BRPI1001312A2 - process of obtaining modified nanoargyl for the production of polymeric nanocomposites and modified nanoargyl - Google Patents

Abstract

PROCESS OF OBTAINING MODIFIED NANO-CLAY FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITES AND MODIFIED NANO-CLAY, which comprises a method in which a clay, of the phyllosilicate family, is subjected to a chemical treatment in water, during which its basal spacing increases as a result of the intercalation of a surfactant, sodium stearate precipitated in the form of calcium stearate or sodium lauryl sulphate or sodium propyl sulphate precipitated in the form of a salt between the layers of the mineral; calcium stearate or calcium lauryl sulfate or calcium propyl sulfate or any surfactant also acts as a swelling agent and at the same time as a mineral surface modifier; the modified clay has a high basal spacing and thermal stability in the temperature range used in the processing of the polymers of interest in this work (about 220 ° C), in addition to having functional groups on its surface that allow good adhesion with polymer matrices.

Description

"PROCESS FOR OBTAINING MODIFIED NANOARGIL FOR PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL"

FIELD OF INVENTION

The present invention is a novel method of obtaining an organophilic nanoargyl from the chemical treatment of a pure natural clay with a carboxylic acid derived or alkyl sulfate or propyl sulfate surfactant, a surfactant modifying chemical inside the clay and the clay itself.

BACKGROUND OF THE INVENTION

Clay is a finely divided rock, consisting essentially of clay minerals, and may contain other minerals such as calcite, dolomite, gibbsite, quartz, aluminite, pyrite, etc., organic matter and other impurities. They are generally crystalline minerals; chemically composed of hydrated aluminum silicates and may contain other elements such as iron, magnesium, lithium, potassium, sodium, among others [Patent, Pl 0601384-8 A].

The main factors controlling the properties of clays are their mineralogical composition, particle size distribution, exchangeable ion and soluble salt electrolyte content, nature and content of organic matter and texture. Variations in the chemical and structural nature between clay materials provide applications in various fields. The most common and important are in the paper, plastic and rubber industries. Clays are also used for their catalytic properties and their ability to absorb fats and other organic materials [Patent, Pl 0601384-8 A],

Crystalline clay minerals can be divided into two general classes: 1) Iamelas-structured clay minerals - also called leaf silicates or phyllosilicates. These may be subdivided into groups or families: (i) 1: 1 lanes or dipormic; / '/) Iamelas 2: 1 or triformic. The 1: 1 and 2: 1 nomenclature is due to the number of layers of silicon oxide tetrahedra (SiO4) and aluminum oxide octahedra (AI2O3) that form the unit cell of the crystal structure of the argilomineral; 2) Fibrous-structure clay minerals - these consist of only two components, sepiolite and paligorsquite, the latter also called attapulgite [Patent, Pl 0601384-8 A. Patent, Pl 0515822-2 A].

The Yamelas structure is the most common among clay minerals. These compounds may also be subdivided on the basis of the following properties: (i) at an interplanar distance of 0,7 nm in 1: 1 clay minerals (kaolinite), 1 nm in anhydrous 2: 1 clay minerals and 1,4 nm in hydrated clay minerals; ii) the degree of substitution in the octahedral layer of AI2O3 of the unit cell; iii) the possibility of the Yamelas expanding by the introduction of polar molecules, thus increasing the interplanar distance; iv) the type of crystallographic arrangement along the axes, which distinguishes mineral specimens from the same group [Patent, Pl 0601384 8 A];

The main group of lamellar-shaped clay minerals are those called phyllosilicates (Greek phylos, leaves). In this group there are the clay minerals of the montmorillonite group, which have the general formula Mx (AU-XMgx) SisC40 (OH) 4 and consist of a central foil formed of aluminum oxide octahedra located between two sheets of tetrahedron. silicate. The leaves are connected to each other by sharing oxygen centers of the coordinating polyhedra. These units are continuous in directions a and b according to the crystallographic coordinates and are stacked on top of one another. The forces holding the leaves together are relatively weak, which makes it possible to interchange ions or molecules between them, often spacing them apart. In octahedral leaves, some Al3 + centers may be isomorphically replaced by Mg2 + ions, which leads to a negative charge accumulation distributed between the coverslips. The charge balance is achieved by inserting positive counter ions between these coverslips, these being typically sodium ions, commonly called exchangeable cations [Patent, Pl 0601384-8 A. Patent, Pl 0515822-2 A. Paiva, L. B .; Morales A. R .; Diaz, F. R. V .. Organophilic clays: characteristics, preparation methodologies, intercalation compounds and characterization techniques. Pottery, v. 54, p. 213-226, 2008. Rabbit, Α. YOU.; Santos, P. S .; Santos, H. S .. Special Clays: Chemically Modified Clays: A Review. New Chemistry, v. 30, p. 1282-1294, 2007. Paul, D. R .; Roberson, L.M .. Polymer Nanotechnology: Nanocomposites. Polymer, 49, 3187-3204, 2008].

