EP4341366A1

EP4341366A1 - Process for preparing a spray dried detergent particle

Info

Publication number: EP4341366A1
Application number: EP22729207.5A
Authority: EP
Inventors: Abraham Chacko; Girish Kumar; Sharavan KUMAR; Kunal Shankar PAWAR; Nadeem Shaikh
Original assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Current assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Priority date: 2021-05-19
Filing date: 2022-05-17
Publication date: 2024-03-27
Also published as: WO2022243264A1; BR112023024027A2; CN117321182A

Abstract

The present invention relates to a process for preparing of a particulate, free flowing detergent particle by a slurry making and spray drying technique. In particular it relates to the process for preparing a slurry with lower alkalinity for the production of spray dried laundry detergent particle. Accordingly, it is one object of this invention to provide a process for preparing a spray dried detergent particle where the spray dried particle has excellent powder properties and provides a wash liquor with lower alkalinity and provides good stain removal performance without being harsh on hands and fabrics.. The present inventors have found that a spray-dried detergent particle having a combination of silicate salt and/or disilicate salt of alkaline earth metal, alkali metal silicate and low levels of carbonate salt prepared by a process where the silicate and/or disilicate salt of alkaline earth metal is formed in-situ provides for excellent powder properties with extended shelf life without getting caked and the spray-dried particles provides desired pH in wash solution to provide for good stain removal performance without being harsh on the hands or the fabrics.

Description

Process for preparing a spray dried detergent particle

Field of the invention

The present invention relates to a process for preparing a particulate, free flowing detergent particle by a slurry making and spray drying technique. The spray-dried particle is suitable for use as a solid laundry detergent composition, or for incorporation into a solid laundry detergent composition.

Background of the invention

Typically, granular laundry detergent composition is prepared by spray-drying. In spray drying process the detergent components, such as surfactants and builders are mixed with around 20% to 50% by weight water to form an aqueous slurry, the aqueous slurry is maintained at temperatures ranging from 60°C to 85°C and then spray-dried in a spray-drying tower.

Many consumers launder fabrics by hand, in addition to good cleaning performance these consumers desire for a laundry composition that provide mildness to the skin and a desirable feel while washing. In the past, such milder compositions have been formulated by lowering the alkalinity of the composition. This necessitates significantly reducing or completely removing the alkaline ingredients such as sodium carbonate and sodium silicate. Yet another advantage of reducing carbonate-based builder is the reduction in ash build-up on fabrics and machine parts under medium and hard water conditions.

It is well-known that, within limits, detergency tends to improve as pH is increased. Hence it may be desired to maintain the pH of the finished detergent composition relatively unchanged. Carbonate salts and silicate salts provide a wash liquor with desired pH of about 10.5. In addition to influencing the pH of the wash liquor, carbonate salt and silicate salt also function as effective builders to sequester calcium and magnesium ions present in water. Besides these benefits, presence of carbonate salt provides good physical attributes to the spray-dried detergent particle. Such physical characteristics include lower caking tendency and good flowability of the powder during extended shelf storage period. Any reduction in the levels of carbonate salt will directly affect the abovementioned properties. Silicate salt which is typically a sodium salt of silicate is generally considered a critical ingredient in spray dried particulate detergent compositions and serves to provide stability and integrity to the detergent particles formed during the spray-drying operation. Attempts at reducing or eliminating sodium silicate caused deterioration of flow properties and the particles were prone to caking. Lowering the silicate levels also impact the viscosity and flow behaviour of the slurry and it was observed that the slurry was difficult to pump due to gelation of slurry.

The present inventors have further observed that a spray dried detergent particle prepared from a slurry with sodium carbonate levels below 8 wt.% and silicate salt (sodium silicate) levels below 7 wt.% may form into spray-dried detergent particle with the freshly prepared spray dried detergent particle initially having good powder properties, but under storage conditions these spray-dried particle exhibit severe caking tendency.

In a carbonate-built spray-dried detergent particle, the choice of fillers play an important role in determining the powder properties. Inorganic material like sodium sulphate contribute towards powder properties by forming burkeite, however, in a low carbonate formulation, sodium sulphate may not be used at very higher levels due to cost considerations. In these formulations, sodium carbonate is replaced with fillers such as sodium chloride. However, replacing sodium carbonate with fillers like sodium chloride, calcium carbonate, calcium magnesium carbonate (dolomite) brings in additional challenge, as these fillers tend to cake on storage due to their hygroscopic nature.

It is thus a challenge to provide a spray dried detergent particle with good powder properties such as free-flowability and extended storage life while providing compositions which are milder on hand and fabrics without adversely affecting the cleaning performance. US3849346 (Lion, 1974) discloses a process for preparing a granular detergent composition containing particles of relatively high mechanical strength and which are essentially non-caking. The process includes the step of spray-drying a slurry comprising anionic surface-active agent, sodium tripolyphosphate, sodium silicate and magnesium sulphate to form in-situ magnesium silicate and magnesium phosphate.

More recently, WO 2006/029676 A1 (Unilever) discloses a laundry detergent composition with a soluble alkali metal silicate and 0.01 wt.% to 25 wt.% alkaline earth silicate seeds. The alkaline earth silicate seeds are formed in-situ by reaction of sodium silicate and soluble alkaline earth metal salt in presence of anionic surfactant during the laundry detergent base powder processing.

EP 2138565 A1 (Procter & Gamble, 2009) discloses a spray-drying process where an alkaline slurry is formed in a mixer, and a portion of the acid anionic detersive surfactant precursor is contacted with the alkaline slurry after the mixer and before the spray pressure nozzle to form a mixture, the mixture is then sprayed through the spray pressure nozzle into the spray-drying tower to form a spray-dried powder.

US 3975280 A (Hachmann Klaus et. al.,1976) discloses a washing composition with high stability on storage and where the embedded active agent des not lose its activity even on prolonged storage.

US 4139486 A (Bailey John et. al. , 1979) discloses a detergent composition having superior whiteness maintenance and lower undesirable residual deposits on the fabrics which composition includes orthophosphate and pyrophosphate together as builder along with the addition of magnesium silicate.

WO 2005/037712 A1 (Osinga Theo Jan, 2005) discloses a detergent composition having a soluble carbonate salt in combination with a soluble alkali metal silicate. It discloses a method of preparing amorphous particles of silicate-based calcium salt or silicate based magnesium salt having the step of mixing an aqueous solution of a calcium salt or magnesium salt with a soluble alkali metal silicate salt and a soluble carbonate salt.

Thus, there is a need to provide a granular laundry detergent composition which is less harsh on the hands of the user and on fabrics without adversely affecting the cleaning performance and the free-flowing powder properties over extended storage life.

It is thus an object of the present invention to provide a process for preparing a a spray-dried detergent particle which provides for incorporating a sodium carbonate builder and silicate salt at levels which provides good cleaning performance and good powder properties.

It is yet another object of the present invention to provide a process for preparing a detergent slurry which upon spray drying provides for a spray-dried detergent particle having lower reserve alkalinity and a desired pH for providing good cleaning performance.

It is a further object of this invention to provide a process for preparing a spray-dried particles characterized by a relatively good powder structure and which do not have an increased tendency towards caking.

