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WO1995023697A1 - Films thermosensibles - Google Patents

Films thermosensibles Download PDF

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Publication number
WO1995023697A1
WO1995023697A1 PCT/US1995/002578 US9502578W WO9523697A1 WO 1995023697 A1 WO1995023697 A1 WO 1995023697A1 US 9502578 W US9502578 W US 9502578W WO 9523697 A1 WO9523697 A1 WO 9523697A1
Authority
WO
WIPO (PCT)
Prior art keywords
film
layer
ethylene
olefin
polymer
Prior art date
Application number
PCT/US1995/002578
Other languages
English (en)
Inventor
David T. Ou-Yang
Original Assignee
Minnesota Mining And Manufacturing Company
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 Minnesota Mining And Manufacturing Company filed Critical Minnesota Mining And Manufacturing Company
Publication of WO1995023697A1 publication Critical patent/WO1995023697A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D51/00—Closures not otherwise provided for
    • B65D51/18—Arrangements of closures with protective outer cap-like covers or of two or more co-operating closures
    • B65D51/20—Caps, lids, or covers co-operating with an inner closure arranged to be opened by piercing, cutting, or tearing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/308—Heat stability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/71—Resistive to light or to UV
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/748—Releasability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2251/00—Details relating to container closures
    • B65D2251/0003—Two or more closures
    • B65D2251/0006—Upper closure
    • B65D2251/0015—Upper closure of the 41-type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2251/00—Details relating to container closures
    • B65D2251/0003—Two or more closures
    • B65D2251/0068—Lower closure
    • B65D2251/0093—Membrane

Definitions

  • the present invention relates to film materials for use in the packaging industry as sealing films, particularly as lidding films. More particularly, the film materials of the present invention are heat sealable multilayer composites containing a layer of an unsaturated polymeric film, such as polyester, and a layer of an ethylene- ⁇ - olefin polymer.
  • heat sealable packaging films should be generally heat-resistant, tough, as well as resistant to penetration by moisture and atmospheric gases. They should also provide strong seals over a wide temperature 5 range, preferably at a relatively low heat seal initiation temperature to reduce energy costs, and almost immediately after the application of heat. In certain applications, such as with lidding films, it is also desirable to remove the film from the container cleanly, i.e., leaving little or no residue.
  • lidding films for polypropylene containers generally include a layer of heat sealable material, e.g., 5 ethylene vinyl acetate copolymer or polypropylene, bonded to a layer of polyethylene terephthalate, i.e., polyester, or nylon.
  • a layer of heat sealable material e.g., 5 ethylene vinyl acetate copolymer or polypropylene
  • an adhesive tie layer bonds the two layers together.
  • ultraviolet radiation is used to bond the two layers together.
  • lidding films have limitations. They either adhere o poorly to polypropylene, particularly at high relative humidity and low temperatures, or do not peel cleanly from polypropylene after heat sealing. In some instances the bond between the two layers is so poor that delamination occurs. Furthermore, the ethylene vinyl acetate copolymer layer will block on the polyester layer when the film is stored in a roll unless a paniculate material, such as starch or talc, or a matte finish, is used. Moreover, the utility of certain of these composite film structures is limited. This is because migrating solvents present in adhesive tie layers are undesirable for use in food packaging. Also, ethylene vinyl acetate copolymers can be used for direct food contact only under conditions of low temperature.
  • ethylene- ⁇ -olefin polymers in the heat sealable layers. They are primarily used in packaging applications that require sealing of a film to itself. Many of these materials have relatively broad composition distributions and varying properties that are difficult to control, thereby limiting their use. Furthermore, many of them do not adhere well to dissimilar substrates, such as polypropylene, or are not useful lidding films because they leave a residue upon removal. New ethylene- ⁇ -olefin polymers having a narrow composition distribution, however, have been developed. Examples of these are described in U.S. Patent No. 5,206,075 (Hodgson, Jr. et al., April 27, 1993) and International Publication No.
  • WO 93/03093 (Meka et al., February 18, 1993). Although these materials display significant improvements over previous ethylene- ⁇ -olefin polymers, they are not universally useful for all packaging applications, particularly those that require sealing of a film to a dissimilar substrate. Thus, there is a need for heat sealable film materials that bond strongly to typical packaging containers, particularly polypropylene containers, over a broad temperature range. Furthermore, there is a need for heat sealable film materials that are capable of being removed from the container leaving little or no residue.
  • the present invention provides a multiple-layer composite film containing a base layer of a polymeric material that is capable of absorbing ultraviolet radiation and a layer of heat sealable material.
