WO2003035391A2 - Multilayer sealing materials or peelable seals - Google Patents

Multilayer sealing materials or peelable seals Download PDF

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Publication number
WO2003035391A2
WO2003035391A2 PCT/FR2002/003669 FR0203669W WO03035391A2 WO 2003035391 A2 WO2003035391 A2 WO 2003035391A2 FR 0203669 W FR0203669 W FR 0203669W WO 03035391 A2 WO03035391 A2 WO 03035391A2
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WO
WIPO (PCT)
Prior art keywords
layer
typically
material according
ema
weight
Prior art date
Application number
PCT/FR2002/003669
Other languages
French (fr)
Other versions
WO2003035391A3 (en
Inventor
Jean-Marc Andre
Patrick Barranx
Bertrand Fillon
Original Assignee
Pechiney Emballage Flexible Europe
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Pechiney Emballage Flexible Europe filed Critical Pechiney Emballage Flexible Europe
Priority to EP02801936A priority Critical patent/EP1509393A2/en
Priority to AU2002356226A priority patent/AU2002356226A1/en
Publication of WO2003035391A2 publication Critical patent/WO2003035391A2/en
Publication of WO2003035391A3 publication Critical patent/WO2003035391A3/en

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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
    • B32B27/02—Layered products comprising a layer of synthetic resin in the form of fibres or filaments
    • 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
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/302—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding 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
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/31—Heat sealable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/10—Polypropylene
    • 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
    • B32B2325/00—Polymers of vinyl-aromatic compounds, e.g. polystyrene
    • 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
    • B32B2581/00—Seals; Sealing equipment; Gaskets

Definitions

  • the invention relates to lids intended to seal, by heat-sealing, containers or pots of thermoplastic material, typically of PS or PP, these lids are then peelable so as to be able to open said container or pot by separating the lid by simple pulling. manual on an edge of said cover.
  • the invention relates more particularly to multilayer covers not comprising aluminum foil.
  • lids are typically used for the packaging of fresh dairy products, such as for example yogurts.
  • lids comprise at least one layer known as of structure S ensuring the mechanical strength of the lid and a heat-sealing layer T adapted to the material forming said container or said pot, so as to form the material represented symbolically by S / T, the outer layer being the left most and the sealing layer right.
  • an intermediate bonding layer I joins the external layers S and T so as to ensure the cohesion of the multilayer material represented by S / 1 / T.
  • the cover may also comprise a protective outer layer P capable of thermally resisting heat sealing, the typical structure of the material then being P / S / 1 / T or possibly P / 1 / S / T, or also P / 1 / S / l '/ T, I and T being two bonding layers.
  • P capable of thermally resisting heat sealing
  • lids of the type are known:
  • PBT (8-40 ⁇ m) / SBS (20/250 ⁇ m) / PBT (8-40 ⁇ m) / SBS (5-30 ⁇ m), where PBT denotes a polybutylene terephthalate and SBS a copolymer of styrene and butadiene.
  • lids of the type are known:
  • PET or PA / PE + thermoplastic elastomer PET or PA / PE + thermoplastic elastomer.
  • PET or PA / paper or PP or PE or P A / PET or PE / T sealing layer PET or PA / paper or PP or PE or P A / PET or PE / T sealing layer.
  • EP 0795 491-A2 discloses lids of the type: silicone layer / PP / sealing layer T.
  • document DE 43 20 796-A1 discloses a heat-sealable and co-extruded material with three layers of the type: PS / PET / SBS + vinyltoluene-styrene copolymer, or with four layers of the type: PET / PS / PET / SBS + vinyltoluene-styrene copolymer.
  • the sealing material or cover forms a multilayer material with a thickness E of between 30 ⁇ m and 140 ⁇ m, and intended to seal by sealing a container or pot typically based on PP or PS, and comprises: a ) an external polyolefin layer CE, of thickness Ee ranging from 0.9.E to 0.6E, b) a sealing layer CS, of thickness Es ranging from 0.11E to 0.4. E, said sealing layer and said outer polyolefin layer having a melting temperature, denoted respectively Ts for the sealing layer and To for the polyolefin layer, such that To - Ts is at least 20 ° C, and preferably at least 30 ° C.
  • the Applicant has found that it is possible to form lids on the one hand with a limited number of layers, and on the other hand, by using to form the main layer, or support layer, a polyolefin, with know the typically most economical plastic material, so as to solve the main problems posed, and by using a sealing layer at "low" melting temperature. Thanks to this combination of means, the sealing material according to the invention and the derived lids can be sealed on PS or PP jars without destruction of the seal or pronounced marking of the lids by the sealing jaws. In addition, it was observed that it was no longer necessary with this type of lid to use a sheet of alumim 'um or a metallization layer forming a barrier layer.
  • FIG. 1 is a graph plotting on the abscissa the percentage of methyl acrylate in the EMA and on the ordinate the melting temperature T ° C measured by DSC (differential scanning calorimetry) corresponding to the maximum of the DSC curve.
  • Curve I corresponds to a so-called “tabular” EMA according to tests 2 and 4, and for which the gradient ⁇ T / ⁇ %, in absolute value, is worth approximately 0.70.
  • Curve II corresponds to a so-called “autoclave” EMA according to tests 1 and 3, and for which the gradient ⁇ T / ⁇ %, in absolute value, is approximately 2.
  • FIGS 2a to 2d illustrate, by schematic sections, 3 methods of sealing material according to the invention.
  • Figure 2a corresponds to a structure CE / CS where CE denotes the outer layer and CS the sealing layer.
  • Figure 2b corresponds to the structure CE / CC / CS where CC designates the central layer.
  • FIG. 2c corresponds to the structure NS / IP / CE / CS where IP denotes an impression applied to the material of FIG. 2a, where NS denotes an overprint varnish intended to protect the impression IP.
  • Figure 2d corresponds to the structure NS / IP / CE / CC / CS.
  • Figures 3a and 3b are DSC curves relating to two types of external layers, that of Figure 3a corresponding to 100% of PP, as in tests ⁇ o 1 and 2, that of Figure 3b corresponding to a mixture 70% by weight of PP and 25% by weight of PE, as in test 5.
  • FIG. 4 is a DSC curve relating to a sealing layer comprising a mixture of 65% by weight of EMA and 35% of metallocene PE according to test ⁇ o 10.
  • FIG. 5 is a DSC curve relating to a sealing material comprising an outer layer of PP, a central layer of PE, and a sealing layer of EMA, according to test 1.
  • said outer layer can form a mixture of polyolefins comprising a polyolefin, at least 50% by weight in said mixture, having said melting temperature To.
  • said sealing layer may comprise a majority component by weight having said melting temperature Ts.
  • the invention does not require that all of the constituents of said outer layer have a temperature To, and that all of the constituents of the sealing layer have said melting temperature Ts, such that we have To-Ts at least equal to 20 ° C. It suffices only that the majority constituents by weight in each of the mixtures satisfy the condition To-Ts> 20 ° C.
  • the sealing material may also comprise a central layer CC of polyolefin, optionally loaded with pigment, and in this case, typically loaded with pigment white mineral, said central layer CC of thickness Ec such that Ee + Ec ranges from 0.9.E to 0.66E, being interposed between said outer layer CE and said sealing layer CS, so as to form a structure multilayer symbolically represented by CE / CC / CS.
  • the advantage of having a central layer CC also lies in the possibility of adapting the formulation of each of the layers CE and CC so as to confer on them two distinct functions or properties, namely sufficient printability for said outer layer CE, and a high mechanical strength (for example a tensile modulus) for said central layer.
  • said central layer CC also has a melting temperature Te close to To.
  • said polyolefin of said outer layer CE and of said central layer CC can be chosen from homopolymer or copolymer PP or PE with a density greater than 0.930, typically HDPE, or a mixture or a copolymer of PP and PE.
  • Said central layer may typically comprise, as white pigment, titanium oxide or zinc oxide, at a weight content ranging from 0.5% to 25%.
  • said sealing layer can be chosen from: a) an EMA with a weight content of methyl acrylate ranging from 12% to 24%, b) an EVA with a vinyl acetate content ranging from 12% to 24%, c) an EBA with a butyl acrylate content ranging from 12% to 24%, d) an EEA with an ethyl acetate content ranging from 12% to 24%, e) a mixture of EMA or EVA or EBA or EEA with PE or PP, the DSC melting point of said sealing layer being between 70 ° C and 120 ° C, and preferably between 90 ° C and 100 ° C .
  • Said sealing layer may comprise EMA with a weight content of methyl acrylate ranging from 16 to 24%, and preferably from 18% to 24%.
  • said gradient ⁇ T / ⁇ % may be less in absolute value to 1 ° C /%, and preferably less in absolute value to 0.80 ° C /%.
  • melt index MI made it possible to obtain a particularly sealing material advantageous. In fact, they simultaneously allow, on the one hand, to obtain sealing forces significantly greater than those obtained with standard EMAs, on the other hand, to be able to manufacture the sealing material by any coextrusion process, including the process said "bubble" for which bonding problems are prohibitive, and finally to obtain a seal at a temperature low enough to be able to use as external or central layer a material based on polyolefin, including PE-based.
  • said EMA can be a so-called “tabular” EMA obtained by tabular copolymerization of ethylene and methyl acrylate, this EMA can be used alone or as a mixture.
  • this EMA has a gradient or coefficient ⁇ T / ⁇ % low in absolute value, typically less than that of an EMA obtained by an autoclave polymerization process.
  • the applicant has not been able to put forward a hypothesis to explain the particular properties of this type of EMA with a low gradient ⁇ T / ⁇ %.
  • said EMA can also be an EMA known as an "autoclave” obtained by autoclave copolymerization of ethylene and methyl acrylate, this EMA can be used alone or as a mixture, said EDMA preferably having at least 20% by weight d 'methyl acrylate and in particular having 24% by weight of methyl acrylate.
  • said applicant has found it advantageous to use an EMA which, at the same time, has a high level of methyl acrylate, and which is extrudable in a bubble, that is to say without bonding of the film bubble extradited.
  • said sealing layer can comprise said "autoclave” EMA and an SBS resin (styrene-butadiene-styrene copolymer), the content by weight of EMA ranging from 55% to 85%, and typically from 65% to 75%, the content by weight in SBS ranging from 45% to 15% and typically from 35% to 25%.
  • said EMA can comprise a mixture of "tabular” EMA and “autoclave” EMA, in a weight ratio ranging from 80-20 to 20-80. In this case, a synergistic effect was observed, the "tabular” EMA contributing to improving the resistance to pressure, and the "autoclave” EMA helping to provide a highly sought-after opening smoothness.
  • said sealing layer may typically comprise from 10 to 50% by weight of a low-melting point metallocene PP-based terpolymer, so as to obtain a predetermined level for the sealing force.
  • said sealing layer can comprise from 30% to 100% by weight of metallocene PE, and from 70% to 0% by weight of EMA.
  • said central layer can have a thickness Ec ranging from 0.2. (Ee + Ec) to 0.9. (Ee + Ec).
  • said central layer may comprise - or be formed by - an extrudable plastic recycling material. Said central layer alone or associated with the outer layer can thus form the structural layer of the sealing material.
  • said external layer it is not necessary for said external layer to form the essential of the structural layer intended to provide the required mechanical characteristics, or to form a heat shield resistant to impact. sealing jaws, taking into account the relatively low sealing temperatures made possible with the sealing material according to the invention.
  • said multilayer material can be a co-extruded material, either using an annular die by co-extrusion called "bubble", or using 'a flat die by co-extrusion called “cast”.
  • co-extrusion called "bubble” is preferred to co-extrusion cast, because it is more advantageous than co-extrusion "cast” both for economic reasons (lower investment cost) and for its flexibility.
