FIELD OF THE INVENTION:

The present invention relates to a highly gas impermeable nano-composites suitable for the fabrication of membranes with gas impermeability. More particularly the present invention relates to a highly impermeable rubber nano-composite based on novel nanoclay blend system for nitrogen and oxygen transport.

BACKGROUND OF THE INVENTION AND PRIOR ART:

The researchers of Toyota Central Research and Development Laboratories (Japan), from the late 1980s, are credited for the development of the concept of polymer nano reinforcement with layered silicate [1-3]. The most interesting property of layered silicates of natural and synthetic origin, which contribute to the property modification of polymers, is their disc-like structure with very high aspect ratio (up to 2000) offering very large polymer/ silicate interface area and surface area. By the isomorphic substitution of the constituting Si and Al atoms in the crystal structure, the layers become negatively or positively charged which are balanced by cations and anions located between the layers [4]. Different organic modifiers can easily exchange these ions, thereby producing organophilic clays or organoclays. Organophilic modification makes the silicate compatible with the polymer. Due to the intercalation of polymers into the added clay, the gallery spacing of the matrix is increased greatly. Intercalated structures, exfoliated structures and partially exfoliated structures (consisting of partially exfoliated and partially intercalated structures) [5] are the three types of polymer nanocomposites that make numerous applications in the field of aerospace, automobiles, package industries and so on.

Detailed literature survey report many number of permeability studies of different nanocomposites. A 30% reduction in the N2 gas permeability values was reported by Usuki et al. for ethylene propylene diene rubber (EPDM)/clay hybrids nanocomposites [6]. Wang et al. observed 50% reduction in permeability upon the addition of 7% rectorite clay into the NR matrix [7]. Gas permeation properties of nanocomposites based on butyl rubber with high loading of vermiculite, showed a substantial reduction in permeability as investigated by Takahashi et al. [8]. Wang et al.[9] studied the gas permeabilities of rectorite/SBR and N326/SBR composites. The rectorite/SBR and N326/SBR permeability are 68.8% and 39.0% lower than that of pure SBR, respectively.

Many numbers of studies have been reported on the preparation of blend nanocomposites [10-13]. Thomas and co-workers have investigated the gas transport, mechanical and dynamic properties of NR/XSBR latex blends [14-16].

Many numbers of patents were cited using the organically modified nanoclay loaded nanocomposites.Tracey et al. claimed [17] a green (uncured) composition suitable for a tire innerliner comprising a halobutyl elastomer and natural rubber filler selected from at least one of carbon black and clay (clay loading is ranging from 1-30 phr), a curative, at least one processing aid selected from resins, plastomers, polybutenes, and polyalphaolefin oils in the amount of 5 to 20 phr, at least one processing oil selected from naphthenic oil, paraffinic oil, 50 aromatic oil, MES (mild extraction solvate), and TDAE (treated distillate aromatic extract), and at least one processing aid selected from fatty acid metal salts in the amount of 1 to 5 phr.

Dias et al. claimed a (18) composition including an isobutylene-based copolymer and polybutene. The copolymers may be mixed with an exfoliating compound and clay, the entire composition forming a nanocomposite. The clay may or may not have an additional exfoliating treatment present prior to mixing with the interpolymer. The composition of the invention has improved air barrier properties and processing properties, and is suitable as an air barrier. One embodiment of the invention is an elastomeric composition including at least one random copolymer of at least a C4 to C7 isomonoolefin derived unit, at least one filler, and polybutene oil having a number average molecular weight greater than 400. The copolymer may be selected from a halogenated poly (isobutylene-co-p-methylstyrene), a halogenated star-branched butyl rubber, or a halogenated butyl rubber, and mixtures thereof. The composition also consists of a secondary elastomer selected from natural rubber, polyisoprene rubber, styrene butadiene rubber (SBR), polybutadiene rubber, isoprene butadiene rubber (IBR),styreneisoprene- butadiene rubber (SIBR), ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), polysulfide, nitrile rubber, propylene oxide
polymers, star-branched butyl rubber and halogenated star-branched butyl rubber, brominated butyl rubber, chlorinated butyl rubber, starbranched polyisobutylene rubber, star-branched brominated butyl (polyisobutylene/isoprene copolymer) rubber; isobutylene/ methylstyrene copolymers such as isobutylene/ metabromomethylstyrene, isobutylene bromomethylstyrene,isobutylene/chloromethylstyrene, halogenated isobutylene cyclopentadiene, and isobutylene/chloromethylstyrene and mixtures thereof.

