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
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • 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
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
• • 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
• • 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
• • 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
  • B32B2307/31—Heat sealable
• • 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
  • B32B2323/04—Polyethylene
  • B32B2323/046—LDPE, i.e. low density polyethylene
• • 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
  • B32B2439/00—Containers; Receptacles
  • B32B2439/70—Food packaging
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • 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
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
• • 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 more than three carbon atoms
  • C08L23/0815—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
  • C08L2314/06—Metallocene or single site catalysts

Definitions

• This invention relates to a pouch used in consumer packaging useful for packaging flowable materials, (for example, liquids such as milk).
• the pouch is made from certain film structures comprising at least one homogeneously branched linear ethylene interpolymer.
• U.S. Patent Nos. 4,503,102, 4,521,437, 5,288,531, and 5,360,648 disclose the preparation of a polyethylene film for use in the manufacture of a disposable pouch for packaging of liquids such as milk.
• U.S. Patent No. 4,503,102 discloses pouches made from a blend of a linear ethylene copolymer copolymerized from ethylene and an alpha- olefin at the C4-C10 range and an ethylene- vinyl acetate polymer copolymerized from ethylene and vinyl acetate.
• the linear polyethylene copolymer has a density of from
• the ethylene-vinyl acetate polymer has a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of from 0.2 to 10 g/10 min.
• the blend disclosed in U.S. Patent No. 4,503,102 has a weight ratio of linear low density polyethylene to ethylene-vinyl acetate polymer of from 1.2: 1 to 4: 1.
• U.S. Patent No. 4,503,102 also discloses laminates having as a sealant film the aforementioned blend.
• U.S. Patent No. 4,521,437 describes pouches made from a sealant film which is from 50 to 100 parts of a linear copolymer of ethylene and octene- 1 having a density of from 0.916 to 0.930 g/cm ⁇ and a melt index of 0.3 to 2.0 g/10 min and from 0 to 50 parts by weight of at least one polymer selected from the group consisting of a linear copolymer of ethylene and a Cj-Cio alpha-olefin having a density of from 0.916 to 0.930 g/cm-' and a melt index of from 0.3 to 2.0 g/10 min, a high-pressure polyethylene having a density of from 0.916 to 0.924 g/crn- ⁇ and a melt index of from 1 to 10 g/10 min and blends thereof.
• the sealant film disclosed in the U.S. Patent No. 4,521,437 is selected on the basis of providing (a) pouches with an M-test value substantially smaller, at the same film thickness, than that obtained for pouches made with film of a blend of 85 parts of a linear ethylene/butene- 1 copolymer having a density of about 0.919 g/crc and a melt index of about 0.75 g/10 min and 15 parts of a high pressure polyethylene having a density of about 0.918 g/crn- ⁇ and a melt index of 8.5 g/10 min, or (b) an M(2)-test value of less than about 12 percent, for pouches having a volume of from greater than 1.3 to 5 liters, or (c) an M(1.3)-test value of less than about 5 percent for pouches having a volume of from 0.1 to 1.3 liters.
• the M, M(2) and M(1.3)-tests are defined pouch drop tests in U.S. Patent No. 4,521
• U.S. Patent No. 5,288,531 discloses pouches made from a film structure having a blend of (a) from 10 to 100 percent by weight of at least one polymeric seal layer of an ultra low density linear ethylene copolymer interpolymerized from ethylene and at least one alpha-olefin in the range of C3-C10 with a density of from 0.89 g/cm 3 to less than 0.915 g/cm 3 and (b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a linear copolymer of ethylene and a C3-C 18-alpha-olefin having a density of greater than 0.916 g/cm and a melt index of from 0.1 to 10 g/10 minutes, a high-pressure low density polyethylene having a density of from 0.916 to 0.930 g/cm ' and a melt index of from 0.1 to 10 g/10 minutes, or ethylene-vinyl acetate copolymer having
• U.S. Patent No. 5,360,648 discloses pouches made from a film structure having a blend of (a) from 10 to 100 percent by weight of at least one homogeneously branched substantially linear ethylene/ ⁇ -olefin interpolymer having certain characterizing properties described therein, and (b) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-C 18 ⁇ -olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer.
• the film structure of the U.S. Patent No. 5,360,648 provides, among other things, a broad heat sealing range.
• the polyethylene pouches known in the prior art have some deficiencies.
• the problems associated with films known in the prior art relate to the sealing properties and performance properties of the film for preparing pouches.
• prior art films made into pouches have a high incident of "leakers", that is, seal defects such as pinholes which develop at or near the seal in which flowable material, for example milk, escapes from the pouch.
