WO2005068365A1 - Intercalated layered materials particularly nanoclays - Google Patents

Abstract

Exfoliated nanoclays and a process for the preparation of exfoliated nanoclays from ordinary layered smectic clays [such as bentonite mineral clay] is described. The procedure by which exfoliation occurs in clay is by insertion of intercalants (chemicals/swelling agents/solvents/ monomers/ polymers). The intercalants may or may not form a compound with clay and after appropriate time interval may be kept in a heat sink. This process disturbs regularity in the arrangement of layers. By this process it is possible to obtain partially or fully exfoliated nanoclays. Since in the present invention there is direct exfoliation, no spacing exists in the completely disordered stacks of nanoclay. Nanoclays are very useful in improving the properties of thermoplastics and thermoset matrices by formation of nanocomposites. In the example shown above, tensile strength-at-break in PP nanocomposites goes up 350% in comparison with that obtained using 'Cloisite 20A', although at a slight reduction in impact strength.

Description

INTERCALATED LAYERED MATERIALS PARTICULARLY NANOCLAYS FIELD OF THE OF THE INVENTION The present invention relates to intercalated layered materials. In particular, the present invention relates to exfoliated nanoclays and processes for the preparation thereof. More particularly, the present invention relates to a process for the preparation of exfoliated nanoclays by contacting and thereby intercalating a layered silicate clay material such as bentonite by sorption of an aqueous intercalant. The intercalant solution enters inside clay and causes it to interact with water present inside the clay mineral. The resulting clay is put in a heat sink, dried and tested by x-ray diffraction. This results in producing exfoliated nanoclays from layered mineral clays. Once exfoliated, the platelets of the intercalant are predominantly completely separated into individual platelets. The originally adjacent platelets no longer are retained in a parallel, spaced disposition, but are free to move. BACKGROUND OF THE INVENTION Recent advances in polymer/clay and polymer/silicate nano-composite materials have inspired efforts to disperse montmorillonite-based fillers in PP. Although it has been long known that polymers can be mixed with appropriately modified clay minerals and synthetic clays, the field of polymer/silicate nano-composites has gained large momentum only recently. Two major research findings pioneered the revival of nanomaterials: first the report of a nylon-6/montmorillonite material from Toyota research [Y.; Kurauchi T.T., Kamigaito, O.J Mater. Res. 1993, 8, 1179-1185 and Kojima, Y.; Usuki, A; Kawasumi, M; Okada, A.; Kurauchi, T.T.; Kamigaito. O.J Polym. Sci. Part A: Polym. Chem. 1993, 31 983], where very moderate inorganic loadings resulted in concurrent and remarkable enhancements of thermal and mechanical properties. Second , Giannelis et al. [Naia, R.A.; Ishii, H.; Giannelis, E. P. Chem. Mater, 1993, 5, 1694-1696] found that it is possible to melt-mix polymers with clays without the use of organic solvents. Since then, the high promise for industrial applications has motivated vigorous research, which revealed concurrent dramatic enhancements of many materials properties by the nano-dispersion of inorganic silicate layers. Intercalated and exfoliated structures may coexist in nanocomposites. Nanoclay is the latest layered clay for making plastics nanocomposites which have superior mechnical properties, barrier properties and flame resistance over conventional plastics and yet their optical properties remain intact because the addition level of nanoclay is in 1 to 6% range. In market the availability of nanoclay is very expensive [$55/lb] and it is marketed as masterbatches to mask their identity. This exorbitant cost is an inhibiting factor, which prevents widespread use of nanoclays in plastics and wider use of nanocomposites in many areas. International companies such as Polyone, Nanocor, RTP Inc., TNO, Southern Clay Products Inc., etc. are well known supplies of nanoclays/masterbatches. Nanoclays are surface modified montmorillonite minerals available for a range polymer resins from commodity polyolefins to specialty polyamides. Incorporation into these resins forms a nanocomposite plastic. Because Nanoclays are used at low addition levels, significant property improvement is achieved with lighter weight parts. Nanoclays have a platey morphology.

