A PROCESS FOR THE PRODUCTION OF SULFUR CONTAINING SILANES BY UTILIZATION OF PHASE TRANSFER CATALYSIS

Abstract

The invention relates to a process for the production of sulfur containing silanes by the following steps (a) preparing an aqueous phase preparation by mixing sodium hydrosulfide or sodium sulfide, sulfur, Na2C03 and/or NaOH and a brine of step (f) and optionally of aqueous suspension of step (h), (b) adding 20 - 100 wt. -% of the total amount of phase transfer catalyst (c) continuously or in portions adding halogen alkyl silane, and simultaneously adding the rest of the total amount of phase transfer catalyst, in portions or continuously, (d) optionally adding brine from (f), optionally adding aqueous suspension from (h), optionally adding solid residue from step (k), separate the phase into a lower aqueous suspension and an upper organic phase and draw off the organic phase, (e) supply of the aqueous suspension from (d), optionally adding aqueous suspension from (h), separate in a salt cake and brine, (f) recycle all or a part of the brine of step (e) into step (a) and optional into step (d), (g) optionally distillate the rest of the brine from step (e) to yield aqueous distillate and aqueous suspension, (h) optionally recycle the aqueous suspension of step (g) into step (a) and /or (d) and/ or (e), (i) route the organic phase of step (d) to an evaporation step to yield a organic residue and low boiling distillate, (j) separate the organic residue from the evaporation step (i) into a sulfur containing silane and a solid residue, (k) optionally the solid residue of step (j) is recycled to step (d).

Claims

1. Process for the production of sulfur containing silanes by the following steps (a) preparing an aqueous phase preparation by mixing sodium hydrosulfide or sodium sulfide, sulfur, Na.sub.2CO.sub.3 and/or NaOH and a brine of step (f) and optionally of aqueous suspension of step (h), (b) adding 20 - 100 wt.-% of the total amount of phase transfer catalyst (c) continuously or in portions adding halogen alkyl silane, and simultaneously adding the rest of the total amount of phase transfer catalyst, in portions or continuously, (d) optionally adding brine from (f), optionally adding aqueous suspension from (h), optionally adding solid residue from step (k), separate the phase into a lower aqueous suspension and an upper organic phase and draw off the organic phase, (e) supply of the aqueous suspension from (d), optionally adding aqueous suspension from (h), separate in a salt cake and brine, (f) recycle all or a part of the brine of step (e) into step (a) and optional into step (d), (g) optionally distillate the rest of the brine from step (e) to yield aqueous distillate and aqueous suspension, (h) optionally recycle the aqueous suspension of step (g) into step (a) and /or (d) and/or (e), (i) route the organic phase of step (d) to an evaporation step to yield a organic residue and low boiling distillate, (j) separate the organic residue from the evaporation step (i) into a sulfur containing silane and a solid residue, (k) optionally the solid residue of step (j) is recycled to step (d).

2. Process for the production of sulfur containing silanes according to claim 1, characterized in that the sulfur containing silanes is a polysulfansilane of the formula I (R.sup.1).sub.3-mR.sup.2.sub.mSi-R.sup.3-S.sub.x-R.sup.3-SiR.sup.2.sub.m(R.sup.1).sub.3-m | wherein R.sup.1 are identical or different and are C1-C10-alkoxygroups, phenoxygroups or alkylpolyethergroups -O-(R'-O).sub.rR" with R′ are identical or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon groups, r is an integer from 1 to 30 and R″ unsubstituted oder substituted, branched or unbranched monovalent alkyl-, alkenyl-, aryl- or aralkylgroup, R.sup.2 are identical or different and are C6-C20-arylgroups, C1-C10-alkylgroups, C2-C20-alkenylgroups, C7-C20-aralkylgroups or halogen, R.sup.3 are identical or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30- hydrocarbon groups, and m are identical or different and 0, 1, 2 or 3, x is 2-10.

