WO2005028363A2

WO2005028363A2 - Organophilic clays and their use in the preparation of nanocomposite materials

Info

Publication number: WO2005028363A2
Application number: PCT/EP2004/010693
Authority: WO
Inventors: Saverio Russo; Giovanni Camino; Vittorio Bortolon
Original assignee: P. Group S.R.L.
Priority date: 2003-09-23
Filing date: 2004-09-23
Publication date: 2005-03-31
Also published as: WO2005028363A3; ITMI20031806A1

Abstract

Nanocomposite material comprising: a thermoplastic polymer with a transformation temperature ranging from 90 to 400 °C and an organophilic clay obtained by the intercalation reaction of at least one clay with a lamellar structure in powder form having an average particle size, measured according to ASTM B330/00, ranging from 10 nm to 25 µm, with a dendritic polymer selected from those having the general formula: [A(B)n]m (I); C-(G)n-Ym (V) or with a dendritic polymer having an intermediate structure between (I) and (V).

Description

ORGANOPHILIC CLAYS AND THEIR USE IN THE PREPARATION OF NANOCOMPOSITE MATERIALS The present invention relates to organophilic clays and their use in the preparation of nanocomposite materials . More specifically, the present invention relates to organophilic clays and their use with thermoplastic polymers in the preparation of nanocomposite materials with an improved structural resistance. Composite materials consisting of an organic-inorganic hybrid can have higher mechanical properties than those of single components evaluated individually. A polymeric composite material, for example, can be easily obtained by adding an inorganic component to the polymer, improving not only its mechanical properties but also other properties such as electric conductivity or impermeability to gases such as oxygen or water vapour, or flame resistance, or thermal dilation. In order to obtain these improvements, it is important to increase the length/diameter ratio (form factor) of the inorganic phase, as well as its dispersion. In filled polymers of the conventional type, there is a distinct separation, at a microscopic level, between the organic phase and the inorganic phase which represents a limit to the possibility of improving the properties of the polymeric materials . This limit can be overcome with a new group of composite materials, called nanocomposites or PLSN (Polymer Lay- ered Silicate Nanocomposites) based on a polymer and a phyllosilicate. They form a hybrid between the organic phase (polymer) and the inorganic phase. The lamellas which form the dispersed phase have a thickness in the order of a nanometer, whereas the other two dimensions can reach a micron ("lamellar" nanocomposites) . In order to improve the compatibility between the continuous polymeric phase and the dispersed inorganic phase, the latter is modified with organic cations, for example alkylammonium or alkylphosphonium ions, which, by substituting the alkaline or alkaline-earth metal ions interposed in the lamellar structure of the phyllosilicate, increase the dimension of the interlayer and make it organophilic favouring its interaction with the polymer. This new group of composite materials is described in literature, for example in U.S. patent 6,380,295. This patent describes organophilic clays obtained by modifying a clay, for example a smectite clay, with one or more compounds of quaternary ammonium and one or more non-ionic or- ganic compounds. The organophilic clays thus modified have a swollen layered structure, as the interlayer spacing has increased after the chemical-organic treatment. This swollen structure makes organophilic clays particularly suitable for forming nanocomposites with thermoplastic polymers such as polyolefins, polyester resins, polyamides, etc. The Applicant has now found a new group of organophilic clays obtained by