Organopolysiloxane-alkyltrialkoxysilane emulsions for impregnati

Details Organopolysiloxane-alkyltrialkoxysilane emulsions for impregnati Organopolysiloxane-alkyltrialkoxysilane emulsions for impregnati

1993-08-20

1995-08-22

Group, Karl

Compositions: coating or plastic

Coating or plastic compositions

Coating repellent

106724, 10628714, 10628716, 427387, 4273936, C04B 2442, C04B 4164

Patent

active

054436273

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to aqueous emulsions of alkoxy-containing nitrogen-free organopolysiloxane and alkyltrialkoxysilane.
Aqueous emulsions of alkyltrialkoxysilanes, alkoxy-containing organopolysiloxanes with or without basic nitrogen are known from U.S. Pat. No 4,661,551 (issued 28 Apr. 1987, H. Mayer et al., Wacker-Chemie GmbH). These emulsions are highly suitable for imparting water repellency on building materials, including concrete and structural fibre-reinforced cement components. However, the building materials treated therewith yellow under the influence of light and air.
Aqueous emulsions of alkyltrialkoxysilanes for imparting water repellency on building materials are known inter alia from U.S. Pat. No. 4,877,654 (issued 31 Oct. 1989, M. E. Wilson, PCR Inc.). However, the alkyltrialkoxysilanes are relatively expensive.
The use of less costly emulsions of alkoxy-containing organopolysiloxanes for imparting water repellency on building materials is described in U.S. Pat. No. 4,704,416 (issued 3 May 1988, H. Eck and M. Roth, Wacker-Chemie GmbH). However, the water repellency imparting by such organopolysiloxanes is unsatisfactory.
When emulsions containing methyltriethoxysilane and polymethylsiloxane are used for impregnating the surfaces of building materials, the methyltriethoxysilane and the polymethylsiloxane separate, and the methyltriethoxysilane penetrates more deeply into the building materials while the polymethylsiloxane remains predominantly at the surface where it causes an undesirable sheen.
It is an object of the present invention to provide inexpensive aqueous emulsions for the water repellent impregnation of building materials, in particular structural fibre-reinforced cement components, which do not yellow under the influence of light and air and which show a good impregnating effect without causing any sheen at the surface of the building materials.
This object is achieved by the present invention by providing aqueous emulsions of (A) an organopolysiloxane which is free of basic nitrogen and (B) an alkyltrialkoxysilane, which contain (C) an emulsifier and (D) water, wherein the organopolysiloxane (A) has the formula ##EQU1## where R denotes identical or different monovalent, substituted or unsubstituted, SiC-attached C.sub.1 -C.sub.18 -hydrocarbon radicals, R.sup.1 denotes identical or different monovalent C.sub.1 -C.sub.6 -hydrocarbon radicals, a is 0, 1, 2 or 3, on average from 0.75 to 1.5, and b is 1, 2 or 3, on average from 0.2 to 2.0, and has a molecular weight of at least 600 g/mol.
Although not indicated in the above-indicated formula, some of the radicals R may be replaced by hydrogen atoms bonded directly to silicon atoms. However, this is not preferred.
Preferably, the radicals R contain at the most 12 carbon atoms per radical. Examples of radicals R are alkyl radicals, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, such as n-hexyl, heptyl, such as n-heptyl, octyl, such as n-octyl and isooctyl, such as 2,2,4-trimethylpentyl, nonyl, such as n-nonyl, decyl, such as n-decyl and dodecyl, such as n-dodecyl, alkenyl radicals, such as vinyl and allyl, cycloalkyl, such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl, aryl, such as phenyl and naphthyl, alkaryl, such as o-, m- and p-tolyl, xylyl and ethylphenyl and aralkyl, such as benzyl and alpha- and .beta.-phenylethyl.
Examples of substituted radicals R are cyanoalkyl radicals such as .beta.-cyanoethyl, and halogenated hydrocarbon radicals, for example haloalkyl radicals, such as 3,3,3-trifluoro-n-propyl, 2,2,2,2', 2',2'-hexafluoroisopropyl and heptafluoroisopropyl, and haloaryl, such as o-, m- and p-chlorophenyl.
On account of better accessibility, preferably at least 50% of the radicals R, in particular at least 80% of the radicals R, are methyl radicals.
In the foregoing formula, a is preferably on average from 0.9 to 1.1 and b preferably from 0.8 to 1.4, in particular from 1.0 to 1.2.
It is possible to use one organopolysi

REFERENCES:
patent: 3623895 (1971-11-01), Nitzsche et al.
patent: 4486476 (1984-12-01), Fritsch et al.
patent: 4877654 (1989-10-01), Wilson
patent: 5039724 (1991-08-01), Demlehner et al.
patent: 5091002 (1992-02-01), Schamberg et al.

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