Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
1999-04-28
2001-07-03
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S413000, C523S200000, C428S405000, C427S445000
Reexamination Certificate
active
06255513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stable composition of water-soluble organosiloxanes obtained by
a) reacting a water-soluble amino-functional alkoxysilane with at least one water-insoluble alkoxysilane
b) by adding water and, optionally, an organic or inorganic acid, to form a mixture, and
c) removing the alcohol formed during step b) from the mixture,
wherein the amino-functional alkoxysilane and the water are present in the reaction at least in amounts such that all of the alkoxy groups of the water-insoluble silane can react and such that when the resulting composition is diluted with water, essentially no alcohol is liberated by hydrolysis, and also to a process for its preparation and to its use.
2. Discussion of the Background
Compositions of water-based organopolysiloxanes usually contain completely hydrolyzed and oligomerized units: the alkoxy groups of the organoalkoxysilanes used in the synthesis being virtually completely substituted by OH groups. Such water-based organopolysiloxane-containing systems becoming widely used since they are essentially free from solvents and they liberate virtually no alcohols by hydrolysis even when diluted with water and upon application. EP-A 0 716 127 and EP-A 0 716 128 discloses water-based organopolysiloxane-containing compositions which are prepared by hydrolytically oligomerizing a “carrier silane”, a water-soluble aminoalkoxysilane and water-insoluble alkylalkoxysilanes and ureidoalkoxysilanes in a pH ranging from 1 to 11, and removing most of the alcohol formed in the reaction from the reaction mixture.
The above compositions are usually clear liquids having a long shelf life and a flash point of more than 70° C., and they are widely used, inter alia for improving the rheological properties of polymer dispersions and emulsions and for silanizing surfaces. However, adjusting the rheological properties and modifying surface properties requires an agent specifically matched to the product to be modified. Thus, the as yet unpublished German patent application No. 196 39 782.0 discloses water-based amino-, glycidyl ether-, acrylic- and methacrylic-functional organopolysiloxane-containing compositions.
In addition, EP 0 675 128 A1 discloses a process for the preparation of a stable composition of water-soluble organosiloxanes which includes reacting a water-soluble amino-functional alkoxysilane with a water insoluble vinyl-functional alkoxysilane with the addition of water, and removing the alcohol formed in this reaction from the mixture, wherein the aminofunctional alkoxysilane and the water are used in the reaction in amounts such that all of the alkoxy groups of the water-insoluble silane can react, so that when the resulting composition is diluted with water, essentially no alcohol is liberated by hydrolysis.
Such compositions of water-soluble organosiloxanes are used commercially, inter alia as adhesion promoters in compounds, and fillers and pigments are silanized in mostly complex processes. It is frequently necessary, however, to dry surface-modified fillers on a tray and then to comminute them again by energy-intensive measures. The use of spray-drying as a alternative for tray-drying requires a pumpable composition, and it is frequently necessary to add large amounts of processing auxiliaries to adjust the rheology.
SUMMARY OF THE INVENTION
The object of the present invention is to prepare a stable composition of water-soluble organosiloxanes. A particular aim of the invention is to use such compositions in an advantageous manner in the silanization of fillers and pigments.
These and other objects have been achieved by the present invention.
The first embodiment of the present invention relates to a stable water-soluble organosiloxane composition that includes the reaction product of a process including reacting
a) a water-soluble amino-functional alkoxysilane with at least one water-insoluble alkenyl-functional alkoxysilane
b) by adding water and, optionally, adding an organic or inorganic acid, to form a mixture, and
c) removing the alcohol formed in the reaction from the mixture,
wherein the amino-functional alkoxysilane and the water are present in the reaction at least in amounts wherein substantially all of the alkoxy groups of the water-insoluble alkenyl-functional alkoxysilane react and wherein when the resulting composition is diluted with water, essentially no alcohol is liberated by hydrolysis, and wherein the pH of the composition is from 2 to 6.
The second embodiment of the present invention relates to a process for the preparation of a stable composition of water-soluble organosiloxanes, which includes reacting
a) a water-soluble amino-functional alkoxysilane with at least one water-insoluble alkenyl-functional alkoxysilane
b) by adding water and, optionally, adding an organic or inorganic acid, to form a mixture, and
c) removing the alcohol formed in the reaction from the mixture,
wherein the amino-functional alkoxysilane and the water are present in the reaction at least in amounts wherein substantially all of the alkoxy groups of the water-insoluble alkenyl-functional alkoxysilane react and wherein when the resulting composition is diluted with water, essentially no alcohol is liberated by hydrolysis, and wherein the pH of the composition is from 2 to 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description, which is not intended to be limiting unless otherwise specified.
Preferably, a stable composition of water-soluble organosiloxanes is obtained by reacting
a) a water-soluble amino-functional alkoxysilane, preferably a 3-aminopropyltrialkoxysilane, with at least one water-insoluble alkenyl-functional alkoxysilane, preferably a vinyltrialkoxysilane,
b) by adding water to form a mixture, and
c) removing the alcohol formed during step b) from the mixture, to wherein the amino-functional alkoxysilane and the water are used in the reaction at least in amounts such that all of the alkoxy groups of the water-insoluble alkenyl-functional silane can react, and wherein the composition has a pH of from 2 to 6, preferably a pH of from 3 to 5, particularly preferably a pH of from 3.5 to 5, very particularly preferably a pH of from 3.5 to 4.5. The pH is preferably adjusted before or during the reaction or both by adding an organic or inorganic optionally aqueous, acid, preferably formic acid, acetic acid, HCl, HNO
3
or H
2
SO
4
. The composition is especially useful to improve the processing conditions during the silanization of a filler, in which case a mixture of filler (e.g. aluminum hydroxide), water and the composition of the invention exhibits a significant drop in viscosity while being stirred after just a few minutes, so that the starting paste can be conveyed in a low-viscosity state easily and in a simple and economic manner via a pump, for example to a spray dryer.
Moreover, fillers and pigments which are silanized using the composition of the invention also advantageously have functional properties which are particularly useful in paints, surface coatings, adhesives, sealants, polymer compositions and compounds.
The composition of the invention can be diluted with water as desired. The composition of the invention preferably has a content of organosiloxanes of from 1 to 150 g of Si/kg of the composition, preferably from 60 to 130 g of Si/kg, particularly preferably from 90 to 120 g of Si/kg.
Moreover, it is advantageous that the flash point of the present compositions is also generally above 70° C., the content of alcohol usually being less than 1%, so that the water-based compositions according to the invention can also be used in a particularly advantageous manner. Preference is given to those compositions which contain alcohol, for example methanol or ethanol, in amounts of from 0.3 to 0.1% by weight, particularly preferably less than 0.1% by weight.
In th
Barfurth Dieter
Edelmann Roland
Frings Albert-Johannes
Horn Michael
Jenkner Peter
Huels Aktiengesellschaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Shaver Paul F.
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