MXPA96005771A - Film that contains alpha-olefine copolymer / aromat vinyl - Google Patents

Abstract

Film and sheet materials, and articles produced therefrom such as bag sacks, trays, etc. they comprise one or more layers of a homogeneous aromatic alpha-olefin / vinyl copolymer, preferably an ethylene / styrene copolymer. The alpha-olefin / vinyl aromatic copolymer has properties that can provide characteristics of a desired performance such as impact resistance, printability, radiofrequency sealing ability, free shrinkage, optics, high permeability, etc. The homogeneous aromatic alpha-olefin / vinyl copolymer may be present in a monolayer film, either alone in a mixture or may be included in one or more layers of a multilayer film. Also included is a thermoformable multi-layer article comprising a continuous ribbon having a film of these alpha-olefin / vinyl aromatic copolymers.

Description

"FILM THAT CONTAINS ALPHA-OLEFINE COPOLYMER / AROM TICO VINYL" FIELD OF THE INVENTION The present invention relates to films comprising an olefin / vinyl aromatic copolymer.

The present invention relates especially to multilayer films containing an ethylene-styrene copolymer.

BACKGROUND OF THE INVENTION The homogeneous olefin / vinyl aromatic copolymers have been prepared using single site catalysts, such as metallocene catalysts. These polymers have up to 50 molar percent vinyl aromatic polymerization units, because the active site of the catalyst becomes stacked with the incorporation of the hindered sterically hindered aromatic comonomer, making it unlikely or impossible for another comonomer prevented can enter the polymerization as the next monomer in the sequence.

These homogeneous aromatic vinyl alpha-olefin / vinyl copolymers are similar in at least some properties to other homogeneous single site catalyzed copolymers, such as the homogeneous single-site catalyzed ethylene / alpha-olefin copolymers. That is, the alpha-olefin / vinyl aromatic copolymers present are characterized as having a critical molecular weight distribution (M D) and a critical composition distribution (CD).

COMPENDIUM OF THE INVENTION It has been found that homogeneous alpha-olefin / vinyl aromatic copolymers can be used to prepare thermally shrinkable films having a high impact strength. This high impact resistance is believed to result from the more rigid amorphous regions of the polymer. Furthermore, it is believed that films containing a homogeneous aromatic alpha-olefin / vinyl aromatic copolymer can have a high permeability to gaseous oxygen, etc., due to the high void volume and / or high solubility of the gases in the alpha copolymers. -olefin / aromatic vinyl homogeneous. In addition, the high void volume and / or polarizability of the homogeneous alpha-olefin / vinyl aromatic copolymer when used in films can be used to produce films having an increased capacity for absorption of relatively low molecular weight additives, such as anti-fogging additives, anti-blocking additives, anti-slip additives. In addition, the recesses can be used to produce films that have the characteristic of absorbing and retaining flavor additives, color additives, printing dyes, etc. which can result in less contamination to the product within the package, or from one product to another. In addition, the aromatic olefin / vinyl copolymers can be used to produce films having good quality and / or luster, in combination with stiffness due to the aromatic component in the polymer. The use of the olefin / vinyl aromatic copolymers in the films, both monolayer films and multi-layer films, can provide one or more of a wide variety of improved properties to the film, and may be advantageous in certain end uses. For example, a film of improved printing capacity, eg, improved ink adhesion can be prepared using menors having the polarity of the olefin / vinyl aromatic copolymers. The aromatic olefin / vinyl copolymers can be used to provide a film capable of being machined having a high gas transmission rate, which is advantageous both in the packaging of ready meat in a box of fresh meat, especially red meat fresh as well as in the packaging of the product. Films comprising a homogeneous aromatic alpha-olefin / vinyl polymer can also be used: in multilayer film layers to improve adhesion between the layers, especially for polar polymers and styrenic polymers; - to prepare films having good sealing capacity in terms of improved hot pairing, improved seal strength and / or stamp initiation temperature; for preparing films having improved thermoforming characteristics, such as improved deep drawing characteristics; to provide films having improved organoleptic characteristics; to provide films that have a lower level of extractable materials; to provide films having improved low temperature shrink characteristics; to provide films that have improved wetting capacity; to provide films having improved slip properties; to provide films that are radiofrequency sealable; - for films having improved sealing capacity after irradiation; Olefin / vinyl aromatic copolymers can also be used in the preparation of foams, especially a foam sheet having improved thermoforming characteristics, especially having improved resistance to cracking. The olefin / vinyl aromatic copolymer can be used to provide a barrier tray to polystyrene, such as a barrier foam tray, with improved delamination resistance and structural integrity. These advantages can be obtained by using the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer in combination with other styrenic polymers, e.g., a polystyrene homopolymer. As a first aspect, the present invention is directed to a thermally shrinkable film comprising a oriented film layer comprising a homogeneous aromatic alpha-olefin / vinyl copolymer present in an amount of about 30 percent to 100 percent by weight , based on the weight of the film layer. The homogeneous aromatic vinyl alpha-olefin / vinyl copolymer has an aromatic vinyl copolymer content of about 1 percent to 50 mole percent. The homogeneous aromatic vinyl alpha-olefin / vinyl copolymer in the film of the present invention comprises periodic units of the formula: - [(CH-CH)? - (CH-CH) and] - RX R2 R3 R4 In the formula, x is greater than or equal to y, that is, there must be a mole fraction of polymerization units (monomers) derived from the "ilfa-olefin monomer (a molar fraction represented by" x ", as determined by x / { x + y.}.) which is at least as large as the molar fraction of the polymerization units derived from the aromatic monomer (a molar fraction represented by "y", as determined by y /. x + y.}. R ^ comprises at least one member selected from the group consisting of hydrogen, alkyl of 1 carbon atom, alkyl of 2 carbon atoms, alkyl of 3 carbon atoms, alkyl of 4 atoms of carbon, alkyl of 5 carbon atoms and alkyl of 6 carbon atoms R.sup.2 comprises at least one member selected from the group consisting of hydrogen, alkyl of 1 carbon atom, alkyl of 2 carbon atoms, 3 carbon atoms, alkyl of 4 carbon atoms, alkyl that of 5 carbon atoms and alkyl of 6 carbon atoms. Both R ^ and R2 can not both be alkyl. R3 comprises a member selected from the group consisting of hydrogen, an aromatic material and mixtures thereof. R4 is a member selected from the group consisting of hydrogen, an aromatic material and mixtures thereof, as long as one member, and only one member selected from the group consisting of R3 and ^ 4, is aromatic. In addition, a portion of the copolymer between each two adjacent members that is selected from the group consisting of aromatic CHR3 and aromatic CHR4 comprises at least two groups of -CH2-. A preferred film comprises a composition consisting of (a) at least one member selected from the group consisting of the heterogeneous ethylene / vinyl aromatic copolymer and the homogeneous aromatic vinyl / propylene copolymer and (b) at least one member which is selected from the group consisting of a polyethylene homopolymer, polypropylene homopolymer, aliphatic ethylene / alpha-olefin copolymer, ethylene / vinyl ester copolymer, ethylene / acrylic ester copolymer, ethylene / acrylic acid copolymer, homopolymer polystyrene, styrene / aliphatic diene copolymer, aliphatic propylene / alpha-olefin copolymer and an ionomer. Preferably, the homogeneous aromatic alpha-olefin / vinyl aromatic copolymer comprises an ethylene monomer and a styrene monomer. Preferably, the ethylene monomer is present in an amount of about 75 mole percent to about 99 mole percent, and the styrene monomer is present in an amount of about 1 mole percent to 25 mole percent. In another preferred film, the homogeneous aromatic alpha-olefin / vinyl copolymer comprises a propylene monomer and a styrene monomer. Optionally, the alpha-olefin / vinyl aromatic copolymer comprises a network of cross-linked polymer. Preferably, the film of the invention has a free shrink at 90 ° C of at least 30 percent in at least one direction. Preferably, the film comprises a film layer having a modulus of about 351.50 to 10,545 kilograms per square centimeter; more preferably from about 703 to 10,545 kilograms per square centimeter; and still more preferably from about 1.054 to 3.515 kilograms per square centimeter. Preferably, the film is a multi-layer film and even when the film can be asymmetric, the symmetrical multi-layer films provide a balanced structure which may be advantageous. Another preferred multilayer film comprises a first layer and a second layer. The first layer is an oxygen barrier layer and the second layer comprises the homogeneous aromatic alpha-olefin / vinyl copolymer. The oxygen barrier layer preferably comprises at least one member selected from the group consisting of a copolymer of ethylene / vinyl alcohol, polyvinylidene chloride, polyamide, polyacrylonitrile, polyester and silica. Yet another preferred multilayer film comprises a first layer and a second layer. The first layer comprises at least one member which is selected from the group consisting of polyolefin, polyamide, polyester and the second layer comprises the homogeneous aromatic alpha-olefin / vinyl copolymer. Preferably the polyolefin comprises at least one member selected from the group consisting of a polyethylene homopolymer, polypropylene homopolymer, aliphatic ethylene / alpha-olefin copolymer, ethylene / vinyl ester copolymer, ethylene / acrylic ester copolymer , ethylene / acrylic acid copolymer, polystyrene homopolymer, styrene / aliphatic diene copolymer, aliphatic propylene / alpha-olefin copolymer and an ionomer. As a second aspect, the present invention relates to a printed film comprising a film layer consisting of a homogeneous aromatic alpha-olefin / vinyl copolymer in an amount of about 30 percent to 100 percent by weight based on the weight of the film layer. The film layer is imprinted thereon and the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer has an aromatic vinyl monomer content of about 1 percent to 50 mole percent. Preferably, the printed film is a multilayer film, the film layer being an outer film layer having an imprint on an outer surface thereof. As a third aspect, the present invention relates to a multilayer film comprising an outer seal layer, an internal oxygen barrier layer, an inner core layer and an external abuse layer.

