Title of Invention	A METHOD OF PRODUCING AN ACTIVATED CLAY
Abstract	The present invention relates to a method of producing an activated clay exhibiting enhanced decoloring activity, color-forming activity and catalytic activity, comprising treating dioctahedral smectite clay mineral as herein described with an acid to obtain a three-layer structure of said dioctahedral smectite, said clay having a crystallite size which is a half-value width of an X-ray diffraction peak of an index of a plane of said smectite and is within the range of 10 to 30 nm, the crystallite sectional area of said activated clay being defmed by the following formula (1), VI = Rl x R2 ---(1) which is from 60 to 150 nm<sup>2</sup> and wherein Rl denotes the above-mentioned crystallite size (nm), and R2 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol.

Title of Invention

A METHOD OF PRODUCING AN ACTIVATED CLAY

Abstract

The present invention relates to a method of producing an activated clay exhibiting enhanced decoloring activity, color-forming activity and catalytic activity, comprising treating dioctahedral smectite clay mineral as herein described with an acid to obtain a three-layer structure of said dioctahedral smectite, said clay having a crystallite size which is a half-value width of an X-ray diffraction peak of an index of a plane of said smectite and is within the range of 10 to 30 nm, the crystallite sectional area of said activated clay being defmed by the following formula (1), VI = Rl x R2 ---(1) which is from 60 to 150 nm<sup>2</sup> and wherein Rl denotes the above-mentioned crystallite size (nm), and R2 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol.

