SE203057C1 - - Google Patents

Description

Inventors: J W Beamesderfer and H H Morris Priority as of August 7, 1957 (USA) The present invention relates to a process for treating clay, consisting mainly of aluminosilicate, for the recovery of phosphate-containing pigments and silica.

In the treatment of aluminosilicate-containing clay according to the present invention, the clay is subjected, e.g. kaolin clay from Georgia, calcination at a temperature in the range of 500-900 ° C, after which the calcined clay is treated with yarm, 20 to 50% by weight phosphoric acid or a warm, 20 to 50% mixture of phosphoric acid and sulfuric acid, whereby the phosphoric acid is added in an amount sufficient to form aluminum phosphate with the alumina content of the clay, and the phosphoric acid and the mixture of the phosphoric acid and the sulfuric acid, respectively, are supplied in sufficient excess to dissolve the dissolved aluminum salts, so that the acidic alumina solution formed is mainly separated from the oxide. permanent solid residue, which is recovered, and that the acidic aluminum salt solution is continued with an alkaline medal for precipitation of a water-insoluble pigment, consisting of aluminum phosphate or a compound aluminum phosphate sulphate.

The clay used in the present process is mainly made of aluminosilicate, e.g. kaolin coating clay. Sadana leror fOrekommer hi. a. in Georgia in North America and lima-11111a in addition to aluminosilcates usually stud amounts of iron and titanium compounds.

It has been found that a clay of the above-mentioned type, which is calcined at temperatures duplicate. at 12 m: 7; 12 i: 38; 22 f: 9 above temperature range, can be easily treated with dilute phosphoric acid or a mixture of diluted phosphoric acid and diluted sulfuric acid for extraction with alumina therefrom; and all the use of such dilute acids has advantages over the use of concentrated acids for such extraction. The diluted acids can be used with less corrosion problems than hot concentrated acids. An excess, but joke a large excess, of the diluted acid is required to 115.11a the dissolved aluminum salts in the solution, and the excess acid is recovered directly as part of the composite pigment product by the addition to the solution, containing the extracted aluminum, ay alkaline compounds , which form insoluble precipitates with the excess acid.

Extraction process en, dd. diluted phosphoric acid used only for the extraction of ammonia oxide from the calcining clay differs in significant respects from the process in which a mixture of diluted phosphoric and sulfuric acids was used; and the composite pigment produlites produced differ in their respective two different conditions. When dilute phosphoric acid is used alone, the resulting solution of aluminum phosphate with excess phosphoric acid after neutralization with the alkaline compound forms a composite phosphate precipitate. When a mixture of dilute phosphoric and sulfuric acids was used, the resulting solution of alumina in the mixed acids after neutralization with the alkaline compound was formed to form a uniform pigment, containing both insoluble phosphates and. sulfates.

In the first of the two methods, e.g. whereby hot diluted phosphoric acid is used to extract the alumina from the calcined clay, by treatment of the solution obtained, after loading cargo material with a lime slurry, a compound pigment will be precipitated, which essentially consists of a phosphate pigment and probably a mixture of aluminum phosphates, calcium aluminum phosphates and calcium phosphates. In the second of the two methods, in which a mixture of sylavic acid and phosphoric acid is used in the solid of the phosphoric acid alone, the solution obtained, after separating the undissolved material, can be similarly treated with a lime slurry to form a compound pigment. , as lane-hailer both phosphates and sulfates and sour are likely to be derived from a mixture of aluminum phosphates, calcium phosphates, calcium sulfate and. calcium-aluminum phosphate.

The use of hot dilute phosphoric acid solely for the extraction of the alumina from the clay has the advantage that a composite pigment can be produced which is essentially a mixed phosphate pigment. The use of a mixture of dilute phosphoric acid and dilute sulfuric acid together has the advantage that less of the more expensive phosphoric acid is required and that a precipitated composite pigment is produced which contains both phosphates and. sulfates.

