GB2121062A - Heat sealable plastics pouches - Google Patents

Heat sealable plastics pouches Download PDF

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Publication number
GB2121062A
GB2121062A GB08315071A GB8315071A GB2121062A GB 2121062 A GB2121062 A GB 2121062A GB 08315071 A GB08315071 A GB 08315071A GB 8315071 A GB8315071 A GB 8315071A GB 2121062 A GB2121062 A GB 2121062A
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United Kingdom
Prior art keywords
ethylene
film
copolymer
vinyl acetate
pouch
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Granted
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GB08315071A
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GB2121062B (en
GB8315071D0 (en
Inventor
Alistair Norman Mollison
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DuPont Canada Inc
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DuPont Canada Inc
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Priority to GB08315071A priority Critical patent/GB2121062B/en
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    • 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
    • B32B1/00—Layered products having a non-planar shape
    • B32B1/08—Tubular products
    • 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
    • B32B27/302—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
    • 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
    • B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
    • 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
    • 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
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B32B27/322—Layered products comprising a layer of synthetic resin comprising polyolefins comprising halogenated polyolefins, e.g. PTFE
    • 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
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • 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
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • 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
    • 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
    • B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
    • 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
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/718—Weight, e.g. weight per square meter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/72—Density
    • 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
    • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
    • B32B2309/08—Dimensions, e.g. volume
    • B32B2309/10—Dimensions, e.g. volume linear, e.g. length, distance, width
    • B32B2309/105—Thickness
    • 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
    • B32B2367/00—Polyesters, e.g. PET, i.e. polyethylene terephthalate
    • 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
    • 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
    • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
    • C08L23/0853—Vinylacetate

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

Pouches for flowable materials e.g. milk, ice cream mix are made from films comprising a blend of (1) a linear ethylene-C4-C10 ???-olefin copolymer having a density of 0.916 to 0.930 g/cm<3> and a melt index of from 0.3 to 2.0 dg/min and (2) an ethylene-vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate from 2.2 to 24 and a melt index of from 0.2 to 10 dg/min. The blend has a ratio of linear ethylene-C4-C10 ???-olefin copolymer to ethylene vinyl acetate copolymer of from 1.2:1 to 9:1. The film may be a laminate, e.g. with nylon.

