EP3377577A1

EP3377577A1 - Polymer composition comprising a dispersed plant material

Info

Publication number: EP3377577A1
Application number: EP16815572.9A
Authority: EP
Inventors: Jean-Marc Boutillier; Axel SALINIER
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2015-11-16
Filing date: 2016-11-15
Publication date: 2018-09-26
Also published as: WO2017085394A1; FR3043682B1; US20180327601A1; JP2018535300A; CN108350247A; FR3043682A1

Abstract

The invention relates to a composition comprising: - a polymer matrix comprising an elastomer phase having a glass transition temperature of less than or equal to 20°C; - particles of plant matter dispersed in said polymer matrix. The invention also relates to the use of this composition for the manufacture of various articles such as plates and in particular insulation plates, films, profiles, shells, domestic electrical appliance parts, spectacles and soles.

Description

POLYMER COMPOSITION COMPRISING A VEGETABLE MATERIAL

SCATTERED

FIELD OF THE INVENTION

The present invention relates to a composite material comprising a polymer matrix as well as dispersed plant material particles, as well as articles that can be made from this composite material.

TECHNICAL BACKGROUND

Plant materials such as cork have many interesting properties, for example in terms of thermal insulation, sound insulation, natural appearance, lightness and pleasant smell.

However, these materials and especially cork often have the disadvantage of being easily friable and brittle. They can not therefore be implemented according to the techniques commonly used for thermoplastic materials, such as injection molding, extrusion, extrusion blow molding, thermoforming, etc.

To overcome the disadvantages associated with the use of pure plant materials (such as cork), they can be mixed with a polymer.

Thus, CN 104608270, according to its abstract, describes a mixture of cork and ethylene-vinyl acetate. Cork is previously combined with natural rubber. But natural rubber is known to have very poor resistance to UV radiation, and moreover it must be crosslinked to prevent creep, especially at high temperatures.

The document FR 2451350 describes a layer based on a mixture of cork particles and ethylene-vinyl acetate which is adhesively bonded to a floor.

US 2010/0319282 discloses a multi-layer floor covering, one of which is made of a mixture of cork and polyvinyl chloride. There is a need to produce various articles based on plant materials such as cork, using conventional implementation techniques of thermoplastic materials, and without altering the properties of the plant material, for example with an implementation at one time. temperature below 200 ° C. There is also a need for these articles, based on plant materials such as cork and implemented using the techniques used for thermoplastic materials, are resistant to shocks and have excellent resistance to UV radiation. SUMMARY OF THE INVENTION

The invention firstly relates to a composition comprising:

a polymer matrix comprising an elastomer phase having a glass transition temperature of less than or equal to 20 ° C .;

particles of plant material dispersed in said polymer matrix.

According to one embodiment, the particles of plant material have a density of less than or equal to 500 kg / m ³ , preferably less than or equal to 200 kg / m ³ , more preferably less than or equal to 150 kg / m ³ , or even less than or equal to 100 kg / m ³ .

According to one embodiment, the particles of plant material are wood particles, and preferably cork particles.

The particles may be in the form of granules or powder.

According to a first embodiment, the elastomer phase represents at least 1% by weight, preferably at least 5% by weight, more preferably at least 10% by weight and even more preferably at least 15% by weight, by weight. relative to the total weight of the composition.

According to this first embodiment, the ratio of the weight content of vegetable material particles to the elastomer phase weight content is less than or equal to 1, preferably less than or equal to 0.9, and more preferably less than or equal to 0 8. According to a second embodiment, the polymer matrix comprises at least one block copolymer, the elastomer phase being constituted at least partially by at least one block of the block copolymer, and preferably, the block copolymer is an acrylic block copolymer .

According to this second embodiment, the ratio of the weight content of plant material particles to the elastomer phase weight content of the block copolymer is greater than or equal to 1 but less than or equal to 3 and preferably less than or equal to 1. 5.

According to this second embodiment, the composition comprises: from 30 to 99% by weight of block copolymer, preferably from 40 to 95% by weight, and more particularly preferably from

50 to 90% by weight;

from 1 to 70% by weight of vegetable material particles, preferably from 5 to 60% by weight, and more preferably from 10 to 50% by weight.

According to one embodiment, the block copolymer comprises at least one block A having a glass transition temperature greater than or equal to 50 ° C, preferably greater than or equal to 80 ° C, and at least one block B having a temperature of vitreous transition less than or equal to 20 ° C, which constitutes at least partially the elastomeric phase.

