Treatment of steel surfaces

Patent metadata

Field	Value
Publication number	US-9528179-B2
Application number	US-201214355923-A
Country	US
Kind code	B2
Filing date	Oct 17, 2012
Priority date	Nov 2, 2011
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

The content of phosphorus in polycrystalline silicon prepared by the Siemens process is reduced by treating phosphorus-containing steel surfaces with an α-amino-functional alkoxysilane. The treated surface exhibits less corrosion in an atmosphere of moist hydrogen chloride, and less loss of phosphorus as a result.

First claim

The invention claimed is:

1. A treated, phosphorus-containing steel surface, prepared by exposing the phosphorus-containing steel surface directly to an α-amino-functional alkoxysilane in a gas phase, wherein the treated, phosphorus-containing steel surface is resistant to corrosion by a gas mixture containing chlorine, hydrogen chloride, chlorosilanes, hydrogen, moisture, and optionally reactive elemental silicon.

2. The treated, phosphorus-containing steel surface of claim 1 , wherein at least one α-amino-functional alkoxysilane is selected from the group consisting of N,N-(diethylaminomethyl)dimethoxymethylsilane, and a mixture of (2-aminoethyl)aminomethyltrimethoxysilane and cyclic aza compounds derived therefrom.

3. A process for treating a phosphorus-containing steel surface, comprising exposing the steel surface directly to a vapor of alpha-amino-functional alkoxysilane, wherein the temperature of the steel surface is less than 50° C., and the vapor-treated steel surface is subsequently exposed to a corrosive atmosphere of a gas mixture of residual moisture, chlorine, hydrogen chloride, chlorosilanes, hydrogen and optionally reactive elemental silicon.

4. The process of claim 3 , wherein the alkoxysilanes are N,N-(dietxhylaminomethyl)-dimethoxymethylsilane or a mixture of (2-aminoethyl)aminomethyltrimethoxysilane and a cyclic aza compound derived therefrom.

5. The process of claim 3 , wherein an aerosol is conveyed onto the steel surface during the treatment.

6. In a process for the preparation of polycrystalline silicon by chemical vapor deposition from a chlorosilane and hydrogen at elevated temperature in a reactor, wherein unreacted hydrogen is recovered and recycled to the reactor, the recycled hydrogen containing HC1 and residual moisture, wherein the recycled hydrogen contacts a phosphorus-containing steel surface, the improvement comprising reducing the phosphorus content of the polycrystalline silicon by treating a phosphorus-containing steel surface by the process of claim 3 .

Assignees

• Wacker Chemie Ag

Inventors

• Fabry Laszlo
• Mueller Barbara
• Stepp Michael

Classifications

• C09D183/04

  Polysiloxanes · CPC title

• C09D183/08

  containing silicon bound to organic groups containing atoms other than carbon, hydrogen, and oxygen · CPC title

• C23G1/085

  solutions containing HNO3 · CPC title

• C23C16/24

  Deposition of silicon only · CPC title

• Y10T428/31663

  As siloxane, silicone or silane · CPC title