Method of making siloxane compositions
AssigneeDow Corning Corporation
InventorsJean de la Croi Habimana, Stephen Westall
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Abstract
A method of making a dispersion of a high viscosity siloxane in a volatile, especially cyclic siloxane, comprises first dispersing organopolysiloxanes having at least 2 Si--OR groups, wherein R is H or alkyl in a volatile siloxane and adding a catalyst which is either a phosphonitrile halide having the general formula [X(PX.sub.2 .dbd.N).sub.n PX.sub.3 ].sup.+ [MX.sub.(v-t+1) R.sub.t ].sup.-, or a heterogeneous catalyst selected from Li, Mg, Ca, Sr or Ba hydroxide, Na or K borate or phosphate, Rb or Cs carbonate or carboxylates of Rb or Cs wherein M is an element having an electronegativity of from 1.0 to 2.0, R is alkyl, X is halide, n is 1 to 6, v is the valence of M and t is from 0 to (v-1).
Claims20
A method of making a dispersion of a high viscosity siloxane in a volatile siloxane, which comprises
- (I) dispersing at least one organopolysiloxane having at least 2 silicon-bonded groups --OR, wherein R is selected from the group consisting of hydrogen and alkyl groups having up to 6 carbon atoms, in a volatile siloxane, followed by
- (II) contacting the dispersion of (I) with a catalyst which is selected from the group consisting of
- (A) a phosphonitrile halide having the general formula {X(PX.sub.2 .dbd.N).sub.n PX.sub.3 }.sup.+ {MX.sub.(v-t+1) R.sub.t }.sup.- and
- (B) a heterogeneous catalyst selected from the group consisting of lithium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, sodium borate, sodium phosphate, potassium borate, potassium phosphate, rubidium carbonate, caesium carbonate, carboxylates of rubidium and carboxylates of caesium, said carboxylates having the general formula Q.CO.OZ wherein M is an element having a electronegativity of from 1.0 to 2.0 according to Pauling's scale,
- Q is selected from alkyl groups having from 1 to 6 carbon atoms or alkenyl groups having from 2 to 5 carbon atoms,
- R is an alkyl groups having up to 12 carbon atoms,
- X denotes a halide atom,
- Z is selected from Cs or Rb,
- n has a value of from 1 to 6,
- v is the valence or oxidation state of M and
- t has a value of from 0 to (v-1).
Dependencies are inferred from the claim text.