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WO2003040199A1 - Article d'emballage thermoscelle facile a ouvrir contenant des polyolefines homogenes tres ramifiees - Google Patents

Article d'emballage thermoscelle facile a ouvrir contenant des polyolefines homogenes tres ramifiees Download PDF

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Publication number
WO2003040199A1
WO2003040199A1 PCT/US2002/035369 US0235369W WO03040199A1 WO 2003040199 A1 WO2003040199 A1 WO 2003040199A1 US 0235369 W US0235369 W US 0235369W WO 03040199 A1 WO03040199 A1 WO 03040199A1
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heat
seal
polymer
film
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Blaine C. Childress
Ronald D. Moffitt
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Cryovac LLC
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Cryovac LLC
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
    • C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/06—Polyethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/10—Homopolymers or copolymers of propene
    • C08L23/14—Copolymers of propene
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C09J123/02—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
    • C09J123/04—Homopolymers or copolymers of ethene
    • C09J123/08—Copolymers of ethene
    • C09J123/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
    • C09J123/0815—Copolymers of ethene with aliphatic 1-olefins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2314/00—Polymer mixtures characterised by way of preparation
    • C08L2314/08—Polymer mixtures characterised by way of preparation prepared by late transition metal, i.e. Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru or Os, single site catalyst
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
    • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
    • C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
    • C08L2666/06—Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof

Definitions

  • the present invention is directed to heat-sealed articles having easy-open heat seals.
  • the invention is particularly directed to packaging articles, including flexible films as well as rigid packaging structures such as molded articles.
  • the present invention provides an easy-open heat-sealed article in which at least a portion of the heat seal contains a highly branched homogeneous polyolefin.
  • This highly branched homogeneous polymer provides the seal layer with an easy-open character by lowering the seal strength of the heat seal formed using the seal layer. The strength of the heat seal is lowered at least 25 percent below the seal strength which would otherwise occur without the presence of the highly branched homogeneous polymer. It has been discovered that during heat sealing the highly branched homogeneous polymer imparts a lower seal strength because the branches of the polymer do not entangle to an extent other polyolefms exhibit.
  • the individual branches of the highly branched polymer are not long enough to generate a type of entanglement which results in seals having the strength exhibited by other relatively low melting polyolefms such as very low density polyethylene, linear homogeneous ethylene/alpha-olefm copolymer which are not "highly branched”, long chain branched homogeneous ethylene/alpha-olefin copolymer which are not "highly branched”, linear low density polyethylene, high density polyethylene, low density polyethylene, etc.
  • Blends of the highly branched homogeneous polyolefms with other polymers can be used to produce an easy-open seal having a strength higher than can be produced if the seal layer is made of 100 percent highly branched homogeneous polyolefin.
  • the present invention is directed to a heat-sealed easy-open article comprising a film heat sealed to itself or another component of the article.
  • the film comprises a heat seal layer containing a blend of a first polymer and a second polymer.
  • the first polymer is a highly branched homogeneous polyolefin having at least 60 branches per 1000 methylene groups, and for every 100 branches that are methyl, about 4 to 20 ethyl branches, about 1 to 12 propyl branches, about 1-12 butyl branches, about 1 to 10 amyl branches, and about 1 to 20 hexyl or longer branches.
  • the second polymer is present in an amount of at least 5 weight percent based on the weight of the blend, the second polymer having a glass transition temperature or melt temperature which is higher than the first polymer.
  • the heat seal has a strength of from 5 to 75 percent of an ultimate seal strength formed by heat sealing to itself a corresponding film having a heat seal layer containing 100 percent of the second polymer.
  • the heat seal has a strength of from about 10 to 70 percent of the ultimate seal strength, more preferably from 20 to 60 percent.
  • the second polymer comprises at least one member selected from the group consisting of olefin homopolymer, olefin copolymer, olefin/unsaturated ester copolymer, olefin/unsaturated acid copolymer, ionomer, and olefin styrene copolymer.
  • the second polymer comprises at least one member selected from the group consisting of polyethylene, polypropylene, propylene/ethylene copolymer, ethylene/alpha-olefin copolymer, ethylene/vinyl acetate copolymer, ethylene/butyl acrylate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, and ethylene/styrene copolymer. More preferably, the second polymer comprises at least one member selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, very low density polyethylene, ultra low density polyethylene, and homogeneous ethylene/alpha- olefin copolymer.
  • the highly branched polymer is present in an amount of from about 1 to 75 percent, based on total weight of the blend; more preferably from 1 to 50 percent, more preferably from 1 to 40 percent, more preferably from 10 to 40 percent.
