WO2000074929A1 - Films en polyethylene a haute densite, a poids moleculaire eleve et orientes dans le sens machine, presentant des proprietes ameliorees de transmission de la vapeur d'eau - Google Patents

Films en polyethylene a haute densite, a poids moleculaire eleve et orientes dans le sens machine, presentant des proprietes ameliorees de transmission de la vapeur d'eau Download PDF

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Publication number
WO2000074929A1
WO2000074929A1 PCT/US1999/012302 US9912302W WO0074929A1 WO 2000074929 A1 WO2000074929 A1 WO 2000074929A1 US 9912302 W US9912302 W US 9912302W WO 0074929 A1 WO0074929 A1 WO 0074929A1
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WIPO (PCT)
Prior art keywords
film
mil
oriented
less
machine direction
Prior art date
Application number
PCT/US1999/012302
Other languages
English (en)
Inventor
Louis R. Duckwall, Jr.
David H. Bostian
Eric Hatfield
Original Assignee
Printpack Illinois, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Printpack Illinois, Inc. filed Critical Printpack Illinois, Inc.
Priority to PCT/US1999/012302 priority Critical patent/WO2000074929A1/fr
Priority to AU48183/99A priority patent/AU4818399A/en
Publication of WO2000074929A1 publication Critical patent/WO2000074929A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/005—Shaping by stretching, e.g. drawing through a die; Apparatus therefor characterised by the choice of materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/06—PE, i.e. polyethylene
    • B29K2023/0658—PE, i.e. polyethylene characterised by its molecular weight
    • B29K2023/0683—UHMWPE, i.e. ultra high molecular weight polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/08—Copolymers of ethylene
    • B29K2023/083—EVA, i.e. ethylene vinyl acetate copolymer
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene

