CA1092934A - Light duty non-irritating detergent compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A liquid detergent system wherein the active content is a combination of an anionic surfactant and a nonionic surfactant in the form of alkoxylated partial glycerol esters of a higher, detergent grade fatty acid and optionally containing a foam stabilizing agent. These systems are particularly useful for formulating shampoos and light duty liquid household cleaning compositions having low eye and skin irritation properties.

Description

~)9Z~34 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 -:

.

9~934 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 ~ - 4 -~929;~4 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 ~:J9~34 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 ~0~2~

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.

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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 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.

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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 1'1L)9~93~

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.

Claims (2)

1. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
   
   l. A low irritant detergent composition having an active content consisting essentially of (a) an alkylene oxide adduct of a partial glycerol ester of a C10-C18 fatty acid having a monoglyceride content of from about 15 to 45 wt. % with di-glycerides essentially constituting the balance, said adduct prepared by reacting one mole of the partial glycerol ester with from 15-100 moles of ethylene oxide, propylene oxide or the mixture thereof in the molar ratio of 2:1 to 4.5:1 re-spectively, and (b) an anionic surface active agent selected from the group consisting of a salt of a higher alkyl sulfate, a salt of a higher alkyl ether sulfate, and a salt of a higher alkyl benzene sulfonate; wherein the weight ratio of (a) to (b) is between about 1:1 and 4:1 respectively.
2. 2. A low irritant detergent composition having an active content consisting essentially of (a) a 15 to 100 mole alkylene oxide adduct of a partial glycerol ester of a C10-C18 fatty acid having a monoglyceride content of from about 15 to 45 wt.
   % with diglycerides essentially constituting the balance, said adduct prepared by reacting one mole of the partial glycerol ester with from 15-100 moles of ethylene oxide, propylene oxide and the mixtures thereof in the molar ratio of 2:1 to 4.5:1, respectively; and (b) an anionic surface active agent selected from the group consisting of a salt of a higher alkyl sulfate, a salt of a higher alkyl ether sulfate, and a salt of a higher alkyl benzene sulfonate; and (c) an alkanolamide foam stabilizing agent; wherein the weight ratio of (b) to (c) is between about 4:1 and 5:1, respectively, and wherein the weight ratio of (a) to (b) is between about 2:1 and 5:1, respectively.