Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
  • B65D81/24—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants
  • B65D81/28—Applications of food preservatives, fungicides, pesticides or animal repellants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • 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
  • C08L23/10—Homopolymers or copolymers of propene
  • C08L23/14—Copolymers of propene
  • C08L23/142—Copolymers of propene at least partially crystalline copolymers of propene with other 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
• • 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
  • B32B2307/732—Dimensional properties
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2203/00—Applications
  • C08L2203/16—Applications used for films
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31909—Next to second addition polymer from unsaturated monomers
  • Y10T428/31913—Monoolefin polymer
  • Y10T428/31917—Next to polyene polymer

Definitions

• the present invention relates to a polymer film especially suitable for the packaging of fresh foodstuff, like salad and vegetables.
• polypropylene films and particularly biaxially oriented polypropylene films (BOPP) are widely used for the packaging of foodstuff using automatic machines.
• the said films are characterized by a particular good balance of processability (“machinability”), optical and mechanical properties, and low permeability to gases, in particular oxygen and carbon dioxide, and water vapour.
• Monolayer and multilayer films suitable for packaging fresh produce items that continue to respire after they are harvested are described in U.S. Pat. No. 6,348,271.
• the films therein described are characterized by the presence of at least one layer of a propylene resin composition comprising a propylene polymer component and up to 70% by weight of an ethylene/propylene copolymer. Additional layers made of propylene polymers can be present.
• the water vapour transmission rate should not be greater than 50 g/m 2 *day.
• a high oxygen transmission rate would be desirable, but an increase of oxygen transmission rate can easily raise the water vapour transmission rate to excessively high values.
• the vapour transmission rate becomes as high as 60 g/m 2 *day.
• the said propylene copolymer Due to its valuable properties, the said propylene copolymer provides valuable film performances, in particular a valuable balance of resistance to solvents (low amounts of fraction soluble in organic solvents, in particular hydrocarbons), ink and dye printability and heat sealability, as it makes it possible to seal the film at advantageously low temperatures.
• the present invention provides a multilayer film comprising at least one layer A) and at least one layer B), wherein the layer A) comprises a copolymer (i) of propylene with hexene-1 containing from 3 to 9% by weight, preferably from 5 to 9% by weight, more preferably from 6 to 9% by weight, in particular from 6.5 to 9% by weight, of recurring units derived from hexene-1, said copolymer having a melting temperature from 125° C. to 143° C., preferably from 128° C. to 143° C., and the layer B) comprises a polyolefin composition (ii) containing (all percentages being by weight):
• a temperature of 25° C. is meant.
• the films of the present invention can have a A)/B) or a A)/B)/A) structure, wherein layers A) and B) are as above defined.
• copolymer includes polymers containing more than one kind of comonomers, such as terpolymers.
• the said amounts of hexene-1 units are referred to the total weight of the copolymer (i).
• the said melting temperature values for the copolymer (i) are determined by differential scanning calorimetry, according to ISO 11357-3, with a heating rate of 20° C./minute.
• Recurring units derived from other comonomers selected in particular from ethylene and CH 2 ⁇ CHR 1 ⁇ -olefins where R I is a C 2 —C 8 alkyl radical, hexene-1 excluded, can be present in copolymer (i), provided that the final properties of the copolymer are not substantially worsened.
• Examples of the said CH 2 ⁇ CHR I ⁇ -olefins are butene-1, 4-methyl-1-pentene, octene-1.
• ethylene is preferred.
• the total amount of recurring units derived from comonomer(s) different from propylene and hexene-1 in copolymer (i) is from 0.5 to 2% by weight, preferably from 0.5 to 1.5% by weight, referred to the total weight of the copolymer.
• the copolymer (i) is semicrystalline, as it has a crystalline melting point, and typically has a stereoregularity of isotactic type.
• said copolymer (i) exhibits at least one of the following features:
• the copolymer (i) has preferably a Melt Flow Rate (MFR, measured according to ISO 1133, 230° C./2.16 kg, i.e. at 230° C., with a load of 2.16 kg) from 0.1 to 10 g/10 min., more preferably from 0.1 to 5 g/10 min., in particular from 0.1 to 3 g/10 min.
• MFR Melt Flow Rate
• Such copolymer (i) can be obtained with polymerization processes carried out in the presence of stereospecific Ziegler-Natta catalysts supported on magnesium dihalides.
• the molecular weight regulator preferably hydrogen
• the said preferred Melt Flow Rate values and melting temperature values are obtained, when the amount of recurring units derived from hexene-1 is within the above said range of from 3 to 9% by weight, preferably from 5 to 9% by weight.
