Patent Description:
Said polymer composition can be advantageously used for producing manufactured articles, such as films or slabs, having improved barrier properties and good mechanical properties. Said polymer composition can also be advantageously used for producing manufactured articles, such as films or slabs, having good electrical conductivity properties. Said films or slabs can, in turn, be advantageously used in various applications such as, for example, the production of manufactured articles with reduced gas permeability for packaging and tanks, or manufactured articles with improved electrical conductivity for 3D printing applications, or manufactured articles with improved electromagnetic radiation shielding (EMI shielding).

Consequently, the present invention also relates to the manufactured articles obtained from the aforesaid polymer composition.

Further subject matter of the present invention is also a process for the preparation of said polymer composition.

Polymer compositions having good barrier properties, and/or good mechanical properties, and/or good electrical conductivity properties, are known in the state of the art.

For example, international patent application <CIT> describes a polymer composition comprising: from about <NUM>% by weight to <NUM>% by weight of a polyolefin resin; from about <NUM>% by weight to <NUM>% by weight of a nucleating agent or a clarifying agent; from about <NUM>% by weight to <NUM>% by weight of a filler that can be selected from mica and/or clay and/or graphite and/or graphene. The aforesaid polymer composition is said to have improved barrier properties to gas, volatile organic compounds and water vapor.

International patent application <CIT> describes a masterbatch for preparing a nanocomposite polymer, said masterbatch comprising a polymer and at least <NUM>% by weight of graphite. In said patent application, examples are provided, among others, related to the preparation of a graphene/linear-low-density polyethylene (LLDPE) composite and a graphene-high-density polyethylene (HDPE) composite: said composites are extruded obtaining films which, when subjected to analysis for the purpose of measuring the tensile properties thereof, are said to display an improvement both in relation to the elongation at yield and to the elongation at break.

European patent application <CIT> describes a process for preparing a composition comprising graphene and at least one polymer, said process comprising the steps of: (i) providing an aqueous suspension of graphene (dispersion G); (ii) mixing the dispersion (G) with an aqueous polymer lattice obtaining an aqueous mixture (mixture M); (iii) co-coagulating the mixture (M) obtaining said composition. The films obtained from the aforesaid composition display higher barrier properties with respect to those of films obtained from polymers without graphene added.

International patent application <CIT> describes a process for preparing a polymer composition comprising a polymer and graphene, comprising the steps of: A) providing an aqueous dispersion of graphene, said dispersion comprising a non-ionic surfactant; B) mixing the graphene dispersion with an aqueous lattice of the polymer or with a water soluble or dispersible precursor of the polymer; C) removing water from the mixture obtained; D) heating the product obtained in step C) to the temperature wherein the polymer is able to flow or wherein the polymer is formed by its precursor(s); and E) processing and/or solidifying the product of step D) in the desired form. The polymer composition obtained is said to be usable in different applications wherein its mechanical and barrier properties are advantageously exploited, as well as other properties such as, for example, conductivity, flame retarding and heat conduction.

As polymer compositions usable for producing manufactured articles, such as films or slabs, having improved barrier properties and/or mechanical properties, and/or good electrical conductivity properties, can be used for various applications, their study, like the study of new processes for obtaining them, is still of great interest.

The Applicant therefore set out to find a new polymer composition that can be used for producing manufactured articles, such as films or slabs, having improved barrier properties, and/or good mechanical properties, and/or good electrical conductivity properties.

The Applicant has now found a polymer composition comprising: (a) at least one homopolymer or copolymer of ethylene; (b) a paste with a high concentration of exfoliated layered material which can be advantageously used for producing manufactured articles such as, for example, films or slabs, having improved barrier properties and good mechanical properties. Said polymer composition can also be advantageously used for producing manufactured articles such as, for example, films or slabs, having good electrical conductivity properties. Said films or slabs can, in turn, be advantageously used in various applications such as, for example, the production of manufactured articles with reduced gas permeability for packaging and tanks, or manufactured articles with improved electrical conductivity for 3D printing applications, or manufactured articles with improved electromagnetic radiation shielding (EMI shielding). Furthermore, said paste with a high concentration of exfoliated layered material can be added directly to said homopolymer or copolymer of ethylene without having to be subjected to treatments for removing the solvent. Furthermore, said paste with a high concentration of exfoliated layered material makes it possible to work in the absence of nanometric powders and, therefore, its use is advantageous both from an environmental point of view, and from the point of view of operators' health.

