PROCESS OF REACTING SILICONE WITH HYDROTHERMAL OR SUPERCRITICAL WATER

Abstract

A process for reacting silicone with hydrothermal water is at temperatures from 140? C. or supercritical water. A solids mixture containing silicon is formed.

Claims

1-8. (canceled)

9. A process for reacting silicone with hydrothermal water at temperatures from 140? C. or supercritical water to give a solids mixture containing silicon, wherein the term silicone encompasses oligomeric or polymeric organosiloxanes in which silicon atoms are bonded via oxygen atoms and in which at least some of the silicon atoms carry one or more organic substituents, and also compositions comprising organosiloxanes.

10. The process as claimed in claim 9, wherein the silicones contain at most 1 wt % of halogens.

11. The process as claimed in claim 9, wherein the solids mixture contains 25 to 50 wt % of silicon.

12. The process as claimed in claim 9, wherein a methane-containing gas mixture is produced.

13. The process as claimed in claim 9, wherein the temperature is 160? C. to 700? C.

14. The process as claimed in claim 9, wherein the pressure is 10 to 400 bar.

15. The process as claimed in claim 9, wherein the solids mixture produced is supplied to raw silicon production.

Description

EXAMPLE 1

[0027] An autoclave is charged with an amount of 30 g of finely chopped (cubes with an edge length of 0.5 cm) silicone and 150 ml of water, and closed. Over the course of 120 minutes, the autoclave is heated to a temperature of 350? C., and the temperature is held for 90 minutes. In the course of the experiment, the pressure climbs to 160 bar. Over the course of 12 hours, the autoclave cools to room temperature. After cooling of the reactor, the sample is taken for gas analysis. The gas space of the autoclave is subsequently purged with nitrogen and the autoclave is opened.

[0028] A clear liquid and a white or slightly grey solid are obtained. After the liquid has been removed and the solid has been dried, 21 g of solid are obtained.

[0029] 3 experiments were conducted. The results of the EDX analyses of the solids mixture are listed in table 1. MV denotes mean value.

TABLE-US-00001 TABLE 1 Experiment no. 1 2 3 Max Min MV C (wt %) 23.96 34.09 29.64 34.09 23.96 29.23 O (wt %) 41.35 32.64 38.46 41.35 32.64 37.48 Na (wt %) 0.00 0.21 0.29 0.29 0.00 0.17 Si (wt %) 34.70 33.05 31.61 34.70 31.61 33.12 Total (wt %) 100.01 99.99 100.00

EXAMPLE 2

[0030] 1000 kg of solid silicone wastes, consisting of silicone rubber in plastic containers, are comminuted, containers included, and reacted in a stirred tank with a size of 3 m 3 together with 1500 kg of water at 350? C. and 160 bar for 2 h. Two tanks are operated in parallel. The preheating of the one tank is realized by cooling of the other tank, via heat recovery; the rest of the heat required is supplied externally. The products of the reaction are a solids/liquid mixture and a gas phase. The solids/liquid mixture is filtered; the solid obtained has the composition from table Table 1. According to present knowledge of the hydrothermal carbonization, any plastic containers added are reacted to give carbon-rich particulate solids. The liquid phase contains biproducts of the reaction and, depending on the degree of contamination, may be used for the further reaction of silicone wastes. As well as water, the gas phase contains volatile biproducts, possibly including methane, depending on reaction regime and starting products.

[0031] The solids are passed on for profitable utilization from example 3.

EXAMPLE 3

[0032] Profitable utilization of the solids from example 1 and example 2 for producing metallurgical silicon.

[0033] The solids obtained in examples 1 and 2 are pressed to give pellets and supplied as a starting material for raw silicone production. In that process, the silicon is reduced to raw silicon.