Natural sodium bentonite clay with improved rheological properties

Abstract

Bentonite clay having improved rheological properties is provided. The present invention relates to a method for treating a natural clay material comprising sodium bentonite, the method comprising the steps of: i) preparing an aqueous slurry of the natural clay material comprising sodium bentonite; ii) removing non-sodium bentonite impurities from the aqueous slurry; and iii) removing the aqueous solution from the aqueous slurry by spray drying in a spray dryer to prepare a solid treated sodium bentonite clay.

Description

Technical Field

[0001] The present invention relates to a method for treating natural clay materials containing sodium bentonite, the treated natural sodium bentonite clay obtained by this method, the use of this treated natural sodium bentonite clay, and a method for controlling the rheology of aqueous compositions.

Background Art

[0002] Different types of bentonite are each named based on their dominant cation. For industrial purposes, two main classes of bentonite are recognized, namely sodium and calcium bentonite. Sodium bentonite is more valuable, but calcium bentonite is more common. Naturally occurring sodium bentonite is typically not available in high purity. Typically, they carry a significant amount of inert minerals as impurities in the mineral, which impairs their use as rheology additives.

[0003] Natural calcium bentonite can be converted to sodium bentonite by an ion exchange process to exhibit many of the properties of sodium bentonite, which is called sodium beneficiation or sodium activation. As commonly practiced, this means adding 5 - 10% soluble sodium salt (e.g., sodium carbonate) to wet calcium bentonite, mixing well, and taking a period that allows ion exchange to occur and a period that allows the exchanged calcium to be removed by water. Some properties of sodium-beneficiated calcium bentonite, such as viscosity and fluid loss of the suspension, are not completely equivalent to those of natural sodium bentonite. For example, residual calcium carbonate formed when the exchanged cation is not sufficiently removed can result in poor performance of artificial sodium bentonite.

[0004] CN111269606A describes a method for modifying calcium bentonite powder into sodium bentonite powder. This method includes treating calcium bentonite with a sodium cation source in the presence of water, preparing an aqueous slurry, followed by centrifugation, pH adjustment, and drying.

[0005] CN102283860A relates to a method for preparing montmorillonite formulations belonging to the pharmaceutical technology field. The examples describe the treatment of bentonite with water, removal of sand, and spray drying of the resulting suspension. [Overview of the project] [Problems that the invention aims to solve]

[0006] There is an ongoing need to provide bentonite clay with improved rheological properties, particularly bentonite exhibiting improved thickening efficiency in aqueous formulations. Furthermore, it is highly desirable that the clay can be easily and rapidly dispersed in water or aqueous formulations with reduced need for shear force application. [Means for solving the problem]

[0007] The present invention provides a method for processing natural clay materials containing sodium bentonite, and this method is: i) Prepare an aqueous slurry of natural clay material containing sodium bentonite. ii) Removing non-sodium bentonite impurities from aqueous slurry, and iii) Prepare a solid treated sodium bentonite clay by removing water from an aqueous slurry by spray drying in a spray drying apparatus. Includes, The solid treated bentonite clay has an exchangeable sodium ion content of 100 mmol / 100g or less and an exchangeable calcium ion content of 18 mmol / 100g or less, calculated based on the dry weight of the clay. [Modes for carrying out the invention]

[0008] The present invention provides a treated bentonite clay having improved thickening efficiency in aqueous formulations. Furthermore, the treated clay can be easily and rapidly dispersed in water or aqueous formulations with reduced need for shear force application.

[0009] The starting material used in the method of the present invention is a natural clay material containing sodium bentonite. The natural clay material is a material obtained from clay minerals that has not been treated or modified by means other than physical methods, such as grinding or sieving to obtain a desired particle size.

[0010] Bentonite is a natural clay mineral whose main component is montmorillonite. Generally, bentonite contains montmorillonite in the range of 30-90% by weight. The montmorillonite present in bentonite is plate-like aluminum silicate stacked on top of each other. The plates are typically slightly negatively charged. Therefore, they carry cations (positive ions) in the intermediate layer between the plates to compensate for the negative charge of the layer. Their uses are typically due to their high surface area and plate-like structure, which gives them particular advantages in gelling water or solvents, adsorbing certain substances, or providing barrier properties. In most of these applications, separation of the plates into single or small stacked plates is required to achieve the best properties. Bentonite can provide this swelling to the plates when the intermediate layer cation is single-charged, especially when the intermediate layer cation is sodium or lithium. Bentonite clay, which primarily supports divalent cations between its layers, is slightly swollen with Ca and Mg ions, and the single granules of aluminum silicate cannot be completely removed from each other in water.

