FR2855179A1 - AGGLOMERATE OF PARTICLES, ESPECIALLY CORK, COMPRISING A VULCANIZED SILICONE BINDER, USE OF THIS AGGLOMERATOR FOR THE MANUFACTURE OF PLUGS - Google Patents

Abstract

The field of the invention is that of the manufacture of agglomerates of particles comprising a vulcanized silicone composition. The object of the invention is to provide a new raw material consisting of an agglomerate of particles, the consistency of which is given by a crosslinked silicone binder, and suitable for serving as a raw material for the manufacture of stoppers for wine bottles allowing effective corking. and a good vinification. For this, the binder comprises: (1) at least one vinylated polyorganosiloxane (POS), (2) at least one hydrogenated POS, (3) a platinum catalyst, (4) at least one hydrogenated POS resin (4.1), optionally alkenylated and / or combined with at least one other alkenylated POS resin (4.2), (5) and possibly at least one crosslinking inhibitor / retarder; The particles are made of cork. However, it is conceivable that the agglomerate further comprises particles of expandable plastic. The invention also relates to the methods of manufacturing the agglomerate and of the stoppers.

Description

Agglomerate of particles, in particular cork, comprising a silicone binder

  The field of the invention is that of the manufacture of particle agglomerates comprising a vulcanized silicone composition. More specifically, these particles can be particles of plant, lignocellulosic materials, in particular cork. The articles likely to be produced from this agglomerate are more specifically stoppers.

  More precisely still, the stoppers considered are, for example, those intended for closing bottles of alcoholic or non-alcoholic drinks, such as wines and spirits.

  Cork is a material that has been known for a long time for corking wine bottles or other sparkling drinks or not. It is a plant tissue produced by cork oaks and partly made up of dead cells with alveolar structure and filled with gases of composition similar to that of air. Cork is therefore a compressible, elastic, waterproof and hydrophobic natural material. Its tightness is expressed vis-à-vis liquids, but cork remains permeable vis-à-vis air gases (water vapor, oxygen, carbon dioxide). It therefore allows the breathing of wines or the like, thus allowing them to age properly, without oxidizing, in order to achieve the desired organoleptic qualities.

  To be suitable for corking, cork is nonetheless a natural material of variable quality. The resources of noble natural cork, free from defects, are limited.

  The professionals concerned therefore sought to develop advantageous alternative materials, particularly in terms of quality / price ratio.

  This is how agglomerated materials based on particles, in particular cork, have been proposed. Conventionally, these agglomerates based on cork 30 are shaped into stoppers, for example for bottles, according to a compression / molding procedure at high temperature (greater than 50 ° C. and less than 150 ° C.).

  By way of illustration of this distant technological background from the invention, mention may be made of French patent application FR-A-2 528 346 which discloses a method for manufacturing agglomerated cork stoppers, as well as a machine for the implementation of this process. These plugs are obtained by extruding a paste consisting of a mixture of pieces of cork and binder, so as to obtain solidified extruded bars, of rectangular section and in which the plugs are cut transversely to the direction of extrusion.

  In the same vein, European patent EP-B-0 496 687 describes a composition useful as a base for the preparation of agglomerated cork intended for the manufacture of stoppers. This composition comprises: between 5 and 15% of expandable microspheres (100-200 μm) of copolymers of methyl methacrylate and of acrylonitrile forming a thermoplastic material with a cellular structure capable of providing elasticity; - between 40 and 60% cork powder and / or granules; - between 35 and 50% of polyurethane glue; - less than 10% latex, wax, water and polymerization catalyst for the cellular thermoplastic material.

  EP-B-0 496 687 describes in fact an agglomerated composite of acrylic plastic material / cork particles / polyurethane binder / latex-wax-water catalyst.

  In an attempt to improve the physico-chemical and mechanical characteristics of such agglomerated stoppers comprising cork particles, it has been proposed, in PCT patent application WO-A-99/00230, a process for manufacturing agglomerated stoppers in cork, from cork granules selected for their richness in suberin. The selection of these granules is effected by grinding cork sheets into granules, decomposition of these cork granules by means of shock waves produced by a plasma created in an aqueous medium, so as to obtain, on the one hand, granules rich in lignin and on the other hand granules rich in suberin which are separated. The isolated granules rich in suberin can then be mixed with a binder formed for example by a food adhesive of the polyurethane or acrylic type.

  These binders of the polyurethane glue type used in known cork agglomerates contain, inter alia, variable amounts of extractable isocyanates of low molecular weight and therefore toxic and unfit for food contact. Such binders should also soon be prohibited by law.

  Japanese patent application JP-A-9235469 describes a silicone composition crosslinkable by polyaddition and containing cork particles as an additive. This composition constitutes a raw material for molding stoppers for bottles of various drinks, in particular wines or whiskeys. This composition comprises 100 parts by weight of polyorganosiloxanes (POS) per 5 to 25 parts by weight of cork particles with an average diameter of between 0.2 and 10 mm. The POSs in question include at least one POS having at least two -Si-unsaturated units per molecule and at least one hydrogenated POS comprising at least two -Si-H units per molecule, as well as a platinum catalyst. A molded stopper is obtained by crosslinking this composition. The latter does not include adhesion promoters, so it adheres very poorly to the cork particles. This explains the use of a large amount of silicone elastomer to obtain a plug which shows a suitable mechanical strength. The silicone is no longer a binder, but constitutes the continuous phase of the agglomerate. This corresponds to amounts of at least 75% w / w, or even 95% w / w of silicone elastomer in the agglomerate. These amounts of silicone are totally prohibitive from an economic point of view. In fact, this material is more like a piece of silicone rubber loaded with cork particles than a cork stopper agglomerated using a silicone binder.

  In this state of the art, one of the essential objectives of the present invention is to provide a new raw material consisting of an agglomerate of particles whose consistency is given by a crosslinked silicone binder, said agglomerate having to present interesting physico-chemical and mechanical properties and to be otherwise economical.

  Another essential objective of the present invention is to provide a new raw material formed by an agglomerate of particles bound by a crosslinked silicone, this raw material being perfectly suitable for the production of stoppers constituting advantageous substitutes for stoppers entirely made of natural cork. noble free from defect.

  Another essential objective of the present invention is to provide a new agglomerated material essentially constituted by particles, for example of cork, and a crosslinked silicone binder which is a good material for the capping and the preservation of drinks such as wines or other alcohols, that is to say a material which is compressible, sufficiently elastic, liquid-tight and gas-permeable, hydrophobic and which contains little moisture (eg 5%) but which is capable of hydrating slowly , so as to ensure correct aging and improvement of wines or other alcohols, without oxidation.

  Another essential objective of the present invention is to provide an agglomerate of particles, for example of cork, linked by a crosslinked silicone, which can be used as a raw material for the manufacture of stoppers, which is economical and which has an almost zero toxicity of so as to be perfectly harmless and suitable for food contact.

  Another essential objective of the present invention is to provide a new material agglomerated with particles, for example cork, bound by a crosslinked silicone, which is economical, easy to prepare and easily transformable for example by molding and / or extrusion and / or machining into caps for containers of beverages, eg wine bottles.

