remainder comprises at least one resin or additive, such as abrasion resistant resins, colorants, stabilizers, UV absorbers, and the like. In an exemplary embodiment, PP is a polypropylene copolymer plastic material commercially available from Basell Polyolefins of Hoofddorp, The Netherlands, under the name Basell Pro-fax SA861. The PP has a density of approximately 0.900 g / m3, and a speed of "mass flow (MFR) of approximately 6.50 g / 10 rain, as determined by ASTM test methods D792 and D1238, respectively." In another exemplary embodiment, HDPE is a high density polyethylene plastic material, commercially available from the Westlake Chemical Corporatio of Houston Texas, under the name Westlake HDPE HC 6008. The HDPE has a density of approximately 0.962 g / cm3, and an MFR of approximately 8.2 g / 10 min, as determined by the ASTM D1505 test methods and D1238, respectively, the adherent layer 104 generally comprises a polymeric composition that produces high adhesion.The adhesive strength of the adherent layer 104 to the sliding layer 102, when wrapped around a merchandise or cargo, is at least greater than about 5. g / inch (1.96 g / cm) In one embodiment, the adhesive strength of the adherent layer 104 to the sliding layer 102 is approximately 50 g / inch (19.68 g / cm). it comprises a styrenic block copolymer (SBC). The SBC can be provided in a range of about 50% by weight to about 100% by weight. In one embodiment, the SBC is provided at approximately 100% by weight of the slider layer 102. In another embodiment, the SBC is provided at about 50% to about 95% by weight, and the remainder it comprises at least one additional additive or resin, such as UV protective additives, puncture-resistant resins, and the like. In an exemplary embodiment, the SBC is a styrenic block copolymer material commercially available from Kraton Poly ers LLC of Houston, Texas, under the name Kraton MD6718 Compound. The SBC has a density of about 0.9 g / cm 3, and an MFR of between about 2 g / 10 min and about 25 g / 10 min. Adherent layer 104 may additionally comprise additional resins and additives. In . a modality, the adherent layer 104 comprises a puncture-resistant resin. In another embodiment, the adherent layer 104 may also comprise a low density polyethylene (LDPE) resin having a density of between about 0.91 g / cm 3 and 0.94 g / cm 3, an LLDPE resin having a density of between about 0.915 g / cm3 and 0.925 g / cm3, or a very low density polyethylene resin (VLDPE) having a density between about 0.88 g / cm3 and 0.915 g / cm3. In another embodiment of the present invention, the adherent layer 104 may additionally comprise an ethylene-octene copolymer resin having a density between about 0.850 g / cm3 and about 0.900 g / cm3. In an exemplary embodiment, the ethylene-octene copolymer is a copolymer, commercially available from the Dow Chemical Company of Midland, Michigan, under the name Dow Affinity KC-8852. The ethylene-octene copolymer has a density of about 0.875 g / cm3 and an MFR of about 3.0 g / 10 min, as determined by the ASTM D792 and D1238 test methods, respectively. Additional examples of useful tackifying additives include polyisobutylenes (PIB) having an average molecular weight number in the range of about 1,000-3,000, preferably about 1,200,1800, as measured by vapor phase osometry, amorphous atactic polypropylenes, for example those that have an average molecular weight of approximately 2,000, and polyterpenes. Examples of tackifying resin resins include, but are not limited to, ethylene vinyl acetate (EVA) copolymers containing from about 5% to about 15% by weight of copolymerized vinyl acetate and VLDPE resins having densities from 0.88 g / cm3 at 0.912 g / cm3 and melting rates from 0.5 g / 10 min to 10 g / 10 min. Optional tackifying additives may be present in the adherent layer 104 in a concentration of from about 0.5% by weight to about 10% by weight of the adherent layer composition 104. Optionally, in some embodiments, the polyethylene resins are used in the layer adherent 104, and it further mixed with minor amounts, for example, up to about 20% by total weight, of one or more suitable resins to achieve a desired range of physical and / or mechanical properties in the film product. For example, suitable resins such as ethyl vinyl acetate copolymer, and LLDPE resins may be useful when mixed with the adherent layer 104. In many embodiments, conventional film additives such as antioxidants, UV stabilizers, pigments, dyes, etc., are used in the adherent layer 104 of the film 100. The intermediate layer 106 generally comprises one or more layers of polymeric compositions that produce necessary mechanical properties of the film 100, such as extensibility, load containment, tear strength and puncture, and the like. In one embodiment, the intermediate layer 106 comprises a linear low density polyethylene (LLDPE). In another embodiment, the intermediate layer 106 additionally comprises a white pigment such as titanium dioxide. The LLDPE can be provided in a range of between about 50% and 100% by weight. In particular embodiments, the titanium dioxide may be provided between about 0.1% to about 5% by weight. In one embodiment, LLDPE is provided in approximately 98% by weight, and titanium dioxide is provided in about 2% by weight of the intermediate layer 106. In. In another embodiment, the composition may additionally comprise additives, conventional resins and the like, to provide the desired performance characteristics. In an exemplary embodiment, LLDPE is a linear low density polyethylene material commercially available from the Dow Chemical Company of Midland, Michigan, under the name Dowlex 2045G. The LLDPE has a density