  • the polymeric material in the base layer includes one or more polar functional groups.
  • One particularly preferred such material contains -C(O)-C ⁇ H 4 - moieties.
  • the heat sealable material includes an ethylene- ⁇ -olefin polymer containing a total ⁇ -olefin content of about 10-30%, preferably about 10-20%. As used herein, all percentages are weight percentages unless otherwise specified.
  • the ethylene- ⁇ -olefin polymer preferably has a density of less than about 0.910 g/cm and a polydispersity of less than about 3.5.
  • the density is less than about 0.900 g/cm and the polydispersity is less than about 3.0.
  • These ethylene- ⁇ -olefin polymers are preferably single site polymers, as defined below.
  • the polymeric base layer is directly adhered to the heat sealable layer.
  • preferred films of the present invention are free of a tie layer between the polymeric base layer and the heat sealable layer.
  • the films of the present invention are also advantageous in that they are both capable of adhering to a substrate comprising a propylene polymer and being cleanly peelable from the substrate.
  • Certain preferred embodiments of the present invention include a layer of heat sealable material comprising an ethylene- ⁇ -olefin polymer and about 10-40% elastomeric polymer.
  • the elastomeric polymer is polyisobutylene.
  • the present invention is also directed to containers comprising a body having an opening therein and a covering over the opening, the covering comprising a multiple-layer composite film as described above. Brief Description of the Drawings
  • Figure 1 is a cross-sectional view of a multiple layer composite film of the present invention.
  • Figure 2 is a cross-sectional view of a tray having a lidding film formed from a multiple layer composite film of the present invention.
  • Figure 3 is a side view of a bottle having a lidding film formed from a multiple layer composite film of the present invention.
  • Figure 4 is a schematic of a system used to perform the Burst Test described in the Examples. 0
  • the present invention provides multiple-layer, i.e., multilayer, composite packaging films made of a base layer of a polymeric material capable of absorbing ultraviolet radiation and a layer of heat sealable material that includes an ethylene- ⁇ - 5 olefin polymer.
  • the polymeric material used in the base layer includes one or more polar functional groups and is capable of interacting with the ethylene- ⁇ -olefin polymer under ultraviolet radiation such that a bonding interaction is formed between the two layers.
  • the strength of this bonding interaction is preferably at least about 80 ounces/inch (893 g/cm) as determined by a 180° peel test.
  • the films of the present o invention eliminate the need for a tie layer or interdispersed anchor to bond the heat sealable layer to the base layer.
  • tie layer could be used if desired.
  • Useful tie layers include ethylene vinyl acetate or polyethylene, for example.
  • 5 corona treating can be used, for example, to clean the surface of the base layer.
  • the multilayer composite films of this invention are capable of forming a strong bond with a polypropylene substrate. Furthermore, they are capable of being substantially cleanly separated from the polypropylene substrate such that little or no residue remains after removal of the film. Accordingly, the multilayer composite films of o this invention can be used as lidding films or sealing films for containers made of polymers including a significant percentage, i.e., a majority, of propylene monomeric units. As used herein, these polymers are referred to as propylene polymers or simply polypropylene, although they may contain monomeric units other than propylene, such as ethylene, for example.
  • the films of the present invention are particularly useful in packaging 5 materials that undergo processing conditions at elevated temperatures (e.g., up to about 100°C) and/or elevated pressures (e.g., greater than 1 atmosphere).
  • a material includes packages for foods (e.g., frozen vegetables, etc.) and medical instruments.
  • the films of the present invention have a heat seal window, i.e., temperature range in which the films can be heat sealed to a substrate, of greater than o about 30°F (16°C), and preferably greater than about 50°F (28°C).
  • Certain preferred embodiments have a heat seal window of greater than about 80°F (44°C), and even greater than about 100°F (56°C).
  • the films of the present invention are not tacky at room temperature and peel substantially cleanly from a variety of polypropylene substrates, even after the sealed substrate is stored at a high relative 5 humidity, i.e., greater than about 95%, and low temperature, i.e., less than about 32°F (0°C), for about one week.
  • This film includes a base layer 12 of polymeric material, and a layer 14 of a heat sealable material adhered to layer 12.
  • the material for layer 12 can include any o polymer that is capable of absorbing ultraviolet radiation and contains one or more polar functional groups. Such materials should be able to form a strong bond, i.e., at least about 80 ounces/inch (893 g/cm) peel adhesion (180° peel test), with the heat sealable layer.
  • this material contains conjugated carbon-caibon double bonds.