  Another essential objective of the present invention is to provide an agglomerate of particles (for example of cork) linked together by means of a crosslinked silicone, said agglomerate being intended inter alia for the manufacture of stoppers for bottles of wine or other drinks, and having the following properties, among others: * tightness to liquids, * controlled permeability to gases (02, C02, water vapor), * mechanical consistency, * harmlessness making it suitable for food contact, 20 * absence of taste production undesirable, * good compromise elasticity / compressive force, so as to produce an effective closure which allows good vinification.

  Another essential objective of the present invention is to provide new stoppers constituted by an agglomerate of cork particles bound by a crosslinked silicone, which stoppers have to be competitive in economic, food and at least quality as close to that of noble corks free from defects, as the agglomerated cork substitutes known until then.

  Another essential objective of the present invention is to provide a method of manufacturing agglomerates based on particles, for example cork, bound by a crosslinked silicone, which is simple to implement and economical.

  Another essential objective of the present invention is to provide a process for manufacturing cork stopper substitutes, from a raw material consisting of an agglomerate essentially comprising particles, for example cork, and as a minor constituent , a binder formed by a crosslinkable silicone.

  These objectives, among others, are achieved by the present invention which primarily relates to an agglomerate of particles comprising a vulcanized silicone composition characterized in that this vulcanized silicone composition is a binder present in a mass concentration of less than 75% by weight. / p, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w.

  It is therefore to the credit of the inventors to have used in this agglomerate a vulcanized or crosslinked silicone binder. This binder constitutes a continuous phase in which is included a dispersed phase consisting of solid particles, for example of woody or lignocellulosic vegetable material (cork, wood) or of mineral or organic nature. The continuous binder phase in crosslinked silicone ensures the cohesion of the assembly, in particular giving it good mechanical behavior making it possible, among other things, to prevent it from crumbling under stress. This crosslinked or vulcanized silicone binder provides the agglomerate with elastic properties (elastic return) which are suitable under the effect of compressive forces which remain acceptable, with regard to the industrial constraints of plugging on bottling lines. This crosslinked or vulcanized silicone binder is moreover compatible with the liquid tightness and gas permeability properties sought in the field of capping of beverage containers, in particular of wine.

  Within the meaning of the invention, the term “vulcanized” means “crosslinked” or “hardening” of the silicone binder composition. These terms will be used interchangeably in this presentation.

  In practice, weight proportions of dispersed particles / crosslinked silicone are between 45 / 55-65 / 35, for example of the order of 50/50 by weight.

  In accordance with the invention, it has appeared advantageous to use silicone compositions which can be crosslinked into an elastomer and more particularly silicone compositions which can be crosslinked, the viscosity of which is between 100 and 000, preferably 1,000 and 10,000 Pa.s at 25 C.

  All the viscosities referred to in the present description correspond to a quantity of dynamic viscosity which is measured, in a manner known per se, at 25 ° C., for example to a gradient of shear speed sufficiently low so that the viscosity measured is independent of the speed gradient.

  The viscosities selected in accordance with the invention for the 5 vulcanizable silicone compositions used correspond to compositions preferably chosen from the group comprising: * the single-component silicone compositions (EVF I) which can be cold vulcanized into elastomers, in the presence of moisture, ambient temperature and comprising at least one polyorganosiloxane (POS) carrying hydroxyl units functionalizable by oxime, acyl, amine, amide or alkoxy radicals and at least one crosslinker carrying at least one type of these functionalization radicals; * the mono or bicomponent silicone compositions (EVF I or 11) which can be vulcanized when cold, into elastomers at room temperature by polyaddition, in the presence of a metallic catalyst.

  To further improve the mechanical properties, in particular the cohesion, the harmlessness ("food contact") and the organoleptic compatibility of this agglomerate, in particular with a view to applications for capping beverages such as wines, it is recommended to use in accordance with the invention a vulcanized binder silicone composition obtained from a silicone composition vulcanizable by hydrosilylation and comprising: ò (a) at least one POS species having, per molecule, at least two alkenyl groups, preferably of C2-C6 , related to silicon; In (8) and at least one POS species having, per molecule, at least two hydrogen atoms bonded to silicon; ò (6) optionally, in addition to or in replacement of the POS species (a) and / or of the POS species (fA), at least one POS species (a) having, per molecule, at least two alkenyl groups, preferably C2-C6 bonded to silicon and at least two hydrogen atoms bonded to silicon; (y) and a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the platinum group; with the condition that at least one of the POS species (a) and / or (/ i) 35 and / or (6) is a linear or branched POS and at least one other of the POS species (f) and / or (6) is a POS resin with -SiH patterns, preferably adjacent.

  Preferably, the vulcanized silicone composition is obtained from a vulcanizable silicone composition comprising: (1) at least one polyorganosiloxane having, per molecule, at least two alkenyl groups, in C2-C6 bonded to silicon, (2) and / or at least one polyorganosiloxane having, per molecule, at least two hydrogen atoms bonded to silicon, (3) a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the platinum group, (4 ) at least one polyorganosiloxane resin (4.1) having, per molecule, at least two hydrogen atoms bonded to silicon (= SiH), and optionally at least two alkenyl groups (preferably C2C6), this resin (4.1) being optionally combined with at least one other resin (4.2) having, per molecule, at least two alkenyl groups (preferably C2-C6), linked to silicon, (5) and optionally at least one crosslinking inhibitor / retarder .

  Advantageously, these POS compositions comprise -SiOH or Si-OR functions with R = preferably C1-C6 alkyl, e.g. methyl, hydrolyzable to = Si-OH.

  Such silicone compositions (1), (2), (3), (4), (5) allow good adhesion of the silicone binder to the particles, for example cork or other mineral or organic woody plant material (lignocellulosic). In the case where the particles contain OH, the presence of = Si-OH, or possibly = Si-OR functions as defined above, can only promote the bonds between the continuous binder phase and the particulate dispersed phase, and therefore the cohesion and mechanical strength of the agglomerate.

  In this regard, the hydrogenated POS resin (4.1) of the preferred binder silicone composition of the agglomerate of the invention constitutes an important component because of its function of promoting adhesion between the particles (for example of rich cork in cellulosic OH) and the silicone binder. Indeed, the hydrogenated POS resin (4.1), advantageously with a high rate of units = -SiH, and more advantageously still with adjacent units -SiH, is - without wishing to be bound by theory - strongly involved in the binding effect.

  Within the meaning of the invention: The term "high rate of units = SiH" corresponds, for example, to hydrogen contents by weight greater than or equal to 0.0001%, preferably 0.001%, and even more preferably 0.003 %; the term "-SiH adjacent" means that the -SiH are in position D relative to each other, as is for example the case in the following product: Ra Ra'Si (H) -O- If (H) Ra2Ra3 with RRa Ra Ra2Ra3 = -O-SiMe3; -O- SiMe2-O-; -O-SiMe (O-) 2; -0-Si (O-) 3; alkyl; aryle etc ...

  We will return later to the qualitative and quantitative characteristics of this POS resin (4), and we will first of all endeavor to give some details on the constituent of the predominantly weighty silicone composition, namely the POS. alkenylated (1). Preferably, the POS (1) has: (i) siloxy units of formula: Ta Zb SiO 4- (a + b) (1.1) in which: - T is an alkenyl group, preferably vinyl or allyl, - Z is a monovalent hydrocarbon group, free from any adverse action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms included, optionally substituted with at least one halogen atom, and also among aryl groups, - a is 1 or 2, best 0, 1 or 2 eta + best between 1 and 3, and (2i) optionally other siloxy units of formula: ZcSiO 4 -c (1.2) 2 in which Z a the same meaning as above and ca a value between 0 and 3.

