BRPI0619285B1 - PERFORATED FILM, PACKAGING AND METHOD FOR FORMING A PERFORATED FILM - Google Patents

Description

BACKGROUND OF THE INVENTION BACKGROUND OF THE INVENTION [0001] The invention relates to perforated films comprising at least one layer, and packages prepared therewith. Such films and packages contain a combination of perforation density and perforation sizes that allow for effective air removal and improved moisture resistance. In particular, inventive packages allow effective removal of air during pressurized filling of fine powdered substances. The invention also relates to methods for forming such perforated packages and films, and methods for filling such packages. In addition, the invention relates to perforated films that are strong enough to withstand hot fill heat, substantial loads and rough surfaces associated with routine packaging and dispensing processes.

In the field of powder packaging, it is critical to have breathable packaging when the packages are charged by pressurized air which fluidizes the dust particles. The trapped air must be removed from the package or the internal pressure of the bag will increase and the bag will rupture. Trapped air should be removed from the package in a controlled manner to allow maximum capture of the fluidized powder. Currently, air trapped by perforations in plastic bags is removed.

Optimal packaging should prevent dust leakage; however, dust retention should be balanced with the need to allow air to escape during the filling process. However, the size and number of perforations will dictate the amount of dust that may leak from the packaging.

U.S. Patent No. 3,085,608 discloses a polyethylene sheet or bag in which the polyethylene material is perforated to a more or less regular pattern with a large number of perforations spaced at predetermined distances. The bag is air permeable at pressures slightly above or below atmospheric pressure and is substantially impermeable to moisture or water. This reference discloses perforations having an average diameter of between 0.508 and 1.143 mm (0.020 and 0.045 inch).

U.S. Patent No. 4,672,684 discloses a thermoplastic carrier bag having a thermoplastic inner layer, comprising a mesh that allows the packaging of finely pulverized materials without releasing unacceptable levels of powders into the atmosphere during or after filling. This reference discloses an inner mesh with pore sizes from 0.1 to 1.0 mm.

European Patent Application No. 0391661A discloses a layered sheet material formed of a first layer and a second layer. The first layer has predetermined density / m2 micropores of a size in the range 0.1 to 0.4 mm, which provides this layer with a controlled degree of porosity, whereby the layer is air permeable through said layers. pores. The second layer has an air permeable fibrous structure, and is substantially impermeable to liquid and particles.

U.S. Patent No. 4,743,123 discloses a plastic bag of polyolefinic material for packaging materials comprising particles of less than 50 μπι, and a closed bag containing such materials and a thin blade material for such a bag. The thin blade wall is provided with smooth-edged ventilation openings obtained by laser radiation having a maximum size of 50-100 μπι. The distance between the ventilation perforations is such that the tensile strength limit of the thin lamina is substantially the same as the tensile strength limit of the similar non-perforated thin blade. On a slender low density polyethylene blade of 130-190 μπι thickness, the distance between the 80 μπι perforations is more than 20 mm, on a slender linear low density polyethylene blade about 50-110 μπι perforation is at least 5 mm. The bag may consist of two layers of perforated thin blades, the perforations being zigzagged with respect to each other.

US Patent No. 4,332,845 discloses a bag in which at least part of the bag constituent material in which an oxygen absorber is sealed is comprised of a laminated sheet in which a gas permeable sheet is laminated. on one or both sides of a microporous film to provide an outer two-layer lamination. The two outer layers have different softening points, and the layer having a smaller softening point constitutes the inner surface of the bag. It is disclosed that the microporous film has a plurality of thin apertures, and is gas permeable and water impermeable when there is none between the internal and external pressures of the bag. The size of the apertures is preferably from 0.01 to 50 μπι, and the distance along the short axis is less than 2 μπι.

GB 1,265,547 discloses a process and apparatus for packaging particulate or powdery products in containers made of laminated plastics material. This reference discloses a container made of perforated oriented plastic laminate material in which the perforations have a diameter smaller than the average particle size of the packaged product. This reference discloses a bag made from a tube of high pressure polyethylene laminate material having 0.02 mm perforations in a given area of the laminate material.

Film and packaging applications are disclosed in U.S. Patent Nos. 5,493,844, 4,672,684, 4,456,570, 4,579,154, 5,427,807, 6,086,967, 5,389,448, 6,579,607, 5,139 855, US Patent Publication No. 2003/0085213, European Patent Application Nos. EP0060599 and 0500931 A1, and International Publication Nos. WO 03/074594 and WO 03/095197.

However, these references do not provide flexible packaging prepared with breathable films, which are inexpensive to produce and have good mechanical properties, and which can be effectively pressure-filled with a pulverulent material, and which will effectively allow the release of trapped air. , with reduced dust or dust leakage.

Accordingly, there is a need for breathable films which are inexpensive to produce, preferably on existing packaging lines, and which have good mechanical properties. There is still a need for flexible packaging prepared with such films which can be effectively filled under pressure with a pulverulent material and which will effectively allow release of trapped air. As discussed above, trapped air should be removed in a controlled manner to allow maximum capture of fluidized dust and reduction of dust (dust) on the outer surface of the bag. Thus, there is a need to minimize dust while allowing quick and efficient release of trapped air during a filling process. The packaging must also maintain a good moisture barrier and good structural integrity, especially at elevated temperatures. In a typical powder filling process, the heat generated during the filling of a bag may increase the bag temperature to 100 ° C.

There is also a need to develop films with minimal surface defects, printable surfaces and good structural integrity. There is still a need to develop a breathable film that does not require high load loading. At least some of these needs and others have been met by the following invention.

SUMMARY OF THE INVENTION The invention provides a perforated film comprising at least one layer, wherein at least one layer comprises perforations which are individually smaller than or equal to 100 microns (μπι), and the perforation area ratio. Total surface area of the total film is 62,000 to 310,000 ((μιη) 2 / (cm2)) (400,000 to 2,000,000 square microns per square inch ((pm) 2 / (inch) 2)) of film.

Furthermore, the invention provides a method for forming a perforated film comprising at least one layer, said method comprising: (a) selecting a thermoplastic polymer or polymer mixture suitable for at least one layer; (b) forming a film, for example a cast or expanded layer, from the thermoplastic polymer or polymer mixture; (c) perforating said film to form a perforated film; and wherein the at least one layer comprises perforations that are individually smaller than or equal to 100 microns (μιη) in size, and the ratio of the total perforation area to the total film surface area is 62,000 to 310,000 ((μπι ) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μπι) 2 / (inch) 2)) film.

The invention also provides a method for filling a package with powdered merchandise comprising: adding the powdered merchandise using a pressurized gas to a package of suitable capacity to form a charged package, and the package being formed by a perforated film comprising at least one layer and the at least one layer comprising perforations which are individually smaller than or equal to 100 microns (μπι), and the ratio of the total perforation area to the surface area of Total film is 62,000 to 310,000 ((μπι) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μπι) 2 / (inch) 2)) of film.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of permeability Gurley (s) against the total perforation area ((μπι) 2 / (inch) 2) of perforated polyolefin films as compared to a porous paper bag;

[0018] Figure 2 shows alternative drilling patterns;

Figure 3 is a schematic of an exhaust valve bag 1 with a uniform (evenly spaced) placement of perforations (perforation noted as 2), and an opening 3;

Figure 4 is a schematic of an exhaust valve bag 1 with several different perforation densities (perforation noted as 2), and an opening 3; and Figure 5 is an exhaust valve bag with a higher perforation density (perforation noted as 2) on a side surface area 5 relative to a front surface area 4 and an opening 3.

Detailed Description of the Invention The invention provides perforated films and packages that have a good balance of permeability, moisture resistance and mechanical properties. Perforated packages formed from the inventive films also sufficiently permit the release of trapped air during the pressurized dust filling process, while reducing the amount of dust (dust) on the outer surface of the bag. In particular, the invention provides a perforated film comprising at least one layer, and the at least one layer comprising perforations which are individually smaller than or equal to 100 microns (μπι), and the ratio of total perforation area to the total film surface area is 62,000 to 310,000 ((μιη) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μιη) 2 / (inch) 2)) of film.

In yet another aspect of the invention, perforations range from 10 microns to 100 microns. In another aspect, the film comprises at least three layers, and at least one inner layer is a porous layer that can be resealed and / or opened.

