WO2005037546A1 - Film multicouche et son procede de preparation - Google Patents

Film multicouche et son procede de preparation Download PDF

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Publication number
WO2005037546A1
WO2005037546A1 PCT/IB2004/003280 IB2004003280W WO2005037546A1 WO 2005037546 A1 WO2005037546 A1 WO 2005037546A1 IB 2004003280 W IB2004003280 W IB 2004003280W WO 2005037546 A1 WO2005037546 A1 WO 2005037546A1
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WO
WIPO (PCT)
Prior art keywords
film
resin
layer
weight
ethylene
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PCT/IB2004/003280
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English (en)
Inventor
Naoki Takagi
Tatsuo Tanaka
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Asahi Kasei Life & Living Corporation
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Publication of WO2005037546A1 publication Critical patent/WO2005037546A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • 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
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/0012—Mechanical treatment, e.g. roughening, deforming, stretching
    • B32B2038/0028—Stretching, elongating
    • 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
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/582—Tearability
    • B32B2307/5825—Tear resistant
    • 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

Definitions

  • the present invention relates to a multilayer film that can be used in a packaging machine particularly for food packaging such as a tray pack.
  • Patent Document 1 discloses a stretch film comprising a core layer made of a polypropylene copolymer resin, two surface layers made of an ethylene-vinyl acetate copolymer, and two intermediate layers made of a linear low-density polyethylene resin having a specific density. While this film has a high flexibility and recoverability, its high self-adhesion is not in compliance with the high speed of a continuous packaging machine. Further, its high flexibility rather deteriorates it cuttability in a packaging machine.
  • Patent Document 2 discloses a stretch shrink film having at least three layers, which comprises an inner layer made of a polypropylene copolymer and two surface layers made of a polyethylene resin.
  • This film can be suitably used as a stretch shrink packaging film, however, a tear strength biased in the transverse direction, which deteriorates its cuttability, and causes longitudinal tear propagation.
  • a tear strength biased in the transverse direction which deteriorates its cuttability, and causes longitudinal tear propagation.
  • the balance of tear strength is to be improved, it would adversely affect the control of stretching in bubble inflation method, thus deteriorating its stretching property.
  • Patent Document 3 discloses a film, which comprises an inner layer having at least two layers including a layer made of a soft polypropylene resin and a layer made of an ethylene polymer, and two surface layers made of an ethylene-vinyl acetate copolymer, and has specific properties required for shrink packaging.
  • this film has suitable properties for shrink packaging, and shows little changes when packaged goods are heated in a microwave oven due to its specific heat shrinkage stress property, it does not have a balanced tear strength, which causes a problem of longitudinal tear propagation in a high speed continuous packaging machine.
  • Patent Document 1 Japanese Laid-Open Patent Publication No.
  • Patent Document 2 Japanese Laid-Open Patent Publication No.
  • Patent Document 3 Japanese Laid-Open Patent Publication No. 2003-112395 SUMMARY OF THE INVENTION It is the object of the present invention to provide a film that can be suitably used in a high speed continuous packaging machine, and has greatly improved moisture resistance.
  • the present invention provides a multilayer film, which comprises five layers consisting of two surface layers, a core layer, and two intermediate layers, each intermediate layer being positioned between the core layer and each surface layer, and has thickness of 7-30 ⁇ .
  • each of the two surface layers comprises an ethylene-vinyl acetate copolymer resin, and contains 0.5-5.0% by weight of glycerin fatty acid ester type surfactant, the surfactant existing on the surface of the film in the form of a layer in an amount of 3.0 ⁇ 30.0mg/m 2 ;
  • the core layer comprises 55-95% by weight of a crystalline polypropylene resin, which has ethylene contents of 2-10%, and 45-10% by weight of non-crystalline polypropylene copolymer or 45-10% by weight of ethylene- ⁇ -olefin resin having density of 0.865-0.91 Og/cm 3 , which is polymerized using a single site catalyst;
  • each of the intermediate layers comprises 10-80% by weight of the resin comprised in the surface layer and the core layer, 10-40% by weight of ethylene-vinyl acetate copolymer, and 10-80% by weight of ethylene- ⁇ -olefin resin having density of 0.900 ⁇ 0.920g/