According to one embodiment, the block B represents from 10 to 90% of the total mass of the block copolymer, preferably from 20 to 80% and more preferably from 30 to 70%.

According to one embodiment, the block B has a weight average molar mass of between 10,000 g / mol and 300,000 g / mol, preferably between 20,000 and 150,000 g / mol.

According to one embodiment, the block A is an acrylic or methacrylic homopolymer or copolymer block, or a polystyrene block, or an acrylic-styrene copolymer block or a methacrylic-styrene block, preferably a polymethyl methacrylate block, phenyl polymethacrylate, benzyl polymethacrylate or isobornyl polymethacrylate, and more preferably a block polymethyl methacrylate, optionally modified with acrylic or methacrylic comonomers.

According to one embodiment, the block B is an acrylic or methacrylic homopolymer or copolymer block that may contain styrene, preferably a polyacrylate block, ethyl polyacrylate, butyl polyacrylate, ethylhexyl polyacrylate, butyl polymethacrylate, and more preferably a butyl polyacrylate block.

According to one embodiment, the block copolymer is chosen from the following triblock copolymers:

- polymethyl methacrylate / butyl polyacrylate / polymethyl methacrylate,

copolymer of methyl methacrylate and methacrylic acid / butyl polyacrylate / copolymer of methyl methacrylate and methacrylic acid,

polymethyl methacrylate / butyl acrylate / styrene / polymethyl methacrylate copolymer, and

copolymer of methyl methacrylate and methacrylic acid / copolymer of butyl acrylate and styrene / copolymer of methyl methacrylate and methacrylic acid.

- Polystyrene / Butyl polyacrylate / Polystyrene.

- Poly (styrene-co-methacrylic acid) / Butyl polyacrylate / Poly (styrene-co-methacrylic acid)

According to one embodiment, the block copolymer is chosen from the following diblock copolymers:

- polymethyl methacrylate / butyl polyacrylate,

copolymer of methyl methacrylate and methacrylic acid / butyl polyacrylate,

methyl methacrylate / butyl acrylate / styrene copolymer, and

copolymer of methyl methacrylate and methacrylic acid / copolymer of butyl acrylate and styrene. According to one embodiment, the composition is expanded by means of a chemical expansion agent and / or an expansion gas.

According to one embodiment, the composition of the invention further comprises a thermoplastic polymer, preferably a fluorinated polymer and more particularly preferably polyvinylidene fluoride.

The invention also relates to a method for preparing a composition as described above, comprising:

the supply of the polymer matrix as well as particles of plant material;

- Hot mixing of the polymer matrix in the softened state and comprising the elastomer phase with the particles of plant material preferably in an extruder, the vegetable particles being introduced laterally after the introduction of the polymer matrix which is introduced. in the hopper at the beginning of extrusion.

The invention also relates to an article comprising the composition described above, preferably selected from plates including insulation plates, films, profiles, shells, appliances, glasses and soles.

The present invention overcomes the disadvantages of the state of the art. It provides more particularly a composition containing plant materials such as cork, which can be shaped by conventional techniques of thermoplastic materials to produce various articles.

This shaping can be done quickly and at a relatively low temperature, which makes it possible to avoid altering the properties of the plant material.

The invention also makes it possible to manufacture objects of complex shape and / or of small thickness, for example reels of films, sheets or plates of great length, by extrusion.

The invention also makes it possible to manufacture objects having excellent resistance to UV radiation and which can therefore be used for outdoor applications. The material of the invention is flexible and impact resistant. It advantageously has a natural appearance and a pleasant smell, because of the presence of plant material.

These various advantages are obtained in particular by virtue of a composition comprising particles of plant material (in particular cork or the like) in a polymer matrix comprising an elastomer phase at a low glass transition temperature, which is preferably provided by an acrylic block copolymer.

With respect to the same material comprising an elastomer phase devoid of plant material (for example with respect to the acrylic block copolymer as such), the composite material of the invention advantageously has improved antistatic, thermal and acoustic properties, as well as an aspect very close to that of the vegetable material.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows.

The composition of the invention is a composite material, which comprises at least one polymer matrix and particles dispersed in the polymer matrix.

By polymer matrix is meant the non-plant phase regardless of the proportion of polymer in the polymer-plant material mixture.

