WO2002046341A2

WO2002046341A2 - Process for manufacture of non-granular solid detergent composition

Info

Publication number: WO2002046341A2
Application number: PCT/EP2001/012996
Authority: WO
Inventors: Michael Cristopher Cafe; Satish Kumar Goel
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Lever Ltd
Priority date: 2000-12-05
Filing date: 2001-11-07
Publication date: 2002-06-13
Also published as: AU2002221834A1; WO2002046341A3

Abstract

A process for preparing a non-granular solid detergent product comprising:-from 5% to 70%, preferably from 10% to 30% by weight of detergent active;from 0.5% to 30%, preferably from 1% to 15% by weight of boron containing structuring system;from 5% to 30% by weight of water; from 0%-30%, preferably from1% to 30%, more preferably from 10% to 25% by weight of detergent builder; andoptionally other benefit agents;the process comprising the steps of(a) neutralising the acid precursor of the detergent active using an alkaline material selected from a silicate, carbonate, hydroxide, alkaline aluminium-containing material such as an aluminate, a phosphate and mixtures thereof;(b) providing the structuring system in situ by reacting a boron compound with an alkaline reactant comprising an alkali metal salt of silicate optionally in presence of aluminium and/or phosphate prior to, during or after neutralisation of the acid precursor of the detergent active;(c) adding if desired, any other ingredients such as detergent actives, builders and minor additives such as herein described to the mixture of step (a); and(d) converting the resultant mass into the desired product form, preferably by a conventional method.

Description

NON-GRANULAR SOLID DETERGENT COMPOSITION AND PROCESS FOR ITS

MANUFACTURE

Technical field

The present invention relates to a process for the preparation of non-granular solid soap/detergent compositions for personal/fabric washing or for hard surface cleaning and processes for their manufacture. This invention particularly relates to an improved process for preparing low density detergent bar comprising high levels of water and other liquid benefit agents by in situ generation of boro-silicate containing structuring system.

Background and prior art

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. Products are formulated as liquids, powders, gels, bars, tablets, cakes, compacts etc.

Cleaning compositions in the bar, tablet or compact forms are economically superior as compared to other product forms. 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.

Detergent Bars, in particular 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 also gritty to feel. Commercially available detergent bars contain detergent active components and detergent builders together with optional components for example abrasives, fillers, perfumes, alkaline salts 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.

Conventional detergent bars, based on soap for personal washing contain over about 70% by weight total fatty matter (TFM) , the remainder being water (typically about 10-15%) and other ingredients such as colour, perfume, preservatives, etc. Structurants and fillers are also present in such compositions in small amounts which 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 content 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 about 8-15% and the hard non- milled bars have a water content of about 20-35%. Increased water structuring of the bar help in improving the in use properties of the bar without affecting its physical properties in an economical way. It enables one to manufacture detergent bars cost effectively. It is important to deliver sensory properties such as lather, cleaning, product feel and improved economy in use by reducing mush and wear without altering the processability and physical properties of the bar and to process the formulations using the existing equipment.

This would enable products to be processed by the conventional methods of manufacture and without altering the through-put.

The use of borate compounds or boric acid in personal care products generally is not new. When previously used with soaps, however, borax has been used as a soluble scrubber in powdered hand soap compositions of the type used to clean medium to heavy soils found in industrial operations; or in liquid soaps.

US-A-3, 708, 425 teaches a detergent bar containing about 5 to 60% by wt. puffed borax. This work specifically calls for puffed borax or other puffed salts to which the user properties of the bar are attributed. The puffed borax is compositionally different than borax or other boron-containing compounds of the invention.

US-A-3, 798 , 181 teaches enzymatic detergent bars containing 10- 40% synthetic detergent, 0.5-5% enzymes, 5-40% binder (e.g., to help retain water), 20-60% inorganic builder and 12-25% water. Borax may be used as possible inorganic builder.

DE-A-3 824 252 discloses use of pre-formed boro-silicate particles as low density fillers. WO9403283 (FMC) discloses encapsulation of bleaches by boro-silicate generated by in-situ reaction of meta borate and silicate and the encapsulated bleach particles are dosed into the detergent formulation.

These refer to incorporation of pre formed boro-silicate in the formulation.

IN-A-171326 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.

GB-A-2 099 013 discloses detergent bar compositions produced by mixing precursors for aluminosilicate with the bar components under alkaline conditions so that aluminosilicate is formed in situ. These bars have improved hardness, rate of wear in use, and mush characteristics.