Description

SPECIFICATION Pouches of ethylene-a-olefin copolymer/ethyleneDvinyl acetate copolymer blends The invention relates to pouches filled with flowable materials, e.g. liquids, particularly to pouches made on so-called vertical form and fill machines.
It is well known to package flowable materials, for example, milk, on a so-called vertical form and fill machine. Using such a machine, a flat web of synthetic thermoplastic film is unwound from a roll and formed into a continuous tube, in a tube-forming section by sealing the longitudinal edges of the film together to form a so-called lap seal or a so-called fin seal. The tube thus formed is pulled vertically downwards to a filling station. The tube is then collapsed across a transverse cross-section of the tube, the position of such cross-section being at a sealing device below the filling station. A transverse heat seal is made, by the sealing device, at the collapsed portion of the tube, thus making an air-tight seal across the tube. The sealing device generally comprises a pair of jaws, and is described more fully hereinbelow.After making the transverse seal, but before the jaws of the sealing device are opened, a pre-set quantity of material to be packaged e.g. liquid is allowed to enter the tube, at the filling station, and fill the tube upwardly from the aforementioned transverse seal. The tube is then allowed to drop a predetermined distance under the influence of the weight of the material in the tube. The jaws of the sealing device are closed again, thus collapsing the tube at a second transverse section, which is above, usually just above, the air/material interface in the tube. The sealing device seals and severs the tube transversely at the second transverse section. The material-filled portion of the tube is now in the form of a pillow shaped pouch.Thus the sealing device has sealed the top of a filled pouch, sealed the bottom of the next-to-be-formed pouch and separated the filled pouch from the next-to-be-formed pouch, all in one operation.
One vertical form and fill machine of the type described above is a Prepac*lS-6 liquid packaging machine.
A sealing device commonly used is a so-called impulse sealer which has a sealing element mounted in sealing jaws and electrically insulated therefrom. In operation the sealing jaws are closed and an electrical current is caused to flow through a sealing element e.g. a wire, for a fraction of the time that the jaws are closed. The jaws remain closed during a cooling period in which the seals partially solidify before the sealing jaws are opened. The transverse seal thus obtained suppots the weight of the flowable material e.g. liquid, in the next-to-be-formed pouch.
A sealing element made of round wire e.g. "piano" wire about 1.6 to 2.5 mm diameter, electrically insulated from a water cooled supporting jaw, may be used but a wire of rectangular cross-section is preferred. These types of sealing elements may be used for making both the longitudinal and transverse seals.
The temperature of the sealing element during passage of the electrical current is largely determined by the resistance of the sealing element, the voltage applied across the element, the heat transfer rate through the film being sealed and the temperature and mass of the jaw of the sealing device. As may be seen, operation of the impulse sealer may affect the seal strength and it is desirable to optimize such operation.
When a liquid is packaged in pouches as described above, the liquid, especially if aqueous, aids in cooling the transverse seal in the tube after the sealing jaws are opened, because of the liquid's relatively high thermal conductivity. It appears that the cooling effect of the liquid on the seal takes effect before the weight of the liquid can weaken or rupture the bottom seal.
U.S. Patent 3 682 767 issued 1979 August 8 to Britton et al, discloses liquid filled pouches made from films of blends of a) 90-50 wt.% of a random copolymer of ethylene and an olefinic unsaturated monomer e.g. vinyl acetate, which is present in the amount of 2-10 wt.% of the copolymer and b) 10-50% of a linear copolymer of ethylene and a C3-C20 a-olefin of a density of about 0.930 to 0.960 g/cm3.
It is more common, commercially, to use film made from a blend containing 70-90% linear ethylene-butene copolymer having a density of about 0.919 g/cm3 and a melt index of about 0.75 dg/min and 10-30% high pressure polyethylene i.e. a homopolymer, having a melt index of about 2 to 10 and a density of from 0.916 to 0.924 g/cm3. Density is determined by ASTM Procedure D1505-68 and melt index by ASTM Procedure D1238-79 (Condition E). Such films having a thickness of about 76 micrometres, have been used for making pouches containing about 1.3 litres of milk. Pouches made from such film are generally satisfactory from the standpoint of pouch toughness and puncture resistance, but suffer from a tendency to have weak transverse end and/or longitudinal seals even though the operating conditions of the impulse sealer have been optimized.Defective seals may lead to the phenomenon known as "leakers", in which the flowable material e.g. milk, may escape from the pouch through pinholes which develop at or close to the seal. It has been estimated that leakers account for about 1-2% of the 1.3 litre milk pouch production.