Therefore the subject matter of the present invention is a polymer composition comprising:.

For the purpose of the present description and of the following claims, the definitions of the numeric ranges always include the extremes unless specified otherwise.

For the purpose of the present description and of the following claims, the term "comprising" also includes the terms "which essentially consists of" or "which consists of". According to a preferred embodiment of the present invention, said polymer composition comprises:.

According to a preferred embodiment of the present invention, said homopolymer or copolymer of ethylene can be selected, for example, from:.

According to a particularly preferred embodiment of the present invention, said homopolymer or copolymer of ethylene is linear-low-density polyethylene (LLDPE). Examples of homopolymers or copolymers of ethylene that can be advantageously used in the present invention and that are currently available on the market are the products Flexirene®, Riblene®, Eraclene®, Clearflex® by Versalis; MDPE HT <NUM> by Total Petrochemical; Engage® by DuPont-Dow Elastomers; Exact® by Exxon Chemical.

The homopolymers or copolymers of ethylene mentioned above may be obtained through polymerization techniques known in the state of the art, in presence of Ziegler-Natta catalysts, or in presence of chromium catalysts, or in presence of single-site catalysts such as, for example, metallocene or hemi-metallocene catalysts, or through radical processes.

According to a preferred embodiment of the present invention, said paste with a high concentration of an exfoliated layered material comprises:.

the sum of (i) + (ii) + (iii) being equal to <NUM>.

According to a further preferred embodiment of the present invention, said paste with a high concentration of an exfoliated layered material comprises:.

the sum of (i) + (ii) + (iv) being equal to <NUM>.

the sum of (i) + (ii) + (iii) + (iv) being equal to <NUM>.

According to the present invention, said at least one exfoliated layered material (i) is selected from: graphene; graphene oxide; reduced graphene oxide; graphene nanoplates; boron nitride; phosphorene (monoatomic layer of black phosphorus); di- and tri-chalcogenides of transition metals such as, for example, tungsten disulfide (IV), tungsten diselenide (VI), molybdenum disulfide, bismuth tellurium; or mixtures thereof. Preferably, said at least one exfoliated layered material (a) is selected from graphene, graphene nanoplates, or mixtures thereof.

For the purpose of the present invention, said exfoliated layered material (i) can be prepared through exfoliation processes in the liquid phase known in the state of the art such as, for example, wet-jet milling, ultra-sonication, shear mixing. Preferably, said exfoliated layered material can be prepared through wet-jet milling: more details related to said wet-jet milling can be found, for example, both in international patent application <CIT> and in the examples which follow. Generally, said wet-jet milling comprises the exfoliation of a layered material (for example, graphite) using shear forces that are generated thanks to the passage of said layered material, appropriately dispersed in an organic solvent [for example, N-methyl-<NUM>-pyrrolidinone (NMP)], through a micronization device (known as a nozzle), adapted to generate forces that can compress the dispersion of layered material/organic solvent obtained. By checking the chemical/physical parameters of the dispersing medium used (i.e. said organic solvent) and the fluid dynamic parameters of the dispersion (i.e. layered material/organic solvent dispersion), it is possible to process said layered material by exposing it to one or more wet-jet-milling cycles through said micronization device (i.e. nozzle). Subsequently, said dispersing medium (i.e. said organic solvent) is removed through the use of a rotating evaporator and the exfoliated material obtained is dispersed again in an organic solvent suitable for the subsequent freeze-drying [for example, dimethylsulfoxide (DMS)] in order to obtain a powder comprising flakes of exfoliated layered material.

For the purpose of the present description and of the following claims, said exfoliated layered material is defined dimensionally with reference to a system of Cartesian axes x, y and z, meaning that the particles that compose it are substantially flat platelets but that can also have an irregular shape. In any case, the lateral dimension and thickness provided with reference to directions x, y and z, are to be considered the maximum dimensions in each of the aforesaid directions.

The lateral dimensions (x, y) of the particles of said exfoliated material are determined by direct measurement with the Transmission Electron Microscope - TEM. For that purpose, an aliquot of the dispersion obtained through wet-jet milling is picked and diluted appropriately, for example with a dilution ratio of <NUM>:<NUM> with the same organic solvent used for the exfoliation process. After depositing a drop on a suitable grid for an electronic microscope, it is possible to obtain images of the flakes of exfoliated material, using the aforesaid transmission electron microscope - TEM. Through processing software coupled to said microscope, the lateral dimensions of the flakes of exfoliated material are measured and said dimensions are calculated from statistical data deriving from the analysis of at least a hundred flakes.

