NO147112B - AQUEY, SKIN-FRIENDLY FINE DISHWASH - Google Patents

Description

The present invention relates to an aqueous, skin-friendly delicate detergent containing a combination of an anionic surfactant and a non-ionic surfactant in the form of alkoxylated partial glycerol esters of a higher fatty acid of surfactant quality, and which optionally contains a foam stabilizer. These agents are particularly useful for the production of shampooing agents and liquid cleaning materials for household use and show little tendency to cause eye and skin irritation.

The majority of household shampoos and surfactants are based on the combination of an anionic surfactant (such as sodium lauryl sulfate, sodium lauryl ether sulfate ("SLES"), and linear alkylbenzene sulfonate) and a surfactant that acts as a foaming agent and stabilizer (such as a tertiary amine oxide or alkanolamide). All these surfactants and especially the anionic ones cause severe eye irritation and also slight to moderate skin irritation in certain people. In recent times, however, there has been a development in the direction of using the anionic substance in combination with a surface-active substance of the amphoteric type, whereby an oxylate of a partial polyol ester of a higher fatty acid has also been combined with these compounds in order to reduce the irritation .

Products of this type, e.g. the so-called baby shampoo preparations are "slightly irritating" in the eye irritation test according to Draize. Although it would be desirable to provide systems that are even milder in this respect than those currently available, an equally important goal is to provide systems that allow control of the viscosity properties of the final products. The majority of surfactant materials of the type in question are marketed in the form of water systems containing from approx. 10 to 30% active component. The standard method when it comes to increasing the viscosity at the indicated range for dry matter content has been the addition of table salt, which increases eye irritation.

The present invention thus relates to an aqueous, skin-friendly delicate detergent containing the combination of non-ionic and anionic surface-active compounds, which delicate detergent is characterized in that the mixture contains 20 - 37% by weight of a surfactant mixture consisting of (a) an alkylene oxide adduct of a partial glycerol ester of a (<C>10<-C>1Qj-fatty acid with a monoglyceride content of from 15 to 45% by weight, with the remainder made up of diglycerides,

which adduct is produced by reacting 1 mol of the partial glycerol ester with from 15 to 100 mol of ethylene oxide, propylene oxide or a mixture thereof in respective

molar ratio from 2:1 to 4.5:1, and

(b) an anionic surfactant selected from the group consisting of a salt of a 10 - 18 C alkyl sulfate, a salt of a higher alkyl ether sulfate and a salt of a higher alkylbenzene sulfonate, wherein the weight ratio of (a) to (b) is between 1 :1 and 4:1.

The invention is further explained in connection with accompanying drawings in which: fig. 1 illustrates the change in eye irritation, where the determinations are made with the eye irritation test according to Draize, which originates from the combination of the anionic surfactant "SLES" (sodium lauryl ether sulfate) with varying amounts of nonionic surfactant, i.e. component a),

fig. 2 illustrates the way in which the viscosity of a typical shampoo preparation at a conventional range in terms of dry matter content can be varied by suitably changing the hydrophobicity properties of the non-ionic surfactant component. The lower the amount of alkylene oxide present in the non-ionic substances, the lower the viscosity of the surfactant system, and

fig. 3 shows the same viscosity effect as that shown in fig. 2, with alkoxylates prepared from mixtures of propylene oxide and ethylene oxide.

The anionic surface-active substances that can be used in carrying out the present invention are standard products that occur in the trade, and these thus do not need to be described further. Useful salts of these are salts of an alkali metal hydroxide, preferably sodium hydroxide, ammonium hydroxide, a hydroxyalkylamide, etc. Although the nonionic surfactants are available from commercial sources, it is believed to be appropriate with a brief description of how these can is produced. These nonionic surfactants are derived from partial glycerol esters of a higher fatty acid. The usable higher fatty acids are of the saturated or unsaturated, preferably saturated type of the so-called surfactant quality acids with a carbon atom number from 10 - 18. Such partial esters mainly consist of a mixture of monoglycerides and diglycerides, where the monoglyceride content is from 15 - 45% by weight, preferably from 25 - 35% by weight. The remaining part of the partial ester product is predominantly corresponding to diglyceride.