  • the conjugated carbon-carbon double bond system can be in a ring or in a straight chain.
  • useful materials for the base layer that have these characteristics also must withstand the temperatures involved in heat sealing the films to polypropylene substrates, e.g., food packaging containers. That is, the most preferred polymeric materials for the base layer do not melt or deteriorate significantly at temperatures up to about 350°F (177°C).
  • a particularly preferred class of polymers that possesses these characteristics includes moieties that contain a conjugated carbon-carbon double bond system having a carbonyl group in the backbone chain. One example of this is a phenyl- carbonyl moiety, i.e., -C(O)-C 6 H 4 -.
  • Such moieties allow the polymer to readily absorb ultraviolet radiation and form a strong bond to the layer of polymeric material that are in contact with layer 12, i.e., the heat sealable layer 14.
  • the polymer for the base layer is 5 preferably chosen such that its melting or softening point is at least about 50°F higher than that of the heat sealable layer.
  • a representative example of a polymer suitable for use in base layer 12 is polyethylene terephthalate, i.e., often referred to as simply "polyester,” preferably biaxially oriented polyethylene terephthalate.
  • polyesters such as poly(l,4- o cyclohexylenedimethylene terephthalate) and poly(ethylene naphthalate) can also be used as a material for base layer 12.
  • Aromatic polyamides are also suitable for use in base layer 12, whether partly aromatic, i.e., aliphatic-aromatic, or wholly aromatic. Examples of such materials include metaxylenediamine/adipic acid.
  • base layer 12 Commercially available polymers suitable for base layer 12 include the polyesters "Melinex 850" 5 commercially available from ICI Americas, Inc., Wilmington, DE, "Mylar 48LB” commercially available from E.I. DuPont de Nemours and Co., Wilmington, DE, and "MXD-6 Nylon” commercially available from Toyobo Corp., Osaka, Japan. Particularly preferred polymers for use in the base layer are high melting temperature polyesters, i.e., those having a melting point of at least about 230°C. o Base layer 12 can also include additives of a type and in an amount that does not substantially detrimentally impact its strength.
  • slip or antiblock agents such as silica or fatty acids (preferably in an amount no greater than about 1%); antifogging agents such as silicates (preferably in an amount no greater than about 1%); antioxidants or uv-stabilizers such as butylated hydroxy toluene 5 (preferably in an amount no greater than about 1%); pigments such as titanium dioxide, zinc oxide, iron oxide, or carbon black (preferably in an amount no greater than about 5%); and fillers such as calcium carbonate (preferably in an amount no greater than about 30%).
  • the total amount of additives in base layer 12 generally should not exceed about.40% of the total weight of the composition, i.e., unsaturated polymer and 0 additives.
  • Base layer 12 can be of any suitable thickness.
  • the material for layer 14 is a heat sealable material containing an ethylene- ⁇ -olefin polymer.
  • the ethylene- ⁇ -olefin polymer is chosen such that the films of the present invention are heat sealable to polypropylene substrates at a temperature of about 200-350°F (93-177°C), preferably at as low a temperature as possible, e.g., 200- 230°F (93-110°C).
  • the ethylene- ⁇ -olefin polymer is chosen such that o layer 14 does not delaminate from layer 12, and that layer 14 readily forms a peelable bond to polypropylene substrates.
  • the ethylene- ⁇ -olefin polymer is chosen such that the peel force, i.e., the amount of force required to peel a film of the present invention from a polypropylene substrate to which it is sealed, is less than the internal cohesive strength of the ethylene- ⁇ -olefin polymer itself and less than the adhesive 5 strength between the ethylene- ⁇ -olefin polymer and the base layer. In this way, the film can be peeled from the polypropylene substrate leaving little or no residue.
  • the ethylene- ⁇ -olefin polymer is chosen such that the peel strength of a film having a 1 mil (2.54 x 10 " cm) thick ethylene- ⁇ -olefin layer is at least about 30 ounces inch (335 g/cm) (as measured by the 180° peel strength test described o below) after the film is sealed to a polypropylene substrate containing about 5% ethylene at a temperature of about 270°F (132°C) and pressure of about 40 psi (2815 g cm 2 ) for a dwell time of about 1.5 seconds), and the burst strength is at least about 25 inches H 2 O (as measured by the burst test described below) after the film is sealed to a polypropylene substrate containing about 5% ethylene at a temperature of about 230°F 5 (110°C) and pressure of about 40 psi (2815 g/cm ) for a dwell time of about 2 seconds).