In another aspect of the invention, the at least one layer is formed of a composition comprising at least one thermoplastic polymer. In another aspect of the invention, the thermoplastic polymer is a polyolefin. In another aspect of the invention, the composition comprises 50 weight percent or more of an ethylene based homopolymer or interpolymer. In yet another aspect of the invention, the composition comprises 40 weight percent or less of a propylene based homopolymer or interpolymer. The propylene-based homopolymer or interpolymer polymer molecules may be coupled.

In yet another aspect of the invention, the film has a Gurley permeability of less than 50 s per 100 cm3 of air, and more preferably, the film comprises from 60 to 1000 perforations per square inch of film.

The invention also provides a package prepared with an inventive film as described herein. In one aspect, the package contains two or more seams and contains perforations in one or more designated areas within the surface of the package.

The invention also provides additional embodiments of the films and / or packages described herein, and combinations of these embodiments.

Further, the invention provides a method for forming a perforated film comprising at least one layer, said method comprising: (a) selecting a thermoplastic polymer or polymer mixture suitable for the at least one layer; (b) forming a film, for example a cast or expanded layer, from the thermoplastic polymer or polymer mixture; (c) perforating said film to form a perforated film; and wherein the at least one layer comprises perforations that are individually smaller than or equal to 100 microns (μπι) in size, and the ratio of total perforation area to total film surface area is 62,000 to 310,000 ((pm ) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μιη) 2 / (inch) 2)) of film. In one embodiment, the perforations are located in one or more designated areas of the film. The invention also provides additional embodiments of this method described herein, and combinations of these embodiments.

The invention also provides a method for filling a package with powdered goods, said method comprising: adding the powdered goods, using a pressurized gas, into a suitable capacity package to form a loaded package, and the package being formed by a perforated film comprising at least one layer and the at least one layer comprising perforations which are individually smaller than or equal to 100 microns (μιη), and the ratio of the total perforation area to the Total film surface is 62,000 to 310,000 ((μιη) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μπι) 2 / (inch) 2)) of film. The invention also provides additional embodiments of this method described herein, and combinations of these embodiments.

Inventive perforated films have a better balance of permeability, moisture resistance and mechanical properties compared to comparative films that fall outside the perforation size, area and / or density ranges of the inventive films. Packages formed with such films may be filled with powdery, pressurized merchandise and have good trapped air permeability formed during the filling process. As discussed, such packages have excellent moisture barrier properties and excellent mechanical properties such as Elmendorf rupture, 2 percent modulus of elasticity, puncture resistance and dart impact.

As discussed above, the invention provides breathable films and flexible packages prepared from such films. The flexible packages can be effectively filled under pressurized conditions (e.g. pressurized air) with powdery materials. A package of the invention is based on a perforated film containing at least one layer (or cover). In one embodiment the film contains only one layer or cover.

Packages formed with the films of the invention may hold powdery merchandise of various sizes. In one embodiment, the particle size of such merchandise may range from 1 μπι to 100 μπι. The particle may be of any shape such as spherical or irregular and nonuniform in shape.

The films of the invention may be used for packaging any kind of merchandise, including particulate, powder, granular and bulk merchandise, and in particular for packaging moisture-sensitive merchandise and moisture-sensitive powdery merchandise. A package formed from a film of the invention is especially useful for packaging powdery goods such as cement, lime, talcum powder, talcum powder, polyvinyl chloride, gypsum, cocoa, maize flour, wheat flour and sugar. in powder.

A package prepared with an inventive film may be heat treated or mechanically treated with additional process steps when required for particular packaging needs. However, the invention provides a package that can be used in routine powder packaging process steps, without the need for an additional process step, or the need to change a process step.

The films of the invention may be prepared without requiring a large amount of filler, such as calcium carbonate. Typically the loading components are present in amounts of 50 weight percent or more. Fillers are often used in a film composition to produce pores within the final film. Typically, a film is cast from such a film composition, and the cast film is then stretched to form holes around the charge particle agglomerate. In another embodiment, the inventive film does not contain 25 weight percent of more than one filler. In another embodiment, the film does not contain a loading component.

General Film / Package Idea The useful perforation sizes in the films of the invention are less than 100 microns (μιη), preferably less than 90 μπι, and more preferably less than 80 μιη. In one embodiment, the perforation size is from 10 μπι to 100 μιη, preferably from 30 μπι to 100 μπι, more preferably from 50 μπι to 100 μπι, and even more preferably from 60 μπι to 100 μπι. All individual values and sub ranges from 10 μπι to 100 μπι here are included and disclosed. In another embodiment, the perforation size is from 60 μπι to 90 μπι. In another embodiment, the perforation size is from 10 μπι to 40 μπι. In another embodiment, the perforation size is greater than or equal to 10 μιη, preferably greater than or equal to 20 μιη, and more preferably greater than or equal to 30 μιη. In another embodiment, the perforation size is less than or equal to 100 μιη, preferably less than or equal to 90 μπι, and more preferably less than or equal to 80 μιη.

Typically, the perforation size is an average diameter, if the hole is circular in shape, or if the shape is not circular, an equivalent average diameter. For example, if the drilling size of an elliptical hole would be the average of its two diameters.

Perforations within the film layers may be of any size or shape, including, but not limited to, holes of varying degrees of circularity, various triangular shapes, various rectangular shapes, and other shapes of polygons, irregular shapes, and slits. In one embodiment of the invention, the film layers (or layers) have perforations of the same size or size gradient. The size of the perforations will vary depending on the size of the merchandise contained. In another embodiment, the perforations are circular.

The films of the invention are typically perforated by mechanical means including, but not limited to, drilled pin cylinders or sheet pins; or by laser treatment. In one embodiment, perforations are formed on either side of a film, such as an expanded film, or on either side of a package. In another embodiment, craters resulting from the perforations are located on the outer surface of a package formed of an inventive film.

In another embodiment, the ratio of the total perforation area to the total surface area of the film is 62,000 to 310,000 ((μπι) 2 / (cm2)) (400,000 square microns per square inch ((μιη) 2 / ( inch) 2) film to 2,000,000 (μπι) 2 / (inch) 2), preferably from 77,500 to 155,000 ((mm) 2 / (cm2)) (500,000 (μπι) 2 / (inch) 2 to 1,000 .000 (μπι) 2 / (inch) 2), and more preferably from 93,000 to 124,000 ((μπι) 2 / (cm2)) (600,000 (μπι) 2 / (inch) 2 to 800,000 (μπι) 2 / ( inch) 2). All individual values and sub ranges of 62,000 to 310,000 ((μπι) 2 / (cm2)) (400,000 (μπι) 2 / (inch) 2 to 2,000,000 (μπι) 2 / (inch) 2) are included and disclosed herein. . In another embodiment, the ratio of the total perforation area to the total surface area of the film is greater than or equal to 62,000 ((μπι) 2 / (cm2)) (400,000 (μπι) 2 / (inch) 2), preferably greater than or equal to equal to 77,500 ((μπι) 2 / (cm2)) (500,000 (μπι) 2 / (inch) 2), and more preferably greater than or equal to 93,000 ((μπι) 2 / (cm2)) (600,000 (μπι) 2) / (inch) 2).

In another embodiment, the ratio of the total perforation area to the total surface area of the film is less than or equal to 310,000 ((μπι) 2 / (cm2)) (2,000,000 (μπι) 2 / (inch) 2), preferably smaller. or equal to 294,500 ((μπι) 2 / (cm2)) (1,900,000 (μπι) 2 / (inch) 2), and more preferably less than or equal to 279,000 ((μπι) 2 / (cm2)) (1,800. 000 (μπι) 2 / (inch) 2).

In another embodiment, the perforation density is 40 to 1,500 per square inch perforations, preferably from 60 to 1,000 per square inch perforations, more preferably from 65 to 750 per square inch perforations, and even more preferably from 100 to 500 perforations per square inch. per square inch of film.

In another embodiment, the Gurley permeability of the film is less than 50, preferably less than 30, and more preferably less than 20 seconds per 100 cm3 of air. In another embodiment, the Gurley permeability is from 2 to 50 seconds per second per 100 cm3 of air, more preferably from 5 to 40 seconds per 100 cm3 of air, and even more preferably from 10 to 30 seconds per 100 cm3 of air. All individual values and sub ranges of 2 to 50 seconds per 100 cm3 of air are included and disclosed herein.