These mono- and diglyceride mixtures can be readily prepared by glycerolysis of a triglyceride in the presence of a basic catalyst, preferably an alkali metal hydroxide. Alternatively, they can be produced by direct esterification of glycerol with the fatty acids. The molar ratio between triglyceride and glycerol can, when carrying out the preferred glycerolysis method, be regulated so that a reaction product with the desired monoglyceride content (normally equimolar) is obtained.

The non-ionic surfactants are alkylene oxide adducts of the partial glycerol esters described above. Structurally, they can be characterized as having a polyoxyalkylene chain with oxyethylene, oxypropylene or occasionally distributed oxyethylene and oxypropylene residues in the respective ratio 2:1::4,5:1. The chain length of the polyoxyalkylene group is mainly determined by the amount of alkylene oxide used in relation to the partial ester. On this basis, it generally applies that a range from 15 to 100 mol of alkylene oxide per moles of partial ester are applicable. ,

When mixtures of propylene oxide and ethylene oxide are used, the random nature of the polyoxyalkylene chain is a significant factor in providing liquid products. This random distribution is provided primarily by the way in which the ethylene oxide and propylene oxide are reacted with the partial ester. The preferred method consists in simultaneously adding both alkylene oxides in the chosen ratio to the partial ester when carrying out the adduct reaction. Alternatively, the alkylene oxides can be added in the form of a previously formed mixture thereof. The otherwise used process conditions correspond to those usually used when carrying out such a reaction. This includes the use of a suitable catalyst, e.g. an alkali metal hydroxide, and an operating temperature which is preferably of the order of 150 to 180° C. The reaction is usually carried out in a closed system at a pressure of from 2 to 10 atmospheres.

The non-ionic surfactant is combined with the amount of the anionic surfactant which gives a total composition that is "minimally irritating" to the eye according to the Draize test. A maximum average eye irritation from 1 to 18 is considered to give this degree of irritation. The general method of assessment and grading according to this test is described in J. Pharmacol. and Exp. Ther. 82, p. 377 (1944) as well as "Section 191.12 of the Federal Hazardous Substance Act.". The ratio of non-ionic substance to anionic substance when it comes to achieving the specified irritation level is at least one part by weight of the non-ionic surfactant per part of the anionic surfactant, and the incorporation of a foam stabilizer normally means that a higher proportion of non-ionic substance is required.

Fig. 1 shows the eye irritation levels exhibited by various combinations of a representative ethoxylated Lr^'..' surfactant and "SLES'1 A maximum average eye irritation of from 1 to 18 is classified as "minimally" irritating. It can thus be seen that when the non-ionic and anionic surfactants are combined on an approximately equal weight basis, this low level of irritation is achieved. As can further be seen from the diagram, the effect of an increasing proportion of the non-ionic surfactant relative to the anionic surfactant is such that an irritation value substantially less than 10 is achieved asymptotically at an approximate ratio between the respective components of 2:1. Even if only a minimal change in the eye irritation value occurs beyond this ratio, there may still be a need for or an advantage in the use of higher ratio between the non-ionic and the anionic surfactant from the point of view of viscosity regulation, h which will be explained in what follows.

The incorporation of a foam stabilizer has the effect of increasing the system's eye irritation properties beyond what can normally be expected. However, this increase can be compensated for with a moderate increase in the minimum ratio between non-ionic and anionic surfactant. In general, the amount of foam stabilizer is based on the amount of anionic surface-active component present in the system and that the amount is from 20 to 25% of the anionic surface-active component.

Amounts of the foam stabilizer less than 20% result in less than optimal foam stabilization properties, while amounts in excess of 25% cause rinsing problems. When such foam stabilizers are incorporated in an amount within the specified range, a minimum ratio of 2 parts by weight of the nonionic surfactant to 1 part by weight of the anionic surfactant provides a total composition which provides an average eye irritation classifiable as "minimal".