  • the peel strength of a film is greater
  • the total ⁇ -olefin content of 0 the ethylene- ⁇ -olefin polymer is about 10-30%.
  • the total ⁇ -olefin content of the polymer is within a range of about 10-20%, based on the total weight of the polymer. More preferably, the ⁇ -olefin content is about 10-19% for applications requiring food grade materials, although most preferably this is about 10-15%.
  • the ethylene- ⁇ -olefin polymers are prepared from olefins having at least 4 5 carbon atoms, more preferably 4-20 carbon atoms, and most preferably 4-12 carbon atoms.
  • ⁇ -olefins are 1-butene, 1-octene, and 1-hexene. Of these, 1-butene is the most preferred.
  • the ethylene- ⁇ -olefin polymers can include more than one or more types of ⁇ -olefin comonomers. For example, they can be copolymers, i.e., combinations of ethylene and one type of ⁇ -olefin monomer, or terpolymers, i.e., o combinations of ethylene and two types of ⁇ -olefin monomers.
  • the material used in the heat sealable layer can also include mixtures of different ethylene- ⁇ -olefin polymers.
  • Useful ethylene- ⁇ -olefin polymers are characterized as having a low degree of crystallinity and a low degree of elasticity such that the polymers readily flow in the molten state.
  • the density is less than about 0.910 g/cm , more
  • Useful ethylene- ⁇ -olefin polymers are also characterized as having a relatively narrow molecular weight distribution and/or a relatively small number of carbons in the short side-chain branches of the otherwise linear ethylene polymer.
  • useful ethylene- ⁇ -olefin polymers have a polydispersity, i.e., a molecular weight distribution Mw Mn), of less than about 3.5, more preferably less than about 3.0, and greater than about 1.5.
  • the ethylene- ⁇ -olefin polymers used in the heat sealable layers of the packaging films of the present invention have a polydispersity within a range of about 2.0-3.0.
  • composition distribution of useful ethylene- ⁇ -olefin polymers is preferably less than about 40 total carbons in the short chain branches (which result from the addition of the ⁇ -olefin monomers) per 1000 carbons in the polymer, and more preferably within a range of about 5-35 per 1000.
  • the composition distribution of useful ethylene- ⁇ -olefin polymers can be reported as the composition o distribution breadth index (CDBI).
  • CDBI composition o distribution breadth index
  • the CDBI is at least about 50%, and more preferably at least about 70%.
  • the CDBI is the weight percent of the polymer molecules having a comonomer content within 50% of the median molar comonomer content. Either way of reporting, the composition distribution can be determined by Temperature Rising Elution Fractionation as described by Wild et al., J. Poly. Sri.. Poly. 5 Phvs. Ed.. 20, 441 (1982).
  • the ethylene- ⁇ -olefin polymers should also have an essentially single melting point characteristic with a peak melting point (T m ) of no greater than about 100°C, as determined by Differential Scanning Calorimetiy (DSC).
  • T m peak melting point
  • DSC Differential Scanning Calorimetiy
  • T m peak melting point
  • Essentially single melting point as used herein o means that at least about 80% by weight of the material corresponds to a single T m peak.
  • the melt index of useful ethylene- ⁇ -olefin polymers for the films of the present invention is greater than about 1.0 gram/10 minutes, preferably about 1-100 grams/10 minutes, as determined by ASTM Test Method D1238-90B, Method A, 1990.
  • Ethylene- ⁇ -olefin polymers that meet all the requirements of the 5 polymers used in the heat sealable layers of the films of the present invention include those prepared using single-site catalysts, i.e., catalysts that permit olefins such as ethylene and ⁇ -olefin to react only at single sites on the catalyst molecules.
  • Suitable such ethylene- ⁇ -olefin polymers are described in U.S. Patent No. 5,206,075 (Hodgson, Jr. et al., April 27, 1993) and International Publication No. WO 93/03093 (Meka et al., o February 18, 1993). They are commercially available from Exxon Chemical Company,
  • single site polymers are distinguished from ethylene- ⁇ -olefin 5 polymers made using Ziegler Natta catalysts, which have multiple active sites, in that the single site polymers typically have narrower molecular weight distributions and more desirable ⁇ -olefin short-chain branching distributions.
  • the single site polymers typically have narrower molecular weight distributions and more desirable ⁇ -olefin short-chain branching distributions.
  • not all single site ethylene- ⁇ -olefin polymers are suitable for use in the films of the present invention. For example, those having an ⁇ -olefin content of 9.0% or less do not adhere well to polypropylene substrates. Also, those having an ⁇ -olefin content of greater than about 30% are generally too tacky.
