Self-adhesive hot melt composition

Abstract

The invention relates to a 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, and - at least one tackifying resin, in which the weight ratio of mixture S to tackifying resin is at least 67 / 33. The present invention also relates to a multilayer structure comprising the self-adhesive hot-melt composition according to the invention, its manufacturing process, and its use. Furthermore, the present invention relates to a resealable package. Figure for the abstract: none

Description

Title of the invention: Self-adhesive hot melt composition Scope of the invention

[0001] 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. Technical background

[0002] Multilayer articles (or laminated articles) are used in many fields for packaging a wide variety of products, particularly in the food, cosmetics, and detergent industries. Depending on the requirements, these articles can be flexible or rigid. They are notably used for flexible packaging. These articles are generally made of different materials (composite multilayer articles). The materials can be chosen from paper, metal, or thermoplastic polymers.

[0003] The characteristics and properties of multilayer articles will depend in particular on the materials used to obtain the layers. Thus, it is common to combine layers comprising different materials in order to obtain multilayer articles, most commonly composite multilayer articles, combining the characteristics and properties of the different individual layers and therefore having particular characteristics and properties.

[0004] Among multilayer articles, there are resealable packages used in the food industry and large-scale distribution for packaging foodstuffs, particularly fresh produce. These packages generally comprise a container (or receptacle) and a lid (or sealing film) which are hermetically sealed together by heat sealing. After the lid is opened and some of the food product in the receptacle is consumed, the user can reposition the lid on the receptacle to re-seal the package in a substantially airtight manner, thus preserving the remaining portion of the product. Repeated opening and resealing is also possible.

[0005] The container for these packages generally comprises a thermoformed plastic sheet designed to have a flat base on which the food product rests and a flat, strip-shaped perimeter. This perimeter, generally parallel to the base, is heat-sealed to the lid, which is made of a multilayer film.

[0006] When the consumer opens the packaging, the sealing film is manually separated from the receptacle at the level of the flat strip around its perimeter. This operation reveals the adhesive layer initially contained within the sealing film.

[0007] A simple manual pressure then allows the packaging to be resealed, once the lid has been repositioned on the receptacle in accordance with their position in the packaging before opening.

[0008] In most resealable packaging available on the market, the lidding film is a multilayer structure which includes a layer comprising a self-adhesive hot meltable composition (or HMPSA for "Hot Melt Pressure Sensitive Adhesive") bonding a complexable layer and a heat-sealable layer.

[0009] The HMPSA composition typically comprises one or more tackifying resins and one or more styrenic block copolymers. When applied in its molten state, it solidifies upon cooling, thus forming an adhesive layer that ensures the bonding of the complexable and heat-sealable layers.

[0010] The complexable layer can be complexed with other layers for the production of the lidding film, for example with a rigid layer to improve the mechanical strength of said film.

[0011] The heat-sealable layer allows the lidding film to be sealed onto the receptacle by heat sealing.

[0012] The laminating and heat-sealable layers can be based on a thermoplastic polymer such as a polyolefin like polyethylene and / or polypropylene. These polymers have a low melt flow index (MFI), while the HMPSA composition generally has a high MFI. Because of these differences, it is therefore difficult to co-extrude these different materials (particularly by bubble blowing) to obtain a sealing film.

[0013] However, a very low MFI implies very cohesive properties, which are in opposition to the adhesive properties necessary to obtain a resealable lidding film.

[0014] The present invention aims to provide a self-adhesive hot-melt composition that can be co-extruded (for example, by bubble blowing), in particular with a polyolefin such as polyethylene and / or polypropylene, while maintaining good adhesion properties, so that the lidding film using said composition can undergo several opening / closing cycles while maintaining good sealing quality.

[0015] Furthermore, the present invention aims to provide a self-adhesive hot melt composition ensuring good sealing quality even when resealable packages are placed in the freezer.

[0016] Furthermore, it is desirable that the self-adhesive hot-melt composition be able to be stored even at high temperatures (for example, 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, preventing 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 (for example, between 40°C and 50°C). Summary of the invention

[0017] The present invention relates to a self-adhesive, hot-melt composition comprising:

[0018] - a mixture S of styrenic block copolymers comprising at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, and

[0019] - at least one tackifying resin,

[0020] in which the weight ratio of mixture S / tackifying resin is at least 67 / 33.

[0021] The present invention also relates to a multilayer structure comprising:

[0022] - an adhesive layer made of the self-adhesive hot melt composition according to the invention,

[0023] - a heat-sealable layer, and

[0024] - a complexable layer,

[0025] 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 a resealable package.