Zhao et al. (19) claimed dual phase rubber composition and pneumatic tire with a rubber sidewall thereof, namely a dual phased non-black colored rubber composition composed of a first pre-formed elastomer phase comprised of butyl-type rubber and EPDM rubber containing a dispersion therein of reinforcing filler comprised of a particulate amorphous precipitated silica and a second pre¬formed elastomer phase comprised of a nanocomposite of natural rubber containing a dispersion therein of exfoliated clay platelets. Said exfoliated clay platelets may be substantially oriented within the tire sidewall in a parallel direction to each and may also be substantially oriented in an annular direction about the axis of the tire. The tire sidewall rubber composition may contain at least one additional elastomer which may be included in either or both of said elastomer phases. Such tire sidewall rubber composition may contain a nonblack colorant pigment, such as for example a white colored titanium dioxide pigment. The dual phased tire sidewall rubber composition is prepared by a phase mixing process comprised of pre-blending said butyl-type rubber and EPDM rubber together with said precipitated silica reinforcing filler to form a pre-mix thereof, and thereafter mixing therewith said nanocomposite as a pre-formed blend of natural rubber and exfoliated clay platelets.

Ajbani et.al [20] used 0.1 to 25 phr organically and unmodified nanoclays for the development of nano-composite US 7,659,355 discloses air barriers made from elastomeric compositions. In particular, the invention relates to novel air barriers such as innerliners, air sleeves, and innertubes made from C4 to C7 isoolefin based polymers with new sequence distributions or that are substantially free of long chain branching.

The composition further includes filler comprises of carbon black, modified carbon black, silicates, carbonates, clay, exfoliated clay, clay treated with organic molecules, or mixtures thereof.

US 8,013,054 disclose elastomeric compositions comprising at least one C4 to C7 monoolefin elastomer, at least one polyalphaolefin, and optionally at least one hydrocarbon polymer additive. The composition may further comprise a filler which may be selected from calcium carbonate, mica, silica, silicates, talc, titanium dioxide, starch, wood flour, carbon black, and mixtures thereof.

US 7,485,677 disclose low permeability nanocomposites. The nanocomposites is a blend of an halogenated elastomer and a clay, desirably an exfoliated clay, The halogenated elastomer is a polymer comprising C4 to C7 isoolefin derived units, a para-methylstyrene derived units, and para-(halomethylstyrene) derived units. The clay may or may not have an additional exfoliating treatment present prior to blending with the interpolymer. The interpolymer/clay mixture forms a distinct phase in the nanocomposite blend of the invention. The nanocomposites also comprising a filler selected from the group consisting of carbon black, modified carbon black, silica, precipitated silica, and blends thereof.

The prior art discussed above discloses various elastomeric composition or nanocomposites having better impermeability. But all the compositions or nanocomposites discussed above involves additives such as carbon black, silica or processing oil. The presence of additives in the rubber composition suffers disadvantages such as, it prevents the localization of the clay at the interface and in the rubber continuous phase and it prevents the attainment of optimum viscosity ratio required for the attainment of suitable morphology of the nanocomposite for low permeation. Hence there exists a need to formulate elastomeric nanocomposites which are devoid of additives and has suitable morphology for high impermeation.

References:

1. 1.A. Usuki, M. Kawasumi, Y. Kojima, A. Okada, T. Kurauchi, and O. Kamigaito, J. Mater. Res., 8, 1174 (1993).

2. A. Usuki, Y. Kojima, M. Kawasumi, A. Okada, Y. Fukushima, T. Kurauchi, and O. Kamigaito, J. Mater. Res., 8, 1179 (1993).

3. Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, Y. Fukushima, T. Kurauchi, and 0. Kamigaito, J. Mater. Res., 8,1185 (1993).

4. E. P . Giannelis.R. Krishnamoorti E.manias, Adv. Polym. Sci. 118 ,108 (1999).

5. S. J. Ahmadi, Y. D. Huang, W. Li, J. Mater. Sci. 39,1919 (2004)

6. A. Usuki, A. Tukigase, and M. Kato, Polymer, 43, 2185(2002).

7. Y. Wang, H. Zhang, Y. Wu, J.Yang, L. Zhang, Euro. Polym. Jour. 41,2776(2005)

8. S. Takahashi, H.A. Goldberg, C.A. Feeney, D.P. Karim, M. Farrell ,K. O'Leary, D.R. Paul, Polymer 47,3083 (2006)

9. Z.F. Wang, B. Wang,, N. Qi, H.F. Zhang, L.Q. Zhang, Polymer 46,719 (2005).

10. S.Varghese, J.Karger-Kocsis.Polymer 44,4921 (2003)

11. S.Varghese, K.G.Gatos, A.A.Apostolov, J.Karger-Kocsis, J Appl Polym
Sci. 92,543(2004)

12.S.Varghese, J. Karger-Kocsis, K.G.Gatos, Polymer 44,3977(2003)

