Compositions of resin-linear organosiloxane block copolymers
View Patent ↗A process is disclosed for preparing a resin-linear organosiloxane block copolymer. The resin-linear organosiloxanes block copolymers prepared by the disclosed process may provide optically solid compositions which may be considered as “reprocessable”.
1. A process for preparing an organopolysiloxane block copolymer comprising:
I) reacting
a) a linear organosiloxane having the formula:
R 1 q (E) (3-q) SiO(R 1 2 SiO 2/2 ) n Si(E) (3-q) R 1 q ,
wherein each R 1 , at each occurrence, is independently a C 1 to C 30 hydrocarbyl or a hydrolyzable group containing at least one carbon atom,
n is 10 to 400,
q is 0, 1 or 2,
E is a hydrolyzable group containing at least one carbon atom, and
b) an organosiloxane resin comprising at least 60 mole % of [R 2 SiO 3/2 ] siloxy units in its formula, wherein each R 2 , at each occurrence, is independently a C 1 to C 20 hydrocarbyl,
in c) an organic solvent
to form a resin-linear organosiloxane block copolymer;
wherein the amounts of a) and b) used in step I) are selected to provide the resin-linear organosiloxane block copolymer with 5 to 65 mole % of disiloxy units [R 1 2 SiO 2/2 ] and 35 to 95 mole % of trisiloxy units [R 2 SiO 3/2 ], and
wherein at least 95 weight percent of the linear organosiloxane used in step I) is incorporated into the resin-linear organosiloxane block copolymer;
II) contacting said resin-linear organosiloxane block copolymer from step I) with a base bodying agent to reduce the silanol content of the resin-linear organosiloxane block copolymer to 5 mole % or less;
III) optionally, further processing the resin-linear organosiloxane block copolymer; and
IV) optionally, removing the organic solvent.
2. The process of claim 1 , wherein the base bodying agent comprises a strong base.
3. The process of claim 2 , wherein said strong bases comprises KOH or NaOH.
4. The process of claim 1 , wherein R 2 is phenyl.
5. The process of claim 1 , wherein R 1 is phenyl or methyl.
6. The process of claim 1 , wherein the disiloxy units have the formula [(CH 3 )(C 6 H 5 )SiO 2/2 ].
7. The process of claim 1 , wherein said further processing comprises contacting the resin-linear organosiloxane from step II) with water and removing acetic acid.
8. The process of claim 1 , wherein said further processing comprises contacting the resin-linear organosiloxane from step II) with an endcapping compound selected from an alcohol, oxime, or trialkylsiloxy compound.
9. The process of claim 1 , wherein instead of or in addition to said further processing, the organosiloxane block copolymer from step II) is contacted with a stabilizer or a superbase.
10. The organopolysiloxane block copolymer prepared by the process of claim 1 .
11. The organopolyxiloxane block copolymer of claim 10 , wherein the organopolysiloxane block copolymer is the reaction product of step II).
12. A composition comprising the organopolysiloxane block copolymer of claim 10 .
13. The composition of claim 12 , which is curable.
14. The composition of claim 12 , which is solid.
15. The cured product of the composition of claim 13 .
16. A solid film composition comprising the composition of claim 12 .
17. The solid film composition of claim 16 , wherein the solid composition has an optical transmittance of at least 95%.
18. An LED encapsulant comprising the composition of claim 12 .