It has been proposed that increasing the film thickness would overcome the problem of leakers. However, it has been shown that even at film thicknesses of up to about 1 27 micrometres the percentage of leakers is not substantially reduced and yet the cost of the unfilled pouch is increased in proportion to the increase in thickness of the film.
It has been suggested that melt strength, hot tack strength and heat-seal strength would be good measures on which to select films to produce pouches having improved seal integrity and therefore reduce the number of leakers. On these bases, however, it appears that one skilled in the art would not have any reason to believe that other polyolefins or blends of polyolefins perform any better than the aforementioned blend of linear ethylene-butene copolymer and high pressure polyethylene. Surprisingly, however, it has now been found that pouches made from certain films of linear copolymers of ethylene and a C4-Cro a-olefin, admixed with ethylene-vinyl acetate copolymers (EVA resins) give substantially better performance with respct to the problem of leakers.Indeed, because of this improved performance it is possible to make pouches of film with thinner film than was heretofore possible with the aforementioned film of the blend of ethylene-butene copolymer and high pressure polyethylene.
Accordingly the present invention provides a pouch containing a flowable material, said pouch being made from a sealant film in tubular form and having transversely heat-sealed ends, said film being made from a blend of a linear ethylene-C4-C10 a-olefin copolymer and an ethylenevinyl-acetate copolymer, said ethylene-C4-C10 a-olefin copolymer having a density of from 0.916 to 0.93Q g/cm3 and a melt index of from 0.3 to 2.0 dg/min, said ethylene-vinyl acetate 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 10 dg/min, said blend having a weight ratio of linear ethylene-C4-C,O CL- olefin copolymer to ethylene vinyl acetate copolymer of from 1.2:1 to 9:1.
A preferred blend has a weight ratio of linear ethylene-C4-C10 a-olefin copolymer to ethylenevinyl acetate copolymer of 2.33:1 to 9:1.
In a further embodiment the blend of linear ethylene-C4-C,0 a-olefin copolymer and ethylene vinyl acetate copolymer additionally contains from 1 3 to 1 8 parts of a high pressure polyethylene having a density in the range of 0.916 to 0.924 g/cm3 and a melt index in the range of 2 to 10 dg/min per 100 parts of said copolymer blend.
In another embodiment the ethylene-C4-C10 a-olefin is selected from ethylene-butene or ethylene-octene copolymer, especially ethylene-octene copolymer.
In a further embodiment the film has a thickness from 38 to 127 ym, preferably from 51 jtm to 102 im.
In another embodiment the pouch contains from about 1.25 to 2 litres of a liquid or emulsion and the film thickness is from about 51 to 1 27,us.
While the invention is particularly useful for packaging flowable liquids, e.g. water, milk, or thin emulsions e.g. ice cream mix, it is also applicable to other flowable materials e.g. powders, nuts.
In a specific embodiment the pouch contains from about 0.1 to 5 litres, particularly from 1 to 2 litres, of a flowable material. Preferably the flowable material is a liquid, especially milk, water, fruit juice, or an emulsion, e.g. ice cream mix, soft margarine.
The present invention also provides a pouch containing a flowable material, said pouch being made from a film in tubular form and having transversely heat-sealed ends, said film comprising a laminate of a base film selected from nylon film, polyethylene terephthalate film, polyvinylidene chloride film, polyvinylchloride film, polyacrylonitrile film, polystyrene film and saponified ethylene-vinyl acetate film and a sealant film of a blend of a linear ethylene-C4-C10 a-olefin copolymer and an ethylene-vinyl acetate copolymer, said ethylene-C4-C,O a-olefin copolymer having a density of from 0.916 to 0.930 g/cm3 and a melt index of from 0.3 to 2.0 dg/min, said ethylene-vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate of from 2.2:1 to 24::1 and a melt index of from 0.2 to 10 dg/min, said blend having a weight ratio of linear ethylene C4-C10 a-olefin copolymer to ethylene-vinyl acetate copolymer of from 1.2:1 to 9:1, said sealant film being on the inside of the pouch. The laminate may comprise a base film sandwiched between two sealant films.
In a preferred embodiment the weight ratio of ethylene-C4-C,0 a-olefin copolymer to ethylenevinyl acetate co-polymer is from 2.33:1 to 9:1.
In another embodiment the blend of ethylene-C4-C10 a-olefin copolymer and ethylene-vinyl acetate copolymer contains from 1 3 to 1 8 parts of a high pressure polyethylene per 100 parts of said blend, said high pressure polyethylene having a melt index in the range of 2 to 10 dg/min and a density of from 0.916 to 0.924 g/cm3.
In a further embodiment the base film is selected from nylon 66, nylon 6, nylon 66/6 copolymer, nylon 6/10 copolymer, nylon 6/11 copolymer and nylon 6/12 copolymer.
Preferably the base film is nylon 66, nylon 6 or nylon 66/6 copolymer.
In yet another embodiment, the base film and the sealant film have a layer of PVDC interposed there between.
In another embodiment the flowable material is an oil, especially vegetable oil or motor oil and the base film is a nylon film.
