MULTILAYER FILM

Abstract

The current invention relates to a multilayer film. The multilayer film is characterized by a combination of desirable properties, such as excellent thermoformability, good optical properties, excellent sealability, puncture resistance and recycling capacity.

Claims

1. A multilayer film comprising an outer layer, an oxygen barrier layer, and an inner sealing layer, wherein the oxygen barrier layer is located between the outer layer and inner sealing layer, wherein the oxygen barrier layer comprises an ethylene vinyl ester copolymer (EVOH), and wherein the multilayer film comprises at least 90% per weight polypropylene or polybutene polymers or copolymers, not more than 8% per weight EVOH, and at least 25% per weight random propylene-ethylene copolymer having a melting point in the range from 135 C. to 148 C., based on the total weight of the multilayer film, and wherein the multilayer film does not comprise any polyamide, polyester, polyvinyl chloride (PVC), or polyvinylidene chloride (PVDC).

2. The multilayer film according to claim 1, wherein the multilayer film comprises a homopolymer polypropylene, preferably wherein the multilayer film comprises a homopolymer polypropylene in the outer layer.

3. The multilayer film according to claim 2, wherein the homopolymer polypropylene is a homopolymer polypropylene produced by either Ziegler-Natta- or metallocene catalysts and having a melting point of at least 150 C., more preferably_the homopolymer polypropylene has a melting point in the range from 150 C. to 170 C. and further preferably a melt flow rate in the range from 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes).

4. The multilayer film according to claim 1, wherein the multilayer film comprises, in the outer layer a random propylene-ethylene copolymer, preferably, the random propylene-ethylene copolymer has a melting point in the range from 135 C. to 148 C. and further preferably a melt flow rate in the range from 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes).

5. The multilayer film according to claim 1, wherein the multilayer film comprises, in the outer layer a propylene ethylene copolymer with less than 10% per weight ethylene and a melting point of less than 130 C., more preferably less than 125 C., even more preferably less than 120 C.

6. The multilayer film according to claim 1, wherein the multilayer film comprises at least one polypropylene polymer, preferably a blend of different polypropylene polymers, in the inner heat sealing layer, preferably the melting point of the polypropylene material in the inner heat sealing layer is at least 10 C. lower than the melting point of any polypropylene material used in any other layer of the multilayer film.

7. The multilayer film according to claim 6, wherein the multilayer film comprises a propylene ethylene copolymer in the inner heat sealing layer, preferably the propylene ethylene copolymer has a melting point of less than 135 C., preferably less than 130 C., more preferably a melting point of less than 125 C., even more preferably a melting point of less than 120 C.

8. The multilayer film according to claim 6, wherein the multilayer film comprises at least 10% of the propylene ethylene copolymer, based on the total weight of the multilayer film.

9. The multilayer film according to claim 1, wherein the inner sealing layer further comprises a propylene butene copolymer, preferably said copolymer has a melting point of less than 135 C., preferably less than 130 C., more preferably a melting point of less than 125 C., even more preferably a melting point of less than 120 C.

10. The multilayer film according to claim 1, wherein the inner sealing layer further comprises a propylene-ethylene-butene copolymer, preferably the sum of the ethylene and butene content in the propylene-ethylene-butene copolymer is less than 10% by weight based on the total weight of the copolymer.

11. The multilayer film according to claim 1, comprising at least one intermediate layer between the outer layer and the oxygen barrier layer and/or between the oxygen barrier layer and the inner heat sealing layer, preferably the multilayer film comprises the following layer structure: outer layer/intermediate layer 1/barrier layer/intermediate layer 2/inner sealing layer.

12. The multilayer film according to claim 1, comprising the following layer structure: outer layer/intermediate layer 1/intermediate layer 2/intermediate layer 3/barrier layer/intermediate layer 4/intermediate layer 5/intermediate layer 6/inner sealing layer, or the following layer structure: outer layer/intermediate layer 1/intermediate layer 2/barrier layer/intermediate layer 3/intermediate layer 4/inner sealing layer.