The thickness (z) of the particles of said exfoliated layered material was determined with an Atomic Force Microscope - AFM, which is essentially a profilometer with sub-nanometer resolution, widely used for the (mainly morphological) characterization of surfaces and nanomaterials. This type of analysis is commonly used to evaluate the thickness of flakes of exfoliated layered material, in particular graphene, obtained according to any process reported above, and therefore to obtain the number of layers of which they are composed. For that purpose, an aliquot of the dispersion obtained through wet-jet milling is picked and diluted appropriately, for example with a dilution ratio of <NUM>:<NUM> with the same organic solvent used for the exfoliation process. <NUM> microliters of the sample thus obtained are deposited on a silicon wafer that is dried at a temperature of <NUM>, for a night and then subjected to scanning through an atomic force microscope - AFM (AFM Bruker Innova) in tapping mode. Through processing software coupled to said microscope, the thicknesses of the flakes of exfoliated material are measured and said dimensions are calculated from statistical data deriving from the analysis of at least a hundred flakes.

According to a preferred embodiment of the present invention, the particles of said exfoliated layered material (i) have a lateral dimension (x, y) not higher than <NUM>, preferably ranging from <NUM> to <NUM>.

According to a preferred embodiment of the present invention, the particles of said exfoliated layered material (i) have a thickness (z) not higher than <NUM>, preferably ranging from <NUM> to <NUM>.

It is to be noted that, in any case, the lateral dimension is always a lot higher than the thickness (x, y > z).

According to a preferred embodiment of the present invention, the particles of said exfoliated layered material (i) have a surface area higher than <NUM><NUM>/g, preferably higher than <NUM><NUM>/g.

According to a particularly preferred embodiment of the present invention, the particles of said exfoliated layered material (a) have a surface area ranging from <NUM><NUM>/g to <NUM><NUM>/g, preferably ranging from <NUM><NUM>/g to <NUM><NUM>/g.

The surface area was measured according to the BET nitrogen adsorption method. According to a preferred embodiment of the present invention, said first additive selected from liquid stabilizers at room temperature (ii) can be selected, for example, from:.

Specific examples of antioxidants that can be advantageously used for the purpose of the present invention and that are currently available on the market are: Anox® <NUM> by Addivant (sterically hindered phenol), Weston® <NUM> by Addivant (phosphite), Irgafos® <NUM> by Basf (phosphite), Irganox® E <NUM> by Basf (antioxidant based on vitamin E). According to a preferred embodiment of the present invention, said first additive selected from liquid stabilizers at room temperature (ii) can comprise:.

According to a preferred embodiment of the present invention, said organic solvent (iii) can be selected, for example, from: high boiling point aromatic solvents such as, for example, benzene, methylbenzene, ethylbenzene, xylene, toluene, or mixtures thereof; hydrocarbon solvents with a low aromatic content (i.e. aromatic content ≤ <NUM>) such as, for example, hydrocarbon solvents of the Spirdane® series of Total (e.g., Spirdane® D60), or mixtures thereof; or mixtures thereof. Ethylbenzene is preferred.

According to a preferred embodiment of the present invention, said second additive (iv) can be selected, for example, from:.

Specific examples of sterically hindered amines that can be advantageously used for the purpose of the present invention and that are currently available on the market are: Tinuvin® <NUM>, Tinuvin® <NUM> by Ciba.

Specific examples of UV stabilizers (UV absorbers) that can be advantageously used for the purpose of the present invention and that are currently available on the market are the products Chimassorb® <NUM> by Basf (benzophenone), Ciba® Tinuvin® <NUM> by Ciba (benzotriazole).

As mentioned above, the present invention also relates to a process for preparing the aforesaid polymer composition.

Therefore, further subject matter of the present invention is also a process for the preparation of a polymer composition as defined by claim <NUM>.

In particular, said process comprises the following steps:.

According to a preferred embodiment of the present invention, said step (a<NUM>) comprises the following steps:.

According to a preferred embodiment of the present invention, said step (a<NUM>) can be carried out at a temperature ranging from <NUM> to <NUM>, preferably ranging from <NUM> to <NUM>, for a time ranging from <NUM> minute to <NUM> minutes, preferably ranging from <NUM> minutes to <NUM> minutes, at a rotation speed ranging from <NUM> rpm to <NUM> rpm, preferably ranging from <NUM> rpm to <NUM> rpm.

