MXPA97001781A - Copolimero de alto encogimie film - Google Patents

Abstract

A biaxially oriented polymer shrink film having a machine direction shrinkage (DM) greater than a shrinkage in the transverse direction (DT), so that the DT is less than or equal to the DM / 2 in the scale from 100øC to140øC. The film comprises at least one of the following: a) a polyolefin copolymer, b) a polyolefin terpolymer, c) blends of polyolefin copolymers and homopolymers, d) blends of polyolefin copolymers and terpolymers, e) mixtures of terpolymers, and polyolefin homopolymers, and f) blends of polyolefin copolymers, homopolymers and terpolymers, wherein the copolymer comprises a first and second monomer, the first monomer is selected from the group consisting of ethylene, propylene, butylene, and mixtures thereof; and the second monomer is selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof. The first monomer is present in the range of 99.5% to 75% by weight and the second monomer is present in the range of 0.5% to 25% by weight. The terpolymer comprises: (i) a primary monomer of ethylene, propylene, butylene, and mixtures thereof, (ii) a secondary monomer of alpha-olefin monomers having from 2 to 10 carbon atoms and mixtures thereof; tertiary monomer of alpha olefin monomers having from 2 to 10 carbon atoms and mixtures thereof, wherein the primary monomer is present in the range of 50% to 99% by weight, and the secondary and tertiary monomers are present in the scale from 0.5% to 49.5% by weight, the homopolymer is polyethylene, polypropylene and polybutylene

Description

HIGH SHRIMP FILM FILM BACKGROUND OF THE INVENTION The present invention is directed to shrink films having a high unidirectional shrinkage in the machine direction (DM) compared to the transverse direction (TD). The invention is also directed to processes for producing said shrink films, methods for using shrink films to produce sheets and sheets resulting from said shrink films. The invention also includes methods for using said shrink films and sheets for packaging and / or labeling articles, and resulting articles, to which said films or shrinking sheets of said shrink film are applied. More specifically, the present invention is directed to the previously mentioned embodiments with respect to the use of oriented polymer films, ie oriented polypropylene (OPP) films, having a variable polymer content, to produce films and shrink sheets. of polyolefin having a high unidirectional shrinkage, which is particularly advantageous for labeling articles, such as beverage containers, which may have an irregular shape. A unique feature of a shrink film is its ability, under heat exposure, to shrink or, if restricted, to create shrinkage tension within the film. When said shrink film is used in a method for labeling or wrapping a container, and then this is subjected to a heating history, this method causes the film to shrink around the product, producing a hermetic, transparent or opaque envelope, which it adapts to the contour of the article and provides useful functions required for labeling or packaging materials. The shrinkage capacity of a film, when exposed to a certain level of heat, arises from the orientation of the film during manufacture. During the manufacture of the film, the films are usually heated to their orientation temperature scale, which varies with the different polymers used for the films, but is usually above ambient temperature and below the melting temperature of the film. polymer. Then, the film is stretched in the cross or cross direction (DT) and in the machine or longitudinal direction (DM) to orient it. After being stretched, the film is quickly cooled until it is extinguished, thus freezing the film in its oriented state. By heating, the orientation tensions are relaxed and the film will begin to shrink to its original, unoriented dimension.

The families of polyvinyl chloride (PVC), polystyrene, polyester, and polyolefins, of shrink films, provide a wide variety of physical and performance characteristics of the film. The characteristics of the film play a very important role in the selection of a particular film and can differ for each type of packaging or labeling applications. Polyolefins have been very successful in applications where moderate to high shrinkage forces are preferred. Polyolefin films are also used in automatic shrink wrapping equipment, at high speed, where the shrinkage and sealing temperature scales are more clearly controlled. Polyolefin films are particularly useful for those types of applications, since polyolefin films tend to be cleaner, leave less deposits and less waste, which extends the life of the equipment, as well as reduces equipment maintenance. PVC films generally have lower shrinkage forces, and will seal and shrink on much broader temperature scales than for polyolefins. Nevertheless, a disadvantage of PVC films, is their tendency to emit noxious gases during heat sealing and combustion during incineration, resulting in corrosion of machinery, as well as a health hazard. Currently, polyolefin shrink films are produced according to the invention, by a secondary orientation (DM) of a biaxially oriented film to increase shrinkage of the DM. The amount of DM shrinkage is defined by the degree of DM orientation.

Polyolefin shrink films having a greater shrinkage in the machine direction than in the transverse direction are described or suggested in the prior art. Peiffer et al., In the patent of E. U.A. 5,292, 561, both single-ply and multi-ply plastic films are described, which have a greater shrink capacity in the machine direction than in the transverse direction. In the single layer product, the film is 60-95% polypropylene, the remainder being a hydrocarbon hydrocarbon. In the form of multiple layers of the product, the core has the same composition as the single layer product; mainly, 60-95% polypropylene, the rest being hydrogenated hydrocarbon. Also, in the multi-layer form of the invention, the outer layer (s) may be an ethylene-propylene copolymer, with a preferred ethylene content in the range of 2% to 10% by weight , and most preferably from 3% to 6%, approximately, by weight. Absolutely, there is no description of the formation of the core layer of the multilayer or single layer film in the single layer film of the aforementioned ethylene-propylene copolymer copolymer. The Japanese patent of Kokoku No. 63 [1988] -62, 390, describes a shrink film, wherein the core is a physical mixture of a copolymer of propylene-ethylene (content of ethylene, 4.5% by weight) and a copolymer of butene-ethylene (content of ethylene, 3% by weight). This polymer mixture constitutes the core layer described in Example 1 of the Japanese publication. It should be noted that although the publication generally states that the shrinkage, either in the DM or DT direction, may be the largest, there is no specific description of any biaxially oriented film, which has a superior orientation (ie, greater shrinkage). ) in the DM address than in the DT address, nor is there any method described to form that product. In this way, the only teaching of the Japanese publication '390 is with respect to the formation of conventional shrink films of the prior art, which have a DT shrinkage capacity greater than the DM shrinkage capacity. Japanese publication No. 89005545, like the Japanese publication '390 mentioned above, only establishes in general that the capacity of heat shrinkage in the transverse or longitudinal direction is more than twice that of the other direction. However, the only specific teaching in the publication '545, is with respect to the formation of a biaxially oriented, conventional film, which has a DT shrinkage greater than DM shrinkage. European publication No. 0 498 249, which was published on August 21, 1992, corresponding to the request of E. U.A Series No. 08/144, 629, the description of which is incorporated herein by reference, and which is assigned to the same assignee of the present invention, generally discloses a biaxially oriented polyolefin film, of a single layer or multiple layers, with the predominant orientation in the MD direction and having a DM shrinkage capacity of 4% to 40%, on the temperature scale of 100 to 140 ° C, and a DT shrinkage capacity in the scale of - 15% to 15%, between 100 ° C and 140 ° C. According to this publication, the highly preferred film is formed of a homopolymer of polypropylene. Although the European publication '249 generally does not state that polypropylene copolymers can also be used with minor amounts of ethylene or an alpha-olefin and the respective mixtures, there is no description of specific compositions of copolymer with percentage scales of their components. The European publication '249 also describes various methods for making biaxially oriented polymer shrink films. These methods involve subjecting a biaxially oriented polymer film to effective processing conditions and temperatures to produce biaxially oriented polymer shrink films., which have thermal properties of shrinkage including shrinkage in the machine direction of the film and in the transverse direction of the film, as a ratio of the MD of DM reorientation / stretching of DT. The invention described in the European publication '249 is also directed to methods for making biaxially oriented polymer shrink films, which involve subjecting a biaxially oriented polymer film to effective processing conditions and temperatures to produce biaxially oriented polymer shrink films. , which have thermal properties of shrinkage, including shrinkage in the machine direction of the film, and in the transverse direction of the film, as a function of temperature. It is important that the shrink film should manifest a resistance to the directional alteration of the DM in dimension, during the typical preparation and application of labels, to maintain a uniform repetition length and record as imparted by the applied heat / tension history. . The film must also be resistant to wrinkling of the MD label and / or directional DT, to maintain the uniform flat appearance of the label in such applications. The film should maintain all the flat aspect of the strip, as exhibited by typical oriented polyolefin films, as well as the stiffness of the individual strip or lamination, as required for conventional printing, laminating and labeling operations. Up to now, these features are not found in prior art films. The invention of the European publication '24 is based on the discovery of temperature parameters, machine traction and film parameters that allow control of the shrinkage resulting from a polymer film. More particularly, by achieving a balance of temperature, stretch ratio, line speed, and oriented film properties, the method of said invention is capable of producing an improved shrinkage in machine direction (DM) with a very low degree of shrinkage in the transverse direction (DT). Said shrinkage equilibrium in MD and DT, particularly in oriented polypropylene (OPP) films, imparts unique characteristics of shrinkage labeling and packaging of said invention. Hercules, Incorporated, prior to the invention described and claimed here, sold biaxially oriented, opaque polyolefin films with a DM shrinkage capacity greater than the DT shrinkage capacity. These films were sold under the designations VISION® 370W and VISION® 370 HW, respectively. These two products included multiple layers, the core layer including a polypropylene homopolymer and a propylene-ethylene copolymer (ethylene content, 2.2%). Again, before the present invention, the core composition of each of these products was changed to a copolymer with 100% propylene-ethylene (ethylene content, 0.6%). Although this product achieved some commercial success, it was determined that the cross directional expansion is more than desirable for the intended primary application of the film, ie to be used in the formation of labels on metal cans and other containers. However, it is highly desirable to be able to achieve better control over the shrinkage characteristics of the transverse direction, by selecting the film components, instead of manipulating the manufacturing process previously discussed with respect to the European publication. 249 These results are obtained by the present invention.