At least one member selected from the group consisting of the outer sealing layer and the inner core layer comprises a homogeneous aromatic alpha-olefin / vinyl copolymer. The polyamide is present in at least one member that is selected from the group consisting of the internal oxygen barrier layer, the inner core layer and the external abuse layer. As a fourth aspect, the present invention relates to a thermoformed article comprising a multilayer film consisting of an outer seal layer, an internal oxygen barrier layer, an inner core layer and an external abuse layer. At least one member that is selected from the group consisting of the outer sealing layer and the inner core layer comprises a homogeneous aromatic alpha-olefin / vinyl copolymer. In addition, the polyamide is present in at least one member which is selected from the group consisting of the internal oxygen barrier layer, the inner core layer and the external abuse layer. As a fifth aspect, the present invention relates to a patch bag comprising a thermally shrinkable patch adhered to a thermally shrinkable bag. The thermally shrinkable patch comprises a first thermally shrinkable film and the thermally shrinkable bag comprises a second thermally shrinkable film. At least one member selected from the group consisting of the first thermally shrinkable film and the second thermally shrinkable film comprises a film layer comprising a homogeneous aromatic alpha-olefin / vinyl copolymer. As a sixth aspect, the present invention relates to a laminate comprising a foam sheet and a film adhered to the foam sheet. At least one member selected from the group consisting of the foam sheet and the film comprises a homogeneous aromatic alpha-olefin / vinyl copolymer. The foam sheet comprises polystyrene. Preferably the foam sheet further comprises a composition consisting of a polystyrene homopolymer and the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer. [As used herein, the phrase "polystyrene homopolymer" includes block and graft polystyrene copolymers comprising a styrene monomer in an amount of at least 50 weight percent, based on the weight of the copolymer] . Preferably, the film is a multilayer film comprising a composition comprising the homogeneous aromatic alpha-olefin / vinyl copolymer. The composition is directly adhered to the foam sheet. The film also comprises an oxygen barrier layer. As a seventh aspect, the present invention relates to a package comprising a rigid package having a flexible lid adhered directly thereto. The rigid package comprises polystyrene, and the flexible lid comprises a homogeneous aromatic alpha-olefin / vinyl copolymer. As an eighth aspect, the present invention relates to a package consisting of a rigid package having a flexible lid adhered thereto. The rigid package comprises polystyrene and the flexible lid comprises polyolefin. At least one member selected from the group consisting of the rigid container and the flexible cap further comprises a homogeneous aromatic alpha-olefin / vinyl copolymer.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a trace of data points for the films of Examples 1 to 16 and of Examples 17 to 21 of Compration, with the trace of: (a) a relationship of the storage modules relaxed to non-relaxed for the beta-relaxation, versus (b) crystallinity of mass percentage.

Figure 2 is a trace of the data points for the films of Examples 1 to 15 and Comparative Examples 17 to 21, with the trace of: (a) peak beta relaxation temperature, versus (b) crystallinity of percentage of mass.

DETAILED DESCRIPTION OF THE INVENTION As used herein, the term "sealing" refers to any and all means for closing a package, such as heat sealing through hot air and / or heated rod, ultrasonic sealing and even the use of staples in, for example, a folded box, etc. As used herein, "EVOH" refers to a copolymer of ethylene and vinyl alcohol. EVOH includes copolymers of ethylene and vinyl acetate saponified or hydrolyzed and refers to a copolymer of vinyl alcohol having an ethylene comonomer, and which is prepared for example, by hydrolysis of vinyl acetate copolymers or by chemical reactions with alcohol of polyvinyl. The degree of hydrolysis is preferably at least 50 percent and more preferably at least 85 percent. As used herein, the term "barrier" and the phrase "barrier layer" as applied to films and / or film layers, are used with reference to the capacity of a monolayer film or a multilayer film. to serve as a barrier to one or more gases. The oxygen barrier layers may comprise, for example, ethylene / polymerized vinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyacrylonitrile, etc., as is known to those skilled in the art. Preferably, the oxygen barrier layer comprises vinyl alcohol and polymerized ethylene, polyvinyl chloride, polyvinylidene chloride, a polyamide, as is known to those skilled in the art. As used herein, "oxygen transmission regime" which is also referred to as "OTR" and "oxygen permeability", is measured according to Method D 3985 of the American Society for the Testing of Materials, a test known to those skilled in the art of films. As used herein, the term "lamination" and the phrase "laminated film" refers to the process, and the resulting product produced by ligating together two or more layers of film or other materials. The lamination can be achieved by bonding layers with adhesives, bonding with heat and pressure and still coating by dispersion and extrusion coating. The term laminate also includes co-extruded multi-layer films comprising one or more coupling layers. The term "oriented" as used herein, refers to oriented films or film layers, wherein the orientation may occur in one or more of a variety of ways. Many of the thermoplastic films of the present invention are thermally shrinkable. The term "oriented" is used herein interchangeably with the term "thermally shrinkable" with each of these terms designating a material that has been elongated and then "solidified" by cooling, while retaining essentially its oriented dimensions. A oriented material will tend to return to its original non-oriented dimensions (not extended) when heated to an appropriate elevated temperature. Guidance can be achieved in many ways, such as, for example, by "blown bubble" or "stretch in tenter" techniques. These processes are well known to those skilled in the art. The phrases "essentially oriented" and "thermally shrinkable" as used herein with respect to the films, require elongation of at least 50 percent in at least one direction, with elongation being carried out at a lower temperature than the melting temperature of and / or less than the glass transition temperature of the homogeneous aromatic alpha-olefin / vinyl copolymer without subsequent annealing of the film. As used herein, the phrase "orientation relationship" refers to the multiplication product of the degree to which the plastic film material is expanded in various directions, usually two directions perpendicular to each other. The degree of orientation is also referred to as the orientation reaction sometimes as the "stretch ratio". As used herein, the term "comonomer" refers to a monomer that is copolymerized with at least one different monomer or a copolymerization reaction, the result of which is a copolymer. As used herein, the term "polymer" refers to the product of a polymerization reaction, and includes homopolymers, copolymers, terpolymers, etc. In general, the layers of a film may consist essentially of a single polymer, or may have additional polymers still mixed therewith. As used herein, the term "homopolymer" is used with reference to a polymer-lime resulting from the polymerization of a single monomer, i.e., a polymer consisting essentially of a single type of repeating unit. As used herein, the term "Copolymer" refers to polymers formed by the polymerization reaction of at least two different monomers. For example, the term "copolymer" includes the polymerization reaction produced from ethylene and an alpha-and-olefin, such as 1-hexene.

The "copolymer" also includes, for example, the copolymerization of a mixture of ethylene, propylene, 1-hexene and 1-octene. The term copolymer includes random copolymers, block copolymers, graft copolymers, etc. 15 As used herein, the term "Polymerization" includes homopolymerizations, copolymerizations, terpolisations, etc. and includes all types of copolymerizations, such as random, graft, block, etc. In general, polymers In the films used in accordance with the present invention, they can be prepared in accordance with any suitable catalytic polymerization process including solution polymerization, slurry polymerization, gas phase polymerization and process high pressure polymerization.