IN-A-177828 discloses a process wherein by providing a balanced combination of aluminium hydroxide and TFM it is possible to prepare a low TFM bar having high water content but with satisfactory hardness. The patent teaches the generation of colloidal alumina hydrate in-situ by a reaction of fatty acid with an aluminium containing alkaline material such as sodium aluminate to form bars which are obtained by plodding.

The present invention aims to provide an improved process for the manufacture of low density detergent compositions with in situ generation of boro-silicate as a structuring system.

It has now been found that in the manufacture of non-granular high moisture containing solid detergent product for personal wash or fabric wash or hard surface cleaning, in si tu generation of boron containing structuring system such as boro- silicate or boro-silicate in presence of an aluminium and/or phosphate salt to obtain boro-aluminosilicate or boro-alumino- phospho-silicate imparts superior properties such as good processability, in-use properties and improved water retention capacity.

Description of the invention :

Accordingly, this invention provides an improved process for preparing non-granular solid detergent product comprising

from 5% to 70%, preferably from 10% to 30% by weight of detergent active; from 0.5% to 30%, preferably from 1% to 15% by weight of boron containing structuring system; from 5% to 30% by weight of water; from 0%-30%, preferably froml% to 30%, more preferably from 10% to 25% by weight of detergent builder; and optionally other benefit agents;

the process comprising the steps of

(a) neutralising the acid precursor of the detergent active using an alkaline material selected from a silicate, carbonate, hydroxide, alkaline aluminium-containing material such as an aluminate, a phosphate and mixtures thereof;

(b) providing the structuring system in si tu by reacting a boron compound with an alkaline reactant comprising an alkali metal salt of silicate optionally in presence of aluminium and/or phosphate prior to, during or after neutralisation of the acid precursor of the detergent active; (c) adding if desired, any other ingredients such as detergent actives, builders and minor additives such as herein described to the mixture of step (a) ; and

(d) converting the resultant mass into the desired product form, preferably by a conventional method.

The product may be formulated as a bar, tablet, cake or a compact and is preferably in the form of a detergent bar. It is particular preferred that the structuring system is generated after the neutralisation of the detergent active.

Detailed description of the invention

Structuring system:

The structuring system is generated in situ by a combination of the boron compound and an alkali metal salt of a silicate optionally in presence of aluminium or phosphate prior to during or after neutralisation of the acid precursor of the detergent active. It is particularly preferred that the structuring system is generated after neutralisation of the detergent active.

The weight ratio of the boron compound to the alkali metal silicate is preferably from 1:10 to 10:1, more preferably 1:2 to 2:1.

The aluminium when present during the generation of the structuring system may be present as an aluminium salt such as aluminium sulphate or as an alkali metal aluminate such as sodium aluminate, at a level of about 0.1% to 10% of the final product formulation, preferably at a level similar to that of boron compound. The phosphate may be present as various sodium phosphates such as orthophosphate, trisodium polyphosphate or tetra sodium pyrophosphate at a level of 0.1 to 10% by weight of the formulation. For the phosphate to be a part of the structuring system it is preferred that it is added in the acidic medium, prior to neutralisation of the active.

Boron compound:

The boron compound may be selected from one or more various hydrated or anhydrous borates (e.g. alkali metal borates) , boric oxides, boric acid, and other compounds such as the ones listed on page 366 of volume 4, Encyclopedia of Chemical Technology, edited by Kirk and Othmer. The preferred compound is boric acid.

Preferably, it is provided at from 0.1% to 10% by weight of the detergent product .

Alkaline materials:

The alkaline material used for neutralisation of the acid precursor detergent active is selected from a silicate, carbonate, hydroxide, alkaline aluminium-containing compounds such as aluminates phosphate and mixtures thereof, preferably in reaction (a) is at least equal to stoichiometric amount required for the neutralisation of the precursor of detergent active. For the purpose of the invention the especially preferred alkaline material used for the neutralisation of the detergent active is sodium silicate, sodium aluminate, sodium carbonate. The most preferred alkaline material is sodium silicate. The alkaline reactant used to react with the boron compound is an alkali metal silicate such as a sodium or potassium silicate, optionally in the presence of aluminium (e.g. provided as an aluminium compound such as an aluminium salt, e.g. the sulphate).

