Hot-melt self-adhesive composition

Abstract

The invention relates to a hot-melt self-adhesive composition comprising: - a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, the melt flow index at 200°C and 5 kg of the mixture S being between 3 g / 10 min and 20 g / 10 min, and - at least one tackifying resin, in which the weight ratio of mixture S to tackifying resin is between 67:33 and 77:23. The present invention also relates to a multilayer structure comprising the hot-melt self-adhesive composition according to the invention, to the method for manufacturing same and to the use thereof. In addition, the present invention relates to a resealable packaging.

Description

[0001] Self-adhesive hot melt composition

[0002] Scope of the invention

[0003] The present invention relates to a self-adhesive hot melt composition, a multilayer structure, a manufacturing process and the use of the multilayer structure, as well as a resealable package.

[0004] Technical background

[0005] Multilayer (or laminated) products are used in many fields for packaging a wide variety of goods, particularly in the food, cosmetics, and detergent industries. Depending on the requirements, these products can be flexible or rigid. Flexible packaging is a common example. These products are generally made of different materials (composite multilayer products). Materials can include paper, metal, or thermoplastic polymers.

[0006] The characteristics and properties of multilayer articles will depend, in particular, on the materials used to create the layers. Thus, it is common to combine layers made of different materials to obtain multilayer articles, most often composite multilayer articles, which combine the characteristics and properties of the different individual layers and therefore have specific characteristics and properties.

[0007] Among multi-layered products are resealable packages used in the food industry and retail for packaging food, particularly fresh produce. These packages typically consist of a container (or receptacle) and a lid (or sealing film) that are hermetically sealed together by heat sealing. After the lid is opened and some of the food in the receptacle is consumed, the user can reposition the lid on the receptacle to essentially re-seal the package, thus preserving the remaining portion of the product. Repeated opening and resealing is also possible.

[0008] The container for these packages typically consists of a thermoformed plastic sheet with a flat base on which the food product rests and a flat, band-shaped rim. This rim, usually parallel to the base, is heat-sealed to the lid, which is made of a multi-layered film. When the consumer opens the package, the lidding film is manually separated from the container at the flat band around its rim. This exposes the adhesive layer that was originally part of the lidding film.

[0009] A simple manual press then allows the packaging to be resealed, once the lid has been repositioned on the receptacle according to its position in the packaging before opening.

[0010] In most resealable packaging available on the market, the lidding film is a multilayer structure that includes a layer comprising a self-adhesive hot melt adhesive (or HMPSA for "Hot Melt Pressure Sensitive Adhesive") bonding a complexable layer and a heat-sealable layer.

[0011] The HMPSA composition typically comprises one or more tackifying resins and one or more styrenic block copolymers. Applied in a molten state, it solidifies upon cooling, forming an adhesive layer that ensures the bonding of the complexable and heat-sealable layers.

[0012] The complexable layer can be complexed with other layers to produce the lidding film, for example with a rigid layer to improve the mechanical strength of said film.

[0013] The heat-sealable layer allows the lidding film to be sealed onto the receptacle by heat sealing.

[0014] The laminating and heat-sealable layers can be based on thermoplastic polymers such as polyolefins like polyethylene and / or polypropylene. These polymers have a low melt flow index (MFI), while HMPSA compositions generally have a high MFI. Because of these differences, it is difficult to co-extrude these different materials (particularly by bubble blowing) to obtain a lidding film.

[0015] However, a very low MFI implies very cohesive properties, which are in opposition to the adhesive properties needed to obtain a resealable lidding film.

[0016] The present invention aims to provide a self-adhesive, heat-fusible composition that can be co-extruded (for example, by bubble blowing), particularly with a polyolefin such as polyethylene and / or polypropylene, while maintaining good adhesion properties, so that the lidding film using said composition can withstand several opening / closing cycles while maintaining a good seal. Furthermore, the present invention aims to provide a self-adhesive, heat-fusible composition that ensures a good seal even when resealable packages are placed in a freezer.

[0017] Furthermore, it is desirable that the self-adhesive hot-melt composition can be stored even at high temperatures (e.g., in hot weather or in containers) without loss of processability. In particular, high temperatures promote agglomeration of the composition when it is in granular form before final shaping, hindering the proper functioning of the co-extruder. The present invention therefore aims to provide a self-adhesive hot-melt composition that is less prone to agglomeration at high temperatures (e.g., between 40°C and 50°C).

[0018] Summary of the invention

[0019] The present invention relates to a self-adhesive, hot-melt composition comprising:

[0020] - a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, and

[0021] - at least one tackifying resin, in which the ratio by weight of mixture S / tackifying resin is at least 67 / 33.

[0022] The present invention also relates to a multilayer structure comprising:

[0023] - an adhesive layer consisting of the self-adhesive, hot-melt composition according to the invention,

[0024] - a heat-sealable layer, and

[0025] - a complexable layer, in which the adhesive layer is located between the heat-sealable layer and the complexable layer.

[0026] Furthermore, the present invention relates to a method of manufacturing the multilayer structure according to the invention by lamination or by coextrusion.

[0027] The present invention also relates to a resealable package comprising the multilayer structure according to the invention.

[0028] Finally, the present invention relates to the use of the multilayer structure according to the invention for the manufacture of resealable packaging. The self-adhesive, heat-fusible composition according to the invention makes it possible to achieve one or more of the objectives mentioned above. In particular, it makes it possible to obtain both good resealing quality, at least up to the 5 ème opening, and a hot melt index suitable for its use in bubble blow coextrusion, especially with a polyolefin such as polyethylene and / or polypropylene.

[0029] Furthermore, the glass transition temperature of the self-adhesive hot melt composition according to the invention allows its use in a resealable package suitable for the freezer.

[0030] Furthermore, the self-adhesive hot melt composition according to the invention is not very prone to agglomeration at 40°C and 50°C, and can therefore be stored without risk of loss of processability.

[0031] Description of the invention

[0032] Self-adhesive hot melt composition

[0033] The term "hot melt" is used in this text to indicate that the composition is solid at room temperature (e.g., between 18°C ​​and 25°C) and requires heating to melt before being applied to a substrate. The composition according to the invention is generally in a molten state at a temperature of at least 115°C, preferably at least 130°C. The molten state can, for example, be characterized by the intersection temperature of the elastic modulus G' and viscous modulus curves on a temperature-versus-temperature plot performed by Dynamic Mechanical Analysis (DMA). DMA conditions are given in Example 1 below.

[0034] Mixture S

[0035] The composition according to the invention comprises a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer.

[0036] "Styrenic block copolymers" refers to block copolymers comprising at least one polystyrene block (whether entirely or partially block-based, like gradient copolymers, preferably entirely block-based). Styrenic block copolymers may be linear or branched (e.g., star, brush, or comb-shaped), preferably linear.

[0037] Advantageously, mixture S comprises between 10% and 60% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 40% and 90% by weight of at least one styrene-isoprene diblock copolymer relative to the total weight of mixture S, preferably between 15% and 55% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 45% and 85% by weight of at least one styrene-isoprene diblock copolymer, more preferably between 40% and 55% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 45% and 60% by weight of at least one styrene-isoprene diblock copolymer.

[0038] Within the framework of the invention, the ranges of values ​​are understood to include the limits. For example, the range "between 0% and 25%" includes, in particular, the values ​​0% and 25%.

[0039] Mixture S may have a styrenic motif content of between 10% and 50% by weight relative to the total weight of mixture S, preferably between 13% and 19% by weight.

[0040] The hot melt flow rate at 200°C and 5 kg of mixture S can be between 3 g / 10 min and 20 g / 10 min, preferably between 4 g / 10 min and 18 g / min, and more preferably between 5 g / 10 min and 15 g / min. The hot melt flow rate can be measured according to ISO 1133 (in particular according to procedure A).