The present invention also provides, in a process for making pouches filled with a flowable material on a vertical form and fill machine, in which each pouch is made from a flat web of film by forming a tubular film therefrom with a longitudinal seal and subsequently flattening the tubular film at a first position and transversely heat sealing said tubular film at the flattened position, filling the tubular film with a predetermined quantity of flowable material above said first position, flattening the tubular film above the predetermined quantity of flowable material at a second position and transversely heat sealing said tubular film at the second position, the improvement comprising making the pouches from a flat web of film made from 60 to 90 parts ethylene-C4-C,0 a-olefin copolymer having a density from 0.916 to 0.930 g/cm3 and a melt index from 0.3 to 2.0 dg/min admixed with 10 to 40 parts ethylene-vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate of from 2.2. 24 and a melt index of from 0.2 to 10 dg/min.
In a preferred embodiment the film web used in the process is made from the blend of the linear ethylene-C4-C,0 a-olefin copolymer and ethylene-vinyl acetate copolymer which additionally contains from 1 3 to 1 8 parts of a high presure polyethylene having a density in the range of 0.916 to 0.924 g/cm3 and a melt index in the range of 2 to 10 dg/min per 100 parts of said blend.
In another embodiment the ethylene-C4-C10 a-olefin is selected from ethylene-butene or ethylene-octene copolymer, especially ethylene-octene copolymer.
The linear ethylene-C4-C,0 a-olefin copolymer useful in the present invention may be made from ethylene and an a-olefin by a process disclosed in Canadian patent 856 1 37 which issued 1970 November 7 to W.E. Baker, l.C.B. Saunders and J.M. Stewart. The linear ethylene-C4-C,0 a-olefin copolymer may also be made by other processes known to those skilled in the art.
The ethylene-C4-C,0 a-olefin copolymer ethylene-vinyl acetate copolymer and high pressure polyethylene are often available in pellet form.
Blends of the pelleted polymers may be fed into a film extruder and extruded into film form. A preferred film manufacturing method is the so-called blown film process disclosed in Canadian patent 460 963 issued 1949 November 8 to E.l. Fuller. Films may also be made using an internal or external cooling mandrel with the blown film process, as disclosed for example in Canadian patent 893 216 issued 1972 February 15 to M. Bunga and C.V. Thomas. The copolymers, and high pressure polyethylene if present, may be blended prior to feeding to the film extruder hopper, or may be blended at the time of extrusion just prior to melting in the extruder, or alternatively may be melt blended in the extruder. The film, after manufacture, is slit longitudinally into appropriate widths.The width determines the diameter of the tube formed on the vertical form and fill machine.
Preferably, film having a thickness of 51 to 127,um in thickness, especally 63 to 76 cm in thickness, is used for the pouches of the present invention.
Pouches containing flowable materials may then be formed in the general manner described hereinbefore on a vertical form and fill machine e.g. Prepac IS-2 or IS-6 liquid packaging machine, using the ethylene-C4-C10 a-olefin copolymer/ethylene-vinyl acetate copolymer film described herein.
When the film is a single layer, the pouch may have a fin seal or a lap seal.
When the pouch is made from a laminate as described hereinbefore, the sealing device may more advantageously comprise two sealing elements and a severing element as described in U.K. patent 1 377 149 granted 1 975 April 9 to R.E. Pedersen. With such a sealing device two transverse seals are made across the tubular film above and below the transverse sections described hereinbefore and the tubular film is severed between the two transverse seals.
Film laminates as described herein, having nylon, particularly nylon 66, nylon 6 or nylon 66/6 copolymer base film are particularly desirable for packaging oleagenous liquids e.g.
cooking oil, motor oil. The nylon film may be cast or oriented.
As indicated hereinbefore, examination of melt strength, hot tack strength and heat seal strength data for the linear ethylene-C4-C,0 a-olefin copolymer/ethylene-vinyl acetate copolymer blends used in the present invention leads one skilled in the art to believe that there would be no improvement in the number of leakers with pouches from such blends compared to that experienced with pouches made from a blend of linear ethylene-butene copolymer and high pressure polyethylene. In order to illustrate the lack of correlation between melt strength, hot tack strength and heat seal strength with pouch performance, several samples of films, were taken and melt strength, hot tack strength and heat seal strength were measured. 2 litre pouches of water were made using such films and the number of leakers determined by means of a drop test.In the drop test the pouches were dropped end-wise 1 52.4 cm onto a concrete floor.
Melt strength, is the weight of extrudate which will remain suspended for a period of 3 minutes from the orifice of a standard melt index tester (ASTM Procedure D1238-79). Heat seal strength is determined using a peel strength test similar to that used in ASTM Procedure D903 on a sample of film sealed using a Sentinel heat seal apparatus. Hot tack strength may be determined by ASTM Procedure D3706.
