Note: Descriptions are shown in the official language in which they were submitted.
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B~CKGROUND OF THE INVENTION
Most shampoos and light duty household detergent
products are based on the combination of an anionic surfactant
(such as sodium lauryl sulfate, sodium lauryl ether sulfate
(SLES) and linear alkyl benzene sulfonate) and a surface active
agent serving as a foam promoter and stabilizer (such as a
tertiary amine oxide or an alkanolamide), All of these surface
active agents and particularly the anionics are severe eye
irritants and are capable of causing mild to moderate skin
irritation to some persons. Lately, there has been a trend
toward use of the anionic in combination with an arnphoteric type
surfactant and combining with these compounds an ethoxylate of
a partial polyol ester of a higher fatty acid to reduce irritation.
Products of this type, such as the so-called baby
shampoo formulations, are "mildly irritating" in accordance with
the Draize eye irritation test. While it would be desirable to
provide even blander systems in this respect than are now av~ail-
.
a~le, an equally important objective is obtaining systems which ~allow control of viscosity characteristics of the final products.
Most detergent compositions of the type herein concerned are
marketed as water systems containing from about 10 to 30 percent
active content. The standard method for increasing viscosity
at the indicated range of solids content has been the addition
of common salt, which increases eye irritation.
SUMMARY OF THE INVENTION
A low irritation detergent system for formulating
household aqueous cleaning compocitions consists of a nonionic
surfactant in the form of an alkylene oxide adduct of partial
glycerol esters of a detergent grade fatty acid in combination
with an anionic surface active agent selected from the group
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consisting of a salt of a hiyher alkyl sulate, a salt of a
higher alkyl ether sulfate and a salt of a higher alkyl henzene
sulfonate, and which combination optionally includes a foam
stabilizing amount of an alkanolamide or a tertiary amine oxide,
The nonionic must be present in an amount at least equal by
weight to the amount of anionic. Control of the viscosity of
detergent systems whose concentxations vary between 15 - 65~
solids is easily attained by use of the proper nonionic in more
than equal amounts by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates the change in eye irritation as
determined in accordance with the Draize eye irritation test
resulting from combining the anionic surfactant S~ES with varying
amounts of a representative nonionic surfactant.
Figure 2 illustrates the manner whereby the viscosity
of a typical shampoo formulation at a conventional range of solids
content can be varied by appropriately altering the hydrophobicity
characteristics of the nonionic surfactant component, The lower
the amount of alkylene oxide in the nonionics the lower the
viscosity of the detergent system,
Figure 3 shows the same viscosity effect as that shown
in Figure 2 with alkoxylates prepared from mixtures of propylene
oxide and ethylene oxides,
DESCRIPTION OF THE PREFERRED EMBODIMENT
:
The anionic surfactants useful in the practice of this
invention are standard items of commerce and hence need not be
further elaborated upon herein, Applicable salts thereof are
~ those of an alkali metal hydroxide, preferably sodium hydroxide,
ammonium hydroxide, a hydroxy alkyl amine, etc. The nonionic
surfactants althouyh available from commercial sources neverthe-
less warrant a brief aescription as to how they can be ma
. . . .
1~;~934
These nonionic surfactants are derived froTn partial glycerol
esters of a higher fatty acid. The applicable higher fatty acids
are the saturated or unsaturated, preferably the saturated type,
of the so-called detergent grade acids having a carbon atom
content of from about 10 to 18. Such partial esters consist
essentially of a mixture of monoglycerides and digylcerides,
where the monoglyceride content is from about 15 to 45 wt, ~,
preferably from 25 to 35 wt. ~, The balance o the partial ester
product will be predominantly the corresponding diglyceride,
These mono- and diglyceride mixtures can be readily
prepared by the glycerolysis of a triglyceride in the presence
of a basic catalyst, preferably an alkali metal hydroxide,
Alternatively, they can be prepared by directly esterifying
glycerin with the fatty acids, The molar ratio of triglyceride
to glycerin can be adjusted in carrying out the preferred
glycerolysis method to result in a reaction product having the
desired monoglyceride content (normally equimolar),
The nonionic surfactants are the alkylene oxide adduct
of the partial glycerol esters described ahove. They are struc-
turally~characterized as having a polyoxyalkylene chain of oxy-
ethylene, oxypropylene, or randomly distributed oxyethylene and
oxypropylene residues in the ratio of 2~ 4.5:1, respectively.
