Shear stable aminosilicone emulsions

Details Shear stable aminosilicone emulsions Shear stable aminosilicone emulsions

1999-02-16

2002-09-17

Dawson, Robert (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...

C524S284000, C524S287000, C524S296000, C524S291000, C524S292000, C524S300000, C524S417000, C524S421000, C524S422000, C524S429000, C524S837000, C524S838000, C008S115600, C008S115700, C008S116100, C162S080000, C252S008610, C252S008630, C528S033000, C528S038000

Reexamination Certificate

active

06451905

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a shear stable aqueous emulsion of a polysiloxane containing at least one amino group per molecule and a mono acid. The present invention also relates to an aqueous emulsion which when applied to fibrous substrate imparts softness to the substrate.
BACKGROUND OF THE INVENTION
Many aqueous emulsions containing organomodified polysiloxanes are used in the textile and paper industry to impart softness to the substrates. The polysiloxane emulsions usually are applied to textiles and papers using a padder, a kiss roller or a spraying nozzle, thus the polysiloxane emulsions are subjected to a certain extent of shear depending on the application method. Since the polysiloxane emulsions are heterogeneous mixtures containing small droplets of polysiloxane oils in water, coalescence of oil droplets to cream or surface oil occurs when the shear condition is severe enough. This not only causes problems in the manufacturing process, it also may result in deposit of the polysiloxane oils on textiles and papers and increase rejects. Therefore, a shear stable polysiloxane emulsion is very important in the application of polysiloxane emulsions.
The use of certain acids, e.g., citric acid, in the preparation of aminosilicone emulsions is known, but only to modify the pH of the emulsion, not to impart any stability to it. See e.g., U.S. Pat. No. 4,601,902 to Fridd et al. Acids also have been used to neutralize catalysts in emulsion polymerization systems containing aminosiloxanes, but the aminosiloxane herein are cross-linkable, reactive species, and the the neutralization is of the catalyst, not the siloxane or the emulsion. See, e.g., U.S. Pat. No. 4,894,412 to Okada et al. The selection of the particular acid is important in that certain acids will not provide benefits for shearing properties of the emulsion.
SUMMARY OF THE INVENTION
The present invention provides a method for the preparation of a shear stable aqueous emulsion comprising a polysiloxane containing at least one amino group per molecule (“amino polysiloxane”), and a mono acid. The aqueous emulsion, when applied to a fibrous substrate, imparts softness to the substrate. Preferred acids used herein, include, but are not limited to (a) hydroxy carboxylic acids; (b) amino dicarboxylic acids; (c) amic acids; (d) monoesters of dicarboxylic acids; (e) monoesters of di-inorganic acids; and (f) diesters of tri-inorganic acids.
DETAILED DESCRIPTION OF THE INVENTION
Aminopolysiloxane
The aminopolysiloxane has at least one amino or substituted amino group linked to a siloxy unit through an organic bridge that is bonded to the silicon atom of the siloxy unit by a carbon-to-silicon bond. The aminopolysiloxanes may be linear, branched or cyclic. They may have a viscosity ranging from about 1 to 20,000 centipoises measured at 25° C., preferably, about 10 to 10,000 at 25° C. The aminopolysiloxanes preferably have an amine content ranging from about, 0.05% to 3%, by weight, preferably from about 0.1% to 2% by weight as measured as NH
2
. The aminopolysiloxanes may contain other functionalities, e.g., polyether. The aminopolysiloxane may be linear or branched or even by alternating linkages of aminoalkyl functionality and siloxane functionality; however, they should not contain reactive silanol (i.e., Si-OH) which would cause the aminopolysiloxane to crosslink in the emulsion. The preferred aminopolysiloxane is a linear structure illustrated by Formula MD
a
D*
b
M wherein D is O
½
Si(CH
3
)
2
O
½
; D* is O
½
Si(CH
3
)QO
½
; and M is O
½
SiQ
j
(CH
3
)
3−j
, a ranges in value from about 0 to 1,000, and most preferably a ranges in value from about 0 to 500; j=0 or 1; and b ranges in value from about 0 to 100, preferably b ranges in value from about 1 to 50, most preferably b ranges in value from about 1 to 20, b+j>0 and a/(b+j) is 0.5 to 5.
