Process for preparing polysulfane silanes

Abstract

Process for preparing polysulfane silanes of the formula I
(R.sup.1O).sub.3-mR.sup.2.sub.mSi—R.sup.3—S.sub.x—R.sup.3—SiR.sup.2.sub.m(OR.sup.1).sub.3-m  I,
by reaction of silane of the formula II
(R.sup.1O).sub.3-mR.sup.2.sub.mSi—R.sup.3-Hal  II,
with one or more metal sulfides of the formula III
Me(SH).sub.f and/or Me.sub.3-fS.sub.x-y  III,
optionally in the presence of one or more salts of monohydric or polyhydric acids,
with the optional addition of y mol of sulfur in aqueous R.sup.1—OH solution, wherein the water content of the aqueous R.sup.1—OH solution is 5% to 40% by weight,
wherein a. the process stream from the reaction of silane of the formula II with one or more metal sulfides of the formula III, optionally in the presence of one or more salts and optionally with the addition of sulfur, in aqueous R.sup.1—OH solution, comprising polysulfane silanes of the formula I, silane of the formula II, metal sulfides of the formula III, solvent R.sup.1—OH, water and process salts,
is combined with the wash solution from step d, comprising solvent R.sup.1—OH, water and polysulfane silanes of the formula I, b. the solvent R.sup.1—OH and water are removed by distillation, c. the remaining suspension comprising polysulfane silane of the formula I and process salt is subjected to a filtration or a sedimentation and d. the process salt from step c is washed with solvent R.sup.1—OH and then dried, the wash solution comprising solvent R.sup.1—OH, water and polysulfane silane of the formula I is recycled to process step a.

Claims

1. A process for preparing polysulfane silanes of the formula I
(R.sup.1O).sub.3-mR.sup.2.sub.mSi—R.sup.3—S.sub.x—R.sup.3—SiR.sup.2.sub.m(OR.sup.1).sub.3-m  I, wherein R.sup.1 are identical or different and are C1-C10 alkyl groups, phenyl groups or alkyl polyether groups —(R′—O).sub.r—R″, where R′ are identical or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, r is an integer from 1 to 30, and R″ are unsubstituted or substituted, branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl group, R.sup.2 are identical or different and are C6-C20 aryl groups, C1-C10 alkyl groups, C2-C20 alkenyl groups, C7-C20 aralkyl groups or halogens, R.sup.3 are identical or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon groups, and m are identical or different and are 0, 1, 2 or 3, x is 1-10, by reaction of silane of the formula II
(R.sup.1O).sub.3-mR.sup.2.sub.mSi—R.sup.3-Hal  II where R.sup.1, R.sup.2, R.sup.3 and m are as defined above and Hal is a halogen, with one or more metal sulfides of the formula III
M(SH).sub.f and/or M.sub.3-fS.sub.x-y  III where M is an element of main group 1 or 2, f=1 for M of main group 1 and f=2 for M of main group 2 and y has a value from 0 to x−1, optionally in the presence of one or more salts of monohydric or polyhydric acids, with the optional addition of y mol of sulfur, in aqueous R.sup.1—OH solvent, wherein R.sup.1 is as defined above, the water content of the aqueous R.sup.1—OH solution is 5% to 40% by weight, characterized in that a. the process stream from the reaction of silane of the formula II with one or more metal sulfides of the formula III, optionally in the presence of one or more salts and optionally with the addition of sulfur, in aqueous R.sup.1—OH solution, comprising polysulfane silanes of the formula I, solvent R.sup.1—OH, water and process salts, is combined with a wash solution from step d, comprising solvent R.sup.1—OH, water and polysulfane silanes of the formula I, b. the solvent R.sup.1—OH and water are removed by distillation, c. a remaining suspension comprising polysulfane silane of the formula I and process salt is subjected to a filtration or a sedimentation, d. the process salt from step c is washed with solvent R.sup.1—OH and then dried, and the wash solution comprising solvent R.sup.1—OH, water and polysulfane silane of the formula I is recycled to process step a.

2. The process of claim 1, characterized in that the process is carried out at temperatures from 0° C. to 180° C.

3. The process of claim 1, characterized in that the polysulfane silanes of the formula I are [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.2, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.3, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.4, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.5, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.6, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.7, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.8, [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.9, or [(EtO).sub.3Si(CH.sub.2).sub.3].sub.2S.sub.10.

