Increasing the molecular weight of low molecular weight alpha,omega-polysiloxanediols
AssigneeEvonik Operations GmbH
InventorsBerend-Jan de Gans, Philippe Favresse, Wilfried Knott, Horst Dudzik, Monika Johannes
Life of this patent
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Abstract
A process can be used for increasing the molecular weight of low molecular weight α,ω-polysiloxanediols. The process involves heating the low molecular weight α,ω-polysiloxanediols in the presence of acetic anhydride at temperatures of 80° C. to 220° C., preferably at temperatures of 100 to 200° C., and particularly preferably at temperatures of 120-180° C., for 1 h to 24 h, preferably for 2 h to 16 h, and particularly preferably for 3 h to 12 h. The molar amount of the silanol groups used is greater than that of the acetic anhydride used.
Claims13
A process for increasing the molecular weight of at least one low molecular weight α,ω-polysiloxanediol, the process comprising:
- heating the at least one low molecular weight α,ω-polysiloxanediol in the presence of acetic anhydride in a reaction mixture, at a temperature of 80° C. to 220° C. for 1 h to 24 h, to obtain an end product comprising at least one linear α,ω-polysiloxanediol, and
- neutralizing the reaction mixture after the heating with a weak base,
- wherein a molar amount of silanol groups used is greater than that of the acetic anhydride used,
- the at least one linear α,ω-polysiloxanediol satisfies at least formula (I):
- wherein R1 is an alkyl radical, comprising 1 to 2 carbon atoms, and wherein 10≤n≤10,000, and
- the end product contains≤0.15% by weight of a combined amount of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane.
Dependencies are inferred from the claim text.