In another embodiment, the air permeability of a package prepared with the inventive film is at least 30 m3 per hour, more preferably at least 50 m3 per hour, and most preferably at least 100 m3 per hour. In another embodiment, an air permeability of at least 200 m3 per hour is achieved.

Typically, the films of the invention have a thickness of 25 μιη (micron) to 1000 μπι, preferably from 40 μπι to 600 μπι, more preferably from 50 μπι to 400 μπι. All individual values and sub ranges from 25 μπι to 1000 μπι here are included and disclosed. In another embodiment, the film thickness is greater than or equal to 25 μπι, preferably greater than or equal to 30 μπι, and more preferably greater than or equal to 45 μπι. In another embodiment, the film thickness is less than or equal to 1000 μπι, preferably less than or equal to 800 μπι, and more preferably less than or equal to 600 μπι. The films may also have a thickness greater than 1000 μπι.

In another embodiment, the inventive films have 2% secant modulus (or modulus of elasticity) (MD and / or CD) of at least 0.344 MPa (50,000 psi).

Already in another embodiment, the inventive films have an Elmendorf (MD and / or CD) tear of at least 40 grams per millipeg of film thickness, and more preferably at least 70 grams per millipeg of film thickness.

The invention provides a package formed with an inventive film. The invention also provides a package comprising at least one component formed with an inventive film. Packages prepared with the films of the invention may contain a weight of 1 kg to 100 kg, 1 kg to 50 kg, or 1 to 25 kg.

The configuration of the perforations within a film will vary, and will depend on the end use of the film. Film sheets may have perforations in designated areas within the sheet. Designated areas can be of any size and shape. Within these designated areas, perforations may exist in various configurations, including, but not limited to, perforation size gradients along a particular axis of an area, perforation density gradients along a particular axis of an area. , and piercing gradients of different shapes and / or sizes. Ideally the perforation pattern (perforation size, number of perforations and perforation spacing) should be such that a container is air permeable under pressure but substantially impermeable to moisture. Figure 2 shows examples of alternative perforation cell patterns.

In one embodiment, the film is perforated in one or more designated areas. In such a design, the designated areas may be located within a specific area of the package, or the designated areas may cover the entire surface of the film. In another embodiment, the film is perforated such that a packet formed of such a composition contains perforations only within one or more horizontally flat surfaces. The perforations may be evenly spaced within one or more designated areas, or spaced at different perforation densities within one or more designated areas. In one embodiment, a package comprises at least four sides, and at least one side has a greater number of perforations per square inch of film compared to at least one other side. In another embodiment, a package comprises at least four sides, and at least two sides have a greater number of perforations per square inch of film compared to at least two other sides. In each of these embodiments, the size and shape of the perforations may vary. Perforation sizes may increase as the number of perforations decreases. Inventive packages typically contain one or more seams.

In a preferred embodiment, inventive films are used to form relief valves. Figures 3-5 show three representations of such a bag, respectively. As these figures show, the top portion of the bag contains an opening for inserting the filler rail. In one embodiment, the lower portion and its top portion area are heat sealed to maintain a closed environment other than the opening for the filler rail. Thus, the bag is designed to fit around the filling chute, leaving small open areas for dust to escape during the filling process. The perforations, as shown in Figures 3-5, serve primarily as an indication of configuration patterns, and are not necessarily drawn to scale.

The inventive films and / or packages may have a combination of two or more of the embodiments described herein. Resins Overview The films of the invention contain at least one layer or cover. In one embodiment, the film contains only one layer or cover. Each layer or layer is formed of a composition typically containing at least one thermoplastic polymer. The choice of resin for each layer will depend on the location of the layer, the softening and / or melting temperature of the resin, and the adhesion forces between consecutive layers.

The amount of thermoplastic polymer in each layer will vary depending upon the desired properties, e.g., film strength properties, and the other film components, and / or the type or types of polymers employed. Generally, for polyolefins, the amount is at least 40 percent, preferably at least 45 percent, more preferably at least 60 percent by weight of the total weight of the composition. Preferred polyolefins include ethylene based polymers and propylene based polymers.

In the practice of this invention any thermoplastic polymer or thermoplastic polymer mixture may be used, and representative polymers include natural or synthetic resins, such as, but not limited to, styrene block copolymers; rubbers; polyolefins, such as polyethylene, polypropylene and polybutene; ethylene / vinyl acetate (EVA) copolymers; ethylene / acrylic acid (EAA) copolymers; ethylene / acrylate copolymers (EMA, EEA, EBA); polybutylene; polybutadiene; nylon; polycarbonates; polyesters; poly (ethylene oxide); poly (propylene oxide); ethylene / propylene interpolymers, such as ethylene / propylene rubber and ethylene / propylene / diene monomer rubbers; chlorinated polyethylene; thermoplastic vulcanates; ethylene / ethyl acrylate (EEA) polymers; ethylene / styrene (ESI) interpolymers; polyurethanes; as well as functionally modified polyolefins, such as silane graft or maleic anhydride graft modified olefin polymers; and combinations of two or more of these polymers.

The thermoplastic polymer or thermoplastic polymer mixture may comprise one or more ethylene-based interpolymers or homopolymers and / or one or more propylene-based interpolymers or homopolymers, each as the sole polymeric component or as a polymeric component (in addition to one or more other polymeric components).

Suitable comonomers useful for polymerizing with an olefin such as ethylene or propylene include, but are not limited to, ethylenically unsaturated monomers, conjugated or unconjugated polyenes or dienes. Examples of such comonomers include ethylene and C3 -C20 α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene , 1-decene, and the like. Preferred comonomers include ethylene, propylene, 1-butene, 1-hexene and 1-octene, the latter being especially preferred. Other suitable monomers include styrene, alkyl or halogen substituted styrenes, tetrafluoroethylenes, vinylbenzocyclobutanes, butadienes, isoprenes, pentadienes, hexadienes, octadienes, and cycloalkenes, for example cyclopentene, cyclohexene and cyclooctene. Ethylene is typically copolymerized with a C3 -C20 α-olefin. Preferred comonomers include C3 -C8 α-olefins such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-olefin. hexene, 1-heptene, and 1-octene, and more preferably propylene, 1-butene, 1-hexene, and 1-octene.

In one embodiment, an olefin-based interpolymer has a comonomer content comprising no more than 20, preferably less than 15, more preferably less than 10, even more preferably less than 7, and most preferably less than 5 percent by weight. weight of said polymer. All individual weight percentages and sub-ranges of 5 to 20 weight percent are included and disclosed herein.

In another embodiment, an olefin-based interpolymer has a comonomer content comprising no more than 7, preferably less than 5, more preferably less than 3, most preferably less than 2 weight percent, of said polymer. All individual weight percentages and sub-ranges of 2 to 7 weight percent, are included and disclosed herein.

In another embodiment, an olefin-based interpolymer has a comonomer content comprising no more than 50, preferably less than 40, more preferably less than 30, most preferably less than 20 weight percent, of said polymer. All individual weight percentages and sub-ranges of 20 to 50 weight percent are included and disclosed herein.

The amount of comonomer content in an interpolymer of the invention may be greater than 50 weight percent, or may be less than 2 weight percent.

Ethylene-based polymers include ethylene homopolymers as well as randomized block and interpolymers of ethylene. Such polymers include copolymers, terpolymers, tetrapolymers and higher order polymers of ethylene, propylene and other olefins, such as optional dienes.

Ethylene-based polymers include linear low density polyethylene (LLDPE), high density polyethylene (HDPE), low density polyethylene (LDPE), ultra low density polyethylene (ULDPE), very low density polyethylene (VLDPE) homogeneously branched linear ethylene polymers, homogeneously branched substantially linear ethylene polymers, and heterogeneous linear ethylene polymers. The amount of one or more of these polymers, if any, in a film will vary depending upon the desired properties, the other components, and the type of polyethylene (s).

The terms "homogeneous" and "homogeneously branched" are used to refer to ethylene / α-olefin interpolymers, in which the α-olefin comonomer is randomly distributed within a given polymer molecule, and substantially all of Polymer molecules have the same ratio of ethylene to comonomer.

Homogeneously branched ethylene interpolymers that may be used in the practice of this invention include homogeneously branched linear ethylene interpolymers and homogeneously branched substantially linear ethylene interpolymers.