of about 0.920 g / cm3 and an MFR of about 1.0 g / 10 min, as measured by ASTM D792 and D1238, respectively. In another exemplary embodiment, LLDPE is a linear low density polyethylene material commercially available from the Dow Chemical Company of Midland, Michigan, under the name Tuflin HSE-7002. Titanium dioxide is provided as an element of a white concentrate. In one embodiment, the titanium dioxide is contained within a white concentrate of Ampacet Corporation of Tarrytown, New York, under the name Ampacet White 110359-C. Alternative embodiments of the present invention provide an intermediate layer 106 comprising at least two or more individual layers. It is understood that the embodiments of the present invention can comprise as many individual layers in the intermediate layer 106 as necessary or feasible to achieve the properties of desired material in a film 100. For example, at least one embodiment of the present invention provides a three-layer film having a single intermediate layer, while an alternative embodiment provides a film of up to forty layers, which has twelve individual layers in the intermediate layer. The additional embodiments provide any number of layers contained within the range of the embodiments described above, as well as any number of feasible layers within the scope of the embodiments of the present invention. The individual layers of the intermediate layer 106 may comprise several optional material compositions. Such materials include, but are not limited to, any feasible grade of LLDPE, metallocene catalyzed LLDPE, Low Density Polyethylene (LDPE), Medium Density Polyethylene (MDPE), High Density Polyethylene (HDPE), or Polypropylene (PP). , including homopolymers, copolymers or mixtures of the foregoing. In one embodiment, the intermediate layer 106 comprises three layers 108, 110, 112. In such an embodiment, the three layers comprise an ABA structure, wherein A is a layer of LLDPE and wherein B is a layer of LLDPE and a white concentrate . In one embodiment of the present invention, a multilayer film comprises a sliding layer comprising a blend of polypropylene copolymer and high density polyethylene, an adherent layer comprising a mixture of styrenic block copolymer and ethylene octene copolymer, and an intermediate layer comprising at least three individual layers, comprising at least two layers of linear low density polyethylene, and a layer of a mixture of linear low density polyethylene and additive. The additives and / or resins can be provided in the intermediate layer 106, such as those discussed above with respect to the sliding layer 102 and the adherent layer 104. The additional resins include homopolymers and polyolefin copolymers suitable for the improvement of mechanical properties such as tensile strength, elongation at break, resistance to tearing and puncture. To ensure that the film 100 meets the desired parameters in accordance with the embodiments of the present invention, tests can be made to determine its physical properties. A parameter used to analyze the performance of such films is the force required to stretch the film to a desired percentage of its original length. This force is indicative of the face retention characteristics of the film. The films of the embodiments of the present invention generally have a strength to stretch the film to 100% at least about 5 pli (pounds per linear inch) (0.89 kg / cm). In many embodiments, the films generally have tensile strength of at least about 5000 psi and elongation at break of at least about 400%, as determined by ASTM D882. Generally, the modalities of the film 100 are constructed in accordance with conventional practices. The film 100 can be manufactured using co-extrusion of molten film or blown film. In one embodiment, a melt film manufacturing process provides resin materials that are heated to their molten state, and their viscosities are coordinated to prepare multilayer films in a uniform manner. The molten materials are transported to a co-extrusion adapter that combines the molten materials to form a multi-layer co-extruded structure. The polymeric layer material is transferred through an open extrusion die to a predetermined opening commonly in the range of between about 0.05 inches (0.13 cm) and 0.012 inches (0.03 cm). The material is then extracted to the proposed gauge thickness by means of a primary casting or cooling roll maintained between about 50 ° F (10 ° C) to about 130 ° F (54.4 ° C). The typical extraction ratios vary from about 5: 1 to about 40: 1. The total thickness of the elastic wrapping film can vary widely according to the end-use specifications, but it is generally in the range of typical thicknesses for elastic wrapping films. In one embodiment of the present invention, the total thickness of the film 100 is between about 0.012 mm to about 0.125 mm. In one embodiment, the thickness of the film 100 is approximately 0.025 mm. Once manufactured, in some embodiments, the sliding layer 102 and / or the adherent layer 104 of the film can be treated by post-formation implementing operations such as corona discharge, chemical treatment, flame treatment, etc., to modify the printability or ink receptivity of the surfaces or to impart other desirable characteristics to it. In accordance with the embodiments of the invention, the film can be provided in an unstretched state, that is, not oriented, or only modestly stretched prior to use. Film 100 is capable of being stretched from at least between about 40% and 400% during a final merchandise wrapping stage. In accordance with the embodiments of the present invention, the film sliding properties are unexpectedly improved when the film is stretched.