DESCRIPTION OF THE PRIOR ART The layered clays originated from volcanic ash. Common clays are naturally occurring minerals. The term "Bentonite" was applied for the first time to a particular kind of clay discovered near Fort Benton, Wyoming. This clay displays strong colloidal properties and when in contact with water, increases its volume several fold by swelling, giving rise to a thixotropic, gelatinous substance, but the other clay minerals such as illite and kaolinite may be present. The composition of montmorillonite [MMT] itself varies from one bentonite to another, but lies in the range of 75-95%. Layered smectite- type MMT, a hydrous alumina silicate mineral whose lamellae are constructed from octahedral alumina sheets sandwiched between two tetrahedral silicate sheets, exhibits a net negative charge on the lamellar surface, which enables them to adsorb cations, such as Na+ or Ca++. Compatibility with various polymers is accomplished by modifying the silicates with alkylammonium cations via an ion exchange reaction [[Y.; Kurauchi T.T., Kamigaito, O.J Mater. Res. 1993, 8, 1179-1185 and Kojima, Y.; Usuki, A; Kawasumi, M; Okada, A.; Kurauchi, T.T.; Kamigaito. O.J Polym. Sci. Part A: Polym. Chem. 1993, 31 983]]. Because the negative charge orginates from the silicate layer, the cationic head groups of the alkylammonium molecule preferentially resides at the layer surface, while the aliphatic tail is removed from the surface. The presence of these aliphatic chains in the galleries modifies the original hydrophilic silicate surface to be organophillic. Furthermore, the organic cations contain various functional groups that react with the polymers and reinforce adhesion between the particles and the matrix, thus producing nanocomposites with excellent dispersion quality in organic solvents. As the surfactant chain length gets larger, the charge density of the clay and the spacing between the clay layers increase. There have been several innovations in this area and many patents have been granted. AMCOL International Corporation has been active in seeking patent protection in this field and Nanocor is the beneficial holder of over two dozen US patents. US 6,399,690 (2002) granted the above said company describes preparation of layered compositions with multicharged onium ions as exchange cations and their application to prepare intercalated and nanocomposites. US Patent No. 6,391,449 (2002) issued to the same company reveals methods of preparing polymer clay intercalates, exfoliates and nanocomposites having improved gas permeability. US Patent No. 6,287,634 (2001) granted to the same company describes intercalates and exfoliates formed with monomeric ethers and esters and composites formed with polymer matrix. EP 084662 (1998) and WO 93 04118 of the same company describe process for manufacturing intercalates and exfoliates with an intercalant surface modifier selected from the group consisting of a compound having an alkyl radical, a compound containing an aromatic ring and mixtures thereof. US Patent No. 6,380,295 (2002) of Rheox Inc. teaches the preparation of hybrid organoclay that consist of an organic chemical / phyllo silicate clay intercalate that has been ion-exchanged with quaternary ammonium compounds and further their nanocomposites and also as Theological additives. US Patent No.6,07,988 (2000) granted to Eastman Chemical Company illustrates a method for the manufacture of polyester composite material comprising platelet particles treated with at least one polyalkoxylated ammonium salt. JP Kokai 9-176461 discloses method of making polyester bottles wherein the polyester contains swellable laminar silicate. WO 97/31057 discloses polymer composites having dispersed therein inorganic materials such as clay, which is separated with an inorganic intercalant. WO 97/31973 discloses producing a composite material by mixing potassium ionomer in which an ethylene methacrylate copolymer is either partially or completely neutralized with an organic polymer. US Patent Nos. 4,739,007 and 5,164,460 disclose polyamide and polyimide composite materials respectively containing layered clay mineral intercalated with organic salts. In all the above patents, the intercalant were organic solvents. The organic pretreatment of the clay adds to the cost of the clay, even though the clay are relatively cheap. Need for intercalated and exfoliated clays has been growing as the field of Nanocomposites is at an embryonic stage of development today. A decade ago nanocomposite technology was a concept with great potential. Today, it is a reality. OBJECTS OF THE INVENTION It is an object of the present invention to provide a process for the preparation of intercalated clay that is simple to use and economical to practice. It is another object of the present invention to provide a process for the preparation of intercalated exfoliated clay that is simple to use and economical to practice. It is another object of the present invention to provide a process for the preparation of intercalated exfoliated clay that is simple to use and economical to practice from smectic mineral clay [e.g., bentonite, of local or international origin] for preparation of polymer nanocomposites. It is yet another object of the present invention to provide a process for the preparation of intercalated exfoliated clay employing intercalants or exfoliating agents that are environmental friendly.

SUMMARY OF THE INVENTION The above and other objects of the present invention are achieved by the process of the present invention, which makes use of water-friendly nature of clay (and not ion-exchange). A hydroxyl-rich molecules enters clay enters gallery of clay, forms hydrogen bonds with -OH groups present in clay. This process is repeated until the gallery expands and swelling of clay occurs. Water molecules of clay are absorbed by intercalant, thus breaking crystal lattice of clay partially of totally. Another method to convert clay into nanoclay is to use a "thermal shock" technique [at temperatures varying or stationery between ~100°C and 100°C which eliminates water molecules from various locations in clay: the crystallites, inter- and intralayer water, water absorbed on surface of platelets etc. The purpose of this invention is to increase unrestricted availability of nanoclays to plastic producers and plastics processors-small as well as large-to create vast, untapped markets for plastics. The present invention thus relates to production of nanoclays for creating new markets for polymer nanocomposites from all types of plastics [biopolymers. thermoplastics, engineering plastics, thermosets, fibers, etc.] and boosting the per capita consumption of plastics without posing and threat to environment. Accordingly, the present invention provides exfoliated nanoclay which comprises layered clay [e.g., sodium bentonite] and an intercalation material sorbed between layers of said layered clay. In a preferred embodiment, said intercalation material is present in a concentration of from 10 to 100 % by weight based on the dry weight of said layered clay. In another embodiment, said intercalation material is pure or an aqueous solution of a hydroxyl-rich molecule. Preferably, said hydroxyl-rich molecule has the general formula:

n In another preferred embodiment, said hydroxyl - rich molecule is selected from the group consisting of one or more of water, ethanol, butanol or C4 alcohol, ethylene glycol, glycerol, poly (ethylene) glycol and poly (vinyl alcohol). Said hydroxyl - rich molecule preferably comprises aqueous poly (ethylene) glycol (0-20%) having a molecular weight in the range of 400 to Preferably, said hydroxyl - rich molecule comprises poly (vinyl alcohol) having a molecular weight in the range of 400 to 2000000. Preferably, said hydroxyl - rich molecule comprises glycerol in an amount of up to 10 %, preferably up to 5%, more preferably from 2 to 6%. Preferably, said hydroxyl - rich molecule comprises ethanol in an amount of up to 10 %. Preferably, said hydroxyl - rich molecule comprises about 6% butanol and 18% ethanol. Preferably, said hydroxyl - rich molecule comprises aqueous methanol with the water content being from 95 to 99.5% . Preferably, said layered clay comprises a phyllosilicate. Preferably, said phyllosilicate is a smectite clay, particularly, a bentonite such as sodium bentonite In another preferred embodiment, said bentonite comprises of from 5 to 700% by weight, preferably, 5 to 10 to 15% by weight of water. The present invention also provides a process for the preparation of exfoliated nanoclays which comprises intercalating between the adjacent layers of a layered clay an aqueous intercalation solvent or solution followed by swelling with or without agitation to produce intercalated clay, and treating said intercalated clay in a heat sink, freezing, freeze-drying or thermal shock to obtain exfoliated nanoclays. Preferably, the concentration of said intercalating solution is in range 0-20%.

More preferably, said treatment in a heat sink is carried out for 4-48 hours. Any swellable layered materials that sufficiently sorbs the intercalant monomer to increase the interlayer spacing between adjacent phyllosilicate plastelets to at least about 5 A preferably, to at least about 10 A (when the phyllosilicate is measured dry) may be used in the practice of the present invention. Useful swellable layered materials include phyllosilicates, such as smectite clay, minerals, e.g., montmorillonite, particularly, sodium montmorillonite, magnesium montmorillonite and/or calcium montmorillonite; nontronite; beidellite; volkonskoite; hectorite; saponite; sauconite; sobockite; stevensite; svinfordite; vermiculite; and the like. Other useful layered materials include micaceous minerals, such as illite and mixed layered illite/ smectite minerals, such as rectorite, tarosovite, ledikite and admixtures of illites with the clay minerals named above. The present invention is carried out to fulfill the requirement for a cost effective intercalated, more preferably exfoliated bentonite clay and nanocomposites thereof with at least one polyolefin polymer such as polypropylene. The composites disclosed in this invention can be used for a myriad number of applications, such as furniture, automobile components, body parts, etc, and can be left to the imagination of the moulder. Smectite clays contain absorbed rnolecular water (H O), which is loosely held.

Therefore, the hydrolysis process, which occurs during weathering, involves two kinds of hydrogen - bound as either as OH or H₂O, which is found in two different types of crystallographic sites. Under laboratory or factory conditions, the crystalline water is lost at higher temperatures than the absorbed interlayer water. Glycerol is often used as a lubricant because its high viscosity and ability to remain fluid at low temperatures make it valuable without modification. To increase its lubricating power, the exfoliated phyllosilicate platelets are dispersed in it. The viscosity of the nanocomposite may be decreased by addition of water, alcohol, or glycols, and increased by increased loading of phyllosilicated platelets. Pastes of such nanocomposite compositions may be used in packing pipe joints, in gas lines, or in similar applications. For use in high pressure gauges and valves, soaps are added to glycerol to increase its viscosity and improve its lubricating ability. Mixture of glycerine and glucose is employed as a nondrying lubricant in the die-pressing of metals. In the textile industry, glycerol is frequently used in connection with so-called textile oils, in spinning, knitting, and weaving operations.

