Polymerization of an organofunctional cocyclic siloxane

Details Polymerization of an organofunctional cocyclic siloxane Polymerization of an organofunctional cocyclic siloxane

1999-08-20

2001-03-27

Lovering, Richard D. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S037000, C528S038000, C556S425000

Reexamination Certificate

active

06207781

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not applicable.
FIELD OF THE INVENTION
This invention is directed to the polymerization of an organofunctional cocyclic siloxane. In a first embodiment, a dialkyl, alkyl aminoalkyl cocyclic siloxane is polymerized using a bulk polymerization technique. In a second embodiment, a dialkyl, alkyl aminoalkyl cocyclic siloxane is polymerized using an emulsion polymerization technique. In a third embodiment, a dialkyl, alkyl aminoalkyl cocyclic siloxane is polymerized using a microemulsion polymerization technique.
The dialkyl, alkyl aminoalkyl cocyclic siloxane, most preferably a dimethyl, methyl aminoalkyl cocyclic siloxane, is used to prepare copolymeric siloxane fluids, copolymeric siloxane gums, and terpolymeric siloxanes, according to the three polymerization techniques.
BACKGROUND OF THE INVENTION
In bulk polymerization techniques for the preparation of aminoalkylpolysiloxanes, it is not uncommon to employ an aminoalkyl siloxane polymer or an aminoalkyl trialkoxysilane as a precursor. However, aminoalkyl siloxane polymers are generally quite viscous and very sticky materials, and these properties make it difficult to pump the aminoalkyl siloxane polymer through existing equipment, and make it difficult to disperse the aminoalkyl siloxane polymer in the reaction medium. While aminoalkyl trialkoxysilanes generally disperse well in the reaction medium, they liberate significant amounts of an alcohol as a by-product.
In contract, and according to the present invention, the dialkyl, alkyl aminoalkyl cocyclic siloxane is (i) low in viscosity, (ii) nonsticky, (iii) easy to pump through existing equipment, and (iv) it can easily dispersed into the reaction medium. In addition, the dialkyl, alkyl aminoalkyl cocyclic siloxane liberates no by-products.
In emulsion and microemulsion polymerization techniques for the preparation of aminoalkylpolysiloxanes, it is also not uncommon to employ an aminoalkyl trialkoxysilane as one of the precursors in order to impart functionality to the siloxane polymer. However, aminoalkyl trialkoxysilanes typically have a considerable solubility in water, and therefore only partially incorporate into the siloxane polymer droplets formed during the ring opening polymerization reaction. As a consequence, one can only expect a low level of the aminoalkyl trialkoxysilane to become incorporated into the siloxane polymer. In addition, as noted above, the aminoalkyl trialkoxysilane generates a significant amount of alcohol as a by-product, most commonly methanol, according to the reaction:
RSi(OCH
3
)
3
+3H
2
O→RSi(OH)
3
+3CH
3
OH.
While methanol is not classified as carcinogenic, it can be acutely toxic if ingested, and may even be fatal or result in blindness. Methanol is a general irritant to the skin and mucous membranes, and prolonged skin contact with methanol vapor or liquid can cause dermatitis. Therefore, it would be advantageous in applications especially in the personal care arena, to eliminate its presence.
In contrast, and according to the present invention, one can expect that the extent of incorporation of amine functionality into the siloxane polymer will improve with the use of the dialkyl, alkyl aminoalkyl cocyclic siloxane due to its increased nonpolarity and hence its decreased water solubility. In addition, the dialkyl, alkyl aminoalkyl cocyclic siloxane liberates no by-product of any kind.
BRIEF SUMMARY OF THE INVENTION
In a first embodiment, silicone copolymers and silicone terpolymers are prepared by bulk polymerization according to a method comprising heating a mixture of (i) an organofunctional cocyclic siloxane; and optionally (ii) a C
8