When anhydrous montmorillonite clay minerals are brought into contact with water, the exchangeable cations hydrate and thereby the solvent molecules insert between the coverslips. This process, called swelling, causes the basal spacing to increase, reaching the total separation of the lamellae when the interplanar distances are greater than 4 nm. The weak bonds between these structures and the high degree of isomorphic substitution make it easy to cleave the montmorillonite clay particles in a liquid medium. Because of these characteristics, montmorillonite particles are generally small in size and extremely thin [Paul, D. R .; Roberson, L.M .. Polymer Nanotechnology: Nanocomposites. Polymer, 49, 3187-3204, 2008].

The inherent swelling property of clays makes it possible to chemically modify the surface of their structures. Following this process, Na + ions between the lamellae (montmorillonite clay minerals may contain other counterions inserted between their lamellae. However, the most common are sodium ion-containing structures) are susceptible to exchange by other cations via stoichiometric chemical reactions. The main focus of the chemical modification of clays has been directed to materials science, whose objective is to obtain organophilic clays for application in polymeric nanocomposites. Modified clays are used as additives (reinforcing, barrier and rheological control agents) in various thermoplastics and elastomers, and their use is of great commercial importance [Sinha Ray, S .; Okamoto, M .. Polymer / layered silicate nanocomposites: A review from preparation to processing. Progress in Polymer Science, v. 28, p. 1539-1641, 2003].

The properties of the polymer / clay composites obtained are strongly related to the degree of clay delamination and dispersion in the polymer matrix. When the clay is nanoscale dispersed, the product obtained is called nanocomposite. On this scale, even in small quantities (generally less than 5% by mass), the presence of clays exhibits improvements in the mechanical, thermal, optical and physicochemical properties of polymers compared to pure polymers and traditional polymer composites [Patent Pl 0701345-0 A2. Patent, Pl 0701188-1 A2. Paul, D. R .; Roberson, L.M. Polymer nanotechnology: Nanocomposites. Polymer, 49, 3187-3204, 2008. Camargo, Ρ. H. C .; Satyanarayana, K. G .; Wypych, F. .. Nanocomposites: Synthesis, Structure, Properties and New Application Opportunities. Materials Research, 12, 1-39, 2009],

The field of application of polymers has been greatly expanded in recent years, occupying spaces previously belonging to other materials such as ceramics and metals [Camargo, Ρ. H. C .; Satyanarayana, K. G .; Wypych, F. .. Nanocomposites: Synthesis, Structure, Properties and New Application Opportunities. Materials Research, 12, 1-39, 2009]. These new applications necessarily require new properties often not achieved with the use of pure polymer. It is within this context that the branch of materials chemistry that deals with the modification of the properties of these solids, through the preparation of polymer nanocomposites, is inserted. These nanoclays are also conveniently called nanocarbons. The use of nanocharges allows the improvement of barrier properties, thermal and dimensional stability, flame retardance and mechanical properties with the use of low load contents (up to 5% by mass) which differentiates them from traditional composites, where the percentage in mass can reach 40%. Interest in polymer nanocomposites has grown rapidly since the discovery by a group of Toyota researchers. They obtained nylon-6 / organophilic clay nanocomposites by the in situ polymerization process of ε-caprolactone. The result was a significant improvement in several properties compared to those of pure polymer [Ray, S. S .; Okamoto, M .. Polymer / layered silicate nanocomposites: a review from preparation to processing. Progress in Polymer Science, v. 28, p. 1539-1641, 2003].

Depending on the nature of the components used and the method of preparation, two types of polymer / nanoargyl nanocomposites can be obtained: /) Interleaved nanocomposites: These are formed when the polymeric chain is interspersed between the silamines, resulting in a morphology in which they are formed. well-ordered multilayer, alternating between inorganic and organic phases; / '/) Nanocomposites with Exfoliated Structure: They are formed when clay yamels are uniformly dispersed (exfoliated) as individual entities in a continuous polymeric matrix [Camargo, Ρ. H. C .; Satyanarayana, K. G .; Wypych1 F .. Nanocomposites: Synthesis1 Structure1 Properties and New Application Opportunities. Materials Research, 12, 1-39, 2009]. Figure 1 shows a schematic representation of the structures of these types of nanocomposites. X-ray diffractometry and transmission electron microscopy analyzes are usually employed in the structural characterization of these materials [Patent, Pl 0601384-8 A],

Different methodologies may be employed in the preparation of polymer nanocomposites. The four main processes are: i) Exfoliation-adsorption; / '/) In situ polymerization interleaving; / 77) Merging in the molten state; / V) Synthesis in polymeric matrix.

