STERILIZABLE TAPPING ADHESIVE

Description

[0001] The present invention relates to a solvent-based two-component polyurethane adhesive composition, which is suitable for the complexing (or lamination) of thin layers of materials, in particular polymeric and / or metallic materials. It also relates to a multilayer film comprising at least 2 thin layers of said materials bonded together by said crosslinked adhesive composition. Finally, it relates to the use of said film for the manufacture of flexible packaging for agri-food products, more particularly intended for sterilization.

[0002] Flexible packaging, intended in particular for packaging agri-food products, generally consists of several thin layers (in the form of sheets or films) with a thickness of between 5 and 150 µm and which are made of different materials such as paper, a metal (for example aluminium) or even thermoplastic polymers. These thin layers are bonded together by gluing, and the corresponding complex (or multi-layer) film, whose thickness can vary from 20 to 400 µm, makes it possible to combine the properties of the different individual layers of material (also called "supports") and thus offer the consumer a set of characteristics adapted to the final flexible packaging, such as, for example: its visual appearance (in particular that of the printed elements presenting information concerning the packaged product and intended for the consumer, or its transparency), a barrier effect to light or atmospheric humidity or gases, in particular oxygen, food contact without risks of toxicity or modification of the organoleptic properties of the packaged foods, chemical resistance for certain products such as ketchup, and appropriate thermal resistance.

[0003] Such thermal resistance is understood to mean the maintenance of the cohesion of the multilayer film when exposed to high temperatures, and in particular the absence of separation between the thin layers bonded by adhesives that constitute it. Such separation is generally referred to as "delamination".

[0004] This thermal resistance is indeed necessary during the shaping of the multilayer film for the production of the final packaging. This shaping generally includes a heat-sealing step, during which the film is subjected for a few seconds to a temperature between 120 and 250 °C and a pressure of a few bars. This latter technique is also used for closing the packaging around the food product.

[0005] This thermal resistance is also required for multi-layer films intended for sterilization treatments of food products packaged in the packaging. Such treatment exposes the multi-layer film to a temperature between 100 and 135°C for a duration generally longer than that of heat sealing, which can be up to one hour.

[0006] The various layers of materials that make up the multilayer film are combined or assembled by lamination, during industrial laminating processes (or "lamination"). These processes use adhesives (or glues) and equipment (or machines) that are designed for this purpose and that operate continuously with generally very high line speeds, of the order of several hundred meters per minute. The multilayer film thus obtained is often itself referred to by the term "laminate".

[0007] These lamination methods firstly comprise a step of coating the adhesive on a first film of material, which consists of depositing a continuous layer of glue with a controlled thickness generally less than 10 µm, corresponding to a quantity of glue (or grammage) generally not exceeding 10 g / m 2 < . This coating step is followed by a step of laminating a second film of material, identical or different from the first, consisting of applying this second film under pressure to the first film covered with the layer of glue.

[0008] The complex films are thus finally obtained in very large width and are generally packaged by winding, in the form of large reels of 1 m to 1.50 m in diameter having, like the film they store, up to 2 m in width. These large reels can be stored and transported, with a view to their use: either directly by food manufacturers, for the packaging of their product, or by processors (or complexers, also known by the English term "converters").

[0009] In both cases, the film is cut to reduce its width and shaped to make bags, which are then used to package a product, for example a food product.

[0010] Two-component polyurethane laminating adhesives with solvent are widely used as glue for the manufacture of multi-layer systems intended for the field of flexible packaging. The implementation of said solvent-based adhesives in the laminating process requires an evaporation step of the organic solvent. This step is carried out before the laminating step by passing the first film covered with glue through an oven following the coating step.

[0011] Two-component polyurethane laminating adhesives with solvent are supplied to the complexer in the form of 2 compositions (or components): one (called the -NCO component) comprising chemical entities bearing -NCO isocyanate end groups, and the other (called the -OH component) comprising chemical entities bearing -OH hydroxyl end groups.

[0012] Being a solvent-based adhesive, these two compositions are organic solutions of these chemical entities.

[0013] The mixing of these two organic solutions is carried out at room temperature by the operator of the complexing machine before starting it up, which allows it to function correctly, thanks to an appropriate viscosity obtained where necessary by adding solvent.

[0014] At the end of the coating step of the mixture thus obtained on the 1st thin layer, and the counter-bonding step of the 2nd layer, the isocyanate groups of the -NCO component react with the hydroxyl groups of the -OH component, according to a so-called crosslinking reaction, to form a polyurethane which is in the form of a three-dimensional network with urethane groups, ensuring the cohesion of the adhesive joint between the 2 laminated thin layers. Two-component polyurethane laminating adhesives with solvent are particularly suitable for multi-layer films which are capable of resisting sterilization treatments.

[0015] This cohesion must be ensured in part from the laminating stage, at a sufficient level so that the bilayer (or duplex) film made up of the 2 supports is sufficiently strong to withstand the mechanical stresses, in particular shear stresses, applied by the laminating machine. These stresses result in particular from the very high running speed of the bilayer film and the multiple cylinders (or rollers) with which it is in contact, in particular for its guidance and the regulation of its tension. The resistance of such a duplex film to said stresses is particularly critical when said film is used in the laminating machine as an intermediate product for the manufacture of a triplex film, by coating a new layer of glue on one of the faces of said duplex, then counter-gluing a 3rd film of material on said face.Similarly, the resistance of a triplex film to these mechanical stresses is also critical when said film is implemented in the laminating machine as an intermediate product for the manufacture of a quadruplex film.

[0016] The ability of two-component solvent-based PU adhesives to ensure, from the coating and laminating stage for the production of a duplex, triplex or quadruplex film, this initial cohesion is referred to in the trade as "initial tack" or "initial adhesive".

[0017] The time required to fully complete the crosslinking reaction, and thus ensure the level of cohesion required for the use of the complex film in the manufacture of flexible packaging, is called "crosslinking time". It is very long, generally of the order of 3 to 7 days, and is obtained, in practice, by storing the reels of complex film either at room temperature or at a higher temperature, which leads to disadvantages for the organization of the industrial production of complexers, linked to the need for suitable storage spaces.

[0018] Complex films manufactured by such a process using two-component polyurethane laminating adhesives with solvent are generally well suited for the manufacture of sterilization-resistant flexible packaging due to their good level of cohesion.

[0019] Such laminating adhesives are known, in particular from application EP 1283232 from MITSUI CHEMICALS, as well as EP-A1-1985679 describing laminating adhesives for high temperature sterilization treatment.

[0020] The chemical entities present in the -OH component are generally polymeric or non-polymeric chemical compounds, sometimes of natural origin (such as castor oil), and which generally include polymers of the polyether polyol and / or polyester polyol type, with a molar mass often between 400 and 4000 g / mol.