OBJECTS OF THE INVENTION Accordingly, it is a general object of this invention to provide a high shrink film, and a method for producing the film, which overcomes the disadvantages of the prior art. It is a further object of this invention to provide a film and method for producing the film, which is a polyolefin copolymer with a variable content of ethylene, or a mixture of homopolymers and / or copolymers and / or polyolefin terpolymers to produce a film with a superior shrinkage with lower DM orientation levels. It is another object of this invention to provide a film and method for producing the film at a lower mechanical DM orientation, to provide higher shrinkages with a better surface equality of the band.

COMMENT OF THE INVENTION These and other objects of this invention are achieved by providing shrinkage films that are biaxially oriented, single layer or multilayer polymer films that have a machine direction shrink capacity (DM) greater than the capacity of shrinkage in the transverse direction (DT), so that the DT is less than or equal to DM / 2, most preferably on the temperature scale of 100 ° C to 140 ° C. The film consists of single-layer or multi-layer films. Multilayer films include a core layer and one or more outer layers. The single layer of the single layer film and the core layer of the multilayer film comprises a polymer composition composed of at least one of the following: a) a polyolefin copolymer; b) a polyolefin terpolymer; c) physical mixtures of polyolefin copolymers and polyolefin homopolymers; d) physical mixtures of polyolefin copolymers and polyolefin terpolymers; e) physical mixtures of polyolefin terpolymers and polyolefin homopolymers; and f) physical blends of polyolefin copolymers, polyolefin homopolymers and polyolefin terpolymers; wherein the copolymer is composed of first and second monomers: (i) the first monomer being selected from the group consisting of ethylene, propylene, butylene, and mixtures thereof; and (ii) the second monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; wherein the first monomer is present in the copolymer in an amount in the range of 99.5% to 75% by weight, and the second monomer is present in the copolymer in an amount in the range of 0.5% to 25% by weight, since either in a random or non-random sequence within the copolymer; wherein the terpolymer is composed of a primary, secondary and tertiary monomer: (i) the primary monomer being selected from the group consisting of ethylene, propylene, butylene and mixtures thereof; (ii) the secondary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; and (iii) the tertiary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms and mixtures thereof, wherein the primary monomer is present in the terpolymer in an amount on the 50% scale to 99% by weight, and the secondary and tertiary monomers are present in the terpolymer in an amount in the range of 0.5% to 49.5% by weight; wherein the homopolymer is selected from the group consisting of polyethylene, polypropylene and polybutylene; and wherein the shrinkage capacities of DM and DT are as follows: Capability of Capable of Temo, Shrinkage DM shrink DT 100 ° C > 5% > - 10% 120 ° C > 10% > - 12% 140 ° C > 15% > - 10% In another embodiment of the invention, the defined shrinkage capacity occurs within the range of 100 ° C to 120 ° C. In another embodiment of the invention, the defined shrinkage capacity occurs at 120 ° C. In the preferred embodiment of this invention, the polyolefin copolymers are from the group consisting of linear, low density polyethylene copolymers, including a monomer of the class consisting of butylene, hexene and octane, said monomer being present in an amount between 0.5% and 49.5%. ; propylene / ethylene copolymers; propylene / butylene copolymers; and butylene / ethylene copolymers. In the preferred embodiment of this invention, the polyolefin homopolymers are selected from the group consisting of low density polyethylene, having a density in the range of 0.910 to 0.930 g / cm3 (measured at 23 ° C in accordance with ASTM D1505, as are all the density measurements discussed here), high density polyethylene, which has a step density of 0.931 to 0.960 g / cm3, isotactic polypropylenes with heptane insolubles greater than 90% and greater than 0.5 g / 10 min.

MFR (MFR = melt flow rate according to ASTM D 1238 at 230 ° C and 2.6 kilograms), and poly-1-butene. In the preferred embodiment of this invention, the polymer composition comprises a primary polymer of the group consisting of: a) polyolefin copolymers; and b) physical blends of polyolefin copolymers and polyolefin homopolymers; and wherein the polyolefin copolymers are copolymers of propylene with a co-monomer selected from the group consisting of alpha olefins with from 2 to 10 carbon atoms, said co-monomer being present in the range from 0.5% to 25% by weight; and wherein the homopolymers are selected from the group consisting of polyethylene, polypropylene and polybutylene homopolymers. Most preferably, the polymer composition used in this invention comprises primarily polyolefin copolymers selected from the group consisting of: (a) propylene copolymers having a co-monomer selected from the group consisting of alpha olefins with from 2 to 10 carbon atoms , said co-monomer being present in the range of 0.5% to 25% by weight; and (b) a mixture of polypropylene and a propylene / ethylene copolymer, in which ethylene is present in the range of 0.5% to 25% by weight. According to the invention described and claimed herein, the reference to "polyolefin homopolymers", in addition to including polyolefin polymers of only a single monomer, also includes polyolefin copolymers with less than 0.5% of a co-monomer therein.