  • the heat seal has a strength of from about 0.5 pounds per inch to about 7 pounds per inch; more preferably from 0.5 to 5 pounds per inch; more preferably from 1 to 3 pounds per inch.
  • the highly branched polyolefin has from about 60 to about 200 branches per 1000 methylene groups; more preferably, from about 60 to about 120 branches per 1000 methylene groups; more preferably, from about 70 to about 120 branches per 1000 methylene groups; more preferably, from about 80 to about 100 branches per 1000 methylene groups.
  • the article is an end-seal bag made from a seamless tubing, having an open top and a transverse heat seal across a bottom region of the bag, the heat seal being of the seal layer to itself.
  • the article is a side-seal bag having a folded bottom edge, a first side seal, and a second side seal, the first and second side seals being heat seals of the heat seal layer to itself.
  • the present invention is directed to a heat-sealed article comprising a film and a heat seal of the film to itself or another component of the article, the film comprising a heat seal layer containing a blend of (A) a highly branched polyolefin having at least 60 branches per 1000 methylene groups, and which contains for every 100 branches that are methyl, about 4 to 20 ethyl branches, about 1 to 12 propyl branches, about 1-12 butyl branches, about 1 to 10 amyl branches, and about 1 to 20 hexyl or longer branches, and (B) a second polymer comprising at least one member selected from the group consisting of polyamide, polyester (aliphatic and aromatic), polystyrene, polycarbonate, and polyurethane.
  • A a highly branched polyolefin having at least 60 branches per 1000 methylene groups, and which contains for every 100 branches that are methyl, about 4 to 20 ethyl branches, about 1 to 12 propyl branches, about 1-12 buty
  • the heat seal has a strength of from 5 to 75 percent of a seal strength of an ultimate seal strength formed by heat sealing to itself a corresponding film having a heat seal layer containing 100 percent of the second polymer.
  • the heat seal has a strength of from 1 to 6 pounds per inch.
  • the present invention is directed to a packaged product comprising a form-fill-and-seal package and a product within the package.
  • the form- fill and seal package comprises a film heat sealed to itself in an upper transverse seal, a lower transverse seal, and a longitudinal seal.
  • the film comprises a heat seal layer in accordance with the first aspect of the present invention.
  • a fiowable product is within the package.
  • the present invention is directed to a packaged product including a blister or clamshell package and a product within the package.
  • the blister clamshell package comprises a film having a heat seal layer in accordance with the first aspect of the present invention.
  • the present invention is directed to a container including an interior having at least two compartments separated by a peelable seal.
  • the peelable seal is constructed from a film comprising a heat seal layer in accordance with the first aspect of the invention, except that the peelable seal has a seal strength of from 0.1 to 6 pounds per inch
  • the ultimate seal strength of the second polymer is carried out as follows.
  • the second polymer is compression molded at least 20°C above T t into a monolayer film of about 5 mils.
  • the second polymer is a single polymer if the second polymer in the blend is a single polymer, or is a blend of polymers in the relative proportions present in the blend with the highly branched polymer(s), but without the highly branched polymer.
  • T t is the highest transition temperature for the polymer or polymer blend as determined by the DSC second heat endotherm. Tt may correspond to either a melting temperature, T m , or a glass transition temperature, T g .
  • the ultimate seal strength is obtained heat sealing this compression molded monolayer film to itself, using an impulse heat sealer operating under the following conditions: (A) A sealing temperature range of -10°C ⁇ T sea ⁇ - T t ⁇ 10°C (i.e., the sealing temperature is within a range which is plus or minus ten degrees C from T t );
  • a minimum heat sealing dwell time for the polymer or polymer blend is determined by the computed reptation time at the chosen heat sealing temperature.
  • the reptation time at the melt reference temperature is determined as the reciprocal of the shear rate or angular frequency of a shear viscosity mastercurve of the polymer melt at which the shear viscosity has decreased to 80% of the zero-shear viscosity asymptote at the prescribed reference melt temperature;
  • the heat sealing reptation time is shifted via time-temperature superposition to the prescribed heat sealing temperature;
  • the heat sealing temperature and the melt reference temperature at which the measurement of shear viscosity is performed need not be the same temperature; and
  • C A pressure of 40 psi.
  • the language: wherein the heat seal has a strength of from 5 to 75 percent of a seal strength of an ultimate heat seal formed by sealing to itself a corresponding film having a heat seal layer containing 100 percent of the second polymer refers to the seal strength of the heat seal in the article of the invention relative to the ultimate seal strength as described above.