  • the present invention also provides a method for preparing a multilayer film comprising five layers consisting of two surface layers, a core layer, and two intermediate layers, each intermediate layer being positioned between the core layer and each surface layer, using circular dies, which method comprises: adding 0.5-5.0% by weight of glycerin fatty acid ester type surfactant to ethylene-vinyl acetate copolymer resin to form a mixture for the two surface layers; melt kneading the resin mixture at a temperature of 220 ⁇ 250°C at a shear rate of 50 ⁇ 200[1/sec] and melt extruding it using circular dies; rapidly cooling the extruded resin with water to form a non- stretched multilayer tube; and stretching the tube at a temperature of 40 ⁇ 70°C at a ratio of 2-6 times both in the longitudinal and transverse directions, wherein temperature during stretching in the transverse direction is 10 ⁇ 40°C lower than that in the longitudinal direction.
  • the multilayer film according to the present invention has a greatly improved cuttability and thus does not involve a problem of longitudinal tear propagation.
  • the multilayer film is suitable for use in a high speed continuous packaging machine, and also has a highly improved moisture resistance.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be explained in detail. First, one embodiment of a process for obtaining packaged goods using the multilayer film according to the present invention will be explained.
  • a packaging method using a film includes stretch packaging, heat shrink packaging, stretch shrink packaging, L-type packaging, etc., and although any method can be employed, a method of continuous packaging by stretch shrink packaging will be explained hereinafter.
  • Packaged goods include foods to be filled in a plastic container such as meat, fishes and shellfishes, fish cakes, a lunch, and a side dish, and non-foods such as miscellaneous goods.
  • a continuous packaging machine has been developed, wherein meat, fishes and shell fishes, Japanese confectionary, a side dish, etc. are filled in a foam tray made of plastics, and packaged without the upper cover.
  • a high speed packaging machine has also been developed. For packaging without the upper cover, moisture resistance is required for a film, and for high speed packaging, cuttability and sealing property are required.
  • goods to be packaged are covered with a film in a cylindrical shape, and then joined and sealed using a rotation roller type center sealing apparatus (wherein the goods are often compressed without adding heat) such that a sealing line (compression line) is located on the back of the goods.
  • a sealing line compression line
  • the front and rear parts of the film case are cut with a saw blade type cutter, and then the cut front and rear portions of the film are folded toward the bottom of the goods.
  • the film folded toward the bottom of the goods is sealed, the goods are passed through a hot wind shrink tunnel using a conveyer, and the packaging film is heat shrunk to finish packaging.
  • the packaging speed of a continuous packaging machine is approximately 20-40 packages/min, and in the case of a high speed continuous packaging machine, the speed can be approximately 60-100 packages/min.
  • a packaging film may require properties such as tear strength, slipping property, bottom sealing property, heat-shrinkability, etc. to withstand the packaging speed.
  • tear strength measured according to ASTM-D-1992 it is very important that tear strength in the longitudinal direction of a film should be higher than that in the transverse direction. If tear strength in the longitudinal direction is lower than that in the transverse direction, longitudinal tear propagation will be caused and thus the film is not suitable for use.
  • the longitudinal direction of a film means a moving direction (MD) of a packaging machine
  • the transverse direction means a direction perpendicular (transverse) to the moving direction of a packaging machine (TD).
  • MD moving direction
  • TD packaging machine
  • the moving direction of the packaging machine is generally the same as the flow direction of the film. If tear strength in the longitudinal direction of a film is low, a notch, if generated, would be continuously propagated to stop continuous packaging. And, since a film is generally cut in the transverse direction with a cutter blade, if cuttability is poor, a film would not be cut and thus a lot of film waste will be generated. Therefore, tear strength in the transverse direction is preferably low.
  • the high speed of the packaging machine may also require that the film becomes molten quickly since heat sealing is generally employed for sealing the bottom.
  • a balance between tear strength in the longitudinal direction and that in the transverse direction of the multilayer film will be explained.
  • a heat shrinkable film made of polyolefin resin continuously forms by bubble inflation, tenter process, etc. Particularly, a process for forming a film by bubble inflation will be explained.