Full Text	METHOD OF PRODUCING ACTIVATED CLAY AND ITS USE BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates to activated clay and its use. More specifically, the invention relates to activated clay which exhibits excellent decoloring performance, color-forming performance and catalytic performance owing to the three-layer structure of the dioctahedral smectite that remains maintaining a predetermined crystallite size, and to the use thereof. (Prior Art) It has long been known that the dioctahedral smectite clay minerals exhibit adsorptive performance and decoloring performance- In Britain, the dioctahedral smectite clay minerals have also been called fuller's earth or bleaching earth. It has also been known since the old times to produce so-called activated clay having increased specific surface areas by treating the dioctahedral smectite clay minerals with an acid. For example, Japanese Patent Publication No, 335/1948 teaches a method of producing activated clay by kneading acidic clay or a similar clay in the water into a size of 0.5 to 30 nm so will not to collapse, introducing the clay in an acid-resistant container, and heating and circulating an inorganic acid to impart activity thereto. Furthermore, Japanese Patent Publication No, 2960/1957 discloses a method of producing granular activated clay by adding sulfuric acid to acidic clay to obtain it in the form of an agent, followed by drying until it can he pulverized, and, then, pulverizing and sieving the product to obtain those having a predetermined particle size, and activating them by a predetermined method. Japanese Patent Publication No. 11209/1970 discloses a method of treating an alumina silicate clay with an acid wherein, in producing activated clay or fine powdery silica by treating an alumina silicate clay containing acid- soluble basic components with an acid, 1.0 to 1.5 equivalents of acid or an aqueous solution thereof relative to the basic metal components to be removed from the alumina silicate clay is added in an amount not larger than the amount of an acid aqueous solution with which the clay particles in the dispersion of the clay formed by the addition of the acid starts precipitating, so that the basic metal components in the clay react with the acid in the dispersion, and, then, the reaction product is separated from the dispersion solution, and the reaction product particles are treated in an aqueous medium at a pH of lower than 1, thereby to extract the basic metal components from the product. According to the conventional method of producing activated clay by the treatment with an acid, the conditions of treatment with acid are adjusted, such as acid concentration, temperature, treating time, etc., so that the acid-soluble basic components are at least partly eluted out from the clay minerals, in order to enhance the decoloring performance and to increase the specific surface areas. Use of the activated clay is encountering severe conditions in recent years. That is, in refining oils or fats, there is inevitably by-produced waste clay that is difficult to discard. It is therefore required that a high and sustained decoloring performance is obtained by the use in an amount which is as small as possible and that the oil component contained in the waste clay is low, i.e,, oil retention is low at the time of separating oils or fats from the waste clay by filtration. When used as a color-forming agent for pressure- sensitive papers, furthermore, it is required that a color is formed maintaining a sufficiently large density with a small amount of application, color of the image fades little, viscosity is low despite of a high solid component concentration from the standpoint of production, and that it can be excellently applied. So far, however, no crystallographical study has been conducted in regard to selecting clay minerals for use as starting materials or evaluating the obtained Activated clay, but empirical judgements have simply been rendered without quite meeting the above-mentioned demands for obtaining activated clay of high quality. SUMMARY OF THE INVENTION The present inventors have discovered the fact that the sectional area of a crystallite related to an index of a particular plane as observed by an X-ray diffraction method plays an important role for producing activated clay of a high quality and, further, determines the starting material for obtaining the activated clay. That is, the object of the present invention is to provide activated clay of a high quality and of a high function, exhibiting high and sustained decoloring ability with the use in a small amount when it is used for refining oils or fats, exhibiting a low oil retention, giving a sufficient degree of color-forming density with the application in a small amount when it is used as a color-forming agent for pressure-sensitive papers, permitting the color of the image to fade little, I exhibiting a low viscosity despite of its high solid component concentration, and capable of being favorably applied, as well as to provide a method of producing the same. According to the present invention, there is provided a method of producing an activated clay obtained by treating dioctahedral smectite clay minerals with an acid. wherein a crystallite size (Rl) of the activated clay found from a half-value width of an X-ray diffraction peak of an index of a plane (06) of the smectite is within a range of from 10 to 30 nm, and a crystallite sectional area (VI) of the activated clay defined by the following formula (1), VI == Rl X R2 (1) wherein Rl denotes the above-mentioned crystallite size (nm),*and R2 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2, preferably, from 60 to 145 nm2 and, most preferably, from 70 to 140 nm2. According to the present invention, it is desired that the activated clay (1) has a specific surface area of from 250 to 350 m2/g as measured by the BET method, and (2) has an X-ray diffraction peak over a spacing of from 17 to 19 angstroms as measured in a state of being treated with an ethylene glycol. According to the present invention, furthermore, there is provided a decoloring agent for oils or fats, and a color-forming agent for pressure-sensitive papers, comprising the activated clay. According to the present invention, there is further provided a method of producing activated clay by treating, with an acid, dioctahedral smectite clay minerals having a crystallite size (RIO) found from a half-value width of an X-ray diffraction peak of an index of a plane (06) of the smectite of from 15 to 30 nm and, particularly, from 20 to 28 nm, and a crystallite sectional area (VO) defined by the following formula (2), ; VO = R10 X R20 (2) wherein R10 denotes the above-mentioned crystallite size (nm), and R20 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, of from 100 to 230 nm2, preferably, from 120 to 230 nm2 and, most preferably, from 120 to 225 nm2, so that the crystallite size (Rl) found from the half-value width of the X-ray diffraction peak of the index of plane (06) of the smectite is from 10 to 3 0 nm and that the crystallite sectional area (VI) defined by the following formula (1), VI = Rl X R2 (1) wherein Rl denotes the above-mentioned crystallite size (nm), and R2 denotes a crystallite size (nm) found from a half-value width of the X-ray diffraction peak of the index of plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2, preferably, from 60 to 145 nm2 and, most preferably, from 70 to 140 nm2. BRIEF DESCRIPTION OF THE DRAWINGS Fig, 1 is a diagram showing an X-ray diffraction image of an activated clay prepared in Example 2; Fig. 2 is a diagram showing an X-ray diffraction image of a starting clay used for producing the activated clay of Example 2; Fig. 3 is a diagram showing an X-ray diffraction image of an activated clay prepared in Comparative Example 2; Fig. 4 is a diagram showing an X-ray diffraction image of a starting clay used for producing the activated clay of Comparative Example 2; Fig. 5 is a diagram showing an X-ray diffraction t image of the activated clay prepared in Example 2 as measured in a state of being treated with an ethylene glycol; and Fig. 6 is a sectional view of a decoloring tester. DETAILED DESCRIPTION OF THE INVENTION In the X-ray diffraction of crystals, it has been known that an intensity peak appears in the interference when the following Bragg's formula (3), wherein Lhkl is a size of the crystal in a direction perpendicular to the plane (hkl) , K is a constant of about 0.9, H is a half-value width (radian) of the interference peak, and λ and θ are the same as those mentioned in the above formula (3), exists between the sharpness of the interference peak and the size of the crystals. The reflection peaks on the bottom surface (001) of the clay minerals are symmetrical in the right-and-left direction, but asymmetrical peaks are exhibited in many cases by the reflection (hkl). This is because, the layers are overlapped in parallel but their positions are irregular relative to each other. Such asymmetrical peaks are called two-dimensional reflection. The index (1) does not assume a particular value and is, hence, expressed by (hk). The index of a plane (06) referred to in this specification just means this fact. Fig. 1 in the accompanying drawings shows an X-ray diffraction image of the activated clay of the present invention. Fig, 2 shows an X-ray diffraction image of a starting clay used for the production of the activated clay of Fig. 1, and Figs. 3 and 4 show, respectively, an X-ray diffraction image of the activated clay and an X-ray diffraction image of a starting clay therefor outside the scope of the present invention (see Example 2 and Comparative Example 2 appearing later). : The dioctahedral smectite is constituted by a laminated-layer structure having, as a basic layer unit, a three-layer structure in which an A10g octahedral layer is sandwiched by two SiO4 tetrahedral layers, Al in the AlO6 octahedral layer is isomorphously substituted by Fe and Mg, and Si in the SiO4 tetrahedral layer is isomorphously substituted by Al, the basic layer units being laminated in the direction of a c-axis, and metal cations existing among the layers to compensate for the lack of electric charge caused by the isomorphous substitution. When the clay minerals of the laminated-layer structure are treated with an acid, metal cations existing among the layers of the laminated-layer structure elute out, and the laminated-layer structure of the basic three-layer structure is partly cut apart. Even in the basic three-layer structure, portions of the intermediate AlO6 octahedral layer elute out from the edges of the basic three-layer structure. The activated clay of the present invention exhibits vivid diffraction peaks in the index of a plane (06) indicating that the basic three-layer structure is remaining in the activated clay. Furthermore, the crystallite size (Rl) found from a half-value of the diffraction peak of the index of a plane (06) represents the size of the three-layer structure in the direction of the plane, On the other hand, the crystallite size (R2) found from a half-value width of the diffraction peak of the index of a plane (001) represents the degree of lamination of the layers of the basic three-layer structure. It can therefore be said that the crystallite sectional area (VI) expressed by the above-mentioned formula (1) is expressing, by the sectional area, the three-dimensional size of the laminar crystal structure in the activated clay. In the activated clay of the present invention, it is important that the crystallite sectional area (VI) lies within the above-mentioned range from the standpoint of obtaining the activated clay of a high quality. That is, as the crystallite sectional area (VI) exceeds the range specified by the present invention, the activated clay ; used for refining oils or fats exhibits performance for adsorbing pigments, etc. and sustenance thereof that are decreased compared to those having the crystallite sectional area (VI) lying within the range of the present invention. When used as a color-forming agent for pressure-sensitive papers, the color-forming performance drops when the crystallite sectional area (VI) exceeds the range specified by the present invention. On the other hand, when the crystallite sectional area (VI) becomes smaller than the range specified by the present invention, the clay used for refining oils or fats exhibits decreased performance for adsorbing colors, etc., and exhibits an increased oil retention, which is not desirable. When used as the color-forming agent for pressure-sensitive papers, furthermore, the color-forming performance decreases and the color of the image tends to fade out to a conspicuous degree. When applied as a slurry, furthermore, the clay exhibits an increased viscosity, which is not desirable, either. In the activated clay, it is important that the crystallite sectional area (VI) must be maintained to be not smaller than a lower-limit value specified by the present invention. That is, in the conventional activated clay, the crystallite sectional area (VI) is smaller than the lower-limit value of the present invention accounting for a large oil retention or a high viscosity. According to the present invention in which the crystallite sectional area (VI) is maintained to be not smaller than a predetermined value, it is made possible to enhance the coloring matter-adsorbing performance and color-forming performance while maintaining the oil retention and the viscosity at low values. To produce the activated clay of the present invention, the conditions for treatment with an acid plays important roles as a matter of course. Basically, however, it is important to select dioctahedral smectite clay minerals that meet a predetermined standard. The crystallite sectional area (VI) of the activated clay varies much depending upon the conditions for treatment with an acid. When the crystallite sectional area (VO) of the starting clay minerals exceeds the range specified by the present invention, the obtained activated clay tends to have the crystallite sectional area (VI) that is larger than the range specified by the present invention. When the crystallite sectional area (VO) of the starting clay minerals is smaller than the range specified by the present invention, the obtained activated clay tends to have the crystallite sectional area (VI) that is smaller than the range specified by the present invention. In either case, it becomes difficult to accomplish the object of the present invention, [Starting clay minerals] The starting dioctahedral smectite clay used in the present invention has the crystallite size (RIO) and the crystallite sectional area (VO) that lie within the ranges specified by the present invention. Minute structure of the starting clay differs depending upon the components of the clay, place where it is produced and site where it is buried (working face) even in the same place of production. Therefore, those satisfying the above-mentioned requirements should be selected by conducting the X-ray diffraction testing. It is considered that the dioctahedral smectite is formed as the volcanic ash or lava is modified being affected by the seawater. Described below is a chemical composition of representative starting clay minerals, SiO2 64.4% by weight, Al2O3 16.3% by weight Fe203 3,3% by weight MgO 6.5% by weight CaO 0.9% by weight K2O 0.5% by weight Na2O 1,4% by weight Ignition loss 6.7% by weight As required, the thus selected dioctahedral smectite clay minerals are subjected to the refining operation such as stone-sand separation, ore dressing by buoyancy, magnetic ore dressing, hydraulic elutriation or air elutriation, and are then subjected to the treatment with an acid. [Treatment with an acid] The treatment with an acid can be effected by either the above-mentioned granular activation method or the sludge activation method. Described below is the case of the granular activation to which only, however, the present invention is in no way limited, [ In the granular activation, the starting clay minerals must be prepared in the form of particles suited for being treated with an acid prior to bringing them into contact with the acid. The ore that is dug usually contains the water in an amount of about 35 to about 40% by weight, and this water serves as a medium for granulating the clay. By using a rag crasher as a coarse milling machine, the core is coarsely milled and, then, the clay is kneaded. The kneading is effected by using a grooved roll, a plain roll or a combination thereof. Then, the kneaded clay is granulated into a predetermined size. It is desired that the particles have a diameter of, usually, from 3 to 10 mm and, particularly, from 5 to 7 mm, • A suitable granulating machine will be a pair of perforated rolls. The clay is supplied to a nipping position of the rolls; i,e., the clay is passed from the outside to the inside of the rolls so as to be granulated into a predetermined size. The conditions for treatment with an acid are so determined that the obtained acid-treated product will have the above-mentioned crystallite size (Rl) and the crystallite sectional area (VI), The treatment with an acid is carried out by filling a treatment vessel with the granular clay and circulating an aqueous solution containing an acid. The aqueous solution contains mineral acids, such as sulfuric acid, hydrochloric acid, or the like acid and, particularly, contains sulfuric acid, at a concentration of about 20 to about 35% by weight. The treating temperature is selected from a range of from 80 to 95°C and the treating time is selected from a range of from 3 to 20 hours to satisfy the above-mentioned requirements. The mother liquor after the treatment with the acid contains basic components such as alumina, magnesium, iron, etc. Therefore, the mother liquor can be used as an inorganic liquid coagulating agent or as a starting material of gypsum. After the mother liquor is recovered, the acid-treated product contained in the treatment vessel is washed with water by circulating the washing water. After washing with water, the acid-treated product is dried, milled and is classified to obtain a product of activated clay. In the present invention, it is desired that the water-soluble salts contained in the acid-treated product are removed to such an extent that the amount of the residue thereof is not larger than 3% by weight and, particularly, not larger than 1% by weight in terms of acid radicals of the acid that is used. This is because, the