[0029] The self-adhesive hot-melt 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 5th opening, and a hot flow index suitable for its use in bubble blow coextrusion, particularly with a polyolefin such as polyethylene and / or polypropylene.

[0030] 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.

[0031] In addition, 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. Description of the invention Self-adhesive hot melt composition

[0032] The term "hot melt" is used in this text to indicate that the composition is solid at room temperature (for example, between 18°C ​​and 25°C) and needs to be heated to melt and then be 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 obtained by Dynamic Mechanical Analysis (DMA). DMA conditions are given in Example 1 below. Mixture S

[0033] 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.

[0034] By "styrenic block copolymers" is meant block copolymers comprising at least one polystyrene block (whether entirely or partially block-based, such as gradient copolymers, preferably entirely block-based). Styrenic block copolymers may be linear or branched (for example, star, brush, or comb-shaped), preferably linear.

[0035] Advantageously, 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, 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.

[0036] In the context 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%.

[0037] The mixture S may have a styrenic motif content of between 10% and 50% by weight relative to the total weight of the mixture S, preferably between 13% and 19% by weight.

[0038] 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. The hot melt flow rate can be measured according to ISO 1133 (in particular according to procedure A).

[0039] Unless otherwise indicated, the standards mentioned throughout the application are those in force on the date of filing of the application.

[0040] 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, in particular with polystyrene standards.

[0041] Preferably, the mixture S consists of at least one styrene-isoprene-styrene triblock copolymer and at least one styrene-isoprene diblock copolymer, that is to say, 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).

[0042] 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. Tackifying resin

[0043] The composition according to the invention comprises at least one tackifying resin.

[0044] At least one tackifying resin may be selected from:

[0045] - natural and modified rosins, such as gum rosin, the wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, polymerized rosin

[0046] - natural and modified rosin esters, in particular glycerol esters and pentaerythritol 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,

[0047] - polyterpenic resins, generally resulting from polymerization of terpenic 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),

[0048] - terpene copolymers with a diene monomer, preferably a aromatic diene monomer such as a styrene monomer (e.g. styrene, methylstyrene, etc.),

[0049] - phenolic modified terpene resins, such as those resulting from the condensation, in an acidic medium, of a terpene and a phenol,

[0050] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0051] - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers,

[0052] - petroleum hydrocarbon resins (C5 / C9), resulting from the polymerization of a mixture of C5 aliphatic hydrocarbon monomers and C9 aromatic monomers,

[0053] - dicyclopentadiene petroleum resins (DCPD), resulting from polymerization of dicyclopentadiene monomers possibly mixed with C9 aromatic hydrocarbon monomers and / or C5 aliphatic hydrocarbon monomers, in particular C5 aliphatic hydrocarbon monomers,

[0054] - their corresponding hydrogenated derivatives (resulting from a total hydrogenation or (partial later), and

[0055] - their mixtures.

[0056] 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.

[0057] Examples of C9 aromatic hydrocarbon monomers useful for preparing the petroleum resins mentioned above include vinyltoluene, indene, methylstyrene, α-methylstyrene, styrene and / or methylindene.

[0058] Preferably, at least one tackifying resin is chosen from:

[0059] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0060] - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers,

[0061] - petroleum hydrocarbon resins (C5 / C9), resulting from the polymerization of a mixture of C5 aliphatic hydrocarbon monomers and C9 aromatic monomers,

[0062] - dicyclopentadiene petroleum resins (DCPD), resulting from polymerization of dicyclopentadiene monomers possibly mixed with C9 aromatic hydrocarbon monomers and / or C5 aliphatic hydrocarbon monomers, in particular C5 aliphatic hydrocarbon monomers,

[0063] - their corresponding hydrogenated derivatives (resulting from a total hydrogenation or (partial later), and

[0064] - their mixtures.

[0065] In particular, at least one tackifying resin is selected from:

[0066] - petroleum resins of aliphatic hydrocarbons (C5), resulting from the polymerization of C5 hydrocarbon monomers,

[0067] - dicyclopentadiene petroleum resins (DCPD), resulting from polymerization of dicyclopentadiene monomers possibly mixed with C5 aliphatic hydrocarbon monomers,

[0068] - their corresponding hydrogenated derivatives (resulting from a total hydrogenation or (partial later), and

[0069] - their mixtures.

[0070] The tackifying resin may have a softening temperature of at least 80°C, preferably between 80°C and 150°C, 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.

[0071] The weight-average molecular weight of the tackifying resin can vary between 200 g / mol and 5000 g / mol, preferably between 300 g / mol and 3000 g / mol. The weight-average molecular weight can be measured by size-exclusion chromatography, in particular with polystyrene standards.

[0072] The total content of at least one tackifying resin in the composition according to the invention can 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. Additives

[0073] 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.