An advantageous method of carrying out the process, i.e. a mixture of phosphoric acid and sulfuric acid, is used, or that any amount of dilute phosphoric acid which is equal to or approximately equal to the man: gd theoretically required to produce A1PO4 together with the aluminum wd content in the clay and that use sulfuric acid as the excess amount of acid required to carry out the process. Since the lasing obtained by any respiration of this mixture of acids is neutralized, e.g. with lime for the formation of a composite pigment, the aluminum and phosphoric acid will be present in approximately the proportions of aluminum phosphate and the proportions of kaleiuna and, sulfuric acid In the approximate proportions of gypsum, although more complex composite products may also be present.

The alkalis used to neutralize the excess acid of the acidic solution to precipitate the compound undiluted pigment are alkaline compounds which form insoluble precipitates, such as calcium, barium or magnesium oxides or hydroxides, etc.

The silicic acid feed residue, which remains after the extraction of the alumina from the calcining clay by the treatment with dilute acid, is itself a valuable product. It consists essentially of silicic acid with a liquid-like structure similar to that of kaolin clay, with a hay surface area, a particle size distribution, similar to that of starting clay and of an acidic nature. Small amounts of undissolved clay or partially dissolved clay or alumina, which are high donors, may be present in this silicic acid product. The properties of this acidic product make it a volatile material for use as a catalyst or catalyst-borer oc-13. Above for anyandning shsom pale words. due to the acidic nature of this silicic acid product, it can anyandas e.g. such as an acidic bleaching soil, bleaching of oils or other products in the stable for bleaching clays or other bleaching soils. Its acidic properties Ora den Oven to a valuable catalyst are used in dot-type catalytic cracking processes, the catalyst being in suspension with the oil being cracked.

This acidic silicic acid product can also be used to advantage as a filling material for addition to pulp, e.g. in m, the ash mill, drawing part of the acidic properties for neutralization of the alkaline compounds present in the pulp, and for introducing a filling pigment into the paper.

The aura of silicic acid product, which is produced yid! procedure, Or ph due to its acidic nature joke appropriate to use sasom Coating pigment. But embarrass to treat the acidic silicic acid product with a base, e.g. aluminum hydroxide or sodium hydroxide, for neutralizing the acid, or by removing the salt obtained by washing, a silicic acid product is produced of somewhat different properties and with an alkaline surface, rather on an acidic surface, which can suitably be used as a coating pigment for paper.

The acidic silica product, which is directly produced as a residue from the dilute acid extraction of the calcined clay, still contains some joke extracted alumina and some impurities in the original clay. Some of the titanium compounds, which flames present in a small amount in the original clay, resist the extraction by the acid removed and remain in the silica residue. In the case of titanium or other compounds, such as iron compounds, the soluble in the diluted acid, which is allandes for the extraction of the alumina, may also be deposited. But titanium and other compounds, which are not properly extracted, remain in the silicic acid product and reduce its whiteness as pigment.

It has now been found that it. The by-product silicic acid thus produced can suitably be further treated with hot, sulfuric acid and transferred to a refined silicic acid product of high whiteness. The treatment of this silicic acid product with ordinary sulfuric acid results in the removal of alumina, which it contains, and compounds such as titanium compounds, and the formation of a refined ethylene acid product, which maintains a plate-like structure similar to that of kaolin clay with a high surface area. , which is similar to that of the starting clay, and with acidic properties.

The refined silicic acid product, which is prepared in the further treatment of the first silicic acid product with its sulfuric acid, itself constitutes a valuable product for use as a cur catalyst, e.g. in catalytic processes for cracking oil, or as bleaching earth or as catalyst catalysts. Delta acid pigments can also be used as a filler for paper. The use is similar to that of the above-mentioned lake refined acidic silicic acid product, but has the advantage that it consists of a refined silicic acid product and a pigment of high whiteness.

By neutralizing this refined acidic silicic acid product with a hash, e.g. ammonium hydroxide or sodium hydroxide, it can be transferred to an excellent coating pigment for paper of good whiteness. Upon removal of the salts formed by neutralization by washing, the silicic acid pigment leaves an alkaline surface as opposed to the acidic surface of the acidic silicic acid product which is first prepared and neutralized.

