NO122012B - - Google Patents

Description

Synthetic silicate with a structure that

resembles the structure of clay minerals of

smectite type, as well as method for

production of such a silicate.

Most clay minerals, as they occur in nature,

are in an impure state and the complete purification of some of them is difficult and expensive and in some cases impossible, furthermore there is the case where the supply of a clay mineral of a certain chemical composition, either in a pure or impure state, is insufficient. Thus, it is desirable to be able to produce synthetic clay-like minerals in a substantially pure form.

It is of particular interest that one can be able to

to produce synthetic, clay-like minerals that have rheological properties similar to or better than hectorite, as natural hectorite has valuable properties, but large quantities of hectorite are not obtainable. Natural hectorite is always mixed with impurities, which are uncommonly difficult to remove.

Only two methods of synthetic preparation of hectorite-type clay minerals capable of yielding greater than a few milligrams of product under conditions feasible on a commercial scale are known. A method is described by Granquist and Pollack in "Clays and Clay Minerals", Nat. Acad. Soi., Nati. Res. Council Publ., 8, pp. 150-169 (1960) and the other is described by Strese and Hofmann in "Z. Anorg. Chem.", 247, pp. 65-95 (1941). It is not possible with any of these methods to obtain products that are completely pure. thus the product according to Strese and Hofmann's method contains a high proportion of amorphous silicic acid or silicate and some crystalline silicic acid, or quartz. The removal of the amorphous substance is impossible, and a product obtained by this method necessarily contains such a large amount of impurities that the rheological properties of aqueous dispersions of the product are adversely affected. The product obtained by the process described by Granquist and Pollack contains some magnesium hydroxide. The removal of this is difficult and it is probably impossible to remove everything. It is known that the presence of even quite small amounts of magnesium hydroxide interferes with the rheological properties of aqueous dispersions of clay minerals.

Many clay-like minerals contain fluoride, and although they are purified ever so often, there is always a risk that some fluoride may be extracted from the minerals in certain applications. This is a major disadvantage in e.g. pharmaceutical and cosmetic preparations. The invention is of particular value, as it quickly allows the production of fluoride-free, clay-like minerals and also fluoride-free swelling clays.

The synthetic swelling clays according to the invention have swelling properties which are even greater than those according to the applicant's previous invention. This is indeed surprising, since it was critical in the method of the prior application to use fluoride-containing materials above a certain minimum level. However, a method has now been discovered where fluorine-containing materials are not necessary, where the clay products have excellent properties and can of course be used in the cosmetic as well as in the pharmaceutical field.

According to the invention, a synthetic silicate is provided with a structure similar to the structure of clay minerals of the smectite type, suitable for use as a gelatinizing agent, characterized in that the general structural formula is where M is a sodium, a lithium or an equivalent of an organic cation,

the value of a, b and c is such that either

and b+c ( 2; the numerical value of (a+b+c-6) <»2;

or a<6; b=0; + c 4. 2 ;

and the numerical value of (a+c-6) K 2

and the cation exchange capacity is approx. 50 to 120 mek/100 g, while the Bingham Yield Value is between 50 and 250 dyne/cm 2 , measured as a 2% dispersion in tap water.

Furthermore, the invention provides a method for producing a silicate as indicated above. This occurs by simultaneous precipitation from an aqueous solution of a sodium compound. The pH value of this solution is kept in the range 8-12.5. Incidentally, reference is made to requirement 3.

The method is of particular value because it is now possible to produce a new group of synthetic, clay-like minerals that have X-ray spectra similar to those of natural hectorites. However, the aqueous dispersions of these new clay-like minerals have rheological properties that are much better than those of natural clay species with similar X-ray spectra.

An important property for a usable swelling clay is characterized by the Bingham Yield Value for an aqueous dispersion of the clay. The name Bingham Yield Value (also known as Bingham Yield Stress, as these names are alternatives for exactly the same property) is referred to in standard works on rheology, e.g. "Rheology Theory and Applications", ed. F. R. Eirich (Acad. Press), vol. 1 (1956), p. 658; "Colloidal Dispersions", L. K. Fischer (N. Y. Bureau of Standards), 2nd ed., 1953, pp. 150-170 and "The Chemistry and Physics of Clays and Other Ceramic Materials", 3rd ed., p. 463, A. B. Searle and R. W. Grimshaw. The term can be defined as the shear stress that must be exceeded before the degree of shear shows a linear relationship to the shear stress, the former being proportional to the difference between the shear stress and the Bingham Yield Value.

The Bingham Yield Value is determined by first creating a flow curve with the shear stress as a function of the shear rate, and then extrapolating the part of the curve that is a straight line. The cutoff is the Bingham Yield Value. It can be conveniently determined

on any viscometer with a measuring range for shear rates and shear stresses. In the experimental work reported here, a Fann rotational viscosities was used in the manner described in the book "Oil Well Drilling Technology" by A.W. McCray and F.W. Cole, Union of Oklahoma Press, pages 94-96

(1958). When measuring on this instrument, the results are labeled Ibs/100 sq. ft and is converted to dyne/cm 2 by o multiplying by 4.8.

The relationship between a, b and c in the structural formula for the silicate according to the invention, which is stated above, is a "shorthand" way of indicating that in all cases the number of magnesium ions per unit crystal cell less than 6, and the total number of octahedral ions does not differ from 6 by more than 2. If lithium is present, the total number of hydrogen ions, including those normally assumed to be present as hydroxyl, is greater than or equal to 4, and the total number of octahedral ions other than magnesium is less than 2. If lithium is not present, the total number of hydrogen ions must not differ from 4 by more than 2.