DEFINITIONS Whenever used in this Specification, the terms set forth shall have the following meanings:

Phyllosilicate: A layered material

Intercalation: Penetration of any chemical, monomer or polymer in between adjacent layers of clay. "Intercalation": A process for forming an Intercalate.

Exfoliation: Separation of clay layers resulting in their random dispersion.

"Exfoliation": A process for forming an Exfoliate from an Intercalate.

"Exfoliate" or "Exfoliated": Individual platelets of an Intercalated layered Material so that the adjacent platelets of the Intercalated Layered Material can be dispersed individually throughout a carrier material, such as a matrix polymer.

"Interlacement Polymer" or "Intercalant": An oligomer or polymer that is sorbed between platelets of the layered material to form an Intercalant.

Bentonite: A rock name given to the clay ore, which consists of smectite clay and impurities such as gravel, shale, and limestone. Smectite: A mineral clay that has the ability to swell in water. The most commercially important forms are hectorite and montmorillonite

The small particle sizes and melt dispersion potential of nanoclays allow thin sections to maintain clarity with filler loadings as high as 5%.

Montmorillonite: The most available form of clay, classified as a magnesium aluminum silicate having a dioctahedral structure and a platy or sheetlike morphology.

Cation : A positively charged ion.

Gallery: The spacing between parallel layers of montmorillonite clay platelets. The spacing changes depending upon which polymer or surface treatment occupies the space. Intercalate: An organic or semiorganic chemical capable of entering the smectite clay gallery and bonding to the surface.

Intercalate: Treated clay that has a complex formed between the clay surface and an organic molecule. ""Intercalate" or "Intercalated": A Layered Material that includes oligomer and / or polymer molecules disposed between adjacent platelets o the layered material to increase the interlayer spacing between the adjacent platelets to at least 10 angstroms.

Interlayer spacing: Also known as the gallery.

Layered Material: An an inorganic material, such as a smectite clay mineral, that is in the form of a plurality of adjacent, bound layers and has a maximum thickness, for each layer, of about 100 Angstroms.

Platelets: A thermoplastic or thermosetting polymer in which the Exfoliate is dispersed to form a Nanocomposite.

Nanocomposites: A new class of plastics derived from the incorporation of nanoscale particles into polymers.

"Nanocomposite": An oligomer, polymer or copolymer having dispersed therein a plurality of individual platelets obtained from an Exfoliated, Intercalated Layered

Material.

X - Ray Diffraction (XRD): It is also known as wide-angle x-ray scattering. It is one of the fundamental techniques of Materials Science. It gives a plot of scattered x-ray intensity as a function of scattering angle [two-theta]. XRD is used to determine crystal structure, crystallinity, crystal/amorphous ratio in polymers, metals, catalystd, adsorbents, etc.

DETAD ED DESCRIPTION The present invention will now be described in greater detail with reference to the accompanying drawing wherein the sole figure depicts: X-ray diagrams of exfoliated clay showing a minimum intensity of diffraction peak. Water itself or water compatible or soluble, hydroxyl-rich alcohols, glycols- both polymers and non-polymers are chosen as intercalants for making nanoclay from layered silicate materials (clays). These swell clay and can provide the necessary hydrogen bridge bond between the hydroxyl groups of the platelets. Addition of polar substance attains delamination ["exfoliation"] by penetrating between the platelets forcing them apart by internal pressure. Application of shear forces may sometimes be necessary to achieve a complete exfoliation of clay into so-called nanoclay. When shear is employed for exfoliation, any method, which can be used to apply a shear to the intercalant/carrier composition can be used. The shearing action can be provided by any appropriate method, as for example by mechanical means, by thermal shock, by pressure alteration, by freezing or by ultrasonics. When shear is employed for exfoliation, any method which can be used to apply a shear to the intercalant/ carrier composition can be used. The shearing action can be provided by any appropriate method, for example, by mechanical means, by thermal shock, by pressure alternation, or by ultrasonics, all known in the art. In particularly useful procedures, the composition is sheared by mechanical methods in which the intercalate, with or without the carrier or solvent is sheared by use of mechanical means such as stirrers, Banbury