[0021] The chemical entities present in the -NCO component are most often polymeric chemical compounds that are called prepolymers, since they are precursors to the final crosslinked polyurethane constituting the adhesive sealant. These prepolymers with -NCO end groups are generally themselves polyurethanes produced by the polyaddition reaction of a molar excess of a diisocyanate monomer, generally aromatic such as diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), with polyether polyols and / or polyester polyols.

[0022] However, for reasons related to the specificity of this polyaddition reaction and the presence of the molar excess of diisocyanate, a certain quantity of unreacted diisocyanate monomer remains in the -NCO component thus obtained. These residual quantities of low molecular weight (so-called free) aromatic diisocyanate monomers are likely to migrate through the multilayer film, after the implementation of the two-component adhesive, and therefore through the final flexible packaging. Thus, said compounds are likely to form, by hydrolysis, upon contact with water or humidity present in particular in packaged foods, primary aromatic amines (often referred to by the English terms Primary Aromatic Amines or PAA), which are considered to be very harmful to human health and the environment.

[0023] The aim of the present invention is to provide a two-component polyurethane with solvent, which can be used in a multilayer film without the risk of subsequent formation of aromatic primary amines.

[0024] Another aim of the invention is to propose a two-component polyurethane with solvent which offers complexing manufacturers, during the manufacture of said film, a suitable initial tack (or adhesive).

[0025] Another aim of the invention is to propose a two-component polyurethane with solvent which offers complexing manufacturers, during the manufacture of said film, a suitable crosslinking time at room temperature, preferably less than or equal to 5 days, even more preferably less than or equal to 2 days.

[0026] Another aim of the invention is to propose a two-component polyurethane laminating adhesive with solvent which leads, after lamination, and in particular after lamination of metallic or metallized supports, to the production of a complex film which has the required cohesion properties.

[0027] Another aim of the invention is to propose a two-component solvent-based polyurethane leading to multi-layer films, in particular films comprising a metallic or metallized support, the cohesion of which is maintained after the sterilization treatments applied to the packaging by food industry manufacturers.

[0028] It has now been found that these objects can be achieved in whole or in part by the adhesive composition described below.

[0029] The present invention therefore relates to a two-component solvent-based adhesive composition of polyurethane type, comprising an -OH component and an -NCO component such as: the -OH component is a composition (A) comprising an amorphous prepolymer which includes 2 -OH end groups, the number-average molar mass Mn of which ranges from 8000 to 12000 g (corresponding to an IOH ranging from 9.4 to 14 mg KOH / g) and which is chosen from: a copolyester (A1) obtained by a polycondensation reaction: of at least one aliphatic diol (i); with at least one aromatic diacid (ii) chosen from terephthalic acid, isophthalic acid, phthalic acid and one of their diester or anhydride derivatives; and at least one aliphatic diacid (iii) or one of its diester or anhydride derivatives; and a polyurethane (A2) obtained by a polyaddition reaction between an aliphatic diisocyanate compound (A2.P1) and an amorphous diol copolyester (A2.P2) whose number-average molecular weight Mn ranges from 4000 to 11500 g / mol, said copolyester being obtained by the polycondensation reaction as defined above for (A1); and the -NCO component is a composition (B) comprising a compound (B1) which includes 3 -NCO end groups, and which is obtained by the reaction of meta-xylylene diisocyanate (m-XDI) with a triol, said compound (B1) being: either the only compound included in (B) including 3 -NCO end groups; or in a mixture with another compound (B2) including 3 -NCO end groups, (B2) being an isocyanurate (B2-1) of an aliphatic diisocyanate and the content of (B1) in said mixture being at least 40% by weight, based on the total weight of said mixture.

[0030] The solvent-based two-component adhesive composition as defined above advantageously makes it possible to obtain, after a crosslinking time at room temperature of less than or equal to 2 days, a complex film which is free from any risk of subsequent formation of PAAs harmful to human health. Indeed, the diisocyanate monomers used where appropriate in the preparation of the -NCO and -OH components which constitute it are aliphatic monomers.

[0031] Said adhesive composition also advantageously allows the production of duplex film which has an initial tack greater than 2 N / 15 mm, allowing the online production of a triplex or quadruplex film, without intermediate storage of the duplex or triplex films respectively.

[0032] Finally, the complex films obtained by means of said adhesive composition have excellent cohesion properties, in particular when one of the supports of said film is a metallized support, such as for example an aluminum film. These cohesion properties are also excellent after heat treatment for sterilization.

[0033] Obtaining these properties for the complex film is accompanied by easy implementation of the corresponding two-component adhesive composition, whether it is an easy introduction, by means of a pump, into the complexing machine of the components - NCO and -OH due to their viscosity properties, or whether it is still the implementation, in the complexing machine itself, of the composition resulting from the mixing of said components, again due to an appropriate viscosity profile, for said composition. Composition (A) (component -OH) :

[0034] Composition (A) comprises an amorphous prepolymer including 2 -OH terminal groups (also called diol), which may be linear or branched, and is selected from copolyester (A1) and polyurethane (A2). Amorphous copolyester diol (A1) :

[0035] According to one embodiment, the amorphous prepolymer included in the composition (A) is the amorphous copolyester diol (A1).

[0036] The amorphous copolyester diol (A1) can be linear or branched and has a number-average molar mass (also called Mn) ranging from 8000 to 12000 g / mol, which corresponds to an IOH ranging from 9.4 to 14 mg KOH / g.

[0037] The number-average molar mass Mn is measured by size exclusion chromatography (SEC), which is also referred to as gel permeation chromatography (GPC). The calibration used is usually a PEG (PolyEthyleneGlycol) or PS (PolyStyrene) calibration, preferably PS.

[0038] The hydroxyl number (denoted IOH) of the amorphous linear copolyester diol (A1), and more generally of a polyol, (denoted IOH) represents the number of hydroxyl functions per gram of polyol and is expressed in the form of the equivalent number of milligrams of potash (KOH) used in the determination of the hydroxyl functions, determined by titrimetry. according to the ISO 14900:2017 standard. The IOH is related to the number-average molar mass Mn by the relationship: IOH = 56 , 1 × 2 × 1000 / Mn

[0039] The amorphous copolyester diol (A1) is obtained by a polycondensation reaction: of at least one aliphatic diol (i), with at least one aromatic diacid (ii) chosen from terephthalic acid, isophthalic acid, phthalic acid and one of their diester or anhydride derivatives; and at least one aliphatic diacid (iii) or one of its diester or anhydride derivatives.