[0011] Natural clay materials containing sodium bentonite used as raw materials in the present invention generally have a certain sodium ion content. The sodium ion content is appropriately expressed as the amount of sodium ions exchangeable with ammonium chloride. Typically, natural clay materials containing sodium bentonite contain at least 20 mmol / 100g of sodium cations, as determined by ion exchange with ammonium chloride.

[0012] The sodium ion content can be determined by a method that involves refluxing the natural clay material in water with an excess of ammonium chloride for one hour, followed by filtration and analysis of the filtrate by inductively coupled plasma atomic emission spectroscopy (ICP-OES).

[0013] In preferred embodiments, the natural clay material containing sodium bentonite contains at least 30 mmol / 100g, and more preferably at least 40 mmol / 100g, of sodium cations. Generally, the amount of sodium cations is in the range of 20 mmol / 100g to 100 mmol / 100g, preferably in the range of 30 to 90 mmol / 100g.

[0014] A higher content of replaceable sodium ions indicates a higher content of sodium bentonite in the natural clay material. A higher sodium bentonite content is desirable because it means that a smaller amount of non-sodium bentonite material needs to be removed.

[0015] In relation to the present invention, the natural clay material containing sodium bentonite preferably has a swelling volume of 12 ml or more, which is determined by adding 2.0 g of the natural clay material containing sodium bentonite to 100 ml of deionized water. Generally, a higher swelling volume indicates a higher sodium bentonite content in the natural clay material, which is preferable. In some embodiments, the natural clay material containing sodium bentonite preferably has a swelling volume of 15 ml or more, or 20 ml or more, for example, 25 ml or more, or 30 ml or more. The swelling volume is generally 70 ml or less, or 60 ml or less.

[0016] The swelling volume can be appropriately determined visually. For this purpose, fill a measuring cylinder with 100 ml of deionized water and add 2 g of each clay material to the water in several portions over 30 minutes. 60 minutes after the last addition of clay material, the volume of the swollen material in the measuring cylinder can be visually determined.

[0017] The natural clay material containing sodium bentonite used in accordance with the present invention comprises sodium bentonite and other materials collectively referred to as non-sodium bentonite impurities. Preferably, the natural clay material containing sodium bentonite contains 10 to 90% by weight of sodium bentonite, calculated based on the dry weight of the natural clay material. In a preferred embodiment, the sodium bentonite content in the natural clay material is in the range of 30 to 90% by weight, calculated based on the dry weight of the natural clay material.

[0018] The sodium bentonite content in natural clay material can be determined by removing non-sodium bentonite impurities from the natural clay material by dispersing the natural clay material in water, then removing non-sodium bentonite impurities by centrifugal separation at 3700g for 10 minutes, and finally drying the remaining aqueous phase.

[0019] The content of non-sodium bentonite impurities in the natural clay material is appropriately calculated based on the dry weight of the natural clay material and is in the range of 10 to 90% by weight, preferably 10 to 60% by weight.

[0020] In most embodiments, the non-sodium bentonite impurities include at least one of feldspar, calcite, mica, quartz, cristobalite, dolomite, and calcium bentonite.

[0021] In step i) of the method of the present invention, an aqueous slurry of a natural clay material containing sodium bentonite is prepared. The aqueous slurry can be prepared by mixing the natural clay material and water in a suitable container. The order in which the natural clay material and water are added to the container is not important. It is also possible to introduce water and natural clay material into the container at the same time. Tap water or water of similar purity is very suitable for use. If necessary, higher purity water or deionized water can be used. However, from an economic standpoint, the use of deionized water is less preferable.

[0022] Generally, the aqueous slurry contains natural sodium clay material, including sodium bentonite, in an amount of 2 to 20% by weight, calculated based on the weight of the aqueous slurry. While this method can also be carried out in embodiments where the amount of natural sodium clay material, including sodium bentonite, is less than 2% by weight of the aqueous slurry, such embodiments are less economically attractive because they require handling large amounts of water. If the amount of natural sodium clay material, including sodium bentonite, exceeds 20% in the aqueous slurry, the viscosity of the slurry becomes very high, which can impair handling of the aqueous slurry, such as stirring and pumping. In preferred embodiments, the aqueous slurry contains natural sodium clay material, including sodium bentonite, in an amount of 3 to 15% by weight, based on the weight of the aqueous slurry.