• the polymerization process which can be continuous or batch, is carried out following known techniques and operating in liquid phase, in the presence or not of inert diluent, or in gas phase, or by mixed liquid-gas techniques. It is preferable to carry out the polymerization in gas phase.
• Polymerization reaction time, pressure and temperature are not critical, however it is best if the temperature is from 20 to 100° C.
• the pressure can be atmospheric or higher.
• the regulation of the molecular weight is carried out by using known regulators, hydrogen in particular.
• the said stereospecific Ziegler-Natta polymerization catalysts comprise the product of the reaction between:
• Said catalysts are preferably capable of producing homopolymers of propylene having an isotactic index higher than 90% (measured as weight amount of the fraction insoluble in xylene at room temperature).
• the solid catalyst component (1) contains as electron-donor a compound generally selected among the ethers, ketones, lactones, compounds containing N, P and/or S atoms, and mono-and dicarboxylic acid esters.
• Catalysts having the above mentioned characteristics are well known in the patent literature; particularly advantageous are the catalysts described in U.S. Pat. No. 4,399,054 and European patent 45977.
• Particularly suited among the said electron-donor compounds are phthalic acid esters and succinic acid esters.
• Suitable succinic acid esters are represented by the formula (I):
• radicals R 1 and R 2 are a C1—C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms;
• the radicals R 3 to R 6 equal to or different from each other, are hydrogen or a C1—C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms, and the radicals R 3 to R 6 which are joined to the same carbon atom can be linked together to form a cycle.
• R 1 and R 2 are preferably C1—C8 alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl groups. Particularly preferred are the compounds in which R 1 and R 2 are selected from primary alkyls and in particular branched primary alkyls. Examples of suitable R 1 and R 2 groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl, and neopentyl.
• R 3 to R 5 are hydrogen and R 6 is a branched alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl radical having from 3 to 10 carbon atoms.
• Another preferred group of compounds within those of formula (I) is that in which at least two radicals from R 3 to R 6 are different from hydrogen and are selected from C1—C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms.
• Particularly preferred are the compounds in which the two radicals different from hydrogen are linked to the same carbon atom.
• the compounds in which at least two radicals different from hydrogen are linked to different carbon atoms that is R 3 and R 5 or R 4 and R 6 are particularly preferred.
• the electron-donor compounds (3) that can be used as external electron-donors (added to the Al-alkyl compound) comprise the aromatic acid esters (such as alkylic benzoates), heterocyclic compounds (such as the 2,2,6,6-tetramethylpiperidine and the 2,6-diisopropylpiperidine), and in particular silicon compounds containing at least one Si—OR bond (where R is a hydrocarbon radical).
• Examples of the said silicon compounds are those of formula R a 1 R b 2 Si(OR 3 ) c , where a and b are integer numbers from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R 1 , R 2 , and R 3 are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.
• Thexyltrimethoxysilane (2,3-dimethyl-2-trimethoxysilyl-butane) is particularly preferred.
• Other preferred silicon compounds are diisopropyl dimethoxy silane and dicyclopentyl dimethoxysilane.
• the previously said 1,3-diethers are also suitable to be used as external donors.
• the internal donor is one of the said 1,3-diethers, the external donor can be omitted.
• the catalysts may be precontacted with small quantities of olefin (prepolymerization), maintaining the catalyst in suspension in a hydrocarbon solvent, and polymerizing at temperatures from room to 60° C., thus producing a quantity of polymer from 0.5 to 3 times the weight of the catalyst.
• the operation can also take place in liquid monomer, producing, in this case, a quantity of polymer up to 1000 times the weight of the catalyst.
• Examples of the said CH 2 ⁇ CHR ⁇ -olefins where R is a C 2 —C 8 alkyl radical, present in the composition (ii), are butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, and octene-1. Butene-1 is preferred.
• the amount of diene in component (b) of the composition (ii) is preferably from 1 to 10% by weight with respect to the total weight of component (b).
• dienes are butadiene, 1,4-hexadiene, 1,5-hexadiene, and ethylidene-1-norbornene.
• the intrinsic viscosity of the fraction soluble in xylene at room temperature of the composition (ii) is from 2 to 4 dl/g.
• composition (ii) examples are described in published European patent application EP-A-0472946 and in WO03/011962, whose content is incorporated in this patent application for reference purposes.