  It is advantageous that this polydiorganosiloxane has a viscosity at least equal to 100 mPa.s and preferably between 5,000 and 200,000 mPa. s.

  The polyorganosiloxane (1) can be formed only of units of formula (1.1) or can additionally contain units of formula (1.2). Likewise, it may have a linear, branched, cyclic or network structure.

  Z is generally chosen from methyl, ethyl and phenyl radicals, at least 60 mol% (or by number) of the radicals Z being methyl radicals.

  Examples of siloxyl units of formula (1.1) are the vinyldimethylsiloxyl unit, the vinylphenylmethylsiloxyl unit, the vinylmethylsiloxyl unit and the vinylsiloxyl unit.

  Examples of siloxyl units of formula (1.2) are the SiO4 / 2, 5 dimethylsiloxyl, methylphenylsiloxyl, diphenylsiloxyl, methylsiloxyl and phenylsiloxyl units.

  Examples of polyorganosiloxanes (1) are linear and cyclic compounds such as: dimethylpolysiloxanes with dimethylvinylsilyl ends, (methylvinyl) (dimethyl) polysiloxanes with trimethylsilyl ends, (methylvinyl) (dimethyl) polysiloxanes copolymers with dimethylvinylsilyl ends; cyclic methylvinylpolysiloxanes.

  The polyorganosiloxane (2) is preferably of the type of those comprising: (i) siloxy units of formula: Hd SiO 4- (d + e) (2.1) in which - L is a monovalent hydrocarbon group, free of action unfavorable on the activity of the catalyst and preferably chosen from alkyl groups having from 1 to 8 carbon atoms included, optionally substituted with at least one halogen atom, advantageously from methyl, ethyl, propyl and 3,3,3-trifluoropropyle and as well as among the aryl groups and, advantageously, among the xylyl, tolyl and phenyl radicals, - d is 1 or 2, e is 0, 1 or 2, d + has a value between 1 and 3, preferably between 2 and 3, and (2i) optionally other siloxy units of average formula Lg SiO4_g (2.2) in which L has the same meaning as above and g has a value of between 0 and 3, preferably between 2 and 3.

  The dynamic viscosity of this polyorganosiloxane (2) is at least equal to mPa.s and, preferably, it is between 20 and 1000 mPa.s.

  The polyorganosiloxane (2) can be formed only of units of formula 35 (2.1) or additionally comprise units of formula (2.2).

  The polyorganosiloxane (2) can have a linear, branched, cyclic or network structure.

  Group L has the same meaning as group Z above.

  Examples of units of formula (2.1) are: H (CH3) 2SiO1 / 2, HCH3SiO2 / 2, H (C6H5) SiO2 / 2 The examples of units of formula (2.2) are the same as those given above for the units of formula (1.2).

  Examples of polyorganosiloxane (2) are linear and cyclic compounds such as: - dimethylpolysiloxanes with hydrogenodimethylsilyl ends, - copolymers with (dimethyl) (hydrogenomethyl) polysiloxanes with trimethylsilyl ends, - copolymers with (dimethyl) (hydrogenomethyl) units polysiloxanes with hydrogenodimethylsilyl ends, - hydrogenomethylpolysiloxanes with trimethylsilyl ends, - cyclic hydrogenomethylpolysiloxanes.

  The ratio of the number of hydrogen atoms bound to silicon in the polyorganosiloxane (2) to the total number of alkenyl unsaturated groups of the polyorganosiloxane (1) and of the resin (4) is between 0.4 and 10, preferably between 0.6 and 5.

  The bases of polyaddition silicone compositions may contain only linear polyorganosiloxane (1) and (2) such as, for example, those described in the patents: US-A-3,220,972, US-A-3,697,773 and US-A -4,340,709 or contain both branched or networked polyorganosiloxane (1) and (2), such as for example those described in the patents: US-A-3,284,406 and US-A-3,434,366.

  Preferably, use is made of: - at least one linear polyorganosiloxane (1) comprising chains formed of units of formula (1.2) oc = 2, blocked at each of their ends by units of formula (1.1) oa = 1 and b = 2, and - and / or at least one linear polyorganosiloxane (2) comprising in its structure at least three hydrogen atoms bonded to silicon, located in the chains and / or at the chain ends.

  Even more preferably, use is made of: - at least one linear polyorganosiloxane (1) comprising chains formed of units of formula (1.2) oc = 2, blocked at each of their ends by units of formula (1.1) oa = 1 and b = 2, and - and / or at least one linear polyorganosiloxane (2) comprising chains formed of units of formula (2.1) od = 1 and e = 1 and possibly of units of formula (2.2) og = 2 , blocked at each of their ends by patterns of formula (2.1) od = 1 and e = 2.

  Catalysts (3) are also well known. The compounds of platinum and rhodium are preferably used. It is possible, in particular, to use the complexes of platinum and of an organic product described in patents US-A3 159 601, US-A-3 159 602, US-A-3 220 972 and European patents EP-A0 057 459, EP-A-0 188 978 and EP-A-0 190 530, the platinum and vinyl organosiloxane complexes described in patents US-A-3,419,593, US-A3 715,334, US-A- 3,377,432 and US-A-3,814,730. The generally preferred catalyst is platinum. In this case, the quantity by weight of catalyst (3), calculated by weight of platinum-metal, is generally between 2 and 400 ppm, preferably between 5 and 200 ppm based on the total weight of the polyorganosiloxanes (1) and ( 2).

  The silicone binder composition of the agglomerate according to the invention preferably further comprises at least one polyorganosiloxane resin (4.1) comprising, per molecule, at least two -SiH, and optionally at least two -Si-alkenyl, this same resin (4.1) being possibly associated with at least one other resin (4.2) having per molecule at least two = -Si-alkenyl.

  The hydrogenated polyorganosiloxane resin (4.1) has e.g .: * a hydrogen content by weight of between 0.0001 and 1% by weight and preferably between 0.0001 and 0.5% by weight.

  The possible alkenylated polyorganosiloxane resin (4.2) has e.g. * a content by weight of alkenyl group (s) of between 0.1 and 20% by weight and preferably between 0.2 and 10% by weight.

  These resins [(4): (4.1) and (4.2)] are well known and commercially available branched organopolysiloxane oligomers or polymers. They have, in their structure, at least two different units chosen from those of formula R 3SiO1 / 2 (unit M), R 2SiO2 / 2 (unit D), R SiO3 / 2 (unit T) and SiO4 / 2 (unit Q ), At least one of these units being a unit Q. The radicals R are identical or different and are chosen from hydrogen, linear or branched C1-C6 alkyl radicals, C2-C4 phenyl alkenyl radicals , trifluoro-3,3,3 propyl. Mention may, for example, be made: as alkyl radicals R, methyl, ethyl, isopropyl, tert-butyl and n-hexyl radicals, and as alkenyl radicals R, vinyl radicals.

  It should be understood that in the resins (4) of the aforementioned type, a part of the radicals R are hydrogen and / or alkenyl radicals. In this case, the 10 siloxyl units considered are annotated M ', D', T 'for R = H and Malc, Dalc, Talc, for R = alkenyl and for example MvT, Dvi, TVT for R = vinyl.

