Multilayer film with cyclic olefin seal layer

Abstract

The present invention is related to a heat-sealable multilayer packaging film comprising: a support layer, and a peelable seal layer comprising a polymer blend, said polymer blend comprising: from 40 to 85% by weight of one or more first amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of at least 120° C., from 10 to 55% by weight of one or more second amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of less than 120° C., and from 0.5 to 15% by weight, preferably 0.5 to 10% by weight of at least one elastomeric copolymer comprising at least one polymerized monovinylarene and at least one polymerized acyclic olefin.

Claims

1. A heat-sealable multilayer packaging film comprising: a support layer comprising at least one polymer layer selected from the group consisting of polyamide, polyester, polycarbonate, polyvinyl chloride and polyester-glycol copolymer, and a peelable seal layer comprising a polymer blend, said polymer blend comprising: from 40 to 85% by weight of one or more first amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of at least 120° C.; from 10 to 55% by weight of one or more second amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of less than 120° C.; and from 0.5 to 15% by weight of at least one elastomeric copolymer comprising at least one polymerized monovinylarene and at least one polymerized acyclic olefin, wherein the monovinylarene content is up to 50% by weight and characterized by a Shore A hardness (30 sec), according to ASTM D 2240, between 20 and 90; the glass-transition temperature being measured by differential scanning calorimetry, according to ASTM D3418 with a heating gradient of 10° C./min.

2. The heat-sealable multilayer packaging film according to claim 1, characterized in that: the first amorphous cyclic olefin polymer of the peelable seal layer is characterized by an elongation at break of 30% or less, and the second amorphous cyclic olefin polymer of the peelable seal layer is characterized by an elongation at break of more than 30%, the elongation at break being determined by tensile testing in accordance with EN ISO 527.

3. The heat-sealable multilayer packaging film according to claim 1, characterized in that the cyclic olefin polymer is hydrogenated.

4. The heat-seal able multilayer packaging film according claim 1, characterized in that the elastomeric copolymer is selected from the group consisting of styrene-isobutylene-styrene copolymer, styrene-ethylenebutylene-styrene copolymer, styrene-propylene-styrene copolymer, styreneethylene-propylene-styrene copolymer, styrene-isoprene copolymer, styreneisoprene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-butylene-butadienestyrene copolymer and styrene-butadiene-styrene copolymer.

5. The heat-sealable multilayer packaging film according claim 2, characterized in that the elastomeric copolymer is selected from the group consisting of styrene-isobutylene-styrene copolymer, styrene-ethylenebutylene-styrene copolymer, styrene-propylene-styrene copolymer, styreneethylene-propylene-styrene copolymer, styrene-isoprene copolymer, styreneisoprene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-butylene-butadienestyrene copolymer and styrene-butadiene-styrene copolymer.

6. The heat-sealable multilayer packaging film according to claim 1, characterized in that the elastomeric copolymer is hydrogenated.

7. The heat-sealable multilayer packaging film according to claim 1, characterized in that the peelable seal layer has a thickness of between 3 and 100 μm.

8. The heat-sealable multilayer packaging film according to claim 1, characterized in that the peelable seal layer is characterized by a stress at break, according to ASTM D882, of 65 N/mm.sup.2 or less.

9. The heat-sealable multilayer packaging film according to claim 1 wherein the peelable seal layer is characterized by a modulus of elasticity, according to ASTM D882, of 2100 N/mm.sup.2 or less.

10. A package comprising the heat-sealable multilayer packaging film according to claim 1, and a multi- or monolayer substrate, comprising at least one cyclic olefin polymer layer in contact with the peelable seal layer of the heat-sealable multilayer film upon heat sealing.

11. The package according to claim 10, characterized in that a peel strength for separating the heat-sealable multilayer film and the substrate, measured according to ASTM F88, is between 1.0 and 15.0 N/15 mm.

