WO2002086043A1

WO2002086043A1 - Improved detergent bar composition

Info

Publication number: WO2002086043A1
Application number: PCT/EP2002/003702
Authority: WO
Inventors: Debojit Chakrabarty; Subhash Shivshankar Mhatre; Amitava Pramanik; Uday Shanker Racherla
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2001-04-20
Filing date: 2002-03-29
Publication date: 2002-10-31
Also published as: ZA200307930B; BR0209119A; CN1289650C; CN1513053A

Abstract

A detergent bar comprising a layered inorganic material for personal or fabric washing or hard surface cleaning. The detergent compositions have improved water retention capacity without affecting sensory and physical properties. A process for the preparation of the detergent bar composition is also provided.

Description

IMPROVED DETERGENT BAR COMPOSITION

The invention relates to a synergistic composition of soap/detergent bars for personal or fabric washing or for hard surface cleaning. This invention particularly relates to detergent bar composition with improved water retention capacity without affecting sensory and physical properties.

Conventional detergent bars, based on soap for personal washing contain over about 70% by weight TFM, the remainder being water (about 10-20%) and other ingredients such as colour, perfume, preservatives, etc. Structurants and fillers are also present in such compositions in small amounts that replace some of the soap in the bar while retaining the desired hardness of the bar. A few known fillers include starch, kaolin and talc.

Hard non-milled soaps containing moisture of less than 35% are also available. These bars have a TFM of about 30-65%. The reduction in TFM has been achieved by the use of insoluble particulate materials and/or soluble silicates.

Milled bars generally have a water content of about 8-15% and the hard non-milled bars have a water content of about 20-35%.

Fabric washing compositions contain, as an essential ingredient, a surfactant system whose role is to assist in removal of soil from the fabric and its suspension in the wash liquor. Detergent bars require an acceptable physical strength so that they retain their structural integrity during handling, transport and use. The hardness of the bars, at the time of manufacture and subsequently, is an especially important property. The water content in the detergent bars is .generally maintained around 6%. The binders and fillers used in NSD bars are typically minerals which generally exhibit wide variability in quality, by virtue of the fact that they are mined. Increasing the water content and retaining it in the bar is particularly useful for producing larger sized bars, which have an enhanced consumer impact. Commercially available detergent bars contain detergent active components and detergent builders, fillers, structurants, hardeners together with optional components for example abrasives, perfumes, colour and bleaching agents.

Commercial hard surface cleaning compositions typically comprise one or more surfactants and a plurality of abrasives dispersed therein. Combinations of these together with electrolytes are generally used to form a suspending system as is well known in the art.

Inorganic particulates form an essential ingredient of detergent formulations used for personal wash, fabric and especially of many hard surface cleaning compositions. Inorganic particulates generally employed are calcites, dolomites, feldspars, silica, silicates, other carbonates, bicarbonates, borates, sulphates.

Hydroxy carbonates of alkaline earth metals and layered double hydroxides of one or more alkaline earth and aluminium are also known to exist in their mineral form but have not been generally used in soaps and detergents. Hydroxy carbonates of alkaline earth metals are used as flow aids, as precursors for ceramics, refractories and layered double hydroxides of one or more alkaline earth and aluminium are used as catalyst precursors, adsorbents, antacids .

EP557089 (Unilever, 1993) , W09616634 (Unilever, 1996) , disclose the use of layered double hydroxides in cosmetic compositions for enhanced delivery of benefit agents.

WO 96/25913 discloses the use of monophasic zinc hydroxycarbonate as antimicrobial agents in personal care products, particularly products containing soap or synthetic detergents. This is restricted to making the zinc ions, which are known to provide antimicrobial activity available without affecting the product itself.

WO94/03574 and W095/21234 refer to the use of double layer hydroxide materials such as hydrotalcites in machine dishwashing compositions. WO 89/08693 describes the use of crystalline mixed metal hydroxides as thickeners or viscosity modifiers.