[0041] Unless otherwise stated, the standards mentioned throughout the application are those in effect on the date the application was filed.

[0042] The styrenic block copolymers of mixture S can have a number-average molar mass between 50,000 g / mol and 400,000 g / mol. The number-average molar mass can be determined by size-exclusion chromatography, particularly with polystyrene standards.

[0043] Preferably, the mixture S consists of at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, i.e. it consists solely of styrene-isoprene-styrene and styrene-isoprene block copolymers, and does not include other styrenic block copolymers (in particular those having at least one ethylene, propylene, butylene or butadiene block).

[0044] The content of mixture S in the composition according to the invention can be between 60% by weight and 85% by weight relative to the total weight of the composition, preferably between 61% by weight and 82% by weight, more preferably between 63% by weight and 80% by weight, in particular between 65% by weight and 77% by weight.

[0045] Tackifying resin

[0046] The composition according to the invention comprises at least one tackifying resin. This at least one tackifying resin may be selected from:

[0047] - natural and modified rosins, such as gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, polymerized rosin,

[0048] - natural and modified rosin esters, in particular glycerol and pentaerythritol esters such as glycerol esters of pale wood rosin, glycerol esters of polymerized rosin, pentaerythritol esters of pale wood rosin, pentaerythritol esters of tall oil rosin, phenolically modified pentaerythritol esters of rosin,

[0049] - polyterpene resins, generally resulting from the polymerization of terpene hydrocarbons, such as the monoterpene known as pinene, in the presence of Friedel-Crafts catalysts preferably at moderately low temperatures (e.g. about 20°C-50°C),

[0050] - terpene copolymers with a diene monomer, preferably an aromatic diene monomer such as a styrene monomer (e.g., styrene, methylstyrene, etc.),

[0051] - Phenolic modified terpene resins, such as those resulting from the condensation, in an acidic medium, of a terpene and a phenol,

[0052] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0053] - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers,

[0054] - petroleum hydrocarbon resins (C5 / C9), resulting from the polymerization of a mixture of aliphatic C5 and aromatic C9 hydrocarbon monomers,

[0055] - dicyclopentadiene petroleum resins (DCPD), resulting from the polymerization of dicyclopentadiene monomers possibly mixed with C9 aromatic hydrocarbon monomers and / or C5 aliphatic hydrocarbon monomers, in particular C5 aliphatic hydrocarbon monomers,

[0056] - their corresponding hydrogenated derivatives (resulting from subsequent total or partial hydrogenation), and

[0057] - their mixtures.

[0058] Examples of C5 aliphatic hydrocarbon monomers useful for preparing the petroleum resins mentioned above include trans-1,3-pentadiene, cis-1,3-pentadiene, 2-methyl-2-butene, cyclopentadiene, methylcyclopentadiene and / or cyclopentene.

[0059] Examples of C9 aromatic hydrocarbon monomers useful for preparing the petroleum resins mentioned above include vinyltoluene, indene, methylstyrene, α-methylstyrene, styrene and / or methylindene.

[0060] Preferably, at least one tackifying resin is chosen from:

[0061] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0062] - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers,

[0063] - petroleum hydrocarbon resins (C5 / C9), resulting from the polymerization of a mixture of aliphatic C5 and aromatic C9 hydrocarbon monomers,

[0064] - dicyclopentadiene petroleum resins (DCPD), resulting from the polymerization of dicyclopentadiene monomers possibly mixed with C9 aromatic hydrocarbon monomers and / or C5 aliphatic hydrocarbon monomers, in particular C5 aliphatic hydrocarbon monomers,

[0065] - their corresponding hydrogenated derivatives (resulting from subsequent total or partial hydrogenation), and

[0066] - their mixtures.

[0067] In particular, at least one tackifying resin is chosen from:

[0068] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0069] - dicyclopentadiene petroleum resins (DCPD), resulting from the polymerization of dicyclopentadiene monomers possibly mixed with C5 aliphatic hydrocarbon monomers,

[0070] - their corresponding hydrogenated derivatives (resulting from subsequent total or partial hydrogenation), and

[0071] - their mixtures.

[0072] The tackifying resin may have a softening temperature of at least 80°C, preferably between 80°C and 150°C, and more preferably between 90°C and 140°C. The softening temperature may be measured by a ball-and-ring method, for example, according to ASTM E28. The weight-average molecular weight of the tackifying resin may vary between 200 g / mol and 5000 g / mol, preferably between 300 g / mol and 3000 g / mol. The weight-average molecular weight may be measured by size-exclusion chromatography, particularly with polystyrene standards.

[0073] The total content of at least one tackifying resin in the composition according to the invention may be between 13% by weight and 33% by weight relative to the total weight of the composition, preferably between 16% by weight and 32% by weight, more preferably between 18% by weight and 30% by weight, in particular between 21% by weight and 28% by weight.

[0074] Additives

[0075] The composition according to the invention may further comprise one or more additives, for example selected from fillers, ultraviolet stabilizers (or antioxidants), additional polymers other than styrenic block copolymers, rheological agents, core-bark type impact modifiers, pigments, and mixtures thereof, in particular from ultraviolet stabilizers (or antioxidants).

[0076] The total content of additives in the composition according to the invention can be up to 10% by weight relative to the total weight of the composition, preferably up to 5% by weight, more preferably up to 3% by weight.

[0077] The filler can be chosen from organic fillers, mineral fillers, and mixtures thereof.

[0078] As an example of mineral fillers, one can cite any mineral filler commonly used in adhesive compositions. These fillers typically take the form of particles with various geometries. They can be, for example, spherical, fibrous, or irregularly shaped.

[0079] The mineral filler can be chosen from clays (such as talc), quartz, carbonate fillers (especially calcium carbonate, which can be coated with fatty acids (the latter preferably being precipitated)), kaolins, gypsum, silica, hollow mineral microspheres (especially hollow glass microspheres, such as those made of sodium and calcium borosilicate or aluminosilicate), zeolites, and mixtures thereof.

[0080] The mineral feed can be untreated or treated, for example with an organic acid including stearic acid. The average particle size of the mineral feed can range from 10 nm to 400 pm, preferably from 20 nm to 100 pm, more preferably from 30 nm to 10 pm.

[0081] In this text and unless otherwise indicated, the average particle size advantageously corresponds to the d50 particle size, i.e. the maximum size of 50% of the smallest particles by volume, and can be measured with a particle size analyzer, in particular by laser diffraction on a MALVERN type device (for example according to ISO 13320).

[0082] As an example of an organic filler, one can cite any organic filler, especially polymeric, commonly used in the field of adhesive compositions.

[0083] The organic filler can be selected from polyvinyl chloride (PVC), polyolefins, ethylene vinyl acetate (EVA), expandable or non-expandable thermoplastic polymer hollow microspheres (such as vinylidene chloride / acrylonitrile hollow microspheres), aramid fibers (such as Kevlar®), and mixtures thereof.

[0084] The average particle size of the organic load may be less than or equal to 15 pm, preferably between 5 and 15 pm.

[0085] The filler content can be up to 10% by weight relative to the total weight of the composition according to the invention, preferably up to 5% by weight.

[0086] Ultraviolet (UV) stabilizers are typically introduced to prevent degradation resulting from a reaction with oxygen that can form under the influence of heat or light. UV stabilizers may include antioxidants capable of scavenging free radicals.

[0087] The UV stabilizer (or antioxidant) can be chosen from among benzotriazoles, benzophenones, phosphites (such as tris(2,4-di-tert-butylphenyl)phosphite, tris-(p-nonylphenyl)-phosphite), so-called hindered phenols (such as rethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 2,2'-methylenebis(6-(tert-butyl)-4-methylphenol), 2,2'-methylenebis(6-(tert-butyl)-4-ethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4,6-di(tert-butyl)phenol), 4,4'-methylenebis(2,6-di(tert-butyl)phenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di(tert-butyl)-4-methylphenol), so-called hindered amines (such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (CAS No: 41556-26-7), methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate (CAS No: 82919-37-7), 4,4'-bis(a,a-dimethylbenzyldiphenylamine), and mixtures thereof. The UV stabilizer (or antioxidant) content may be up to 5% by weight relative to the total weight of the composition according to the invention, preferably up to 3% by weight.