[0040] The aliphatic diol (i) may be linear or branched and is selected from the group consisting of ethylene glycol (CAS: 107-21-1), diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, 1,6-hexanediol, 3-ethyl-2-methyl-1,5-pentanediol, 2-ethyl-3-propyl-1,5-pentanediol, 2,4-dimethyl-3-ethyl-1,5-pentanediol, 2-ethyl-4-methyl-3-propyl-1,5-pentadiol, 2,3-diethyl-4-methyl-1,5-pentanediol, 3-ethyl-2,2,4-trimethyl-1,5-pentadiol, 2,2-dimethyl-4-ethyl-3-propyl-1,5-pentanediol, 2-methyl-2-propyl-1,5-pentanediol, 2,4-dimethyl-3-ethyl-2-propyl-1,5-pentanediol, 2,3-dipropyl-4-ethyl-2-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,5-pentanediol, 2-butyl-2,3-diethyl-4-methyl-1,5-pentanediol, 2-butyl-2,4-diethyl-3-propyl-1,5-pentanediol, 3-butyl-2-propyl-1,5-pentanediol, 2-methyl-1,5-pentanediol (CAS: 42856-62-2), 3-methyl-1,5-pentanediol (MPD,CAS: 4457-71-0), 2,2-dimethyl-1,3-pentanediol (CAS: 2157-31-5), 2,2-dimethyl-1,5-pentanediol (CAS: 3121-82-2), 3,3-dimethyl-1,5-pentanediol (CAS: 53120-74-4), 2,3-dimethyl-1,5-pentanediol (CAS: 81554-20-3), 2,2-dimethyl-1,3-propanediol (Neopentylglycol - NPG, CAS: 126-30-7), 2,2-diethyl-1,3-propanediol (CAS: 115-76-4), 2-methyl-2-propyl-1,3-propanediol (CAS: 78-26-2), 2-butyl-2-ethyl-1,3-propanediol (CAS: 115-84-4), 2-methyl-1,3-propanediol (CAS: 2163-42-0), 2-benzyloxy-1,3-propanediol (CAS: 14690-00-7), 2,2-dibenzyl-1,3-propanediol (CAS: 31952-16-6), 2,2-dibutyl-1,3-propanediol (CAS: 24765-57-9), 2,2-diisobutyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,6-hexanediol (CAS: 15208-19-2), 2,5-dimethyl-1,6-hexanediol (CAS: 49623-11-2), 5-methyl-2-(1-methylethyl)-1,3-hexanediol (CAS: 80220-07-1), 1,4-dimethyl-1,4-butanediol, 1,5-hexanediol (CAS: 928-40-5), 3-methyl-1,6-hexanediol (CAS: 4089-71-8),3-tert-butyl-1,6-hexanediol (CAS: 82111-97-5), 1,3-heptanediol (CAS: 23433-04-7), 1,2-octanediol (CAS: 1117-86-8), 1,3-octanediol (CAS: 23433-05-8), 2,2,7,7-tetramethyl-1,8-octanediol (CAS: 27143-31-3), 2-methyl-1,8-octanediol (CAS: 109359-36-6), 2,6-dimethyl-1,8-octanediol (CAS: 75656-41-6), 1,7-octanediol (CAS: 3207-95-2), 4,4,5,5-tetramethyl-3,6-dioxa-1,8-octanediol (CAS: 76779-60-7), 2,2,8,8-tetramethyl-1,9-Nonanediol (CAS: 85018-58-2), 1,2-nonanediol (CAS: 42789-13-9), 2,8-dimethyl-1,9-nonanediol (CAS: 40326-00-9), 1,5-nonanediol (CAS: 13686-96-9), 2,9-dimethyl-2,9-dipropyl-1,10-decanediol (CAS: 85018-64-0), 2,9-dibutyl-2,9-dimethyl-1,10-decanediol (CAS: 85018-65-1), 2,9-dimethyl-2,9-dipropyl-1,10-decanediol (CAS: 85018-64-0), 2,9-diethyl-2,9-dimethyl-1,10-decanediol (CAS: 85018-63-9), 2,2,9,9-tetramethyl-1,10-decanediol (CAS: 35449-36-6), 2-nonyl-1,10-decanediol (CAS: 48074-20-0), 1,9-decanediol (CAS: 128705-94-2), 2,2,6,6,10,10-hexamethyl-4,8-dioxa-1,11-undecanediol (CAS: 112548-49-9), 1-phenyl-1,11-undecanediol (CAS: 109217-58-5), 2-octyl-1,11-undecanediol (CAS: 48074-21-1), 2,10-diethyl-2,10-dimethyl-1,11-undecanediol (CAS: 85018-66-2), 2,2,10,10-tetramethyl-1,11-undecanediol (CAS: 35449-37-7), 1-phenyl-1,11-undecanediol (CAS: 109217-58-5), 1,2-undecanediol (CAS: 13006-29-6), 1,2-dodecanediol (CAS: 1119-87-5), 2,11-dodecanediol (CAS: 33666-71-6), 2,11-diethyl-2,11-dimethyl-1,12-dodecanediol (CAS: 85018-68-4), 2,11-dimethyl-2,11-dipropyl-1,12-dodecanediol (CAS: 85018-69-5), 2,11-dibutyl-2,11-dimethyl-1,12-dodecanediol (CAS: 85018-70-8), 2,2,11,11-tetramethyl-1,12-dodecanediol (CAS: 5658-47-9), 1,11-dodecanediol (CAS: 80158-99-2), 11-methyl-1,7-dodecanediol (CAS: 62870-49-9), 1,4-dodecanediol (CAS: 38146-95-1), 1,3-dodecanediol (CAS: 39516-24-0), 1,10-dodecanediol (CAS: 39516-27-3), 2,11-dimethyl-2,11-dodecanediol (CAS: 22092-59-7), 1,5-dodecanediol (CAS: 20999-41-1), 6,7-dodecanediol (CAS: 91635-53-9), and cyclohexanedimethanol.

[0041] Preferably, the diol (i) is chosen from ethylene glycol, diethylene glycol, trimethylene glycol, hexamethylene glycol, propylene glycol (or propane-1,2-diol), propane-1,3-diol, butanediol (-1,4, -1,3 or -1,2), neopentyl glycol, 2-methyl-1,3-propane diol, hexane diol or cyclohexanedimethanol.

[0042] According to a preferred variant, the diol (i) is chosen from ethylene glycol and diethylene glycol.

[0043] Even more preferably, 2 diols (i) are used, consisting, respectively, of ethylene glycol and diethylene glycol.

[0044] Among the diester derivatives of terephthalic acid, isophthalic acid or phthalic acid which can be used as monomers (ii), mention may be made, for example, of dimethyl terephthalate or dimethyl isophthalate. As an example of an anhydride derivative of an aromatic diacid for monomer (ii), mention may be made of phthalic anhydride.

[0045] Preferably, 2 diacids (ii) are used, consisting, respectively, of terephthalic acid and isophthalic acid.

[0046] The aliphatic diacid (iii) may be linear or branched and is for example chosen from adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, dodecanedicarboxylic acid, 1,10-decanedicarboxylic acid and succinic acid.

[0047] Preferably, adipic acid is used as the aliphatic diacid (iii).

[0048] A person skilled in the art can determine the nature of the comonomers (i), (ii) and (iii) and their relative quantity so as to obtain a copolyester diol (A1) whose number-average molecular mass Mn is in the range indicated above and which is also amorphous, that is to say whose analysis by differential scanning calorimetry (DSC) shows that it does not have a melting point.