  • the multilayer material according to the invention, and in particular the sealing layer having in a large number of cases having a structure allowing to take off the two walls of the "bubble" at the extruder outlet - condition essential for the implementation of this process.
  • said sealing layer may be a coating layer, said external layer CE, and possibly said central layer CC, forming a support film - typically extruded or co-extruded - for said coating layer.
  • said coating layer can be a layer of varnish, typically a varnish based on EVA or EMA, said varnish being identified, or not identified and applied to the whole of said film.
  • said coating layer can be a hot-melt layer.
  • Said hot-melt layer can form a mixture typically comprising from 20 to 30% by weight of elastomeric resin, typically SEBS, from 20 to 30% by weight of paraffin, from 20 to 30% by weight of talc, and from 20 at 30% by weight of a tackifying agent, typically a hydrogenated petroleum resin.
  • elastomeric resin typically SEBS
  • paraffin from 20 to 30% by weight of talc
  • a tackifying agent typically a hydrogenated petroleum resin.
  • said support can be an OPP or BOPP of thickness ranging from 50 ⁇ m to 100 ⁇ m, and preferably from 60 ⁇ m to 90 ⁇ m, white or transparent.
  • said OPP or BOPP can be a cavity, white OPP or BOPP, with a density ranging from 0.50 to 0.80, with a thickness between 70 ⁇ m and 80 ⁇ m, and typically equal to 75 ⁇ m.
  • An OPP or BOPP is said to be "cavity" when it has a density much lower than the standard density of PP, OPP, or BOPP (bioriented PP).
  • said outer layer may also contain a typically white mineral pigment at a weight content ranging from 0.5 to 5%.
  • said outer layer may contain a micronized mineral filler, such as talc, at a weight content ranging from 2% to 12% by weight and typically from 5 to 10%. This mineral filler makes it possible in particular to obtain a "hand" or a particular feel which particularly pleases the end consumer.
  • a print covers all or part of said external layer, and a layer of protective varnish can cover said print and / or said external layer.
  • said layer of protective varnish may comprise a dispersed filler, typically mineral, so as to increase the thermal resistance of said material, and possibly to reduce the damage to said printing during said heat sealing.
  • Said sealing layer may comprise a dispersed filler, typically mineral, so as to control the sliding coefficient of said lids, their peeling force after heat sealing, and optionally their unstacking.
  • Said dispersed filler typically mineral
  • Said filler dispersed in the sealing layer may be present in said sealing layer at a weight content ranging from 2 to 10%, and typically from 4% to 8%.
  • Said dispersed filler may be talc.
  • Said dispersed filler may also comprise a slip agent typically chosen from: erucamide, oleamide, a HDPE, a polyether block amide copolymer.
  • the sealing material has a total thickness E preferably ranging from 60 ⁇ m to 110 ⁇ m.
  • Another object of the invention consists of the precut lids formed from the lidding material according to the invention.
  • Another object of the invention is constituted by a method of manufacturing a multilayer sealing material by co-extrusion.
  • said multilayer material can be typically bubble-blown, said sealing layer of said multilayer material comprising a mixture comprising a first EMA and typically a complementary resin chosen from: a second EMA of a different nature from said first EMA, a PE metallocene, an SBS in a proportion by weight ranging from 30/70 to 70/30, said outer layer, and optionally said central layer, comprising a PP or consisting of typically homopolymer PP.
  • said multilayer material a central layer comprising at least 50% of PE and an external layer comprising from 50 to 65% of PP and from 15 to 35% of PE, so as to facilitate the printing of said external layer , the thickness Ec of said central layer being 1.5 to 2.5 times greater, and typically two times greater, than the thickness Ee of said outer layer.
  • Another object of the invention is constituted by a process for manufacturing a multilayer sealing material by coating with varnish or hot-melt on a support film which can be an OPP or BOPP cavity film, white, of density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and with a thickness typically between 60 ⁇ m and 90 ⁇ m, and typically equal to 75 ⁇ m.
  • a support film which can be an OPP or BOPP cavity film, white, of density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and with a thickness typically between 60 ⁇ m and 90 ⁇ m, and typically equal to 75 ⁇ m.
  • Another object of the invention is constituted by the use of an OPP or BOPP cavity film, white, with a density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and thickness typically between 60 ⁇ m and 90 ⁇ m, and typically equal to 75 ⁇ m to form a support film of a multilayer material in the process for manufacturing a multilayer sealing material by coating.
  • Tests carried out Tests were carried out by extrusion (series A1), and tests by coating (series A2)
  • - MM2 masterbatch of PE at 55% by weight of talc
  • EMA with 20% methyl acrylate which corresponds to curve I of FIG. 1, and which has a ⁇ T / ⁇ % gradient of 0.7 ° C /% (in absolute value).
  • This EMA was manufactured by a tabular polymerization process. Its melting point (DSC) is 92 ° C.
  • - EMA Elvaloy 1218 from Dupont: EMA containing 18% methyl acrylate. This EMA was manufactured by a tabular polymerization process. Its melting point (DSC) is 94 ° C. - EMA TC120 from Exxon: EMA with 21% methyl acrylate which corresponds to curve II of FIG. 1, and which has a gradient ⁇ T / ⁇ % of approximately 2 ° C /% (in absolute value). Its melting point (DSC) is 76 ° C.
  • sealing material typically free from tailing or "curling", the sealing material remaining flat, even after cutting into lids.
  • EVA lacquer Sovereign J9184AT lacquer in toluene medium at 25.5% dry extract and with a melting point below 110 ° C.
  • Control A a standard commercial product, for example of the POLYMIX® or MLXPAP® type, and of structure:
  • the sealing materials were heat sealed on PS pots with penetrating jaws, with a pressure of 0.4 bar on a BHS Werk ® machine type VL1600, and for 1 second, and this for different sealing temperatures T .
  • the sealing materials were also heat sealed with flat jaws - with a flat 1 to 3 mm wide - not penetrating into the PS, the so-called penetrating jaws being jaws with a warhead profile.
  • the advantage of being able to use a flat jaw lies in making the sealing bead not very visible to invisible.
  • tests 1 to 7 very clearly show the excellent results obtained with a sealing layer comprising “tabular” EMA containing 20% methyl acrylate. (tests 2, 4 and 5) compared to those obtained with a sealing layer comprising on an "autoclave” EMA (tests 1 and 3).
  • test 1 is still superior to the control test, while test 3 is less than the control, which shows the advantage of using an "autoclave" EMA having at least 20% by weight of methyl acrylate.
  • test 7 has properties inferior to that of the control test
  • test 6 - with a sealing layer comprising 6.6% by weight of talc has properties at least equal to those of the control test.
  • test 11 Although leading to results slightly inferior to those of the control test, is of the greatest interest, in particular on the economic level, taking into account its very simple manufacturing process, process based on coating and not coextrusion. It should also be noted that results at least equal to those of the control test were obtained by loading the sealing lacquer of test 11 with 6% talc.
  • the sealing material according to the invention therefore has several advantages, beyond the required use properties. Indeed, whatever the type of sealing material considered:
  • the sealing material according to the invention being based on polyolefin, and therefore basically in monomaterial, it can be easily recycled.

Abstract

The invention concerns a sealing material or a seal forming a multilayer material of thickness E ranging between 30 νm and 140 νm, and designed to close by heat-sealing a container or jar typically based on PP or PS. It comprises a) an outer polyolefin layer (CE), of thickness Ee ranging between 0.9E and 0.6E; b) a sealing layer (CS), of thickness Es ranging between 0.1E and 0.4E, said sealing layer and said outer polyolefin layer having a melting point, respectively Ts for the sealing layer and To for the polyolefin layer, such that To - Ts is at least equal to 20 °C, and preferably at least equal to 30 °C. The invention provides the advantages of an inexpensive material easy to use and to be recycled.

Description

MATERIAUX D'OPERCULAGE OU OPERCULES PELABLES MULTICOUCHESMULTI-LAYER PEELABLE LID OR LID MATERIALS
DOMAINE DE L'INVENTIONFIELD OF THE INVENTION
L'invention concerne des opercules destinés à obturer, par thermoscellage, des récipients ou des pots en matière thermoplastique, typiquement en PS ou PP, ces opercules étant ensuite pelables de manière à pouvoir ouvrir ledit récipient ou pot en séparant l'opercule par simple traction manuelle sur un bord dudit opercule.The invention relates to lids intended to seal, by heat-sealing, containers or pots of thermoplastic material, typically of PS or PP, these lids are then peelable so as to be able to open said container or pot by separating the lid by simple pulling. manual on an edge of said cover.
L'invention concerne plus particulièrement des opercules multicouches ne comprenant pas de feuille d'aluminium.The invention relates more particularly to multilayer covers not comprising aluminum foil.
Ces opercules sont typiquement utilisés pour le conditionnement de produits laitiers frais, tels que par exemple des yogourts.These lids are typically used for the packaging of fresh dairy products, such as for example yogurts.
ETAT DE LA TECHNIQUESTATE OF THE ART
On connaît déjà de nombreux opercules multicouches pelables exempts de feuille d'aluminium.We already know many peelable multilayer lids free of aluminum foil.
Ces opercules comprennent au moins une couche dite de structure S assurant la tenue mécanique de l'opercule et une couche de thermoscellage T adaptée au matériau formant ledit récipient ou ledit pot, de manière à former le matériau représenté de manière symbolique par S / T, la couche extérieure étant le plus à gauche et la couche de scellage à droite.These lids comprise at least one layer known as of structure S ensuring the mechanical strength of the lid and a heat-sealing layer T adapted to the material forming said container or said pot, so as to form the material represented symbolically by S / T, the outer layer being the left most and the sealing layer right.
Mais généralement une couche intermédiaire I de liaison vient lier les couches externes S et T de manière à assurer la cohésion du matériau multicouche représenté par S / 1 / T.But generally an intermediate bonding layer I joins the external layers S and T so as to ensure the cohesion of the multilayer material represented by S / 1 / T.
L'opercule peut en outre comprendre une couche extérieure protectrice P apte à résister thermiquement au thermoscellage, la structure type du matériau étant alors P / S / 1 / T ou éventuellement P / 1 / S / T, ou encore P / 1 / S / l' /T, I et T étant deux couches de liaison.The cover may also comprise a protective outer layer P capable of thermally resisting heat sealing, the typical structure of the material then being P / S / 1 / T or possibly P / 1 / S / T, or also P / 1 / S / l '/ T, I and T being two bonding layers.
Ainsi, on connaît, par le document EP 0 475 887-B1, des opercules du type :Thus, from document EP 0 475 887-B1, lids of the type are known:
PBT (8-40μm) / SBS (20/250 μm) / PBT (8-40 μm) / SBS (5-30 μm), où PBT désigne un polybutylène-téréphtalate et SBS un copolymère de styrène et butadiène.PBT (8-40μm) / SBS (20/250 μm) / PBT (8-40 μm) / SBS (5-30 μm), where PBT denotes a polybutylene terephthalate and SBS a copolymer of styrene and butadiene.
De même, on connaît, par le document EP 0524488-A1, des opercules du type :Likewise, from the document EP 0524488-A1, there are known covers of the type:
PBT / SBS+Polymère incompatible / SBS + PS ou HIPS / Couche de scellage T, où PS et HIPS désignent du polystyrène et du polystyrène choc. De même, on connaît, par le document EP 0258 527-B1, des opercules du type :PBT / SBS + Incompatible polymer / SBS + PS or HIPS / T sealing layer, where PS and HIPS denote polystyrene and impact polystyrene. Likewise, from the document EP 0258 527-B1, lids of the type are known:
PET ou PA / PE + élastomère thermoplastique.PET or PA / PE + thermoplastic elastomer.