[0088] Additional polymers other than styrenic block copolymers include, for example, polyolefins (including polyethylene, polypropylene, polyisobutylene, polybutadiene, etc., functionalized or not), ethylene-vinyl acetate copolymers, acrylic copolymers (functionalized or not) and / or acrylic block copolymers.

[0089] By "acrylic block copolymer" is meant a block copolymer comprising at least one acrylic block, that is to say, comprising at least one block consisting of a polymer obtained from at least one acrylic monomer. By "acrylic monomer" is meant in particular a monomer comprising a group of formula -X-(C=O)-C(R')=CH2, in which R' represents a hydrogen atom or a methyl radical, and -X- represents -O- or -NR"- with R" representing a hydrogen atom or an alkyl radical (cyclic, linear or branched) comprising from 1 to 22 carbon atoms, preferably from 1 to 14, more preferably from 1 to 8. Preferably, -X- represents -O-.

[0090] The content of additional polymers can be up to 5% by weight relative to the total weight of the composition according to the invention.

[0091] The rheological agent may be chosen from among thixotropic agents, for example from: fumed silica (hydrophilic and / or hydrophobic), urea derivatives from the reaction of a diisocyanate monomer, preferably aromatic such as diphenylmethylene diisocyanate (in particular 4,4'-MDI), with a primary aliphatic amine such as butylamine, waxes derived from castor oil, such as THIXCIN® R by ELEMENTIS, amide waxes, preferably micronized, such as CRAYVALLAC® SLT by ARKEMA, beeswax (in particular CAS 8006-40-4 and / or 8012-89-3), and mixtures thereof.

[0092] By "waxes derived from castor oil" we mean waxes obtained from castor oil, in particular hydrogenated castor oil.

[0093] The term "amide waxes" refers to waxes comprising one or more compounds with at least one amide group. In particular, amide waxes can be obtained from organic acid(s) (e.g., fatty acid(s)) and (di)amine(s).

[0094] The amide waxes are preferably micronized, that is to say, they have an average particle size of less than 1 mm. Advantageously, the amide waxes have an average particle size of less than 500 pm, preferably less than 100 pm, more preferably less than 15 pm.

[0095] The content of rheological agent can be up to 10% by weight relative to the total weight of the composition according to the invention.

[0096] Core-shell impact modifiers can generally be described as polymeric substances, typically in particulate form, comprising a core (inner part) consisting of a core polymer and a shell (outer part) consisting of a shell polymer. One or more intermediate polymer layers may be included between the core and shell polymers.

[0097] The core polymer may comprise a polymer (homopolymer and / or copolymer) of a conjugated diene comprising from 4 to 12, preferably from 4 to 8, carbon atoms (such as isoprene and / or butadiene), and / or a polymer (homopolymer and / or copolymer) of an acyclic alkyl (meth)acrylate in which the alkyl chain (linear or branched) comprises from 1 to 12, preferably from 1 to 8, carbon atoms (such as butyl acrylate).

[0098] The bark polymer may comprise a polymer (homopolymer and / or copolymer) of an acyclic alkyl (meth)acrylate in which the alkyl chain (linear or branched) comprises from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, more preferably from 1 to 4 carbon atoms, such as methyl methacrylate.

[0099] When one or more intermediate polymer layers are present, each intermediate polymer may comprise a polymer (homopolymer and / or copolymer) of an acyclic alkyl (meth)acrylate in which the alkyl chain (linear or branched) comprises from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, more preferably from 1 to 4 carbon atoms, such as methyl methacrylate. Each intermediate polymer may be identical to or different from the shell polymer.

[0100] The bark polymer and / or intermediate polymer (if present) may further comprise functional groups different from the groups derived from the polymerization of an acyclic alkyl (meth)acrylate (i.e., different from the acyclic alkyl esters remaining after polymerization of said alkyl (meth)acrylate). These functional groups can be selected from epoxy groups (such as the glycidyl group), carboxylic acid groups, carboxamide groups (such as N,N-dialkylcarboxamide groups, notably N,N-dimethylcarboxamide), alkoxy groups (such as methoxy, ethoxy), amine groups (e.g. primary amine), cycloalkyl ester groups (e.g. C8-C12 cycloalkyl such as isobornyl ester, 3,3,5-trimethylcyclohexyl, tert-butylcyclohexyl and / or (octahydro-4,7-methano-1 H-indenyl)methyl), and mixtures thereof.

[0101] Each of the core, shell and intermediate polymers can be crosslinked. The crosslinking agent(s) / monomer(s) can be selected from polyfunctional vinylaromatic compounds such as divinylbenzene and divinyltoluene, polyhydric alcohols such as ethylene glycol di(meth)acrylate and 1,3-butanediol di(meth)acrylate, tri(meth)acrylates, allyl carboxylates such as allyl acrylate and allyl methacrylate, and di- and triallylic compounds such as diallyl phthalate, diallyl sebacate and triallyl triazine.

[0102] The volume-average diameter of the functionalized core-shell filler can range from 10 to 900 nm. The volume-average diameter can be measured by dynamic light scattering (DLS).

[0103] Examples of commercially available core-shell fillers include Clearstrength® (e.g., Clearstrength® XT100) or Durastrength® sold by Arkema, or Paraloid™ (Paraloid™ 2650A, Paraloid™ 2691A) sold by Dow.

[0104] The core-bark type impact modifier content can be up to 15% by weight relative to the total weight of the composition according to the invention.

[0105] The pigment can be chosen from organic pigments, inorganic pigments, and mixtures thereof. For example, the pigment can be chosen from phthalocyanine-based pigments (such as copper phthalocyanine, halogenated copper phthalocyanine, metal-free phthalocyanine), anthraquinone-based pigments (such as 1-methylamino-4-o-tolylaminoanthraquinone, 1,4-diisopropyl aminoanthraquinone, 1,4-diaminoanthraquinone, 1,4-dibutyl-aminoanthraquinone, 1-amino-4-anilinoanthraquinone), quinacridone-based pigments, perylene-based pigments, thioindigo-based pigments, quinophthalone-based pigments, titanium dioxide, carbon black, manganese ferrite, and mixtures thereof.

[0106] The pigment content can be up to 3% by weight relative to the total weight of the composition according to the invention. Preferably, the composition according to the invention comprises less than 5% by weight of plasticizer relative to the total weight of the composition according to the invention, more preferably less than 3% by weight, and even more preferably no plasticizer.

[0107] Examples of plasticizers are naphthenic and / or paraffinic oils. Naphthenic and paraffinic oils are petroleum-based oils consisting of a mixture of naphthenic hydrocarbons (e.g., aliphatic C4-C7 hydrocarbon rings, saturated or unsaturated, including cycloalkanes such as cyclopentane, cyclohexane, and cycloheptane), paraffinic hydrocarbons (saturated, linear, or branched alkanes), and aromatic hydrocarbons (aromatic hydrocarbon rings, monocyclic or polycyclic, preferably aromatic C6).

[0108] The classification of naphthenic and paraffinic oils is based on the quantity of each type of hydrocarbon in the oil. As a general rule, paraffinic oils have a paraffinic hydrocarbon content of at least 50% by weight relative to the total weight of the paraffinic oil, and naphthenic oils have a naphthenic hydrocarbon content of between 30% and 40% by weight, relative to the total weight of the naphthenic oil.

[0109] Other features

[0110] The weight ratio of S mixture / tackifying resin can be between 67 / 33 and 85 / 15, preferably between 68 / 32 and 82 / 18, more preferably between 70 / 30 and 80 / 20, in particular between 72 / 28 and 77 / 23.