  • a pellet type resin is melt extruded at a high temperature which may be a melting point of the resin or higher.
  • the resin is continuously extrusion molded in a tube shape through dies, and the molded resin is cooled and solidified by water cooling.
  • the resin in a tube shape is often referred to as a parison.
  • the stretching ratio of the multilayer film according to the present invention is 2-6 times both in longitudinal and transverse directions, and 3-5 times are preferable because heat shrinkability, balance of tear strength, production stability, etc are good at this ratio.
  • a stretching process includes tenter process, bubble inflation process, etc, a bubble inflation process is preferably used to optimize transparency.
  • For stretching temperature a temperature of the surface measured using a contact thermometer is employed.
  • the multilayer film according to the present invention employs high crystalline polypropylene resin in the core layer.
  • stretching is generally carried out at a temperature of 100 ⁇ 130°C, which is about 30°C lower than the melting point of the resin. Since the resin sufficiently softens in this temperature range, stretching can be carried out at high ratio and bubble internal pressure lowers. Therefore, generation of punctures is decreased, and production efficiency is good.
  • the temperature range described above is generally considered as a preferable range. However, when the temperature range described above is employed, the orientation of a parison is maintained even after the stretching process is completed, and thus tear strength in the longitudinal direction remains low.
  • stretching temperature is in a range of 40-70 °C , and preferably 50-60 °C .
  • stretching temperature in the transverse direction of the film is 10 ⁇ 40°C , preferably 15 ⁇ 25°C lower than that in the longitudinal direction. Accordingly, in the present invention, it is possible to control a balance between longitudinal tear strength and transverse tear strength.
  • tear strength of the multilayer film of the present invention is 0.05-2.00N, measured according to ASTM-D- 1992, and tear strength in the longitudinal direction of the film is 1.5-20 times as strong as that in the transverse direction, and thus the film is suitable for use in a high speed continuous packaging machine.
  • the tear strength is preferably 0.1-1.00N, because in this range, the packaged goods are easily prepared and easily opened.
  • the tear strength in the longitudinal direction is preferably 2-5 times as strong as that in the transverse direction.
  • a film is heated in a heating furnace or hot wind ring, etc. to be longitudinally stretched. After passing through the heating furnace or hot wind ring, the film is cooled in an empty cooling ring, etc. to be inflated and transversely stretched in a bubble shape. At this time, some longitudinal stretching may occur. However, most longitudinal stretching occurs in a heating furnace, and successively, transverse stretching occurs while cooling and maintaining bubbles. Therefore, a temperature during stretching in the transverse direction is preferably lower than that in the longitudinal direction. As a result of low temperature stretching in the transverse direction, orientation of the resin is improved, and thus desired balance between longitudinal tear strength and transverse tear strength can be secured.
  • the core layer is important for controlling the orientation of the resin at the stretching temperature.
  • the core layer comprises crystalline polypropylene resin as main ingredient, which has ethylene contents of 2-10%, preferably 4-7%, and non-crystalline polypropylene resin or very low density ethylene- ⁇ -olefin resin.
  • the melting point of the crystalline polypropylene resin is preferably 156 ⁇ 164°C in order to give good heat resistance during sealing, and more preferably 158 ⁇ 163°C in order to allow easy stretching.
  • the melt flow rate of the polypropylene resin measured according to JIS-K-7210 (230 °C , 2.16kgf (21.18N): hereinafter, the same conditions are employed for crystalline polypropylene copolymer and non-crystalline polypropylene copolymer) is preferably 0.5-7.0, and more preferably 2.0-4.0 to allow very easy stretching.
  • the core layer preferably comprises 55-90% by weight of crystalline polypropylene, and more preferably 60-80% by weight to allow easy stretching and easy control of the balance between the longitudinal tear strength and transverse tear strength.
  • non- crystalline polypropylene resin propylene- ⁇ -olefin copolymer
  • any commercially available resin which control stereo- regularity and thus inhibit crystallization
  • atactic polypropylene of which main ingredient is propylene homopolymer and crystallinity is 10-30% is preferable because they give desirable properties such as transparency, recoverability, easy control of the balance between longitudinal tear strength and transverse tear strength, and heat shrinkability.
  • the core layer comprises 10-45% by weight of the non-crystalline polypropylene resin, and preferably 20-40% by weight in order to allow easy stretching.
