Detergent composition

Abstract: The liquid detergent composition of the present invention contains 5 to 60% by weight of a potassium or alkanolamine salt of a secondary amide-type N-acylamino acid represented by the following general formula (I): RCONH(CH₂) n COOH (I) wherein R represents a straight-chain saturated hydrocarbon acyl group having 10 to 14 carbon atoms; and n is a number of 2. Further, the detergent composition of the present invention comprises an N-acyl compound (A) represented by the following general formula (II) and surfactant(s) [other than the component (A)] (B) at a weight ratio of (A)/(B) of from 99/1 to 1/1; RCONH(CH₂) n COOM (II) wherein RCO represents a straight-chain acyl group having 8 to 22 carbon atoms; n is an integer of from 1 to 11; and M represents an alkali metal or an inorganic or organic ammonium.

Description: [Field of the Invention] This invention relates to a detergent composition. More particularly, it relates to a detergent composition which is suitable for washing the body including the hair and the skin and comfortable in its use. [Description of the Prior Art] Body detergent compositions usually comprise common anionic surfactants. Namely, soaps, i.e., higher fatty acid salts are mainly used for cleansing the skin while alkyl sulfates or sulfonates are mainly used for shampooing the hair. The soaps used for cleansing the skin are disadvantageous in that the soap scum (calcium salts of higher fatty acids) formed during rinsing would adhere to the skin, which seriously deteriorates the lubricity of the surface of the skin and causes coarseness or tension. In order to improve this disadvantage, attempts have been made to develop composite type detergents by blending an oily component such as a higher alcohol or a humectant such as propylene glycol with the aforesaid soaps or by using an anionic surfactant which never forms any scum. However the addition of such an oily component in a small amount cannot give the desired effect. On the other hand, the addition of a large amount thereof might cause another problem that the foaming properties are substantially deteriorated. When such an anionic surfactant forming no scum is used, the coarseness would decrease with an increase in said component. When it is used in such an amount as to give a satisfactory effect, however, the foam breaking is retarded and the detergent composition becomes slimy. On the other hand, the aforesaid alkyl sulfates and sulfonates used in shampoos form no scum and thus never give such coarseness or tension as those observed when a soap is used. However a detergent composition containing such components is poor in foam breaking and cannot impart a lubricity to the hair. In order to improve these disadvantages, there has been attempted to add oily components such as higher alcohols, hydrocarbons or silicone. In this case, however, the addition of these oily components in a small amount cannot give the desired effect and the addition of a large amount thereof would substantially deteriorate the foaming properties of the detergent composition. There have been known detergents comprising N-alkylacylamino acid surfactants. For example, JP-A-150701/1975, JP-A-2962/1988, JP-A-60 139612 and JP-A-59 207 944 disclose each a liquid detergent composition comprising an N-(long-chain acyl)amino acid surfactant, which is a less irritative surfactant, as a base. Further, JP-A-132007/1978 discloses an improved solid detergent comprising an N-(long-chain acyl)neutral amino acid. Although the tertiary amide-type N-alkyl-N-acylamino acid salts employed in the detergent compositions described in these references are highly soluble in water, they are poor in foam breaking and the comfort in its use, namely, they are somewhat slimy. JP-A-2962/1988 and JP-A-1178597 further show N-lauroyl-β-alanine sodium salt which is a secondary amide type N-acylamino acid salt (refer to Example 5). However this compound has a low solubility in water, which makes it unsuitable for a liquid detergent composition. Furthermore, the addition of this compound at a concentration of 1% (as specified in Table 1 in the aforesaid reference) cannot achieve a desirable comfort in its use. SUMMARY OF THE INVENTION It is an object of the present invention to provide a detergent composition which is highly soluble in water has good foaming properties during cleansing, shows a rapid foam breaking during rinsing, gives no sliminess, imparts a high lubricity to the surface of the material to be cleansed from the rinsing step to after the drying, is less irritative, causes neither coarseness nor tension after the completion of the use and is excellent in the comfort in its use. The present inventors have conducted extensive studies and thus found out that the aforesaid objects can be achieved by using specific N-acyl compounds the main base of a detergent composition. Accordingly, the present invention, which has been completed based on the above finding, provides a liquid detergent composition containing 5 to 60% by weight of a potassium salt of a secondary amide-type N-acylamino acid represented by the following general formula (I) RCONHCH₂CH₂COOH (I) wherein R represents a straight-chain saturated hydrocarbon acyl group having 10 to 14 carbon atoms. Each of the liquid detergent compositions of the present invention is highly soluble in water, has good foaming properties during cleansing, shows a rapid foam breaking during rinsing, gives no sliminess, imparts a high lubricity to the surface of the material to be cleansed from the rinsing step to after the drying, is less irritative, causes neither coarseness nor tension after the completion of the use and is excellent in the comfort in its use. Thus it is particularly suitable for cleansing the skin (body and face) or shampooing the hair. DETAILED DESCRIPTION OF THE INVENTION The potassium salt of the N-acylamino acid represented by the above general formula (I) (hereinafter also called the N-acyl compound), which is one of the components of the detergent composition, reacts with calcium in tap water to form highly lubricant platy crystals. RCO in the above general formula (I) of the aforesaid N-acyl compound is a straight-chain saturated hydrocarbon acyl group having 10 to 14 carbon atoms, in particular, a lauroyl group having 12 carbon atoms. When the carbon atom number thereof exceeds 14, the lubricity of the formed platy crystals and the foaming properties of the composition are deteriorated. When the carbon atom number thereof is less than 10, on the other hand, the foaming properties are deteriorated. Thus both of these cases are undesirable. The lubricity of the platy crystals formed by the reaction between the aforesaid N-acyl compound and calcium may be determined by, for example, measuring the coefficient of static friction of the platy crystals on dried pigskin (ALLOASK; a product of Kotai Kasei Kogyo K.K.) which has been reconstituted with physiological saline. Namely, platy crystals showing a coefficient of static friction lower than that of the blank lot throughout the moisture-containing point to after the completion of the drying are rated high. It is very important that the aforesaid N-acyl compound has a secondary amide-type structure wherein the N-acyl group consists of the above-mentioned straight-chain acyl. When the acyl group constituting the N-acyl group is branched or the amide has a tertiary amide type structure, the formation of the platy crystals is suppressed or the formed crystals are poor in lubridity and thus sticky. In these cases, therefore, a desirable texture can be hardly obtained. The aforesaid N-acyl compound is a potassium (hereinafter sometimes abbreviated as K) salt of an N-acylamino acid represented by the above general formula (I). It is undesirable to use a sodium (hereinafter sometimes abbreviated as Na) salt of the N-acylamino acid since it has a high Krafft point and a low solubility in water and is therefore unsuitable for a liquid detergent. The content of the aforesaid N-acyl compound may range from 5 to 60% by weight, preferably from 20 to 50% by weight, based on the liquid detergent composition. When the content thereof is less than 5% by weight, the state of feeling refreshed and comfort in its use due to the platy crystals formed during rinsing cannot be obtained. When it exceeds 60% by weight, on the other hand, the liquid composition would set to gel and thus a good liquid detergent composition cannot be obtained. The aforesaid N-acyl compound (secondary amide-type N-acylamino acid salt) may be produced by, for example, the following method. An amino acid is acylated by commonly known Schotten-Baumann reaction wherein an alkali aqueous solution of the amino acid and sodium hydroxide is reacted with a fatty acid chloride. Then the reaction mixture is acidified by adding hydrochloric acid to thereby give an N-acylamino acid (acid type). The obtained product is filtered, dried and then neutralized with potassium hydroxide. Thus the secondary amide-type N-acylamino acid can be obtained. The liquid detergent composition may be formulated into a paste or a gel by adding a thickener or a binder, if required. The liquid detergent composition may further contain components commonly employed in detergent compositions, for example, humectants, touch improvers, viscosity modifiers, bactericides, perfumes or colorants, as long as the formation of the highly lubricant platy crystals during the rinsing step is not inhibited thereby. The pH value of the liquid detergent composition may be 6 or above and preferably range from 7 to 10. The liquid detergent composition, which has been described in detail above, is suitable for cleansing the body including the skin and the hair. It is particularly suitable for cleansing the skin. To further illustrate the present invention, and not by way of limitation, the following Examples will be given. Example 1 Each liquid detergent composition of the formulation as specified in Table 1 was prepared and the solubility, foaming properties, precipitation of platy crystals and comfort in the use thereof were evaluated in accordance with the criteria as specified below. Table 1 summarizes the results. Evaluation of solubility The appearance of each liquid detergent composition at 10°C was evaluated with the naked eye in accordance with the criteria as specified below. Criteria: ○ : transparent. X: turbid or a precipitate is observed due to the formation of crystals. Evaluation of foaming properties The foam volume was measured by the following method and thus the foaming properties were evaluated in accordance with the criteria as specified below. Each liquid detergent composition was diluted 10-fold with water. 