The acidic silica pigments, including both those which remain after the extraction of the alumina from the clay with dilute acids and those which are produced by the further treatment with concentrated sulfuric acid of this pigment, constitute acidic silicic acid products which still retain their acidic properties even after repeated washing. When this acidic surface is neutralized with alkali, the free silicic acid product loses its acidic properties and when the salts obtained in the neutralization are washed away, the obtained silicic acid product has an alkaline surface in the sense that it apparently retains small amounts of the alkali used for the neutralization. , adsorbed, which are even retained after repeated washing. The. The neutralized product is obtained, in particular the concentrated sulfuric acid obtained after the treatment, from a highly purified product of high whiteness and a valuable product for use as a coating pigment on paper.

The strength of the diluted phosphoric acid, or the diluted phosphoric and sulfuric acids used in the extraction of the alumina from the calcined clay, may vary somewhat. between 20% and approx. %, preferably about 25% to 30%. An advantage of using dilute acids for the extraction of clay Or is that the resulting acidic weld, containing the dissolved aluminum, can be easily separated from the silicic acid residue; and the silicic acid residue can then be further treated to rid it of adhering valuable aluminum salts.

The ExtraMion of Clay Tried the diluted acid is advantageously carried out at elevated temperature and using an apparatus which is resistant to impact. of the -diluted acid at elevated temperature, e.g. a glass-lined reactor.

The invention will now be described by the following examples, which illustrate the same, but it should be noted that the invention is not limited thereto. The parts feed to the weight.

Example 1. 200 parts kaolin clay Iran Georgia, previously calcined 1 hour. at 788 ° C, heated for 1 hour. at 95-105 ° C with a dilute acid mixture prepared by diluting 210 parts of 8% phosphoric acid and 80 parts of 98% sulfuric acid with 860 parts of water.

At the end of the reaction, the reaction mixture was cooled to 60 ° C and the undissolved residue was removed by filtration. The residue was washed with 600 parts of a 5% phosphorus acid solution and filtered anyo. After drying Overnight. at 160 ° C 129.6 parts of residue were obtained.

The washings were added to the original filtrate and the combined filtrate was then added with vigorous stirring to a slurry containing 300 parts of calcium oxide in 1500 parts of water. This addition of the acid solution to the lime slurry, during vigorous mining, maintains an excess of lime and a successive reaction of the acid solution. with the excess lime saint Or a suitable method of effecting the neutralization and precipitation of the compound pigment. The final pH of the mixture was 6.7.

The resulting white pigment product was collected by filtration and washed by resuspension in water and filtration: the product was dried at about 100 ° C and then pulverized using a 4-speed high-speed mill (Micropowder). 510 parts by weight of the product are obtained.

The compound pigment produced had a whiteness according to G. E. (General Electric) of about 10 to 14 points more than for high grade clay from Georgia. The pigment is a valuable pigment for use in coating pepper and its use instead of Georgia coating clays' Mar G. E. whiteness of the coated sheet material is usually of 10 G. E. whiteness units. Its use also provides improved printing properties as well as a faster curing time for the ink.

The pigment constitutes gym a valuable pigment for use as a filler for cardboard, whereby an improvement of e.g. about 5-6 units G. E. whiteness and an increase in the opacity of about 23 units beyond what is obtained for a sheet, filled with conventional filling clay.

When used in Coating or Filling compositions, the composite pigment in the above example gives a Coating Mixture of substantially increased viscosity compared to the pigment prepared according to Example 3 using only dilute phosphoric acid.

To illustrate the advantages of the pigment over the high grade Georgia Coating Clay for coating paper, the coating provided paper with the clay, with the pigment of the above example and with a mixture of 0% Georgia Coating Clay and 10% pigment coated sheets with a GE coating. whiteness, in the case of the clay of the coated paper, of 79.2 for the paper coated with the mixture of 90% clay and 10% of the aforementioned pigments, a GE whiteness of 81.5 and a sheet coated with the above-mentioned pigments only of 88.8.