13. W. Wu,D.Chen, J. Appl. Polymer Sci.,101, 4462 (2006).

14. R.Stephen, S.Thomas, K.Joseph. J Appl Polym Sci 98,1125(2005)

15. R.Stephen, K.V.S.N.Raju, S.V.Nair, Z.Oommen, S.Thomas, J Appl PolymSci 88,2640(2003)

16. R.Stephen, C. Ranganathaiah, S.Varghese, K.Joseph, S.Thomas, Polymer 47,858 (2006).

17.D.S. Tracey; D.F. Rouekhout, W.H. Waddell, Patent No.: US 7,770,621 B2,Date of Patent: Aug. 10,2010.

18.A. J. Dias, G.E.Jones, D.S Tracey, W.H Waddell.Pub. No.: US 2004/0132894 AI;Pub. Date: J ul. 8, 2004.

19.J.Zhao, M.J.Crawford, A.S.Puhala, M.P.Cohen, Pub. No.: US 2006/0135671 Al (43) Pub. Date: Jun. 22, 2006

20.M.Abjani, W.L.Hsu, A.F. Halasa, G.Lee, E.S.Castner, Patent No. US
705556 B2, Date: Jun.6, 2006

21. G. Choudalakis , A.D. Gotsis.Eur. Polym. Jour. 45,967 (2009).

22. L.E.Nielsen. J Macromol Sci (Chem) A1, 929 (1967).

OBJECT OF THE INVENTION:

The main object of the present invention is to formulate a highly gas impermeable elastomeric rubber-rubber blend nanocomposite which is devoid of additives such as carbon black, silica and process aid.

Another object of the present invention is to formulate elastomeric nanocomposite comprising of chlorobutyl rubber, natural rubber and nanoclay as filler.

Yet another object of the present invention is to utilize modified natural montmorillonite clay as filler

Yet another object of the present invention is to utilize natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium (l.44p) as the filler in the formulation of the nanocomposite to increase nitrogen permeability.

Yet another object of the present invention is to utilize natural montmorillonite clay surface modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium (cloisite 10A) in the formulation of the nanocomposite to increase nitrogen and oxygen permeabilities.

Yet another object of the present invention is to attain a tortuous path in the morphology of the nanocomposite thereby achieving high impermeation.

Yet another object of the present invention is to fabricate highly impermeable membrane to oxygen and nitrogen gases utilizing the formulated nanocomposites.

Further object of the present invention is to utilize the formulated nanocomposite for the preparation of different components of tyre.

These and other objects, features, and advantages will become apparent as reference is made to the following .detailed description, preferred embodiments, and appended claims

SUMMARY OF THE INVENTION:

The present invention relates to a highly gas impermeable elastomeric rubber-rubber blend nanocomposite green formulation and process of preparation thereof. The nanocomposite comprises 70 phr chlorobutyl rubber and 30 phr natural rubber with 1-10 phr nanoclay as filler. Alternatively the nanocomposite comprises 70 phr chlorobutyl rubber and 30 phr natural rubber with 0-10 phr nanoclay as filler. The filler used in the present invention is modified natural montmorillonite clay which shall be either natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium (I.44P) or natural montmorillonite clay surface modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium (cloisite 10A). The process of preparing the formulation comprising of masticating 70 phr chlorobutyl rubber and masticating 30 phr natural rubber separately, then mixed them and again masticated. Then nanoclay as filler and curatives were added. The curative addition was done after proper mastication of rubbers.

The prepared samples were made into sheets at 160°C at a pressure of 120Kg/Cm2 using a compression molding press. The fabricated sheets are highly impermeable to oxygen and nitrogen gases and therefore the membrane is utilized for the preparation of different components of tyre.

BRIEF DESCRIPTION OF DRAWINGS:

Figure 1 describes nitrogen permeability of 70 chlorobutyl rubber/30 natural rubber Nanocomposites having different amounts of I.44P clay loadings.

Figure 2 describes comparison of nitrogen permeability of 70 Chlorobutyl Rubber/30 Natural Rubber with Chlorobutyl Rubber Nanocomposites having different amounts of I.44P clay loadings.

Figure 3 discusses about the diffusion of gas molecules through the special morphology generated by the new formulation (CIIR/NR/I.44P nanocomposites).