TABLE I Heat Seal Hot Tack Melt Strength Strength Strength (g/1/2") (9/ 1) Seal Film (g/3min) 180"C 190"C Failures A 0.31 2080 300 11.6 B 0.63 2040 300 2.3 C 0.38 2300 300 1.7 D 0.29 1950 800 10.3 E 0.49 1397 500 0.4 Film A is 76,um in thickness and is made from a blend of 85 parts of a linear ethylene-abutene copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min and 15 parts of a high pressure polyethylene having a density of 0.918 g/cm3 and a melt index of 8.5 dg/min.
Film B is 76 jim in thickness and is made from a blend of 85 parts of the blend of Film A and 1 5 parts of an ethylene-vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 1 2 wt%.
Film C is 76 m in thickness and is made from a blend of 85 parts of Polymer A and 1 5 parts of an ethylene-vinyl acetate copolymer having a melt index of 0.7 dg/min and a vinyl acetate content of 18 wt%.
Film D is 51 ym in thickness and is made from an ethylene-a-octene copolymer having a density of 0.918 g/cm3 and a melt index of 0.84 dg/min.
Film E is 51 pm in thickness and is made from the ethylene-a-octene copolymer of Film D and 20 wt% of the ethylene-vinyl acetate of Film B.
Pouches made from Films B, C and E are within the scope of the present invention.
From the values of melt strength, hot tack strength and heat seal strength data it would be expected that the ethylene-a-olefin copolymer/ethylene-vinyl acetate copolymer and, optionally, high pressure polyethylene blend film would show little, if any, advantage over the ethylenebutene copolymer/high pressure polyethylene blend film.
The following examples further serve to illustrate the invention.
Example 1 The following resins and/or resin blends were evaluated for their performance as liquid packaging films: A. 85 parts of an ethylene-butene copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min blended with 1 5 parts of a high pressure polyethylene having a density of 0.918 g/cm3 and a melt index of 8.5 dg/min; B. 85 parts of the resin blend in A in turn blended with 1 5 parts of an ethylene-vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 1 2 wt%; C. 85 parts of the resin blend in A in turn blended with 1 5 parts of an ethylene-vinyl acetate copolymer having a melt index of 0.7 dg/min and a vinyl acetate content of 18 wt%.
Blend A is not within the scope of the present invention and exemplifies the prior art.
The resins or resin blends were extruded into films of various gauges at 409 kg/hr using a extruder equipped with a 81.3 cm diameter circular die, and a melt temperature of 232"C, and cooled by an internal cooling mandrel.
The films were processed into 2 litre pouches, substantially filled with water, using a Prepac IS-6 liquid packaging machine. The pouches were subsequently tested for seal integrity by dropping them from a height of 152.4 cm and determining the percentage seal failures.
% Seal Failures 51 cm 76 jum 102 fim A 100 11.6 11.3 B 0.9 2.3 2.7 C 1.0 1.7 0.3 Example 2 Resin composition A of Example I above was blended with a number of ethylene-vinyl acetate copolymers (EVA resins) outlined below and extruded into 76 pm films. The resin blends were extruded at a rate of 38.6 kg/hr through a 22.9 cm diameter circular die at a melt temperature of 221"C. The films were processed into 1.3 litre pouches, substantially filled with water using a Prepac IS-6 liquid packaging machine. The pouches were subsequently tested for seal integrity by dropping them from a height of 152.4 cm. and determining the percentage seal failures.
Wt.% EVA Resin Vinyl Acetate Melt Index in the EVA % Seal Sample (dg/min) Resin Failures A - 50 A+15%EVAl 0.3 12.0 2 A 15% EVA II 1.2 7.5 40 A+30%EVAIl 1.2 7.5 23 A+45%EVAIl 1.2 7.5 5 A + 30% EVA lil 0.8 9.5 38 A + 15% EVA IV 3.0 28.0 0 A+15%EVAV 0.7 18.0 0 A+30%EVAVl 7.0 9.0 7 A+45%EVAVl 7.0 9.0 3 A+15%EVAVll 8.0 18.0 5 Example 3 The following resins and/or resin blends were evaluated for their performance as liquid packaging films:: A. 85 parts of an ethylene-butene copolymer having a density of 0.919 gm/cm3 and a melt index of 0.75 dg/min blended with 15 parts of a high pressure polyethylene having a density of 0.918 gm/cm3 and a melt index of 8.5 dg/min; E. 85 parts of an ethylene-octene copolymer having a density of 0.918 g/cm3 and a melt index of 0.84 dg/min blended with 15 parts of an ethylene-vinyl acetate copolymer having a melt index of 3 dg/min and containing 28 wt% vinyl acetate; F. 70 parts of an ethylene-octene copolymer having a density of 0.918 g/cm and a melt index of 0.84 dg/min blended with 30 parts of an ethylene-vinyl acetate copolymer having a melt index of 1.2 dg/min and containing 7.5 wt% vinyl acetate.
Blend A is not within the scope of the present invention and exemplifies the prior art.
The resins were extruded at a rate of 38.6 kg/hr. through a 22.9 cm diameter circular die at a temperature of 221 C, and cooled by an internal cooling mandrel. The films were subsequently processed into 1.3 litre pouches using a Prepac IS-6 liquid packaging machine. The pouches were subsequently tested for seal integrity by dropping them from a height of 152.4 cm. and determining the percentage failures.
Blend % Seal Failures A 50 E 0 F 0 * denotes trade mark.