The figures from Bingham Yield Value (BYV) listed above refer to values in tap water. However, it is the case that the Bingham Yield Value for synthetic clay dispersions largely depends on the concentration and type of electrolytes present in the water. The general one is that adding electrolyte to a dispersion of synthetic clay in distilled water or tap water first causes the BYV to rise, and then to fall. The maximum value, which is achieved at optimum electrolyte concentration, is several times as high as that prevailing in dispersions in water from the local water supply network. This effect will be illustrated in the following.

In addition to being free of fluorides, the new silicates according to the invention are substantially clean, as they are substantially free of magnesium hydroxide, amorphous silicic acid or silicates and other contaminants. By "essentially clean" is meant that the clay species are either completely free of impurities or that they only contain such small amounts that the rheological properties of aqueous dispersions of the materials are not seriously affected, as the preferred materials with a structural formula as stated above still have a BYV , as a 2% dispersion in water, of at least 40 or 50, and preferably of o at least 75 dyne/cm 2. The silicates may contain a maximum of 5 to 10 percent by weight of impurities, but the impurities will always be of the nature and amount of them be such that X-ray analysis does not reveal their presence. Thus, any contaminants that are present in larger amounts than traces will be amorphous.

In the information here, BYV always means the value that is

reached on a dispersion prepared by dispersing 2 g of the material in 100 ml of hot water with subsequent cooling.

BYV, which is at least 40 or 50 and usually on

at least 75 dyn/cm, corresponding to values of less than approx. 15 dyne/cm for products produced by Granquist and Pollack's method, even when the magnesium hydroxide originally present in the product is visibly completely removed, and based on the probability of X-ray analysis, as well as for products produced by Strese and Hofmann's method , and for naturally occurring hectorite. The crystal structure of the new materials, as determined by X-ray analysis, is similar to the structure of natural hectorite, and it is not possible to identify, by readily available experimental methods, exactly which properties in the microstructure and chemical composition of the new materials causes such a high Bingham Yield Value when dispersed in water. However, by choosing the riWi-

provide ratios between the components of the solution from which the clay species are precipitated together, and thus the correct ratios between the atoms in the materials, and the correct conditions for the method, synthetic materials with a Bingham Yield Value that is even higher than 75 dyne/cm 2 can thus be easily obtained o synthetic materials with a Bingham Yield Value higher than 100, often higher than 150 and some

times higher than 250 dyne/cm 2 even, especially in the materials containing lithium. These values apply to 2% dispersion

into tap water. The values can be increased as discussed above. The preferred new clay-like minerals have a very high specific surface area. Usually it is at least 100 m 2 /g and often 350 m 2 /g, or more, although it should not be too high. This corresponds to a value of approx. 70 m 2/g for natural hectorite.

When studying the structural formula given above

for the preferred new synthetic materials, it will be seen that it has been calculated that the number of hydrogen atoms can be more or less

re than the 4 required for the 4 hydroxyl groups assumed to be present in a fluoride-free hectorite molecule according to the traditional

notion of the smectite structure. The likelihood of this possibility is based on the fact that many of the preferred materials have a cation exchange capacity that was not compatible with the conventional formula, although the formula is applicable to natural hectorite or the synthetic hectorites produced by the two known processes discussed above. The cation exchange capacity for the preferred materials according to the invention can e.g. be 64 meq/100 g and the chemical analytical equivalent to formula

SiQMg5 397Hx.024 NaQ 4Q.j where x cannot immediately be determined by analysis. The cation exchange capacity can only be brought into line with the composition if one assumes that x = 4.723, i.e.

c = 0.723 according to the formula given above. The conventional formula would require a cation exchange capacity of 2 (6 - 5.397) - 1.206 equivalents per unit cell, or approx. 160

meq. per 100 g, which is much higher than the experimentally measured value. Generally, the new materials can have cation exchange capacities in the range of 40 or 50 to 120 meq/100 g, normally 60 to 90, and this is highly desirable.

A high proportion of magnesium, lithium and silicon ions, which are present in the solution from which the materials are precipitated together, are included in the formed materials and consequently an adjustment of the relative proportions of the amounts of these ions will result in variations in the product's empirical formula. The proportion that is retained is even higher than in the method according to the applicant's previous invention, and thus represents an even more economical use of materials.

For the production of the preferred fluoride-free materials with a satisfactory Bingham Yield Value and which contain lithium, it is preferred that the amounts in the solution are such that per

8 silicon atoms are from 0.4 or 0.6 to 1.45 lithium atoms, and

preferably from 0/5 to 1.12. Bingham Yield Value greater than 100 can be achieved in this way. BYV greater than 150 can be achieved using solutions containing from 0.7 to 1.45 lithium atoms per 8 silicon atoms. In the final product, it is preferred that the number of lithium atoms per unit cell (i.e. 8 silicon atoms) is approx. 0.6 to 1.05.

When the solution and the material to be precipitated simultaneously from it are also free of lithium, it is preferred that there are fewer than 6 magnesium atoms per 8 silicon atoms in the solution and the product. For satisfactory BYV, the magnesium deficit is preferably at least 0.1 atom per unit cell, but is usually no more than approx. 1.5 atoms per unit cell. Preferably, the deficit is greater than approx. 0.2, and the most satisfactory results are obtained with a magnesium deficit of from approx. 0.5 to 1 atom per unit cell with the preferred deficit of approx. 0.7. So, when b = 0, a is preferably approx. 5.3.