or more carbon atom containing alkylmethyl, dimethyl silicone cocyclic, in the presence of (iii) an alkaline catalyst, at a temperature and for a time sufficient to cause polymerization of (i) and optionally (ii) to the desired silicone copolymer and silicone terpolymer, respectively.
The mixture can further include (iv) a short chain linear silicone endblocker, and (v) a dimethyl cyclosiloxane. The catalyst (iii) is preferably an alkali-metal silanolate having the formula R
a
w
Si(OM)
4-w
or an alkali metal siloxanolate having the formula MO(R
a
2
SiO)
n
M, in which R
a
represents an alkyl radical of 1-6 carbon atoms, an aryl radical, an alkenyl radical, or an alkylamino radical; w is 0-3; and n is 2-20.
In a second embodiment, there is provided a process of emulsion polymerization in which the polymerization reaction involves opening of polysiloxane rings of a cyclic organosilicon precursor using an anionic catalyst or a cationic catalyst in the presence of water, to form higher molecular weight polysiloxanes in the emulsion. The improvement according to the second embodiment comprises using as the cyclic organosilicon precursor in the reaction mixture an organofunctional cocyclic siloxane.
As in the first embodiment, the reaction mixture can further include the C
8
or more carbon atom containing alkylmethyl, dimethyl silicone cocyclic, the short chain linear silicone endblocker, or the dimethyl cyclosiloxane.
The third embodiment is a classical method of microemulsion formation involving mixing an oil and water with a surfactant (S1), and a co-surfactant (S2). The oil is an organofunctional cocyclic siloxane. The oil is added to a solution of the surfactant (S1) and water. A two-phase system containing the siloxane results. The two-phase system is then titrated with co-surfactant (S2) until a clear isotropic microemulsion results. An emulsion polymerization catalyst is added to the clear isotropic microemulsion, and polymerization of the cocyclic siloxane is initiated. The polymerization is allowed to advance until the reaction is complete, or a desired degree of polymerization (DP) has been obtained. Microemulsions of high molecular weight silicone polymers with low polydispersity can be produced.
As in the first and second embodiments, the reaction mixture can further include the C
8
or more carbon atom containing alkylmethyl, dimethyl silicone cocyclic, the short chain linear silicone endblocker, or the dimethyl cyclosiloxane.
These and other features of the invention will become apparent from a consideration of the detailed description.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
Copolymeric siloxane fluids, copolymeric siloxane gums, and terpolymeric siloxanes, are prepared by polymerizing an organofunctional cocyclic siloxane using a bulk polymerization technique, an emulsion polymerization technique, or a microemulsion polymerization technique.
The Organofunctional Cocyclic Siloxane
The organofunctional cocyclic siloxane used as a precursor in accordance with the present invention is a composition of matter having the formula
where R1 to R3 are each an alkyl group containing 1-6 carbon atoms; a and b are each a positive integer having a value of 1-10; and R4 is an aminoalkyl group having the formula
where R′″ and R″″ are each hydrogen or an alkyl group containing 1-4 carbon atoms, R
V
is hydrogen or a group having the formula
where c is a positive integer having a value of 2 or 3, and R
v
′
and R
v
″
are hydrogen or an alkyl group containing 1-4 carbon atoms.
Alkyl groups represented by R1, R2, R3, R′″, R″″ R
v
′
, and R
v
″
include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl. Some representative R4 aminoalkyl groups, and R4 groups most preferred are —CH
2
CH
2
CH
2
NH
2
, —CH
2
CH
2
CH
2
NHCH
2
CH
2
NH
2
, and —CH
2
CH(CH
3
)CH
2
NHCH
2
CH
2
NH
2
.
This organofunctional cocyclic siloxane, and methods for its preparation, are described in detail in copending U.S. Pat. No. application Ser. No. 09/354,675, filed Jul. 16, 1999 now U.S. Pat. No. 6,118,014, in the name of Daniel J. Halloran and Brett L. Zimmerman, entitled
“Organofunctional Cocyclic Siloxanes

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