Cross-linked cationic polymers for use in personal care products

Personal care compositions are provided which have as a thickening agent a lightly cross-linked cationic vinyl addition polymer. Such compositions include water, at least one cosmetically-active agent, and such thickening agent, preferably one derived from the polymerization of a cationic vinyl addition monomer, acrylamide, and a small amount of a difunctional vinyl addition monomer for cross-linking purposes. Alternatively, the cross-linking functionality can be provided by the incorporation of an anionic vinyl addition monomer into the polymer.

TECHNICAL FIELD OF THE INVENTION 
The present invention is in the technical field of thickening agents for 
water-based compositions, and more particularly in the field of thickening 
agents for water-based personal care products, such as shampoos, hair 
treatment compositions of both the rinse-off and leave-on type, hand 
lotions, and the like, compositions containing such agents, and thickening 
methods. 
BACKGROUND OF THE INVENTION 
Many industries have a need for materials that can increase the viscosity 
of aqueous-based compositions such as aqueous solutions or dispersions or 
emulsions having an aqueous continuous phase. In many instances, a 
particular viscosity is desired or necessary for ease in handling, 
dispensing, or otherwise using a product. Coating compositions, such as 
latex paints, must have sufficient viscosity to avoid excessive dripping 
from the applicator. Personal care products, which are often applied by 
hand, generally must have sufficient viscosity to cling to the hand of the 
user, and then to the hair, or skin, or other point of application. For 
instance, if a hand lotion had a fluidity approaching that of water, until 
completely dried a significant portion would be transferred to and 
deposited on anything the user may touch. A watery hair-set lotion would 
run through the user's fingers and off the hair during application. To 
such type of formulations a separate ingredient or ingredients are often 
added to increase viscosity to the desired level. Such materials are 
called thickeners or thickening agents. 
It is desirable that such thickening agents provide the desired viscosity 
at a low add-on level to minimize cost. It is desirable that such agents 
be compatible with other ingredients in the formulation at use level. Thus 
the nature of a given thickener must be taken into consideration together 
with that of the other components of the composition. Moreover, desired 
activity of the thickener at low use levels may diminish potential 
incompatibilities. It is also desirable to have available a group of 
thickening agents from which to select one to provide a particular 
viscosity level at a particular add-on level. 
In the personal care product industry thickening agents based on anionic 
polymers are widely known, such as carboxy vinyl polymers. 
There are sufficient compatibility problems between such anionic polymers 
and other formulation components that effective alternatives are being 
sought. 
DISCLOSURE OF THE INVENTION 
The present invention provides personal care composition including, as a 
thickening agent, a lightly cross-linked cationic vinyl addition polymer. 
Such polymers may be homopolymers of certain quaternary ammonium salts of 
vinyl addition monomers, in particular the quaternary ammonium salt of 
dimethylaminoethylmethacrylate. Other suitable cationic vinyl addition 
monomers from which such polymer could be formed include the quaternary 
ammonium salts of dimethylaminoethylacrylate, diallyldimethyl ammonium 
chloride, and methylacrylamidopropyltrimethyl ammonium chloride. Such 
polymers also include the polymerization of one or more of such cationic 
vinyl additon monomers together with other vinyl addition monomers having 
suitable reactivity ratios for such polymerizations. These other vinyl 
addition monomers that may be incorporated into such polymers may be 
nonionic, cationic, or anionic, or combinations thereof. A particularly 
useful monomer for such polymerizations is acrylamide. As expalined below, 
a particularly useful combination of monomers for such polymerizations is 
a combination of acrylamide and acrylamidomethyl propane sulfonic acid. 
Such polymers are lightly cross-linked with a suitable cross-linking agent, 
such as a difunctional vinyl addition monomer polymerized together with 
the polymeric formulation. Preferred cross-linking agents are certain 
polyethylene glycol diacrylic esters. The light cross-linking can also be 
provided by an ionic cross-linking mechanism, by the inclusion of a 
suitable anionic monomer together with the cationic monomer in the vinyl 
addition polymerization utilized for the preparation of the polymers used 
in the present invention. The cross-linking can also be provided by a 
combination of both such mechanisms. 
The cationic thickeners utilized in the present invention have been found 
to have highly desirable viscosity development efficiency, and in 
preferred embodiment have been found superior to those of commercial 
carboxy vinyl polymer thickeners. 
PREFERRED EMBODIMENTS OF THE INVENTION 
The present invention, in one embodiment, is a personal care composition 
including at least one cosmetically-active agent in a water-base, together 
with a lightly cross-linked cationic vinyl addition polymer as a 
thickening agent. In another embodiment, the present invention is a method 
of thickening a water-based personal care composition including at least 
one cosmetically-active agent, by admixing therewith an effective amount 
of a lightly cross-linked cationic vinyl addition polymer to increase the 
viscosity of the composition. 