As used herein, the term "copolymerization" refers to the simultaneous polymerization of two or more monomers. As used herein, a copolymer identified in terms of a plurality of monomers,. e.g., "propylene / ethylene copolymer" refers to a copolymer in which either the monomer is copolymerized at a higher percentage by weight or molar. However, the first listed monomer is preferably polymerized in a higher percentage by weight than the second listed monomer and for polymers that are terpolymers, quadripymers, etc., preferably, the first monomer is copolymerized in a percentage by weight higher than the second monomer, and the second monomer is copolymerized at a higher weight percentage than the third monomer, etc. As used herein, terminology employing a "/" with respect to the chemical identity of a copolymer (e.g., "an ethylene / alpha-olefin copolymer") identifies the comonomers that are copolymerized to produce the copolymer. These phrases such as "ethylene / alpha-olefin copolymer" is the respective equivalent of "ethylene / alpha-olefin copolymer". As used herein, the phrase "heterogeneous polymer" refers to the polymerization reaction products of a relatively broad variation in molecular weight and a relatively wide variation in composition distribution, i.e., polymers produced, for example, using conventional Ziegler-Natta catalysts. Heterogeneous polymers are useful in the various layers of the film used in the present invention. These polymers typically contain a relatively wide variety of chain lengths and percentages of comonomer. As used herein, the phrase "homogeneous polymer" refers to polymerization reaction products of relatively critical molecular weight distribution and relatively critical composition distribution. Homogeneous polymers are useful in the different layers of the multilayer film used in the present invention. The homogeneous polymers exhibit a relatively uniform comonomer sequence within a chain, a mirror image of the sequence distribution in all chains, and the length similarity of all chains, and are typically prepared using metallocene, or other type catalysis. from a single site. More particularly, homogeneous copolymers can be characterized by one or more methods known to those skilled in the art, such as molecular weight distribution (Mw / Mn), latitude index of composition distribution (CDBI) and scale of critical melting temperature and behavior of a single melting temperature. The molecular weight distribution (Mw / Mn) also known as polydispersity, can be determined by gel permeation chromatography. The homogeneous copolymers useful in this invention will have an (Mw / Mn) of less than about 3.5. Preferably, the (Mw / Mn) will have a scale of approximately 1.9 to 2.9. In a particularly preferred manner, the (Mw / Mn) will have a scale of about 1.9 to 2.5. Preferably, the latitude index of the composition distribution (CDBI) of these homogeneous copolymers, will generally become greater than about 70 percent. The CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50 percent (ie, plus or minus 50 percent) of the content of the median total molar comonomer. The CDBI of linear polyethylene, which does not contain comonomer is defined as being 100 percent. The CDBI determination clearly distinguishes the homogeneous copolymers used in the present invention (distribution of critical composition as evaluated by the CDBI values generally greater than 70 percent) of commercially available VLDPE, generally having a broad composition distribution as it is valued by CBDI values, preferably lower than 55 percent. The CDBI of a copolymer is easily calculated from data obtained from techniques known in the art, such as, for example, temperature rise elution fractionation (TREF), as described, for example, in Wild's article and others, J. Poly. Sci. POlv. Phvs. Ed., Volume 20, page 441 (1982). Most preferably, the homogeneous copolymers have a CDBI of about 70 percent to 99 percent. In general, the homogeneous polymers in the films of the present invention also exhibit a relatively critical melting temperature scale, as compared to "heterogeneous copolymers", ie, polymers having a CDBI of less than 55 percent. A homogeneous ethylene / alpha-olefin copolymer can, in general, be prepared by the copolymerization of ethylene and one or more alpha-olefins. Preferably, the alpha-olefin is an alpha-monoolefin of 3 to 20 carbon atoms, more preferably an alpha-monoolefin of 4 to 12 carbon atoms and still more preferably, an alpha-monoolefin of 4 to 8. carbon atoms. Still more preferably, the alpha-olefin comprises at least one member which is selected from the group consisting of buten-1, hexen-1 and octen-1, ie 1-butene, 1-hexene and 1-octene, respectively. Particularly preferably, the alpha-olefin comprises octene-1 and / or a mixture of hexene-1 and butene-1. The processes for preparing the homogeneous ethylene / alpha-olefin copolymers are disclosed in U.S. Patent Number 5,206,075, the Patent American Number 5,241,031 and the PCT Application International Number WO 93/03093, each of which is hereby incorporated by reference in its entirety. Additional details related to the production and use of a heterogeneous ethylene-alpha-olefin copolymer sort are disclosed in U.S. Patent No. 5,206,075, issued to HODGSON, Jr; U.S. Patent Number 5,241,031, issued to MEHTA; International PCT Publication Number WO 93/03093, in the name of Exxon Chemical Company; PCT Publication Number WO 94/03414 in the name of Exxon Chemical Patents, Inc., all four of which are hereby incorporated by reference into their totals. Still another genus of homogeneous ethylene / alpha-olefin copolymers is disclosed in U.S. Patent No. 5,272,236, issued to LAI et al., And U.S. Patent No. 5,278,272, issued to LAI and others, both of which are incorporated herein by reference. present in their totalities by refererence to them.