DESCRIPTION OF THE DRAWINGS Other objects and many features of this invention will be readily appreciated as they are better understood by reference to the following detailed description, when considered in conjunction with the accompanying drawings, in which: Figure 1 depicts a schematic illustration showing a sequential blown film process to make a shrink film; Figure 2 represents a schematic illustration showing a sequential run film method for making a shrink film; Figure 3 is a schematic illustration showing an off-line procedure for making a shrink film; and Figure 4 is a schematic illustration showing a method for making sheets of shrink film.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The basic procedures for producing polymer films, to be used in accordance with the present invention, to make the novel polymer shrinkage films, can be selected from the group of conventional methods such as tubing and laying techniques, such as those described in ASN. 08 / 144,629, the description of which is incorporated herein by reference. DM reorientation involves placing a conventional biaxially oriented polymer film on a series of hot rollers or in an oven, and keeping the temperature of the hot rollers or the furnace below the melting temperature of the film, reduces the tension needed to orient the film. For example, the polymer begins to shrink near 100 ° C, and the shrinkage continues to increase until it melts at more than about 160 ° C. The reorientation of DM can occur after the biaxially oriented film has been produced, or in some cases, the reorientation of DM can occur in a continuous process, while the biaxially oriented film is produced. Most polymer films respond to this DM orientation with improved shrinkage at high temperature. Most of the responses of the films are in the direction of the imposed effort. The basic procedures for producing polymer films for use in accordance with the present invention for making novel polymer shrinkage films can be selected from the group of conventional processes for producing biaxially oriented polymer films., such as tubular and lining techniques. In general, in the tubular or bubble process, the molten polymer is extruded from an annular die and then extinguished to form a tube. The wall thickness of the tube is partially controlled by the void of the annular die, and partly by the relative speeds of the extrusion and the drive. The tube passes through press rolls that run slowly, and then reheated to a uniform temperature. The transverse stretch is achieved by increasing the air pressure in the tube, the stretch ratio, and / or by adjusting the volume of the trapped air. The air is trapped by pressure rollers at the end of the bubble far from the extruder, and these generally operate at a faster speed than the first pair, thus causing the film to stretch in the machine direction. The tubular process, in this way, obtains the simultaneous transversal orientation (DT) and the machine direction (DM). In the laying process, the polymer is extruded through a slot die and extinguished. The extruded sheet is normally oriented in two sequential steps. The first step is usually longitudinal or MD orientation between rollers running at different speeds. In the second step, the film enters the laying frame, which is stretched laterally or DT by means of chains of divergent fasteners. While the bubble process operates at a constant pressure, the laying frame procedure operates at a constant rate of elongation. A little higher stretching forces are required in the second stage, which can be obtained at slightly higher temperatures. This is mainly due to the crystallization of the film during the first stretching operation. The laying frame procedure can also be carried out as a simultaneous operation, wherein an extruded sheet with chamfered edges is biaxially oriented in a laying frame equipped with wide divergent roll holders to hold and stretch the film. The laying operation has the advantage of production films, of considerable versatility with a wide range of shrinkage properties. After stretching, the orientation of the polymer is locked in the film by cooling. When the oriented film is subsequently heated to temperatures close to the stretching temperature, the freezing stresses become active and the film shrinks. The stresses and stresses that are related to the degree of orientation, and the forces that are applied during stretching, are thus recovered. For purposes of the present invention, the biaxially oriented polyolefin MD shrink films may be a transparent, opaque or metallized film. The biaxially oriented polyolefin DM shrink films may be single layer films, multi-layer films, co-extruded films, extrusion coated films or coated films. The biaxially oriented polyolefin DM shrink films may also contain additives or coatings, which reduce the coefficient of friction between two film surfaces or between the film surface and another object, such as a part of the equipment. of packaging or labeling, or can be a part of the container handling line, with containers labeled with films of this invention. The biaxially oriented polyolefin DM shrink films may consist of outer layers that allow the ability to be heat sealed to form an adhesive bond to a second heat sealable film, or be heat sealed to another surface of said heat sealable film. container. The outer layers of heat sealing can be an inherent part of the film, such as that achieved by coextrusion, or may be an added layer after the initial processing of film formation, such as can be achieved by extrusion coating techniques or other standard solution coating techniques, normal in the film industry. The biaxially oriented polyolefin DM shrink films may contain other oriented film additives, such as antiblocking agents, lubricants, antistats, antioxidants, and antacids, and opacifiers, bleaches, and colorants. Biaxially oriented polyolefin shrink films can be treated by corona, flame or other surface treatment techniques, well known in the oriented film industry, and contain coextruded additives or coatings or layers to improve surface functionality , which will improve the adhesion of the surface to other requirements of the surface of the film, such as printing, lamination, adhesion, label adhesion and metallization. The biaxially oriented polyolefin DM shrink films should preferably have a total thickness of between 40 to 250 gauge, and most preferably in the range of 70 to 140 gauge. The biaxially oriented polyolefin DM shrink films can be used as labels or other forms of packaging. They can be used as individual layers of films or can be used as lamination for films with two or more shrink films, or with at least one shrink film and one or more films without shrinkage.

Description of the Polymer For purposes of the present invention, the polymer composition or the composition of the core layer, of the multi-layer films, of the biaxially oriented MD shrink films consists mainly of polyolefin copolymers, terpolymers , or mixtures of polyolefin copolymers and / or terpolymers, or physical blends of polyolefin copolymers or terpolymers with polyolefin homopolymers. For purposes of the present invention, a physical mixture of polymers does not require a chemical reaction between the polymers, but is achieved by mechanical mixing. The polyolefin copolymers of this invention can be selected from copolymers, which are composed of ethylene, propylene or butylene, as a primary component, and are composed of other alpha-olefin monomers with from 2 to 10 carbon atoms. The alpha-olefin co-monomer may be present on a scale of 0.5% to 25% by weight and may exist in a random or non-random sequence within the copolymer composition. These include, but are not limited to, linear, low density polyethylene copolymers, which are typically composed of ethylene with minor amounts of butylene, hexene, or octane, such as the co-monomer; propylene / ethylene copolymers; propylene / butylene copolymers; and butylene / ethylene copolymers. For purposes of the present invention, polyolefin copolymers with less than 0.5% by weight of a co-monomer are classified as a homopolymer of the predominant component. The polyolefin terpolymers of this invention may be selected from terpolymers, which are composed of ethylene, propylene, or butylene, as the primary component, and may be composed of secondary and tertiary monomers of other alpha olefins with from 2 to 10 carbon atoms. carbon. The composition of the primary monomer may be from 50% to 99% by weight, with the composition of the secondary and tertiary monomers from 0.5% to 49.5% by weight. The homopolymers of this invention may be selected from polymers of polyethylene, polypropylene, or polybutylene. Polyethylene homopolymers, which are generally designated as low density polyethylenes (density = 0.910 to 0.930), and high density polyethylenes. The polypropylenes are generally from the group of isotactic polypropylenes with an insoluble content of heptane greater than 90% and greater than 0.5 g / min. MFR. Polybutylene homopolymers are generally poly-1-butene. Polyolefin copolymers with less than 0.5% of a co-monomer, for the purposes of this invention, are considered as homopolymers, and are classified as a homopolymer of the predominant component.

Polymer Description The preferred polymer composition of this invention is composed primarily of polyolefin copolymers or mixtures of polyolefin copolymers and homopolymers, wherein the copolymers are selected from the group consisting of propylene copolymers, the co-monomer selected from the group of alpha olefins with from 2 to 10 carbon atoms, wherein the co-monomer is present at a composition of 0.5% to 25% by weight, and the homopolymers are selected from polyethylene, polypropylene or polybutylene homopolymers. The highly preferred polymer composition of this invention is composed primarily of polyolefin copolymers, wherein the copolymers are selected from the group of propylene copolymers, the co-monomer selected from the group of alpha olefins having from 2 to 10 carbon atoms, wherein the co-monomer is present at a composition of 0.5% to 25% by weight, or is composed primarily of a mixture of polypropylene and a propylene / ethylene copolymer, wherein the ethylene is present at a composition of 0.5% to 25%. %.

