DE2426306B2 - METHOD FOR CHEMICAL MODIFICATION OF SOLID SURFACES USING SILANES - Google Patents

Description

-SO ₃ H

-SH -OH

- CN

-NO ₂ -COOH-SO-R
-CH CH ₂ -CH = CH ₂ -NR ₂

35

40

NR ₃

-O-R-S-R groups

are introduced, where R is an alkyl chain

8. The method according to claims 1 to 7, characterized in that with as starting material reactive surface silica, in particular silica gel, glass, metal oxides or brick dust be used.

9. The method according to dei «claims 1 to 8, characterized characterized in that a gas-impermeable solid with reactive, porous surface is used.

10. The method according to claims 1 to 9, characterized in that the dried Solid suspended in a dried solvent, the suspension with the silane and the Added catalyst and then held for a few hours at an elevated temperature. (> o

The invention relates to a method for chemical modification of the surfaces of inorganic, reactive ones Solids containing hydroxyl groups due to silanes.

Several methods of modifying solids have been devised. In the German Patent specification 1902 226 describes the esterification of silicon dioxide with substituted alcohols. The organic molecules are bound to the surface of the solid by the = Si-O-C = bond, However, it is known that it is not sufficiently stable to hydrolysis and temperature

According to the German Offenlegungsschft 22 36 862, the silanol groups of silicon dioxide (e.g. Silica gel) by chlorination into the = Si — Cl groups These reactive groups are converted in the second stage with amines to form the = si — N = bond converted. Such products are only stable to hydrolysis in a pH range of 4-8, i. H. Can only be used to a limited extent in practical application. It is not possible for the catalysis that Ion exchange and chromatography to regenerate important -SOjH groups

(-SO ₃ Na + HCl- -SO3H + NaCI),

because for the regeneration dilute acids with a pH value <1 can be used. Buffer solutions are often used for liquid chromatographic separations needs whose pH value is outside the stability limits of such stationary phases. Under these conditions the Si-N = bond is broken quickly.

Another method for modifying inorganic solids is in German Offenlegungsschrift 23 13 073 described. After this Processes are converted into solids with alkylchlorosilanes, after which they are converted into the alkyl chains bonded to the surface of the solid introduce halogen atoms, and these become then substituted by functional groups. It is known that the = Si-C = bond is particularly hydrolysis and temperature stable. Since the organic molecules bind to the Are surface bound, such modified solids are characterized by high stability. A The disadvantage of this method is the large amount of time required for such conversions; the modification reactions take more than ten days. Another disadvantage is that the binding of the functional groups on the solid via alkyl chains through multi-stage reactions on the Solid surface happens. In multi-stage reactions, however, the yields are lower, so that the desired maximum surface concentration of functional groups according to this method is not reachable.

The object of the invention is to develop a method by which chemically surface-modified oneself Allow solids to be obtained that are more stable to hydrolysis and temperature than the known ones chemically modified solids and a much greater surface concentration of functional Groups are labeled as this.

This object is achieved in that the solid surfaces in the presence of catalysts reacts with the exclusion of moisture with alkyl, aryl or aralkylalkoxysilanes, which through functional groups, preferably in the ω-position, are substituted.

Further aspects and features of the invention emerge from the following description and the Subclaims.

Such chemically modified solids can be used, for example, as catalysts, ion exchangers or sorbents. The application of For such processes, chemically modified solids offer the possibility of varying their selectivity

According to the invention, the dried solids with a reactive surface in a dried solvent (for example toluene, dimethylformamide) and treated with alkoxysilane, and catalyst (amine or sulfonic acid) was added The suspension is some hours under air exclusion of moisture at an elevated temperature (for example, 110 ⁰ C) gehaltea The solid state which now have modified surfaces are filtered off, freed from excess alkoxysilane, catalyst and solvent by washing with suitable liquids and dried

It was found that the chemical modification of the reactive solid surfaces with the inert substituted alkoxysilanes is accelerated with the aid of catalysts and the reaction temperature is reduced. This makes it possible to use those silanes for the modification reactions that contain functional groups.

