Hydrophobic material based on modified thermally expanded graphite

Abstract

The group of inventions relates to the field of producing carbon materials which are modified by silicon-containing compounds and exhibit enhanced hydrophobicity for the manufacture of low-density carbonaceous sorbents for removing hydrocarbons from the surface of water, or for the manufacture of graphite foil that exhibits enhanced sealing ability with respect to water, steam and aqueous media. A method for manufacturing a hydrophobic material based on thermally expanded graphite includes the steps of: saturating intercalated graphite with a composition containing at least one organosilicon compound selected from alkyl-substituted and phenyl-substituted silanes and / or polyalkyl and polyphenyl siloxanes, an aqueous solution of ammonia and an organic solvent, where the ratio of the mass of intercalated graphite to the mass of the saturating composition is equal to 1:(0.02-5); removing the excess liquid phase; drying the mixture to a free-flowing state; and heat treating the dried mixture at a temperature of from 300 to 1000°С. The invention makes it possible to produce particles of thermally expanded graphite with improved hydrophobic characteristics.

Description

[0001] HYDROPHOBIC MATERIAL BASED ON MODIFIED THERMALLY EXPANDED GRAPHITE.

[0002] Field of technology

[0003] The invention relates to the field of obtaining carbon materials modified with organosilicon compounds with increased hydrophobicity, characterized by improved surface characteristics (high water contact angle, low water absorption, high buoyancy) and can be used in the chemical industry for the production of low-density carbon sorbents of hydrocarbons from a water surface, and graphite foil with increased sealing capacity for water, steam and aqueous media (solutions, emulsions, dispersions, etc.).

[0004] State of the art

[0005] In the state of the art, expanded graphite (111) or thermally expanded graphite (TEG) is understood to be a low-density porous material that can be pressed without a binder into products of various shapes and densities from 0.01 to 2.0 g / cm 3 (RU2706103).

[0006] To obtain thermally expanded graphite, the first stage involves intercalation of natural flake graphite in concentrated solutions of nitric acid or sulfuric acid in the presence of an oxidizer to form an intercalated graphite compound (IGC). In chemical synthesis, concentrated nitric acid, potassium dichromate, potassium permanganate, peroxide, ammonium persulfate, etc. can act as an oxidizer. Electrochemical synthesis of ICG is also possible, which does not require the use of an oxidizer, and intercalation is carried out due to anodic oxidation of graphite by electric current in a solution of nitric or sulfuric acid. With an increase in the amount of added oxidizer or the amount of electricity during electrochemical synthesis, the amount of introduced intercalate increases and the ICG stage number decreases.The ICG stage number is the number of graphite layers between two nearest layers of intercalate, characterizes the degree of filling of the graphite matrix with intercalate: the lower the stage number, the more intercalate has been introduced. After obtaining ICG, they are washed with water to remove excess acid, which forms a non-stoichiometric adduct intercalated graphite (IG) or oxidized graphite. To obtain thermally expanded graphite, heat treatment of intercalated graphite is carried out by means of thermal shock at temperatures up to 1400°C.

[0007] Several publications indicate that thermally expanded graphite has non-zero wettability with water and its water contact angle can vary from 45° to 70°, which indicates hydrophilic properties of the surface of the TEG material (Kozbial A., Trouba C., Liu H., Li L. Characterization of the Intrinsic Water Wettability of Graphite Using Contact Angle Measurements: Effect of Defects on Static and Dynamic Contact Angles. / / Langmuir. 2017. V. 33. P. 959-967). It has also been shown that with a decrease in the foaming temperature, the hydrophilicity of TEG increases significantly (Lutfullin M.A., Shomikova O.N., Vasiliev A.V., Pokholok K.V., Osadchaya V.A., Saidaminov M.I., Sorokina N.E., Avdeev V.V. Petroleum products and water sorption by expanded graphite enhanced with magnetic iron phases. / / Carbon. 2014. Vol. 66. P. 417-425.).

[0008] When using products made of TEG, the penetration of liquid into the volume of the material plays a major role. In the case of using TEG and low-density products as a sorbent of oil and hydrocarbons, low water absorption and buoyancy of the material play a major role. Low water absorption ensures selectivity of sorption of oil and hydrocarbons from the water surface, i.e. the sorbent should sorb oil (hydrocarbons), but not absorb water. Also, when the pores of the sorbent are gradually filled with water, it begins to sink, which causes difficulties with its removal and disposal after the sorption process. When using TEG to manufacture sealing materials, its hydrophilicity can lead to swelling and a decrease in the sealing capacity with respect to water and aqueous media, which will penetrate through the pores of TEG and leak into the external environment.

[0009] To increase the hydrophobicity of thermally expanded graphite or a material based on it, two approaches to this problem are used. The first approach involves obtaining thermally expanded graphite with a structure in which, along with a high content of porous particles, there is a strictly limited number of particles with closed pores.