Any magnesium and lithium salt can be used to introduce these cations into the solution, e.g. magnesium chloride, magnesium sulphate, magnesium nitrate and lithium chloride, sulphate and nitrate. The reaction solution must be kept alkaline throughout the simultaneous precipitation and must thus contain sufficient alkali to neutralize anions that are released during the precipitation, e.g. to neutralize sulfate ions released from magnesium sulfate. One therefore prefers to add more than the stoichiometric amount of alkali which is necessary to neutralize the anions released during the reaction and also the anion in the clay molecule. An amount that lies between the stoichiometric amount and approx. 3 times this amount, preferably 1 1/2 times this amount.

The simultaneous precipitation is preferably induced by mixing a hot solution containing the magnesium salt, and a lithium salt to be included, with a cold, silicon-containing solution. This cold solution usually also contains the alkali. The silicon can be introduced in the form of any suitable silicate. The addition of one solution to the other can be carried out quickly or slowly, but it was found satisfactory to carry out the addition over a period of approx. 20 minutes.

The properties of the material obtained do not seem to vary much with the concentration of the reaction partners, nor with the concentration of the precipitation product. However, for experimental reasons it is usually preferred to choose the concentrations of the reaction partners so that the concentration of the precipitation product is not higher than approx. 5 percent by weight. Above this value, one may experience difficulties when filtering and washing the precipitation product.

After the precipitate has formed, it can be boiled, before being heated under pressure, to facilitate subsequent processing of the precipitate. This particularly simplifies washing and filtering the precipitation product. Boiling periods of approx. 4 hours is found to be satisfactory.

The heating under pressure, which is carried out in an autoclave, should preferably take place at a pressure of at least 7 kg/cm<2> (170°c) if lithium is present, with suitable pressures from approx. 10 to 50 kg/ cm<2> (186 to 263°C). Pressures from 50 to 70 kg/cm<2> are advantageous when, as will be referred to hereafter, an organic derivative is to be prepared afterwards. However, when this is not the case, good results can be obtained with pressures of from 14 to 42 kg/cm 2 (198 to 254°C). A suitable pressure has been found to be approx. 28 kg/cm<2> (231°C). When lithium is absent, the lower pressures discussed are not entirely satisfactory, and usually the pressure must be at least 17 kg/cm<2> (207°C). A suitable pressure range when lithium is not present,

is 35 tii 70 kg/cm 2 , with a preferred value of ■> approx. 49. However, in all cases there is no critical upper limit, and pressures held up to 210 kg/cm 2 may well prove to be suitable in certain cases as an aid to reducing the time required for the process. This can enable a continuous process, feeding and draining through suitably constructed and arranged valves.

The autoclaving results in crystallization of the clay-like mineral, and if continued too long, there will be too much crystallization, and the rheological properties of aqueous dispersions of the product will be adversely affected. However, the autoclaving should, especially when carried out at 28 kg/cm 2 , continue for at least 1 hour, but usually 8 hours is long enough. A preferred time period is approx. 4 hours. When, on the other hand, as will be referred to in more detail later, an organic derivative is to be prepared afterwards, it may sometimes be preferred to continue the autoclaving for as much as 24 hours.

The product from the autoclaving is usually a suspension. The solid substance is usually separated by filtration or centrifugation, and washed, e.g. with water, to remove soluble by-products, e.g. sodium sulfate, from the simultaneous precipitation. This wet product can then either be used, e.g. in chemical reaction, as it is, or it can be dried. The drying can e.g. take place by heating to 11-0°C for 16 hours.

In the following examples in accordance with the invention, examples 1 and 2 show the production of new materials according to the invention which have an X-ray spectrum similar to the spectrum for hectorite, and which are free of fluoride, but contain lithium. Example 2 also illustrates the variation in Bingham Yield Value with the increase in electrolyte. Example 3 shows that when you increase the lithium content to 1.75 atoms per unit crystal, the Bingham Yield value decreases, and Example 4 shows that lithium contents greater than 2 give no appreciable Bingham Yield value. Examples 5 and 6 are examples of the production of a material that is free of both lithium and fluorine. Example 7 illustrates a process with very high pressure and short duration.

In all the examples, the cation exchange capacity of the products was measured by the method developed by R. G. Mackenzie, in J. Colloid Sei., 6_, 216 (1951).

Example 1

130.7 g of magnesium sulfate heptahydrate and 2.97 g of lithium chloride were dissolved in 900 ml of water in a flask of approx. 5 liter capacity and heated to the boiling point. In a separate vessel, 38.6 g of sodium carbonate were dissolved in 900 ml of water, and 166 g of sodium silicate solution containing 29 g of SiO 2 and 8.8 g of Na 2 O per 100 g, was added. The second solution was added to the first, after a white precipitate had formed. The mixture was brought to a boil with reflux cooling under effective stirring. After 2 hours of boiling, the contents of the flask were transferred to an autoclave fitted with a stirrer, heated for 1/2 - 1 hour to 250°C, with a gauge pressure of

39.5 kg/cm 2 and kept at this temperature for 4 hours with continuous stirring. The mixture was then allowed to cool to below 100°C, was emptied from the autoclave, and the solids present were filtered off and washed with tap water by filtration, until the filtrate showed no appreciable sulfate reaction when tested with barium chloride solution. The filter cake was dried in a drying cabinet at 110°C

for 16 hours and was ground to powder.