Shrinking Scale The shrinkage capabilities of DM and DT of the films of the present invention are as follows: TEMP. MD DT 100 ° C: > 5% > - 1 0% 120 ° C: > 1 0% > - 1 2% 140 ° C: > 1 5% > - 1 0% The films of the present invention, which are biaxially oriented multilayer single layer polymer films, have a machine direction shrink capacity (MD) greater than the shrinkage capacity of the transverse direction (DT ), so that the DT is less than or equal to DM / 2 at 120 ° C. In a highly preferred embodiment, the film of the present invention has a shrinkage capacity in the machine direction (DM) greater than a shrinkage capacity in the transverse direction (DT), so that the DT is less than or equal to DM / 2 through the entire temperature range from 100 ° C to 120 ° C. In another highly preferred embodiment, the film of the present invention has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is less than or equal to DM / 2 across the entire temperature range from 100 ° C to 140 ° C. The shrink films of this invention may also exhibit a variety of surface behaviors or characteristics, common to typical biaxially oriented packaging films, as is well known in the art. The character of a polymer surface can be changed in several ways. One method is to expose the surface to an energy source, such as corona discharge, flames, plasma, X-ray or electron bombardment. This can be done over a wide range of temperatures, in an inert atmosphere or in a reactive atmosphere. Depending on the temperature, the intensity, the speed of application and the frequency of the energy, and the nature and concentration of the chemical medium in contact with the surface before, during, and / or after the application of energy, a wide scale of physical and / or chemical modifications of the surface of the film. A second way to change a polymer surface is to make an internal chemical additive debase the surface by applying or removing heat from the film. Alternatively, a substance on the surface of the film can migrate into the film and away from the surface by applying or removing heat from the film. The chemical nature of the substance or additive, and the time / temperature history to which it is exposed, can lead to a wide variety of possible surface modifications. A third way to change a polymer surface is to cause a change in morphology by applying heat and / or pressure to the film. The physical and topological nature of the surface can be altered, for example by annealing a film and changing the crystal structure present on the surface of the film. The reorientation of DM of biaxially oriented polymer films is more complex than for conventional films, due at least in part to the initial residual stresses placed on the film. In prior art processes, the fibers and strips of polymer films can be stretched or stretched to reorient the structure to produce different properties from the original product.

Measurement of Unrestricted Linear Shrinkage In the present invention, the following procedure, derived from the method ASTM D2732-83, which is designed to measure unrestricted linear shrinkage, in both machine and transverse directions, was used to measure shrinkage of unrestrained linear thermal film in one direction at a time. First, a bath of polydimethylsiloxane fluid (0.5 is) was preheated to the desired temperatures within the range of about 100 ° C to 140 ° C. The film samples were cut at 1.27 cm by 22 cm and an opening of 20 cm was marked in the center of the sample. The ends were left on a sample, so that the sample could be anchored for immersion. One end of at least three films of each sample was placed on an immersion support. A metal connection clamp of 1.2 grams was attached to the free long end of each film strip, to keep the film floating in the bath. The direction of the machine and the transverse direction were tested for each film. Afterwards, the heater / agitator was turned off and the samples on the support were immersed in the bath at the appropriate temperature, for 5 seconds before being removed from the liquid. The samples were measured and their percent shrinkage was calculated. For example, with a sample with a length of 20 centimeters, a shrinkage of one millimeter is equal to a shrinkage of 0.5%. The average shrinkage percentage of all the samples that run in one direction (DM or DT) is then recorded for a particular film sample. If there is an elongation instead of a shrinkage, then a negative value is reported. The unique thermal shrinkage properties, combined with the orientation / tension properties of the novel polymer shrinkage films of the present invention, allow the useful practice of using conventional labeling equipment of the novel films of the present invention. The tensile strength, elongation and modulus were measured using the ASTM D882 test procedure. The methods of the present invention for producing shrink film and resultant shrink film layers and sheets, as described herein, are polymer-based polyolefin films. In this regard, the character of the polyolefin in the film is preferably a copolymer of propylene with ethylene or other alpha-olefin co-monomers. Copolymers of ethylene or butene can be used with an alpha-olefin co-monomer of C2 to Cio or copolymers of propylene, ethylene or butene as mixtures with other polyolefin homopolymers or copolymers.

Commercially available, typical film-forming propylene homopolymers are crystalline or isotactic in their molecular structure and typically have a flow rate of about 0.5 to 10 dg / min. Conventionally, the polyolefins are mixed with conventional additives such as antioxidants, light stabilizers, inorganic antacids, such as calcium oxide or magnesium-aluminum hydroxide carbonate hydrate, in addition to fatty acid amide slip agents and anti-block particles. common for packaging film technology. According to the present invention, the novel polymer shrink films of the present invention can be used as a single band or formed into a sheet, the use as a sheet being particularly beneficial. For the purposes of the present invention, any conventional lamination process can be used, provided that the novel polymer shrink film of the present invention is capable of being properly laminated using known technology, for example, selected from the group consisting of wet bond, dry bond, heat melt or wax lamination, extrusion lamination, or thermal or heat lamination; however, dry bonding and thermal or heat lamination are preferred. Dry bonding involves applying adhesive to one of the films or bands. The solvent is evaporated from the adhesive, and the adhesive coated web is combined with the other web material by heat and pressure, or only by pressure. Thermal lamination gathers coated substrates under heat and pressure. Typically, the bands are heated to the softening point of the coating; however, improved results are obtained, for example, when using preheated rolls and a steam box. In this regard, labels are usually printed, and printing is expected to be permanent. If the exposed printed surface is abraded, then the print can be removed or scratched. If, however, the print is on the inner surface of a transparent film, and this transparent film is laminated to another film, the print is protected by the transparent film. Alternatively, printing can be done on the internal surface of the transparent or opaque strip, which is then laminated to the transparent protective band. In addition, the outermost surface of the sheet can be made matt, glossy, with a low coefficient of friction, different in functionality or surface composition, independent of the nature of the surface required to accept inks. The printing can also be applied to a transparent film layer and can be laminated to the printed band either a transparent or opaque film, or a metallized version of any type of film. For the purposes of the invention, novel polymer shrink films can be printed using conventional printing techniques, including flexographic printing and rotogravure printing. Flexographic printing processes typically employ presses selected from the group consisting of stack presses, central printing, and inline printing. Flexographic printing is preferred, which employs a common printing or central printing plate. The method for using the novel polymer shrink films of the present invention to produce sheets, which are applied to an article according to the present invention, has been found to overcome the aforementioned disadvantages. Also, shrink films with different shrinkage properties can be laminated to a common printed shrink film, to give sheets with different shrinkage properties designed for the particular container or application requirements. further, shrinkage films of different shrinkage properties can also be laminated together to give a sheet whose shrinkage properties can be difficult to obtain using only a single film. With regard to the embodiment of the present invention employing the film sheets, the heat shrink laminations may be composed of two or more polymer shrink films or heat shrink films. Each polymer shrinkage film or band can itself function as a heat shrinkable label, or each film can be transparent or opaque, metallized or non-metallized, and have similar or different character and shrinkage properties in the film. surface. The process of the present invention can be further appreciated by reference to the following examples, which, of course, are only representative of the present invention and are in no way intended to limit the present invention to any of the particular forms that are described. In this way, the following examples are presented merely as non-limiting examples to further explain the present invention.