[0010] Patent US5282975A discloses the production of thermally expanded graphite having a special hydrophobic and oleophilic vermicular structure with the property of selectively absorbing large quantities of petroleum products from an aqueous medium. This thermally expanded graphite is characterized by three main properties: (a) a specific density in the range of 0.003-0.1 g / ml; (b) a surface area in the range of 50-200 m2 g / ml; and (c) closed pores in the range of 3% to 20%. The special structure of the expanded graphite can be used in the form of particles, pillows, blankets, booms or as a filter material. Preferred particle sizes of the expanded graphite are in the range of 0.5 to 3 mm.

[0011] The most important characteristic of this thermally expanded graphite, which has selective absorption of oil products from the aqueous medium, is the presence of graphite particles with closed pores in the range from 3% to 20%. This amount of closed pores ensures the buoyancy of the graphite after absorption of the oil product so that it does not sink in the aqueous medium. As is known, ordinary graphite has a density of 2.2 g / ml and sinks in water. However, expanded graphite, which has the above-mentioned narrow range of closed pores, ensures an optimal reduction in the specific density of the said graphite, but retains a high capacity for selective absorption of oil products.

[0012] Another way to improve the hydrophobic properties of thermally expanded graphite is to modify the particles of thermally expanded graphite using various types of chemical compounds.

[0013] Patent RU2766081 discloses a method for producing a carbon material based on graphite, including the methods of mixing the original graphite with a chemical reagent and subsequent thermal heating. In this case, a mixture consisting of liquid ammonia and one of the compounds of alkali metal acetylides with the general structural formula is used as a chemical reagent: Me-C=CR, where Me is Na, K; R is H, -CxHy at x=1-6, y=2-13, where alkali metal acetylides are used in a concentration of 1-5 mol.% with respect to graphite, before heating, the graphite is kept under a layer of solution for 15-60 minutes, after which it is removed, dried at room temperature and then subjected to heating at 500-800°C in thermal shock mode. The technical result of this invention consists in achieving indicators for bulk density and sorption capacity that ensure high reactivity of the target product.The products of pyrolysis of acetylides in the burner flame (globules, carbon fibers and nanotubes) increase the hydrophobicity of the material, which ensures higher selectivity of sorption of oil and oil products from water-oil mixtures.

[0014] The disadvantages of this technical solution, which includes obtaining TEG with a large volume of closed pores, include the difficulty of technological control of such pores, since when obtaining TEG, they always strive to obtain a completely porous TEG. Closed pores are formed mainly in TEG that has not been foamed well enough, i.e. under-foamed and contains inclusions of under-foamed intercalated graphite, under-decomposed acid and oxygen groups, which negatively affects the quality and environmental friendliness of the product. In addition, alkali metal acetylides react violently with water, releasing flammable gases, causing skin burns and can cause damage to the upper respiratory tract and lungs.

[0015] Patent CN116020421 (A), which is the closest to the claimed invention, discloses a method for producing a three-dimensional porous material for separating oil and water based on thermally expanded graphite. The material is a block three-dimensional porous sponge body containing a framework of TEG and a binder - polydimethylsiloxane (PDMS). The preparation method provides for the following stages: (A) dissolving PDMS in a hexane solution, (B) mixing the PDMS solution with TEG, (C) low-temperature vulcanization of the resulting mixture at 100 ° C to obtain a three-dimensional sponge structure. At stage (B), a blowing agent (NaCl) can be optionally added to the mixture, and after vulcanization, the blowing agent can be removed by soaking the sponge structure obtained at stage (C). In this technical solution, PDMS has good chemical stability and can reduce the surface energy of porous materials, further improving the hydrophobicity of the three-dimensional porous sponge.The three-dimensional porous material disclosed in patent CN 116020421 has a high adsorption capacity for oil / organic solvents and is positioned as a hydrophobic and lipophilic material. Further improvement of the hydrophobic properties is achieved by spraying the solution from step (B) with added nanosilica particles onto the surface of the three-dimensional sponge structure.

[0016] The disadvantages of the technical solution, which includes mixing a solution of polydimethylsiloxane and TEG particles, include high labor intensity and low production technology of the process: TEG is particles with a large volume and low bulk density, therefore, during the technological process, the productivity of obtaining the material will be extremely insignificant: due to the low bulk density of TEG, a small mass can be impregnated per unit of time. Also, both the impregnation itself and the subsequent separation of TEG from the solution and its drying can significantly worsen the porosity of TEG - the material will lump and be pressed during mixing and separation. This, in turn, will lead to a decrease in the sorption properties of TEG and the mechanical properties of materials from it. Thus, the method, which is the closest analogue of the invention, only creates certain technical problems, but does not solve them.

[0017] The technical problem solved by the claimed invention is the development of a method for producing a hydrophobic material based on modified thermally expanded graphite, eliminating the above-mentioned disadvantages.