As discussed above, a significant distinctive feature of the present invention is that it provides the possibility of regulating the viscosity of water-based solutions of the surfactant systems in question by appropriate selection of non-ionic surface-active component. This special feature is illustrated in fig. 2 where the viscosity is set against the percentage content of solid material in a typical water-based shampoo system. The content of active material in the system used to illustrate this corresponds to preparation no. 8 in example 1 (table I) and which, active component included, calculated on a weight basis and on solids content, 23.9% "SLES'j

71.4% of the ethoxylated nonionic surfactant

and 4.6% of a commercial diethanolamide. The preparation of the two ethoxylates shown in fig. 2, is described in the example.

As can be seen from fig. 2, the viscosity of the water-based system depends on the nature of the ethoxylated nonionic surfactant and also on the percentage content of total solids in the system. As can be seen from the figure, the largest increase in viscosity can be obtained using a 40 mol adduct of a mixture of mono- and diglycerides derived from tallow, a 60 or 100 mol adduct should give an even greater increase in viscosity. If, on the other hand, a 30 mol adduct of a comparable partial ester mixture of coconut fatty acids is used instead, it is possible to use a higher solids content to achieve a similar viscosity to that obtained by using tallow adducts. Furthermore, it can be seen that complete control of the viscosity properties can be obtained within the normal range for the solids concentration of the surfactant system by a judicious mixture of these two representative partial glycerol adducts.

Preparation' of a 30 mol ethylene oxide adduct of a glycerol-coconut fatty acid partial ester

In a suitable reaction vessel, 2335 parts (3.57 mol) of refined coconut oil, 345 parts (3.75 mol) of glycerol and 5.4 parts of a 50% water solution of KOH were added. While stirring, the reaction mixture was heated to 110° C. and held at this temperature for 1 hour at a vacuum of 20 mm. The reaction mixture was then heated to 165°C under nitrogen gas bubbling and held at this temperature for 3 hours.

254.5 parts (0.6 mol) of the above mono- and diglyceride mixture were introduced into a pressure vessel. The reactor was purged twice with nitrogen gas and heated to 150° C. Ethylene oxide in an amount of 800 parts (18.2 mol) was added over an 8-hour period while the temperature was maintained at 150-160° C. While cooling the reaction mixture to 110°C, 25% aqueous sulfuric acid was added for neutralization (pH 8), after which the reaction mixture was filtered.

Preparation of a 40 mol ethylene oxide adduct with a glycerol tallow fatty acid partial ester

In the manner indicated above, 1 mol of tallow was reacted with 1.05 mol of glycerol in the presence of potassium hydroxide, forming a mixture of tallow, mono- and diglycerides. After stripping for the purpose of removing moisture, the partial ester mixture was reacted with 40 mol of ethylene oxide in accordance with the method described above, after which the ethoxylated product was cooled, stripped and filtered.

In the following table I, the stated irritation data refer to data obtained by the test method according to Draize. The indicated foam stabilizer is a coconut diethanolamide ("Varamid MAI" - Aschland Chemical Co.). The percentage content of the active components is indicated in the table, whereby the residue is made up of water, thus sample no. 1-10 contains 28% active components, while the rest is water.

Preparation of a 35 mol ethylene oxide-propylene oxide adduct

( 3 mol EO) of glycerol partial esters of coconut fatty acid

Into a suitable reaction vessel were introduced 2335 parts (3.57 mol) of refined coconut oil, 345 parts (3.75 mol) of glycerol and 5.4 parts of a 50% water solution of KOH. While stirring, the reaction mixture was heated to 110° C. and held at this temperature for 1 hour at a vacuum of 20 mm. The reaction mixture was then heated to 165°C under hydrogen gas flow and was held at this temperature for 3 hours.

140 parts (0.33 mol) of the above mono- and diglyceride mixture were introduced into a pressure vessel. The reactor was purged twice with nitrogen gas and heated to 150° C. A preformed mixture of alkylene oxides containing 385 parts (8.75 mol) ethylene oxide and 169 parts (2.bl mol) propylene oxide was added over an 8 -hour period, while the temperature was maintained at 150 - 160° C. During cooling of the reaction mixture to approx. At 110° C, a 25% aqueous sulfuric acid solution was added for neutralization (pH 8), after which the reaction mixture was filtered.