13. The multilayer film according to claim 1, wherein the multilayer film as a haze of less than 10% measured according to ASTM D 1003.

14. The multilayer film according to claim 1, wherein the multilayer film has a gloss of at least 100 GU (45 angle) measured according to ASTM D2457.

15. A method for packaging, the method comprising using the multilayer film according to claim 1, for packaging applications, in particular for packaging food.

16. A method of using the multilayer film according to claim 1, as top film and/or bottom film in deep-drawing packaging.

17. A deep-drawing package comprising as a top film and/or as a bottom film a multilayer film according to claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0073] In a first aspect, the present invention relates to a multilayer film comprising an outer layer, an oxygen barrier layer, and an inner sealing layer, wherein the oxygen barrier layer is located between the outer layer and inner sealing layer, wherein the oxygen barrier layer comprises an ethylene vinyl ester copolymer (EVOH).

[0074] The multilayer film comprises at least 90% per weight polypropylene or polybutene polymers or copolymers, not more than 8% per weight EVOH, and at least 25% per weight random propylene-ethylene copolymer having a melting point in the range from 135 C. to 148 C., based on the total weight of the film. Further the multilayer film does not comprise any polyamide, polyester, polyvinyl chloride (PVC), or polyvinylidene chloride (PVDC).

[0075] In one embodiment the multilayer film comprises at least one intermediate layer between the outer layer and the oxygen barrier layer and/or between the oxygen barrier layer and the inner heat sealing layer.

[0076] In a further embodiment the multilayer film comprises the following layer structure: outer layer/intermediate layer 1/barrier layer/intermediate layer 2/inner sealing layer.

[0077] In a further embodiment the multilayer film comprises the following layer structure: outer layer/intermediate layer 1/intermediate layer 2/intermediate layer 3/barrier layer/intermediate layer 4/intermediate layer 5/intermediate layer 6/inner sealing layer.

[0078] In a further embodiment the multilayer film comprises the following layer structure: outer layer/intermediate layer 1/intermediate layer 2/barrier layer/intermediate layer 3/intermediate layer 4/inner sealing layer.

Outer Layer

[0079] The outer layer of the film is the layer that is in contact with the atmosphere.

[0080] According to a first embodiment of the invention, the outer layer comprises a homopolymer polypropylene (PP). Preferably, the homopolymer polypropylene has a melting point of at least 150 C., more preferably the homopolymer polypropylene has a melting point in the range from 150 C. to 170 C. and further preferably a melt flow rate in the range from 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes). Preferably, the homopolymer polypropylene is produced by either Ziegler Nata or metallocene catalysts.

[0081] According to a second embodiment of the invention, the outer layer comprises a random propylene-ethylene copolymer. Preferably, the random propylene-ethylene copolymer has a melting point in the range from 135 C. to 148 C. and further preferably a melt flow rate in the range from 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes).

[0082] According to a third embodiment of the invention, the outer layer comprises a propylene ethylene copolymer with less than 10% per weight ethylene and a melting point of less than 130 C., more preferably less than 125 C., even more preferably less than 120 C.

[0083] According to a further embodiment of the invention, the outer layer comprises a blend of at least two polymers of the above first, second, or third embodiment.

[0084] According to a further embodiment of the invention, the outer layer comprises a blend of polymers of the above first, second, and third embodiment.

Inner Layer

[0085] In the film according to the present invention, the inner heat sealing layer may comprise a single polypropylene polymer or a blend of different polypropylene polymers.

[0086] Preferably the melting point of the polypropylene material in the inner heat sealing layer is at least 10 C., preferably at least 20 C. lower than the melting point of any polypropylene material used in any other layer of the film.