The first report that demonstrates the possibility of obtaining nanocomposites directly by intercalation of the molten polymer was that made by Giannelis et al. [Vaia, R. A .; Giannelis, E. P. Lattice of polymer melt intercalation in organically modified Iayered silicates. Macromolecules, v. 30, p. 7990-7999, 1997]. This methodology has become the main means of obtaining these materials, as it is the most efficient, simple and economical alternative. In addition, it is an environmentally appropriate technique and compatible with industrial processes as it does not use solvents.

In this technique, the molten polymer is mixed with the clay to allow intercalation of the polymer chains between their coverslips. Depending on the degree of polymer penetration between these lines1 nanocomposites are obtained with structures ranging from interleaved to delaminated. The polymeric materials resulting from finite expansion of the lamellae produce intercalated nanocomposites. When the penetration of the polymeric chains is sufficient to increase the interlamellar distance, to the point of nullifying the effect of the attractive forces between them, a delamined nanocomposite is obtained, where the lamellas start to behave as individual entities dispersed in the polymeric matrix [Paul , DR; Roberson, L.M .. Polymer nanotechnology: Nanocomposites. Polymer, 49, 3187-3204, 2008],

Modification employing ammonium salts introduces a hydrophobic character to clay, reducing its surface tension and consequently improving compatibility with the polymer matrix. This process also increases the spacing between the coverslips, facilitating polymer intercalation and thereby delamination of the clay. Clays modified by alkylammonium and alkylphosphonium salts are known as organophilic clays. These clays are currently one of the main precursors for obtaining nanocomposites. However, these have some limitations compared to the requirements in the field of composite materials [Patent, Pl 0601384-8 A].

It is known that the properties of composite materials are strongly related to the degree of dispersion of the inorganic particle as well as the degree of interaction of the polymeric matrix with it. Clay, when treated with some ammonium salts, for example, has poor Iamela-Iamela and particle-particle interaction. Because of this, it undergoes a high degree of delamination and therefore of dispersion of the clay in the polymer matrix. However, this chemical treatment results in poor interaction with the polymer at the same time. In view of this, although nanocomposite presents a high degree of clay delamination in the polymeric matrix, literature data show that, in some cases, no mechanical properties superior to traditional composites were obtained.

The fact that some ammonium salts block the access of the polymer chains to the clay polar sites is what causes the weak interaction between the polymer and this charge. In addition, the ammonium salts usually employed in chemical modification do not have functional groups in their structures capable of promoting chemical bonding with clay or even proper interaction with this matrix [Pinavaia, T. J .; et al. Homostructured mixed organic and inorganic cation exchange tapered compositions. Int C13B22 C01B 033/24. US 5,993,769. 14 May 1998, 30 Nov. 1999].

Another important factor is related to the low thermal stability of ammonium salts [Park, C. I .; et al. The manufacture of syndiotactic polystyrene / organophilic clay nanocomposites and their properties. Polymer1 v. 42, p. 7465-7475, 2001], As already described, the principal method of obtaining the nanocomposite is via melt-polymer intercalation. In this method, the polymer is mixed with clay in equipment such as extruders, calenders, internal mixers, among others. The polyethylene / clay mixture is subjected to high temperatures and high shear rates. Under these conditions, ammonium salts are not sufficiently stable, being eliminated by Hoffman [Fornes, T. D .; Yoon, P. J .; Paul, D. R .. Polymer matrix degradation and color formation in melt processed nylon 6 / clay nanocomposites. Polymer, v. 44, p. 7545-7556, 2003].

Thermogravimetric analysis revealed that the degradation of ammonium salts occurs at temperatures around 180 ° C under non-oxidizing atmosphere. As many polymers are processed at temperatures close to or above 180 ° C, ammonium salt degradation products can act as degraders of the polymeric matrix, inducing color appearance and compromising the thermal stability and properties of the final product [ Patent, Pl 0601384-8 A],

In view of the limitations mentioned above, there is a need to develop new chemical clay modification processes that will replace traditional ammonium salts with other modifying agents. This is based on meeting the requirements of thermal stability, mineral swelling capacity, as well as promoting an improved interaction between the mineral and the polymer.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a novel methodology for the production of expanded clay from the chemical modification of a pure clay by a surfactant derived primarily from a carboxylic acid or other surfactant having the desired characteristics, such as an alkyl derivative. or propyl sulfate. The clay is subjected to a chemical treatment in aqueous solution in the presence of the appropriate surfactant with the aid of mechanical stirring. The surfactant in question also acts as a swelling agent, that is, it increases the spacing between the clay wires. Once expanded, and the surfactant inside separating its coverslips, a chemical agent capable of reacting with the surfactant is introduced into the solution containing the clay in order to alter the surfactant characteristics so as to cause the surfactant to dissolve. precipitate inside the coverslips. At the same time, the surfactant acts as a mineral surface modifier, leaving on its surface nonpolar functional groups capable of acting as polarity modifiers of the clay, which becomes hydrophobic, and can thus interact strongly with a polymeric matrix. .