Definitions

  • the present invention is directed to machine direction oriented high molecular weight, high density polyethylene (HMW HDPE) films having enhanced water vapor transmission properties and superior toughness properties, and articles made therefrom.
  • the present invention is also directed to a method of making machine direction oriented HMW HDPE films having enhanced water vapor transmission properties and superior toughness properties, and articles made therefrom.
  • the present invention is further directed to articles, particularly bags, made from machine direction oriented HMW HDPE films having enhanced water vapor transmission properties.
  • LMW HDPE Low molecular weight high density polyethylene
  • MMW HDPE medium molecular weight high density polyethylene
  • One method of improving the moisture barrier properties of HDPE film is to monoaxially orient the film.
  • U.S. patents disclose a method of monoaxially orienting a HDPE film to improve the water vapor transmission of the film. See for example U.S. Patent No. 4,183,893 to Eastwood et al. and U.S. Patent No. 4,870,122 to
  • HMW HDPE high molecular weight high density polyethylene
  • MMW HDPE MMW high density polyethylene
  • the present invention is directed to a unidirectionally oriented film comprising high molecular weight (HMW) high density polyethylene (HDPE).
  • HMW high molecular weight
  • HDPE high density polyethylene
  • the present invention is also directed to a method of making the above-described films.
  • the method comprises forming a film comprising HMW HDPE, and subsequently orienting the film in the machine direction.
  • the film may be formed by a film blowing process or cast extrusion process.
  • the film may be formed as a single layer film or a multi-layer film comprising x layer sets, wherein each layer set comprises a layer containing HMW HDPE.
  • the present invention is further directed to articles of manufacture made from the above-described films.
  • bags for packaging dry foods, such as cereal are produced from the films.
  • Figure 1 illustrates the apparatus for unidirectionally orienting the films of the present invention.
  • the present invention is directed to a unidirectionally oriented film comprising high molecular weight (HMW) high density polyethylene (HDPE).
  • HMW high molecular weight
  • HDPE high density polyethylene
  • HDPE high density polyethylene
  • the melt index range of the HMW HDPE used in the present invention is from about 1.0 to about 0.008 g/10 min, more desirably from about 0.3 to about 0.01 g/10 min, and even more desirably from about 0.1 to about 0.01 g/10 min.
  • the high density polyethylene of the present invention may comprise an ethylene homopolymer, a copolymer of ethylene and up to about 5 weight percent of one or more monomers, and any combination thereof. Suitable monomers for polymerization with the ethylene monomer include, but are not limited to, propylene, butene-
  • the high density polyethylene of the present invention may also comprise a composition containing the high density polyethylene and one or more additives including, but not limited to, antioxidants, pigments, antiblock, slip, inorganic fillers, and other additives.
  • the films of the present invention may comprise a single layer of HMW HDPE or a multi-layer composite comprising at least one layer of HMW HDPE and at least one additional layer.
  • the films of the present invention may be formed simultaneously with or subsequently laminated to suitable films by processes including, but not limited to, adhesive and extrusion lamination processes.
  • Suitable laminating films include, but are not limited to, polymeric films, metallized polymer films, metal foils, fabrics, paper and paper products, adhesive layers, release layers, and a combination thereof.
  • Suitable polymeric coextruded film layers include, but are not limited to, layers of ethylene-vinyl acetate (EVA) copolymers, ethylene-methacrylic acid salt ionomers, polypropylene, linear low density polyethylene (LLDPE), low density polyethylene (LDPE), and blends thereof.
  • EVA ethylene-vinyl acetate
  • LLDPE linear low density polyethylene
  • LDPE low density polyethylene
  • the multi-layer composites may also comprise a thin "barrier" layer, which provides a barrier to oxygen or organic materials.
  • the barrier layer may be internal to the composite structure and /or on an outer surface of the composite structure.
  • the barrier layer may comprise, but is not limited to, nylon, ethylene-vinyl alcohol copolymer, polyester, or a combination thereof.
  • CAL coextrudable adhesive layer
  • Suitable CAL materials for use in the present invention include, but are not limited to, DuPont's BYNELTM products, Mitsui's ADMERTM products, and Equistar's PLEXARTM products.
  • the present invention is also directed to a method of making the above-described films.