  • the heat sealable material of layer 14 contains a blend of an ethylene- ⁇ -olefin
  • the term "compatible" means that the elastomeric polymer does not bloom from the composition.
  • the compatible elastomeric polymer has a glass transition temperature (Tg) of less than about 0°C, and a molecular weight (Staudinger) of greater than about 10,000, more preferably about 11,000- o 99,000.
  • Tg glass transition temperature
  • Staudinger molecular weight
  • the elastomeric polymer is food grade, i.e., contains no toxic extracts.
  • Suitable such elastomeric polymers include polyisobutylene and ethylene propylene rubber.
  • the preferred elastomeric polymer is polyisobutylene.
  • the addition of the elastomeric polymer increases the heat seal window of the films to greater than about 80°F (44°C), preferably greater than about 100°F 5 (56°C), thereby allowing the films to withstand inexact heat sealing processes.
  • this blend includes at least about 10%, more preferably about 10% to about 40%, and most preferably about 10% to about 30% elastomeric polymer, e.g., polyisobutylene, based on total weight of the blend. If the compatible elastomeric polymer content of the blend is less than about 10% by weight, there is no significant 0 increase in the heat seal operation temperature window. If it is greater than about 40% by weight, the composition, i.e., blend, is too tacky, does not flow well, and causes blocking problems.
  • elastomeric polymer e.g., polyisobutylene
  • the ethylene- ⁇ -olefin/elastomeric polymer blend can be prepared by blending the rubber using a twin screw extruder designed for rubber, such as is available 5 from the Bonnot Co., Creen, OH, with the ethylene- ⁇ -olefin polymer using a standard twin screw extruder.
  • the molten polymeric blend is then extruded as a rod form into a water bath.
  • the solid blend can then be pelletized using a standard chopper.
  • Layer 14 can also contain small amounts of other materials, such as the additives described above for the base layer 12 (except for the uv-stabilizers), so long as o these materials do not adversely affect the function of the polymers.
  • the total amount of additives in layer 14 generally should not exceed about 40% of the total weight of the composition; however, for food grade films, the total amount of additives in layer 14 should not exceed about 5%.
  • the thickness of layer 14 is not necessarily critical, but it preferably ranges from about 0.3 mil (0.0008 cm) to about 10.0 mils (0.0254 cm), more preferably 5 from about 0.7 mil (0.0018 cm) to about 3.0 mils (0.008 cm). The choice of thickness is determined by intended use of the film.
  • Layer 14 can be bonded to layer 12 by a number of techniques.
  • the material of layer 14 is applied to layer 12 by means of extrusion to form a composite structure.
  • the material of layer 12 is provided as a film of polymeric o material.
  • the material of layer 14 is coated onto the supporting polymer film in a molten state by a conventional extrusion process.
  • the temperature of the material of layer 14, when in the extruder typically ranges from about 280°F (138°C) to about 560°F (293 °C).
  • a typical process temperature profile for a three-zone extruder is 410°F (210°C) (Zone 1), 470°F (243°C) (Zone 2), 510°F (266°C) (Zone 3), 510°F 5 (266°C) (die).
  • the temperature of the material of layer 14, as it exits the extruder typically ranges from about 350°F (177°C) to about 560°F (293°C).
  • the thus-formed composite structure can be allowed to cool to ambient temperature, which is generally below about 180°F (82°C). However, such cooling is not necessarily required.
  • the composite structure is 0 then heated, if necessary, to a temperature of at least about 180° (82°C), preferably about 240°F (116°C) to about 310°F (154°C).
  • the additional heating step is not necessary if the temperature of the composite structure is at the desired level for the irradiating step of the bonding process (e.g., 240°F (116°C) to 310°F (154°C)).
  • the heated composite structure is then subjected to ultraviolet radiation, whereby layer 14 is 5 securely bonded to layer 12.
  • the length of time that the composite structure must be irradiated is dependent upon the source of radiation utilized and the distance that the composite structure is from the source of radiation.
  • the irradiation is carried out at an intensity and for a time effective to cause a bonding interaction between the ethylene- ⁇ -olefin and base layer of a strength of at least about 80 ounces/inch (893 o g cm).
  • One particularly useful set of irradiation conditions comprises irradiating the composite structure for a period of about 5 to 10 seconds at a distance of from about 3 to 5 centimeters from a conventional source of ultraviolet radiation, such as, for example, an apparatus having the trade designation "Fusion UN Curing System".