water-soluble salts contained in the acid-treated product adversely affect the quality of the product despite their amounts are very small. As required, the obtained acid-treated product is reformed by drying or firing. Upon drying or firing, it is considered that the concentration of silanol groups decreases on the surface of the activated clay, and the clay acquires a structure which difficultly swells in the water. It is desired that the drying or firing is conducted usually at a temperature of from 80 to 500°C and, particularly, from 100 to 300°C for a period of from 0.5 to 10 hours and, particularly, from 0,7 to 5 hours. [Activated clay and its use] The feature of the activated clay of the present invention resides in the possession of a crystallite size (Rl) found from a half-value width of a diffraction peak of the index of the plane (06) and in the possession of a crystallite sectional area (VI). Described below is a representative chemical composition of the activated clay, to which only, however, the invention is in no way limited. SiO2 76.6% by weight. Al2O3 10,4% by weight Fe2O3 2.4% by weight MgO 2.5% by weight CaO 0,5% by weight Ignition loss 6.5% by weight It was pointed out already that the crystallite sectional area (VI) of the activated clay represents a three-dimensional size of the laminar crystalline structure, which, at the same time, is related to the mesopores in the activated clay. That is, the clay particles have a diameter very larger than the size of the crystallite and, hence, it is believed that space among the crystallites is forming a mesopore. In practice, the porous volume of the activated clay of the present invention at porous radii of 20 to 150 angstroms is as large as from 0-20 to 0.30 ml/g, which is believed to be very helpful for increasing the diffusion rate which determines the rate for adsorbing coloring matter, etc. The activated clay of the present invention has a specific surface area over a range of from 250 to 350 m2/g as measured by the BET method in relation to the above-mentioned crystallite size (Rl). The activated clay of the present invention has an X-ray diffraction peak over a spacing of from 17 to 19 angstroms as measured in a state of being treated with an ethylene glycol. Fig. 5 in the accompanying drawings shows an X-ray diffraction image of the activated clay of the present invention as measured in a state of being treated with the ethylene glycol (see Example 2 appearing later). The treatment with the ethylene glycol is carried out so that spacings of bottom surface reflection of an index of the plane (001) are confined within the above-mentioned predetermined range, from which it will be obvious that the activated clay of the present invention is not basically losing the laminar structure of the dioctahedral smectite clay minerals. The activated clay of the present invention has, as another property, a cation-exchange capacity of from 3 0 to 55 meq/100 g. The activated clay of the present invention is useful as an agent for refining oils or fats or mineral oils and, particularly, as a decoloring agent for oils or fats or mineral oils, or as an acid-removing agent therefor. The oils or fats to be refined will be at least those of plant oils or fats, animal oils or fats and mineral oils. The starting oils or fats widely exist in the natural animal and plant worlds, and have, as a chief component, an ester of a fatty acid and glycerin, which includes plant oils or fats such as safflower oil, soybean oil, rape oil, palm oil, palm seed oil, cotton seed oil, coconut oil, rice bran oil, sesame oil, castor oil, linseed oil, olive oil, tung oil, tsubaki oil, peanut oil, kapok oil, cacao oil, Japan wax, sunflower oil and corn oil, fish oils such as sardine oil, herring oil, squid oil and saury oil, and animal oils or fats such as liver oil, whale oil, and tallows including beef tallow, horse oil, lard and mutton tallow, which may be used alone or being combined together. As the mineral oils, there can be exemplified a variety of lubricating oils such as spindle oil, refrigerator oil, dynamo oil, turbine oil, machine oil, lubricating oil for internal combustion engines for ships, lubricating oil for gasoline engines, lubricating oil for diesel engines, cylinder oil, marine engine oil, gear oil, cutting oil, insulating oil, automatic transmission oil, compressor oil, hydraulic operation oil, roller oil, an the like oil. To carry out the refining treatment, the activated clay is added in a powdery form as a decoloring agent or as a refining agent to the oils or fats or to the mineral oils that are to be decolored or refined, and the two are homogeneously stirred, so that the clay particles adsorb color components and impurities contained in the oils or fats or in the mineral oils. The clay separated after the decoloring or refining treatment, holds oils or fats or mineral oils in amounts corresponding to the amounts of oil adsorbed by the clay that is used. According to the present invention, the amount of the clay used for the refining can be decreased while decreasing the oil retention. The treatment for decoloring the oils or fats or mineral oils is conducted under widely known conditions. For example, the decoloring agent or the refining agent is added in an amount of not larger than 5% by weight with respect to the oils or fats or mineral oils, the two are stirred at a temperature of 90 to 150°C for 5 to 30 minutes thereby to complete the decoloring or refining processing. The mixture after the decoloring or refining treatment is supplied to any filter of the type of reduced pressure or increased pressure, such as filter press, belt filter, Oliver filter, American filter or centrifugal filter, so that the refined oils or fats or mineral oils are separated from the used decoloring agent or the refining agent which is the so-called waste clay. The present invention makes it possible to decrease the amount of the waste clay. The clay of the present invention has the oil retention of generally from about 25 to about 40%, The activated clay of the present invention is applied as a color-forming agent (developer) onto the surface of the pressures-sensitive paper, and is used as a color-forming agent layer on the pressure-sensitive copying paper. The pressure-sensitive copying paper is produced by preparing an aqueous slurry which contains the developer in an amount of from 25 to 45% by weight and, particularly, from 30 to 40% by weight, and a binder in an amount of from 4 to 10% by weight and, particularly, from 6 to 8% by weight, and applying the aqueous slurry onto the surface of the paper followed by drying. In this case, the slurry is applied in an amount of from 2 to 15 g/m2 and, particularly, from 3 to 10 g/m2 in terms of a developer on the surface of the paper on dry basis. Examples of the binder include aqueous latex binders such as styrene-butadiene copolymer latex, carboxyl-modified styrene-butadiene copolymer latex; self-emulsifying binder such as self-emulsifying acrylic resin; water-soluble binders such as carboxymethyl cellulose, polyvinyl alcohol, cyanoethylated starch, casein, which is used in one kind or in a combination of two or more kinds. The activated clay of the present invention can be used alone as a developer and can, further, be used as a developer for leuco pigment in combination with known developers for leuco pigment, such as phenols, phenol resins, zinc salicylate or derivatives thereof, or montmorillonite treated with an acid. It is also allowable to blend minerals such as calcium carbonate, zeolites, attapulgite, kaolin, talc or the like, as a ! filler or a developer assistant. In carrying out the copying operation by using the pressure-sensitive paper of the present invention, it is allowed to use any leuco pigment that has been used for the pressure-sensitive recording of this type, such as triphenylmethane-type leuco pigment, fluoran-type leuco pigment, spiropyran-type leuco pigment, Rhodamine lactam-type leuco pigment, Auramine-type leuco pigment and phenothiazine-type leuco pigment in a single kind or in a conribination of two or more kinds. An upper sheet provided with a layer of microcapsules of these leuco pigments is used in combination for the pressure-sensitive recording. The developer of the present invention exhibits particularly excellent effect when it is used in combination with a black leuco pigment. EXAMPLES Described below are Examples of the present invention. Measurements were taken according to the methods described below, (1) X-ray analysis. Measured by using a Geiger-Flex RAD-IB system manufactured by Rigaku Denki Co, and Cu-Ka under the following conditions. Target Cu Filter Ni Tube voltage 35 kV Tube current 15 mA Scanning rate 2 deg/min Time constant 1 sec Slit DS(SS) 1 deg RS 0,3 mm (2) X-ray diffraction conditions for measuring crystallite sizes. ! Measured by using a Geiger-Flex RAD-IB system manufactured by Rigaku Denki Co. and Cu-Ka under the following conditions. Target Cu Filter Ni Tube voltage 40 kV Tube current 20 mA Scanning rate 0.5 deg/min Time constant 2 sec Slit DS(SS) 2 deg RS 0.3 mm (3) X-ray diffraction of samples treated with ethylene glycol, A sample dried at 110°C for 2 hours was picked in an amount of 1.0 g, and to which was added 5 ml of an aqueous solution containing 10% of ethylene glycol by using a whole pipette. The mixture was stirred well with a stirrer rod and was dried at 60°C for 12 hours. The dried product was ground down in an agate mortar, and the resulting powder was subjected to the X-ray diffraction measurement under the following conditions. Measured by using a Geiger-Flex RAD-IB system manufactured by Rigaku Denki Co. and Cu-KQ£ under the following conditions. Target Cu Filter Ni Tube voltage 40 kV Tube current 20 mA" Scanning rate 1 deg/min Time constant 2 sec Slit DS(SS) 1/2 deg RS 0.3 mm (4) Measurement of CEC, Measured in compliance with the testing method TIKS-413 issued by the Study Group of Inorganic Sand-Mold, Japanese Foundation of Minerals, Tokai Branch. (5) BET Specific Surface Area. Measured by using Sorptomatic Series 1900 manufactured by Carlo Erba Co. in compliance with the BET method, (6) Porous volume- Porous volume of radii of not larger than 150 angstroms was measured by using Sorptomatic Series 1900 manufactured by Carlo Erba Co. by the N2 adsorption method, (7) Oil-absorbing amount. Measured in compliance with JIS K-5101-21, (8) Viscosity, 100 Grams of alumina balls for pulverization and 24 g of the sample (dried at 110°C) were introduced into a glass container, followed by the addition of the water and a 30% caustic soda solution, to form a slurry having a concentration of solid components of 25% and a pH of from 9.8 to 10.7, The slurry was wet-milled in a paint conditioner for 15 minutes. Viscosity was measured by using a type-B viscometer after one minute has passed from the milling. (9) pH. A pH of a 5% suspension was measured in compliance with JIS K-'5101-26. (10) Testing of decoloring. A decoloring tester shown in Fig. 6 was used for testing the performance of an adsorbing agent for decoloring. For details, see "Chemistry and Industry", A, 125, 1951. The decoloring tester permits eight large test tubes (having a content of 200 ml) made of a hard glass to be set in an oil bath. Each test tube contains a corrugated stirrer rod having a round lower end which is adjusted by a rubber tube to come in contact with the^ bottom of the test tube at all times. Eight stirrer rods are rotated by pinions separated from a central master gear and, hence, their rotational speeds are all equal to each other. Stirrer vanes are provided under the central master gear to stirrer the oil bath and, hence, to uniformly maintain the temperature in the oil bath. The decoloring test can be conducted in any number of up to a maximum of eight. Each test tube was filled with 50 g of rape oil that has been treated for removing an acid component, followed by the addition of the adsorbing agent in an amount of 0.5 g (1% with respect to the oil). The mixture was stirred well by the stirrer rod for decoloring testing. Each test tube was set to the above-mentioned decoloring tester maintained at 110'C and, after stirred for 20 minutes, was removed from the decoloring tester. Then, a mixture slurry of the oil and the adsorbing agent was filtrated to obtain the decolored oil. A white light ray transmission factor (relative value of when a transmission factor through distilled water is regarded to be 100%) through the decolored oil was measured by using a photoelectric colorimeter, model 2C, manufactured by Hirama Rika Kenkyujo Co., and the obtained value was regarded to be decoloring performance of the adsorbing agent. The larger the value of transmission factor, the higher the decoloring performance of the adsorbing agent that was used. (11) Testing the developing performance• A coated front appliecl with a sample was introduced into a desiccator (75%RH) containing a saturated saline solution, and was preserved in a dark place at room temperature (25°C). After about 24 hours have passed from the application, the to-be-stamped paper was taken out and was exposed in the room (constant temperature and constant humidity: a temperature of about 25°C and a humidity of about 60%RH) for 16 hours, and was developed. Developing was effected by superposing a coated back on which has been applied microcapsules containing a black leuco pigment on the coated front in a manner that the applied surface was faced thereto, rotating them with the application of pressure between two steel rolls, so that the microcapsules were nearly completely ground down. The color-forming (developing) density (hereinafter also simply referred to as density) one hour after the color formation (developing) was measured by using a densitometer (Fuji Densitometer, Model FSD-103, manufactured by Fuji Photo Film Co.)/ and the developing performance of the coated front was represented by the measured density. The higher the density, the higher the developing performance. (Example 1) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials, and were coarsely milled and kneaded into particles of 5 mm in diameter. 1500 Grams of the particles were introduced into a treating vessel. An aqueous solution containing 30% by-weight of sulfuric acid prepared by adding 1727 g of water to 733 g of 97% by weight sulfuric acid, was circulated therein. The treating temperature was 90°C and the treating time was 5 hours. After the treatment with the acid, the acid-treated product was washed with water by circulating the washing water, and was then dried at 110°C, milled, and classified to obtain activated clay. Physical properties were measured to be as shown in Table 1, (Example 2) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1, Figs. 1 and 2 show X-ray diffraction images of the obtained activated clay and of the starting clay minerals, and Fig. 5 shows an X-ray diffraction image of the activated clay as measured in a state of being treated with an ethylene glycol. (Example 3) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. (Comparative Example 1) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. (Comparative Example 2) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. Figs. 3 and 4 show X-ray diffraction images of the obtained activated clay and of the starting materials. (Comparative Example 3) The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. The activated clay obtained by the treatment with an acid in such a manner that the three-layer structure of the dioctahedral smectite remains maintaining a predetermined crystallite size according to the present invention, exhibits high and sustained decoloring performance despite it is used in a small amount. The activated clay has a low oil retention and is suited for use as an agent for refining oils or fats, exhibits a sufficient color-forming density even when it is applied in small amounts, permits the color of the image to fade little, exhibits a low viscosity despite of its high solid component concentration, and is useful as a color-forming agent exhibiting excellent applicability. We CLAIM: 1. A method of producing an activated clay by treating dioctahedral smectite clay minerals with an acid, wherein a crystallite size (R1) of the activated clay ' found from a half-value width of an X-ray diffraction peak of an index of a plane (06) of the smectite is within a range of from 10 to 30 nm, and a crystallite sectional area (VI) of the activated clay defined by the following formula (1), VI = R1 X R2 --- (1) wherein Rl denotes the above-mentioned crystallite size (nm) , and R2 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2, 2. A method of producing activated clay according to claim 1, wherein the activated clay has a specific surface area of from 250 to 350 m2/g as measured by the BET method. 3. A method of producing activated clay according to claim 1 or 2, wherein the activated clay has an X-ray diffraction peak over a spacing of from 17 to 19 angstroms i as measured in a state of being treated with an ethylene glycol, 4. A method of producing an activated clay by treating, with an acid, dioctahedral smectite clay minerals having a crystallite size (R10) found from a half-value width of an X™ray diffraction peak of an index of a plane (06) of the smectite of from 15 to 30 nm, and a crystallite sectional area (VO) of the starting clay minerals defined by the formula (2), VO = R01 X R20 (2) wherein R10 denotes the above-mentioned crystallite size (nm), and R20 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, of from 100 to 230 nm2, so that the crystallite size (R1) found from the half-value width of the X-ray diffractioh peak of the index of plane (06) of the smectite is from 10 to 30 nm and that the crystallite sectional area (VI) defined by the following formula (1), VI = R1 X R2 --- (1) wherein Rl denotes the above-mentioned crystallite size (nm) , and R2 denotes a crystallite size (nm) found from a half-value width of the X-ray diffraction peak of the index of plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2. 5, A decoloring agent for oils or fats, comprising the activated clay obtained by the method of any one of claims 1 to 4, 6. A color-forming agent for pressure-sensitive papers, comprising the activated clay obtained by the method of any one of claims 1 to 4. 7. A method of producing an activated clay by treating dioctahedral smectite clay minerals with an acid, substantially as herein described with reference to the 3 . accompanying drawings-