  • the method comprises forming a film comprising HMW HDPE, and subsequently orienting the film in the machine direction.
  • the film may be formed by a HMW HDPE film blowing process or a HMW HDPE cast extrusion process, both of which are well known to those of ordinary skill in the art.
  • a HMW HDPE film blowing process or a HMW HDPE cast extrusion process, both of which are well known to those of ordinary skill in the art.
  • a HMW HDPE film blowing process or a HMW HDPE cast extrusion process, both of which are well known to those of ordinary skill in the art.
  • a HMW HDPE film blowing process or a HMW HDPE cast extrusion process, both of which are well known to those of ordinary skill in the art.
  • a HMW HDPE film blowing process or a HMW HDPE cast extrusion process, both of which are well known to those of ordinary skill in the art
  • HMW HDPE film is made by a film blowing process, wherein HMW HDPE material is extruded, preferably between 400°F and 500°F (200°C - 260°C), through an annular die to form a tube.
  • the diameter of the annulus may vary significantly, depending on whether a "high stalk" or
  • the die gap may also vary as desired, but is typically between about 30 and 100 mils (0.8 and 2.5 mm).
  • a "high stalk” blown extrusion die diameter is typically about 10 inches (-250 mm).
  • the extrudate exits the die in the form of a tubular "stalk," having a diameter that is approximately the same as the diameter of the annulus.
  • the stalk has a length of about four to nine times the diameter of the annulus, more desirably about six and eight times the diameter of the annulus.
  • the length of the stalk may be controlled with air rings, which cool the film to a temperature below the softening point of the HMW HDPE film, typically below 135°C.
  • the tubular film is inflated to a final diameter greater than the original stalk diameter by injecting cooled air (typically cooler than 25°C) into the tubular film.
  • the blow up ratio, or the ratio of final diameter to original diameter is desirably between about 2 and 7, and more desirably between about 2.5 and 4.5.
  • An "in pocket" blown extrusion die diameter is typically about 20 inches (-500 mm).
  • the extrudate exits the die in the form of a tube of the same diameter as that of the annulus.
  • the tube is controlled with air rings, which cool the film to a temperature below the softening point of the
  • An "in pocket" tube diameter may be maintained at the original die diameter, or desirably inflated to a diameter between 1.5 and 4 times the die diameter, or more desirably between 2 and 3 times the die diameter.
  • the extruded tube in the "in pocket” process is typically inflated as the tube exits the extrusion die.
  • the take-off speed of a "high stalk” or "in pocket” blown film is controlled by a nip at the top of a collapsing frame where the tube is flattened, and cools further to a temperature close to ambient temperature.
  • the cooled tube may be wound onto a paper core, or other mandrel, or the tube may be slit open to form one or more films, which may be subsequently wound and stored prior to further processing. Alternatively, the tubular or slit film may proceed directly to the orientation process step.
  • the resulting film of the above-described film blowing processes may desirably have a film thickness of about 1 mil to about 14 mil. More desirably, the resulting film has a thickness of about 1.5 mil to about 8 mil.
  • a HMW HDPE film is made by a cast extrusion process, wherein HMW HDPE material is extruded through a flat die onto a continuously moving cooling roll or onto a continuously moving stack of at least 2 rolls, which form a cooling and smoothing nip for transporting the resulting film to the orientation process or to storage on paper cores or mandrels.
  • the material is extruded preferably between 450°F and 500°F (230°C - 260°C), and the take-off speed of the extruded material is controlled to maintain the most uniform cross section of film in the cooling nip.
  • the width of the die may vary as desired, but practically is typically between about 24 and 200 inches (60 - 500 cm).
  • the die gap may also vary as desired, but is typically between about 80 and 200 mils (2 and 5 mm).
  • the HMW HDPE film is cooled below the softening point of the HMW HDPE, typically about 135°C.
  • the film exiting the cooling nip described above may be further cooled to ambient temperature for winding onto a paper core or mandrel and stored prior to further processing.
  • the film may proceed directly to the orientation process step at a temperature below the softening point of the HMW HDPE.
  • the resulting film of the above-described cast extrusion process desirably has a film thickness of about 1 mil to about 30 mil. More desirably, the resulting film has a thickness of about 2 mil to about 12 mil.
  • Machine direction orientation of HMW HDPE may proceed by any process known to those of ordinary skill in the art.