For this product, M = Na<+>, a = 5.29, b = 0.47, c = 0.49.

By dispersing 2 g of the powder in 100 ml of warm tap water (containing 39 ppm Ca<++>and 4 ppm Mg<++>) it was found that a white, translucent gel had formed after cooling. Using a rotational viscometer (Fann VG model), the following rheological parameters were measured on this dispersion:

Plastic viscosity 13 centipoise

Bingham Yield Value 72 dyne/cm<o>

The cation exchange capacity was found to be 0.59 meq/g. X-ray analysis using the powder diffraction method showed that the structure corresponded to the structure of natural hectorite and that no other crystalline material could be detected. Differential thermoanalysis gave a pattern similar to that of natural hectorite, having only endothermic peaks in the range 600-800°C.

Example 2

The same procedure was followed as in example 1, except that the amount of certain components was changed. thus 122.0 g of magnesium sulfate hexahydrate and 4.45 g of lithium chloride were used.

For this product M = Na+, a = 5.03, b = 0.63, c = 0.78.

The cation exchange capacity was 0.67 meq/g. The X-ray analysis showed the same pattern as for hectorite and the differential thermal analysis in the range 600-800°C showed only endothermic peaks.

A dispersion of 2 g of the product in 100 ml of warm tap water gave, after cooling, an almost clear thixotropic gel which gave a plastic viscosity of 18 centipoise and a BYV of o 210 dyne/cm 2 .

This dispersion BYV was measured again after the addition of different amounts of sodium sulphate in the form of a concentrated solution. The following results were obtained:

Example 3

The same procedure as in Example 1 was again followed, but the amount of magnesium sulfate heptahydrate used was 105.0 g and of lithium chloride 7.42 g.

For this product, M = Na+, a = 4.63,

b = 0.82, c = 1.42, i.e. b + c = 2.24.

A dispersion of 2 g of the product in 100 ml of warm water

gave, after cooling, a white, opaque, thixotropic gel with a plastic viscosity of o 13 _centipoise and a BYV of o 38 dyne/cm 2 . The cation exchange capacity was 0.65 meq/g. The X-ray analysis gave the hectorite pattern, but the diffraction lines were more diffuse than those obtained from the products according to examples 1 and 2. Differential thermo-

the analysis showed both endothermic and exothermic peaks in the range 600 - 800°C, the exothermic peak being sharp and relatively small compared to the endothermic peak.

Example 4

Again, the same procedure as in the example was followed

1, but the amount of magnesium sulfate heptahydrate was 96.1 g, and of lithium chloride 8.90 g.

, For this product, M<=>Na<+>, a = 4.42,

b = 0.92, c = 1.71,

i.e. b + c = 2.63.

When 2 g of the product was dispersed in hot water, found

it was observed that the solids settled almost immediately after stirring had ceased, and no thixotropic gel formed.

The cation exchange capacity was 0.69 meq/g. The X-ray analysis gave a pattern that resembled hectorite, but was very diffuse, with a high degree of scattering indicating poorly crystallized or amorphous material. The differential thermal analysis showed both exothermic and endothermic peaks between 600-800°C. The two types were of similar size.

The amounts of chemicals used in examples 1-4 were calculated for the introduction of silicon, magnesium and lithium in the following atomic ratios:

At the same time, the amount of sodium carbonate was calculated according to the following formula:

where W is the quantity in grams of JSa^ CO^ which is required for every 100 g of sodium silicate used, if the concentration of SiO2i sodium silicate is p weight percent and the molar ratio between Si02 and NaOH is r.

Example 5

The same procedure as in example 1 was followed,

but the amount of magnesium sulfate heptahydrate was 139.3 g, no lithium chloride was used, and the amount of sodium carbonate was 42.5 g.

For this product, M = Na<+>, a = 5.09, b = 0, c = 1.38.

in

A dispersion of 2 g of the product in 100 ml of hot water gave, after cooling, an almost clear, colorless, thixotropic gel with a plastic viscosity of 12 centipoise and a BYV of 95 dyne/cm 2 . The cation exchange capacity was 0.55 meq/g. The X-ray analysis showed the typical hectorite pattern. The differential thermal analysis showed large exothermic and endothermic peaks in the range 600 - 800°C.

The chemicals used in this example were calculated for the introduction of silicon and magnesium in the atomic ratio of 8:5.65. The amount of sodium carbonate that was added was calculated according to the formula in example 4, plus 10% excess.

Example 6

125.7 g of magnesium sulfate heptahydrate was dissolved in 630 ml of water and heated to the boiling point. In a separate vessel, 38.7 g of sodium carbonate was dissolved in 630 ml of water, and 166 g of sodium silicate of the same type used in the other examples was added over a period of 30 minutes. The mixture was boiled with reflux for 2 hours and then heated to 280°C (corresponding to a manometer pressure of 70 kg/cm 2 ) and kept at this temperature for 4 hours with stirring. The subsequent treatment was the same as that used in the previous examples.

For this product, M=Na<+>, a - 5.38, b=0, c = 0.78. The rheological parameters of the product were:

to increase the electrolyte content of the solution to 45 meq/1 stepBYV

to a maximum of 382 dyne/cm 2 .