Summary of the invention

The present inventors have found that a spray dried detergent particle having an in-situ formed silicate and/or a disilicate a salt of alkaline earth metal, formed by reacting an alkali metal silicate with an alkaline earth metal salt, along with an alkali metal silicate salt and low levels of sodium carbonate provides for excellent powder properties and extended shelf life without getting caked when the spray-dried detergent particle has a filler in a weight ratio between sodium carbonate to filler in the range of 1:1.4 to 1:20. It is also surprisingly found that the spray-dried particle provides desired pH in wash solution required for good stain removal performance without being harsh on the hands or the fabrics. The spray dried detergent particle according to the present invention incorporates optimum amounts of alkaline builders, particularly alkali metal silicates and alkali metal carbonates. The spray-dried detergent particle has good powder properties and better free-flowing properties even after extended storage period.

Further the spray-dried detergent particle has lowered reserve alkalinity levels while maintaining the pH levels required for optimum cleaning performance thereby providing better fabric care benefits.

As used herein the term “reserve alkalinity” refers to the grams of NaOH/100 grams when titrated till 10 pH with HaSCU.The alkali reserve is determined by an acid/base titration of a solution with 0.5 mol/l sulphuric acid till pH of 10.00. The reserve alkalinity of the spray-dried detergent particle to pH 10 is from 1.5 to 5 grams NaOH/100g. Preferably less than 5.0 grams NaOH/100g, preferably less than 4 grams NaOH/100g, still preferably 3.5 grams NaOH/100g, further preferably less than 2 grams NaOH/100g. According to a first aspect of the present invention, disclosed is a process for preparing a spray dried detergent particle, said process comprising the steps of:

(i) contacting an alkaline earth metal salt with an alkali metal silicate salt in an aqueous mixture comprising a detersive surfactant, wherein the alkaline earth metal salt reacts with the alkali metal silicate salt to form in-situ silicate salt and/or disilicate salt of alkaline earth metal;

(ii) adding 3 wt.% to 13 wt.% carbonate salt and a filler selected from the group consisting of alkali metal chloride, alkaline earth metal carbonate or mixtures thereof to the aqueous mixture to form an aqueous slurry, wherein the aqueous slurry comprises alkali metal silicate, in-situ formed silicate salt and/or disilicate salt of alkaline earth metal, filler and sodium carbonate; (iii) spray-drying said aqueous slurry to form said spray dried detergent particle wherein the weight ratio of the filler and the carbonate salt in the aqueous slurry ranges from 1 : 1.4 to 1 :20.

Detailed description of the invention

Process of making a spray-dried detergent particle

According to a first aspect disclosed is a process for preparing a spray-dried detergent particle comprising the steps as described herein below.

Step (D: Contacting an alkaline earth metal salt with an alkali metal silicate According to the first aspect of the present invention disclosed is a process of contacting an alkaline earth metal salt with an alkali metal silicate in an aqueous mixture. Preferably the aqueous mixture comprises a detersive surfactant.

Alkaline earth metal salt:

The alkaline earth metal salt is preferably a magnesium or a calcium salt or mixtures thereof. The alkaline earth metal salt may be preferably selected from calcium sulphate, magnesium sulphate, calcium chloride, magnesium chloride or mixtures thereof. Preferably the alkali earth metal is a magnesium salt selected from magnesium sulphate, magnesium chloride or mixtures thereof and still preferably the alkaline earth metal salt is magnesium sulphate.

Alkali metal silicate salt:

The process according to the present invention includes addition of an alkali metal silicate to the aqueous mixture. Preferably the alkali metal silicate is a soluble silicate. Soluble silicates are common ingredients in the laundry detergent compositions. Some commercial grades of silicates may contain a trace level of alkaline earth metal silicate, as contamination. The composition of trace materials in the water used for making an aqueous mixture preferably having detersive surfactant may also contribute to the alkaline earth metal. However, the amount of amorphous material introduced through this impurity route will be low. The spray dried detergent particle prepared according to the process of the first aspect of the present invention preferably includes from 0.1 wt.% to 2.5 wt.% amorphous alkaline earth metal silicate prepared in-situ.

The alkali metal silicate salt preferably has a weight ratio of SiC^I hO where M is an alkali metal, within the range of 1.6 to 3.3 more preferably 1.6 to 2.4, and most preferably 2.0 to 2.85. The alkali metal silicate salt employed is in the form of an aqueous solution, generally having 30 wt.% to 45 wt.% solid content.

Preferably the alkali metal silicate salt may be selected from the group consisting of sodium silicate, potassium silicate, sodium-potassium double silicate or mixtures thereof. Preferably the alkali metal silicate salt is water-soluble. Preferably the alkali metal silicate salt employed is sodium silicate. Preferably the sodium silicate has a weight ratio, SiC>₂:Na₂0 within the range of 1.6 to 3.3 more preferably 1.6 to 2.4, and most preferably 2.0 to 2.85. Preferably the amount of alkali metal silicate present in the aqueous mixture is in stoichiometric excess of the amount required for reacting with alkaline earth metal salt. Preferably the amount of alkali metal silicate present in the aqueous mixture is such that the spray dried detergent particle formed preferably comprises from 5 wt.% to 17 wt.% alkali metal silicate salt. The amount of alkali metal silicate added to the aqueous mixture is preferably from 8 wt.% to 30 wt.% by weight of the aqueous mixture.

Alternately, the excess amount of alkali metal silicate (after the formation of the in-situ alkaline earth metal silicate) may be added into the slurry at any stage before spraydrying, more preferably after the addition of filler. Preferably the weight ratio of the alkali metal silicate to alkaline earth metal salt added the aqueous mixture is in the range from 260:1 to 5:1, preferably 24:1 to 12:1.

Aqueous mixture:

Preferably the aqueous mixture comprises a detersive surfactant. Preferably the detersive surfactant present in the aqueous mixture is an anionic surfactant. Preferably all of the detersive surfactant is added to the aqueous mixture before the in-situ formation of silicate salt or disilicate salt of alkaline earth metal. More preferably all of the anionic detersive surfactant is added to the aqueous mixture before the in-situ formation of silicate salt or disilicate salt of alkaline earth metal, preferably the anionic surfactant is linear alkyl benzene sulphonate. Detersive surfactant: The aqueous mixture includes a detersive surfactant. The detersive surfactant is preferably an anionic surfactant. The detersive anionic surfactant is either pre-neutralized and added into the aqueous mixture or a liquid acid form of the anionic surfactant is added to the aqueous mixture and neutralized in-situ. Alternately, the acid form of the anionic surfactant may be partly neutralized and thereafter added into the aqueous mixture such that the remaining un-neutralized part of the liquid acid form of the anionic surfactant is neutralized in-situ in the aqueous mixture. Pre-neutralized surfactant is commercially available in solid form or in the form of paste. Preferably the detersive surfactant is added to the aqueous mixture before addition of the alkaline earth metal salt. In some embodiments the detersive surfactant is added to the aqueous mixture after addition of the alkaline earth metal salt or along with the alkaline earth metal salt.