Process

The invention may be carried out in any suitable mixer, for example as conventionally used in soap/detergent manufacture and is preferably a high shear kneading mixer. The preferred mixers include ploughshare mixer, mixers with kneading members of Sigma type, ulti wiping overlap, single curve or double arm. The double arm kneading mixers can be of overlapping or tangential in design. Alternatively the invention can be carried out in a helical screw agitator vessel or multi head dosing pump/high shear mixer and spray drier combinations as in conventional processing.

To prepare the detergent bars according to the invention, the boron compound is reacted with an alkali metal salt of a silicate prior to or during or after the neutralisation of the acid precursor of the detergent active. Most preferably the boro-silicate structuring system is generated after the neutralisation of the acid precursor of the detergent active. Preferably, it is carried out using an alkaline material selected from a silicate, carbonate, hydroxide, aluminate or a phosphate or a mixture thereof. It is preferred to neutralise the precursor of the detergent active the alkaline material selected from a silicate, carbonate, aluminate or a phosphate or a mixture thereof and then form boro-silicate by a reaction of a boron compound with sodium silicate, optionally in the presence of one or more other materials as herein described.

Then the other ingredients such a builders, fillers, other detergent actives, minor ingredients etc. are added and mixed in any mixer mentioned above and is followed by conventional extrusion and bar stamping

Neutralisation is preferably effected by the known procedure of dry neutralisation, in which a carbonate is added to the acidic mixture. Neutralisation in other ways, such as with very concentrated sodium hydroxide solution or a mixture of sodium hydroxide and soda ash is also possible. It is also possible to neutralise the acid precursor of the detergent active using alkaline silicate or an aluminium-containing alkaline material such as sodium aluminate, e.g. with a solid content of 20 to 55% and preferably wherein, Al₂0 to Na₂0 is in a ratio of 0.5 to 1.55 by weight. However, the specified A1₂0₃ to Na₂0 ratio is preferably 1.0 to 1.5.

Detergent active

The detergent active used in the process may be soap or non- soap surfactants. 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 any accompanying cations .

The detergent active acid precursor is preferably selected from fatty acids, synthetic anionic surfactant acid precursors, and mixtures thereof.

The term "soap" as used herein, 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.

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

The soap may be obtained by saponifying a fat and/or fatty acid. The fats or oil generally used in soap manufacture may be such as tallow, tallow stearines, palm oil, palm stearines, soya bean oil, fish oil, castor 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. Naphthenic 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% palimitic acid, 23% stearic acid, 2% palmitoleic acid, 41.5% oleic acid, and 3% linoleic acid. Other similar mixtures, 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% C₁₀, 48% C_i2, 17% C₁₄, 8% Ci₆, 2% Ci₈, 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.

Fatty acid

A typical fatty acid blend consisted of 5 to 30% coconut fatty acids and 70 to 95% fatty acids ex hardened rice bran oil. Fatty acids derived from other suitable oils/fats such as groundnut, soybean, tallow, palm, palm kernel, etc. may also be used in other desired proportions.

Non-soap detergents

The composition according to the invention will preferably comprise detergent actives which are generally chosen from both anionic and nonionic detergent actives. The former are preferably incorporated in their entirety by the neutralised reaction (a) . However, at least some preneutralised material may be incorporated.

Suitable anionic detergent active compounds are water soluble salts or 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.

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 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, fort instance methyltetradecyl sulphoxide; fatty acid alkylolamides; alkylene oxide condensates of fatty acid alkylolamides and alkyl mercaptans .

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

Suitable cationic detergent actives that can be incorporated are alkyl substituted quaternary ammonium halide salts e.g. bis (hydrogenated tallow) dimethylammonium chlorides, cetyltrimethyl ammonium bromide, benzalkonium chlorides and dodecylmethylpolyoxyethylene ammonium chloride and amine and imidazoline salts for e.g. primary, secondary and tertiary amine hydrochlorides and imidazoline hydrochlorides .

Suitable amphoteric detergent-active compounds that optionally can be employed are derivatives of aliphatic secondary and tertiary amines containing an alkyl group of 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water- solubilising group, for instance sodium 3-dodecylamino- propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyltaurate.

Suitable zwitterionic detergent-active compounds that optionally can be employed are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having an aliphatic radical of from 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilising group, for instance 3- (N-N-dimethyl-N-hexadecylammonium) propane-1-sulphonate betaine, 3- (dodecylmethyl sulphonium) propane-1-sulphonate betaine and 3- (cetylmethylphosphonium) ethane sulphonate betaine.