modifying lamellar-structured clays with organic compounds, which, after mixing with thermoplastic polymers, allow nanocomposites to be obtained with improved mechanical properties such as tensile strength, elastic modulus, flexural strength, HDT and with improved flame resistance and thermal dilation properties. These organic compounds belong to a new group of polymers characterized by a highly branched structural architecture which has recently appeared in scientific literature. This group of polymers is called dendritical if: the structure has 100% of possible branchings, the polymer is defined as a dendrimer; the percentage is lower, due to accidental growth de- fects, the polymer is defined as hyperbranched. Dendritic polymers (dendrimers and hyperbranched polymers) have unusual properties, as described in "Synthesis and Properties of Dendrimers and Hyperbranched Polymers", J.M.J. Frechet and C.J. Hawker, Chapter 3 of "Comprehensive Polymer Science", 2^nd Supplement Volume, Pergamon, Oxford 1996, or in "Dendrimers and other Dendritic Polymers", J.M.J. Frechet and D.A. Tomalia, Wiley, Chichester, 2001, which make them appropriate for being studied for new applications. Two general methods have been developed for preparing dendritic polymers, depending on the structural type of the one or other subset (dendrimers or hyperbranched macromole- cules) . A multi-step preparation is applied for the former group, described for example in the above references, which almost always involves protection, growth, deprotection cycles . A simpler single-step preparative procedure is used, on the contrary, for the second group, as described, for example, in "New Developments in Hyperbranched Polymers", B. Voit, "Journal of Polymer Science Part A: Polymer Chemistry" 38 (2000), 2505. The most interesting properties of dendritic polymers are linked to their globular or almost globular structure and to the high number of chain-ends carrying functional groups of the same type which, in the case of the present invention, have proved to be particularly suitable for modifying lamellar-structured clays to be used in the preparation of PLSN. An object of the present invention therefore relates to organophilic clays comprising a reaction product ioni- cally exchanged and obtained by the intercalation of: a) at least one lamellar-structured clay in powder form having an average particle size, measured according to ASTM B330/00, ranging from 10 nm to 25 μm; with b) a dendritic polymer selected from those having the general formula: [A(B)_n]_m (I) wherein n is an integer greater than or equal to 2, preferably from 2 to 4, whereas m is an integer greater than or equal to 4, preferably from 10 to 2,000, A and B, the same or different, are functional groups capable of reacting with each other according to a polymerization mechanism selected from radicalic polymerization, controlled or living radicalic polymerization, ionic polymerization, polyconden- sation, polymerization by metathesis, polymerization by the opening of a non-aromatic cyclic ring possibly containing hetero-atoms, Ziegler-Natta polymerization and polymerization with metallocenes wherein component (a) is present in an amount of 100 parts by weight and component (b) is pres- ent in an amount of 5-40 by weight, preferably 8-30%. Examples of functional groups A or B are: - a group comprising at least one vinyl function having the general formula: Yi - CH = CH₂ (II) wherein Yi represents a Cι-C₂₅ aliphatic radical or a C₆-Cι₈ aryl or C₇-C₃₀ alkylaryl or arylalkyl radical; a group comprising at least one vinylidene function having the general formula Y₂Y₃ - C = CH₂ (III) wherein Y₂ and Y₃, the same or different, have the same meaning defined above for the radical Yi; a group comprising at least one acetylene function having the general formula:

Yi - C ≡ CH (IV) wherein Yi is defined as above in formula (II) ; a C₃-C₂₀ cyclo-aliphatic functional group, possibly containing at least one hetero-atom selected from nitrogen, oxygen, sulfur; functional groups deriving from Cι-C₃₀ hydrocarbons con- taining at least one function selected from alcohol, amine, aldehyde, ketone, carboxylic functions, optionally esterified or salified, amide, nitrile, ester, ether functions, their combinations, or containing at least one halogen; or the dendritic polymer consists of: a core (C) and growth generations (G) according to the general formula: C-(G)_n-Ym (V) wherein C is a molecule with a functionality equal to or higher than 3, characterized by functional groups selected from those listed above in the definition of A and B; G consists of identical branches, wherein each branch is made up of constitutional repetition units attributable to the specific monomer used which units are selected from Cι~C₂o aliphatic and cycloaliphatic, saturated or unsatu- rated hydrocarbons or C₆-Cι₂ (alkyl) aromatic hydrocarbons or of the polyether, polyester, polyamide, polyimide, polyurethane type; n generally ranges from 2 to 10, m generally ranges from 12 to the product between the specific core functionality and the functionality of the monomer used raised to the tenth power, whereas Y represents a terminal functional group, as defined above for A and B, or protection/functionalization groups deriving from the reaction between the dendritic polymer having general formula (I) having hydroxyl or primary amino terminal func- tional groups with a reagent containing the isocyanic or carboxylic or epoxy function or with an acyl halide R-CO- Hal, wherein R is a Cι-C₃₀ hydrocarbon radical; or the dendritic polymer has an intermediate structure between (I) and (V), for example that known as "dendrigraft" or "arborescent", as defined in the publications cited above. The dendritic polymers used in the preparation of the organophilic clays, object of the present invention, have a branching degree DB, expressed as: DB = (N_t + N_b)/(N_t + N_b + Ni) wherein N_t represents the number of chain-end groups of the dendritic polymer, N_b the number of branched groups and N_x the number of linear groups, ranging from 20 to 100%, generally from 25 to 60%. These dendritic polymers have an av- erage molecular weight up to 140,000, especially from 500 to 120,000, preferably ranging from 500 to 30,000, especially from 14,000 to 30,000, more preferably from 1,500 to 20,000, for example from 2,000 to 10,000. Dendritic polymers which are particularly suitable for the present invention are those wherein A and B are selected from amines and/or amides and derivatives, carbox- ylic acids and their salts or derivatives, halogen derivatives, alcohols and phenols, n ranges from 2 to 3, whereas m ranges from 10 to 100. Examples of these products are those available on the market under the trade-name of PAMAM, and sold by SIGMA ALDRICH, or those described in "High Performance Polymers", 2001, 13, 545-559. According to the present invention, the lamellar- structured clay is preferably a phyllo-silicate such as vermiculite, montmorillonite, cloisite, ectorite, saponite, beidellite, nontronite, stevensite and other analogous products. These products are well known in literature. Details on their chemical composition and structural morphology are available in "Crystal Structure of Clay Minerals and Their X-ray Diffraction", S.W. Bridley and G. Brown, Mineralogical Society, London 1980 and in "Science" 220, T.J. Pinnavaia, 365 (1983). Before treatment with the dendritic polymer, the clay is preferably converted, if not already so, into sodium form. In order to obtain this result, the clay is diluted in water and the suspension thus prepared is percolated through a fixed bed of an ion exchange resin of the sodium type. Alternatively, the clay suspension is mixed with a sodium compound soluble in water, for example sodium car- bonate or bicarbonate or sodium hydroxide, and then stirred vigorously. At the end of the possible preparation of the clay in sodium form, it is filtered, dried and added to the solution of dendritic polymer for the intercalation reaction. Any intercalation technique can be used for preparing the organophilic clays, object of the present invention. For example, direct intercalation can be adopted, by adding the clay, under stirring, in powder form, in sodium form, to a solution of the dendritic polymer. The solution of dendritic polymer generally consists of an inert solvent, which said dendritic polymer is dissolved in weight concentrations ranging from 0.5 to 25%. Examples of solvents are polar solvents, such as dimethylformamide, dimethylacet- amide, N-methylpyrrolidone, dimethylsulfoxide, etc. for hy- drophobic systems; water and C1-C4 alcohols, such as metha- nol, ethanol or isobutanol, in the case of hydrophilic systems . Once the solution of the dendritic polymer in the respective solvent has been obtained, the clay is added in weight concentrations ranging from 0.5% to 10% with respect to the total, the temperature being maintained at a value ranging from room temperature to the boiling point of the solvent, preferably from 25 to 100°C. The clay is added to the organic solution in powder form with an average parti- cle size ranging from 10 nm to 25 μm, preferably from 100 nm to 10 μm, suitably from 1 to 13 μm. Examples of clays in sodium form suitable for the present invention are listed below: "Cloisite Na⁺" commercialized by Southern Clay Products, Inc. (USA); "Somasif ME-100" commercialized by Unicoop Chemical Co. (JAPAN) ; "Dellite HPS" commercialized by Laviosa Chimica Mineraria S.p.A. (ITALY). According to an alternative embodiment for effecting the direct intercalation reaction, the clay, in sodium form, is exchanged with one or more alkylphosphonium or alkylammonium salts having general formula (VI) and (VII) :