Typical samples of the pigment prepared according to the above example showed, after powder coating, a particle size distribution (determined by electron microscope) of 18% between 1 and 2 microns, 81% less than 1 micron and 1% between 2 and 5 microns. The specific gravity of the pigment was about 2.81; the specific surface area was about 250 m2 / g and the slip loss was about 15%.

The composite pigment in the above-mentioned examples is made of a mixed pigment, containing both aluminum and calcium as well as simple or complex phosphates and sulphates. Smaller amounts of other materials are present such as fOrorenin.gar, e.g. iron phosphates, as small amounts of jam are extracted together with the aluminin, colloidal silicic acid or silicic acids or phosphoric silicic acids, which can act as protective colloids due to the precipitation of a pigment with a fine particle size, etc.

Example 2. The extraction of the calcined clay was challenged as in Example 1 and the resulting solution was removed from the residue as described in the same example.

To the combined filtrates, prepared according to 1, were added 405 parts of barium hydroxide (B.a (OH) 2. H 2 O) in 1400 parts of water to install pH pH 6.0. The resulting precipitated product, recovered by filtration, was washed by resuspension and filtration, dried at about 80 ° C and micropowdered to saint gay 668 parts by weight of dried product, which in this case had a glazing loss of 9%.

The product prepared in this case is made up of a phosphate-sulphate pigment which differs from the pigment of Example 1 in that it contains aluminum and barium in the form of simple or complex phosphates or sulphates.

Example 3. 200 parts kaolin clay from Georgia, previously calcined 1 hour. at 788 ° C, for 1 hour. at. 95-100 ° C with dilute phosphoric acid, prepared by mixing 300 parts of 85% phosphoric acid and 860 parts of water.

The reaction mixture was cooled to about 50 ° C and the alosta residue was removed by filtration. The residue was washed with 600 parts of 5% phosphoric acid solution and filtered anyo. 159.8 parts remained after drying overnight at 100-110 ° C.

The washings were added to the original filtrate and the branched filtrates were then added with vigorous stirring to a lime slurry containing 300 parts of calcium oxide in 1500 parts of water. The final pH of the material was about 6.7.

The white product thus prepared was collected by filtration and washed once by resuspension in water and filtration. The product was dried at 100 ° C and then pulverized using a high-speed impact mill (micro-pulverizer).

The product produced had a G. E. whiteness of 97100, which is about 10-14 units of MDT On for a Georgia grade high grade clay. By the use of this pigment in the place of Georgia clay coating clay, in an increase in whiteness, a coated sheet having about 5-10 G. E. whiteness units is obtained and the printing properties of the sheet are somewhat improved, e.g. the curing time of the ink.

The viscosity of the coating mixture prepared with the above-mentioned pigment will be approximately the same or in some cases lower On for a coating mixture, containing only kaolin clay. In addition, when used in a slurry with a clay, a & fling ay of the G.E. yity of the coated sheet is obtained. Sheets, coated with the above mentioned pigments do not become dark after calendering.

To illustrate the advantages of the above-mentioned pigments, sheets similarly coated in one case with a high-grade Georgia-type coating clay and in the other file with the non-pigmented pigment showed a GE whiteness of the clay-coated sheet of 78.8 and for the sheet, coated with the above-mentioned pigment, of 83.5. After calendering, the G. E. yity of the clay-coated sheet was 77.1 and for the sheet coated with the aforementioned pigment 83.2. The coating viscosity of a coating composition yid 35% solids content was lower for the above pigment than the clay.

The composite pigment in this example is a complex phosphate pigment, containing aluminum and calcium as simple or complex phosphates, and, in this case, as in Example 1, minor amounts of other materials, such as ferrous phosphates, colloidal silicic acid or silicic acids or phosphorous silicas. .

Example 4. Calcined clay was treated with hot dilute phosphoric acid as described in Example 3, and the resulting solution was separated from the residue by filtration and the residue was decomposed as described in Example 1.