RTM type mixers, Brabender RTM type mixers, long continuous mixers, and extruders. Another procedure employs thermal shock in which shearing is achieved by alternatively raising or lowering the temperature of the composition, causing thermal expansions and resulting in internal stresses which cause the shear. In still other procedures, shear is achieved by sudden pressure changes in pressure alteration methods; by ultrasonic techniques in which cavitations or resonant vibrations which cause portions of the composition to vibrate or to be excited at different phases and thus subjected to shear. These methods of shearing are merely representative of useful methods, and any method know in the art of shearing intercalates may be used. In the present invention, clay is interacted with a solution of a polar molecule, e.g.; water, methanol, ethanol, water-ethanol-butanol, ethylene glycerol, glycerol, poly (vinyl alcohol), poly (ethylene glycol), etc. till its penetration and absorption reaches saturation. Such intercalated phyllosilicates easily can be exfoliated into individual phyllosilicate platelets before or during admixture with a liquid carrier or solvent, for example, one or more monohydric alcohols, such as methanol, ethanol, propane, and / or butanol; polyhydric alcohols, such as glycerols and glycols, e.g., ethylene glycol, propylene glycol, butylenes glycol, glycerine and mixtures thereof with water; aldehydes; ketones; carboxylic acids; amines; amides; and other organic solvents. The hydroxyl-rich molecule penetrates between the platelets, forcing them apart. The treatment is carried out in a heat sink. Application of shear completes the dispersion of nanoclay. The intercalation or exfoliation of treated clay is judged by x- ray diffraction. Intercalated clay is not a nanoclay but is a precursor of it. When an intercalated clay is subjected to high shear is an twin-screw extruder, it gets exfoliated to different extents depending upon degrees of applied shear. Exfoliated clay is the true nanoclay as it shows an amorphous, non-crystalline structure and does not need shear to disperse individual clay layers or platelets. In the X-ray diagrams shown in the sole figure of the accompanying drawings, exfoliated clay shows a minimum intensity of diffraction peak. Usually, intercalated structures that are characterized by parallel registry give rise to X-ray peak at d- spacings in the range 20-30 A. In a preferred embodiment of the invention, raw mineral clay is spread like a fluidized bed. Nanoclay is made by intercalation of an aqueous solution of hydroxyl- rich molecule into layered smectic clay by an aqueous solution [intercalating solution concentration being in range 0-20%], followed by swelling (with or without agitation), treatment in a heat sink for 4-48 hours, and drying. Exfoliation should be sufficiently thorough to provide at least about 80% by weight, preferably at least about 85% by weight, more preferably at least about 90% by weight, and most preferably at least about 95% by weight delamination of the layers to form two layer tactoids that include three platelets or, more preferably, individual platelet particles that can be substantially homogeneously dispersed in the carrier or solvent. Mechanical shearing methods may be employed such as by extrusion, injection molding machines, Banbury RTM. type mixers Brabender. RTM type mixers and the like. Shearing can also be achieved by introducing the layered material and intercalant monomer at one end of an extruder (single or double screw) and receiving the sheared material at the other end of the extruder. The temperature of the layered material/intercalant monomer composition, the length of the extruder, residence time of the composition in the extruder and the design of the extruder (single screw, twin screw, number of flights per unit length, channel depth, flight clearance, mixing zone, exc.) are several variables which control the amount of shear to be applied for exfoliation. Exfoliation did not occur unless the bentonite clay included water in an amount of at least about 5% by weight, based on the dry weight of the clay, preferably at least about 10% to about 15% water, to about 700%. The water can be included in the clay as received, or can be added to the clay prior to or during intercalant, melt or solution contact. The emerging field of polymer-layered nanocomposites is unique in that it addresses shortcomings of polymers for both packaging and engineered applications, and it does so with favorable cost, processing and weight profiles. Polymer-layered silicate nanocomposites are plastics containing low levels of dispersed platy minerals with at least one dimension in the nanometer range. The most common mineral is Montmorillonite clay, which forms a very large part [80 - 95%] of Bentonite clay. Its aspect ratio exceeds 300, giving rise to enhanced barrier and mechanical properties. In general, every one weight-percent of these "nanoclays" creates a 10% property improvement. Their interaction with resin molecules alter the morphology and crystallinity of the matrix polymer, leading to improved processability in addition to the benefits to barrier, strength and stability. Advantages that nanoclays can provide in comparison to both their conventional filler counterparts and base polymer include: Mechanical properties e.g. strength, modulus and dimensional stability. Decreased permeability to gases, water and hydrocarbons ^■ Thermal stability and heat distortion temperature Flame relardancy and reduced smoke emissions Chemical resistance Surface appearance Electrical conductivity ^■ Optical clarity in comparison the conventionally filled polymers. Reinforcing polymers at the molecular level with inorganic fillers can bring about property improvements that are truly exceptional. Thermoplastic resins and rubbers for use as matrix polymers in the practice of this invention may vary widely. Illustrative of useful thermoplastic resins, which may be used alone or in admixture, are polyactones such as poly (pivalolactone), poly

(caprolactone) and the like; polyurethanes derived from reaction of diisocyanates such as 1, 5-naphthalene siisocyanate; p-phenylene dϋsocyanate, m-phenylene diisocyanate,