Homogeneously branched linear ethylene interpolymers include long chain unbranched ethylene polymers, but having short chain branches, derived from the interpolymer polymerized comonomer, and which are homogeneously distributed, both within the same polymeric chain as between different polymer chains. That is, homogeneously branched linear ethylene interpolymers lack long chain branching, as is the case with low density linear polyethylene polymers or high density linear polyethylene polymers, and are produced using uniformly distributed branching polymerization processes. , described, for example, by Elston in US Patent No. 3,645,992. Commercial examples of homogeneously branched linear ethylene / α-olefin interpolymers include TAFMER ™ polymers supplied by Mitsui Chemical Company and EXACT ™ polymers provided by Exxon Chemical Company.

Homogeneously branched substantially linear ethylene interpolymers are described in U.S. Patent Nos. 5,272,236, 5,278,272, 6,054,544, 6,335,410, and 6,733,810, the entire contents of which are incorporated herein by reference.

In addition, substantially linear ethylene interpolymers are homogeneously branched ethylene polymers having long chain branching. Long chain branches have the same comonomer distribution as that of the polymer backbone, and may be approximately the same length as the length of the polymer backbone. Typically "substantially linear" means that the bulk polymer is replaced on average with 0.01 long chain branch per 1000 total carbons (including both main chain and branch carbons) to 3 long chain branches per 1000 total carbons. In one embodiment, the polymer is replaced with 0.01 long chain branch per 1000 total carbons to 1 long chain branch per 1000 total carbons, more preferably 0.05 long chain branch per 1000 total carbons to 1 long chain branch per 1000 total carbons, and especially 0.3 long chain branch per 1000 total carbons to 1 long chain branch per 1000 total carbons.

Commercial examples of substantially linear polymers include ENGAGE ™ polymers and AFFINITY ™ polymers (both obtainable from The Dow Chemical Company).

Substantially linear ethylene interpolymers form a unique class of homogeneously branched ethylene polymers. They differ substantially from the well-known class of conventional homogeneously branched linear ethylene interpolymers described by Elston in US Patent No. 3,645,992, and furthermore they are not in the same class of heterogeneous Ziegler-Natta catalyst polymerized linear ethylene polymers. conventional (e.g. linear low density polyethylene (LLDPE), high density polyethylene (HDPE), low density polyethylene (LDPE) or ultra low density polyethylene (ULDPE) produced, for example, using the technique disclosed by Anderson et al ., U.S. Patent No. 4,076,698); nor are they in the same class as high-pressure free radical-initiated, highly branched polyethylenes such as, for example, low density polyethylene (LDPE), ethylene / acrylic acid (EAA) copolymers and ethylene / vinyl acetate copolymers ( EVE).

The homogeneously branched substantially linear ethylene interpolymers useful in the invention have excellent processability, although they have relatively narrow molecular weight distribution. Surprisingly, the melt flow rate according to ASTM D 1238 (I10 / I2) of the substantially linear ethylene interpolymers can vary widely, and essentially independent of molecular weight distribution, Mw / Mn, or MWD. This surprising behavior is contrary to homogeneously branched substantially linear ethylene interpolymers, such as those described, for example, by Elston in US Patent No. 3,645,992, and to conventional heterogeneous Ziegler-Natta catalyst-polymerized linear ethylene interpolymers such as those described, for example, Anderson et al., in US Patent No. 4,076,698.

Unlike homogeneously branched substantially linear ethylene interpolymers, linear (either homogeneously, or heterogeneously branched) ethylene interpolymers have rheological properties that are most influenced by molecular weight distribution.

Homogeneously branched substantially linear ethylene interpolymers are characterized by having a narrow molecular weight distribution (Mw / Mn). For substantially linear and substantially linear ethylene interpolymers, the molecular weight distribution, Mw / Mn, is, for example, less than or equal to 5, preferably less than or equal to 4, and more preferably from 1.5 to 4, and furthermore. more preferably from 1.5 to 3, and most preferably from 2.5 to 3.5. All individual values and sub-ranges from 1 to 5 herein are included and disclosed.

The distribution of comonomer branches to substantially linear and linear ethylene interpolymers is characterized by their SCBDI (short chain branching distribution index), and is defined as the percentage by weight of polymeric molecules having a comonomer content. within 50 percent of the average total comonomer molar content. The SCDBI of a polymer is calculated from data obtained from techniques known in the art, such as, for example, temperature-elution fractionation (abbreviated herein as "TREF"), described for example by Wild et al. ., Journal of Polymer Science, Poly. Phys. Ed., Volume 20, page 441 (1982), or in U.S. Patent Nos. 4,798,081 and 5,008,204. The SCBDI or CDBI for the substantially linear polymers useful in the compositions of the present invention is preferably greater than 50 percent, especially greater than 70 percent, more preferably greater than 90 percent.

The homogeneously branched substantially linear ethylene polymers used in the film composition of the invention are known, and they, and their method of preparation, are described in U.S. Patent Nos. 5,272,236, 5,278,272 and 5,703,187, which are incorporated herein in their entirety by reference.

Substantially linear or homogeneous linear ethylene polymers may be suitably prepared using constricted geometry metal complex, as disclosed in U.S. Patent Nos. 5,272,236 and 5,278,272. See also, U.S. Serial Patent Application No. 5,445,403, filed July 3, 1990 (EP-A-416,815; U.S. 5,703,187; 5,872,201); U.S. Serial Patent Application No. 702,475, filed May 20, 1991 (EP-A-514,828; U.S. 6,118,013); as well as U.S.-A Patent Nos. 5,470,993, 5,374,696, 5,231,106, 5,055,438, 5,057,475, 5,096,867, 5,064,802 and 5,132,380. U.S. Serial Patent Application No. 720,041, filed June 24, 1991 (EP-A-514,828) discloses certain borane derivatives of the above constricted geometry catalysts, and teaches and claims a method for their preparation. U.S.-A-5,453,410 discloses combinations of cationic constrained geometry catalysts with aluminoxane as appropriate olefin polymerization catalysts.

Heterogeneous linear ethylene polymers may also be used in the present invention. Heterogeneous linear ethylene polymers include ethylene copolymers and one or more C3 to Cs α-olefins. Ethylene homopolymers can also be prepared using the same catalysts that are used to prepare heterogeneous systems, such as Ziegler-Natta catalysts. Both the molecular weight distribution and the short chain branch distribution having origin of α-olefin copolymerization are relatively broad compared to those of heterogeneous linear ethylene polymers. Heterogeneous linear ethylene polymers may be prepared by a process in solution, semifluid paste, or gas phase using a Ziegler-Natta catalyst, and are well known to those skilled in the art. For example, see U.S. Patent No. 4,339,507, which is incorporated herein by reference in its entirety.

For the film compositions of the present invention, mixtures of homogeneous and heterogeneous ethylene polymers ("composite polyethylene"), examples of which are disclosed by Kolthammer et al., In US-A Nos. 5,844,045 may also be used. , 5,869,575, and 6,448,341, all of which are incorporated herein by reference. Examples of mixtures of polyethylenes in a substantially linear polyethylene reactor and LLDPE are disclosed in U.S. Patent Nos. 5,844,045 and 5,869,575. Preferably, the LLDPE fraction of the reactor polyethylene mixture is at least fifty percent by weight (50 percent by weight) of the reactor mixture, more preferably at least about fifty five percent by weight (55 percent). percent by weight), most preferably at least about sixty percent by weight (60 percent by weight). Preferably, the LLDPE fraction of the reactor polyethylene mixture does not exceed about eighty-five percent by weight (85 percent by weight) of the reactor mixture, more preferably it does not exceed eighty percent by weight (80 percent). most preferably not more than about seventy-five weight percent (75 weight percent).

Additional polymers suitable for use in the invention include propylene based polymers. Propylene based polymers include propylene homopolymer, interpolymers as well as propylene impact and random interpolymers, and coupled propylene based polymers. Such polymers include copolymers, terpolymers, tetrapolymers and higher order polymers of ethylene, propylene and other olefins, such as optional dienes. Suitable propylene-based polymers are disclosed in U.S. Patent Nos. 6,593,005 and 6,939,919 and EP 1263873, which are incorporated herein by reference in their entirety.