When the detersive surfactant is added into the aqueous mixture in the form of a partly neutralized surfactant, the partly neutralized anionic surfactant is preferably prepared by a neutralization process which involves the step of mixing a liquid acid form of the anionic surfactant and a neutralizing agent to form a partially neutralized solution; preferably the neutralizing agent is an alkali metal hydroxide, more preferably sodium hydroxide, wherein the amount of alkali metal hydroxide neutralizing agent is sufficient to react with a portion of liquid acid anionic surfactant precursor to form in-situ anionic surfactant salt. The neutralized anionic surfactant formed by neutralizing the acid form with the alkali metal hydroxide neutralizing agent preferably contributes from 28 parts to 98 parts of the total anionic surfactant by weight present in the spray-dried particle. On addition of alkali metal silicate salt to the partly neutralized anionic surfactant in the aqueous mixture, the remaining unreacted acid form of the anionic surfactant reacts with the alkali metal silicate salt to form fully neutralized salt form of the anionic surfactant. In one embodiment of the present invention a fully neutralized anionic surfactant is added to the aqueous mixture. In this embodiment the liquid acid anionic surfactant precursor is reacted with an alkali metal hydroxide to form fully neutralized anionic surfactant salt before addition to the aqueous mixture. More preferably the liquid acid precursor of the anionic surfactant is partly or fully neutralized in-situ. It is most preferred that the detersive surfactant is present when the alkaline earth metal salt is contacted with the alkali metal silicate salt. The order of addition is to contact the pre-neutralized detersive surfactant or the acid detersive surfactant precursor with water followed by contacting with the alkali metal silicate and then adding the alkaline earth metal salt. Preferably the part or full neutralization may be carried out in the same vessel by contacting the acid precursor form of the anionic surfactant with an aqueous solution of neutralizing agent (alkali metal hydroxide) to form the neutralized anionic surfactant salt. Alternately in the process of the present invention, the order of addition may be reversed wherein the step involves adding alkaline earth metal salt to the aqueous mixture followed by the alkali metal silicate salt. Suitable detersive surfactants include anionic detersive surfactants, non-ionic detersive surfactant, cationic detersive surfactants, zwitterionic detersive surfactants and amphoteric detersive surfactants. Suitable detersive surfactants may be linear or branched, substituted or un-substituted, and may be derived from sources well known to the person skilled in the art.

Preferably the detersive surfactant is an anionic surfactant. Suitable anionic detersive surfactants include sulphonate and sulphate surfactants. Suitable sulphonate surfactants include methyl ester sulphonate, alpha olefin sulphonate, alkyl benzene sulphonate, especially alkyl benzene sulphonate, preferably Cio to C13 alkyl benzene sulphonate. A preferred detersive anionic surfactant is linear alkyl benzene sulphonate, where the alkyl chain has 5 to 20 carbon atoms, more preferably the linear alkylbenzene sulphonate surfactant has a C12 to C18 alkyl group. Suitable alkyl benzene sulphonate (LAS) is obtainable, preferably obtained, by sulphonating commercially available linear alkyl benzene (LAB); suitable LAB includes low 2-phenyl LAB, other suitable LAB includes high 2-phenyl LAB, such as those supplied by Sasol under the tradename Hyblene®. Suitable sulphate surfactants include alkyl sulphate, preferably Cs to Ci8 alkyl sulphate, or predominantly C12 to Cis alkyl sulphate. One or more anionic surfactant may be present in the spray-dried detergent particle.

A preferred sulphate detersive surfactant is alkyl alkoxylated sulphate, preferably alkyl ethoxylated sulphate, preferably a Cs to Cis alkyl alkoxylated sulphate, preferably a Cs to Cis alkyl ethoxylated sulphate, preferably the alkyl alkoxylated sulphate has an average degree of alkoxylation of from 0.5 to 20, preferably from 0.5 to 10, preferably the alkyl alkoxylated sulphate is a Cs to Cis alkyl ethoxylated sulphate having an average degree of ethoxylation of from 0.5 to 10, preferably from 0.5 to 5, more preferably from 0.5 to 3 and most preferably from 0.5 to 1.5. The alkyl sulphate, alkyl alkoxylated sulphate and alkyl benzene sulphonate may be linear or branched, substituted or un-substituted and may be derived from petrochemical material or biomaterial. Other suitable anionic detersive surfactants include, soaps, alkyl ether carboxylates. Suitable anionic detersive surfactants may be in salt form, suitable counter-ions include sodium, calcium, magnesium, amino alcohols, and any combinations thereof. A preferred counterion is sodium. Preferably the detersive surfactant is anionic surfactant selected from alkyl benzene sulphonate, primary alkyl sulphate, secondary alkyl sulphate, alkyl ether sulphate or mixtures thereof, still preferably selected from linear alkyl benzene sulphonate, alkyl ether sulphate or mixtures thereof, still preferably selected from LAS, SLES or mixtures thereof.

Suitable non-ionic detersive surfactants are selected from the group consisting of: Cs to C1₈ alkyl ethoxylates, such as, NEODOL® non-ionic surfactants from Shell; C₆ to C12 alkyl phenol alkoxylates wherein preferably the alkoxylate units are ethyleneoxy units, propyleneoxy units or a mixture thereof; C12 to Cis alcohol and Cs to C12 alkyl phenol condensates with ethylene oxide/propylene oxide block polymers such as Pluronic® from BASF; alkyl polysaccharides, preferably alkyl polyglycosides; methyl ester ethoxylates; polyhydroxy fatty acid amides; ether capped poly(oxyalkylated) alcohol surfactants and mixtures thereof.

Suitable non-ionic detersive surfactants are alkyl polyglucoside and/or an alkyl alkoxylated alcohol. Suitable non-ionic detersive surfactants include alkyl alkoxylated alcohols, preferably Cs to Cis alkyl alkoxylated alcohol, preferably a Cs to Cis alkyl ethoxylated alcohol, preferably the alkyl alkoxylated alcohol has an average degree of alkoxylation of from 1 to 50, preferably from 1 to 30, or from 1 to 20, or from 1 to 10, preferably the alkyl alkoxylated alcohol is a C₈ to Cis alkyl ethoxylated alcohol having an average degree of ethoxylation of from 1 to 10, preferably from 1 to 7, more preferably from 1 to 5 and most preferably from 3 to 7. The alkyl alkoxylated alcohol can be linear or branched and substituted or un-substituted. Suitable nonionic detersive surfactants include secondary alcohol-based detersive surfactants. Zwitterionic surfactant: Suitable zwitterionic detersive surfactants include amine oxides and/or betaines.

One or more detersive surfactant may be present in the spray-dried particle according to the present invention. The surfactants are preferably those which are thermally stable during processing conditions of a tower with inlet air temperature ranging from 250°C to 500°C and those which are chemically stable at the pH conditions of the spray-drying slurry. Non-limiting examples of the anionic surfactant includes the ones mentioned above. Preferably the aqueous slurry includes LAS. In some embodiments the detersive surfactant present in the aqueous slurry is a combination of LAS and alkyl ether sulphate, still preferably a combination of LAS and SLES (1 EO to 3EO). The aqueous slurry may also preferably include a combination of anionic surfactant and non-ionic surfactant as the cosurfactant.

Step (ii): Forming in-situ silicate salt and/or disilicate salt of alkaline earth metal The alkali metal silicate reacts with the alkaline earth metal salt to form in-situ silicate or disilicate salt of alkaline earth metal or mixtures thereof. Preferably the alkaline earth metal salt present in the reaction is magnesium sulphate or magnesium chloride, more preferably magnesium sulphate. Preferably the magnesium sulphate reacts with alkali metal silicate to form in-situ magnesium silicate or magnesium disilicate or mixtures thereof. Preferably the alkali metal silicate is sodium silicate. Preferably the reaction of the alkali metal silicate with the alkaline earth metal salt is carried out by heating the aqueous mixture in a mixer at a temperature of 20°C to 80°C, more preferably from 70°C to 80°C. The reaction is carried out for a duration of 0.5 minutes to 30 minutes by continuously stirring the aqueous mixture in the slurry handling system.