2,4-tolene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3 '-dimethyl 4,4'- diphenyl diisocyanate, 4,4'-dophenylisopropylidene diisocyanate, 3,3'-dimethyl-4,4'- diphenyl diisocyanate, 3,3'-dimethyl-4,4' - diphenylmethane diisocyanate, 3,3'- dimethoxy-4,4'diphenyl diisocyanate, dianisidine diisocyanate, toluidine diisocyasnate, hexamethylene diisocyanate, 4,4'-diisocyanatodiphenylmethane and the like and liner long-chain diols such as poly (tetramethylene adipate), poly (ethylene adipate), poly

(1,4-butylene adipate), poly (ethylene succinate), poly (2,3-butylene succinate), polyether diols and the like; polycarbonates such as poly>methane bis (4-phenyl) carbonate poly>,l -ether bis(4-phenyl) carbonate, poly>diphenylmethane bis(4- phenyl)carbonate, ply>l,l-cyclohexane bis(4-phenyl carbonate, and the like; polysulones; polyethers; polyketones; polyamides such as poly (4-amino butyric acid), poly (hexamethylene adipamide), poly (6-aminohexanoic acid), poly (m-xylylene adipamide), poly (p-xylylene sebacamide), poly (2,2,2-trimethyl hexamethylene terephthalamide), poly (metaphenylene isophthalamide) (NOMEX), poly (p-phenylene terephthalamide) (KEVLAR), and the like; polyesters such as poly (ethylene azelate), poly (ethylene- 1,5-naphthalate, poly (1,4-cyclohexane dimethylaen terephthalate), poly (ethylene oxybenzoate) (A-TELL), poly (para-hydroxy benzoate) (EKONOL), poly (1,4-cyclohexylidene dimethylene terephthalate) (KODEL) (as), poly (1,4- cyclohexylidene dimethylene terephthalate) (Kodel) (trans), polyethylene terephthalate, polybutylene terephthalate and the like; poly (arylene oxides) such as poly (2, 6- dimethyl-1, 4-phenyl ene oxide,) poly (2,6-diphenyl-l, 4-phenyl ene oxide) and the like; poly (arylene sulfides) such as poly (phenylene sulfide) and the like; polyetherimides; vinyl polymers and their copolymers such as polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride; polyvinyl butyral, polyvinylidene chloride, ethylene-vinyl acetate copylymers, and the like; polyacrylics, polyacrylate and their copylymers such as polyethyl acrylate, poly (n-butyl methacrylate), poly (n-propyl methacrylate), polyacrylamide, polyacrylonitrile, polyacrylic acid, ethylene-ethyl acrylate copolymers, methacrylate-styrene copolymers, ethylene-ethyl acrylate copolymers, methacrylate butadiene-styrene copolymers and the like; polylefins such as low density poly (ethylene), poly (proylene), chlorinated low density poly (ethylene), poly (4-methyl-l- pentene), poly (ethylene), Poly (urethane) such as the polymerization product of diols such as glycerin, trimethylol-propane, 1,2,6-hexanetroil, sorbitol, pentaerythritol, polyether polyols, polyester polyols and the like with a polyisocyunate such as 2,4- tolylene diisocyanate, 2,6-tolylene diisocyante, 4,4'-dicyclohexylmethane diisocyanate, 1,6- hexamethylene diisocyanate, 4,4' - dicyclohexylmethane diisocyanate an the like; and polysulfones such as the reaction product of the sodium salt of 2,2-bis (4- hydroxyphenyl) propane and 4,4' - dichlorodiphenyl sulfone; furan resins such as poly (furan); cellulose ester plastics such as cellulose acetate, cellulose acetate butyrate, celluslose propionate and the like; silicones such as poly (dimethyl siloxane), poly (dimethyl siloxane), poly (dimethyl siloxane), poly (dimethyl siloxane co-phenylmethyl siloxane), and the like; protein plastics; and blends of two or more of the foregoing. Nulcanizable and thermoplastic rubbers useful as matrix polymers in the practice of this embodiment of the invention may also vary widely. Illustrative of such rubbers are brominated butyl rubber, chlorinate butyl rubber, polyurethane elastomers, fluoroesastomers, polyester elastomers, polyvinylchloride, butadiene/acrylonitrile elastomers, silicone elastomers, poly (isobutylene), poly (isobutylene), ethylene- propylene copolymers, ethylene-propylene-diene terpolymers, sulfonated ethylene- propylene-diene terpolymers, poly (chloroprene), poly (2, 3-dimethylbutadiene), poly (butadiene-pentadiene), chlorosulphonated poly (ethylenes), poly (butadiene- pentadiene), chlorosulphonate poly (ethylenes), poly (sulfide) elastoemrs, block copoymers, made up of segments of glassy or crystalling blocks such as poly (styrene), poly (vinyl-toluene), poly (t-butyl styrene), polyesters and the like and the electrometric blocks such as poly (butadiene), poly (isoprene), ethylene-propylene copolymers, ethylene-butylene copylymers, polyether and the like as for example the copolymers in poly (styrene)-poly (butadiene)-poly (styrene) block copolymer manufactured by Shell Chemical company under the trade name KRAMTON. RTM. Thermosetting resins useful as matrix polymers include, for example, the polyamides; polylkylamides; polyesters; polyurethanes; polycarbonates; polyepoxides; and mixtures thereof. Most preferred thermoplastic polymers for use as a matrix polymer are thermoplastic polymers such as polyamides, polyesters, and polymers of alpha-beta unsaturated monomers and copolymers. The present invention will now be described with reference to the following non limiting example, whose purpose is merely to illustrate the present invention. Examples 1 to 3 Preparation of Nanoclay Example 1 Bentonite clay [5 gms] from Kutch region of Gujarat was immersed in 100 cc pure water which was then kept in the freezer compartment at 0 ° C for 2 days. It was then thawed at ambient temperature till ice surrounding clay became water. It was then dewatered and dried to constant weight at 90 °C. Lumps of clay thus obtained were finely ground in an agate mortar and sieved in a 100-mesh sieve. X-ray diffractogram of treated clay showed a broad hump which confirmed exfoliation and a near absence of crystal structure in it Example 2 Bentonite clay [5 gms] from Kutch region of Gujarat was immersed in 100 cc pure water which was then kept surrounded with solid carbon dioxide for 6-8 hours. It was then thawed at ambient temperature till ice formed surrounding clay became water.