[0018] Disclosure of invention

[0019] The technical result of the claimed invention is the production of hydrophobic thermally expanded graphite modified with organosilicon compounds with improved hydrophobic characteristics while simplifying the method for its production. The claimed method is characterized by improved production manufacturability, i.e. modified graphite at the production stage can be manufactured with the least labor and cost, in a simple and technologically advanced way.

[0020] The technical result is achieved by a composition for impregnating intercalated graphite, containing at least one organosilicon compound selected from the group including alkyl-substituted and phenyl-substituted silanes and polyalkyl- and polyphenylsiloxanes, an aqueous solution of ammonia and an acceptable organic solvent in the following mass ratio of components, parts by weight: organosilicon compound 1, aqueous solution of ammonia 0.001-0.15, organic solvent 1-10.

[0021] In this case, monosubstituted alkylsilanes RlSiR33 and phenylsilanes: R2SiR33, disubstituted alkyl and phenyl silanes: R12SiR32, R22SiR32, RlR2SiR32, polyalkyl and polyphenyl siloxanes -[SiR12 - O]n -[SiR22 - O]n-, -[SiRlR2 - O]n where Rl= -CnH2n+l, R2 = - C6H5, R3 = -OH, -Cl, -OCnH2n+l are used as organosilicon compounds.

[0022] The technical result is also achieved by a hydrophobic material, which is thermally expanded graphite impregnated with the above-described composition, in the form of a powder, while the TEG is modified with organosilicon compounds to a density of 0.01 g / cm3 to 1.9 g / cm3.

[0023] The technical result is also achieved by a method of manufacturing a hydrophobic material based on thermally expanded graphite modified with organosilicon compounds, which includes the following stages:

[0024] (A) impregnating the intercalated graphite with a composition containing at least one organosilicon compound selected from the group consisting of alkyl-substituted and phenyl-substituted silanes and polyalkyl- and polyphenylsiloxanes, an aqueous ammonia solution and an acceptable organic solvent in the following mass ratio of components, mass parts: organosilicon compound 1 aqueous ammonia solution 0.001-

[0025] 0.15 organic solvent 1-10 and with a ratio of the mass of intercalated graphite to the mass of the impregnating composition, mass parts: 1: (0.02-5);

[0026] (B) removal of excess liquid phase;

[0027] (B) drying the mixture obtained in step (B) to a free-flowing state;

[0028] (G) heat treatment of the dried mixture from step (B) at a temperature from 300 to 1000°C to obtain particles of thermally expanded graphite modified with organosilicon compounds.

[0029] In particular embodiments of the invention, monosubstituted alkylsilanes R^iR^ and phenylsilanes are used as the organosilicon compound in stage (A): R 2 SiR 3 3, disubstituted alkyl and phenyl silanes: R 1 2SiR 3 2, R 2 2SiR 3 2, R 1 R 2 SiR 3 2, polyalkyl and polyphenyl siloxanes - [SiR X 2 - O] n -, - [SiR 2 2 - O] n -, -[SiR^2 - ABOUT] п -., where R x = -CnH 2n+ i, R 2 = -C6H5, R 3 = -OH, -Cl, -OCnH 2n+ i.

[0030] In particular embodiments of the invention, after stage (G), the particles of thermally expanded graphite modified with organosilicon compounds are compacted to a density of 0.01 g / cm 3 up to 1.9 g / cm 3 In this case, compaction is carried out by pressing and / or rolling.

[0031] In particular embodiments of the invention, heat treatment at stage (G) is carried out at a temperature of 300-700°C in air.

[0032] In particular embodiments of the invention, heat treatment at stage (G) is carried out at a temperature of 600-1000°C in a nitrogen environment.

[0033] The technical result is also achieved by using the claimed hydrophobic material modified with organosilicon compounds as a hydrophobic sorbent for the selective sorption of oil, liquid hydrocarbons and organic substances from water.

[0034] The technical result is also achieved by using the claimed hydrophobic material modified with organosilicon compounds for the production of compacted materials. Compacted materials can be obtained by pressing or rolling into foil.

[0035] Implementation of the invention

[0036] The essence of the invention is as follows.

[0037] A more promising method for producing hydrophobic TEG modified with organosilicon compounds compared to the method described in patent CN116020421 is a method that involves introducing organosilicon compounds not to TEG, but to intercalated graphite. When foaming the IG, organosilicon compounds are uniformly distributed over the surface and volume of the resulting TEG, and thus, when manufacturing the product, the hydrophobicity increases over the entire volume of the TEG material. In addition, compared to the known method, a number of technological operations are excluded and the manufacturing processability of the resulting modified TEG is improved: the products at the manufacturing stage are manufactured with the least labor and cost.

[0038] The method is carried out in the following order.

[0039] Stage (A).