Propylene-based polymers include impact propylene copolymers. Such copolymers are commercially obtainable and are well known within the art training, for example, as described by EP Moore, Jr. in Polypropylene Handbook, Hanser Publishers, 1996, page 220 and in US Patent Nos. 3,893,989 and 4,113,802. . The term "impact copolymer" is used herein to refer to heterophasic propylene copolymers where polypropylene is the continuous phase and an elastomeric phase is uniformly dispersed therein. Impact copolymers result from one reactor process other than physical mixing. Usually impact copolymers are formed in a two or multistage process, optionally involving a single reactor, a single reactor with at least two process stages occurring therein, or optionally multiple reactors. Advantageously, the impact copolymers are at least 5 weight percent, preferably at least about 10 weight, preferably up to about 40 weight, more preferably up to about 35 weight percent, even more preferably up to about 25 weight percent. and most preferably up to about 20 weight percent of ethylene. Examples of some suitable impact polypropylene copolymers are disclosed in U.S. Patent No. 6,593,005 to Tau et al., Which is incorporated herein by reference.

In one embodiment, a film layer is formed or prepared from a composition containing at least the following: a coupled propylene-based polymer, and a "reactor blend" of a substantially linear polyethylene (or a homogeneously branched linear polyethylene) and a linear low density polyethylene. The "reactor mixture" may also contain LDPE, LLDPE, HDPE, substantially linear polyethylene, homogeneously branched linear polyethylene, and mixtures thereof. The polymer composition may also contain another ethylene-based polymer, such as a LLDPE and / or substantially linear (or homogeneously branched linear polyethylene) polyethylene in order to improve compatibility between the coupled propylene-based polymer and the "reactor blend" . Examples of such compositions are disclosed in U.S. Patent No. 6,593,005, which is incorporated herein by reference in its entirety.

In another embodiment, a film layer is formed or prepared from a composition containing at least the following components: propylene-based interpolymer or homopolymer, which may or may not be coupled; and one or more ethylene-based homopolymers and / or interpolymers.

The polymeric compositions containing an ethylene-based polymer and a propylene-based polymer may also contain an ethylene / propylene / rubber polymer to make the main component polymers compatible. Stabilizers and antioxidants may be added to a resin formulation to protect it from degradation caused by oxygen reactions that are induced by such things as heat, light, or residual catalyst from the raw materials.

Antioxidants are commercially obtainable from Ciba-Geigy, located in Hawthorn, N.Y., and include IRGANOX® 565, 1010 E 1076, which are hindered phenolic antioxidants. These are primary antioxidants that act as free radical scavengers, and may be used alone or in combination with other antioxidants such as phosphite antioxidants such as Ciba-Geigy IRGAFOS® 168 obtainable. Phosphite antioxidants are considered secondary antioxidants and are generally not used alone. These antioxidants are mainly used as peroxide decomposers. Other available antioxidants include, but are not limited to, CYANOX® LTDP, obtainable from Cytec Industries at Stamford, Conn., And ETHANOX® 1330 obtainable from Albemarle Corp. in Baton Rouge, Louisiana. Many other antioxidants are obtainable for use by themselves, or in combination with other such oxidants. Other resin additives include, but are not limited to, ultraviolet light absorbers, antistatic agents, pigments, dyes, nucleating agents, fillers, sliding agents, flame retardants, plasticizers, processing aids, lubricants, stabilizers, smoke inhibitors. , viscosity controlling agents and nonstick agents.

The film must maintain its structural integrity in response to high pressures and temperatures. In one embodiment, materials for one or more film layers include one or more polyolefin interpolymers and homopolymers. Examples of such polymers include, but are not limited to, polyethylene based polymers such as DOWFLEX ™ and ELITE ™, and polypropylene based polymers such as INSPIRE ™ (all from The Dow Chemical Company). Each layer may contain one polymer or two or more polymers, such as a polymer blend.

The specific properties of each layer will depend on the polymer composition used. The properties provided below are representative of polyolefin compositions containing one or more polymers, and used in one or more film layers. These properties are also representative of other polymeric compositions that fall within the bounds of the noted properties. The properties of the polymer compositions provided below are not intended to limit the scope of this invention in terms of the range of polyolefins and other polymers and mixtures suitable for use in the invention. Preferably, the polymeric composition comprises at least one ethylene based polymer and / or at least one propylene based polymer.

In one embodiment, the polymeric composition will typically be characterized by a Vicat softening point from 50 ° C to 230 ° C, preferably from 70 ° C to 200 ° C, and more preferably from 100 ° C to 150 ° C. Ç. All individual values and sub ranges of 50 ° C to 230 ° C herein are included and disclosed.

In another embodiment, the polymeric composition will typically be characterized by a DSC melting point of from 50 ° C to 250 ° C, preferably from 70 ° C to 200 ° C, and more preferably from 100 ° C to 180 ° C. C, and even more preferably from 120 ° C to 170 ° C. All individual values and sub ranges of 50 ° C to 250 ° C herein are included and disclosed.

In another embodiment, the polymeric composition will typically be characterized by a melt index (R 2) a. 190 ° C and 2.16 kg load (ASTM D-1238-04), from 0.1 to 100 g / 10 minutes, preferably from 0.2 to 50 g / 10 minutes, more preferably from 0.3 to 10 minutes. g / 10 minutes, and even more preferably from 0.4 to 5 g / 10 minutes. All individual values and sub-ranges of 0.1 to 100 g / 10 minutes herein are included and disclosed.

In another embodiment, the polymeric composition will typically be characterized by a melt flow rate at 230 ° C and a loading of 2.16 kg (ASTM D-1238-04) from 0.1 to 100 µm. g / 10 minutes, preferably from 0.2 to 50 g / 10 minutes, more preferably from 0.3 to 10 g / 10 minutes, and most preferably from 0.4 to 5 g / 10 minutes. All individual values and sub-ranges of 0.1 to 100 g / 10 minutes herein are included and disclosed.

In another embodiment, the polymeric composition will be characterized by a weight average molecular weight (Mw) of from 20,000 to 1,000,000, and all individual values and sub-ranges of from 20,000 to 1,000,000 are included and disclosed herein.

In another embodiment, the polymeric composition will typically be characterized by a total percent crystallinity of less than 60%, and preferably less than 50%, as measured by DSC.

In another embodiment, the polymeric composition will typically be characterized by a density of 0.88 g / cm3 to 0.96 g / cm3, preferably from 0.89 g / cm3 to 0.95 g / cm3, and more preferably from 0.90 g / cm3 to 0.94 g / cm3 (ASTM D7 92-00). All individual values and sub ranges of 0.88 g / cm3 to 0.96 g / cm3 are included and disclosed herein.

In another embodiment, the polymeric composition will typically be characterized by a molecular weight distribution, Mw / Mn, from 2 to 20, preferably from 3 to 10, and more preferably from 4 to 8, and even more preferably from 2 to 20. 5 through 7. All individual values and sub-ranges 2 through 20 herein are included and disclosed.

In another embodiment, the polymeric composition contains at least one polymer having a DSC melting point of from 50 ° C to 250 ° C, preferably from 70 ° C to 200 ° C, and more preferably from 100 ° C to 180 ° C. More preferably from 120 ° C to 170 ° C. All individual values and sub ranges of 50 ° C to 250 ° C herein are included and disclosed. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer. In another embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a melt index (I2) at 190 ° C and a loading of 2.16 kg (ASTM D-1238-04) from 0.1 to 100. g / 10 minutes, preferably from 0.2 to 50 g / 10 minutes, more preferably from 0.3 to 10 g / 10 minutes, and most preferably from 0.4 to 5 g / 10 minutes. All individual values and sub-ranges of 0.1 to 100 g / 10 minutes herein are included and disclosed. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a melt flow rate at 230 ° C and a loading of 2.16 kg (ASTM D-1238-04) from 0.1 to 100 µm. g / 10 minutes, preferably from 0.2 to 50 g / 10 minutes, more preferably from 0.3 to 10 g / 10 minutes, and most preferably from 0.4 to 5 g / 10 minutes. All individual values and sub-ranges of 0.1 to 100 g / 10 minutes herein are included and disclosed. In one embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a weight average molecular weight (Mw) of 20,000 to 1,000,000, and all individual values and sub-ranges of 20,000 to 1,000,000 herein are included and disclosed. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer. In another embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a total percent crystallinity of less than 60%, and preferably less than 50%, as measured by DSC. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer. In another embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a density of 0.87 g / cm3 to 0.97 g / cm3, preferably 0.90 g / cm3 to 0.95 g / cm3, and more preferably from 0.91 g / cm3 to 0.94 g / cm3 (ASTM D792-00). All individual values and sub ranges of 0.87 g / cm3 to 0.97 g / cm3 herein are included and disclosed. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer. In another embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In another embodiment, the polymeric composition contains at least one polymer having a molecular weight distribution, Mw / Mn, from 1 to 10, preferably from 1 to 7, and more preferably from 1.5 to 5, and even more. preferably from 1.5 to 3.5. All individual values and sub-ranges from 1 to 10 herein are included and disclosed. In one embodiment, the at least one polymer is an ethylene homopolymer. In another embodiment, the at least one polymer is an ethylene based interpolymer. In another embodiment, the at least one polymer is a propylene homopolymer. In another embodiment, the at least one polymer is a propylene based interpolymer.