The polymer matrix comprises an elastomeric phase having a glass transition temperature of less than 20 ° C.

This elastomeric phase is formed by a macromolecular block, which may be a polymer or a part of a polymer (such as one or more blocks of block copolymers), or a mixture of polymers and / or polymer parts.

Preferably, the polymer matrix comprises at least one block copolymer, and the elastomeric phase is formed at least partially, preferably completely, formed by at least one block of the block copolymer. The block copolymer can be a diblock or triblock copolymer, or it can have four, five or more than five blocks.

Diblock and triblock copolymers are preferred.

Preferably, the block copolymer is an acrylic block copolymer: it is a block copolymer, at least one block of which is formed at least partially from acrylic monomers.

According to a preferred embodiment, all the blocks are formed at least partially from acrylic monomers.

According to a preferred embodiment, at least one block is formed entirely from acrylic monomers.

According to a preferred embodiment, all the blocks are formed entirely from acrylic monomers

By "acrylic monomers" is meant monomers comprising a vinyl group, substituted or unsubstituted, and a carboxylic acid group, optionally in salt or ester form.

They include, in particular, the following monomers: acrylate, methacrylate, acrylic acid, methacrylic acid, methyl methacrylate, phenyl methacrylate, benzyl methacrylate, isobornyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, acrylate and the like. ethylhexyl, butyl methacrylate.

In a particularly preferred manner, the block copolymer is an amorphous copolymer.

In a particularly preferred manner, the block copolymer is a thermoplastic copolymer.

By "thermoplastic" is meant here a polymer which softens when heated to a sufficiently high temperature, and which can therefore be reformed by application of heat and pressure.

According to a particularly preferred embodiment, the block copolymer (preferably acrylic) comprises at least one block A and at least one block B, in which block A has a glass transition temperature greater than or equal to 50 ° C. and block B is the elastomer phase mentioned above, and therefore has a glass transition temperature less than or equal to 20 ° C. In particular embodiments, the block A has a glass transition temperature greater than or equal to 60 ° C; or at 70 ° C; or at 80 ° C; or at 90 ° C; and block B has a glass transition temperature of less than or equal to 15 ° C; or at 10 ° C; or at 5 ° C; or at 0 ° C.

The glass transition temperature can be determined by differential scanning calorimetry (DSC) according to ASTM E1356.

Block A has the particular function of imparting rigidity and hardness to the copolymer and therefore to the composite material. Block B has the particular function of imparting flexibility and impact resistance to the copolymer and thus to the composite material. Block B also ensures optimum mixing and contact between the copolymer and the plant material.

The block copolymer (in particular acrylic block copolymer) may in particular be a copolymer of structure AB, or ABA, or A3B, or A4B, or more generally A _n B with n an integer greater than or equal to 1. AB and ABA structures are particularly preferred.

When several A blocks are present, they are preferably identical. According to an alternative embodiment, they may be different.

Block B preferably represents from 10 to 90%, preferably from 20 to 80% and even more preferably from 30 to 70% of the total weight of the block copolymer.

Pattern levels from particular monomers in a polymer or block as well as block levels in a block copolymer can be determined by nuclear magnetic resonance analysis and / or infrared spectrophotometry. They can also be deduced from the respective amounts of monomers used in the polymerization operations, taking into account the respective conversion rates of these monomers.

Block B has a weight average molecular weight of between 10,000 g / mol and 300,000 g / mol, preferably 20,000 to 150,000 g / mol. This molar mass can be measured by size exclusion chromatography.

Each block may be a homopolymer or a copolymer.

Block A can be for example a polystyrene block. However, it is preferred that block A is formed in part from one or more acrylic monomers, or may be formed entirely from one or more acrylic monomers. Optionally, the acrylic monomers may comprise one or more functions chosen from acid, amide, amine, hydroxy, epoxy and alkoxy functional groups.

Thus, the block A may be a homopolymer chosen from polymethyl methacrylate (PMMA or pMMA), phenyl polymethacrylate, benzyl polymethacrylate and isobornyl polymethacrylate. It may also be a copolymer formed from styrene and an acrylic monomer, such as acrylate or methacrylate in particular. In one embodiment, the block A is formed in part from methacrylic acid monomer, which gives it an improved thermal resistance.