[0074] 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.

[0075] The filler can be chosen from organic fillers, mineral fillers, and mixtures thereof.

[0076] As an example of mineral fillers, any mineral filler commonly used in adhesive compositions may be cited. These fillers typically take the form of particles of various geometries. They may, for example, be spherical, fibrous, or have an irregular shape.

[0077] The mineral filler can be chosen from clays (such as talc), quartz, carbonate fillers (in particular calcium carbonate, which can be coated with acids) fats (the latter being preferably 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.

[0078] The mineral charge can be untreated or treated, for example with an organic acid including stearic acid.

[0079] The average particle size of the mineral charge can range from 10 nm to 400 pm, preferably from 20 nm to 100 pm, more preferably from 30 nm to 10 pm.

[0080] 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).

[0081] As an example of an organic filler, any organic filler, in particular polymeric, commonly used in the field of adhesive compositions may be cited.

[0082] 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.

[0083] The average particle size of the organic load may be less than or equal to 15 pm, preferably between 5 and 15 pm.

[0084] 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.

[0085] Ultraviolet (UV) stabilizers are typically introduced to prevent degradation resulting from a reaction with oxygen that may be formed by the action of heat or light. UV stabilizers may include antioxidants capable of scavenging free radicals.

[0086] 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(l-octyloxy-2,2,6,6- tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-4-piperidyl)sebacate (CAS No: 41556-26-7), methyl l,2,2,6,6-pentamethyl-4-piperidyl sebacate (CAS No: 82919-37-7), 4,4'-bis(a,a-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0087] The UV stabilizer (or antioxidant) content can 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 (in particular polyethylene, polypropylene, polyisobutylene, polybutadiene, etc., functionalized or not), ethylene and 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 made 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 R1 represents a hydrogen atom or a methyl radical, and -X- represents -O- or -NR11- with R11 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 can be chosen from among thixotropic agents, for example from: - fumed silica (hydrophilic and / or hydrophobic), - urea derivatives resulting 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 (particularly CAS 8006-40-4 and / or 8012-89-3), and - their mixtures.

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

[0093] By "amide waxes" is meant waxes comprising one or more compounds having at least one amide group. In particular, amide waxes can be obtained from organic acid(s) (for example 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 rheological agent content can be up to 10% by weight relative to the total weight of the composition according to the invention.

[0096] Core-shell type impact modifiers can generally be described as polymeric substances, typically in the form of particles, comprising a core (inner part) comprising a core polymer and a shell (outer part) comprising 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 the 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 isobomyl ester, 3,3,5-trimethylcyclohexyl, tert-butylcyclohexyl and / or (octahydro-4,7-methano-1H-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 triallyl compounds such as diallyl phthalate, diallyl sebacate and triallyl triazine.

[0102] The volume average diameter of the functionalized core-shell charge can be between 10 and 900 nm. The volume average diameter can be measured by dynamic light scattering (DLS).

[0103] As an example of commercially available core-bark filler, we can cite the Clearstrength® (for example Clearstrength® XT100) or the Durastrength® marketed by Arkema, or the Paraloid™ (Paraloid™ 2650A, Paraloid™ 2691A) marketed 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 selected from organic pigments, inorganic pigments, and mixtures thereof. For example, the pigment can be selected from phthalocyanine-based pigments (such as copper phthalocyanine, halogenated copper phthalocyanine, metal-free phthalocyanine), anthraquinone-based pigments (such as l-methylamino-4-o-tolylaminoanthraquinone, 1,4-diisopropyl aminoanthraquinone, 1,4-diaminoanthraquinone, 1,4-dibutyl-aminoanthraquinone, l-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. Other features

[0107] Advantageously, the weight ratio of S mixture / tackifying resin is 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.

[0108] Advantageously, the composition according to the invention does not include any other styrenic block copolymers than those of mixture S.

[0109] According to one embodiment, the composition according to the invention comprises:

[0110] - between 60% by weight and 85% by weight of a mixture S of block copolymers styrenic compounds 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,

[0111] - between 13% by weight and 33% by weight of at least one tackifying resin, and

[0112] - 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-shell type impact modifiers, pigments, and mixtures thereof,

[0113] wherein the weight ratio of S mixture / tackifying resin is between 67 / 33 and 85 / 15,

[0114] the percentages by weight being, unless otherwise indicated, in relation to the total weight of the composition.

[0115] 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.

[0116] The ingredients of this embodiment and their particular contents are as described above, including preferred embodiments and features.