Example 7

In this example, initially the same method was used as in example 2, but the amount of water used to make the two solutions was 630 ml instead of 900 ml. The slurry containing the precipitate was heated as quickly as possible to 336°c, corresponding to 140 kg/cm<2> (total heating time from boiling

the point was 2 3/4 hours), and it was immediately cooled as quickly as possible by placing the autoclave in cold water. The product was then treated in the same way as the other preparations, and it was found to have the following properties:

The maximum BYV at optimal electrolyte concentration was 475 dyne/cm o. The cation exchange capacity was 0.70 meq/g.

Example 8

122 g of magnesium sulfate heptahydrate was dissolved in 450 ml of water, and in another vessel 166 g of sodium silicate solution of that type. which was used in examples 1-5, mixed with 450 ml of water. Solution No. 2 was added to the first, and the resulting precipitate was washed by filtration until sulfate-free. It was then dried at 110°C for 16 hours, ground and mixed with 600 ml of a 2N solution of sodium hydroxide. The resulting mixture was transferred to an autoclave and heated for 36 hours at 240°C. After cooling, the solid was washed by filtration until the filtrate was almost alkali-free. Finally, the product was dried at 110°C and ground.

On dispersing 2 g of the product in hot water, it was found that part of the material set almost immediately, while the rest, after cooling, formed a white, opaque, weak gel with a plastic viscosity of 6 centipoise and a BYV of o 14 dyne/cm 2. The cation exchange capacity was 0.55 meq/g. The X-ray analysis showed

a complex pattern containing weak and diffuse lines for hectorite and much stronger and sharper lines for at least one other crystalline substance, mainly quartz. The differential thermal analysis showed only small exothermic and endothermic peaks between 600 - 800°C.

The amount of chemicals used for this preparation corresponds to a Si/Mg atomic ratio of 1.6. The amount of sodium hydroxide is significantly higher than the equivalent amount of sodium carbonate calculated in accordance with the formula given in Example 4.

Example 9

In this experiment, the amounts and type of chemicals were the same as those used in Example 2, while the procedure followed was the same as in Example 8. Thus, the magnesium sulfate and sodium silicate solutions were mixed to form a precipitate which was then washed , dried and redispersed in 600 ml of a solution containing sodium carbonate and lithium chloride. After autoclaving, washing, drying and painting as in Example 8, the product was tested and gave results very similar to the results from Example 8.

All the synthetic clay-like minerals discussed in detail above have an inorganic cation M, but useful derivatives where the cation is organic can be made. Thus, the inorganic materials can be converted into new synthetic clay mineral-organophilic products, where at least some of the exchangeable cations consist of one or more organic cations equipped with organophilic properties. These new organophilic products can be produced by reaction between one of the new synthetic clay minerals, either before washing, after washing or after drying, in a liquid, preferably aqueous, environment, and an organic compound or a salt thereof which in this environment induces an organic cation that is able to undergo a cation exchange with the synthetic clay. It is preferred that at least the majority of the exchangeable cations in the organophilic product are of the specified organic cations.

Examples of organic compounds or salts thereof from which such cations can be derived can be found among organic groups of ammonium, phosphonium, stibonium, arsonium, oxonium and sulfonium.

Generally, the cations of primary importance for this invention are based on nitrogen, i.e. the organic ammonium salts. For example, this group of compounds includes the salts (including the quaternary salts) of primary, secondary and tertiary amines, including mono-, di-, tri- and polyamines as well as aliphatic, aromatic, cyclic and heterocyclic amines and substituted derivatives thereof . Other monovalent or polyvalent compounds which are of particular value in the practice of this invention are the so-called "Ethomeenes" (Armour & Company Ethomeene is a trademark). These compounds can be considered tertiary amines with a single alkyl group and 2 polyoxyethylene groups attached to the nitrogen atom. Likewise, the so-called "Ethoduomeener" (Armour&Company) are also of value.

Preferably, the organic radical present has at least 10 carbon atoms, desirably at least 12, and advantageously at least 18. The compounds may have up to 30, 40 or even 50 or more carbon atoms, depending on the availability of such materials .

Specific examples of suitable organic ammonium cations are dimethyldioctadecylammonium, trimethyloctadecylammonium, dodecylammonium, hexadecylammonium, octadecylammonium, dioctadecylmorpholinium, 1-propyl-2-octadecyl-imidazolinium and bis(-2-hydroxyyl)-octadecylammonium. These can be used individually or in combination with the aim of producing an organosilicate with desired properties.

When substantially complete cation exchange is desired, it is preferable to use from 0.9 to 1.4 equivalents of the organic cation, although occasionally it is found very advantageous to use as much as 1.7 to 1, 8, and even up to 2.2 equivalents. However, the areas indicated above,

when the clay is synthesized at higher pressure, i.e. 49 - 70 kg/cm 2,

be 0.6 to 1.4 and 1.0 to 2.2 equivalents respectively.

The product can be separated by the usual steps of removing water and drying, and can finally be painted if desired. Normally, the product will also be washed.

The methods described can use dried, synthetic clay as starting material. However, when the reaction, as preferred, is carried out in an aqueous environment, it is clearly advantageous to use the aqueous slurry, i.e. a cake-like mass, without heat treatment.

Certain cation-modified clays conform

with the invention possess oleophilic and gelling properties, which makes them very useful materials in the production of, for example, lubricating grease. Other types have the ability to form organosols.

The following examples 10 to 14 are some examples of the preparation of organic derivatives of the new materials according to the invention.