• homogeneously branched linear ethylene/ ⁇ -olefin mterpolymers offer significant advantages m film structures of pouches
• the homogeneously branched linear ethylene/ ⁇ -olefin mterpolymers when used as a seal layer, have higher hot tack strength than homogeneously branched subtantially linear ethylene/ ⁇ -olefin mterpolymers They have good heat sealabihty at temperatures lower than those necessary for heterogeneously branched linear ethylene/ ⁇ -olefin mterpolymers and are also easily processed on conventional film and heat seal equipment
• One aspect of the present invention is directed to a pouch made from a film structure in tubular form and having transversely heat sealed ends, the film structure having at least one film layer comprising:
• composition distribution branching or breadth index (a) a composition distribution branching or breadth index (CDBI) greater than 50 percent
• (II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-C ⁇ 8 ⁇ -olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer.
• One embodiment of the present invention is a pouch made from a two-layer (that is, A/B) coextruded film containing an outer layer of a heterogeneously branched linear low density polyethylene and an inner seal layer of the aforementioned homogeneously branched linear ethylene interpolymer.
• Another embodiment of the present invention is a pouch made from a three-layer (that is, A/B/A or A/B/C) coextruded film containing an outer layer and a core layer comprising heterogeneously branched linear low density polyethylene (either the same or different heterogeneously branched linear low density polyethylenes) or a high pressure low density polyethylene and an inner seal layer comprising the aforementioned homogeneously branched linear ethylene interpolymer.
• Another aspect of the present invention is a process for preparing the aforementioned pouch.
• Another aspect of the present invention is directed to a pouch made from a film structure in tubular form and having transversely heat sealed ends, the film structure having at least one film layer comprising:
• (c ) a single differential scanning calo ⁇ metry (DSC) melting peak between -30 and 150 C, and (II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-Ci8 ⁇ -olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vinyl acetate copolymer
• Another embodiment of the present invention is a pouch made from a two-layer (that is, A/B) coextruded film containing an outer layer of a heterogeneously branched linear low density polyethylene and an inner seal layer of the aforementioned homogeneously branched linear ethylene polymer
• Yet another embodiment of the present invention is a pouch made from a three-layer (that is, A B/A or A/B/C) coextruded film containing an outer layer and a core layer comprising heterogeneously branched linear low density polyethylene (either the same or different heterogeneously branched linear low density polyethylenes) or a high pressure low density polyethylene and an inner seal layer comprising the aforementioned homogeneously branched linear ethylene polymer
• Another aspect of the present invention is a process for preparing the aforementioned pouch
• Film structures for the pouches of the present invention have a better seal at lower sealing temperatures and greater hot tack strength than currently obtainable with commercially available film
• Figure 1 shows a perspective view of a pouch package of the present invention
• Figure 2 shows a perspective view of another pouch package of the present invention
• Figure 3 shows a partial, enlarged cross-sectional view of the film structure of a pouch of the present invention
• Figure 4 shows another partial, enlarged cross-sectional view of another embodiment of the film structure of a pouch of the present invention
• Figure 5 shows yet another partial, enlarged cross-sectional view of another embodiment of the film structure of a pouch of the present invention
• Firgure 6 is a graphical illustration of maximum film hot tack strength versus resin density for a pouch of the present invention, based on resms 9-1 1 and comparative res s 1 -3 of Table 3
• the pouch of the present invention for example as shown in Figures 1 and 2, for packaging flowable materials is manufactured from a monolayer film structure of a polymeric seal layer which is a homogeneously branched linear ethylene/ ⁇ -olefin interpolymer (referred to hereinafter as "HBLEP")
• HLEP homogeneously branched linear ethylene/ ⁇ -olefin interpolymer
• the HBLEP of the present invention is generally an interpolymer of ethylene with at least one ⁇ -olefin having from 3 to 20 carbon atoms.
