Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2000-09-11
2002-07-09
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S012000, C528S021000, C528S023000, C528S014000, C556S455000, C556S462000
Reexamination Certificate
active
06417310
ABSTRACT:
BACKGROUND OF THE INVENTION
As is well known in the art, branched organopolysiloxanes are improved in low-temperature properties and thixotropy over linear organopolysiloxanes. Recently, the branched organopolysiloxanes are considered useful as anti-foaming agents (see JP-A 5-271689, 8-196811 and 8-309104) and aqueous coating agents (see JP-B 60-22018 and JP-A 8-85760). However, it was difficult to introduce branched structure units into organopolysiloxane units. Although JP-A 10-60115 discloses a method for preparing branched organopolysiloxane, a further improvement in productivity is desired.
As to the preparation of branched organopolysiloxane emulsions, emulsion polymerization of a cyclic siloxane and a trialkoxysilane is disclosed in JP-B 56-38609 and JP-A 63-286434. Since this method is equilibration reaction using an acidic or basic catalyst, the resulting siloxane product generally contains about 8 to 15% by weight, most often about 12% by weight of volatile low molecular weight siloxanes.
There were developed methods for preparing an organopolysiloxane emulsion such that the content of volatile low molecular weight siloxanes is reduced. For example, JP-A 4-178429 discloses polymerizing an emulsion containing a both end hydroxy-blocked organopolysiloxane and a catalyst at a temperature below 40° C. In JP-A 4-198321, a both end hydroxy-blocked organopolysiloxane and a both end aminoxy-blocked organopolysiloxane are emulsion polymerized. Emulsion polymerization of a both end hydroxy-blocked organopolysiloxane in the presence of a sulfonic acid is disclosed in JP-A 11-71522. In these patents, no reference is made to the preparation of a branched organopolysiloxane emulsion.
SUMMARY OF THE INVENTION
An object of the invention is to provide an efficient method for preparing branched organopolysiloxane.
Another object of the invention is to provide an method for preparing a branched organopolysiloxane emulsion having a minimized content of low molecular weight siloxanes and suited as a base of a fiber treating agent and coating agent.
We have found that a branched organopolysiloxane can be prepared in an efficient manner by polymerizing an organopolysiloxane mixture of an organopolysiloxane containing branch units of a specific structure and a low molecular weight organopolysiloxane in the presence of an acidic or basic catalyst, or by adding a surfactant to such an organopolysiloxane mixture, dispersing it in water to form an emulsion, and polymerizing the emulsion in the presence of an acidic or basic catalyst.
According to a first aspect, the invention in one embodiment provides a method for preparing a branched organopolysiloxane, comprising the step of polymerizing an organopolysiloxane mixture comprising (A) a branched organopolysiloxane of the following general formula (1) and (B) a low molecular weight organopolysiloxane in the presence of an acidic or basic catalyst. In another embodiment, the method involves the steps of adding (C) an acidic or basic surfactant to an organopolysiloxane mixture of components (A) and (B) and dispersing the organopolysiloxane mixture in water with the aid of the surfactant to form an emulsion, and polymerizing the organopolysiloxane mixture in the emulsion.
Herein R
1
is a monovalent organic group of 1 to 20 carbon atoms, R
2
is independently a monovalent organic group of 1 to 20 carbon atoms, R
3
is a hydroxyl group, alkoxy group of 1 to 6 carbon atoms or monovalent organic group of 1 to 20 carbon atoms, m is a number from 1 to 100, “a” is equal to 0 or 1, “b” is equal to 3 or 4, and a+b is equal to 4.
We also attempted to prepare a branched organopolysiloxane emulsion having a minimized content of volatile low molecular weight siloxanes. We have found that by polycondensing a hydroxy-terminated branch unit-bearing organopolysiloxane and a hydroxy-terminated diorganopolysiloxane, both containing up to 5% by weight of cyclic low molecular weight siloxanes having up to 10 silicon atoms, in water in the presence of an acidic or basic catalyst and a surfactant, there is obtained a branched organopolysiloxane emulsion containing up to 5% by weight of cyclic low molecular weight siloxanes having up to 10 silicon atoms. This emulsion causes less environmental pollution because of the minimized volatilization of low molecular weight siloxanes and is thus suited as a fiber treating agent and coating agent.
According to a second aspect, the invention in one embodiment provides a method for preparing a branched organopolysiloxane, comprising the step of polymerizing an organopolysiloxane mixture in the presence of an acidic or basic catalyst. The organopolysiloxane mixture contains (D) a branched organopolysiloxane of the following general formula (2):
wherein R
1
is a monovalent organic group of 1 to 20 carbon atoms, R
2
is independently a monovalent organic group of 1 to 20 carbon atoms, p is an integer of 4 to 100, “a” is equal to 0 or 1, “b” is equal to 3 or 4, and a+b is equal to 4, the organopolysiloxane containing up to 5% by weight of cyclic low molecular weight siloxanes having up to 10 silicon atoms, and (E) a hydroxy-terminated organopolysiloxane of the following general formula (3):
wherein R
4
is a monovalent organic group of 1 to 20 carbon atoms, and q is an integer of 10 to 700, the organopolysiloxane containing up to 5% by weight of cyclic low molecular weight siloxanes having up to 10 silicon atoms. In another embodiment, the method involves the steps of adding (C) an acidic or basic surfactant to an organopolysiloxane mixture of components (D) and (E) and dispersing the organopolysiloxane mixture in water with the aid of the surfactant to form an emulsion, and polymerizing the organopolysiloxane mixture in the emulsion. The resulting branched organopolysiloxane contains up to 5% by weight of cyclic low molecular weight siloxanes having up to 10 silicon atoms.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The method for preparing a branched organopolysiloxane according to the first aspect of the invention uses components (A) and (B) and optionally component (C), to be defined below.
Component (A)
One starting reactant (A) used herein is an organopolysiloxane containing branch structure units, represented by the following general formula (1).
Herein R
1
is a monovalent organic group of 1 to 20 carbon atoms, R
2
which may be the same or different is a monovalent organic group of 1 to 20 carbon atoms, R
3
is a hydroxyl group, alkoxy group of 1 to 6 carbon atoms or monovalent organic group of 1 to 20 carbon atoms, and m is a number from 1 to 100.
The monovalent organic groups represented by R
1
include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, and eicosyl, cycloalkyl groups such as cyclopentyl and cyclohexyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl, tolyl, and naphthyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, hexyloxy, heptyloxy, octyloxy, decyloxy, and tetradecyloxy, and substituted ones in which some of the hydrogen atoms in these organic group structures are replaced by halogen atoms or organic groups containing a polar group such as amino, acryloxy, methacryloxy, epoxy, mercapto or carboxyl. Of these, methyl, vinyl and phenyl are especially preferred.
R
2
stands for one or more monovalent organic groups selected from the same monovalent organic groups as R
1
. It is preferred that methyl account for at least 90 mol % of the R
2
groups.
R
3
stands for hydroxyl groups, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, pentoxy and hexoxy, and the same monovalent organic groups as R
1
. Of these, hydroxyl groups are especially preferred.
Letter m having a value of less than 1 leads to a lower polymerization rate. If m has a value in excess of 100, the amount of component (A) formulated must be increased, inviting inefficiency. For this reason, m is a number from 1 to 100 on the average, and preferably 10 to 50 on the average. The letter “a” is equal to 0 or 1, “b” is
Kuwata Satoshi
Omura Naoki
Osawa Yoshihito
Millen White Zelano & Branigan P.C.
Moore Margaret G.
Shin-Etsu Chemical Co. , Ltd.
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