100 ml of the aqueous solution (liquid temperature: 20°C) thus obtained was poured into a volumetric cylinder. Next, stirring blades were placed in the solution and the volume (ml) of the foam formed 30 seconds after the initiation of stirring was measured. The value thus determined was referred to as the foam volume. The stirring blades were rotated at 1,000 rpm and the rotation was reversed every 5 seconds. Criteria: o ○: foam volume is 200 ml or above. ○: foam volume ranges from 150 to 200 ml. X: foam volume is less than 150 ml. Evaluation of the precipitation of lubricant platy crystals Each liquid detergent composition was diluted 10-fold with ion-exchanged water. 1 ml of the obtained aqueous solution was poured into 50 ml of 4° DH hard water at 20°C. After 10 seconds, the formation of crystals was observed with the naked eye and thus evaluated in accordance with the criteria as specified below. Criteria: o ○: crystals are formed and the solution becomes cloudy. ▵: crystals are formed and the solution becomes slightly cloudy. X: no crystal is formed and the solution remains transparent. Evaluation of comfort in the use Ten male panelists and 10 female ones washed their bodies with each liquid detergent composition for a week and the comfort in the use of the product was organoleptically evaluated. The results given in Table 1 were the averages of the data obtained in accordance with the criteria as specified below. Criteria: (1) Foam breaking during rinsing: 5: good. 4: somewhat good. 3: moderate. 2: somewhat poor. 1: poor. (2) Slippage during rinsing; (3) Slippage after rinsing; and (4) Slippage after drying: 5: good. 4: somewhat good. 3: moderate. 2: somewhat poor. 1: poor. Example 2 Regarding the K salts of the secondary amide-type N-acylamino acid to be used in the liquid detergent compositions, the solubility, formation of lubricant platy crystals and comfort in the use were evaluated in accordance with the criteria as specified below. For comparison, secondary amide-type N-acylamino acid Na salts and tertiary amide-type N-alkyl-N-acylamino acid salts were evaluated in the same manner. Table 2 shows the results and the Krafft points of these amino acid salts. Evaluation of solubility A 5% by weight aqueous solution of each amino acid salt was prepared and the solubility of the solution thus obtained at 10°C was evaluated in accordance with the criteria as specified below. Criteria: ○: soluble. X: insoluble (precipitation of crystals). Evaluation of the formation of lubricant platy crystals A 5% by weight aqueous solution of each amino acid salt was prepared and 1 ml of the obtained solution was poured into 50 ml of 4°DH hard water at 20°C. After 10 seconds, the formation of crystals was determined and evaluated in accordance with the criteria as specified below. Criteria: ○ : crystals are formed. X: no crystal is formed. Evaluation of comfort in the use A 5% by weight aqueous solution of each amino acid salt was prepared and a subject washed the body with the obtained solution. Then the slippage from the rinsing step to after drying was evaluated in accordance with the criteria as specified below. Criteria: o ○: very good. ○: good. X: poor. Kraft point Solubility Crystal formation Comfort in the use caprinoyl-β-alanine K salt < 0°C ○ ○ ○ Na salt 20°C X - - lauroyl-β-alanine K salt < 0°C ○ ○ o ○ Na salt 35°C X - - myristoyl-β-alanine K salt < 0°C ○ ○ ○ Na salt 45°C X - - lauroyl-N-methyl-β-alanine K salt < 0°C ○ X X Na salt < 0°C ○ X X Example 3 [Formulation] (% by weight) (1) N-lauroyl-β-alanine K salt 28 (2) dibutylhydroxytoluene 0.2 (3) perfume 0.5 (4) ethanol 3 (5) purified water the balance In accordance with the above formulation, the component (1) was dissolved in hot water. After cooling, the components (2) to (4) were added thereto. Thus a transparent liquid detergent composition was prepared. When the skin and the hair were washed with the liquid detergent composition obtained above, the product showed good foaming properties, good foam breaking, good slippage from the rinsing step to after drying and an excellent comfort in the use.

Claims: A liquid detergent composition containing 5 to 60% by weight of a potassium salt of a secondary amide-type N-acylamino acid represented by the following general formula (I): RCONHCH₂CH₂COOH (I) wherein RCO represents a straight-chain saturated hydrocarbon acyl group having 10 to 14 carbon atoms. A liquid detergent composition as claimed in claim 1, wherein RCO in the general formula (I) is a lauroyl group.

Inventors: KOJIMA MASAYO, NOZAKI TOSHIO, WATANABE HIROSHI, KOJIMA, MASAYO, NOZAKI, TOSHIO, WATANABE, HIROSHI
Applicants: KAO CORP, KAO CORPORATION
Application year: 1991
Main classification: C11D1
IPC codes: C11D1