• interpolymer is used herein to indicate a copolymer, or a terpolymer, or the like That is, at least one other comonomer is polymerized with ethylene to make the interpolymer
• a HBLEP terpolymer comprising ethylene/ 1 -octene/ 1-hexene may be employed m the film structure as the polymeric seal layer Copolymers of ethylene and a C3-C20 ⁇ -olefin are especially preferred, for example, the HBLEP may be selected from ethylene/propene, ethylene/ 1-butene, ethylene/ 1-pentene, ethylene/4-methyl- 1-pentene, ethvlene/ 1-hexene, ethylene/ 1-heptene, ethylene/ 1 -octene and ethylene/ 1 -decene copolymers, preferably ethylene/ 1 -octene copolymer
• “homogeneously branched linear ethylene polymer” means that the olefin polymer has a homogeneous short branching distribution but does not have long chain branching That is, the linear ethylene polymer has an absence of long chain branching
• Such polymers include linear low density polyethylene polymers and linear high density polyethylene polymers and can be made using polymenzation processes (for example, as described by Elston in USP 3,645,992) which provide uniform branching (that is, homogeneously branched) distribution
• Uniform branching distributions are those in which the comonomer is randomly distributed withm a given interpolymer molecule and wherein substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer In his polymerization process, Elston uses soluble vanadium catalyst system to make such polymers, however others such as Mitsui Petrochemical Corporation and Exxon Chemical Company have used so-called single site catalyst systems to make linear ethylene polymers having a similar homogeneous structure Examples of
• homogeneously branched linear ethylene polymer does not refer to high pressure branched polyethylene which is known to those skilled in the art to have numerous long chain branches
• the homogeneously branched linear ethylene polymer is an ethylene/OC-olefin interpolymer, wherein the °c-olef ⁇ n is at least one C3-C20 Ot-olef in (for example, 1-propylene, 1-butene, 1-pentene, 4-methyl- 1-pentene
• the ethylene/ ⁇ -olefin interpolymer is a copolymer of ethylene and a C3-C20 OC -olefin, especially an ethylene/C4-C D ⁇ -olefin copolymer
• homogeneously branched linear ethylene polymer does not refer to, and differs from, homogeneously branched substantially linear polymer (referred to hereinafter as "SLEP"), such as described by Falla et al in U S Patent 5,360,648 In a SLEP, the interpolymer backbone is substituted with 0 01 to 3 long chain branches/ 1000 carbons
• SLEP include ENGAGE ® and AFFINITY ® , trademarks of and made by The Dow Chemical Company
• the Short Chain Branch Distribution Index (SCBDI) or Composition Distribution Branch Index (CDBI) is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar content
• the CDBI of a polymer is readily calculated from data obtained utilizing well known techniques, such as, for example, temperature rising elution fractionation (abbreviated herein as "TREF") as desc ⁇ bed, for example, in, Journal of Polymer Science, Poly Phvs Ed , Vol 20, p 441 (1982) by Wild et al, or in U S Patent 4,798,081
• the SCBDI or CDBI for the homogeneously branched linear ethylene/ ⁇ -olefin interpolymers and copolymers used in the present invention is greater than about 50 percent, preferably greater than about 70 percent, more preferably greater than about 80 percent and most preferable greater than about 90 percent
• the linear ethylene/ ⁇ -olefin mterpolymers and copolymers used in this invention essentially
• the "high density" polymer fraction can be described as a polymer fraction with a degree of branching less than or equal to about 2 methyls/1000 carbons.
• the terms "essentially lacks a measurable high density fraction” means that the linear interpolymers and copolymers do not contain a polymer fraction with a degree of branching less than or equal to about 2 methyls/1000 carbons.
• narrow short chain distribution refers to mterpolymers and pertains to the distribution of ⁇ -olefin monomer branches of the interpolymer as characterized by its SCBDI or CDBI.
• the term is defined herein as greater than about 50 weight percent of the interpolymer molecules have an ⁇ -olefin monomer content within 50 percent of the median total molar ⁇ -olefin monomer content. Techniques for calculating CDBI is generally described hereinabove.
• the preferred TREF technique does not include purge quantities in CDBI calculations
• the monomer distribution of the interpolymer and CDBI are determined using 1 C nuclear magnetic resonance analysis in accordance with techniques described in US Patent 5,292,845 and in Rev Macromol Chem Phvs , C29, pp. 201-317, by J C Randall.
• the homogeneously branched very low density polyethylene (hmVLDPE) and homogeneously branched linear low density polyethylene (hmLLDPE) are well known in the art, for example, Elston's disclosure in U S. Pat. No. 3,645,992.
• hmVLDPE and hmLLDPE can be prepared in solution, slurry or gas phase processes using hafnium, zirconium and vanadium catalyst systems
• Ewen, et al describe a method of preparing such polyethlenes using metallocene catalysts.
• hmVLDPE and hmLLDPE are linear polyethylenes which are homogeneously branched polymers, but like the Ziegler-type heterogeneous linear polyethylene, they do not have any long- chain branching.
• Commercial examples of these polymers are sold by Mitsui Petrochemical under the trademark TAFMER ® and by Exxon Chemical under the trademarks EXACT ® and EXCEED ® .
• homogeneously branched linear ethylene polymers for the preferred homogeneously branched linear ethylene polymers the term "homogeneously branched" means that the comonomer is randomly distributed within a given interpolymer molecule and wherein substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer.
• linear ethylene/ ⁇ -olefm interpolymer does not refer to high pressure branched (free- radical polymerized) polyethylene which is known to those skilled in the art to have numerous long chain branches.