[0117] In particular, the composition according to the invention comprises:

[0118] - between 63% by weight and 80% by weight of a mixture S of block copolymers styrenic compounds 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 the mixture S,

[0119] - between 18% by weight and 30% by weight of at least one tackifying resin, of preference selected from aliphatic hydrocarbon C5 petroleum resins, aromatic hydrocarbon C9 petroleum resins, C5 / C9 hydrocarbon petroleum resins, dicyclopentadiene petroleum resins (possibly in mixture with C9 and / or C5 monomers), their corresponding hydrogenated derivatives, and mixtures thereof, and

[0120] - 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-shell type impact modifiers, pigments, and mixtures thereof,

[0121] wherein the weight ratio of the S mixture / tackifying resin is between 70 / 30 and 80 / 20,

[0122] the percentages by weight being, unless otherwise indicated, in relation to the total weight of the composition.

[0123] Preferably, the composition according to the invention consists essentially of the ingredients mentioned above.

[0124] The ingredients of this embodiment and their particular contents are as described above, including preferred embodiments and features.

[0125] 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.

[0126] 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).

[0127] 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.

[0128] The composition according to the invention may be in the form of granules, preferably of ovoidal or spheroidal shape, the average size of which is between 1 mm and 10 mm, preferably between 2 and 6 mm.

[0129] The average size of the granules can be measured using a caliper.

[0130] Said granules are preferably coated with a layer of a sliding and / or anti-blocking agent at a maximum of 1.5% by weight relative to the total weight of the granules.

[0131] 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, in particular talc.

[0132] The composition according to the invention can be prepared by a process comprising:

[0133] - a step of mixing the ingredients while hot, for example between 90°C and 200°C, of preferably using a twin-screw extruder, then

[0134] - a cutting step of the extruded mixture, preferably at the exit of the die, then

[0135] - a cooling step, for example to room temperature (23°C).

[0136] Preferably, the cutting step is implemented so 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.

[0137] An example of preparation is described in Example 2. Multilayer structure

[0138] The present invention also relates to a multilayer structure comprising:

[0139] - an adhesive layer made of the self-adhesive hot melt composition according to the invention,

[0140] - a heat-sealable layer, and

[0141] - a complexable layer,

[0142] in which the adhesive layer is located between the heat-sealable layer and the complexable layer. Adhesive layer

[0143] The self-adhesive hot melt composition according to the invention is as described above, including preferred embodiments and features.

[0144] The adhesive layer may have a thickness of between 5 µm and 50 µm, preferably between 7 µm and 25 µm. 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 receptacle), 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. This softening temperature can be measured according to ASTM E28-67.

[0146] The heat-sealable layer may be based on a thermoplastic polymer. In particular, the heat-sealable layer comprises at least 90% by weight of a or several thermoplastic polymers relative to the total weight of said layer, preferably at least 95% by weight, more preferably at least 99% by weight.

[0147] The thermoplastic polymer can be selected from:

[0148] - polyethylene (PE),

[0149] - polypropylene (PP),

[0150] - polyamide (PA),

[0151] - a polyester polymer, for example comprising at least one motif derived from cyclic or acyclic diol (preferably acyclic) and at least one motif derived from 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),

[0152] - 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 alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0153] - polystyrene (PS),

[0154] - polyvinyl chloride (PVC),

[0155] - polyvinylidene fluoride (PVDF),

[0156] - a lactic acid polymer (PLA),

[0157] - a polyhydroxyalkanoate (PHA), and

[0158] - their mixtures.

[0159] 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, even more preferably polyethylene.

[0160] The heat-sealable layer may further include one or more additives, for example selected from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, anti-fog agents, anti-static agents, and mixtures thereof.

[0161] 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.

[0162] 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(l-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl l,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(a,a-dimethylbenzyl)diphenylamine), and their mixtures.

[0163] 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.

[0164] The anti-fog agent may be selected from sorbitan esters, glycerol esters, poly(oxyethylene) esters, alkylbenzene sulfonates, and mixtures thereof; said esters are in particular fatty acid(s) esters.

[0165] The antistatic agent may be selected from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0166] The heat-sealable layer is advantageously breakable.

[0167] The heat-sealable layer can be pre-cut over all or part of its thickness, for example using a laser or a cutting plate.

[0168] The heat-sealable layer can be bi-oriented.

[0169] The bi-orientation of one (or more) layer(s) can be achieved by stretching the layer(s) under heating (for example, by infrared heating, for example, at a temperature above 100°C) in the machine direction (also called axial) and by stretching under heating (for example, 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 (in particular about 3.0) in the machine direction, and between 3.0 and 4.0 (in particular about 3.4) in the transverse direction.

[0170] By "approximately X", we are aiming for plus or minus 10% of the value of X.