[0087] In a first preferred embodiment the inner heat sealing layer comprises a propylene-ethylene-butene copolymer, preferably the sum of the ethylene and butene content in the propylene-ethylene-butene copolymer is less than 10% by weight based on the total weight of the copolymer.

[0088] In a second preferred embodiment the inner heat sealing layer comprises a copolymer of propylene and butene, preferably the melting point of such a copolymer is less than 135 C., more preferably less than 130 C.

[0089] In a third preferred embodiment the inner heat sealing layer comprises a copolymer of propylene and ethylene, preferably the melting point of such a copolymer is less than 135 C., preferably less than 130 C., more preferably less than 125 C., even more preferably less than 120 C.

[0090] According to a further preferred embodiment of the invention, the inner heat sealing layer comprises a blend of at least two polymers of the above first, second, or third embodiment.

[0091] In a preferred version of the invention, the sealing layer may be a peel layer, e.g. specially designed to offer easy to open effect. In such a case, materials like Borpeel or Steripeel from Borealis or special blends of PP and PE are used as known in the art.

Oxygen Barrier Layer

[0092] The multilayer film comprises an oxygen barrier layer comprising EVOH.

[0093] The oxygen barrier material is located in an intermediate layer of the film between the outer layer and inner heat sealing layer.

[0094] In general, EVOH with an ethylene content of between 48 and 24% per mol is preferred, more preferably 27 to 44% per mol, even more preferably 38 to 44% per mol.

Other Intermediate Layers

[0095] Between the sealing layer and the oxygen barrier layer, tie layers can be used. Preferred materials for the tie layer may be maleic anhydride modified PP grades, such as Bynel 50E109 from Dow or Admer 541E from Mitsui Chemicals, materials well known in the art.

[0096] Other intermediate layers can be used as abuse layers.

[0097] According to a preferred embodiment of the invention, intermediate abuse layer comprise a homopolymer polypropylene, having a melting point in the range from 150 C. to 170 C. and a melt flow rate of 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes).

[0098] According to another preferred embodiment of the invention, the intermediate abuse layer comprises a random propylene-ethylene copolymer having a melting point of 135 C. to 148 C. and a melt flow rate of 0.2 to 20 grams as measured by ASTM D1238 (230 C., 10 minutes).

[0099] According to another preferred version of the invention, the intermediate abuse layer comprises a propylene ethylene copolymer with less than 10% per weight ethylene and preferably a melting point of less than 130 C., more preferably less than 125 C., even more preferably less than 120 C.

Other Film Features

[0100] Any of the layers described above may also include additives well known in the art such as slip agents, antiblock, polymer processing aids, antistatic, antifog, acid scavengers, odour scavengers, nucleating agents, hydrocarbon resins and the like. A person skilled in the art may select the right additives according to any particular needs.

[0101] The thickness of the film is preferably in the range 10 to 300 microns, more preferably 20 to 250 microns. The thickness of the outer layer is from 1 to 50 microns, more preferably 3 to 25 microns. The thickness of the inner layer is 5 to 100 microns, more preferably 10 to 60 microns.

[0102] In a further aspect of the invention the film or some layers of the film are irradiated.

[0103] A preferable method is e-beam or UV radiation or gamma ray. Other methods are also known in the art. Irradiation with use of electron beam is preferred.

[0104] For the production of the film of the invention the hot blown film process is suitable, either air cooled or fast quenched e.g. cooled by water or other means more efficient in cooling effect than air. Fast quenched process is preferred. Cast process is also suitable.

[0105] The multilayer film of the present invention have preferablya haze of less than 10% measured according to ASTM D 1003 and a gloss of at least 100 GU (45 angle) measured according to ASTM D2457.