[0049] According to a preferred embodiment, the number-average molecular mass Mn of the copolyester diol (A1) is within a range from 8980 to 11810 g / mol, corresponding to an IOH ranging from 9.5 to 12.5 mg KOH / g.

[0050] According to a preferred embodiment, the copolyester diol (A1) is obtained by polycondensation: of 2 aliphatic diols (i) consisting, respectively, of ethylene glycol and diethylene glycol; with 2 diacids (ii) consisting, respectively, of terephthalic acid and isophthalic acid; and adipic acid as aliphatic diacid (iii).

[0051] When some of the monomers (ii) and optionally (iii) are diester derivatives, such as for example methyl or ethyl diester derivatives, said monomers are, in a 1st step, mixed with one or more diol monomers (i), said mixture being brought to a temperature of up to 190°C, so as to carry out, preferably in the presence of a titanium or zinc-based catalyst, a transesterification reaction and remove the methanol or ethanol formed. In a 2nd step, the monomers (ii) and optionally (iii) which are diacids are added, mixed with one or more diol monomers (i), the reaction medium being brought to a temperature of up to 230°C, so as to carry out the esterification reaction and remove the water formed.Finally, in a 3rd step, the pressure is lowered to a value lower than approximately 5 mbar, and the reaction medium is brought to a higher temperature, up to a value close to 250°C, in order to increase the length of the copolyester chains to reach an IOH within the range indicated previously. Amorphous polyurethane diol (A2):

[0052] According to one embodiment, the amorphous prepolymer included in the composition (A) is the amorphous polyurethane diol (A2).

[0053] The amorphous polyurethane diol (A2) can be linear or branched and has a number-average molecular weight Mn ranging from 8000 to 12000 g / mol. It is obtained by a polyaddition reaction between an aliphatic diisocyanate compound (A2.P1) and a stoichiometric excess of an amorphous copolyester diol (A2.P2), linear or branched, whose number-average molecular weight Mn ranges from 4000 to 11500 g / mol and which is obtained by the polycondensation reaction as defined above for (A1).

[0054] The aliphatic diisocyanate compound (A2.P1) is advantageously chosen from isophorone diisocyanate (IPDI), meta-xylylene diisocyanate (m-XDI), hydrogenated meta-xylylene diisocyanate (m-H6XDI), pentamethylene diisocyanate (PDI) and hexamethylene diisocyanate (HDI). These different diisocyanates are widely available commercially. Meta-xylylene diisocyanate (m-XDI) is for example available under the name TAKENATE ®< 500 from MITSUI CHEMICALS. Hydrogenated meta-xylylene diisocyanate (m-H6XDI) also called bis(isocyanatomethyl) cyclohexane is for example available under the name TAKENATE ®< 600 from MITSUI CHEMICALS.

[0055] According to a preferred variant, the aliphatic diisocyanate compound (A2.P1) is isophorone diisocyanate (IPDI).

[0056] In this text, an aliphatic diisocyanate compound is understood to mean a hydrocarbon compound of low molar mass (less than 300 g / mol) having two isocyanate groups, which compound is either non-aromatic or such that none of the NCO groups is linked by a covalent bond to a carbon atom forming part of an aromatic hydrocarbon ring such as a phenyl group. For the purposes of this definition, m-XDI, of formula: is thus an aliphatic diisocyanate.

[0057] In this text, the term aromatic diisocyanate compound is therefore understood to mean a hydrocarbon compound of low molar mass (less than 300 g / mol) having two isocyanate groups, which compound is aromatic and such that all the NCO groups are linked by a covalent bond to a carbon atom forming part of the aromatic hydrocarbon cycle.

[0058] The amounts of aliphatic diisocyanate compound (A2.P1) and linear copolyester diol (A2.P2) used in the polyaddition reaction are such that the molar equivalent ratio -NCO / -OH is less than or equal to 0.5, preferably less than or equal to 0.4, preferably less than or equal to 0.3, preferably less than or equal to 0.2, preferably less than or equal to 0.1. The molar equivalent ratio -NCO / -OH is understood to mean the ratio of the equivalent number of -NCO groups present in the aliphatic diisocyanate compound (A2.P1) to the equivalent number of -OH groups present in the amorphous copolyester diol (A2.P2).

[0059] The polyaddition reaction generally takes place at a temperature between 70 and 85°C for a period of several hours, possibly in the presence of a catalyst.

[0060] The amorphous, linear or branched polyurethane diol obtained at the end of this reaction has a number-average molecular mass Mn in a range from 8000 to 12000 g / mol, preferably from 8980 to 11810 g / mol. Composition (B) (component -NCO) :

[0061] The composition (B) includes a compound (B1) including 3 terminal groups - NCO, which is obtained by the reaction of meta-xylylene diisocyanate (m-XDI) with a triol, said compound (B1) being: or the only compound included in (B) including 3 terminal groups -NCO; or in mixture with another compound (B2) including 3 end groups - NCO, (B2) being an isocyanurate (B2-1) of an aliphatic diisocyanate and the content of (B1) in said mixture being at least 40% by weight, based on the total weight of said mixture.

[0062] Preferably, said compound (B2) is other than the product of the reaction of m-XDI with a triol.

[0063] According to a first embodiment, the composition (B) comprises the compound (B1) as the only trifunctional compound.

[0064] Said compound (B1), also referred to as an adduct of m-XDI and triol, is obtained by an addition reaction using said compounds. The methods of such an addition reaction are for example described in patent application EP3101044 from MITSUI CHEMICALS.

[0065] The triol used is preferably a trimethylolalkane comprising an alkane comprising from 1 to 20 carbon atoms and 3 methylol groups such as, for example, trimethylolmethane, trimethylolethane, trimethylolpropane, tri-methyloln-butane, trimethylolisobutane, trimethylols-butane, trimethylolt-butane, trimethylolpentane, trimethylolhexane, trimethylolheptane, trimethyloloctane, trimethylolnonane, trimethyloldecane, trimethylolundecane, and trimethyloldo-decane.

[0066] More preferably, among the triols that can be used to obtain the adduct of m-XDI and triol, mention may be made of Glycerol of formula HOH 2 C-CHOH-CH 2 OH, Trimethylolmethane (TMM) of formula HC(CH 2 -OH) 3 , Trimethylolethane (TME) of formula H 3 CC(CH 2 -OH) 3 and Trimethylolpropane (TMP) of formula CH 3 -CH 2 -C(CH 2 -OH) 3 .

[0067] According to a particularly preferred embodiment, compound (B1) is the adduct of m-XDI and TMP, of formula:

[0068] Adducts of m-XDI and triol are also commercially available.

[0069] For example, the adduct of m-XDI and TMP is available, in solution in 75% ethyl acetate, from MITSUI CHEMICALS under the name TAKENATE ®< D-1 10N. The adduct of m-H6XDI and TMP is also available, in solution in 75% ethyl acetate, from MITSUI CHEMICALS under the name TAKENATE ®< D-120N.