  • the ultimate seal strength is determined from a seal made using a corresponding film which is a monolayer film of identical thickness to the subject film and which has a composition which differs from the heat seal layer only in that it does not contain the highly branched homogeneous polymer.
  • the corresponding film has a thickness which is the same as the thickness of the seal layer of the film containing the highly branched homogeneous polymer.
  • highly branched polymer refers to polymers such as those synthesized using transition metal catalysts such as the Ni(II) Dupont- Brookhart catalyst disclosed in, for example, U.S. Patent No. 5,880,241 to Brookhart et al. At least some of these polymers could be characterized as being “highly branched homogeneous polymers", which phrase is inclusive of both hyperbranched and dendritic chain structures.
  • Dendrimers are monodisperse and perfectly branched, and the terminal groups are located on the surface of the molecule. They are synthesized by multi-step reactions requiring time-consuming purification, which generally precludes their commercial development.
  • Hyperbranched polymers have a less regular structure, are not mono-disperse, and the functional groups are distributed throughout the molecule. See Chun-Yan Hong and Cai-Yuan Pan in Polymer, 42, 9385-9391 (2000), and M. Yamguchi and M. Takahashi Polymer, 42, 8665-8670 (2001), both of which are also hereby incorporated, in their entirety, by reference thereto. See also R.G. Larson, "Combinatorial Rheology of Branched Polymer Melts", Macromolecules 2001, Vol. 34, No. 13, 4556-4571, which is hereby incorporated, in its entirety, by reference thereto.
  • the ethyl ene-based homogeneous hyperbranched polymers useful in the present invention all have highly branched structures, i.e., at least 60 branches per 1000 methylene groups.
  • the branching may be only first degree branching, or can be up to second degree, or up to third degree, or up to fourth degree, or even higher than fourth degree branching.
  • the polymer has a branching within the range of from up to second degree to up to fourth degree.
  • Second degree branching refers to "a branch on a branch", with the branches being distinguished from the main chain;
  • third degree refers to "a branch on a branch on a branch", and so on.
  • the second polymer is inclusive of non-highly branched homogeneous copolymers, as well as highly branched homogeneous polymers having a branching level of less than 60 branches per 1,000 carbon atoms.
  • blister package refers to the enclosing of articles in thermoformed, transparent "blisters” shaped to more or less fit the contours of the articles.
  • the preformed blisters usually slightly oversized to provide ample room, are made of thermoplastics such as vinyl, polystyrene, or cellulosic plastics. They are placed inverted in fixtures and loaded with the articles to be packaged, then cards coated with adhesive are applied and sealed to the flanges between and around the blisters by means of heat and pressure.
  • the phrase "clamshell package” refers to a package produced using the modern version of the oldest form of blow molding: preheating two sheets of plastic, placing them between halves of a split mold, closing the mold, drawing the sheets against their respective mold surfaces by means of vacuum, then completing the forming with air pressure between the sheets.
  • the modern process, mechanized and conveyorized is superior to blow molding from a parison for very large parts and for those in which uniformity of wall thickness is important.
  • bag is inclusive of L-seal bags, side-seal bags, end- seal bags, backseamed bags, and pouches.
  • An L-seal bag has an open top, a bottom seal, one side-seal along a first side edge, and a seamless (i.e., folded, unsealed) second side edge.
  • a side-seal bag has a an open top, a seamless bottom edge, with each of its two side edges having a seal therealong.
  • An end-seal bag has an open top, seamless side edges, and a seal across the bottom of the bag.
  • seals along the side and/or bottom edges can be at the very edge itself, (i.e., seals of a type commonly referred to as "trim seals"), preferably the seals are spaced inward (preferably 1/4 to 1/2 inch, more or less) from the bag side edges or bag bottom edge, and preferably are made using a impulse-type heat sealing apparatus, which utilizes a bar which is quickly heated and then quickly cooled.
  • a backseamed bag is a bag having an open top, a seal running the length of the bag in which the bag film is either fin-sealed or lap-sealed, two seamless side edges, and a bottom seal along a bottom edge of the bag.
  • heat-shrinkable As used herein, the phrases "heat-shrinkable,” “heat-shrink” and the like refer to the tendency of a film, generally an oriented film, to shrink upon the application of heat, i.e., to contract upon being heated, such that the size (area) of the film decreases if the film is not restrained when heated. Likewise, the tension of a heat-shrinkable film increases upon the application of heat if the film is restrained from shrinking.
  • the phrase "heat-contracted” refers to a heat-shrinkable film, or a portion thereof, which has been exposed to heat such that the film or portion thereof is in a heat-shrunken state, i.e., reduced in size (unrestrained) or under increased tension (restrained).
