Alkoxysiloxanols

Abstract

Alpha-alkoxy-omega-siloxanols, R'O(R 2 SiO) x H, are produced by contacting cyclic siloxanes with alcohols under mild conditions. For example, hexamethylcyclotrisiloxane heated at reflux in methanol for four hours gives 5-methoxyhexamethyltrisiloxan-1-ol in high yield. The reaction proceeds more rapidly in the presence of weak acids .[.or bases.].. The products are useful as antistructure agents, coupling agents, and filler-treating agents for silicone elastomers.

The invention claimed is: .[.1. Alpha-alkoxy-omega-siloxanols having the formula R'O(R 2  SiO) x  H, in which R is selected from the group consisting of a monovalent hydrocarbon radical, a halogenated monovalent hydrocarbon radical and a cyanoalkyl radical having up to 8 carbon atoms, R' is a radical derived from a primary or secondary alcohol and is selected from the group consisting of alkyl radicals, cycloalkyl radicals, alkeny radicals, aralkyl radicals and substituted derivatives thereof having up to 20 carbon atoms, and x is an integer of from 2 to 10..]. .[.2. The alpha-alkoxy-omega-siloxanols of claim 1, in which at least 50 percent of the R radicals are methyl, R' is an alkyl radical of up to four carbon atoms, and x is an integer of from 3 to 5..]. .[.3. The composition of claim 2 wherein the alpha-alkoxy-omega-siloxanol is 
     
        5-methoxyhexamethyltrisiloxan-1-ol..]. 4. .[.The composition of claim 2 wherein the alpha-alkoxy-omega-siloxanol is.]. 
     
     
        7-methoxyoctamethyltetrasiloxan-1-ol. 5. .[.The composition of claim 2 wherein the alpha-alkoxy-omega-siloxanol is.]. 9-methoxydecamethylpentasiloxan-1-ol. .[.6. The composition of claim 2 wherein the alpha-alkoxy-omega-siloxanol is 
     
     
        5-methoxy-1,3,5-trimethyl-1,3,5-trivinyltrisiloxan-1-ol..]. 7. A method for preparing an alpha-alkoxy-omega-siloxanol having the formula R'O(R 2  SiO) x  H which comprises reacting .Iadd.in the absence of a basic catalyst .Iaddend.a cyclic polysiloxane with a primary or secondary alcohol of the formula R'OH in which R is selected from the group consisting of a monovalent hydrocarbon radical, a halogenated monovalent hydrocarbon radical and a cyanoalkyl radical having up to 8 carbon atoms, R' is selected from the group consisting of alkyl radicals, cycloalkyl radicals, alkenyl radicals, aralkyl radicals and substituted derivatives thereof having up to 20 carbon atoms and x is an integer of from 2 to 10 in a mol ratio of alcohol to cyclic polysiloxane of at least 
     
     
        2:1 and at temperatures up to the reflux temperature of the alcohol. 8. The method of claim 7 in which the cyclic polysiloxane has the formula (R 2  SiO) y , in which R is selected from the group consisting of a hydrocarbon radical, a halogenated monovalent hydrocarbon radical and a cyanoalkyl radical having up to 8 carbon atoms and y is an integer of from 3 to 10. .[.9. The method of claim 8 in which a catalyst is added, said 
     
     
        catalyst having a pH a  or pK b  value of from 1.5 to 10..]. 10. The method of claim .[.9.]. .Iadd.13 .Iaddend.in which the catalyst is formic 
     
     
        acid. 11. The method of claim .[.9.]. .Iadd.13 .Iaddend.in which the catalyst is acetic acid. .[.12. The method of claim 9 in which the catalyst is ammonia..]..Iadd. 13. The method of claim 7 in which the reaction is conducted in the presence of an acid catalyst having a pK a  value of from 1.5 to 10. .Iaddend.