12. The package according to claim 10, characterized in that said package is sterilizable at 115° C. for 30 minutes or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) According to the present invention, there is provided a heat-sealable multilayer film comprising a support layer and a peelable seal layer of a polymer blend comprising a first cyclic olefin polymer, a second cyclic olefin polymer and at least one elastomeric copolymer, said elastomeric copolymer comprising at least one polymerized monovinylarene and at least one polymerized acyclic olefin, said peelable seal layer allowing a controlled peel-force of the multilayer film and a smooth peel area upon opening, said peelable seal layer further being characterized by a satisfying chemical inertness and resistance to penetration of substances.

(2) The peelable seal layer of the present invention comprises a polymer blend comprising: from 40 to 85% by weight, preferably from 45 to 80% by weight of one or more first amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of at least 120° C. and an elongation at break of 30% or less; from 10 to 55% by weight, preferably from 15 to 50% by weight of one or more amorphous cyclic olefin polymer(s) characterized by a glass-transition temperature of less than 120° C. and an elongation at break of more than 30%; and from 0.5 to 15% by weight of at least one elastomeric copolymer comprising at least one polymerized monovinylarene and at least one polymerized acyclic olefin, wherein the monovinylarene content is up to 50% by weight and characterized by a Shore A hardness (30 sec) according to ASTM D 2240 comprised between 20 and 90,
wherein the glass-transition temperature is measured by differential scanning calorimetry, according to ASTM D3418 with a heating gradient of 10° C./min. and the elongation at break is determined by tensile testing in accordance with EN ISO 527.

(3) Suitable cyclic olefin polymers for being used in the polymer blend of the peelable seal layer of the present invention include homopolymers or copolymers of any cyclic olefin monomers known in the art.

(4) The cyclic olefin monomers in general are mono- or polyunsaturated polycyclic ring systems, such as cycloalkenes, bicycloalkenes, tricycloalkenes, tetracyclo-alkenes, pentacycloalkenes and hexacycloalkenes which may be mono- or polysubstituted.

(5) Non-limiting examples of suitable cyclic olefin monomers include bicyclo[2,2,1]hept-2-ene, 5-methylbicyclo[2,2,1]hept-2-ene, 10-methyltricyclo[4.4.0.1.sup.2,5]-3-undecene, tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]-3-dodecene, 8-methyltetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]-3-dodecene, pentacyclo[7.4.0.1.sup.2,5.1.sup.9,12.0.sup.8,13], hexacyclo[6.6.1.1.sup.3,6.1.sup.10,13.0.sup.2,7.0.sup.9,14]-4-hepta-decene and tricyclo[5.2.1.0.sup.2,6]deca-3,8-diene.

(6) The cyclic olefin polymers are produced by ring-opening metathesis polymerization of one or more cyclic olefin monomers.

(7) The cyclic olefin polymers for being used in the polymer blend of the peelable seal layer of the present invention preferably comprise hydrogenated homopolymers or copolymers of bicyclo[2,2,1]hept-2-ene, 8-methyltetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]-3-dodecene and tricyclo[5.2.1.0.sup.2,6] deca-3,8-diene.

(8) Preferably, the cyclic olefin polymer is hydrogenated. When an unsaturated bond remaining in the molecular chain of cyclic polyolefin is saturated by hydrogenation, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, and particularly preferably 99% or more.

(9) The cyclic olefin polymer is preferably characterized by a number average molecular weight comprised between 10,000 and 200,000, preferably between 20,000 and 100,000, more preferably between 25,000 and 50,000 g/mole, measured by gel permeation chromatography using toluene as a solvent, relative to polystyrene.

(10) The vinyl aromatic elastomeric copolymer used in the polymer blend of the peelable seal layer of the present invention is preferably a block polymer in which the aromatic portion is a polymer of styrene, α-methylstyrene, (o-, m-, p-)methylstyrene or 1,3-dimethylstyrene and preferably a polymer of styrene, and wherein the elastomeric portion is an unsaturated polymer of butadiene and/or isoprene, or the hydrogenated derivative thereof, or a saturated olefin polymer of ethylene/butylene or ethylene/propylene.

(11) The vinyl aromatic elastomer is preferably characterized by a weight average molecular weight comprised between 20,000 and 500,000, preferably between 30,000 and 450,000, more preferably between 50,000 and 400,000 g/mole, measured by gel permeation chromatography using toluene as a solvent, relative to polystyrene.