[0111] Advantageously, the weight ratio of S mixture / tackifying resin is between 68 / 32 and 77 / 23, more preferably between 70 / 30 and 77 / 23, for example between 70 / 30 and 75 / 25.

[0112] Advantageously, the composition according to the invention does not include any other styrenic block copolymers than those of mixture S.

[0113] According to one embodiment, the composition according to the invention comprises:

[0114] - between 60% by weight and 85% by weight of a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, preferably between 10% and 60% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 40% and 90% by weight of at least one styrene-isoprene diblock copolymer relative to the total weight of mixture S,

[0115] - between 13% by weight and 33% by weight of at least one tackifying resin, and - optionally up to 10% by weight of one or more additives, for example selected from fillers, ultraviolet stabilizers (or antioxidants), additional polymers other than styrenic block copolymers, rheological agents, core-bark type impact modifiers, pigments, and mixtures thereof, wherein the weight ratio of mixture S / tackifying resin is between 67 / 33 and 85 / 15, preferably between 67 / 33 and 77 / 23, the weight percentages being, unless otherwise stated, relative to the total weight of the composition.

[0116] Preferably, the composition according to the invention consists essentially of the ingredients mentioned above. By "consists essentially of" means that the composition according to the invention comprises less than 5% by weight of ingredients other than the aforementioned ingredients, relative to the total weight of said composition, preferably less than 2% by weight, and even more preferably less than 1% by weight.

[0117] The ingredients of this embodiment and their particular contents are as described above, including preferred embodiments and characteristics.

[0118] In particular, the composition according to the invention comprises:

[0119] - between 63% by weight and 80% by weight of a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, preferably consisting of between 10% and 60% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 40% and 90% by weight of at least one styrene-isoprene diblock copolymer relative to the total weight of mixture S,

[0120] - between 18% by weight and 30% by weight of at least one tackifying resin, preferably chosen from aliphatic hydrocarbon C5 petroleum resins, aromatic hydrocarbon C9 petroleum resins, C5 / C9 hydrocarbon petroleum resins, dicyclopentadiene petroleum resins (possibly mixed with C9 and / or C5 monomers), their corresponding hydrogenated derivatives, and mixtures thereof, and

[0121] - optionally up to 3% by weight of one or more additives, for example selected from fillers, ultraviolet stabilizers (or antioxidants), additional polymers other than styrenic block copolymers, rheological agents, core-bark type impact modifiers, pigments, and mixtures thereof, wherein the weight ratio of mixture S / tackifying resin is between 70 / 30 and 80 / 20, preferably between 70 / 30 and 77 / 23, the weight percentages being, unless otherwise stated, relative to the total weight of the composition.

[0122] Preferably, the composition according to the invention consists essentially of the ingredients mentioned above.

[0123] The ingredients of this embodiment and their particular contents are as described above, including preferred embodiments and characteristics.

[0124] Advantageously, the composition according to the invention has a fifth-opening adhesion strength by 180° peel greater than or equal to 0.55 N / cm for a thickness of 15 µm of said composition between two polyethylene substrates. The fifth-opening adhesion strength can, for example, be measured in accordance with Example 1.

[0125] Advantageously, the composition according to the invention has a hot melt flow rate at 190°C and 2.16 kg of less than 25 g / 10 min, preferably less than or equal to 21 g / 10 min, more preferably less than or equal to 19 g / 10 min, for example less than or equal to 15 g / 10 min. The hot melt flow rate can be measured in accordance with ASTM D1238-10 (Procedure A).

[0126] Advantageously, the composition according to the invention has a glass transition temperature below -17°C. The glass transition temperature can be determined by Dynamic Mechanical Analysis, for example as described in Example 1.

[0127] The composition according to the invention can be in the form of granules, preferably ovoidal or spheroidal in shape, with an average size of between 1 mm and 10 mm, preferably between 2 and 6 mm.

[0128] The average size of the granules can be measured using a caliper.

[0129] The said granules are preferably coated with a layer of a slippery and / or anti-blocking agent at a maximum of 1.5% by weight relative to the total weight of the granules.

[0130] The sliding and / or anti-blocking agent may be selected from organic and / or inorganic sliding and / or anti-blocking agents. For example, the sliding and / or anti-blocking agent may be selected from erucamide, oleamide, docosanamide, stearamide, palmitamide, ethylene bis-stearamide, ethylene bis-oleamide, silica, talc, calcium carbonate, glass beads, and mixtures thereof, particularly talc. The composition according to the invention may be prepared by a process comprising:

[0131] - a hot mixing stage for the ingredients, for example between 90°C and 200°C, preferably using a twin-screw extruder, then

[0132] - a cutting step of the extruded mixture, preferably at the exit of the die, then

[0133] - a cooling stage, for example to room temperature (23°C).

[0134] Preferably, the cutting step is implemented in such a way as to obtain granules (in particular of ovoidal or spheroidal shape) whose average size is between 1 mm and 10 mm, preferably between 2 and 6 mm.

[0135] An example of preparation is described in Example 2.

[0136] Multilayer structure

[0137] The present invention also relates to a multilayer structure comprising:

[0138] - an adhesive layer consisting of the self-adhesive, hot-melt composition according to the invention,

[0139] - a heat-sealable layer, and

[0140] - a complexable layer, in which the adhesive layer is located between the heat-sealable layer and the complexable layer.

[0141] Adhesive layer

[0142] The self-adhesive hot melt composition according to the invention is as described above, including preferred embodiments and features.

[0143] The adhesive layer can have a thickness between 5 µm and 50 µm, preferably between 7 µm and 25 µm.

[0144] Heat-sealable layer

[0145] The heat-sealable layer allows the multilayer structure to be sealed to a substrate when heated (for example, the perimeter of a container), particularly at a temperature between 80°C and 180°C, preferably between 100°C and 160°C. Thus, the heat-sealable layer advantageously has a softening temperature between 80°C and 180°C, preferably between 100°C and 160°C. This softening temperature can be measured according to ASTM E28-67. The heat-sealable layer may be based on a thermoplastic polymer. In particular, the heat-sealable layer comprises at least 90% by weight of one or more thermoplastic polymers relative to the total weight of said layer, preferably at least 95% by weight, and more preferably at least 99% by weight.

[0146] The thermoplastic polymer can be chosen from:

[0147] - polyethylene (PE),

[0148] - polypropylene (PP),

[0149] - polyamide (PA),

[0150] - a polyester polymer, for example comprising at least one motif derived from a cyclic or acyclic diol (preferably acyclic) and at least one motif derived from a cyclic dicarboxylic acid (preferably aromatic), in particular polyethylene terephthalate (PET) or one of its derivatives (for example further comprising a motif derived from isophthalic acid),

[0151] - an ethylene copolymer, for example a maleic anhydride grafted copolymer, an ethylene and propylene copolymer, an ethylene and vinyl acetate (EVA) copolymer, an ethylene and vinyl alcohol (EVOH) copolymer, an ethylene and an alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0152] - polystyrene (PS),

[0153] - polyvinyl chloride (PVC),

[0154] - polyvinylidene fluoride (PVDF),

[0155] - a lactic acid polymer (PLA),

[0156] - a polyhydroxyalkanoate (PHA), and

[0157] - their mixtures.

[0158] Preferably, the thermoplastic polymer is chosen from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof, more preferably from polyethylene, polypropylene, an ethylene-propylene copolymer, and mixtures thereof, and even more preferably polyethylene.

[0159] The heat-sealable layer may also include one or more additives, for example chosen from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, anti-fog agents, anti-static agents, and mixtures thereof.