In a preferred embodiment, the at least one polymer is a propylene / α-olefin interpolymer or a propylene / ethylene copolymer. In a further embodiment, α-olefin is selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-butene, 1-nonene, 1-decene, 4-methyl 1-pentene and mixtures thereof. In another embodiment, the propylene / α-olefin interpolymer or propylene / ethylene copolymer has a melt index (I 2) of 0.1 g / 10 minutes to 100 g / 10 minutes. In another embodiment, the propylene / α-olefin interpolymer or propylene / ethylene copolymer has a density of from 0.86 to 0.93 g / cm3, preferably from 0.86 to 0.92 g / cm3, and even more preferably. from 0.86 to 0.91 g / cm3. The propylene / α-olefin interpolymer or propylene / ethylene copolymer may each have a combination of two or more of these embodiments.

In a preferred embodiment, the at least one polymer is a propylene / α-olefin interpolymer or a propylene / ethylene copolymer, and has a melt index (I 2) of 0.1 g / 10 minutes at 50 g / 10 minutes, a density of 0.86 to 0.92 g / cm3, and a molecular weight distribution, Mw / Mn, of 2 to 10.

In a preferred embodiment, the at least one polymer is an ethylene / α-olefin interpolymer. In a further embodiment, the ethylene / α-olefin interpolymer comprises a copolymer formed from monomers selected from the group consisting of ethylene and 1-octene, ethylene and 1-butene, ethylene and 1-hexene, ethylene and 1-pentene, ethylene and 1 -heptene, ethylene and propylene, ethylene and 4-methyl-1-pentene and mixtures thereof. Preferably, the monomers are selected from the group consisting of ethylene and 1-octene, and ethylene and 1-butene. In another embodiment, the ethylene / α-olefin interpolymer has a melt index (I 2) of 0.1 g / 10 minutes to 100 g / 10 minutes. In another embodiment, the ethylene / α-olefin interpolymer has a density of 0.900 to 0.950 g / cm3, preferably from 0.900 to 0.945 g / cm3, and more preferably from 0.900 to 0.940 g / cm3. The ethylene / α-olefin interpolymer may have a combination of two or more of these embodiments.

In another embodiment, the ethylene / α-olefin interpolymer has a melt index of 0.2 to 50 g / 10 minutes, and a density of 0.900 to 0.950 g / cm3, and preferably 0, 900 to 0.940 g / cm3, and a molecular weight distribution, Mw / Mn, of 1.5 to 5.

In another embodiment, the at least one polymer is a propylene-based propylene / ethylene interpolymer. In a further embodiment, the propylene / ethylene interpolymer has a melt index (I 2) of 0.1 g / 10 minutes to 100 g / 10 minutes. In another embodiment, the propylene / ethylene interpolymer has a melt index (I 2) of 0.1 to 50 g / 10 minutes, a density of 0.86 to 0.92 g / cm3, and a molecular weight distribution, Mw / Mn, from 2 to 10. The propylene / ethylene interpolymer may have a combination of two or more of these embodiments.

The polymer composition may have a combination of two or more embodiments described above.

The polymeric components of such compositions may have a combination of two or more of the above embodiments.

Suitable polymeric compositions may contain an ethylene based interpolymer or homopolymer and a propylene based interpolymer or homopolymer. In one embodiment, the polymeric composition contains 50 weight percent or more of an ethylene based interpolymer or homopolymer. In a further embodiment, the polymeric composition contains 40 weight percent or less of a propylene based interpolymer or homopolymer. In another embodiment, the polymeric composition contains from 50 to 90 weight percent, preferably from 55 to 80 weight percent, and more preferably from 60 to 75 weight percent of an ethylene-based interpolymer or homopolymer. In a further embodiment, the polymeric composition contains from 10 to 50 weight percent, preferably from 20 to 40 weight percent, and most preferably from 25 to 35 weight percent of a propylene-based interpolymer or homopolymer. The polymeric molecules of the propylene-based interpolymer or homopolymer may be coupled.

Process for forming the films of the invention A film of the invention may be prepared by selecting the appropriate thermoplastic mixtures or polymers to make each layer, forming a film of each layer, and where the film contains more than one layer, bonding the layers together. or co-extruding or leaking one or more layers. Desirably, the film layers are continuously bonded throughout the interfacial area between films (film layers).

The films may be perforated before or during the manufacture of a container. In addition, the manufactured container may be pierced at a later date. Drilling mechanisms include, but are not limited to, drill pin cylinders, plate drill pins, and laser techniques. In a preferred embodiment, the perforations are on both sides of the film, and the perforation crater is located on the outer surface of a container formed of such film. The shape and size of the perforations, and the amount of perforations will depend on the end use of the film.

Typically, for each layer, extrusion mixing of the components and any additional additives such as sliding agents, non-sticking agents, and polymer processing aids is appropriate. Mixing is performed by extrusion in such a manner as to achieve an adequate degree of dispersion. Extrusion blending parameters will necessarily vary depending on the components. However, typically total polymer deformation, i.e. the degree of blending, is important, and is controlled, for example, by the propeller design and melting temperature. The melting temperature during film formation will depend on the film components.

A film structure is formed after extrusion mixing. Film structures may be made by conventional manufacturing techniques, for example bubble extrusion, biaxial orientation processes (such as stretch structures or double bubble processes), sheet casting / extrusion, coextrusion and lamination. Conventional bubble extrusion processes (also known as hot expanded film processes) are described, for example, in The Encyclopedia of Chemical Technology, Kirk-Othmer, Third Edition, John Wiley & Sons, New York, 1981, Volume 16 , pages 416-417 and volume 18, pages 191-192. Biaxial orientation film making processes as described in the "double bubble" process of US-A-No. 3,456,044 (Pahlke), and the processes described in US-A-No. 4,352,849 (Mueller), US-A Patent Nos. 4,820,557 and 4,837,084 (both to Warren), US-A Patent No. 4,865,902 (Golike et al.), US-A Patent No. 4,927,708 (Herran et al.), US Patent No. 4,952,451 (Mueller), and US-A Patent Nos. 4,963,3,419 and 5,059,481 (both to Lustig et al.) May also be used to prepare the novel film structures of this invention. All of these patents are incorporated herein by reference.

The melting temperature during film formation will vary depending on the components of the film, generally the melting temperature is from 175 ° C to 300 ° C, preferably from 185 ° C to 240 ° C, and more preferably from 195 ° C. ° C to 220 ° C.

Manufacturing techniques for fabricating structures of the invention include vertical forming / filling / sealing techniques, such as those described in Packaging Machinery Oparation, Chapter 8: Form-Fill-Sealing, by C. Glenn Davis (Packaging Machinery Manufacturers, 2000 K Street, NW, Washington, DC 20006); The Wiley Encyclopedia of Packaging Technology, Marilyn Bakker, Editor-in-Chief, pages 364-369 (John Wiley &Sons); U.S. Patent Nos. 5,288,531 (Falia et al.), 5,721,025 (Falia et al.), 5,360,648 (Falia et al.) and 6,117,465 (Falia et al.); other filmmaking techniques, such as those discussed in Plastic Films, Technology and Packaging Applications (Technomic Publishing Co., Inc. (1992)), by Kenton R. Osborn and Wilmer A. Jenkens, pages 39-105. All of these patents and references are incorporated herein by reference.