Example IO

51.15 liters of water were heated in the autoclave to the boiling point, and 9.9 kg of magnesium sulfate heptahydrate and 0.4 kg of lithium

chloride was dissolved in this. A separate solution was prepared which consisted of 51.15 liters of water and 13.5 kg of sodium silicate of the type used in all the other examples and 4.7 kg of anhydrous sodium carbonate. Solution No. 2 was gradually added to the first solution in the autoclave over the course of 1 hour. The mixture was then boiled at atmospheric pressure with continuous stirring for 2 hours, where

after the autoclave was sealed and heated to 207°C (17 kg/cm<2>)

for 4^5 hours. The same temperature and the same pressure were created

held for 8 hours, then the heating was stopped and the mix-

no cool to below 100°C. It was then drained from the autoclave.

1000 g of the unwashed slurry from the autoclave in-

holding 60 g of synthetic clay was diluted with 2 liters of hot water.

A solution of 50.8 g (1.1 equivalents) of the material sold

under the trade name "Arquad" 2HT - 75%T (which is dimethyldioctadecyl ammonium chloride 75% in isopropanol) in 1.5 liters of hot water was added

set under vigorous stirring. The mixture was heated to the boiling point, and one could then observe that the dispersed solid substance clumped and settled on standing. The precipitate was filtered off under vacuum, washed with hot water until the filtrate was substantially free of chloride and was dried at 80°C for 2 hours. A soft, powdery product was obtained which could easily be ground into a fine powder suitable for use in the production of lubricating grease.

Example 11

The same procedure was followed as in example 10 with

the difference being that the autoclaving lasted 24 hours. The result-

end soft, powdered product was even better suited for use in the production of lubricating grease.

Example 12

The same procedure was followed as in example 10 with

the exception that the slurry, from the autoclave, was washed by filtration until the filtrate was substantially free of sulfate. The filter cake was dried at 120°C for 8 hours and finely ground. 60 g of the dried solid was dispersed in 3 liters of hot water with mixing for 15

minutes and was mixed with a solution of 50.8 g "Arquad" 2HT, continuing the preparation as described in Example 10.

A soft, powdery product was again obtained which

could easily be ground into a fine powder suitable for use in the production of lubricating grease.. -

Example 13

The same procedure was followed as in Example 10

with the exception that 74 g (1.7 equivalents) of "Arquad" 2HT was used. In this case, the resulting product was suitable for the production of an organosol.

Example 14

The product obtained in Example 6 was converted

into organophilic form by dispersing 15 g of dry clay in 150 ml of hot water, adding a solution of 11.6 g of "Arquad" 2HTi in 375 ml of hot water, and continuing the preparation as described in Example 10.

The product was dispersed in a low-viscosity lubricating oil, and it was found that in a concentration of 8 - 10% stiff lubricating greases were formed, in consistency similar to the types of lubricating greases available in the trade.

Generally, lubricating grease can be prepared by mixing

the organic ammonium clay derivatives, in a suitably finely divided form, with a surfactant and a lubricating grease base oil. The mixing is preferably carried out as a mill operation and preferably in two stages, the first with part of the required quantity of lubricating grease base oil, the second with the rest of the oil. Finally, the grease must be centrifuged to more easily remove trapped air bubbles.

The greases usually include a major amount of a grease base oil and a minor amount, suitably 2 to 29% by weight (suitably 5-15% and preferably 10%), of the organic clay derivative.

The following examples 15 and 16 respectively illustrate the production of certain organic clay derivatives and the use of these materials in the production of lubricating grease.

Example 15

174 g of light spindle oil ("Carnea" 21) was mixed with 4 g of methyl alcohol, and 29 g of the powder prepared earlier in accordance with Example 10 was added. The mixture was re-

stirred with a high shear mixer for 3 minutes and then run through a colloid mill whose cutting surface was set at 0.5

mm clearance. After the mill operation, 150 g of the obtained lubricating grease, which had a solids content of 14%, was mixed with 60 g of light spindle oil of the same type as previously used, to reduce the solids content to 10%, and the mixture was again run in the colloid mill . After this, the grease obtained was centrifuged to facilitate the removal of trapped air bubbles. The consistency of the grease was tested by means of a Gallenkamp miniature penetrometer using a cone with a fixed angle of 90° and with a total weight of 15.3 g. A value of 30 (1/10 mm units) was obtained.

Example 16

In the preparation of organosols according to the invention

the organic ammonium compound used for reaction with the synthetic swelling clay preferably has a chain length of at least 18 C atoms and is used in an amount of at least 1.5 equivalents, preferably not more than 2.2 and suitably between 1.7 and 1.8 . But if the synthetic clay is produced at higher pressure, i.e.

in

49 - 70 kg/cm 2 , then the amount of ammonium compound used can be as low as 1.0 equivalent.

As a result, the product has almost all of its exchangeable cations as organic cations. The rest of the cations that take part in the reaction (ie 50% or greater excess) are retained by the clay.

It seems as if a multi-layer deposition of organic matter has taken place on the silicic acid layer in the synthetic clay structure.

Such organic products are capable of forming organosols with liquid aliphatic and aromatic hydrocarbons, particularly petroleum ether, white spirit, benzene, toluene and xylene. They are organosols with a dispersed phase of substantial inorganic content. When the organosol is mixed with water or an aqueous solution and shaken, an aqueous emulsion is formed where the organic liquid is usually the outer phase.

For example, an organoclay derivative was prepared in accordance with Example 10 above, but using 74 g (1.7 equivalents) of the amine.