[0040] To obtain hydrophobic TEG modified with an organosilicon compound, the following components are taken: intercalated graphite, an aqueous solution of ammonia and a solvent acceptable for organosilicon substances. In the prior art, intercalated graphite (IG) or oxidized graphite is understood to be a non-stoichiometric adduct formed during the hydrolysis of intercalated graphite compounds (IGC) with the preservation of the planar structure of the original graphite, containing a certain amount of residual intercalate, water molecules in the intercrystalline space and oxygen-containing functional groups on its surface.

[0041] In turn, ICG refers to graphite interstitial compounds formed by introducing various ions or molecules into the interplanar space of a graphite matrix, representing a certain number of graphite layers alternating with an intercalate layer. The ICG step number is the number of graphite layers between two adjacent intercalate layers, characterizing the degree of filling of the graphite matrix with intercalate: the lower the step number, the more intercalate has been introduced.

[0042] Any IG can be used as intercalated graphite, in particular, one obtained by hydrolysis of the following intercalated graphite compounds:

[0043] • Overoxidized graphite nitrate obtained by anodic overoxidation of graphite in a 50-98% nitric acid solution until the first stage of intercalation is reached and subsequent overoxidation of graphite and introduction of an excess amount of nitric acid based on the stoichiometric production of an intercalated graphite compound with the structural formula [Cf. + ]MO3'(ZN Yuz), p = 4-24. Overoxidation allows foaming of this IG at low temperatures starting from 300°C.

[0044] • Graphite nitrate stage II obtained by chemical interaction of graphite with fuming 98% nitric acid in a mass ratio of graphite: acid 1: (1-1.5) in order to obtain an intercalated graphite compound with the structural formula [C48 + ]NO3'(ZN Yuz). Chemical oxidation with fuming nitric acid allows foaming of IG at temperatures starting from 500°C.

[0045] • Graphite bisulfate of stage I and stage II obtained by the interaction of graphite with concentrated 96-98% sulfuric acid in the presence of an oxidizer (H2SO4, K2CG2O7, KMnSC, H2O2, etc.) based on the stoichiometric production of an intercalated graphite compound with the structural formula [C 24 + ]HSO4(2H2SO4) And [C48 + ]HSO4'(2H2SO4), respectively for stage I and stage II. These types of IG at the stage of thermal expansion begin to foam at temperatures of 400 and 500°C, respectively.

[0046] The IG is impregnated with a composition containing at least one organosilicon compound selected from the group consisting of alkyl-substituted and phenyl-substituted silanes and polyalkyl- and polyphenylsiloxanes, an aqueous ammonia solution and an acceptable organic solvent in the following mass ratio of components: organosilicon compound 1, aqueous ammonia solution 0.001-0.15, organic solvent 1-10.

[0047] Mixing an organosilicon compound with an organic solvent results in a more uniform distribution of silane or siloxane over intercalated graphite. In this case, organosilicon compounds condense with each other to form long-chain siloxane molecules with organic (alkyl and phenyl) substituents and condense siloxanes with oxygen groups under the influence of an aqueous solution of ammonia, which acts as a catalyst for the condensation of silanes and siloxanes and significantly accelerates the condensation process.

[0048] The ratio of components in the impregnating composition is selected within the limits that ensure the completeness of the hydrolysis-condensation process of organosilicon compounds and their application to the surface of the IG.

[0049] The composition is obtained by ordinary mixing until a homogeneous mixture is obtained, which ensures its uniform distribution over the surface of the IG flakes.

[0050] The ratio of the mass of the IG to the mass of the impregnating composition is 1:(0.02-5), which ensures uniformity of impregnation, since the liquid mixture in such quantity completely covers the IG particles.

[0051] The term "organosilicon compound" includes silanes or siloxanes with organic substituents. Silanes are a silicon atom connected to four functional groups. Siloxanes are a polymer chain of silicon atoms with two functional groups and oxygen atoms. The organosilicon compounds used in the invention may be compounds selected from the group of monosubstituted alkylsilanes i SiR^ and phenylsilanes R 2 SiR 3 3 where R x = - СН3, -С2Н5, -С3Н7, etc. (in general -C n H2n+i), R 2 = -Сб (phenyl group), R 3 = -C1, -OC2H5, disubstituted alkyl and phenyl silanes: R SiR 3 2, R 2 2SiR 3 2, R 1 R 2 SiR3 2. polyalkyl and polyphenyl siloxanes - [SiR^- O] n -, -[SiR 2 2 -O] n -, -[SiR^ 2 -O] n -.

[0052] Alkyl and phenyl substituents R 1 and R 2 are hydrophobic and thus form the basis of the hydrophobic modification. Chlorine and ethoxy groups R 3 are the binding groups by which silanes bind to the oxygen groups of the IG and are retained on its surface. In the case of polysiloxanes, such groups are the terminal -OH, -C2H5 groups, which are located at the ends of the polymer chains.