In a preferred embodiment, block A is PMMA. In another preferred embodiment, block A is a copolymer of methyl methacrylate and another acrylic comonomer. It may be in particular a copolymer of methyl methacrylate and methacrylic acid, denoted p (MMA-co-AMA); or a copolymer of methyl methacrylate and acrylic acid, denoted p (MMA-co-AA).

In another variant, the block A is PMMA containing a small proportion of units derived from an acrylate comonomer, in order to obtain improved thermal stability.

Block B is advantageously formed at least in part from one or more acrylic monomers. Preferably, it is formed entirely from acrylic monomers. Optionally, the acrylic monomers may comprise one or more functions chosen from acid, amide, amine, hydroxy, epoxy and alkoxy functional groups.

Preferred acrylic monomers for block B are methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate and butyl methacrylate. Butyl acrylate is particularly preferred. Block B can be a homopolymer or a copolymer. In a preferred embodiment, block B is butyl polyacrylate (pABu). In another preferred embodiment, block B is butyl acrylate-styrene copolymer. Preferably, the block copolymer is chosen from the triblock and diblock copolymers listed in the summary of the invention.

The block copolymers can be obtained by controlled radical polymerization or by anionic polymerization.

Preferably, controlled radical polymerization is used, especially in the presence of nitroxides, for block copolymers of type (A) _n B; and anionic or radical radical anionic or nitroxide polymerization for ABA type structures.

It is understood that several block copolymers as described above may be used in admixture. However, preferably, a single block copolymer as described above is present in the polymer matrix of the composite material of the invention.

According to one embodiment, the polymer matrix of the composite material of the invention consists essentially or even consists of the block copolymer described above (or the mixture of such copolymers).

According to one embodiment, the composite material may comprise at least one other polymer mixed with the block copolymer. This other polymer may be present in intimate mixture with the block copolymer as part of the polymer matrix, or alternatively in the form of particles dispersed in the polymer matrix.

Thus, the composite material, and preferably the polymer matrix of the composite material, may comprise another thermoplastic polymer. Preferably, this other thermoplastic polymer may be chosen from PMMA, polystyrene, PVC plasticized or not, MABS (Methylmethacrylate Acrylonitrile Butadiene Styrene), polyolefins and their copolymers (PE, homo PP or copolymers), terpolymer-type polymers acrylonitrile-butadiene-styrene (ABS), thermoplastic elastomers such as thermoplastic copolyamides, thermoplastic polyurethanes or elastomers of the styrenic family such as polystyrene-b-poly (ethylene-butylene) -b-polystyrene, organic polymers -sourced and in particular the PLA. It may be advantageously polyvinylidene fluoride or any other fluorinated polymer to improve the fire resistance. It can also be a copolymer acrylic composition which contains, by weight, 20 to 80% of units derived from methyl methacrylate, from 20 to 80% by weight of units derived from butyl methacrylate and from 0 to 15% of units derived from methacrylic acid or from acrylic acid. More preferably, this acrylic copolymer contains, by weight, from 50 to 80% of units derived from methyl methacrylate and from 20 to 50% of units derived from butyl methacrylate. This acrylic copolymer advantageously has a weight average molar mass of between 40,000 and 300,000 g / mol, and preferably between 40,000 and 100,000 g / mol. When this acrylic copolymer is added to the composition, the material according to the invention may then preferably contain, by weight, from 5 to 40% of this acrylic copolymer, preferably from 5 to 20%. This acrylic copolymer makes it possible in particular to improve the adhesion of the material of the invention to styrenic substrates such as polystyrene (PS) crystal (PS homopolymer) or shock PS or a mixture of these two types of PS. Shock PS means a PS reinforced with shocks by the addition of rubber such as polybutadiene or EPDM (ethylene propylene diene monomer) which is found dispersed in the PS matrix in the form of nodules.

When the block A is polystyrene or a styrenic copolymer, polyphenylene oxide (PPO) may be introduced into the composition of the invention, especially into the matrix, in order to increase the fire resistance.

When such a thermoplastic polymer is present, it is generally at a content by weight of 1 to 20% relative to the block copolymer described above, but levels up to 90% can also be used with certain thermoplastics such as certain polyolefins.

The composite material (and preferably the polymer matrix of the composite material) may also comprise a highly crosslinked acrylic polymer. Such a polymer is likely to impart to the material after implementation a non-glossy surface state and / or a different feel. When such a polymer is present, it is generally at a content by weight of 5 to 20% with respect to the block copolymer described above.