  • the heat shrinkable film has a total free shrink (i.e., machine direction plus transverse direction), as measured by ASTM D 2732 (which is hereby incorporated, in its entirety, by reference thereto), of at least as 5 percent at 185°C, more preferably at least 7 percent, still more preferably, at least 10 percent, and, yet still more preferably, at least 20 percent.
  • heterogeneous copolymer refers to polymerization reaction products of relatively wide variation in molecular weight and relatively wide variation in composition distribution, i.e., typical polymers prepared, for example, using conventional Ziegler-Natta catalysts. Heterogeneous copolymers typically contain a relatively wide variety of chain lengths and comonomer percentages.
  • homogeneous polymer refers to polymerization reaction products of relatively narrow molecular weight distribution and relatively narrow composition distribution, compared with heterogeneous polymers. In addition to possessing a narrower molecular weight distribution, homogeneous copolymers differ from heterogeneous copolymers in exhibiting a more even sequencing of comonomers within a chain, and a mirroring of sequence distribution in all chains. Homogeneous polymers have been prepared using metallocene, or other single-site type catalysis, rather than using Ziegler Natta catalysts.
  • homogeneous ethylene/alpha-olefin copolymers may be characterized by one or more processes known to those of skill in the art, such as molecular weight distribution (Mw/Mn), Mz Mn, composition distribution breadth index (CDBI), and narrow melting point range and single melt point behavior.
  • Mw/Mn molecular weight distribution
  • Mz Mn Mz Mn
  • CDBI composition distribution breadth index
  • the homogeneous ethylene/alpha- olefin copolymers useful in this invention generally has (Mw Mn) of less than 2.7; preferably from about 1.9 to 2.5; more preferably, from about 1.9 to 2.3.
  • composition distribution breadth index (CDBI) of such homogeneous ethylene/alpha- olefin copolymers will generally be greater than about 70 percent.
  • the CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50 percent (i.e., plus or minus 50%) of the median total molar comonomer content.
  • the CDBI of linear polyethylene, which does not contain a comonomer, is defined to be 100%.
  • the Composition Distribution Breadth Index (CDBI) is determined via the technique of Temperature Rising Elution Fractionation (TREF).
  • CDBI determination clearly distinguishes the homogeneous copolymers (narrow composition distribution as assessed by CDBI values generally above 70%) from VLDPEs available commercially which generally have a broad composition distribution as assessed by CDBI values generally less than 55%.
  • the CDBI of a copolymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation as described, for example, in Wild et. al., J. Poly. Sci. Poly. Phys. Ed., Vol. 20, p.441 (1982).
  • homogeneous ethylene/alpha-olefin copolymers have a CDBI greater than about 70%, i.e., a CDBI of from about 70% to 99%.
  • the homogeneous ethylene/alpha- olefin copolymers also exhibit a relatively narrow melting point range, in comparison with heterogeneous copolymers.
  • the homogeneous ethylene/alpha-olefin copolymers exhibit an essentially singular melting point characteristic, with a peak melting point (Tm), as determined by Differential Scanning Calorimetry (DSC), of from about 60°C to 110°C.
  • Tm peak melting point
  • DSC Differential Scanning Calorimetry
  • the homogeneous ethylene/alpha-olefin copolymer has a DSC peak Tm of from about 80°C to 100°C.
  • the phrase "essentially single melting point" means that at least about 80%, by weight, of the material corresponds to a single Tm peak at a temperature within the range of from about 60°C to 110°C, and essentially no substantial fraction of the material has a peak melting point in excess of about 115°C, as determined by DSC analysis.
  • DSC measurements are made on a Perkin Elmer System 7 Thermal Analysis System. Melting information reported are second melting data, i.e., the sample is heated at a programmed rate of 10°C./min. to a temperature below its critical range. The sample is then reheated (2nd melting) at a programmed rate of 10°C/min.
  • a homogeneous ethylene/alpha-olefin copolymer can, in general, be prepared by the copolymerization of ethylene and any one or more alpha-olefin.
  • the alpha-olefin is a C 3 -C 20 alpha-monoolefin, more preferably, a C -C 12 alpha-monoolefin, more preferably, a C 4 -C 8 alpha-monoolefin, and still more preferably, a C ⁇ -Cs alpha- monoolefin.
  • the alpha-olefin comprises at least one member selected from the group consisting of butene-1, hexene-1, and octene-1, i.e., 1-butene, 1-hexene, and 1-octene, respectively. Most preferably, the alpha-olefin comprises hexene-1 and/or octene-1.