[0023] In most embodiments, a shear force is applied to the aqueous slurry prepared in step i) of the method of the present invention. The shear force can be applied by means known to those skilled in the art, such as a mixer, stirrer or dissolver, or a combination thereof. Application of the shear force can reduce the particle size of the slurry and / or result in a more uniform particle size distribution within the slurry.

[0024] In a preferred embodiment, at least one dispersing additive is present during the preparation of the aqueous slurry of the natural clay material containing sodium bentonite. The presence of the dispersing additive reduces the viscosity of the slurry for a given content of the natural clay material containing sodium bentonite and water. Furthermore, the presence of the dispersing additive can also improve the separation of non-sodium bentonite impurities in step ii) of the method of the present invention. Thus, the dispersing additive can improve the efficiency of the method.

[0025] Preferably, the dispersing additive comprises at least one of an organic polymer or oligomer and an inorganic phosphate or polyphosphate. Suitable organic polymers or oligomers include linear and branched polymers or oligomers having pendant or terminal carboxylic acid groups or salts thereof, phosphate groups or salts thereof, or phosphonate groups. Suitable types of polymers or oligomers include polymers and oligomers of polyester and polyacrylate. The weight average molecular weight of the polymer or oligomer generally ranges from 200 to 250000 g / mol, preferably from 500 to 50000 g / mol.

[0026] When present, the amount of the dispersing additive is suitably in the range of 0.5 to 5.0% by weight, calculated based on the weight of the natural clay material containing sodium bentonite. If the dispersing additive is used in an amount less than 0.5% by weight, the beneficial effect of the dispersing additive may not be fully achieved.

[0027] In some embodiments, the dispersion additive may contain sodium ions. However, the amount of sodium ions introduced with the dispersion additive is always lower than the amount of sodium ions required for the sodium activation of calcium bentonite.

[0028] In step ii) of the method of the present invention, non-sodium bentonite impurities are removed from the aqueous slurry. Non-sodium bentonite impurities are mainly present in the aqueous slurry in the form of solid particles or incompletely swollen material, which can be separated from the aqueous phase by physical separation processes commonly known to those skilled in the art. Examples of suitable separation processes include sedimentation, decantation, suspension, and centrifugation. If desired, such processes can be combined or carried out sequentially.

[0029] The removed non-sodium bentonite impurities consist mostly of crystalline impurities, as well as low-swelling amorphous minerals and low-swelling clays, such as calcium bentonite. The better-swelling sodium bentonite is mainly not removed and remains in the slurry.

[0030] As described above, the non-sodium bentonite impurities removed typically include at least one of the following: feldspar, calcite, mica, quartz, cristobalite, dolomite, and calcium bentonite.

[0031] After the separation process, the aqueous slurry is recovered and the water is removed from the aqueous slurry by spray drying in a spray dryer to prepare solid treated sodium bentonite clay.

[0032] If necessary, shear force may be applied to the aqueous slurry before removing water by spray drying. Any known technique for applying shear force can be used in this optional processing step. Examples of suitable methods for applying shear force include processing in a high-speed dissolver or passing the slurry through holes under pressure.

[0033] In step iii) of the method of the present invention, water is removed from the aqueous slurry by spray drying in a spray drying apparatus to prepare a solid treated sodium bentonite clay.

[0034] Spray drying is an essential feature of the method of the present invention, and it has been found that drying methods other than spray drying result in solid treated sodium bentonite clay with inferior properties.

[0035] A spray dryer takes in a liquid stream, separates the solute or suspension as a solid, and separates the solvent into water vapor. The solid is usually collected in a drum or cyclone. The liquid input stream is sprayed through a nozzle into a high-temperature vapor stream and vaporized. As moisture rapidly leaves the droplets, solid matter is formed. Nozzles are usually used to make the droplets as small as possible to maximize heat transfer and the rate of water evaporation. Droplet sizes generally range from 20 to 180 μm, depending on the nozzle. There are two main types of nozzles: high-pressure single-fluid nozzles (50 to 300 bar) and two-fluid nozzles, where one fluid is the liquid for drying and the second is compressed gas (generally air at 1 to 7 bar). Instead of spraying liquid using nozzles, rotary atomizers can also be used. Rotary atomizers operate on the principle of centrifugal energy, which is used to generate the high relative velocity between the fluid and air that is essential for atomization. A rotary sprayer is equipped with a rotary surface. This surface can be in the form of a flat or vaned disc, a cup, or a slotted wheel. The liquid first flows radially outward within the disc and is then discharged from the outer edge of the disc at a relatively high speed. Atomization depends on the liquid flow rate and the rotation speed of the disc.