Preparation of an 82 mol ethylene oxide-propylene oxide adduct (3 EO) from a glycerol partial ester of tallow fatty acid

In the manner indicated above, 1 mole of tallow was reacted

with 1.05 mol of glycerol in the presence of potassium hydroxide to form a mixture of tallow mono- and diglycerides. After stripping for the purpose of removing moisture, a 1 mol sample amount of the partial ester mixture was reacted with a previously formed mixture of 61.5 mol ethylene oxide and 20.5 mol propylene oxide in the manner indicated above, after which the alkoxylated product was cooled, decanted and filtered.

Example 1-3

An 82 (3EO/PO)-glycerol coco fatty acid ester (non-

ionic A) and a 35 (2EO/PO)-glycerol tallow fatty acid ester (nonionic B) were prepared according to the general procedure described above. Water-based shampoo preparation was prepared using the specified adducts as non-ionic surfactant component and was tested for eye irritation properties according to the test method according to Draize. The specified foam stabilizer in formulation #2 was a commercial coconut fatty acid diethanolamide ("Varamide MAI" - Ashland Chemical Co.). Further details regarding the composition of these systems and the test results obtained are set out in the following Table II.

Alkoxylation can also be carried out using mixtures of ethylene oxide and propylene oxide. The viscosity-percent solids ratio for mixed propylene-ethylene alkoxylates is shown in fig. III. The active components of the system used for fig. III corresponds to preparation no. 2 in example 3 (table II), and the composition is here calculated on a dry matter basis, 39.6% by weight "SLES" 64.3% of the non-ionic surfactant and 6.1% of a commercial diethanolamide. The production of the non-ionic surfactants is described in example 2.

As can be seen from the drawing, the viscosity of the water-based system is primarily dependent on the nature of the non-ionic surface-active substance and on the total percentage of dry substance content in the system. The figure shows that the greatest increase in viscosity can be achieved using an 82 mol polyoxyalkylene adduct of a reaction mixture with an equilibrium ratio of mono- and diglycerides derived from tallow, in which the polyoxyalkylene chain includes randomly distributed oxyethylene and oxypropylene residues in a ratio of 3:1. If, on the other hand, one uses instead a similar 35 mol oxyalkylene adduct of a comparable partial ester mixture of coconut fatty acids,

can one achieve a higher solids content to achieve a similar viscosity as when using said tallow adduct. Furthermore, it can be seen that a regulation of the viscosity properties can be obtained within the normal range for the solids concentration of a surfactant system by mixing these representative partial glycerol ester adducts in a suitable manner.

Example 3 (Table II) illustrates the low degree of eye irritation that can be achieved for typical surfactant shampoo systems based on mixed propylene/ethylene alkoxylates.

Claims (2)

1. Aqueous, skin-friendly delicate detergent containing the combination of non-ionic and anionic surface-active compounds, characterized in that the mixture contains 20 - 37% by weight of a surfactant mixture consisting of (a) an alkylene oxide adduct of a partial glycerol ester of a (C^0-< C>^<g>j<-fe>tt acid with a monoglyceride content of from 15 to 45% by weight, where the remainder is made up of diglycerides, which adduct is produced by reacting 1 mol of the partial glycerol ester with from 15 to 100 mol of ethylene oxide, propylene oxide or a mixture thereof in respective molar ratios from 2:1 to 4.5:1, and (b) an anionic surfactant selected from the group consisting of a salt of a 10 - 18 C alkyl sulfate, a salt of a high alkyl ether sulfate and a salt of a higher alkylbenzene sulfonate, wherein the weight ratio of (a) to (b) is between 1:1 and 4:1. 2. Detergent according to claim 1, characterized in that it also contains (c) an alkanolamide foam stabilizer known per se, where the weight ratio between (b) and (c) is between 4:1 and 5:1, and the weight ratio between (a) and (b) are between 2:1 and 5:1.