In addition to the in-situ formed silicate salt or disilicate salt of alkaline earth metal or mixtures thereof, the reaction may also produce hydroxide of alkaline earth metal and some amount of the alkaline earth metal salt may remain unreacted. Such as the aqueous may include an amount of unreacted magnesium sulphate. After the reaction, the aqueous mixture includes the in-situ formed silicate salt or disilicate salt of alkaline earth metal or mixtures thereof, alkali metal silicate salt, preferably detersive surfactant and water. At this stage after the reaction between the alkaline earth metal salt and the alkali metal silicate, the resulting aqueous mixture preferably includes:

(i) 0.1 wt.% to 4.5 wt.% in-situ formed silicate salt or disilicate salt of alkaline earth metal or mixtures thereof;

(ii) 8 wt.% to 30 wt.% alkali metal silicate salt; (iii) preferably 11 wt.% to 31 wt.% detersive surfactant; and,

(iv) from 50 wt.% to 60 wt.% water.

Preferably the silicate salt or disilicate salt of the alkaline earth metal is 50% amorphous, more preferably 60% amorphous, still preferably 80%, further preferably 90% amorphous. In a highly preferred embodiment, all of the in-situ formed silicate salt and/or disilicate salt of alkaline earth metal salt is amorphous.

In addition to this, the aqueous mixture may optionally include hydroxide of alkaline earth metal and some amount of unreacted alkaline earth metal salt. Preferably the detersive surfactant is anionic surfactant.

Step (iii): Adding sodium carbonate to the aqueous mixture to form an aqueous slurry The next step involves adding sodium carbonate to form an aqueous slurry. In the process according to the first aspect, 3 wt.% to 13 wt.% of sodium carbonate is added to the aqueous mixture obtained in step (ii) to form an aqueous slurry. In addition to the sodium carbonate a filler selected from the group consisting of alkali metal chloride, alkaline earth alkaline earth metal carbonate or mixtures thereof is also added to the aqueous mixture to form an aqueous slurry. Preferably other minor laundry ingredients may be added to the aqueous slurry.

Preferred alkali carbonate salt which may be added along with sodium carbonate includes potassium carbonate. It is further preferred that when potassium carbonate is added, sodium carbonate makes up at least 75 wt.%, more preferably at least 85 wt.% and even more preferably at least 90 wt.% of the total weight of the carbonate salt.

Preferably other non-carbonate builder may be included. Typically, inorganic builders include crystalline and amorphous aluminosilicates for example, zeolites as disclosed in GB 1 473201 (Henkel), amorphous aluminosilicates as disclosed in GB 1 473202 (Henkel) and mixed crystalline/amorphous aluminosilicates as disclosed in GB 1 470 250 (Procter & Gamble); sodium alkaline silicates and layered silicates as disclosed in EP 164514 B (Hoechst).

Inorganic phosphate builders for example sodium orthophosphate, pyrophosphate and tripolyphosphate are preferably present at relatively low levels, for example less than 5 wt.%, still preferably less than 3 wt.%, further preferably less than 1 wt.%. Preferably the aqueous slurry includes 0 wt.% phosphate builders. Most preferably the spray-dried detergent particle prepared from the process according to the first aspect of the present invention is substantially free of inorganic phosphate builders. By substantially free it is meant that the spray dried particle prepared according to the process of the first aspect does not include any deliberately added inorganic phosphate builder. Zeolite builders used in most commercial particulate detergent compositions is zeolite A. Advantageously, aluminium zeolite P (zeolite MAP) described and claimed in EP 384070A (Unilever) may be used. Zeolite MAP is an alkali metal aluminosilicate of the P type having a silicon to aluminium ratio not exceeding 1.33, preferably not exceeding 1.15, and more preferably not exceeding 1.07. Zeolite builders are preferably present at relatively low levels, for example less than 5 wt.%, still preferably less than 3 wt.%, further preferably less than 1 wt.% in the aqueous slurry. Preferably the aqueous slurry includes 0 wt.% zeolite builder. Most preferably the spray-dried detergent particle prepared from the process according to the first aspect of the present invention is substantially free of zeolite builders. By “substantially free” it is meant that the spray dried particle prepared according to the process of the first aspect does not include any deliberately added inorganic zeolite builder.

Optionally the aqueous slurry may include an organic builder. Non-limiting examples of organic builder include polycarboxylate polymers such as polyacrylates, acrylic/maleic copolymers, and acrylic phosphinates; monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono-, di-and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, alkyl- and alkenylmalonates and succinates; and sulphonated fatty acid salts. Preferably the organic builder is selected from monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono-, di-and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, alkyl- and alkenylmalonates and succinates, more preferably alkali metal citrate, most preferably it is sodium citrate. Organic builders may be used in minor amounts as supplement to carbonate salt builder.

Preferred supplementary organic builders are citrates, suitably used in amounts of from 0.1 wt.% to 30 wt.%, preferably from 10 wt.% to 25 wt.%; and acrylic polymers, more especially acrylic/maleic copolymers, suitably used in amounts of from 0.5 wt.% to 15 wt.%, preferably from 1 wt.% to 10 wt.%.

Powder flow properties may be improved by the incorporation of a small amount of a powder structurant, for example, a fatty acid (or fatty acid soap), a sugar, an acrylate or acrylate/maleate polymer. One preferred powder structurant is fatty acid soap, suitably present in an amount of from 1 wt.% to 5 wt.%. Further optional ingredients may be added to the aqueous slurry which includes but are not limited to, any one or more of the following: soap, sequestrants, calcium chloride, sodium bicarbonate, other inorganic salts, fluorescers, foam controllers, foam boosters, dyes, anti-redeposition agents, colourants, shading dyes and combinations thereof. A filler selected from alkali metal chloride, alkaline earth metal carbonate or mixtures thereof is added to the aqueous slurry before spray-drying. The filler may be added either before the addition of the sodium carbonate or after the addition of the sodium carbonate to the aqueous mixture to form the aqueous slurry. Preferably the filler is added after the addition of the sodium carbonate. Preferably the alkali metal chloride filler is sodium chloride, preferably the alkaline earth metal filler is selected from the group consisting of calcium carbonate (calcite), magnesium carbonate, calcium magnesium carbonate (dolomite) or mixtures thereof. The filler acts as a balancing ingredient and is preferably sodium chloride. The amount of alkali metal silicate remaining in the aqueous slurry after forming the in-situ silicate, disilicate of alkali earth metal is from 5 wt.% to 14 wt.% of the aqueous slurry. It was also found that when the filler is sodium chloride and is used along with the carbonate in the weight ratio ranges according to the present invention, the spray-dried detergent particle has improved solubility even at lower wash temperatures. The spray-dried detergent particle having the sodium chloride were readily soluble and left lesser residues which is an added advantage as there is lesser residue left in the detergent dispenser of the washing machine and the spray-dried detergent particle also provides good wash performance and minimizes wastage. The aqueous slurry obtainable according to the process of the first aspect preferably comprises:

(i) 5 wt.% to 20 wt.% detersive surfactant;

(ii) 0.05 wt.% to 2 wt.% silicate salt, disilicate salt of alkaline earth metal or mixtures thereof; (iii) 3 wt.% to 13 wt.% sodium carbonate;

(iv) 5 wt.% to 14 wt.% alkali metal silicate;

(v) 25 wt.% to 40 wt.% water; (vi) a filler selected from the group consisting of alkali metal chloride, alkaline earth metal carbonate or mixtures thereof, preferably the filler is present in an amount ranging from 22 wt.% to 50 wt.%, more preferably the filler is selected from the group consisting of sodium chloride, calcium carbonate (calcite), calcium magnesium carbonate (dolomite), magnesium carbonate or mixtures thereof;

(vii) optionally, from 0 wt.% to 2 wt.% hydroxide salt of alkaline earth metal;

(viii) optionally, from 0 wt.% to 2 wt.% unreacted alkaline earth metal salt;

(ix) optionally, from 0 wt.% to 3 wt.% polymer;

(x) optionally organic builder, preferably 0 to 10 wt.% citrate salt;

(xi) optionally optical brighteners which is preferably selected from fluorescers, colourants, shading dye, pigments;

(xii) optionally antifoams, preferably a silicone oil.