• the polyolefin composition (ii) can be prepared by mixing the previously prepared components (a) and (b) in the fluid state, i.e., at temperatures greater than their softening or melting point, or, more preferably, by sequential polymerization in two or more stages. It is preferred to carry out the polymerization processes for the preparation of the single components or of the polyolefin composition (ii) (sequential polymerization) in the presence of a highly stereospecific Ziegler-Natta catalyst.
• the Ziegler-Natta catalysts described in detail in connection with the preparation of the copolymer (i) of propylene with hexene-1 of layer A) can be used for the preparation of the polyolefin composition (ii) as well.
• the film layer B) can comprise a blend of the polyolefin composition (ii) with a copolymer of propylene with hexene-1 falling within the definition of the copolymer (i).
• Preferred relative amounts are from 30% to 70% by weight of polyolefin composition (ii) and from 30% to 70% by weight of the said copolymer (i). Such amounts are referred to the total weight of the polyolefin composition (ii) and of the copolymer (i).
• All the film layers may also contain the additives that are commonly used for the film manufacturing, and especially for the films used for packaging applications with automatic machines, such as anti-oxidants, process stabilizers, slip agents, antistatic agents, antiblock agents.
• the overall film thickness is preferably from 9 to 100 microns, the thickness of the layer(s) A) is preferably from 0.5 to 15 microns, and that of the layer(s) B), typically used as inner layer(s), is from 9.5 to 99.5 microns.
• the said films are produced by using processes well known in the art.
• extrusion processes can be used.
• the polymer materials to be used for the various layers are molten in different extruders and extruded through a narrow die slit. Subsequent from the exit from the die, the material can be cooled, heated and optionally oriented in several ways or in combination. Examples of such processes are cast, blown, extrusion coating, uniaxially oriented, simultaneous biaxially oriented, and sequential biaxially oriented film processes.
• the molten polymer materials are forced through a circular shaped die.
• the extrudate which is drawn off has the shape of a tube, which is inflated by air to form a tubular bubble.
• the bubble is cooled and collapsed before winding-up.
• the blown film process is preferred for the preparation of the film of the present invention.
• the molten polymer materials are forced continuously through a narrow die.
• the extruded molten material is pulled away from the die and cooled, then heated again and stretched both in the Machine Direction (MD) and in the Transverse Direction (TD). After the stretching process, the film is cooled and then wound-up.
• MD Machine Direction
• TD Transverse Direction
• the samples are dissolved in 1,1,2,2-tetrachloroethane-d2 at 120° C. with a 8% wt/v concentration.
• Each spectrum is acquired with a 90° pulse, 15 seconds of delay between pulses and CPD (WALTZ 16) to remove 1 H- 13 C coupling.
• About 1500 transients are stored in 32 K data points using a spectral window of 6000 Hz.
• the peak of the Propylene CH is used as internal reference at 28.83 ppm.
• a C2 Area (A C2 ) of the absorption band due to methylenic sequences (CH 2 rocking vibration) after a proper digital subtraction of an isotactic polypropylene (IPP) reference spectrum.
• the range 660 to 790 cm ⁇ 1 is used for both heterophasic and/or random copolymers.
• the melting temperature is determined using the following procedure according to ISO 11357 Part 3.
• DSC Differential scanning calorimetric
• the samples are subjected to a first heating run from 5° C. to 200° C. with a heating rate of 20° C./minute, and kept at 200° C. under isothermal conditions for 5 minutes. Then the samples are cooled from 200° C. to 5° C. with a cooling rate of 20° C./minute, and kept at 5° C. under isothermal conditions for 5 minutes, after which they are subjected to a second heating run from 5° C. to 200° C. with a heating rate of 20° C./minute.
• the melting temperature is the temperature of the highest melting peak obtained in the second heating run.
• MWD and particularly the ratio M w / M n is determined using a Waters 150-C ALC/GPC system equipped with a TSK column set (type GMHXL-HT) working at135° C. with 1,2-dichlorobenzene as solvent (ODCB) (stabilized with 0.1 vol. of 2, 6-di-t-butyl p-cresole (BHT)) at flow rate of 1 ml/min.
• ODCB 1,2-dichlorobenzene as solvent
• BHT 2, 6-di-t-butyl p-cresole
• the solution is filtered through a 0.45 ⁇ m Teflon membrane.
• the filtrate (concentration 0.08-1.2g/l injection volume 300 is subjected to GPC.
• Monodisperse fractions of polystyrene (provided by Polymer Laboratories) are used as standard.
• Three layer films are prepared using the hereinafter described polymer materials.