Full Text

METHOD OF PRODUCING ACTIVATED CLAY AND ITS USE
BACKGROUND OF THE INVENTION (Field of the Invention)
The present invention relates to activated clay and its use. More specifically, the invention relates to activated clay which exhibits excellent decoloring performance, color-forming performance and catalytic performance owing to the three-layer structure of the dioctahedral smectite that remains maintaining a predetermined crystallite size, and to the use thereof. (Prior Art)
It has long been known that the dioctahedral smectite clay minerals exhibit adsorptive performance and decoloring performance- In Britain, the dioctahedral smectite clay minerals have also been called fuller's earth or bleaching earth.
It has also been known since the old times to produce so-called activated clay having increased specific surface areas by treating the dioctahedral smectite clay minerals with an acid. For example, Japanese Patent Publication No, 335/1948 teaches a method of producing activated clay by kneading acidic clay or a similar clay in the water into a size of 0.5 to 30 nm so will not to collapse, introducing the clay in an acid-resistant container, and heating and circulating an inorganic acid to impart activity thereto.
Furthermore, Japanese Patent Publication No, 2960/1957 discloses a method of producing granular activated clay by adding sulfuric acid to acidic clay to obtain it in the form of an agent, followed by drying until it can he pulverized, and, then, pulverizing and sieving the product to obtain those having a predetermined particle size, and activating them by a predetermined method.