  As examples of resins (4), mention may be made of MQ resins, MDQ resins, DTQ resins and MDTQ resins, hydrogen or alkenyl residues which may be carried by the units M, D and / or T. As examples of resins which are particularly suitable, mention may be made, for example, of: * hydrogenated MDQ resins (4.1) having a hydrogen content by weight of between 0.0001 and 0.016% by weight and preferably between 0.001 and 0.013% by weight; * vinylized MDQ resins (4.2) having a weight content of vinyl group of between 0.2 and 10% by weight.

  This resin (4) has the function of increasing the mechanical resistance of the silicone elastomer as well as its adhesion. According to a preferred characteristic of the invention, the hydrogenated POS resin (4.1), optionally alkenylated, (preferably vinylated), comprises: * -SiH functions, preferably adjacent; * and optionally OR functions advantageously included in Si-OR units in which R = H or alkyl (preferably Cl-C6, e.g. methyl). The OR = alkyl groups are hydrolyzable into OH groups.

  These H, OH or OR functions are capable of binding with OH or 35 OR functions present in the particles of dispersed phase of the agglomerate. This is particularly the case when these particles are particles of plant, woody or lignocellulosic material (cork, wood), so it should be emphasized that in such cases the mechanical cohesion of the agglomerate does not is that improved.

  The optional alkenylated resin (4.2) associated with the hydrogenated resin (4.1) may also include OR functions.

  In quantitative terms, the resin (4) is present in an amount of 10 to 70% by weight relative to all of the constituents of the silicone binder composition.

  In practice, the concentration of resin (4) in the silicone binder composition is between 10 and 30% by dry weight, preferably between 15 and 25% by dry weight, for example of the order of 20% by dry weight per relative to all the constituents of the silicone binder composition of the agglomerate according to the invention. According to another advantageous characteristic of the invention, the proportions of (1) and / or (2) and (4) in the silicone binder composition are such that the ratio of the number of hydrogen atoms bonded to silicon in the polyorganosiloxane (2) and / or in the resin (4.1), on the number of alkenyl radicals provided by the polyorganosiloxane (1) and / or the resin (4.2) is between 0.4 and 10.

  Advantageously, the silicone composition according to the invention may also comprise at least one inhibitor / retarder (5) of the addition reaction (crosslinking inhibitor), chosen from the following compounds: - polyorganosiloxanes substituted by at least one alkenyl which may be optionally present in cyclic form, tetramethylvinyltetracyclosiloxane D4 being particularly preferred, - pyridine, - organic phosphines and phosphites, - unsaturated amides, - alkyl maleates - and acetylene alcohols.

  Advantageously, the agglomerates according to the invention designed so that they are acceptable from the food point of view (contact), in particular for the plug application. In this perspective, inhibitors / retarders (5) of the pyridine type, phosphines, organic phosphites, unsaturated amides and alkylated maleates, should be avoided.

  These acetylenic alcohols, (Cf. FR-B-1 528 464 and FR-A-2 372 874), which are part of the preferred hydrosilylation reaction thermal blockers, have the formula: R '- (R ") C ( OH) - C _ CH formula in which, - R 'is a linear or branched alkyl radical, or a phenyl radical; - R "is H or a linear or branched alkyl radical, or a phenyl radical; the radicals R', R "and the carbon atom located at oc of the triple bond possibly forming a ring; the total number of carbon atoms contained in R 'and R" being at least 5, preferably from 9 to 20.

  Said alcohols are preferably chosen from those having a boiling point above 250 C. Mention may be made, by way of examples: - 1-ethynyl-cyclohexanol-1; - 3-methyl-dodecy-1 ol-3; - trimethyl-3,7,1 1 dodecy-1 ol-3; - Diphenyl-1,1 propyne-2 ol-1 ethyl-3 ethyl-6 nonyne-1 ol-3; - 2-methyl-butyne-3 ol-2; - 3-methyl-pentadecyne-1 ol-3.

  These cL-acetylenic alcohols are commercial products.

  Such a retarder (5) is present at a rate of 3000 ppm at most, preferably at the rate of 100 to 1000 ppm relative to the total weight of the organopolysiloxanes (1) and (2).

  In a manner known per se, the silicone binder elastomer composition of the agglomerate according to the invention can be added with various conventional additives such as, for example, treated or untreated silicas, TiO2, FeO3, A1203, carbon black, ground quartz. ..

  Advantageously, the cold-vulcanizable silicone composition, precursor of the crosslinked silicone binder, is a two-component system which is defined as follows: - it is in two distinct parts A and B intended to be mixed to form the composition, - one of these parts A and B comprise the catalyst (3) and a single species (1) and / or (2) of polyorganosiloxane, - and the resin (4) can be used in part A or part B or in the two parts A and B, the catalyst (3) not having to be present in part A or B containing POSs with -SiH units and POSs with -Si-alkenyl (vinyl) units.

  Thus, part A can, for example, contain a part of the polyorganosiloxane (1), of the resin (4.1) with patterns = SiH, of the possible resin (4.2) with patterns -Si-vinyl and optionally the 'crosslinking inhibitor (5); while part B may, for example, contain the remaining part of the polyorganosiloxane (1), the catalyst (3), the remaining part of the optional resin (4.2) with patterns = -Si-vinyl and possibly another additive (eg silica).

  The viscosity of parts A and B and their mixture can be adjusted by varying the amounts of the constituents and by choosing polyorganosiloxanes of different viscosity.

  Once mixed together, parts A and B form a silicone composition (EVF II) ready for use.

  The crosslinking of the binder and crosslinkable silicone composition, in admixture with the dispersed phase particles, can be caused and / or activated thermally and / or by electromagnetic radiation (accelerated electron radiation or "electron beam").

  As already appears in the description above, one of the preferred embodiments of the agglomerate according to the invention corresponds to that in which the particles of dispersed phase are particles of woody, even lignocellulosic plant material, preferably cork particles possibly associated with polymerizable / expandable (thermo) plastic material particles.

  Naturally, these cork particles are perfectly suitable for an agglomerate intended to form the material constituting caps for beverage containers, in particular for wine bottles.

  As other examples of particles of dispersed phases, mention may be made of: wood particles, - particles of plastic materials, in particular expandable polymer or copolymer microspheres as described in European patent EP-B-0 496 687; this polymer or copolymer is for example chosen from the group comprising: polymers or copolymers of vinyl chloride, polymers or copolymers of vinylidene, polymers or copolymers of vinyl chloride and acrylonitrile, polymers or copolymers of chloride vinylidene, acrylonitrile and methyl methacrylate, polymers or copolymers of styrene and acrylonitrile, polymers or copolymers of ethylene or vinyl acetate, polymers or copolymers of methyl methacrylate and acrylonitrile or mixtures thereof , the copolymers of methyl methacrylate and acrylonitrile being more especially selected - and their mixtures.

  According to a variant of the invention, the particulate dispersed phase can be eg composed of 60 to 90% by weight of lignocellulosic plant material powder (eg cork) and 40 to 10% by weight of expandable plastic microspheres (eg microspheres expandable copolymers of methyl methacrylate and acrylonitrile according to EP-B-0 496 687), the ratio 80/20 cork / expandable plastic microspheres is one example among others.