De même, on connaît, par le document EP 0 669206-A1, des opercules du type :Likewise, from the document EP 0 669206-A1, there are known covers of the type:
PET ou PA / papier ou PP ou PE ou P A / PET ou PE / Couche de scellage T.PET or PA / paper or PP or PE or P A / PET or PE / T sealing layer.
De même, on connaît, par le document EP 0795 491-A2, des opercules du type : Couche de silicone / PP / Couche de scellage T.Likewise, EP 0795 491-A2 discloses lids of the type: silicone layer / PP / sealing layer T.
De même, on connaît, par le document DE 43 20 796-A1, un matériau thermoscellable et co-extrudé à trois couches du type : PS / PET / SBS + copolymère vinyltoluène- styrène, ou à quatre couches du type : PET / PS / PET / SBS + copolymère vinyltoluène- styrène.Likewise, document DE 43 20 796-A1 discloses a heat-sealable and co-extruded material with three layers of the type: PS / PET / SBS + vinyltoluene-styrene copolymer, or with four layers of the type: PET / PS / PET / SBS + vinyltoluene-styrene copolymer.
PROBLEMES POSESPROBLEMS POSED
Dans le domaine des opercules ou les matériaux d'operculage multicouches, des recherches sont effectuées en permanence, pour apporter au moins une des améliorations suivantes qui visent prioritairement :In the field of lids or multilayer lidding materials, research is carried out continuously, to bring at least one of the following improvements which aim primarily:
- soit à réduire le prix de revient des opercules, que ce soit par le choix des matières premières et/ou par le procédé de fabrication,- either to reduce the cost price of the lids, whether by the choice of raw materials and / or by the manufacturing process,
- soit à abaisser la température de thermoscellage, de manière à limiter les risques de dégradation du décor, les opercules étant généralement imprimés, et à réduire le coût énergétique du thermoscellage, et qui, en outre, visent :either to lower the heat-sealing temperature, so as to limit the risks of degradation of the decoration, the lids being generally printed, and to reduce the energy cost of heat-sealing, and which also aim to:
- soit à élargir la plage de température de thermoscellage, afin d'obtenir un scellage de qualité requise dans une plage d'au moins 20°C,- either to widen the heat-sealing temperature range, in order to obtain a seal of required quality in a range of at least 20 ° C,
- soit enfin à obtenir un toucher ou une "main", ou une ouverture, particulièrement agréable pour le consommateur final.- or finally to obtain a touch or a "hand", or an opening, particularly pleasant for the end consumer.
DESCRIPTION DE L'INVENTIONDESCRIPTION OF THE INVENTION
Selon l'invention, le matériau d'operculage ou opercule forme un matériau multicouche d'épaisseur E comprise entre 30μm et 140 μm, et destiné à obturer par thermoscellage un récipient ou pot typiquement à base de PP ou de PS, et comprend : a) une couche externe CE en polyoléfine, d'épaisseur Ee allant de 0,9.E à 0,6.E, b) une couche de scellage CS, d'épaisseur Es allant de 0,1.E à 0,4.E, ladite couche de scellage et ladite couche externe en polyoléfine présentant une température de fusion, notée respectivement Ts pour la couche de scellage et To pour la couche en polyoléfine, telle que To - Ts soit au moins égal à 20°C, et de préférence au moins égal à 30°C.According to the invention, the sealing material or cover forms a multilayer material with a thickness E of between 30 μm and 140 μm, and intended to seal by sealing a container or pot typically based on PP or PS, and comprises: a ) an external polyolefin layer CE, of thickness Ee ranging from 0.9.E to 0.6E, b) a sealing layer CS, of thickness Es ranging from 0.11E to 0.4. E, said sealing layer and said outer polyolefin layer having a melting temperature, denoted respectively Ts for the sealing layer and To for the polyolefin layer, such that To - Ts is at least 20 ° C, and preferably at least 30 ° C.
De manière surprenante, la demanderesse a constaté qu'il était possible de former des opercules d'une part avec un nombre limité de couches, et d'autre part, en utilisant pour former la couche principale, ou couche support, une polyoléfine, à savoir le matériau plastique typiquement le plus économique, de manière à résoudre ainsi les principaux problèmes posés, et en utilisant une couche de scellage à "basse" température de fusion. Grâce à cette combinaison de moyens, le matériau d'operculage selon l'invention et les opercules dérivés peuvent être scellés sur pots en PS ou PP sans destruction de l'opercule ou marquage prononcé des opercules par les mors de scellage. En outre, il a été observé qu'il n'était plus nécessaire avec ce type d'opercule d'utiliser une feuille d'alumim'um ou une couche de métallisation formant une couche barrière.Surprisingly, the Applicant has found that it is possible to form lids on the one hand with a limited number of layers, and on the other hand, by using to form the main layer, or support layer, a polyolefin, with know the typically most economical plastic material, so as to solve the main problems posed, and by using a sealing layer at "low" melting temperature. Thanks to this combination of means, the sealing material according to the invention and the derived lids can be sealed on PS or PP jars without destruction of the seal or pronounced marking of the lids by the sealing jaws. In addition, it was observed that it was no longer necessary with this type of lid to use a sheet of alumim 'um or a metallization layer forming a barrier layer.
DESCRIPTION DES FIGURES La figure 1 est un graphique portant en abscisse le pourcentage d'acrylate de méthyle de l'EMA et en ordonnée la température de fusion T°C mesurée par DSC (differential scanning calorimetry) correspondant au maximum de la courbe DSC. La courbe I correspond à un EMA dit "tabulaire" selon les essais 2 et 4, et pour lequel le • gradient ΔT/Δ%, en valeur absolue, vaut environ 0,70. La courbe II correspond à un EMA dit "autoclave" selon les essais 1 et 3, et pour lequel le gradient ΔT/Δ%, en valeur absolue, vaut 2 environ.DESCRIPTION OF THE FIGURES FIG. 1 is a graph plotting on the abscissa the percentage of methyl acrylate in the EMA and on the ordinate the melting temperature T ° C measured by DSC (differential scanning calorimetry) corresponding to the maximum of the DSC curve. Curve I corresponds to a so-called "tabular" EMA according to tests 2 and 4, and for which the gradient ΔT / Δ%, in absolute value, is worth approximately 0.70. Curve II corresponds to a so-called "autoclave" EMA according to tests 1 and 3, and for which the gradient ΔT / Δ%, in absolute value, is approximately 2.
Les figures 2a à 2d illustrent, par des coupes schématiques, 3 modalités de matériau d'operculage selon l'invention.Figures 2a to 2d illustrate, by schematic sections, 3 methods of sealing material according to the invention.
La figure 2a correspond à une structure CE/CS où CE désigne la couche externe et CS la couche de scellage.Figure 2a corresponds to a structure CE / CS where CE denotes the outer layer and CS the sealing layer.
La figure 2b correspond à la structure CE/CC/CS où CC désigne la couche centrale. La figure 2c correspond à la structure NS/IP/CE/CS où IP désigne une impression appliquée sur le matériau de la figure 2a, où NS désigne un vernis de surimpression destiné à protéger l'impression IP.Figure 2b corresponds to the structure CE / CC / CS where CC designates the central layer. FIG. 2c corresponds to the structure NS / IP / CE / CS where IP denotes an impression applied to the material of FIG. 2a, where NS denotes an overprint varnish intended to protect the impression IP.
La figure 2d correspond à la structure NS/IP/CE/CC/CS.Figure 2d corresponds to the structure NS / IP / CE / CC / CS.
Les figures 3 a et 3b sont des courbes de DSC relatives à deux types de couches externes, celle de la figure 3 a correspondant à 100% de PP, comme dans les essais Νo 1 et 2, celle de la figure 3b correspondant à un mélange 70% en poids de PP et de 25% en poids de PE, comme dans l'essai 5.Figures 3a and 3b are DSC curves relating to two types of external layers, that of Figure 3a corresponding to 100% of PP, as in tests Νo 1 and 2, that of Figure 3b corresponding to a mixture 70% by weight of PP and 25% by weight of PE, as in test 5.
La figure 4 est une courbe de DSC relative à une couche de scellage comprenant un mélange de 65% en poids d'EMA et de 35% de PE métallocène selon essai Νo 10.FIG. 4 is a DSC curve relating to a sealing layer comprising a mixture of 65% by weight of EMA and 35% of metallocene PE according to test Νo 10.
La figure 5 est une courbe de DSC relative à un matériau d'operculage comprenant une couche externe en PP, une couche centrale en PE, et une couche de scellage en EMA, selon l'essai 1. DESCRIPTION DETAILLEE DE L'INVENTIONFIG. 5 is a DSC curve relating to a sealing material comprising an outer layer of PP, a central layer of PE, and a sealing layer of EMA, according to test 1. DETAILED DESCRIPTION OF THE INVENTION
Selon l'invention, ladite couche externe peut former un mélange de polyoléfines comprenant une polyoléfine, à au moins 50% en poids dans ledit mélange, présentant ladite température de fusion To.According to the invention, said outer layer can form a mixture of polyolefins comprising a polyolefin, at least 50% by weight in said mixture, having said melting temperature To.
De même, ladite couche de scellage peut comprendre un constituant majoritaire en poids présentant ladite température de fusion Ts.Likewise, said sealing layer may comprise a majority component by weight having said melting temperature Ts.
En effet, comme l'a observé la demanderesse, l'invention n'exige pas que l'ensemble des constituants de ladite couche externe présentent une température To, et que l'ensemble des constituants de la couche de scellage présente ladite température de fusion Ts, telle que l'on ait To-Ts au moins égal à 20°C. Il suffit seulement que les constituants majoritaires en poids dans chacun des mélanges satisfassent à la condition To-Ts > 20°C.Indeed, as observed by the applicant, the invention does not require that all of the constituents of said outer layer have a temperature To, and that all of the constituents of the sealing layer have said melting temperature Ts, such that we have To-Ts at least equal to 20 ° C. It suffices only that the majority constituents by weight in each of the mixtures satisfy the condition To-Ts> 20 ° C.
Comme représenté schématiquement sur la figure 2b, et dans tous les exemples sauf les exemples 8 et 11, le matériau d'operculage peut comprendre en outre une couche centrale CC en polyoléfine, éventuellement chargée en pigment, et dans ce cas, typiquement chargée en pigment minéral blanc, ladite couche centrale CC d'épaisseur Ec telle que Ee+Ec aille de 0,9.E à 0,6.E, étant intercalée entre ladite couche externe CE et ladite couche de scellage CS, de manière à former une structure multicouche représentée symboliquement par CE / CC / CS.As shown diagrammatically in FIG. 2b, and in all of the examples except Examples 8 and 11, the sealing material may also comprise a central layer CC of polyolefin, optionally loaded with pigment, and in this case, typically loaded with pigment white mineral, said central layer CC of thickness Ec such that Ee + Ec ranges from 0.9.E to 0.66E, being interposed between said outer layer CE and said sealing layer CS, so as to form a structure multilayer symbolically represented by CE / CC / CS.
Dans ce cas, on obtient typiquement un matériau totalement opaque et de couleur blanche, ce qui permet d'obtenir à la fois un aspect attractif et un contraste élevé avec l'impression qui est généralement formée sur ce matériau. Cependant, tout type, de pigment et de couleur peut être utilisé selon l'invention, pour autant qu'il soit conforme aux réglementations en vigueur.In this case, a completely opaque and white material is typically obtained, which makes it possible to obtain both an attractive appearance and a high contrast with the impression which is generally formed on this material. However, any type, pigment and color can be used according to the invention, provided that it complies with the regulations in force.