Japanese Patent Publication No. 11209/1970 discloses a method of treating an alumina silicate clay with an acid wherein, in producing activated clay or fine powdery silica by treating an alumina silicate clay containing acid- soluble basic components with an acid, 1.0 to 1.5 equivalents of acid or an aqueous solution thereof relative to the basic metal components to be removed from the alumina silicate clay is added in an amount not larger than the amount of an acid aqueous solution with which the clay particles in the dispersion of the clay formed by the addition of the acid starts precipitating, so that the basic metal components in the clay react with the acid in the dispersion, and, then, the reaction product is separated from the dispersion solution, and the reaction product particles are treated in an aqueous medium at a pH of lower than 1, thereby to extract the basic metal components from the product.
According to the conventional method of producing activated clay by the treatment with an acid, the conditions of treatment with acid are adjusted, such as acid concentration, temperature, treating time, etc., so that the acid-soluble basic components are at least partly eluted out from the clay minerals, in order to enhance the decoloring performance and to increase the specific surface areas.
Use of the activated clay is encountering severe conditions in recent years. That is, in refining oils or fats, there is inevitably by-produced waste clay that is difficult to discard. It is therefore required that a high and sustained decoloring performance is obtained by the use in an amount which is as small as possible and that the oil component contained in the waste clay is low, i.e,, oil retention is low at the time of separating oils or fats from the waste clay by filtration.
When used as a color-forming agent for pressure-

sensitive papers, furthermore, it is required that a color is formed maintaining a sufficiently large density with a small amount of application, color of the image fades little, viscosity is low despite of a high solid component concentration from the standpoint of production, and that it can be excellently applied.
So far, however, no crystallographical study has been conducted in regard to selecting clay minerals for use as starting materials or evaluating the obtained Activated clay, but empirical judgements have simply been rendered without quite meeting the above-mentioned demands for obtaining activated clay of high quality. SUMMARY OF THE INVENTION
The present inventors have discovered the fact that the sectional area of a crystallite related to an index of a particular plane as observed by an X-ray diffraction method plays an important role for producing activated clay of a high quality and, further, determines the starting material for obtaining the activated clay.
That is, the object of the present invention is to provide activated clay of a high quality and of a high function, exhibiting high and sustained decoloring ability with the use in a small amount when it is used for refining oils or fats, exhibiting a low oil retention, giving a sufficient degree of color-forming density with the application in a small amount when it is used as a color-forming agent for pressure-sensitive papers,
permitting the color of the image to fade little,
I
exhibiting a low viscosity despite of its high solid component concentration, and capable of being favorably applied, as well as to provide a method of producing the same.
According to the present invention, there is provided a method of producing an activated clay obtained by treating dioctahedral smectite clay minerals with an acid.

wherein a crystallite size (Rl) of the activated clay found from a half-value width of an X-ray diffraction peak of an index of a plane (06) of the smectite is within a range of from 10 to 30 nm, and a crystallite sectional area (VI) of the activated clay defined by the following formula (1),
VI == Rl X R2 (1)
wherein Rl denotes the above-mentioned crystallite size (nm),*and R2 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2, preferably, from 60 to 145 nm2 and, most preferably, from 70 to 140 nm2.
According to the present invention, it is desired that the activated clay (1) has a specific surface area of from 250 to 350 m2/g as measured by the BET method, and (2) has an X-ray diffraction peak over a spacing of from 17 to 19 angstroms as measured in a state of being treated with an ethylene glycol.
According to the present invention, furthermore, there is provided a decoloring agent for oils or fats, and a color-forming agent for pressure-sensitive papers, comprising the activated clay.
According to the present invention, there is further
provided a method of producing activated clay by treating,
with an acid, dioctahedral smectite clay minerals having a
crystallite size (RIO) found from a half-value width of an
X-ray diffraction peak of an index of a plane (06) of the
smectite of from 15 to 30 nm and, particularly, from 20 to
28 nm, and a crystallite sectional area (VO) defined by
the following formula (2), ;
VO = R10 X R20 (2)
wherein R10 denotes the above-mentioned crystallite

size (nm), and R20 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, of from 100 to 230 nm2, preferably, from 120 to 230 nm2 and, most preferably, from 120 to 225 nm2, so that the crystallite size (Rl) found from the half-value width of the X-ray diffraction peak of the index of plane (06) of the smectite is from 10 to 3 0 nm and that the crystallite sectional area (VI) defined by the following formula (1),
VI = Rl X R2 (1)
wherein Rl denotes the above-mentioned crystallite size (nm), and R2 denotes a crystallite size (nm) found from a half-value width of the X-ray diffraction peak of the index of plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2, preferably, from 60 to 145 nm2 and, most preferably, from 70 to 140 nm2. BRIEF DESCRIPTION OF THE DRAWINGS
Fig, 1 is a diagram showing an X-ray diffraction image of an activated clay prepared in Example 2;
Fig. 2 is a diagram showing an X-ray diffraction image of a starting clay used for producing the activated clay of Example 2;
Fig. 3 is a diagram showing an X-ray diffraction image of an activated clay prepared in Comparative Example 2;
Fig. 4 is a diagram showing an X-ray diffraction image of a starting clay used for producing the activated clay of Comparative Example 2;
Fig. 5 is a diagram showing an X-ray diffraction t image of the activated clay prepared in Example 2 as measured in a state of being treated with an ethylene

glycol; and
Fig. 6 is a sectional view of a decoloring tester.
DETAILED DESCRIPTION OF THE INVENTION
In the X-ray diffraction of crystals, it has been
known that an intensity peak appears in the interference
when the following Bragg's formula (3),

wherein Lhkl is a size of the crystal in a direction perpendicular to the plane (hkl) , K is a constant of about 0.9, H is a half-value width (radian) of the
interference peak, and λ and θ are the same as those mentioned in the above formula (3),
exists between the sharpness of the interference peak and
the size of the crystals.
The reflection peaks on the bottom surface (001) of the clay minerals are symmetrical in the right-and-left direction, but asymmetrical peaks are exhibited in many cases by the reflection (hkl). This is because, the layers are overlapped in parallel but their positions are irregular relative to each other. Such asymmetrical peaks are called two-dimensional reflection. The index (1) does not assume a particular value and is, hence, expressed by (hk). The index of a plane (06) referred to in this specification just means this fact.
Fig. 1 in the accompanying drawings shows an X-ray diffraction image of the activated clay of the present invention. Fig, 2 shows an X-ray diffraction image of a

starting clay used for the production of the activated
clay of Fig. 1, and Figs. 3 and 4 show, respectively, an
X-ray diffraction image of the activated clay and an X-ray
diffraction image of a starting clay therefor outside the
scope of the present invention (see Example 2 and
Comparative Example 2 appearing later). :
The dioctahedral smectite is constituted by a laminated-layer structure having, as a basic layer unit, a three-layer structure in which an A10g octahedral layer is sandwiched by two SiO4 tetrahedral layers, Al in the AlO6 octahedral layer is isomorphously substituted by Fe and Mg, and Si in the SiO4 tetrahedral layer is isomorphously substituted by Al, the basic layer units being laminated in the direction of a c-axis, and metal cations existing among the layers to compensate for the lack of electric charge caused by the isomorphous substitution.
When the clay minerals of the laminated-layer structure are treated with an acid, metal cations existing among the layers of the laminated-layer structure elute out, and the laminated-layer structure of the basic three-layer structure is partly cut apart. Even in the basic three-layer structure, portions of the intermediate AlO6 octahedral layer elute out from the edges of the basic three-layer structure.
The activated clay of the present invention exhibits vivid diffraction peaks in the index of a plane (06) indicating that the basic three-layer structure is remaining in the activated clay. Furthermore, the crystallite size (Rl) found from a half-value of the diffraction peak of the index of a plane (06) represents the size of the three-layer structure in the direction of the plane,
On the other hand, the crystallite size (R2) found from a half-value width of the diffraction peak of the index of a plane (001) represents the degree of lamination