Preferably the detersive surfactant present in the aqueous slurry is an anionic surfactant. It may also be a mixture of anionic surfactant and nonionic surfactant where the mixture has a higher content of anionic surfactant. Preferably the polymer is selected from a cleaning polymer, soil releasing polymer, care polymer, antiredeposition polymer or mixtures thereof. Step (iv): Spray drying the aqueous slurry to form the spray-dried particle

In the next step, the aqueous slurry is spray dried to form a spray-dried particle.

The spray-drying is carried out using any of the conventional spray drying system known in the art. Preferably in the spray drying system the aqueous slurry is transferred through a pipe system to a pump system consisting of one or more pump and then further to a spray nozzle through which the slurry is released under pressure into a drying tower.

A typical spray-drying process involves the step of transferring the aqueous slurry through a pipe system leading to a first pump and then through a second pump and from a second pump to a plurality of spray nozzles. The first pump is typically a low- pressure pump, such as a pump that can generate a pressure of from 1x10⁵ Nnr² to 1x10⁶ Nnr² , which ensures proper flooding of the second pump. Typically, the second pump is a high-pressure pump, such as a pump that is capable of generating a pressure ranging from 2x10⁶ Nnr² to 2x10⁷ Nnr². Optionally, the aqueous slurry may be transferred through bolt catchers, magnetic filters, lump breakers, disintegrators such as the Ritz Mill, during the transfer of the aqueous slurry through the pipe system downstream the pump system/mixer in which the aqueous slurry is formed. The disintegrator is preferably positioned between the pumps. The flow rate of the aqueous slurry along the pipes is typically in the range from 800 Kg/hour to more than 50,000 Kg/hour.

Optionally, the spray drying system may include a deaeration system. The deaeration system is preferably a vacuum assisted de-aerator, which is preferably fed by a transfer pump. The deaeration system remove air bubbles formed during the slurry preparation, thus increasing the bulk density of the spray-dried detergent particle. De- aeration of the slurry may also be carried out by other mechanical means or chemical de-aeration means using antifoams or de-foamers.

Optionally, air injection system may be provided along the pipe system. The air injection system may be provided before or after the pump system. The air injection includes air flow and pressure controls, static mixer, pulsation dampener and compressor set which can aerate the slurry to get a lower bulk density for the spray dried particle. The gas injected into the slurry may be nitrogen, carbon dioxide, or simply atmospheric air introduced under a pressure higher than the pressure of the aqueous slurry maintained in the pipe system. A typical spray drying system can optionally include both the de-aeration system and air injection system to optimize the desired bulk density of the spray dried particle.

Typical spray drying tower for detergent applications are counter-current spray drying tower. To obtain the desired moisture content and the particle size distribution the inlet hot air/hot steam temperature introduced into the spray drying tower is the range from 250°C to 500°C depending on the evaporation capacity and sizing of the tower. Preferably the tower exhaust air temperature can range from, 60°C to 200°C, more preferably 80°C to 200°C, still more preferably 80°C to 100°C depending on the loading of the tower. The aqueous slurry introduced into the spray nozzle of the spray drying tower is preferably at a temperature ranging from 60°C to 95°C. The spray drying tower may be a co-current spray drying tower, but these are less common. The spray-dried detergent particle existing the tower is maintained at a temperature less than 150°C, still preferably less than 100°C. The spray-drying is preferably conducted where the spray drying zone is under a negative pressure of at least 50 Nnr², still preferably the negative pressure is from 50 Nnr² to 600 Nnr². Preferably, the vacuum conditions is achieved by controlling the speed and/or dampener setting of the inlet and the outlet air fans.

The spray-dried particle collected at the bottom of the tower may be subjected to cooling and conditioning by using an air lift or any similar process. Preferably the collected spray dried particle may be mixed with flow aids which includes zeolite or similar fine particles of minerals such as dolomite, calcite or mixtures thereof. The spray-dried particle is mixed with flow aid just before the airlift operation. Preferably, the spray-dried detergent is subject to particle size classification to remove oversize material (> 2 mm typically) to provide a spray dried detergent particle which is free flowing. Preferably the fine material (< 100 microns typically) is elutriated with the exhaust air in the spray drying tower and captured and recycled back into the system via the dry cyclone, wet cyclone or bag filter system.

Spray-dried detergent particle:

According to an aspect of the present invention disclosed is a spray-dried particle obtainable by the process of the first aspect. Spray-dried particle formed from the process of the first aspect of the present invention preferably has a pH of 11.5 or less, preferably a pH ranging from 10.5 to 11.5 when measured using a 1 wt.% solution with distilled water at 25°C. The spray-dried particle is generally referred to as the base powder. This base powder may be used as a fully formulated laundry detergent composition.

Preferably the spray-dried detergent particle includes: (i) 7 wt.% to 30 wt.% detersive surfactant;

(ii) 5 wt.% to 20 wt.% sodium carbonate;

(iii) 5 wt.% to 17 wt.% alkali metal silicate;

(iv) 0.1 wt.% to 2.5 wt.% in-situ formed silicate salt or disilicate salt of alkaline earth metal or mixtures thereof;

(v) 0.1 wt.% to 4.5 wt.% water;

(vi) a filler selected from alkali metal chloride, alkaline metal carbonate or mixtures thereof, the filler is preferably present in an amount ranging from 29 wt.% to 65 wt.%, more preferably selected from sodium chloride, calcium carbonate (calcite), magnesium carbonate, calcium magnesium carbonate (dolomite) or mixtures thereof;

(vii) optionally from 0 wt.% to 4 wt.% polymer;

(viii) optionally organic builder, preferably from 0 wt.% to 10 wt.% citrate salt;

(ix) optionally from 0 wt.% to 2 wt.% hydroxide salt of alkaline earth metal;

(x) optionally, from 0.1 wt.% to 2 wt.% unreacted alkaline earth metal salt; wherein the weight ratio of the sodium carbonate to the filler in the spray-dried detergent particle ranges from 1:1.4 to 1:20.

Preferably the sodium carbonate is present in an amount ranging from 5 wt.% to 15 wt.% by weight of the spray dried particle, still preferably from 5 wt.% to 14 wt.%, further preferably from 5 wt.% to 12 wt.% and most preferably the sodium carbonate levels in the spray dried detergent particle is from 5 wt.% to 8 wt.%. It is preferred to keep the moisture content of the spray-dried detergent particle not more than 4.5 wt.% to ensure that the spray-dried particle is free-flowing and shows improved powder properties and extended shelf life. Preferably the alkali metal silicate salt is present in an amount ranging from 5 wt.% to 17 wt.% by weight of the spray dried particle, still preferably from 8 wt.% to 17 wt.%, still more preferably from 5 wt.% to 12 wt.%, further preferably from 5 wt.% to 12 wt.% and most preferably the alkali metal silicate salt levels in the spray dried detergent particle is from 5 wt.% to 8 wt.%.