[0053] Suitable solvents for organosilicon compounds are also widely presented in the prior art, and it is noted that virtually any organic solvent can be used for these purposes. Organic solvents for organosilicon compounds include solvents such as alcohols, ketones or alkanes, ethers including methanol, ethanol, pentane, hexane, cyclohexane or toluene, and others.

[0054] An aqueous solution of ammonia is used as a catalyst for the hydrolysis and intermolecular crosslinking of silanes / siloxanes, which leads to the formation of larger chains of polysiloxanes that condense on the IG matrix. An aqueous solution of ammonia that meets the requirements of GOST 9-92 "Technical aqueous ammonia" can be used for these purposes. The catalyst significantly accelerates these processes, which without a catalyst last several days. An aqueous solution of ammonia is the most suitable for these processes, since it contains both ammonia, which catalyzes the process, and water, which is directly involved in hydrolysis. In this case, ammonia is easily removed at the drying stage and does not remain in the IG and then in the TEG as an impurity.

[0055] Suitable solvents for organosilicon compounds are widely presented in the prior art, and the presented prior art notes that virtually any organic solvent can be used for these purposes. Organic solvents for organosilicon compounds include solvents such as alcohols, ketones or alkanes, ethers, including methanol, ethanol, pentane, hexane, cyclohexane or toluene, and others.

[0056] Stage (B) At stage (B), the excess liquid of the mixture is filtered from the intercalated graphite, while condensed particles of siloxanes remain on the surface of the IG particles.

[0057] Stage (B)

[0058] During drying at stage (B), volatile organic solvents are removed from the surface of the IG particles, and drying is carried out to a free-flowing state. Drying is carried out at temperatures from room temperature and above. It is clear that a higher temperature reduces the drying time, but in this situation, temperatures at which the IG begins to decompose should be avoided, which can lead to worse foaming at the stage of thermal expansion.

[0059] Stage (G)

[0060] At stage (G), heat treatment of the IG with condensed siloxanes on its surface is carried out. Heat treatment is carried out in the thermal shock mode (heating rates can reach 400-600%). The heat treatment temperature is from 300 to 1000 °C. In this case, the most desirable foaming temperature for IG based on electrochemically oxidized ICG with nitric acid is 300-700 °C, IG based on stage II graphite nitrate obtained by a chemical method is 500-700 °C, IG based on stage I graphite bisulfate is 400-700 °C, IG based on stage II graphite bisulfate is 500-700 °C. In these ranges, effective thermal expansion occurs with the formation of TEG with a low bulk density of 3-7 g / l, which allows pressing materials and compacts of various densities from TEG starting from 0.01 g / cm3. During thermal expansion of IG, TRG is formed, containing particles of siloxanes with alkyl and phenyl substituents.These silanes concentrate on the residual oxygen groups in the structure of TEG, on defects in the volume and on the surface of TEG, and thus C-O-Si-R bonds are formed in which an alkyl or phenyl substituent R with a hydrophobic nature is located on the surface, which leads to an increase in the hydrophobicity of TEG.

[0061] At the same time, siloxanes that are on the surface of the IG practically do not decompose due to the high strength of the bond between silicon and the alkyl or phenyl substituent.

[0062] At heat treatment temperatures up to 700°C the best results are achieved, i.e. TEG with maximum hydrophobicity is formed, i.e. minimum water contact angle and minimum water absorption. At temperatures from 700°C to 1000°C the decomposition of siloxanes and reduction of hydrophobicity begin, however TEG samples obtained at this temperature have acceptable hydrophobicity exceeding the hydrophobicity of unmodified samples. Foaming above 1000°C is impractical, since at this temperature active oxidation of graphite begins and the yield of TEG decreases significantly.

[0063] After stage (G), it is possible to compact the obtained hydrophobic TEG into compacts of various shapes by pressing or rolling. Density 0.01 g / cm 3 is the minimum at which the compact has mechanical strength and integrity, density 1.9 g / cm 3 - the maximum density to which the TRG can be rolled.

[0064] Low-density organosilicon-modified TEG from the density of TEG in powder form to a density of 0.5 g / cm 3 can be used as a hydrophobic sorbent for selective sorption of oil, liquid hydrocarbons and organic substances from water. In this case, TRG will sorb oil, hydrocarbons and organic substances and will not sorb water. Compacted materials based on TRG with a density higher than 0.5 g / cm 3can be obtained by pressing or rolling into foil. Graphite foil is a promising sealing material and has such unique properties as thermal stability in a wide temperature range (up to 450°C), high chemical resistance, mechanical strength, elasticity, and recoverability. Modification of TEG to increase hydrophobicity and reduce water absorption improves the sealing of TEG products due to reduced penetration of liquid into the pores of the material, which will have a positive effect on the sealing ability of the material in relation to aqueous media: water, steam, aqueous solutions.

[0065] Examples of the invention

[0066] Example 1

[0067] Intercalated graphite obtained by electrochemical oxidation of natural flake graphite in 60% nitric acid solution was used. The IG sample from electrochemical graphite nitrate is designated as NG-E in Table 1.

