RU2089499C1 - Method of preparing hydrophobic disperse material - Google Patents

Abstract

FIELD: disperse materials. SUBSTANCE: essence of invention consists in activation of silicon dioxide or metal oxide by alkali metal carbonates under mechanical stirring and chemically modifying surface at elevated temperature with organoelemental compound with general formula Cl_4-nSiR_n where n = 1-3, R is methyl, ethyl, chloromethyl, or phenyl followed by chemical treatment with 0.5-1.0 wt % of compound selected from group: tetramethoxysilane, tetraethoxysilane, polymethyl(ethyl)siloxane oligomer, and polymethylsilazane oligomer. Chemical modification of disperse material is carried out at 20-200 C and disperse material to organoelemental modifier weight ratio (4- 15):1. According to invention, starting material is preliminarily dried to moisture content not higher than 1 wt %, and activation and surface modification are conducted for 30-120 min, evolved gas products being removed using inert gas or air blowing through alkali neutralizer. EFFECT: essentially simplified chemical modification process and 27-40 times reduced power consumption. 4 cl, 1 tbl

Description

 The invention relates to the field of physical chemistry, and specifically to methods for chemical modification of the surfaces of finely dispersed materials to give them a selective and protective effect and can be used in the oil and gas industry. The use of such materials in wells changes the oil and water permeability of formations. The application of chemically modified silicas (KHMK) in the form of coatings on the elements of oil and gas complexes increases the resistance of the latter to chemically aggressive environments, metal corrosion, icing, fouling and liming. The coating of the internal surfaces of pipelines from KMC reduces the hydraulic resistance of moving fluids, which leads to a reduction in energy costs during transportation. The invention can also be used for hydrophobization of solid powders, for example amorphous silicas, used as components of water repellents for products from ceramics, wood, paper, fabric, metals, brick, concrete and other building materials in order to increase their resistance to external influences and improve operational characteristics.

The method of chemical modification of silicas used in adsorption, heterogeneous catalysis, chromatography, as carriers for immobilizing enzymes, fillers of rubbers and rubbers, thickeners of greases, etc. is widely known [1-2]
The process of chemical modification of amorphous silicas using Cl-silanes is time-consuming and includes the following stages:
hydroxylation of the starting silica (boiling in water, 24 hours);
removal of physically adsorbed water from the surface of the carrier (1.3 Pa, 200 ^o C, 6-8 hours);
preliminary absolute organic solvents to form an easily mixed suspension with a carrier and organic bases used to bind hydrogen chloride;
silica modification in solutions for at least 8 hours at a temperature of at least 95 ^o C;
extraction of the obtained product with absolute non-polar, and then polar solvents, including aqueous-organic mixtures;
drying modified silica.

Closest to the claimed method (prototype) is a method of producing a hydrophobic dispersion, including surface treatment of the starting material (aerosil, white soot, perlite, graphite, talc, asbestos, cement, mica or metal oxides) with sodium, potassium or ammonium hydroxide or carbonate and the subsequent Chemical modification by steam of an organosilicon compound on copper or brass gratings [3]
The disadvantages of this method are:
a) the absence on the surface of chemically modified silica grafted polysiloxane chains, contributing to an increase in the hydrophobicity of the material and greater adhesion of the grafted layer to the surface of the silica;
b) hydrogen chloride formed as a result of the reaction is not removed from the reaction zone, which leads to a slowdown of the chemical modification process, environmental pollution and an increase in the acidity of the resulting product.

 The objective of the present invention is to simplify and intensify the process while reducing energy consumption, as well as increasing the hydrophobicity of the target product due to the appearance of grafted polysiloxane chains on the surface of the particles.