Claims (11)

1. A pouch containing a flowable material said pouch being made from a sealant film in tubular form and having transversely heat-sealed ends, said film being made from a blend of a linear ethylene-C4-C,0 a-olefin copolymer and an ethylene-vinyl acetate copolymer, said ethylene-C4-C10 a-olefin copolymer having a density of from 0.916 to 0.930 g/cm3 and a melt index of from 0.3 to 2.0 dg/min, said ethylene-vinyl acetate 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 10 dg/min, said blend having a weight ratio of linear ethylene-C4-C10 a-olefin copolymer to ethylene-vinyl acetate copolymer of from 1.2:1 to 9:1.
2. A pouch according to claim 1 wherein the weight ratio of linear ethylene-C4-C10 a-olefin copolymer to ethylene-vinyl acetate copolymer is from 2.3:1 to 9:1.
3. A pouch according to claim 1 or claim 2, wherein the blend of linear ethylene-C4-C10-aolefin copolymer and ethylene-vinyl acetate copolymer additionally contains from 1 3 to 1 8 parts of a high pressure polyethylene having a density in the range of 0.916 to 0.924 g/cm3 and a melt index in the range of 2 to 10 dg/min per 100 parts of said copolymer blend.
4. A pouch according to any preceding claim wherein the ethylene-C4-C10 a-olefin copolymer is ethylene-a-butene or ethylene-a-octene copolymer.
5. A pouch according to any preceding claim wherein the film has a thickness from 38 to 127,us.
6. A pouch according to claim 5 wherein the film thickness is from 51 to 127 jum and the pouch contains from about 1.25 to 2 litres of the flowable material.
7. A pouch according to any preceding claim wherein the flowable material is a liquid or an emulsion.
8. A pouch according to claim 1, wherein the film is substantially the same as any one of the examples herein, other than the examples included for comparison only.
9. A pouch containing a flowable material said pouch being made from a film in tubular form and having transversely heat-sealed ends, said film comprising a laminate of a base film, and a sealant film, said base film being selected from nylon film, polyethylene terephthalate film, polyvinylidene chloride film, polyvinylchloride film, polyacrylonitrile film, polystyrene film and saponified ethylene vinyl acetate film and said sealant film being made from a blend of a linear ethylene-C4-C10 a-olefin copolymer and an ethylene-vinyl acetate copolymer, said ethylene-C4-C10 a-olefin copolymer having a density of from 0.916 to 0.930 g/cm3 and a melt index of from 0.3 to 2.0 dg/min, said ethylene-vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate of from 2.2:1 to 24: :1 and a melt index of from 0.2 to 10 dg/min, said blend having a weight ratio of linear ethylene-C4-C10 a-olefin copolymer to ethylene-vinyl acetate copolymer of from 1.2:1 to 9:1 said sealant film being on the inside of the pouch.
10. A pouch according to claim 9 wherein the base film is selected from nylon 66, nylon 6, nylon 66/6 copolymer, nylon 6/10 copolymer, nylon 6/11 copolymer and nylon 6/12 copolymer.
11. A pouch according to claim 9 or claim 10 wherein the laminate comprises a base film sandwiched between two sealant films.
GB08315071A 1982-06-02 1983-06-01 Heat sealable plastics pouches Expired GB2121062B (en)