[0036] Spray drying equipment can dry articles very quickly compared to other drying methods. They also convert solutions (or slurries) into dry powder in a single step, which simplifies the process.

[0037] The inlet air temperature of the spray drying apparatus is generally in the range of 150 to 600°C, preferably in the range of 200 to 450°C.

[0038] The spray drying process removes water, providing solid particles of treated sodium bentonite clay. Generally, treated sodium bentonite clay still contains a residual amount of water, for example, 20.0% by weight or less, calculated by the total weight of the treated sodium bentonite clay. Preferably, the water content is in the range of 0.1 to 18.0% by weight, more preferably 0.5 to 15.0% by weight, calculated by the total weight of the treated sodium bentonite clay.

[0039] The present invention also relates to treated sodium bentonite clay that can be obtained or is obtained by the method of the present invention.

[0040] Processed sodium bentonite clay exists in the form of particles. The particles typically have a shape where all three dimensions are of roughly equal size, as opposed to the needle-like or plate-like shape, in which case one or two dimensions are significantly larger than the others. Generally, the length, width, and height of the particles differ from each other by less than 35%.

[0041] Preferably, the particles have a d50 number average particle size in the range of 5 to 60 μm, preferably 8 to 40 μm, as determined by laser diffraction.

[0042] The particles typically have a morel-like structure. This means that the particles have an irregular surface characterized by a network of ridges.

[0043] The treated sodium bentonite clay obtained by the method of the present invention preferably has a crystalline impurity content of less than 10% by weight, more preferably less than 5% by weight, and more preferably less than 3% by weight.

[0044] The treated sodium bentonite clay has an exchangeable sodium ion content of 100 mmol / 100g or less and an exchangeable calcium ion content of 18 mmol / 100g or less, calculated based on the dry weight of the clay.

[0045] The amount of exchangeable sodium ions is preferably in the range of 50 to 100 mmol / 100g, and more preferably in the range of 50 to 90 mmol / 100g, relative to the treated sodium bentonite.

[0046] The amount of exchangeable calcium ions is preferably in the range of 2 to 18 mmol / 100g, and more preferably in the range of 2 to 15 mmol / 100g, relative to the treated sodium bentonite.

[0047] The amounts of exchangeable sodium and calcium ions are appropriately determined by a method that includes refluxing the treated clay material in water with an excess of ammonium chloride for 1 hour, followed by filtration and analysis of the filtrate by inductively coupled plasma atomic emission spectroscopy (ICP-OES). An excess of ammonium chloride means that more ammonium chloride is used than the exchangeable ions present in the treated clay material. Preferably, 120 mg of treated clay material is refluxed with 8 ml of an aqueous solution of ammonium chloride at a concentration of 2 mol / l.

[0048] The treated sodium bentonite clay obtainable by the method of the present invention is highly suitable for controlling the rheology of aqueous compositions. In particular, the treated sodium bentonite clay can be easily dispersed in a wide variety of aqueous compositions, producing desirable rheological effects. Therefore, the present invention also relates to the use of treated sodium bentonite clay for controlling the rheology of aqueous compositions.

[0049] The present invention further relates to a method for controlling the rheology of an aqueous composition, the method comprising adding treated sodium bentonite clay, which can be obtained by the method of the present invention, to the aqueous composition.

[0050] In the above use or method, the treated sodium bentonite clay is appropriately added to the aqueous composition in an amount ranging from 0.1 to 7.0% by weight, preferably 0.1 to 5.0% by weight, calculated based on the total weight of the aqueous composition.

[0051] When treated sodium bentonite clay is added to an aqueous composition, the viscosity of the aqueous composition generally increases. Generally, the greater the amount of treated sodium bentonite clay, the higher the viscosity. In some embodiments, the addition of treated sodium bentonite clay induces thixotropic behavior in the aqueous composition.