  Another object of the present invention consists of a plug characterized in that it comprises agglomerated material as defined above. Preferably, the stopper according to the invention is produced from an agglomerate comprising particles of lignocellulosic plant material, in particular cork particles, and a crosslinked silicone binder of composition (1) and / or (2), (3), (4) or even (5), as described above.

  In the remainder of the description, the question of the manufacture of the agglomerate according to the invention as well as of the agglomerated stopper constituting one of the preferred embodiments of said invention is addressed.

  As regards the agglomerate, its manufacturing process is characterized in that it consists essentially in mixing the particles with the vulcanizable silicone binder composition in proportions such that the mass concentration of silicone binder is less than 75% w / p, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, optionally shaping this mixture by subjecting it or not to compression, then making sure that the vulcanization of the silicone binder takes place to finally recover the hardened agglomerate.

  The means for mixing the crosslinking binder silicone composition with the particles, for example cork, are mixers of a type known per se, and suitable for kneading and homogenizing pasty products having a viscosity between 100 and 10,000 mPa .s, preferably around 5,000 mPa.s.

  In the variant according to which the mixture of particles / non-crosslinked silicone binder is shaped and optionally compressed, it is possible to use for this purpose molding (or extrusion) devices under pressure known in themselves and perfectly the scope of the skilled person.

  It is advantageous that the vulcanization / crosslinking takes place at a temperature above room temperature, for example between 100 and 150 ° C., to activate / accelerate the hardening process. The molding and extrusion devices capable of being used are equipped with heating means contributing to the promotion of the crosslinking of the silicone binder and of the expansion of any expandable plastic microspheres.

  In the case where an extruder is used, it is possible to use, as described in French patent application FR-A-2 528 346, extrusion dies producing cylindrical tubes which can be cut according to the desired length, or alternatively plates or bars which can also be cut to the desired dimensions or else machined or worked with suitable tools, for example cookie cutters to produce articles of desired shapes.

  As regards the manufacture of agglomerated stoppers, it essentially consists, according to a first embodiment, of mixing the particles with the vulcanizable binder silicone composition in proportions such that the mass concentration of binder silicone is less than 75 % w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, to put this mixture in the form of a plug by subjecting it to compression, then to make so that the vulcanization of the silicone binder intervenes to freeze this form and recover after hardening the targeted plug.

  The compression of the agglomerate forming the stopper is important because it partly determines the elastic return, which must have a sufficient value to ensure the tightness of the bottle closed using the stopper considered.

  This shaping and this compression can be carried out in molding devices known in themselves and suitable. The mixture of dispersed phase / compressed crosslinkable silicone binder is then vulcanized at room temperature or preferably at a temperature between 50 and 150 ° C., for example 120 ° C., for a few minutes.

  To do this, either the mold is equipped with integrated heating means, or the mold is introduced into an oven capable of bringing the compressed agglomerated material to the desired temperature.

  After hardening and cooling, the plug is removed from the mold.

  According to a second embodiment of the method for manufacturing the stopper according to the invention, the methodology adopted essentially consists in mixing the particles with the vulcanizable binder silicone composition in proportions such that the mass concentration of binder silicone is less than 75 % w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, possibly compressing this mixture, then ensuring that the vulcanization of the silicone binder takes place to hardening of the mixture of agglomerated material, from which the plug is then shaped.

  In this method of implementation, the binder / particle mixture, possibly compressed, is hardened by vulcanization preferably at a temperature above room temperature (for example between 50 and 150 C: - 120 C), then setting final shape of the plug is produced on the hardened chipboard 15 vulcanized by conventional machining techniques, for example by cutting.

  Naturally, the agglomerated plugs obtained by these two examples of embodiments of the method according to the invention, consist of the continuous phase and the dispersed phase as defined above, namely in particular that the silicone binder is of the type (1) (2) (3) (4) (5) and the particles are preferably particles of cork, or even particles of other lignocellulosic materials, optionally added with particles of possibly expandable plastic material, preferably expandable microspheres of copolymers of methyl methacrylate and of acrylonitrile as described in EP-B-0 496 687.

  In practice, the composition of the raw materials of the agglomerate could consist of: - 100 parts by weight of cork powder; - 40 to 100 parts by weight of silicone binder (1) and / or (2) (3) (4) (5); - 0 to 20 parts by weight, preferably 10 parts by weight of polymerizable expandable plastic microspheres; - 0 to 5 parts by weight of water and / or wax and / or paraffin and / or latex emulsion; - 0 to 1 part by weight of catalyst for polymerization of the expanding microspheres of thermoplastic (co) polymer.

  The examples which follow, of preparation of the agglomerate and of its application for the manufacture of closures with technical evaluation of the latter, will make it possible to better understand the invention and to highlight its advantages and its variant embodiments. The performance of the composition of the invention will be highlighted by comparative tests.

EXAMPLES:

  In these examples, the viscosity is measured using a BROOKFIELD viscometer according to the indications of standard AFNOR NFT 76 106 10 of May 82.

  The acronyms EVF (Cold Vulcanizable Elastomer) and RTV (<"Room Temperature Vulcanizing") will be used interchangeably in the following, to design POS belonging to this family.

  Example 1: EXAMPLE OF PREPARATION OF BINDING COMPOSITIONS 1.- Preparation of a silicone binder composition for the agglomerate according to the invention (composition C): 1.1 - Preparation of part A of the bicomponent: In a reactor at room temperature is mixed : parts by weight of a polyorganosiloxane (1.1) consisting of a polydimethylsiloxane oil blocked at each end of the chains by an MVi motif: (CH3) 2ViSiO1 / 2, having a viscosity of 3500 mPa.s and containing 0.2 functions Si-Vi per 100 g of oil constituting hereinafter referred to as oil (1.1).

  parts by weight of resin (4.2) of MDVIQ structure containing 2.2% by weight of vinyl groups (Vi) and consisting of 41% by weight of M units: (CH3) 3SiO1 /, 2, of 7% by weight of Dvi units: (CH3) ViSiO2 / 2, 52% by weight of Q units: SiO4 / 2 constituent hereinafter called resin (4.2).

  0.001 parts by weight of platinum metal, introduced in the form of an organometallic complex at 12% by weight of platinum metal, known under the name of Karstedt catalyst, hereinafter constituting platinum of catalyst (3).

  1.2 - Preparation of part B of the two-component: In a reactor at room temperature, 45 parts by weight of a polyorganosiloxane (1.1) consisting of a polydimethylsiloxane oil blocked at each of the ends of the chains by a Mvi unit are mixed: (CH3) 2ViSiO1,2, having a viscosity of 3500 mPa.s and containing 0.2 Vi functions per 100 g of oil constituting hereinafter referred to as oil (1.1).

  40 parts by weight of resin (4.1) structure M'4Q containing 80% by weight of units M ': (CH3) 2HSiO1 / 2 and 20% by weight of units Q: SiO4 / 2 constituent hereinafter referred to as resin (4.1) .

  parts by weight of resin (4.2) MDvQ structure containing 2.2% by weight of 15 vinyl groups (Vi) and consisting of 41% by weight of M units: (CH3) 3SiO1 / 2, of 7% by weight of DVi units : (CH3) ViSiO2 / 2, 52% by weight of Q SiO4 / 2 units constituting hereinafter called resin (4.2).