L'intérêt d'avoir une couche centrale CC réside aussi dans la possibilité de d'adapter la formulation de chacune des couches CE et CC de manière à leur conférer deux fonctions ou propriétés distinctes, à savoir une imprimabilité suffisante pour ladite couche externe CE, et une résistance mécanique (par exemple un module de traction) élevée pour ladite couche centrale.The advantage of having a central layer CC also lies in the possibility of adapting the formulation of each of the layers CE and CC so as to confer on them two distinct functions or properties, namely sufficient printability for said outer layer CE, and a high mechanical strength (for example a tensile modulus) for said central layer.
De préférence, ladite couche centrale CC présente également une température de fusion Te voisine de To.Preferably, said central layer CC also has a melting temperature Te close to To.
Typiquement, ladite polyoléfine de ladite couche externe CE et de ladite couche centrale CC peut être choisie parmi le PP homopolymère ou copolymère ou le PE de densité supérieure à 0,930, typiquement le HDPE, ou un mélange ou un copolymère de PP et de PE. Ladite couche centrale peut comprendre comme pigment blanc typiquement de l'oxyde de titane ou de l'oxyde de zinc, à une teneur pondérale allant de 0,5 % à 25%.Typically, said polyolefin of said outer layer CE and of said central layer CC can be chosen from homopolymer or copolymer PP or PE with a density greater than 0.930, typically HDPE, or a mixture or a copolymer of PP and PE. Said central layer may typically comprise, as white pigment, titanium oxide or zinc oxide, at a weight content ranging from 0.5% to 25%.
Selon l'invention, ladite couche de scellage peut être choisie parmi : a) un EMA à une teneur pondérale en acrylate de méthyle allant de 12% à 24%, b) un EVA à une teneur en acétate de vinyle allant de 12% à 24%, c) un EBA à une teneur en acrylate de butyle allant de 12% à 24%, d) un EEA à une teneur en acétate d'éthyle allant de 12% à 24%, e) un mélange d'EMA ou d'EVA ou d'EBA ou d'EEA avec du PE ou du PP, le point de fusion DSC de ladite couche de scellage étant compris entre 70°C et 120°C, et de préférence entre 90°C et 100°C. Ladite couche de scellage peut comprendre de l'EMA à une teneur pondérale en acrylate de méthyle allant de 16 à 24 %, et de préférence de 18% à 24%.According to the invention, said sealing layer can be chosen from: a) an EMA with a weight content of methyl acrylate ranging from 12% to 24%, b) an EVA with a vinyl acetate content ranging from 12% to 24%, c) an EBA with a butyl acrylate content ranging from 12% to 24%, d) an EEA with an ethyl acetate content ranging from 12% to 24%, e) a mixture of EMA or EVA or EBA or EEA with PE or PP, the DSC melting point of said sealing layer being between 70 ° C and 120 ° C, and preferably between 90 ° C and 100 ° C . Said sealing layer may comprise EMA with a weight content of methyl acrylate ranging from 16 to 24%, and preferably from 18% to 24%.
Etudiant en particulier les propriétés intrinsèques des EMA et des EVA, la demanderesse a observé qu'il était avantageux que ledit EMA soit un EMA présentant un gradient ΔT/Δ% inférieur en valeur absolue à 1,5 °C/%, comme illustré sur la figureStudying in particular the intrinsic properties of EMAs and EVAs, the Applicant observed that it was advantageous for said EMAs to be an EMAs having a gradient ΔT / Δ% lower in absolute value at 1.5 ° C /%, as illustrated in the figure
1.1.
Typiquement, ledit gradient ΔT/Δ% peut être inférieur en valeur absolue à 1 °C/%, et de préférence inférieur en valeur absolue à 0,80 °C/%.Typically, said gradient ΔT / Δ% may be less in absolute value to 1 ° C /%, and preferably less in absolute value to 0.80 ° C /%.
En effet, la demanderesse a observé que les EMA selon l'invention, toutes choses égales par ailleurs, à savoir à même pourcentage d'acrylate de méthyle dans l'EMA et à mêmeIndeed, the Applicant has observed that the EMAs according to the invention, all other things being equal, namely with the same percentage of methyl acrylate in the EMA and with the same
"melt index" MI, permettaient d'obtenir un matériau d'operculage particulièrement avantageux. En effet, ils permettent simultanément d'une part, d'obtenir des forces de scellage significativement supérieures à celles obtenues avec les EMA standards, d'autre part de pouvoir fabriquer le matériau d'operculage par tout procédé de coextrusion, y compris le procédé dit "bulle" pour lequel les problèmes de collage sont rédhibitoires, et enfin d'obtenir un scellage à température assez basse pour pouvoir utiliser comme couche externe ou centrale un matériau à base de polyoléfine, y compris à base de PE."melt index" MI, made it possible to obtain a particularly sealing material advantageous. In fact, they simultaneously allow, on the one hand, to obtain sealing forces significantly greater than those obtained with standard EMAs, on the other hand, to be able to manufacture the sealing material by any coextrusion process, including the process said "bubble" for which bonding problems are prohibitive, and finally to obtain a seal at a temperature low enough to be able to use as external or central layer a material based on polyolefin, including PE-based.
Selon l'invention, ledit EMA peut être un EMA dit "tabulaire" obtenu par copolymérisation tabulaire d'éthylène et d'acrylate de méthyle, cet EMA pouvant être utilisé seul ou en mélange.According to the invention, said EMA can be a so-called "tabular" EMA obtained by tabular copolymerization of ethylene and methyl acrylate, this EMA can be used alone or as a mixture.
Comme illustré sur la figure 1, et comme observé par la demanderesse, cet EMA présente un gradient ou coefficient ΔT/Δ% faible en valeur absolue, typiquement inférieur à celui d'un EMA obtenu par un procédé de polymérisation en autoclave. A ce jour, la demanderesse n'a pu émettre d'hypothèse pour expliquer les propriétés particulières de ce type d'EMA à faible gradient ΔT/Δ%.As illustrated in FIG. 1, and as observed by the applicant, this EMA has a gradient or coefficient ΔT / Δ% low in absolute value, typically less than that of an EMA obtained by an autoclave polymerization process. To date, the applicant has not been able to put forward a hypothesis to explain the particular properties of this type of EMA with a low gradient ΔT / Δ%.
Cependant, ledit EMA peut être aussi un EMA dit "autoclave" obtenu par copolymérisation en autoclave d'éthylène et d'acrylate de méthyle, cet EMA pouvant être utilisé seul ou en mélange, ledit EDMA ayant de préférence au moins 20% en poids d'acrylate de méthyle et ayant notamment 24% en poids d'acrylate de méthyle. En effet, la demanderesse a trouvé avantageux d'utiliser un EMA qui, à la fois, présente un taux élevé d'acrylate de méthyle, et qui soit extrudable en bulle, c'est-à-dire sans collage de la bulle de film extradé.However, said EMA can also be an EMA known as an "autoclave" obtained by autoclave copolymerization of ethylene and methyl acrylate, this EMA can be used alone or as a mixture, said EDMA preferably having at least 20% by weight d 'methyl acrylate and in particular having 24% by weight of methyl acrylate. Indeed, the applicant has found it advantageous to use an EMA which, at the same time, has a high level of methyl acrylate, and which is extrudable in a bubble, that is to say without bonding of the film bubble extradited.
Ainsi, ladite couche scellante peut comprendre ledit EMA "autoclave" et une résine SBS (copolymère styrène-butadiène-styrène), la teneur pondérale en EMA allant de 55% à 85%, et typiquement de 65% à 75%, la teneur pondérale en SBS allant de 45% à 15% et typiquement de 35% à 25%. De même, ledit EMA peut comprendre un mélange d'EMA "tabulaire" et d'EMA "autoclave", dans un rapport pondéral allant de 80-20 à 20-80. Dans ce cas, il a été observé un effet de synergie, l'EMA "tabulaire" contribuant à améliorer la tenue à la pression, et l'EMA "autoclave" contribuant à apporter une douceur d'ouverture très recherchée.Thus, said sealing layer can comprise said "autoclave" EMA and an SBS resin (styrene-butadiene-styrene copolymer), the content by weight of EMA ranging from 55% to 85%, and typically from 65% to 75%, the content by weight in SBS ranging from 45% to 15% and typically from 35% to 25%. Likewise, said EMA can comprise a mixture of "tabular" EMA and "autoclave" EMA, in a weight ratio ranging from 80-20 to 20-80. In this case, a synergistic effect was observed, the "tabular" EMA contributing to improving the resistance to pressure, and the "autoclave" EMA helping to provide a highly sought-after opening smoothness.
Dans le cas où ledit pot est en PP, ladite couche de scellage peut comprendre typiquement de 10 à 50% en poids d'un terpolymère à base PP métallocène à bas point de fusion, de manière à obtenir un niveau prédéterminé pour la force de scellage. Dans le cas où ledit pot est en PS ou en PP, ladite couche de scellage peut comprendre de 30 % à 100% en poids de PE métallocène, et de 70% à 0% en poids d'EMA.In the case where said pot is made of PP, said sealing layer may typically comprise from 10 to 50% by weight of a low-melting point metallocene PP-based terpolymer, so as to obtain a predetermined level for the sealing force. . In the case where said pot is made of PS or PP, said sealing layer can comprise from 30% to 100% by weight of metallocene PE, and from 70% to 0% by weight of EMA.
Selon l'invention, ladite couche centrale peut avoir une épaisseur Ec allant de 0,2. (Ee+Ec) à 0,9.(Ee+Ec). Avantageusement, ladite couche centrale peut comprendre - ou être formée par - un matériau plastique extrudable de recyclage. Ladite couche centrale seule ou associé à la couche externe peut ainsi former la couche de structure du matériau d'operculage. Ainsi, dans le matériau d'operculage selon l'invention, il n'est pas nécessaire que ladite couche externe forme l'essentiel de la couche de structure destinée à apporter les caractéristiques mécaniques requises, ou forme un écran thermique résistant à l'impact des mors de scellage, compte tenu des températures de scellage relativement basses rendues possibles avec le matériau d'operculage selon l'invention.According to the invention, said central layer can have a thickness Ec ranging from 0.2. (Ee + Ec) to 0.9. (Ee + Ec). Advantageously, said central layer may comprise - or be formed by - an extrudable plastic recycling material. Said central layer alone or associated with the outer layer can thus form the structural layer of the sealing material. Thus, in the sealing material according to the invention, it is not necessary for said external layer to form the essential of the structural layer intended to provide the required mechanical characteristics, or to form a heat shield resistant to impact. sealing jaws, taking into account the relatively low sealing temperatures made possible with the sealing material according to the invention.