3. Process for the production of sulfur containing silanes according to claim 1, characterized in that the phase transfer catalyst is tetraalkylammonium halogenid of the general formula [(Alk).sub.4N].sup.+Hal.sup.- where the Alk can be similar or different C.sub.2 to C.sub.10 hydrocarbon, and the Hal.sup.- can be chloride, iodide or bromide.

4. Process for the production of sulfur containing silanes according to claim 1, characterized in that the phase transfer catalyst is tetrabutylammonium bromide.

5. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (d) before or during the phase separation, an additional amount of brine of step (f) can be added to the phase separator.

6. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (d) before or during the phase separation, the aqueous suspension from step (h) can be added.

7. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (d) before or during or after the phase separation, the solid residue of step (k) can be added.

8. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (f) 5 to 100 wt.-% of the brine is recycled into step (a) and 0 to 95 wt.% of the brine is recycled into step (d).

9. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (h) 0 to 100 wt.-% of the aqueous suspension is recycled into step (a), 0 to 100 wt.-% of the aqueous suspension is recycled into step (d) and 0 to 100 wt.-% of the aqueous suspension is recycled into step (e).

10. Process for the production of sulfur containing silanes according to claim 1, characterized in that the process is batchwise.

11. Process for the production of sulfur containing silanes according to claim 1, characterized in that the brine of step (f) added in step (a) and/or step (d) is of any previous batch.

12. Process for the production of sulfur containing silanes according to claims 1, characterized in that the aqueous suspension of step (h) added in step (a) and/or step (d) and/or step (e) is of any previous batch.

13. Process for the production of sulfur containing silanes according to claims 1, characterized in that the solid residue of step (k) added in step (d) is of any previous batch.

14. Process for the production of sulfur containing silanes according to claims 1, characterized in that in the recycling steps the brine of step (f) and/or the aqueous suspension of step (h) and/or the solid residue of step (k) are feed into any successive batch.

15. Process for the production of sulfur containing silanes according to claim 1, characterized in that in step (e) before or during the separation, the aqueous suspension from step (h) can be added.

Description

[0173] An exemplary process is shown in Figure 1.

[0174] The stepwise or continuous addition of phase transfer catalyst during the reaction can result in an overall lower retention time of the catalyst and therefore a lower amount of catalyst which is lost by decomposition and enables the reduction of the overall amount of catalyst.

[0175] Since the reaction recipe is set up in a way that most of the side products generated precipitate, no/low amount of water is needed during reaction to keep them in solution. Therefore, the reaction apparatus and downstream equipment can be considerable smaller than predicted for the known art, thus reducing the cost of investment.

[0176] As mentioned above, unreacted educts in the aqueous phase tend to stay in solution. This results in a salt cake which is free of sulfides. Therefore, the salt generated as a side product does not need to be treated to oxidize the sulfides, resulting in a fraction of cost for equipment and chemicals for detoxification.

[0177] The invented process does not use any / or less amount of pure water during the preparation of the aqueous phase. Instead, a portion of the brine from previous batches is used to serve as fluid for also keeping the solid components of the reaction mixture in suspension. Only water brought into the process by raw materials and water generated in the reaction need to be removed. This results in considerable less water consumption and to a fraction of costs for equipment and energy to desalinate water by distillation and to treat distillate in a biological treatment plant.

[0178] The solubility of the educts and phase transfer catalyst in aqueous solution are generally better than of the side products. Left over educts added in excess and phase transfer catalyst therefore tend to stay in solution, while the side products tend to make up the filter cake. This brine containing these valuable raw materials is recycled into successive batches. Therefore, the addition of raw materials and phase transfer catalysts per batch can be reduced while maintaining the desired excess of these raw materials.

EXAMPLES

[0179] The average sulfur chain length and the S2 to S10 content of the final products were determined according to ASTM D 6844-02 using an Aglient Technologies series 1260 Infinity II HPLC apparatus with the following parameters:

[0180] Column: Bakerbond C18 (RP), 5 .Math.m, 4.6 × 250 mm, Flow Rate 1.50 ml/min, λ = 254 nm, Column Temperature 30° C., Mobile phase: Mixture of 200 ml tetrabutylammonium bromide-solution (made from 400 mg tetrabutylammonium bromide in 1 l deionized water), 450 ml ethanol and 1350 ml methanol.