Sequential Blow Film Method The manufacturing apparatus used in the sequential blown film process, as shown in Figure 1, consists of an extrusion system 1, a tubular die 2, a water bath extinguishing system 3 , a press roller assembly 4, a reheat furnace 5, a single lid bubble blowing section 6 (where the DM and DT stretch occurs), a convergence section 7, including converging rollers 7a, 7b and 7c and drag rollers 8, a heating furnace 9 for altering the shrinkage properties, drag rolls 10 and a mill roll winder 1 1. The extrusion system 1 consists of an extruder with output capacities of 1 1, 340 g / hr. The terminal end of the extruder has an annular die 2, which forms the molten polymer to a hollow polymer tube (diameter 15.24 cm). After the polymer tube has been extruded, it is cooled in a temperature-controlled water bath 3. The tube continues towards a contact line 4 and towards the ovens 5, where the polymer tube is reheated. At this point, the tube is blown into a thin wall bubble 5. The controlled internal pressure in the polymer tube causes the hot tube to expand, stretching the film in the DT direction. A fast contact line (with speed S1) of the driving rollers 8, located after the v-shaped converging section 7, of multiple rollers 7, causes the bubble to be stretched in the MD simultaneously with the DT stretch. The wide stretched film (W1) passes through a heating furnace 9. The width is followed to contract at the end of the furnace (W2), resulting in altered shrinkage properties in the DT. The film is pulled through the heating furnace by a contact line of the drag rollers 10, located at the end of the furnace. The speed at which the contact line pulls the film through the furnace is represented by S2. By controlling the speeds S 1 and S 2, the shrinkage properties of the DM are altered. The speed S2 may be greater than, equal to, or less than S 1, depending on the desired final shrinkage properties. Then, the film is wound on a roller using a mill roller reel 1 1. In the present invention, the normal tubular procedure can be used although it is not necessary. Further, in the present invention, the heat setting step in the starting tower film is not necessary, but it can be used.

Sequential Laying Film Process The manufacturing process used for the purposes of the present invention is illustrated schematically in Figure 2. It is composed of four extruders in an extruder section and given 21, a driving section in the DM of a / two stages, 22, a laying furnace 23, a stretching unit in the rear DM 24, and a mill roll winder 25 The extrusion system 21 is composed of a main extruder (maximum output 60 kg / hr ) and 3 satellite extruders (two with a maximum output of 12 kg / hr and one with a maximum output of 6 kg / hr), (not shown). The one-stage casting unit of the one-stage / two-stage DM section, 22, is composed of an air knife (not shown), a chrome casting roller 26, a water bath (not shown) , and a drainage air knife (not shown). The melt bath is laid on a cold roll (not shown), which places one side of the cast in contact with a cold mirror chrome surface. Seconds later, the other side of the casting is introduced to the water bath. The drum or casting roller 26 is heated and cooled with oil, allowing rapid change of temperature.

The front drag unit 27 of the drag section 22 in the DM allows the film to travel around an oscillating roller (not shown), six pre-heated rollers (not shown), about six drag rollers (not shown), four (fast) annealing rollers (not shown), and an oscillating output roller (not shown). Using circulation oil, all rollers are capable of heating and cooling. The laying furnace 23 consists of six sections (not shown). Each section has a separate temperature control (not shown) and a fan (not shown) for airflow control. The oven has electrically heated air, with a variable temperature range of 50 ° C to 250 ° C in any section. The maximum drag for any single section, which uses a normal uniaxial width, is seven times. Using two orientation sections, the run is capable of presenting a maximum DT drag of 10 times. The furnace is equipped with a clamping cooling, which allows the drag to temperatures above 200 ° C. The laying apparatus is a trailing unit 24 in the rear DM, in line, which takes the film directly from the laying furnace. The MD laying apparatus consists of 9 mirror chrome preheating rolls (not shown), one or two stage drag (not shown), and four fast chrome rolls (annealing) (not shown). The unit uses 180 ° wraps on the nine preheating rollers (not shown) to reduce slippage. The rollers are mounted alternately on two separate frames. The temperature of the preheating rollers is controlled in joint pairs. Infrared heating is an option at the point of drag.

Off-line Procedure The manufacturing apparatus shown in Figure 3 consists of a winder platform 31, fifteen driven film rollers 32, (each with a variable speed and heating control), including a driven cooling roller, and a winder platform 33. The biaxially oriented film that is to be converted to the shrink film is loaded onto the winder platform 31. This film can be produced by any procedure; However, generally biaxially oriented films made by a laying or bubble process are used. This film can be transparent or opaque, and single-layer or multi-layer. The film usually has a thickness scale of a caliber of 50 to 200, most preferably of a nominal caliber of 60 to 140. After winding, the film passes from the feeding section (three driven rollers, i.e. ), towards a preheating section. This section of three driven rollers, ie 4-6, contains two preheated rolls of large diameter with a 180 ° film wrap, to raise the input film to the proper operating temperature.

Then, the film is passed through a driving zone of 5 driving rollers, ie 7-1 1, followed by a corona treatment zone with two driving ceramic rollers, ie, 12 and 13 , then on a cooling roll 14 of large diameter, which reduces the temperature of the film before winding, and finally, through an output contact line (15) before winding. The speeds of the drive roller increase from winding to winding, allowing the film to be stretched or tensioned in the machine or longitudinal direction. The roller speed of roller 1 at the entrance to the feeding zone is nominally 243.8 meters / minutes. The speed of the roller in the cooling roller 14 varies from 30.48 to 52.2 meters / minutes, depending on the amount of desired drag that is to be imparted to the film. The average operating temperature of the process is usually between 90 ° C and 150 ° C, with the temperature of the cooling roller varying from 15.5 ° C to 32.2 ° C. As used herein, "roller speeds" are machine speeds that are measured using a tachometer, where "S 1" is the roller input speed measured in meters / minutes; and "S2" is the exit speed of the roller measured in meters / minutes. The "film speeds" are the actual speeds of the surface film as measured by a tachometer, where "F1" is the speed of film input measured in meters / minutes; and "F2" is the output speed of the film measured in meters / minutes. "T1" is defined as the input thickness of the film and "W1" is the input width of the film. "T2" is the output thickness of the film, and "W2" is the output width of the film. As used in this: Operation Speed Ratio is RS = S2 / S 1 Film Drag Ratio is RD = T1 xW1 / (T2xW2) Mechanical Drag in the DM is the ratio of the output speed of the roller to the roller input speed. For the purposes of the present invention, the roller input speed (S1) has a preferred scale of 60.9 to 457.2 m / min, a preferred scale being from 228.6 to 259.08 m / min, a highly preferred scale being 243.8 m / min. min. The exit speed of the roller (S2) has a preferred scale of 61.2 to 457.5 m / min, a preferred scale being 320.04 to 426.7 m / min, and a highly preferred scale being 335.2 to 396.2 m / min. RD is calculated as a preferred scale of .01 to 1.5, preferably on a scale of 1.1 to 1.34, and most preferably of a scale of 1.25 to 1.4. The preferred temperature scale for imparting the desired properties of shrinkage is 70 ° C to 160 ° C, a preferred scale being from 90 ° C to 130 ° C and a very preferred scale being from 100 ° C to 120 ° C. The preferred method and means for heating the film can be done by the use of hot rollers, a hot air oven or an infrared oven. The most preferred method of heating the film is by the use of hot rolls and infrared ovens, the most preferred method being hot roll. The preferred number of entrainment voids is between 1 and 12, the most preferred number being between 1 and 6. The film thickness in S1 has a preferred scale with a caliber from 40 to 200, with a very preferred caliber in the transparent film in the scale of 60 to 1 10, and in the opaque film in the scale of 90 to 140. The most preferred caliber in the transparent film is between 70 to 90, and within the scale of 120 to 140 for the opaque film. The type of film anchor during the drag includes clamping rollers and electrostatic pressers, both types being preferred. The film tension during the drag has a preferred scale of 140.6 kg / cm2 to 703 kg / cm2.