It has now been found that use of these layered inorganic materials in detergent formulations can improve the water retention in the bars without affecting the other physical and sensory properties. It also enables the incorporation of other liquid benefit agents in the bar. According to the present invention there is provided an improved detergent bar composition comprising:

- 10-80% detergent active

1-30% layered inorganic material having the general formula:

(M²⁺)ι (N^{3 +})_a (OH^_1)_b (A^"C)_d . eH₂0 2+

Wherein M = one or more bipositive metal ion;

N = tripositive metal ion and 'a' ranges from 0 to 1; OH = hydroxyl, and 'b' ranges from 0.1 to 4;

-c A = ' c ' refers to the valency of the inter layer anion 'A' and 'd' ranges from 0 to 1 ; H₂0 = water of crystallisation where 'e' ranges from 0 to 10; wherein the charge neutrality is maintained (i.e. 2 + 3a - (b + cd) = 0) ;

- 12-52% water or other liquid benefit agents; and optionally other conventional ingredients.

It is particularly preferred that the bipositive metal ion may be magnesium, calcium and/or zinc and the tripositive metal ion is aluminum. The anion may be mono-negative such as chloride or nitrate or di-negative such as carbonate or sulphate or tetraborate or tri-negative such as phosphate or borate.

According to the preferred aspect of the invention there is provided an improved detergent bar composition comprising:

- 10-80% detergent active; - 1-30% inorganic material having the general formula (M²⁺)_α (OH^"1)_!, (A^"c)_d. eH₂0

wherein M²⁺ = bi-positive metal ion is magnesium OH^"1 = hydroxyl, and 'b¹ is 0.2 to 0.8

A^"c = anion is carbonate and 'd' is 0.6 to 0.9 H₂0 = water of crystallisation where ' e' is 1 to 5; wherein the charge neutrality is maintained (i.e. 2 - (b +cd) = 0) ; - 12-52% water or other liquid benefit agents; and optionally other conventional ingredients.

According to another aspect of the invention there is provided a process for the preparation of an improved detergent bar composition comprising 10-80% detergent active wherein the 1-30% layered inorganic material having the general formula:

(M²⁺)_x (N³⁺)_a (OH^'1)], (A^'c)_d .eH₂0

wherein M²⁺ = one or more bipositive metal ion

N³⁺ = tripositive metal ion and ' a ' ranges from 0 to 1

OH^~1= hydroxyl, and ' b' ranges from 0.1 to 4 A^"c = c' refers to the valency of the inter layer anion 'A' and ' d' ranges from 0 to 1 H₂0 = water of crystallisation where 'e' ranges from 0 to 10; wherein the charge neutrality is maintained (i.e. 2 + 3a - (b + cd) = 0) ;

- 12-52% water or other liquid benefit agents; and optionally other conventional ingredients;

wherein the said layered inorganic material is generated in situ by mixing the mixed metal oxide precursor with the soap mass at a temperature range of 20-80°C in presence of water.

The mixed metal oxide precursor may be obtained by calcining the corresponding layered double hydroxide at a temperature range of 450-550°C.

An essential feature of the invention is that the incorporation of certain layered inorganic basic salts such as hydroxy carbonates and layered double hydroxide in soaps and detergents helps in improving the water structuring and thus retention of the structured water in the bar during storage and use .

A number of natural and synthetic layered double hydroxides are known with various metallic cations wherein the divalent cations are magnesium, manganese, iron, cobalt, nickel, copper, zinc or calcium and the trivalent ones are aluminium, chromium, manganese, iron, cobalt, nickel and lanthanum. It is particularly preferred that, the bipositive metal ion may be magnesium, calcium and/or zinc, the tripositive metal ion is aluminum, and the anion may be mono-nega ive such as chloride or nitrate or di-negative such as carbonate or sulphate or tetraborate or tri-negative such as phosphate or borate .

The layered inorganic materials used in the composition may be obtained commercially or may be prepared separately. The layered double hydroxides may be added to the neat soap before spray drying of the soap or to the dried soap noodles. Alternatively, the layered double hydroxides may also be generated in situ from its corresponding mixed metal oxide precursor. The mixed metal oxide precursor is obtained by calcining the corresponding layered double hydroxide at a temperature range of 450-550°C. The mixed metal oxide precursor is added to the soap before spray drying of the soap or to the dried soap noodles where it gets reformed to give the layered double hydroxide. Some of these layered inorganic materials are also available naturally as minerals .