The product was moistened with methyl alcohol and dispersed in toluene at 8% concentration. A clear sol with low viscosity is formed. The sun was stable between 0°c and 100°C. When a portion of this sol was mixed with half its volume of water and shaken for 1 minute, a rigid emulsion was obtained in which the outer phase was toluene.

Natural hectorite does not form sols or water/organic solvent emulsions.

The inorganic swelling clays according to the invention, i.e. those where M is Na or Li, can be used by themselves, but the introduction into different media can be simplified by using a peptizing agent.

Another feature of the invention is that inorganic clay species with the indicated general formula and where M is Na or Li, can be used in a composition with up to 25% (weight of the material) of one or more peptizing agents selected from alkali metal salts with multivalent anions. As cation M, Na<+> or Li<+> is preferred. Alternatively, organic materials can be used as peptizing agents, e.g. quebracho or a lignosulfonate.

Preferred amount of peptizing agent is from 3 - 12%

(calculated on the weight of the clay), suitably from 5 to 10%, and preferably 5% or 6%. These amounts are particularly suitable when the peptizing agent is tetrasodium pyrophosphate.

Among other peptizing agents that can be used are the product sold under the trade name "Calgon" and sodium tripolyphosphate. Generally, the most suitable peptizing agents are sodium salts with polyvalent anions, these anions being capable of forming either complex or insoluble salts with magnesium.

These compositions can conveniently be prepared by dry mixing the synthetic, clay-like material and the peptizing agent. The particle size of the resulting mixture is not critical, as it mainly depends on the area of application of the mixture.

One may find it desirable that the compositions occasionally also contain small amounts of one or more additives, the properties of which are determined by the field of application of the final composition.

Certain compounds, e.g. those where the cation M is Na<+> or Li<+> have the unexpected property that they have the ability to form substantially transparent, colloidal dispersions in the form of sols when mixed with water. Aqueous sols either made from these compositions, or directly from the components, represent a further feature of the invention and can have a total solids content (synthetic material + peptizing agent) of up to 10%, although it is normally from 2 to 6%. Such suns cannot be obtained from naturally occurring swelling clays. In practice, the soles provide an easy method for introducing the synthetic swelling clay in the environment where such clay is needed.

Although dilute aqueous dispersions of the kind just described do not exhibit any thixotropy or appreciable BYV, both of these properties can be developed by mixing with specific reagents. Such a property makes a composition and/or a sol according to the invention particularly suitable in emulsion paints, e.g. poly-vinyl acetate paint.

In this connection, it has actually been found that the compositions are very effective gel formers, which are also the lithium-containing clay species when they are used without the peptizing agent.

A further application for the synthetic clay types and mixtures thereof with a peptizing agent is as a binder for foundry sand.

Samples were taken of sodium clays, alone and with 6% tetrasodium pyrophosphate. 5 parts of each were mixed with 100 parts. quartz sand and 3.5 parts water, and then milled for 5 minutes.

A commercially available type of natural swelling clay was treated in the same way.

in

It was found that the two synthetic clay types containing sand mixtures had green strengths that were 50% better than the strength of the natural clay/sand mixture. The refractoriness (as measured at the melting point in an electric furnace of refractory material ) for all samples was essentially the same at approx. 1300°c.

A further, very important feature of this invention lies in a further use of the mixtures of inorganic swelling clay and peptizing agent which have just been described. If you start with such mixtures - or the separate ingredients - you can achieve useful plastering mixtures.

According to this characteristic of the invention, a plastering mixture includes the following components:

(a) Cement

(b) Fly ash and/or other filler.

(c) Up to a sum of 5% by weight (of the total weight of (a) + (b)) of one or more of the synthetic inorganic clay materials as described in UK Patent Specification 1 054 111 and/or in this application,

and

(d) up to a sum of 5% by weight (based on the weight of (c)) of one or more peptizing agents selected from alkali metal salts with polyvalent anions.

The ratio between cement and filler is suitable in the range 1:4 to 1:1, the desired range is 1:3 to 1:2, preferably approx. 1:2,3.

It is desirable that the synthetic clay material is present in the mixture until approx. 1% by weight of the sum of (a) + (b), advantageously from 0.1 to 0.5% by weight.

The total amount of peptizing agent used is suitably in the range of 1-4% by weight of (c); about. 2% is a beneficial amount.

Such compounds are useful when tunneling through soft ground, for sealing dams, rock fissures and boreholes, as well as when constructing partition walls and other permanent water barriers.

Important properties of plaster mixtures, especially those used in tunnel boring, are: (I) They can be easily mixed with water or other suitable liquid to form a pumpable slurry, (II) they begin to solidify within approx. 1 hour, (III) they are plastic for up to 12 - 16 hours, (IV) they solidify completely within 12 - 24 hours, (V) they have a final strength of o 14 - 56 kg/cm 2, (VI) they shrink little or nothing during solidification, (VII) there is little or no excretion of water during solidification, (VIII) no excretion of solids in the solidified cement, (IX) fine pore structure.

Generally, similar requirements are made if the mixture, instead of being used as plaster, is to be used for prefabricated tunnel boring segments. In this case, however, the final solidification time (for removal from the mold) must be shorter and the final strength higher.

The plaster used in tunnel boring, etc., is essentially an aqueous mixture of cement, filler and a swelling clay. However, in all known cases the swelling clay must be gelatinized in advance in order to be used, and this includes a separate step in the production of an aqueous plaster. The ideal would be to dry mix all the necessary components, so that you only need to add water to make the aqueous plaster. This is now possible with the help of the synthetic silicate according to the invention.