Other film-making techniques are disclosed in U.S. Patent No. 6,723,398 (Chum et al.). Postprocessing techniques, such as radiation treatment and corona treatment, especially for printing applications, may also be performed with the materials of the invention. The film made from the invention may also be silane cured, or the other polymers used to make the inventive article may be grafted post-manufacture (such as maleic anhydride grafted polymers), including techniques disclosed in U.S. Patent Nos. 4,927,888. (Strait et al.), 4,950,541 (Tabor et al.), 4,762,890 (Strait et al.), 5,346,963 (Hughes et al.), 4,684,576 (Tabor et al.). All of these patents are incorporated herein by reference.

[0115] After film formation, it can be stretched. Stretching is performed by any method conventionally used in the art.

Film sheets may be bonded by heat sealing or by use of an adhesive. Heat sealing may be performed using conventional techniques, including, but not limited to, heated bar, side welding, ultrasonic welding, or other alternative heating mechanisms.

The films of the above processes may be made to any thickness depending on the application. Typically, the films have a total thickness of 25 to 1000 microns, preferably 50 to 500 microns, more preferably 50 to 250 microns.

Definitions [0118] Any numeric range mentioned here includes all values of the value lower than the upper value, in increments of one unit, so that at least 2 units are separated between any lower value and any higher value. As an example, if it is established that the amount of a component, or a value of a composition or physical property, such as, for example, amount of a mixing component, softening temperature, melt index, etc., is between 1 and 100, all individual values such as 1, 2, 3, etc., and all sub ranges, such as 1 to 20, 55 to 70, 197 to 100, etc., are intended to be expressly listed in this report. For values that are less than one, a unit is considered to be 0.0001, 0.001, 0.01, or 0.1, when appropriate. These are only examples of what is specifically intended, and all possible combinations of numerical values between the minimum and maximum values listed will be deemed to be expressly set forth in this patent application. Numerical ranges which have been mentioned herein with reference to Vicat softening point, DSC melt temperature, perforation size, film thickness, melt index, melt flow rate, weight average molecular weight, weight distribution molecular weight, percent crystallinity, density, percent by weight of component, pressure and other properties.

The term "film" as used herein means a single or multilayer film structure.

The term "composition" as used herein includes one or more components comprising the composition, as well as reaction products and decomposition products of the components of the composition.

The term "perforations" as used herein refers to holes made within the film using an impact mechanism, laser or other mechanical or optical device. The perforations can be of varying sizes and shapes. The perforations are individually, and consequently each independently, of a size less than or equal to 100 microns (μπι).

The phrase "perforations of the same size" and similar phrases as used herein refer to a polymeric compound prepared by polymerization techniques, either of the same or different type. The generic term "polymer" encompasses the term homopolymer, commonly used to refer to polymers made from a single type of monomer, and the term interpolymer as defined hereinafter.

The term "interpolymer" as used herein refers to polymers prepared by polymerizing at least two different types of monomers. Therefore, the generic term interpolymer includes copolymers, commonly used to refer to polymers made from two different types of monomers, and polymers made from more than two different types of monomers.

The term "thermoplastic polymer" or "thermoplastic composition" and similar terms mean a polymer or polymer composition that is substantially thermally deformable or extrudable, although relatively aggressive conditions may be required.

The term "mixture" and "polymer mixture" as used herein means a mixture of two or more polymers. Such polymers may be coupled and / or crosslinked. Such a mixture may or may not be miscible (not phased at the molecular level). Such a mixture may or may not be separated into phases. Such a mixture may or may not contain one or more domain configurations, determined by electron transmission spectroscopy, light scattering, X-ray scattering, and other methods known in the art.

The term "ethylene-based interpolymer" as used herein means an interpolymer containing at least 50 mol percent and preferably more than 50 mol percent ethylene.

The term "propylene based interpolymer" as used herein means an interpolymer containing at least 50 mol percent, and preferably more than 50 mol percent, of propylene.

Test Procedures Various test methods were used to evaluate the films. The specific test parameters within each test will depend on the polymer or polymer composition used. Some of the tests below describe test parameters that are indicated as representative of polyolefin resins. The test parameters are not intended to limit the scope of this invention. Those skilled in the art will understand the limitations of a particular set of test parameters, and will be able to determine appropriate parameters for other types of polymers. Gurley air resistance [0129] The "permeability" of film samples can be assessed using the Gurley Hill porosity brow method according to the TAPPI T460 om-02 test method. This test measures the air resistance of a small sample (approximately one square inch), in terms of the time required for a given volume of air at a given pressure to "permeate" the sample.

Haver & Boecker Bag Permeability Test [0130] Manufactured plastic bags can be tested for volumetric air permeability using an apparatus similar to that used to fill a bag with cement, except that only air is introduced into the bag. The filling apparatus maintains a pressure of approximately 50 mbar and measures the volume of air escaping from the bag per unit of time. Moisture Barrier [0131] The moisture barrier of a film sample is measured according to a water column pressure test (ISO 1420 Al (2001)).

Perforation Microscopy [0132] Optical microscopy can be used to characterize the appearance and size of perforations in films. For each film sample, three "holes" are randomly selected from each expanded film surface for analysis (12 holes total). Images were observed with a LEICA MP AZO microscope using incident and reflected backlighting and a SONY DKC-5000 digital camera. Images were captured using an 80x objective lens and processed using Adobe Photoshop 5.0. "Adjusted image levels" were used to maximize image information and achieve optimal contrast. The images are then observed to estimate the size of the hole. For holes of circular or elliptical shape two dimensions are required to estimate the hole area. Mechanical Property Test [0133] Dart impact strength is measured according to ASTM D1709-03. Elmendorf rupture is measured according to ASTM D1922-03. Traction is measured according to ASTM D882-02. The modulus of elasticity (secant modulus) is measured according to ASTM D882-02.

Composition Property Test The density of the interpolymers and homopolymers of ethylene and other polyolefins according to ASTM D-792-00 is measured. Some samples are annealed under ambient conditions for 24 hours prior to measurement. ASTM D-792-00 can also be used to measure density of other polymers as noted in this test procedure.

The melt index (I2) of ethylene-based interpolymers and homopolymers according to ASTM D-1238-04, condition 190 ° C / 2.16 kg, is measured. As noted in this test procedure ASTM D-1238-04 can also be used to measure the melt index of other polymers. The melt melt rate (MFR) of propylene-based interpolymers and homopolymers according to ASTM D-1238-04, condition 230 ° C / 2.16 kg is measured.

Molecular weight distributions for polyethylene based resins may be determined with a chromatographic system consisting of either a Polymer Laboratories model PL-210 or a Polymer Laboratories model PL-220. The carousel and column compartments are operated at 140 ° C. The columns are three 10 micron Polymer Laboratories Mixed-B columns. The solvent is 1,2,4-trichlorobenzene. Samples are prepared at a concentration of 0.1 gram of polymer in 50 milliliters of solvent. The solvent used to prepare the samples contains 200 ppm butylated hydroxytoluene (BHT). Samples are prepared by gently shaking for 2 hours at 160 ° C. The injection volume is 100 microliters and the flow rate is 1.0 mL / min.

A fifth-order polynomial adjustment of the gel permeation chromatography (GPC) column set with 21 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 is arranged. in 6 "cocktail" mixtures, with at least a dozen separate molecular weights. Standards are purchased from Polymer Laboratories (UK). Standards are prepared at 0.025 g in 50 ml solvent for molecular weights greater than or equal to 1,000,000 and 0.05 g in 50 ml solvent for molecular weights less than 1,000,000. Narrow pattern mixtures are first used, and in descending order of the highest molecular weight component, to minimize degradation. The maximum molecular weights of polystyrene standard are converted to polyethylene molecular weights using the following equation (described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)): Mpoiethylene = A x (Mpoiethylene) B / where M is the molecular weight, A is 0.4315 and B is 1.0.

Polyethylene equivalent molecular weight calculations are performed using Viscotek software from TriSEC version 3.0. Molecular weights for polypropylene-based polymers can be determined using Mark-Houwink ratios according to ASTM D6474.9714-1, where for polystyrene a = 0.702 and log K = -3.9, and for polypropylene, a = 0.725 and log K = -3.721. For polypropylene based samples, the column and carousel compartments were operated at 160 ° C.