  • a preferred such UN lamp emits a wavelength range of about 200-500 nm with a peak wavelength of about 254 nm.
  • a typical radiation intensity is at least about 90 5 watts/inch, preferably about 120 watts/inch.
  • the process for irradiation with ultraviolet radiation is described in more detail in U.S. Patent No. 3,188,266 and U.S. Patent No. 3,186,265. The specific conditions of heating and irradiation depend on the thickness of layer 14.
  • the multiple-layer composite film of this invention can be used for o lidding and sealing functions.
  • the film is particularly useful as a lidding or sealing material for containers made of polymers having a high concentration of propylene monomeric units, at least at the point where the lid or seal is attached to the container.
  • Figure 2 illustrates a container 20 in the form of a tray 22 having a wide mouth 24. Surrounding mouth 24 is a lip 26. Lip 26 of tray 22 is preferably formed 5 from a propylene polymer, which can contain small amounts of other monomers such as ethylene. Multiple-layer composite film 10 is bonded to lip 26 of tray 22 by means of layer 14.
  • Figure 3 illustrates a container 30 in the form of a bottle 32 having a mouth 34. Surrounding mouth 34 is a lip 36. Lip 36 of bottle 32 is preferably formed o from a propylene polymer. Multiple-layer composite film 10 is bonded to lip 34 of bottle 32 by means of layer 14. Container 30 can also have a cap 38. Cap 38 can be of conventional construction. It can be made of metal or polymer, but is preferably polymer, such as polyethylene or polypropylene. Cap 38 can be placed over mouth 34 and lip 36 of container 30 and secured to container 30 by tightening. Multiple-layer 5 composite film 10 can be sealed to lip 36 by means of heating, such as, for example, conduction heating.
  • heating such as, for example, conduction heating.
  • Lids and innerseals can be applied to the lip of a container manually by means of a heated platen, but it is economically advantageous to use heated rollers to kiss seal the multiple-layer composite film to the lip of a container.
  • sealing layer 14 to a substrate comprising a propylene polymer include induction heating, i.e., when the multiple-layer composite film is a component of a seal, e.g., an innerseal.
  • the multiple-layer composite film of this invention can be used in several packaging areas.
  • the film can be used as a peelable film. For example, it can be adhered to the lip of a polypropylene container, from which it can be peeled away when desired.
  • the film can also be used as a fusible film. For example, it can be adhered to the lip of a polyethylene container by means of fiision. However, if fused it can be removed only by penetrating the film, e.g., with a cutting tool, and tearing the penetrated film away from the container.
  • the film can also be used as the sealing component of an induction innerseal.
  • Induction innerseals are described in greater detail in U.S. Patent Nos. 4,684,554 and 4,778,698.
  • the innerseal can be peelable or tamper resistant. Peelable innerseals operate in the same manner as the peelable films described previously. Tamper resistant innerseals operate in the same manner as the fusible films described previously. In other words, penetration of the tamper resistant innerseal indicates that the innerseal has been subjected to tampering.
  • the multiple- layer composite film of this invention can be used in either a standard innerseal or a one- piece innerseal.
  • a standard innerseal comprises, from top to bottom, (1) a pulp board backing, (2) a wax coating, (3) a layer of aluminum foil, and (4) a heat sealable polymeric film coating.
  • a one-piece innerseal avoids the use of the pulp board backing and the wax coating.
  • multiple-layer composite films were prepared by extruding a layer of ethylene- ⁇ -olefin polymer, or a blend of ethylene- ⁇ - olefin polymer and a compatible rubber, onto a polyethylene terephthalate film, allowing the thus-formed composite structure to cool, heating the cooled composite structure to a temperature of about 280°F ( 138°C), and then exposing the heated composition to ultraviolet radiation for a duration of about five (5) seconds, unless otherwise indicated.
  • a "Fusion UN Curing Systems" apparatus containing a lamp that emits radiation over a wavelength range of about 200-500 nm with a peak wavelength at about 254 nm, commercially available from Fusion Systems Corporation, was used as the source of ultraviolet radiation. The lamp was located about 2 inches (5.08 cm) from the 5 composite structure. The intensity was about 120 watts/inch.