  1.3 - Preparation of the bicomponent: For the tests in which A / B = 100/10, the bicomponent is obtained by mixing, at room temperature, 100 parts by weight of part A and 10 parts by weight of part B. Composition C is thus obtained, the constituents of which are indicated in Table I given below:

Table I

  Product Composition C (parts by weight) Resin (4.1) 3.6 Resin (4.2) 24, 1 Oil (1) 72.3 Catalyst (3) 0.0009 Example 2: FORMULA OF THE PREPARATION FOR THE MANUFACTURE OF THE AGGLOMERATOR ACCORDING TO THE INVENTION Formula: * 50% COMPOSITION C OF EXAMPLE 1 * 50% of a cork powder Example 3: PREPARATION OF A COMPARATIVE EXAMPLE COMP 1 10 3.1) Preparation of part A of the bicomponent In a reactor with room temperature is mixed: 32.9 parts by weight of a ground quarz.

  25.2 parts by weight of a polyorganosiloxane (1.1) consisting of a polydimethylsiloxane oil blocked at each of the ends of the chains with an MVi motif: (CH3) 2ViSiO1 / 2, having a viscosity of 60,000 mPa.s and containing 0.08 20 Vi functions per 100 g of oil constituting the following oil (1.1).

  17.4 parts by weight of a polyorganosiloxane (1.2) consisting of a polydimethylsiloxane oil blocked at each end of the chains by an MVi motif: (CH3) 2ViSiO1 / 2, having a viscosity of 100,000 mPa.s and containing 0.07 25 Vi functions per 100 g of oil constituting the following oil (1.2).

  16.3 parts by weight of resin (4.2) MDVIQ structure containing 2.2% by weight of vinyl groups (Vi) and consisting of 41% by weight of M units: (CH3) 3SiO1 / 2, of 7% by weight of DVi units: (CH3) ViSiO2 / 2, 52% by weight of Q units: SiO4 / 2 30 constituent hereinafter called resin (4.2).

  7.5 parts by weight of a polyorganosiloxane (2) consisting of a polydimethylsiloxane oil blocked at each of the ends of the chains with an MVi motif: (CH3) 2ViSiO1 / 2, having a viscosity of 10,000 mPa.s and containing 0.13 35 Vi functions per 100 g of oil constituting hereinafter referred to as oil (2).

  0.7 parts of tert-butyl titanate.

  0.004 parts by weight of platinum metal, introduced in the form of an organometallic complex at 12% by weight of platinum metal, known under the name of Karstedt catalyst constituting below platinum of the catalyst (3).

  3.2) Preparation of part B of the two-component In a reactor at room temperature, 29.5 parts by weight of a ground quartz are mixed.

  22.7 parts by weight of a polyorganosiloxane (1.1) consisting of a polydimethylsiloxane oil blocked at each end of the chains by an MVi unit: (CH3) 2ViSiO1l / 2, having a viscosity of 60,000 mPa.s and containing 0.08 15 Vi functions per 100 g of oil constituting the following oil (1.1).

  15.5 parts by weight of a polyorganosiloxane (1.2) consisting of a polydimethylsiloxane oil blocked at each of the ends of the chains by an MVi unit: (CH3) 2ViSiO1 / 2, having a viscosity of 100,000 mPa.s and containing 0.07 20 Vi functions per 100 g of oil constituting the following oil (1.2).

  14.7 parts by weight of resin (4.2) MDViQ structure containing 2.2% by weight of vinyl groups (Vi) and consisting of 41% by weight of M units: (CH3) 3SiO1 / 2, of 7% by weight of DVi units: (CH3) ViSiO2 / 2, 52% by weight of Q units: SiO4 / 2 25 constituent hereinafter called resin (4.2).

  6.8 parts by weight of a polyorganosiloxane (2) consisting of a poly (dimethyl) (hydrogenomethyl) siloxane oil blocked at each of the ends of the chains by a unit M ': (CH3) 2HSiO / 2, having a viscosity of 25 mPa.s and 30 containing a total of 0.7 -SiH functions per 100 g of oil (including 0.6 -SiH functions located in the chain) constituting hereinafter referred to as oil (2).

  6.7 parts by weight of a polyorganosiloxane (1.3) consisting of a polydimethylsiloxane oil blocked at each end of the chains by a 35 Mvi motif: (CH3) 2ViSiO1l2, having a viscosity of 10,000 mPa.s and containing 0.13 functions Vi per 100 g of oil constituting the following oil (1.3).

  1.8 parts by weight of vinyltriethoxysilane.

  1.8 parts by weight of glycidoxypropyltrimethoxysilane 0.4 parts by weight of a coloring base based on blue pigment in a PolyDiMethylSiloxane (PDMS) silicone oil.

  0.04 parts by weight of inhibitor (5) consisting of ethynylcyclohexanol (constituent hereinafter inhibitor).

  3.3) Preparation of the bicomponent The bicomponent is obtained by mixing, at room temperature, 100 parts by weight of part A and 10 parts by weight of part B. This gives part C, the constituents of which are indicated in Table II given below: Table II Product COMP 1 (parts by weight) Ground quartz 32.59 Resin (4.2) 16.16 Oil (1.1) 24.97 Oil (1.2) 17.23 Oil (1.3) 7.43 Oil (2) 0.62 T-butyl titanate 0.64 Glycidoxypropyltrimethoxysilane 0.16 Vi nyltriethoxysilane 0.16 Color base 0.04 Catalyst (3) 0.0036 Inhibitor (5) 0.0036

Example 4:

  4.1) Typical preparation of the reactive mixture and molding 2.91 g of composition C part A and 3.49 g of a powder of cork particles are introduced into a 250 ml beaker. The mixture is homogenized. 0.29 g of composition C part B is added (A / B = 100/10; Cork / Silicone = 50/50).

  After homogenization, this mixture is transferred to a stainless steel mold with a Teflon piston. The mixture is compressed by 250%, which corresponds to a reduction in volume of 3.5 times or else to the reduction of the initial volume to 28.6%. At the end of compression, this mold guarantees the correct size of the finished caps (38x22mm).

  The compressed mass is heated in an oven at 120 ° C. for 15 min in order to initiate the crosslinking of the silicone elastomer. Then the mold is cooled to ambient temperature before opening.

The extraction of the plug is easy.

  4.2) Application tests 4.2.1) Qualitative assessment of cohesion The good dispersion of the silicone elastomer is checked by optical microscopy (10x). At the same time, possible product shortages are revealed which are manifested by the presence of crevices, and therefore poor cementing of the cork powder.

  4.2.2) Compression force The compression force is measured by a dynamometric traction device, on which are fitted two plates between which the plug is compressed.

  Compression is done in accordance with ISO 9727 at 10mm / min. The force is measured at a compression of 28.6% which corresponds to the compression 35 undergone by the stopper during bottling with a stopper with a final diameter of 15.5 mm (the most common in the profession).

  The result is expressed in N and rounded to the daN in accordance with the recommendations of the Grouping for the Codification of Measures in the Use of Cork Stoppers (Codiliège).

  4.2.3) Elastic return The cap is relaxed to a diameter of 18.5mm, which corresponds to the interior dimensions of a standard neck. The relaxation force is measured 10 after 2 min (elastic return). This value is important for the tightness of the bottle. It is expressed in N and rounded to the unit.