By cosmetically-active agent is meant herein any material applied to the 
body, typically to the skin, hair, or nails, for the cosmetic treatment 
thereof. Such agents, include emollients and lubricants for softening or 
smoothing, surfactants for cleansing and other purposes, natural or 
synthetic polymers for various purposes including the topical coating of 
the hair to build body or to enhance setting characteristics, and the 
like. Such agents include, without limitation, mineral oils, glycerin, 
beeswax, lanolin, acetylated lanolin, stearic acid, palmitic acid, cetyl 
alcohol, sodium lauryl sulfate, sodium salts of olefin sulfonates, various 
proteins and polymeric sugars, and the like. This list is intended to 
exemplitive only and not limiting as to the materials that are encompassed 
by the term cosmetically-active agent. In water-based personal care 
compositions the water is a vehicle for application to some part of the 
body of some cosmetically-active agent that will have a cosmetic effect of 
some type, whether such effect is a softening or cleansing or 
strengthening or body enhancing effect. It is the intent here to include 
within the terms cosmetically-active agent any and all of such materials 
that are provided for a cosmetic effect. 
The personal care compositions of the present invention can also include 
combinations of cosmetically-active agents of various types, coloring 
agents, fragrances, preservatives, and the like. 
As mentioned above, the lightly cross-linked cationic vinyl addition 
polymers used in the present invention can be formed not only from wholly 
cationic vinyl addition monomers, but may also include nonionic monomers, 
particularly acrylamide, and certain anionic vinyl addition monomers, 
particularly an alkali metal salt of acrylamidomethyl propane sulfonic 
acid. When such an anionic vinyl addition monomer is incorporated into 
such polymer, it is incorporated at a mole percent that is less than the 
mole percent of the cationic vinyl addition monomer therein. 
A preferred embodiment of the invention is a personal care composition 
having as a thickening agent a lightly cross-linked cationic vinyl 
addition polymer derived from the polymerization of 5 to 100 mole percent 
of a cationic vinyl addition monomer, 0 to 90 mole percent of acrylamide, 
and from 0.005 to 0.05 weight percent of a difunctional vinyl addition 
monomer. In more preferred embodiment, the difunctional vinyl addition 
monomer is a polyethylene glycol diacrylic ester having a molecular weight 
of from 300 to 3,000, and the cationic vinyl addition monomer is a 
quaternary ammonium salt of dimethylaminoethylmethacrylate. In highly 
preferred embodiment, the lightly cross-linked cationic vinyl addition 
polymer is derived from the polymerization of from 15 to 70 mole percent 
of a quaternary ammonium salt of dimethyl/aminothylmethacrylate and from 
30 to 85 mole percent of acrylamide, and from 0.005 to 0.025 weight 
percent of the polyethylene glycol diacrylic ester, particularly where the 
polyethylene glycol diacrylic eester is polyethylene glycol 
dimethacrylate. It has been found that such a personal care composition 
wherein the thickener is even more particularly such a polymer derived 
from about 50 mole percent of dimethylaminoethylmethacrylate mmonium 
chloride and about 50 mole percent of acrylamide provides a highly 
desirable viscosity and rheological properties at a one weight percent 
addition level. 
In other embodiment, the personal hair compositions of the present 
invention may contain, as the thickening agent, a lightly cross-linked 
vinyl addition polymer derived from the polymerization of from 15 to 60 
mole percent of a cationic vinyl addition monomer, from 25 to 80 mole 
percent of acrylamide and from 2 to 30 mole percent of an anionic vinyl 
addition monomer. In preferred embodiment, the cationic vinyl addition 
monomer is a quaternary ammonium salt of dimethylaminoethylmethacrylate, 
and the anionic vinyl addition monomer isan alkali metal salt of 
acrylamidomethyl propane sulfonic acid. A more preferred embodiment, the 
thickening agent of the personal care composition is derived from the 
polymerization of from 20 to 50 mole percent of a quaternary ammonium salt 
of dimethylaminoethylmethacrylate, from 40 to 75 mole percent of 
acrylamide and from 5 to 10 mole percent of an alkalic metal salt of 
acrylamidomethyl propane sulfonic acid. Although cross-linking is provided 
therein by the inclusion of both cationic and anionic functionalities, 
such polymers may also further include from 0.005 to 0.05 weight percent 
of a difunctional vinyl addition monomer, particularly a polyethylene 
glycol diacrylic ester having a molecular weight of from 300 to 3,000. 