[0160] The total content of additive(s) may be up to 10% by weight relative to the total weight of the heat-sealable layer, preferably up to 5% by weight, more preferably up to 1% by weight.The UV stabilizer (or antioxidant) can be chosen from among benzotriazoles, benzophenones, phosphites (such as tris(2,4-di-tert-butylphenyl)phosphite, tris-(p-nonylphenyl)-phosphite), so-called hindered phenols (such as rethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 2,2'-methylenebis(6-(tert-butyl)-4-methylphenol), 2,2'-methylenebis(6-(tert-butyl)-4-ethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4,6-di(tert-butyl)phenol), 4,4'-methylenebis(2,6-di(tert-butyl)phenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di(tert-butyl)-4-methylphenol), so-called hindered amines (such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0161] The sliding and / or anti-blocking agent can be chosen from organic and / or inorganic sliding and / or anti-blocking agents. For example, the sliding and / or anti-blocking agent can be chosen from erucamide, oleamide, docosanamide, stearamide, palmitamide, ethylene bis-stearamide, ethylene bis-oleamide, silica, talc, calcium carbonate, glass beads, and mixtures thereof.

[0162] The anti-fog agent may be chosen from sorbitan esters, glycerol esters, poly(oxyethylene) esters, alkylbenzene sulfonates, and mixtures thereof; said esters are in particular fatty acid(s) esters.

[0163] The antistatic agent may be chosen from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0164] The heat-sealable layer is advantageously tearable.

[0165] The heat-sealable layer can be pre-cut over all or part of its thickness, for example using a laser or a cutting plate.

[0166] The heat-sealable layer can be bi-oriented.

[0167] The bi-orientation of one (or more) layer(s) can be achieved by stretching the layer(s) under heating (e.g., infrared, at a temperature above 100°C) in the machine direction (also called axial) and by stretching under heating (e.g., between 100°C and 135°C) in the direction perpendicular to the machine direction (also called transverse). The layer(s) can then be heated up to 220°C and relaxed at 220-170°C in the transverse direction. The stretch factor can be between 2.0 and 4.0 (particularly around 3.0) in the machine direction, and between 3.0 and 4.0 (particularly around 3.4) in the transverse direction.

[0168] By "approximately X", we are aiming for more or less 10% of the value of X.

[0169] The heat-sealable layer may have undergone surface treatment, such as embossing (preferably hot), plasma treatment like corona treatment, atmospheric pressure plasma treatment, flame plasma treatment, chemical plasma treatment, etc.

[0170] The heat-sealable layer can have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm.

[0171] Complexable layer

[0172] The layerable can be complexed (or bonded, or laminated, preferably bonded) with other layers, for example with a rigid layer to improve the mechanical strength of the multilayer structure.

[0173] The complexable layer may be based on a thermoplastic polymer. In particular, the complexable layer comprises at least 90% by weight of one or more thermoplastic polymers relative to the total weight of said layer, preferably at least 95% by weight, more preferably at least 99% by weight.

[0174] The thermoplastic polymer can be chosen from:

[0175] - polyethylene (PE),

[0176] - polypropylene (PP),

[0177] - polyamide (PA),

[0178] - a polyester polymer, for example comprising at least one cyclic or acyclic diol-derived motif (preferably acyclic) and at least one cyclic dicarboxylic acid-derived motif (preferably aromatic), in particular polyethylene terephthalate (PET) or one of its derivatives (for example further comprising an isophthalic acid-derived motif, preferably PET,

[0179] - an ethylene copolymer, for example a maleic anhydride grafted copolymer, an ethylene and propylene copolymer, an ethylene and vinyl acetate (EVA) copolymer, an ethylene and vinyl alcohol (EVOH) copolymer, an ethylene and an alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0180] - polystyrene (PS),

[0181] - polyvinyl chloride (PVC),

[0182] - polyvinylidene fluoride (PVDF),

[0183] - a lactic acid polymer (PLA), - a polyhydroxyalkanoate (PHA), and

[0184] - their mixtures.

[0185] Preferably, the thermoplastic polymer is chosen from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof, more preferably from polyethylene, polypropylene, an ethylene-propylene copolymer, and mixtures thereof, and even more preferably polyethylene.

[0186] The complexable layer may also include one or more additives, for example chosen from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, antistatic agents, and mixtures thereof.

[0187] The total content of additive(s) may be up to 10% by weight relative to the total weight of the complexable layer, preferably up to 5% by weight, more preferably up to 1% by weight.

[0188] The UV stabilizer (or antioxidant) can be chosen from among benzotriazoles, benzophenones, phosphites (such as tris(2,4-di-tert-butylphenyl)phosphite, tris-(p-nonylphenyl)-phosphite), so-called hindered phenols (such as rethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 2,2-methylenebis(6-(tert-butyl)-4-methylphenol), 2,2'-methylenebis(6-(tert-butyl)-4-ethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4,6-di(tert-butyl)phenol), 4,4'-methylenebis(2,6-di(tert-butyl)phenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di(tert-butyl)-4-methylphenol), so-called hindered amines (such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0189] The sliding and / or anti-blocking agent can be chosen from organic and / or inorganic sliding and / or anti-blocking agents. For example, the sliding and / or anti-blocking agent can be chosen from erucamide, oleamide, docosanamide, stearamide, palmitamide, ethylene bis-stearamide, ethylene bis-oleamide, silica, talc, calcium carbonate, glass beads, and mixtures thereof.

[0190] The antistatic agent may be chosen from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0191] The complexable layer can be bi-oriented. The complexable layer may have undergone a surface treatment, such as embossing (preferably hot), plasma treatment such as corona treatment, atmospheric pressure plasma treatment, flame plasma treatment, chemical plasma treatment, etc.

[0192] The complexable layer can have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm.

[0193] Additional layers

[0194] The multilayer structure according to the invention may also include one or more additional layers (in addition to the adhesive, heat-sealable and complexable layers described above).

[0195] For example, the multilayer structure according to the invention may include: one or more additional layers on the heat-sealable layer (preferably between the adhesive layer and the heat-sealable layer), and / or one or more additional layers on the complexable layer (between the adhesive layer and the complexable layer, and / or on the surface not directed towards the adhesive layer, preferably between the adhesive layer and the complexable layer).

[0196] In this text, "heat-sealable film" means the assembly formed by the heat-sealable layer and the additional layer(s) on the heat-sealable layer, and "complexable film" means the assembly formed by the complexable layer and the additional layer(s) on the complexable layer.

[0197] Advantageously, the heat-sealable layer has a free side (not covered by another layer); it is therefore an outer layer. When the multilayer structure is used as the lid of a resealable package, the lid is heat-sealed to the receptacle via the heat-sealable layer.

[0198] It is possible that one or more of the additional layers may also be heat-sealable layers, identical or different from the heat-sealable layer as described above.

[0199] Each additional layer may be based on a thermoplastic polymer. In particular, each additional layer comprises at least 90% by weight of one or more thermoplastic polymers relative to the total weight of said layer, preferably at least 95% by weight, more preferably at least 99% by weight.

[0200] The thermoplastic polymer can be chosen from:

[0201] - polyethylene (PE), - polypropylene (PP),

[0202] - polyamide (PA),

[0203] - a polyester polymer, for example comprising at least one motif derived from a cyclic or acyclic diol (preferably acyclic) and at least one motif derived from a cyclic dicarboxylic acid (preferably aromatic), in particular polyethylene terephthalate (PET) or one of its derivatives (for example further comprising a motif derived from isophthalic acid),

[0204] - an ethylene copolymer, for example a maleic anhydride grafted copolymer, an ethylene and propylene copolymer, an ethylene and vinyl acetate (EVA) copolymer, an ethylene and vinyl alcohol (EVOH) copolymer, an ethylene and an alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0205] - polystyrene (PS),

[0206] - polyvinyl chloride (PVC),

[0207] - polyvinylidene fluoride (PVDF),

[0208] - a lactic acid polymer (PLA),

[0209] - a polyhydroxyalkanoate (PHA), and

[0210] - their mixtures.