As used herein, the phrase "aromatic vinyl" with respect to the monomers, refers to styrene, vinyl naphthalene and vinyl anthracene, with or without one or more substituents (for hydrogens) present in the ring (s) aromatic and / or the olefin carbon connected to the aromatic ring. The substituents could also include one or more additional vinyl groups. In addition, this phrase is used herein with reference to monomers, ie, polymerization s of the aforementioned monomers. Preferably, the aromatic vinyl monomer is styrene. As used herein, the phrase "alpha-olefin" and the phrase "alpha-olefin monomer" refers to olefinic and monomeric compounds either unsubstituted or substituted, wherein the first two carbon atoms in the chain have a double link between them. As used herein, these phrases include ethylene and propylene. In addition, the phrase "aliphatic alpha-olefin" refers to alpha-olefin monomers (and monomers) that do not contain an aromatic residue (i.e., a substituent group) therein and that are hydrocarbons, i.e., they contain only carbon and hydrogen atoms. As used herein, the phrase "polymerization unit" and the term "monomer" refer to <; - > a unit of a polymer derived from a monomer used in the polymerization reaction. For example, the phrase "alpha-olefin polymerization units" refers to a unit, for example, in an alpha-olefin / vinyl aromatic copolymer, the polymerization unit being that residue which is derived from the alpha-olefin monomer after that it reacts to become a component of the polymer chain. As used herein the phrase "aromatic vinyl polymerization unit" refers to a corresponding polymerization unit of the polymerization polymer, which is the residue derived from the aromatic vinyl monomer after it reacts to become a component of the polymerization. the polymer chain. As used herein, copolymers, terpolymers, etc. they are named in terms of the monomers from which they are produced, for example, an "ethylene / alpha-olefin copolymer" is a copolymer comprising the polymerization units derived from the copolymerization of an ethylene monomer and an alpha-monomer. olefin, with or without additional comonomer (s). Also, the alpha-olefin / vinyl aromatic copolymer is a copolymer comprising polymerization units derived from the copolymerization of the alpha-olefin monomer with the aromatic vinyl comonomer, with or without an additional comonomer (s). As used herein, the term "polyolefin" refers to any polymerized olefin that may be linear, branched, cyclic, aliphatic, aromatic, substituted or unsubstituted. More specifically, the term "polyolefin" includes the homopolymers of olefins, copolymers of olefins, copolymers of an olefin and a non-olefinic comonomer copolymerizable with the olefin, such as vinyl monomers, modified polymers thereof and the like. Specific examples include polypropylene homopolymers, polyethylene homopolymers, polybutene, propylene / alpha-olefin copolymers, ethylene / alpha-olefin copolymers, butene / alpha-olefin copolymers, ethylene / vinyl acetate copolymers, ethylene / copolymers. ethyl acrylate, ethylene / butyl acrylate copolymers, ethylene / methyl acrylate copolymers, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, modified polyolefin resins, ionomer resins, polymethylpentene, etc. Modified polyolefin resins include modified polymers prepared by copolymerizing the homopolymer of the olefin or the copolymer thereof, with an unsaturated carboxylic acid e.g., maleic acid, fumaric acid or the like, or a derivative thereof, such as anhydride, ester or metal salt or the like. It could also be obtained by incorporating into the homopolymer or olefin copolymer, an unsaturated carboxylic acid e.g., maleic acid, fumaric acid or the like, or a derivative thereof, such as the anhydride, ester or metal salt or the like. As used herein, the terms identifying the polymers, such as "polyamide", "polyester", etc., include not only the polymers comprising the repeating units derived from the known monomers to polymerize in order to form a polymer of the type mentioned, but include comonomers, derivatives, etc. which can be copolymerized with known monomers to polymerize in order to produce the said polymer. For example, the term "polyamide" embraces both polymers comprising repeating units derived from the monomers, such as caprolactam, which are polymerized to form a polyamide as well as the copolymers derived from the copolymerization of caprolactam with a comonomer which when polymerized only does not result in the formation of a polyamide. In addition, the terms identifying the polymers also include "blends" of these polymers with other polymers of a different type.As used herein,. the term "polypropylene" refers to any polymer comprising propylene polymerization units, regardless of whether the polymer is a homopolymer or a copolymer and that it further includes mixtures of these homopolymers and copolymers. The phrase "propylene polymerization units" as used herein refers to the polymerization units of a polymer chain, the repeating units being derived from the polymerization of an unsubstituted propylene monomer and / or a proprietary polymer. replaced, opening in double bond in the polymerization reaction. As used herein, the phrase "anhydride functionality" refers to any form of anhydride functionality, such as maleic acid anhydride, fumaric acid, etc., whether it is mixed with one or more polymers, grafting into a polymer or copolymerizing with a polymer and in general also includes derivatives of these functionalities, such as acids, esters and metal salts derived therefrom. Polymers having anhydride functionalities therein are typically used in the layers. As used herein, the phrase "modified polymer" as well as more specific phrases such as "modified ethylene vinyl acetate copolymer" and "modified polyolefin" refer to those polymers having an anhydride functionality as defined immediately in the foregoing, grafted thereto and / or copolymerized therewith and / or mixed therewith. Preferably these modified polymers having the functionality of anhydride grafted on or polymerized with as opposed to simply mixed therewith. As used herein, the phrase "ethylene / alpha-olefin copolymer" refers to those heterogeneous materials such as linear low density polyethylene (LLDPE) and very low and ultra low density polyethylene (VLDPE and ULDPE); and to homogeneous polymers, such as metallocene-catalyzed polymers, for example, the EXACT (TM) materials supplied by Exxon, and the TAFMER (TM) materials supplied by Mitsui Petrochemical Corporation. These materials generally include copolymers of ethylene with one or more comonomers that are selected from alpha-olefin of 4 to 10 carbon atoms, such as buten-1, ie, (1-butene), hexen-1, octen-1, etc., wherein the molecules of the copolymers comprise long chains with secondary chain branches or relatively few crosslinked structures. This molecular structure should be contrasted with conventional low or medium density polyethylenes that are more highly branched than their respective duplicates. LLDPE, as used herein, has a density usually within the range of about 0.91 gram per cubic centimeter to about 0.94 gram per cubic centimeter. Other ethylene / alpha-olefin copolymers such as the branched homogeneous long chain ethylene / alpha-olefin copolymers obtainable from Dow Chemical Company, known as AFFINITY (TM) resins are also included as another type of alpha-olefin copolymers useful in the present invention. Generally, the ethylene / alpha-olefin copolymer comprises a copolymer resulting from the copolymerization of about 80 percent to 99 percent by weight of ethylene and from 1 percent to 20 percent by weight of alpha-olefin. Preferably, the copolymer? ethylene / alpha-olefin comprises a copolymer resulting from the copolymerization of about 85 percent to 95 percent by weight of ethylene, and from 5 percent to 15 percent by weight of alpha-olefin. As used herein, the phrases "inner layer" and "inner layer" refer to any layer of a multilayer film having both of its principal surfaces adhered directly to another layer of the film. As used in this, the phrase "outer layer" refers to any film layer of a multilayer film having only one of its principal surfaces adhered directly to another layer of the film. As used herein, the phrase "inside layer" refers to the outer layer of a multilayer film packaging a product that is closer to the product relative to the other layers of the multilayer film. As used herein, the phrase "outer layer" refers to the outer layer of a multilayer film that packages a product that is further away from the product relative to the other layers of the multilayer film. As used herein, the phrase "directly adhered" is applied to the layers of the film is defined as the adhesion of the film layer present to the film layer of the object without a coupling cap, adhesive and another layer between the same. In contrast, as used herein, the word "between" as applied to a layer of film expressed as being between two other specified layers includes both direct adhesion of the subject matter layer between the two other layers that remain in the middle. as well as including a lack of direct adhesion to either or both of the other two layers in which the present layer lies between them, i.e., one or more additional layers may be imposed between the present layer and one or more of the layers where the present layer is between them. As used herein, the term "core" and the phrase "core layer" as applied to multi-layer films, refers to any inner film layer (ie, internal) which has a main function other than to serve as an adhesive or compatibilizer to adhere two layers one to the other, usually, the core layer or layers provide the multi-layer film with a desired strength level , that is, a module and / or optics and / or additional resistance to mistreatment and / or specific impermeability. As used herein, the phrases "seal layer", "sealing layer", "thermal sealing layer" and "sealing layer", refers to a layer of the film or layers involved in the sealing of the film in itself or another outer layer of the same film, or an outer layer of another film or article. It should also be recognized that, in general, up to the external distance of .0762 mm of a film may be involved in sealing the film itself or at another stage. With respect to packages having only fin-type seals, as opposed to overlapping seals, the phrase "sealing layer" usually refers to the inner film layer of a package, as well as to the layers of support adjacent to this sealing layer, which frequently seals itself and frequently serves as a food contact layer in food packaging. Generally, a thermal seal layer comprises any thermoplastic polymer; preferably the thermal sealing layer comprises, for example, thermoplastic polyolefin, thermoplastic polyamide, thermoplastic polyester and thermoplastic polyvinyl chloride, more preferably thermoplastic polyolefin; still especially preferred, thermoplastic polyolefin having less than 60 weight percent crystallinity. As used herein, the phrase "coupling layer" refers to any inner layer whose main purpose is to adhere two layers one to the other. In general, polymers suitable for use in the coupling layer include polymers having polar functional groups. As used herein, the phrase "abuse layer" refers to an outer film layer and / or an inner film layer so long as the film layer serves to resist abrasion, perforation and other potential causes of reduction of the integrity of the package, as well as potential causes of reduction in the quality of the appearance of the package. The abuse layers can comprise any polymer as long as the polymer contributes to achieving the integrity sight and / or a look of appearance; Preferably, the abuse layers comprise a polymer having a modulus of at least 10 Pascais at room temperature. As used herein, the term "co-extrusion" refers to the process of extruding two or more materials through a single matrix with two or more orifices placed so that the extruded materials are melted and welded together in a laminar structure before to cool down, that is, to cool down quickly. Co-extrusion can be used in film blowing, free film extrusion and extrusion coating processes. As used herein, the phrase "machine direction" abbreviated herein as "MD" refers to the direction "along the length" of the film, ie, in the direction of the film to as the film is formed during extrusion and / or coating.

As used herein, the phrase "transverse direction" which is abbreviated herein as "TD" refers to the direction through the film perpendicular to the direction of the longitudinal machine. As used in the present, the phrase "Free shrink" refers to the percentage of the dimensional change in a 10 cm by 10 cm film specimen when subjected to selected heat, as measured by the D 2732 method of the American Society for the Testing of Materials as is known from those persons skilled in the art. The homogeneous alpha-olefin / vinyl aromatic copolymers to be used in the films of the present invention are described, generally, and with respect to many of the specific issues including the structure of the copolymer and the methods for the preparation of the copolymer in: (1) Patent Number EP 0 416 815 A2, issued to STEVENS and others, in the name of The Dow Chemical Company; (2) Patent Number WO 94/00500, granted to R.B. PANNELL et al., In the name of Exxon Chemical Patents Inc., and (3) Plastics Technology, page 25 (September 1992), each of which is hereby incorporated by reference in its entirety. The thermoplastic films of the present invention are preferably formed by extrusion processes and, more preferably, by coextrusion methods known in the art. After coextrusion, the film is cooled to a solid state by, for example, dropping a cascade of water or rapid cooling with cold air. For some structures, a layer or layers of precursor film can be formed by extrusion with additional layers which are subsequently extrusion coated thereon to form multilayer films. Two multi-layer tubes can also be formed with one of the tubes being then coated or laminated one on the other. The extrusion coating method of film formation is preferred to the coextrusion of the entire film when it is desired to subject one or more of the layers of the film to a treatment that may be detrimental to one or more of the others layers. That is, production of the film by extrusion coating is preferred to production through pure co-extrusion, if it is desired to irradiate one or more layers of a film with high-energy electrons (see the discussion of irradiation as follows). noted below) without irradiating the additional layers, one or more of which comprises a barrier layer consisting of one or more copolymers of vinylidene chloride (e.g., Saran (TM)), such as sodium chloride. inylidene / vinyl chloride, vinylidene chloride / methyl acrylate, vinylidene chloride / ethyl acrylate or vinylidene chloride / acrylonitrile. Films formed through extrusion coating, for example, can comprise those wherein the barrier layer is a layer of vinylidene chloride copolymer in addition to or instead of the layer of the ethylene / vinyl alcohol copolymer (EVOH). . Those skilled in the art generally recognize that irradiation with high-energy electrons is generally detrimental to those polyvinylidene chloride copolymer barrier layer compositions since the irradiation can degrade and discolor the polyvinylidene copolymer. Vinylidene chloride causing it to turn a brown color. Therefore, if the complete co-extrusion is followed by irradiation with high-energy electrons the multilayer structure is carried out with a film having a barrier layer of vinylidene chloride copolymer, the ratio should be out at low levels. However, it is completely preferred to avoid subjecting the radiation sensitive polymers, such as copolymers of vinylidene chloride, etc., to irradiation. Avoidance of this can be achieved by using the extrusion coating method of multilayer film production as described above. As mentioned above, the films present optionally can be subjected to an energy radiation treatment, including but not limited to corona discharge, plasma, flame, ultraviolet and high energy electron treatment. The irradiation with ultraviolet light or high energy electron treatment can be carried out in such a way as to produce a crosslinked polymer network. In this case, this irradiation is preferably carried out before any orientation step and in the case of a barrier structure containing SARAN (TM) irradiated by electron beam before the extrusion coating of the barrier component. The electronic radiation dosages are referred to herein in terms of a "RAD" radiation unit with one million RADs or one megarad designated "MR". A suitable radiation dosage of high-energy electrons is within the range of up to about 12 MR, more preferably, from about 2 to about 9 MR. However, irradiation after orientation independently of the structure and carried out at lower dosage levels is also within the scope of the present invention.