Expanded clay, obtained by the method described by this invention, has a basal spacing comparable to those of organophilic clays obtained by chemical modification of pure clay by ammonium salts. The cost associated with the method described in the present invention is estimated to be 3 times lower than the methods using ammonium salts, based on the prices obtained from the suppliers of carboxylic acid derived or alkyl or propyl sulfate surfactant and different commercially available primary, tertiary and quaternary ammonium salts.

The expanded clay obtained by this new method has thermal stability in the processing temperature range of the polymers of interest in this work (about 220 ° C). This stability prevents the loss of mechanical and physical properties of the polymer due to possible degradation during processing with the clay.

Thus, the objectives to be achieved with the present invention are as follows:

1) Replacement of ammonium salts by another modifying agent that presents thermal stability in the processing temperature range of the polymers of interest in this work;

2) Replacement of ammonium salts with another lower cost modifying agent;

3) Coating the clay surface with a modifying agent that has the ability to act as an adhesion promoter between polymer and mineral; 4) Obtaining a modified clay with potential to act as a reinforcing agent in polymeric matrices;

5) Obtaining a modified clay with potential to act as a gas barrier agent in polymeric matrices.

DESCRIPTION OF THE FIGURES

The present invention will be further described based on the following related figures, in which:

Figure 1 illustrates the schematic representation of the structure of two types of composites derived from the interaction between polymer surface modifying agents;

Figure 2 illustrates the schematic representation of the structure of a sodium montmorillonite, adapted from Polymer reference, v. 49, p. 3187-3204, 2008;

Figure 3 shows the infrared absorption spectra of pure and modified clay;

Figure 4 shows the X-ray diffractograms obtained for pure and modified clay;

Figure 5 illustrates the thermogravimetric curve of pure clay; and

Figure 6 illustrates the thermogravimetric curve of the modified clay.

DETAILED DESCRIPTION OF THE INVENTION

The clay employed in the present invention is natural, belongs to the family of phyllosilicates, preferably from the 2: 1 group. Its lamellar structure consists of silica tetrahedra and aluminum oxide octahedra. In tetrahedral positions there may be isomorphic substitution of Si4 + sites by Al3 + and in octahedral positions, the cation may be Al3 +, Mg2 +, Fe2 + or other. A schematic representation of the structure of a sodium montmorillonite is shown in Figure 2 [Patent, Pl 0601384-8 A. Patent, Pl 0515822-2 A. Camargo, Ρ. H. C .; Satyanarayana, K. G .; Wypych, F. .. Nanocomposites: Synthesis, Structure1 Properties and New Application Opportunities. Materials Research, 12, 1-39, 2009. Rabbit, Α. YOU.; Santos, P. S .; Santos, H. S .. Special Clays: Chemically Modified Clays: A Review. New Chemistry, v. 30, p. 1282-1294, 2007. Paul, D. R .; Roberson, L.M .. Polymer nanotechnology: Nanocomposites. Polymer, 49, 3187-3204, 2008]. The recommended carboxylic acid derived surfactant for this invention is sodium stearate, CH3 (CH2) 16 COO Na +. The recommended alkyl sulfate derived surfactant for this invention is sodium lauryl sulfate, CH3 (CH2) 10 SO4 Na +. However, all carboxylic acids, alkyl sulphates and propyl sulphates in the form of sodium or potassium salt which precipitate when in the presence of a calcium, barium, magnesium, iron, aluminum, silver or copper salt (any element which enables precipitation interfacial agent when inside the clay) may be used in this invention.

In the present invention, the amount of surfactant recommended for obtaining modified clay is up to 64% based on the mass of the pure clay.

In the present invention, a metal salt (alkaline earth or, for example, Al, Fe, Cu or Ag) is employed to precipitate the modifying agent between the clay lamellas, maintaining it with the suitable sparse for application in the polymer. which may be any engineering thermoplastic or polymer. The use of calcium chloride is recommended, however, this recommendation does not limit the invention to the form disclosed herein. Other salts may also be employed. For example, we mention magnesium chloride, aluminum chloride or iron, aluminum, silver or copper chlorides. Similarly, the same cations may be employed with fluoride, bromide and iodide anions.

In the process of chemical treatment of clay, the use of water as a solvent is recommended. In the present invention, there is no need for pH corrections of this solvent.