  • the core layer may comprise very low density ethylene- ⁇ -olefin resin, which is polymerized using a single site catalyst, instead of the non-crystalline polypropylene resin.
  • a single site catalyst also known as a metallocene catalyst, can control distribution of a resin composition
  • resin that is polymerized using the single site catalyst has improved compatibility with polypropylene resin and thus does not damage transparency, even if mixed with polypropylene.
  • the density of the resin is 0.865-0.91 Og/cm 3 , and preferably 0.868-0.905g/cm 3 in order to allow easy stretching.
  • the melt index of the resin measured according to JIS-K-
  • 7210 (190°C, 2.16kgf (21.8N): hereinafter the same conditions are employed for polyethylene resin), is preferably 0.1-15.0, and more preferably 0.3-9.0 to allow easy stretching.
  • mineral oil consisting of petroleum-based hydrocarbons, named process oil, may be used as the plasticizer.
  • a method for polymerization of ethylene- ⁇ -olefin resin using a single site catalyst includes a gas phase process, a high pressure process, etc.; however, high pressure process is preferably used in order to polymerize low density area.
  • the surface layer comprises ethylene-vinyl acetate copolymer.
  • the ethylene-vinyl acetate copolymer preferably comprise 5-25% by weight of vinyl acetate, and more preferably 10-20% by weight of vinyl acetate because in this range, a moisture proofing agent can be easily kneaded and bled out in the layer.
  • the melt index of the ethylene-vinyl acetate copolymer measured according to JIS-K-7210 (190 °C , 2.16kgf (21.18N); hereinafter the same conditions are employed for ethylene-vinyl acetate copolymer), is preferably 0.5-15, and 1.0-5.0 is more preferable because in this range, transparency and bottom sealing property are enhanced.
  • Polyethylene resin can be added to the surface layer, to the extent not detrimental to bottom sealing property.
  • ethylene- ⁇ -olefin copolymer that is polymerized using a single site catalyst is added, transparency or gloss often improves, but it may be difficult to form a layer of moisture proofing agent.
  • the single site type ethylene- ⁇ -olefin copolymer should be added in an amount that does not negatively affect the formation of moisture proofing agent layer.
  • the glycerin fatty acid ester type surfactant will be explained.
  • glycerin fatty acid ester is polyhydric alcohol fatty acid ester and its hydrophilicity and lipophilicity can be controlled by changing polymerization degree of glycerin, kinds of fatty acid or esterification degree, its presence on the film surface gives moisture resistance and slipping property to the film.
  • the surfactants comprising diglycerin oleate, diglycerin laurate, or glycerin monooleate as main ingredient are preferable, and those comprising the mixture thereof are more preferable because they does not negatively affect slipping property and optical property of the film and can be conveniently used.
  • 'film surface amount' the amount of the surfactant existing on the film surface.
  • a moisture proofing agent it is preferable to add to the resin and bleed it out. Then, the surface amount can be easily controlled, the moisture proofing agent can be easily distributed in the form of a layer, and moisture resistance lasts. It is preferable to add moisture proofing agent by a master batch process or an extruder injection process.
  • an extruder equipped with a mixing part which is capable of maintaining a temperature in a range of 220 ⁇ 250°C, to finely disperse it in the resin.
  • An extruder may include any twin screw extruder and single screw extruder.
  • a screw having good kneading property such as Dulmadge type screw, cross Dulmadge type screw, etc. which is equipped with a part having shear rate of 50 ⁇ 200[sec/1].
  • resin may enter there between, and thus is subjected to vigorous shear.
  • the shear rate is a measure of kneading property.
  • the shear rate distribution can be calculated using simulation software ANSYS® from ANSYS company.
  • glycerin fatty acid ester type surfactant When glycerin fatty acid ester type surfactant is kneaded with ethylene-vinyl acetate copolymer, it is easily deteriorated at high temperature, and thus, generally, temperature of the extruder is set within a range of 180-210°C.
  • the surfactant may be deposited on the film surface in the form of a layer, rather than in the form of liquid drops. This layer may be a continuous layer. Distribution in the thickness direction of an additive layer comprising the surfactant can be measured by a Scanning Probe Microscope such as Nanoscope® IIIA from Digital Instruments, Inc. or SPM-9500-WET-SPM® from Shimadzu Manufacturing, Inc. Although the surfactant is distributed in the form of layer, it is not necessarily distributed with the uniform thickness.
  • the thickness of the additive layer may differ according to the irregularity of a film base.
  • the additive may be continuously distributed on the film surface without exposing the film base, while the film base varies in thickness.