[0052] The aqueous composition may be any liquid aqueous composition whose viscosity should be increased or which should be made thixotropic. The aqueous composition is a composition in which the primary or sole liquid diluent used is water. Preferably, the aqueous composition contains less than 35% by weight, less than 25% by weight, less than 20% by weight, or even less than 10% by weight of (volatile) organic solvents, based on the total weight of water and organic solvents in the liquid formulation. In some embodiments, the aqueous composition does not contain organic solvents. The aqueous composition may contain water-soluble organic or inorganic compounds, such as ionic compounds such as salts.

[0053] Examples of suitable aqueous liquid compositions include coating compositions, (pre)polymer compositions, pigment concentrates, ceramic products, sealants, cosmetic preparations, adhesives, casting compounds, lubricants, inks, cleaning agents, liquids for use in gas or oil production, putties, metalworking fluids, sprayable liquids, such as deposition aids for crop protection, wax emulsions, liquids for use in energy storage media such as batteries, liquids for use in electrical or electronic components, casting or potting compositions, and building materials.

[0054] Aqueous compositions, which are coating compositions or inks, can be used in a variety of application areas, including automotive coatings, architectural coatings, protective coatings (such as marine or bridge coatings), can and coil coatings, wood and furniture coatings, industrial coatings, plastic coatings, wire enamels, food and seed coatings, leather coatings (for natural and artificial leather), and color resists (such as those used for LC display devices). Typical coating materials include paste-like materials with high solid content and low liquid content, such as pigment pastes or effect pigment pastes (using pigments based on aluminum, silver, brass, zinc, copper, bronze such as copper, and iron oxide-aluminum); other examples of effect pigments are interference pigments and pearlescent pigments, such as metal oxide-mica pigments, bismuth chloride oxide, or basic lead carbonate.

[0055] Cosmetic compositions can be any type of aqueous liquid composition used for personal care and healthcare purposes. Examples include lotions, creams, pastes such as toothpaste, foams such as shaving foam, gels such as shaving gels and shower gels, pharmaceutical compounds in gel-like delivery forms, hair shampoos, liquid soaps, nail polishes, lipsticks, and hair coloring lotions.

[0056] A preferred wax emulsion is an aqueous dispersion of wax particles formed from a wax that is solid at room temperature.

[0057] Sprays (preferably used as deposit aids) may comprise the treated sodium bentonite of the present invention to achieve drift reduction. They may contain, for example, fertilizers or herbicides, fungicides, and other pesticides.

[0058] Compounds used for construction purposes may be materials that are liquid or paste-like during handling and processing. These aqueous materials are used in the construction industry and solidify after curing time, and include, for example, concrete, cement, mortar / plaster, tile adhesives, and hydraulic binders such as gypsum.

[0059] Metalworking fluids are aqueous compositions used for processing metals and metal parts. Examples include cutting fluids, drilling fluids (used in metal drilling), mold release agents (mainly aqueous emulsions, e.g., used in aluminum die casting and casting applications), casting cleaning fluids, casting coatings, and liquids used for metal surface treatment (surface finishing, surface cleaning, and plating, etc.).

[0060] Lubricants are aqueous compounds used for lubrication purposes, i.e., to reduce wear and friction loss, or to improve cooling, power transmission, vibration damping, sealing effect, and corrosion protection. Liquid formulations used in the production of gases and oils are aqueous formulations used to develop and utilize deposits. Aqueous drilling fluids or "drilling mud" are preferred examples. An example of application is hydraulic fracturing.

[0061] Cleaning agents can be used to clean various types of objects. They help remove contaminants, residual dirt, and attached debris. Cleaning agents also include detergents (especially those for cleaning textiles, their precursors, and leather), cleaning agents and abrasives, laundry formulations, fabric softeners, and personal care products.

[0062] Preferred aqueous compositions include aqueous coating compositions, aqueous compositions containing a hydraulic binder, aqueous cleaning compositions, and aqueous personal care compositions.

[0063] The aqueous compositions described above may also contain other components and additives commonly used in aqueous compositions, such as organic cosolvents, crosslinking agents, defoaming agents, dispersing aids, and UV stabilizers. The treated sodium bentonite according to the present invention provides excellent thickening properties and can be used in combination with other rheological control agents if desired.