Comme déjà indiqué, et selon une première modalité de l'invention, ledit matériau multicouche peut être un matériau co-extrudé, soit à l'aide d'une filière annulaire par co- extrusion dite "bulle", soit à l'aide d'une filière plate par co-extrusion dite "cast". Cependant la co-extrusion dite "bulle" est préférée à la co-extrusion cast, car elle est plus avantageuse que la co-extrusion "cast" à la fois pour des raisons économiques (coût de l'investissement moindre) et pour sa souplesse de production, le matériau multicouche selon l'invention, et en particulier la couche de scellage, ayant dans un grand nombre de cas d'avoir une structure de permettant de décoller les deux parois de la "bulle" en sortie d'extrudeuse - condition indispensable pour la mise en œuvre de ce procédé. Cependant, selon une seconde modalité de l'invention, et comme illustré dans l'exemple 11, ladite couche de scellage peut être une couche d'enduction, ladite couche externe CE, et éventuellement ladite couche centrale CC, formant un film support - typiquement extradé ou co-extrudé - pour ladite couche d'enduction. Selon une première variante de ladite seconde modalité, ladite couche d'enduction peut être une couche de vernis, typiquement un vernis à base d'EVA ou d'EMA, ledit vernis étant repéré, ou non repéré et appliqué sur la totalité dudit film. Selon une seconde variante, ladite couche d'enduction peut être une couche de hot-melt. Ladite couche de hot-melt peut former un mélange comprenant typiquement de 20 à 30% en poids de résine élastomère, typiquement un SEBS, de 20 à 30% en poids de paraffine, de 20 à 30% en poids de talc, et de 20 à 30% en poids d'un agent tackifiant, typiquement une résine de pétrole hydrogénée.As already indicated, and according to a first embodiment of the invention, said multilayer material can be a co-extruded material, either using an annular die by co-extrusion called "bubble", or using 'a flat die by co-extrusion called "cast". However, co-extrusion called "bubble" is preferred to co-extrusion cast, because it is more advantageous than co-extrusion "cast" both for economic reasons (lower investment cost) and for its flexibility. production, the multilayer material according to the invention, and in particular the sealing layer, having in a large number of cases having a structure allowing to take off the two walls of the "bubble" at the extruder outlet - condition essential for the implementation of this process. However, according to a second embodiment of the invention, and as illustrated in example 11, said sealing layer may be a coating layer, said external layer CE, and possibly said central layer CC, forming a support film - typically extruded or co-extruded - for said coating layer. According to a first variant of said second method, said coating layer can be a layer of varnish, typically a varnish based on EVA or EMA, said varnish being identified, or not identified and applied to the whole of said film. According to a second variant, said coating layer can be a hot-melt layer. Said hot-melt layer can form a mixture typically comprising from 20 to 30% by weight of elastomeric resin, typically SEBS, from 20 to 30% by weight of paraffin, from 20 to 30% by weight of talc, and from 20 at 30% by weight of a tackifying agent, typically a hydrogenated petroleum resin.
Dans le cas de ladite seconde modalité de l'invention, ledit support peut être un OPP ou BOPP d'épaisseur allant de 50 μm à 100 μm, et de préférence de 60 μm à 90 μm, blanc ou transparent.In the case of said second embodiment of the invention, said support can be an OPP or BOPP of thickness ranging from 50 μm to 100 μm, and preferably from 60 μm to 90 μm, white or transparent.
De préférence, ledit OPP ou BOPP peut être un OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80, d'épaisseur comprise entre 70 μm et 80 μm, et typiquement égale à 75 μm. Un OPP ou BOPP est dit "cavité" lorsqu'il présente une densité très inférieure à la densité standard du PP, de l'OPP, ou du BOPP (PP biorienté).Preferably, said OPP or BOPP can be a cavity, white OPP or BOPP, with a density ranging from 0.50 to 0.80, with a thickness between 70 μm and 80 μm, and typically equal to 75 μm. An OPP or BOPP is said to be "cavity" when it has a density much lower than the standard density of PP, OPP, or BOPP (bioriented PP).
Dans le matériau d'operculage selon l'invention, ladite couche externe peut aussi contenir un pigment minéral typiquement blanc à une teneur pondérale allant de 0,5 à 5%. En outre, ladite couche externe peut contenir une charge minérale micronisée, telle que du talc, à une teneur pondérale allant de 2% à 12% en poids et de typiquement de 5 à 10%. Cette charge minérale permet notamment d'obtenir une "main" ou un toucher particulier qui plait particulièrement au consommateur final. Généralement, une impression recouvre en totalité ou en partie ladite couche externe, et une couche de vernis de protection peut recouvrir ladite impression et/ou ladite couche externe.In the sealing material according to the invention, said outer layer may also contain a typically white mineral pigment at a weight content ranging from 0.5 to 5%. In addition, said outer layer may contain a micronized mineral filler, such as talc, at a weight content ranging from 2% to 12% by weight and typically from 5 to 10%. This mineral filler makes it possible in particular to obtain a "hand" or a particular feel which particularly pleases the end consumer. Generally, a print covers all or part of said external layer, and a layer of protective varnish can cover said print and / or said external layer.
Selon l'invention, ladite couche de vernis de protection peut comprendre une charge dispersée, typiquement minérale, de manière à augmenter la résistance thermique dudit matériau, et éventuellement à réduire l'endommagement de ladite impression durant ledit thermoscellage.According to the invention, said layer of protective varnish may comprise a dispersed filler, typically mineral, so as to increase the thermal resistance of said material, and possibly to reduce the damage to said printing during said heat sealing.
Ladite couche de scellage peut comprendre une charge dispersée, typiquement minérale, de manière à contrôler le coefficient de glissement desdits opercules, leur force de pelage après thermoscellage, et éventuellement leur dépilage.Said sealing layer may comprise a dispersed filler, typically mineral, so as to control the sliding coefficient of said lids, their peeling force after heat sealing, and optionally their unstacking.
Ladite charge dispersée, typiquement minérale, peut être choisie parmi les charges suivantes : silice, talc, argile exfolié sous forme de nanoparticules. Ladite charge dispersée dans la couche de scellage peut être présente dans ladite couche de scellage à une teneur pondérale allant de 2 à 10%, et typiquement de 4% à 8%. Ladite charge dispersée peut être du talc.Said dispersed filler, typically mineral, can be chosen from the following fillers: silica, talc, exfoliated clay in the form of nanoparticles. Said filler dispersed in the sealing layer may be present in said sealing layer at a weight content ranging from 2 to 10%, and typically from 4% to 8%. Said dispersed filler may be talc.
Ladite charge dispersée peut comprendre en outre un agent de glissement typiquement choisi parmi : l'érucamide, l'oléamide, un PEHD, un copolymère polyéther bloc amide.Said dispersed filler may also comprise a slip agent typically chosen from: erucamide, oleamide, a HDPE, a polyether block amide copolymer.
Selon l'invention, le matériau d'operculage présente une épaisseur totale E allant de préférence de 60 μm à 110 μm.According to the invention, the sealing material has a total thickness E preferably ranging from 60 μm to 110 μm.
Un autre objet de l'invention est constitué par les opercules prédécoupés formés à partir du matériau d'operculage selon l'invention.Another object of the invention consists of the precut lids formed from the lidding material according to the invention.
Un autre objet de l'invention est constitaé par un procédé de fabrication d'un matériau d'operculage multicouche par co-extrusion. Selon ce procédé, on peut extrader typiquement en bulle ledit matériau multicouche, ladite couche de scellage dudit matériau multicouche comprenant un mélange comprenant un premier EMA et typiquement une résine complémentaire choisie parmi : un second EMA d'une nature différente dudit premier EMA, un PE métallocène, un SBS dans une proportion pondérale allant de 30/70 à 70/30, ladite couche externe, et éventuellement ladite couche centrale, comprenant un PP ou étant constituée par du PP typiquement homopolymère. On peut également choisir pour ledit matériau multicouche une couche centrale comprenant au moins 50% de PE et une couche externe comprenant de 50 à 65% de PP et de 15 à 35% de PE, de manière à faciliter l'impression de ladite couche externe, l'épaisseur Ec de ladite couche centrale étant de 1,5 à 2,5 fois plus grande, et typiquement deux fois plus grande, que l'épaisseur Ee de ladite couche externe.Another object of the invention is constituted by a method of manufacturing a multilayer sealing material by co-extrusion. According to this process, said multilayer material can be typically bubble-blown, said sealing layer of said multilayer material comprising a mixture comprising a first EMA and typically a complementary resin chosen from: a second EMA of a different nature from said first EMA, a PE metallocene, an SBS in a proportion by weight ranging from 30/70 to 70/30, said outer layer, and optionally said central layer, comprising a PP or consisting of typically homopolymer PP. It is also possible to choose for said multilayer material a central layer comprising at least 50% of PE and an external layer comprising from 50 to 65% of PP and from 15 to 35% of PE, so as to facilitate the printing of said external layer , the thickness Ec of said central layer being 1.5 to 2.5 times greater, and typically two times greater, than the thickness Ee of said outer layer.
Un autre objet de l'invention est constitué par un procédé de fabrication d'un matériau d'operculage multicouche par enduction de vernis ou de hot-melt sur un film support qui peut être un film OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80 et de préférence de 0,55 à 0,75, et d'épaisseur typiquement comprise entre 60 μm et 90 μm, et typiquement égale à 75 μm.Another object of the invention is constituted by a process for manufacturing a multilayer sealing material by coating with varnish or hot-melt on a support film which can be an OPP or BOPP cavity film, white, of density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and with a thickness typically between 60 μm and 90 μm, and typically equal to 75 μm.
Un autre objet de l'invention est constitaé par l'utilisation d' un film OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80 et de préférence de 0,55 à 0,75, et d'épaisseur typiquement comprise entre 60 μm et 90 μm, et typiquement égale à 75 μm pour former un film support d'un matériau multicouche dans le procédé de fabrication d'un matériau d'operculage multicouche par enduction.Another object of the invention is constituted by the use of an OPP or BOPP cavity film, white, with a density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and thickness typically between 60 μm and 90 μm, and typically equal to 75 μm to form a support film of a multilayer material in the process for manufacturing a multilayer sealing material by coating.
EXEMPLES DE REALISATIONEXAMPLES OF REALIZATION
A) Essais réalisés On a réalisé des essais par extrusion (série Al), et des essais par enduction (série A2)A) Tests carried out Tests were carried out by extrusion (series A1), and tests by coating (series A2)
Al) Essais d'extrusionAl) Extrusion tests
Figure imgf000013_0001
Figure imgf000014_0001
Figure imgf000013_0001
Figure imgf000014_0001
Figure imgf000015_0001
Figure imgf000015_0001
- C ou B = matériau d'operculage sous forme de film coextrudé "Cast" ou "Bulle"- C or B = sealing material in the form of coextruded "Cast" or "Bubble" film
- PPH = PP homopolymère de densité égale à 0,90- PPH = PP homopolymer with a density equal to 0.90
- HDPE = PE haute densité de densité égale à 0,955- HDPE = high density PE with density equal to 0.955
- MM1 = mélange maître de PE à 70% en poids de TiO2 - MM1 = masterbatch of PE at 70% by weight of TiO 2
- MM2 = mélange maître de PE à 55% en poids de talc- MM2 = masterbatch of PE at 55% by weight of talc
- MM3 = mélange maître de PE et de silice (1500 ppm de silice)- MM3 = masterbatch of PE and silica (1500 ppm of silica)
- MM4 = mélange maître d'EVA contenant un agent glissant- MM4 = EVA masterbatch containing a slip agent
- EMA Elvaloy 1820 de Dupont : EMA à 20% d'acrylate de méthyle qui correspond à la courbe I de la figure 1, et qui présente un gradient ΔT/Δ% de 0,7 °C/% (en valeur absolue). Cet EMA a été fabriqué par un procédé de polymérisation tabulaire. Son point de fusion (DSC) est de 92°C.- EMA Elvaloy 1820 from Dupont: EMA with 20% methyl acrylate which corresponds to curve I of FIG. 1, and which has a ΔT / Δ% gradient of 0.7 ° C /% (in absolute value). This EMA was manufactured by a tabular polymerization process. Its melting point (DSC) is 92 ° C.
- EMA Elvaloy 1218 de Dupont : EMA à 18% d'acrylate de méthyle. Cet EMA a été fabriqué par un procédé de polymérisation tabulaire. Son point de fusion (DSC) est de 94°C. - EMA TC120 de Exxon : EMA à 21% d'acrylate de méthyle qui correspond à la courbe II de la figure 1, et qui présente un gradient ΔT/Δ% de 2 °C/% environ (en valeur absolue). Son point de fusion (DSC) est de 76°C.- EMA Elvaloy 1218 from Dupont: EMA containing 18% methyl acrylate. This EMA was manufactured by a tabular polymerization process. Its melting point (DSC) is 94 ° C. - EMA TC120 from Exxon: EMA with 21% methyl acrylate which corresponds to curve II of FIG. 1, and which has a gradient ΔT / Δ% of approximately 2 ° C /% (in absolute value). Its melting point (DSC) is 76 ° C.