[0106] The present invention is now described by the following Examples:

EXAMPLES

Example 1

[0107] A 9-layer film was produced in a hot blown film line operating with a very efficient fast quench process. The multilayer film comprises the following structure: [0108] Outer layer, 99% PPH1+1% slip antiblock masterbatch, thickness 25 microns [0109] Intermediate layer 1, 100% PPR1, thickness 10 microns [0110] Intermediate layer 2, 100% PPR1, thickness 8 microns [0111] Intermediate layer 3, 100% TIE1, thickness 5 microns [0112] Barrier Layer 100% EVOH1, thickness 4 microns [0113] Intermediate layer 4, 100% TIE1, thickness 5 microns [0114] Intermediate layer 5 100% PPPE1, thickness 10 microns [0115] Intermediate layer 6, 100% PPR1, thickness 10 microns [0116] Sealing layer, 70% PPB1+29% PPPE1+1% slip antiblock masterbatch, thickness 13 microns

[0117] See table 1

[0118] Film of example 1 has a weight percentage of random propylene ethylene copolymer of 30.8%, a weight percentage of EVOH of 5.71% and a weight percentage of propylene ethylene of low melting points (less than 130 C.) of 15%.

Example 2

[0119] A 9-layer film was produced in a hot blown film line operating with a very efficient fast quench process [0120] Outer layer, 99% PPR1+1% slip antiblock masterbatch, thickness 45 microns [0121] Intermediate layer 1, 100% PPR1, thickness 20 microns [0122] Intermediate layer 2, 100% PPR1, thickness 12 microns [0123] Intermediate layer 3, 100% TIE1, thickness 7 microns [0124] Barrier Layer 100% EVOH1, thickness 5.5 microns [0125] Intermediate layer 4, 100% TIE1, thickness 7 microns [0126] Intermediate layer 5, 100% PPPE1, thickness 15 microns [0127] Intermediate layer 6, 100% PPR1, thickness 15 microns [0128] Sealing layer, 70% PPB1+29% PPPE1+1% slip antiblock masterbatch, thickness 25 microns

[0129] Film of example 2 has a weight percentage of random propylene ethylene copolymer of 30.8%, a weight percentage of EVOH of 4.7% and a weight percentage of propylene ethylene of low melting points (less than 130 C.) of 14.5%.

TABLE-US-00001 TABLE 1 Melt Index g/10 min Melting (230 C. for Density point Type Description Description Manufacturer all resins) g/cm.sup.3 C. PPH1 homopolymer TIPPLEN MOL 1.7 0.9 Approx. polypropylene H 659 F Petrochemicals 160 C. with medium Co. LTD molecular weight EVOH 1 38 mol % Ethylene EVAL EVAL, Kuraray 1 1.17 172 C. Vinyl-Alcohol H171B Copolymer PPR1 Propylene Polypropylene TotalEnergies 1.8 0.902 142 C. ethylene random PPR 3221 copolymer PPPE1 Propylene DOW 2.2 0.885 Less than ethylene 120 C. copolymer TIE1 Maleic anhydride Bynel DOW 3.1 0.908 125 C. modified PP 50E109 PPB1 Propylene butene 5 0.895 131 C. olefin copolymer

COMPARATIVE EXAMPLES

[0130] A conventional top and a conventional bottom film was produced as per the prior art

Comparative Example 1

[0131] A 9 layer film was produced in a hot blown film line operating with a very efficient fast quench process [0132] Outer layer, 99% PA1+1% slip antiblock masterbatch, thickness 25 microns [0133] Intermediate layer 1, 100% TIE2, thickness 10 microns [0134] Intermediate layer 2, 70% PE1+30% PE2, thickness 8 microns [0135] Intermediate layer 3, Next Layer, 100% TIE1, thickness 5 microns [0136] Barrier Layer 100% EVOH1, thickness 4 microns [0137] Intermediate layer 4, 100% PA1, thickness 5 microns [0138] Intermediate layer 5, 100% TIE2, thickness 10 microns [0139] Intermediate layer 6, 70% PE1+30% PE2, thickness 10 microns [0140] Sealing layer, 70% PE1+29% PE2+1% slip antiblock masterbatch, thickness 23 microns