[0171] The heat-sealable layer may have undergone surface treatment, such as embossing (preferably hot), plasma treatment such as corona treatment, atmospheric pressure plasma treatment, flame plasma treatment, chemical plasma treatment, etc.

[0172] The heat-sealable layer may have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm. Complexable layer

[0173] The complexable layer 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.

[0174] 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.

[0175] The thermoplastic polymer can be selected from:

[0176] - polyethylene (PE),

[0177] - polypropylene (PP),

[0178] - polyamide (PA),

[0179] - a polyester polymer, for example comprising at least one motif derived from cyclic or acyclic diol (preferably acyclic) and at least one motif derived from 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, preferably PET,

[0180] - 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 alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0181] - polystyrene (PS),

[0182] - polyvinyl chloride (PVC),

[0183] - polyvinylidene fluoride (PVDF),

[0184] - a lactic acid polymer (PLA),

[0185] - a polyhydroxyalkanoate (PHA), and

[0186] - their mixtures.

[0187] 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, even more preferably polyethylene.

[0188] The complexable layer may further comprise one or more additives, for example chosen from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, antistatic agents, and mixtures thereof.

[0189] 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.

[0190] 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(l-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl l,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(a,a-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0191] 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.

[0192] The antistatic agent may be selected from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0193] The complexable layer can be bi-oriented.

[0194] The complexable layer may have undergone a surface treatment, such as an embossing treatment (preferably hot), a plasma treatment such as a corona treatment, an atmospheric pressure plasma treatment, a flame plasma treatment, a chemical plasma treatment, etc.

[0195] The complexable layer can have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm. Additional layers

[0196] 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).

[0197] For example, the multilayer structure according to the invention may comprise: - 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).

[0198] 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.

[0199] Advantageously, the heat-sealable layer has a free face (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 onto the receptacle via the heat-sealable layer.

[0200] It is not excluded 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.

[0201] 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.

[0202] The thermoplastic polymer may be selected from:

[0203] - polyethylene (PE),

[0204] - polypropylene (PP),

[0205] - polyamide (PA),

[0206] - a polyester polymer, for example comprising at least one motif derived from cyclic or acyclic diol (preferably acyclic) and at least one motif derived from 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),

[0207] - 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 alkyl acrylate copolymer such as methyl acrylate (EMA) or butyl acrylate (EBA),

[0208] - polystyrene (PS),

[0209] - polyvinyl chloride (PVC),

[0210] - polyvinylidene fluoride (PVDF),

[0211] - a lactic acid polymer (PLA),

[0212] - a polyhydroxyalkanoate (PHA), and

[0213] - their mixtures.

[0214] Each additional layer may further comprise one or more additives, for example selected from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, antistatic agents, and mixtures thereof.

[0215] 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.

[0216] The UV stabilizer (or antioxidant) can be selected 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(l-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl l,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(a,a-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0217] 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.

[0218] The antistatic agent may be selected from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof.

[0219] Each additional layer can be bi-oriented.

[0220] 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.

[0221] Each additional layer may have a thickness between 0.1 pm and 100 pm, preferably between 1 pm and 50 pm.

[0222] The heat-sealable film may have a thickness of between 2 pm and 150 pm, preferably between 3 pm and 100 pm.

[0223] The complexable film can have a thickness between 5 pm and 150 pm, preferably between 10 pm and 100 pm.

[0224] The heat-sealable film is advantageously tearable.

[0225] The heat-sealable film can be pre-cut along all or part of its thickness, for example using a laser or a cutting plate.

[0226] The heat-sealable film can be bi-oriented.

[0227] The complexable film can be bi-oriented. Other features

[0228] 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.

[0229] According to one embodiment, the multilayer structure according to the invention comprises:

[0230] - 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,

[0231] - a heat-sealable and breakable layer, preferably based on a polymer thermoplastic selected from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof,

[0232] - a complexable layer, preferably based on a thermoplastic polymer selected from polyethylene, polypropylene, a polyester polymer, an ethylene-propylene copolymer, and mixtures thereof, and

[0233] - optionally one or more additional layers,

[0234] in which the adhesive layer is located between the heat-sealable layer and the complexable layer.

[0235] The layers of this embodiment are as described above, including preferred embodiments and features.

[0236] 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.

[0237] Method for manufacturing the multilayer structure

[0238] 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 blow coextrusion.

[0239] According to a first embodiment, the manufacturing process for the multilayer structure according to the invention comprises:

[0240] - a step of coating with an adhesive comprising the self-adhesive composition hot-melt according to the invention on a surface of a first film, then

[0241] - a step of laminating (bonding) a surface of a second film onto the coated surface of the first film,

[0242] wherein one of the films comprises the heat-sealable layer or is bonded to the heat-sealable layer after the lamination step, and

[0243] wherein one of the films comprises the complexable layer or is bonded to the complexable layer after the lamination step.