Preferably the weight ratio of the sodium carbonate to the filler in the spray dried detergent particle ranges from 1:1.45: 1:18, still preferably from 1:1.5 to 1:18, still preferably from 1:1.5 to 1:16, more preferably from 1:3 to 1:16, still more preferably from 1:5 to 1:16, further more preferably from 1:5 to 1:15.

The spray dried detergent particle may preferably include from 0 wt.% to 4 wt.% polymer selected from antiredeposition polymer, soil release polymer, structuring polymer or mixtures thereof. Preferably the polymer is a polymeric carboxylate, preferably polyacrylate or a copolymer of acrylic acid and maleic acid. However other polymers may also be suitable such as polyamines (including the ethoxylated variants thereof), polyethylene glycol and polyesters. Polymeric soil suspending aids and polymeric soil release agents are particularly suitable.

Preferably the spray-dried detergent particle has a bulk density of less than 550g/L. Preferably the spray-dried detergent particle has a weight average particle size of from 300 micrometres to 600 micrometres.

The spray-dried detergent particle preferably comprises from 7 wt.% to 30 wt.% anionic surfactants, which is preferably a Cio to C20 linear alkyl benzene sulphonate, still C10 to Ci3 linear alkyl benzene sulphonate preferably and which is substantially neutralized with little or no acid residues. It is also preferred that the anionic surfactant is a combination of alkyl benzene sulphonate and either or both alkyl sulphate surfactant and alkyl ethoxylated sulphate.

The spray-dried particle is typically post dosed with ingredients that are incompatible with the spray-drying process conditions to form a fully formulated laundry detergent composition. Typically, a fully formulated laundry detergent composition includes from 30 wt.% to 95 wt.% of the spray-dried particle according to the first aspect. The other laundry ingredients are post dosed by dry mixing the spray-dried particle with other laundry ingredients. These laundry ingredients and generally those that are not thermally stable. Non-limiting example of the other post dosed laundry ingredients includes enzymes, shading dye, fragrance, antifoams, cleaning polymers, care polymers, foam boosters, visual cues, chelating agents and mixtures thereof. These components may be incompatible for many reasons including heat sensitivity, pH sensitivity or degradation in aqueous systems.

Laundry detergent composition Detergent compositions of low to moderate bulk density may be prepared by spray drying the aqueous slurry to form a spray-dried particle and optionally post-dosing (dry mixing) further laundry ingredients. Alternately "compact" detergent compositions may be prepared by further mixing the spray dried particle prepared according to the present invention in a high-speed mixer/granulator, or other non-tower processes. The spray dried detergent particle may also be used for preparing a tablet composition by compacting powders, especially "concentrated" powders using the known tabletting process. Further, the spray dried detergent particle may be used for preparing an unit dose product where the spray-dried detergent particle is enclosed in a pouch, preferably a water-soluble pouch, more preferably a water-soluble pouch comprising a film forming polymer selected from polyvinyl alcohol, polyvinylpyrrolidone and other known film forming polymer.

The spray-dried particle also known as base powder is preferably formulated into a finished detergent composition by dry mixing heat sensitive ingredients into the base powder. In addition to heat sensitive ingredients some amount of alkalinity may be added back into the base powder by addition of alkaline ingredients, additionally other acidic or neutral may also be added to formulate the finished detergent composition.

The spray-dried detergent particle may be used as a fully formulated laundry detergent composition or may be additionally combined with other optional laundry ingredients to form a fully formulated laundry detergent composition. Non-limiting examples of the optional post-dosed laundry ingredients includes but is not limited to enzymes, anti redeposition polymers, perfumes, additional surfactant selected from amphoteric surfactant, zwitterionic surfactant, cationic surfactant and non-ionic surfactant, optical brighteners, antifoaming agent, foam boosters, fabric softeners such as smectite clays, amine softeners and cationic softeners; bleach and bleach activators; dyes or pigments, fillers, fluorescers, salts, soil release polymers, dye transfer inhibitors. These optional ingredients are well known to be used in a laundry detergent composition and added preferably by post-dosing.

Non-limiting examples of the post-dosed polymers include cleaning polymers, antiredeposition polymers, soil release polymers structuring polymers. Some examples include PET-PEOT polymer (Repel-o-Tex® SF2 ex.Solvay), copolymer of acrylic acid and maleic acid (Sokalan CP5 ex. BASF).

Fluorescers: Suitable fluorescent brighteners include dis-styryl biphenyl compounds example Tinopal® CBS-X, di-amino stilbene di-sulfonic acid compounds, e.g. Tinopal® DMS pure Xtra and Blankophor® HRH, and Pyrazoline compounds, e.g. Blankophor® SN, and coumarin compounds, e.g. Tinopal® SWN. Preferred brighteners are: sodium 2 (4- styry)-3-sulfophenyl)-2H-napthol(1,2-d]triazole, disodium 4,4’bis{[4-anilino-6-(N methyl- N-2 hydroxyethyl)amino 1,3,5- triazin-2-yl)]amino]stilbene-2-2' disulfonate, disodium

4,4’bis([(4-anilino-6-morpholino-l,3,5-triazin-2-yl)]amino} stilbene-2-2'disulfonate, and disodium 4,4’- bis(2-sulfostyryl)biphenyl. A suitable fluorescent brightener is S C.l. Fluorescent Brightener 260, which may be used in its beta or alpha crystalline forms, or a mixture of these forms.

Enzymes:

The composition of the present invention preferably includes an enzyme. It may preferably include one or more enzymes. Preferred examples of the enzymes include those which provide cleaning performance and/or fabric care benefits.

Examples of suitable enzymes include, but are not limited to, hemicellulases, peroxidases, proteases, cellulases, xylanases, lipases, xyloglucanase, phospholipases, esterases, cutinases, pectinases, mannanases, pectate lyases, keratinases, reductases, oxidases, phenoloxidases, lipoxygenases, ligninases, pullulanases, tannases, pentosanases, mannanases, G-glucanases, arabinosidases, hyaluronidase, chondroitinase, laccase, and amylases, or mixtures thereof. A typical combination is an enzyme combination that includes a protease and lipase in conjunction with one or more of amylase, mannanase and cellulase. When present in a detergent composition, the enzymes may be present at levels from about 0.00001% to about 2%, from about 0.0001% to about 1% or from 0.001% to about 0.5% enzyme protein by weight of the detergent composition.

Packaging and dosing

According to another aspect of the present invention disclosed is a packaged laundry product in which a package encloses a laundry detergent composition or a spray-dried detergent particle. The spray dried detergent particle or a laundry composition having the spray dried detergent particle prepared according to the invention may be packaged as unit doses in polymeric film soluble in the wash water. Alternatively, the spray-dried detergent particle or a composition including the spray-dried detergent particle of the invention may be supplied in multidose plastics packs with a top or bottom closure. A dosing measure may be supplied with the pack either as a part of the cap or as an integrated system. The packaging material suitable for packaging may include but not limited to multilayer polyethylene film, laminate, paper based and other materials known to a person skilled in the art. Preferably the packaging material is selected from material which are biodegradable or recyclable. The package is preferably a paper-based package, a plastic based flexible package, still preferably a plastic based flexible package having at least 50 wt.% consumer recycled plastic.