The method of obtaining expanded clay using the carboxylic acid derived or alkyl sulfate or propyl sulfate surfactant, which is one of the objects of the present invention, has the following steps:

1. Transfer the appropriate volume of water to a container to swell the clay;

2. Swell the clay in water;

3. Keep the clay / water mixture at rest for at least 20 hours, more preferably 24 hours;

4. Shake the clay / water mixture mechanically and vigorously for 20 min.

5. Keep the suspension, after shaking, at rest for at least 20 h, more preferably 24 h;

6. Filter the mesh suspension ABNT 200 mesh;

7. Preparing a solution containing the carboxylic acid derived surfactant and maintaining it at a temperature between 55 ° C - 75 ° C, more preferably between 60 ° C - 70 ° C and most preferably at 65 ° C. In the case of alkyl sulfate or propyl sulfate surfactants there is no need to heat the solution above room temperature;

8. Add the solution of the carboxylic acid derived, alkyl sulfate derived or propyl sulfate derived surfactant at the temperature specified in the above to the water-swollen clay and keep the clay / water suspension under vigorous mechanical stirring for 20 min;

9. Keep the suspension at rest for at least 20 h, more preferably 24 h;

10. Heating the reaction mixture to a temperature between 55 ° C - 75 ° C, more preferably between 60 ° C - 70 ° C and most preferably at 65 ° C. The reaction mixture prepared with the alkyl sulfate or propyl sulfate derived surfactants does not require heating above room temperature;

11. Add to the reaction mixture, under vigorous mechanical agitation, a suspension containing a chemical element in the form of halide salt (eg calcium chloride). Allow the reaction mixture to stir for 20 min;

12. Keep the reaction mixture at rest for 24 h;

13. After reaction time, filter the mixture using ABNT 500 mesh screen. The material may also, prior to filtration, be added with ethyl alcohol to facilitate filtration and drying. For each part of the suspension containing the modified clay, 2 parts of the ethyl alcohol (1: 2 mixture). Mixtures of the modified clay: ethyl alcohol suspension can also be prepared in the following proportions: 1: 1 and 1: 3, without changes in the characteristics of the final product;

14. Dry the modified clay at 65 ° C until completely free of water;

15. Grind the modified clay in a ball mill for sufficient time to allow the clay particles to pass through the ABNT 250 mesh.

Modified clay, obtained through the process explained above, has some important characteristics not observed in clays modified by prior art processes. These features are:

• High basal spacing, which facilitates the intercalation of macromolecules such as polymers;

• Thermal stability in the processing temperature range of the polymers of interest in this work, which prevents the loss of physical, mechanical and thermal properties of polymeric matrices during eventual processing steps involving high shear rates and temperatures;

• Existence of nonpolar functional groups on its surface, which allows a good adhesion with several polymeric matrices;

• Lower costs compared to ammonium salt-based organophilic clays;

• Low toxicity of interfacial agent compared to ammonium salts.

In order to more clearly illustrate the present invention, three examples are described below. It should be understood that these examples are illustrative only and do not limit the invention disclosed herein. EXAMPLE 1 - Preparation of modified clay producing sodium stearate in situ

First, 300 g of pure clay was swollen in 7500 mL of H2O. The procedure is performed by spreading small amounts of clay over the water surface. When it absorbed water and precipitated, more clay was scattered over the water. The procedure was repeated until all the clay was added to the water. The total time for this procedure is dependent on the amount of clay to be swollen. Thereafter, the resulting mixture was kept at rest for 24 h.

After this time, the clay / water mixture was placed in a 25 L industrial blender and stirred for 20 min. After stirring, the resulting suspension was kept at rest for 24 h. The suspension was then filtered through ABNT 200 mesh and placed back into the industrial blender. At the same time, a colorless solution containing 24 g of NaOH in 3750 ml of water was prepared. The solution was heated to 65 ° C and then 168 g of stearic acid was added. The sodium stearate thus produced was diluted by the addition of 3750 mL of water, leading to a final volume of 7500 mL sodium stearate solution. Sodium stearate solution at 65 ° C was added with stirring to the clay suspension in the blender and the resulting mixture was stirred for 20 min. After this time, it was kept at rest for 24 h. After 24 hr, the reaction mixture turned to a gel. This gel was transferred to a suitable container and as it was heated returned to the liquid phase. When the suspension reached 65 ° C it was transferred back to the blender and immediately added with a suspension containing 49.05 g CaCb in 900 mL H2O and the reaction mixture was allowed to stir for 20 min and then allowed to stand. 24 h.

After the reaction, the suspension containing the modified clay was added with ethyl alcohol (1: 2 ratio, modified clay: ethyl alcohol). After addition of alcohol, the resulting mixture was kept at rest for 24 h and then filtered through ABNT 500 mesh. The solid phase, isolated by filtration, was dried at 65 ° C until completely dry. The modified clay was then transferred to a 10 L capacity ball mill and kept under grinding until its particles passed through ABNT 250 mesh.

