RU2211206C2 - Method for surface hydrophobization of sedimentary and metamorphous rocks - Google Patents

Abstract

FIELD: mineralogy. SUBSTANCE: invention relates to treatment of naturally occurring stones and can be applied for restoration of historical monuments (sculptures, columns, buildings, and constructions). Method is characterized by that stone surface is treated with 0.005-0.12% solution of fulleren mixture in organic solvent and then with hydrophobizing organosilicon fluid, in particular with 24-26% solution of polydiethylhydrosiloxane in tetraethoxysilane or, in another embodiment, silane-siloxan-based impregnating solution Funcosil 1C serving for protection of stone materials. EFFECT: imparted durable hydrophobization to marble and alike materials. 3 cl, 1 dwg, 2 tbl, 7 ex

Description

 The invention relates to the processing of natural stone, in particular to the hydrophobization of sedimentary and metamorphic carbonate rocks (limestones, dolomites, marble), and may find application in works to protect historical monuments from destruction and in the restoration of historical monuments of sculpture, columns, buildings and structures.

 The destruction of stone materials, including marble and marble-like limestones, is associated with the penetration of water into the stone structure. To protect against penetration of water, the surface layer of stone is tried to be hydrophobized by applying hydrophobizing substances to the surface.

 Silicon-containing monomeric, oligomeric and polymeric compounds, such as alkali metal silicates, alkyl alkoxy or alkyl hydroxysilanes, polyalkyl hydrosilanes, polyalkyl (aryl) siloxanes with terminal hydroxyl groups, or mixtures thereof, are most often used as hydrophobizing agents. They are applied to the surface of the stone in the form of aqueous solutions, emulsions or solutions in organic solvents. Water repellents reduce the water absorption characteristics of the stone.

 Marble and dense marbled limestone exhibit a low ability to protect with hydrophobic compounds. The decrease in water adsorption after processing marble and stone types similar to it is not long-term, and the amount of water absorption on its surface is restored after several years of marble exposure in an industrial atmosphere. The difficulty of hydrophobizing the surface of marble and similar stones is due to the low porosity of the material, which makes it difficult to penetrate deep into the stone, as well as poor interaction of calcite and dolomite with organosilicon compounds. To increase the adhesion of the water-repellent agent to the stone, pre-treatment of its surface with substances capable of increasing the degree of adhesion of the reagent is used.

 A known method of surface hydrophobization of stone, including surface pretreatment with γ-amnopropyltriethoxysilane [AGM-9], followed by treatment with silicones with ethoxy groups [Rohov ED The world of silicon. - M.: Chemistry, 1990, p. 119 and 120]. Modification of the surface with this preparation leads to the formation on the hydrophilic surface of the stone of a layer of chemisorbed γ-aminopropyltriloxysilane molecules capable of more strongly adsorbing the hydrophobizing molecule, an organosilicon polymer.

 However, according to our data, the AGM-9 modifier does not give a satisfactory result on all stones, and, in particular, the marble does not produce a hydrophobic effect that is stable over time when exposed to atmospheric factors.

 Also known is a method of surface hydrophobization of heavily destroyed Carrara marble, comprising pre-treating the surface with hydrolyzed tetraethoxysilane and subsequent processing of the marble with methyl phenyl polysiloxane [Alessandrini G., R. Bonecchi, E. Broglia, et al. Les colones de San Lorenzo (Milan, Italie): identification des materiaux, causes d'alteration, convervasion. "The Enginering geology of ancient works, monuments and historical sites. Preservation and protection: Proceedings of the international symposium organizated by Greek national group of IAEG, Athens, 19-23 September, 1988, pp. 925-932"].

 Such processing of the destroyed marble turned out to be effective, however, this coating proved to be unstable in time in more severe climatic conditions of Russia and, in particular, St. Petersburg.

 Also known is a method of surface hydrophobization of building materials and, in particular, concrete by emulsion of polydiethyl hydrosiloxane in tetraethoxysilane [USSR Author's Certificate 872518, MKI C 04 B 41/28, publ. 15.10.81, BI 381. Processing with the specified water repellent agent allows to successfully protect the concrete surface from atmospheric influences, but in the case of marble and marble-like limestones this treatment is insufficient and the hydrophobicity is quickly lost.

 The technical result, which is achieved by the claimed method, is to impart long-term surface hydrophobicity to marble and similar materials, that is, sedimentary and metamorphic carbonate rocks.

 The specified technical result is achieved in the method of surface hydrophobization of sedimentary and metamorphic carbonate rocks, characterized in that the surface of the stone from these rocks is pre-treated with a 0.005-0.12% solution of a mixture of fullerenes in an organic solvent, and then with a hydrophobizing organosilicon liquid.

 In the inventive method, a 24-26% solution of polydiethyl hydrosiloxane in tetraethoxysilane and a ready-to-use impregnating composition for protecting stone materials based on Silcosiloxanes Funcosil 1C (Remmers) are used as a hydrophobizing liquid.

 These solutions (and their components) are commercially available.

We obtained fullerenes as described in [Optical Journal, 1997, v. 64 (9), 12, p. 4-8]. The mixture contains 80-99.5% of fullerene C ₆₀ and 0.5-20% of fullerene C ₇₀ , and may also contain a small amount of other fullerenes. A mixture containing 0.5% fullerene C ₇₀ was used in the processing of white marble. Mixtures containing more than 0.5% C ₇₀ fullerene, especially mixtures with a high (up to 20%) C ₇₀ fullerene content, were used to process colored (yellow, pink) marbles and marble-like limestones.