To the combined filtrates was added with vigorous stirring a bleach containing 300 parts of barium hydroxide (Ba (OH) 2 • H 2 O) in 10,000 parts of water to adjust the pH to 6.1. The composite precipitate thus formed was collected by filtration, washed by resuspension and the filtrate was dried at 80 ° C to give 479 parts by weight of dried product. This product was micropolyzed. It had a glazing loss of 9.15%. It had a significantly lower coating viscosity than the coating clay and had a slightly increased density, as it was different for coating paper.

The composite product in this case consisted of a composite phosphate pigment, containing both aluminum and barium as well as simple or complex phosphates.

The silicic acid residue which remains after the extraction with dilute phosphoric and sulfuric acids, as described in Example 1, or after extraction with the calcined clay with dilute phosphoric acid, as described in Example 3, is essentially a silicic acid, containing some unreacted reaction clay and some aluminum phosphates, or phosphates and sulphates, which are absorbed or mechanically bound phleric or silicic acid, together with some phosphoric acid or phosphoric or sulfuric acids and some of the sparingly occurring impurities present in present in the calcined clays, such as small amounts of titanium ores or compounds.

This silicic acid residue consists of an acidic material and has a large surface area and a plate-like structure (microscopic) and a particle size distribution similar to that of the treated clay. Its whiteness resembles or is somewhat better than the clay that anyandes as starting material.

This silicic acid residue is of sufficient purity for it to be able to be used for various purposes, e.g. as acid catalyst or as catalyst catalyst or as bleached words, etc. Some of the impurities in the calcined clay, in which they are soluble in and extracted by the treatment with dilute acid, are removed by this treatment. But the pollutants, e.g. certain titanium ores or titanium-iron compounds, which amo. insoluble in dilute acid, kyarbliya in the acidic silica product.

This acidic residue is transferred, after neutralization with an alkali, such as ammonium hydroxide or sodium hydroxide, and washing to remove any soluble salts formed by neutralization, to an alkaline silicic acid residue rued adsorbed alkali and forming a volatile material for use e.g. . Yid Oyerdragning ay papper.

The insoluble silica residue, which is prepared and separated as described in Example 1 and remains after the extraction of the aluminum with a mixture of phosphoric acid and sulfuric acid, was further treated to prepare an improved silica product by the following treatment: 480 parts of silica stearate to 1359 parts of concentrated sulfuric acid and the mixture was heated to boiling, about 250 ° C, kept at this temperature for 1/2 hour. The product obtained was then allowed to cool and spade, then by successive and careful addition of 3000 parts of water. The remaining insoluble residue consisted of a very white product and was removed from the dilute acidic solution by filtration, and the product thus removed was washed by redispersion in water and filtered any. The yield was about 90% by weight, calculated on the basis of the treated silicic acid product.

This treatment of the slightly impure silicic acid product with concentrated sulfuric acid results in the imposition of impurities and in particular the impurities which reduce the whiteness of the product, such as titanium compounds or titanium-iron compounds, with the result that a purified silica pigment is obtained with high whiteness. surface area, a flat structure and with a particle size distribution, similar to that of the silicic acid residue before the treatment. And this improved silicic acid product also showed an acidic surface, which was maintained even after repeated washing with water. In addition, it exhibited a very high content of impurities and is substantially free of impurities which can be extracted from the concentrated sulfuric acid.

The thratted and purified silicic acid products, which are prepared. pai this example be-. written, had a G. E. whiteness value Mom ranged from 93 to 100, zero values ranging from 40 to 127 mg, a specific resistance Mom ranged from 34,000 to 39,000 ohms and pH value Mart on the acidic side (pH 1-3). Electron micrographs showed that the product was composed of flat, plate-like particles, which could not be distinguished from kaolinite by 8gat. The particle size distribution is similar to that of a high grade clay. The surface area varied from Indian 250 and 300 m2 / g.