Figure 4 describes about X-ray Diffractogram (XRD) of the nanocomposites (CIIR/NR/I.44P).

Figure 5 describes atomic force mteroscopic (AFM) pictures of 70 CUR/30 NR nanocomposites having (a) 0 phr I.44P clay,(b) 2.5 phr I.44P clay ,(c) 5 phr I.44P clay, (d) 7.5 phr I.44P clay and (e) 10 phr I.44P clay.

Figure 6 describes oxygen permeability of 70 CIIR/30 NR and 100 CUR nanocomposites having different amounts of cloisite 10A clay loading.

Figure 7 illustrates nitrogen permeability of 70 CIIR/30 NR and 100 CIIR nanocomposites having different amounts of cloisite 10A clay loading.

Figure 8 describes about relative nitrogen permeability of 70 CIIR/30 NR and 100 CIIR nanocomposites against the filler (cloisite 10A)volume fraction.

Figure 9 describes relative oxygen permeability of 70 CIIR/30 NR and 100 CIIR nanocomposites against the filler (cloisite 10A ) fraction.

Figure 10 is a diagrammatical illustration of the newly developed tortuous path for the blend nanocomposite system (CIIR/NR/Cloisite 10A).

Figure 11 describes X-ray Diffractogram (XRD) of the nanocomposites (CIIR/NR/Cloisite 10A).

Figure 12 discusses about the atomic force microscopic (AFM) pictures of 70 CIIR/30 NR nanocomposites having different Cloisite 10A clay loading.

DETAILED DESCRIPTION OF THE INVENTION:

The present invention relates to a highly gas impermeable elastomeric rubber-rubber blend nanocomposite green formulation and process of preparation thereof. The nanocomposite comprises chlorobutyl rubber and natural rubber with nanoclay as filler.

The filler used in the present invention is modified natural montmorillonite clay which shall be either natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium (I.44P) or natural montmorillonite clay surface modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium (cloisite 10A).

The chlorobutyl rubber is a copolymer of isoprene unit and isobutylene unit. These are particularly useful for making tire innerliners, inner tubes etc.

The composition according to the invention should also contain conventional curatives, as set forth previously, in conventional amounts.

The curatives used for the development of highly impermeable system are nanoclay as fillers, ZnO, Sulphur, stearic acid and DPG and does not contain carbon black, process oil, process aids etc. The presence of additives such as carbon black, process oil has following limitations.

a. Presence of additives will prevent the localization of the nano clay at the interface and in the chlorobutyl rubber continuous phase.

b. Presence of additives will prevent viscosity ratio requirement for a special morphology. In particular the presence of large amount of processing oil alters the viscosity ratio leading to an undesirable morphology.

c. Further any processing aids acts as an external network material in the matrix and leads to heat development during service.

In one aspect of the present invention the filler used in the present study is organically modified nano clay I.44PT Organic modifier used for the I.44P clay is 35-45 wt. %, dimethyl dialkyl (C14-C18) amine having high cation exchange capacity (CEC) of about 70-150 meq/100 g.

In another aspect of the present invention the filler used in the present study is Organically modified clay Cloisite 10A. Characteristic features of Cloisite 10A and I.44P are shown in Table 1.

Table 1. Characteristics of nanoclays

The rubber-rubber-clay ternary nanocomposites were prepared using a two-roll mill. The detailed recipes utilizing the fillers I.44P and Cloisite 10A were furnished in the Table 2 and Table 3 respectively. The preparation of rubber-rubber blend was done by masticating each rubber first, then mixed them and again masticated. The curative addition was done after proper mastication of rubbers. The cure time of these nanocomposites was determined using a Rubber Processor Analyzer at 160°C. The prepared samples were made into sheets at 160°C at a pressure of 120 Kg/Cm2 using a compression moulding press.

Table 2. Formulation of rubber/OMC nanocomposites.

Table 3. Formulation of rubber/OMC nanocomposites.

The gas permeability measurements of CIIR/NR/I.44P nanocomposites were done using ATS FAAR gas permeability tester in manometric method in accordance with the ASTM standard D1434. The permeability of N2 gas through NR/CIIR blends was tested at 1atm. pressure (Table 4). The d-spacing of the layer structure of the clay itself as well as that of nanocomposites were examined by using a wide angle X-ray diffractometer (WAXD) with Ni filtered CuK∞ source having wavelength,X=0.154 nm operated at 40 KV and 30 mA with a step size of 0.02(D8 Adavnce, Bruker AXS,Germany).The scanning and analysis of the samples were done using the Multi Mode Atomic Force Microscopy with a Nanoscope Ilia controller and by Digital Instruments Inc. (Veeco Metrology Group), Santa Barbara, CA, US

Table 4. Nitrogen permeability values of different types of rubber nanocomposites.