  • the measuring mode of a Scanning Probe Microscope includes a contact mode and a dynamic mode.
  • the present invention employs a dynamic mode.
  • a dynamic mode which is also referred to as a vibration mode or a tapping mode, enables observation of a soft sample, which cannot be observed well by a contact mode, and thus enables measurement of the thickness of the additive layer using difference in adsorptivity or elasticity of the surfaces of resin and additive layer.
  • the distribution of the additive layer may be confirmed by sampling the layer in every direction approximately 10mm from the disk without damaging the film surface and observing the whole surfaces.
  • the thickness of the additive layer is approximately 3 ⁇ 70nm, and more preferably 5 ⁇ 40nm.
  • the surfactant exists in the form of layer or in the form of liquid drops can be identified as follows. First, by observation in a dynamic mode using a Scanning Probe Microscope (ratio of 100-3000 times), distribution state of the additive can be intermittently identified by the naked eye.
  • the distribution of functional groups or kind of chemicals on the film surface can be mapped and identified using time-of-f light secondary ion mass spectrometry (Tof-SIMS) or microinfrared spectroscopy (ATR).
  • the amount of the additive layer on the surface of the film is 3.0-30. Omg/m 2 , and 5.0-10.0mg/m 2 is preferable because in this range, slipping property is enhanced.
  • the moisture proofing agent is intended to exist on the film surface in an amount of 3.0 ⁇ 30.0mg/m 2 , it is added to the ethylene- vinyl acetate copolymer layer in an amount of 0.5-5.0% by weight, and more preferably 1.0-3.0% by weight. Also, in order to give durable moisture resistance, the moisture proofing agent is added to the intermediate layer in an amount of 0.5-5.0% by weight. And, it may be added to the core layer in an amount of 0.5-5.0% by weight, or may not be added thereto because adding to the core layer does not largely influence on the physical properties.
  • liquid additives such as an antioxidant, an antistatic agent, a petroleum resin, and a mineral oil can be added such that the physical properties of the film do not deteriorate.
  • additives may be added as long as moisture resistance is not degraded.
  • Both intermediate layers comprise 10-80% by weight of the resin comprised in both surface layers and the resin comprised in the core layer. In some cases, this may be due to a desire to limit the number of resins used. For example, resins may be limited due to space limitations (i.e. storage facilities) and/or equipment used (i.e., a material supplying machine). Generally, it is preferable to use reprocessed pellet called recycle material in order to optimize cost vs.
  • the intermediate layer comprises 10-40% by weight of ethylene-vinyl acetate copolymer, and 10-80% by weight of ethylene- ⁇ -olefin resin having density of 0.900 ⁇ 0.920g/cm 3 .
  • the intermediate layer preferably comprises 30-60% by weight of the resin comprised in the core layer and two surface layers, 10-30% by weight of ethylene-vinyl acetate copolymer, and 30-50% by weight of ethylene- ⁇ -olefin.
  • the composition of the film may be determined by balancing the factors of costs and performances (i.e., ease of stretching, etc).
  • the ethylene-vinyl acetate copolymer that is employed in two intermediate layers preferably comprises 5-25% of vinyl acetate, and more preferably 10-20% such that bleeding may easily occur in the layer.
  • the melt index of the ethylene-vinyl acetate copolymer measured according to JIS-K-7210, is preferably 0.5-15.0, and more preferably 1.0-5.0 to give good transparency. It is more preferable to employ, if possible, the ethylene-vinyl acetate copolymer that is comprised in two surface layers, to optimize transparency after heat shrink.
  • the density of the ethylene- ⁇ -olefin resin employed in two intermediate layers is 0.900 ⁇ 0.920g/cm 3 , and preferably 0.904-0.916g/cm 3 to allow easy stretching.
  • the melt index of the ethylene- ⁇ -olefin resin measured according to JIS-K-7210, is preferably 0.1-15.0, and more preferably 0.3-9.0 to allow easy stretching. It can be polymerized using a multi-site catalyst or a single site catalyst, but the resin is preferably polymerized using a single site catalyst to optimize transparency.
  • the glycerin fatty acid ester type surfactant is added to the intermediate layer in an amount of 0.5-5.0% by weight.
  • the thickness of the multilayer film of the present invention is preferably 7-30 m, and more preferably 8-16 m.
  • a thickness of the multilayer film may be determined by considering a mechanical strength required for use in a continuous packaging machine, and/or ease of opening after packaging.
  • Each surface layer preferably constitutes 10-20% of total thickness of the layer, within a range that is not detrimental to moisture resistance and sealing property.