This purified acidic silica pigment constitutes a valuable acid catalyst for use e.g. in the cracking of petroleum oils, for use as catalyst catalysts and for use as bleaching earth. It also constitutes a valuable pigment for use as a filler in paper, whereby the color of the paper is improved and the acid of the pigment is intended to neutralize a part of the alkali in the pulp. By neutralizing this acidic silicic acid product with an alkali such as a solution of ammonium hydroxide or sodium hydroxide and by washing the neutralized product to remove soluble salts, a highly refined alkaline silicic acid catalyst is obtained with an alkaline surface instead of an acidic surface. Such a neutralized product constitutes a valuable white pigment for use in coating paper, either alone or in admixture with coating clays, imparting an improved whiteness to the coated paper compared to the paper coated with the coating clay of any kind.

The process, according to the above example, can be varied somewhat with respect to the amount of acid used or the temperature used, e.g. concentrated sulfuric acid at a temperature of 200 ° -300 ° C was used for varying periods of time up to about 1 hour. and the remaining uncharged silica residue Iran acid is removed, containing the soluble materials extracted from the residue by the treatment with concentrated sulfuric acid. Thus, since the slightly impure silicic acid residue from the dilute acid extraction of Examples 1 or 3 contains up to 3% -7% alumina, this residual alumina is substantially completely removed by the concentrated sulfuric acid treatment to form a purified silica product substantially free of aluminum. The aluminum, which salunda Mists and is present in the concentrated acid, can be recovered as alum by conventional methods.

It is thus apparent that the present invention provides improved processes for treating clay for the preparation of valuable phosphate composite pigments or valuable phosphate-sulphate composite pigments and also for the preparation of a valuable silicic acid residue. The process consists of one in which the clay is first calcined at a controlled temperature and then treated with hot dilute phosphoric acid or with a mixture of hot diluted phosphoric and sulfuric acid to extract the alumina from the calcined clay without leaving an acidic silicic acid residue. The diluted acidic solution, containing the dissolved aluminum, is neutralized by treatment with an alkaline compound of a metal which forms an insoluble formation, e.g. lime or barium hydroxide, for the formation of aluminum-calcium or aluminum-barium composite pigments. And these pigments differ depending on the different methods of extraction, the pigments obtained when dilute phosphoric acid being used for extracting the alumina being composed of phosphate pigments, while those obtained when a mixture of dilute phosphoric acid and sulfuric acid are used. for extraction with the alumina, form phosphate-sulphate pigments.

It can also be seen that the extraction with dilute acid in the alumina from the calcined clay gives a silicic acid residue of acidic properties, free from impurities which are soluble in the dilute acid, which is used for the extraction of the alumina, but which still contains impurities. as aro, insoluble in the dilute acid but soluble in concentrated sulfuric acid. A further treatment of this silicic acid residue, which is first prepared, can, by further treatment with concentrated sulfuric acid, transfer it to an improved white silica pigment in a highly refined form Deli, with valuable properties such as pigments, e.g. a catalyst or catalyst catalyst, etc. and co by neutralization can be transferred to a neutral or alkaline silicic acid product, which is valuable as a pigment, e.g. for coating paper.

Claims (1)

Patent claim: Process for the treatment of clay consisting mainly of aluminosilicate, for the purpose of recovering phosphate-containing pigments and silica, characterized in that a clay calcined at 500900 ° C is treated with hot, 20 to 50% by weight phosphoric acid or a hot, to a 50% by weight mixture of phosphoric acid and sulfuric acid, the phosphoric acid being supplied in at least as large an amount as is necessary to pour aluminum phosphate with the alumina content of the clay, and the phosphoric acid and the mixture of the phosphoric acid and the sulfuric acid, respectively. is dissolved in solution, that the acidic aluminum salt solution formed is separated from the solid residue consisting mainly of silica, which is recovered, and that the acidic aluminum salt solution is continued with an alkaline agent to precipitate a water-insoluble pigment, consisting of aluminum phosphate or a composite aluminum phosphate . Request publications: Patents treat Great Britain 641 698; Germany 391 297; USA 2 58.8 867.