Laminations of Shrink Films for Labels Figure 4 schematically illustrates a film lamination process, wherein a film lamination is prepared by coating one side of a roll of the film 31 with an adhesive solution 42, evaporating the solvent in a furnace 43 , then bringing the coated side into contact with the other roll of the film 44 on a combination contact line 45. The roll resulting from the shrink film lamination 46 for labels is then wound. A roll 41 with a width of 50.8 cm, of film, is mounted on the primary winder platform of a printer-coater-laminator of Faustel. This film can be a shrink film either transparent or opaque. A thermosetting urethane adhesive, Morton Adcoat 333, is diluted with methyl ethyl ketone until a cup viscosity # 2 Zahn of 17.5 is obtained. This adhesive solution 42 is placed in a reservoir 47 in contact with a four-pattern gravure cylinder 48, chosen to supply an adhesive coating with a weight of 0.3178 to 0.681 kg / ream for the film at 609.6 m / min. One side of the shrink film for labels is coated with the adhesive by direct gravure coating. If the film becomes opaque with voids, it is preferred that the side be coated with an adhesive consisting of a thin skin, without gaps. The solvent is evaporated from the film coated with the adhesive, in a drying tunnel 43 maintained at 170 ° C to 180 ° C for a period of resistance of 3.5 seconds. The tension in this film band is maintained at 13.38 kg / linear m. A second roller 44 of a shrink film for labels with a width of 50.8 cm was mounted on a secondary winder platform. It can be a shrink film for labels either transparent or opaque, coated or metallized.

The tension of this film web is maintained from approximately 17.85 to 22.31 kg / linear m. The coated surface of the primary film is then contacted with one side of the second label shrink film roll, under a pressure on a combination contact line 45. If the second film becomes opaque containing voids, it is preferred that the side that comes into contact with the adhesive coated side consist of a thin, non-void layer. The resulting laminated roll 46 is wound on a winder platform. The novel shrink films of the present invention have been found to be particularly advantageous for labeling articles having irregular shapes, for the purposes of the present invention, the article may be a straight walled container of contoured aluminum, of steel, of metal, plastic, glass, mixed material, or tubular or spiral wound cardboard (especially a tin or tin container), for beverages, especially soft drinks and beer, food or aerosols. Either a single layer or laminated layers of the novel polymer shrinkage films, according to the present invention, are capable of being shrunk with heat onto an article, such as a beverage can, the upper and lower parts of which they are tapered inwards. The novel shrink films and sheets of the novel shrink films of the present invention are particularly advantageous for labeling more modern beverage cans, which taper inwards at the upper and lower ends, so that a label avoids spreading towards these extremities or conform closely to the forms thereof; for example, according to the procedures described in the patent of E. U.A. No. 4, 844,957, the description of which is incorporated herein by reference. For the purposes of this particularly described embodiment of the present invention, the input packages are separated by a power spindle, and transferred, via the power star, to a central rotating carousel. Here, firmly located between a base platform and a central upper bell, they are rotated around their own axis. As the label on the film is removed laterally from the group, it receives heat-melt adhesives to provide the overlapping bond, although other previously described adhesion methods may also be used, according to the present invention, for example, to provide a layer of heat sealing. The continuous rotation of the packet beyond a short sweep section ensures a positive overlap seal. The fully labeled packages are then transferred, via the discharge star wheel, to the downstream conveyor. The labeling machine is particularly useful for applying wrapping film labels made of a shrink plastic film, in which case the overlap bonding is achieved by the aforementioned heat fusion adhesion technique. The adhesive used depends on the type of plastic film used. The plastic film label is applied in the conventional manner described above by the labeller, using the heat fusion adhesive, and the size of the film label is such that it extends (upper and lower) beyond the cylindrical portion. of the bottle or the can. After labeling, the bottles or cans are passed through a heating section to ensure that the film label areas, top and bottom, shrink tightly and uniformly to the contours of the bottle. For the purposes of the present invention, it has been discovered that hot air can preferably be directed towards the upper and lower part of the film label or another specific area of the labeled container, where a non-uniform contour is located to allow the preferential shrinkage of film labels that shrink by heat, in these areas. In contrast to the present invention, it has been observed that none of the conventional film labels, without shrinkage, is suitable for labeling irregularly shaped beverage containers, and other irregularly shaped articles, as contemplated in accordance with the present invention. For example, it has been observed that conventional, non-shrinkable film labels are deformed during the process of applying them to irregular articles, for example, by heat shrinkage. More particularly, however, such conventional non-shrinkable film labels, and particularly non-shrinkable laminated film labels, easily do not conform to the irregular configuration of the article, especially at the tapered ends of beverage containers such as cans. . Thus, according to the present invention, an irregularly shaped article, such as a beverage container, which includes a cylindrical wall of metal, glass or plastic, and an upper part and a bottom on the wall, wherein the wall tapers inward adjacent the top / bottom to form upper and lower tapered portions, is provided with a heat shrink film, or lamination of novel shrink films produced in accordance with the present invention, to enclose the wall and forming the tapered portions, for example, as described in the E patents. U .A. 4,704, 172 and 4,844,957, the description of which is incorporated herein by reference. Preferably, the shrink film label comprises first and second films as a lamination.