The highly crosslinked acrylic polymer is formed from methyl methacrylate as a single monomer, or as a major monomer. Thus, the polymer comprises by weight more than 50%, advantageously more than 65% by weight of units derived from methyl methacrylate. The highly crosslinked acrylic polymer is therefore either a PMMA or a copolymer obtained with at least one comonomer radically copolymerizable with methyl methacrylate.

The comonomer may be a vinyl aromatic comonomer, for example styrene or alpha-methylstyrene and / or (meth) acrylic comonomer. The level of comonomer, when present, is preferably less than or equal to 50% by weight of the highly crosslinked acrylic copolymer.

The crosslinking is obtained by using at least one crosslinking agent which may for example be an allyl (meth) acrylate, divinylbenzene, a di- or tri-methacrylate such as polyethylene glycol dimethacrylate.

The term "highly crosslinked" means that the acrylic polymer particles are insoluble in a polar solvent such as tetrahydrofuran or methylene chloride.

Reference is made here to WO 2012/136941, which describes in detail acrylic block copolymer matrices as described above, containing highly crosslinked acrylic polymer particles as described above.

According to a preferred embodiment, the polymer matrix of the composite material of the invention is not crosslinked.

According to a preferred embodiment, the material of the invention is devoid of, or essentially devoid of, natural rubber.

According to a preferred embodiment, the material of the invention is free or essentially free of ethylene vinyl acetate.

According to a preferred embodiment, the material of the invention is free or essentially free of polyvinyl chloride.

According to a preferred embodiment, the material of the invention is free or substantially free of polyolefins such as polyethylene (PE) or polypropylene homopolymer (PP), or copolymers containing PE or PP. According to a preferred embodiment, the material of the invention is free or essentially free of polymers containing a crystalline or semi-crystalline phase.

Various additives may be added to the composite material according to the invention, and in particular to the polymer matrix of the composite material.

These additives can be especially antioxidants, thermal stabilizers, photo-stabilizers, plasticizers, UV absorbers, antistats, flame retardants or pigments.

It is also possible to use as additive a chemical expansion agent or an expansion gas such as CO2. The expansion of the material according to the invention makes it possible to reduce its density and / or to increase its thermal and / or phonic insulation properties.

Furthermore, the composite material according to the invention comprises particles of plant material dispersed in the polymer matrix. Advantageously, these particles are derived from the grinding of plants or parts of plants. The plants in question are preferably trees. More particularly preferably, these are particles of tree bark, and most preferably cork particles or cork oak bark.

It is preferred that the particles of plant material used have a low density, in particular to impart good lightness properties to the material.

Thus, the density of the plant material is preferably less than or equal to 500 kg / m ³ ; or 400 kg / m ³ ; or 300 kg / m ³ ; or 200 kg / m ³ ; or at 150 kg / m ³ ; or at 100 kg / m ³ ; or 80 kg / m ³ ; or at 70 kg / m ³ ; or 60 kg / m ³ .

The density of the plant material can be measured according to ISO 2031 (2015).

The particle size distribution of the plant material particles may be such that at least 80% (by mass) of the particles have a size of less than or equal to 2 mm.

According to a variant, at least 80% (by weight) of the particles have a size of between 1 and 2 mm. According to one variant, at least 80% (by mass) of the particles have a size of between 0.5 and 1 mm.

According to a variant, at least 80% (by weight) of the particles have a size less than or equal to 0.5 mm.

Particle size distribution can be measured by mechanical sieving according to ISO 2030 (1990).

The use of small particles in particular makes it possible to obtain a composite material with a smoother and uniform appearance.

The composite material according to the invention preferably comprises, by weight: from 30 to 99%, advantageously from 40 to 95% and preferably from 50 to 90% of polymer matrix; and from 1 to 70%, preferably from 5 to 60% and preferably from 10 to 50%, of plant material particles.

Preferably, the content by weight of the vegetable material particles in the composite material is at least 10% less, preferably at least 15%, and more preferably at least 20%, at the content of the blocks B of the block copolymer described above in the composite material.

