Emulsion polymerization using a cocylic silicone

Details Emulsion polymerization using a cocylic silicone Emulsion polymerization using a cocylic silicone

1999-07-08

2001-03-13

Moore, Margaret G. (Department: 1712)

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

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S837000, C528S038000, C528S023000, C556S425000

Reexamination Certificate

active

06201063

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 emulsion polymerization in which the improvement in the process resides in the use of a cocyclic silicone.
BACKGROUND OF THE INVENTION
Emulsion polymerization is a known technique for making emulsions containing silicone polymers, and is explained in detail in numerous references in the prior art, the most notable of which are U.S. Pat. No. 2,891,920 (Jun. 23, 1959), U.S. Pat. No. 3,294,725 (Dec. 27, 1966), U.S. Pat. No. 4,999,398 (Mar. 12, 1991), and European Patent 0 459 500 B1 (Dec. 4, 1991), all of which are assigned to the same assignee as the present application.
According to the standard technique, the polymerization reaction involves the opening of cyclic polysiloxane rings using an anionic or a cationic catalyst in the presence of water. The anions and the cations act as a polymerization catalyst for such reactions by functioning to open the ring of the cyclic polysiloxane, and allowing it to form linear siloxane oligomers having terminal hydroxy groups. These oligomers then react with other oligomers by means of a condensation reaction, with the result that higher molecular weight polysiloxanes are formed. A surfactant(s) is generally used to stabilize the polysiloxane in the emulsion in the form of small sized droplets.
Most typically, the cyclic polysiloxane used in these ring opening reactions has a structure generally corresponding to the formula:
where n generally has a value of about 3-6, and R1 and R2 represent alkyl groups containing 1-6 carbon atoms. Some examples of these cyclic polysiloxanes are hexamethylcyclotrisiloxane (D
3
), octamethylcyclotetrasiloxane (D
4
), decamethylcyclopentasiloxane (D
5
), and dodecamethylcyclohexasiloxane (D
6
).
In contrast, the cyclic polysiloxane used in the reaction according to this invention is a cocyclic silicone having a structure generally corresponding to the formula:
where a and b each represent an integer having a value of 1-10; R3, R4, and R5 each represent an alkyl group containing 1-6 carbon atoms; and R6 represents a higher carbon atom containing alkyl group, i.e., C
8
or higher, such as —(CH
2
)
7
CH
3
, —(CH
2
)
11
CH
3
, or —(CH
2
)
15
CH
3
. R6 it is noted may contain more than sixteen carbon atoms, if desired. For example, R6 could contain as many as thirty or more carbon atoms.
The reason the present invention is unique, therefore, is that by using such a cocyclic silicone one can prepare silicone polymers containing two or more dissimilar repeating units, without the necessity of adding other types of precursors to the reaction mixture, as in the case of prior art processes.
BRIEF SUMMARY OF THE INVENTION
It is the object of this invention to prepare emulsions containing silicone copolymers and silicone terpolymers generally the structure corresponding to the formula:
where x has a value of 1-2000; y has a value of 1-100; z has a value of 0-100; R′ is an alkyl group containing at least 8 carbon atoms; R″ is an aminoalkyl group represented by
where R′″ and R″″ are hydrogen or a methyl group; R
V
is hydrogen or the group
in which c is 2 or 3; R
V′
is hydrogen or a methyl group; and R
V″
is hydrogen.
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
This invention relates to new silicone copolymers and to new silicone terpolymers prepared in the form of oil-in-water emulsions by emulsion polymerization. These new copolymers and terpolymers are made by (i) combining and mixing together certain organosilicon precursors, one or more surfactants, and water; (ii) optionally subjecting the mixture prepared in Step (i) to high shear; (iii) adding a catalyst to the mixture; (iv) heating the reaction mixture to initiate polymerization of the precursors; (v) cooling and neutralizing the mixture; and (vi) recovering an oil-in-water emulsion containing the silicone copolymer or the silicone terpolymer.