For those modalities in which the film is a multi-layer film, each layer will usually serve a certain function or provide a certain feature to the overall structure. For example, the chemical composition and the thickness of an external layer destined may be selected so that the layer is suitable for use as a sealing layer, ie, suitable for thermal sealing and / or RF (radio frequency) sealing and depending on the proposed end-use application for this outer layer, other factors such as grease resistance may be of importance. The composition of the other outer layer of the film may be selected for abuse resistance or when a certain end-use application requires an overlapped "overlap" seal on itself, a sealing capability on the seal layer. If an internal barrier layer is required, its specific chemical composition and thickness will be selected to provide a degree of gas or moisture impermeability necessary for a specific packaging end use, that is, a specific product that will be packaged in the film . In addition, the inner layers can serve to provide the film with additional volume, increased shrinkage capacity, higher interlayer adhesion, increased elasticity, enhanced gas permeability with respect to one or more specific gases as well as any combination of these properties. The thermoplastic films of the present invention contain homogeneous copolymers resulting from the copolymerization of an olefin monomer of 2 to 8 carbon atoms and an aromatic vinyl comonomer. Ethylene and propylene are preferred as the olefin monomers of 2 to 8 carbon atoms and styrene is a preferred aromatic vinyl comonomer. Other suitable aromatic vinyl comonomers include vinyl naphthalene and vinyl anthracene. For purposes of the present invention, the alpha-olefin / aromatic vinyl copolymer preferably the ethylene / styrene copolymer may be present in either a monolayer film or in one or more layers of a multilayer film structure. As such, the alpha-olefin / vinyl aromatic copolymer may comprise 100 percent of the layer in which it is present or may be present in a mixture with another thermoplastic homopolymer or copolymer. If a thermally shrinkable structure is prepared using a blend of the olefin / vinyl aromatic copolymer with at least one member selected from the group consisting of the ethylene / alpha-olefin copolymer, ethylene / vinyl acetate copolymer, ethylene copolymer / alkyl acrylate, ethylene / acrylic acid copolymer, a metal neutralized salt of the ethylene / acrylic acid copolymer, a low density polyethylene, the olefin / vinyl aromatic copolymer present provides the resulting film with elastic memory properties similar to those of polyvinyl fluoride. A plasticizer may also be mixed with the alpha-olefin / aromatic vinyl copolymer used in the film according to the present invention. In addition, if present in a mixture with any of a wide variety of thermoplastic homopolymers or copolymers, the olefin / vinyl aromatic copolymer will improve the toughness of the structure of the resulting film. If mixed with atactic or syndiotactic polystyrene, impact strength is improved and flexural cracks (caused by brittleness) are reduced. If mixed with homopolymers and / or ethylene or propylene copolymers, the olefin / vinyl aromatic copolymers improve clarity and increase the gas and moisture vapor permeability of the overall film structure. The olefin / vinyl aromatic copolymer can also be used as a mixing modifier in a seal layer to improve the radiofrequency sealing capacity or to improve the initiation of the seal at low temperature for thermal sealing. The olefin / vinyl aromatic copolymer either alone in a monolayer film and / or only as a surface layer of a multilayer film and / or as a component in a mixture in either monolayer or multiple layers can be used for improve the printing capacity of the film. Specifically, the present copolymers will improve the printability through both ethylene / alpha-olefin copolymers and known styrene homopolymers. It is the polarizability imparted by the aryl group of the olefin / vinyl aromatic copolymer which is believed to provide improved wetting capacity and, therefore, improved printability if present in the outer surface layer of a film. It is this polarizability of the aryl group that is also believed to render the copolymers active both as a component in a mixture as discussed above and especially as the sole component of a radio frequency sealing layer or a susceptor layer. A "susceptor layer" is a layer within a multilayer structure that is either immediately adjacent to the sealing layer or close enough to the sealing layer so that when heated by radio frequency irradiation, the susceptor layer in turn, heat the sealing layer to assist in the sealing process. The ability to seal radio frequency is desirable if the olefin-based packaging materials will compete with plasticized polyvinyl chloride (PVC) in a medical packaging area. Even when the risks of PVC are well known, such as the possibility of migration of the plasticizer (preferably dioctyl phthalate) to the packaged medical solution, and the reaction of the PVC itself with the packaged medical solution and the fact that PVC becomes brittle at low temperatures, PVC has several specific performance characteristics that are required for packaging for medical solutions and for other medical applications, such as ostomy bags to retain different medical fluids, for example, the appropriate fluids for intravenous end use. That is, PVC provides the necessary characteristics for end-use applications that require crushing capacity, transparency, adequate mechanical strength and ability to withstand the relatively high temperatures required for thermal sterilization. Olefin-based materials are being developed which can compete with PVC from an operational perspective, but many converters of medical packaging are still using radio-frequency sealing equipment. Therefore, olefin-based materials for use in the medical packaging industry frequently must be sealable by radiofrequency. These materials include the films used to produce the accessory bags that are required to establish fluid communication between the container and the external environment. In general, the accessories are tubes that can be monolayer or multiple layers. In order to form the bag, the external outer layer of the accessory must be sealed in the outer layer inside the film. Preferably, the outer layer inside the film and the outer outer layer of the accessory are identical in chemical composition. Therefore, if the outer layer inside the film is active at radio frequency, the external outer layer of the accessory is preferably composed of the same polymer or active mixture at radiofrequency. If the film has a sealing layer which is not active at radio frequency, but depends on the inner susceptor layer, the accessory preferably has an outer layer identical to the film sealing layer and also includes an inner susceptor layer.

Another application for the olefin / vinyl aromatic copolymer is incorporation into a protective patch for use in a thermally shrinkable thermoplastic bag used for the packaging of meat with bone. The patch preferably is produced by extruding a thermoplastic film comprising a copolymer? olefin / aromatic vinyl. This patch film may be a monolayer film having an olefin / vinyl aromatic copolymer present alone or in a mixture, or the patch film may be a multilayer film having an aromatic olefin / vinyl copolymer in it. less one layer, either alone or in a mixture. In the production of a multi-layer patch film, a film tube is crushed, irradiated, heated, inflated and oriented and then crushed again, and flattened in such a way that the outer layer on the inside of the tube is also adhered, that is, it is a self-adhering layer thereby forming the multi-layer patch film. The patches cut from the patch film adhere to the outer surface of the thermally shrinkable bags used to pack cuts of meat with bone, in order to protect the bag against perforation by the bones, in case of a patch comprising a film of Multiple layers, the olefin / aromatic vinyl copolymer may be present in any layer of a multilayer patch including the self-adhering layer, in order to improve the overall performance of the patch film especially the impact strength of the patch film. In accordance with the present invention, thermoformed trays, for example, foam trays for stopping meat, may comprise an olefin / vinyl aromatic copolymer. The lamination of a film to the foamed or unfoamed polystyrene is already known and is used to provide gas barrier properties to the trays and / or to provide the trays with a surface for sealing capability in a lid and / or overwrap of the tray. However, delamination of the polystyrene ribbon film produces unpleasant appearance blisters and other forms of product failure. In accordance with the present invention, the olefin / aromatic vinyl copolymer particularly the ethylene / styrene copolymer can be employed in an outer sealing layer of a multilayer film, this outer sealing layer having to adhere directly to a foamed tray. Alternatively, the ethylene / styrene copolymers can be employed in an adhesive layer adjacent to a polystyrene binding layer in order to prevent delamination of the film.

The following examples are representative of the preferred embodiments of the present films containing the homogeneous olefin / vinyl aromatic copolymers catalysed in a single site.

Examples 1 to 15 and Comparison Examples 16 to 21 Several copolymers of ethylene and styrene were prepared according to the procedures essentially as will be described below. A polymerization reactor was charged with dry deoxygenated toluene, purified styrene (vacuum distillation through calcium hydride), a solution of methyl aluminoxane in toluene (10 weight percent aluminum) and an appropriate catalyst as outlined continuation. Ethylene gas was introduced at the pressure indicated below, while maintaining the polymerization temperature indicated below. After less than 50 percent of the styrene comonomer had been consumed, the resulting polymerization reaction was terminated by the addition of methanol. For Examples 1 to 12, the polymerization was carried out in a glass polymerization reactor, catalyzed with isopropylidene- (cyclopentadienyl) (9-fluorenyl) zirconium dichloride. Gas was introduced - 4í of ethylene at pressure of approximately 2.11 kilograms per square centimeter, while maintaining a polymerization temperature of approximately 40 ° C. For Examples 13 to 15, the polymerization was carried out in a Parr reactor of 2 liters capacity equipped with an internal cooling coil. The polymerization was catalyzed with Me2Si dichloride [Cp (Me) 4] [N-ter-Bu] titanium. The ethylene gas was introduced at approximately 12.65 kilograms per square centimeter gauge, while the polymerization temperature was maintained at approximately 90 ° C. The content of the styrene monomer and the total purity, ie, less than 5 percent of the impurity of the polystyrene homopolymer present) of the resulting copolymers was ensured using ^ 3C-nuclear magnetic resonance spectroscopy. Molecular weights were analyzed by gel permeation chromatography (GPC) with polystyrene reference standards. Table 1A, which is presented below, identifies the copolymers prepared from Examples 1 to 15, together with the analytical results that provide the content of the styrene monomer and the molecular weight data for each of Examples 1 to 15. Table IB gives the molecular weight, copolymer composition and density for Comparison Examples 16 to 21, each of which was a commercially available homogenous ethylene / alpha-olefin copolymer.