Advantageously, the composite material according to the invention has a semi-rigid character, even flexible, while maintaining a very good resistance to shock and UV radiation. In the context of the present invention, a semi-rigid material is characterized by a flexural modulus ranging from 500 to less than 1800 MPa, preferably less than 1500 MPa, whereas a flexible material has a flexural modulus of 10 to less than 500 MPa, measured according to ISO 178 (2001).

Advantageously, the composite material according to the invention has a Charpy resilience with a specimen greater than 6 kJ / m ² , preferably greater than 10 kJ / m ² , measured according to the standard EN ISO 179-1 eU (1993) at 23 ° C. .

Advantageously, the composite material according to the invention has a surface resistivity of less than 10 × 10 ¹² Ω / sq (ohms per square), preferably less than 10 × 10 ¹¹ Ω / sq, measured according to the ASTM D257-99 (2005) standard. Advantageously, the composite material according to the invention has a density of less than 1.

The composite material of the invention can be obtained by dispersing the particles of plant material, as well as any other particles of one or more additives chosen from those mentioned above, in the polymer matrix in the softened state (compounding). This step can be carried out by conventional techniques for manufacturing thermoplastic compounds, for example by using an internal mixer, by performing a single-screw or twin-screw extrusion, or a calendering.

In a first embodiment, the composite material according to the invention is first manufactured in the form of granules, which can then be softened and shaped into various articles and articles.

In an alternative embodiment, objects and articles of composite material according to the invention are manufactured directly by mixing the constituents of the composite material and shaping the material.

In one or the other embodiment, the objects and articles made of composite material according to the invention may be manufactured in particular by injection molding, extrusion, coextrusion or extrusion blow molding.

These different techniques make it possible to produce parts, profiles, plates or films.

The composite material of the invention can also be used as a coating on other materials. For example, the technique of coextrusion or film lamination can be used on a substrate. It is also possible to produce profiles that can be used, for example, in optical applications.

It is also possible to manufacture multilayer structures comprising a first layer made of the composite material according to the invention and a second layer comprising at least one substrate made of a thermoplastic polymer material.

The composite material according to the invention then preferably represents from 1 to 99% of the total thickness expressed in units of length, from 1 to 50%, more particularly preferably from 2 to 15%. When the composite material of the invention is coextruded or laminated on a substrate, the latter may be for example a saturated polyester such as polyethylene terephthalate PET or PETg, or polybutylene terephthalate, ABS, a styrene-acrylonitrile copolymer, an acrylic-styrene-acrylonitrile copolymer, a crystal or impact PS, a thermoplastic polyolefin (TPO), polypropylene, polyethylene, polycarbonate (PC), polyphenylene oxide (PPO), a polysulphone, an optionally chlorinated polyvinyl chloride or expanded, polyurethane, TPU, polyacetal, non-shock PMMA or shock. It may also be a mixture of two or more thermoplastic polymers from the above list. For example, it may be a PPO / PS or PC / ABS blend. When the substrate is a crystal or impact PS, the composite materials according to the invention may advantageously contain as an additive from 5 to 40% of acrylic copolymer composed of 20 to 80% of units derived from methyl methacrylate, from 20 to 80% units derived from butyl methacrylate and 0 to 15% acrylic acid or methacrylic acid.

A layer of another polymer may be present between the substrate and the products according to the invention to improve adhesion, in particular in the case of substrates made of crystal or impact PS, TPO and PO.

More generally, the composite material of the invention can be used to manufacture plates, films, profiles or articles such as telephone shells, glasses, shoe soles, layers or insulating sub-layers for floors or plates. insulation, deck boards, cladding profiles, automotive interior parts, electrical or electronic appliance parts or furniture, leather goods, bracelets, frames or internal parts of timepieces, or sporting goods .

The composite material according to the invention can be coated with a varnish, in particular to increase its gloss and / or its resistance to abrasion.

EXAMPLES

The following examples illustrate the invention without limiting it. A composite material formulation according to the invention is manufactured from:

a pMMA-pBA-pMMA triblock copolymer containing 50% by weight of pBA, the weight average molar mass of the pBA block being 50,000 g / mol;

- and a powder of cork granules.

In test A, the cork granules have a density of between 50 and 60 kg / m ³ , and at least 80% of the granules (by mass) have a size of between 0.5 and 1 mm.

In a test B, the cork granules have a density of between 50 and 60 kg / m ³ , and at least 80% of the granules (by mass) have a size of between 1 and 2 mm.

In both tests, the mass ratio triblock copolymer / cork particles is 80/20.