[0244] 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 features. In particular, the heat-sealable layer preferably has a free face.

[0245] The first film and the second film can each be single-layer or multi-layer.

[0246] The coating step can be carried out on all or part of the surface of the first film, preferably in a continuous or substantially continuous manner.

[0247] 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.

[0248] The solvent content may be between 10% and 95% by weight relative to the total weight of the adhesive, preferably between 50% and 90% by weight.

[0249] 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.

[0250] 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 by lamination with one or more layers of the multilayer structure.

[0251] According to a second embodiment, the manufacturing process of the multilayer structure according to the invention comprises 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.

[0252] The multilayer structure, the self-adhesive hot-melt composition, the heat-sealable layer, the complexable layer, and the additional layers are such that described above, including preferred embodiments and characteristics. In particular, the heat-sealable layer preferably has a free side.

[0253] 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 by lamination with one or more layers of the multilayer structure.

[0254] 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:

[0255] - the melting, in separate extruders, of the constituent compositions and materials adhesive, heat-sealable and laminateable layers, and optionally additional layers, then

[0256] - the passage of the corresponding flows through a set of annular channels and concentric, so as to form a multi-layered tubular bubble, in the order corresponding to that desired for the final structure, then

[0257] - radial expansion (relative to the annular channel) and stretching (in the direction axial) of the bubble, then

[0258] - the cooling of the bubble.

[0259] The geometric characteristics of the dies, as well as the process parameters such as the radial expansion rate and the stretching speed, are fixed to obtain the desired thickness for the various constituent layers of the multilayer structure. Reference is made, in particular, to US patent application 2013 / 0029553 for a more detailed description of the bubble blow coextrusion process. Resealable packaging

[0260] The present invention also relates to a resealable package comprising the multilayer structure according to the invention.

[0261] In particular, the resealable packaging includes a receptacle and a lid made up of the multilayer structure according to the invention.

[0262] Advantageously, the lid is heat-sealed around the perimeter of the receptacle.

[0263] The receptacle is preferably made of a plastic polymer, for example selected from:

[0264] - polyethylene (PE),

[0265] - polypropylene (PP),

[0266] - polyamide (PA),

[0267] - polyethylene terephthalate (PET),

[0268] - an ethylene copolymer, for example a maleic anhydride grafted copolymer, an ethylene-propylene copolymer, an ethylene-acetate copolymer vinyl (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),

[0269] - polystyrene (PS),

[0270] - polyvinyl chloride (PVC),

[0271] - polyvinylidene fluoride (PVDF),

[0272] - a lactic acid polymer (PLA),

[0273] - a polyhydroxyalkanoate (PHA), and

[0274] - their mixtures.

[0275] The total thermoplastic polymer(s) content 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.

[0276] The receptacle may further include one or more additives, for example selected from UV stabilizers (or antioxidants), sliding and / or anti-blocking agents, pigments, antistatic agents, and mixtures thereof.

[0277] 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.

[0278] The UV stabilizer (or antioxidant) can be selected 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(l-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl l,2,2,6,6-pentamethyl-4-piperidyl sebacate and 4,4'-bis(a,a-dimethylbenzyl)diphenylamine), and mixtures thereof.

[0279] 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.

[0280] The pigment may be selected from organic pigments, inorganic pigments, and mixtures thereof. For example, the pigment may be selected from manganese ferrite, titanium dioxide, carbon black, iron oxide, aluminum, talc, and mixtures thereof, in particular titanium dioxide, carbon black, and mixtures thereof.

[0281] The antistatic agent may be selected from alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes, tertiary amines, glycerol monostearate, mixtures of glycerol monostearate and tertiary amines, and mixtures thereof. Use of the multilayer structure

[0282] 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.

[0283] Advantageously, the multilayer structure is used as the lid of the resealable packaging.

[0284] Preferably, the resealable packaging is as described above, including preferred embodiments and features.

[0285] All the embodiments described above can be combined with each other. In particular, the various aforementioned constituents of the composition, and especially the preferred embodiments, can be combined with each other.