These advantageous results can be a close result of the specific HDPE and PP compositions used in the sliding layer with various embodiments of the present invention. Specifically, when the film is stretched, microscopic configurations appear on the surface of the sliding layer film reducing the smoothness of the film as well as the contact area. As a result, the sliding surface of the visibly described embodiments loses its relatively bright appearance when the film is stretched to approximately 100%. In one example, the static COF changes from about 0.65 before a stretch to about 0.49 after stretching. As understood by those of ordinary skill in the art, low friction is advantageous for the ease of movement and for the reduction of possible damage to articles wrapped in a film in accordance with the embodiments of the present invention. While the foregoing is directed to the embodiments of the present invention, other and additional embodiments of the invention can be contemplated without departing from the basic scope thereof. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (28)

CLAIMS Having described the invention as above, the contents of the following claims are claimed as property:

1. Multilayer film, characterized in that it comprises: a sliding layer comprising at least one mixture of copolymer of polypropylene and high density polyethylene; an adherent layer comprising at least one styrenic block copolymer; and an intermediate layer comprising a plurality of individual layers; wherein at least one layer of the intermediate layer comprises linear low density polyethylene resin or its mixture.

2. Multilayer film according to claim 1, characterized in that at least one layer of the intermediate layer comprises titanium dioxide.

3. Multilayer film according to claim 1, characterized in that it comprises the sliding layer between about 5% to about 20% by weight, the adhesive layer between about 3% to about 20% by weight, and the intermediate layer between about 60% to about 90% by weight.

4. Multi-layer film according to claim 3, characterized in that it comprises the sliding layer in approximately 15% by weight, the adhesive layer in approximately 7% in weight, and the intermediate layer in approximately 78% in weight.

5. Multi-layer film according to claim 1, characterized in that the sliding layer has a coefficient of friction between about 0.3 to about 0.9, and wherein the adherent layer has an adherent force to the sliding layer between about 5 g / inch (1.96 g / cm) to approximately 80 g / inch (31.49 g / cm).

6. Multi-layer film according to claim 5, characterized in that the sliding layer has a coefficient of friction of approximately 0.5, and wherein the adherent layer has an adherent force to the sliding layer of approximately 50 g / inch (19.68 g). / cm).