  • the inner and outer surface layers may not be symmetrical. However, they are preferably almost symmetrical because it is suitable that two layers have equal moisture resistance and slipping properties.
  • the core layer preferably constitutes 10-40% of total thickness of the layer, within a range that is not detrimental to stretching property, tear strength balance, and heat shrink property.
  • Each intermediate layer if above-explained recycle material is employed therein, preferably constitutes 20-35% of the total thickness of the layer. To optimize the cost vs. performance of the intermediate layer, it may be beneficial that the intermediate layer is thick.
  • the inner and outer intermediate layers are symmetrical because symmetrical layers would not curl. Alternatively, the inner and outer intermediate layers may not be symmetrical.
  • Each layer of the multilayer film according to the present invention may comprise moisture proofing agent, plasticizer, antioxidant, surfactant, coloring agent, UV absorbent, lubricant, inorganic filler, antiblocking agent, flame retardant, adhesive, gloss remover, antistatic agent, oxygen or carbonate gas absorbent, gas absorbent, freshness maintaining agent, odor proofing agent, aromatics, etc., within a range that is not detrimental to the unique properties of each layer. If necessary, other ingredients may be added to the extent not detrimental to the properties of the present invention. Examples The present invention will be explained in detail with reference to the following Examples and Comparative Examples. Measuring methods employed in the present invention are as follows. ⁇ Stretching temperature> It was measured using a commercially available contact thermometer.
  • ⁇ Stretching ratio> As longitudinal stretching ratio, the ratio of the moving speed before stretching and the speed after stretching was employed. As transverse stretching ratio, the ratio of the width of parison before stretching and the width of the film after stretching was employed.
  • ⁇ Measurement of film surface amount of glycerin fatty acid ester> Whole surface of a film (1m 2 ) was cleaned using a glass cleaning cloth, which had been completely extracted to determine that no glycerin fatty acid ester was added thereto. This procedure was repeated 4-5 times with changing glass cleaning cloth. The glass cleaning cloth was extracted, and the extract was dried and solidified using an evaporator to measure the weight of the residue.
  • the film surface amount was measured using gas chromatography or liquid chromatography.
  • the balance between the longitudinal tear strength and transverse tear strength was measured according to ASTM-D-1992. Longitudinal tear strength and transverse tear strength was respectively measured using a light load tear tester (from Toyoseiky). From the ratio of tear strength, the balance between longitudinal tear strength and transverse tear strength was measured. For example, in case the tear strength in the longitudinal direction is 0.5N and that in the transverse direction is 0.1 N, the balance was expressed as 5 times.
  • Moisture resistance was evaluated as follows. In a 500ml beaker, water that had been controlled to 20°C was introduced, and the inlet of the beaker was closed with a film. The beaker was stored in a refrigeration show case, of which temperature had been controlled to 10°C . After 30 minutes, moisture resistance was evaluated. In terms of visibility or state of dew-condensed water drop on the film, 5 points means excellent.
  • the film is of a difficult-to-use level.
  • X 1 point: The film is clouded with small water drops, and visibility is very poor. The film is of an impracticable level.
  • Continuous packaging was carried out 100 times in the speed of 80 packages per 1 minute using a linear stretch shrink packaging machine (STN-8600 from Omori machinery Co. Ltd.), which is a commercially available packaging machine of bottom sealing and overlap shrink type.
  • a high speed test packaging machine was used to evaluate inferiority % and completion of packaging.
  • a PSP tray was employed, and cubic resin mass of about 200g was employed as the goods to be packaged.
  • Inferiority includes breakage, sealing inferiority, etc. Those requiring repackaging are particularly problematic in the market. Particularly, when tear strength in the longitudinal direction is lower than that in the transverse direction, longitudinal tear was propagated to cause continuous inferiority. A film that was torn by the angle of the resin mass was observed.
  • Evaluation of completion of packaging included evaluation for aesthetic factors such as whitening, gloss, deformation, relax of the film, etc., which are largely influenced by conditions such as a shrink tunnel. Each film was evaluated under optimum conditions. ®: When the inferiority % is 0%, the film has good aptitude for a high speed packaging machine: High quality level in completion of packaging
