Process for producing sperhical polysilsesquioxane particles
AssigneeWacker Chemie AG
InventorsSebastian Knoer, Kathrin Seilinger
Life of this patent
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Abstract
Spherical organopolysiloxane resin particles with improved flow properties can be reproducibly obtained employing trialkoxysilanes having different hydrolysable chlorine contents by regulating pH in a first, acid hydrolysis step, and then adjusting pH in a second step to a desired value between 1 and 6. Particles are allowed to grow without agitation in a subsequent basic condensation step.
Claims15
A process for improving batch to batch reproducibility in a process for producing spherical polysilsesquioxane particles, where a trialkoxysilane raw material contains differing amounts of chlorine compounds in different batches, the process comprising:
- in a first step, reacting trialkoxysilane T which contains trialkoxysilanes of formula (I)
- RSi(OR1)3 (I),
- in which
- R represents a hydrocarbon radical having 1 to 16 carbon atoms whose carbon chain may be interrupted by nonadjacent groups —O—,
- R1 represents a C1- to C4-alkyl radical,
- and which contains chlorine compounds,
- by mixing the trialkoxysilane T with acidified water having a pH of at most 6 to afford a hydrolyzate,
- in a second step the hydrolyzate is mixed with a solution of a base in water or C1-C4 alkanol,
- and in a third step the mixture is stored for at least 2 h before isolating polysilsesquioxane particles,
- wherein following the first step, the pH of a hydrolysate produced in the first step is measured and compared with a selected value, and if different from the selected value, the pH of the hydrolysate is adjusted to reduce the difference between the pH of the hydrolysate and the selected value.
A process for producing spherical polysilsesquioxane particles in a reproducible manner, the process comprising:
- in a first step, reacting trialkoxysilane T which contains trialkoxysilanes of formula (I)
- RSi(OR1)3 (I),
- in which
- R represents a hydrocarbon radical having 1 to 16 carbon atoms whose carbon chain may be interrupted by nonadjacent groups —O—,
- R1 represents a C1- to C4-alkyl radical,
- and which contains chlorine compounds,
- by mixing the trialkoxysilane T with acidified water having a pH of at most 6 to afford a hydrolyzate,
- in a second step, measuring the pH of the hydrolysate, comparing the pH of the hydrolysate to a selected pH, and when different from the selected pH, adjusting the hydrolysate pH to minimize the difference between the hydrolysate pH and the selected pH to within ±0.5 pH units of the selected pH,
- in a third step the hydrolyzate is mixed with a solution of a base in water or C1-C4 alkanol,
- and in a fourth step, storing the mixture for at least 2 h before the polysilsesquioxane particles are isolated.
Dependencies are inferred from the claim text.