The layered inorganic material, namely the hydroxy carbonate or layered double hydroxides may be prepared by combining appropriate stoichiometric amounts of aqueous solutions of metal salts/co-mixtures of metal salts with aqueous sodium carbonate solutions at typically high temperatures of 80- 90°C. The precipitate containing the layered inorganic material is filtered and washed thoroughly with copious amounts of water to remove all soluble electrolytes. This wet cake obtained is subjected to drying over night in an oven at 130°C. These materials suitable for the detergent composition are typically white powders, and have an average particle size in the range 5-12 microns. In case the particle size is larger, the material may be subjected to milling to get the desired particle size range.

Examples of layered materials are hydromagnesite, hydrotalcites with carbonate, nitrate, sulphate, tetraborate as inter layer anions . The detergent active may be soap or non-soap surfactants. In certain embodiments, the composition is a foaming bar; it may preferably contain some soap, preferably at a level of at least 5% by weight of the bar. In other embodiments it may preferably contain at least 2%, and preferably at least 5% by weight synthetic or non-soap anionic surfactant.

The term soap denotes salts of carboxylic fatty acids. The soap may be derived from any of the triglycerides conventionally used in soap manufacture - consequently the carboxylate anions in the soap may contain from 8 to 22 carbon atoms .

The soap may be obtained by saponifying a fat and/or a fatty acid using a suitable alkaline material containing sodium, potassium, aluminium or a mixture thereof. The saponification may also be carried out by reacting one or more precursors of detergent active with an aluminium containing alkaline material such as sodium aluminate with a solid content of 20 to 55% wherein the Al₂0₃ to Na₂0 is in a ratio of 0.5 to 1.55 by weight either in the presence or absence of one or more carboxylic acid which may have an equivalent weight less than 150. The carboxylic acid may be selected from aliphatic monocarboxylic acids that are not fatty acids and their polymers, and more preferably they are Ci to C₅ carboxylic acids and their polymers. Other suitable carboxylic acids are aliphatic or aromatic di, -tri-, or polycarboxylic acids and hydroxy- and amino carboxylic acids. The fats or oils generally used in soap manufacture may be such as tallow, tallow stearines, palm oil, palm stearines, soya bean oil, fish oil, caster oil, rice bran oil, sunflower oil, coconut oil, babassu oil, palm kernel oil, and others . In the above process the fatty acids are derived from oils/fats selected from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed, soybean, castor etc. The fatty acid soaps can also be synthetically prepared (e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process) . Resin acids, such as those present in tall oil, may be used. Maphthenic acids are also suitable.

Tallow fatty acids can be derived from various animal sources and generally comprise about 1-8% myristic acid, about 21-32% palmitic acid, about 14-31% stearic acid, about 0-4% palmitoleic acid, about 36-50% oleic acid and about 0- 5% linoleic acid. A typical distribution is 2.5% myristic acid, 29% palmitic acid, 23% stearic acid, 2% palmitoleic acid, 41.5% oleic acid, and 3% linoleic acid. Other mixtures with similar distribution, such as those from palm oil and those derived from various animal tallow and lard are also included.

Coconut oil refers to fatty acid mixtures having an approximate carbon chain length distribution of 8% C₈, 7% Ci_o, 48% C₁₂, 17% C₁₄, 8% C₁₆ , 2% C₁₈, 7% oleic and 2% linoleic acids (the first six fatty acids listed being saturated) . Other sources having similar carbon chain length distributions, such as palm kernel oil and babassu kernel oil, are included within the term coconut oil. The non-soap surfactants may be anionic, nonionic, cationic, amphoteric or zwitterionic, or a mixture thereof.

Suitable anionic detergent active compounds are water soluble salts of organic sulphuric reaction products having in the molecular structure an alkyl radical containing from 8 to 22 carbon atoms, and a radical chosen from sulphonic acid or sulphuric acid ester radicals and mixtures thereof.