Priority Applications (1)

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GB8216101 1982-06-02
GB08315071A GB2121062B (en) 1982-06-02 1983-06-01 Heat sealable plastics pouches

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GB2121062A true GB2121062A (en) 1983-12-14
GB2121062B GB2121062B (en) 1985-10-30

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4684573A (en) * 1985-03-07 1987-08-04 W. R. Grace & Co., Cryovac Div. High oxygen barrier composite film
EP0244982A2 (en) * 1986-04-25 1987-11-11 REXENE PRODUCTS COMPANY (A Delaware Corporation) Film compositions
US4729926A (en) * 1986-05-16 1988-03-08 W. R. Grace & Co., Cryovac Div. Packaging material for long-term storage of shelf stable food products and method of making same
US4792488A (en) * 1985-10-11 1988-12-20 W. R. Grace & Co. High oxygen barrier coextruded film
EP0316037A1 (en) * 1987-11-05 1989-05-17 van der Groep, Lambertus Adrianus A polymer composition, a process for its manufacture, and a thermoplastic polymer composition
EP0323852A2 (en) * 1988-01-06 1989-07-12 Viskase Corporation Multilayer thermoplastic film
EP0346944A2 (en) * 1982-04-26 1989-12-20 American National Can Company Polymeric composition of matter, oriented polymeric films and shrink bags made therefrom
EP0372886A2 (en) * 1988-12-05 1990-06-13 Du Pont Canada Inc. Film laminate with easy TD tear
US5035851A (en) * 1986-11-25 1991-07-30 W. R. Grace & Co.-Conn. Method of making very high barrier film
US5061534A (en) * 1988-04-22 1991-10-29 American National Can Company High oxygen barrier film
EP0479579A1 (en) * 1990-10-02 1992-04-08 Mitsui Petrochemical Industries, Ltd. Ethylene/pentene-1 copolymer compositions
WO1993002859A1 (en) * 1991-08-09 1993-02-18 The Dow Chemical Company Pouch for packaging flowable materials
WO1998018620A1 (en) * 1996-10-29 1998-05-07 Cryovac , Inc. Rf-sealable pillow pouch
WO2004005021A2 (en) * 2002-07-08 2004-01-15 Amcor Flexibles Denmark A/S A sheet material, a package thereof and use thereof for packing