According to another aspect of the present invention, provided is a method of laundering fabric using a spray dried detergent particle or a laundry composition comprising a spray dried detergent particle according to the present invention which involves the step of diluting the dose of detergent composition with water to obtain a wash liquor and washing fabrics with the wash liquor so formed. In automatic washing machines the dose of detergent composition is typically put into a dispenser and from there it is flushed into the machine by the water flowing into the machine, thereby forming the wash liquor. From 5 up to about 65 litres of water may be used to form the wash liquor depending on the machine configuration. The dose of detergent composition may be adjusted accordingly to give appropriate wash liquor concentrations. The dilution step preferably provides a wash liquor which comprises inter alia from about 3 to about 20 g/wash of detersive surfactants (as are further defined above). Examples

Example 1: Preparing an aqueous slurry and a spray dried particle according to the present invention

A spray-dried laundry detergent composition according to the present invention was prepared by first mixing water, neutralizing agent (NaOH, 50% aqueous solution) and linear alkyl benzene sulphonic acid in a crutcher where they were agitated to neutralize the linear alkyl benzene sulphonic acid to its salt form. Thereafter an excess of sodium silicate (47% aqueous solution, alkali metal silicate) was added to the aqueous mixture. The sodium silicate has a Na₂0 to S1O2 ratio of 1:2.4. The addition of sodium silicate was followed by addition of magnesium sulphate (alkaline earth metal salt). The aqueous mixture was continuously agitated, and the mixture was heated to a temperature of around 78°C to 80°C upon addition of sodium silicate and the temperature was maintained till the end of the batch preparation. The sodium silicate and magnesium sulphate react to form in-situ magnesium silicate, in-situ magnesium disilicate or mixtures thereof. Further sodium carbonate, sodium chloride as filler was added in this order to form an aqueous slurry. The composition of the ingredients added to the form a batch of 1193 Kg aqueous slurry is provided in Table 1.

A. Preparing the aqueous slurry: Table 1 Total slurry batch size (kg) | 1192.74 |

B. Preparing the spray-dried detergent particle:

The aqueous slurry of Example 1 was spray dried to prepare a spray dried detergent and the spray-dried particle was thereafter evaluated.

The aqueous slurry was spray-dried in a conventional counter current spray drying tower to form a spray dried detergent particle with a moisture content of around 2 wt.% to 3.5 wt.%. The composition of the spray dried powder is provided in Table 2 below. Table 2

Example 2: Evaluation of the powder properties of the spray dried detergent particle The spray-dried detergent particle prepared according to the present invention (Ex 1) was evaluated for powder properties as described below. Compression test : This test evaluates the tendency of the powder towards caking. A split cylinder with a polished internal surface is positioned on a firm base to form a hollow cylindrical mould with a diameter of 9 centimetres. Spray dried detergent particle prepared according to the present invention (Ex 1) was filled inside the hollow cylindrical mould and levelled. A plastic disc is placed on levelled spray-dried detergent particle mass. A weight of 12 kilogram is slowly placed on the plastic disc in such a way that the weight is uniformly applied on the spray-dried detergent particle mass in the mould and the disc was allowed to compact the spray-dried detergent particle mass to form a compacted cake. After 2 minutes the weight was removed, and the cylindrical mould is opened slowly without disturbing the compacted cake mass. Next, incremental weights of 200 grams is added at an interval of 10 seconds till the compacted cake mass collapses. Total vertical load required to collapse the compacted cake mass is noted and expressed in grams and this amount in grams is indirectly defined as the caking tendency. Higher the value of the vertical load required to collapse the compacted cake mass the greater is the caking tendency of the powder under evaluation. For the present evaluation, values lower than 1 Kilogram is considered good and values beyond 2 Kilogram is classified as cohesive and classified as powder with high caking tendency. In addition to the spray dried detergent particle according to the present invention, different comparative spray-dried detergent particle was similarly prepared but having different compositions as provided in Table 3. The different comparative spray dried particle (Comp A, Comp B, Comp C) were evaluated for their tendency to cake using the compression test as described above. The performance of the comparative examples and the example according to the present invention was evaluated and is provided in table 3 below.

Each of the comparative spray-dried detergent particle and the spray dried detergent particle prepared according to the present invention were packed in laminates with water vapour transmission rate of less than 5 gram/m²/day and stored at storage condition of 45°C and 80 RH for a period of 8 weeks and 12 weeks., following which the compression test (UCT) was performed again. The measured values of various spray dried detergent particles both according to the present invention and comparative examples are provided in Table 3. In the table below a compression test value of 2 or more indicates that the powder has a higher caking tendency. Table 3

It is clear from the data provided in Table 3 that the comparative spray-dried particle having no silicate (Comp A) and even in presence of carbonate the slurry could not be processed, as it was very sticky and could not be spray dried. It is also seen that when the comparative spray-dried particle (Comp B) has lower levels of silicate and similar carbonate levels as that of Comp A, but with no in-situ formed alkaline earth metal silicate (Mg silicate) then although the spray-dried particle with acceptable compression values could be prepared, however such particle suffered from severe caking issue upon prolonged storage. Further, comparative spray-dried particle (Comp C) having higher levels of silicate but without any sodium carbonate also showed higher compression test values which indicates that they have higher tendency to cake. Comparative spray-dried detergent particle Comp C also caked fully upon storage suggesting that a spray-dried detergent particle without sodium carbonate does not provide extensive shelf life with good powder properties. On the other hand, the spray- dried detergent particle according to the present invention having optimum levels of silicate and sodium carbonate along with the in-situ formed magnesium silicate delivered a good spray-dried particle which has good flow properties even when with a higher detersive active content (30 wt.%) as compared to all the comparative spray dried particle (25 wt.%). In addition to this, the inventive spray-dried particle (Ex 1) showed lower tendency to cake both when measured fresh (to) as well as post storage under hot and humid conditions. Example 2: Evaluation of the reserve alkalinity of the spray dried detergent particle according to the present invention

The spray dried detergent particle according to the present invention and a control spray-dried detergent particle as provided in table 4 were prepared and their reserve alkalinity and harshness on hands were determined as provided below.

Measurement of Reserve alkalinity:

The spray dried detergent particle of Comp D and Ex 1 were prepared using same method of slurry making and spray-drying as described above. The two spray-dried detergent particle were then analysed for their reserve alkalinity using the following method.

The reserve alkalinity was determined by an acid titration of a 1% solution of the spray- dried detergent particle with 0.5 mol/l sulphuric acid till pH of 10.00. First a 1% aqueous solution of the spray dried particle was prepared by dissolving 20 grams of the spray- dried detergent particle (W) in 1980 ml_ of distilled water. The prepared aqueous solution was then titrated with 0.5 mol/l sulphuric acid (t) till a pH of 10 was reached. The amount of titrant (V) was noted. The Reserve alkalinity (amount of NaOH per 100 grams) of the spray-dried detergent particle was then calculated using the formula:

Irritancy index: The irritancy index indicates degree of harshness of the spray-dried detergent particle on the skin. A lower irritancy index value indicates that the spray- dried detergent particle is milder on skin, while higher value indicate that the spray- dried detergent particle is harsher on the skin. The irritancy index is determined using the formula: pH + (Reserve alkalinity)/6.