• the homogeneously branched linear ethylene/ ⁇ -olefin copolymers and interpolymers of the present invention have a single melting point, as opposed to traditional Ziegler polymerized (heterogeneously branched) polymers having two or more melting points, as determined using differential scanning calorimetry (DSC) over a temperature range of from -20°C to 150°C.
• DSC differential scanning calorimetry
• the novel homogeneously branched linear ethylene/ ⁇ -olefin copolymers and interpolymers have melting points which correlate with the density of the copolymer or interpolymer. As the density of the polymer decreases, the peak melting decreases in a direct linear relationship.
• heterogeneously branched ethylene polymers have peak melting points which do not vary substantially with the density of the polymer, primarily due to the presence of a high density polymer fraction which melts at about 122°C (the melting point of homopolymer linear polyethylene).
• the density of the homogeneously branched linear ethylene/ ⁇ -olefin interpolymers or copolymers (as measured in accordance with ASTM D-792) for use in the present invention is generally less than about 0.94 g/cm ⁇ > and preferably from 0.90 g/c ⁇ to 0.94 g/c ⁇
• the homogeneously branched linear ethylene/ ⁇ -olefin polymer is used alone in the seal layer of the film or film structure.
• the homogeneously branched linear ethylene/ ⁇ -olefin polymer can be blended with other polymers for use as the heat seal layer.
• the amount of the homogeneously branched linear ethylene/ ⁇ -olefin polymer is from 10 percent to 100 percent, by weight of the polymer composition for the film structure.
• the molecular weight of the homogeneously branched linear ethylene/ ⁇ - olefin interpolymers and copolymers for use in the present invention is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition
• melt index 190°C/2.16 kg (formerly known as "Condition (E)" and also known as 12)- Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index. The relationship, however, is not linear.
• the melt index for the homogeneously branched linear ethylene/ ⁇ -olefin interpolymers and copolymers of the present invention is generally about 10 grams/10 minutes (ldg/10 min) or less, preferably from 0.01 g/10 min to 10 g/10 min, most preferably 0.4 g/10 minutes to 1.2 g/10 minutes.
• the molecular weight distribution (M /M n ) of the homogeneously branched linear ethylene/ ⁇ -olefin mterpolymers and copolymers is analyzed by gel permeation chromatography (GPC) on a Waters 150C high temperature chromatographic unit equipped with three mixed porosity columns (Polymer Laboratories 10 ⁇ , 10 ⁇ , 10 ⁇ , and 10"), operating at a system temperature of 140°C
• the solvent is 1,2,4- t ⁇ chlorobenzene, from which 0 3 percent by weight solutions of the samples are prepared for injection
• the flow rate is 1 0 millihters/minute and the injection size is 200 microliters.
• the molecular weight determination is deduced by using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in conjunction with their elution volumes.
• the equivalent polyethylene molecular weights are determined by using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol 6, (621) 1968) to derive the following equation
• the M w /M n is preferably from 1.5 to 2.5, especially 2 to 2.5.
• Additives known to those skilled in the art, such as antioxidants (for example, hindered phenohcs (for example, Irganox® 1010 or Irganox® 1076 made by Ciba Geigy Corp.), phosphites (for example, Irgafos® 168 made by Ciba Geigy Corp.), cling additives (for example, polyisobutylene (PIB)), Standostab PEPQ_ supplied by Sandoz, anti-block additives, slip additives, UV stabilizers, pigments, processing aids (especially fluoroelastomers such as Dynamar® FX 5920 made by 3M are useful to improve processabihty for the homogeneously branched linear ethylene polymers) can also be added to the polymers for film structures, from which the pouches of the present invention are made.
• antioxidants for example, hindered phenohcs (for example, Irganox® 1010 or Irganox® 1076
• the films and film structures disclosed herein can be monolayer or multilayer film structures, with the proviso that the homogeneously branched linear ethylene/ ⁇ -olefin copolymers and interpolymers be used as at least one layer, preferably the seal layer.
• the thickness of the seal layer may be from at least about 0 1 mil (2.5 microns) and greater, preferably from 0 2 mil (5 microns) to 10 mil (254 microns) and more preferably from 0 4 mil ( 10 microns) to 5 mil ( 127 microns).
• a surprising feature of the film structure for pouches of the present invention is the broad heat seal range, especially in view of the narrow melting point range associated with the linear ethylene polymer (measured using differential scanning calo ⁇ metry)
• the heat seal range of the film structure can be from 50°C to 160°C and preferably from 75°C to 130°C It has been found that the seal layer of the present invention has a broader heat seal range than prior art polyethylene film made from heterogeneously branched ethylene polymers, even at comparable densities.
• the melting point range of the linear ethylene polymer used to make the film structure having the heat seal ranges specified above can be from 50°C to 130°C and preferably from 55°C to 115°C
• Another unexpected feature of the pouch film structure of the present invention is the film's maximum hot tack strength, using the DTC Hot Tack Strength Method defined herembelow.