EXAMPLE 2 - Preparation of Modified Clay Using Sodium Stearate

First, 300 g of pure clay was swollen in 7500 mL of H2O. The procedure was performed as described in EXAMPLE 1. Thereafter, the resulting mixture was kept at rest for 24 h.

After this time, the clay / water mixture was placed in an industrial 25 L capacity blender and kept under stirring for 20 min. After stirring, the resulting suspension was kept at rest for 24 h. After this time the suspension was filtered through 200 mesh ABNT mesh and placed back into the industrial blender. At the same time, a solution at 65 ° C containing 192 g of sodium stearate in 7500 ml of water was prepared. The solution was further added at 65 ° C under stirring to the clay suspension in the blender and the resulting mixture was stirred for 20 min. After that, it was left to stand for 24 h. After standing, the gel reaction mixture was transferred to a suitable vessel and, as warmed, returned to the liquid phase. When the mixture reached 65 ° C, it was transferred back to the blender and immediately added to a suspension containing 49.05 g CaCl 2 in 900 mL H 2 O. The reaction mixture was allowed to stir for 20 min and then allowed to stand for 24 h.

After the reaction, the modified clay was isolated, dried and ground as described in EXAMPLE 1.

EXAMPLE 3 - Preparation of modified clay by direct incorporation of sodium stearate

First, 300 g of pure clay was swollen in 7500 mL of H2O. The procedure was performed as described in EXAMPLE 1. Thereafter, the resulting mixture was kept at rest for 24 h.

After this time, the clay / water mixture was placed in a 25 L industrial blender and stirred for 20 min. After stirring, the resulting suspension was kept at rest for 24 h. It was then transferred to a suitable container, added with 7500 mL of water and heated to a temperature of 65 ° C. After heating, it was kept under stirring in the industrial blender and slowly added 192 g of sodium stearate. After complete addition of the stearate, the reaction mixture was stirred for 20 min and then rested for 24 h. After standing, the reaction mixture as a gel was transferred to a suitable vessel and, as it was heated, returned to the liquid phase. When the mixture reached 65 ° C, it was transferred back to the blender and immediately added to a suspension containing 49.05 g CaCl2 in 900 mL H2O. The reaction mixture was allowed to stir for 20 min and then allowed to stand for 24 h.

After the reaction, the modified clay was isolated, dried and ground as described in EXAMPLE 1.

EXAMPLE 4 - Preparations of modified clay employed solutions / suspensions with different reagent concentrations (reactions using sodium stearate)

Reactions with changes in reagent concentrations without changes in the characteristics of the final product were also tested. Variations in concentrations were made for the three examples described above as follows: (i) The clay / water suspension obtained after the swelling step has a concentration of 4% clay in water. Concentrations between 2 - 4% may also be employed; (ii) The sodium stearate solution has a concentration of 2.6% of this reagent in water. Concentrations between 3.0 - 5.2% may also be employed; (iii) CaCl2 solution has a concentration of 2.12% of salt in water. Concentrations between 3.0 - 4.24% may also be employed.

Regarding the isolation of the modified clay, the procedure is performed by ABNT 500 mesh mesh filtration as described in EXAMPLE 1. Modifications in the filtration process were also performed without changes in the characteristics of the final product. Thus, the modified clay can also be isolated by filtration through analytical filter paper, vacuum filtration employing a Buchner funnel or through filtration employing a 10 micron liquid retained polyester filter.

EXAMPLE 5 - Preparation of modified clay employing sodium lauryl sulfate

First, 50 g of pure clay was swollen in 1250 mL of H2O. The procedure was performed as described in EXAMPLE 1. Thereafter, the resulting mixture was kept at rest for 24 h.

After this time, the clay / water mixture was stirred under magnetic stirrer for 20 min. After stirring, the resulting suspension was kept at rest for 24 h. Then the suspension was filtered by passing through ABNT 250 mesh to remove possible contaminants.

In parallel, a solution containing 30 g of

sodium lauryl sulfate in 200 mL of water. This solution was then slowly added to the clay suspension. After complete addition of sodium lauryl sulfate solution, the reaction mixture was stirred for 20 min and then allowed to stand for 24 h.

After standing, the reaction mixture was again subjected to filtration by passing through ABNT 250 mesh to remove possible contaminants. Thereafter, it received the addition of a suspension containing 5.77 g CaCl 2 in 62 mL H 2 O, was stirred for 20 min and then rested for 24 h. After this time, the reaction mixture was placed for oven drying at 60 ° C long enough for the modified clay to be free of water. EXAMPLE 6 - Preparations of modified clay employed solutions / suspensions with different reagent concentrations (reactions using sodium lauryl sulphate)

The method of obtaining modified clay using sodium lauryl sulfate, as described in EXAMPLE 5, was also employed in reactions containing different concentrations of reagents. The variations in concentrations for EXAMPLE 5 were as follows: (i) The clay / water suspension obtained after the swelling step has a concentration of 4% of 25 clay in water. Concentrations between 2 - 4% may also be employed; (ii) The sodium lauryl sulfate solution has a concentration of 13% of this reagent in water. Concentrations between 10 - 15% may also be employed; (iii) CaCl2 solution has 8.5% concentration of this salt in water. Concentrations between 3.0 - 10.0% may also be employed.