[0068] A mixture was prepared consisting of 2 ml of dichloromethylphenylsilane dissolved in 30 ml of isopropanol, then 60 μl of aqueous ammonia solution were added to the resulting solution using a pipette (data recalculated for the mass of reagents are given in Table 1, see column 3). 10 g of IG were added to the container with the mixture, and the IG was soaked in the solution for about 30 minutes. Then the IG was filtered on a porous glass filter and dried for 6 hours in air.

[0069] The process of thermal expansion of IG was carried out in an air atmosphere at a temperature of 300°C. Then the TRG was pressed to densities of 0.01; 0.03; 0.05; 0.07, 0.1 g / cm 3 in the form of a cylinder 4 mm high and 20 mm in diameter. TRG was also pressed into flat plates with a density of 0.5; 1.0; 1.5; 1.9 g / cm 3 and with a height of 50 mm, a width of 10 mm and a thickness of 0.5 mm.

[0070] Also, IG was foamed at temperatures of 400, 500°C and pressed to a density of 0.03 g / cm 3 .

[0071] The contact angle of water, octane and glycerol was determined by the force method using an Attension Sigma tensiometer. The force tensiometer measures the weight when a solid sample is brought into contact with the test liquid. The contact angle was then calculated using the equation:

[0072] F = yP-cos9 where y is the coefficient of surface tension of the liquid, P is the perimeter of the sample, 9 is the dynamic wetting angle. The measurement error of the angle was ± 2.

[0073] As a result, the "immersion" angle (9ADV) and the "removal" angle (9REC) obtained by lowering the sample into the liquid and extracting it back, respectively, were measured. The cosine of the equilibrium contact angle of wetting with water COSOEQU was calculated as:

[0074] COSOEQU = 0.5-(COS9ADV + COSOREC)

[0075] After which 9EQU was calculated from the arccosine of the COSOEQU value.

[0076] Water absorption of TEG was measured as the ratio of the sorbed substance to the mass of the sorbent. For the study, pre-weighed materials from TEG were placed in a sieve with 1 mm holes, which was immersed in the liquid being studied for 15 minutes. Then the sieve with the material was removed and the mass of the material with the sorbed liquid was measured. Sorption capacity (S, g / g) was determined by the formula:

[0077] Zvvdkost = (GP2 — TP1) / TP1, where mi is the mass of TRG before sorption, m2 is the mass of TRG after sorption.

[0078] Equilibrium contact angle with water for a modified sample with a density of 0.03 g / cm 3 was 92°, and water absorption was 0.45 g / g (Table 1, No. 1.2), which is 30 times greater than that of the unmodified sample of the same density, for which water absorption was 15 g / g.

[0079] Water absorption of modified samples No. 1.1 -1.9 decreased from 0.53 to 0.02 g / g with an increase in density from 0.01 to 1.9 g / cm 3(Table 1 No. 1.1-1.9). In this case, the wetting angle of samples No. 1.1-1.9 was higher than 90°, which indicates their hydrophobicity.

[0080] Samples of compressed TRG with a density of 0.03 g / cm 3 at a temperature of 400 and 500°C, the TRGs had water absorption of 0.48 and 0.51 g / g (No. 1.10 and 1.11 in Table 1).

[0081] Example 2.

[0082] To obtain the TEG modified with organosilicon compounds, stage I graphite bisulfate was used, which was obtained by reacting 50 g of natural flake graphite with potassium dichromate (8.5 g) and sulfuric acid (100 ml). The sample of IG from stage I graphite bisulfate is designated as BSG-1 in Table 1.

[0083] A mixture was prepared consisting of 2 ml of dichloromethylphenylsilane dissolved in 30 ml of solvent (isopropyl alcohol, acetone, heptane), then 60 μl of 25% aqueous ammonia solution were added to the resulting solution using a pipette. 0.7 g of IG was added to the container with the mixture. IG was impregnated in the solution for about 30 minutes. Then IG was filtered on a glass porous filter and dried for 6 hours in air.

[0084] The process of thermal expansion of IG was carried out in an air atmosphere at a temperature of 400°C. Then the TRG was pressed to a density of 0.03 g / cm 3 in the form of a cylinder 4 mm high and 20 mm in diameter and rolled to a density of 0.5 g / cm 3 in the form of a plate 50 mm high, 10 mm wide and 0.5 mm thick.

[0085] The wetting angle of water, octane and glycerol was determined by the force method using an Attension Sigma tensiometer, the water absorption of the TRG was measured as the ratio of the sorbed substance to the mass of the sorbent, as described in Example 1.