(12) Preferably, the vinyl aromatic elastomer is hydrogenated. When an unsaturated bond remaining in the molecular chain of vinyl aromatic elastomer is saturated by hydrogenation, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, and particularly preferably 99% or more

(13) The vinyl aromatic elastomer is preferably selected from the group consisting of styrene-isobutylene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-propylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene-styrene copolymer, hydrogenated styrene-isoprene-butadiene-styrene copolymer, hydrogenated styrene-isoprene-butadiene-styrene copolymer, hydrogenated styrene-butylene-butadiene-styrene copolymer and hydrogenated styrene-butadiene-styrene copolymer.

(14) More preferably, the vinyl aromatic elastomer is styrene-ethylene-butylene-styrene copolymer (SEBS) or styrene-ethylene-propylene-styrene copolymer (SEPS).

(15) The vinyl aromatic elastomer is characterized by a vinyl aromatic content of up to 50% by weight and by a Shore A hardness (30 sec.) according to ASTM D 2240 comprised between 20 and 90, preferably between 30 and 80.

(16) The inventors have found that the particular combination of cyclic olefin polymers and vinyl aromatic polymer(s) allow the realization of a polymer blend characterized by an elasticity modulus, according to ASTM D882, of 2100 N/mm.sup.2 or less, preferably of 2000 N/mm.sup.2 or less and a stress at break, according to ASTM D882, of 65 N/mm.sup.2 or less, preferably of 60 N/mm.sup.2 or less, more preferably of 55 N/mm.sup.2 or less.

(17) The inventors have surprisingly found that both the elasticity modulus and the stress at break of the intimate polymer blend of the present invention, are lower than the theoretical value based on the proportional contribution of the respective values of the first cyclic olefin polymer and of the blend of the second cyclic olefin polymer and the vinyl aromatic elastomer, constituting the seal layer, i.e. lower than the theoretical elasticity modulus or stress at break calculated from the sum of the elasticity modulus or the stress at break of a 100% first cyclic olefin polymer layer, multiplied by its weight fraction as in the seal layer of the present invention, and of the elasticity modulus or the stress at break of a layer consisting of an intimate blend of the second cyclic olefin polymer and the vinyl aromatic polymer, in the ratio as in the seal layer of the present invention, multiplied by the weight fraction of the second olefin polymer and the vinyl aromatic elastomer as in the seal layer of the present invention, wherein the weight fraction equals the weight percentage divided by 100.

(18) The thickness of the peelable seal layer is in general comprised between 3 and 100 μm, preferably between 5 and 80 μm, more preferably between 7 and 50 μm, most preferably between 10 and 30 μm.

(19) The heat-sealable multilayerfilm of the present invention comprises a support layer, said support layer preferably comprising at least one polymer layer selected from the group consisting of polyamide, polyester, polycarbonate, polyvinyl chloride, polypropylene, low density polyethylene, medium density polyethylene, high density polyethylene, polyester-glycol copolymer and ethylene vinyl acetate.

(20) The support layer may further comprise one or more ceramic-coated films like AlO.sub.x or SiO.sub.x-coated polymer films or a metal foil like an aluminum foil.

(21) Multilayer films in accordance with the present invention can be produced by known methods. However, it is generally preferred to produce them by coextruding melts of the polymers and additives required for the various layers of the final films, followed by cooling to solidify the polymers in the form of a film.

(22) Films in accordance with the present invention can also be produced by coextrusion coating of the heat-seal layer on to a suitable support layer.

(23) The support layer of the multilayer packaging film of the present invention typically comprises a polyester layer, such as a polyethylene terephthalate layer, with a thickness comprised between 5 and 60 μm, preferably between 10 and 40 μm; an aluminum foil with a thickness comprised between 20 and 70 μm, preferably between 30 and 60 μm and the peelable seal layer with a thickness comprised between 10 and 30 μm, most preferably between 15 and 25 μm.

(24) The heat-sealable multilayer film of the present invention is used for the production of peelable heat-sealed packages through heat sealing said multilayer film to a substrate wherein the substrate is a cyclic olefin polymer substrate or comprises a cyclic olefin polymer layer for contacting the peelable seal layer upon heat sealing.