  • This same test can be used to determine the adhesion between the base layer and the heat sealable layer of the films of the present invention, i.e., self-adhesion, 0 by placing two portions of the film together, heat sealable layers facing each other. The two portions of the film are then placed in the jaws of the Instron apparatus and the maximum force required to separate the bond recorded
  • the burst apparatus 40 consists of a source of air or nitrogen 41 capable of providing the air or nitrogen at least about 40 psi, which is connected to an air inlet 42 and an air probe 43 for insertion into a sealed sample tray. Between the air inlet 42 and the air o probe 43 are a solenoid valve 44, a pressure regulator 45, a flow control valve 46, and a series of pressure gauges 47, 48, and 49. Also attached to the apparatus is a flow meter
  • the procedure is carried out by connecting the burst apparatus to the air supply 41 and adjusting the air supply pressure to 45 psi.
  • the solenoid valve is activated 5 and the pressure regulator 45 adjusted to 40 psi.
  • the solenoid valve is then turned off.
  • Tables 1 and 2 compare the burst strength, adhesion (180° peel strength), and peelability of three conventional films (I-IH and V) and a film of the present invention (TV) after being heat sealed to a polypropylene substrate.
  • the films in 5 Table 1 were sealed to a tray made of polypropylene homopolymer/copolymer blend containing 2% ethylene.
  • the films in Table 2 were sealed to a sheet of polypropylene/ethylene copolymer containing 5% ethylene available as HIMONT SD613 from Himont USA, Wilmington, DE.
  • PET polyethylene terephthalate
  • PP polypropylene
  • EVA ethylene vinyl acetate
  • E-O l o ethylene- ⁇ -olefin polymer.
  • the tie layer is ethylene vinyl acetate.
  • Mylar RL-3 available from DuPont and Film _H is "SP-125” available from Minnesota Mining and Manufacturing Company, St. Paul, MN.
  • Tables 1 and 2 demonstrate that the films of the present invention display good adhesion strength at lower temperatures than conventional heat 15 sealable films and over a wider heat seal operation temperature window.
  • Construction Film(s) (inches of H 2 0) Peelability
  • Table 3 demonstrates the effect of the type and amount of olefin comonomer on density, melt index, and peel strength for films containing 1 mil (2.54 x 10 " cm) thick heat sealable layers. The films were heat sealed at 270°F
  • polymers XDI, XIV, and XV were obtained from Dow Chemical (AFFINITY "single site" polymers).
  • E-O copolymers IX, XIV, and XV were tested for adhesion between the base layer and the E-O copolymer layer.
  • Each copolymer was coated onto a polyethylene terephthalate base film, 1 mil thick, and treated with heat (350°F) under 40 psi (2815 g cm ) pressure for 1.5 seconds.
  • Certain of these samples were treated with ultraviolet radiation (200-500 nm) for about 5 seconds.
  • These samples were then tested for l o adhesion between the two layers using a 180° peel test.
  • the samples that were merely treated with heat showed no adhesion.
  • the samples that were treated with heat and ultraviolet radiation showed significant adhesion between the two layers, e.g., 165-168 ounces/inch (1.8-1.9 kg/cm).
  • PP Homo/Copolymer Blend polypropylene sheet material, Ferro Corporation's DPP30WA8285BK, available from Ferro Corp., Evansville, IN.
  • the rubber was extruded with the Bonnot Co.'s single screw extruder at a temperature of 250°F (121°C) to 450°F (232°C), depending on the viscosity of the rubber.
  • the molten rubber met the partially molten ethylene- ⁇ -olefin at port 3 of the APNs twin screw extruder, which then continuously blended these molten materials at a temperature of about 285°F (141°C).
  • the blended material was extruded into a cool water trough in a rod shape before being cut into pellet form.
  • Table 4 compares the peel strength, peelability, and heat seal window for several prior art constructions (XVI-XVIII) with constructions containing a layer of polyethylene terephthalate and a layer of ethylene- ⁇ -olefin (XEX and XX) or a layer of a blend of ethylene- ⁇ -olefin and polyisobutylene (XXI).
  • XVI-XVIII ethylene- ⁇ -olefin
  • XXI ethylene- ⁇ -olefin
  • LDPE low density polyethylene
  • LLDPE linear low density polyethylene
  • HDPE high density polyethylene
  • PI polyisobutylene.
  • Film XVI was an experimental sample prepared at 3M; film XVII was obtained from Shell Oil, Houston, TX; film XNUI was obtained from Paxon Polymer Company, Baton Rouge, LA Film XIX was prepared from Exxon's EXACT 2009 containing 7.5% 1-hexene. Films XX and XXI were prepared from a blend of 60% of Exxon's EXACT 4042 and 40% of Exxon's EXACT 4011.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Laminated Bodies (AREA)

Abstract

Film composite multicouche (10) comprenant: une couche de matériau polymère (12) susceptible d'absorber les rayons ultraviolets et contenant un ou plusieurs groupes fonctionnels polaires, ainsi qu'une couche d'un matériau thermosensible (14) contenant un polymère d'éthylène-α-oléfine. Le film composite multicouche selon l'invention peut former une forte liaison avec un substrat de polypropylène tout en étant susceptible d'être nettement détaché de celui-ci lorsqu'on le souhaite. En conséquence, on peut utiliser le film composite multicouche en tant que couvercle ou scellement de récipients réalisés dans des polymères comprenant un pourcentage important d'unités monomères de propylène.