[0086] Compacts TRG based on BSG-1 with a density of 0.03 and 0.5 g / cm 3 without modification have water absorption of 16 and 6.5 g / g and water contact angle of 43 and 56°. TRG compacts obtained from IG impregnated in isopropanol, acetone and heptane solutions of silane have water absorption of 0.04-0.3 g / g and 0.001-0.006 g / g, respectively, for densities of 0.03 and 0.5 g / cm 3 (No. 2.1-2.6 in Table 1). In this case, the water contact angle is 91-95 and 92-102° for these densities. Example 3.

[0087] To obtain TEG modified with organosilicon compounds, intercalated graphite was used, obtained by the interaction of natural flake graphite with fuming nitric acid in a mass ratio of w(graphite):w(NUO3) = 1: 1.4. The IG sample from stage II graphite nitrate is designated as NG-II in Table 1.

[0088] A mixture was prepared consisting of 2 ml of silane (dichlorodimethylsilane, dichlorodiphenylsilane, dichloromethylphenylsilane or trichloromethylsilane) dissolved in 30 ml of isopropyl alcohol, then 85, 45, 60 and 70 μl of a 25% aqueous ammonia solution were added to the corresponding silane solutions using a pipette. A mixture was also prepared consisting of 2 ml of trichloromethylsilane with 1.55 ml of an aqueous ammonia solution in 120 ml of isopropyl alcohol, with 250 μl of an aqueous ammonia solution in 50 ml of isopropyl alcohol, with 20 μl of an aqueous ammonia solution in 20 ml of isopropyl alcohol. 10 g of IG were added to the container with each mixture. IG was impregnated in the solution for about 30 minutes. Then the IG was filtered on a glass porous filter and dried for 6 hours in air.

[0089] The process of thermal expansion of IG was carried out in an air atmosphere at a temperature of 500°C. Then the TRG was pressed to a density of 0.03 g / cm 3 in the form of a cylinder 4 mm high and 20 mm in diameter.

[0090] The wetting angle of water, octane and glycerol was determined by the force method using an Attension Sigma tensiometer, the water absorption of TRG was measured as the ratio of the sorbed substance to the mass of the sorbent, as described in Example 1.

[0091] TRG compacts with a density of 0.03 g / cm3 based on NG-P without modification had a water absorption of 12 g / g. TRG compacts (density 0.03 g / cm3) based on NG-P, which was impregnated in an isopropane solution of dichloromethylphenylsilane, dichlorodimethylsilane, dichlorodiphenylsilane had a water absorption of 0.37; 0.11; 0.13 g / g (No. 3.1-3.4 in Table 1) and wetting angles of 92-98°. Samples from NG-P impregnated in trichloromethylsilane solutions in isopropanol had a water absorption of 0.085-0.18 g / g (No. 3.5-3.7 in Table 1).

[0092] Example 4.

[0093] For impregnation with siloxane solutions, samples of intercalated graphite (NG-E, NG-P, BSG-I) obtained in accordance with examples 1-3 were used, as well as IG based on stage II graphite bisulfate (designated as BSG-P), obtained using a method similar to the method for obtaining stage I bisulfate (example 2), but using 4.25 g of potassium dichromate to introduce sulfuric acid into 50 g of graphite.

[0094] A mixture was prepared consisting of 2 ml of siloxane (dimethylsiloxane and methylphenylsiloxane) dissolved in 30 ml of diethyl ether, then 10 μl of 25% aqueous ammonia solution were added to the corresponding siloxane solutions using a pipette. 3 g of IG were added to the container with each mixture. The dimethylsiloxane-based mixture was also mixed with IG (NG-P) in the proportions w(NG-P):w(composition) = 1:0.02 and 1:5. IG was impregnated in the solution for about 60 minutes. Then IG was filtered on a porous glass filter and dried for 6 hours at a temperature of 40°C.

[0095] The process of thermal expansion of IG was carried out in an air atmosphere. Intercalated graphite NG-E was foamed at 300°C, NG-P - at 500°C, BSG-1 at 400°C and 600°C, BSG-P - at 500°C. Then TRG was pressed to a density of 0.03 g / cm 3 in the form of a cylinder 4 mm high and 20 mm in diameter.

[0096] The wetting angle of water, octane and glycerol was determined by the force method using an Attension Sigma tensiometer, the water absorption of TRG was measured as the ratio of the sorbed substance to the mass of the sorbent, as described in Example 1.

[0097] Pressed TRG from NG-E, NG-P, BSG-P, BSG-1, impregnated in a solution of dimethylsiloxane and obtained at temperatures of 300, 500, 500, 400°C, respectively, had water absorption of 1.8; 2.1; 2.3; 1.9 g / g (No. 4.1-4.4 in Table 1). Pressed TRG from BSG-1, impregnated in a solution of dimethylsiloxane and obtained at a temperature of 600°C, had slightly higher water absorption of 2.8 g / g (No. 4.5 in Table 1). Pressed TRG from BSG-1, impregnated in a methylphenylsilane solution and obtained at a temperature of 400 and 600°C, had slightly higher water absorption of 2.1 and 3.4 g / g, respectively (No. 4.6, 4.7 in Table 1). Samples pressed to 1 g / cm 3 thermally expanded graphite from NG-P, impregnated in a mixture with a ratio of w(NG-P):w(composition) = 1:0.02 and 1:5 had water absorption of 0.12 and 0.086 g / g (No. 4.7, 4.8 in Table 1).