[0064] Other examples of rheology control agents include polysaccharides (cellulose derivatives, guar, xanthan gum, etc.), urea compounds, (poly)amides, polyacrylates (alkali-soluble or swelling emulsions, etc.), or associative thickeners (polyurethane thickeners, aminoplast-based thickeners, hydrophobic modified alkali-soluble emulsion-type thickeners, etc.).

[0065] The treated sodium bentonite of the present invention can be used as an adsorbent in certain compositions, for example, to absorb undesirable impurities. [Examples]

[0066] Example 1: The naturally occurring sodium bentonite raw material clay is commercially available as "natural sodium bentonite powder," and does not contain soda ash, has a moisture content of 8% by weight, and a montmorillonite content exceeding 65% by weight. The analyzed swelling volume in deionized water was 19 ml / 2 g. Crystalline impurities were analyzed by powder X-ray diffraction. The amount of crystalline impurities was 12% by weight.

[0067] 250 kg of natural sodium bentonite powder was slurryed in 4800 kg of tap water using a propeller mixer and a serrated dissolving disc for 30 minutes, with vigorous stirring. This slurry was then purified by removing crystalline impurities and non-swelling mineral components by passing it through a Flottweg decanter centrifuge with a feed centrifugal force of approximately 3700 G. This decanter centrifugation process removed approximately one-third of the initial clay content. The removed material consisted of most crystalline impurities, low-swelling amorphous minerals, and low-swelling clay, such as calcium bentonite. Better-swelling sodium bentonite remained in the slurry, largely unremoved. The overall crystalline impurities were reduced to approximately 2% by this treatment.

[0068] To ensure complete dispersion, the resulting slurry was further homogenized in a Manton-Gaulin homogenizer at a pressure of 150 bar.

[0069] The obtained slurry was dried in an Anhydro spray dryer with an inlet dry air temperature of 380°C. The spray feed rate was adjusted to achieve a moisture content of 6% by weight in the obtained dried powder. The outlet temperature of the spray dryer was in the range of 70-100°C. The obtained powder had a number-average d50 particle size of 15 μm. The treated sodium bentonite had an exchangeable sodium ion content of 61 mmol / 100g and an exchangeable calcium ion content of 11 mmol / 100g, calculated based on the dry weight of the material.

[0070] Example 2: 400 kg of natural sodium bentonite powder was slurryed in a mixture of 3600 kg of tap water and 12 kg of BYK-155 / 35 polyacrylate dispersant. For further processing, the same procedure as in Example 1 was followed. The processed sodium bentonite had an exchangeable sodium ion content of 83 mmol / 100g and an exchangeable calcium ion content of 12 mmol / 100g, calculated based on the dry weight of the material.

[0071] Example 3: 400 kg of natural sodium bentonite powder was slurryed in a mixture of 3600 kg of tap water and 4 kg of Na-pyrophosphate dispersant. For further processing, the same procedure as in Example 1 was followed.

[0072] Comparative Example 1: Natural sodium bentonite powder supplied from a mineral mine was ground without purification to the same fineness and moisture content as in Example 1. The treated sodium bentonite had an exchangeable sodium ion content of 72 mmol / 100g and an exchangeable calcium ion content of 46 mmol / 100g, calculated based on the dry weight of the material.

[0073] Comparative Example 2: The purified and homogenized slurry from Example 1 (before spray drying) was lab-dried to less than 12% moisture content in a lab-drying oven at 70°C, and then pulverized to the same fineness as in Example 1 in a lab mill.

[0074] Comparative Example 3: The purified and homogenized slurry from Example 1 (before spray drying) was dried in a drum dryer to a moisture content of less than 12%, and then pulverized in a lab mill to the same fineness as in Example 1.

[0075] Comparative Example 4: Artificial sodium bentonite, produced by alkali-soda activation of Optigel CK:calcium bentonite, commercially available from BYK-Chemie GmbH, was treated in the same manner as in Example 1. The treated sodium bentonite had an exchangeable sodium ion content of 135 mmol / 100g and an exchangeable calcium ion content of 20 mmol / 100g, calculated based on the dry weight of the material.