[0286] The following examples are given purely for illustrative purposes of the invention and should not be interpreted as limiting its scope. Examples Example 1#: Ingredients and Measurement Methods Ingredients used

[0287] The following ingredients were used: - JH8161 (by Ningbo Jinhai Chenguang Chemical Corporation): copolymer styrene-isoprene-styrene blocks having a styrenic motif content of approximately 16% by weight, a dibloc copolymer content of approximately 50% by weight, and a hot melt index at 200°C and 5 kg of approximately 11 g / 10 min, - YH1126 (by SINOPEC): styrene-isoprene-styrene block copolymer having a styrenic motif content of approximately 16% by weight, a diblock copolymer content of approximately 50% by weight, and a hot melt index at 200°C and 5 kg between 8 and 14 g / 10 min, - JH-3204 (by Jinhai): C5 aliphatic hydrocarbon resin having a Softening temperature between 96 and 104°C, tackifying resin, - Escorez™ 1310LC (by ExxonMobil): C5 aliphatic hydrocarbon resin with a softening temperature of approximately 94°C, tackifying resin, 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. Measurement methods

[0288] The meltflow index (MFI) was measured in accordance with 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 weight of 2.16 kg was then placed on the sample. The material flowing through the die over a given time was weighed to determine the MFI. This is expressed in g / L at 190°C for a weight of 2.16 kg.

[0289] A Dynamic Mechanical Analysis (DMA) was performed on a sample of the composition to be tested on an ARES rheometer (marketed by TA Instruments), using 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 sample holder designed for this purpose. The temperature was raised to 190°C to obtain a melt, then a temperature ramp down to -40°C was applied simultaneously with a shear at a frequency of 10 rad / s. The temperature ramp applied was -8°C / min for temperatures from 190°C to 0°C, then -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 θ peak is observed.

[0290] The elastic modulus G' (also called the conservation modulus) and the loss factor (tan ô) were determined at 24°C, during the temperature descent.

[0291] The adhesion strength of the 5th opening was determined as follows: the composition was first dissolved in ethyl acetate to obtain a 20% wt. 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 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 composite (20 sq m / 55 sq m, respectively) was laminated to each side of the stack (PE face on the PE substrates), then heat-sealed between jaws of 1 cm x 5 cm heated to 130°C for 1 second and under a pressure of 600N. The areas thus heat-sealed define the test specimens used for adhesion and resealability measurements.

[0292] Adhesion measurements were carried out 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 reclosed (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.

[0293] The agglomeration properties were evaluated using the compositions to be tested 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 obtain 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, so that the total mass of material above the granules was equivalent to 62.5 g / cm². The resulting stack was then placed in an oven at 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.

[0294] Example 2: Self-adhesive hot melt compositions comprising the JH8161 copolymer

[0295] Compositions 1-8 were prepared by extrusion in a twin-screw extruder of the ingredients listed in Table 1 below (percentages being 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, then the mixture was fed into the twin-screw extruder and recovered at the outlet either as rods or as granules (for the latter, a cold-water cutting was performed, then the granules were dried and talc-coated). A consistent temperature ramp is present on the body of the twin-screw extruder, so as to have 90°C at the inlet and 170°C at the outlet, while the screws have a co-rotation speed ranging from 400 to 700 rpm. The compositions are usable directly after cooling.

[0296] Their properties were then evaluated according to the methods described in Example 1 above.

[0297] [Tables 1] No. JH8161 JH-32 04 Escorez™ 1310LC MFI (g / 10 min) Tg (° C) cm „ 5 opening (N / cm) G' (Pa ) tan ô 1 (comp •) 60% 40% - 35.4 -6.2 1.02 46020 0.36 2 (comp •) 63% 37% - 27 -15 0.99 62720 0.32 3 (inv.) 72% 28% - 16.8 -23.6 1.04 79827 0.27 4 (inv.) 77% 23% - 11.3 -32 0.64 86014 0.28 5 (comp •) 60% - 40% 33.6 -8.5 0.67 39452 0.32 6 (comp •) 63% - 37% 29 -13 0.64 49340 0.29 7 (inv.) 73% - 27% 21 -21 0.58 77983 0.27 8 (inv.) 77% - 23% 18 -31 0.55 87432 0.25

[0298] All the tested compositions have a 5th opening strength of at least 0.5 N / cm for an adhesive composition thickness of 15 micrometers. They are therefore suitable for the manufacture of resealable packaging that can withstand several opening / closing cycles while maintaining good sealing quality.

[0299] However, comparative compositions 1, 2, 5, and 6 are not suitable for resealable packages intended for freezing. Indeed, their Tg is above -17°C. On the other hand, 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.

[0300] 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, particularly with a polyolefin such as polyethylene and / or polypropylene, to obtain lidding films.

[0301] 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 that they are less likely to undergo a deformation at the study temperature) and their loss factor tan θ is lower (meaning they are less prone to flow). The loss factor tan θ is a more important parameter than the modulus of elasticity G' for assessing the risk of agglomeration.