  4.2.4) Extraction force To measure the extraction force, fill a bottle with water, leaving a 55mm slope (see also the recommendations of the corker Trescases / FFSL "Fédération Française des Sociétés du Liège" ). The bottle is closed with a stopper using a manual capper with a final diameter of 15.5 mm.

  After an hour, the corkscrew is placed so that its helical rod penetrates straight and pierces the cork, protruding by about 3mm.

  The stopper is removed from the bottle using a dynamometer by launching the crosspiece above 300mm / minute. The extraction force corresponds to the maximum force measured. The results are expressed in N by rounding to daN according to the recommendations of Codiliège.

  4.3) RESULTS 4.3.1) Macroscopic results The results of our tests are collated in Table III below: 2855179 26

Table III

  Contact Product Type Cohesion Food observations RTV II Difficult dispersion, COMP 1 Reactive oils / Pt No Good very fast reaction Adhesion promoters and deep RTV II Easy dispersion, ComposiOils and resins Yes Good setting speed C reactive / Pt correct, reticle in depth 4.3.2) Validation of the choice of RTV by optical microscopy The microscopic visualization (10x) of the surfaces and sections of different stoppers prepared with composition C shows the wetting power of this elastomer.

  Composition C makes it possible to obtain good dispersion (absence of crevices) and good cohesion of the agglomerated plugs (resistance to bending). In addition, in this case the cohesion of the plugs can be improved by increasing the compression ratio. The silicone / cork ratio chosen at 50/50 w / w allows us to stay at cost level within the limits of the specifications.

  4.3.3) Comparison of composition C according to the invention in two different proportions C1 & C2 and with a witness from the prior art with identical compression ratio The silicone incorporation rate is 50/50 w / w, which is economically acceptable.

  The compression ratio has been set at 250%.

  This test makes it possible to evaluate the formulations for their performance in terms of leaktightness between bottle and stopper: reduction of the risks of sagging between neck and stopper, especially in an industrial environment where the bottles are tilted in a horizontal position after three minutes after traffic jam.

  The caps with an initial diameter of 21.7mm are compressed to 15.5mm (end of compression by a capper). Then release at 18.5mm (diameter of a neck) and measure the relaxation force after 2 minutes (according to ISO 9727).

  In this test, composition C provides rapid elastic return, therefore suitable for an industrial rate.

  If the rate of part B of composition C is increased from 10% to 20%, the performance is improved.

Table IV

  Binder Return Force Rate silicone Part A / B Cork / Silicone compression elastic compression [N] [%] [N] C1 100/10 50/50 250 680 145 C2 100/20 50/50 250 740 152 Witness Witness - - --- 250 810 155 PU binder The cap based on composition C shows, for a comparable elastic return 10, a compressive force less than the reference. Industrial bottling is thus made easier.

  Technical centers and plug manufacturers recommend the ranges for the compression forces of the plugs according to ISO 9727 as follows: Centro Technologico da Cortiça: 600 - 800 N (agglomerated caps) Jelinek Cork: 500 - 700 N (natural cork caps ) The caps remain perfectly within the range defined for agglomerated caps.

  The dimensional recovery is specified as> 90%. For our stoppers prepared with composition C (A / B: 100/10; RTV / Liège: 50/50; compression rate of 250%), 98% is obtained for the binder composition in accordance with the preferred formulation of the agglomerate according to the invention.

  4.3.4) Influence of the compression ratio in the case of composition C In order to optimize the processing parameters, the evolution of the mechanical performance of the silicone binder stoppers has been studied as a function of the compression ratio.

Results:

TABLE IV

  Cork Binder Strength / Return Rate Part A / B silicone compression Silicone compression [%] elastic compression [N] [N] C3 100/10 50/50 250 680 145 C4 100/10 50/50 300 810 171 C5 100 / 20 50/50 250 740 152 Control --- 250 810 155 PU binder With these obtained rates, compression of 250 conforms to standards.

  and 300%, the characteristics 4.3.5) Influence of the RTV / cork powder ratio The tests were carried out on the basis of an optimized compression rate of 250% for an optimized A / B ratio of 100/20.

  The mechanical properties obtained with a cork / silicone ratio of 70/30 show the limits of the system. The plug is not very stable, cracks are observed during compression and the elastic return is too weak.

  At a rate of 60/40, values are obtained which approach the target. The plug is relatively stable with a correct compressive force, but the elastic return is slightly too weak.

  From a 50/50 ratio, good results are obtained.

TABLE Vl

  Lièg / Force Rate of A / B Cork! / Binder return Part A / B Silicone compression elastic compression [N] [%] [N] C6 100/20 70/30 250 480 86 C7 100/20 60/40 250 660 130 C8 100/20 50/50 250 740 152 Witness Witness --- --- 250 810 155 PU binder 4.3.6) Validation of the choice of binder EVF II C nar evaluation of the extraction force The extraction force of the cork on a standard wine bottle neck is an important feature for its end use. Normally, the cap manufacturer is obliged to treat the surface of natural, agglomerated and even plastic caps (PE / PP / EVA ...) with lubricants.

  There are non-permanent agents like waxes and organic oils, as well as silicone oils and emulsions. These products are inexpensive but can migrate into wine.

  There are also permanent treatments, such as the more expensive silicone elastomers, which do not modify the organoleptic quality of the wine.

  If the binder can also fulfill the lubricating function, this will eliminate an important step in the preparation of the caps and will reduce costs.

  The plug extraction force is measured according to ISO 25 9727 (see paragraph 3.2.4).

  Table VII below collates the results

TABLE VI

  lB Liège Binding Force Rate Part A / B Extraction compression silicone Remarks [%] IN] Crumbling at the interface, C9 100/10 50/50 100 130 Crumbling at the interface, cohesion problem Crumbling at the interface , C10 100/10 50/50 150 230 Crumbling at the interface, cohesion problem C11 100/10 50/50 200 230 Slight cooling at the interface C12 100/10 50/50 250 320 No problem C13 100/10 50/50 300 390 Bend at the bottom of the cap C14 100/20 50/50 200 240 No problem C15 100/20 50/50 250 350 No problem C16 100/20 50/50 300 430 Bend at the bottom of the cap Witness The cap has been treated by Tmliant PU- 250 320 a professional with a ____ P U___________ __________ _____________ ___________ lu b rifia nt plug The cap agglomerated by PU has an extraction force of 320N. Compared to this reference treated as a lubricant, comparable values are obtained for the caps whose compression ratio is 250% with the two ratios part A / B of the composition C: 100/10 and 100/20.

  If a lower compression ratio (200%) is chosen, only the caps with a part A / B ratio of composition C of 100/20 is acceptable in terms of its mechanical strength.

  If a higher compression ratio (300%) is chosen, excessive extraction forces are obtained and the plug is too hard to be able to penetrate the neck without bending.

  A compression rate of 250% is therefore ideal for caps bound with silicone. Additional lubrication treatment is not necessary and in addition the cork makers can use their industrial tool without modification.

CONCLUSION

  The use of a low viscosity product allows good dispersion, therefore good wetting of the cork surface. The use of the crosslinking system by hydrosilylation (-SiH / -SiVi) catalyzed by platinum (Karstedt) ensures a satisfactory setting speed which can be accelerated when hot. The choice of crosslinkers of the resin type with adjacent -SiH functions and possibly of the POS resin type with residual = SiOH functions makes it possible to optimize the cohesion of the cork particles (10 R-OH functions of the cellulose) and of the other integrated particles (fillers mineral and organic) with the binder. A plug is thus obtained which meets the requirements of the application.