[0076] Test results Underwater viscosity A suspension was prepared by adding clay (3.5% or 5% based on dry clay weight) to deionized water at room temperature in a 70 mm diameter glass beaker to a total of 200 g of water and clay. The addition was carried out slowly with stirring at a mixing speed of 930 rpm using a Pendraulik 4 cm diameter toothed cowl disc attached to a Pendraulik LD 50 laboratory stirrer. Once completely added, the dissolution rate was increased to 2800 rpm over a dispersion time of 10 minutes. After dispersion, the viscosity was measured at 10 rpm using a Brookfield DV II. The value was read after a measurement time of 2 minutes. The glass beaker was then covered and stored at room temperature for the indicated storage time (e.g., 1 hour, 1 day, 1 week), and the measurement was repeated.

[0077] [Table 1]

[0078] [Table 2]

[0079] The results in Table 1 demonstrate that the thickening effect of the treated sodium bentonite according to the present invention occurs much faster than the thickening effect of comparative sodium bentonite.

[0080] Alpina Weiss Paint 100g of Alpina weiss Innenfarbe "Das Original" (flat emulsion paint, DAW SE), 0.2g of BYK-035, and 24.43g of the 3.5% aqueous formulation (Pregel) listed in Table 1 or 17.0g of the 5% aqueous formulation (Pregel) listed in Table 1 + 6.8g of deionized water were added to Delbrouck beaker No. 211. This was mixed in a Pendraulik lab stirrer LD 50 at 2800 rpm for 5 minutes using a 4cm diameter toothed cowl disc. The mixture was then covered and stored at room temperature for 1 day. Viscosity was measured at 10 rpm in a Brookfield DV II. The value was read after a 2-minute measurement time.

[0081] [Table 3]

[0082] [Table 4]

[0083] From Table 2, it can be seen that the treated sodium bentonite according to the present invention provides far better viscosity in aqueous paints than sodium activated Ca bentonite treated in the same manner.

[0084] Determination of sagging resistance of white paint White paint was prepared from the components listed in Table 3 below.

[0085] [Table 5]

[0086] Measurement of sag resistance Slack resistance was measured according to ASTM D440-84. This standard test method utilizes a drawdown blade with a series of notches having progressively larger clearances. The coating was applied to the test chart using a multi-notch applicator. The chart was immediately suspended vertically, and the drawdown strip was positioned horizontally. Slack resistance is measured from the drawdown after the film has completely dried. The results indicate the maximum layer thickness that can be applied without paint slack. The results are summarized in Table 4 below:

[0087] [Table 6]

[0088] From Table 4, it can be concluded that the treated sodium bentonite clay according to the present invention provides better sagging resistance in water-based paints than comparative bentonite clay. The inventions relating to this disclosure include the following aspects: <Aspect 1> A method for processing natural clay materials containing sodium bentonite, (i) Prepare an aqueous slurry of natural clay material containing sodium bentonite. (ii) Removing non-sodium bentonite impurities from the aqueous slurry, and (iii) Remove water from the aqueous slurry by spray drying in a spray drying apparatus to prepare a solid treated sodium bentonite clay. Includes, The treated solid bentonite clay has, calculated based on the dry weight of the clay, an exchangeable sodium ion content of 100 mmol / 100g or less and an exchangeable calcium ion content of 18 mmol / 100g or less. method. <Aspect 2> The method according to embodiment 1, wherein the natural clay material containing sodium bentonite has a swelling volume of 12 ml or more, determined by adding 2.0 g of the natural clay material containing sodium bentonite to 100 ml of deionized water. <Aspect 3> The method according to embodiment 1 or 2, wherein the non-sodium bentonite impurity includes at least one of feldspar, calcite, mica, quartz, cristobalite, dolomite, and calcium bentonite. <Aspect 4> The method according to any one of embodiments 1 to 3, wherein the natural clay material containing sodium bentonite has a content of non-sodium bentonite impurities in the range of 10 to 90% by weight, preferably 10 to 60% by weight. <Aspect 5> The method according to any one of embodiments 1 to 4, wherein in step (i), a shear force is applied to the aqueous slurry. <Aspect 6> The method according to any one of embodiments 1 to 5, wherein a dispersion additive is present during the preparation of the aqueous slurry of a natural clay material containing sodium bentonite. <Aspect 7> The method according to embodiment 6, wherein the dispersion additive comprises at least one of an organic polymer and an inorganic phosphate. <Aspect 8> The method according to any one of embodiments 1 to 7, wherein non-sodium bentonite impurities are removed from the aqueous slurry by sedimentation or centrifugation. <Pattern 9> The method according to any one of embodiments 1 to 8, wherein the inlet air temperature of the spray drying apparatus is in the range of 150 to 600°C. <Aspect 10> The method according to any one of embodiments 1 to 9, wherein the residual water content in the solid treated sodium bentonite clay is 20% by weight or less, calculated based on the total weight of the solid treated sodium bentonite clay. <Aspect 11> A treated sodium bentonite clay that can be obtained by the method described in any one of embodiments 1 to 10. <Aspect 12> The treated sodium bentonite clay according to embodiment 11, wherein the treated sodium bentonite clay exists in the form of particles having a morel-like structure. <Aspect 13> The treated sodium bentonite clay according to embodiment 11 or 12, wherein the particles have a d50 number average particle size in the range of 5 to 60 μm as measured by laser diffraction. <Aspect 14> Use of treated sodium bentonite clay according to any one of embodiments 11 to 13 for controlling the rheology of an aqueous composition. <Aspect 15> The use according to embodiment 14, wherein the aqueous composition is selected from an aqueous coating composition, an aqueous composition containing a hydraulic binder, an aqueous cleaning composition, and an aqueous personal care composition. <Aspect 16> The use according to embodiment 14 or 15, wherein the treated sodium bentonite clay is added to the aqueous composition in an amount ranging from 0.1 to 7.0% by weight, preferably 0.1 to 5.0% by weight, calculated based on the total weight of the aqueous composition. <Aspect 17> A method for controlling the rheology of an aqueous composition, comprising adding the treated sodium bentonite clay described in any one of embodiments 11 to 13 to the aqueous composition.