The present invention also provides a method of thickening a personal care 
composition comprising admixing with a mixture of water and at least one 
cosmetically-active agent an effective amount of a lightly cross-linked 
cationic vinyl addition polymer to increase the viscosity thereof. In 
preferred embodiment, the lightly cross-linked cationic vinyl addition 
polymer is derived from the polymerization of from 5 to 100 mole percent 
of a cationic vinyl addition monomer, from 0 to 90 mole percent of 
acrylamide, and from about 0.005 to 0.05 weight percent of a difunctional 
vinyl addition monomer. In other preferred embodiment, the lightly 
cross-linked cationic vinyl addition polymer is derived from the 
polymerization of from 15 to 60 mole percent of a cationic vinyl addition 
monomer, from 25 to 80 mole percent of acrylamide and from 2 to 30 mole 
percent of an anionic vinyl addition monomer. Such anionic-containing 
vinyl addition monomer may further include from 0.005 to 0.05 weight 
percent of a difunctional vinyl addition monomer. 
The present invention also includes a thickening agent for water-based 
compositions comprising a lightly cross-linked vinyl addition polymer 
containing from 15 to 60 mole precent of a cationic vinyl addition 
monomer, from 25 to 80 mole percent of acrylamide and from 2 to 30 mole 
percent of an anionic vinyl addition monomer. In preferred embodiments, 
the cationic vinyl addition monomer is a quaternary ammoinum salt of 
dimethylaminoethylmethacrylate, the anionic vinyl addition monomer is an 
alkali metal salt of acrylamidomethyl propane sulfonic acid, and the 
lightly cross-linked cationic vinyl addition polymer further contains from 
0.005 to 0.01 weight percent of a polyethylene glycol diacrylic ester 
having a molecular weight of 300 to 3,000. 
All of the above-delineated polymers may be prepared using conventional 
solution polymerization techniques or preferably methods in which 
water-soluble vinyl addition monomers are polymerized in the form of 
water-in-oil emulsions. In the latter instance, the water-in-oil latex 
polymerization product is typically inverted, utilizing conventional 
techniques, to release the polymer into some solution or composition 
having water as the continuous phase. In any application in which the oil 
of the continuous phase of the polymerization latex is to be separated 
from the polymer itself, the polymer may be isolated by precipitation from 
the emulsion latex, for instance with ethanol.

EXAMPLES 1 TO 27 
In the following examples various cationic vinyl addition polymers useful 
in the present invention were prepared utilizing the water-i-oil emulsion 
technique described above. The relative mole percentages of the various 
monomers that were incorporated into the polymer are expressed in the 
table below without regard to the branching or cross-linking agent, 
although such agents were added to the monomer solutions before 
polymerization and thus incorporated into the polymer, because such agents 
are added at only a fraction of a mole percentage. Hence the amount of 
cross-linking agent is expressed in terms of weight percentage based on 
total polymer. In each of the examples, the viscosities of aqueous 
solutions of the polymer were measured at various polymer concentrations 
using a Brookfield viscometer LVT Model at 12 rpm at ambient room 
temperature. The viscosity development efficiencies shown by the viscosity 
measurements set forth below demonstrate the efficiencies of these 
polymers as thickeners, and particularly for personal care compositions 
the presence of a polyethylene glycol diacrylic ester has been shown to 
provide desired short rheological properties at low use levels without 
pititous characteristics. 
In the following Tables I and II, the following abbreviations are utilized. 
"NaAMPS" for sodium salt of acrylamidomethyl propane sulfonic acid; 
"DMAEM-MCQ" for the methyl chloride quaternary ammonium salt of 
dimethylaminoethylmethacrylate; "AcAm" for acrylamide; "MBA" for methylene 
bis acrylamide; and "PEG 600 DMA" for polyethylene glycol dimethylate 
having an ethylene oxide content of about 12 units. 