Ri R₂ Ri R . / \ / P⁺ X- N⁺ X^"

wherein Ri, R₂, R₃ and R₄, the same or different, are Cι-C₂₀ (iso)alkyl or Cδ-C₂o aryl or alkylaryl radicals, on the condition that at least one of Ri, R₂, R₃ and R₄ is an (iso)alkyl radical with from 10 to 20 carbon atoms, X represents an organic anion, for example an anion of carboxylic acid, mono- or multi-functional, C1-C10, or an inorganic an- ion such as, for example, a halide, a phosphate, a sulfate, a nitrate, a carbonate. The exchange operation with the products having general formula (VI) and (VII) substantially takes place with the same procedures described above for the preparation of clay in sodium form. Once the exchange reaction has been completed, the clay is treated with the solution of dendritic polymer under the same conditions described above. At the end of the intercalation reaction, for example after a contact time be- tween the solution and clay ranging from 5 min. to 48 h., during which the suspension is maintained under continuous stirring, the organophilic clay is recovered with the known methods, for example by centrifugation, filtration and/or evaporation of the solvent. A further technique for effecting the intercalation reaction is polymerization in situ, i.e. polymerization in the presence of the sodium clay in powder form, optionally exchanged with the alkylammonium or alkylphosphonium salts having general formula (VI) or (VII), of the monomer or monomers forming the dendritic polymer. This technique can be carried out by dispersing the clay powder in the monomer or mixture of monomers and effecting the synthesis of the dendritic polymer according to the methods of the known art. At the end of the intercalation reaction in situ, the organic clay is recovered with the known filtration technique and evaporation of the reaction solvents and non- reacted monomers. A further object of the present invention relates to a nanocomposite material comprising: i) a thermoplastic polymer with a transformation temperature ranging from 90 to 400°C; and ii) an organophilic clay obtained by the intercalation reaction of at least one lamellar-structured clay in powder form having an average particle size, measured ac- cording to ASTM B330/00, ranging from 10 nm to 25 μm, with a dendritic polymer having the general formula: [A(B)„]„ (I) wherein n is an integer greater than or equal to 2, preferably from 2 to 4, whereas m is an integer greater than or equal to 4, preferably from 10 to 2,000, A and B, the same or different, are functional groups, described above, capable of reacting with each other according to a polymerization mechanism selected from radicalic polymerization, controlled or living radicalic polymerization, ionic polymerization, polycondensation, polymerization by metathesis, polymerization by the opening of a non- aromatic cyclic ring possibly containing hetero-atoms, Ziegler-Natta polymerization and polymerization with met- allocenes; or the dendritic polymer consists of: a core (C) and growth generations (G) according to the general formula: C-(G)_n-Y_m (IV) wherein C is a molecule with a functionality equal to or higher than 3, characterized by functional groups selected from those listed above; G consists of identical branches, wherein each branch is made up of constitutional repetition units attributable to the specific monomer used selected from C₁-C₂₀ aliphatic, cyclo- aliphatic, saturated or unsaturated hydrocarbons or C₆~Cι₂ (alkyl) aromatic hydrocarbons or of the polyether, polyester, polyamide, polyimide, polyurethane type, optionally with a sulfur atom instead of an oxygen atom; n generally ranges from 2 to 10, m generally ranges from 12 to the product between the specific core functionality and the functionality of the monomer used raised to the tenth power, whereas Y represents a terminal functional group, as defined above, or protection/functionalization groups deriving from the reaction between the dendritic polymer having general formula (I) having hydroxyl terminal functional groups with a reagent containing the isocyanic or carboxylic function or with an acyl halide R-CO-Hal, wherein R is a Cι-C₃₀ hydrocarbon radical; or the dendritic polymer has an intermediate structure between (I) and (V), for example that known as "dendri- graft" or "arborescent", as defined in the publications cited above. Any thermoplastic polymer can be used in the preparation of the nanocomposite materials object of the present invention. Illustrative examples comprise: polyolefins, such as high, medium or low density polyethylene, linear polyethylene, polypropylene, poly (iso) butene, polymers and copolymers of styrene such as polystyrene, impact resistant