of the layers of the basic three-layer structure. It can therefore be said that the crystallite sectional area (VI) expressed by the above-mentioned formula (1) is expressing, by the sectional area, the three-dimensional size of the laminar crystal structure in the activated clay.
In the activated clay of the present invention, it is important that the crystallite sectional area (VI) lies within the above-mentioned range from the standpoint of obtaining the activated clay of a high quality. That is, as the crystallite sectional area (VI) exceeds the range specified by the present invention, the activated clay ; used for refining oils or fats exhibits performance for adsorbing pigments, etc. and sustenance thereof that are decreased compared to those having the crystallite sectional area (VI) lying within the range of the present invention. When used as a color-forming agent for pressure-sensitive papers, the color-forming performance drops when the crystallite sectional area (VI) exceeds the range specified by the present invention. On the other hand, when the crystallite sectional area (VI) becomes smaller than the range specified by the present invention, the clay used for refining oils or fats exhibits decreased performance for adsorbing colors, etc., and exhibits an increased oil retention, which is not desirable. When used as the color-forming agent for pressure-sensitive papers, furthermore, the color-forming performance decreases and the color of the image tends to fade out to a conspicuous degree. When applied as a slurry, furthermore, the clay exhibits an increased viscosity, which is not desirable, either.
In the activated clay, it is important that the crystallite sectional area (VI) must be maintained to be not smaller than a lower-limit value specified by the present invention. That is, in the conventional activated

clay, the crystallite sectional area (VI) is smaller than the lower-limit value of the present invention accounting for a large oil retention or a high viscosity. According to the present invention in which the crystallite sectional area (VI) is maintained to be not smaller than a predetermined value, it is made possible to enhance the coloring matter-adsorbing performance and color-forming performance while maintaining the oil retention and the viscosity at low values.
To produce the activated clay of the present invention, the conditions for treatment with an acid plays important roles as a matter of course. Basically, however, it is important to select dioctahedral smectite clay minerals that meet a predetermined standard.
The crystallite sectional area (VI) of the activated clay varies much depending upon the conditions for treatment with an acid. When the crystallite sectional area (VO) of the starting clay minerals exceeds the range specified by the present invention, the obtained activated clay tends to have the crystallite sectional area (VI) that is larger than the range specified by the present invention. When the crystallite sectional area (VO) of the starting clay minerals is smaller than the range specified by the present invention, the obtained activated clay tends to have the crystallite sectional area (VI) that is smaller than the range specified by the present invention. In either case, it becomes difficult to accomplish the object of the present invention, [Starting clay minerals]
The starting dioctahedral smectite clay used in the present invention has the crystallite size (RIO) and the crystallite sectional area (VO) that lie within the ranges specified by the present invention. Minute structure of the starting clay differs depending upon the components of the clay, place where it is produced and site where it is

buried (working face) even in the same place of production. Therefore, those satisfying the above-mentioned requirements should be selected by conducting the X-ray diffraction testing.
It is considered that the dioctahedral smectite is formed as the volcanic ash or lava is modified being affected by the seawater.
Described below is a chemical composition of representative starting clay minerals,
SiO2 64.4% by weight,
Al2O3 16.3% by weight
Fe203 3,3% by weight
MgO 6.5% by weight
CaO 0.9% by weight
K2O 0.5% by weight
Na2O 1,4% by weight
Ignition loss 6.7% by weight As required, the thus selected dioctahedral smectite clay minerals are subjected to the refining operation such as stone-sand separation, ore dressing by buoyancy, magnetic ore dressing, hydraulic elutriation or air elutriation, and are then subjected to the treatment with an acid. [Treatment with an acid]
The treatment with an acid can be effected by either the above-mentioned granular activation method or the sludge activation method.
Described below is the case of the granular
activation to which only, however, the present invention
is in no way limited, [
In the granular activation, the starting clay minerals must be prepared in the form of particles suited for being treated with an acid prior to bringing them into contact with the acid. The ore that is dug usually contains the water in an amount of about 35 to about 40%

by weight, and this water serves as a medium for granulating the clay.
By using a rag crasher as a coarse milling machine, the core is coarsely milled and, then, the clay is kneaded. The kneading is effected by using a grooved roll, a plain roll or a combination thereof. Then, the kneaded clay is granulated into a predetermined size. It is desired that the particles have a diameter of, usually, from 3 to 10 mm and, particularly, from 5 to 7 mm, •
A suitable granulating machine will be a pair of perforated rolls. The clay is supplied to a nipping position of the rolls; i,e., the clay is passed from the outside to the inside of the rolls so as to be granulated into a predetermined size.
The conditions for treatment with an acid are so determined that the obtained acid-treated product will have the above-mentioned crystallite size (Rl) and the crystallite sectional area (VI),
The treatment with an acid is carried out by filling a treatment vessel with the granular clay and circulating an aqueous solution containing an acid. The aqueous solution contains mineral acids, such as sulfuric acid, hydrochloric acid, or the like acid and, particularly, contains sulfuric acid, at a concentration of about 20 to about 35% by weight. The treating temperature is selected from a range of from 80 to 95°C and the treating time is selected from a range of from 3 to 20 hours to satisfy the above-mentioned requirements.
The mother liquor after the treatment with the acid contains basic components such as alumina, magnesium, iron, etc. Therefore, the mother liquor can be used as an inorganic liquid coagulating agent or as a starting material of gypsum.
After the mother liquor is recovered, the acid-treated product contained in the treatment vessel is

washed with water by circulating the washing water. After washing with water, the acid-treated product is dried, milled and is classified to obtain a product of activated clay. In the present invention, it is desired that the water-soluble salts contained in the acid-treated product are removed to such an extent that the amount of the residue thereof is not larger than 3% by weight and, particularly, not larger than 1% by weight in terms of acid radicals of the acid that is used. This is because, the water-soluble salts contained in the acid-treated product adversely affect the quality of the product despite their amounts are very small.
As required, the obtained acid-treated product is reformed by drying or firing. Upon drying or firing, it is considered that the concentration of silanol groups decreases on the surface of the activated clay, and the clay acquires a structure which difficultly swells in the water. It is desired that the drying or firing is conducted usually at a temperature of from 80 to 500°C and, particularly, from 100 to 300°C for a period of from 0.5 to 10 hours and, particularly, from 0,7 to 5 hours. [Activated clay and its use]
The feature of the activated clay of the present invention resides in the possession of a crystallite size (Rl) found from a half-value width of a diffraction peak of the index of the plane (06) and in the possession of a crystallite sectional area (VI).
Described below is a representative chemical composition of the activated clay, to which only, however, the invention is in no way limited.
SiO2 76.6% by weight.
Al2O3 10,4% by weight
Fe2O3 2.4% by weight
MgO 2.5% by weight
CaO 0,5% by weight

Ignition loss 6.5% by weight
It was pointed out already that the crystallite sectional area (VI) of the activated clay represents a three-dimensional size of the laminar crystalline structure, which, at the same time, is related to the mesopores in the activated clay. That is, the clay particles have a diameter very larger than the size of the crystallite and, hence, it is believed that space among the crystallites is forming a mesopore.
In practice, the porous volume of the activated clay of the present invention at porous radii of 20 to 150 angstroms is as large as from 0-20 to 0.30 ml/g, which is believed to be very helpful for increasing the diffusion rate which determines the rate for adsorbing coloring matter, etc.
The activated clay of the present invention has a specific surface area over a range of from 250 to 350 m2/g as measured by the BET method in relation to the above-mentioned crystallite size (Rl).
The activated clay of the present invention has an X-ray diffraction peak over a spacing of from 17 to 19 angstroms as measured in a state of being treated with an ethylene glycol. Fig. 5 in the accompanying drawings shows an X-ray diffraction image of the activated clay of the present invention as measured in a state of being treated with the ethylene glycol (see Example 2 appearing later). The treatment with the ethylene glycol is carried out so that spacings of bottom surface reflection of an index of the plane (001) are confined within the above-mentioned predetermined range, from which it will be obvious that the activated clay of the present invention is not basically losing the laminar structure of the dioctahedral smectite clay minerals.
The activated clay of the present invention has, as another property, a cation-exchange capacity of from 3 0 to