[0211] Each additional layer may further include one or more additives, for example chosen from LIV stabilizers (or antioxidants), sliding and / or anti-blocking agents, antistatic agents, and mixtures thereof.

[0212] The total content of additive(s) may be up to 10% by weight relative to the total weight of each additional layer, preferably up to 5% by weight, more preferably up to 1% by weight.

[0213] The UV stabilizer (or antioxidant) can be chosen from among benzotriazoles, benzophenones, phosphites (such as tris(2,4-di-tert-butylphenyl)phosphite, tris-(p-nonylphenyl)phosphite), so-called hindered phenols (such as ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 2,2-methylenebis(6-(tert-butyl)-4-methylphenol), 2,2'-methylenebis(6-(tert-butyl)-4-ethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4,6-di(tert-butyl)phenol), 4,4'-methylenebis(2,6-di(tert-butyl)phenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di(tert-butyl)-4-methylphenol), so-called hindered amines (such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0214] The sliding and / or anti-blocking agent can be chosen from organic and / or inorganic sliding and / or anti-blocking agents. For example, the sliding and / or anti-blocking agent can be chosen from erucamide, oleamide, docosanamide, stearamide, palmitamide, ethylene bis-stearamide, ethylene bis-oleamide, silica, talc, calcium carbonate, glass beads, and mixtures thereof.

[0215] The antistatic agent may be chosen from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0216] Each additional layer can be bi-oriented.

[0217] Each additional layer may have undergone a surface treatment, such as embossing (preferably hot), plasma treatment such as corona treatment, atmospheric pressure plasma treatment, flame plasma treatment, chemical plasma treatment, etc.

[0218] Each additional layer can have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm.

[0219] The heat-sealable film can have a thickness between 2 µm and 150 µm, preferably between 3 µm and 100 µm.

[0220] The complexable film can have a thickness between 5 pm and 150 pm, preferably between 10 pm and 100 pm.

[0221] The heat-sealable film is advantageously tearable.

[0222] Heat-sealable film can be pre-cut through all or part of its thickness, for example using a laser or a cutting plate.

[0223] The heat-sealable film can be bi-oriented.

[0224] The complexable film can be bi-oriented.

[0225] Other features

[0226] One or more of the layers of the multilayer structure according to the invention can be covered in whole or in part by an ink.

[0227] According to one embodiment, the multilayer structure according to the invention comprises:

[0228] - an adhesive layer having a thickness between 5 µm and 50 µm made up of the self-adhesive, heat-fusible composition according to the invention, - a heat-sealable and breakable layer, preferably based on a thermoplastic polymer selected from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof,

[0229] - a complexable layer, preferably based on a thermoplastic polymer selected from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof, and

[0230] - optionally one or more additional layers, in which the adhesive layer is located between the heat-sealable layer and the complexable layer.

[0231] The layers of this embodiment are as described above, including preferred embodiments and features.

[0232] The multilayer structure according to the invention can be used as a lid for packaging comprising a receptacle. In this case, it is understood that the multilayer structure does not include the receptacle.

[0233] Manufacturing process for the multilayer structure

[0234] The present invention also relates to a method of manufacturing the multilayer structure according to the invention by lamination or by coextrusion, in particular by bubble blowing coextrusion.

[0235] According to a first embodiment, the manufacturing process for the multilayer structure according to the invention comprises:

[0236] - a step of coating an adhesive comprising the self-adhesive hot-melt composition according to the invention onto a surface of a first film, then

[0237] - a step of laminating a surface of a second film onto the coated surface of the first film, wherein one of the films comprises the heat-sealable layer or is bonded to the heat-sealable layer after the laminating step, and wherein one of the films comprises the complexable layer or is bonded to the complexable layer after the laminating step.

[0238] The multilayer structure, the self-adhesive hot-melt composition, the heat-sealable layer, and the laminating layer are as described above, including preferred embodiments and characteristics. In particular, the heat-sealable layer preferably has a free face.

[0239] The first and second films can each be single-layer or multi-layer. The coating step can be carried out on all or part of the surface of the first film, preferably continuously or substantially continuously.

[0240] To facilitate the coating of the hot melt self-adhesive composition, the adhesive preferably comprises an organic solvent, for example butanone, toluene, xylene, benzene, monochlorobenzane, dichloromethane, 2-nitropropane, nitroethane, nitrobenzene, dichlorobenzene, dioxolane, tetrahydrofuran, an ester (ethyl acetate, n-butyl acetate, 2-ethoxyethyl acetate), cyclohexanone and / or dioxane, in particular an ester such as ethyl acetate, n-butyl acetate, 2-ethoxyethyl acetate, etc.

[0241] The solvent content can be between 10% and 95% by weight relative to the total weight of the adhesive, preferably between 50% and 90% by weight.

[0242] When the adhesive contains a solvent, the manufacturing process for the multilayer structure according to the invention advantageously includes an adhesive drying step after the coating step and before the laminating step. The drying step can be carried out at a temperature between 18°C ​​and 100°C, preferably between 20°C and 90°C, for a period sufficient to allow the solvent to evaporate.

[0243] When one or more additional layers (as described above) are present in the multilayer structure, they can be obtained by co-extrusion, coating and / or lamination with one or more layers of the multilayer structure.

[0244] According to a second embodiment, the manufacturing process of the multilayer structure according to the invention includes a co-extrusion step of the self-adhesive heat-fusible composition according to the invention and the constituent materials of the heat-sealable and complexable layers.

[0245] The multilayer structure, the self-adhesive hot-melt composition, the heat-sealable layer, the complexable layer, and the additional layers are as described above, including preferred embodiments and characteristics. In particular, the heat-sealable layer preferably has a free face.

[0246] When one or more additional layers (as described above) are present in the multilayer structure, they can be obtained by co-extrusion, coating and / or lamination with one or more layers of the multilayer structure.

[0247] The coextrusion device is preferably a bubble blow coextrusion device (also known as "sheath blow coextrusion"). As is known to those skilled in the art, this process comprises: - the melting, in separate extruders, of the compositions and materials constituting the adhesive, heat-sealable, and laminating layers, and optionally any additional layers, then

[0248] - the passage of the corresponding flows through a set of annular and concentric dies, so as to form a multi-layered tubular bubble, in the order corresponding to that desired for the final structure, then

[0249] - radial expansion (relative to the annular channel) and stretching (in the axial direction) of the bubble, then

[0250] - the cooling of the bubble.

[0251] The geometric characteristics of the dies, as well as process parameters such as the radial expansion rate and the stretching speed, are set to obtain the desired thickness for the various constituent layers of the multilayer structure. For a more detailed description of the bubble blow coextrusion process, reference is made to US patent application 2013 / 0029553.

[0252] Resealable packaging

[0253] The present invention also relates to a resealable package comprising the multilayer structure according to the invention.

[0254] In particular, the resealable packaging includes a receptacle and a lid made up of the multilayer structure according to the invention.

[0255] Advantageously, the lid is heat-sealed around the perimeter of the receptacle.

[0256] The receptacle is preferably made of a plastic polymer, for example chosen from:

[0257] - polyethylene (PE),

[0258] - polypropylene (PP),

[0259] - polyamide (PA),

[0260] - polyethylene terephthalate (PET),

[0261] - an ethylene copolymer, for example a maleic anhydride grafted copolymer, an ethylene and propylene copolymer, an ethylene and vinyl acetate (EVA) copolymer, an ethylene and vinyl alcohol (EVOH) copolymer, an ethylene and an alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0262] - polystyrene (PS),

[0263] - polyvinyl chloride (PVC),

[0264] - polyvinylidene fluoride (PVDF), - a lactic acid polymer (PLA),

[0265] - a polyhydroxyalkanoate (PHA), and

[0266] - their mixtures.

