GB2120672A

GB2120672A - Guanidinium (organo)-siliconates and (organo)-silicates

Info

Publication number: GB2120672A
Application number: GB08314613A
Authority: GB
Inventors: Gotz Koerner; Ulrich Holtschmidt; Jaroslav Langner
Original assignee: TH Goldschmidt AG
Current assignee: Evonik Operations GmbH
Priority date: 1982-05-29
Filing date: 1983-05-26
Publication date: 1983-12-07
Also published as: DE3220393A1; FR2527612B1; GB2120672B; GB8314613D0; DE3220393C2; FR2527612A1

Abstract

Guanidinium (organo)-siliconates and (organo)-silicates are useful for impregnating mineral building materials to render them hydrophobic. The compounds are of formula: <IMAGE> wherein each R<1> is alkyl of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms or phenyl; each R<2> is hydrogen, alkyl of 1 to 4 carbon atoms or alkenyl of 3 or 4 carbon atoms; a is 0 to <3.9, b is 0.1 to 4 and x is 0 to 1.25, with the proviso that x is >0 if R<2> is hydrogen, and ??? a+b+x</=4.

Description

SPECIFICATION Guanidinium (organo)-siliconates and (organo)-silicates This invention relates to guanidinium (organo)-siliconates and (organo)-silicates which are useful for impregnation of mineral building materials.

It is known to use alkali metal methylsiliconates in the form of their aqueous solutions for impregnating mineral building materials. A process for the preparation of particularly suitable alkali metal methylsiliconates is described in German Patent Specification 1,176,137. In this process, monomethylsilicon trichloride is reacted with an alkali metal hydroxide solution in such a way that the methylsilicic acid is precipitated, below 600 C, from the alkali metal methylsiliconate solutions containing alkali metal chloride by adding acid or compounds which split off acid until a pH value of about 4 is reached, and the methylsilicic acid which has been isolated is dissolved in equimolar quantities of alkali metal hydroxide solution and, if desired, the resulting solution is freed from water.

The products of the process are excellently suitable for impregnating mineral building materials, for example for impregnating facades or roof tiles. They can also be used in the form of powder and are, for example, mixed into mortar in this form. A particular advantage of the alkali metal siliconates prepared by this process is their low content of alkali metal chlorides. It is desirable for this content to be as low as possible, in order to avoid efflorescence of sodium chloride on the surface of the impregnated building materials.

However, even in the process of the abovementioned German Patent Specification 1,176,137, the difficulty persists that the precipitated methylsilicic acid is not stable on storage and must therefore be applied immediately. In addition, in this process, the precipitated methylsilicic acid also contains considerable quantities of water so that, even if only a 30% strength solution is prepared, water must be removed by distillation from the resulting solution of the sodium methyl-siliconate.

European Patent Application 0,01 5,366 is directed to a process in which alkali metal organosiliconate solutions free from alkali metal chloride are obtained, and in which, as far as possible, a filtration stage can be avoided, and which makes it possible to prepare solutions of any desired concentration.This European Application provides a process for the preparation of aqueous solutions of alkali metal organosiliconates in which an organoalkoxypolysiloxane of formula:

wherein R' is an alkyl radical of 1 to 3 carbon atoms, a vinyl radical and/or a phenyl radical; R2 is an alkyl radical of 1 to 4 carbon atoms; a is a number 62 and xis 1 to 1.25, is reacted at temperatures 800C with an aqueous solution of NaOH or KOH of a concentration of 0.7 to 0.9 [molx 100 9-1], and, if appropriate, the alcohol R20H which is liberated is removed by distillation and/or the solution of the reaction product is adjusted to the desired concentration with water.

However, it is a disadvantage inherent in the alkali metal siliconates of the state of the art, regardless of the manner in which they are prepared, that, when they are precipitated on the masonry with the formation of, for example, an organosiiicic acid, alkali metal carbonates are formed and these can result in efflorescence. A further disadvantage of the alkali metal siliconates is their low solubility in organic solvents. For practical purposes they can only be used from aqueous solutions. For this reason it is also possible to treat for example masonry once only, since it is rendered hydrophobic, at least on the surface, by the treatment and an aqueous siliconate solution cannot therefore penetrate, so that great difficulties are encountered in treating masonry repeatedly with such aqueous solutions.

The present invention provides guanidinium (organo)-silicates and (organo)-siliconates of formula:

which have been found to possess the desired properties. In formula I R' is an alkyl radical having 1 to 4 carbon atoms, for example a methyl, ethyl, propyl or butyl radical, it being also possible for the propyl or butyl radical to be branched; an alkenyl radical having 2 to 4 carbon atoms, particularly a vinyl or allyl radical; and/or a phenyl radical. Within the polymeric molecule, R1 can have a variety of these indicated meanings.