  • ethylene/alpha-olefin copolymer refers to such materials as linear low density polyethylene (LLDPE), and very low and ultra low density polyethylene (NLDPE and ULDPE); and homogeneous polymers such as metallocene catalyzed polymers such as EXACT ® resins obtainable from the Exxon Chemical Company, and TAFMER ® resins obtainable from the Mitsui Petrochemical Corporation.
  • LLDPE linear low density polyethylene
  • NLDPE and ULDPE very low and ultra low density polyethylene
  • homogeneous polymers such as metallocene catalyzed polymers such as EXACT ® resins obtainable from the Exxon Chemical Company, and TAFMER ® resins obtainable from the Mitsui Petrochemical Corporation.
  • All these materials generally include copolymers of ethylene with one or more comonomers selected from C 4 to C 10 alpha-olefin such as butene-1 (i.e., 1-butene), hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures.
  • This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts.
  • the heterogeneous ethylene/alpha-olefins commonly known as LLDPE have a density usually in the range of from about 0.91 grams per cubic centimeter to about 0.94 grams per cubic centimeter.
  • ethylene/alpha-olefin copolymers such as the long chain branched homogeneous ethylene/alpha-olefin copolymers available from the Dow Chemical Company, known as AFFINITY ® resins, are also included as another type of homogeneous ethylene/alpha-olefin copolymer useful in the present invention.
  • the ethylene/alpha-olefin copolymer comprises a copolymer resulting from the copolymerization of from about 80 to 99 weight percent ethylene and from 1 to 20 weight percent alpha-olefin.
  • the ethylene/alpha-olefin copolymer comprises a copolymer resulting from the copolymerization of from about 85 to 95 weight percent ethylene and from 5 to 15 weight percent alpha-olefin.
  • very low density polyethylene refers to heterogeneous ethylene/alpha-olefin copolymers having a density of 0.915 g/cc and below, preferably from about 0.88 to 0.915 g/cc.
  • linear low density polyethylene refers to, and is inclusive of, both heterogeneous and homogeneous ethylene/alpha-olefin copolymers having a density of at least 0.915 g/cc, preferably from 0.916 to 0.94 g/cc.
  • the phrases “inner layer” and “internal layer” refer to any layer, of a multilayer film, having both of its principal surfaces directly adhered to another layer of the film.
  • the phrase "outer layer” refers to any film layer of film having less than two of its principal surfaces directly adhered to another layer of the film.
  • the phrase is inclusive of monolayer and multilayer films.
  • multilayer films there are two outer layers, each of which has a principal surface adhered to only one other layer of the multilayer film.
  • monolayer films there is only one layer, which, of course, is an outer layer in that neither of its two principal surfaces are adhered to another layer of the film.
  • the phrase “inside layer” refers to the outer layer of a multilayer film packaging a product, which is closest to the product, relative to the other layers of the multilayer film.
  • the phrase “outside layer” refers to the outer layer, of a multilayer film packaging a product, which is furthest from the product relative to the other layers of the multilayer film.
  • the “outside surface” of a bag is the surface away from the product being packaged within the bag.
  • the term "adhered" is inclusive of films which are directly adhered to one another using a heat seal or other means, as well as films which are adhered to one another using an adhesive which is between the two films.
  • the films used in the sealed article according to the present invention can be monolayer films or multilayer films
  • the sealed article comprises at least two films laminated together.
  • the sealed article is comprised of films which together comprise a total of from 2 to 20 layers; more preferably, from 2 to 12 layers; and still more preferably, from 4 to 12 layers.
  • the multilayer film(s) used in the present invention can have any total thickness desired, so long as the film provides the desired properties for the particular packaging operation in which the film is used, e.g.
  • multilayer structures can be used in the formation of the first heat- shrinkable film according to the invention. Given below are some examples of preferred combinations in which letters are used to represent film layers. Although only 1 through 3 -layer embodiments are provided here for illustrative purposes, the multilayer films of the invention also can include more layers, as follows:
  • A represents a highly branched homogeneous polyolefin homopolymer or copolymer;
  • B represents a heterogeneous ethylene/alpha-olefin copolymer having a density greater than about 0.915 g/cm 3 .
  • C represents a homogeneous ethylene/alpha-olefin copolymer having a density of less than about 0.915 g/cm 3 .
  • D represents a polymer comprising at least one member selected from the group consisting of polyolefin, polystyrene, polyamide, polyester, and polyurethane.
  • X represents a layer comprising an ethylene/alpha-olefin copolymer having a density greater than about 0.915 g/cm 3 , as described in the description of the first component.
  • Y represents a layer containing a second component comprising heterogeneous ethylene/alpha-olefin copolymer having a density of less than about 0.915 g cm 3 , as described in the description of the second component.