• decreasing the density of heterogeneously branched linear ethylene/ ⁇ -olefin interpolymers has no effect on the maximum hot tack strength.
• the film of present invention achieves greater maximum hot tack strength as the density of the homogeneously branched linear ethylene/ ⁇ -olefin copolymers and mterpolymers is decreased.
• films of the present invention achieve greater hot tack strengths over broader region than films made from homogeneously branched substantially linear ethylene/ ⁇ -olefm copolymers and interpolymers
• a film made using a heterogeneously branched linear ethylene/ ⁇ -olefin interpolymer will have a maximum hot tack strength of 2 7 N/m at a density of 0 905 g/cm
• a film made using a the homogeneously branched substantially linear ethylene/ ⁇ -olefin copolymers will have a maximum hot tack strength of 7 0 N/m at a density of 0 902 g/cm
• a film of the present invention made from a homogeneously branched linear ethylene/ ⁇ -olefin copolymer having a density of 0 900 g/cm 3 will have a maximum hot tack strength of 9 8 N/in
• the film structure of the present invention also has a hot tack or heat seal initiation temperature of less than about 110°C at a force of at least about 1 N/inch (39 4 N/m) It has been found that a seal made with the seal layer of the present invention has a higher strength at lower sealing temperatures than seals with a p ⁇ or art polyethylene having higher densities
• a high heat seal strength at low temperatures and a broad hot tack range are important to allow conventional packaging equipment such as a vertical form, fill and seal machine to run at faster rates and to produce pouches with fewer leakers
• the use of at least one homogeneously branched linear ethylene polymer m a seal layer of a film structure for pouches of the present invention provides ( 1 ) a pouch that can be fabricated at a faster rate through a form, fill and seal machine, and (2) a pouch having fewer leakers, particularly when the pouch of the present invention is compared to pouches made with linear low density polyethylene, ultra linear low density polyethylene, high pressure low density polyethylene, or a combination thereof
• a pouch is made from a film structure in tubular form and having transversely heat sealed ends
• the film structure has at least one film layer comprising
• composition distribution branching or breadth index (a) a composition distribution branching or breadth index (CDBI) greater than 50 percent
• (II) from 0 to 90 percent by weight of at least one polymer selected from the group consisting of a heterogeneously branched linear ethylene/C3-C 18 ⁇ -olefin copolymer, a high-pressure low density polyethylene, and an ethylene-vmyl acetate copolymer.
• the heterogeneously branched linear ethylene/C3-C ⁇ 8 ⁇ -olefin copolymer of (II) is generally a linear low density polyethylene (such as that made using Ziegler catalysts).
• the linear low density polyethylene is often further divided into subsets labeled as very low density polyethylene (VLDPE) or ultra low density polyethylene (ULDPE)
• VLDPE and ULDPE are interchangeable terms herein and are generally used in this manner by those skilled in the art.
• the density of the linear low density polyethylene of (II) ranges from 0 87 g/cm ⁇ to 0.94 g/cm ⁇ , preferably from 0 87 g/cm ⁇ to 0.915 g/c ⁇
• the heterogeneously branched linear low density ethylene/C3-C 18 ⁇ -olefin copolymer of (II) has a melt index from 0.1 to 10 g/10 minutes
• the high-pressure low density polyethylene of (II) has a density from 0.916 to 0 93 g/cm ⁇ and a melt index from 0 1 to 10 g/10 minutes.
• the ethylene-vinyl acetate copolymer of (II) has a weight ratio of ethylene to vinyl acetate from 2.2.1 to 24.1 and a melt index from 0.2 to 10 g/10 minutes.
• the film structure of the pouch of the present invention also includes a multilayer or composite film structure 30, preferably containing the above-described polyme ⁇ c seal layer being the inner layer of the pouch.
• the multilayer film structure for the pouch of the present invention may contain various combination of film layers as long as the seal layer forms part of the ultimate film structure.
• the multilayer film structure for the pouch of the present invention may be a coextruded film, a coated film or a laminated film.
• the film structure also includes the seal layer m combination with a barrier film such as polyester, nylon, EVOH, polyvinyhdene dichlo ⁇ de (PVDC) such as Saran ® - (Trademark of The Dow Chemical Company) and metallized films.
• a barrier film such as polyester, nylon, EVOH, polyvinyhdene dichlo ⁇ de (PVDC) such as Saran ® - (Trademark of The Dow Chemical Company) and metallized films.
• PVDC polyvinyhdene dichlo ⁇ de
• Saran ® - Trademark of The Dow Chemical Company
• the film structure 30 for the pouch of the present invention comp ⁇ ses a homogeneously branched linear ethylene polymer seal layer 31 and at least one polymeric outer layer 32.