Organic amines and sulfonic acids have proven particularly useful as catalytically active reagents. For steric reasons, primary amines are preferred (e.g. n-butylamine, ethylenediamine). from Sulphonic acids are both aliphatic (e.g. dodecylsulphonic acid) and aromatic (e.g. benzenesulphonic acid) used

According to the invention, substituted alkyl, aryl or aralkylalkoxysilanes are used for the modification reactions used. These organosilicon compounds are understood to be reagents in which the functional groups via alkyl, aryl and aralkyl radicals are bound to the SiCium atom. In addition, there is at least one alkoxy group on the silicon atom (e.g. methoxy, ethoxy group) bound.

From the large number of organosilicon reagents that can be used, let us consider the following called:

3-cyanopropyltriethoxysilane,

bis- (N, N-dimethyl-3-aminopropyl) -dimethoxysilane,

4-aminobutylmethyl diethoxysilane,

3-mercapto-propyl-methyldimethoxysilane,

Octadecyldimethylpropoxysilane,

(p-nitrophenyl-N-aminomethyl) dirnethylethoxysilane,

Dimethoxymethylsilyl (4-butylsulfonic acid Na salt),

N.N.N Trimethylammonium-S-p.ropylhydrochloride) -

methyldimethoxysilane,

3-phenyl-propylmethyldimethoxysilane,

[N-2 (aminoethyl) -3-aminopropyl] trimethoxysilane,

3-glycidoxypropylmethyldimetnoxysilane.

However, this list is by no means imitative.

The following have proven to be particularly suitable materials with a reactive surface:
Silica gel, metal oxides (AI ₂ O ₃ , TiO ₂ , ZK) ₂ ), porous glass, carrier materials (glass spheres, glass plates, ground bricks) and similar substances that have a porous silicon dioxide or metal oxide layer on the surface.

The solids modified according to this invention contain organic molecules bound on the surface via the hydrolysis- and temperature-stable = Si — C = bond. By introducing different functional groups, the chemical nature of the surface and thereby the selectivity of the modified solids is varied. This is particularly advantageous when using such products as sorbents, e.g. B. in chromatography, for environmental protection, as ion exchangers or as catalysts. Since the functional groups according to the invention in a one-step reaction and under mild reaction conditions to the solid surface

ίο be bound is their surface concentration very large.

It is still possible in many cases to use the functional groups on the surface of the Solid bound in a subsequent To implement the reaction further and thereby introduce new functional groups. The selectivity and the Sorption properties of the modified solid can thus also be changed in the desired manner.

The invention is illustrated by the following examples

example 1

20 g of silica gel with a specific surface area of 310 mVg and an average particle size of 80 μπι are dried for 12 hours at 150 ° C, with 100 ml of dried xylene, 5 ml of 3-cyanopropylmethyl diet

oxysilane and 1 ml of ethylenediamine (as a catalyst) were added and the mixture was kept at 11 5 ° C. for 5 hours with exclusion of atmospheric moisture.

Then, the silica gel is filtered off, several times with methylene chloride, methanol, methanol-water (1: 1), methanol and diethyl ether and dried in vacuum at 140 ⁰ C dried.

The surface of the solid has become hydrophobic as a result of the treatment and contains chemically bound CN groups. The product is very suitable as a stationary phase in gas chromatography.

Example 2

Example 1 is repeated, but the silica gel

with 100 ml of toluene, 5 ml of bis (N, N-dimethyl-3-aminopropyl) dimethoxysilane and 2 ml of butylamine (as a catalyst) are added and the mixture is left with the exclusion of moisture for 3 hours kept at 110 ° C.

The surface of the solid is basic due to the bound -N (CH ₃ ) 2 groups, and the product is an anion exchange ^.

Example 3

Example 1 is repeated, but instead of the silica gel, fine brick powder is used and this is reacted with 5 ml of 3-mercapto-propylmethyldimethoxysilane. Oxidation (e.g. with HNO ₃ ) converts the - SH groups on the surface into - SO ₃ H groups. The product is a strongly acidic cation exchanger.