Example 1 (4,4,13,13-Tetraethoxy-3,14-Dioxa-8,9-Dithia-4,13-Disilahexadecane) Without Recycling Step (Comparative Example)

[0181] Sodium carbonate (94.5 g, 0.89 mol, 1.153 eq.), sodium hydrosulfide hydrate (112.9 g, 0.81 mol, 1.044 eq., 43%) and water (286.0 g, 15.9 mol, 20.6 eq.) were heated to 72° C. The reaction mixture is stirred for 5-10 minutes at 72° C. Subsequently, sulfur (27.5 g, 0.86 mol, 1.112 eq.) is added, while maintaining the temperature between 70 and 75° C. After stirring the reaction mixture for 45 min at 72° C., tetra-n-butylammonium bromide (TBAB, 9.4 g, 15.5 mmol, 0.020 eq., 50% in deionized water) and (3-chloropropyl)triethoxysilane (CPTEO, 372 g, 1.54 mol, 2.00 eq.) were added to the reaction mixture, while maintaining the temperature between 72 and 78° C. The suspension was stirred at 75° C. for 3 hours. The conversion of 3-chloropropyl)triethoxysilane in the organic phase was determined by GC and was found to be 98.6%. Then, water (412.5 g) was added to dissolve all salts and the phases were separated at 75° C. The aqueous phase (0.94 kg) was disposed of. After cooling, the organic phase to room temperature, it underwent removal of light boilers by thin-film evaporation. After filtration, the product was obtained as a clear yellowish liquid with an average sulfur chain length of 2.17 and a concentration of S2 to S10 of 93.32%

Example 2 (4,4,13,13-Tetraethoxy-3,14-Dioxa-8,9-Dithia-4,13-Disilahexadecane) with Recycling Step (Inventive Example)

[0182] (a) A sodium hydrosulfide solution (102 g, 0.785 mol, 1.00 eq., 43%), Na.sub.2CO.sub.3 (83.2 g, 0.785 mol, 1.00 eq.), and a brine (f) (containing a saturated aqueous solution of left over reagents, phase transfer catalyst and/or products from one or more previous reaction batches using the same recipe, 291 g) were mixed and stirred at 72° C. for 10 minutes. Subsequently, sulfur (28.0 g, 0.873 mol, 1.112 eq.) was added while maintaining a temperature between 70° C. and 75° C. After stirring the reaction mixture for 45 minutes at 72° C.,

[0183] (b) tetra-n -butylammonium bromide (TBAB, 5.06 g, 7.9 mmol, 0.010 eq., 50% in deionized water) was added.

[0184] (c) Then, (3-chloropropyl)triethoxysilane (CPTEO, 378 g, 1.57 mol, 2.00 eq.) are added with a rate of 6.3 g/minute to the reaction mixture, while maintaining the temperature between 72 and 78° C. The suspension was stirred at 75° C. for 3 hours. The conversion of 3-chloropropyl)triethoxysilane in the organic phase was determined by GC and was found to be 98.2%.

[0185] (d) After this step, 424 g brine (containing an aqueous solution of left over reagents, phase transfer catalyst, and/or products from one or more previous reactionbatches using the same recipe) was added and the phases were separated at 75° C.

[0186] (e) Afterwards, aqueous suspension (h) from the brine distillation of a previous batch were added to the aqueous phase of the phase separation step and the mixture was filtered, rendering a salt cake (176 g) and brine (aqueous solution for the next brine-recycling reaction).

[0187] (f) The remainder of the brine (839 g) was used in the following batch.

[0188] (g) 130 g of this brine were introduced into a rotary evaporator for distillation. Water was partially drawn off at 300 mbar absolute, leaving behind an aqueous suspension (85 g),

[0189] (h) to be used in the following batch.