  • the film has an aptitude for a high speed packaging machine: No problem in completion of packaging ⁇ : When the inferiority % is 11% or more 50% or less, although the film can be used in a high speed packaging machine, a lot of losses are generated; or optical properties such as whitening, gloss, etc. are damaged, container is deformed, or the film relaxes: Completion of packaging cannot be satisfied.
  • ⁇ When all the results are ⁇ , the film is of suitably applicable level. O: When all the results are ⁇ or O, the film is of practical use level. ⁇ : When the results include ⁇ , the film is of difficult-to-use level. X: When the results include X, the film is of impracticable level.
  • Examples 1-19 Resin and additives as shown in Examples 1-19 of the following Tables 1 , 2, 3 and 4 (the column titles of Tables 2, 3 and 4 are omitted because they are the same as in Table 1 ) were employed.
  • a tube comprising 5 layers consisting of two surface layers, a core layer and two intermediate layers were melt extruded from 3 kinds of 5 layered circular dies using 3 extruders, and the extruded substance was rapidly cooled using water cooling ring to obtain non-stretched tube (parison). Each extrusion amount was established so that each layer constitutes predetermined ratio, and the construction of the layers was identified by sectional observation.
  • Additives comprising glycerin fatty acid ester type surfactant as main ingredient (purity of 70% or more) as shown in Examples 1-19 of the Tables were injected ahead of the handle of compression part of the screw of the extruder using a high pressure pump.
  • the extruder had 6 temperature controlling blocks in the lengthwise direction. Temperatures of the extruders for the surface layers and intermediate layers were fixed at 180°C, 200°C, 210°C, 220°C, 230°C and 230°C from the resin supplying hopper, and those for the core layer were fixed at 200°C, 200°C, 200°C, 190°C, 190°C and 190°C.
  • the obtained non-stretched tube was transmitted to stretching section, and heated using UV heater, such that the tube was stretched in the longitudinal direction.
  • the stretching ratio was controlled by the ratio of the speed of a pinch roller, where heating starts, and the speed of a winder. While the tube was cooled with an empty cooling ring, air was injected therein to form a bubble. At this time, stretching temperature was set as shown in Examples 1-19 of the Table 1. Deflated portion of the tube was folded to form a double film, which was heat-set at 50°C and wound using a winder. At this time, stretching ratio in the transverse direction was controlled by the width of the film and the width of the parison.
  • Stretching ratio was used at the safest bubble, and the extrusion amount was controlled so that a predetermined thickness was reached.
  • the double film disk was stripped to a single film using a slitter, thus obtaining the multilayer films of Examples 1-19.
  • Each multilayer film was stored in a chamber that had been controlled to 40°C for 3 days.
  • measurement of the film surface amount of glycerin fatty acid ester, identification of distribution state of glycerin fatty acid ester on the film surface, evaluation of balance of longitudinal tear strength and transverse tear strength, evaluation of moisture resistance, aptitude for a high speed continuous packaging machine and overall evaluation were carried out. As results, it can be seen that in case the obtained multilayer film has good tear strength balance, it also has good aptitude for a high speed packaging machine.
  • Multilayer films were manufactured by the same method as in
  • Comparative Example 16 moisture proofing agent was not added but coated.
  • temperatures of the extruder were set low as 180°C, 200°C, 200°C, 200°C, 200°C and 200°C, and extrusion kneading was reduced using a screw of a design which reduces shear speed. From the results of Comparative Examples 1-5, it can be seen that tear strength balance deteriorates due to stretching temperature in the longitudinal direction and that in the transverse direction. From the results of Comparative Examples 6-10, it can be seen that tear strength balance varies according to the kind of polypropylene and elastomer, and the mixed amount thereof in the core layer.
  • Comparative Example 11 From the results of Comparative Example 11 , it can be seen that moisture resistance cannot be satisfied without ethylene- vinyl acetate copolymer in the intermediate layer. From the result of Comparative Example 12, it can be seen that tear strength balance deteriorates unless the intermediate layer comprise ethylene- ⁇ -olefin copolymer. From the results of Comparative Examples 13-17, it can be seen that moisture resistance may not be satisfied depending on the distribution state of moisture proofing agent or its added amount. From the results of Comparative Examples 18 and 19, it can be seen that aptitude for a high speed packaging machine may be damaged depending on the thickness of the film. c
  • the multilayer film of the present invention is suitable for use in a high speed continuous packaging machine, as well as for a common packaging machine. In addition, it has a greatly improved moisture resistance.