EXAMPLES In the present invention, the polymers that can be used to produce this new shrink film in DM include: a) a polyolefin copolymer; b) a polyolefin terpolymer; c) physical mixtures of polyolefin copolymers and polyolefin homopolymers; d) physical mixtures of polyolefin copolymers and polyolefin terpolymers; e) physical mixtures of polyolefin terpolymers and polyolefin homopolymers; and f) physical blends of polyolefin copolymers, polyolefin homopolymers and polyolefin terpolymers; wherein the copolymer is composed of first and second monomers: (i) the first monomer being selected from the group consisting of ethylene, propylene, butylene, and mixtures thereof; Y (ii) the second monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; wherein the first monomer is present in the copolymer in an amount in the range of 99.5% to 75% by weight, and the second monomer is present in the copolymer in an amount in the range of 0.5% to 25% by weight, since either in a random or non-random sequence within the copolymer; wherein the terpolymer is composed of a primary, secondary and tertiary monomer: (i) the primary monomer being selected from the group consisting of ethylene, propylene, butylene and mixtures thereof; (ii) the secondary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; and (iii) the tertiary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms and mixtures thereof, wherein the primary monomer is present in the terpolymer in an amount on the 50% scale to 99% by weight, and the secondary and tertiary monomers are present in the terpolymer in an amount in the range of 0.5% to 49.5% by weight; wherein the homopolymer is selected from the group consisting of polyethylene, polypropylene and polybutylene; and wherein the shrinkage capacities of DM and DT are as follows: Temp. Shrinkage DM Shrink DT 100 ° C > 5% > -10% 120 ° C > 10% > -12% 140 ° C > 5% > - 10% The examples of this invention are presented as a demonstration of I object of this invention, wherein the level of shrinkage in the DM is a function of the composition of the polymer employed, when it is prepared under similar conditions of orientation procedure in the DM. Of course, the orientation conditions in the DM, mainly the degree of orientation in the DM, and to a lesser degree, the orientation temperature in the DM, also have a significant relationship with the level of shrinkage in the DM in the films of shrinkage in the DM. Examples are listed using polyolefin polymer compositions including polypropylene, polypropylene with 7% hydrogenated hydrocarbon resin additive, propylene / ethylene copolymers at about 1.4%, about 2.2%, and about 4.5% ethylene, a mixture of polypropylene and a copolymer of approximately 2.2% propylene / ethylene, and a copolymer of approximately 8% propylene / butylene. These polymer compositions were processed at three orientation levels in the DM by an off-line MD orientation procedure, as described above. As described in Table I, it is shown that the level of shrinkage in DM, especially at temperatures up to 140 ° C, is a function of the polymer composition. The normal polypropylene polymer composition of Example 1 results in a very low level of shrinkage in the DM at 140 ° C. The level of shrinkage in DM can be increased by other polymer additives, such as a hydrogenated hydrocarbon resin, as detailed in example 2, but the object of this invention is to obtain this improved performance in DM by modifying the base polymer, by adding a co-monomer or co-monomers to the polyolefin polymer. This results in a reduction in the melting point and a total crystallinity and under equivalent processing conditions of shrinkage films in the DM, as described in this invention, a higher level of shrinkage in the DM, especially at higher temperatures. up to 140 ° C. These new polymer shrink films are advantageous with respect to the prior art, since they achieve a higher level of maximum shrinkage in the DM and achieve a given level of shrinkage in the DM at a lower temperature. These aspects are useful to obtain a shrink film in the DM, which has a higher level of shrinkage in the DM, which is useful when shrinking the non-uniform contour of articles or containers with a higher percentage of dimensional change. These aspects are also useful for obtaining a shrink film in the DM, which has a shrinkage in the DM given at a lower temperature, which is advantageous for certain labeling or packaging procedures, or it is beneficial to minimize the shrinkage. exposure to the temperature of the article or container labeled or packaged. The approach of this invention, by modifying the polyolefin polymer composition to obtain higher levels of shrinkage in DM, is preferred over other approaches described in the prior art, such as employing a higher level of orientation in DM in the manufacturing process, which results in increased manufacturing difficulties, or add polymer additives without polyolefin to the polymer composition, such as a hydrogenated hydrocarbon resin, which is typically more complex, more expensive and may have other effects harmful side effects, as a consequence of additives without polyolefin, such as plate out of production, labeling equipment or packaging. These examples are only considered as a demonstration of this invention and are not intended to be inclusive or limiting in any way.

EXAMPLES-PROCEDURE An off-line MD orientation procedure was used to prepare polyolefin shrink films. This procedure is similar to the off-line procedure described in the detailed description. First, all samples were prepared as biaxially oriented films, by a normal polypropylene, tubular oriented film forming process. The total biaxial film orientation was approximately 7 times in the DM and DT directions. The off-line procedure is as described in Figure 3, and consists of a winder platform, a series of 15 heated and driven rollers (variable speed and temperatures), a cooling roller, a treatment section, and a section of winding or support. Three orientation procedure conditions were used in the DM to prepare polyolefin shrink films. These procedural conditions varied mainly in the degree of orientation of the DM. This was achieved by changing the ratio of maximum to minimum roll speed. An increase in the roll speed ratio results in an increase in the orientation of the film in the DM and consequently, shrinkage in the DM.

PROCEDURE 1 The minimum roll speed for the orientation procedure in the off-line MD was 304.8 m / min, and this was the first roll after the winding section. The maximum speed of the roller was 320 .04 m / min, and this was the tenth roller in this series of rollers. Roller surface temperatures varied from 100 ° C to 125 ° C.

PROCEDURE 2 The minimum speed of the roller for the orientation procedure in the DM off-line was 304.8 m / min, and this was the first roller after the winder section. The maximum speed of the roller was 376.1 m / min, and this was the tenth roller in this series of rollers. Roller surface temperatures varied from 100 ° C to 125 ° C.

PROCEDURE 3 The minimum speed of the roller for the orientation procedure in the DM off-line was 304.8 m / min, and this was the first roller after the winder section. The maximum speed of the roller was 396.2 m / min, and this was the tenth roller in this series of rollers. Roller surface temperatures varied from 100 ° C to 125 ° C.

EXAMPLE 1 The polymer composition of Example 1 consisted of a polypropylene polymer sold by EXXON Corporation, under the designation Exxon Escorene PD 4222 E 1, MRF = 4 g / 10 min, and about 94% insoluble heptane. This sample also contained minor amounts of other additives such as an amide slip agent (0.35% by weight of Kenamide B, from Witco Chemical Company) and a clay antiblocker (0.20% by weight of Kaophile® 2, from Georgia Kaoline).

EXAMPLE 2 The polymer composition of Example 2 consisted of isotactic polypropylene sold under the designation Himont Profax® 6501, MFR = 4 g / 10 min, and 7% by weight of a hydrogenated hydrocarbon resin sold by Hercules Incorporated (under the designation Hercules Regalrez ® 1 128). This example also contained minor amounts of other additives such as an amide slip agent (0.12% by weight of Kenamide B, Witco Chemical), a clay antiblocker (0.36% by weight of equal parts of Kaophile 2, Georgia Kaolin and Kaopolite SFO). , by Antor, Inc), and an antioxidant (0.10% by weight of Ethanox 330, Ethyl Chemical) and an antacid (0.10% calcium stearate).

EXAMPLE 3 The polymer composition of Example 3 is a propylene / ethylene copolymer, Exxon Escorene PP 9122 (about 2.2% ethylene).

EXAMPLE 4 The polymer composition of Example 4 is a propylene / ethylene copolymer, Exxon Escorene PLTD 994 (approximately 1.4% ethylene).

EXAMPLE 5 The polymer composition of Example 5 is a propylene / ethylene copolymer, Fina 8573 (about 4.5% ethylene).

EXAMPLE 6 The polymer composition of Example 6 is a 50/50 mixture of a polypropylene, Exxon Escorene PD 4222 E1 and a propylene / ethylene copolymer, Exxon Escorene PP 9122 (about 2.2% ethylene).

EXAMPLE 7 The polymer composition of Example 7 is a propylene / butylene copolymer, Shell Cefor SRD4-12 (approximately 8% butylene). Without further elaboration the above will fully illustrate the invention that others may, applying current or future knowledge, adapt it for use under various service conditions.

