GB2153381A - Stabilised detergent bleach compositions - Google Patents

Abstract

In a process for preparing a detergent and bleaching composition comprising a detergent, a builder, a percompound bleach, an organic activator for the percompound bleach and ethylene diamine tetra-(methylene phosphonate) -EDTMP-, by spray-drying an aqueous detergent slurry comprising the detergent and builder in a spray-drying tower, followed by dry-mixing the dried powder with the percompound and the activator, the improvement being that a separate aqueous EDTMP-slurry comprising calcium hydroxide is spray-dried simultaneously with the main aqueous detergent slurry in the same spray-drying tower via a separate nozzle system at about the same level as the main detergent nozzle system or lower.

Description

SPECIFICATION Manufacture of detergent and bleaching compositions This invention relates to a process for preparing detergent and bleaching compositions comprising a percompound bleach and an organic activator.

Detergent and bleaching compositions containing inorganic percompounds and organic activators therefor are known in the art.

These organic activators are generally carboxylic acid derivatives, e.g. esters (such as those described in British Patent Specification 836,988 and 970,950), acylamides (such as those described in British Patent Specifications 907,356; 855,735; 1,246,339 and US Patent Specification 4,128,494), acylazoles (such as those described in Canadian Patent Specification 844,481) and triacylcyanurates (such as those described in US Patent Specification 3,332,882).

A representative but by no means comprehensive list of activators known in the art is given below: (1) Acyl organoamides of the formula RCONR,R2, where RCO is a carboxylic acid radical, R, is an acyl radical and R2 is H or an organic radical, as disclosed in US Patent Specification 3,117,148. Examples of compounds falling under this group are: (a) N,N-diacetylaniline and N-acetylphthalimide.

(b) N-acylhydantoins, such as N,N'-diacetyl-5,5-dimethylhydantoin.

(c) Polyacylated alkylene diamines, such as N,N,N',N'-tetraacetylmethylene diamine and N,N,N', N'-tetraacetyl-ethylene-diamine, as disclosed in British Patent Specification 907,356.

(d) Acylated glycolurils, such as tetraacetyl glycoluril, as disclosed in British Patent Specification 1,246,338.

(e) Alpha-acyloxy-(N,N')polyacyl malonamides, such as alpha-acetoxy-(N,N')-diacetyl malonamide, as disclosed in US Patent Specification 4,128,494.

(2) Acylated sulphonamides, such as N-methyl-N-benzoyl-methane sulphonamide and Nphenyl-N-acetyl methane sulphonamide, as disclosed in British Patent Specification 3,183,266.

(3) Carboxylic esters of the type as disclosed in British Patent Specification 836,988.

Examples of activators of this type include phenyl acetate, sodium acetoxy benzene sulphonate, trichloroethylacetate, sorbitol hexaacetate, fructose-pentaacetate, p-nitrobenzaldehyde diacetate, isopropenyl acetate, acetyl acetohydroxamic acid, and acetyl salicylic acid. Other examples are esters of a phenol or substituted phenol with an alpha-chlorinated lower aliphatic carboxylic acid, such as chloroacetylphenol and chloroacetylsalicylic acid, as disclosed in US Patent Specification 3,130,165.

(4) Acyl-cyanurates, such as triacetyl- or tribenzoylcyanurates, as disclosed in US Patent Specification 3,332,882.

(5) Carbonic acid or pyrocarbonic acid esters of the formula R,OCOOR2 or R3OCO-O- CO-OR2, as disclosed in British Patent Specification 970,950, for example p-carboxy-phenylethyl-carbonic acid ester, p-carboxyphenyl-ethyl pyrocarbonic acid ester, and sodium sulpho phenylethyl carbonic acid ester.

(6) Optionally substituted anhydrides of benzoic or phthalic acid, for example benzoic anhydride, m-chlorobenzoic anhydride and phthalic anhydride.

Preferred activators are the polyacylated alkylene diamines of group (1) (c) above, particularly N,N,N',N'-tetraacetyl ethylene diamine.

These activators are generally used in a weight ratio of from about 1:1 to 1:35 to the percompound.

Such detergent and bleaching compositions exert bleaching action by the formation of organic peracids from the reaction of the organic activator with the percompound, which organic peracids, unlike the inorganic percompounds , are effective in bleaching at lower temperatures.