polystyrene, styrene-acrylonitrile copolymer (SAN) , acrylo- nitrile-butadiene-styrene copolymer (ABS) , copolymers of styrene with α-methylstyrene, copolymers of styrene with Cι~C₄ esters of (meth) acrylic acid, polymers of Cι~C₄ esters of (meth) acrylic acid, thermoplastic condensation polymers such as thermoplastic (co) polyester resins, for example polyethyleneterephthalate (PET) , polybutyleneterephthalate (PBT) and their copolymers, aliphatic (co) polyamides, polycarbonates, and in general thermoplastic polymers of the engineering type, such as crystalline liquid thermotropic polyesters, polyetherimides, polyetheretherketones, etc. Preferred polymers are thermoplastic (co) polyester resins, PET, PBT and their copolymers, (co) polyamides such as PA 6, PA 6, 6, PA 11 and PA 12. The hybrids between thermoplastic polymer and organophilic clays, wherein the latter are dispersed in the poly- meric matrix at a nanoscopic level, can be subdivided into two groups, intercalated nanocomposites and delaminated or exfoliated nanocomposites. In an intercalated hybrid, the single polymeric chains are interposed between the laminas of the clay whereas the latter maintains a well-defined layered structure characterized by the regular alternation of polymer and lamellas. The distance between the various laminas, which represents the space occupied by the polymer, is generally a few nanometers . In a delaminated hybrid, the clay is completely exfo- liated and is uniformly dispersed in the polymeric matrix. The clay has completely lost its ordinate structure and the distance between the lamellas is in the order of the gyration radius of the polymer. According to this subdivision, it can be said that an intercalated nanocomposite material forms a system with a limited miscibility whereas a delaminated nanocomposite material represents a system with a complete miscibility. This schematization obviously represents two extremes within which various systems can actually be found in which both the intercalated hybrid and delaminated hybrid can be contemporaneously present in different percentages. In contrast with these structures, the conventional composites have a microscopic distribution in the polymeric matrix, of the clay wherein the lamellar structure maintains its original layered aggregation state. Both in the case of intercalated nanocomposites and in the case of delaminated or exfoliated nanocomposites, the concentration of organophilic clays in the thermoplastic polymer ranges from 0.5 to 30% by weight, preferably from 2 to 6%. The nanocomposites, object of the present invention, can be prepared with conventional methods. For example, the organophilic clay can be added to the thermoplastic polymer in the molten state using equipment normally used for transforming thermoplastic polymers, for example single- or twin-screw extruders and internal mixers. This technique is particularly suitable for organophilic clays comprising dendritic polymers with a high thermal stability. Other methods comprise polymerization in situ and mixing in solution. Some illustrative and non-limiting examples are provided hereunder for a better understanding of the present invention and for its embodiment. EXAMPLE 1 The product polyamidoamine-OH (4^th generation), PAMAM- OH of Aldrich was used as compatibilizing dendritic polymer. The polymer is sold as an alcohol solution (10% by weight in methanol) and in order to be used as compatibi- lizing agent, it is dissolved in water. For this reason, the methanol was eliminated by treating the solution at a rotavapor and adding water to the partially anhydrous polymer. The clay is cloisite-Na⁺, purchased from Southern Clay Products, of which 90% has a particle size lower than 13 μm. 50 ml of demineralized water are poured into a beaker, containing non-modified clay, with stirring at room temperature. The beaker is then heated on a heating plate to about 100°C for approximately ten minutes and subsequently, the aqueous solution of the dendrimer is added, under constant stirring, in such a quantity as to form, after evaporation of the water, 30% by weight of the material obtained. The temperature is raised to about 150 °C and the stirring is continued until a homogeneous suspension is obtained. It is then left to evaporate, under bland stirring, until a gel is obtained. The gel is dried in an oven for a day at 50°C and subsequently for another day at 100°C. X-ray diffractometry and TEM analysis showed the intercalation of the dendritic polymer in the clay. Table 1 below indicates the data relating to the interplanar distances dooi which verify, through an increase in the inter- lamellar distances, the insertion of the dendrimer. Table 1