Builders :

The optional 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 (preferably alkali metal citrates), sodium nitrilotriacetate (NTA) and combinations of these. Builders are suitably used in an amount ranging from 1 to 30% by wt. Optional Other Benefit agents:

Examples of moisturisers and humectants include polyols, glycerol, cetyl alcohol, carbopol 934, ethoxylated castor oil, paraffin oils, lanolin and its derivatives. Silicone compounds such as silicone surfactants like DC3225C (Dow Corning) and/or silicone emollients, silicone oil (DC-200 Ex-Dow Corning) may also be included. Sun-screens such as 4-tertiary butyl-4'- methoxy dibenzoylmethane (available under the trade name PARSOL 1789 from Givaudan) and/or 2-ethyl hexyl methoxy cinnamate (available under the trade name PARSOL MCX from Givaudan) or other UV-A and UV-B sun-screens. Water soluble glycols such as propylene glycol, ethylene glycol, glycerol, may be employed at levels up to 10%.

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 particular phase comprises a particulate structurant and/or abrasive which is insoluble in water. In the alternative; the abrasive may be soluble and present in such excess to any water present in the composition that the solubility of the abrasive in the aqueous phase is exceeded and consequently solid abrasive exists in the composition.

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, kaolin and silica.

Calcite, talc, kaolin, feldspar and dolomite and mixtures thereof are particularly preferred due to their low cost and colour.

The inorganic particulate structurants such as alumino silicate may be generated in situ using aluminium sulphate and sodium silicate in the formulation. It is also possible to incorporate readily available sodium alumino silicate into the formulation.

Other additives:

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

Minor additives:

In step (b) of the process minor and conventional ingredients preferably selected from enzymes, antiredeposition agents, fluroescers, 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%.

EXAMPLES : The following are non-limiting examples are showing comparative results of compositions prepared by the present invention and control compositions prepared by methods not in accordance with the present invention.

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. Other ingredients such as 720 gms of STPP builder, approximately 3 kg of fillers, water and minor ingredients were then added. These were thoroughly mixed and plodded in a conventional manner (Example 1) .

b. Process for generation of boro-silicate structured bars:

Other batches were prepared similarly as in point (a) above with the addition of 120 gms of boric acid (Example 2) ; 120 gms of silicate (Example 3) ; 60 gms of Boric acid and 60 gms of silicate (Example 4); 120gms of Boric acid and 120 gms of silicate (Example 5) at a stage after adding approximately half the filler materials into the batch.

c. Process of generation of boro-silicate and postdosing it (Example 6) :

A small adjunct of borosilicate was prepared by reacting equal amounts of boric acid and alkaline silicate in a small container in the lab. 240 gms of this borosilicate adjunct were added to a 6 kg batch prepared in the same manner as above in point (a) , at a stage after adding approximately half the filler materials into the batch. This sample represents the bar which has similar amount of preformed borosilicate postdosed into the batch.

d. Process for generation of alumino-silicate (Example 7):

A 6 kg batch was prepared in the same manner as in point (a) above with the addition of 150 gms of aluminum sulphate and 90 gms of silicate at a stage after adding approximately half the filler materials into the batch. In a similar manner, a low AD bar was processed (example 9) .

e. Process for generation of boro-alumino-silicate bar (Example 8) :

A 6 kg batch was prepared in the same manner as in point (a) above with the addition of 150 gms of aluminum sulphate, 120 gms of boric acid and 210 gms of silicate at a stage after adding approximately half the filler materials into the batch. In a similar manner, a low AD bar was also processed (example 10) .

f . Process for generation of bars structured with aluminosilicate (example 11) , boro- alumino-silicate (example 12) and boro-alumino-phospho-silicate (example 13) bars using silicate neutralization of AD:

A batch of 6kg detergent bar was prepared by taking 1.2 kg of linear alkyl benzene sulphonic acid in a sigma mixer and neutralising it with 630 gms of alkaline sodium silicate. Other ingredients such as 720 gms of STPP builder, approximately 3 kg of fillers, water and minor ingredients were then added. These were thoroughly mixed and plodded in a conventional manner. Structuring system was generated in-situ at a stage after adding approximately half the filler materials into the batch. The structuring systems examined were (I) 240 gms of sodium aluminosilicate (example 11) , (II) 240 gms of sodium aluminosilicate plus 240 gms of borosilicate (example