The permeation of gases through an organic membrane, such as a polymer film, is a complex process that consists of four stages: the sorption of gas molecules on the surface of the membrane; the dissolution of the gas inside the membrane; the diffusion through it; and, finally, the desorption of gas from the other surface of the membrane [21]. In the case of layered polymer nanocomposites, the permeation is quite similar to that of semicrystalline polymers in which the oriented nanoclay platelets decide the permeation of the gases through membranes. Major factors that decide the gas permeation through nanocomposites are (a) amount of the nanoclay used for the preparation of nanocomposites, (b) aspect ratio of the nanoclay used for the study in which the exfoliation of the nanoclay into the permeable polymer membrane results in high aspect ratio whereas intercalated nanocomposites provides much lower aspect ratio, (c) orientation of the nanoplatelets relative to the diffusion direction. Figure.1. illustrates the nitrogen permeability of the blend nanocomposites CIIR/NR/I.44P. In the case of blend nanocomposites CIIR/NR/I.44P, 44% reduction of the gas permeability was observed up on the addition of 2.5 phr I.44P clay and for the 7.5 phr loaded sample, 63% reduction of gas permeability was noticed. Figure 2 compares the relative permeability of CUR nanocomposites and CIIR/NR blend nanocomposites. The permeability of chlorobutyl rubber nanocomposites are expected to be very low due to the high steric hindrance of methyl groups in chlorobutyl rubber. It is very important to note that in 100 percent CIIR nanocomposites, the reduction in the gas permeation after the addition of nanoclay I.44P is much less than that of the blend nanocomposites (Figure2). The high degree gas impermeation of the blend nanocomposite is due to the formation of a finely dispersed phase separated morphological structure of NR stabilized by the nanoparticles'and the emulsifier used for the clay surface. The morphology formation could be explained as follows: Up on the addition of 30 weight percent of NR to CIIR, heterogeneous phase separated morphology is obtained in which of NR domains are well dispersed in the continuous CIIR. On the addition of I.44P clay into the blend, the clay will predominantly locate at the polar CIIR phase and at the interface between NR and CIIR phases. Due to the preferential localization of the I.44P clay at the CIIR phase, the viscosity of the CIIR phase will be increased leading to a change in the viscosity ratio that favors a nice dispersion of the NR domains in the continuous CIIR phase. In addition, the surfactant present in the l.44Pclay surface (dimethyl dialkyl (C14-C18) amine) may act as a good compatibiliser for the CIIR/NR interface with amine group interacting with the CIIR phase and the alkyl group directed towards the NR phase. Thus a fine dispersion of natural rubber in the continuous CIIR phase is stabilized by the nanoparticles and by the surfactant of the I.44P clay. Thus a highly tortuous path is developed by the new morphology in which natural rubber domains uniformly dispersed in the butyl rubber matrix are stabilized by the shell of nanoparticles and the surfactant: The exfoliated clay platelets and the tactoids in the CIIR matrix makes the permeation of nitrogen gas through the matrix extremely difficult as illustrated in the figure 3. Since the more permeating natural rubber is the discontinuous phase, the natural rubber phase does not contribute to transport process. Relative permeability values of the nanocomposites were furnished in Table 4. 70CIIR/30 NR nanocomposite systems show a dramatic reduction of permeability after the addition of just 2.5 phr I.44P clay; the impermeability values are better than CIIR filled with 2.5 phr clay. For 7.5phr loaded system, the relative permeability values of both the systems (the blend nanocomposite and the CIIR nanocomposite) are almost the same. These results were confirmed by morphological characterization of the nanocomposites using atomic Force Microscopy (AFM) and X ray Diffractogram (XRD). Nanoclay used for the present study shows a 29 value of 3.75° having d-value of 2.35 nm (Table 5).

Table 5. 20 and d-values (in nm) of 70 CIIR/30 NR rubber nanocomposites.

Samples with 2.5 phr and 7.5 phr nanoclay loaded systems do not show any peak and this indicate excellent exfoliation of the I.44P nanoclay platelets (figure 4). Very interestingly, the samples with 2.5 phr and 7.5 phr clay loaded samples show excellent barrier towards nitrogen gas (figures 1 and 2). The agglomeration of the nanoclay in the 10phr loaded sample shows a distinct peak at 2.25° having d-value 3.92 nm. As expected, 10 phr filler loaded systems, agglomeration occurs, leading to an increase in the relative permeability values. The agglomeration is very clear from Atomic Force Microscopic pictures (figure 5). The present study clearly shows that by the judicious macromolecular engineering, one can substitute the expensive CIIR rubber with a more economical blend of CIIR/NR/I.44P clay system for making membranes towards nitrogen gas.