[0070] According to a 2nd embodiment, the composition (B) comprises a mixture of compound (B1) and another compound (B2) including 3 -NCO end groups, which is an isocyanurate (B2-1) of an aliphatic diisocyanate.

[0071] According to a preferred variant, said aliphatic diisocyanate is chosen from isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), meta-xylylene diisocyanate (m-XDI), hydrogenated meta-xylylene diisocyanate (m-H6XDI).

[0072] Isocyanurate (B2-1) may also be referred to as the cyclic trimer of said aliphatic diisocyanate. It is thus advantageously chosen from the compounds in the following list: IPDI isocyanurate, of formula: HDI isocyanurate, of formula: PDI isocyanurate, of formula: m-XDI isocyanurate, of formula: m-H6XDI isocyanurate of formula:

[0073] These isocyanurates are generally obtained by a trimerization reaction of the corresponding diisocyanates, as described for example in patent applications EP 0047452 or US 8097691 from BAYER.

[0074] Some isocyanurates are also available industrially, such as IPDI isocyanurate (or IPDI cyclic trimer) from the company EVONIK, under the name VESTANAT ®< T1890 / 100, which is a solvent-free product.

[0075] These adducts are generally obtained by an addition reaction of the corresponding diisocyanates to triols according to the procedure described in patent application EP3101044 from MITSUI CHEMICALS.

[0076] According to a more preferred variant, the aliphatic diisocyanate from which compound (B2) is derived is isophorone diisocyanate (IPDI).

[0077] According to an even more preferred variant of this 2nd embodiment, composition (B) comprises a mixture of: the adduct (B1) of m-XDI and Trimethylolpropane (TMP); and IPDI isocyanurate as compound (B2).

[0078] When, in accordance with the 2nd embodiment of the invention, the composition (B) comprises a mixture of compound (B1) and another compound (B2) comprising 3 -NCO end groups, the content of (B1) in the mixture (B1) + (B2) is at least 40% weight / weight. Said content is expressed as the weight of (B1) based on the total weight of said mixture and is hereinafter referred to as: weight ratio (B1) / [(B1) + (B2)].

[0079] The weight ratio (B1) / [(B1) + (B2)] is preferably at least 50% weight / weight and even more preferably 60% weight / weight, a minimum limit of 65% weight / weight being particularly advantageous.

[0080] According to a particularly preferred variant, the weight ratio (B1) / [(B1) + (B2)] is within a range from 40% to 80% weight / weight, preferably from 50 to 80%, and even more preferably from 60 to 80%. The resistance to sterilization of a PET / ALU / OPA / cPP quadruplex is then particularly improved. Two-component adhesive composition :

[0081] Said adhesive composition preferably comprises an adhesion promoter selected from an aminosilane or a ureidosilane, preferably an aminosilane which may be included in the -NCO component or in the -OH component, preferably in the -OH component.

[0082] The said promoter is for example advantageously chosen from those listed in the table below which are available from MOMENTIVE: Trade name Chemical name CAS No. Silquest ®< A-1100 Aminopropyltriethoxysilane 919-30-2 Silquest ®< A-1110 Aminopropyltrimethoxysilane 13822-56-5 Silquest ®< A-1170 Bis(3-trimethoxysilyl)propylamine 82985-35-1 Silquest ®< A-1120 Aminoethylaminopropyltrimethoxysilane 1760-24-6 Silquest ®< A-1130 Diethtylenetriaminopropyltrimethoxysilane 35141-30-1 Silquest ®< A-1524 gammma-ureidopropyltrimethoxysilane 35141-30-1

[0083] An aminosilane is preferred as the adhesion promoter.

[0084] The content of said adhesion promoter may vary from 0.5 to 5% by weight, based on the total weight of composition (A) or (B).

[0085] According to a more preferred variant, the adhesion promoter is aminopropyltrimethoxysilane.

[0086] Composition (A) (component -OH) comprises the amorphous, linear or branched prepolymer, selected from (A1) and (A2) in solution in an organic solvent.

[0087] The latter can be an ester such as ethyl acetate and butyl acetate, a ketone such as methyl ethyl ketone and methyl isobutyl ketone, and an aromatic compound such as toluene and xylene.

[0088] The quantity of solvent is adjusted by dilution so as to obtain a specialty intended for complexers which is as concentrated as possible; a quantity of dry extract between 55 and 65% weight / weight being generally encountered in practice.

[0089] Composition (B) (component -NCO) comprises compound (B1) and optionally (B2) also in solution in an organic solvent whose nature and quantity are as defined for composition (A).

[0090] Compositions (A) and (B) are prepared by simply mixing their ingredients at room temperature, if necessary with stirring.

[0091] The viscosity measured at 23°C of each of the 2 components -NCO and -OH is advantageously less than or equal to 10 Pa.s, preferably 5 Pa.s. Said viscosity is also measured using a Brookfield viscometer according to standard ISO 2555, published in 1999. Each of the 2 components, which are in practice stored separately in tanks of appropriate capacity (for example 200 l drums), can thus be conveniently introduced by means of a pump into the complexing machine.

[0092] The quantities of the -NCO and -OH components of the two-component adhesive composition according to the invention are such that the -NCO / -OH molar equivalent ratio is within a range from 3 to 5, preferably from 3.5 to 4.5. The term -NCO / -OH molar equivalent ratio is understood to mean the ratio of the equivalent number of -NCO groups (present in the -NCO component) to the equivalent number of -OH groups (present in the -OH component).

[0093] The mixing of the -NCO and -OH components, in the indicated ratio, is carried out at room temperature by the operator of the laminating machine, prior to its start-up. The viscosity of the adhesive composition thus obtained can be adjusted by simply adding solvent, resulting in a final quantity of dry extract of the adhesive composition which can vary in practice from 30 to 40% weight / weight. The adhesive composition thus obtained is entirely suitable for its use in a laminating machine and for its correct operation.

[0094] The two-component adhesive composition according to the invention may further comprise additives which may be included in the -NCO component and / or in the -OH component, such as rheological additives, catalysts or even plasticizers. The total content of these optional additives, in each of the -NCO and / or -OH components, may be up to 2% by weight, based on the total weight of the component in question.

[0095] Thus, and according to a preferred variant, the two-component adhesive composition according to the invention is such that composition (A) consists of an organic solution: of the amorphous prepolymer selected from (A1) and (A2), and optionally of an adhesion promoter present in an amount of 0.5 to 5% by weight, based on the total weight of the composition (A), and optionally of optional additives present in an amount of up to 2% by weight, based on the total weight of the composition (A).

[0096] According to another preferred variant, the two-component adhesive composition according to the invention is such that composition (B) consists of an organic solution: of compound (B1) alone or in admixture with compound (B2), and optionally of an adhesion promoter present in an amount of 0.5 to 5% by weight, based on the total weight of composition (B), and optionally of optional additives present in an amount of up to 2% by weight, based on the total weight of composition (B).