- EMA Lotryl 18MG02 de Atofina : EMA à 18% d'acrylate de méthyle qui correspond à la courbe II de la figure 1, et qui présente un gradient ΔT/Δ% de 2 °C/% environ (en valeur absolue). Son point de fusion (DSC) est de 87°C.- EMA Lotryl 18MG02 from Atofina: EMA with 18% methyl acrylate which corresponds to curve II of FIG. 1, and which has a gradient ΔT / Δ% of approximately 2 ° C /% (in absolute value). Its melting point (DSC) is 87 ° C.
Ces deux derniers EMA ont été fabriqués par polymérisation en autoclave.These last two EMAs were produced by autoclave polymerization.
- EMA 24% d'acrylate de méthyle : EMA autoclave 24MBG005 de Atofina.- EMA 24% methyl acrylate: EMA autoclave 24MBG005 from Atofina.
- PE métallocène : Affinity PL 1881 de Dow Plastics. Son point de fusion est de 100°C.- Metallocene PE: Affinity PL 1881 from Dow Plastics. Its melting point is 100 ° C.
Il est important de noter que les matériaux d'operculage fabriqués selon l'invention par co-extrusion en bulle (essais N° 3 à 10) permettent d'obtenir :It is important to note that the sealing materials produced according to the invention by bubble co-extrusion (tests No. 3 to 10) make it possible to obtain:
- une mise en œuvre aisée avec une séparation des deux films en contact formant la bulle, en sortie d'extradeuse,- easy implementation with separation of the two films in contact forming the bubble, at the outlet of the extradeuse,
- une productivité élevée, et typiquement au moins égale à 185 kg/h pour une machine de coextrusion avec filière de sortie de 300 mm de diamètre.- a high productivity, and typically at least equal to 185 kg / h for a coextrusion machine with an output die of 300 mm in diameter.
- un matériau d'operculage typiquement exempt de tailage ou "curling", le matériau d'operculage restant plan, même après découpage en opercules.- a sealing material typically free from tailing or "curling", the sealing material remaining flat, even after cutting into lids.
A2) Essais d'enductionA2) Coating tests
Figure imgf000016_0001
* laque EVA : laque J9184AT de Sovereign en milieu toluène à 25,5% d'extrait sec et à point de fusion inférieur à 110°C.
Figure imgf000016_0001
* EVA lacquer: Sovereign J9184AT lacquer in toluene medium at 25.5% dry extract and with a melting point below 110 ° C.
B) Résultats obtenus :B) Results obtained:
Les essais ont été comparés à un produit témoin "Témoin A" correspondant à un produit standard du commerce, par exemple du type POLYMIX ® ou MLXPAP ®, et de structure :The tests were compared with a control product "Control A" corresponding to a standard commercial product, for example of the POLYMIX® or MLXPAP® type, and of structure:
Impression / Papier / adhésif / PET (métallisé) / Vernis Primaire / Vernis de thermoscellagePrinting / Paper / adhesive / PET (metallized) / Primary varnish / Heat sealing varnish
Dans tous les cas, les matériaux d'operculage ont été thermoscellés sur pots en PS avec mors pénétrant, avec une pression de 0,4 bar sur machine BHS Werk ® type VL1600, et pendant 1 seconde, et cela pour différentes températures T de scellage. On a également thermoscellé les matériaux d'operculage avec des mors plats - avec un plat de 1 à 3 mm de large- non pénétrant dans le PS, les mors dits pénétrants étant de mors à profil en ogive. L'avantage de pouvoir utiliser un mors plat réside dans le fait de rendre peu visible à invisible le cordon de scellage.In all cases, the sealing materials were heat sealed on PS pots with penetrating jaws, with a pressure of 0.4 bar on a BHS Werk ® machine type VL1600, and for 1 second, and this for different sealing temperatures T . The sealing materials were also heat sealed with flat jaws - with a flat 1 to 3 mm wide - not penetrating into the PS, the so-called penetrating jaws being jaws with a warhead profile. The advantage of being able to use a flat jaw lies in making the sealing bead not very visible to invisible.
On a mesuré successivement la tenue à la pression à sec (voir Bl), la tenue à la pression à froid et à sec, et à froid et milieu humide (voir B2), ainsi que l'adhérence des opercules (voir B3). Lorsque, pour une température de scellage donnée, ne figure pas une valeur numérique, cela signifie que cette température de scellage est exclue, soit parce qu'il n'y a pas de scellage pour les températures inférieures à celle considérées pour les mesures en question, soit parce que le film est détérioré pour les températures de scellage supérieures à celle considérées pour les mesures en question.The resistance to dry pressure (see B1), the resistance to cold and dry pressure, and to cold and wet pressure (see B2), as well as the adhesion of the lids (successive) were successively measured. When a numerical value is not given for a given sealing temperature, this means that this sealing temperature is excluded, either because there is no sealing for temperatures below that considered for the measurements in question , or because the film is deteriorated for the sealing temperatures higher than that considered for the measurements in question.
Bl - Résultats de tenue à la pression à sec :Bl - Dry pressure withstand results:
Les résultats indiquent, pour chaque température de scellage, la pression en bar à laquelle il n'y a plus d'étanchéité.The results indicate, for each sealing temperature, the pressure in bar at which there is no longer any seal.
ESSAIS TEMPERATURE de SCELLAGE sur pots PS SEALING TEMPERATURE TESTS on PS jars
Figure imgf000018_0001
Figure imgf000018_0001
Figure imgf000018_0002
Figure imgf000018_0002
- Tenue à la pression (en bar) en milieu humide et froid (après 72 heures), soit avec vide, soit avec pot contenant une solution aqueuse d'acide lactique à 3% :- Resistance to pressure (in bar) in a humid and cold environment (after 72 hours), either with vacuum, or with pot containing an aqueous solution of lactic acid at 3%:
Figure imgf000018_0003
Figure imgf000018_0003
Figure imgf000019_0001
Figure imgf000019_0001
Il est considéré qu'une bonne valeur se situe à partir d'environ 0,4 bar, mais les produits ayant une tenue à la pression d'au moins 0,30 bar sont déjà intéressants et utilisables. Si l'on voulait augmenter la sécurité de la fermeture, il conviendrait d'avoir au moins 0,5 bar.It is considered that a good value is situated from around 0.4 bar, but the products having a pressure resistance of at least 0.30 bar are already interesting and usable. If you want to increase the security of the closure, you should have at least 0.5 bar.
Les essais en milieu froid et humide simulent les conditions de stockage des pots de yaourts.The tests in cold and humid environments simulate the storage conditions of the yoghurt pots.
Il convient de noter que certains produits (voir par exemple les essais 1, 2, 4, 5', 8, 9,It should be noted that certain products (see for example tests 1, 2, 4, 5 ', 8, 9,
10, 11) présentent une tenue à la pression assez peu sensible à la température, ce qui est avantageux sur un plan pratique puisque la température des mors de scellage peut présenter une certaine latitude sans risque d'avoir de grandes variations de tenue à la pression.10, 11) have a pressure resistance relatively insensitive to temperature, which is advantageous on a practical level since the temperature of the sealing jaws can have a certain latitude without risk of having large variations in pressure resistance .
Figure imgf000019_0002
0,4 à200°C
Figure imgf000019_0002
0.4 to 200 ° C
Les essais avec solution lactique sont très voisins des essais sur pot vide.The tests with lactic solution are very similar to the tests on an empty pot.
B3 Adhérence des opercules thermoscellés sur pots (force exprimée en grammes : 1000 g = 9,81 N) et mesurée à 3 moments désignés par "pop", "tour" et "fin" pour indiquer respectivement la force exercée sur l'opercule respectivement soit en début d'ouverture, soit ensuite durant le délaminage de l'opercule, soit en fin d'ouverture.B3 Adherence of heat-sealed lids on jars (force expressed in grams: 1000 g = 9.81 N) and measured at 3 times designated by "pop", "turn" and "end" to indicate respectively the force exerted on the seal respectively either at the start of opening, or then during delamination of the cover, or at the end of opening.
Figure imgf000020_0001
Figure imgf000020_0001
C) Conclusions générales :C) General conclusions:
D'une part, les essais 1 à 7 montrent très clairement les excellents résultats obtenus avec une couche de scellage comprenant de l'EMA "tabulaire" à 20 % d'acrylate de méthyle (essais 2, 4 et 5) comparés à ceux obtenus avec une couche de scellage comprenant sur un EMA "autoclave" (essais 1 et 3).On the one hand, tests 1 to 7 very clearly show the excellent results obtained with a sealing layer comprising “tabular” EMA containing 20% methyl acrylate. (tests 2, 4 and 5) compared to those obtained with a sealing layer comprising on an "autoclave" EMA (tests 1 and 3).
Toutefois, en ce qui concerne ces essais 1 et 3, il convient de noter que l'essai 1 reste encore supérieur à l'essai témoin, alors que l'essai 3 est inférieur au témoin, ce qui montre l'intérêt d'utiliser un EMA "autoclave" ayant au moins 20% en poids d'acrylate de méthyle.However, with regard to these tests 1 and 3, it should be noted that test 1 is still superior to the control test, while test 3 is less than the control, which shows the advantage of using an "autoclave" EMA having at least 20% by weight of methyl acrylate.
Il en est de même dans le cas de l'EMA "tabulaire. En effet, les résultats des essais 6 et 7, dans lesquels la couche de scellage comprend un EMA tabulaire à 18 % d'acrylate de méthyle, sont inférieurs à ceux des essais 2, 4 et 5 dans lesquels l'EMA "tabulaire" est à 20% d'acrylate de méthyle.The same is true in the case of the tabular EMA. In fact, the results of tests 6 and 7, in which the sealing layer comprises a tabular EMA containing 18% methyl acrylate, are lower than those of tests 2, 4 and 5 in which the "tabular" EMA is 20% methyl acrylate.
Mais il convient de noter qu'à même teneur pondérale en acrylate de méthyle, les EMA "tabulaire" conduisent à de meilleurs résultats que les EMA "autoclave". En effet, l'essai 3 dans lequel la couche de scellage comprend 90% d'EMA "autoclave" à 18% d'acrylate de méthyle est inférieur à l'essai 6 dans lequel la couche de scellage comprend 88% d'EMA "tabulaire" à 18% d'acrylate de méthyle.However, it should be noted that at the same methyl acrylate content by weight, "tabular" EMAs lead to better results than "autoclave" EMAs. In fact, test 3 in which the sealing layer comprises 90% of "autoclave" EMA with 18% of methyl acrylate is lower than test 6 in which the sealing layer comprises 88% of EMA " tabular "with 18% methyl acrylate.
A noter que l'emploi d'EMA obtenu par un procédé de polymérisation tabulaire (typiquement essais 2 et 4) conduit à un gradient ou coefficient ΔT/Δ% faible en valeur absolue, ce qui est avantageux pour obtenir un produit final peu sensible aux variations sur le taux d'acrylate de méthyle. A ce jour, la demanderesse n'a pu émettre d'hypothèse pour expliquer les propriétés particulières de ce type d'EMA à faible gradient ΔT/Δ%.Note that the use of EMA obtained by a tabular polymerization process (typically tests 2 and 4) leads to a gradient or coefficient ΔT / Δ% low in absolute value, which is advantageous for obtaining a final product that is not very sensitive to variations in the methyl acrylate level. To date, the applicant has not been able to put forward a hypothesis to explain the particular properties of this type of EMA with a low gradient ΔT / Δ%.