The gas permeability measurements of CIIR/NR/Cloisite 10A nanocomposites were done using ATS FAAR gas permeability tester in manometric method in accordance with the ASTM standard D1434. The permeability of 02 and N2 gas through NR/CIIR blends was tested at 1atm. pressure (Tables. 6-7). The d-spacing of the layer structure of the clay itself as well as that of nanocomposites were examined by using a wide -angle X-ray diffractometer (WAXD) with Ni filtered CuK°° source having wavelength,=0.154 nm operated at 40 KV and 30 mA with a step size of 0.02(D8 Adavnce, Bruker AXS,Germany).The scanning and analysis of the samples were done using the Multi Mode Atomic Force Microscopy with a Nanoscope Ilia controller and by Digital Instruments Inc. (Veeco Metrology Group), Santa Barbara, CA, USA.

Table 6. Oxygen permeability values of rubber nanocomposites as a function of cloisite 10 A loading.

Table 7. Nitrogen permeability values of rubber nanocomposites as a function of cloisite 10 A loading.

Figure 6 illustrates the oxygen permeability of the blend nanocomposites and Figure 7 illustrates nitrogen permeability as a function of cloisite 10 A loading. For the case of blend nanocomposites having Cloisite 10 A, a reduction of 51.02 % is observed in 2.5 phr loaded sample and a reduction of 55.24% for the 7.5 phr loaded sample for 02 gas permeability. For N2, a quite different picture is observed (figure 7.).Upon the addition of the 2.5 phr 10 A, a reduction of 63.54% of gas is observed and for 5 phr and 7.5 phr loaded samples, a reduction of 49.98% and 46.94% is observed respectively. The gas permeation in these nanocomposites can be explained by considering two types of mechanisms; (a) the aspect ratio of the nanocomposites (b) phase separated structure formed by natural rubber. High aspect ratio means good orientation of nanoplatelets into the matrix in which 2.5 phr loaded 10 A samples provided an aspect ratio value of 302.49. The aspect ratio values are tabulated in Table 8. This has been calculated from the concept coined by Nielson, according to equation (1) and the model is otherwise called as Nielson's Model [22].

P/Po = (1-d3)/(1+(a/2)cb) (1)

Where P and P0 are permeability values of the composite and polymer without filler respectively, cp is the volume fraction of the filler and a is the aspect ratio.

Table 8 .Correlation of aspect ratios and gas permeability

From the table, it is clearly observed that the high gas impermeation is observed for the high aspect ratio samples. The distributions of clay platelets in these systems are good.

These values are in good agreement with the permeability values observed. The second mechanism suggests that the high gas impermeation due to the formation of the phase separated structure by natural rubber added to the matrix. The tortuous path developed by the new system in which natural rubber and clay factoids in the matrix made the
permeation through the matrix more difficult, i.e.; there observed a combined effect of these two mechanisms. This makes the gas permeation more difficult and is shown in the figure 10. From the relative permeability analyses (figure 8 and 9), it is clear that all samples containing CloisitelO A varieties, except 10 phr loaded samples, show good gas impermeability. Also from the morphological characterization analyses, nanoclay incorporated systems show intercalated structures (figure 11). Nanoclay peak at 26=4.80 corresponds to d-spacing of 1.80 nm. The nanoclay incorporation into the rubber-rubber blend matrix results in intercalated structures in which the d-spacing values increases from 1.80 nm to 4.10 nm (Table 9). These results were confirmed using the AFM analyses presented in figure 12. The nanoclay incorporation at higher loading results in the formation of an agglomerated structure. It is important to add that 70CIIR/30NR blend with small amount of clay (=2.5 phr) is much superior to neat CIIR. Thus, the Cloisite 10 A filled CIIR/NR blend nanocomposites will be potential candidates for development of highly impermeable membranes.

Table 9. 26 and d-values (in nm) of 70 CIIR/30 NR rubber nanocomposites.

In one of the preferred embodiment the present invention shall disclose a highly gas impermeable elastomeric rubber-rubber blend nanocomposite comprising of 70 phr chlorobutyl rubber and 30 phr natural rubber with 1-10 phr filler characterized in the said filler being a modified natural montmorillonite clay and the nanocomposite has a morphology with highly complicated tortuous path for the diffusion of gas molecules thereby making the nanocomposite highly gas impermeable.