7. Multilayer film according to claim 1, characterized in that the sliding layer comprises between about 70% and about 99% by weight of polypropylene and between about 1% to about 30% by weight of low density polyethylene.

8. Multi-layer film according to claim 7, characterized in that the sliding layer it comprises about 80% by weight of polypropylene and about 20% by weight of high density polyethylene.

9. Multi-layer film - according to claim 1, characterized in that the intermediate layer comprises between about 50% and 100% by weight of linear, low density polyethylene.

10. Multi-layer film according to claim 9, characterized in that the intermediate layer additionally comprises between about 0.1% to about 5% by weight of titanium dioxide.

11. Multilayer film according to claim 10, characterized in that the intermediate layer comprises approximately 98% by weight of linear, low density polyethylene and approximately 2% by weight of titanium dioxide.

12. Multilayer film according to claim 1, characterized in that it can withstand a stretching force of the film at about 400% to about 5000 psi.

13. Multi-layer film according to claim 1, characterized in that the thickness of the total multilayer film is between about 0.012 mm to about 0.125 mm.

14. Multi-layer film according to claim 13, characterized in that the thickness of the Total multiple layer film is approximately 0.025 mm.

15. Multi-layer film according to claim 1, characterized in that at least the three individual layers comprise a material selected from the group consisting of linear low density polyethylene., low density polyethylene catalyzed by metallocene, low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, and any of the homopolymers, copolymers or mixtures thereof.

16. Multilayer film according to claim 1, characterized in that the intermediate layer additionally comprises at least one additive.

17. Multi-layer film according to claim 1, characterized in that the adhesive layer additionally comprises at least one additive.

18. Multi-layer film according to claim 1, characterized in that the adhesive layer additionally comprises an ethylene-octene copolymer.

19. Multilayer film, characterized in that it comprises: a first surface having a coefficient of friction at least less than 0.9, comprising at least one copolymer of polypropylene and high density polyethylene; a second surface that has a strength adhering to the first surface at least greater than about 5 g / inch (1.96 g / cm), comprising at least one styrenic block copolymer; and a core layer, positioned between the first surface and the second surface, comprising a plurality of layers; 1 wherein at least one layer of the intermediate layer comprises linear low density polyethylene resin or its mixture.

20. Multi-layer film according to claim 19, characterized in that the coefficient of friction of the first surface is approximately 0.5, and between the adhesive strength of the second surface to the first surface is approximately 50 g / inch (19.68 g / cm).

21. Multilayer film according to claim 19, characterized in that it comprises the first layer between about 5% to about 20% by weight, the second layer between about 3% to about 20% by weight, and the core layer between about 60% to about 90% by weight.

22. Multi-layer film according to claim 19, characterized in that it comprises the first layer in approximately 15% by weight, the second layer in approximately 7% by weight, and the core layer in approximately 78% by weight.

23. Multiple layer film according to claim 19, characterized in that the first layer comprises between about 75% and about 99% by weight of polypropylene and between about 1% to about 25% by weight of high density polyethylene.

24. Multi-layer film according to claim 23, characterized in that the first layer comprises approximately 80% by weight of polypropylene and approximately 20% by weight of high density polyethylene.

25. Multilayer film according to claim 19, characterized in that the second layer comprises between about 80% and 100% by weight of a styrenic block copolymer.

26. Multilayer film according to claim 19, characterized in that the core layer comprises between about 50% and 100% by weight of linear, low density polyethylene.

27. Multilayer film according to claim 26, characterized in that the core layer additionally comprises between about 0.1% to about 5% by weight of titanium dioxide.

28. Multi-layer film, characterized in that it comprises: a sliding layer comprising a mixture of polypropylene copolymer and high density polyethylene; an adherent layer comprising a mixture of styrenic block copolymer and ethylene-octene copolymer; and an intermediate layer comprising at least three individual layers, comprising: at least two layers of linear low density polyethylene; and a layer of a mixture of low density, linear polyethylene and additive.