R2 denotes hydrogen, an alkyl radical having 1 to 4 carbon atoms and/or an alkenyl radical having 3 or 4 carbon atoms. The alkyl radical can again be a methyl, ethyl, propyl or butyl radical and can optionally be branched. The alkenyl radical can be, for example, an isopropenyl radical or an allyl radical. Within the polymeric molecule, R2 can also have a variety of meanings.

The index a has a value from 0 to < 3.9 and indicates the content of OR2 groups. The index b has a value from 0.1 to 4. x has a value from 0 to 1.25 and indicates the number of hydrocarbon groups attached to silicon. In the event that R2 denotes a hydrocarbon radical, xis > O. The total a+b+x must not be greater than 4.

Particularly preferred compounds are those in which R' is a methyl and/or phenyl radical, R2 is a hydrogen, methyl and/or ethyl radical, a=0.5 to 2, b=0.5 to 2, x=0.5 to 1.15 and ya+b+x=~ 4.

These guanidinium salts are soluble in water or polar solvents, such as alcohols, in particular methanol or ethanol, or in aqueous mixtures of these alcohols.

The compounds of formula I can be prepared in a simple manner by reacting guanidinium hydroxide with an organosilicon compound of formula

and, if desired, reacting the product of the process with finely divided SiO2 or with a silicic acid ester which is optionally partially hydrolysed. In this formula, R', R2 and x are as defined above and c has a value from > 0 to 4.

Since it was known from European Patent Application 0,01 5,366 that the reaction of the alkoxypolysiloxanes with the aqueous solutions of NaOH or KOH must be carried out at temperatures > 800C the implication to those skilled in the art was that guanidinium salts could not be prepared, since guanidinium compounds decompose to an extent which is already noticeable at temperatures above 800 C it was all the more surprising to discover that the reaction of guanidinium hydroxide with the organosilicon compounds of the formula 11 can be carried out virtually quantitatively even at substantially lower temperatures, namely within a temperature range from 0 to 800 C, in particular 20 to 500 C. Within this low temperature, there is not yet any risk of decomposition of the guanidinium hydroxide, particularly if a reaction temperature of 700C is selected.

The reaction can, if desired, be carried out in the presence of a solvent, examples of such solvents being water, water-miscible organic solvents or mixtures of water and these solvents. Water-miscible solvents which are particularly suitable are lower alcohols, such as methanol or ethanol.

As already indicated, the process of the invention can be carried further by reacting the product initially obtained further with finely divided SiO2 or with a silicic acid ester which is optionally partially hydrolysed. In this case the reaction takes place, for example, in the following partial stages:

This makes it possible to adjust the R':Si ratio in the manner desired.

The compounds according to the invention are particularly suitable for impregnating mineral building materials so as to render them hydrophobic. No carbonates causing efflorescence are formed under the action of carbon dioxide; on the contrary, the guanidine carbonate decomposes into urea and ammonia. in addition, it is possible to employ the guanidinium organosiliconates and silicates in the form of organic solutions, for example solutions in lower alcohols, and thus to effect better penetration of the mineral raw materials.

The process according to the invention will be illustrated in greater detail by the following Examples.

Example 1 24.5 g (0.3 mol) of a methylsilicone resin, described by the average formula

are added dropwise, in the course of 2 hrs., to a solution of 23.1 g (0.3 mol) of guanidinium hydroxide and 33.1 ml of water at 40 to 500C, while stirring vigorously. After stirring for 5 hrs. at 400C, the initially cloudy reaction mixture becomes a clear, 51.1% strength by weight solution of guanidinium methylsiliconate. Elementary analysis of the substance obtained by evaporating off the volatile constituents at 500C/15 mm Hg gives the following results: C 17.6%; H 6.9%; N 26.6%; Si 17.6%.

This leads to the following formula:

which has the theoretical values: C 17.73%; H. 7.53%; N 26.50%; Si 17.71% Example 2 Example 1 is repeated, with the exception that 49.0 g (0.3 mol) of a phenylsilicone resin, described by the average formula

are used instead of the methylsilicone resin. After stirring at 400C for 6 hrs., a clear, 63.2% strength by weight solution of a guanidinium phenylsiliconate is formed. Elementary analysis of the dry substance (dried at 500C/1 5 mm Hg) gives the following result: C 39.3%; H 6.1%; N 19.5%; Si 12.4%.

This leads to the following formula:

which has the theoretical values: C 39.0%; H 6.08%; N 19.5%; Si 13.0%.