In one aspect of the invention the modified natural montmorillonite clay is natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium for increasing nitrogen permeability.

According to the invention a suitable composition comprising of 70 phr chlorinated butyl rubber and 30 phr natural rubber with nanoclay I.44P ranging from 0 to 10 phr without carbon black has been developed for the first time for the fabrication of membranes for nitrogen barrier applications. It is important to note that the new formulation does not need additives such as carbon black or plasticizers. As per the invention a special morphology has been generated in which the NR phase is dispersed as fine spherical domains in a matrix of CUR. The NR domains are stabilized by the shell of clay nanoparticles and the surfactant molecules of the clay. This special morphology generates a highly complicated tortuous path for diffusing nitrogen gas molecules. The new formulation is superior to conventional CUR nanocomposites filled with clay. In accordance with the invention the nanocomposite CIIR/NR/I.44P shows better impermeability for 2.5 phr nanoclay and 7.5 phr nanoclay due to the exfoliation of the nanoclays in the rubber-rubbef blend matrix in which 44% reduction of the gas permeability was observed up on the addition of 2.5 phr clay and 63% reduction of gas permeability for 7.5 phr loaded sample. Thus the nitrogen permeability of the nanocomposite at 7.5 phr of I.44P nanoclay is 38.04 (GTRX102 cc/m2*day*atm).

As per the invention the nanocomposite CIIR/NR/I.44P could be applied for the fabrication of new membranes for nitrogen impermeability. Finally it is very important to add that this new invention offers the possibility to replace conventional CUR based nanocomposites with more economical CIIR/NR/clay nanocomposites for tire inner liners and tubes

In another aspect of the invention the modified natural montmorillonite clay is natural montmorillonite clay surface modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium for increasing nitrogen and increasing oxygen permeabilities.
According to the invention a highly impermeable membranes to nitrogen and oxygen gases with 70 phr chlorinated butyl rubber and 30 phr natural rubber comprising of 0 to 10phr organically modified nanoclay Cloisite 10A without carbon black has been developed for the first time for the fabrication of membranes for nitrogen and oxygen barrier applications. It is important to note that the new formulation does not need additives such as carbon black or plasticizer. As per the invention a special morphology has been generated for nanocomposite CIIR/NR/Cloisite 10A in which the NR is dispersed as fine spherical domains in a matrix of CIIR where the NR domains are stabilized by the shell of clay nanoparticles and the surfactant molecules._This new invention offers the possibility to replace conventional CIIR based composites CIIR/NR/clay composites for the development of impermeable membranes without the use of carbon black, processing aids, processing oils etc. The development of these new composites has been made by a cheapest and most simple but most novel_processing route in which this has been done by a two-roll mill. In accordance with the invention the nanocomposite CIIR/NR/Cloisite 10A shows better impermeability to oxygen for 2.5 phr and 7.5 phr nanoclay may be due to the exfoliation and high aspect ratio of the nanoclays in the rubber-rubber blend matrix in which 51.02% reduction of the gas permeability was observed up on the addition of 2.5 phr clay and for the 7.5 phr loaded sample, 55.24% reduction of gas permeability. In accordance with the invention the nanocomposite CIIR/NR/Cloisite 1QA shows better impermeability to nitrogen for 2.5 phr, 5 phr and 7.5 phr nanoclay may be due to the exfoliation and high aspect ratio of the nanoclays in the rubber-rubber blend matrix in which 63.54% reduction of the gas permeability was observed up on the addition of 2.5 phr, for 5 phr nanoclay loaded samples, 49.98% reduction and for the 7.5 phr loaded sample, 46.39% reduction of gas permeability. Thus the oxygen permeability of the nanocomposite at 7.5 phr of Cloisite 10A nanoclay is 27.53 (GTRX102 cc/m2*day*atm) and the nitrogen permeability of the nanocomposite at 2.5 phr of Cloisite 10A nanoclay is 36.62 (GTRX102 cc/m2*day*atm).

According to the invention the nanocomposite may further include curing agents. The curing agents comprises of combination of ZnO, sulphur, stearic acid and DPG.
In another preferred embodiment the present invention shall disclose a process of preparing the nanocomposite comprising of masticating chlorobutyl rubber and masticating natural rubber separately, then mixed them and again masticated. Then filler nanoclay and curatives were added to form the nanocomposite. The curative addition was done after proper mastication of rubbers.