55 meq/100 g.
The activated clay of the present invention is useful as an agent for refining oils or fats or mineral oils and, particularly, as a decoloring agent for oils or fats or mineral oils, or as an acid-removing agent therefor.
The oils or fats to be refined will be at least those of plant oils or fats, animal oils or fats and mineral oils.
The starting oils or fats widely exist in the natural animal and plant worlds, and have, as a chief component, an ester of a fatty acid and glycerin, which includes plant oils or fats such as safflower oil, soybean oil, rape oil, palm oil, palm seed oil, cotton seed oil, coconut oil, rice bran oil, sesame oil, castor oil, linseed oil, olive oil, tung oil, tsubaki oil, peanut oil, kapok oil, cacao oil, Japan wax, sunflower oil and corn oil, fish oils such as sardine oil, herring oil, squid oil and saury oil, and animal oils or fats such as liver oil, whale oil, and tallows including beef tallow, horse oil, lard and mutton tallow, which may be used alone or being combined together.
As the mineral oils, there can be exemplified a variety of lubricating oils such as spindle oil, refrigerator oil, dynamo oil, turbine oil, machine oil, lubricating oil for internal combustion engines for ships, lubricating oil for gasoline engines, lubricating oil for diesel engines, cylinder oil, marine engine oil, gear oil, cutting oil, insulating oil, automatic transmission oil, compressor oil, hydraulic operation oil, roller oil, an the like oil.
To carry out the refining treatment, the activated clay is added in a powdery form as a decoloring agent or as a refining agent to the oils or fats or to the mineral oils that are to be decolored or refined, and the two are homogeneously stirred, so that the clay particles adsorb

color components and impurities contained in the oils or fats or in the mineral oils. The clay separated after the decoloring or refining treatment, holds oils or fats or mineral oils in amounts corresponding to the amounts of oil adsorbed by the clay that is used. According to the present invention, the amount of the clay used for the refining can be decreased while decreasing the oil retention.
The treatment for decoloring the oils or fats or mineral oils is conducted under widely known conditions. For example, the decoloring agent or the refining agent is added in an amount of not larger than 5% by weight with respect to the oils or fats or mineral oils, the two are stirred at a temperature of 90 to 150°C for 5 to 30 minutes thereby to complete the decoloring or refining processing.
The mixture after the decoloring or refining treatment is supplied to any filter of the type of reduced pressure or increased pressure, such as filter press, belt filter, Oliver filter, American filter or centrifugal filter, so that the refined oils or fats or mineral oils are separated from the used decoloring agent or the refining agent which is the so-called waste clay. The present invention makes it possible to decrease the amount of the waste clay. The clay of the present invention has the oil retention of generally from about 25 to about 40%,
The activated clay of the present invention is applied as a color-forming agent (developer) onto the surface of the pressures-sensitive paper, and is used as a color-forming agent layer on the pressure-sensitive copying paper. The pressure-sensitive copying paper is produced by preparing an aqueous slurry which contains the developer in an amount of from 25 to 45% by weight and, particularly, from 30 to 40% by weight, and a binder in an amount of from 4 to 10% by weight and, particularly, from

6 to 8% by weight, and applying the aqueous slurry onto the surface of the paper followed by drying.
In this case, the slurry is applied in an amount of from 2 to 15 g/m2 and, particularly, from 3 to 10 g/m2 in terms of a developer on the surface of the paper on dry basis.
Examples of the binder include aqueous latex binders such as styrene-butadiene copolymer latex, carboxyl-modified styrene-butadiene copolymer latex; self-emulsifying binder such as self-emulsifying acrylic resin; water-soluble binders such as carboxymethyl cellulose, polyvinyl alcohol, cyanoethylated starch, casein, which is used in one kind or in a combination of two or more kinds.
The activated clay of the present invention can be used alone as a developer and can, further, be used as a developer for leuco pigment in combination with known developers for leuco pigment, such as phenols, phenol resins, zinc salicylate or derivatives thereof, or montmorillonite treated with an acid. It is also allowable to blend minerals such as calcium carbonate, zeolites, attapulgite, kaolin, talc or the like, as a ! filler or a developer assistant.
In carrying out the copying operation by using the pressure-sensitive paper of the present invention, it is allowed to use any leuco pigment that has been used for the pressure-sensitive recording of this type, such as triphenylmethane-type leuco pigment, fluoran-type leuco pigment, spiropyran-type leuco pigment, Rhodamine lactam-type leuco pigment, Auramine-type leuco pigment and phenothiazine-type leuco pigment in a single kind or in a conribination of two or more kinds. An upper sheet provided with a layer of microcapsules of these leuco pigments is used in combination for the pressure-sensitive recording. The developer of the present invention exhibits particularly excellent effect when it is used in

combination with a black leuco pigment. EXAMPLES
Described below are Examples of the present invention. Measurements were taken according to the methods described below,
(1) X-ray analysis.
Measured by using a Geiger-Flex RAD-IB system
manufactured by Rigaku Denki Co, and Cu-Ka under the following conditions.
Target Cu
Filter Ni
Tube voltage 35 kV
Tube current 15 mA
Scanning rate 2 deg/min
Time constant 1 sec
Slit DS(SS) 1 deg RS 0,3 mm
(2) X-ray diffraction conditions for measuring crystallite
sizes. !
Measured by using a Geiger-Flex RAD-IB system
manufactured by Rigaku Denki Co. and Cu-Ka under the following conditions.
Target Cu
Filter Ni
Tube voltage 40 kV
Tube current 20 mA
Scanning rate 0.5 deg/min
Time constant 2 sec
Slit DS(SS) 2 deg RS 0.3 mm
(3) X-ray diffraction of samples treated with ethylene
glycol,
A sample dried at 110°C for 2 hours was picked in an amount of 1.0 g, and to which was added 5 ml of an aqueous solution containing 10% of ethylene glycol by using a whole pipette. The mixture was stirred well with a stirrer rod and was dried at 60°C for 12 hours. The dried

product was ground down in an agate mortar, and the resulting powder was subjected to the X-ray diffraction measurement under the following conditions.
Measured by using a Geiger-Flex RAD-IB system
manufactured by Rigaku Denki Co. and Cu-KQ£ under the following conditions.
Target Cu
Filter Ni
Tube voltage 40 kV
Tube current 20 mA"
Scanning rate 1 deg/min
Time constant 2 sec
Slit DS(SS) 1/2 deg RS 0.3 mm
(4) Measurement of CEC,
Measured in compliance with the testing method TIKS-413 issued by the Study Group of Inorganic Sand-Mold, Japanese Foundation of Minerals, Tokai Branch.
(5) BET Specific Surface Area.
Measured by using Sorptomatic Series 1900 manufactured by Carlo Erba Co. in compliance with the BET method,
(6) Porous volume-
Porous volume of radii of not larger than 150 angstroms was measured by using Sorptomatic Series 1900 manufactured by Carlo Erba Co. by the N2 adsorption method,
(7) Oil-absorbing amount.
Measured in compliance with JIS K-5101-21,
(8) Viscosity,
100 Grams of alumina balls for pulverization and 24 g of the sample (dried at 110°C) were introduced into a glass container, followed by the addition of the water and a 30% caustic soda solution, to form a slurry having a concentration of solid components of 25% and a pH of from 9.8 to 10.7, The slurry was wet-milled in a paint

conditioner for 15 minutes. Viscosity was measured by using a type-B viscometer after one minute has passed from the milling.
(9) pH.
A pH of a 5% suspension was measured in compliance with JIS K-'5101-26.
(10) Testing of decoloring.
A decoloring tester shown in Fig. 6 was used for testing the performance of an adsorbing agent for decoloring. For details, see "Chemistry and Industry", A, 125, 1951. The decoloring tester permits eight large test tubes (having a content of 200 ml) made of a hard glass to be set in an oil bath. Each test tube contains a corrugated stirrer rod having a round lower end which is adjusted by a rubber tube to come in contact with the^ bottom of the test tube at all times. Eight stirrer rods are rotated by pinions separated from a central master gear and, hence, their rotational speeds are all equal to each other. Stirrer vanes are provided under the central master gear to stirrer the oil bath and, hence, to uniformly maintain the temperature in the oil bath. The decoloring test can be conducted in any number of up to a maximum of eight.
Each test tube was filled with 50 g of rape oil that has been treated for removing an acid component, followed by the addition of the adsorbing agent in an amount of 0.5 g (1% with respect to the oil). The mixture was stirred well by the stirrer rod for decoloring testing. Each test tube was set to the above-mentioned decoloring tester maintained at 110'C and, after stirred for 20 minutes, was removed from the decoloring tester. Then, a mixture slurry of the oil and the adsorbing agent was filtrated to obtain the decolored oil. A white light ray transmission factor (relative value of when a transmission factor through distilled water is regarded to be 100%) through