[0097] According to a more preferred variant, the optional additives present in composition (A) and / or composition (B) are chosen from rheological additives, catalysts or even plasticizers. Multi-layer film :

[0098] The invention also relates to a multilayer (or complex) film comprising 2 thin layers of material bonded together by a continuous layer, characterized in that said layer is constituted by the two-component adhesive composition according to the invention in the crosslinked state, in an amount of less than 7 g / m 2 <.

[0099] According to a variant of the invention, said quantity is within a range from 0.5 to 5 g / m 2< , and preferably from 1 to 4 g / m 2< .

[0100] The materials from which the thin layers surrounding the adhesive layer are made are generally chosen from paper, a metal, such as aluminum, or thermoplastic polymers such as: polyethylene (PE), polypropylene (PP), and in particular cast polypropylene (abbreviated as cPP), a copolymer based on ethylene and propylene, polyamide (PA), and in particular biaxially oriented polyamide (or OPA or boPA), polyethylene terephthalate (PET), or an ethylene-based copolymer such as, for example, a maleic anhydride graft copolymer, a copolymer of ethylene and vinyl acetate (EVA), a copolymer of ethylene and vinyl alcohol (EVOH), a copolymer of ethylene and an alkyl acrylate such as methyl acrylate (EMA) or butyl acrylate (EBA), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), a polymer or copolymer of lactic acid (PLA), or a polyhydroxyalkanoate (PHA).

[0101] The materials preferably chosen to constitute the thin layers surrounding the adhesive layer are aluminum, PE, PP, PET and PA.

[0102] We can also cite a thin layer made of a thermoplastic polymer, preferably PE, PP or PET, covered with a layer of less than 1 µm of aluminum, alumina or silica SiOx. A thin layer coated with such a layer is, for example, denoted PET SiOx.

[0103] The thickness of the 2 thin layers adjacent to the adhesive layer and of the other layers used in the multilayer film according to the invention is likely to vary within a wide range from 5 to 150 µm, preferably from 7 to 80 µm. The total thickness of said film is also likely to vary within a wide range from 20 to 400 µm.

[0104] According to a preferred variant, the film comprises 2 to 4 thin layers of materials, said film then being called, respectively, duplex, triplex or quatruplex.

[0105] According to one embodiment, said film is chosen from: a duplex film: boPA / cPP; a triplex film: PET / ALU / cPP or PET SiOx / boPA / cPP; or a quadruplex film: PET / ALU / boPA / cPP.

[0106] In the case of a triplex, quadruplex or more generally a multiplex film comprising several thin layers of material (or individual films), each pair of adjacent thin layers of material is bonded by a layer of adhesive composition.

[0107] The invention also relates to a process for the continuous preparation of the multilayer film as defined above, comprising the sequential steps of: (i) combining the -NCO and -OH components, and, if necessary, diluting with a solvent, to form an adhesive mixture; (ii) coating with said adhesive mixture a first thin layer of material in the form of a substantially continuous layer; (iii) evaporating the organic solvent; (iv) laminating a second thin layer onto the first thin layer coated in accordance with step (ii), and then (v) crosslinking the adhesive mixture.

[0108] When the multilayer film is an A / B / C triplex film: in a 1st step, the duplex A / B is prepared in accordance with said method, then steps (i), (ii), (iii) and (iv) are repeated using said duplex A / B as the 1st thin layer of material, and film C as the 2nd thin layer.

[0109] Such an A / B / C triplex film can be obtained, according to a first variant, by recovering the reel of A / B duplex film obtained at the end of the 1st step, and using it to feed the laminating machine in combination with the reel of film C. According to a second variant, the coating of layer A, the lamination of layer B, then the coating of the A / B duplex and the lamination of layer C are carried out directly in line, by a laminating machine adapted to such in-line triplexing.

[0110] The invention finally relates to the use of the multilayer film according to the invention for the manufacture of flexible packaging. The complex films according to the invention can in fact be used for the manufacture of the most diverse flexible packaging, which is shaped and then closed (after the step of packaging the product intended for the consumer) by heat-sealing techniques (or heat-welding).

[0111] According to a preferred variant, the multilayer films according to the invention are used for the manufacture of flexible packaging intended for sterilization treatments, such as the sterilization of food products packaged in said flexible packaging.

[0112] The invention is now described in the following exemplary embodiments which are given purely for illustrative purposes and should not be interpreted to limit its scope. Example 1 (reference): Component -OH - Preparation of a composition (A) comprising an amorphous copolyester diol (A1) and aminopropyltrimethoxysilane:

[0113] First, a linear amorphous copolyester diol (A1) is prepared according to the procedure indicated below.

[0114] In a closed 1 liter reactor, equipped with stirring, a distillation column, heating means, a thermometer and connected to a vacuum pump, 35.120 g of monoethylene glycol and 154.435 g of diethylene glycol are introduced.

[0115] When the temperature of the reaction mixture reaches 120°C, the following are introduced into the reactor: 76.190 g of adipic acid, 170.035 g of isophthalic acid, 64.165 g of terephthalic acid and 0.035 g of a titanium chelate catalyst (TYZOR ®< LA from DuPont).

[0116] Then a temperature ramp is programmed to reach a temperature of 230°C in 3 hours. The acid number (I a ) is then measured. The reaction is stopped when the acid number I a is less than 25 mg KOH / g.

[0117] 0.020 g of a titanium-based catalyst (of formula (nBuO) 4 Ti, TYZOR ®< TnBT from DuPont) is then introduced, then the reactor is placed under vacuum (reaching 15 mbar in 2 hours) and the reaction mixture is heated to 240°C.

[0118] I a and Brookfield viscosity measurements are carried out at 180°C. The reaction is stopped when I a is less than 3 mg KOH / g and when the viscosity is between 8000 and 9000 mPa.s.

[0119] The copolyester diol obtained is then cooled to 200°C and then slowly poured into ethyl acetate at room temperature with stirring, to form a 59.47% weight / weight solution.

[0120] The IOH of the copolyester diol thus obtained was measured according to ISO 14900:2017 and is equal to 10 mg KOH / g, corresponding to an Mn of 11220 g / mol.

[0121] Silquest ®< A1110 is added to the said solution, as an adhesion promoter, after cooling to 45°C and at a content of 0.89% weight / weight.

[0122] The weight content of -OH functions in the -OH component is 0.18% weight / weight.

[0123] The Brookfield viscosity at 23°C of the -OH component is 5 Pa.s. Example 2 (reference): Component -NCO- Preparation of a solution (B) in ethyl acetate of the adduct (B1) of m-XDI and Trimethylolpropane (TMP):

[0124] For the adduct (B1) of m-XDI and TMP, the product TAKENATE ®< D-110N marketed by the company MITSUI CHEMICALS is used, which is a solution of said adduct at 75% weight / weight in ethyl acetate and whose content of -NCO function, expressed in % weight / weight, is 11.5%.