[0141] See table 2

Comparative Example 2

[0142] A 9 layer film was produced in a hot blown film line operating with a very efficient fast quench process [0143] Outer layer, 99% PA1+1% slip antiblock masterbatch, thickness 45 microns [0144] Intermediate layer 1, 100% TIE2, thickness 20 microns [0145] Intermediate layer 2, 70% PE1+30% PE2, thickness 12 microns [0146] Intermediate layer 3, 100% TIE2, thickness 7 microns [0147] Barrier Layer 100% EVOH1, thickness 4 microns [0148] Intermediate layer 4, 100% PA1, thickness 7 microns [0149] Intermediate layer 5, 100% TIE2, thickness 15 microns [0150] Intermediate layer 6, 70% PE1+30% PE2, thickness 15 microns [0151] Sealing layer, 70% PE1+29% PE2+1% slip antiblock masterbatch, thickness 25 microns

TABLE-US-00002 TABLE 2 Melting Melt Index Density point Type Description Description Manufacturer g/10 min g/cm.sup.3 C. PA1 Polyamide 6 Ultramid BASF 01.13 218 C. grade B40 LN EVOH 1 38 mol % EVAL EVAL, 1 1.17 172 C. Ethylene H171B Kuraray Vinyl- Alcohol Copolymer TIE 2 Maleic ADMER Mitsui 1.6 0.91 122 C. anhydride NF358E Chemicals grafted, LLDPE- based tie resin PE1 ETHYLENE MarlexD139 CHEVRON 1 0.918 Approx. HEXENE PHILIPS 120 C. METALLOCENE CHEMICAL COPOLYMER PE2 Low Density DOW DOW 0.7 0.923 110 C. Polyethylene LDPE 310E Resin

Testing-Evaluation

[0152] The following evaluation testing was done on both films of the invention and comparative examples.

Haze Measurement

[0153] The haze measurement is done according to ASTM D 1003.

Gloss Measurement

[0154] The gloss measurement is done according to ASTM D2457.

Puncture Resistance

[0155] Puncture resistance is measured using a MECMESIN instrument comprising a vertical stand VERSA TEST, a load cell AFG 100N, which is mounted on the stand, and a digital height gauge MITUTOYO SDV 60B. A cylindrical shaft ending to a conical indenter is attached to the load cell. The indenter has an angle of 600 and a tip of 0.5 mm in diameter.

[0156] The film is conditioned at 23 C. and about 50% RH for at least 24 hours prior to the measurement. Square samples of 8.5 cm8.5 cm are prepared and clamped on a 5 cm diameter circular base. The indenter moves perpendicular to the film and force is measured as the indenter comes into contact with and ruptures the film. The speed of the indenter is set to 25 mm/min. Maximum force needed to puncture the film is recorded. The puncture force of a material is determined by averaging the values obtained for at least 5 samples of the material tested.

Thermoformability Test

[0157] The test was done on a thermoforming VC999 machine.

[0158] The films of example 1 and comparative example 1 were used as top films, having films of example 2 and comparative example 2 as bottom films respectively.

[0159] Features that were examined were thickness uniformity of the thermoformed pockets, ability to thermoform in a quite broad processing window and ability to have enough heat resistance to allow efficient sealing in the sealing station without burn of the tow film.

[0160] The combination of top example 1 and bottom example 2 was equally good to the comparative films combination and all were characterized as A. [0161] A=Good thermoformability [0162] B=Medium thermoformability [0163] C=Bad thermoformability

TABLE-US-00003 TABLE 3 PERFORMANCE IN THERMOFORMER PUNCTURE HAZE GLOSS evaluation RESISTANCE Example 1 6 120 A 22 Newtons Example 2 9 112 A 37 Newtons Comparative 6.7 110 A 24 Newtons Example 1 Comparative 9.2 120 A 35 Newtons Example 2