The emulsion containing the silicone can be used as obtained by this process, or the silicone can be recovered and isolated from the emulsion by using a standard emulsion breaking technique.
The organosilicon precursors which are used in the process include as an essential ingredient, the (i) C
8
or higher carbon atom containing alkylmethyl, dimethyl cocyclic silicone. Optionally, the reaction mixture may also contain organosilicon precursors such as (ii) an aminoalkylsiloxane homopolymer or an aminoalkylsilane, as well as (iii) a dimethyl cyclosiloxane.
Silicone copolymers according to the invention can be prepared using only organosilicon precursor (i), while the silicone terpolymers require the presence of at least organosilicon precursors (i) and (ii). However, the silicone copolymers can also be prepared using organosilicon precursors (i) and (iii), if desired.
A catalyst and a surfactant(s) are required for the reaction to proceed and for forming an emulsion. Certain acid catalysts such as dodecylbenzene sulfonic acid (DBSA) are capable of functioning as the acid catalyst as well as an anionic surfactant. When DBSA is used, therefore, it eliminates the need for using a separate acid catalyst and a separate anionic surfactant. Thus, DBSA will function as acid catalyst in the ring opening reaction, and then when the reaction is stopped and DBSA is neutralized, it will take on the characteristics of an anionic surfactant, i.e., sodium dodecylbenzene sulfonate, for purposes of forming the desired emulsion.
The C
8
or higher carbon atom containing alkylmethyl, dimethyl cocyclic silicone used in the accompanying examples to prepare the terpolymers is shown below
In the formula, R6 represents the C
8
alkyl group —(CH
2
)
7
CH
3
or the C
16
alkyl group —(CH
2
)
15
CH
3
, a has an average value of about five, and b has an average value of about one. Such cocyclic silicones are known in the art, and methods for their preparation are described in detail, for example, in U.S. Pat. No. 5,160,494 (Nov. 3, 1992).
When it is desired to prepare terpolymers according to the invention, the reaction mixture must also include as one of the organosilicon precursors, an aminoalkylsiloxane homopolymer or an aminoalkylsilane. An aminoalkylsilane is most preferred, however.
The aminoalkylsiloxane homopolymer to be copolymerized typically consists of a mixture of linear and cyclic species. The species have a structure generally corresponding to the formulas:
wherein c represents an integer having a value of 1-20, and A represents an aminoalkyl group of the same type defined above for R″. Examples of two aminoalkyl groups most preferred are the group —CH
2
CH
2
CH
2
NHCH
2
CH
2
NH
2
or the group —CH
2
CH(CH
3
)CH
2
NHCH
2
CH
2
NH
2
.
The aminoalkylsilane is most preferred, however, and comprises a trialkoxysilane generally corresponding to the formula R
a
Si(OR
b
)
3
where R
a
represents the aminoalkyl group, and R
b
is an alkyl group containing 1-6 carbon atoms. Some examples of aminoalkyltrialkoxysilanes which can be used are compounds such as 4-aminobutyltriethoxysilane H
2
NCH
2
CH
2
CH
2
CH
2
Si(OC
2
H
5
)
3
, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane H
2
NCH
2
CH
2
NHCH
2
CH
2
NHCH
2
CH
2
CH
2
Si(OCH
3
)
3
, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane H
2
NCH
2
CH
2
NHCH
2
CH
2
CH
2
Si(OCH
3
)
3
, N-(6-aminohexyl)aminopropyltrimethoxysilane H
2
N(CH
2
)
6
NHCH
2
CH
2
CH
2
Si(OCH
3
)
3
, 3-aminopropyltriethoxysilane H
2
NCH
2
CH
2
CH
2
Si(OC
2
H
5
)
3
, and 3-aminopropyltrimethoxysilane H
2
NCH
2
CH
2
CH
2
Si(OCH
3
)
3
. Of these compounds, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is the most preferred.
Another organosilicon precursor which may be included as an optional ingredient in the reaction is a dimethyl cyclosiloxane.

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