[0267] The total content of thermoplastic polymer(s) may be at least 90% by weight relative to the total weight of the receptacle, preferably at least 95% by weight, more preferably at least 99% by weight.

[0268] The receptacle may also include one or more additives, for example chosen from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, pigments, antistatic agents, and mixtures thereof.

[0269] The total content of additive(s) may be up to 10% by weight relative to the total weight of the receptacle, preferably up to 5% by weight, more preferably up to 1% by weight.

[0270] The UV stabilizer (or antioxidant) can be chosen from among benzotriazoles, benzophenones, phosphites (such as tris(2,4-di-tert-butylphenyl)phosphite, tris-(p-nonylphenyl)-phosphite), so-called hindered phenols (such as rethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], 2,2-methylenebis(6-(tert-butyl)-4-methylphenol), 2,2'-methylenebis(6-(tert-butyl)-4-ethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4,6-di(tert-butyl)phenol), 4,4'-methylenebis(2,6-di(tert-butyl)phenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di(tert-butyl)-4-methylphenol), so-called hindered amines (such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0271] The sliding and / or anti-blocking agent can be chosen from organic and / or inorganic sliding and / or anti-blocking agents. For example, the sliding and / or anti-blocking agent can be chosen from erucamide, oleamide, docosanamide, stearamide, palmitamide, ethylene bis-stearamide, ethylene bis-oleamide, silica, talc, calcium carbonate, glass beads, and mixtures thereof.

[0272] The pigment can be chosen from organic pigments, inorganic pigments, and mixtures thereof. For example, the pigment can be chosen from manganese ferrite, titanium dioxide, carbon black, iron oxide, aluminum, talc, and mixtures thereof, particularly titanium dioxide, carbon black, and mixtures thereof. The antistatic agent can be chosen from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glyceryl monostearate, mixtures of glyceryl monostearate and tertiary amines, and mixtures thereof.

[0273] Use of the multilayer structure

[0274] The present invention also relates to the use of the multilayer structure according to the invention for the manufacture of a resealable package, preferably for food, in particular for chilled or frozen food.

[0275] Advantageously, the multilayer structure is used as the lid of the resealable packaging.

[0276] Preferably, the resealable packaging is as described above, including preferred embodiments and features.

[0277] All the embodiments described above can be combined with one another. In particular, the various aforementioned components of the composition, and especially the preferred embodiments, can be combined with one another.

[0278] The following examples are given purely to illustrate the invention and should not be interpreted as limiting its scope.

[0279] Examples

[0280] 1. Ingredients and Measurement Methods

[0281] Ingredients used

[0282] The following ingredients were used:

[0283] JH8161 (by Ningbo Jinhai Chenguang Chemical Corporation): styrene-isoprene-styrene block copolymer having a styrenic motif content of about 16% by weight, a diblock copolymer content of about 50% by weight, and a hot melt index at 200°C and 5 kg of about 11 g / 10 min,

[0284] YH1126 (by SINOPEC): styrene-isoprene-styrene block copolymer with a styrene motif content of approximately 16% by weight, a diblock copolymer content of approximately 50% by weight, and a hot melt flow index at 200°C and 5 kg between 8 and 14 g / 10 min; JH-3204 (by Jinhai): aliphatic C5 hydrocarbon resin with a softening temperature between 96 and 104°C, tackifying resin; Escorez™ 1310LC (by ExxonMobil): aliphatic C5 hydrocarbon resin with a softening temperature of approximately 94°C, tackifying resin.

[0285] - SU-130 (for SUKOREZ® SU-130 by KOLON INDUSTRIES): resin obtained by polymerization and hydrogenation of C5 and DCPD cycles having a softening temperature between 126°C and 135°C, tackifying resin.

[0286] Measurement methods

[0287] The melt flow index (MFI) was measured according to ASTM D1238-10 (Procedure A). Briefly, a sample of the composition to be tested was introduced into a plastometer, and the temperature was then raised to 190°C. A 2.16 kg weight was then placed on the sample. The material flowing through the die over a specified time was weighed to determine the MFI. This is expressed in g / 10 min at 190°C for a weight of 2.16 kg.

[0288] A Dynamic Mechanical Analysis (DMA) was performed on a sample of the composition to be tested using an ARES rheometer (marketed by TA Instruments), with a temperature sweep and a "plane-plane" type sample holder geometry (parallel plates spaced 1.6 mm apart, each 10 mm in diameter). Briefly, the sample to be analyzed was placed on the designated sample holder. The temperature was raised to 190°C to achieve a melt, then a temperature ramp down to -40°C was applied simultaneously with a shear rate of 10 rad / s. The temperature ramp rate was -8°C / min for temperatures from 190°C to 0°C, and -5°C / min for temperatures from 0°C to -40°C.The sample's response to mechanical stress was recorded every 15 seconds, and then the glass transition temperature (Tg) was determined to be the temperature at which the maximum of the tan 5 peak is observed.

[0289] The elastic modulus G' (also called the conservation modulus) and the loss factor (tan 5) were determined at 24°C, during the temperature decrease.

[0290] The strength of the 5th's adherence èmeThe opening was determined as follows: the composition was first dissolved in ethyl acetate to obtain a 20% wt. solution. This solution was then dispensed onto a 20 µm thick polyethylene (PE) substrate using a Mayer bar. After evaporation of the solvent at room temperature (approximately 23°C), the substrate was placed in an oven at 70°C for 1 h, whereupon a second 20 µm thick PE substrate was deposited on top of the coated and dried adhesive composition layer (15 µm thick), and the stack was held under a hydraulic press at 25 kN for 24 h. Subsequently, a PE / PET complex (20µm / 55µm, respectively) was laminated to each side of the stack (PE face on PE substrates), then heat-sealed between 1 cm x 15 cm jaws heated to 130°C for 1 second and under a pressure of 600N. The heat-sealed areas thus define the test specimens used for adhesion and resealability measurements.

[0291] Adhesion measurements were performed at 23°C on a dynamometer (Instron) by peeling the test specimens 180° at a speed of 300 mm / minute. Each specimen was opened and resealed (manually) five times; the adhesion strength at the fifth opening is considered relevant for comparing the compositions and for the intended applications. The adhesion strength was measured once a plateau value was reached for each opening and averaged over a 10 cm opening.

[0292] The agglomeration properties were evaluated using the test compositions in the form of talc-coated granules at a concentration of 0.8% by solid mass: 150 g of granules were placed in a circular container 10 cm in diameter and 10 cm high to achieve a uniform granule thickness of approximately 5 cm. A sheet of Teflon was then placed on top of the granules, along with a 10 cm high by 10 cm diameter wedge positioned so that the wedge partially fits inside the container and can slide freely within it. A weight was then placed on top of the wedge, resulting in a total mass of material above the granules of 62.5 g / cm³. 2 The resulting stack was then placed in an oven heated to the study temperature (40°C or 50°C) for 30 days, after which the stack was dismantled and the container turned upside down to assess the state of agglomeration. Self-adhesive hot melt compositions comprising the JH8161 copolymer

[0293] Compositions 1-8 were prepared by extrusion in a twin-screw extruder using the ingredients listed in Table 1 below (percentages are weight percentages relative to the total weight of the composition). The ingredients were weighed and mechanically pre-mixed in a container, or introduced separately into dedicated gravimetric feeders. The mixture was then fed into the twin-screw extruder and collected at the outlet either as rods or granules (for the latter, a cold-water cutting process was performed, followed by drying and talc coating). A consistent temperature ramp is present on the twin-screw extruder body, maintaining an inlet temperature of 90°C and an outlet temperature of 170°C, while the screws have a co-rotation speed ranging from 400 to 700 rpm. The compositions are ready for use immediately after cooling.

[0294] Their properties were then evaluated according to the methods described in Example 1 above.