(25) The heat-sealable multilayer film of the present invention may be used for the production of peelable heat-sealed packages through heat sealing said multilayer film to a substrate at a temperature comprised between 200 and 250° C., preferably between 210 and 240° C. using a dwell time comprised between 0.2 and 3 seconds, preferably between 0.5 and 2 seconds, and a pressure comprised between 100 and 500 kPa, preferably between 150 and 250 kPa.

(26) Peelable packages produced from the multilayer films and the cyclic olefin comprising substrate have shown peel strengths, for separating the multilayer film and the substrate, measured according to ASTM F88, comprised between 1.0 and 15.0 N/15 mm, preferably between 2.0 and 10.0 N/15 mm. Peeling strengths are measured with an Instron tensile tester at a 180° peel angle with an opening speed of 300 mm/min.

(27) The inventors have surprisingly found that the peel strength of the package, of the present invention, is lower than the theoretical peel-strength value calculated from the proportional contribution of the respective peel-strength values of a seal layer of the first cyclic olefin polymer and of a seal layer consisting of a blend of the second cyclic olefin polymer and the vinyl aromatic elastomer, wherein the proportions are as in the seal layer of the present invention; i.e. lower than the theoretical peel strength calculated from the sum of the peel strength of a 100% first cyclic olefin polymer seal layer, multiplied by its weight fraction as in the seal layer of the present invention, and of the peel strength of a seal layer consisting of an intimate blend of the second cyclic olefin polymer and the vinyl aromatic polymer, in the ratio as in the seal layer of the present invention, multiplied by the weight fraction of the second olefin polymer and the vinyl aromatic elastomer as in the seal layer of the present invention, wherein the weight fraction equals the weight percentage divided by 100.

(28) Both phenomena, the anti-synergistic effect of blending the first cyclic olefin polymer, the second olefin polymer and the vinyl aromatic elastomer on the mechanical properties (elasticity modulus and tensile strength at break) and on the force to open a package, allow to create a thin cyclic olefin polymer-based heat-seal layer with a film thickness below 100 μm, preferably below 60 μm, more preferably below 40 μm, that are easily processable on blown and cast extrusion lines without web breakages, while having controlled peel forces resulting in clean peels without fiber tears or angel hairs implying that the peel trace is smooth and exempt from all kind of visual disruptions.

(29) Packages processed by heat sealing the multilayer film of the present invention on a cyclic olefin polymer surface of the substrate have proven to be resistant to penetration of substances enclosed in the package, into the cyclic olefin polymer matrix, i.e. the packages have proven non-scalping properties, assuming that the contents of the packaging are into direct contact with the cyclic olefin polymer.

(30) By substances, the present invention means flavor and aroma substances and pharmaceutical agents or parts thereof.

(31) The packages according to the present invention can preferably be sterilized at 115° C. for 30 minutes or more. In another preferred embodiment, the packages according to the present invention can be sterilized at 121° C. for 15 minutes or more.

EXAMPLES

(32) The following illustrative examples are merely meant to exemplify the present invention but are not destined to limit or otherwise define the scope of the present invention.

(33) Peelable layer was prepared from a polymer blend comprising the first cyclic olefin polymer Zeonor® 1430R, characterized by a glass-transition temperature of 136° C. and an elongation at break of 16%, the second cyclic olefin polymer Zeonor® 1020R characterized by a glass-transition temperature of 102° C. and an elongation at break of 90%, and the vinyl aromatic elastomer Kraton® G1643M characterized by a styrene content of 20% by weight and a Shore A hardness (30 sec) of 52, in weight percentages as given in Table 1.

(34) The glass-transition temperature was determined with the Q200 DSC from TA Instruments, according to ASTM D3418. Samples were heated to 220° C. with a speed of 50° C./min in the first run followed by a cooling step to −20° C. at 10° C./min. The glass-transition temperature was measured during the second heating cycle with a speed of 10° C./min.

