WO2003040283A1

WO2003040283A1 - Detergent bar composition and process for its manufacture

Info

Publication number: WO2003040283A1
Application number: PCT/EP2002/011261
Authority: WO
Inventors: Satish Kumar Goel; Vijay Bangalore KRISHNA; Narayanan Subrahmaniam
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Lever Ltd
Priority date: 2001-11-08
Filing date: 2002-10-09
Publication date: 2003-05-15
Also published as: CN1582324A; CN1258586C; MY128769A; BR0213750A

Abstract

A detergent bar comprising: (i) from 5% to 60%, preferably from 10% to 50% by weight of detergent active; and(ii) from 2% to 20%, preferably from 5% to 15% by weight of a structuring system being the reaction product of at least two different polyvalent metal ions with sodium silicate, wherein one of the metal ions is calcium or magnesium and the other being selected from boron, aluminium, zinc, calcium and magnesium.

Description

DETERGENT BAR COMPOSITION AND PROCESS FOR ITS MANUFACTURE

Field of the Invention

The invention relates to detergent bar compositions for fabric washing and for cleaning surfaces and their manufacture . The invention particularly relates to laundry bars capable of structuring higher water content but having the requisite mechanical and structural aspects for satisfactory processability and end user properties.

Background to the Invention

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. Inclusion of certain ingredients to make the bar harder usually results in higher density bars, making the bars considerably smaller and thus less attractive to the consumer and more difficult to handle during fabric washing and sometimes also gritty to feel. Commercially available detergent bars contain detergent active components and detergent builders together with conventional components for example abrasives, fillers, perfumes, alkaline salts and bleaching agents.

Among the various product forms such as liquids, powders, gels, bars, tablets, cakes, compacts etc, in which cleaning compositions are formulated, the bar, tablet or compact forms are economically superior as compared to the other. The product dosage from the bar is highly controlled in comparison to the other forms such as paste, gel or powder. The bar also does not get easily sogged in the presence of water and the active ingredients are not lost. However, for manufacturing of products in the solid form it will be necessary to formulate specific compositions and control processing.

GB-A-209 013 discloses detergent bar compositions produced by mixing precursors for aluminosilicate with the bar components under alkaline conditions so that aluminosilicate is formed in situ.

IN-A-171 326 discloses a two component hardening system comprising a polyvalent metal compound and a siliceous material where it is essential that at least one of these ingredients is present before the neutralisation of the active. The polyvalent metal compounds covered in this patent are salts of Aluminium, magnesium, Boron and salts of group Ila and lib. These bars have improved hardness, rate of wear in use, and mush characteristics .

GB-A-256 647 discloses a route for forming low density bars where starch is premixed with the acid form of detergent active prior to at least partial neutralisation of the active with silicate. The formulation results in a grit free bar if at least part of the starch is added prior to neutralisation. The starch used in this patent is native starch. Combination of the starch and in-situ generated of silica form low density bars with good processability.

We have found a new route for producing detergent bars having superior properties such as good processability, in-use properties and improved water retention capacity. This is achieved by generating a structuring system in-situ that is obtained by reacting at least two different polyvalent metal ions with sodium silicate, wherein one of the metal ions is calcium or magnesium and the other may be anyone of boron, aluminum, zinc, calcium or magnesium.

China clay (Hydrated Aluminum Silicate) is a common filler and is incorporated in bars to provide hardness. Removal of china clay from the formulation therefore makes the bars softer. However, removal of china clay is desirable for environmental reasons as china clay has traces of heavy metals. Also, from an aesthetic point of view, removal of china clay makes the bars brighter. Another object of the present invention is to formulate bars without any china clay and yet retain the bar hardness and improve the brightness of the bar.

According to one aspect of the invention there is provided a detergent bar composition comprising

(i) from 5% to 60%, preferably from 10% to 50% by weight of detergent active; and

(ii) from 2% to 20%, preferably from 5% to 15% by weight of a structuring system being the reaction product of at least two different polyvalent metal ions with sodium silicate, wherein one of the metal ions is calcium or magnesium and the other being selected from boron, aluminum, zinc, calcium and magnesium.