[0302] Example 3: Self-adhesive hot melt compositions comprising the YH1126 copolymer

[0303] Compositions 9-15 were prepared by mixing the ingredients indicated in Table 2 below (the percentages being percentages by weight relative to the total weight of the composition), following the same procedure as that described in Example 2.

[0304] Their properties were then evaluated according to the methods described in Example 1 above.

[0305] [Tables2] N° YH112 6 Escorez™ 1310LC SU-1 30 JH-32 04 MFI (g / l / min) Tg (°C) rème „ 5 overrture (N / cm) G' (Pa) tan ô 9 (with P-) 60% 40% - - 29 -10 0.85 47010 0.37 10 (with P-) 63% 37% - - 25 -12 0.82 59385 0.35 11 (inv •) 72% 28% - - 20 -28 0.79 80400 0.28 12 (inv •) 77% 23% - - 15.3 -32 0.63 92467 0.28 13 (with P-) 60% - 40% - 29.2 -7 0.86 56029 0.34 14 (inv •) 72% - 28% - 20.6 -20 0.76 72590 0.28 15 (inv •) 77% - 23% - 14 -30 0.66 88285 0.23 16 (with P-) 63% - - 37% 32.5 -9 0.59 61181 0.33 17 (inv •) 68% - - 32% 20.8 -24 0.58 58160 0.27 18 (inv •) 73% - - 27% 18.6 -30 0.59 90694 0.25 19 (inv •) 77% - - 23% 17.1 -32 0.55 95734 0.23

[0306] Replacing the JH8161 copolymer with the YH1126 copolymer 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 the 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 ô is lower than comparative compositions 9, 10, 13 and 16.

[0307] Furthermore, the opening force of the 5th 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 carried out. The adhesion force of the 5th opening is 0.82 N / cm; composition 11 according to the invention can therefore be used in a bubble / blow co-extrusion process to obtain lidding films with good resealability.

[0308] The agglomeration properties of compositions 9 and 11 were also evaluated as shown in Example 1 and the conclusions are shown in Table 3.

[0309] [Tables3] Composition 40°C / 30d 50°C / 30d 9 (comp.) Agglomerated, moderately desagglomerable Very agglomerated, difficult to desagglomerate 11 (inv.) Very slightly agglomerated, easily desagglomerable Slightly agglomerated, easily desagglomerable

[0310] Composition 11 according to the invention is more resistant to storage than the comparative composition 9. Indeed, whether after storage for 30 days at 40°C or at 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. A 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, and - at least one tackifying resin, wherein the weight ratio of mixture S / tackifying resin is at least 67 / 33.

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 content of mixture S is between 60% by weight and 85% by weight relative to the total weight of the composition.

4. A composition according to any one of claims 1 to 3, 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, - esters of natural and modified rosins, 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 hydrocarbons terpenes, 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, - aliphatic hydrocarbon (C5) petroleum resins, resulting from the polymerization of C5 hydrocarbon monomers, - aromatic hydrocarbon (C9) petroleum resins, resulting from the polymerization of C9 hydrocarbon monomers, - (C5 / C9) hydrocarbon petroleum resins, resulting from the polymerization of a mixture of aliphatic C5 and aromatic C9 hydrocarbon monomers, - dicyclopentadiene (DCPD) petroleum resins, resulting from the polymerization of dicyclopentadiene monomers, possibly mixed with aromatic C9 hydrocarbon monomers and / or aliphatic C5 hydrocarbon monomers, in particular aliphatic C5 hydrocarbon monomers, - their corresponding hydrogenated derivatives, and - their mixtures.

5. Composition according to any one of claims 1 to 4, 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.

6. Composition according to any one of claims 1 to 5, further comprising one or more additives.

7. Composition according to any one of claims 1 to 6, wherein the weight ratio of mixture S / tackifying resin is 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.

8. Composition according to any one of claims 1 to 7, 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 sliding and / or anti-blocking agent at a maximum of 1.5% by weight relative to the total weight of the granules.

9. Composition according to any one of claims 1 to 8, having a fifth peel opening adhesion strength at 180° greater than or equal to 0.55 N / cm for a thickness of 15 µm of said composition between two polyethylene substrates, an index hot fluidity 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.

10. Multilayer structure comprising: - an adhesive layer made up of the self-adhesive hot melt composition according to any one of claims 1 to 9, - a heat-sealable layer, and - a complexable layer, wherein the adhesive layer is located between the heat-sealable layer and the complexable layer.

11. Method of manufacturing the multilayer structure according to claim 10 by lamination or by coextrusion, in particular by bubble blow coextrusion.

12. Resealable packaging comprising the multilayer structure according to claim 10.

13. Use of the multilayer structure according to claim 10 for the manufacture of a resealable package, preferably for food, in particular for chilled or frozen food.