(35) A 30-μm film was produced on 3-layer 600 mm wide cast line equipped with a Chloeren combining system and two 45 mm and one 60 mm Egan-Davis standard extruders. Prior to extrusion, all polymers were pre-dried to remove air and oxygen to prevent discoloration, carbide formation and voids in the film. Additionally, N.sub.2 was added to the extruder hopper and the extrusion feeding section.

(36) Elasticity modulus and stress at break were measured on pure films according to ASTM D882 and are reproduced in Table 1. The film dimensions for testing were 125 mm length and 15 mm width. The pull velocity of the clamps was 25 mm/min. A load cell of 250 N was applied.

(37) Prior to sealing, the peelable layer was adhesively laminated against a OPET 12 μm/aluminum foil 50 μm laminate to form multilayerfilm. The multilayerfilm was sealed on the multilayer film; sealing was performed with peelable layer against peelable layer with a Kopp sealer using 400 N/20 cm.sup.2 pressure during 1 sec and with one heated seal bar at a temperature of 220° C. and 230° C., respectively. Films were sealed in machine direction and opened in cross direction at a pull velocity of the tensile tester of 300 mm/min. Sample widths of 15 mm were applied. Peel-strength values, according to ASTM F88, are reproduced in Table 1.

(38) The peel aspect is visually evaluated, wherein (+) stands for fiber tears and angel hairs observed over the complete surface of the peel; (++) stands for a few angel hairs observed over part of the surface of the peel; and (+++) stands for a complete intact peel surface.

(39) Samples of the extruded films are cut and sealed into pouches with the dimensions of 10×10 cm. A 25 mg Nicorette™ patch of 22.5 cm.sup.2 is put on the inside of the pouch prior to close sealing. The pouch is stored in an oven at 60° C. during 24 h. After opening the pouch, the nicotine absorbed in the 22.5 cm.sup.2 film, in direct contact with the patch, is put in a tube containing a 4 ml ethanol/hexane (50/50) solution. The solution is stirred in an ultrasonic bath during 30 min. The nicotine content is quantified by GC coupled with a flame ionization detector (FID). The FID uses a hydrogen/air flame into which the sample is passed. In the flame, the nicotine is further oxidized into electrically-charged particles. The ions are collected and create an electrical signal proportional to the concentration of nicotine.

(40) The quantity of nicotine, in μg, penetrated into the seal layer is reproduced in Table 1. By way of comparison, the nicotine quantity of an oriented polypropylene film of the same dimension, under identical conditions equals 562 μg/22.5 cm.sup.2.

(41) TABLE-US-00001 TABLE 1 1 2% 3% 4% 5N/mm.sup.2 6N/mm.sup.2 7N/15 mm 8N/15 mm 9 Eval. 10 μg/22.5 cm.sup.2 Ex. 1 100 0.0 0.0 2200 66 1.9 7.2 23.9 Ex. 2 80 19.0 1.0 1940 55 2.5 7.6 ++ 16.4 Ex. 3 65 33.5 1.5 1883 46 3.2 10.6 ++ 18.1 Ex. 4 50 48.0 2.0 1657 42 5.2 13.5 +++ 13.7 Ex. 5 0 95.0 5.0 1595 33 15.9 24.9 +++ 13.8

(42) Example 1 and 5 are comparative examples. Example 1 only has a first polymeric cyclic olefin and the peel gives angel hairs. Example 5 only uses a second cyclic olefin polymer and an elastomer leading to a glass-transition temperature lower than usual sterilization temperatures, additionally to too-high peel-strength values (too high opening forces).

(43) Key 1. examples 2. weight percentage of the first cyclic olefin polymer (Zeonor® 1430R) 3. weight percentage of the second cyclic olefin polymer (Zeonor® 1020R) 4. weight percentage of the vinyl aromatic elastomer (Kraton® G1643M) 5. elasticity modulus, in N/mm.sup.2, according to ASTM D882 6. stress at break, in N/mm.sup.2, according to ASTM D882 7. peel strength, according to ASTM F88, in N/15 mm, for a sealing temperature of 220° C. 8. peel strength, according to ASTM F88, in N/15 mm, for a sealing temperature of 230° C. 9. visual evaluation of the peel region 10. nicotine uptake of the heat-seal layer in μg/22.5 cm.sup.2