4. The process of claim 1, characterized in that the process steps a and b are carried out in parallel.

5. The process of claim 1, characterized in that the process is carried out continuously or batchwise.

6. The process of claim 1, characterized in that, if carried out in a batchwise operation, the wash solution in process step a originates from step d of a previous batch.

7. The process of claim 1, characterized in that, in process step d, the washed solid may be separated from the wash solution using solid-bowl decanter centrifuges, filter dryers, filter presses or filter centrifuges.

8. The process of claim 1, characterized in that a wetting agent is added before or during the process steps.

9. The process of claim 1, characterized in that the removal of solvent by distillation in process step b takes place in a temperature range from 0° C. to 150° C. at a pressure from 0.5 kPa absolute to 150 kPa absolute.

Description

EXAMPLES

(1) The average sulfur chain length was determined by means of an analysis described in ASTM D 6844.

(2) For the determination of the monomer content, the peak areas of the sample constituents S2 to S10 were multiplied by the response factors listed in ASTM D 6844 and the sum thereof related to that of peak areas S2 to S10 of the corrected response factors of a standard of known monomer content according to the following formula:

(3) ${\mathrm{Mon}}_{\left(\mathrm{sample}\right)}=\frac{{\mathrm{Mon}}_{\left(\mathrm{std}\right)}.Math.{\left(\underset{n=2}{\overset{10}{.Math.}}\left({\mathrm{area}}_{\left(n\right)}.Math.\mathrm{response}{\mathrm{factor}}_{\left(n\right)}\right)\right)}_{\mathrm{sample}}}{\underset{n=2}{\overset{10}{.Math.}}{\left({\mathrm{area}}_{\left(n\right)}.Math.\mathrm{response}{\mathrm{factor}}_{\left(n\right)}\right)}_{\left(\mathrm{std}\right)}}\left[\%\right]$

Example 1 (Comparative Example)

(4) Into a pressure reactor having a capacity of 2000 ml was weighed 477 g of ethanol, 53 g of water, 137.2 g of sodium carbonate, 38.6 g of sulfur, and 109.2 g of sodium hydrogen sulfide having a water content of 29%. The reactor was closed and evacuated to 10 kPa absolute. The reactor contents were then heated to 70° C., with stirring, and 554.5 g of chloropropyltriethoxysilane was added over a period of 45 minutes at a temperature of 70° C. to 73° C. The reactor contents were then heated to 78° C. and held at this temperature for a further 145 min.

(5) After cooling the reactor contents to 45° C., the removal under reduced pressure of ethanol-water mixture from the suspension remaining in the reactor was commenced. On reaching a temperature of 120° C., the suspension present in the reactor was cooled to 30° C. The reactor was opened and the pasty contents thereof transferred to a porcelain suction filter. After filtration for one hour under vacuum, 323.9 g of bis(triethoxysilylpropyl) polysulfane product having an average sulfur chain length of 2.16 and a monomer content of 80.3% was obtained.

(6) The filter cake from example 1 remaining in the porcelain suction filter was then washed with a mixture of 477 g of ethanol and 53 g of water, with application of vacuum. After 60 minutes, 542 g of wash solution was obtained.

Example 2

(7) Into a pressure reactor having a capacity of 2000 ml was weighed 477 g of ethanol, 53 g of water, 137.2 g of sodium carbonate, 38.6 g of sulfur, and 109.2 g of sodium hydrogen sulfide having a water content of 29%. The reactor was closed and evacuated to 10 kPa absolute. The reactor contents were then heated to 70° C., with stirring, and 554.5 g of chloropropyltriethoxysilane was added over a period of 45 minutes at a temperature of 70° C. to 73° C. The reactor contents were then heated to 78° C. and held at this temperature for a further 145 min.

(8) After cooling the reactor contents to 45° C., the removal under reduced pressure of ethanol-water mixture from the suspension remaining in the reactor was commenced. Once 250 g of distillate had been collected, the wash solution previously obtained from washing the filter cake resulting from example 1 was added and distillation was continued. On reaching a temperature of 120° C., the suspension present in the reactor was cooled to 30° C. The viscosity of the reactor contents was sufficiently low for it to be possible to transfer the suspension to a porcelain suction filter via the bottom outlet of the reactor.

(9) After filtration for one hour under vacuum, 525.7 g of bis(triethoxysilylpropyl) polysulfane product having an average sulfur chain length of 2.14 and a monomer content of 86.0% was obtained.