  • Z represents a layer comprising at least one member selected from the group consisting of polyolefin, polystyrene, polyamide, polyester, and polyurethane, as described in the description of the second layer.
  • the film may be a monolayer film comprising (1) A and B, or (2) A, B, & C. Some preferred two layer films are represented in Table II, below. Table II
  • Some preferred three layer films include: X / Y / X; X / Y / Z; Y / X / Y; Y / X / Z; X / Z / Y; A+ B / Z / C; A+C / Z / B; and, B+C / Z / A.
  • a plurality of layers may be formed of the same or different modified compositions and one or more tie-layers added. Examples
  • the respective virgin base heat sealing polymers and polymer blends were compression molded into films approximately 5 mils in thickness. The resulting films were cut into strips and heat sealed on a Sencorp Systems impulse heat sealer.
  • Blends of the highly branched hyperbranched polyethylene (HBP) resins previously prepared and numbered as batch runs 63653 and 63654 each had a weight- average molecular weight, Mw, of 122,000 and total branching levels of 81 and 82 branches per 1,000 carbon atoms, respectively.
  • Blend series #1 constituted HBP 63653 blended into Fina Z9450 at weight percents of 0, 12.5, 25.0, and 50.0.
  • blend series #2 was prepared by blending HBP 63654 into Exxon Exact 3132 at weight percents of 0, 12.5, 25.0, and 50.0 as well.
  • the HAAKE Rheocord 90 torque rheometer with the Rheomix 600 mixing bowl attachment and standard roller blades operating at 100 rpm and a mixing bowl temperature of 200°C was used to mix all blends. Approximately 40 grams of each blend were removed from storage in a nitrogen atmosphere box and were compounded for 8 minutes before the polymer mixture was removed from the mixing chamber. A nitrogen purge was used to blanket the contents of the mixing chamber during the entire eight-minute compounding cycle. The resulting polymer blobs extracted from the mixing bowl were reground for subsequent compression molding. The ground samples were returned to the nitrogen atmosphere box until the material was ready to be compression molded into films. Compression Molding Procedure for Films
  • Polymer films comprising the various blends were compression molded using a Carver Model CMG 302H-12-ASTM hydraulic press.
  • the compression mold assembly employed was characterized by the following six-part bottom-to-top stacked arrangement: (1) a 6" x 6" x 0.125" 304 stainless steel plate, (2) a 6" x 6" sheet of 3.4 mil thick PTFE coated aluminum foil (Caroplast, Inc., T303 PTFE/Aluminum TriFoil tape, P/N 70201666), (3) a mold shim formed by cutting a square frame with an internal opening of dimensions 4" x 4" with 1" borders along each side of the mold shim from a sheet of the same PTFE coated aluminum foil, (4) 2.0 grams of each item for each blend series were evenly sprinkled over the opening of the mold shim, (5) a second 6" x 6" sheet of 3.4 mil thick PTFE coated aluminum foil, and finally (6) a second 6" x 6" x 0.125” 304 stainless steel plate
  • Resin discs 50 mm in diameter, and approximately 2 mm thick were prepared for each resin sample according to ASTM D 1928-96, Procedure C. Discs free of included air bubbles were easily produced for all subject resins using the prescribed molding conditions. Each disc formed was placed between the plates of a 50 mm diameter parallel plate fixture of a Rheometric Scientific, Inc. RMS-800 Mechanical Spectrometer and the plate spacing was adjusted to 1.500 mm. Any rejected melt squeezed beyond the plate edge during gap adjustment was removed with a spatula. The copolymers and polymers comprising blend series #1 and #2 follow the Cox-Merz rule, and consequently dynamic mechanical testing of the melt was employed to measure the melt rheological properties of the blend systems.
  • a dynamic strain in the range of 1 percent to 10 percent is adequate to meet testing requirements for most polymers, especially polyolefin homopolymers, copolymers, and polymer blends.
  • the linear viscoelastic range for melt testing can be easily determine using the dynamic strain sweep test. Dynamic frequency sweeps were performed at each of three melt temperatures usually spaced at 10°C to 20°C intervals upward from about 10°C above the peak melting point or glass transition.
  • a temperature range extending from 180 °C to 140 °C in 20°C increments is used to minimize sample thermal degradation, and to facilitate the construction of a shear viscosity master curve.
  • Exxon Exact 3132 and Fin Z9450 were analyzed over temperature range from 180 °C to 140 °C in 20°C increments.
  • the parallel plate fixture was initially zeroed at the highest experiment melt temperature, and a thermal expansion coefficient of 2.5 Dm °C was specified for the parallel plate fixture to account for the change in plate spacing with temperature, as recommended by Rheometric Scientific, Inc.
