Water-repellent silicones types

The clear-colorless nature of silicone repellents allows preservation of the original appearance of the concrete. Their lack of film formation leaves the masonry pores open, thereby allowing transport of moisture outward to the atmosphere. They are highly durable to environmental conditions and will retain their repellent properties for several years. There are two types of water-repellent silicones (1) one is the resin-solvent type that is characterized as a partially hydrolyzed, partially alcoholized silicone resin dissolved in a hydrocarbon solvent. Generally, such products approach the 5% nonvolatile level. (2) The second is a water-soluble alkaline silicone repellent that is recommended for use on limestone and other nonsiliceous stone and masonry. 

The application of coatings and sealers provides resistance to concrete attack by minimizing the ingress of corrosive species into concrete and increasing the durability of the concrete. They belong to several types depending on applications. The sealers may be applied as lining for the pores which make concrete water repellent. Silicone resins have been successfiilly used. They deposit... 

Leather may similarly be made water repellent by treatment with solutions or emulsions of silicone fluids. A variety of techniques is available, the method chosen depending to some extent on the type of leather to be treated. The water... 

High phenyl content resins are compatible with organic resins of the P-F, U-F, M-F, epoxy-ester and oil-modified alkyd types but are not compatible with non-modified alkyds. Silicone resins are highly water repellent. 

The formation of silicon-flvxyride bonds on the surface of silica after treatment with hydrogen fluoride was never proven directly. However, there is a pronounced change in the adsorption and wetting properties. The silica becomes hydrophobic as was mentioned in a patent to Kimberlin (279a). Neimark and collaborators (279b) found a type V isotherm in the methanol adsorption on silica gel which had been treated with a solution of SiF in absolute alcohol. Wilska (280) obtained a water-repellent silica when solutions of HaSiPg were precipitated with ammonia. The Si—F bond is hydrolyzed only slowly. A considerable fluorine content of 7-10% F was reported in an older patent (281) for a silica that had been prepared by hydrolysis of SiF. ... 

Chemical modification of the wax can improve smear resistance (5). Silicones, which do not harm furniture finishes (6), are incorporated as film-forming ingredients in furniture polishes. The lubricant properties of silicones improve ease of application of the polish and removal of insoluble soil particles. In addition, silicones make dry films easier to buff and more water-repellent, and provide depth of gloss, ie, ability to reflect a coherent image as a result of a high refractive index (7). Wax-free polishes, which have silicones as the only film former, can be formulated to deliver smear resistance (8). Another type of film former commonly used in oil-base furniture polishes is a mineral or vegetable oil, eg, linseed oil. 

A substance that, because of its physicochemical nature, will not mix or blend with another substance.. All hydrophobic materials have water-repellent properties due largely to differences in surface tension or electric charges, e.g., oils, fats, waxes, and certain types of plastics. Silicone resin coatings can keep water from penetrating masonry by lining the pores, not by filling them they will not exclude water under pressure. 

The Engineer Research and Development Laboratory (2) has done extensive work on the use of silicones in paint formulations. The insulative qualities of intumescent water-soluble inorganics are maintained with water resistivity (scrub resistance) improved by the use of water-repellent type silicones. 

The discovery that the methylchlorosilanes in the vapor phase will react with many types of surfaces to produce water-repellent films1 has led to one of the most important developments in the organo-silicon field. The effect was an entirely unexpected outcome of the preparation and handling of large volumes of methylchlorosilanes intended for methyl silicone and serves as an excellent illustration of how the availability of new or of previously scarce intermediates may lead to valuable developments which are entirely unrelated to the original purpose of the investigation. 

As outlined in the previous chapters, the preparation of silicone polymers involves first the preparation of organosilicon halides or esters, secondly the hydrolysis of an appropriate mixture of these intermediates, and finally the condensation or rearrangement of the polymers to achieve the desired molecular arrangement. Only in the first step is there a choice of preparative methods the second and third steps are carried out in much the same way, regardless of how the intermediates were made. From the standpoint of synthesis, the problem therefore comes down to the preparation of the methyl-, ethyl-, and phenylchlorosilanes or ethoxysilanes. Of these the methyl compounds are the most important, because they are used directly for the water-repellent treatment and are the only intermediates required for the oils, elastomers, and some types of resin. 

It would be interesting at this point to predict from the present uses of the silicone materials the future trends of application. However, it is doubtful that present experience gives any dependable basis at all for such predictions. When research on silicone resins began, interest centered in their high-temperature performance, and it could not have been predicted at that time that some oily polymers would become important, purely for their Zow-temperature performance, or that some types of silicone resin would be valued purely for their electrical characteristics, or that some intermediates required for methyl silicone production would render many different kinds of surfaces water-repellent. Neither can it be expected that these unrelated and unforeseen outcomes of research have all appeared and that the flow of discoveries will now cease it is more likely that new developments will appear more rapidly as more people become interested and research in the field accelerates. Extrapolation of the present trend would therefore seem to be idle and misleading. 

The PERSISTOL types are supplied in the form of aqueous emulsions. They are wash-resistant water-repelling agents derived from paraffin wax or silicone and are used mainly for the water-repellent finishing of outerwear. 

ARIDRY SN-25 is a fine silicone emulsion which produces highly durable water repellency on treated fabrics. ARIFIX SN is the catalyst recommended for use with ARIDRY SN-25. These products can be run alone or in conjunction with thermosetting resins, cationic dye fixtures and most all of the organic and inorganic accelerators. Some of the waxy type softeners are compatible with a resin-silicone mix, but each must be checked carefully to be sure that it does not cause back-wetting. 

DOW CORNING 75 emulsion is a reactive, methyl silicone emulsion especially designed for use as a water repellent for all types of fabrics. When used with a catalyst, it provides water repellency used alone it functions as a fabric softener. 

In many cases, this silicone is less costly than other types of water repellents, including fluorocarbons. 

USE Friedel-Crafts catalyst- Component of Ziegler-type catalysis in the condensation of ethylene. Starting material in the synthesis of a number of organic derivs of zirconium, such as alkoxides and zircocene. The alkoxides have been shown to be of value in the curing of silicone plastic films. The alkoxyzirconium carboxylates are said to be useful in the water-repellent treatment of textiles and other fibrous materials. Review Blumenthal, J. Chem. Ed. 39, 604-610 (1962). 

In recent years, fluorochemical repellents have been coapplied mainly with wax dispersions made durable with cross-linking adjuvants. Although a variety of water repellents with hydrocarbon-type hydrophobes enhance the repellency and durability of fluoropolymer repellents, silicones may reduce their oil repellency... 

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