It was then dewatered and dried to constant weight at 90 °C. Lumps of clay thus obtained were finely ground in an agate mortar and sieved in a 100-mesh sieve. X-ray diffractogram of treated clay showed a broad hump which confirmed exfoliation and a near absence of crystal structure in it Example 3 Bentonite clay [5 gms] from Kutch region of Gujarat was immersed in 100 cc pure water which was then kept immersed in liquid nitrogen for 45 min. It was then thawed at ambient temperature till ice surrounding clay became water. It was then dewatered and dried to constant weight at 90 °C. Lumps of clay thus obtained were finely ground in an agate mortar and sieved in a 100-mesh sieve. X-ray diffractogram of treated clay showed a broad hump which confirmed exfoliation and a near absence of crystal structure in it Example 4 Preparation and Test Results of PP nanocomposites 6% of above clays and a commercial clay (Cloisite 20 A) were compounded in our company's 100 gm of polypropylene homopolymer powder having a MFI of 12, with 5% addition of MA-g-PP or a organo-silane. These were dry-mixed for 15 min at ambient temperature. The mixture was premixed for 3 min, molded in DSM microcompounder and injection molder for 1 min. Mechanical property testing data for nanocomposites is given in table below:

Application Of Suitable Intercalants To Form Exfoliated Clay Bentonite was converted into exfoliated nanoclay by an ingenius scheme under which hydroxyl-rich molecules, e.g.

slip layer-by-layer into the interlayer gallery. Once there, these molecules associate with and solubilize water molecules present between adjacent layers. This treatment was performed in a heat sink. The intercalant forcibly separates clay layers which, after getting dismantled, never reassemble. Bentonite clay was kept immersed in a [0-20%] aqueous solution of chosen intercalant till swelling occurs in clay. Then, it was placed in a heat sink. When intercalant was removed, the clay was washed and dried. An X-ray silent- spectrum of exfoliated nanoclay is generally expected due to lattice disorder of layers in clay. The results are shown in the accompanying drawing. Interlayer spacings sufficient for exfoliation have never been achieved by direct intercalation of the above- defined intercalants, without prior sorption of an onium or silane coupling agent. The present method provides easier and more complete exfoliation for or during incorporation of the platelets into a polar organic compound.

Claims

1. Exfoliated nanoclay which comprises layered clay [e.g., sodium bentonite] and an intercalation material sorbed between layers of said layered clay.

2. Exfoliated nanoclay as claimed in claim 1 wherein said intercalation material is present in a concentration of from 10 to 100 % by weight based on the dry weight of said layered clay.

3. Exfoliated nanoclay as claimed in claim 1 or 2 said intercalation material is pure or an aqueous solution of a hydroxyl-rich molecule.

4. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl-rich molecule has the general formula:

5. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule is selected from the group consisting of one or more of water, ethanol, butanol or C4 alcohol, ethylene glycol, glycerol, poly (ethylene) glycol and poly (vinyl alcohol).

6. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises aqueous poly (ethylene) glycol (0-20%) having a molecular weight in the range of 400 to 40000.

7. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises poly (vinyl alcohol) having a molecular weight in the range of 400 to 2000000.

8. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises glycerol in an amount of up to 10 %, preferably up to 5%.

9. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises ethylene glycol in an amount of up to 10 %, preferably from 2 to 6%.

10. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises ethanol in an amount of up to 10 %.

11. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises about 6% butanol and 18% ethanol.

12. Exfoliated nanoclay as claimed in claim 3 wherein said hydroxyl - rich molecule comprises aqueous methanol with the water content being from 95 to 99.5% .

13. Exfoliated nanoclay as claimed in any preceding claim wherein layered clay comprises a phyllosilicate.

14. Exfoliated nanoclay as claimed in claim 13 wherein said phyllosilicate is a smectite clay.

15. Exfoliated nanoclay as claimed in claim 14 wherein said smectite clay is a bentonite.

16. ExfoUated nanoclay as claimed in claim 14 wherein said smectite clay is sodium bentonite

17. Exfoliated nanoclay as claimed in claim 15 wherein said bentonite comprises of from 5 to 700% by weight, preferably, 5 to 10 to 15% by weight of water.

18. A process for the preparation of exfoliated nanoclays which comprises intercalating between the adjacent layers of a layered clay an aqueous intercalation solvent or solution followed by swelling with or without agitation to produce intercalated clay, and treating said intercalated clay in a heat sink, freezing, freeze-drying or thermal shock to obtain exfoliated nanoclays.

19. A process as claimed in claim 17 wherein the concentration of said intercalating solution is in range 0-20%.

20. A process as claimed in claim 17 or 18 wherein said treatment in a heat sink is carried out for 4-48 hours.

21. A process as claimed in any one of claims 17 to 19 wherein said aqueous intercalation solution is a hydroxyl-rich molecule.

22. A process as claimed in claim 20 wherein said hydroxyl-rich molecule has the general formula:

23. A process as claimed in any preceding claim 17 to 21 wherein said exfoliated nanoclays are subjected to shearing to achieve greater degree of exfoliation.

24. A process as claimed in claim 22 wherein said shearing comprises extrusion or injection molding.

25. A process as claimed in any preceding claim 20 to 23 wherein said hydroxyl - rich molecule is selected from the group consisting of one or more of water, ethanol, butanol or C4 alcohol, ethylene glycol, glycerol, poly (ethylene) glycol and poly (vinyl alcohol).

26. A process as claimed in claim 24 wherein said hydroxyl - rich molecule comprises aqueous poly (ethylene) glycol (0-20%) having a molecular weight in the range of 400 to 40000.

27. A process as claimed in claim 24 wherein said hydroxyl - rich molecule comprises aqueous poly (vinyl alcohol) having a molecular weight in the range of 400 to 2000000.

28. A process as claimed in any one of claims 20 to 26 wherein said hydroxyl - rich molecule comprises aqueous glycerol in an amount of up to 10 %, preferably up to 5%.

29. A process as claimed in any one of claims 20 to 26 wherein said hydroxyl - rich molecule comprises aqueous ethylene glycol in an amount of up to 10 %, preferably from 2 to 6%.

30. A process as claimed in any one of claims 20 to 26 wherein said hydroxyl - rich molecule comprises aqueous ethanol in an amount of up to 10 %.

31. A process as claimed in any one of claims 20 to 26 wherein said hydroxyl - rich molecule comprises about 6% butanol and aqueous 18% ethanol.

32. A process as claimed in any one of claims 20 to 26 wherein said hydroxyl - rich molecule comprises aqueous methanol with the water content being from 95 to 99.5% .

33. A process as claimed in any one of preceding claims 17 to 31 wherein said layered clay comprises a phyllosilicate.

34. A process as claimed in claim 32 wherein said phyllosilicate is a smectite clay.

35. A process as claimed in claim 33 wherein said smectite clay is a bentonite.

36. A process as claimed in claim 33 wherein said smectite clay is a sodium bentonite.

37. A process as claimed in claim 34 wherein said bentonite comprises of from 5 to 700% by weight, preferably, 5 to 10 to 15% by weight of water.

38. A process as claimed in any preceding claim 17 to 35 wherein the concentration of intercalant molecule is about 50% to about 100% by weight, based on the dry weight of said layered clay.

39. A naonomposite which comprises a polymer and exfoliated nanoclays dispersed therein.

40. A nanocomposite as claimed in claim 37 wherein said polymer is selected from plastics, resins and rubber.

41. PP nanocomposite made from above indigenous nanoclay has 350% higher tensile strength at break than the one made from commercial nanoclay [Cloisite 20 A].