A thermogravimetric analysis (TGA) in air and nitrogen was also carried out on this system, at a heating rate of 10°C/min and with a gas flow of 30 cm³/min, which allowed the protection effect of the clay on the dendrimer to be revealed. Table 2 indicates the results. Table 2

EXAMPLE 2 The preparation was effected by exactly repeating the procedures described in Example 1, with the only difference that the dendritic polymer was polyamidoamine-NH₂ (4^th generation), again of Aldrich. X-ray diffractometry showed the intercalation of the polymer in the clay. Table 3 below indicates the data relating to the interlamellar distances dooi- Table 3

These results were confirmed by TEM analysis of the clay/polyamidoamine-NH₂ system. Also in this case an inter- calated morphology was revealed. A thermogravimetric analysis (TGA) in air and nitrogen was also carried out on the system thus obtained, at a heating rate of 10°C/min and with a gas flow of 30 cm³/min, which allowed the protection effect of the clay on the dendrimer to be revealed. Table 4 indicates the results. Table 4

EXAMPLE 3 The preparation was effected by exactly repeating the procedures described in Example 1, with the only difference that the dendritic polymer was polyamidoamine-NH₂ of the 5^th generation, again of Aldrich. X-ray diffractometry showed the intercalation of the polymer in the clay. Table 5 below indicates the data relating to the interlamellar distances d₀oι. Table 5

These results were confirmed by TEM analysis of the clay/polyamidoamine-NH₂ system. Also in this case an intercalated morphology was revealed. EXAMPLE 4 The preparation was effected by exactly repeating the procedures described in Example 1, with the only difference that the dendritic polymer was polyamidoamine-NH₂ of the 6^th generation, again of Aldrich. X-ray diffractometry showed the intercalation of the polymer in the clay. Table 6 below indicates the data relating to the interlamellar distances dooi. Table 6

These results were confirmed by TEM analysis of the clay/polyamidoamine-NH₂ system. Also in this case an intercalated morphology was revealed. EXAMPLE 5 The preparation was effected by exactly repeating the procedures described in Example 1, with the only difference that the dendritic polymer was polyamidoamine-OH of the 7^th generation, again of Aldrich. X-ray diffractometry showed the intercalation of the polymer in the clay. Table 7 below indicates the data relating to the interlamellar distances dnoi.

Table 7

These results were confirmed by TEM analysis of the clay/polyamidoamine-OH system. Also in this case an intercalated morphology was revealed. A thermogravimetric analysis (TGA) in air and nitrogen was also carried out on the system thus obtained, at a heating rate of 10°C/min and with a gas flow of 30 cm³/min, which allowed the protection effect of the clay on the dendrimer to be revealed. Table 8 indicates the results. Table 8

The products obtained in Examples 1-5 were used for preparing nanocomposite materials based on PBT (PIBITER of the Applicant) and PA 6 (VIVIONPLAST B again of the Applicant) containing 3.5% and 4.0% by weight of modified clays as indicated above, respectively. The nanocomposite materials were prepared in co-rotating twin-screw extruders, of the Werner ZSK 40 type, operating with a temperature profile of about 250°C. In all cases, composite materials were obtained in which the modified inorganic phase proved to be homogeneously dispersed in the polymer.