This problem is solved by a method including activation of the surface of the starting material with mechanical stirring in the presence of solid alkali metal carbonate and subsequent surface modification with an organosilicon compound at an elevated temperature, in which according to the invention a compound of the general formula Cl _4-n SiR _{n is} used as an organosilicon compound, where n = 1-3, R = H, methyl, ethyl, Cl-methyl, phenyl. The mass ratio of mineral filler and organoelement compounds is (4-15): 1. While the source material is subjected to preliminary drying to a moisture content of not more than 1 wt. Activation and modification is carried out at 20-200 ^o C and mechanical stirring for 30-120 minutes, and the gaseous reaction products formed in the process are removed by purging with an inert gas or air.

 The content of the organosilicon compound used depends on the structural characteristics of the modified silicas (particle size, surface size, diameter and pore volume).

The presence of finely divided soda ash in this process is a prerequisite for the "dry" method of chemical modification of silicas, because It performs two functions: 1) a reaction catalyst and 2) a pH regulator (neutralizes the released HCl). In addition to the gaseous CO ₂ and H ₂ O released during neutralization, sodium chloride (NaCl) is formed in the dry XMK process, the presence of which does not lead to a noticeable decrease in the hydrophobicity of the resulting product. The use of organic bases such as pyridine and triethylamine instead of soda ash complicates the XMK process, since in this case, additional isolation of the hydrochloric acid salts of amines from the reaction products is necessary.

с образованием полисилоксанов. Таким образом, установленное минимальное содержание физически адсорбированной воды (0,5 0,6 мас.) позволяет существенно расширить круг используемых химических модификаторов поверхности и, используя метод поверхностной сборки, осуществить прививку в одну стадию.When using di- and trichlorosilanes as chemical surface modifiers of amorphous silicas, the content of physically adsorbed water in the latter should be no more than 1 wt. As shown by the results of elemental analysis and IR spectroscopy of CMC, in this case, additional condensation of surface Si-Cl bonds with sorption water occurs

with the formation of polysiloxanes. Thus, the established minimum content of physically adsorbed water (0.5 to 0.6 wt.) Allows you to significantly expand the range of chemical surface modifiers used and, using the surface assembly method, vaccine in one stage.

 In addition to silica, Cl-silane and sodium carbonate in the proposed "dry" XMK method, the fourth component is a synergistic additive, the presence of which in the reaction mixture in an amount of 0.5-0.1 wt. leads to an increase in the hydrophobicity effect, and tetramethoxysilane, tetraethoxysilane, polymethyl (ethyl) siloxane oligomers, polymethylsilazanes, etc. can be used.

An example of a specific implementation of this method. 72 wt. previously calcined at 150 ^o Aerosil-380 with a moisture content of 0.5 wt. load at room temperature in the reactor and with the stirrer working gradually add over the course of 10-15 minutes 7 wt. finely ground soda ash. Stirring is continued for another 15 minutes and 20 wt. trimethylchlorosilane. Then the temperature of the reactor was raised to 55 ^° C and stirring was continued for 20 minutes. The reaction is monitored by the liberated hydrogen chloride, which is passed through a neutralizer filled with an aqueous alkali solution. To release reaction products from HCl, the reactor is purged with inert gas or air for 20 minutes. In this case, the exhaust gases at the end of the process should have a slightly acid reaction (pH 6-7). At the end of the reaction, 1 wt. synergistic liquid (tetraethoxysilane) and after 15 minutes of stirring the resulting product is discharged.

The hydrophobicity of the reaction product without taking into account the content of formed NaCl was 99.6%. The composition and structure of the chemically modified aerosil were studied using elemental analysis and IR spectroscopy. Differences in the carbon content in untreated and treated with sulfuric ether at its boiling point samples show that 95.2% of the trimethylchlorosilane used is involved in the chemical modification of the aerosil surface layer. The average concentration of grafted modifying groups on the surface of SiO ₂ is 3.97 μmol / m ² or 2.39 groups / nm ² , which corresponds to a surface area of A _m = 0.49 nm ² per trimethylsilyl group.