  • Machine direction orientation processes may include, but are not limited to, reinflation and reheating of a blown tube to a desired orientation temperature, between two nips, desirably the lead nip moving at substantially faster speed than the trailing nip; and reheating of a blown tube, a slit film, or a cast, nipped film, to a desired orientation temperature over a series of heated rolls directed toward two consecutive sets of nip rolls, wherein the lead nip rolls moving at substantially faster speed than the trailing nip.
  • the formed HMW HDPE film 10 passes over heated rolls 11 and 12 through nip points 13 and 14.
  • Heated roll 11 and 12 may be set at a temperature between 60°C and 130°C, more desirably between 80°C and 120°C, and most desirably between 95°C and 105 °C.
  • the heated rolls 11 and 12 have a roll diameter typically between 15 and 25 inches to stabilize the temperature of film 10, on both sides, most desirably between 95°C and 105°C.
  • Nip rolls 15 and 16 form nip point 13, while nip rolls 17 and 18 form nip point 14.
  • the temperature of the nip rolls is held between 60 °C and 130°C, to maintain a stable temperature for the orientation of the HMW HDPE film. More desirably, the temperature of the HMW HDPE film at nip points 13 and 14 is from about 80°C to 120°C. Even more desirably, the temperature of the
  • HMW HDPE film at nip points 13 and 14 is from about 95 °C to about 105°C.
  • the nip rolls roll diameters are desirably between 4 and 12 inches and are located in as close proximation as is practical to minimize the distance, or gap, between nip points 13 and 14.
  • the gap between rolls 15 and 17 is desirably between 0.020 and 0.100 inches, most desirably between 0.035 and 0.060 inches.
  • the orientation gap is equal to the length of the tangent line between the contact points on the nip rolls 15 and 17. It is most desirable to minimize the length of this tangent line, which is most practically accomplished by minimizing the diameters of nip rolls 15 and 17.
  • the minimum practical limit for the diameter of these rolls is about 4 inches, which will deflect or bow under the pressure of the orientation in the gap, without supporting backup rolls, between nip roll 15 and substantially faster moving roll 17.
  • the HMW HDPE film entering nip point 13 is maintained at linear speed ⁇ : .
  • linear speed ⁇ x ranges from about 1 meter/min to about 40 meters/min.
  • the rotational speed of nip rolls 15 and 16 is thus held constant at ⁇ : .
  • the rotational speeds of nip rolls 17 and 18 forming nip point 14 are held constant at a substantially faster rate, ⁇ 2 , causing the HMW HDPE film 10 to be oriented unidirectionally.
  • the oriented HMW HDPE film 10 exits nip point 14 at linear speed ⁇ 2 , which ranges from about 3 meters/min to about 200 meters/min.
  • the degree of orientation may be expressed as the draw ratio, the ratio of linear speed ⁇ 2 to linear speed ⁇ : .
  • the draw ratio is from about 2 to about 10. More desirably, the draw ratio is from about 3 to about 8, and most desirably the draw ratio is from about 4 to about 5.
  • HDPE film 21 may be annealed by maintaining the film at a temperature desirably from about 180°F to about 240°F (about 80°C to about 115°C).
  • the heated rolls 19 and 20 have a roll diameter between 15 and 25 inches to uniformly maintain the annealing temperature of both sides of oriented film 21 most desirably between 95°C and 115°C.
  • the annealing step improves thermal stability of the film so as to minimize shrinkage during storage and use.
  • Oriented HMW HDPE film 21 is then cooled to ambient temperature and wound onto a paper core or mandrel.
  • the oriented HMW HDPE film may be cooled by any method known in the art.
  • the oriented HMW HDPE film is cooled by passing the film over a cooling roll (not shown).
  • a cooling roll (not shown).
  • One advantage of the oriented HMW HDPE films of the present invention is that a very thin oriented HMW HDPE film having desirable properties for packaging applications may be produced by the above-described process.
  • a single layer of oriented HMW HDPE film of the present invention has a film thickness of less than about 6.0 mil. More desirably, a single layer of oriented HMW HDPE film of the present invention has a film thickness of from about 0.2 mil to about 6.0 mil. Even more desirably, a single layer of oriented HMW HDPE film of the present invention has a film thickness of from about 0.4 mil to about 3.0 mil. In one embodiment of the present invention, a single layer of oriented HMW HDPE film has a film thickness of from about 1.0 mil to about 3.0 mil.
  • the oriented HMW HDPE films of the present invention have unique, desirable properties as a result of the machine direction orientation (MDO) process described above.
  • the oriented HMW HDPE films possess a surprisingly superior moisture vapor transmission rate (MVTR), high modulus, puncture resistance, and tear strength in the machine and cross directions, without undesirable shrinkage.