A particularly advantageous plaster mixture contains (in parts by weight) fly ash - 70, cement - 30, synthetic clay material - 0.12 and tetrasodium polyphosphate - 2% based on the weight of synthetic clay.

Fly ash is pulverized ash from power plant fuel

(B.S.S. 3892:1965).

When preparing an aqueous plaster from the dry mixture, you normally need approx. 35 to 55 parts by weight of water. With the special composition referred to in the previous paragraph, 40 - 45 parts are suitable, depending on the fineness of the filler, especially when this is fly ash.

The following example illustrates this feature of the invention:

Example 17

In the following table, you can compare the results obtained with the nine characteristics as indicated above.

Different designations are used in the results listed below, and they have the following meanings:

Consistency

A The newly mixed plaster is thick, can be touched

with a glass rod, but cannot be poured.

B Can barely be poured from beaker as a continuous

a lot.

C Thin pasta.

Fluid loss

The molds were placed on absorbent paper and any liquid that separated during the initial solidification period appeared as a wet spot around the base.

A - Nothing

B - Track

C - Something

D - A lot

Possibility of removal from the mould.

After 1 hour, an attempt was made to remove the test piece from the mould. Yes means that the test piece did not appear to be deformed or to have collapsed. Exactly, meaning it was easily deformed but could stand firm when propped up. The further comments are clear enough.

Penetration.

This was measured on the surface of the test piece after 1 hour, using a plastic cone that weighed 15.4 g and had a 45° half solid angle. The conventional yield strength was be-

calculated as follows:

where p = read penetration in 1/10 mm's units.

Deformation.

Deformation during the solidification period was noted as

following:

A = no detectable change

B = very small deformation

C = clearly noticeable deformation

D = significant deformation

E = no form (could not be removed after 1 hour) Structure.

The test pieces had to be cut off at both ends to give 7 6 mm high cylinders for strength measurement using a triaxial shear tester. At the same time, the fineness of the pore structure was noted.

A = very good, even, fine pores

B = good

C = usable

D = poor (some very large pores)

E = no test piece (could not be removed after 1 hour). For the experiments indicated in the table, the plaster mixtures were first made and then water was added gradually under continuous mixing to the desired concentration. The resulting aqueous plaster mixtures were filled into cylindrical specimen molds of 38 mm diameter, lined with thin rubber.

The following tables show the effect of addition of synthetic clay, with or without tetrasodium polyphosphate, on the properties of portland cement/fly ash, of different initial consistencies.

Table I gives information on a particular type of synthetic clay, prepared according to Example 2, and Table II on 2 qualities of natural hectorite sold under the trade names

"BEN-A-GEL" and BEN-A-GEL EW".

Empty spaces in the tables show that no measurement was made.

The following conclusions can be drawn from the table above: Addition of the synthetic clay species improves the solidification of the plaster in the direction that mixtures, which are initially thin and pumpable, solidify sufficiently well within 1 hour to could be removed from the mold and still remain piastic for almost a whole day. Such mixtures do not solidify within 1 hour without the synthetic clay. The optimal content is approx. 0.12%, calculated on dry matter.

With the addition of 0.12% synthetic clay, mixtures with varying proportions between cement and fly ash, down to approx. 25 - 30% cement, usually give satisfactory results. If a lower proportion of cement is used, the plaster still sets very well within 1 hour, but is too weak after 24 hours.

Natural hectorite ("Ben-a-Gel" and "Ben-a-Gel EW") used in 30:70 cement/fly ash mixes produces some improvement in setting, but not enough to give a mix that solidifies within i hour. The optimal addition is approx. 0.12% with respect to synthetic clay, but the addition of phosphate results in no further advantage. Other advantages of synthetic clay mixtures are (a) less fluid loss and (b) less deformation after removal from the mold on the first day.

Claims (3)

1. Synthetic silicate with a structure similar to the structure of clay minerals of the smectite type, suitable for use as a gelatinizing agent, characterized in that the general structural formula is where More a sodium, a lithium or an equivalent of an organic cation, the value of a,b and c is such that either and b+c < 2; |(a+b+c-6)|<2 or a < 6, - b=0, - c < 2; and |(a+c-6)| ^ 2 and the cation exchange capacity is approx. 50 to 120 mek/100 g, while the Bingham Yield Value is between 50 and 250 dyne/cm 2 , measured as a 2% dispersion in tap water. 2. Synthetic silicate as stated in claim 1, characterized in that the organic cation is an organic ammonium cation with preferably at least 10 carbon atoms. 3. Process for the production of a synthetic silicate as stated in claim 1, characterized by the simultaneous precipitation from an aqueous solution of a sodium compound which is maintained at pH 8 to 12.5 and which contains a water-soluble magnesium salt, a silicon-releasing material, e.g. a silicate, and possibly a lithium salt, each in an amount calculated so that the required values of a and c are achieved, further that without first drying or washing this precipitation product it is heated to a temperature below 370°C and a pressure of at least 7 kg/cm 2 , preferably 49 to 70 kg/cm 2 , the resulting solid substance is separated from the water phase, washed to remove soluble by-products, and dried, as well as optionally reacting the product with a lithium compound or with a organic salt, preferably an organic ammonium salt with a chain length of 10 to 18 carbon atoms, whereby the exchangeable cation M is replaced by lithium or an equivalent to the organic cation.