Silane, dichlorodimethyl-, reaction products with silica Property

Density 

0.18 g/cm 3 (loose weight)(lit.)

solubility 

Solubility is 1 in 6.7 parts of water (pH 7, 25°C). Practically insoluble in organic solvents(5) and acids, except hydrofluoric acid; soluble in hot solutions of alkali hydroxide.

EPA Substance Registry System

Silane, dichlorodimethyl-, reaction products with silica (68611-44-9)

Safety

Hazard Codes 

Xn,T

Risk Statements 

48/20-36/37-49

Safety Statements 

53-22-26-45

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H330Fatal if inhaled

Precautionary statements

P260Do not breathe dust/fume/gas/mist/vapours/spray.

P271Use only outdoors or in a well-ventilated area.

P284Wear respiratory protection.

P304+P340IF INHALED: Remove victim to fresh air and Keep at rest in a position comfortable for breathing.

P310Immediately call a POISON CENTER or doctor/physician.

P320Specific treatment is urgent (see … on this label).

P403+P233Store in a well-ventilated place. Keep container tightly closed.

P405Store locked up.

P501Dispose of contents/container to..…

Silane, dichlorodimethyl-, reaction products with silica Chemical Properties,Usage,Production

Chemical Properties

Hydrophobic colloidal silica occurs as a light, fine, white or almost white amorphous powder, not wettable by water.

Production Methods

Hydrophobic colloidal silica is prepared by the flame hydrolysis of chlorosilanes, such as silicon tetrachloride, at 1800°C using a hydrogen–oxygen flame. It is rapidly cooled to create an amorphous productand immediately treated with dichlorodimethyl silane in a fluid bed reactor. The resulting surface is covered with dimethylsilyl groups. Aerosil R972 is manufactured by modifying the surface of Aerosil 130 and thus has the same primary particle size and surface area, but the density of silanol groups is reduced from approximately 2.0 SiOH/nm2 to 0.75 SiOH/nm2.

Pharmaceutical Applications

large specific surface area, which provide desirable flow characteristics in dry powders used in tableting and capsule filling. The hydrophobic grades absorb less moistureand may offer an advantage in moisture-sensitive formulations.
Hydrophobic colloidal silica is also used to thixotropically control viscosity, to thicken and stabilize emulsions, or as a suspending agent in gels and semisolid preparations. Hydrophobic colloidal silica has a less pronounced effect on solution viscosity but can thicken and stabilize the oil phase of a water–oil emulsion. With other ingredients of similar refractive index, transparent gels may be formed. Generally, the uses and ranges of hydrophobic colloidal silica are similar to the concentrations used of the standard hydrophilic colloidal silicon dioxide.

Safety

The safety profile of hydrophobic colloidal silica is the same as for the hydrophilic silica types, as the modified silica surface does not significantly alter the toxicological properties.
LD50 (rat, IV): 0.015 g/kg

storage

Hydrophobic colloidal silica should be stored in a well-closed container. It will not absorb moisture but may still absorb volatile substances owing to its high surface area.

Incompatibilities

Use of the hydrophobic colloidal silica Aerosil R972 reduces the strength of starch-based tablets.

Regulatory Status

Approved for use in pharmaceuticals in Europe. Approved by FDA and Europe for food contact articles. Included in nonparenteral medicines (oral tablets; rectal suppositories) licensed in the UK.