BOX ÍA (Examples 1 to 15) Weight% number of MnxlO -3 Mwxl0 ~ 3 M ^ Aw Mn Example styrene monomer in ethylene / styrene copolymer 1 16 161 313 1.9 2 30 131 301 2.3 3 31 65 111 1.7 4 23 76 144 1.9 9 210 673 3.2 6 12 280 867 3.1 7 23 221 662 3.0 8 29 79 177 2.2 9 11 48 123 2.6 30 86 178 2.7 11 11 90 274 3.0 12 18 67 178 2.7 13 18 252 140 1.8 14 8 283 149 1.9 42 177 104 1.7 TABLE IB (Examples 16 to 21 of Comparison) Copolymer number and Mnxl0 ~ 3 Mwxl0 ~ 3 Mw / Mn Example of density Comparison (g / cc) 16 ethylene / octene; 47 103 2.2 0.901 \ 0 17 ethylene / butene; 56 101 1.8 0.888 18 ethylene / butene; 64 116 1.8 0.910 5 19 ethylene / butene / 49 90 1.8 hexene; 0.910 ethylene / hexene; 49 104 2.1 0.920 21 ethylene / hexene; 63 118 1.9 0 0.923 For each of Examples 1 to 15 and of the Comparison Examples 17 to 21, relaxed and unrelaxed storage modules for beta relaxation and peak beta relaxation temperature were determined using a Rheometrics RSA-II Solids Analyzer in accordance with D method 5026-89 of the American Society for the Testing of Materials and D 4065-90 of the Anericana Society for the Testing of Materials. The test specimens were prepared and conditioned according to the method D 1928, Procedure C of the American Society for Testing Materials and Method D 618-61 of the American Society for Testing Materials as follows: A one gram polymer sample was placed between separate sheets of MYLAR (TM) placed horizontally of a press assembly (comprising a Carver Laboratory Press and stainless steel support plates), the resin powder being placed in the center of the lower MYLAR (TM) sheet or sheet, which was placed on top of the a lower stainless steel plate. Then, the upper MYLAR (TM) sheet or sheet was placed above and in contact with the powder, after which the upper stainless steel plate was placed above the top sheet or sheet of MYLAR (TM) giving result a set that contains the resin powder. After placing this assembly in the press the assembly was heated to a temperature of 195 ° C for 5 minutes without considerable additional pressure to be applied to the resin powder. After 5 minutes of this heating, a force of 9,988 kilograms was hydraulically applied to the resin by the press, the 9,988 kilograms of force being maintained for 5 minutes as the powder melted and pressed into a film having a thickness of approximately .0508 millimeter. Then, this additional pressure was maintained for an additional 5 minutes (for a total of 10 minutes in the press), while the film was allowed to cool to a rate of approximately 15 ° C + 2 ° C per minute, until a plate temperature of approximately 38 ° C, after which the film was removed from the press and allowed to cool to room temperature. The film was then conditioned by being retained for at least 40 hours at a temperature of 22 ° C and a relative humidity of 50 percent. Duplicate tests were carried out on each sample, with the resulting data sets merged and a two-point smoothing algorithm supplied in Rheomtrics Rhios 4.2.2 data analysis software that was used to obtain an average spectrum. The crystallinity of the mass percentage was calculated from the integration of the second endothermic heat fusion reaction using a Perkin Elmer Differential Scanning Calorimeter DSC-7, with the assumption of 288 J / gram for the enthalpy of fusion of the crystalline regions in homopolymeric polyethylene. Figure 1 is a plot of a ratio of the relaxed and non-relaxed storage modules (for beta-relaxation) versus the percentage mass crystallinity, for non-oriented films pressed from: (1) ethylene / styrene copolymers of Examples 1 to 15 as well as (2) the homogeneous ethylene / alpha-olefin copolymers of Comparative Examples 17 to 21. As can be seen in Figure 1, the ratio of beta-relaxer storage modules (ie, similar to Young's Modules which is a measure of the stiffness of a material) is greater for ethylene / styrene copolymers than for the homogeneous comparison ethylene / alpha-olefin copolymers also shown graphically in Figure 1. As illustrated in Figure 1, with respect to the homogeneous ethylene / alpha-olefin copolymer comparative films, the copolymer films of Ethylene-styrene exhibited higher amorphous phase stiffness above the beta-relax temperature. Figure 2 is a plot of the peak beta-loosening temperature versus the percent mass crystallinity for non-oriented films pressed from: (1) the ethylene / styrene copolymers of Examples 1 to 15 as well as (2) the homogeneous ethylene / alpha-olefin copolymers of Comparison Examples 17 to 21. As can be seen in Figure 2, the peak beta-relax temperature is higher for the ethylene / styrene copolymers than for the homogeneous ethylene / alpha-olefin copolymers from comparison also represented graphically in Figure 2.

Example 22 The hot pressed films of the ethylene / strirene copolymer of Example 12, having the approximate dimensions of .0508 by 6.35 by 6.35 centimeters, were prepared and oriented in a biaxial orientation apparatus of the laboratory (known as a TM Long Film Stretcher ™ , obtained from TM Long Company Inc. of Somerville, NJ). By an analogous procedure, the oriented hot-pressed films were prepared using the homogeneous ethylene / octene copolymer of Comparison Example 16, these comparison films having the approximate pre-orientation dimensions of 0.356 by 6.35 by 6.35 centimeters. For the copolymers of Examples 12 and 16, the Vicat softening temperatures as calculated from the elastic moduli were 95 ° C and 90 ° C, respectively. The conditions of orientation for each of the pressed films were as follows: Orientation Mode: simultaneous biaxial Temperature During Orientation: 85 ° C Orientation Regimes: 5.08 and 50.80 centimeters per second After orientation, all the films were covered with ambient air, that is, they "solidified", were removed from the apparatus and kept at a temperature of approximately 73 ° C for at least two days before being tested. The Tension module (method D 882-91, Method A of the American Society for the Testing of Materials) and free shrink properties were tested along each of the two orthogonal orientation directions in the film samples, and then they averaged. The impact strength (Method D 3763-86) of the American Society for the Testing of Materials was calculated by dividing the total energy at break between the average film thickness. The impact force was calculated as the minimum impact force divided by the average sample thickness. Table II below shows the comparison data for these two samples. Table II Number Thickness Regimen of Orientation Module Film Tension Example (cm / second) millimeters (Kg / cm2) 12 5.08 046 1127.8 50.80 043 1484.0 16J 5.08 0305 1237.6 50.80 0254 1350.8 Table II (continued) EncogimienEncogimienResistence Number Endeavor of Free to Free to Impact to Impact Example 85 ° C (%) 95 ° C (%) (.138 kilo (.454 kigram / achieves / .0254 mií- .0254 mi meter) liter) 12 35 62 1.41 35.05 36 63 1.00 30.71 16 * 38 65 0.88 22.85 35 64 0.85 26.06 * The pressed films of Example 16 were exposed to a high energy electronic beam source at a preferred calculated dose of 54 Kg before orientation. The aforementioned data show similar free shrinkage values and moduli for the two types of resins, while the impact properties normalized in thickness were from 20 percent to 60 percent higher for the ethylene-styrene copolymer.

Example 23 (Orientation in Hot Air of the Multiple Layer Films Containing a Propylene / Ethylene Copolymer and an Ethylene / Styrene Copolymer) A palindromic three-layer co-extruded film having an A / B / A structure is oriented in hot air at 115 ° C. The outer layers "A" are a propylene / ethylene copolymer having 3 weight percent ethylene. The inner layer "B" is an ethylene / styrene copolymer having 2 mol% styrene (hereinafter "Copolymer Number 2 ES"). The relative thickness of the A / B / A layers is 25 percent / 50 percent / 25 percent, respectively.

Example 24 (Hot Air Orientation of a Multilayer Film Containing a Propylene Homopolymer and an Ethylene / Styrene Copolymer) A palindromic three-layer co-extruded film having an A / B / A structure is oriented in hot air at 115 ° C. The outer "A" layers are a propylene homopolymer. The inner "B" layer is a propylene / styrene copolymer having 19 mole percent styrene (then copolymer number 3 PS). The relative thickness of the A / B / A layers is 25 percent / 50 percent / 25 percent, respectively.