12) and (III) 240 gms of sodium aluminosilicate plus 240 gms of borosilicate with half the phosphate added in acidic medium to generate boro-alumin-phospho-silicate (example 13) .

g. Process for making high active soap bars with/without borosilicate structuring:

In a batch of 6 kg, 5.25 kgs of soap noodles containing approximately 30% moisture content were mixed with 6 gms of soda ash, 6 gms of sodium sulphite and 60 gms of alkaline silicate in a sigma mixer. The dough was then plodded using a single screw extruder (example 14) . In a similar manner, a borosilicate structured soap bar was prepared by mixing additional 120 gms of boric acid and 120 gms of silicate (example 15) .

The samples were tested for various physical and in-use properties by the following procedure.

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.

Bar hardness:

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 weigh of 50 gms for 20 second on top of a flat surface of the bar. The depth of penetration is reported in mm.

Density of the bar:

The density of the bar is measured by the standard method and calculated using the formula

Density (grams/cm³) = Weight of bar (grams)

Volume in cm³

Mush determination:

The Mush refers to the paste like layer formed on the NSD 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. To measure mush the following simple steps were followed. 1) Remove the surface unevenness such as flutes / logo etc, by planing the bar using a carpenter's plane.

2) Weight the planed bar (Wng)

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

4) At the end of two hours, 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) .

Table 1

The data presented in Table 1 show that when the bar is formulated with the conventional material then the bar hardness at a given level of water is much lower. The bars prepared according to the invention wherein the structuring system is generated in-situ, give much harder bars at the same level of water in the bar, and therefore, can provide better structuring of water or other liquid benefit agents. They have good physical properties and also retain higher % of water during storage as compared to a mere admixture of the ingredients, while exhibiting superior in use properties. T a b l e 2

It can be seen from Table 2 that, adding in-situ generate_d boro-silicate to a bar otherwise structured with sodium aluminosilicate, results in ability to structure more than twice the amount of water with significantly reduced mush an_d density, while maintaining comparable penetration and water retention. Table 3

Table 3 above shows that at low active levels also, addition of borosilicate structuring to a bar leads to a substantially harder bar with better water retention at a given water level.

Table 4

* added before neutralisation of the detergent active

Table 4 clearly shows that without the help of boro-silicate, the conventional bars structured with only sodium aluminosilicate cannot be processed with very high moisture levels, whereas it is possible to boro-alumino-silicate system a,s well as with boro-alumino-phospho-silicate system to process bars with moisture levels greater than 20% having acceptable hardness.

Table 5

Table 5 above shows the benefit of boro-silicate structuring for a high active soap bar both in terms of hardness as well as water retention at a given high moisture level.

Claims

1. A process for preparing a non-granular solid detergent product comprising :-

the process comprising the steps of

(b) providing the structuring system in si tu by reacting a boron compound with an alkaline reactant comprising an alkali metal salt of silicate optionally in presence of aluminium and/or phosphate prior to, during or after neutralisation of the acid precursor of the detergent active;

(c) adding if desired, any other ingredients; and

(d) converting the resultant mass into the desired product form.

2. A process according to claim 1, wherein step (b) is effected after step (a) .

3. A process according to either preceding claim, wherein the weight ratio of the boron compound of the alkali metal silicate is from 1:10 to 10:1, preferably from 1:2 to 2:1.

4. A process according to any preceding claim, wherein the boron compound is provided in an amount from 0.1% to 10% by weight of the detergent product.

5. A process according to any preceding claim, wherein the boron compound is selected from hydrated borates, anhydrous borates, boric oxides and boric acid.

6. A process according to any preceding claim, wherein the alkaline reactant is provided in an amount from 0.1% to 10% by weight of the detergent product.

7. A process according to any preceding claim, wherein the detergent active acid precursor is neutralised with an alkaline material which comprises a sodium aluminate.

8. A process according to claim 7, wherein the sodium aluminate has a weight ratio of A1₂0₃ to Na₂0 of from 0.5 to 1.55, preferably from 1.0 to 1.5.

9. A process according to any preceding claim, wherein the detergent product comprises from 1% to 30%. by weight of a detergency builder selected from alkali metal aluminosilicates, alkali metal carbonates, sodium tripolyphosphate, tetrasodium pyrophosphate, citrates, sodium nitrilotriacetate and mixtures thereof.