Mechanical microemulsions of blended silicones

Details Mechanical microemulsions of blended silicones Mechanical microemulsions of blended silicones

2000-09-01

2002-11-05

Webb, Gregory E. (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Liquid composition

C510S466000, C516S055000, C424S070122, C424S078030, C424S401000, C106S287100, C524S837000

Reexamination Certificate

active

06475974

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 microemulsions containing a blend of silicones constituted by (i) a silicone oil component and (ii) an amine functional polysiloxane component. In particular, silicone oil component (i) of the blend is a linear rather than cyclic siloxane.
BACKGROUND OF THE INVENTION
It is generally not known to microemulsify linear polydimethylsiloxanes. While U.S. Pat. No. 4,246,029 (Jan. 20, 1981) teaches that polydimethylsiloxanes can be emulsified when combined with an amine functional polysiloxane, the compositions are not microemulsions. Microemulsions, however, are described in U.S. Pat. No. 5,518,716 (May 21, 1996), but the mixture of silicones in the '716 patent is limited to cyclic siloxanes represented by the formula
in which n is defined as being an integer varying from between about 3 to about 7, and R
d
and R
e
are alkyl radicals containing from 1 to 4 carbon atoms. The '716 patent, for example, refers specifically to the cyclic siloxane octamethycyclotetrasiloxane as being representative.
In contrast, microemulsions according to this invention contain linear polysiloxanes generally conforming to the formula
which is described in more detail hereafter.
BRIEF SUMMARY OF THE INVENTION
This invention relates to a microemulsion and to a method of making microemulsions. According to the method, a mixture is formed by combining (a) water, (b) a nonionic surfactant, a cationic surfactant, an anionic surfactant, or a mixture of such surfactants, (c) a linear:non-volatile polysiloxane, (d) an amine functional polysiloxane, and (e) a carboxylic acid, and the mixture is mechanically agitated until a microemulsion is obtained containing polysiloxane particles having an average diameter of less than 50 nanometer (0.05 micron/500 angstrom Å). The linear non-volatile polysiloxane (c) is a composition of the formula:
where R1 is an alkyl group containing 1-6 carbon atoms, preferably methyl, and a represents an integer having a value greater than 5 and less than about 400.
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
As used herein, the term microemulsion means a single or one phase clear, thermodynamically stable, mixture of two or more immiscible liquids and one or more surfactant(s). It includes transparent compositions containing water, oil, and surfactant(s), including compositions which are transparent by virtue of a very small particle size. Microemulsions are generally always clear or transparent because they contain particles smaller than the wavelength of visible light.
The microemulsion may contain oil droplets dispersed in water (O/W), water droplets dispersed in oil (W/O), or it may have a bicontinuous structure. It can be recognized by several inherent characteristics which are (i) that it contains oil, water, and a surfactant; (ii) the system is optically clear or transparent; (iii) the phases do not separate by centrifugation; and (iv) it is a system which is generally stable indefinitely.
For purposes of this invention, therefore, a microemulsion is considered as being a clear or transparent composition which contains particles having an average diameter of less than 50 nanometer (0.05 micron/500 angstrom Å), preferably less than 40 nanometer (0.04 micron/400 angstrom Å), and most preferably less than 20 nanometer (0.02 micron/200 angstrom Å).
The blend used in forming microemulsions according to the invention is constituted by a silicone oil component and an amine functional polysiloxane component.
The silicone oil component of the blend is a polysiloxane composition, preferably a polydialkylsiloxane, and more preferably a nonvolatile linear polydimethylsiloxane. Such polysiloxanes conform generally to the formula:
where R1 is an alkyl group containing 1-6 carbon atoms, most preferably a methyl group, and a has a value generally greater than 5 and less than about 400. The viscosity of such polysiloxanes generally ranges from about 5 centistoke (mm
2
/s) to about 1,000 centistoke (mm
2
/s), and such polysiloxanes have boiling points generally in excess of about 300° C. Some representative examples of polysiloxanes preferred for use according to this invention are polydimethylsiloxanes having a viscosity of 5, 10, 350, and 1,000 centistoke (mm
2
/s), in which case, the value of a in the above formula is about 8, 15, 180, and 375, respectively.
The amine functional polysiloxane component of the blend is a silicone fluid with highly polar pendant aminoalkyl modifying groups. Particularly preferred amine functional polysiloxanes include reactive and non-reactive hydrolyzable and non-hydrolyzable derivatives which are wholly, or in part, terminally substituted with aminopropyl, aminobutyl, or diamino pendant chains.
The amine functional polysiloxane employed in blends in accordance with the present invention has the formula:
wherein R′ denotes an alkyl group of 1 to 4 carbons or a phenyl group with the proviso that at least 50 percent of the total number of R′ groups are methyl; Q denotes an amine functional substituent of the formula —R″Z wherein R″ is a divalent alkylene radical of 3 to 6 carbon atoms and Z is a monovalent radical selected from the group consisting of —NR
2
′″, and —NR′″ (CH
2
)
b
NR
2
′″; wherein R′″ denotes hydrogen or an alkyl group of 1 to 4 carbons, and b is a positive integer having a value of from 2 to 6; z has a value of 0 or 1; x has an average value of 25 to 3000; y has an average value of 0 to 100 when z is 1, y has an average value of 1 to 100 when z is 0; with the proviso that in all cases y has an average value that is not greater than one tenth the average value of x.
Suitable R′ groups are represented by and may be independently selected from among methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and phenyl, with the proviso that at least fifty percent of the R′ groups are methyl.
The alkylene radicals represented by R″ may include trimethylene, tetramethylene, pentamethylene, —CH
2
CHCH
3
CH
2
—, and —CH
2
CH
2
CHCH
3
CH
2
—. Siloxanes where R″ is a trimethylene or an alkyl substituted trimethylene radical such as —CH
2
CH(CH
3
)CH
2
—, are preferred.
Alkyl groups of 1 to 4 carbon atoms as represented by R′″ include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl.
Useful Z radicals include the unsubstituted amine radical —NH
2
, alkyl substituted amine radicals such as —NHCH
3
, —NHCH
2
CH
2
CH
2
CH
3
, and —N(CH
2
CH
3
)
2
; and aminoalkyl substituted amine radicals such as —NHCH
2
CH
2
NH
2
, —NH(CH
2
)
6
NH
2
, and —NHCH
2
CH
2
CH
2
N(CH
3
)
2
.
When z is zero, the silicone polymer has only pendent amine functional substituents in the polymer chain. When z is one, the silicone polymer may have only terminal amine functional substituents or both terminal and pendent amine functional substituents in the polymer chain. Preferably, x may vary from a value of 25 to 500, and y may vary from zero to 100 when z is one and from one to 100 when z is zero. Most preferably, the value of x+y is in the range of about 50 to 1,000.
The amine content, i.e., the number of amine functional groups in the molecule of the amine functional polysiloxane, is generally expressed as mol percent amine, and this is determined according to the relationship y/DP×100, where y is the value of integer y in the above formula for the amine functional polysiloxane, and the Degree of Polymerization (DP) is x+y+2 which indicates the chain length of the amine functional polysiloxane.
For example, and with reference to the particular amine functional polysiloxane used in the examples, the amine functio

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