The chain length of the polyoxyalkylene group is essentially
governed by amount of the alkylene oxide employed in relation to
the partial ester, On this basis, a range of from 15 to 100
moles of the alkylene oxide per mole of the partial ester is
broadly applicable.
When mixtures of propylené oxide and ethylene oxide are
used, the random nature of the polyoxyalkylene chain is an
important factor in providing liquid products, This randomness
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is realized primarily by the manner in which the ethylene oxide
and propylene oxide are reacted with the partial ester. The
preferred mode consists of simultaneously adding both alkylene
oxides in the selected ratio to the partial ester upon effecting
the adduction reaction. Alernatively, the alkylene oxides can
be added as a preformed mixture thereof. The process conditions
otherwise applicable conform to standard practices observed in
carrying out this reaction. Such include use of a suitable
catalyst; e.g., an alkali metal hydroxide, and an operating
temperature preferably in the order of about 150 to 180C, The
reaction is ordinarily conducted in a closed system at a pressure
of from 2 to 10 atmospheres.
The nonionic surfactant is combined with that amount
of the anionic surfactant which provides an overall composition
denoted as "minimally irritating" to the eye in accordance with
the Draize test. Maximum mean eye irritation scores of from 1
to about 18 are classified as conforming to this category of
.. . .~
irritation. The general method for evaluating and scoring in
accordance wlth this test is outlined in the J. Pharmacol. and
Exp Ther 82, page 377 (1944) as well as in Section 191.12 of
Federal ~azardous Substance Act. The ratio of nonionic to the
anionic for achieving the indicated level of irritation is at
least about one part by weight of the nonionic surfactant to one
part of the anionic surfactant; inclusion of a foam stabilizer
will normally require increased level of nonionic
Figure 1 shows the eye irritation levels exhibited by
various combinations of a representative ethoxylated nonionic
surfactant and SI,ES~ Maximum mean eye irritation scores from
1 to about 18 are classified as being "minimally" irritating.
Thus, it can be seen that where the nonionic and anionic
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surfactants are combined on about an equal weight basis, this
low level of irritation is realized. ~s further shown in the
graph, the effect of increasing the proportion of the nonionic
surfactant to anionic surfactant is such that an irritation
value substantially less than 10 is asymptotically reached at
about a ratio of 2:1, respectively. While onl~ a minimal
change in eye irritation value occurs beyond this ratio
there still may be a need or an advantage attendant to the
use of higher ratios of the nonionic to anionic surfactant
from the standpoint o~ viscosity control, a~l as will be sub-
sequently explained.
The inclusion of a ~oam stabilizer has the effect
of increasing the eye irritation characteristics of the system
beyond that normally to be expected. However, this increase
can be compensated for by moderately increasing the minimum
~atio of nonionic to anionic surfactant~ Generally, the amount
of foam stabilizer is based upon the amount of the anionic
surfactant component present in the system, and is from about
20 to 25% of the anionic surfactant component. Amounts of
the foam stabilizer less than 20~/o results in less than optimum
foam stabilization properties, while amounts in excess of 25%
causes rinsing problems. Thus, when foam stabilizers are in-
cluded within the indicated range of two parts by weight of the
nonionic to one part by weight of the anionic surfactant will
provide an overall composition having a mean eye irritation ;-~
score in the "minimally" category.
As mentioned above, an-important feature of the
present invention resides in the ability to regulate the
viscosity of aqueous solutions of the contemplated detergent
0 systems by appropriate selection of the nonionic surfactant
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component. This feature is illustrated in Fig. 2, whereviscosity is plotted agalnst percent ~olids of a typical
aqueous shampoo system. The active content of the system
used for this illustration cor~esponds to formulation No. 8
of Example 1 (Table I) and as such includes, on a solid
weight basis, 23.9% of SLES, 71.4% of the ethoxylated nonionic
surfactan-t and 4.6% o~ a commercial superamide. The prepara-
tion of the two ethoxylates shown in Figure 2 is described
in the example.