For the purpose of obtaining a more uniform paste with a high concentration of exfoliated layered material, said step (a<NUM>) is preferably carried out in a planetary mixer that allows the simultaneous mixing and de-airing of the mixture.

According to a preferred embodiment of the present invention, said step (b<NUM>) can be carried out at a temperature ranging from <NUM> to <NUM>, preferably ranging from <NUM> to <NUM>, for a time ranging from <NUM> minute to <NUM> minutes, preferably ranging from <NUM> minutes to <NUM> minutes, at a rotation speed ranging from <NUM> rpm to <NUM> rpm, preferably ranging from <NUM> rpm to <NUM> rpm.

Said step (b<NUM>) can be advantageously carried out in a turbomixer.

According to a preferred embodiment of the present invention, the polymer composition obtained in said step (b<NUM>) can be fed to an extruder, operating under the following conditions:.

At the end of extrusion, the polymer composition obtained can be recovered, for example, in the form of "spaghetti" and, subsequently, cooled to room temperature and granulated: further details can be found in the examples reported below.

According to a further embodiment of the present invention, the process according to the present invention can comprise the following steps:.

According to a preferred embodiment of the present invention, said step (i) can be carried out under the following operating conditions:.

According to a preferred embodiment of the present invention, said step (ii) can be carried out under the following operating conditions:.

For the purpose of the aforesaid process, said extruder may be, for example, a single-screw extruder or a co-rotating or counter-rotating twin-screw extruder, preferably a co-rotating twin-screw extruder.

For the purpose of the aforesaid process, the feeding of the polymer or homopolymer of ethylene and the paste with a high concentration of exfoliated layered material to the extruder can be carried out through devices known in the state of the art such as, for example, dosing pumps, metering devices. In particular, the paste with a high concentration of exfoliated layered material can be fed to the extruder through heated dosing pumps for the purpose of increasing the fluidity thereof.

As mentioned above, the present invention also relates to the manufactured articles obtained from the aforesaid polymer composition.

For the purpose of understanding the present invention better and to put it into practice, below are some illustrative and non-limiting examples thereof.

For the purpose, the exfoliation system described and claimed in patent application <CIT> reported above was used.

<NUM> of graphite flakes (Aldrich) were dispersed in <NUM> of N-methyl-<NUM>-pyrrolidone (NMP): the dispersion obtained was loaded into an exfoliation station including a nozzle device for wet-jet milling operating under the following conditions:.

At the end of said wet-jet milling cycles, everything was transferred into a rotary evaporator for the purpose of removing the solvent used and the exfoliated material obtained was dispersed again in <NUM> of dimethylsulfoxide (DMS) (Aldrich), poured into an aluminum container and frozen at -<NUM>. Subsequently, the solid obtained was transferred to a freeze-dryer and heated to <NUM> obtaining <NUM> of a powder comprising graphene flakes having the following dimensions (the measurements are performed as reported above):.

The following were loaded into a planetary mixer, provided with a magnetic stirrer: <NUM> of Weston® <NUM> (Addivant) (phosphite), <NUM> of Irganox® E <NUM> by Basf (antioxidant based on vitamin E) and <NUM> of ethylbenzene (Aldrich): the mixture obtained was kept, under stirring, at <NUM> rpm, at room temperature (<NUM>), for <NUM> minutes. Subsequently, <NUM> of the powder comprising graphene flakes obtained as described in Example <NUM> were added to the mixture obtained: everything was left, under stirring, at <NUM> rpm, at room temperature (<NUM>), for <NUM> minutes, obtaining <NUM> of a graphene paste having the following concentration:.

The following were loaded into a planetary mixer, provided with a magnetic stirrer: <NUM> of exfoliated graphene obtained as described in Example <NUM> and <NUM> of ethylbenzene (Aldrich): the mixture obtained was kept, under stirring, at <NUM> rpm, at room temperature (<NUM>), for <NUM> minutes.

The following were loaded into a planetary mixer, provided with a magnetic stirrer: <NUM> of exfoliated graphene obtained as described in Example <NUM> and <NUM> of n-hexane (Aldrich): the mixture obtained was kept, under stirring, at <NUM> rpm, at room temperature (<NUM>), for <NUM> minutes.