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1312808A (en) * 1969-07-15 1973-04-11 Du Pont Heat-shrinkable ethylene polymer films

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1312808A (en) * 1969-07-15 1973-04-11 Du Pont Heat-shrinkable ethylene polymer films

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0346944A2 (en) * 1982-04-26 1989-12-20 American National Can Company Polymeric composition of matter, oriented polymeric films and shrink bags made therefrom
EP0346944A3 (en) * 1982-04-26 1990-07-25 American National Can Company Polymeric composition of matter, oriented polymeric films and shrink bags made therefrom
US4684573A (en) * 1985-03-07 1987-08-04 W. R. Grace & Co., Cryovac Div. High oxygen barrier composite film
US4792488A (en) * 1985-10-11 1988-12-20 W. R. Grace & Co. High oxygen barrier coextruded film
EP0244982A2 (en) * 1986-04-25 1987-11-11 REXENE PRODUCTS COMPANY (A Delaware Corporation) Film compositions
EP0244982A3 (en) * 1986-04-25 1989-09-27 REXENE PRODUCTS COMPANY (A Delaware Corporation) Film compositions
US4729926A (en) * 1986-05-16 1988-03-08 W. R. Grace & Co., Cryovac Div. Packaging material for long-term storage of shelf stable food products and method of making same
US5035851A (en) * 1986-11-25 1991-07-30 W. R. Grace & Co.-Conn. Method of making very high barrier film
EP0316037A1 (en) * 1987-11-05 1989-05-17 van der Groep, Lambertus Adrianus A polymer composition, a process for its manufacture, and a thermoplastic polymer composition
EP0323852A2 (en) * 1988-01-06 1989-07-12 Viskase Corporation Multilayer thermoplastic film
EP0323852A3 (en) * 1988-01-06 1990-08-16 Viskase Corporation Multilayer thermoplastic film
US5061534A (en) * 1988-04-22 1991-10-29 American National Can Company High oxygen barrier film
EP0372886A3 (en) * 1988-12-05 1991-05-02 Du Pont Canada Inc. Film laminate with easy td tear
AU621686B2 (en) * 1988-12-05 1992-03-19 Du Pont Canada Inc. Film laminate with easy td tear
EP0372886A2 (en) * 1988-12-05 1990-06-13 Du Pont Canada Inc. Film laminate with easy TD tear
US5260382A (en) * 1990-10-02 1993-11-09 Mitsui Petrochemical Industries, Ltd. Ethylene/pentene-1 copolymer compositions
EP0479579A1 (en) * 1990-10-02 1992-04-08 Mitsui Petrochemical Industries, Ltd. Ethylene/pentene-1 copolymer compositions
WO1993002859A1 (en) * 1991-08-09 1993-02-18 The Dow Chemical Company Pouch for packaging flowable materials
US5288531A (en) * 1991-08-09 1994-02-22 The Dow Chemical Company Pouch for packaging flowable materials
US5364486A (en) * 1991-08-09 1994-11-15 The Dow Chemical Company Pouch for packaging flowable materials
AU668879B2 (en) * 1991-08-09 1996-05-23 Dow Chemical Company, The Pouch for packaging flowable materials
WO1998018620A1 (en) * 1996-10-29 1998-05-07 Cryovac , Inc. Rf-sealable pillow pouch
AU727369B2 (en) * 1996-10-29 2000-12-14 Cryovac, Inc. RF-sealable pillow pouch
US6572959B1 (en) 1996-10-29 2003-06-03 Cryovac, Inc. RF-sealable pillow pouch
WO2004005021A2 (en) * 2002-07-08 2004-01-15 Amcor Flexibles Denmark A/S A sheet material, a package thereof and use thereof for packing
WO2004005021A3 (en) * 2002-07-08 2004-05-13 Amcor Flexibles Denmark As A sheet material, a package thereof and use thereof for packing

Also Published As

Publication number Publication date
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GB8315071D0 (en) 1983-07-06

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