As can be noted fxom Fig. 2, the viscosity of the
aqueous system is dependent upon the nature of the ethoxylated
nonionic surfactant and also on the percent of total solids in
the system. As shown, the greatest buildup of viscosity
can be achieved by using a 40 mole adduct of mixture of
mono- and diglycerides deri~ed from tallow; A 60 or 100 mole
adduct would give even greater viscosity buildup. On the other
hand, substituting a 30 mole adduct of a comparable partial
ester mixture of coconut fatty acids therefor permits higher
solids levels in obtaining the corresponding viscosity
associated with the use of the tallowate adduct. Further, it
can be seen that complete control of viscosity characteristics
can be achieved within the normal range of solids concentration
of the detergent system by judiciously blending these two
representative partial glycerol adduct~.
EXAMPLE I
PEG 30 Glycerol Cocoate
Into a suitable reaction vessel were charged 2335
parts (3.57 moles) refined coconut oil, 345 parts (3.75 moles)
glycerin, and 5.4 parts of 50% aqueous KOH. With stirring, the
reaction mixture was then heated to 11-0C. and held for one
hour under 20 mm vacuum. The reaction mixture was then heated
to 165C. with a nitrogen sparge and held for 3 hours.
~Q~25~3~
To a press-lre ves~el was charged 254.5 parts (0.6 mole~
of the above mono- and diglyceride mix-ture. The reactor wa~
purged twice with nitrogen and heated to 150C. Ethylene
oxide in the amount of 800 parts (18.2 moles) was added over
an 8-hour period while maintaining the temperature at
150-160C. Upon cooling the reaction mixture to about 110C.,
25% aqueous sulfuric acid was added for neutralization (pH 8)
and the reaction mixture then filtered.
PEG 40 Glycerol T _lowate
In a manner described above one mole of tallow was
reacted with 1.05 mole of glycerin in the presence of potas~ium
hydxoxide to provide a mixture of tallow mono- and diglycerides.
Following stripping to remove mixture, the partial ester mix-
ture was then reacted with 40 moles of ethylene oxide as
per the procedure outlined above whereup~n the ethoxylated
product was cooled, stripped and filtered. '
In the following Table I, the irritation data given
refer to that derived~ in accordance with the Draize test method. ~'
The foam stabilizer indicated is a coco diethallolamide
20 (VARAMIDE MAl - ASHLA~D CHEMICAL CO. ) . The percentages of,the
active components are set forth with the balance being water.
TABLE I
SHAMPOO FORMUL~TIONS
WT. % OF ACTIVE COMPONENTS
/2i PEG 30 , ~ COCO MEAN IRR RATIO
No.SLES~ ~ GLYC.COCOATE~l~ SUPERAMIDE IRR SCOR:E: LASS. (1)/(2)
1 4! 8 22.0 1.2 ,10.0 Minimally 4.6/1 ~`
2 8~0 18.0 2.019.7 Mildly 2.3/1
3 6.4 20.0 1.6 6.4 Minimally 3.1/1
4 5 . 6 21. 0 1. 46 . 0 Minimally 3.8/1
7.2 19.0 1.8 -9.3 Minimally 2.6/1
- 8 -
6 5.0 22.0 1.0 4.0 Minimally 4.4/1
7 8.3 18.0 1.7 5.3 Minimally 2.2/1
8 6.7 20.0 1.3 3.3 Minimally 3.0/1
9 5.8 21.0 1.2 5.0 Minimally 3.6/1
7.5 1~.0 1.5 5.3 Minimally 2.5~1
~ EX~MPLE 2
_ ~ ) Glycerol Cocoate
Into a suitable reaction vessel were charyed 2335
parts (3.57 moles) refined coconu-t oil, 345 parts (3.75 moles)
glycerin, and 5.4 parts of 5~/0 aqueous KOH. With stirriny,
the reaction mixture was heated to 110 C. and held for one
hour under 20 mm vacuum. The reaction mixture was then heated
to 165 C. with a nitrogen sparye and held for 3 hours.