• the polymeric outer layer 32 is preferably a polyethylene film layer, more preferably a heterogeneously branched linear polyethylene referred to hereinafter as 'linear low density polyethylene" (“LLDPE”) or a combination thereof “ultra linear low density polyethylene” (“ULDPE”) or a combination thereof “very low density polyethylene (“VLDPE”) or a combination thereof "homogeneously branched substantially linear ethylene polymer”(SLEP)
• LLDPE 'linear low density polyethylene
• ULDPE ultra linear low density polyethylene
• VLDPE very low density polyethylene
• SLEP homogeneously branched substantially linear ethylene polymer
• An example of a commercially available LLDPE is DOWLEX ® 2045 (Trademark of and commercially available from The Dow Chemical Company)
• the LLDPE (including both the VLDPE and ULDPE) useful herein are heterogeneously branched linear copolymers of ethylene and a minor amount of an alpha-olefin having from 3 to 18 carbon atoms, preferably from 4 to 10 carbon atoms (for example, 1-butene, 4-methyl- 1 -pentene 1-hexene, 1 -octene, and 1-decene) and most preferably 8 carbon atoms (for example, 1 -octene)
• the heterogeneously branched LLDPE are made using Ziegler catalysts (for example, using the method described in U S Patent No 4,076,698 (Anderson et al )
• the LLDPE for the outer layer 32 generally has a density greater than 0 87 g/cm-', more preferably from 0 9 to 0 93 g/cm ⁇ , generally has a melt index (I2) from 0 1 to 10 g/10 min, preferably from 0 5 to 2 g/10 min, and generally has an l ⁇ /l2 ratl ° from 5 to 20, preferably from 7 to 20
• the I10 I2 ratio tends to increase as the molecular weight (M /M n ) of the
• LLDPE increases, in surprising contradistinction to the novel homogeneously branched linear ethylene/ ⁇ -olefm mterpolymers and copolymers discussed herein
• the homogeneously branched substantially linear ethylene/ ⁇ -olefin interpolymer (SLEP) for the outer layer 32 made using the method described in U S Patent Nos 5,272,236 and 5,278,272, has a melt index, I2, from 0 01 grams/10 minutes to
• the thickness of the outer layer 32 may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)
• Another embodiment of the film structure 30 for the pouch of the present invention, shown in Figure 4 comprises the polymeric layer 32 sandwiched between two polymeric seal layers 31
• Still another embodiment of the film structure 30 for the pouch of the present invention comp ⁇ ses at least one polyme ⁇ c core layer 33 between at least one polyme ⁇ c outer layer 32 and at least one polymeric seal layer 31
• the polymeric layer 33 may be the same LLDPE or a combination thereof SLEP film layer as the outer layer 32 or preferably a different LLDPE or a combination thereof SLEP, and more preferably an LLDPE or a combination thereof SLEP that has a higher density than the outer layer 32
• the thickness of the core layer 33 may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)
• Yet another embodiment (not shown) of the film structure for the pouch of the present invention can be a structure including a seal layer 31 and another polyethylene film layer referred to hereinafter as "high pressure low-density polyethylene" ("LDPE")
• LDPE high pressure low-density polyethylene
• the LDPE layer generally has a density from 0 916 to 0 930 g/c ⁇ H and has a melt index from 0 1 to 10 g/10 mm
• the thickness of the LDPE layer may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)
• Still another embodiment (not shown) of the film structure for the pouch of the present invention can be a structure including a seal layer 31 and a layer of EVA copolymer having a weight ratio of ethylene to vinyl acetate from 2 2 1 to 24 1 and a melt index of from 0 2 to 20 g/10 min
• the thickness of the EVA layer may be any thickness so long as the seal layer 31 has a minimum thickness of about 0 1 mil (2 5 microns)
• the thickness of the film structure used for making the pouch of the present invention is from 0 5 mil (12 7 microns) to 10 mils (254 microns), preferably from 1 mil (25 4 microns) to 5 mils (127 microns)
• the film structure for the pouches of the present invention has design flexibility
• Different LLDPEs for example, VLDPE and ULDPE
• SLEPs can be used in the outer and core layers to optimize specific film properties such as film stiffness and film physical properties
• the film can be optimized for specific applications such as for a form, film and seal machine
• the polyethylene film structure used to make a pouch of the present invention is made by either the blown tube extrusion method or the cast extrusion method, methods well known m the art.
• the blown tube extrusion method is descnbed, for example, in Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 1 1, pages 264 to 266.
• the cast extrusion method is descnbed, for example, in Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 11, pages 256 to 257.
• Embodiments of the pouches of the present invention are hermetically sealed containers filled with "flowable matenals".
