Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2000-10-13
2001-07-24
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S422000, C556S442000, C556S450000, C556S458000, C528S018000, C528S020000, C528S021000, C528S034000
Reexamination Certificate
active
06265598
ABSTRACT:
This invention relates to a method for preparing a hydrolyzable group end-blocked organopolysiloxane useful as the base fluid in room temperature curable organopolysiloxane compositions.
BACKGROUND OF THE INVENTION
In the prior art, a hydrolyzable group end-blocked organopolysiloxane is prepared by reacting an organopolysiloxane having a silanol group at each end of its molecular chain represented by the following general formula (1):
(HO)—(R
2
SiO)
n
—H (1)
with an organosilicon compound of the following general formula (2):
(Z)
4−a
SiR
1
a
(2)
or a partial hydrolyzate thereof in the presence of a condensation catalyst. The hydrolyzable group end-blocked organopolysiloxane thus obtained has the following general formula (3).
Herein, R is a substituted or unsubstituted monovalent hydrocarbon group, and n is such a number that the organopolysiloxane of formula (1) may have a viscosity of 10 to 1,000,000 centistokes at 25° C., Z is a hydrolyzable group, R
1
is a substituted or unsubstituted monovalent hydrocarbon group, and “a” is equal to 0 or 1.
The prior art method, however, suffers from several problems including a need of heating to high temperature and a long time of preparation taken until terminal silanol groups are blocked.
SUMMARY OF THE INVENTION
An object of the invention is to provide an improved method for preparing an organopolysiloxane of the above formula (3) briefly in a simple way, without a need for long-term heating to high temperature, and especially in a continuous manner.
The invention pertains to a method for preparing an organopolysiloxane of the above formula (3) by mixing an organopolysiloxane of the above formula (1) (referred to as major component) with an organosilicon compound of the above formula (2) or a partial hydrolyzate thereof serving as a curing agent, and optionally a condensation catalyst and a reaction aid. It has been found that this reaction can be promoted by using a mixer comprising a conduit through which a fluid flows in a direction and an agitator coupled to a vibrating drive and disposed in the conduit for reciprocal motion mainly in the flow direction. More particularly, use is made of a dynamic mixer comprising a conduit through which a fluid flows in an axial direction, a drive means for producing reciprocal motion, and a vibratory agitator including a shaft coupled to the drive means and extended through the conduit for reciprocal motion in the flow direction and one or more vibrating elements attached to the shaft. By reciprocal motion of vibrating elements at a high speed mainly in the flow direction, the minor components including the curing agent and catalyst can be uniformly mixed with the major component within a very short time in the compact conduit. Even when the major component is a silicone fluid having a relatively high viscosity, efficient dispersion is accomplished.
Accordingly, the invention provides a method for preparing a hydrolyzable group end-blocked organopolysiloxane by reacting (A) an organopolysiloxane having a silanol group at each end of its molecular chain represented by the following general formula (1):
wherein R, which may be the same or different, is a substituted or unsubstituted monovalent hydrocarbon group, and n is such a number as to give a viscosity of 10 to 1,000,000 centistokes at 25° C., with (B) an organosilicon compound of the following general formula (2):
(Z)
4−a
SiR
1
a
(2)
wherein Z is a hydrolyzable group, R
1
is a substituted or unsubstituted monovalent hydrocarbon group, and “a” is equal to 0 or 1, or a partial hydrolyzate thereof, optionally in the presence of (C) a condensation catalyst, to form a hydrolyzable group end-blocked organopolysiloxane of the following general formula (3):
wherein R, R
1
, Z, n and a are as defined above. The method involves the steps of furnishing a vibratory mixer comprising a conduit through which a fluid flows in a direction and an agitator disposed in the conduit for reciprocal motion in the flow direction, and introducing a reactant mixture comprising components (A) and (B) and optionally component (C) into the conduit of the vibratory mixer wherein the reactant mixture is vibro-agitated by the agitator while reaction between components (A) and (B) takes place.
REFERENCES:
patent: 4658006 (1987-04-01), Inoue
patent: 5223636 (1993-06-01), Koshimura et al.
patent: 5605997 (1997-02-01), Yamamoto et al.
patent: 5739246 (1998-04-01), Gralver et al.
patent: 5932757 (1999-08-01), Standke et al.
patent: 6069259 (2000-05-01), Crivello
patent: 6127502 (2000-10-01), Krahnke et al.
Kimura Ken-ichi
Kodana Nobuhiko
Miyake Masatoshi
Birch & Stewart Kolasch & Birch, LLP
Shaver Paul F.
Shin-Etsu Chemical Co. , Ltd.
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