Polysiloxane, finish

Polysiloxanes as shrink-resist finishes have been developed from their traditional uses as softeners and water repellents as such their chemistry is discussed in section 10.10.3. This was a natural trend as many shrink-resist finishes tend to impart a harsh handle to wool. 

Hohberg T, Schaefer O, Mueller J et al. (2003) Textiles coated or finished with polysiloxane-polyurea-polyurethane block copolymers (Wacker-Chemie G.m.b.H., Germany) EP1336683. 

The latest development is the use of silicones for water-repellent finishes. Linear dimethyl polysiloxane ... 

For example, the abrasion-resistant coatings based on a silicone-silica hybrid (33) have provided a scratch- and mar-resistant finish for polycarbonate as well as metals. The chemistry involved is discussed by Vincent, Kimball and Boundy (3iL). The coating consists of polysiloxane and silane-modified submicron silica particles, microscopically dispersed in the solution. The coating is then cured at elevated temperatures. Currently, this type of abrasion resistant coating is marketed in the U.S. by Dow Corning and General Electric Company. 

Uses Slip agent, leveling agent, defoamer for wood finishes, industrial coatings, and solv.-free systems Properties 100% NV EFKA -3239 [EFKA Additives BVj Chem. Descrip. Polysiloxane-based... 

Pinishes are applied to the PAN fiber to improve handling and include silicones (modified polysiloxanes) [132] and trimethylol propane-ethylene oxide adduct [133-135]. These finishes are burned off in the latter stages of stabilization, or in the initial stages of the low temperature carbonization furnace and the breakdown products should be volatile to permit removal. At one time, it was common practice to use adventitious sizes applied prior to the stabilization stage to protect the cosmetics of the oxidized fiber during oxidation. These sizes should preferably break down into gaseous components at about 200° C and typical sizes are the ammonium salt of polystyrene maleic anhydride copolymer, ethyl acrylate, ethyl acrylate/methyl methacrylate and polyacrylic acid. 

Metal salt paraffin dispersions (such as aluminium) are products positively charged due to the trivalent aluminium salt, which produces a counter-polar charge on the fibre surface. Polysiloxanes form a fibre-encircling silicone film with methyl groups perpendicular to the siuface. The hydrophobicity of the finish is affected by the film formation... 

Non-isocyanate acrylics do, in general, display excellent flow when applied direct from the gun. Additives such as silicone oil or polysiloxane derivative have been shown to enhance the final finish in terms of flow and gloss. Care should be taken in the selection of additives to avoid adversely affecting the intercoat adhesion. Taking into consideration all of the parameters, the polysiloxane derivatives would normally be the preferred choice. 

As stated earlier, cellulose acetate butyrate can be used successfully to modify the flow of non-isocyanate acrylics. However, in certain instances this can affect the distinction of image and brightness of the finish. Again, the use of a polysiloxane derivative would be recommended as a replacement. 

Chem. Descrip. Polysiloxane-polyether copolymer Uses Softeners and finishes for textiles and other applies. defoamer in food-con-tact paper/paperboard Features Hydrophilic... 

Chem. Desetip. Polysiloxane, modified Ionic Nature Cationic Uses Textile finish Properties Liq. 

Chloromethylsilanes are corrosive and difficult to handle. Processes for the treatment of textiles with chloromethylsilanes [63] that used ammonia to absorb the hydrochloric acid formed were not successful. The replacement of chlorine, with acetoxy [64], alkoxy [65,66], amino [67], or isocyanato [68] groups has been patented. None of these conversions has resulted in a practical process. Therefore, silanes are not used as such for textile finishing but are converted to polysiloxanes, which can be applied to textiles as solutions in organic solvents or as aqueous emulsions [69]. 

Organic resins, such as polycondensed epoxyamides and epoxyamines, have also been used as adjuvants for water-repellent finishing with polysiloxanes [78]. 

Repellent finishing with polysiloxanes has been reviewed by Madaras [79], Glenz [70b], and Medico [78]. 

The silicones used as water repellents for textiles are supplied in the neat form or as aqueous emulsions. Polysiloxanes are soluble and stable in hydrocarbon solvents (e.g, xylene) or in chlorinated solvents, such as trichloroethylene or tetrachloroethylene, but special equipment is needed for the solvent-finishing operation. Although polysiloxanes used as water repellents for textiles are hydrolytically unstable, sufficiently stable aqueous emulsions are now available. The water repellency achieved with aqueous emulsions is usually somewhat inferior to that obtained with solutions of polysiloxanes because residual emulsifiers can impair repellency. 

The polysiloxanes are applied by padding followed by drying and heating for a few minutes at 120-150°C to cure the finish, or by exhaust procedures [70b]. Because most textile fabrics have a negative surface potential in water, cationic surfactants are used for emulsifying polysiloxanes for exhaust application. The padding or exhaust application should deposit about 1-2% polysiloxane onto the fabric the amount can be smaller in coapplication with a zirconium or titanium catalyst. ... 

Because the cure conditions of the polysiloxane water repellents are similar to durable press cross-linking treatments with methylol compounds, polysiloxanes can be coapplied with a durable press finish [80]. The durable press resins enhance the durability of the silicone water repellent [ 78]. 

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