PCT/US1995/002578 1994-03-02 1995-03-01 Films thermosensibles WO1995023697A1 (fr)

Applications Claiming Priority (2)

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US20454294A 1994-03-02 1994-03-02
US08/204,542 1994-03-02

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WO1995023697A1 true WO1995023697A1 (fr) 1995-09-08

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998034785A1 (fr) * 1997-02-06 1998-08-13 Cryovac, Inc. Emballage souple tres resistant fait d'un film
WO1998037142A1 (fr) * 1997-02-25 1998-08-27 Exxon Chemical Patents Inc. Scellement de polyethylene a un substrat
WO1999028791A1 (fr) * 1997-12-02 1999-06-10 Minnesota Mining And Manufacturing Company Support d'imagerie multicouche comprenant du polypropylene, procede de formation d'image sur ledit support, et support d'image
US6361844B1 (en) 1999-01-27 2002-03-26 David T. Ou-Yang Release article and adhesive article comprising the release article
US6465091B1 (en) 2000-03-27 2002-10-15 3M Innovative Properties Company Release article and adhesive article containing a polymeric release material
US6579584B1 (en) 1998-12-10 2003-06-17 Cryovac, Inc. High strength flexible film package utilizing thin film
AU2004242463B2 (en) * 1997-02-06 2008-04-03 Cryovac, Inc. High strength flexible film package
US9944418B2 (en) 2007-08-23 2018-04-17 Innovia Films, Ltd. Naked collation package

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3188266A (en) * 1963-09-03 1965-06-08 Minnesota Mining & Mfg Interface bonding of polymers and product thereof
EP0353655A2 (fr) * 1988-07-30 1990-02-07 Idemitsu Petrochemical Co., Ltd. Laminés en résine
EP0407880A2 (fr) * 1989-07-10 1991-01-16 Owens-Illinois Plastic Products Inc. Récipients multicouche et leur procédé de fabrication
US5164267A (en) * 1989-05-24 1992-11-17 Solvay & Cie (Societe Anonyme) Laminated composite

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3188266A (en) * 1963-09-03 1965-06-08 Minnesota Mining & Mfg Interface bonding of polymers and product thereof
EP0353655A2 (fr) * 1988-07-30 1990-02-07 Idemitsu Petrochemical Co., Ltd. Laminés en résine
US5164267A (en) * 1989-05-24 1992-11-17 Solvay & Cie (Societe Anonyme) Laminated composite
EP0407880A2 (fr) * 1989-07-10 1991-01-16 Owens-Illinois Plastic Products Inc. Récipients multicouche et leur procédé de fabrication

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998034785A1 (fr) * 1997-02-06 1998-08-13 Cryovac, Inc. Emballage souple tres resistant fait d'un film
US5846620A (en) * 1997-02-06 1998-12-08 W. R. Grace & Co.-Conn. High strength flexible film package
AU2004242463B2 (en) * 1997-02-06 2008-04-03 Cryovac, Inc. High strength flexible film package
WO1998037142A1 (fr) * 1997-02-25 1998-08-27 Exxon Chemical Patents Inc. Scellement de polyethylene a un substrat
WO1999028791A1 (fr) * 1997-12-02 1999-06-10 Minnesota Mining And Manufacturing Company Support d'imagerie multicouche comprenant du polypropylene, procede de formation d'image sur ledit support, et support d'image
US6579584B1 (en) 1998-12-10 2003-06-17 Cryovac, Inc. High strength flexible film package utilizing thin film
US6361844B1 (en) 1999-01-27 2002-03-26 David T. Ou-Yang Release article and adhesive article comprising the release article
US6465091B1 (en) 2000-03-27 2002-10-15 3M Innovative Properties Company Release article and adhesive article containing a polymeric release material
US9944418B2 (en) 2007-08-23 2018-04-17 Innovia Films, Ltd. Naked collation package
US10173796B2 (en) 2007-08-23 2019-01-08 Innovia Films, Ltd Naked collation package

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