Example 25 (3-Layer Oriented Barrier Film Produced by Extrusion Coating) A two-layer co-extruded precursor film is formed, the precursor film having the structure: outer layer number 1 / inner layer number 1). The outer layer number 1 is from an ethylene vinyl acetate resin ELVAX 3128 (TM) having 8.9 percent vinyl acetate (hereinafter, "EVA Number 1), obtained from DuPont de Nemours Corporation, of Wilmington, Delaware. The inner Nummary 1 layer is an ethylene / styrene copolymer having 4 mole percent styrene (hereinafter "Copolymer Number 4 ES"). The precursor film is irradiated to 2 MR and then coated by extrusion with a layer of barrier of a vinylidene chloride / methyl acrylate copolymer (hereinafter "VDCMA copolymer"), preferably a SARÁN (TM) VCCMA copolymer obtained from The Dow Chemical Company, of Midland, MI:, followed by coating with a external abuse known as LD 318.92 (TM) and vinyl acetate and ethylene having 9 percent vinyl acetate (hereinafter "EVA Number 2"), obtained from Exxon Chemical Company, of Baytown, Texas, to yield a film of four layers Which has the structure: EVA number 1 / Copolymer number 4 ES / Copolymer VDCMA / EVA number 2 The four-layer film is then oriented in hot water, through a trapped bubble method, both with preheating and bath temperatures hot at 195 ° C.

Example 26 (5-Layer Oriented Barrier Film Produced by Extrusion Coating) A two-layer co-extruded precursor film is formed, the precursor film having the structure: outer layer number 1 / inner number 1 layer. Layer number 1 external is EVA number 1. Layer number 1 internal is Copolymer Number 4 ES. The precursor film is irradiated to 2 MR and then coated by extrusion with a barrier layer of the VDCMA Copolymer, followed by a layer of Copolymer number 4 ES followed by a layer of EVA external abuse number 2 to yield a film of four. resulting layers that have the basic structure: EVA Number 1 / Copolymer Number 4 ES / Copolymer VDCMA Copolymer number 4 ES / EVA number 2. The five layer film is then oriented by a bubble method trapped with hot water both with preheating temperatures as a hot bath of 195 ° C.

Example 27 (6-layer Oriented Barrier Film Produced by Extrusion Coating) A three-layer coextruded precursor film is formed that has the structure structure: outer layer number 1 / inner layer number 1 / inner layer number 2. The outer layer number 1 it's EVA number 1; inner layer number 1 is a copolymer number 4 ES; inner layer number 2 is Escorene LD-720.92 (TM) an ethylene vinyl acetate copolymer having 19 percent vinyl acetate (hereinafter "EVA number 3"), obtained from Exxon Chemical Company, Baytown, Texas. The precursor film is irradiated to 2 MR and then coated by extrusion with a VDCMA copolymer layer, followed by a layer of Copolymer number 4 ES, followed by a layer of EVA number 2, to produce a six layer film having the structure: EVA number 1 / Copolymer number 4 ES / EVA number 3 // VDCMA / Copolymer number 4 ES / EVA number 2 The six-layer film is then oriented by a bubble method trapped with hot water both at preheating temperatures and of hot bath of 195 ° C.

Example 28 (4-Layer Oriented Barrier Film Produced by Extrusion Coating) A two-layer co-extruded precursor film is formed having an inner layer of an ethylene / styrene polymer having 9 molar percent of styrene (hereinafter "Copolymer number 5 ES"), and a second layer of EVA number 3. After irradiation, the precursor film is coated by extrusion with a barrier layer of VDCMA, followed by a layer of EVA number 2. Then , the coated film is oriented with hot water by means of a trapped bubble technique. The multiple layer structure obtained is: Copolymer number 5 ES / EVA number 3 // VDCMA / EVA number 2 Example 29 (Co-extruded 3 Layer Orientated Film! A palindromic coextruded three-layer film having an A / B / A structure is oriented in hot air at 115 ° C. The outer "A" layers are an ethylene / styrene copolymer having 6 percent molar styrene (hereinafter "Copolymer number 6 ES"). The inner "B" layer is PE 1335 (TM) an ethylene vinyl acetate copolymer having 3.3 percent vinyl acetate (hereinafter "EVA number 4"), obtained from Rexene, of Dallas, Texas. The relative thickness of layers A / B / A is 25 percent / 50 percent / 25 percent, respectively.

Example 30 (Co-extruded 3-Layer Oriented Film Containing a Core Layer Mix) A palindromic coextruded three-layer film having an A / B / A structure is oriented in hot air at 115 ° C. The outer "A" layers are a mixture of 50 percent Copolymer number 6 ES and 50 percent EVA number 3. The internal "B" layer is a copolymer of ethylene and vinyl alcohol (below "EVOH copolymer") . The relative thickness of the A / B / A layers is 25 percent / 50 percent / 25 percent, respectively.

Example 31 (5-layer Coextruded Oriented Film Containing a Core Layer Mix) A palindromic five-layer coextruded film having an A / B / C / B / A structure is oriented in hot air at 113 ° C. The outer "A" layers are EVA number 2. The inner "C" layer is an EVOH copolymer and serves as a barrier to gaseous oxygen. The internal "B" layers are EVA number 3 and serve as coupling layers.

Example 32 (Co-extruded 5-Layer Oriented Film Containing an EVOH Copolymer Barrier Layer) A coextruded five-layer palindromic film having an A / B / C / B / A structure is oriented in hot air at 113 ° C. The external "A" layers are a Copolymer number 2 ES. The internal "C" layer is an EVOH copolymer. The internal "ß" layers are EVA number 3 and serve as coupling layers.

Example 33 (7-layer Coextruded Oriented Barrier Film Containing Nylon, Coupling Layers and Ethylene / Styrene Outer Layers) A co-extruded seven-layer palindromic film having a structure A / B / C / D / C / B / A is oriented in hot air at 113 ° C. The external "A" layers are a Copolymer number 2 ES. The internal "D" layer is from an EVOH copolymer. The internal "B" layers are EVA number 3 and serve as coupling layers. The internal "C" layers are nylon 6.

Example 34 (7-Layer Coextruded Oriented EVOH Barrier Film Containing Layers and Only One External Copolymer Layer ES) A seven-layer film was coextruded and cooled rapidly. The seven layer film has a first outer layer of a heterogeneous ethylene / octene copolymer; followed by an internal number 1 layer, of an ethylene vinyl acetate copolymer having 3.5 percent vinyl acetate (hereinafter "EVA number 5"), followed by an internal layer number 2, which serves as a layer of coupling and is of a polyolefin grafted with anhydride; followed by an internal number 3 layer of an EVOH copolymer; followed by an inner layer number 4, which serves as a coupling layer and is a polyolefin grafted with anhydride; followed by an internal number 5 of EVA number 5; followed by an outer number 2 layer of a Copolymer number 1 ES.

Example 35 (Thermoformed Foam Sheet that has a Laminated Film to it) The multilayer film of Example 14 is adhered to a foamed polystyrene web using heat and pressure. The outer layer number 2 is directly bonded to the foamed polystyrene web. The foamed polystyrene with the seven-layer film is laminated thereto and then thermoformed into a tray.

Example 36 (Quickly Co-extruded 5-Layer Film Containing an EVOH Copolymer Barrier Layer) A five layer multilayer film is quickly extruded and cooled. The multilayer film has a first layer of a copolymer of ethylene and vinyl acetate followed by a second layer of a metal-neutralized salt of a copolymer of ethylene and acrylic acid followed by a third layer of an ethylene-acetate copolymer. vinyl, followed by a fourth layer of an ethylene-styrene copolymer having 30 mole percent styrene (then Copolymer number 7 ES) followed by a fifth layer of polystyrene.

Example 37 (Thermoformed Metallized Continuous Tape with Laminated Film Same) The five layer multilayer film of the Example 16 is adhered to a continuous strip of metallized polyester with an adhesive. The resulting laminated structure is thermoformed in a tray.

Example 38 (8-layer Coextruded Film Thermoformed in a Tray) An eight-layer film is coextruded as a multilayer film followed by rapid cooling. The eight layer film has: a first layer of an ethylene / vinyl acetate copolymer; a second layer of a metal-neutralized salt of a copolymer of ethylene and acrylic acid; a third layer of an ethylene vinyl acetate copolymer; a fourth layer of an adhesive resin; a fifth layer of a copolymer of ethylene and vinyl alcohol; a sixth layer of an adhesive resin; a seventh layer of an ethylene / styrene copolymer having 25 mole percent styrene; and an eighth layer of polystyrene. The film is thermoformed in a tray.