Examples of suitable anionic detergents are sodium and potassium alcohol sulphates, especially those obtained by sulphating the higher alcohols produced by reducing the glycerides of tallow or coconut oil; sodium and potassium alkyl benzene sulphonates such as those in which the alkyl group contains from 9 to 15 carbon atoms; sodium alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulphates; sodium and potassium salts of sulphuric acid esters of the reaction product of one mole of a higher fatty alcohol and from 1 to 6 moles of ethylene oxide; sodium and potassium salts of alkyl phenol ethylene oxide ether sulphate with from 1 to 8 units of ethylene oxide molecule and in which the alkyl radicals contain from 4 to 14 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralised with sodium hydroxide where, for example, the fatty acids are derived from coconut oil and mixtures thereof . The preferred water-soluble synthetic anionic detergent active compounds are the alkali metal (such as sodium and potassium) and alkaline earth metal (such as calcium and magnesium) salts of higher alkyl benzene sulphonates and mixtures with olefin sulphonates and higher alkyl sulphates, and the higher fatty acid monoglyceride sulphates . The most preferred anionic detergent active compounds are higher alkyl aromatic sulphonates such as higher alkyl benzene sulphonates containing from 6 to 20 carbon atoms in the alkyl group in a straight or branched chain, particular examples of which are sodium salts of higher alkyl benzene sulphonates or of higher-alkyl toluene, xylene or phenol sulphonates, alkyl naphthalene sulphonates, ammonium diamyl naphthalene sulphonate, and sodium dinonyl naphthalene sulphonate.

Suitable nonionic detergent active compounds can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

Particular examples include the condensation product of aliphatic alcohols having from 8 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as a coconut oil ethylene oxide condensate having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains from 6 to 12 carbon atoms with 5 to 25 moles of ethylene oxide per mole of alkylphenol; condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensate containing from 40 to 80% of polyoxyethylene radicals by weight and having a molecular weight of from 5,000 to 11,000; tertiary amine oxides of structure R₃NO, where one group R is an alkyl group of 8 to 18 carbon atoms and the others are each methyl, ethyl or hydroxyethyl groups, for instance dimethyldodecylamine oxide; tertiary phosphine oxides of structure R₃PO, where one group R is an alkyl group of from 10 to 18 carbon atoms, and the others are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyldodecylphosphine oxide; and dialkyl sulphoxides of structure R₂SO where the group R is an alkyl group of from 10 to 18 carbon atoms and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide; fatty acid alkylolamides; alkylene oxide condensates of fatty acid alkylolamides and alkyl mercaptans .

It is also possible to include amphoteric, cationic or zwitterionic detergent actives in the compositions according to the invention.

The bar is made by conventional methods, e.g. by the frame cooling method or by extrusion (plodding) method. Typically, in the extrusion method, fatty acids are neutralised with an alkali either as such or in presence of non-soap detergent active/a few selected additives and dried to required moisture. The dried soap is then mixed with remaining minor additives/non-soap detergents if not added earlier in the mixer, mechanically worked in triple roll mill and plodded under vacuum in the form of billets. The billets are later stamped in the form of bars .

Other optional ingredients such as fillers, colour, perfume, opacifier, preservatives, one or more water soluble/insoluble particulate materials such as talc, alumina, borax, kaolin, polysaccharides, liquid benefit agents such as sunscreens, moisturisers, emollients, anti- ageing compounds, hair conditioning agents, and other conventional ingredients may be incorporated in the composition.

The soap/detergent bars of the present invention have been found to demonstrate excellent visual appearance, feel, hardness, cleaning and lathering properties.

Illustrations of a few non-limiting examples are provided herein showing comparative results of the compositions according to the present invention and beyond the scope of the invention.

Examples

i. Process for the preparation of magnesium hydroxy carbonate

100 ml of one molar solution of magnesium sulphate was added drop wise into one molar solution of sodium carbonate in equal volumes over a period of 30 minutes under constant stirring. After the reaction the slurry was filtered through Whatman 1 filter paper. The precipitate was washed with hot water to remove the sodium sulphate and the precipitate was dried at 110°C until the moisture content dropped to <3%. The precipitate of magnesium hydroxy carbonate obtained was characterised using powder pattern X ray diffraction, and the same was used for the preparation of soap bars as described below.

ii. Process for preparing the soap bar

The soap bars having the formulations as described in Table 1 were prepared by the following method.

Soap noodles were taken in a sigma mixer to which in the control formulations the inorganic material such as talc

(Examples 1 and 2) , and the layered inorganic material such as magnesium hydroxy carbonate (Examples 3 and Examples 4) were added. In Example 5, magnesium hydroxide and in Example 6 magnesium carbonate were incorporated. The mass was mixed thoroughly for about 10 minutes, and then processed conventionally by milling and plodding in a two stage plodder, subsequently followed by stamping and wrapping.