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  • Wrappers (AREA)
  • Laminated Bodies (AREA)

Abstract

L'invention concerne un film multicouche présentant une bonne aptitude à l'emballage afin d'être utilisé dans une machine d'emballage en continu à haute vitesse, ainsi qu'une bonne résistance à l'humidité. Ce film multicouche comporte deux couches de surface, une couche centrale et deux couches intermédiaires, chaque couche étant constituée d'une résine spécifique, et présente une résistance à la déchirure équilibrée dans les sens longitudinal et transversal puisqu'il a été étiré à une température spécifique. En outre, ce film multicouche peut contenir un tensioactif du type ester d'acide gras glycériné réparti sous la forme d'une couche à sa surface.
PCT/IB2004/003280 2003-10-15 2004-10-08 Film multicouche et son procede de preparation WO2005037546A1 (fr)

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JP2003354912A JP3526860B1 (ja) 2003-10-15 2003-10-15 多層フィルムとその製造方法
JP2003-354912 2003-10-15

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JP2015120322A (ja) * 2013-12-25 2015-07-02 三菱樹脂株式会社 熱処理用樹脂フィルム、調理用フィルム包装体用蓋材及び底材、調理用フィルム包装体、調理用フィルム包装食品及びその製造方法、調理済みフィルム包装食品及びその製造方法、並びに加熱調理食品の製造方法

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JP2007030262A (ja) * 2005-07-25 2007-02-08 Mitsubishi Plastics Ind Ltd ストレッチシュリンク積層フィルム及びその製造方法
JP4896421B2 (ja) * 2005-03-30 2012-03-14 三菱樹脂株式会社 ストレッチシュリンク積層フィルムおよびその製造方法
WO2006106747A1 (fr) * 2005-03-30 2006-10-12 Mitsubishi Plastics, Inc. Film etirable /retractable et son procede de fabrication
JP5084353B2 (ja) * 2007-06-05 2012-11-28 旭化成ケミカルズ株式会社 熱収縮性多層フィルム

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JPH10291281A (ja) * 1997-04-18 1998-11-04 Tokuyama Corp ストレッチ包装用フィルム
JPH11348204A (ja) * 1998-06-03 1999-12-21 Okura Ind Co Ltd 食品包装用ストレッチフィルム
US6602455B1 (en) * 1998-12-18 2003-08-05 Cryovac, Inc. Highly bi-axially oriented, heat-shrinkable, thermoplastic, multi-layer film and process for the manufacture thereof

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JPH10291281A (ja) * 1997-04-18 1998-11-04 Tokuyama Corp ストレッチ包装用フィルム
JPH11348204A (ja) * 1998-06-03 1999-12-21 Okura Ind Co Ltd 食品包装用ストレッチフィルム
US6602455B1 (en) * 1998-12-18 2003-08-05 Cryovac, Inc. Highly bi-axially oriented, heat-shrinkable, thermoplastic, multi-layer film and process for the manufacture thereof

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JP2015120322A (ja) * 2013-12-25 2015-07-02 三菱樹脂株式会社 熱処理用樹脂フィルム、調理用フィルム包装体用蓋材及び底材、調理用フィルム包装体、調理用フィルム包装食品及びその製造方法、調理済みフィルム包装食品及びその製造方法、並びに加熱調理食品の製造方法

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JP2005119074A (ja) 2005-05-12

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