Claims

CLAIMS 1. Organophilic clays consisting of an ionically exchanged reaction product and obtained by the intercalation of: a) at least one lamellar-structured clay in powder form having an average particle size, measured according to ASTM

B330/00, ranging from 10 nm to 25 μm; with b) a dendritic polymer selected from those having the gen- eral formula: [A⁽B⁾ _n-m (I) wherein n is an integer greater than or equal to 2, preferably from 2 to 4, whereas m is an integer greater than or equal to 4, preferably from 10 to 2,000, A and B, the same or different, are functional groups capable of reacting with each other according to a polymerization mechanism selected from radicalic polymerization, controlled or living radicalic polymerization, ionic polymerization, polycondensation, polymerization by metathe- sis, polymerization by the opening of a non-aromatic cy- clic ring possibly containing hetero-atoms, Ziegler-Natta polymerization and polymerization with metallocenes, wherein component (a) is present in an amount of 100 parts by weight and component (b) is present in an amount of 5-40 by weight.

2. Organophilic clays consisting of an ionically exchanged reaction product and obtained by the intercalation of: a) at least one lamellar-structured clay in powder form hav- ing an average particle size, measured according to ASTM B330/00, ranging from 10 nm to 25 μm; with b) 5-40% by weight, with respect 100 parts by weight of (a) , of a dendritic polymer consisting of a core (C) and growth generations (G) according to the general formula: C-(G)„-Y_m (V) wherein C is a molecule with a functionality equal to or higher than 3, characterized by functional groups selected from those listed in claim 1 in the definition of A and B; G consists of identical branches, wherein each branch is made up of constitutional repetition units attributable to the specific monomer used, which units are selected from Cι-C₂₀ aliphatic and cycloaliphatic, saturated or unsaturated hydrocarbons or C₆-Cι₂ (al- kyl) aromatic hydrocarbons or of the polyether, polyes- ter, polyamide, polyimide, polyurethane type; n gener- ally ranges from 2 to 10, m generally ranges from 12 to the product between the specific core functionality and the functionality of the monomer used raised to the tenth power, whereas Y represents a terminal functional group, as defined above for A and B, or protection/ functionalization groups deriving from the reaction between the dendritic polymer having general formula (I) , as defined in claim 1, having hydrox^'yl or primary amino terminal functional groups with a reagent containing the isocyanic or carboxylic or epoxy function or with an acyl halide R-CO-Hal, wherein R is a Cι-C₃₀ hydrocarbon radical .

3. Organophilic clays consisting of an ionically exchanged reaction product and obtained by the intercalation of: a) at least one lamellar-structured clay in powder form having an average particle size, measured according to

ASTM B330/00, ranging from 10 nm to 25 μm; with b) a dendritic polymer having an intermediate structure be- tween formula (I), as defined in claim 1, and formula (V), as defined in claim 2, wherein component (a) is present in an amount of 100 parts by weight and component (b) is present in an amount of 5-40 by weight.

4. The organophilic clays according to claim 1, wherein A and B are selected from: - a group comprising at least one vinyl function having the general formula: Yi - CH = CH₂ (II) wherein Yi represents a Cι-C₂₅ aliphatic radical or a C₆-Cι₈ aryl or C-Co alkylaryl or arylalkyl radical; a group comprising at least one vinylidene function having the general formula Y₂Y₃ - C = CH₂ (III) wherein Y₂ and Y₃, the same or different, have the same meaning defined above for the radical Yi; a group comprising at least one acetylene function having the general formula: Yi - C ≡ CH (IV) wherein YI is defined as above in Formula (II); - a C₃-C₂₀ cyclo-aliphatic functional group, possibly containing at least one hetero-atom selected from nitrogen, oxygen, sulfur; functional groups deriving from Cι-C₃₀ hydrocarbons containing at least one function selected from alcohol, amine, aldehyde, ketone, carboxylic functions, optionally esterified or salified, amide, nitrile, ester, ether functions, their combinations, or containing at least one halogen.