• flowable materials it is meant matenals which are flowable under gravity or which may be pumped, but the term “flowable matenals” does not include gaseous materials
• the flowable materials include noncarbonated liquids (for example, milk, water, fruit juice, wine) and carbonated liquids (for example, soda, beer, water), emulsions (for example, ice cream mix, soft margarine), pastes (for example, meat pastes, peanut butter); preserves (for example, jams, pie fillings, marmalade), jellies; doughs; ground meat (for example, sausage meat); powders (for example, gelatin powders, detergents), granular solids (for example, nuts, sugar, cereal); and like materials.
• the pouch of the present invention is particularly useful for packaging liquids (for example, milk).
• the flowable material may also include oleaginous liquids (for example, cooking
• a pouch 10 being a tubular member 1 1 having a longitudinal lap seal 12 and transverse seals 13 such that, a "pillow-shaped" pouch is formed when the pouch is filled with flowable mate ⁇ al
• a pouch 20 being a tubular member 21 having a penpheral fin seal 22 along three sides of the tubular member 1 1, that is, the top seal 22a and the longitudinal side seals 22b and 22c, and having a bottom substantially concave or "bowl-shaped” member 23 sealed to the bottom portion of the tubular seal 21 such that when viewed in cross-section, longitudinally, substantially a semi-circular or "bowed-shaped" bottom portion is formed when the pouch is filled with flowable material.
• the pouch manufactured according to the present invention is preferably the pouch shown m Figure 1 made on so-called vertical form, fill and seal (VFFS) machines well known in the art
• VFFS vertical form, fill and seal
• Examples of commercially available VFFS machines include those manufactured by Hayssen or Prepac
• a VFFS machine is descnbed in the following reference F C Lewis, "Form-Fill-Seal," Packaging Encyclopedia, page 180, 1980
• a sheet of the plastic film structure descnbed herein is fed into a VFFS machine where the sheet is formed into a continuous tube in a tube-forming section
• the tubular member is formed by sealing the longitudinal edges of the film together — either by lapping the plastic film and sealing the film using an inside/outside seal or by fin sealing the plastic film using an inside/inside seal
• a sealing bar seals the tube transversely at one end being the bottom of the "pouch", and then the fill material, for example milk, is added to the "pouch " The sealing bar then seals the top
• the capacity of the pouches of the present invention may vary Generally, the pouches may contain from 5 milliliters to 10 liters, preferably from 10 millihters to 8 liters, and more preferably from 1 liter to 5 liters of flowable matenal
• the use of the homogeneously branched linear ethylene/ ⁇ -olefin interpolymer seal layer of the present invention in a two or three-layer coextruded film product will provide a film structure that can be used for making pouches at a faster rate in the VFFS and such pouches produced will contain fewer leakers
• the pouches of the present invention can also be printed by using techniques known in the art, e g , use of corona discharge or flame treatment before pnntmg
• the pouches of the present invention made of thin film, used for liquid packaging, offers many advantages over the containers used in the past
• the pouches ( 1 ) consume less natural resources, (2) require less space in a landfill, (3) can be recycled, (4) can be processed easily, (5) require less storage space, (6) use less energy for storage (heat transfer properties of package), (7) can be safely incinerated and (8) can be reused (for example, the empty pouches can be used for other applications such as freezer bags, sandwich bags, and general purpose storage bags).
• Layer B was an ethylene/ 1 -octene LLDPE having a melt index (I2) of about 1 g/10 minute and a density of about 0 92 g/cm-' and does not contain additives
• resins 1-3 were all heterogeneously branched ethylene/ 1 -octene copolymers
• resins 4-7 were all homogeneously branched substantially linear ethylene/ 1 -octene copolymers
• resins 9 -1 1 were all homogeneously branched linear ethylene polymer (HBLEP),.
• Table 1 summarizes physical properties of the resins used to make A B/A coextruded blown film samples descnbed in the examples and comparative examples.
• Resins 1, 2, 5, 6, and 7 were dry blended to contain 4,000 ppm S1O2 and 1 ,200 ppm Erucamide.
• Resin 3 was dry blended to contain 6,000 ppm S1O2 and 1,200 ppm Erucamide.
• Resin 4 was dry blended to contain 14,000 ppm S1O2 and 1,200 ppm Erucamide.
• Resin 8 was a monolayer milk pouch film designated "SM3" made by and available from DuPont Canada and was believed to be a blend of about 8 percent (by weight) of a low density polyethylene having a density of about 0.92 g/cm ⁇ and about 92 percent (by weight) of a heterogeneously branched linear low density Resin 9, 10 and 11 were dry blended to contain 4,000 PPM S ⁇ 0 2 and 1,000 ppm Erucamide.