[0295] Table 1

[0296] All the tested compositions have a strength of 5 ème They have an opening strength of at least 0.5 N / cm for an adhesive composition thickness of 15 micrometers. They are therefore suitable for manufacturing resealable packaging that can withstand multiple opening / closing cycles while maintaining a good seal.

[0297] However, comparative compositions 1, 2, 5, and 6 are not suitable for resealable packaging intended for freezing. Indeed, their Tg is above -17°C. In contrast, compositions 3, 4, 7, and 8 according to the invention all have a Tg below -17°C, ensuring good sealing and resealability of the packaging even when the resealable packages are placed in the freezer. The MFI of compositions 3, 4, 7, and 8 according to the invention is lower than that of comparative compositions 1, 2, 5, and 6. The compositions according to the invention will therefore have better compatibility with polyethylene or polypropylene polymers commonly used in lidding films, the latter generally having an MFI of less than 10 g / 10 min at 190°C and 2.16 kg.Thus, the compositions according to the invention can be used in a bubble / blowing coextrusion process, in particular with a polyolefin such as polyethylene and / or polypropylene, to obtain lidding films.

[0298] Furthermore, compositions 3, 4, 7, and 8 according to the invention are also less prone to agglomeration than comparative compositions 1, 2, 5, and 6: their modulus of elasticity G' is higher (meaning they are less susceptible to deformation at the study temperature) and their loss factor tan 5 is lower (meaning they are less susceptible to flow). The loss factor tan 5 is a more important parameter than the modulus of elasticity G' for assessing the risk of agglomeration.

[0299] Example 3: Self-adhesive hot melt compositions comprising the YH1126 copolymer

[0300] Compositions 9-15 were prepared by mixing the ingredients listed in Table 2 below (percentages being percentages by weight relative to the total weight of the composition), following the same procedure as described in Example 2.

[0301] Their properties were then evaluated according to the methods described in Example 1 above.

[0302] Table 2

[0303] Replacing copolymer JH8161 with copolymer YH1126 leads to the same observations as those presented in Example 2: compositions 11, 12, 14, 15 and 17-18 according to the invention are suitable for resealable packaging intended to be frozen because they all have a Tg below -17°C, unlike comparative compositions 9, 10, 13 and 16 which have a Tg above -17°C. Furthermore, compositions 11, 12, 14, 15 and 17-18 according to the invention also have a lower MFI than comparative compositions 9, 10, 13 and 16. Finally, compositions 11, 12, 14, 15 and 17-18 according to the invention are less prone to agglomeration, in particular because their loss factor tan 5 is lower than that of comparative compositions 9, 10, 13 and 16.

[0304] Furthermore, the strength of the opening of the 5 èmeThe opening of composition 11 was also determined for a test specimen obtained by bubble / blow co-extrusion between two layers of Total Energies LD 0304 low-density polyethylene (LDPE), with the co-extrusion head at a temperature of approximately 190°C. Once the complex was obtained (adhesive composition thickness of approximately 15 µm, between two LDPE thicknesses: one of 30 µm and the other of 15 µm), a heat-sealing and adhesion measurement procedure identical to that described in Example 1 was performed. The adhesion strength of the 5 ème The opening is 0.82 N / cm; therefore, composition 11 according to the invention can be used in a bubble / blowing coextrusion process to obtain lidding films with good resealability. The agglomeration properties of compositions 9 and 11 were also evaluated as shown in Example 1, and the conclusions are shown in Table 3.

[0305] Table 3

[0306] Composition 11 according to the invention exhibits better storage resistance than comparative composition 9. Indeed, whether stored for 30 days at 40°C or 50°C, composition 11 according to the invention is easily processable. In contrast, comparative composition 9 is agglomerated and more difficult to deagglomerate.

Claims

Demands 1. Self-adhesive, hot-melt composition comprising: - a mixture S of styrene block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, the hot melt index at 200°C and 5 kg of mixture S being between 3 g / 10 min and 20 g / 10 min, and - at least one tackifying resin, in which the weight ratio of S mixture / tackifying resin is between 67 / 33 and 77 / 23.

2. Composition according to claim 1, wherein the mixture S comprises between 10% and 60% by weight of at least one styrene-isoprene-styrene triblock copolymer and between 40% and 90% by weight of at least one styrene-isoprene diblock copolymer relative to the total weight of the mixture S.

3. Composition according to claim 1 or 2, wherein the hot melt index at 200°C and 5 kg of mixture S is between 4 g / 10 min and 18 g / min, more preferably between 5 g / 10 min and 15 g / min.

4. Composition according to any one of claims 1 to 3, wherein the content of mixture S is between 60% by weight and 85% by weight relative to the total weight of the composition.

5. Composition according to any one of claims 1 to 4, wherein at least one tackifying resin is selected from: - natural and modified rosins, such as gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, polymerized rosin, - natural and modified rosin esters, in particular glycerol and pentaerythritol esters such as glycerol esters of pale wood rosin, glycerol esters of polymerized rosin, pentaerythritol esters of pale wood rosin, pentaerythritol esters of tall oil rosin, pentaerythritol esters of phenolically modified rosin, - Polyterpene resins, generally resulting from the polymerization of terpene hydrocarbons, such as the monoterpene known as pinene, in the presence of Friedel-Crafts catalysts preferably at moderately low temperatures, - terpene copolymers with a diene monomer, preferably an aromatic diene monomer such as a styrene monomer, - Phenolic modified terpene resins, such as those resulting from the condensation, in an acidic medium, of a terpene and a phenol, - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers, - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers, - petroleum hydrocarbon resins (C5 / C9), resulting from the polymerization of a mixture of aliphatic C5 and aromatic C9 hydrocarbon monomers, - dicyclopentadiene petroleum resins (DCPD), resulting from the polymerization of dicyclopentadiene monomers possibly mixed with C9 aromatic hydrocarbon monomers and / or C5 aliphatic hydrocarbon monomers, in particular C5 aliphatic hydrocarbon monomers, - their corresponding hydrogenated derivatives, and - their mixtures.

6. Composition according to any one of claims 1 to 5, wherein the total content of at least one tackifying resin is between 13% by weight and 33% by weight relative to the total weight of the composition.

7. Composition according to any one of claims 1 to 6, further comprising one or more additives.

8. Composition according to any one of claims 1 to 7, wherein the weight ratio of mixture S / tackifying resin is between 68 / 32 and 77 / 23, preferably between 70 / 30 and 77 / 23.

9. Composition according to any one of claims 1 to 8, in the form of granules having an average size of between 1 mm and 10 mm, preferably between 2 and 6 mm, said granules being preferably coated with a layer of a slippery and / or anti-blocking agent at a maximum of 1.5% by weight relative to the total weight of the granules.

10. Composition according to any one of claims 1 to 9, having a fifth opening peel strength at 180° greater than or equal to 0.55 N / cm for a thickness of 15 pm of said composition between two polyethylene substrates, a hot melt index at 190°C and 2.16 kg less than 25 g / 10 min, preferably less than or equal to 21 g / 10 min, more preferably less than or equal to 19 g / 10 min, and a glass transition temperature less than -17°C.

11. Multilayer structure comprising: - an adhesive layer consisting of the self-adhesive, hot-melt composition according to any one of claims 1 to 10, - a heat-sealable layer, and - a complexable layer, in which the adhesive layer is located between the heat-sealable layer and the complexable layer.

12. Multilayer structure according to claim 11, wherein the heat-sealable layer has a softening temperature between 80°C and 180°C, preferably between 100°C and 160°C.

13. Method of manufacturing the multilayer structure according to claim 11 or 12 by lamination or by coextrusion, in particular by bubble blow coextrusion.

14. Resealable packaging comprising the multilayer structure according to claim 11 or 12.

15. Use of the multilayer structure according to claim 11 or 12 for the manufacture of a resealable package, preferably for food, in particular for chilled or frozen food.

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