Other changes made to the methodology described in

EXAMPLE 5 are: (i) the modified clay may be isolated by ABNT 500 mesh sieve filtration prior to the drying step; (ii) the reaction mixture may be added with ethyl alcohol in the same ratio as described in EXAMPLE 1 prior to the filtration and / or drying step.

To characterize the structure of the materials obtained by the methodologies described in all the EXAMPLES described above, the infrared absorption spectroscopy (FTIR) and powder X-ray diffractometry (XRD) techniques were used. Modified clays isolated by the procedures described in EXAMPLES 1, 2, 3 and 4 showed very similar structural characterization results, indicating that the same product is being formed through these methodologies. The same behavioral pattern was observed for products obtained from the synthetic methodologies described in EXAMPLES 5 and 6. To illustrate the characterization of modified clays, since the results are similar to each other, the following text shows only one result from characterization for each technique used.

FTIR spectra revealed, for pure and modified clay, proper hydroxyl structural stretching vibrations of clay at 3643 cm "1; OH group stretching vibrations for interlamellar water and adsorbed to smectite at 3411 and 1642 cm" 1 respectively; Si-O group vibrations at 1033 cm-1 and Al-O-Si and Si-O-Si vibrations around 531 and 459 cm-1. In the modified material, in turn, the presence bands at 2928 and 2859 cm-1 corresponding to the asymmetric and symmetrical vibrational modes of the CH2 group, respectively, and flexural vibrations of the CH3 group in the 1474 cm-1 range, evidenced the intercalation of the modifying agent in the interlamellar spaces of its structure. 3

Figure 4 shows the comparison between pure clay and modified clay X-ray diffractograms. In the analysis of these diffractograms, three new diffraction peaks can be observed at values lower than 26>, ie, greater interlamellar distances (12.6 A, for pure clay, versus 53.4 Â, 25.3 A and 16.6 A, for the modified). This result indicates the efficiency in the methodology employed in the chemical modification process of clay.

In conclusion, the absorption spectra in the infrared region of natural and modified clay evidenced the intercalation of the surface modifying agent, which was confirmed by the powder X-ray diffraction data.

The above description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Accordingly, variations and modifications consistent with the above teachings and the skill or knowledge of the relevant art are within the scope of the present invention.

THERMAL PROPERTIES

Thermogravimetric analysis (TGA) was used to evaluate the thermal properties of pure and modified clay. Thermal transformations of pure clay can be observed in Figure 5. Between 59.4 and 138.4 ° C there is a process related to the loss of adsorbed water interspersed between the clay yamels, coordinated to exchangeable cations [Guggenheim, S .; Koster, Van Gro .. Baseline studies of the clay minerals society source clays: Thermal analysis. Clay and Clay Minerals, v. 49, p. 43-443, 2001. Patent, Pl 0601384 8 A]. The lost mass above 587.9 ° C is attributed to dehydroxylation of the alumina layer [Paiva, L. B .; Morales A. R .; Diaz, F. R. V .. Organophilic clays: characteristics, preparation methodologies, intercalation compounds and characterization techniques. Pottery, v. 54, p. 213-226, 2008]. For the modified clay (Figure 6), the first processes of mass loss between 47.60 ° C and 113 ° C are due to the evaporation of water molecules in the interlamellar cations of the modified montmorillonite. The process that occurs between 124 ° C and 135 ° C is related to the dehydration of water molecules from the crystalline reticulum. In the range between 241.4 ° C and 516.4 ° C, mass loss is related to the burning of the modifying agent inserted in the clay structure. The data show that the modifying agent is decomposed at a temperature higher than that generally employed in nanocomposite preparation processes with most of the polymers of interest in this work. The mass loss process occurring in the range between 619.0 ° C and 710.10 ° C can be attributed, as well as that observed in pure clay, to the desorption of physically adsorbed water and dehydroxylation of the alumina layer [Paiva, L. B .; Morales A. R .; Diaz, F. R. V .. Organophilic clays: characteristics, preparation methodologies, intercalation compounds and characterization techniques. Pottery, v. 54, ρ. 213-226, 2008]. The higher mass loss observed for modified clay (total mass loss = 42.30%) compared to pure clay (total mass loss = 14.52%) was already expected, since the presence of the agent modifier, of organic origin, increased the amount of carbonaceous material inside the clay.