Q is a polyether, polyhydric, amine, epoxy, alkyl of C
2
-C
18
, or alkanol, but at least one Q is an amine containing group Z. The group Z is of the formula BN[B
1
O(C
d
H
2d
O)
e
R]
2−z
V
z
, where each d is 2 to 4, preferably 2 to 3, each e is 0 to 15, preferably 0 to 8, z=0 to 2, preferably 2, each V is a univalent group, B
1
is an alkylene divalent bridging group on which there may be hydroxyl substituents, and B is a divalent bridging group.
V groups preferably are alkyl (which may be branched, linear or cyclic) of less than 8 carbons, which may or may not contain hydroxyl functionalities. Another preferred V is an alkyl amine functionality, the nitrogen of which may be further substituted (e.g., with an alkyl) or be further alkoxylated. Exemplary V are ethyl, ethanol, propanol, methyl, and ethyl amine.
B groups may be of the formula B
1
(O)
y
(C
d
H
2d
O)
j
B
1
wherein B
1
and d are as above, j=0 to 6, preferably 0 to 2, and y=0 or 1. Preferably B
1
has 2 to 6 carbon atoms. B may also be a hydroxyl-substituted acyclic alkylene group of two to eight carbon atoms and is illustrated by 2-hydroxypropylene, i.e., —CH
2
CH(OH)CH
2
—, or B is a hydroxyl-substituted cyclic alkylene group having no more than eight carbon atoms, e.g., 2-hydroxycyclohexylene,
of which the cyclic groups having three to six carbon atoms are preferred
When Q or B is a mixture of oxyalkylenes, it may be blocked or random. One skilled in the art will understand the advantages in the position of the oxyethylene relative to the oxypropylene, when the alkyleneoxide group is blocked.
Also contemplated herein are quaternary versions of Z, but said quaternary compounds are not preferred for use in the present invention.
Preferred Z structures are wherein R is hydrogen or methyl, B
1
is a divalent organic group of 2 to 4 carbons, B is a divalent organic group of 2 to 4 carbons, in which at least one carbon radical contains a hydroxyl group, and V is 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, propyl, ethyl or methyl. Exemplary amine groups for Q are:
—C
3
H
6
NH
2
—C
3
H
6
N(C
2
H
5
)
2
—CH
2
CH
2
C(CH
3
)
2
NH
2
—C
3
H
6
N(CH
2
CH
2
OH)
2
—C
3
H
6
N(CH
3
)CH
2
CH
2
NH
2
—C
3
H
6
NHCH
2
CH
2
NH
2
—C
3
H
6
OCH
2
CH(OH)CH
2
NH
2
—C
3
H
6
—N(CH
2
CH
2
OH)(CH
2
CH
2
NH
2
)
—C
3
H
6
OCH
2
CH(OH)CH
2
NHCH
2
CH
2
NH
2
Those functionalities with free hydroxyls may be further alkoxylated with ethylene oxide and propylene oxide.
Aminopolysiloxanes employed in the present invention are commercially available from Witco Corporation.; Alternatively, aminopolysiloxanes used in the present invention can be prepared by the procedures disclosed in U.S. Pat. Nos. 3,033,815; 3,146,250, 3,355,454 and 4,247,592.
Mono Acid
Mono acids which are soluble or dispersible in water and thus, compatible with the aqueous emulsion containing the aminopolysiloxane can be employed in the present invention. In its broadest aspect, the mono acid of the present invention is selected from the group consisting of (i) inorganic mono acids; (ii) organic (i.e., carboxylic) mono acids and (iii) mixtures thereof. The acids need to be proton donors to the amine (pKa<6) and therefore the inorganic acid must be a Bronstead acid and the organic acid a carboxylic acid. Illustrative inorganic mono acids include hydrochloric acid, perchloric acid and nitric acid.
Mono inorganic acids which are preferred are those which are monoesters of a di-inorganic acid, e.g., HSO
4
R wherein R is an alkyl, alkaryl or aryl, or diesters of tri-inorganic acids, e.g., HPO
4
R
2
. It is noted that the salts of such acids do not function well as compared to the esters.
The organic mono acids contain one equivalence of a carboxylic acid, i.e., of the structure R
5
C(═O)OH, wherein R
5
is hydrogen or a neutral monovalent hydrocarbon and includes alkyl such as methyl, ethyl, propyl, butyl and the like; aryl such as phenyl and tolyl; aralkyl such as benzyl; and groups wherein one or more hydrogen atoms of the above mentioned groups are substituted with hydroxy, or halogen. Illustrative organic mono acids include formic acid, and acetic ac

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