  • the employed testing procedure complies with ASTM D 4440.
  • ⁇ is the shear rate and temperature-dependent shear viscosity
  • 770 is the zero- shear viscosity at the reference temperature T r
  • ⁇ o is the Cross Model relaxation time
  • b is the Cross Model exponent
  • ⁇ is the shear rate
  • a is the time-temperature superposition shift factor which establishes how the flow master curve shifts as a function of temperature.
  • the Cross Model takes the following form:
  • EA is the flow activation energy
  • R is the gas constant
  • -T is the system temperature that can be different or the same as the reference temperature, T r , at which the parameters 770 and ⁇ o are determined.
  • the Cross Model exponent, b is considered to be a constant over a wide range of temperatures and shear rates.
  • Equation (3) is obeyed for most polyolefin systems. Once steady shear or dynamic shear melt rheological data have been obtained, the parameters ⁇ o , o , b, and E are usually determined by a non-linear least squares fit of the data. In the present case, Rheometric Scientific, Inc. Orchestrator Version 6.4.4 data analysis software was used to perform the regression analyses for parameter determination. The reptation time, ⁇ mp , at the peak heat sealing temperature is defined by the equation
  • the minimum required heat sealing dwell time is 3 sec to reach the ultimate heat seal strength for Exxon Exact 3132.
  • the reptation time defining the minimum heat sealing dwell time was found to be 11.0 sec at 129°C (264 °C).
  • Heat sealing experiments were conducted using a Sencorp Systems, Inc. Model 12AS/1 impulse sealer.
  • the measured DSC second heat melting points for Exxon Exact 3132 and Fina Z9450 were 96°C and 129°C, respectively.
  • Reptation times as functions of temperature for Exxon Exact and Fina Z9450 were determined from Cross Model fits of the shear viscosity master curves to estimate the minimum time required for the heat sealing dwell time.
  • Each blend series was heat sealed with a peak sealing temperature corresponding to the DSC second heat melting temperature of the virgin base heat sealing polymer to ensure that the ultimate heat seal strength for the virgin base heat sealing polymer was attained.
  • the heat sealing conditions employed for the two heat sealing resin systems were:
  • Film thickness measurements using a digital micrometer indicated that film samples produced using the prescribed molding assembly and the ASTM D 1928-90, Procedure C compression molding protocol, gave an average of 5.5 mils with a range of + 0.7 mils for blend series #1 and #2.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Wrappers (AREA)
  • Laminated Bodies (AREA)

Abstract

Article thermoscellé facile à ouvrir possédant un feuil thermoscellé sur lui-même ou sur un autre élément de cet article. Ce feuil comporte une couche thermoscellée contenant un mélange constitué par un premier polymère et un deuxième polymère. Ce premier polymère est une polyoléfine homogène très ramifiée possédant au moins 60 ramifications pour 1 000 groupes méthylène, et pour toutes les 100 ramifications méthyle, 4 à 20 ramifications éthyle, 1 à 12 ramifications propyle, 1 à 12 ramifications butyle, 1 à 10 ramifications amyle et 1 à 20 ramifications héxyle ou plus longues. Le deuxième polymère représente une quantité d'au moins 5 % en poids du mélange. Ce deuxième polymère possède une température de transition vitreuse ou température de fusion supérieure à celle du premier polymère. Le joint thermique possède une résistance de 5 à 75 % de la résistance d'un dernier joint obtenu par thermoscellement sur lui-même d'un feuil correspondant possédant une couche thermoscellée contenant 100 % du deuxième polymère.