In the IR spectrum of modified silica, a significant decrease in the absorption band of free hydroxyl groups of 3750 cm ^-1 is observed compared with the spectrum of the initial aerosil and the appearance of an intense absorption band of stretching vibrations of CH ₃ trimethylsilyl groups with a frequency of 2915 and 2975 cm ^-1 . The ratio of [(CH ₃ ) ₃ SiO] / [OH] on the surface of silica is 0.55 / 0.45.

Trimethylsilyl groups located near and above the hydroxyl groups remaining on the silica surface form a surface layer with a high hydrophobicity, as can be seen from the obtained results. The resulting surface layer also has high heat resistance. As shown by the results of IR spectroscopy, heating the aerosil modified in this way in vacuum to 400 ^° C does not remove chemically grafted trimethysilyl groups from the surface.

 Depending on the ratio of the starting components, the process temperature, and the reaction time, 20 experiments were carried out. Data on the conditions for the chemical modification of silicas with chlorosilanes and the achieved values of hydrophobicity are given in the table.

From the table it follows that as a result of the modification of silica carried out by the developed method in all cases, the resulting modified products have high hydrophobicity, reaching 99.0-99.6% (experiments 1-14). Small differences in carbon content in untreated and ether-treated samples show that in most cases more than 95% of the modifier used is involved in the formation of a monolayer of grafted molecules. The density of the layer grafted to the surface depends on the structure of the silica used and the content of the modifier. So in the case of the use of Aerosil-380 (experiments 1-5), a high vaccination density of more than 2 groups / nm ^{2 is} achieved.

 A different picture is observed when changing the conditions for the modification of silicas. So with an increase in the initial content of chlorosilane in relation to silica (experiments 11-14), differences in the carbon content in the untreated and ether-treated product samples increase. This indicates a decrease in the percentage of modifier involved in the formation of the grafted layer of molecules of alkyl (aryl) silyl groups. Moreover, the concentration of modifiable groups on the surface of silica practically does not change (cf. experiments 2-14).

 In experiment 15 of the table shows the results on the modification of Aerosil in the absence of soda. As can be seen from the table, under these conditions, the modification reaction — the interaction of the silyl groups of silica with chlorosilane, is very limited.

 According to the proposed method for producing a hydrophobic dispersed material, silica is modified in the entire reactor volume, and not on the surface of copper or brass gratings, as indicated in the prototype. This allows you to significantly intensify the process of chemical modification of silicas in terms of productivity.

Sources of information
1. US patent N 4209432, CL C 08 L 83/04, publ. 1980.

 2. British patent N 1496553, CL C 01 In 33/12, 1977.

 3. RF patent N 2066297, class C 01 B 33/18, 1993.

Claims (4)

1. A method of producing a hydrophobic dispersed material based on silicon dioxide or metal oxide, comprising activating the surface of the starting material with alkali metal carbonates during mechanical stirring and chemical modification with an organoelement compound at an elevated temperature, characterized in that the surface modification is carried out with an organoelement compound of the general formula Cl _{4 - n} SiR _n , where n 1 3, RH, methyl-, ethyl-, Cl-methyl-, phenyl-, followed by further treatment with a compound selected from the group consisting of tetramethoxysilane, tetraethoxysilane, oligomer polymethyl (ethyl) siloxane, polymethylsilazane in an amount of 0.5 to 1.0 wt. 2. The method according to p. 1, characterized in that the chemical modification of the dispersed material with an organoelement compound is carried out at a mass ratio of (4 15) 1 and a temperature of 20 200 ^o C.  3. The method according to claim 1, characterized in that the starting material is preliminarily dried to a moisture content of not more than 1 wt.  4. The method according to claim 1, characterized in that the process of activation and chemical modification of the surface is carried out with mechanical stirring of the components for 30 to 120 minutes, and the gaseous reaction products resulting from this are removed by purging with an inert gas or air through an alkaline catalyst.

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