According to a second aspect of the invention, there is provided a process for manufacturing a detergent bar composition according to the first aspect of the present invention, the process comprising the steps: (i) in a composition comprising at least some of the detergent active or its acid precursor, in-si tu generation of the structuring system by reacting the at least two different polyvalent metal ions with the sodium silicate before, during and/or after partial or complete neutralisation of the acid precursor, one of the metal ions being calcium or magnesium and the other being selected from boron, aluminium, zinc, calcium and magnesium ; (ii) optionally, before, during and/or after step (i) addition of other ingredients such as other detergent actives, builders, fillers, and other conventional ingredients; and (iii) converting the resultant mass into the desired product form.

The percentage by weight of structuring system in the composition is 2 % to 20 %. The structuring system is preferably formed post neutralization of the acid precursor of the detergent active.

The resultant mass is conveniently converted to the desired product form by any conventional method such as plodding and stamping.

Detailed Description of the Invention

The Detergent active:

The detergent active is selected from soap or non-soap actives and is preferably anionic and specific detergent actives used in detergent bar technology are described in literature, for example in Surface Active Agents and Detergents, Volume II by Schwartz, Perry and Berch (Interscience Publishers, N.Y. 1958) .

Specific examples of suitable anionic actives useful in this invention are soap or non soap selected from linear and branched alkyl benzene sulphonates, alkane sulphonates, secondary alcohol sulphates, primary alcohol sulphates, alpha olefin sulphonates, alkyl ether sulphates, fatty acyl ester sulphonates, alkyl carboxylates and mixtures of these. When the detergent active is soap, the term total fatty matter, usually abbreviated to TFM is used to denote the percentage by weight of fatty acid and triglyceride residues present in soaps without taking into account the accompanying cations .

For a soap having 18 carbon atoms, an accompanying sodium cation will generally amount to about 8% by weight. Other cations may be employed as desired for example zinc, potassium, magnesium, alkyl ammonium and aluminium.

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 other detergent active compounds may be anionic, nonionic, cationic, zwitterionic or amphoteric surfactants, or mixtures thereof as are well known to those skilled in the art can also be incorporated in the formulation. Especially preferred are compositions in which the anionic detergent active comprises of alkyl benzene sulphonate (LAS) .

The detergent active is present in quantities normal for detergent bars, e.g. 5 to 60% by weight, preferably 10-50, more preferably about 12 to 45% by weight of the total bar composition.

The in-situ generation of the structuring system is done using silicate which is preferably sodium silicate of the type having a molar ratio of Si0 :M₂0 of less than 4, more preferably less than 3 , most preferably between 3 and 1. Builders :

The detergency builders used in the formulation are preferably inorganic and suitable builders include, for example, alkali metal aluminosilicates (zeolites) , alkali metal carbonate, sodium tripolyphosphate (STPP) , tetrasodium pyrophosphate (TSPP) , citrates, sodium nitrilotriacetate (NTA) and combinations of these. Builders are suitably used in an amount ranging from 0 to 30%.

Inorganic particulates:

Inorganic particulate phase is not an essential ingredient of the formulation but may be incorporated especially for hard surface cleaning compositions. Preferably, the particulate phase comprises a particulate structurant and/or abrasive which is insoluble in water. Suitable inorganic particulates can be selected from, particulate zeolites, calcites, dolomites, feldspars, silicas, silicates, other carbonates, bicarbonates, borates, sulphates and polymeric materials such as polyethylene.

The most preferred inorganic particulates are calcium carbonate (as Calcite) , mixtures of calcium and magnesium carbonates (as dolomite) , sodium hydrogen carbonate, borax, sodium/potassium sulphate, zeolite, feldspars, talc, koalin and silica.

Calcite, talc, kaolin, feldspar and dolomite and mixtures thereof are particularly preferred due to their low cost and colour. Other conventional inorganic particulate structurants such as alumino silicate may be generated in situ or readily available forms can be incorporated.

Other additives :

Other additives such as one or more water insoluble particulate materials such as polysaccharides such as starch or modified starches and celluloses may be incorporated.

Minor additives:

Minor and conventional ingredients preferably selected from enzymes, antiredeposition agents, fluorescers, colour, preservatives and perfumes, also bleaches, bleach precursors, bleach stabilisers, sequestrants, soil release agents (usually polymers) and other polymers may optionally be incorporated up to 10 wt%.