D'autre part, il importe de noter, en comparant les essais 6 et 7, l'effet bénéfique de la, présence de talc dans la couche de scellage : alors que l'essai 7 - avec couche de scellage dépourvue de talc - présente des propriétés inférieures à celle de l'essai témoin, l'essai 6 - avec couche de scellage comprenant 6,6 % en poids de talc, présente des propriétés au moins égales à celles de l'essai témoin.On the other hand, it is important to note, by comparing tests 6 and 7, the beneficial effect of the presence of talc in the sealing layer: while test 7 - with sealing layer devoid of talc - presents properties inferior to that of the control test, test 6 - with a sealing layer comprising 6.6% by weight of talc, has properties at least equal to those of the control test.
En outre, les essais 8 et 9 dont la couche de scellage comprend un EMA à 24 % d'acrylate de méthyle conduisent à de bons résultats. A noter que ces résultats - supérieurs à ceux de l'essai témoin - sont obtenus bien qu'il s'agisse d'un EMA de type autoclave. Il importe de noter que les EMA à taux élevés en acrylate de méthyle utilisés selon l'invention, notamment l'EMA 24MBG005 de Atofina, ont permis une coextrusion en bulle dans des conditions de productivité industrielle, sans collage de la bulle extradée, alors que, pour l'homme du métier, la coextrusion en bulle industrielle suppose l'extrusion d'un EMA à moins de 18% en poids d'acrylate de méthyle ou d'un mélange en mélange 90/10 en poids d'EMA à 18% en poids d'acrylate de méthyle et de PE, ce qui conduit à un taux global d'acrylate de méthyle de 16,2% dans la couche de scellage.In addition, tests 8 and 9, the sealing layer of which comprises an EMA containing 24% methyl acrylate, give good results. Note that these results - superior to those of the control test - are obtained although it is an EMA of the type autoclave. It should be noted that the EMAs with high levels of methyl acrylate used according to the invention, in particular the EMA 24MBG005 from Atofina, have enabled bubble coextrusion under industrial productivity conditions, without bonding of the extruded bubble, whereas , for a person skilled in the art, industrial bubble coextrusion supposes the extrusion of an EMA of less than 18% by weight of methyl acrylate or of a mixture of 90/10 mixture by weight of EMA to 18 % by weight of methyl acrylate and of PE, which leads to an overall level of methyl acrylate of 16.2% in the sealing layer.
Enfin, en ce qui concerne l'essai 11, il est à noter que cet essai, quoique conduisant à des résultats légèrement inférieurs à ceux de l'essai témoin, est du plus haut intérêt, notamment sur le plan économique, compte tenu de son procédé de fabrication très simple, procédé basé sur l'enduction et non la coextrusion. Il est à noter en outre, que des résultats au moins égaux à ceux de l'essai témoin ont été obtenus en chargeant la laque de scellage de l'essai 11 avec 6% de talc.Finally, with regard to test 11, it should be noted that this test, although leading to results slightly inferior to those of the control test, is of the greatest interest, in particular on the economic level, taking into account its very simple manufacturing process, process based on coating and not coextrusion. It should also be noted that results at least equal to those of the control test were obtained by loading the sealing lacquer of test 11 with 6% talc.
AVANTAGES DE L'INVENTIONADVANTAGES OF THE INVENTION
Le matériau d'operculage selon l'invention présente donc plusieurs avantages, au-delà des propriétés d'usage requises. En effet, quelle que soit la modalité de matériau d'operculage considéré :The sealing material according to the invention therefore has several advantages, beyond the required use properties. Indeed, whatever the type of sealing material considered:
- d'une part, étant à base de polyoléfine, il est relativement peu coûteux, en particulier lorsqu'il est obtenu par co-extrusion en bulle, ou par simple enduction, - d'autre part, il permet un thermoscellage de qualité à basse température - température très inférieure à 200°C, et cela dans une plage de température suffisamment large pour que l'obturation des pot soit de mise en œuvre aisée tout en garantissant l'étanchéité des pots,- on the one hand, being based on polyolefin, it is relatively inexpensive, in particular when it is obtained by co-extrusion in bubble, or by simple coating, - on the other hand, it allows a quality heat sealing at low temperature - temperature much lower than 200 ° C, and this in a sufficiently wide temperature range so that the sealing of the pots is easy to implement while guaranteeing the tightness of the pots,
- enfin, le matériau d'operculage selon l'invention étant à base de polyoléfine, et donc fondamentalement en monomatériau, il peut être facilement recyclé. - Finally, the sealing material according to the invention being based on polyolefin, and therefore basically in monomaterial, it can be easily recycled.

Claims

REVENDICATIONS
1. Matériau d'operculage ou opercule formant un matériau multicouche d'épaisseur E comprise entre 30μm et 140 μm, et destiné à obturer par thermoscellage un récipient ou un pot typiquement à base de PP ou de PS, comprenant : a) une couche externe CE en polyoléfine, d'épaisseur Ee allant de 0,9.E à 0,6.E, b) une couche de scellage CS, d'épaisseur Es allant de 0,1.E à 0,4.E, ladite couche de scellage et ladite couche externe en polyoléfine présentant une température de fusion, notée respectivement Ts pour la couche de scellage et To pour la couche en polyoléfine, telle que To - Ts soit au moins égal à 20°C, et de préférence au moins égal à 30°C.1. Sealing material or cover forming a multilayer material with a thickness E of between 30 μm and 140 μm, and intended for sealing by heat sealing a container or a pot typically based on PP or PS, comprising: a) an outer layer CE in polyolefin, of thickness Ee ranging from 0.9.E to 0.66E, b) a sealing layer CS, of thickness Es ranging from 0.11E to 0.44.E, said layer of sealing and said outer polyolefin layer having a melting temperature, denoted respectively Ts for the sealing layer and To for the polyolefin layer, such that To - Ts is at least equal to 20 ° C, and preferably at least equal at 30 ° C.
2. Matériau selon la revendication 1 dans lequel ladite couche externe forme un mélange de polyoléfines comprenant une polyoléfine, à au moins 50% en poids dans ledit mélange, présentant ladite température de fusion To.2. Material according to claim 1 wherein said outer layer forms a mixture of polyolefins comprising a polyolefin, at least 50% by weight in said mixture, having said melting temperature To.
3. Matériau selon une quelconque des revendications 1 à 2 dans lequel ladite couche de scellage comprend un constituant majoritaire en poids présentant ladite température de fusion Ts.3. Material according to any one of claims 1 to 2 wherein said sealing layer comprises a majority component by weight having said melting temperature Ts.
4. Matériau selon une quelconque des revendication 1 à 3 comprenant une couche centrale CC en polyoléfine, éventuellement chargée en pigment, et dans ce cas, typiquement chargée en pigment minéral blanc, ladite couche centrale, d'épaisseur Ec telle que Ee+Ec aille de 0,9.E à 0,6.E, étant intercalée entre ladite couche externe CE et ladite couche de scellage CS, de manière à former une structure multicouche représentée symboliquement par CE / CC / CS.4. Material according to any one of claims 1 to 3 comprising a central layer CC of polyolefin, optionally loaded with pigment, and in this case, typically loaded with white mineral pigment, said central layer, of thickness Ec such that Ee + Ec aille from 0.9.E to 0.6.E, being interposed between said external layer CE and said sealing layer CS, so as to form a multilayer structure symbolically represented by CE / CC / CS.
5. Matériau selon une quelconque des revendications 1 à 4 dans lequel ladite polyoléfine est choisie parmi le PP homopolymère ou copolymère ou le PE de densité supérieure à 0,930, typiquement le HDPE, ou un mélange ou un copolymère de PP et de PE. 5. Material according to any one of claims 1 to 4 wherein said polyolefin is chosen from homopolymer or copolymer PP or PE with a density greater than 0.930, typically HDPE, or a mixture or a copolymer of PP and PE.
6. Matériau selon une quelconque des revendications 4 à 5 dans lequel ladite couche centrale comprend comme pigment blanc typiquement de l'oxyde de titane ou de l'oxyde de zinc, à une teneur pondérale allant de 0,5 % à 25%.6. Material according to any one of claims 4 to 5 wherein said central layer comprises as white pigment typically titanium oxide or zinc oxide, at a weight content ranging from 0.5% to 25%.
7. Matériau selon une quelconque des revendications 1 à 6 dans lequel ladite couche de scellage est choisie parmi : a) un EMA à une teneur pondérale en acrylate de méthyle allant de 12% à 24%, b) un EVA à une teneur en acétate de vinyle allant de 12% à 24%, c) un EBA à une teneur en acrylate de butyle allant de 12% à 24%, d) un EEA à une teneur en acétate d'éthyle allant de 12% à 24%, e) un mélange d'EMA ou d'EVA ou d'EBA ou d'EEA avec du PE ou du PP, le point de fusion DSC de ladite couche de scellage étant compris entre 70°C et 120°C, et de préférence entre 90°C et 100°C.7. Material according to any one of claims 1 to 6 wherein said sealing layer is chosen from: a) an EMA with a weight content of methyl acrylate ranging from 12% to 24%, b) an EVA with an acetate content vinyl ranging from 12% to 24%, c) an EBA with a butyl acrylate content ranging from 12% to 24%, d) an EEA with an ethyl acetate content ranging from 12% to 24%, e ) a mixture of EMA or EVA or EBA or EEA with PE or PP, the DSC melting point of said sealing layer being between 70 ° C and 120 ° C, and preferably between 90 ° C and 100 ° C.
8. Matériau selon la revendication 7 dans lequel ladite couche de scellage comprend de l'EMA à une teneur pondérale en acrylate de méthyle allant de 16 à 24 %.8. Material according to claim 7 wherein said sealing layer comprises EMA with a weight content of methyl acrylate ranging from 16 to 24%.
9. Matériau selon une quelconque des revendications 7 ou 8 dans lequel ledit EMA est un EMA présentant un gradient ΔT/Δ% inférieur en valeur absolue à 1 ,5 °C/%.9. Material according to any one of claims 7 or 8 wherein said EMA is an EMA having a gradient ΔT / Δ% lower in absolute value than 1.5 ° C /%.
10. Matériau selon la revendication 9 dans lequel ledit gradient ΔT/Δ% est inférieur en valeur absolue à 1 °C/%, et de préférence inférieur en valeur absolue à 0,80 °C/%.10. Material according to claim 9 wherein said gradient ΔT / Δ% is less in absolute value to 1 ° C /%, and preferably less in absolute value to 0.80 ° C /%.
11. Matériau selon une quelconque des revendications 7 à 10 dans lequel ledit EMA est un EMA dit "tubulaire" obtenu par copolymérisation tabulaire d'éthylène et d'acrylate de méthyle.11. Material according to any one of claims 7 to 10 wherein said EMA is a so-called "tubular" EMA obtained by tabular copolymerization of ethylene and methyl acrylate.
12. Matériau selon une quelconque des revendications 7 à 10 dans lequel ledit EMA est un EMA dit "autoclave" obtenu par copolymérisation en autoclave d'éthylène et d'acrylate de méthyle, ledit EMA ayant de préférence au moins 20% en poids d'acrylate de méthyle et ayant notamment 24% en poids d'acrylate de méthyle. 12. Material according to any one of claims 7 to 10 wherein said EMA is a so-called "autoclave" EMA obtained by autoclave copolymerization of ethylene and methyl acrylate, said EMA preferably having at least 20% by weight of methyl acrylate and in particular having 24% by weight of methyl acrylate.
13. Matériau selon la revendication 12 dans lequel ladite couche scellante comprend ledit EMA "autoclave" et une résine SBS, la teneur pondérale en EMA allant de 55% à 85%, et typiquement de 65% à 75%, la teneur pondérale en SBS allant de 45% à 15% et typiquement de 35% à 25%.13. The material as claimed in claim 12, in which said sealing layer comprises said “autoclave” EMA and an SBS resin, the content by weight of EMA ranging from 55% to 85%, and typically from 65% to 75%, the content by weight of SBS ranging from 45% to 15% and typically from 35% to 25%.