the decolored oil was measured by using a photoelectric colorimeter, model 2C, manufactured by Hirama Rika Kenkyujo Co., and the obtained value was regarded to be decoloring performance of the adsorbing agent. The larger the value of transmission factor, the higher the decoloring performance of the adsorbing agent that was used. (11) Testing the developing performance•
A coated front appliecl with a sample was introduced into a desiccator (75%RH) containing a saturated saline solution, and was preserved in a dark place at room temperature (25°C). After about 24 hours have passed from the application, the to-be-stamped paper was taken out and was exposed in the room (constant temperature and constant humidity: a temperature of about 25°C and a humidity of about 60%RH) for 16 hours, and was developed. Developing was effected by superposing a coated back on which has been applied microcapsules containing a black leuco pigment on the coated front in a manner that the applied surface was faced thereto, rotating them with the application of pressure between two steel rolls, so that the microcapsules were nearly completely ground down. The color-forming (developing) density (hereinafter also simply referred to as density) one hour after the color formation (developing) was measured by using a densitometer (Fuji Densitometer, Model FSD-103, manufactured by Fuji Photo Film Co.)/ and the developing performance of the coated front was represented by the measured density. The higher the density, the higher the developing performance. (Example 1)
The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials, and were coarsely milled and kneaded into particles of 5 mm in diameter. 1500 Grams of the particles were introduced into a

treating vessel. An aqueous solution containing 30% by-weight of sulfuric acid prepared by adding 1727 g of water to 733 g of 97% by weight sulfuric acid, was circulated therein. The treating temperature was 90°C and the treating time was 5 hours. After the treatment with the acid, the acid-treated product was washed with water by circulating the washing water, and was then dried at 110°C, milled, and classified to obtain activated clay. Physical properties were measured to be as shown in Table 1, (Example 2)
The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1, Figs. 1 and 2 show X-ray diffraction images of the obtained activated clay and of the starting clay minerals, and Fig. 5 shows an X-ray diffraction image of the activated clay as measured in a state of being treated with an ethylene glycol. (Example 3)
The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. (Comparative Example 1)
The dioctahedral smectite clay minerals shown in
Table 1 were used as starting materials and were treated
with the acid in the same manner as in Example 1 to obtain
activated clay. Physical properties were measured to be
as shown in Table 1.
(Comparative Example 2)
The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated

with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1. Figs. 3 and 4 show X-ray diffraction images of the obtained activated clay and of the starting materials. (Comparative Example 3)
The dioctahedral smectite clay minerals shown in Table 1 were used as starting materials and were treated with the acid in the same manner as in Example 1 to obtain activated clay. Physical properties were measured to be as shown in Table 1.

The activated clay obtained by the treatment with an
acid in such a manner that the three-layer structure of
the dioctahedral smectite remains maintaining a
predetermined crystallite size according to the present
invention, exhibits high and sustained decoloring
performance despite it is used in a small amount. The
activated clay has a low oil retention and is suited for
use as an agent for refining oils or fats, exhibits a
sufficient color-forming density even when it is applied
in small amounts, permits the color of the image to fade
little, exhibits a low viscosity despite of its high solid
component concentration, and is useful as a color-forming
agent exhibiting excellent applicability.

We CLAIM:
1. A method of producing an activated clay by
treating dioctahedral smectite clay minerals with an acid,
wherein a crystallite size (R1) of the activated clay '
found from a half-value width of an X-ray diffraction peak
of an index of a plane (06) of the smectite is within a
range of from 10 to 30 nm, and a crystallite sectional
area (VI) of the activated clay defined by the following
formula (1),
VI = R1 X R2 --- (1)
wherein Rl denotes the above-mentioned crystallite
size (nm) , and R2 denotes a crystallite size (nm)
found from a half-value width of an X-ray diffraction
peak of an index of a plane (001) of the smectite as
measured in a state of being treated with an ethylene
glycol,
is from 60 to smaller than 150 nm2,
2. A method of producing activated clay according to claim 1, wherein the activated clay has a specific surface area of from 250 to 350 m2/g as measured by the BET method.
3. A method of producing activated clay according to claim 1 or 2, wherein the activated clay has an X-ray
diffraction peak over a spacing of from 17 to 19 angstroms
i
as measured in a state of being treated with an ethylene glycol,
4. A method of producing an activated clay by
treating, with an acid, dioctahedral smectite clay
minerals having a crystallite size (R10) found from a
half-value width of an X™ray diffraction peak of an index
of a plane (06) of the smectite of from 15 to 30 nm, and a
crystallite sectional area (VO) of the starting clay
minerals defined by the formula (2),
VO = R01 X R20 (2)

wherein R10 denotes the above-mentioned crystallite size (nm), and R20 denotes a crystallite size (nm) found from a half-value width of an X-ray diffraction peak of an index of a plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, of from 100 to 230 nm2, so that the crystallite size (R1) found from the half-value width of the X-ray diffractioh peak of the index of plane (06) of the smectite is from 10 to 30 nm and that the crystallite sectional area (VI) defined by the following formula (1),
VI = R1 X R2 --- (1) wherein Rl denotes the above-mentioned crystallite size (nm) , and R2 denotes a crystallite size (nm) found from a half-value width of the X-ray diffraction peak of the index of plane (001) of the smectite as measured in a state of being treated with an ethylene glycol, is from 60 to smaller than 150 nm2.
5, A decoloring agent for oils or fats, comprising
the activated clay obtained by the method of any one of
claims 1 to 4,
6. A color-forming agent for pressure-sensitive
papers, comprising the activated clay obtained by the
method of any one of claims 1 to 4.
7. A method of producing an activated clay by treating dioctahedral smectite clay minerals with an acid,
substantially as herein described with reference to the
3 .
accompanying drawings-

Documents:

279-mas-1998-abstract.pdf

279-mas-1998-claims filed.pdf

279-mas-1998-claims granted.pdf

279-mas-1998-correspondnece-others.pdf

279-mas-1998-correspondnece-po.pdf

279-mas-1998-description(complete) filed.pdf

279-mas-1998-description(complete) granted.pdf

279-mas-1998-drawings.pdf

279-mas-1998-form 1.pdf

279-mas-1998-form 26.pdf

279-mas-1998-form 5.pdf

279-mas-1998-other documents.pdf

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Patent Number

212507

Indian Patent Application Number

279/MAS/1998

PG Journal Number

07/2008

Publication Date

15-Feb-2008

Grant Date

03-Dec-2007

Date of Filing

11-Feb-1998

Name of Patentee

MIZUSAWA INDUSTRIAL CHEMICALS, LTD

Applicant Address

1-21 NIHONBASHI-MUROMACHI 4 CHOME, CHUO-KU, TOKYO,

Inventors:

#	Inventor's Name	Inventor's Address
1	MASAHIDE OGAWA	MIZUSAWA INDUSTRIAL CHEMICALS, LTD., 1-21, NIHONBASHI-MUROMACHI 4-CHOME, CHUO-KU, TOKYO,
2	MASASHI HATANO	MIZUSAWA INDUSTRIAL CHEMICALS, LTD., 1-21, NIHONBASHI-MUROMACHI 4-CHOME, CHUO-KU, TOKYO,
3	HITOSHI YAMAMOTO	MIZUSAWA INDUSTRIAL CHEMICALS, LTD., 1-21, NIHONBASHI-MUROMACHI 4-CHOME, CHUO-KU, TOKYO,

PCT International Classification Number

C01B 33/40

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	332098/97	1997-12-02	Japan