To a pressure vessel was charged 140 parts (0,33 mole)
of the above mono- and diglyceride mixture. The reactor was
purged twice with nitrogen and heated to 150C. A preformed ---
mixture of alkylene oxides containing 385 parts (8.75 moles) of
ethylene oxide and 169 parts (2.91 moles) of propylene oxide
was added over an 8-hour period while maintaining the -temperature
of 150-160 C. Upon cobling the reaction mixture to about
110 C., 25% aqueous sulfuric acid was added for neutralization
(pH 8) and the reaction mixture then filtered.
82 (3EO/PO) Glycerol Tallowate
In a manner described~above one mole of tallow was ;
reacted with 1.05 mole of glycerin in the presence of potassium
hydroxide to provide a mixture of ta~low mono- and diglycerides.
Following stripping to remove moisture, a mole aliquot of the
partial ester mixture was then reacted with a preformed mixture ;
; of 61.5 moles of ethylene oxide and 20.5 moles of propylene
30 oxide as per the procedure outlined above whereupon the alkoxylated
product was cooled, stripped and filtered.
_ g
.
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EXAMPLE 3
An 82(3~0/P0) glycerol cocoate (Nonionic A) and a
35 (2E0/P0) glycerol tallowate (Nonionic B) were prepared,
following the general procedure outlined in Example 2. Aqueous
shampoo formulations were prepared using said adducts as
the nonionic surfactant component thereof and tested for eye
irritation properties in accoxdance with the Draize me~hod.
The indicated foam,stabilizer in formu]ation No~ 2 was a
commercial coco superamide (VARAMIDE MAl - ASHL~ND CHEMICAL CO.).
Further details relative to the make-up of these systems and
the test results obtained are set forth in the following Table II.
TABLE II
AQUEOUS SHAMPOO FORMULATIONS
WT. % OF ACTIVE COMPONE~TS
~, , , COCO MEAN
SLES NONIO~IC A NONIONIC B UPERAMIDE IRRo SCO~E
1 9.1 18.2 - - 5,3
2 8.3 18.0 - 1.7 4.7
3 ~.1 - 18.2 _ 4 7
The alkoxylation can also be carried out using
mixtures of ethylene oxide and propylene oxide. The viscosity-
percent solids relationships with mixed propylene-ethylene
alkoxylates are shown in Figure III. The active content of
the system used for Figure III corresponds to formulation
No. 2 of Example 3 (Table II) and, as such, includes on a
solid basis 39.6 wt. % SLES, 64.3% of the nonionic surfactant
and 6-1% of a commercial diethanolamide. The-preparation of
the nonionic surfactants is given in Example 2, /`
As can be noted from the drawing, the viscosity of
the aqueous system is primarily dependent upon the nature of
the nonionic surfactant and the percent of total solids in the
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system. As shown, the greatest build-up of viscosity can be
achieved by using the 82-mole polyo~yalkylene adduct o~ an
equilibrated react.ion mixture of mono- and diglycerides
derived from tallow wherein the polyoxyalkylene chain is com-
posed of randomly distributed oxyethylene and oxypropylene r
residues in the ratio o~ 3:1 respectively. On the other
hand, substituting a similar 35-mole oxyalkylene adduct of a
comparable partial ester mixture of coconut ~atty acids therefore
permits higher solids levels in obtaining the corresponding
10 viscosi~y of the use of said tallowate adduct. Furkher, it
can be.seen that control of the viscosity characteristics
can be realized within the normal range oi solids concentration
oi a detergent system by judiciously blending these two repre-
sentative partial glycerol ester adducts.
Example 3 (Table II) illustrates the low degree of
eye irritation associated with typical detergent shampoo systems
based on mixed propylene/ethylene alkoxylates.
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