The samples prepared as described above were tested for hardness, water retention after storage under hot and dry conditions (45°C and 40-70 relative humidity) by the following procedure.

ii. Determination of hardness of the bar: Penetration Value

(PV) Penetration value indicating the hardness of the bar was measured at 37°C using a cone penetrometer; the details of a typical instrument and the method of measurement are given below.

Cone type Penetrometer

MANUFACTURER: Adair Dutt & Company, Bombay.

RANGE OF MEASUREMENT: 0-40mm RANGE OF VERIFICATION: 20 in steps of 5

Procedure of Measurement: Let the entire mass (comprised of penetrometer needle and standard weight) which just rested on the test sample, drop freely and thus penetrate the test mass to a specific distance for a specified period of time, and read of this distance as l/l0^th of mm. Take the average after repeating the exercise for at least 3 times.

iv. Water retention:

The initial moisture in the soap bar was measured using an Infra red balance. Wrapped samples of the bar were weighed initially and stored under hot and dry (HD) conditions where the temperature was maintained at 45°C and relative humidity in the range 40-70% for 3 months. The weight of the samples was determined periodically, and the data at the end of 3 months is presented. The % moisture and %weight loss of the soap bars was calculated. Table 1

The bar is highly alkaline and is unsuitable for use.

The data presented in table 1 show that the physical properties of the bar having high moisture such as hardness, and processability are significantly improved by using magnesium hydroxy carbonate as compared to talc. The moisture retention in the soap bars where layered inorganic materials have been incorporated is higher as compared to control formulations having talc.

It is not possible to process bars having magnesium hydroxide, and it is generally unsuitable for use in soaps because it forms very high alkalinity in the bars. However, use of magnesium hydroxide or magnesium carbonate does not help in providing moisture retention in soap bars that is provided by the use of magnesium hydroxy carbonate. The use of magnesium hydroxy carbonate does not interfere with the sensory properties of the bar such as feel, lather etc. as was recorded by an internal panel .

Claims

A detergent bar composition comprising:

(i) 10 - 80 % detergent active;

(ii) 1 - 30% of a layered inorganic material having the general formula:

(M²⁺)ι (N³⁺)_a (OH)^~ _b (A^"C)_d.e H₂0

2+ wherein M = one or more bipositive metal ion

N = tripositive metal ion

OH = hydroxyl

A = an interlayer anion H₂O = water of crystallisation

A = ranges from 0 to 1 b = ranges from 0.1 to 4 c = refers to the valency of anion A d = ranges from 0 to 1, and wherein the charge neutrality is maintained, and

(iii) 12 - 52% water or other liquid benefit agents.

2. A composition according to claim 1, wherein the bipositive metal ion is selected from magnesium, manganese, iron, cobalt, nickel, copper, calcium, or zinc.

3. A composition according to claim 2, wherein the bipositive metal ion is selected from magnesium, calcium, and/or zinc.

4. A composition according to any one of claims 1 to 3 wherein the tripositive metal ion is selected from aluminium, chromium, manganese, iron, cobalt, nickel or lanthanum.

5. A composition according to claim 4 wherein the tripositive metal ion is aluminium.

6. A composition according to any one of claims 1 to 5 wherein the anion is mononegative, dipositive, or trinegative .

7. A composition according to claim 6, wherein the anion is chloride, nitrate, carbonate, sulphate, tetraborate, phosphate or borate .

8. A composition according to any of the preceding claims, wherein

M i^■s magnesium A is carbonate b is 0.2 to 0.8 d is 0.6 to 0.9 and e is 1 to 5.

9. A composition according to any of the preceding claims, wherein the composition further comprises fillers, colour, perfume, opacifier, preservatives, water soluble/insoluble particulate materials or liquid benefit agents.

10. A composition according to any of the preceding claims, wherein the bar composition is a foaming bar composition.

11. A composition according to any of the preceding claims, wherein the bar composition contains soap.

12. A composition according to claim 11, wherein the composition contains at least 5% soap.

13. A composition according to any of the preceding claims, wherein the bar composition contains at least 2% synthetic or non-soap anionic surfactant.

14. A process for the preparation of a detergent bar composition according to claim 1 comprising:

(i) generating the layered inorganic material in si tu by mixing the mixed metal oxide procures with the soap mass at a temperature range of 20-80°C in the presence of water; and

(ii) calcining the corresponding layered double hydroxide at a temperature range of 450-550°C.