[0139] To measure crystallinity of polyethylene (PE) and polypropylene (PP) based samples, differential scanning calorimetry (DSC) can be used. A sample of 5 to 8 mg of film sample is weighed and placed directly into the DSC pan. The lid is nailed to the pan to ensure a closed atmosphere. The sample is placed in a DSC cell, then heated at a rate of about 10 ° C / min to a temperature of 180 ° C for PE (230 ° C for PP), and isothermally maintained for three minutes at that temperature. . The sample is then cooled at a rate of 10 ° C / min to -60 ° C for PE (-40 ° C for PP), and isothermally maintained for three minutes, after which it is reheated (second heating) at a rate. 10 ° C / min until complete melting. The percentage crystallinity is calculated by dividing the melt heat (Hf) determined on the second heating curve by a theoretical melt heat value of 292 J / g for PE (165 J / g for PP) and multiplying. this amount per 100 (% crystallinity = (Hf-s- 292 J / g) x 100).

The melting points ™ of the polymers can be determined from the second heating curve obtained from DSC, described above. The crystallization temperature (Tc) can be determined from the first cooling curve.

Vicat softening temperatures are measured according to ASTM D1525-00.

The films and processes of this invention and their use are more fully described by the following examples. The following examples are provided for the purpose of illustrating the invention, and should not be construed to limit the scope of the invention.

Experimental The following resins were used individually, or as a composition component, in the experimental compositions. These resins are preferably composed of one or more stabilizers and / or antioxidants.

EAO-D20: Linear, random low-density ethylene-based copolymer prepared using a Ziegler-Natta type catalyst and a solution polymerization process. This copolymer has a density of 0.920 g / cm3 (ASTM D792-00) and a melt index (I2) of 1.0 g / 10 minutes (190 ° C / 2.16 kg, ASTM D1238-04). Comonomer = 1-octene.

EAO-E51: Enhanced ethylene (composite) based copolymer with a density of 0.920 g / cm3 (ASTM D792-00) and a melt index (I2) of 0.85 g / 10 minutes (190 ° C / 2.16 kg, ASTM D1238-04). Comonomer = 1-octene, DSC melting point 124 ° C. 105 ° C Vicat Softening Point (ASTM D1525-00).

EAO-B81: Enhanced ethylene (composite) based copolymer with a density of 0.940 g / cm3 (ASTM D792-00) and a melt index (I2) of 0.80 g / 10 minutes (190 ° C / 2.16 kg, ASTM D1238-04). Comonomer = 1-octene.

RESINA-D14: Random propylene-based copolymer resin system with an overall density of 0.900 g / cm3 (ASTM D792-00) and a melt flow rate (MFR) of 0.50 g / 10 minutes (230 ° C / 2.16 kg, ASTM D1238-04). Comonomer = ethylene; comonomer percentage around 8.5% by weight, DSC melting point 164 ° C (ASTM D3417).

EAO-D62: High density ethylene based copolymer with a density of 0.953 g / cm3 (ASTM D792-00) and a melt index (I2) of 0.3 g / 10 minutes (190 ° C / 2 , 16 kg, ASTM D1238-04). Comonomer = 1-hexene; comonomer percentage = 0.7% by weight. Prepared in gas phase using a chrome catalyst.

To prepare the test films the following compositions were used: Composition 1: 100 weight percent EAO-D20.

Composition 2: 100 weight percent EAO-E51.

Composition 3: 100 percent by weight of RESINA-D14.

Composition 4: 65 weight percent EAO-E51 and 35 weight percent RESINA-D14.

Composition 5: 100 weight percent EA0-B81.

Composition 4: 50 weight percent EAO-D62 and 50 weight percent EAO-E51. Table 1 shows the film manufacturing conditions. Table 2 shows the mechanical properties of the films.

[0150] Fabricated bags were formed from the following film composition; 62 weight percent EAO-E51, 34 weight percent RESINA-D14 and 4 weight percent TiO 2 (pigment). The bags were perforated and tested for volumetric air permeability using the Haver & Boecker bag air permeability test. Table 3 shows the drilling parameters and permeability test results. Table 3 also shows various mechanical properties that were examined.

As can be seen from the results in Table 3, bag 3 has excellent permeability at a smaller perforation size and smaller perforation area. The permeability of bag 3 is comparable to that of comparative bag 2, which has total area and much larger perforation sizes. The permeability of bag 3 is also significantly better than the permeability of comparative bag 1.

In addition, the bag 3 has better overall breaking properties compared to the comparative bag 2, and has conventional limit of comparable elasticity. Therefore, in bag 3, there is no loss in mechanical properties, and there is still an overall break improvement, even though the hole density (holes / inch2) is at least four times that of comparative bag 2.

Table 1: Film Fabrication Conditions Table 2: Mechanical Properties of Films Table 3 Fabricated Bags: Perforation and Permeability Parameters and Mechanical Results

Claims (22)

1. Perforated film, comprising at least one layer, characterized in that the at least one layer comprises perforations (2) which are individually smaller than or equal to 100 microns (μιη), and the ratio of the total perforation area to the total film surface area is 62,000 to 310,000 ((μπι) 2 / (cm2)) (400,000 to 2,000,000 square micron per square inch ((μιη) 2 / (inch) 2)) of film. Film according to Claim 1, characterized in that the perforations (2) are of equal size. Film according to Claim 1, characterized in that the Gurley permeability is less than 50 seconds per 100 cm3 of air. Film according to Claim 1, characterized in that the size of the perforations ranges from 10 microns to 90 microns. Film according to Claim 1, characterized in that the ratio of the total perforation area to the total film surface area is from 500,000 to 1,000,000 square microns per square inch ((μιη) 2 / (inch). ) 2) film. Film according to Claim 1, characterized in that it consists of a layer. Film according to claim 1, characterized in that it does not contain 50 weight percent of more than one filler. Film according to Claim 1, characterized in that the perforations (2) are formed by a mechanical means or by a laser. A film according to claim 1, characterized in that at least one film layer is formed of a composition comprising at least one thermoplastic polymer. Film according to claim 9, characterized in that the at least one thermoplastic polymer is a polyolefin. Film according to Claim 10, characterized in that the polymeric composition comprises 50 weight percent or more of an ethylene-based interpolymer or homopolymer. Film according to Claim 11, characterized in that the polymeric composition further comprises 40 weight percent or less of a propylene-based interpolymer or homopolymer. Film according to Claim 10, characterized in that the polyolefin is a propylene / α-olefin interpolymer. Film according to Claim 10, characterized in that the polyolefin is an ethylene / α-olefin interpolymer. A film according to claim 14, characterized in that the ethylene / α-olefin interpolymer comprises a copolymer formed of monomers selected from the group consisting of ethylene and 1-octene, ethylene and 1-butene, ethylene and 1- hexene, ethylene and 1-pentene, ethylene and 1-heptene, ethylene and propylene, ethylene and 4-methyl-1-pentene and mixtures thereof. Film according to Claim 15, characterized in that the ethylene / α-olefin interpolymer has a melt index (I 2) of 0.1 g / 10 minutes to 100 g / 10 minutes. Film according to claim 15, characterized in that the ethylene / α-olefin interpolymer has a melt index of 0.2 to 50 g / 10 minutes, a density of from 0.900 to 0.940. g / cm3, and a molecular weight distribution, Mw / Mn, of 1.5 to 5. Film according to Claim 10, characterized in that the polyolefin is a propylene / ethylene interpolymer. Film according to Claim 18, characterized in that the propylene / ethylene interpolymer has a melt index (I 2) of 0.1 g / 10 minutes to 100 g / 10 minutes. Film according to Claim 19, characterized in that the propylene / ethylene interpolymer has a melt index of 0.1 to 50 g / 10 minutes, a density of 0.86 to 0.92 g / cm3. , and a molecular weight distribution, Mw / Mn, from 2 to 10. Packaging characterized in that it is prepared with the film as defined by claim 1. A method of forming a perforated film, comprising at least one layer, comprising: (a) selecting a suitable thermoplastic polymer or polymer blend for at least one layer; (b) forming a film from the thermoplastic polymer or polymer mixture; (c) perforating said film to form a perforated film; and wherein at least one layer comprises perforations (2) which are individually less than or equal to 100 microns (μπι) in size, and the ratio of the total perforation area to the total surface area of the film is 62,000. at 310,000 (µm) 2 / (cm2) (400,000 to 2,000,000 square micron per square inch ((μιη) 2 / (inch) 2)) of film.