In another preferred embodiment the present invention shall disclose a process of preparing the nanocomposite (CIIR/NR/I.44P) comprising of masticating 70 phr chlorobutyl rubber and masticating 30 phr natural rubber seperately, then mixed them and again masticated. Then filler 1-10 phr I.44P nanoclay and curatives comprising of 5phr ZnO, 2phr sulphur, 2.5 phr stearic acid and 0.6 phr DPG were added. The curative addition was done after proper mastication of rubbers. The prepared samples were made into sheets at 160°C at a pressure of 120 Kg/Cm2 using a compression mould press.

In another preferred embodiment the present invention shall disclose a process of preparing the nanocomposite (CIIR/NR/I.44P), comprising of masticating 70 phr chlorobutyl rubber and masticating 30 phr natural rubber separately, then mixed them and again masticated. Then filler 1-10 phr Cloisite 10A nanoclay and curatives comprising of 5phr ZnO, 2phr sulphur, 2.5 phr stearic acid and 0.6 phr DPG were added. The curative addition was done after proper mastication of rubbers. The prepared samples were made into sheets at 160°C at a pressure of 120 Kg/Cm2 using a compression mould press.

While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to achieve the benefits provided by the present invention without departing from the scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto.

WE CLAIM:

1. A highly gas impermeable elastomeric rubber-rubber blend nanocomposite comprising of 70 phr chlorobutyl rubber and 30 phr natural rubber with 0-10 phr filler characterized in the said filler being a modified natural montmorillonite clay, the said nanocomposite having a morphology with highly complicated tortuous path for the diffusion of gas molecules thereby making the said nanocomposite highly impermeable.

2. A highly gas impermeable elastomeric rubber-rubber blend nanocomposite comprising of 70 phr chlorobutyl rubber and 30 phr natural rubber with 1-10 phr filler characterized in the said filler being a modified natural montmorillonite clay, .the said nanocomposite having a morphology with highly complicated tortuous path for the diffusion of gas molecules thereby making the said nanocomposite highly impermeable.

3. The nanocomposite as claimed in claim 1 or 2, wherein the said modified natural montmorillonite clay is natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium for increasing nitrogen permeability such that the nitrogen permeability of the claimed nanocomposite at 7.5 phr of said modified nanoclay is 38.04 (GTRX102 cc/m2*day*atm).

4. The nanocomposite as claimed in claim 1 or 2, wherein the said modified natural montmorillonite clay is natural montmorillonite clay surface modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium for increasing nitrogen and increasing oxygen permeabilities such that the oxygen permeability of the claimed nanocomposite at 7.5 phr of said modified nanoclay is 27.53 (GTRX102 cc/m2*day*atm) and the nitrogen permeability of the claimed nanocomposite at 2.5 phr of said modified nanoclay is 36.62 (GTRX102 cc/m2*day*atm).

5. The nanocomposite as claimed in claim 1 or 2, may further include curing agents.

6. The nanocomposite as claimed in claim 5, wherein the said curing agents comprises of combination of ZnO, sulphur, stearic acid and DPG.

7. A process for preparation of a highly gas impermeable elastomeric rubber-rubber blend nanocomposite-, the said process comprises of

a. masticating 70 phr of chlorobutyl rubber

b. masticating 30 phr of natural rubber

c. mixing masticated 70 phr of chlorobutyl rubber and 30 phr natural rubber thoroughly and masticating to form a mixture and

d. adding 0-10 phr of filler to the mixture of step (c) to form the highly gas impermeable blended nanocomposite.

characterized in the said filler being a modified natural montmorillonite clay

8. A process for preparation of a highly gas impermeable elastomeric rubber-rubber blend nanocomposite, the said process comprises of

a. masticating 70 phr of chlorobutyl rubber

b. masticating 30 phr of natural rubber

c. mixing masticated 70 phr of chlorobutyl rubber and 30 phr natural rubber thoroughly and masticating to form a mixture and

d. adding 1-10 phr of filler to the mixture of step (c) to form the highly gas impermeable blended nanocomposite.

characterized in the said filler being a modified natural montmorillonite clay ft.

9. The process as claimed in claim 7 or 8, wherein the said modified natural montmorillonite clay is natural montmorillonite clay surface-modified with dimethyl dialkyl ammonium for increasing nitrogen permeability.

10. The process as claimed in claim 7 or 8, wherein the said modified natural montmorillonite clay is natural montmorillonite clay modified with dimethyl, benzyl, hydrogenated tallow, quaternary ammonium for increasing nitrogen and oxygen permeability.

11. The process as claimed in claim 7 or 8 may further include a step of adding curing agents.

12. The process as claimed in claim 11 wherein the said curing agents.