Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-02-01
2002-03-26
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S411100, C528S036000, C528S016000, C528S018000, C528S017000, C528S012000, C528S042000, C556S458000, C524S858000, C427S387000
Reexamination Certificate
active
06361871
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition comprising at least one organofluorine-functional silane and/or siloxane, to a process for preparing it and to its use and also to correspondingly surface-modified substrates.
2. Discussion of the Background
It is known to prepare a composition comprising at least one organofluorine-functional silane and/or siloxane by mixing, by controlled acid- or base-regulated hydrolysis, or by condensation or cocondensation of organofluorine-functional chlorosilanes and/or alkoxysilanes, with or without further precursor components. Besides organic or inorganic acids or bases, pH regulation in this case is carried out using acidic or basic salts, such as alkali metal carbonate, alkali metal hydrogen sulfate, alkali metal dihydrogen phosphate, magnesium hydroxide or aluminum acetate. In the preparation of the compositions it is also known, for example, to employ other hydrolyzable organosilanes, silicon, titanium or zirconium tetrachlorides, or corresponding metal-acid esters as precursor components.
Compositions of this kind, containing water, solvent or dispersant, are generally employed for giving substrates a hydrophobic and at the same oleophobic and dirt-repellent finish, or else, for example, a hydrophilic finish, or for the special modification of the surface properties of the substrates, for example, for metals, metal oxides, fillers, pigments, glass, enamel, ceramic, construction materials, buildings, fibers, textiles, natural substances, plastics, and coating materials. This modification may involve the formation of a protective layer against UV radiation or mechanical, thermal and chemical influences. Furthermore, scratch proofing, anticorrosive, antiicing, antifouling, antibacterial or antithrombic properties may also be obtained. Besides the organic functional groups, said silane and/or siloxane systems generally possess Si-bonded hydroxyl and/or alkoxy groups, which are intended to permit subsequent attachment to the substrate. However, it is often difficult to achieve satisfactory and permanent attachment of the coating to the substrate.
DE 196 46 662 A1 describes the treatment of a metal surface with an SnCl
2
solution followed by application of amino-functional alkoxysilanes, giving coatings resistant to moisture and corrosion.
Stable hydrophobic coatings on steel can be prepared by combining alkoxides, methyl alkoxides, such as Al(CH
3
)(OC
2
H
5
)
2
, or acetonates of the metals Al. Zr, Ti, Si, W, Ce, Y or Sn with fluoroalkylalkoxysilanes, as is disclosed, for example, in JP 1068477. Similarly, in accordance with JP 4136181, nonmetals can also be given permanent hydrophobicization.
Finally, EP 0 799 873 A1 discloses the preparation of water- and oil-repellent coatings by application of a composition comprising an aqueous solvent, such as alcohol, a fluorinated alkoxysilane, and a Brönsted acid and/or Brönsted base catalyst.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a composition having improved adhesion properties and crosslinking properties on a polar substrate surface and, therefore, better coating properties.
This object is achieved in accordance with the invention as specified in the claims.
It has surprisingly been found that a highly reactive composition comprising organofluorine-functional silanes and/or siloxanes which carry some silanol groups in addition to hydrolyzable groups is obtained by mixing at least one organofluorine-functional chlorosilane or alkoxysilane and, optionally, further organofunctional, hydrolyzable silanes, such as organochloro- or organoalkoxysilanes, in the presence of a small amount of water and in the presence of at least one metal salt of aluminum(III), tin(II), tin(IV), iron(III) or titanium(III) and at least one mineral acid, suitably in an organic solvent or dispersant, such as in an alcohol, and subjecting this mixture, optionally, to partial hydrolysis and, optionally, to condensation or oligomerization.
DETAILED DESCRIPTION OF THE INVENTION
By applying the present composition to a substrate it is possible, surprisingly and advantageously, to obtain a particularly well-adhering and permanent coating. In general, the reactive Si compounds in the composition are in the form of reactive monomeric units. Compositions of the invention can, however, also be formulated so that oligomeric Si compounds predominate.