Claims (7)

1. "PROCESS FOR OBTAINING MODIFIED NANOARGIL FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL", comprising the following steps: 1) Transfer the appropriate volume of water to a suitable container for the swelling of clay so that the final suspension concentration is 4% (w / v); suspensions with concentrations between 2.0 - 4.0% (m / v) may also be employed without changes in the characteristics of the final product; 2) Swell the clay in water; 3) Keep the clay / water mixture at rest for a minimum of 20 h, more preferably 24 h; 4) Shake the clay / water mixture mechanically and vigorously for 20 min; 5) Keep the suspension, after shaking, at rest for at least 20 h, more preferably 24 h; -6) Filter the suspension by ABNT 200 mesh; 7) Preparing an aqueous solution containing the carboxylic acid derived surfactant and maintaining it at a temperature between 50 ° C and 90 ° C, more preferably at 65 ° C; for aqueous solutions containing the alkyl sulfate or propyl sulfate derived surfactants no heating above room temperature is required; the surfactant solution concentration is -1.0 - 5.0% (w / v) for carboxylic acid derivatives and 10-20% (w / v) for alkyl sulfate (or propyl sulfate) derivatives; solutions with concentrations between 2.0 - 5.0% (m / v) (for carboxylic acid derivatives) and between 8.0 - 20.0% (m / v) (for alkyl sulfate or propyl sulfate derivatives) also can be employed without changes in the characteristics of the final product; 8) Adding the solution of the carboxylic acid derived or alkyl sulfate derived surfactant (or propyl sulfate) to the clay / water suspension under vigorous mechanical stirring for 20 min; 9) Keep the suspension at rest for at least 20 h, more preferably 24 h; 10) heating the suspension to a temperature between 50 ° C and 90 ° C, more preferably at 65 ° C; (11) Add to the suspension, under vigorous mechanical agitation, a suspension containing calcium chloride in water under vigorous mechanical agitation for 20 min. CaCl2 concentration is 1.0 - 5.0% (w / v) for reactions employing carboxylic acid derivatives and 5.0 - 10.0% for reactions employing alkyl sulfate (or propyl sulfate) derivatives sodium; suspensions with concentrations between 2.0 - 7.0% (m / v) (for reactions employing carboxylic acid derivatives) and between 1.0 - 15.0% [for reactions employing alkyl sulfate (or propyl sulfate) derivatives ) sodium] can also be employed without changes in the characteristics of the final product; 12) Keep the suspension at rest for 24 h; (13) Transfer the suspension to a suitable container for the addition of alcohol in the case of reactions employing carboxylic acid derivatives. (14) Add to each part of the suspension containing the modified clay 2 parts of an ethyl alcohol (1: 2 mixture); Mixtures of the modified clay suspension: ethyl alcohol can also be prepared in the following proportions: 1: 1 and 1: 3, without changes in the characteristics of the final product; It is also possible not to use the alcohol, proceeding to the direct drying of the product first passing it by a filtration; 15) Keep the prepared mixture at rest for a minimum of 24 hours; 16) Filter the mixture by ABNT 500 mesh; 17) Dry the modified clay at 65 ° C until completely dry; 18) Grinding the modified clay in a ball mill for a period of time sufficient for the clay particles to pass through the ABNT 250 mesh; 18) For methodologies employing sodium alkyl sulfate (or propyl sulfate) derivatives, none of the reaction steps employ heating above room temperature. 2. "MODIFIED NANOARGIL OBTAINING PROCESS FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL" as claimed in 1, characterized by the fact that the solvent is water. 3. "PROCESS OF OBTAINING MODIFIED NANOARGIL FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL" as claimed in 1 and 2, characterized in that the amount of surfactant employed is up to 64% based on the mass of pure clay. 4. "PROCESS FOR OBTAINING MODIFIED NANOARGIL FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL", as claimed in 1, 2 and 3, characterized by the use of natural clay belonging to the family of phyllosilicates, preferably from the 2: 1 group. 5. "PROCESS FOR OBTAINING MODIFIED NANOARGIL FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL" as claimed in 4, characterized in that the natural clay is montmorillonite. 6. "PROCESS FOR OBTAINING MODIFIED NANOARGIL FOR THE PRODUCTION OF POLYMERIC NANOCOMPOSITS AND MODIFIED NANOARGIL" as claimed in 1 and 2, characterized in that the surfactant employed is sodium stearate precipitated as calcium stearate or Precipitated sodium lauryl sulphate or sodium propyl sulphate in the form of calcium lauryl sulphate or calcium propyl sulphate or any other precipitating agent. 7. "MODIFIED NANOARGIL", characterized in that it is produced by the process of claims 1 to 6 and has the following characteristics: high basal spacing, thermal stability, and existence of functional groups on its surface that facilitate interaction with nonpolar polymeric matrices.