Example 4

20 g of dried aluminum hydroxide is mixed with 100 ml of dried dimethylformamide, 4 g (Ν, Ν, Ν-trimethyl-3-arnmoniumpropyl) -methyldimeth-6_s oxysilanchlorid and 3 ml of dipropylamine (as catalyst) and held for 5 hours under air exclusion of moisture at 110 ⁰ C, then washed and dried analogously to Example 1.

The product contains surface-based
-N (CH ₃ ) ₃ C1 - group p

and is a strongly basic anion exchanger.

5 Example 5

Analogously to Example 1, 20 g of porous SiO ₂ coated glass beads with a specific surface area of 15 mVg are mixed with 100 ml of dried dimethyl sulfoxide, 3 g of dimethoxymethylsilyl 4-butyl ι ο sulfonic acid sodium salt and 04 g of benzenesulfonic acid (as a catalyst), and washed and dried

The product is made with 1N hydrochloric acid and water washed and is a strongly acidic cation exchanger.

Example 6

Analogously to Example 1, 20 g of dried porous glass with a specific surface area of 60 m ² / g are mixed with 100 ml of dimethylformamide, 4 g of dimethoxymethylsilyl-3-propylisothiouronium chloride and 1 ml of ethylenediamine (as catalyst), washed and dried. Oxidation (e.g. with H NO ₃ , H2O2) converts the propylisothiouronium chloride groups attached to the surface into propylsulfonic acid groups. The product is a strongly acidic cation exchanger.

Example 7 _{} 0}

A glass plate (7 × 5 cm ² ) covered with titanium hydroxide is dried at 150 ^° C. for 12 hours, with

50 ml of xylene, '3 g (p-nitrophenyl-N-aminomethyl) -dimethyläthoxysilan and 2 ml of benzylamine (as a catalyst) was added and maintained for 8 hours at 120 ⁰ C under Liiftfeuchtigkeitsausschluß. Washing and drying are carried out according to Example 1.

Such surface-porous plates with chemically bonded nitro groups are ideal as Element for thin layer chromatography.

Example 8

20 g of dried porous glass with a specific surface area of ^{150 m 2} / g are reacted with 5 g of N-2 (aminoethyl) -3-aminopropyl-trimethoxysilane analogously to Example 1, washed and dried

The product is washed with 100 ml of ethanol, 5 g of chloroacetic acid and 5 ml of tripropylamine was added (as a catalyst or for binding the hydrochloric acid) for 10 hours under refluxed for several times and dried in vacuo at 6O ⁰ C dried

The modified solid contains chemically bound -N (CH ₂ COOH) 2 groups on the surface, which are able to bind heavy metal ions.

Example 9

100 ml of cumene, 5 ml of 3-phenylpropyldimethylpropoxysilane and 1 ml of hexamethylenediamine (as a catalyst) are added to 20 g of dried zirconium hydroxide and the mixture is ^{kept at 130 °} C. for 10 hours with exclusion of atmospheric moisture. Washing out and drying are carried out as in Example 1. The modified solid surface is hydrophobic and contains chemically bonded phenylpropyl groups.

Claims (7)

Patent claims: 1. Process for chemical modification of the surfaces of inorganic, reactive Solids containing hydroxyl groups by silanes, characterized in that one the solid surfaces in the presence of catalysts with exclusion of moisture Reacts alkyl, aryl or aralkyl-alkoxysilanes, the ι ο are substituted by functional groups, preferably in the ω-position. 2. The method according to claim 1, characterized in that amines, preferably primary amines, are used as catalysts. ι s 3. The method according to claim 1, characterized in that organic sulfonic acids are used as catalysts be used. 4. Process according to claims 1 to 3, characterized in that substituted for modification Alkyl, aryl or aralkyl methoxysilanes are used will. 5. Process according to claims 1 to 3, characterized in that substituted for modification Alkyl, aryl or aralkylethoxysilanes can be used. 6. Process according to claims 1 to 5, characterized in that one in the modified, solids containing functional groups, in a manner known per se, further functional Groups. 7. The method according to claims 1 to 6, characterized in that as functional groups