• Copolymer 1 and Copolymer 2 Two copolymers of propylene with hexene-1, hereinafter called Copolymer 1 and Copolymer 2, are prepared as follows.
• the solid catalyst component used in polymerization is a highly stereospecific Ziegler-Natta catalyst component supported on magnesium chloride, containing about 2.2% by weight of titanium and diisobutylphthalate as internal donor, prepared by analogy with the method described in WO03/054035 for the preparation of catalyst component A.
• the solid catalyst component described above is contacted at 15° C. for about 6 minutes with aluminum triethyl (TEAL) and thexyltrimethoxysilane (2,3 -dimethyl-2-trim ethoxysilyl-butane), in a TEAL/thexyltrimethoxysilane weight ratio equal to about 7 and in such quantity that the TEAL/solid catalyst component weight ratio be equal to about 6.
• TEAL aluminum triethyl
• thexyltrimethoxysilane 2,3 -dimethyl-2-trim ethoxysilyl-butane
• the catalyst system is then subjected to prepolymerization by maintaining it in suspension in liquid propylene at 20° C. for about 20 minutes before introducing it into the polymerization reactor.
• the polymerization is carried out in a gas phase polymerization reactor by feeding in a continuous and constant flow the prepolymerized catalyst system, hydrogen (used as molecular weight regulator), propylene and hexene-1 in the gas state.
• hydrogen used as molecular weight regulator
• propylene used as molecular weight regulator
• the main polymerization conditions are:
• Copolymer 1 Copolymer 2
• C3- propylene
• C6- hexene-1.
• the polymer particles exiting the reactor are subjected to a steam treatment to remove the reactive monomers and volatile substances, and then dried.
• the resulting copolymers have the following properties:
• Copolymer 1 Copolymer 2 Hexene-1 content 4.3% by weight 8.1% by weight MFR: 0.6 g/10 min. 0.5 g/10 min. Amount of fraction soluble in xylene at room temperature: 3.4% by weight 23.2% by weight Melting temperature: 139.7° C. 132.4° C.
• the material used to prepare the layer B) is a polyolefin composition (ii) having a MFR of 0.6 g/10 min. and comprising (weight percentages):
• the intrinsic viscosity of the fraction soluble in xylene at room temperature of the total composition is of 3.2 dl/g.
• composition has been prepared by a sequential polymerization process in the presence of a stereospecific Ziegler-Natta catalyst supported on magnesium dichloride.
• the said two copolymers of propylene with hexene-1 are both extruded with 500 ppm by weight of Dynamar FX5911 and 750 ppm by weight of NA 21, thus obtaining the final products COPO-1, resulting from extrusion with the said additives of Copolymer 1, and COPO-2, resulting from extrusion with the said additives of Copolymer 2.
• DynamarTM FX5911 is a fluoropolymer sold by 3M for use as processing aid.
• NA 21TM is a nucleating agent based on aluminum-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate], sold by Asahi Denka K. K.
• the said extrusions with Dynamar FX5911 and NA 21 are carried out in a co-rotating twin screw three lobs profile extruder (ZSK58 type, length/diameter ratio of 28, manufactured by Coperion) under nitrogen atmosphere in the following conditions:
• Rotation speed 260 rpm
• the three layer films are prepared on a Kiefel three layer coextrusion line.
• the final film thickness of the films is approximately 30 micron, with a structure A/B/A wherein the thickness of each layer A) amounts to 30% of the total thickness and the thickness of layer B) to the remaining 40%.
• the film of Example 1 is prepared by using COPO-1 for both the two layers A) and the above described polyolefin composition (ii) for layer B).
• the film of Example 2 is prepared by using COPO-2 for both the two layers A) and the above described polyolefin composition (ii) for layer B).
• the screw length/screw diameter ratios are 60 mm/24 xD for all three A, B and C extruders.
• No IBCS system Internal Bubble Cooling System
• the melt is extruded through an annular die with a diameter of 200 mm and a quite narrow gap (1.2 mm for the trials).
• the melt tube is subjected to intensive air cooling, immediately blown up to about three times the diameter of the die and stretched in the direction of the flow.

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• 2011
  • 2011-12-08 WO PCT/EP2011/072144 patent/WO2012076633A1/fr active Application Filing
  • 2011-12-08 BR BR112013014016-0A patent/BR112013014016B1/pt active IP Right Grant
  • 2011-12-08 EP EP11796963.4A patent/EP2648910B1/fr active Active
  • 2011-12-08 US US13/991,754 patent/US20130252006A1/en not_active Abandoned
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