In a C test (comparative), the pure copolymer, without cork particles, is used.

The composite material of the invention is manufactured by compounding the acrylic block copolymer and cork particles on a BUSS® brand MKS30 co-kneader.

The co-kneader consists of two single-screw extruders connected perpendicularly.

The first extruder, called a kneading extruder, consists of a screw with a diameter of 30 mm and a length / diameter ratio of 17. The screw is driven both by a rotational and translational movement. Spikes, called kneading fingers, are fixed on the sheath. Unlike a conventional single-screw extruder, the screw elements used on a co-kneader are discontinuous to allow rotation of the screw in the presence of these kneading fingers. The interactions between the blades and the static kneading fingers, which combine a dispersive and distributive mixture, allow a good performance of the co-kneader in terms of dispersion. A side-feeder and a degassing dome are also installed on this extruder. The second single-screw extruder, connected perpendicular to the first, is called a discharge extruder. It is used to reduce the pressure variations caused by the translational movement of the first single-screw extruder. The die through which the material is extruded is at the outlet of the discharge extruder.

The constituents are introduced by gravimetric feeders located above the co-kneader. These feeders make it possible to feed the co-kneader with great precision.

The block copolymer is introduced into the main hopper of the co-kneader while the cork is introduced into the side hopper. The mixture rod obtained is extruded through a die located at the end of the screw of the discharge extruder. This ring is then cooled in a water bath before being granulated using a granulator.

The temperature profile used is as follows:

- 100 ° C in the kneading extruder at the main hopper;

- 160 ° C in the kneading extruder between the main hopper and the side hopper;

- 190 ° C in the kneading extruder after the side hopper; - 190 ° C in the discharge extruder.

In both tests A and B, the rotational speed of the screw of the kneading extruder is 320 tr.min ^-1, the rotational speed of the screw of the discharge extruder is 40 tr.min ^{- 1} , the total flow of material is 8 kg. h ^-1 . The average die pressure is 13 bar in test A and 14 bar in test B.

Both products studied are dried for 8 hours at 50 ° C. They are then injected using a Billon brand H260 press fitted with a 32mm diameter screw and a 90T closing force mold with water cooling.

The temperature profile of the injection screw is 140 ° C for the first zone then 150 ° C for the following five zones. The temperature of the softened product is 150 ° C. The injection speed is 20 mm / s. The mold temperature is 60 ° C. Traction dumbbells and shock bars are injected to characterize the products.

The characterization of the products is shown in Table I:

Table I

The creep index (MFI) is measured according to ISO 1133 (January 1997) using the following parameters: 230 ° C and 3.8 kg. It is expressed in g / 10 mm.

Flexural modulus is measured according to ISO 178 (2001) at 23 ° C. It is expressed in MPa.

The notched Charpy impact and non-notched Charpy shock are measured according to ISO 179-1 eU (1993) at 23 ° C. They are expressed in kJ / m ² .

The softening temperature is Vicat is measured according to ISO 306 (2004), with a force of 10 N. It is expressed in ° C.

The thermal deformation temperature is measured according to ISO 75-2 (1993), with a pressure of 1.80 MPa. It is expressed in ° C. The elongation at break in tension is measured according to ISO 527-2 (1996) at 23 ° C. It is expressed in%.

The density is measured using a helium pycnometer according to the ISO 1 183-3 (1999) standard.

The surface resistivity is measured using a Keithley 6514 electrometer equipped with a model 803B cell from Electro-tech Systems, Inc. It is expressed in Ω / sq.

The results presented in Table I show that the composite products according to the invention, obtained during tests A and B, exhibit flexibility, impact resistance and temperature resistance very close to the properties of the product of the comparative test. C, while they have a cork appearance and a lower surface resistivity. Moreover, their fluidity remains high enough, which allowed them to be injected at a low temperature (150 ° C) to preserve the cork.

Claims

Composition comprising:

cork particles dispersed in said polymer matrix.

Composition according to Claim 1, in which the particles of vegetable material have a density of less than or equal to 500 kg / m ³ , preferably less than or equal to 200 kg / m ³ , more particularly preferably less than or equal to 150 kg / m ³ , or even less than or equal to 100 kg / m ³ .