[0125] The said product TAKENATE ®< D-110N is simply introduced at room temperature into a glass reactor kept under stirring and nitrogen; the content of ingredient (B1) in the solution (B) is indicated in table 1, expressed in % weight / weight.

[0126] The Brookfield viscosity at 23°C is measured and the obtained value is shown in Table 1.

[0127] The weight content in % w / w as a function of -NCO is also shown in Table 1. Example 3 (reference): Component -NCO - Preparation of a solution (B) in ethyl acetate of the adduct (B1) of m-XDI and TMP, and of IPDI isocyanurate (B2):

[0128] For IPDI isocyanurate, the product VESTANAT ®< T1890 / 100 marketed by the company EVONIK is used, which is solvent-free and whose content expressed in % weight / weight in -NCO function is 17.3%.

[0129] The adduct (B1) of m-XDI and TMP is always TAKENATE ®< D-110N.

[0130] In a glass reactor maintained under constant stirring and nitrogen, IPDI isocyanurate (B2) is dissolved in ethyl acetate previously heated to 50°C. After its complete dissolution, the adduct (B1) of m-XDI and TMP is introduced into the mixture at the same temperature.

[0131] The mixture is maintained at 70°C and homogenized for 30 minutes.

[0132] A solution is obtained whose ingredient contents are indicated in Table 1.

[0133] The Brookfield viscosity at 23°C is measured and the obtained value is shown in Table 1.

[0134] The weight content in % weight / weight as a function of -NCO is measured according to standard NF T52-132 and reported in table 1.

[0135] The weight ratio (B1) / [(B1) + (B2)] is also shown in Table 1. Example 4 to 5 (reference) and 6 (comparative): Component -NCO- Preparation of solutions (B) in ethyl acetate of the adduct (B1) of m-XDI and TMP, and of IPDI isocyanurate (B2):

[0136] Example 3 is repeated for different contents of (B1) and (B2).

[0137] The Brookfield viscosity at 23°C, the weight ratio (B1) / [(B1) + (B2)] and the weight content in % w / w as a function of -NCO are also reported in Table 1. Example 1 / 2 (according to the invention): Two-component adhesive composition obtained by mixing the -OH component of example 1 and the -NCO component of example 2:

[0138] The -OH component of Example 1 is mixed with the -NCO component of Example 2 at a molar equivalent ratio of -NCO / -OH equal to 4.13, which corresponds to a weight ratio: -NCO component / -OH component equal to 100 g of -OH component for 16 g of -NCO component.

[0139] Mixing is carried out at room temperature in the feed bin of the laminating machine, via a mixing unit and a static mixer.

[0140] The constituent data of the two-component adhesive composition are reported in Table 2. Examples 1 / 3, 1 / 4 and 1 / 5 (according to the invention) and 1 / 6 (comparative): Two-component adhesive compositions

[0141] The preceding example 1 / 2 is repeated by replacing the -NCO component of example 2 with the -NCO component of examples 3, 4, 5 and 6, respectively.

[0142] The values ​​of the molar equivalent ratio -NCO / -OH, of the weight ratio: -NCO component / -OH component are also reported in Table 2. Example 7 (according to the invention) : Duplex movie boPA / cPP

[0143] A duplex film consisting of a boPA film and a cPP film bonded by a layer of adhesive composition is prepared.

[0144] A 15 µm thick biaxially oriented polyamide film and a 60 µm thick cast polypropylene film are used.

[0145] This duplex film is obtained by feeding the tank of a Nordmeccanica type laminating machine with the two-component adhesive composition, for each of the examples 1 / 2 to 1 / 6.

[0146] Said laminating machine is provided with a roller-type coating device with an open tank, operating at room temperature and at a running speed of 50 m / minute; the adhesive layer binding the boPA and cPP films has a thickness of approximately 3.5 µm corresponding to approximately 3.5 g / m 2< of adhesive composition.

[0147] This duplex film is subjected to the following tests. A. Determination of the crosslinking duration : A.1. Principle of the test :

[0148] The purpose of this test is to measure the time (expressed in days) required for the crosslinking of the two-component adhesive constituting the adhesive layer of the duplex film, starting from the manufacture of said film by lamination.

[0149] This duration is assessed by the number of days required for the film to be sufficiently cohesive, and, more precisely, for the cohesion of said film, measured by the 180° peel test (described below), to be greater than a reference value equal to 3 N / 15 mm. A.2. Film sampling :

[0150] Immediately after manufacture, the duplex film is stored at a temperature of 23°C and under an atmosphere of 50% relative humidity (RH).

[0151] A sample is taken daily from the stored duplex film and subjected to the 180° peel test. A.3. Description of the 180° peel test :

[0152] The 180° peel test is as described in the French standard NF T 54-122. The principle of this test consists of determining the force required to separate (or peel) two individual layers of film bonded by the two-component adhesive.

[0153] A rectangular specimen 15 mm wide and approximately 10 cm long is cut from the duplex film. The two individual layers of film included in this strip and the two free ends thus obtained are manually peeled off from the end of this specimen, and over approximately 2 cm, fixed to two attachment devices connected, respectively, to a fixed part and a mobile part of a traction device which are located on a vertical axis.

[0154] While a drive mechanism communicates to the moving part a uniform speed of 100 mm / minute, leading to the detachment of the 2 layers whose detached ends move progressively along a vertical axis forming an angle of 180°, the fixed part - connected to a dynamometer - measures the force which is supported by the test piece thus held, and which is expressed in N / 15 mm. A.4. Result :

[0155] The curing time is indicated in days, for each of the two-component adhesive compositions 1 / 2 to 1 / 6, in table 2. B. Determination of initial stickiness:

[0156] The initial tack is assessed by measuring the cohesion of the duplex film immediately after its manufacture, using the 180°C peel test described previously in § A.3.

[0157] The result is indicated in N / 15 mm in Table 2, for each of the two-component adhesive compositions 1 / 2 to 1 / 6.

[0158] The values ​​obtained are greater than 2 N / 15 mm, and thus correspond to a completely satisfactory initial tack. Example 8 (according to the invention) : Triplex film PET / ALU / cPP

[0159] A triplex film is prepared consisting of a first PET film, a second aluminum film and a third cPP film bonded at each interface by a layer of adhesive composition.

[0160] A 12 µm thick PolyEthylene Terephthalate film, a 7 µm thick aluminum film and a 60 µm thick cast PolyPropylene film are used.

[0161] This triplex film is obtained using a sequential process by feeding the tank of a Nordmeccanica type laminating machine with the two-component adhesive composition, for each of the examples 1 / 2 to 1 / 6.

[0162] Said laminating machine is provided with a roller-type coating device with an open tank, operating at room temperature and at a running speed of 50 m / minute. The adhesive layer binding the 3 films at each PET / ALU and ALU / cPP interface has a thickness of approximately 3.5 µm corresponding to approximately 3.5 g / m 2 of adhesive composition.

[0163] This triplex film is subjected to the sterilization resistance test described below. Resistance to sterilization:

[0164] After its manufacture, the triplex film is placed for 7 days in a climatic chamber maintained at a temperature of 40°C.