The term "percompound" is used here to indicate those percompounds which liberate active oxygen in solution, such as the alkalimetal perborate, persilicates, percarbonates, persulphates and perphosphates, which may be present at a level of about 4 to 40% by weight of the detergent and bleaching composition.

Uusually such detergent and bleaching compositions will comprise a detergent active material in proportions of about 5-40% by weight, detergency builders in proportions of about 8-65% by weight; and also other components, such as alkaline agents, fillers and the usual adjuncts, such as optical brighteners, soil suspending agents, sequestering agents, perfumes, colouring agents, and enzymes, in minor amounts.

The detergent active material present in the composition may be a single active or a mixture of actives. The actives may be selected from the group of anionic, non ionic, amphoteric and zwitterionic detergent compounds and mixtures thereof. Examples of anionic detergent compounds are alkylaryl sulphonates (e.g. sodium dodecylbenzene sulphonate); products of the sulphonation of olefins, so-called olefinsulphonates; fatty alcohol sulphates; alkylether sulphates, in the form of their alkali metal salts, and alkali metal salts of long-chain C8-C22 fatty acids.

Nonionic detergent compounds can be broadly defined as compounds produced by the condensation of alkylene oxide groups with an organic hydrophobic compound which may be aliphatic or alkyl-aromatic in nature. The length of the polyalkylene oxide group which is condensed with any particular hydrophobic group can be readily adjusted to yield a watersoluble compound having the desired degree of balance between hydrophilic and the hydrophobic elements. Examples of suitable nonionic detergent compounds are the condensation products of C8-C,2-alkylphenols with 5-25 moles of ethylene oxide per mole of alkylphenol; the water-soluble condensation products of C8-C22 aliphatic alcohols, either straight or branched chained, with 5-30 moles of ethylene oxide per mole of alcohol.

Amphoteric detergents include derivatives of apliphatic or aliphatic derivatives of heterocylic secondary or tertiary amines in which the aliphatic moiety can be straight-chain or branched and wherein one of the aliphatic substituents contains from 8 to 1 8 carbon stoms and at least one aliphatic substituent contains an anionic water-solubilizing group.

Zwitterionic detergents include derivatives of aliphatic quaternary ammonium, phosphonium and sulphonium compounds in which the aliphatic moieties can be straight-chain or branched, and wherein one of the aliphatic substituents contains from 8 to 1 8 carbon atoms and one contains an anionic water-solubilizing group.

Other detegent active materials are described in the books "Surface-Active Agents," Vol. l, by Schwartz and Perry (Interscience 1949) and "Surface Active Agents and Detergents, Vol II, by Schwartz, Perry and Berch (Interscience 1958), the disclosures of which are included herein by way of reference.

Examples of detergency builders are sodium and potassium triphosphate, sodium orthophosphate; sodium and potassium pyrophosphate; sodium carbonate; organic non-phosphate builders such as nitrilotriacetic acid and its water-soluble salts, sodium ethylenediamine tetraacetate, carboxymethyloxymalonate, carboxymethyloxysuccinate; and the various alumino silicates such as zeolite.

A conventional and most convenient method of preparing such detergent bleaching compositions is by forming an aqueous slurry of substantially all non-heat-sensitive detergent components including the detergent active material and the builder, which slurry is then fed via a nozzle system into a spray-drying tower to form a spray-dried base powder to which the other heat-sensitive components, such as the percompound bleach, the activator and any enzymes are added.

Perhaps the most essential ingredient required in such detergent and bleaching compositions is a stabilizing agent for the percompound and the peracid formed in solution. Said stabilizing agent improves the bleaching efficiency of percompound/activator bleach systems by its ability to inhibit the deleterious side-reaction occuring in the wash solution between the peracid formed and the percompound, resulting thereby in a loss of bleaching efficiemcy. The stabilizing agents suitable for said purpose are generally organic phosphonate compounds, of which ethylene diamine tetra-(methylene phosphonate)--''EDTM P' '-is the best known respresentative.Since this compound itself is unstable during storage in the presence of a percompound bleach and an activator, it has been proposed to use it in the form of its preformed complex with a metal ion, such as calcium, magnesium, zinc and aluminium (see US Patent Specification 4,259,200).