5. The organophilic clays according to claims 1, 2 or 3, wherein the dendritic polymers have a branching degree DB, expressed as : DB = (N_t + N_b)/(N_t + Nb + Ni) wherein N_t represents the number of chain-end groups of the dendritic polymer, N_b the number of branched groups and Ni the number of linear groups, ranging from 20 to 100%

6. The organophilic clays according to any of the previous claims, wherein the dendritic polymers have an average molecular weight ranging from 500 to 30,000.

7. The organophilic clays according to any of the previ- ous claims, wherein the dendritic polymers are those wherein A and B are selected from amines and/or amides and derivatives, carboxylic acids and their salts or derivatives, halogen-derivatives, alcohols and phenols, n ranges from 2 to 3, whereas m ranges from 10 to 100.

8. The organophilic clays according to any of the previous claims, wherein the lamellar-structured clay is a phyllo-silicate selected from vermiculite, montmorillonite, cloisite, ectorite, saponite, beidellite, nontronite, ste- vensite.

9. The organophilic clays according to any of the previous claims, wherein the lamellar-structured clay is in sodium form.

10. The organophilic clays according to any of the previous claims, wherein the lamellar-structured clay has an av- erage particle size ranging from 100 nm to 10 μm.

11. A process for the preparation of the organophilic clays according to any of the claims from 1 to 10, which comprises adding, under stirring, the clay in powder form to a solution of the dendritic polymer in weight concentra- tions of the clay ranging from 0.5% to 10% with respect to the total, or by adding said polymer solution to the said clay solution, maintaining the temperature at a value ranging from room temperature to the boiling point of the solvent, preferably from 25 to 100°C.

12. A process for the preparation of the organophilic clays according to any of the claims from 1 to 10, which comprises exchanging the clay, in sodium form, with one or more alkylphosphonium or alkylammonium salts having general formula (VI) and (VII) :

R-i R Ri R

P⁺ X^' N⁺ X-

wherein R_l R₂, R₃ and R₄, the same or different, are Cι-C₂₀ (iso)alkyl or C₆-C₂o aryl or alkylaryl radicals, on the condition that at least one of Ri, R₂, R₃ and R₄ is an (iso)alkyl radical with from 10 to 20 carbon atoms, X represents an organic anion, for example an anion of carbox- ylic acid, mono- or multi-functional, Cχ-Cιo, or an inor- ganic anion such as, for example, a halide, a phosphate, a sulfate, a- nitrate, a carbonate, and adding, under stirring, the exchanged clay to a solution of the dendritic polymer in weight concentrations ranging from 0.5% to 10% with respect to the total, or by adding said polymer solu- tion to the said clay solution, maintaining the temperature at a value ranging from room temperature to the boiling point of the solvent, preferably from 25 to 100°C.

13. The process according to claim 11 or 12, wherein the contact time between the solution and the clay ranges from 5 minutes to 48 hours.

14. A process for the preparation of the organophilic clays according to any of the claims from 1 to 10, which comprises polymerizing the monomer or monomers forming the dendritic polymer in the presence of the sodium clay in powder form, optionally exchanged with the alkylammonium or alkylphosphonium salts having general formula (VI) or (VII) .

15. Use of the organophilic clays according to any of the claims 1 to 10 for the preparation of nanocomposite materi- als.

16. A nanocomposite material comprising: i) a thermoplastic polymer with a transformation temperature ranging from 90 to 400°C; and ii) an organophilic clay obtained by the intercalation re- action of at least one lamellar-structured clay in powder form having an average particle size, measured according to ASTM B330/00, ranging from 10 nm to 25 μm, with a dendritic polymer as claimed in claims 1 to 10 or as obtained according to claims 11 to 14.

17. The nanocomposite material according to claim 16, wherein the thermoplastic polymer is selected from thermoplastic (co) polyester resins, PET, PBT and their copolymers, the (co) polyamides PA6, PA 6,6, PA 11 and PA 12.

18. The nanocomposite material according to claim 16, wherein the concentration of organophilic clays in the thermoplastic polymer ranges from 0.5 to 30% by weight, preferably from 2 to 6%.