14. Matériau selon une quelconque des revendications 7 à 12 dans lequel ledit EMA comprend un mélange d'EMA "tubulaire" et d'EMA "autoclave", dans un rapport pondéral allant de 80-20 à 20-80.14. Material according to any one of claims 7 to 12 wherein said EMA comprises a mixture of "tubular" EMA and "autoclave" EMA, in a weight ratio ranging from 80-20 to 20-80.
15. Matériau selon une quelconque des revendications 1 à 14 dans lequel, typiquement dans le cas où ledit pot est en PP, ladite couche de scellage comprend de 10 à 50% en poids d'un terpolymère à base PP métallocène à bas point de fusion.15. Material according to any one of claims 1 to 14 in which, typically in the case where said pot is made of PP, said sealing layer comprises from 10 to 50% by weight of a metallocene PP-based terpolymer with low melting point .
16. Matériau selon une quelconque des revendications 1 à 14 dans lequel, typiquement dans le cas où ledit pot est en PS ou en PP, ladite couche de scellage comprend de 30 % à 100% en poids de PE métallocène, et de 70% à 0% en poids d'EMA.16. Material according to any one of claims 1 to 14 wherein, typically in the case where said pot is made of PS or PP, said sealing layer comprises from 30% to 100% by weight of metallocene PE, and from 70% to 0% by weight of EMA.
17. Matériau selon une quelconque des revendications 4 à 16 dans lequel ladite couche centrale a une épaisseur Ec allant de 0,2.(Ee+Ec) à 0,9.(Ee+Ec).17. Material according to any one of claims 4 to 16 wherein said central layer has a thickness Ec ranging from 0.2. (Ee + Ec) to 0.9. (Ee + Ec).
18. Matériau selon la revendication 17 dans laquelle ladite couche centrale comprend - ou est formée par - un matériau plastique de recyclage extrudable.18. Material according to claim 17 wherein said central layer comprises - or is formed by - an extrudable plastic recycling material.
19. Matériau selon une quelconque des revendications 1 à 18 dans lequel ledit matériau multicouche est un matériau co-extrudé, soit à l'aide d'une filière annulaire par coextrusion dite "bulle", soit à l'aide d'une filière plate par co-extrusion dite "cast".19. Material according to any one of claims 1 to 18 wherein said multilayer material is a co-extruded material, either using an annular die by coextrusion called "bubble", or using a flat die by co-extrusion called "cast".
20. Matériau selon une quelconque des revendications 1 à 7 dans lequel ladite couche de scellage est une couche d'enduction, ladite couche externe, et éventaellement ladite couche centrale formant un film support pour ladite couche d'enduction. 20. Material according to any one of claims 1 to 7 wherein said sealing layer is a coating layer, said outer layer, and optionally said central layer forming a support film for said coating layer.
21. Matériau selon la revendication 20 dans lequel ladite couche d'enduction est un vernis, typiquement à base d'EVA ou d'EMA, ledit vernis étant repéré, ou non repéré et appliqué sur la totalité dudit film.21. The material as claimed in claim 20, in which said coating layer is a varnish, typically based on EVA or EMA, said varnish being identified, or not identified and applied to the whole of said film.
22. Matériau selon la revendication 20 dans lequel ladite couche d'enduction est une couche de hot-melt.22. Material according to claim 20, in which said coating layer is a hot-melt layer.
23. Matériau selon la revendication 20 dans lequel ladite couche d'enduction est une couche de hot-melt formant un mélange comprenant typiquement de 20 à 30% en poids de résine élastomère, typiquement un SEBS, de 20 à 30% en poids de paraffine, de 20 à 30% en poids de talc, et de 20 à 30% en poids d'un agent tackifiant, typiquement une résine de pétrole hydrogénée.23. Material according to claim 20, in which said coating layer is a hot-melt layer forming a mixture typically comprising from 20 to 30% by weight of elastomeric resin, typically SEBS, from 20 to 30% by weight of paraffin. , from 20 to 30% by weight of talc, and from 20 to 30% by weight of a tackifying agent, typically a hydrogenated petroleum resin.
24. Matériau selon une quelconque des revendications 20 à 23 dans lequel ledit support est un OPP ou BOPP d'épaisseur allant de 50 μm à 100 μm, et de préférence de 60 μm à 90 μm, blanc ou transparent.24. Material according to any one of claims 20 to 23 wherein said support is an OPP or BOPP with a thickness ranging from 50 μm to 100 μm, and preferably from 60 μm to 90 μm, white or transparent.
25. Matériau selon la revendication 24 dans lequel ledit OPP ou BOPP est un OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80, d'épaisseur comprise entre 70 μm et 80 μm, et typiquement égale à 75 μm.25. The material as claimed in claim 24, in which said OPP or BOPP is an OPP or BOPP cavity, white, with a density ranging from 0.50 to 0.80, with a thickness between 70 μm and 80 μm, and typically equal to 75 .mu.m.
26. Matériau selon une quelconque des revendications 1 à 25 dans lequel ladite couche externe contient un pigment minéral typiquement blanc à une teneur pondérale allant de 0,5 à 5%.26. Material according to any one of claims 1 to 25 wherein said outer layer contains a typically white mineral pigment at a weight content ranging from 0.5 to 5%.
27. Matériau selon une quelconque des revendications 1 à 26 dans lequel ladite couche externe contient une charge minérale micronisée, telle que du talc, à une teneur pondérale allant de 2% à 12% en poids et de typiquement de 5 à 10%. 27. Material according to any one of claims 1 to 26 wherein said outer layer contains a micronized mineral filler, such as talc, at a weight content ranging from 2% to 12% by weight and typically from 5 to 10%.
28. Matériau selon une quelconque des revendications 1 à 27 dans lequel une impression recouvre en totalité ou en partie ladite couche externe.28. Material according to any one of claims 1 to 27 wherein a print covers all or part of said outer layer.
29. Matériau selon une quelconque des revendications 1 à 28 dans lequel une couche de vernis de protection recouvre ladite impression et/ou ladite couche externe.29. Material according to any one of claims 1 to 28 in which a layer of protective varnish covers said print and / or said outer layer.
30. Matériau selon la revendication 29 dans lequel ladite couche de vernis de protection comprend une charge dispersée, typiquement minérale, de manière à augmenter la résistance thermique dudit matériau, et éventuellement à réduire l'endommagement de ladite impression durant ledit thermoscellage.30. The material as claimed in claim 29, in which said layer of protective varnish comprises a dispersed filler, typically mineral, so as to increase the thermal resistance of said material, and possibly to reduce the damage to said printing during said heat sealing.
31. Matériau selon une quelconque des revendications 1 à 30 dans lequel ladite couche de scellage comprend une charge dispersée, typiquement minérale, de manière à contrôler le coefficient de glissement desdits opercules, leur force de pelage après thermoscellage, et éventuellement leur dépilage.31. Material according to any one of claims 1 to 30 wherein said sealing layer comprises a dispersed filler, typically mineral, so as to control the sliding coefficient of said lids, their peeling force after heat sealing, and optionally their unstacking.
32. Matériau selon une quelconque des revendications 30 à 31 dans lequel ladite charge dispersée typiquement minérale est choisie parmi les charges suivantes : silice, talc, argile exfolié sous forme de nanoparticules.32. Material according to any one of claims 30 to 31 in which said typically mineral dispersed filler is chosen from the following fillers: silica, talc, clay exfoliated in the form of nanoparticles.
33. Matériau selon la revendication 32 dans lequel ladite charge dispersée dans la couche de scellage est à une teneur pondérale allant de 2 à 10%, et typiquement de 4% à 8%.33. Material according to claim 32 wherein said filler dispersed in the sealing layer is at a weight content ranging from 2 to 10%, and typically from 4% to 8%.
34. Matériau selon la revendication 32 dans lequel ladite charge est du talc.34. The material of claim 32 wherein said filler is talc.
35. Matériau selon une quelconque des revendications 30 à 34 dans lequel ladite charge dispersée comprend en outre un agent de glissement typiquement choisi parmi : l'érucamide, l'oléamide, un PEHD, un copolymère polyether bloc amide. 35. Material according to any one of claims 30 to 34 in which said dispersed filler further comprises a slip agent typically chosen from: erucamide, oleamide, a HDPE, a polyether block amide copolymer.
36. Matériau selon une quelconque des revendications 1 à 35 dans lequel ladite épaisseur E va de 60 μm à 110 μm.36. Material according to any one of claims 1 to 35 in which said thickness E ranges from 60 μm to 110 μm.
37. Opercules prédécoupés formés à partir du matériau d'operculage selon une quelconque des revendications 1 à 36.37. Pre-cut lids formed from the lidding material according to any one of claims 1 to 36.
38. Procédé de fabrication d'un matériau selon la revendication 19 dans lequel on extrade typiquement en bulle ledit matériau multicouche, ladite couche de scellage dudit matériau multicouche comprenant un mélange comprenant un premier EMA et typiquement une résine complémentaire choisie parmi : un second EMA d'une nature différente dudit premier EMA, un PE métallocène, un SBS dans une proportion pondérale allant de 30/70 à 70/30, ladite couche externe, et éventuellement ladite couche centrale, comprenant un PP ou étant constituée par du PP typiquement homopolymère.38. A method of manufacturing a material according to claim 19, in which said multilayer material is typically bubble-shaped, said sealing layer of said multilayer material comprising a mixture comprising a first EMA and typically a complementary resin chosen from: a second EMA d 'a different nature of said first EMA, a metallocene PE, an SBS in a weight proportion ranging from 30/70 to 70/30, said outer layer, and optionally said central layer, comprising a PP or consisting of typically homopolymer PP.
39. Procédé selon la revendication 38 dans lequel on choisit pour ledit matériau multicouche une couche centrale comprenant au moins 50% de PE et une couche externe comprenant de 50 à 65% de PP et de 15 à 35% de PE, de manière à faciliter l'impression de ladite couche externe, l'épaisseur Ec de ladite couche centrale étant de 1,5 à 2,5 fois plus grande, et typiquement deux fois plus grande, que l'épaisseur Ee de ladite couche externe.39. The method of claim 38 wherein one chooses for said multilayer material a central layer comprising at least 50% of PE and an outer layer comprising from 50 to 65% of PP and from 15 to 35% of PE, so as to facilitate the printing of said outer layer, the thickness Ec of said central layer being 1.5 to 2.5 times greater, and typically two times greater, than the thickness Ee of said outer layer.
40. Procédé de fabrication d'un matériau selon une quelconque des revendications 20 à 25 dans lequel ledit film support est un film OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80 et de préférence de 0,55 à 0,75, et d'épaisseur typiquement comprise entre 60 μm et 90 μm, et typiquement égale à 75 μm.40. A method of manufacturing a material according to any one of claims 20 to 25 wherein said support film is a white OPP or BOPP cavity film, with a density ranging from 0.50 to 0.80 and preferably from 0.55 at 0.75, and with a thickness typically between 60 μm and 90 μm, and typically equal to 75 μm.
41. Utilisation d' un film OPP ou BOPP cavité, blanc, de densité allant de 0,50 à 0,80 et de préférence de 0,55 à 0,75, et d'épaisseur typiquement comprise entre 60 μm et 90 μm, et typiquement égale à 75 μm pour former un film support d'un matériau selon une quelconque des revendications 20 à 25. 41. Use of a white OPP or BOPP cavity film with a density ranging from 0.50 to 0.80 and preferably from 0.55 to 0.75, and with a thickness typically between 60 μm and 90 μm, and typically equal to 75 μm to form a support film of a material according to any one of claims 20 to 25.
PCT/FR2002/003669 2001-10-26 2002-10-25 Multilayer sealing materials or peelable seals WO2003035391A2 (en)

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FR2831483B1 (en) 2004-01-09

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