[0165] A rectangular sample of A4 size (dimensions 21 x 29.7 cm) is then taken and folded in half lengthwise, applying manual pressure to the fold.

[0166] This sample is placed in an autoclave at 135°C in the vapor phase for one hour to simulate a sterilization treatment.

[0167] The sample is then kept at room temperature for 1 hour and the cohesion of the PET / ALU interface of the film is then measured using the 180°C peel test described previously in § A.3.

[0168] The result is indicated in N / 15 mm in Table 2, for each of the two-component adhesive compositions 1 / 2 to 1 / 6.

[0169] These operations are repeated on another sample of the film to determine the cohesion of the ALU / cPP interface.

[0170] The values ​​obtained are all greater than 3 N / 15 mm, thus corresponding to a completely satisfactory resistance to sterilization of the triplex. Example 9 (according to the invention) : Triplex film PET SiOx / boPA / cPP

[0171] Example 8 is repeated using a 12 µm thick PET film coated with a SiOx silica coating less than 0.1 µm thick, a 15 µm thick biaxially oriented polyamide film and a 60 µm thick cast polypropylene film. The SiOx PET film is, for example, available from AMCOR under the brand name CERAMIS ®<. The results of the sterilization resistance test are reported in Table 2.

[0172] The values ​​obtained at the boPA / cPP interface are greater than 3 N / 15 mm, and entirely satisfactory.

[0173] The values ​​obtained at the PET SiOx / boPA interface are greater than 2 N / 15 mm, which is also considered quite satisfactory, in the case of an interface that comprises a thin layer made of a thermoplastic polymer covered with a layer of less than 1 µm of aluminum, alumina or silica SiOx. Example 10 (according to the invention) : Quadruplex film PET / ALU / boPA / cPP

[0174] A PET / ALU / boPA / cPP quadruplex film is prepared using a process similar to that described in Examples 8 and 9, using individual films of the same thickness as the films used in the previous examples.

[0175] The sterilization resistance test is also repeated, adding a control, by visual examination, of the quality of the lamination at the level of the fold formed in the complex film sample. The results are reported in Table 3.

[0176] The peel values ​​obtained at the 3 interfaces are greater than 3 N / 15 mm, and entirely satisfactory.

Claims

1. Solvent-based two-component polyurethane-type adhesive composition, comprising an -OH component and an -NCO component, such that: - the -OH component is a composition (A) comprising an amorphous prepolymer which includes two -OH end groups, the number-average molar mass Mn of which ranges from 8000 to 12 000 g and which is chosen from: - a copolyester (A1) obtained by a polycondensation reaction: - of at least one aliphatic diol (i); with - at least one aromatic diacid (ii) chosen from terephthalic acid, isophthalic acid, phthalic acid and one of their diester or anhydride derivatives; and - at least one aliphatic diacid (iii) or one of its diester or anhydride derivatives; and - a polyurethane (A2) obtained by a polyaddition reaction between an aliphatic diisocyanate compound (A2.P1) and an amorphous copolyester diol (A2.P2), the number-average molecular weight Mn of which ranges from 4000 to 11 500 g / mol, said copolyester being obtained by the polycondensation reaction as defined above for (A1); and - the component -NCO is a composition (B) comprising a compound (B1) which includes three -NCO end groups, and which is obtained by the reaction of meta-xylylene diisocyanate (m-XDI) with a triol, said compound (B1) being: - either the only compound comprised in (B) including three -NCO end groups; - or else a mixture with another compound (B2) including three -NCO end groups, (B2) being an isocyanurate (B2-1) of an aliphatic diisocyanate and the content of (B1) in said mixture being at least 40% by weight, based on the total weight of said mixture.

2. Adhesive composition according to Claim 1, characterized in that the amorphous prepolymer included in the composition (A) is the amorphous copolyester diol (A1) and the diol (i) is chosen from ethylene glycol, diethylene glycol, trimethylene glycol, hexamethylene glycol, propylene glycol, propane-1,3-diol, (1,4-, 1,3- or 1,2-)butanediol, neopentyl glycol, 2-methyl-1,3-propanediol, hexanediol or also cyclohexanedimethanol.

3. Adhesive composition according to Claim 2, characterized in that the aliphatic diacid (iii) is chosen from adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, dodecanedicarboxylic acid, 1,10-decanedicarboxylic acid and succinic acid.

4. Adhesive composition according to either of Claims 2 and 3, characterized in that the copolyester diol (A1) is obtained by polycondensation: - of two aliphatic diols (i) consisting respectively of ethylene glycol and diethylene glycol; with - two diacids (ii) consisting respectively of terephthalic acid and isophthalic acid; and - adipic acid as aliphatic diacid (iii).

5. Adhesive composition according to Claim 1, characterized in that the compound (B1) is the only compound comprised in the composition (B) including three -NCO end groups.

6. Adhesive composition according to either of Claims 1 and 5, characterized in that the compound (B1) is the adduct of m-XDI and of trimethylolpropane (TMP).

7. Adhesive composition according to Claim 1, characterized in that the compound (B1) is as a mixture with the compound (B2).

8. Adhesive composition according to Claim 7, characterized in that the compound (B2) is an isophorone diisocyanate (IPDI) derivative.

9. Adhesive composition according to either of Claims 7 and 8, characterized in that the composition (B) comprises a mixture of: - the adduct (B1) of m-XDI and of trimethylolpropane (TMP); and of - IPDI isocyanurate as compound (B2).

10. Adhesive composition according to one of Claims 7 to 9, characterized in that the content of (B1) in the mixture of (B1) and (B2) is within a range extending from 40% to 80% weight / weight.

11. Adhesive composition according to one of Claims 1 to 10, characterized in that it comprises an adhesion promoter included in the -NCO component or in the -OH component, preferably in the -OH component.

12. Adhesive composition according to Claim 11, characterized in that the adhesion promoter is an aminosilane.

13. Adhesive composition according to one of Claims 1 to 12, characterized in that the amounts of the -NCO and -OH components are such that the -NCO / -OH molar equivalent ratio is within a range extending from 3 to 5.

14. Multilayer film comprising two thin layers of material bonded together by a continuous layer, characterized in that said layer is constituted by the two-component adhesive composition as defined in one of Claims 1 to 13 in the crosslinked state, in a proportion of an amount of less than 7 g / m2.

15. Process for the continuous preparation of the multilayer film as defined in Claim 14, comprising the sequential stages of: (i) combining the -NCO and -OH components and, if appropriate, diluting with a solvent, in order to form an adhesive mixture; (ii) coating, with said adhesive mixture, a first thin layer of material in the form of a substantially continuous layer; (iii) evaporating the organic solvent; (iv) laminating a second thin layer over the first thin layer coated in accordance with stage (ii), then (v) crosslinking the adhesive mixture.

16. Use of the multilayer film as defined in Claim 14, for the manufacture of flexible packagings.