Claims

1. A method for processing natural clay materials containing sodium bentonite, (i) Prepare an aqueous slurry of natural clay material containing sodium bentonite. (ii) Removing non-sodium bentonite impurities from the aqueous slurry, and (iii) To remove water from the aqueous slurry by spray drying in a spray drying apparatus to prepare a solid treated sodium bentonite clay. Includes, The solid treated bentonite clay has, calculated based on the dry weight of the clay, an exchangeable sodium ion content of 100 mmol / 100 g or less and an exchangeable calcium ion content of 18 mmol / 100 g or less. The treated sodium bentonite clay exists in the form of particles having a morel-like structure. method.

2. The method according to claim 1, wherein the particles having a morel-like structure have a d50 number average particle size in the range of 5 to 60 μm as measured by laser diffraction.

3. The method according to claim 1 or 2, wherein the natural clay material containing sodium bentonite has a swelling volume of 12 ml or more, determined by adding 2.0 g of the natural clay material containing sodium bentonite to 100 ml of deionized water.

4. The method according to claim 1 or 2, wherein the non-sodium bentonite impurity comprises at least one of feldspar, calcite, mica, quartz, cristobalite, dolomite, and calcium bentonite.

5. The method according to claim 1 or 2, wherein the natural clay material containing sodium bentonite has a content of non-sodium bentonite impurities in the range of 10 to 90% by weight.

6. The method according to claim 1 or 2, wherein in step (i), a shear force is applied to the aqueous slurry.

7. The method according to claim 1 or 2, wherein a dispersion additive is present during the preparation of the aqueous slurry of a natural clay material containing sodium bentonite.

8. The method according to claim 7, wherein the dispersion additive comprises at least one of an organic polymer and an inorganic phosphate.

9. The method according to claim 1 or 2, wherein the removal of non-sodium bentonite impurities from the aqueous slurry is performed by sedimentation or centrifugation.

10. The method according to claim 1 or 2, wherein the inlet air temperature of the spray drying apparatus is in the range of 150 to 600°C.

11. The method according to claim 1 or 2, wherein the residual water content in the solid treated sodium bentonite clay is 20% by weight or less, calculated based on the total weight of the solid treated sodium bentonite clay.

12. Use of treated sodium bentonite clay obtained by the method of Claim 1 or 2 for controlling the rheology of an aqueous composition.

13. The use according to claim 12, wherein the aqueous composition is selected from an aqueous coating composition, an aqueous composition containing a hydraulic binder, an aqueous cleaning composition, and an aqueous personal care composition.

14. The use according to claim 12, wherein the treated sodium bentonite clay is added to the aqueous composition in an amount ranging from 0.1 to 7.0% by weight, calculated based on the total weight of the aqueous composition.

15. A method for controlling the rheology of an aqueous composition, comprising adding treated sodium bentonite clay obtained by the method of claim 1 or 2 to the aqueous composition.

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