[0190] (i) After cooling the organic phase to room temperature, it was purified by thin-film evaporation.

[0191] (j) After filtration, 350 g of product, 93% yield were obtained as a clear yellowish liquid with an average sulfur chain length of 2.15 and a concentration of S2 to S10 of 95.16%

Example 3 (4,4,15,15-Tetraethoxy-3,16-Dioxa-8,9,10,11-Tetrathia-4,15-Disilaoctadecane) Without Recycling Step (Comparative Example)

[0192] Sodium hydroxide (40.3 g, 1.01 mol, 0.97 eq.), sodium hydrosulfide hydrate(142.1 g, 1.017 mol, 0.98 eq., 43%) and water (79.2 g, 4.40 mol, 4.24 eq.) were heated to 72° C. The reaction mixture was stirred for 10 minutes at 72° C. Subsequently, sulfur (91.8 g, 2.87 mol, 2.76 eq.) was added in two portions, while maintaining the temperature between 70 and 75° C. After stirring the reaction mixture for 15 min at 72° C., tetra-n -butylammonium bromide (TBAB, 8.7 g, 13.5 mmol, 0.013 eq., 50% in deionized water) and (3-chloropropyl)triethoxysilane (CPTEO 499.7 g, 2.07 mol, 2.00 eq.) are added to the reaction mixture, while maintaining the temperature between 72 and 78° C.

[0193] The suspension was stirred at 75° C. for 2 hours. Then, water (321 g) was added to dissolve all salts and the phases were separated at 75° C. The aqueous phase (464 g) was disposed of. After cooling, the organic phase to room temperature, it underwent removal of light boilers by thin-film evaporation. After filtration, the product was obtained as a clear yellowish liquid with an average sulfur chain length of 3.72 and a concentration of S2 to S10 of 93.33 %

Example 4 (4,4,15,15-Tetraethoxy-3,16-Dioxa-8,9,10,11-Tetrathia-4,15-Disilaoctadecane) with Recycling Step (Inventive Example)

[0194] (a) Sodium hydroxide (40.2 g, 1.01 mol, 0.97 eq.), sodium hydrosulfide hydrate (133 g, 1,017 mol, 0.98 eq., 43%) and brine (containing an aqueous solution of left over reagents, phase transfer catalyst, and/or products from one or more previous reaction batches using the same recipe 79.3 g.) were heated to 72° C. The reaction mixture was stirred for 10 minutes at 72° C. Subsequently, sulfur (91.8 g, 2.86 mol, 2.76 eq.) was added in two portions, while maintaining the temperature between 70 and 75° C. After stirring the reaction mixture for 15 minutes at 72° C.,

[0195] (b) tetra-n -butylammonium bromide (TBAB, 6.7 g, 10.4 mmol, 0.010 eq, 50% in deionized water, addition in 4 equal portions)

[0196] (c) and (3-chloropropyl)triethoxysilane (CPTEO, 500 g, 2.08 mol, 2.00 eq., addition with a rate of 8.5 g/minute) were added to the reaction mixture, while maintaining the temperature between 72 and 78° C. The suspension was stirred at 75° C. for 2 hours.

[0197] (d) Afterwards, brine (containing an aqueous solution of left over reagents, phase transfer catalyst, and/or products from one or more previous reaction batches using the same recipe, 324.6 g) was added and the mixture was allowed to settle into phases which were separated.

[0198] (e) The aqueous suspension was filtered, rendering a salt cake and brine (aqueous solution for the next brine-recycling reaction).

[0199] (f) The brine was used in the following batch.

[0200] (g) -

[0201] (h) -

[0202] (i) After cooling, the organic phase to room temperature, it underwent removal of light boilers by thin-film evaporation.

[0203] (j) After filtration, the product was obtained as a clear yellowish liquid with an average sulfur chain length of 3.71 and a concentration of S2 to S10 of 94.11%