Normally its calcium complex (Ca-EDTMP complex) is used, which must be prepared beforehand from ethylene diamine tetra-(methylene phosphonic acid) or its sodium salt, dried and granulated and thereafter dry mixed with the detergent bleach composition as disclosed US Patent N" 4,259,200. The preparation, drying, granulation and post-dosing of said calcium complex are cumbersome, time-consuming and labour-intensive operations. For example, the preparation of separate Ca-EDTMP complex granules for post-dosing by spray-drying the raction mixture slurry will require certain structuring aids, such as borax or sodium triphosphate, as well as granulating agents, such as a nonionic surfactant.

It has now been found that the method of preparing and incorporating Ca-EDTMP complex as a stabilizer for the percompound and the peracid into detergent bleach compositions can be simplified without detrimental effects as to its stability on storage, by preparing an aqueous "EDTMP-slurry" comprising ethylene diamine tetra-(methylene phosphonate) and calcium hydroxide, which slurry is then spray-dried simultaneously with the detergent base slurry via a separate nozzle system in the same spray-drying tower.

The advantages of the process of the invention are that the calcium-EDTMP complex is homogeneously distributed within the matrix of the detergent composition, with consequently less risk of segregation than when added as separate granules via a dry-mixing process, and furthermore the tremendous cost- and energy-saving achieved by the reduction of processing steps and the elimination of unnecessary structuring and granulating agents.

By using the process of the invention it is also much easier to adjust the dosage of Ca-EDTMP complex into the detergent bleach compositions.

In terms of raw material cost it should also be appreciated that preparing the Ca-EDTMP complex as dry granules is much more expensive owing to the complexity of the ingredients necessary for the formulation and granulation of the Ca-a:DTMP complex, as compared with the much simpler Ca-EDTMP slurry composition.

Accordingly the invention provides a process for preparing a detergent and bleaching composition comprising a detergent active material, a builder, a percompound bleach, an organic activator therefor and ethylene diamine tetra-(methylene phosphate), by spray-drying an aqueous detergent slurry comprising the detergent active material and builder(s) in a spraydrying tower, followed by dry-mixing the spray-dried base powder with the percompound and the activator therefor, which is characterized in that a separate aqueous EDTMP-slurry comprising ethylene diamine tetra-(methylene phosphonate) and calcium hydroxide is prepared, which is spray-dried simultaneously with the main aqueous detergent slurry in the same spray-drying tower via a separate nozzle system comprising one or more nozzles situated in the spray-drying tower at about the same level as the main nozzle system or lower.This separate nozzle system can be situated centrally or excentrally in the spray-drying tower.

Based on a spray-drying tower with a diameter of about 8-9 meters, the nozzle system for the EDTMP-slurry can be situated at a level of up i~ 4-5 meters below the main detergent nozzle system, i.e. at least 7 meters' drying height should preferably be maintained to provide a satisfactory drying of the Ca-EDTMP complex.

The EDTMP-slurry may be prepared from a sodium salt of ethylene diamine tetra-(methylene phosphonic acid), e.g. Na6H2-ethylene diamine tetra-(methylene phosphonate), reacted with calcium hydroxide at a molar ratio of from 1:1 to 3:1, whereby a pH is maintained in the alkaline range of preferably above 12, more preferably above 13, or from ethylene diamine tetra-(methylene phosphonic acid) + sodium hydroxide + calcium hydroxide for pH-adjustment.

A preferred EDTMP-slurry will comprise EDTMP and CaOH at a molar ratio of 1:3, which will produce Ca3-EDTMP-complex in the formulation.

In a preferred embodiment of the invention the separate nozzle or nozzles for spraying the EDTMP-slurry is or are situated in and/or around the centre of the spray-drying tower, as is shown by the schematic diagram of the arrangement in the annexed Figure. The preparation and spray-drying of the main detergent slurry are well-known in the art and need no further explanation. A most convenient circumstance in the process of the invention is that the additional arrangement of a separate nozzle system for the EDTMP-slurry requires no further adjustment of the spray-drying process conditions.