Illustrations of a few non-limiting examples are provided herein showing comparative results of the composition prepared by the present invention. The composition details and their results are described in Tables 1 to 3 with reference to bars. The processing of the detergent bar was done as explained below.

EXAMPLES: Example 1 :

Process for preparing the detergent bar: a. Conventional Process:

A batch of 6 kg detergent bar was prepared by taking 1.2 kg of linear alkyl benzene sulphonic acid in a sigma mixer and neutralising it with 600 gms of sodium carbonate. In-situ aluminosilicate was generated by the reaction of 180 gm aluminium sulphate and 120 gm sodium silicate. Other ingredients such as 720 gms of sodium tripolyphosphate (STPP) builder, approximately 3 kg of fillers, water and minor ingredients were also added. These were thoroughly mixed and plodded in a conventional manner (Example la) .

b. Process according to the invention:

A batch of 6 kg detergent bar was prepared by taking 1.2 kg of linear alkyl benzene sulphonic acid in a sigma mixer and neutralising it with 600 gms of sodium carbonate. The structuring system was generated after the complete neutralisation of the active by reacting 30 gm Aluminium Sulphate, 180 gm Alkaline Silicate and 90 gm Calcium Chloride in the mixer. Other ingredients such as 720 gms of STPP builder, approximately 3 kg of fillers, water and minor ingredients were also added. These were thoroughly mixed and plodded in a conventional manner (Example lb) .

Other structuring systems for comparison were generated as per the details below. In all the formulations the total structuring ingredients were maintained close to 5% of the total weight of the formulation.

Example lc: In-situ calcium silicate generated by the reaction of 180 gm sodium silicate And 120 gm calcium chloride

Example Id: In situ alumino silicate generated by the reaction of 30g aluminum sulphate and 30g alkaline silicate and postdosing calcium silicate generated by reacting 90g calcium chloride and 150g alkaline silicate. Example le: Post-dosing calcium aluminosilicate generated by the reaction of 30 gm Aluminum Sulphate, 180 gm Alkaline Silicate and 90 gm Calcium Chloride.

Example If: In-situ calcium boro-silicate generated by the reaction of 30 gm Boric Acid, 210 gms of Alkaline silicate and 72 gm Aluminium Sulphate.

The bars prepared by the process mentioned above were tested for different physical and in use properties by the following procedure and the formulation details and the data are presented in Table 1.

Determination of hardness of the bar

Bar hardness for a given moisture level is a direct indicator of how well the bar is structured. A penetrometer was used to get an estimate of the hardness and the yield stress of the detergent bars, based on the depth of penetration of a needle.

Higher the penetration, less the hardness and the yield stress and vice-versa. Measurements are made by allowing a needle with a cone angle of 9° degrees to fall under a set weight of 50 gms for 5 seconds on top of a flat surface of the bar. The depth of penetration is reported in mm.

Water retention: Water retention ability of a bar is quantified by measuring the water activity in the bar. This measurement is carried out on AW Sprint model from Novasina of Switzerland. A grated sample of the bar is equilibrated at a set temperature, and the relative humidity calculation is done by the instrument which indicates the water activity. Lower water activity at a given moisture level indicates better ability of the bar to retain water and hence better structuring in the bar. Method for mush estimation

The mush refers to the paste like layer formed on the bar surface upon contact with water. This layer is useful for easy application of the bar on the fabric, however, excessive formation of mush is perceived as wastage (low economy) by the consumer.

Test Procedure

1) Remove the surface unevenness such as flutes/logo etc, by planing the bar using a carpenter's plane.

2) Weigh the planes bar ( i g)

3) Immerse section of bar area (50 cm² ) of above planed bar in 250 ml of distilled water for 20 minutes.

4) At the end of 20 minutes, remove the bar from the water pool and drip dry for some time .

5) Scrape the surface exposed to water gently and collect the loosely adhering material (cling mush) in a pre-weighed petri- dish (P g) . Weigh the dish and cling mush together (W₂ g) and find the weight of the cling mush (W₃ g) by difference in weights (W₃= W₂-P) .

6) The bar loss to solution was measured by measuring the weight gained by the water in the beaker.