Claims (1)

CLAIMS 1 - . 1 - A biaxially oriented shrink film comprising a biaxially oriented individual layer and biaxially oriented multiple layers having a machine direction shrink capacity (DM) greater than the shrinkage capacity of the transverse direction (DT) in a manner that said DT is less than or equal to DM / 2, within the temperature range of 100 ° C to 140 ° C, where the film is selected from the group consisting of single-layer films and multi-layer films , said multilayer films including a core layer and one or more outer layers, characterized in that said single layer of the single layer film and the core layer of the multilayer film comprises a polymer composition composed of less one of the following: a) a polyolefin copolymer; b) a polyolefin terpolymer; c) physical mixtures of polyolefin copolymers and polyolefin homopolymers; d) physical mixtures of polyolefin copolymers and polyolefin terpolymers; e) physical mixtures of polyolefin terpolymers and polyolefin homopolymers; and f) physical blends of polyolefin copolymers, polyolefin homopolymers and polyolefin terpolymers; wherein the copolymer is composed of first and second monomers: (i) the first monomer being selected from the group consisting of ethylene, propylene, butylene, and mixtures thereof; Y (ii) the second monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; wherein the first monomer is present in the copolymer in an amount in the range of 99.5% to 75% by weight, and the second monomer is present in the copolymer in an amount in the range of 0.5% to 25% by weight, either in a random or non-random sequence within the copolymer; wherein the terpolymer is composed of a primary, secondary and tertiary monomer: (i) the primary monomer being selected from the group consisting of ethylene, propylene, butylene and mixtures thereof; (ii) the secondary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof; and (iii) the tertiary monomer being selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms and mixtures thereof, wherein the primary monomer is present in the second polyolefin copolymer in an amount on the scale from 50% to 99% by weight, and the secondary and tertiary monomers are present in the second polyolefin copolymer in an amount in the range of 0.5% to 49.5% by weight; wherein the homopolymer is selected from the group consisting of polyethylene, polypropylene and polybutylene; and wherein the shrinkage capacities of DM and DT are as follows: Temp. Shrinkage DM Shrink DT 100 ° C > 5% > -10% 120 ° C - > 10% > -12% 140 ° C > 15% > -10% 2. The film of claim 1, wherein the first polyolefin copolymer is selected from the group consisting of propylene / ethylene copolymers; propylene / butylene copolymers; butylene / ethylene copolymers and linear low density polyethylene copolymers, which include a monomer selected from the group consisting of butylene, hexene and octane, said monomer being present in an amount of between 0.5% and 49.5% by weight. 3. The film of claim 1, wherein the polyolefin homopolymers are selected from the group consisting of low density polyethylene having a density in the range of 0.910 to 0.930 g / cm3, high density polyethylene having a density on the scale of 0.931 to 0.960 g / cm3, isotactic polypropylenes with heptane insolubles greater than 90% and greater than 0.5 g / 10 minutes MFR, and poly-1-butene. 3. The film of claim 2, wherein the polyolefin homopolymers are selected from the group consisting of low density polyethylene having a density in the range of 0.910 to 0.930 g / cm3, high density polyethylene having a density in the range of 0.931 to 0.960 g. / cm3, isotactic polypropylenes with heptane insolubles greater than 90% and greater than 0.5 g / 10 minutes MFR, and poly- 1 -butene. 5 - A method for making a shrink film tensioned in the MD of biaxially oriented polymer, the film having a shrinkage in the machine direction (DM) greater than a shrinkage in the transverse direction (DT), so that the DT is less than or equal to DM / 2 at temperatures in the range of 100 ° C to 140 ° C, wherein the method comprises the steps of: a) selecting a biaxially oriented film according to claim 1; and c) subjecting the biaxially oriented polymer film to a further orientation in the DM at an effective temperature to produce biaxially oriented polymer shrink films having shrinkage characteristics as defined in claim 1. 6 - In combination, an article that is to be packed as a shrink film, wherein it comprises a film according to claim 1. 7. - The film of claim 1, wherein the polymer composition comprises a primary polymer of the group consisting of: a) polyolefin copolymers; and b) physical blends of polyolefin copolymers and polyolefin homopolymers; and wherein the polyolefin copolymers are copolymers of propylene with a co-monomer selected from the group consisting of alpha olefins with from 2 to 10 carbon atoms, said co-monomer being present in the range from 0.5% to 25% by weight; and wherein the homopolymers are selected from the group consisting of polyethylene, polypropylene, and polybutylene homopolymers. 8. The film of claim 1, wherein the polymer composition comprises primarily polyolefin copolymers selected from the group consisting of: (a) propylene copolymers having a co-monomer selected from the group consisting of alpha olefins with to 10 carbon atoms, said co-monomer being present on the scale of 0.5 to 25% by weight; and (b) a mixture of polypropylene and a propylene / ethylene copolymer wherein ethylene is present in the range of 0.5% to 25% by weight. 9. The film of claim 1, wherein the biaxially oriented shrink film is a multilayer film. 10 - The film of claim 1, wherein the biaxially oriented shrink film is a transparent film.

1 - The film of claim 1, wherein the biaxially oriented shrink film is an opaque film. 12. The film of claim 1, wherein one or more of a lubricant, a slip agent, an antiblocking agent, an antioxidant, an antacid, an antistat agent, an opacifier, a bleach, a colorant, or combinations thereof. 13. The film of claim 1, wherein the biaxially oriented shrink film comprises a heat seal layer. 14 - The film of claim 1, wherein the biaxially oriented shrink film comprises a multilayer film, a coextruded film, an extrusion coated film, a laminated film or a coated film. 15. The film of claim 1, wherein the biaxially oriented shrink film comprises a metallized film. 16. The film of claim 1 wherein the film has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is less than or equal to DM / 2 at a temperature of 120 ° C. 17. The film of claim 16, wherein the first polyolefin copolymer is selected from the group consisting of propylene / ethylene copolymers; propylene / butylene copolymers; butylene / ethylene copolymers and linear low density polyethylene copolymers, which include a monomer selected from the group consisting of butylene, hexedene and octane, said monomer being present in an amount of between 0.5% and 49.5% by weight. 18. The film of claim 16, wherein the polyolefin homopolymers are selected from the group consisting of low density polyethylene having a density in the range of 0.910 to 0.930 g / cm3, high density polyethylene having a density on the scale of 0.931 to 0.960 g / cm3, isotactic polypropylenes with heptane insolubles greater than 90% and greater than 0.5 g / 10 minutes MFR, and poly-1-butene. 19. The method of claim 5, wherein the film has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is smaller or equal to DM / 2 within the temperature range of 100 ° C to 120 ° C. 20. The method of claim 5, wherein the film has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is less than or equal to DM / 2 at the temperature of 120 ° C. 21 - The method of claim 6, wherein the film has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is less or equal to DM / 2 within the temperature range of 100 ° C to 120 ° C. 22. The method of claim 5, wherein the film has a capacity of shrinkage in the machine direction (DM) greater than a capacity of shrinkage in the transverse direction (DT), so that the DT is smaller or equal to DM / 2 at a temperature of 120 ° C. SUMMARY A biaxially oriented polymer shrink film having a machine direction shrinkage (DM) greater than a shrinkage in the transverse direction (DT), so that the DT is less than or equal to the DM / 2 in the scale from 100 ° C to 140 ° C. The film comprises at least one of the following: a) a polyolefin copolymer; b) a polyolefin terpolymer; c) blends of polyolefin copolymers and homopolymers; d) blends of polyolefin copolymers and terpolymers; e) mixtures of terpolymers and polyolefin homopolymers; and f) blends of polyolefin copolymers, homopolymers and terpolymers; wherein the copolymer comprises a first and second monomer; the first monomer is selected from the group consisting of ethylene, propylene, butylene, and mixtures thereof; and the second monomer is selected from the group consisting of alpha-olefin monomers having from 2 to 10 carbon atoms, and mixtures thereof. The first monomer is present in the range of 99.5% to 75% by weight and the second monomer is present in the range of 0.5% to 25% by weight. The terpolymer comprises: (i) a primary monomer of ethylene, propylene, butylene and mixtures thereof; (ii) a secondary monomer of alpha-olefin monomers having from 2 to 10 carbon atoms and mixtures thereof; (iii) a tertiary monomer of alpha olefin monomers having from 2 to 10 carbon atoms and mixtures thereof, wherein the primary monomer is present in the range of 50% to 99% by weight, and the secondary monomers and Tertiary are present in the scale of 0.5% to 49.5% by weight, the homopolymer is polyethylene, polypropylene and polybutylene.