Furthermore, despite their high reactivity, compositions of the invention are, surprisingly, stable for relatively long periods, generally more than 5 months. In addition, the composition of the invention is immediately ready to use and is comparatively simple to apply, for example, by dipping, spraying or polishing, since the composition obtained in accordance with the invention is notable for a particularly rapid and complete reaction with a polar surface. In general, application of the composition of the invention immediately produces a homogeneous, highly crosslinked coating which, depending on the functionality of the organic groups, is outstandingly suited to the full and permanent, chemically bonded, organic modification of polar substrate surfaces. In this context, said metal salts act in conjunction with said mineral acids as catalyst.
The present invention therefore provides a composition comprising at least one organofluorine-functional silane and/or siloxane, at least one mineral acid, and at least one metal salt of aluminum(III), tin(II), tin(IV), iron(III) or titanium(III).
The metal salt content of the composition of the invention is preferably from 0.01 to 10% by weight, especially from 0.01 to 1% by weight, based on the composition.
The composition of the invention also includes as mineral acid preferably hydrogen chloride, nitric acid, phosphoric acid or sulfuric acid, the mineral acid content preferably being from 0.001 to 5% by weight, especially from 0.01 to 1% by weight and, with very particular preference, from 0.05 to 0.5% by weight, based on the composition.
The composition of the invention suitably includes a solvent and/or dispersant. For example, it may include an aromatic hydrocarbon or an aliphatic hydrocarbon or an alcohol or water, or a mixture thereof. Methanol, ethanol, n-propanol, isopropanol, n-butanol, acetone, cyclohexane, n-hexane or toluene, in particular, can be employed advantageously as solvent. In general, the amount of solvent and/or dispersant makes up the sum of the components of the composition of the invention—organosilanes and/or organosiloxanes, mineral acid, metal salt and, optionally, water—to 100%.
Compositions of the invention preferably comprise those silanes and/or siloxanes which comprise organofluorine-functional groups, especially fluoroalkyl-functional groups of the formula CF
3
(CF
2
)
m
(CH
2
)
n
— where m=0 to 18 and n=0 or 2, examples being tridecylfluorooctyl {(C
6
F
13
)—(CH
2
)
2
—}, heptadecafluoro-decyl {(C
8
F
17
)—(CH
2
)
2
—}, nonafluorohexyl {(C
4
F
9
)—(CH
2
)
2
—}, heneicosafluorodecyl {(C
10
F
21
)—(CH
2
)
2
—}, 3,3,3-trifluoropropyl {(CF
3
)—(CH
2
)
2
—} or 3-(1,1,2,2-tetrafluoro-ethoxy)propyl {(HC
2
F
4
)—O—(CH
2
)
3
—} groups, optionally, aminoalkyl groups, examples being 3-aminopropyl, N-2-aminoethyl-3-aminopropyl or N-2-aminoethyl-N′-2-aminoethyl-3-aminopropyl, and also vinyl groups, methacryloxyalkyl groups, an example being 3-methacryloxypropyl, and also alkyl groups, examples being methyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-octyl, isooctyl and hexadecyl, or cycloalkyl groups, examples being cyclopentyl and cyclohexyl, or cycloalkylene groups, examples being cyclohexenyl, cyclooctenyl and cyclododecadienyl groups, and also epoxyalkyl and epoxycycloalkyl groups, such as 3-glycidyloxypropyl or 2,3-epoxycyclohexyl groups, the siloxane containing not more than one of said organofunctional groups attached to one silicon, whose other valences are occupied by —O—Si bonds or OH groups and, optionally, by a
Edelmann Roland
Frings Albert-Johannes
Horn Michael
Jenkner Peter
Laven Ralf
Degussa - AG
Peng Kuo-Liang
LandOfFree
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