Table 1

^® Builders used were Sodium carbonate and STPP. * Fillers used were calcite, calcium hydroxide and washed china clay. Lower the penetration, higher the hardness. We find from the penetration measurements that the Calcium-alumino Silicate structured (Ex lb) bar is harder than in-situ alumino silicate structured bars (Ex la) and in-situ calcium silicate structured bars (Ex lc) . Also, the bars according to the invention where the Calcium Alumino-silicate is generated in- situ (Ex. lb) is significantly harder as compared to the bars where only Aluminosilicate is generated in-situ and Calcium Silicate is post-dosed (Ex. Id) and the bars where Calcium Alumino-silicate is post-dosed (Ex. le) . This reinforces the fact that the structuring has to be necessarily generated in-situ.

Lower water activity is an indication of lower weight loss during storage. The data in Table 1 shows that the bars according to the invention (Ex. lb) have a low<sr water activity as compared to the bars with conventional Alumino-silicate structuring (Ex. la) . This indicates that the bars according to this invention will lose less water during storage.

This invention is not restricted to only one combination of metal ions, i.e., calcium and Aluminum. More than one combination of metal ions can react with sodium Silicate to generate the structuring. Example If demonstrates one such case. In this case, a boron containing salt, boric Acid, and a calcium containing salt, calcium chloride, react with Alkaline silicate to generate calcium boro-silicate structuring in-situ. This structuring also improves hardness of the bar and reduces the water activity. Example 2 :

Processing nil-China clay bars using the structuring system according to the invention; 6 kg batches of bars were prepared with details as described in Example 1. The important formulation ingredients for each case is highlighted below:

Example 2a : Conventional Alumino-silicate structuring with 180 gm aluminum sulphate and 120 gm alkaline silicate. 8.3 % china Clay was present in the formulation. The other fillers were calcite (35 %) and calcium hydroxide (3%) .

Example 2b: Conventional alumino-silicate Structuring with 180 gm aluminum aulphate and 120 gm alkaline silicate. All china clay (8.3%) was replaced by Calcite. The total calcite in the formulation was 43.3 %.

Example 2c: In this example, structuring is done as per the invention. Calcium Alumino-silicate structuring was generated with 30 gm Aluminum Sulphate, 180 gm Alkaline Silicate and 90 gm calcium chloride. All China clay (8.3%) from the formulation was replaced by calcite. The total calcite in the formulation was 43.3 %. Table 2 shows the formulation details.

Table 2

Builder used is STPP and soda In table 2, first compare alumino-silicate structured bars with and without china clay (example 2a and 2b respectively) . Bars without washed china clay (ex. 2b) are softer as compared to bars with china clay (ex. 2a) as indicated by the penetration measurements. This substantiates that removal of washed china clay with conventional alumino-silicate structuring makes the bars softer. However, with calcium alumino-silicate structuring (example 2c) , even after removal of washed china clay, the bars are harder indicating that using this structuring bars can be processed without china clay. Also, the water activity of the bars according to the invention is lower.

Example 3

Cling mush Measurement

Mush measurement of prototypes made as per example la and example lb was done according to the procedure described earlier. The results are presented in table 3.

Table 3

From table 3, it is evident that the calcium alumino-silicate structured bars (ex. lb) has lower cling mush and bar loss to solution as compared to conventional alumino-silicate structuring (ex. la). This suggests that the bars according to the invention would have a consumer-perceivable mush benefit.

Claims

1. A detergent bar comprising:

2. A detergent bar according to claim 1, wherein the sodium silicate is of the type having a molar ratio of Si0₂ : Na₂0 of less than 4 , preferably between 3 and 1.

3. A detergent bar according to claim 1 or claim 2, wherein the bar does not contain any China clay.

4. A process for manufacturing a detergent bar composition according to claim 1, the process comprising the steps: (i) in a composition comprising at least some of the detergent active or its acid precursor, in-si tu generation of the structuring system by reacting the at least two different polyvalent metal ions with the sodium silicate before, during and/or after partial or complete neutralisation of the acid precursor; (ii) optionally, before, during and/or after step (i) addition of other ingredients such as other detergent actives, builders, fillers, and other conventional ingredients; and (iii) converting the resultant mass into the desired product form.

5. A process according to claim 4 , wherein the structuring system is generated post neutralisation of the acid precursor of the detergent active.