Example 3 A solution of 49.2 g (0.3 mol) of n-propyltrimethoxysilane and 28.2 g of ethanol is added dropwise, at 40 to 500C in the course of 1 hr., to a solution of 23.1 g (0.3 mol) of guanidinium hydroxide and 25 g of ethanol, while stirring vigorously. After stirring for 8 hrs. at 400C, 1 2.6 ml. of water are added dropwise. A clear, 39.0% strength by weight solution of a guanidinium npropylsiliconate is formed. Elementary analysis of the dry substance gives the following results: C 26.2%; N 22.7%; Si 15.1%.

This leads to the following formula:

which has the theoretical values: C 26.5%; N 23.2%; Si 15.5%.

Example 4 A solution of 24.5 g of the methylsilicone resin described in Example 1 in 20 g of ethanol is added dropwise at 40 to 500C and in the course of 1 hr., to a solution of 23.1 g (0.3 mol) of guanidinium hydroxide and 13.5 g of ethanol, while stirring vigorously. After stirring for 8 hrs., a cloudy, viscous liquid is formed, and, on adding 26.8 g of ethanol, a clear, 40.0% strength by weight solution in ethanol of a guanidinium methylsiliconate is formed.

Example 5 The process according to Example 4 is repeated, with the modification that the mixture is stirred for 2 hrs. after adding the methylsilicone resin to the guanidine solution. 45.6 g of ethyl silicate 40 (40% of SiO2) are then added dropwise and the mixture is stirred for 6 hrs. at 400C and diluted with 68.7 g of ethanol to give a 40% strength by weight solution of a guanidinium methylsiliconate described by the average formula

Example 6 24.4 g (0.3 mol) of a methylsilicone resin, described by the average formula

are added dropwise, at 40 to 500C and while stirring vigorously, to a solution of 28.5 g (0.3 mol) of guanidine (62.1% strength by weight solution in ethanol) and 27.4 g of water, and stirred for a further 8 hrs. at 400 C A clear 51.4% strength by weight solution of a guanidinium methylsiliconate, described by the average formula

is obtained. Elementary analysis of the dry substance gives the following results: C 17.7%; H 7.5%; N 26.2%; Si 16.9% This leads to the following formula:

which has the theoretical values: C 17.94%; H 7.62%; N 26.47%; Si 17.7%.

Example 7 1.66 g (0.0125 mol) of dimethyldiisopropoxysilane are added to 23.2 g (0.0875 mol) of the 51.1% strength by weight aqueous solution of guanidinium methylsiliconate obtained as product in accordance with Example 1, and the reaction mixture is stirred vigorously at room temperature for 24 hrs. A clear solution of a guanidinium methylsiliconate described by the average formula:

is formed.

Example 8 9.24 g of guanidinium hydroxide in 31.8 g of ethanol are added dropwise, at 500C and while stirring vigorously, to a mixture of 24.5 g (0.3 mol) of the methylsiiicone resin described in Example 1 and 62.5 g (0.3 mol) of tetraethoxysilane, and the mixture is stirred at 500C for 6 hrs. A guanidinium methylsiliconate described by the average formula

is obtained.

Claims

1. A compound of formula:

wherein each R' which is identical or different, represents alkyl of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms or phenyl; each R2 which is identical or different represents hydrogen, alkyl of 1 to 4 carbon atoms or alkenyl of 3 or 4 carbon atoms; a is O to < 3.9; b is 0.1 to 4; x is O to 1.25, with the proviso that x is > O if R2 is hydrogen; and a+b+x14.

2. A compound according to claim 1, wherein R1 is methyl and/or phenyl; R2 is hydrogen, methyl and/or ethyl; a is 0.5 to 2, b is 0.5 to 2, xis 0.5 to 1.15andE:a+b+x~4.

3. A compound according to claim 1 specifically identified herein.

4. A process of preparing a compound as claimed in claim 1 or 2, which comprises reacting guanidinium hydroxide with a compound of formula

wherein R', R2 and x are as defined in claim 1 or 2 and c is > O to 4, with the priviso Sc+x < 4, and, if desired, reacting the resulting product with finely divided SiO2 or a silicic acid ester which is optionally partially hydrolysed.

5. A process according to claim 4, which is carried out in a solvent.

6. A process according to claim 5, which is carried out in water and/or in a water-miscible organic solvent.

7. A process according to any one of claims 4 to 6, which is carried out at O to 800C.

8. A process according to claim 7, which is carried out at 20 to 500 C.

9. A process according to claim 4 substantially as hereinbefore described with reference to any one of the Examples.

10. A method impregnating a mineral building material to render it hydrophobic which comprises applying thereto a compound as claimed in claim 1, 2 or 3.