Example 39 (Preparation of Patch Bags and Bone Protection Patch) A two-layer film in the shape of a tube is co-extruded. The two-layer film has a first layer (the inner layer of the tube) of a vinyl acetate and ethylene that has 25 percent vinyl acetate and a second layer (the outer layer of the tube) of a 50 percent blend of an ethylene / styrene copolymer having 7 percent molar of styrene and 50 percent by weight of an ethylene / vinyl acetate copolymer having 8 percent vinyl acetate. The tube is irradiated and then oriented with hot air. After orientation the tube is flattened and flattened in such a way that the first layer adheres asymmetrically and the tube thus forms the tube of a four-layer film. Then, the four-layer film is cut into patches that adhere to a suitable film tube for the preparation of the protective bone patch bags.

Example 40 (Preparation of Medical Bag Using a 4 Layer Coextruded Molded Film of Multiple Layers) A multi-layer film is formed by coextrusion of downcast molding. The four-layer film has: a first layer of an ethylene-propylene copolymer; a second layer that serves as an adhesive layer; a third layer of an ethylene-styrene copolymer having 25 mole percent styrene; and a fourth layer of an ethylene-propylene copolymer. The four-layer film becomes an appropriate Joolsa for use in medical applications. During the conversion to the bag structure, the film is sealed by radiofrequency with the fourth layer being a sealing layer and the third layer being a susceptor layer.

Example 41 (Preparation of a Medical Bag Using a 5 Layer Film Coextruded Molded in Multiple Layers) A film is formed by descending molded coextrusion. The 5-layer film has: a first layer of a copolyester; a second layer that serves as an adhesive layer; a third layer of a heterogeneous ethylene / octene copolymer having a density of 0.905 gram per cubic centimeter; a fourth layer that serves as an adhesive layer; a fifth layer of an ethylene / styrene copolymer having 30 mole percent styrene. During the conversion of the film into a bag for medical applications, the film is sealed by radiofrequency.

Example 42 (Preparation of a Medical Bag Using a Coextruded 4-Layer Film Containing a Susceptive Layer) A multi-layered film is formed using a co-extrusion process of descending molding. The four-layer film has: a first layer of a copolyester; followed by a second layer that serves as an adhesive layer; followed by a third layer which is a mixture of 50 percent of an ethylene / vinyl acetate copolymer and 50 percent of an ethylene / styrene copolymer having 35 mole percent of styrene; and a fourth layer of a modified ethylene / propylene copolymer. During the conversion of the film into a bag for medical applications, the third layer acts as a radio frequency susceptor layer. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the form. precise information provided and modifications and variations are possible in view of the aforementioned teachings. The modalities were selected and described in order to explain the principles of the invention and their practical application to enable a person skilled in the art to use the invention in the different modalities and with different modifications that are appropriate to the specific use proposed. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (26)

R E I V I N D I C A C I O N E S:

1. A thermally shrinkable film comprising an essentially oriented film layer consisting of a homogeneous aromatic alpha-olefin / vinyl copolymer in an amount of about 30 percent to 100 percent by weight based on the weight of the film layer. film, wherein the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer has an aromatic vinyl monomer content of about 1 percent to 50 mole percent.

2. The film according to claim 1, wherein the film has a free shrink at 90 ° C, of at least 30 percent in at least one direction.

3. The film according to claim 1, wherein the film layer has a modulus of about 351.50 to 10.545 kilograms per square centimeter.

4. The film according to claim 3, wherein the film layer has a modulus of about 703 to 10,545 kilograms per square centimeter.

5. The film according to claim 4, wherein the layer of the film has a modulus of about 1.054 to 3.515 kilograms per square centimeter.

6. The film according to claim 1, wherein the film is a multilayer film.

7. The film according to claim 6, wherein the film is symmetrical.

The multi-layer film according to claim 6, comprising a first layer and a second layer, wherein the first layer is an oxygen barrier layer and the second layer comprises the alpha-olefin / aromatic vinyl copolymer homogeneous.

The multi-layer film according to claim 8, wherein the oxygen barrier layer comprises at least one member selected from the group consisting of a copolymer of ethylene / vinyl alcohol, polyvinylidene chloride, polyamide , polyacrylonitrile, polyester and silica.

The multi-layer film according to claim 6, comprising a first layer and a second layer, wherein the first layer comprises at least one member that is selected from the group consisting of polyolefin, polyamide, polyester and second layer comprises the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer.

The multi-layer film according to claim 10, wherein the polyolefin comprises at least one member selected from the group consisting of polyethylene homopolymer, polypropylene homopolymer, aliphatic ethylene / alpha-olefin copolymer, copolymer ethylene / vinyl ester, ethylene / acrylic ester copolymer, ethylene / acrylic acid copolymer, polystyrene homopolymer, styrene / aliphatic diene copolymer, aliphatic propylene / alpha-olefin copolymer and an ionomer.

The film according to claim 1, wherein the film layer comprises a composition consisting of: at least one member selected from the group consisting of a homogeneous ethylene / vinyl aromatic copolymer and a copolymer of propylene / homogeneous aromatic vinyl; and at least one member selected from the group consisting of polyethylene homopolymer, polypropylene homopolymer, aliphatic ethylene / alpha-olefin copolymer, ethylene / vinyl ester copolymer, ethylene / acrylic ester copolymer, ethylene copolymer / Acrylic acid, polystyrene homopolymer, styrene / aliphatic diene copolymer, aliphatic propylene / alpha-olefin copolymer and an ionomer.

The film according to claim 1, wherein the homogeneous aromatic alpha-olefin / vinyl copolymer comprises an ethylene monomer and a styrene monomer.

The film according to claim 13, wherein the ethylene monomer is present in an amount of about 75 mole percent to about 99 mole percent, and the styrene monomer is present in an amount of about 1 percent molar to 25 molar percent.

15. The film according to claim 1, wherein the homogenous aromatic alpha-olefin / vinyl copolymer comprises a propylene monomer and a styrene monomer.

16. The film according to claim 1, wherein the homogeneous aromatic alpha-olefin / vinyl copolymer comprises a network of cross-linked polymer.

17. A printed film comprising a film layer consisting of a homogeneous aromatic vinyl alpha-olefin / vinyl copolymer in an amount of about 30 percent to 100 percent by weight based on the weight of the film layer, wherein the film layer has an imprint thereon, and wherein the homogeneous aromatic vinyl alpha-olefin / vinyl copolymer has an aromatic vinyl monomer content of about 1 percent to 50 mole percent.

The printed film according to claim 17, wherein the printed film is a multilayer film, and the film layer is an outer film layer, and the printing is on an outer surface of the film layer external

19. A multi-layer film comprising an outer seal layer, an internal oxygen barrier layer, an inner core layer, and an external abuse layer wherein: at least one member is selected from the group consisting of the outer sealing layer and the inner core layer comprises a homogeneous aromatic alpha-olefin / vinyl copolymer; the polyamide is present in at least one member which is selected from the group consisting of the internal oxygen barrier layer, the inner core layer and the external abuse layer.

20. A thermoformed article comprising a multilayer film consisting of an outer sealing layer, a layer is barrier to internal oxygen, an inner core layer and an external abuse layer wherein: at least one mimebra selected from the The group consisting of the outer sealing layer and the inner core layer comprises a homogeneous aromatic vinyl alpha-olefin / vinyl copolymer; the polyamide is present in at least one member selected from the group consisting of the internal oxygen barrier layer, the inner core layer and the external abuse layer.

21. A patch bag comprising a thermally shrinkable patch adhered to a thermally shrinkable bag, the thermally shrinkable patch comprises a first thermally shrinkable film and the thermally shrinkable bag comprises a second thermally shrinkable film wherein at least one member is selected of the group consisting of the first thermally shrinkable film and the second thermally shrinkable film comprises a film layer consisting of a homogenous aromatic alpha-olefin / vinyl copolymer.

22. A laminate comprising a foam sheet and a film adhered to the foam sheet, wherein at least one member selected from the group consisting of the foam sheet and the film comprises an alpha-olefin / aromatic vinyl copolymer homogeneous and the foam sheet comprises polystyrene.

23. The laminate according to claim 22, wherein the foam sheet further comprises a composition consisting of a polystyrene homopolymer and an alpha-olefin copolymer (homogeneous aromatic vinyl).

The laminate according to claim 22, wherein the film is a multilayer film comprising a composition consisting of a homogeneous aromatic vinyl alpha-olefin / vinyl copolymer and wherein the composition adheres directly to the sheet of paper. foam and wherein the film further comprises an oxygen barrier layer.

25. A package consisting of a rigid container having a flexible cap adhered directly thereto, wherein the rigid container comprises polystyrene, and the flexible cap consists of a homogeneous aromatic alpha-olefin / vinyl copolymer.

26. A package comprising a rigid container having a flexible lid adhered thereto, wherein the rigid container comprises polystyrene and the flexible lid comprises polyolefin, and at least one member selected from the group consisting of the rigid container and the flexible cap further comprises a homogenous aromatic alpha-olefin / vinyl copolymer.