TABLE I 
__________________________________________________________________________ 
Wt. % of Cross- 
Polymer Solution Viscosity (cps) at 
Example 
Mole % Monomer Linking Monomer 
Specified Polymer Concentration 
No. Na AMPS 
DMAEM--MCQ 
AcAm 
MBA PEG 600 DMA 
0.18% 
0.35% 
0.7% 1.05% 
__________________________________________________________________________ 
1 10 50 40 0.000 
0.010 100.00 
1187.50 
18000.00 
3000.0 
2 10 50 40 0.000 
0.010 17.50 
137.50 
6150.00 
28500.0 
3 5 20 75 0.000 
0.000 675.00 
2275.00 
4300.00 
7500.0 
4 10 30 60 0.000 
0.000 350.00 
1700.00 
4000.00 
5000.0 
5 5 30 65 0.000 
0.000 1375.00 
1800.00 
3800.00 
3600.0 
6 10 50 40 0.000 
0.000 800.00 
1775.00 
2700.00 
4800.0 
7 20 50 30 0.000 
0.000 12.50 
187.50 
1412.50 
3200.0 
8 20 50 30 0.005 
0.000 12.50 
75.00 
700.00 
2475.0 
9 5 20 75 0.000 
0.010 5.00 50.00 
600.00 
19250.0 
10 10 50 40 0.005 
0.000 2.50 12.50 
237.50 
5500.0 
11 5 15 80 0.000 
0.010 5.00 15.00 
82.50 357.5 
12 10 50 40 0.000 
0.050 12.50 
17.50 
37.50 1025.0 
13 5 20 75 0.000 
0.050 6.25 18.75 
25.00 37.5 
14 30 40 30 0.000 
0.000 6.25 12.50 
18.75 25.0 
15 10 30 60 0.000 
0.050 3.75 5.00 7.50 15.0 
__________________________________________________________________________ 
TABLE II 
__________________________________________________________________________ 
Wt. % of Cross- 
Polymer Solution Viscosity (cps) at 
Example 
Mole % Monomer Linking Monomer 
Specified Polymer Concentration 
No. Na AMPS 
DMAEM--MCQ 
AcAm 
MBA PEG 600 DMA 
0.18% 
0.35% 0.7% 1.05% 
__________________________________________________________________________ 
16 0 15 85 0.0 0.001 202.50 
6650.00 
&gt;100000.00 
&gt;100000.00 
17 0 15 85 0.0 0.010 125.00 
5250.00 
&gt;100000.00 
&gt;100000.00 
18 0 15 85 0.0 0.005 35.00 
1075.00 
&gt;100000.00 
&gt;100000.00 
19 0 50 50 0.0 0.015 250.00 
21500.00 
92500.00 
&gt;100000.00 
20 0 50 50 0.0 0.010 2375.00 
33000.00 
89000.00 
&gt;100000.00 
21 0 50 50 0.0 0.025 50.00 
11200.00 
88000.00 
&gt;100000.00 
22 0 25 75 0.0 0.010 275.00 
26750.00 
&gt;50000.00 
&gt;50000.00 
23 0 15 85 0.0 0.015 262.50 
20750.00 
47500.00 
100000.00 
24 0 70 30 0.0 0.010 1737.50 
15500.00 
40000.00 
87000.0 
25 0 50 50 0.0 0.005 2400.00 
26000.00 
38000.00 
49500.0 
26 0 25 75 0.0 0.005 2100.00 
17000.00 
36250.00 
46000.0 
27 0 100 0 0.0 0.010 1775.00 
7750.00 
11250.00 
18000.0 
__________________________________________________________________________ 
EXAMPLE 28 
The polymer of Example 20 above was incorporated as a thickener in both a 
leave-on hair treatment and in a rinse-off hair treatment at a level of 1 
weight percent based on tota weight of the personal care product. Upon 
test use of both compositions separately, good setting was obtained for 
both. The lightly cross-linked cationic polymer was deemed an acceptable 
alternative to the typical carboxy vinyl polymers typically used as 
thickening agents in such compositions in their commercial form. The same 
polymer was also tested for use in a hand lotin, as a diluent for one-half 
(1/2) of the actives. A very creamy viscous lotion with good skin feel was 
obtained. 
To give a reference frame to the various viscosity development 
sufficiencies set forth above in Tables I and II above, two commercial 
thickeners were tested of the carboxy vinyl polymer types for viscosity 
development efficiency, utilizing the same model Brookfield Viscometer at 
12 rpm. For such thickener sold under the tradename of CARBOPOL 941 by B. 
F. Goodrich, viscosity was only slightly more than 1000 cps at 0.1 weight 
percent concentration, rising to somewhat less than 10,000 cps at a 1.0 
weight percent concentration. For CARBOPOL 934, also sold by B. F. 
Goodrich, at 0.2 weight percent concentration, the viscosity was about 
2,400 cps; at 0.4 weight percent concentration, the viscosity was about 
17,000; and at 0.5 weight percent concentration the viscosity was about 
33,000 cps; and at 1.0 weight percent concentration, the viscosity was 
about 50,000 cps. 
The polymers used in the present invention may be used singly or in 
combination to provide the desired viscosity. 
INDUSTRIAL APPLICABILITY OF THE INVENTION 
The present invention is applicable to those industries, particularly the 
personal care industry, in which a thickening agent for water-based 
solutions, dispersions, or emulsions is desired.