Organofunctional cocyclic siloxanes and polymerization thereof

Details Organofunctional cocyclic siloxanes and polymerization thereof Organofunctional cocyclic siloxanes and polymerization thereof

1999-08-20

2001-03-13

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...

C528S012000, C528S015000, C528S016000, C528S025000, C528S037000

Reexamination Certificate

active

06201091

ABSTRACT:

The dialkyl, alkyl carboxyalkyl cocyclic siloxane, most preferably a dimethyl, methyl carboxyalkyl 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 carboxyalkylpolysiloxanes, it is not uncommon to react a vinyl functional siloxane with thioglycolic acid HSCH
2
COOH, which reaction provides a sulfur containing carboxy functional polymer. However, the sulfur odor inherent in such materials precludes their widespread use. In contrast, and according to the present invention, a sulfur-free route to carboxyalkylpolysiloxanes is provided.
In emulsion and microemulsion polymerization techniques for the preparation of carboxyalkylpolysiloxanes, it is also not uncommon to employ a carboxyalkyl trialkoxysilane as one of the precursors in order to impart functionality to the siloxane polymer. However, carboxyalkyl 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 carboxyalkyl trialkoxysilane to become incorporated into the siloxane polymer. In addition, the carboxyalkyl 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 carboxy functionality into the siloxane polymer will improve with the use of the dialkyl, alkyl carboxyalkyl cocyclic siloxane due to its increased nonpolarity and hence its decreased water solubility. In addition, the dialkyl, alkyl carboxyalkyl cocyclic siloxane liberates no by-product of any kind.
Lastly, carboxyfunctional siloxanes are useful in the treatment of substrates such as hair and textiles, due to their siloxane lubrication properties, and durability imparted by the carboxy group. However, odor issues, i.e., sulfur containing, and poor process economics have generally hindered their widespread use in these commercial applications. This invention improves both the odor profile and the process economics.
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 acid 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 reaction mixture can further include (iv) a short chain linear silicone endblocker, (v) a dialkyl cyclosiloxane, or mixtures thereof.
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 the use of an organofunctional cocyclic siloxane as the cyclic organosilicon precursor in the reaction mixture.
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, the dialkyl cyclosiloxane, or mixtures thereof.
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, the dialkyl cyclosiloxane, or mixtures thereof.
These and other features of the invention will become apparent from a consideration of the detailed description.
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; R4 is a carboxyalkyl or carboxyalkyl derivative group having the formula —(CHR5)
n
COOR6 where R5 is hydrogen or an alkyl group containing 1-6 carbon atoms; R6 is hydrogen, an alkyl group containing 1-6 carbon atoms, or a trialkylsilyl group —Si(R7)
3
in which R7 is an alkyl group containing 1-6 carbon atoms; a and b are each a positive integer having a value of 1-10; and n is a positive integer having a value of 3-20.
This organofunctional cocyclic siloxane, and methods for its preparation, are described in detail in copending U.S. patent 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
”. The copending application is assigned to the same assignee as the present application, and is considered incorporated herein by reference. Such compositions, as explained in detail in the copending application, are prepared by a hydrosilation process in which an ≡SiH containing cocyclic siloxane is contacted with an alkenoic acid such as undecylenic acid H
2
C═CH(CH
2
)
8
COOH, in the presence of a Group VIII transition metal catalyst such as platinum.
The organofunctional cocyclic siloxane precursors used in the accompanying examples of this application had a structure generally corresponding to the formula
wherein R4 was the group —(CH
2
)
10
COOH, a had a value of 4, and b had a value of one.
Bulk Polymerization of an Organofunctional Cocyclic Siloxane
In this embodiment, polymerization of the organofunctional cocyclic siloxane yielded (i) trialkylsiloxy terminated silicone copolymers containing dialkyl and carboxyalkyl repeating units, and (ii) trialkylsiloxy terminated silicone terpolymers containing dialkyl, higher (C8+) alkylmethyl, and carboxyalkyl repeating units. These compositions corresponded generally to polymers of the formula:
R
3
SiO (R
2
SiO)
x
(RR′SiO)
y
(RR″SiO)
z
SiR
3
wherein R is an alkyl group containing one to four carbon atoms, preferably methyl; R′ is an alkyl group containing at least 8 carbon atoms; x and z each have a value of 1-1000; y has a value o

Affiliated with

Also associated with

Rating

Organofunctional cocyclic siloxanes and polymerization thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Organofunctional cocyclic siloxanes and polymerization thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organofunctional cocyclic siloxanes and polymerization thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2460815