Table 4

The data in table 4 shows that the conventionally prepared control spray-dried detergent particle having higher levels of sodium carbonate and silicate showed good powder properties but showed higher tendency to be harsh on the hand of the user and fabrics as shown by its higher reserve alkalinity and irritancy index. On the other hand, the spray-dried detergent particle of the present invention (Ex 1) shows similar pH as that of the control spray-dried detergent particle and therefore will also show similar cleaning performance whilst being less harsh on hands of the user (comparatively lower irritancy index) and the fabric as shown by the much lower reserve alkalinity. As is seen, the inventive spray-dried particle (Ex 1) is 50% lesser in terms of reserve alkalinity.

Claims

1. A process for preparing a spray-dried detergent particle, said process comprising the steps of:

(i) contacting an alkaline earth metal salt with an alkali metal silicate salt in an aqueous mixture comprising a detersive surfactant, wherein the alkaline earth metal salt reacts with the alkali metal silicate salt to form in- situ silicate salt of alkaline earth metal, in-situ disilicate salt of alkaline earth metal or mixtures thereof;

(ii) adding 3.0 wt.% to 13 wt.% sodium carbonate and a filler selected from the group consisting of alkali metal chloride, alkaline earth metal carbonate or mixtures thereof to form an aqueous slurry; wherein the aqueous slurry comprises alkali metal silicate salt, in-situ formed silicate salt and/or disilicate salt of alkaline earth metal, detersive surfactant, filler and sodium carbonate;

(iii) spray-drying the aqueous slurry to form said spray dried detergent particle wherein the weight ratio of the sodium carbonate to the filler in the spray- dried detergent particle ranges from 1:1.4 to 1:20.

2. A process according to claim 1 wherein the alkali metal silicate is used in stoichiometric excess of the amount required for reacting with alkaline earth metal salt.

3. A process according to claim 1 or 2 wherein the alkaline earth metal salt is selected calcium sulphate, calcium chloride, magnesium sulphate, magnesium chloride or combinations thereof, preferably magnesium sulphate.

4. A process according to any one of the preceding claims 1 to 3 wherein the alkali metal silicate is sodium silicate.

5. A process according to any one of the preceding claims wherein the in-situ formed silicate or disilicate salt of alkaline earth metal is at least 50% amorphous.

6. A process according to any one of the preceding claims wherein the weight ratio of the alkaline earth metal salt and the alkali metal silicate salt added to the aqueous mixture is in the range from 260:1 to 5:1, preferably 24:1 to 12:1.

7. A process according to any one of the preceding claims wherein the detersive surfactant is an anionic surfactant, preferably selected from the group consisting of alkyl benzene sulfonate, alkoxylated alkyl sulphate, alkyl sulphate, alkoxylated alcohol, and mixtures thereof.

8. A process according to claim 7 wherein the anionic surfactant is selected from a fully neutralized anionic surfactant salt, a partially neutralized anionic surfactant or an acid form of the anionic surfactant which is fully neutralized to the salt form in-situ.

9. A process according to any one of the preceding claims, wherein the aqueous slurry comprises:

(i) 5 wt.% to 20 wt.% detersive surfactant;

(ii) 0.05 wt.% to 2 wt.% silicate salt or disilicate salt of alkaline earth metal or mixtures thereof;

(iii) 3 wt.% to 13 wt.% sodium carbonate salt;

(iv) 5 wt.% to 14 wt.% alkali metal silicate;

(v) 25 wt.% to 40 wt.% water.

(vi) a filler selected from the group consisting of alkali metal chloride, alkaline earth metal carbonate or mixtures thereof, preferably the filler is present in an amount ranging from 22 wt.% to 50 wt.% filler, more preferably the filler is selected from the group consisting of sodium chloride, calcium carbonate, calcium magnesium carbonate (dolomite), magnesium carbonate or mixtures thereof.

(vii) optionally, from 0 wt.% to 2 wt.% hydroxide salt of alkaline earth metal.

(viii) optionally, from 0 wt.% to 2 wt.% unreacted alkaline earth metal salt.

(ix) optionally, from 0 wt.% to 3 wt.% polymer; (x) optionally organic builder, preferably 0 to 10 wt.% citrate salt;

(xii) optionally antifoam, preferably silicone oil.

10. A process according to any one of the preceding claims, wherein said spray-dried detergent particle comprises:

(i) 7 wt.% to 30 wt.% detersive surfactant;

(ii) 0.1 wt.% to 2.5 wt.% in-situ formed silicate salt or disilicate salt of alkaline earth metal salt or mixtures thereof;

(iii) 5 wt.% to 20 wt.% sodium carbonate;

(iv) 5 wt.% to 17 wt.% alkali metal silicate salt;

(v) 0.1 wt.% to 5 wt.% water;

(vi) a filler selected from alkali metal chloride, alkaline metal carbonate or mixtures thereof, more preferably the filler is selected from the group consisting of sodium chloride, calcium carbonate, calcium magnesium carbonate (dolomite), magnesium carbonate or mixtures thereof, still preferably the filler is present in an amount ranging from 29 wt.% to 65 wt.% ;

(vii) optionally from 0 wt.% to 2.5 wt.% hydroxide of the alkaline earth metal;

(viii) optionally from 0 wt.% to 2.5 wt% unreacted alkaline earth metal salt;

(ix) optionally from 0 wt.% to 4 wt.% polymer selected from antiredeposition polymer, soil release polymer, structuring polymer or mixtures thereof;

(x) optionally organic builder, preferably alkali metal citrate. wherein the weight ratio of the sodium carbonate to the filler in the spray-dried detergent particle ranges from 1:1.4 to 1:20.

11. A spray-dried detergent particle obtainable by a process according to any one of the claims 1 to 9 comprises:

(i) 7 wt.% to 30 wt.% detersive surfactant;

(ii) 0.1 wt.% to 2.5 wt.% in-situ formed silicate salt or disilicate salt of alkaline earth metal salt or mixtures thereof; (iii) 5 wt.% to 20 wt.% sodium carbonate;

(iv) 5 wt.% to 17 wt.% alkali metal silicate salt;

(v) 0.1 wt.% to 5 wt.% water;

(vi) a filler selected from alkali metal chloride, alkaline metal carbonate or mixtures thereof, more preferably the filler is selected from the group consisting of sodium chloride, calcium carbonate, calcium magnesium carbonate (dolomite), magnesium carbonate or mixtures thereof, still preferably the filler is present in an amount ranging from 29 wt.% to 65 wt.%;

(vii) optionally from 0 wt.% to 2.5 wt.% hydroxide of the alkaline earth metal;

(viii) optionally from 0 wt.% to 2.5 wt% unreacted alkaline earth metal salt;

12. A laundry detergent composition comprising from 30 wt.% to 95 wt.% of the spray dried detergent particle according to any one of the preceding claims.

13. A laundry detergent composition as claimed in claim 12 wherein the composition comprises one or more laundry ingredients selected from the group consisting of enzyme, sequestrants, foam boosters, antifoam, perfume, dyes, shading dye, visual cues or mixtures thereof.

14. A packaged laundry product comprising a package enclosing the laundry detergent composition according to claim 12 or 13 or a spray-dried detergent particle according to claim 11.

15. A packaged laundry product according to claim 14 wherein the package is a paper-based package, a plastic based flexible package having at least 50wt.% post-consumer recycled plastic.