<NUM> parts of linear-low-density polyethylene (LLDPE) (Flexirene® CL10 U by Versalis S. ) nascent powder, and <NUM> parts of graphene paste obtained as described in Example <NUM>, were loaded into a PLASMEC TRL10 turbomixer, and maintained under stirring at <NUM> rpm, for <NUM> minutes, at room temperature (<NUM>). Subsequently, the mixture obtained was loaded into a co-rotating twin-screw extruder (D = <NUM>; LID = <NUM>) with a die plate having cylindrical holes with a diameter of <NUM>, a length of <NUM> and flow rate per individual extrusion hole of <NUM>/h. Everything was extruded operating at a constant temperature profile of <NUM>, at a constant pressure profile of <NUM> bar, at a flow rate of <NUM>/h per individual hole, and at a screw rotation speed of <NUM> rpm. The material extruded in "spaghetti" form was cooled in a water bath, dried in air and granulated using a chopper. Part of the granules obtained were compression molded at <NUM>, <NUM> bar, for <NUM> minutes, obtaining a film of dimensions 200x200x0. <NUM> which was subjected to both oxygen permeability analysis according to standard ASTM D3985-<NUM>, and to stress at break analysis according to standard ASTM D638-<NUM>: the data obtained are shown in Table <NUM>.

<NUM> of linear-low-density polyethylene (LLDPE) (Flexirene® CL10 U by Versalis S. ) nascent powder, and <NUM> of graphene paste obtained as described in Example <NUM>, were loaded into a PLASMEC TRL10 turbomixer, and maintained under stirring at <NUM> rpm, for <NUM> minutes, at room temperature (<NUM>). Subsequently, the mixture obtained was subjected to the same process described in Example <NUM> and the film of dimensions 200x200x0. <NUM> obtained was subjected to both oxygen permeability analysis according to standard ASTM D3985-<NUM>, and to stress at break analysis according to standard ASTM D638-<NUM>; the data obtained are shown in Table <NUM>.

<NUM> of linear-low-density polyethylene (LLDPE) (Flexirene® CL10 U by Versalis S. ) nascent powder, and <NUM> of graphene paste obtained as described in Example <NUM>, were loaded into a PLASMEC TRL10 turbomixer, and maintained under stirring at <NUM> rpm, for <NUM> minutes, at room temperature (<NUM>), obtaining a mixture that it was not possible to extrude due to excessive fluidity.

<NUM> of linear-low-density polyethylene (LLDPE) (Flexirene® CL10 U by Versalis S. ) nascent powder, and <NUM> of a masterbatch of pure graphene nanoplates (<NUM>% by weight) in a polyolefin (ZAPP G+ by DirectaPlus), were loaded into a PLASMEC TRL10 turbomixer, and maintained under stirring at <NUM> rpm, for <NUM> minutes, at room temperature (<NUM>). Subsequently, the mixture obtained was subjected to the same process described in Example <NUM> and the film of dimensions 200x200x0. <NUM> obtained was subjected to both oxygen permeability analysis according to standard ASTM D3985-<NUM>, and to stress at break analysis according to standard ASTM D638-<NUM>: the data obtained are shown in Table <NUM>.

Claim 1:
Polymer composition comprising:
(a) at least one homopolymer or copolymer of ethylene;
(b) at least one paste with a high concentration of an exfoliated layered material comprising:
(i) from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, of at least one exfoliated layered material selected from graphene; graphene oxide; reduced graphene oxide; graphene nanoplates; boron nitride; phosphorene (monoatomic layer of black phosphorus); di- and tri-chalcogenides of transition metals such as tungsten disulfide (IV), tungsten diselenide (VI), molybdenum disulfide, bismuth tellurium; or mixtures thereof; preferably, it is selected from graphene, graphene nanoplates, or mixtures thereof;
(ii) from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, of at least one first additive selected from liquid stabilizers at room temperature, said at least one first additive being selected from: (ii<NUM>) phenol-based antioxidants such as sterically hindered phenols; (ii<NUM>) antioxidants based on organic phosphites;
(iii) from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, of at least one organic solvent;
(iv) from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, of at least one second additive selected from: light stabilizers, ultraviolet ray stabilizers (UV absorbers), metallic stearates, alcohols, ketones, ethers, glycols or poly-alkylene glycols;
the sum of (i) + (ii) + (iii) + (iv) being equal to <NUM>.