PCT/US2002/035369 2001-11-06 2002-11-04 Article d'emballage thermoscelle facile a ouvrir contenant des polyolefines homogenes tres ramifiees Ceased WO2003040199A1 (fr)

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Cited By (11)

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US7871697B2 (en) 2006-11-21 2011-01-18 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US7871696B2 (en) 2006-11-21 2011-01-18 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US20120309915A1 (en) * 2010-03-29 2012-12-06 E I Du Pont De Nemours And Company Ethylene polymerization process and polyolefin
US9096780B2 (en) 2010-02-26 2015-08-04 Intercontinental Great Brands Llc Reclosable fasteners, packages having reclosable fasteners, and methods for creating reclosable fasteners
US9382461B2 (en) 2010-02-26 2016-07-05 Intercontinental Great Brands Llc Low-tack, UV-cured pressure sensitive adhesive suitable for reclosable packages
US9533472B2 (en) 2011-01-03 2017-01-03 Intercontinental Great Brands Llc Peelable sealant containing thermoplastic composite blends for packaging applications
US9532584B2 (en) 2007-06-29 2017-01-03 Kraft Foods Group Brands Llc Processed cheese without emulsifying salts
CN107973953A (zh) * 2016-10-21 2018-05-01 中国石油化工股份有限公司 一种热塑性弹性体组合物及其制备方法和密封垫片以及制备皇冠盖中密封垫片的方法
CN109370453A (zh) * 2017-07-25 2019-02-22 杭州星庐科技有限公司 封装组合物及应用，及包含其的封装胶膜及其制备方法
CN116217431A (zh) * 2023-01-14 2023-06-06 浙江巨化新材料研究院有限公司 封装组合物、封装材料及其制备方法以及电子器件组件
WO2024187442A1 (fr) * 2023-03-16 2024-09-19 绍兴鑫凯基新材料有限公司 Film alimentaire en plastique à atmosphère modifiée et son application

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WO1996004178A1 (fr) * 1994-07-29 1996-02-15 Mobil Plastics Europe, Inc. Structure de film pelable
EP0985687A1 (fr) * 1998-09-08 2000-03-15 Idemitsu Petrochemical Co., Ltd. Homopolymère d'éthylène et articles moulés préparés avec celui-ci
WO2001018097A1 (fr) * 1999-09-07 2001-03-15 E.I. Du Pont De Nemours And Company Polyolefines thermoscellables et articles fabriques a partir desdites polyolefines

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WO1996004178A1 (fr) * 1994-07-29 1996-02-15 Mobil Plastics Europe, Inc. Structure de film pelable
EP0985687A1 (fr) * 1998-09-08 2000-03-15 Idemitsu Petrochemical Co., Ltd. Homopolymère d'éthylène et articles moulés préparés avec celui-ci
WO2001018097A1 (fr) * 1999-09-07 2001-03-15 E.I. Du Pont De Nemours And Company Polyolefines thermoscellables et articles fabriques a partir desdites polyolefines

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9309027B2 (en) 2006-11-21 2016-04-12 Intercontinental Great Brands Llc Peelable composite thermoplastic sealants in packaging films
US7871696B2 (en) 2006-11-21 2011-01-18 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US8110286B2 (en) 2006-11-21 2012-02-07 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US8470397B2 (en) 2006-11-21 2013-06-25 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US7871697B2 (en) 2006-11-21 2011-01-18 Kraft Foods Global Brands Llc Peelable composite thermoplastic sealants in packaging films
US9532584B2 (en) 2007-06-29 2017-01-03 Kraft Foods Group Brands Llc Processed cheese without emulsifying salts
US9382461B2 (en) 2010-02-26 2016-07-05 Intercontinental Great Brands Llc Low-tack, UV-cured pressure sensitive adhesive suitable for reclosable packages
US9096780B2 (en) 2010-02-26 2015-08-04 Intercontinental Great Brands Llc Reclosable fasteners, packages having reclosable fasteners, and methods for creating reclosable fasteners
US10287077B2 (en) 2010-02-26 2019-05-14 Intercontinental Great Brands Llc Low-tack, UV-cured pressure sensitive adhesive suitable for reclosable packages
US9175104B2 (en) * 2010-03-29 2015-11-03 E I Du Pont De Nemours And Company Ethylene polymerization process and polyolefin
US20120309915A1 (en) * 2010-03-29 2012-12-06 E I Du Pont De Nemours And Company Ethylene polymerization process and polyolefin
US9533472B2 (en) 2011-01-03 2017-01-03 Intercontinental Great Brands Llc Peelable sealant containing thermoplastic composite blends for packaging applications
CN107973953A (zh) * 2016-10-21 2018-05-01 中国石油化工股份有限公司 一种热塑性弹性体组合物及其制备方法和密封垫片以及制备皇冠盖中密封垫片的方法
CN107973953B (zh) * 2016-10-21 2020-09-15 中国石油化工股份有限公司 一种热塑性弹性体组合物及其制备方法和密封垫片以及制备皇冠盖中密封垫片的方法
CN109370453A (zh) * 2017-07-25 2019-02-22 杭州星庐科技有限公司 封装组合物及应用，及包含其的封装胶膜及其制备方法
CN116217431A (zh) * 2023-01-14 2023-06-06 浙江巨化新材料研究院有限公司 封装组合物、封装材料及其制备方法以及电子器件组件
WO2024187442A1 (fr) * 2023-03-16 2024-09-19 绍兴鑫凯基新材料有限公司 Film alimentaire en plastique à atmosphère modifiée et son application

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