  • Table 2 illustrates some of the properties of a typical oriented HMW HDPE film of the present invention (Column 2) in comparison to a blown HMW HDPE film without machine direction orientation (Column 1) and a conventional blown, medium molecular weight HDPE film with machine direction orientation (Column 3). Table 2
  • the oriented HMW HDPE films of the present invention have a superior moisture vapor transmission rate (MVTR) as measured by ASTM F1249 and having units of grams of water vapor per 100 square inches per 24 hour period per mil of film thickness (expressed as g/lOOSI/day/mil).
  • MVTR superior moisture vapor transmission rate
  • ASTM F1249 ASTM F1249 and having units of grams of water vapor per 100 square inches per 24 hour period per mil of film thickness
  • the oriented HMW HDPE films of the present invention have an MVTR of less than about 0.24 g/lOOSI/day/mil. More desirably, the oriented HMW HDPE films of the present invention have an MVTR of less than about 0.12 g/lOOSI/day/mil.
  • the HMW HDPE films of the present invention have an MVTR of less than about 0.04 g/lOOSI/day/mil. In one embodiment of the present invention, the HMW HDPE films have a MVTR of from about 0.06 to about 0.10 g/lOOSI/day/mil.
  • the oriented HMW HDPE films of the present invention possess an Elmendorf tear strength by ASTM D-689 in both the machine and cross directions such that the film is suitable for use as a packaging material.
  • the oriented HMW HDPE films of the present invention have a notched tear strength in the machine direction of at least about 30 g. More desirably, the oriented HMW HDPE films of the present invention have a tear strength in the machine direction of at least about 40 g. Even more desirably, the oriented HMW HDPE films of the present invention have a tear strength in both the machine and cross directions of at least about 50 g.
  • HDPE films have a tear strength in the machine direction of from about 30 g to about 100 g.
  • the oriented HMW HDPE films have a tear strength in the machine direction of from about 30 g to about 50 g.
  • the oriented HMW HDPE films of the present invention also possess a superior Scott Puncture value as measured by ASTM F-1306 in units of kilograms per mil of film thickness (kg/ mil).
  • the oriented HMW HDPE films of the present invention have a Scott Puncture value of greater than about 1.0 kg/mil. More desirably, the oriented HMW HDPE films of the present invention have a Scott Puncture value of greater than about 2.0 kg/mil. Even more desirably, the oriented HMW HDPE films of the present invention have a Scott Puncture value of greater than about 2.5 kg/mil. In one embodiment of the present invention, the oriented HMW HDPE films of the present invention have a Scott Puncture value of from about 2.0 kg/mil to about 2.6 kg/mil. A further desirable property of the oriented
  • HMW HDPE films of the present invention is low shrinkage at ambient or high temperature use conditions.
  • Conventional machine direction oriented MMW HDPE films have a relatively high "snapback" property, which refers to the gradual or immediate percent shrinkage in the machine direction at ambient or high temperature exposure, once a stretching force in the machine direction is removed from the oriented film.
  • Conventional oriented MMW HDPE films typically have a "snapback" value of from about 5% to about
  • the oriented HMW HDPE films of the present invention possess a snapback value of less than about 3.0%. Desirably, the oriented HMW HDPE films of the present invention possess a snapback value of less than about 1.0%. Further, conventional oriented MMW
  • HDPE films typically have a "snapback" value of between 30% and 40% at temperatures above 115°C (240°F).
  • the oriented HMW HDPE films of the present invention desirably possess a snapback value of less than about 5% at temperatures above 115°C (240°F).
  • the oriented HMW HDPE films of the present invention possess a tensile strength in both the machine and cross directions as measured by ASTM D-828 in units of pounds per square inch (psi). Desirably a one inch wide strip at 1.5 mil thickness of oriented HMW HDPE film of the present invention has a tensile strength in both the machine and cross directions of at least about 6000 psi. More desirably, the oriented HMW HDPE films of the present invention have a tensile strength in the machine direction of at least about 30,000 psi. Even more desirably, the oriented
  • HMW HDPE films of the present invention have a tensile strength in the machine direction of at least about 37,000 psi. In one embodiment of the present invention, the oriented HMW HDPE films have a tensile strength in the machine direction of 37,000 psi.
  • the oriented HMW HDPE films of the present invention also possess a high modulus value in both the machine and cross directions as measured by ASTM D-828 in units of pounds per square inch (kpsi).