Composition according to one of Claims 1 to 2, in which:

the elastomer phase represents at least 1% by weight, preferably at least 5% by weight, more particularly preferably at least 10% by weight and even more preferably at least 15% by weight, relative to the total weight of the composition; and or

the ratio of the weight content of vegetable material particles to the elastomer phase weight content is less than or equal to 1, preferably less than or equal to 0.9, and more preferably less than or equal to 0.8.

Composition according to one of Claims 1 to 3, in which the polymer matrix comprises at least one block copolymer, the elastomer phase being constituted at least partially by at least one block of the block copolymer, and in which, preferably, the Block copolymer is an acrylic block copolymer. The composition of claim 4 comprising:

from 30 to 99% by weight of block copolymer, preferably from 40 to 95% by weight, and more preferably from 50 to 90% by weight;

The composition of claim 5 wherein the ratio of the weight content of plant material particles to the elastomeric phase weight content of the block copolymer is greater than or equal to 1 but less than or equal to 3 and preferably less than or equal to 1. 5

Composition according to one of Claims 5 to 6, in which the block copolymer comprises at least one block A having a glass transition temperature greater than or equal to 50 ° C, preferably greater than or equal to 80 ° C, and at least one a block B having a glass transition temperature of less than or equal to 20 ° C, which at least partially constitutes the elastomeric phase.

Composition according to Claim 7, in which the block B represents from 10 to 90% of the total weight of the block copolymer, preferably from 20 to 80% and more preferably from 30 to 70%.

Composition according to one of Claims 7 or 8, in which the block A is an acrylic or methacrylic homopolymer or copolymer block, or a polystyrene block, or an acrylic-styrene copolymer block or a methacrylic-styrene block, preferably a polymethacrylate block. of methyl, phenyl polymethacrylate, benzyl polymethacrylate or isobornyl polymethacrylate, and more preferably a polymethyl methacrylate block, optionally modified with acrylic or methacrylic comonomers.

10. Composition according to one of claims 7 to 9, wherein the block B is an acrylic or methacrylic homopolymer or copolymer block, preferably a polyacrylate block of methyl, ethyl polyacrylate, butyl polyacrylate, ethylhexyl polyacrylate, butyl polymethacrylate, and more preferably a butyl polyacrylate block.

11. Composition according to one of claims 5 to 10, wherein the block copolymer is chosen from the following triblock copolymers:

- polymethyl methacrylate / butyl polyacrylate / polymethyl methacrylate,

copolymer of methyl methacrylate and methacrylic acid / copolymer of butyl acrylate and styrene / copolymer of methyl methacrylate and methacrylic acid; or wherein the block copolymer is selected from the following diblock copolymers:

- polymethyl methacrylate / butyl polyacrylate,

copolymer of methyl methacrylate and methacrylic acid / butyl polyacrylate,

methyl methacrylate / butyl acrylate / styrene copolymer, and

copolymer of methyl methacrylate and methacrylic acid / copolymer of butyl acrylate and styrene.

- Polystyrene / Butyl polyacrylate / Polystyrene.

Poly (styrene-co-methacrylic acid) / butyl polyacrylate / Poly (styrene-co-methacrylic acid).

12. Composition according to one of claims 1 to 12, further comprising a thermoplastic polymer.

The composition of claim 12, wherein said thermoplastic polymer is a fluorinated polymer, preferably polyvinylidene fluoride.

The composition of claim 12, wherein said thermoplastic polymer is a bio-bored polymer, preferably PLA.

The composition of claim 14, wherein when block A is styrenic, said thermoplastic polymer is a polyphenylene oxide.

Composition according to one of claims 1 to 15, expanded by means of a chemical expansion agent and / or an expansion gas.

Process for the preparation of a composition according to one of Claims 1 to 16, comprising the following steps:

providing the polymer matrix, particles of plant material and optionally one or more additives;

- Hot mixing the polymer matrix in the softened state with the vegetable material particles and optionally with one or more additives, in an extruder, the vegetable particles being introduced laterally after the introduction of the polymer matrix which is introduced into the hopper at the beginning of extrusion

Article comprising the composition according to one of claims 1 to 17, preferably chosen from plates and in particular insulating plates, films, profiles or shells for telephone, glasses, shoe soles, layers or underlays insulation for floors or insulation boards, deck boards, cladding profiles, automotive interior parts, appliance parts household appliances or electronics or furniture, leather goods, bracelets, frames or internal parts of timepieces, or sporting goods.