[0098] Samples of compressed TRG (density 0.03 g / cm 3) from NG-E, NG-P, BSG-P without modification, obtained at the same temperatures had water absorption of 15, 12, 17 g / g. Samples of pressed TRG (density 0.03 g / cm 3 ) from BSG-1 without modification, obtained at 400 and 600°C had water absorption of 18 and 10 g / g.

[0099] As follows from the data provided, the material based on TEG modified with organosilicon compounds, obtained in accordance with the invention, has good hydrophobic characteristics and can be easily implemented in industrial production, i.e. can be manufactured with the least expenditure of labor and resources in a simple and technologically advanced way.

[0100] Table 1

[0101]

[0102]

[0103]

Claims

CLAUSE OF THE INVENTION 1. A composition for impregnating intercalated graphite, comprising at least one organosilicon compound selected from the group consisting of alkyl-substituted and phenyl-substituted silanes and polyalkyl- and polyphenylsiloxanes, an aqueous solution of ammonia and an acceptable organic solvent in the following mass ratio of components, mass, parts: organosilicon compound 1 aqueous solution of ammonia 0.001- 0.15 organic solvent 1-10 2. Composition according to I. 1, characterized in that monosubstituted alkylsilanes i SiR^ and phenylsilanes: R are used as organosilicon compounds. 2 SiR 3 3, disubstituted alkyl and phenyl silanes: R 1 2SiR 3 2, R 2 2SiR 3 2, R 1 R 2 SiR 3 2, polyalkyl and polyphenyl siloxanes -[SiR^ - O] n -, -[SiR 2 2 - O] n -, -[S i R 1 R 2 - ABOUT] п where R x= -CnH 2n+ i, R 2 = -C6H5, R 3 = -OH, -Cl, -OCnH 2n+i 3. A hydrophobic material, which is thermally expanded graphite impregnated with the composition according to item 1, in the form of a powder.

4. Material according to item 3, characterized in that it is modified with organosilicon compounds to a density of 0.01 g / cm 3 up to 1.9 g / cm 3 .

5. A method for producing a hydrophobic material based on thermally expanded graphite modified with organosilicon compounds according to I. 3, comprising the following stages: (A) impregnation of intercalated graphite with a composition according to item 1, containing at least one organosilicon compound selected from the group consisting of alkyl-substituted and phenyl-substituted silanes and polyalkyl- and polyphenylsiloxanes, an aqueous solution of ammonia and an acceptable organic solvent in the following mass ratio of components, mass, parts: organosilicon compound 1 aqueous solution of ammonia 0.001- 0.15 organic solvent 1-10 and with the ratio of the mass of intercalated graphite to the mass of the impregnating composition, mass, parts: 1: (0.02-5); (B) removal of excess liquid phase; (B) drying the mixture obtained in step (B) to a free-flowing state; (G) heat treatment of the dried mixture from step (B) at a temperature from 300 to 1000°C to obtain particles of thermally expanded graphite modified with organosilicon compounds.

6. The method according to item 1, characterized in that in which monosubstituted alkylsilanes R are used as the organic silicon compound in stage (A). x SiR 3 3 and phenylsilanes: R 2 SiR 3 3, disubstituted alkyl and phenyl silanes: R^SiR^, R 2 2SiR 3 2, R 1 R 2 SiR 3 2, polyalkyl and polyphenyl siloxanes -[SiR^ - O]n - [SiR 2 2- O]n-, - [SiR x R 2 - ABOUT] п -., where R x = -CnH 2n+ i, R 2 = -C6H5, R 3 = -OH, -Cl, - OCnH2n+l 7. The method according to item 1, characterized in that after stage (G), the particles of thermally expanded graphite modified with organosilicon compounds are compacted to a density of 0.01 g / cm3. 3 up to 1.9 g / cm 3 .

8. The method according to item 3, characterized in that compaction is carried out by pressing and / or rolling.

9. The method according to item 1, characterized in that the heat treatment at stage (G) is carried out at a temperature of 300-700°C in air.

10. The method according to item 1, characterized in that the heat treatment at stage (G) is carried out at a temperature of 600-1000°C in a nitrogen environment.

11. Use of the material according to I. 3 modified with organosilicon compounds as a hydrophobic sorbent for the selective sorption of oil, liquid hydrocarbons and organic substances from water.

12. Use of material according to I. 3 modified with organosilicon compounds for the production of compacted materials.

13. The use according to item 12, characterized in that the compacted materials can be obtained by pressing or rolling into foil.

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