Fullerenes are soluble in organic solvents, such as benzene, toluene, xylene, white spirit (that is, the fraction of the distillation of oil, boiling at 130-180 ^o C); preferably, a solution of fullerenes in white spirit is used as the least toxic and fire hazardous.

 The invention is further illustrated by examples on marble as the most complex object for hydrophobization, but not limited to.

 Example 1

 Samples of Carrara marble 5 x 5 cm in size were treated with a 0.005% solution of fullerenes, for example, in white spirit at the rate of 100 g of fullerene solution per square meter of marble surface. After drying in air for 2 days, a 25% solution of polydiethyl hydrosiloxane in tetraethoxysilane was applied to pre-treated marble samples at the rate of 200 g of solution per square meter of surface.

 The samples were kept in the open air at a relative humidity of 70-85% for 12 days, after which the adsorption of water was determined by rapidly immersing the samples in water for 24 hours. The result is presented in table.2.

Величина К_гидр составила 0,60.To determine the possibility of long-term protection of the marble surface, the hydrophobicity coefficient (K _hydr ) was determined. This coefficient is defined as the change in the evaporation rate of a calibrated drop of distilled water from the marble surface (S _arr ) compared with the rate (S _para ) of the evaporation of the same droplet from the hydrophobic surface of paraffin (contact angle 105-107 ^o ) and the evaporation rate of the same droplet (S _article ) with a hydrophilic glass surface (contact angle of contact 45 ^o )

The value of K _hydr was 0.60.

Climatic tests were also carried out, including 100 cycles of temperature changes from +60 to -20 ^o C, water treatment and exposure of samples under hard ultraviolet radiation. After 100 test cycles, the value of K _hydr was 0.71, that is, less than 1. Values of K _hydr above unity indicate that water is absorbed by the surface of the sample (see Table 1).

 Example 2

 5 samples of Ural marble were processed and tested as in example 1, but the treatment was carried out with a 0.012% solution of fullerenes in white spirit with the addition of ortho-xylene.

 The test results are shown in table 1.

 Example 3

 5 samples of Carrara marble were processed and tested as in example 1, but pretreatment was carried out with a 0.12% solution of fullerenes in white spirit with the addition of ortho-xylene. The test results are shown in table 1. After processing, the surface of the marble became grayish.

 Example 4 (control).

 5 samples of Carrara marble were processed and tested as in Example 1, but pretreatment was carried out with γ-aminopropyltriethoxysilane [AGM-9] in the form of a 10% solution in an organic solvent.

 The test results are presented in table 1.

 Example 5 (control).

 5 samples of Carrara marble were coated with a solution of polydiethyl hydrosiloxane in tetraethoxysilane without pretreatment.

 The tests were carried out as in example 1, but the test cycles were 50, since the surface of the marble became completely hydrophilic.

 The test results are presented in table 1.

 Example 6

 5 samples of Carrara marble 5 x 5 cm in size were treated with a 0.005% solution of fullerenes in white spirit as in Example 1. After drying in air for 2 days, a prepared solution of the impregnating composition based on Silcosiloxanes Funcosil 1C was applied to pre-treated marble samples. based on 100 g of solution per square meter of surface. Samples were tested as in example 1. The test results are shown in table 1.

 Example 7 (control).

 5 samples of Carrara marble were coated with a solution of an impregnating composition based on Funcosil 1C silane-siloxanes without preliminary treatment.

 The test results are presented in table. 1.

 The remaining breeds obtained similar results.

The graph (see drawing) shows the nature of the change in the coefficient of hydrophobicity during the test:
curve 1 - with pretreatment of AGM-9;
curve 2 - without preliminary processing;
curve 3 - with preliminary treatment with a 0.12% solution of fullerenes;
curve 4 - with pre-treatment with a 0.01% solution of fullerenes.

 The graph shows that the surface of marble treated with a 0.005-0.12% solution of fullerenes followed by hydrophobization with a 25% solution of polydiethylhydrosiloxane in tetraethoxysilane remains practically hydrophobic after 100 test cycles, which corresponds to at least 5-7 years of marble being in the open air. An increase in the concentration of fullerenes does not improve the hydrophobicity of marble, but significantly increases the cost of processing. Pre-treatment with another soil (AGM-9) or the absence of this treatment leads to a rapid loss of hydrophobicity.

After all tests, the water adsorption coefficients were determined for all samples at a water column height of 10.0 cm (K _ads in ml / m ² • h ^0.5 ) (see Table 2).

 From table 2 it is seen that during pre-treatment with fullerene solutions, the surface retains the ability not to pass moisture when creating hydrostatic pressure.

Claims (3)

 1. The method of surface hydrophobization of sedimentary and metamorphic carbonate rocks, characterized in that the surface of the stone from these rocks is pre-treated with a 0.005-0, l2% solution of a mixture of fullerenes in an organic solvent, and then with a hydrophobizing organosilicon liquid.  2. The method according to p. 1, characterized in that a 24-26% solution of polydiethyl hydrosiloxane in tetraethoxysilane is used as a hydrophobizing organosilicon liquid.  3. The method according to p. 1, characterized in that as a hydrophobizing organosilicon liquid, an impregnating composition is used to protect stone materials based on Silcos - Siloxanes Funcosil 1C.

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