  The composition of the cork stopper has been optimized. With a ratio of 50/50 (cork powder / silicone), already satisfactory results are obtained, if a compression ratio of at least 250% is applied.

  The increase in part B of the EVF further improves the result.

  A lubricant post-treatment of the plug is no longer necessary in the case of a compression rate of 250% with a 50/50 cork / silicone ratio and a 100/20 part A / B ratio of composition C.

Claims (14)

  1.- Agglomerate of particles comprising a vulcanized silicone composition characterized in that this vulcanized silicone composition is a binder present in a mass concentration of less than 75% w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w.   2.- agglomerate according to claim 1, characterized in that the vulcanized silicone composition is obtained from a vulcanizable silicone composition whose viscosity is between 1,000 and 100,000, preferably 1,000 and 10,000 Pa.s at 25 C and which is chosen from the group comprising: ò the single-component silicone compositions (EVF I) which can be vulcanized cold into elastomers, in the presence of moisture, at ambient temperature and comprising at least one polyorganosiloxane (POS) carrying hydroxyl units functionalizable by oxime, acyl, amine, amide or alkoxy radicals and at least one crosslinker carrying at least one type of these functionalization radicals; * mono or bicomponent silicone compositions (EVF I or 11) which can be vulcanized when cold, into elastomers at room temperature by polyaddition, in the presence of a metallic catalyst.   3.- agglomerate according to claim 1 or 2, characterized in that the vulcanized silicone composition is obtained from a vulcanizable silicone composition comprising: * (a) at least one POS species having, per molecule, at least two groups alkenyls, preferably C2-C6, bonded to silicon; (, 8) and at least one POS species having, per molecule, at least two hydrogen atoms bonded to silicon; * (ô) optionally, in addition to or in replacement of the POS species (a) and / or of the POS species (, 8), at least one POS species (6) having, per molecule, at least two alkenyl groups , preferably at C2-C6, bonded to silicon and at least two hydrogen atoms bonded to silicon; * (y) and a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the platinum group; with the condition that at least one of the POS species (a) and / or (, 8) and / or (6) is a linear or branched POS and at least one other of the POS species (f /) and / or (6) is a POS resin with -SiH patterns, preferably adjacent.   4.- agglomerate according to claim 3, characterized in that the vulcanized silicone composition is obtained from a vulcanizable silicone composition comprising: (1) at least one polyorganosiloxane having, per molecule, at least two alkenyl groups, in C2- C6 linked to silicon, (2) and / or at least one polyorganosiloxane having, per molecule, at least two hydrogen atoms linked to silicon, (3) a catalytically effective amount of at least one catalyst, composed of at least a metal belonging to the platinum group, (4) at least one polyorganosiloxane resin (4.1) having, per molecule, at least two hydrogen atoms bonded to silicon (-SiH), and optionally at least two alkenyl groups (preferably in C2C6), this resin (4.1) possibly being associated with at least one other resin (4.2) having, per molecule, at least two alkenyl groups, (preferably in C2-C6), bonded to silicon, (5) and optionally at minus a crosslinking inhibitor / retarder.   5.- agglomerate according to claim 4, characterized in that the polyorganosiloxane (1) has: (i) siloxy units of formula: Ta Zb SiO 4- (a + b) (1.1) in which: - T is a group alkenyl, preferably vinyl or allyl, - Z is a monovalent hydrocarbon group, free from any adverse action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms included, optionally substituted with at least one halogen atom, and as well as among the aryl groups, -a is 1 or 2, best 0, 1 or 2 eta + best comprised between 1 and 3, and (2i) optionally other siloxy units of formula: Zc SiO 4 -c (1.2) in which Z has the same meaning as above and ca a value between 0 and 3.   6.- Agglomerate according to claim 4 or 5, characterized in that the polyorganosiloxane (2) comprises: (i) siloxy units of formula: Hd SiO 4- (d + e) (2.1) in which: - L is a monovalent hydrocarbon group, free from an unfavorable action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms included, optionally substituted by at least one halogen atom, and also from aryl groups , - d is 1 or 2, e is 0, 1 or 2, d + has a value between 1 and 3, and (2i) possibly other siloxy units of average formula: Lg SiO4_g (2.2) in which L has the same meaning as above and g has a value between 0 and 3.   7.- agglomerate according to any one of claims 4 to 6, characterized in that it comprises polyorganosiloxane resin (4.2), which comprises in its structure from 0.1 to 20% by weight of group (s) alkenyl (s), and advantageously OR functions.   8.- agglomerate according to any one of claims 4 to 7, characterized in that the resin (4) is present in an amount of 10 to 70% by weight relative to all of the constituents of the silicone binder composition .   9.- agglomerate according to any one of claims 4 to 8, characterized in that the proportions of (1) and / or (2) and (4) in the silicone binder composition are such that the ratio of the number of atoms d hydrogen bonded in the polyorganosiloxane (2) and / or in the resin (4.1), on the number of alkenyl radicals contributed by the polyorganosiloxane (1) and / or the resin (4.2) is between 0.4 and 10.   10.- Agglomerate according to any one of claims 4 to 9, characterized 5 in that the precursor of the cold vulcanized binder silicone composition is a two-component system which is defined as follows: it is in two distinct parts A and B intended to be mixed to form the composition, - one of these parts A and B comprises the catalyst (3) and a single species 10 (1) and / or (2) of polyorganosiloxane, - and the resin (4) can be implemented in part A or part B or in both parts A and B, the catalyst (3) not having to be present in part A or B containing POSs with patterns -SiH and POSs with patterns = Si-alkenyl (vinyl).   11.- Agglomerate according to any one of claims 1 to 10, characterized in that the particles are particles of woody plant material, preferably cork particles, optionally associated with particles of (thermo) plasticizable / expandable plastic material . 20 12.- Cap characterized in that it comprises agglomerate according to one   any of claims 1 to 11.   13.- A method of manufacturing an agglomerate according to any one of claims 1 to 11, characterized in that it consists essentially in mixing the particles with the vulcanizable binder silicone composition in proportions such as the mass concentration of silicone binder is less than 75% w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, optionally to shape this mixture by subjecting it or not to compression, then making sure that the vulcanization of the silicone binder intervenes to finally recover the hardened agglomerate.   14.- A method of manufacturing a plug according to claim 12, characterized in that it consists essentially in mixing the particles with the vulcanizable silicone binder composition in proportions such that the mass concentration of silicone binder is less than 75% w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, to put this mixture in the form of a cap by subjecting it to compression, then to ensure that the vulcanization of the silicone binder intervenes to freeze this form and recover after hardening the targeted plug.   15.- A method of manufacturing a plug according to claim 12, 5 characterized in that it consists essentially in mixing the particles with the vulcanizable binder silicone composition in proportions such that the mass concentration of binder silicone is less than 75% w / w, preferably less than or equal to 65% w / w, and more preferably still between 60 and 10% w / w, optionally compressing this mixture, then ensuring that the vulcanization of the silicone binder occurs to harden the mixture of agglomerated material, from which the plug is then shaped.