  • the oriented HMW HDPE films of the present invention have a modulus value in both the machine and cross directions of at least about 160 kpsi. More desirably, the oriented HMW HDPE films of the present invention have a modulus value in both the machine and cross directions of at least about 200 kpsi. Even more desirably, the oriented HMW HDPE films of the present invention have a modulus value in both the machine and cross directions of at least about 300 kg.
  • the oriented HMW HDPE films have a modulus value in the machine direction of from about 200 kpsi to about 300 kpsi. In a further embodiment of the present invention, the oriented HMW HDPE films have a modulus value in the cross direction of from about 200 kpsi to about 300 kpsi.
  • the present invention is further directed to articles of manufacture made from the above-described oriented HMW HDPE films. In one embodiment, bags for packaging dry foods, such as cereal, are produced from the oriented HMW HDPE films. In packaging applications, the oriented HMW HDPE film may be used alone or in combination with one or more additional layers to form a converted packaging material.
  • a heat seal layer is coextruded with a layer of HMW HDPE making a film for orientation.
  • the heat seal layer comprises polymers and their blends including, but not limited to, ethylene-vinyl acetate copolymers (EVAs), ethylene-methacrylic acid salt ionomers, metallocene catalyzed LLDPE, LDPE, and other LLDPE copolymers.
  • EVAs ethylene-vinyl acetate copolymers
  • the heat seal layer desirably comprises from about 5 to 25 percent of the thickness of the resulting film.
  • the thickness of the resulting film is from about 0.8 mils to about 4 mils.
  • the coextrusion may be carried out using either of the blown methods or the cast method described above.
  • the oriented HMW HDPE films of the present invention may be advantageously employed in the preparation of a wide variety of products, including but not limited to, bags, converted composites, etc. Such products may only comprise a single layer of the HMW HDPE film or may comprise a combination of elements as described above.
  • the oriented HMW HDPE films of the present invention are particularly suited for packaging applications, the oriented HMW HDPE films may be advantageously employed in a wide variety of consumer products.
  • a blown film was prepared by coextruding 85 vol% HMW HDPE (Equistar L4903) having a molecular weight of 2 million, with a 15 vol% heat seal layer comprising EVA copolymer (Dupont 3172).
  • the HMW HDPE had a density of 0.950, a melt index of 0.03 and was extruded at 420°F (216°C).
  • the diameter of the die annulus was 20 cm and the die gap was 60 mils (1.5 mm).
  • the length of the neck was 160 cm.
  • the blow up ratio was 3.5.
  • the film was cooled, slit, and taken up as finished rolls on cores, as typically prepared for packaging applications.
  • the film had a thickness of 1.5 mil (37 microns) and had the following properties:
  • EXAMPLE 1 Comparative Example 1 was repeated except that the thickness of the coextruded feed film as blown was 6.75 mil.
  • the coextruded film was subsequently monoaxially oriented in the machine direction to 1.5 mil thickness. More specifically, the blown film in tubular form with sealant side out was passed over heated rolls to increase its temperature to 105°C, and drawn between two pairs of nip rolls heated at 100°C at a speed ratio of 4.5:1.
  • the orienter in-feed linear speed was 20 meters per minute while the orienter output linear speed was 90 meters per minute.
  • the drawn film was annealed by passing the film over a heated roll at 110°C.
  • the film was then cooled to ambient temperature by passing over a chilled roll having a surface temperature of 20°C.
  • the oriented film had a thickness of 1.5 mils (37 microns) and had the following properties: MVTR 0.12 g/100 sq. in./24 hours
  • Example 1 was repeated except MMW HDPE (Equistar 6180) having a molecular weight of 750,000, a density of 0.958, and melt index of 1.15 was used in place of the HMW HDPE.
  • the thickness of the coextruded blown feed film was 4.5 mil and was subsequently machine direction oriented at a speed ratio of 3 to 1. Increasing the speed ratio any further caused the oriented film to split and break in the orienter.
  • the oriented film had the following properties:
  • EXAMPLE 2 A cast film was prepared by extruding 85 vol% HMW HDPE (Equistar L4903) with a 15 vol% heat seal layer of EVA copolymer (Dupont 3172). The cast film was extruded at 450°F (232°C) through a die of 30 inches width, and of 120 mil (3mm) die gap. The thickness of the cast film as cooled, and trimmed into finished rolls on cores, was 12 mils. This coextruded film was subsequently monoaxially oriented in the machine direction to a thickness of 2.7 mil at 105°C and using a speed ratio of 4.5 to 1. The oriented film had the following properties:

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Abstract

Films en polyéthylène à haute densité, à poids moléculaire élevé (HMW HDPE) et orientés, présentant des propriétés améliorées de transmission de la vapeur d'eau ainsi que des propriétés supérieures de ténacité, et articles produits à partir desdits films. La présente invention concerne également un procédé de fabrication de films HMW HDPE orientés dans le sens machine présentant des propriétés améliorées de transmission de la vapeur d'eau et des propriétés supérieures de ténacité, et d'articles produits à partir desdits films. La présente invention concerne en outre des articles, en particulier des sacs, constitués de films HMW HDPE orientés dans le sens machine présentant des propriétés améliorées de transmission de la vapeur d'eau et des propriétés supérieures de ténacité.
PCT/US1999/012302 1999-06-03 1999-06-03 Films en polyethylene a haute densite, a poids moleculaire eleve et orientes dans le sens machine, presentant des proprietes ameliorees de transmission de la vapeur d'eau WO2000074929A1 (fr)

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PCT/US1999/012302 WO2000074929A1 (fr) 1999-06-03 1999-06-03 Films en polyethylene a haute densite, a poids moleculaire eleve et orientes dans le sens machine, presentant des proprietes ameliorees de transmission de la vapeur d'eau
AU48183/99A AU4818399A (en) 1999-06-03 1999-06-03 Machine direction oriented high molecular weight, high density polyethylene films with enhanced water vapor transmission properties

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PCT/US1999/012302 WO2000074929A1 (fr) 1999-06-03 1999-06-03 Films en polyethylene a haute densite, a poids moleculaire eleve et orientes dans le sens machine, presentant des proprietes ameliorees de transmission de la vapeur d'eau

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009112256A1 (fr) 2008-03-14 2009-09-17 Tetra Laval Holdings & Finance S.A. Film de substrat polymère à orientation monoaxiale
WO2009151963A1 (fr) 2008-05-28 2009-12-17 Alcan Packaging Flexible France Revêtement interne avec eva réticulé
CN109291570A (zh) * 2018-10-18 2019-02-01 浙江金石包装有限公司 一种用于后发酵酸奶的聚苯乙烯塑杯封口膜及其制备方法

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Publication number Priority date Publication date Assignee Title
GB1270954A (en) * 1968-04-18 1972-04-19 Grace W R & Co Process for the production of oriented polyolefin films
US4590020A (en) * 1983-03-23 1986-05-20 Toa Nenryo Kogyo Kabushiki Kaisha Method of producing oriented polyethylene film
US4870122A (en) * 1987-09-28 1989-09-26 Mobil Oil Corporation HdPE films with imbalanced biaxial orientation
WO1996019527A2 (fr) * 1994-12-22 1996-06-27 Exxon Chemical Patents Inc. Articles en polyethylene a resistance amelioree a la transmission de la vapeur d'eau

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1270954A (en) * 1968-04-18 1972-04-19 Grace W R & Co Process for the production of oriented polyolefin films
US4590020A (en) * 1983-03-23 1986-05-20 Toa Nenryo Kogyo Kabushiki Kaisha Method of producing oriented polyethylene film
US4870122A (en) * 1987-09-28 1989-09-26 Mobil Oil Corporation HdPE films with imbalanced biaxial orientation
WO1996019527A2 (fr) * 1994-12-22 1996-06-27 Exxon Chemical Patents Inc. Articles en polyethylene a resistance amelioree a la transmission de la vapeur d'eau

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009112256A1 (fr) 2008-03-14 2009-09-17 Tetra Laval Holdings & Finance S.A. Film de substrat polymère à orientation monoaxiale
WO2009151963A1 (fr) 2008-05-28 2009-12-17 Alcan Packaging Flexible France Revêtement interne avec eva réticulé
CN102083624A (zh) * 2008-05-28 2011-06-01 比密斯公司 由乙烯乙酸乙烯共聚物制成的气密层
CN109291570A (zh) * 2018-10-18 2019-02-01 浙江金石包装有限公司 一种用于后发酵酸奶的聚苯乙烯塑杯封口膜及其制备方法

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