• the SM3 film has a final film density reported by DuPont as 0.918 g/cirA
• Extruder A has a 2.5 inch diameter screw (Barr2 type) equipped with a Maddox mixer, L/D of 24 1 , 60 HP drive
• Extruder B has a 2 5 inch diameter screw (DSB II type) equipped with a Maddox mixer, L/D of 24 1 , 75 HP drive
• Extruder C has a 2 inch diameter screw (Modified MHD (Johnson) type) equipped with a Maddox mixer, L/D of 24 1, 20 HP drive
• the blown film line was also equipped with an 8 inch 3-layer coextruding die body, a Gloucester Tower, a Sano collapsing frame, a Sano bubble sizing cage, and a Sano bubble enclosure
• Puncture Puncture was measured by using an Instron Tensile Tester with an integrator, a specimen holder, and a puncturing device
• the Instron was set to obtain a crosshead speed of 10 inches/minute and a chart speed (if used) of 10 inches/minute Load range of 50 percent of the load cell capacity ( 100 lb load for these tests) should be used
• the puncturing device was installed to the Instron such that the clamping unit was attached to the lower mount and the ball was attached to the upper mount on the crosshead
• Five film specimens were used (each 6 inches square) The specimen was clamped in the film holder and the film holder was secured to the mounting bracket
• the crosshead travel was set and continues until the specimen breaks Puncture resistance was defined as the energy to puncture divided by the volume of the film under test Puncture resistance (PR) was calculated as follows
• PR puncture resistance (ft-lbs/in- 3 )
• Coefficient of friction range was important in order for the film to properly move over the forming collars in a vertical- form-fill and seal machine (for example, a Hayssen form-fill-seal machine): if the coefficient of friction was too low, the film may be too slippery for the pull belts to grip the film and if the coefficient of friction was too high, the film may be too tacky for the machine to pull the film over the forming collar; typical targets for the Hayssen form-fill- seal machine were:
• Heat Seal Strength This test measures the force required to separate a seal after the seal has been allowed to cool. Seals were made using the DTC Hot Tack Tester but only the heat seal portion of the unit was used. Conditions used were: Specimen width: 24.4 mm Sealing time: 0.5 seconds Sealing pressure: 0.27 N/mm/mm No. samples/time: 5
• Seal strength was determined using an Instron Tensile Tester Model No. 1 122. The film samples were exposed to relative humidity of 50 percent and a temperature of 23°C for 24-48 hours prior to testing. Instron test conditions were as follows:
• Hot Tack Performance The hot tack test measures the force required to separate a heat seal before the seal has had a chance to cool. This test simulates filling a pouch with material just after the seal was made. The hot tack strength was typically the limiting factor in increasing line speeds of a pouch manufacturing and filling operation. In this test, the films were tested using a DTC Hot Tack Tester Model No.
• Hot tack failure of the seals generally occurs in three stages: no seal; seals which pull apart (peeling); and film failure (where the molten film pulls apart with no apparent effect on the seal). Film failure region begins where the hot tack strength reaches a maximum level. In each case, film failure occurs just in front of the seal. A force of 1 N/inch was arbitrarily selected to determine the seal initiation temperature.
• Knife on from 146° to 265° Jaw close: from 136° to 275° Platen: on from 136° to 265° Stager: off Auxiliary: on from 137° to 355°
• Bag eject on End air seal: 200 ms
• Type of side seal lap, and Seam seal temperature: 260°F.
• a Pro/Fill 3000 liquid filler was attached to the VFFS
• films made using both the heterogeneously branched ethylene/ ⁇ -olefin copolymers and those made using the novel homogeneously branched linear ethylene/ ⁇ -olefin inte ⁇ olymer have higher dart impact strength than the commercially available SM3 film.
• Table 3 shows that films made using the novel homogeneously branched linear ethylene/ ⁇ -olefin inte ⁇ olymer have higher hot tack strength than film made from homogeneously branched substantially linear ethylene / ⁇ - olefin inte ⁇ olymer or heterogeneously branched ethylene/ ⁇ -olefin copolymers and higher
• resin 10 and comparative resin 2 have similar densities, but pouches made from resin 10 have a lower percent failure than pouches made from comparative resin 2.
• Pouches made using resin 1 1 also have lower percent failure than do pouches made using comparative resin 3, even though the resins have similar density.

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• 1998
  • 1998-07-28 AU AU86057/98A patent/AU8605798A/en not_active Withdrawn
  • 1998-07-28 WO PCT/US1998/016057 patent/WO1999006476A1/en not_active Application Discontinuation
  • 1998-08-03 TW TW087112754A patent/TW403709B/zh not_active IP Right Cessation
  • 1998-08-04 AR ARP980103851A patent/AR016585A1/es unknown

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