Example I Example of preparing the EDTMP-slurry In a 700 litre mixing tank provided with a paddle-type stirrer, an aqueous solution of a sodium salt of ethylene diamine tetra-(methylene phos-phonic acid), i.e. a 32.6% Na6-salt solution and 3 Moi equivalent of calcium hydroxide was prepared at room temperature, to which there was added an amount of an inert salt to form a slurry containing 22.1 % by weight of ethylene diamine tetra-(methylene phosphonate) calculated as acid, 14% salt and 56% by weight of water. The slurry had a viscosity of about 30 cP (0.3 PaS), whikst its temperature was increasing to about 35-40"C and the pH-value increased to about 13.5.

It is believed that during this mixing the following reaction occurs: Na6H2-EDTMP + 3 Ca(OH)2 Ca3Na2-EDTMP + 4 NaOH + 2H2O The slurry was constantly stirred for a few hours in order to be sure that the reaction was completed and to avoid the agglomeration of the suspended Ca-EDTMP complex in the slurry.

The slurry was then ready for spray-drying simultaneously with the main detergent slurry.

Example II Several experiments on simultaneous spray-drying of EDTMP-slurry and a main detergent slurry of varying compositions and post-dosing to the Ca-EDTMP-complex containing detergent base powder, sodium perborate and N,N'-tetraacetyl ethylene diamine (TAED) as activator, which final products were then subjected to storage tests, have shown that the deterioration/stability factor of the EDTMP added by the method of the invention was at least as good as EDTMP added as dry Ca-EDTMP complex granules to the base powder, i.e. from about 60/80% EDTMP remaining after storage of one month in a 37oC/37% RH incubator, which is very satisfactory. The formulations tested are represented in the following Table I.

TABLE I PRODUCT FORMULATIONS Components Formulation No.

(% by weight) I II III Na-alkylbenzene sulphonate 7.0 7.0 6.5 Nonionic surfactant 3.5 3.5 3.0 (C 12/E0 12 + 18) Sodium soap 4.0 4.0 5.0 Sodium tripolyphosphate 25.5 21.64 32.1 Sodium aluminosilicate - 7.0 Sodium silicate 6.0 4.0 6.0 Sodium carboxymethyl cellulose 0.80 0.80 0.8 Sodium sulphate 18.64 23.15 11.37 Sodium perborate 20.00 12.00 20.00 Enzymes 0.50 0.50 0.40 TAEDgranulate (incl. STP) 3.54 5.17 3.08 Perfume 0.18 0.18 0.20 Ca3-EDTMP-compound 1.69 1.88 1.2 Water and minor components to 100 Example Ill A comparison of the storage stability of Ca-EDTMP incorporated according to the process of the invention vs. post-dosing is shown in the following Table II. No substantial difference in stability of Ca-EDTMP-complex can be detected.

TABLE II Storage stability of Ca3-EDTMP EDTMP remaining in % EDTMP-Processing Product Formulation Storage under Storage Route type of ambient conditions in 37 C/70% RH data 1 Month 2 Months 1 Month 2 Months Formulation I average 94 87 66 51 (26.5% STP*) range of 79-100 79-92 51-73 39-58 Dosage through 6 samples central nozzle Formulation II average 95 91 72 67 (23.5 STP/7 Zeolite) range of 3 samples 91-99 91-92 67-78 59-76 Ca3-EDTMP/Borax/ average 91 84 69 43 Sulphate in range of Formulation I 6 samples 84-99 73-91 60-80 26-56 (26.5% STP) Conventional dosing Ca3-EDTMP in average 91 93 63 46 Formulation III range of (# 34% STP) 3 samples 84-100 90-100 48-71 36-63 * STP = Sodium Tripoly Phosphate

Claims (5)

1. A process for preparing a detergent and bleaching composition comprising a detergent active material, a builder, a percompound bleach, an organic activator for said percompound bleach, and ethylene diamine tetra-(methylene phosphonate), by spray-drying an aqueous detergent slurry comprising the detergent active material and builder in a spray-drying tower, followed by dry-mixing the spray-dried base powder with the percompound and the activator, characterized in that a separate aqueous EDTMP-slurry comprising said ethylene diamine tetra (methylene phosphonate) and calcium hydroxide is prepared, which is spray-dried simultaneously with the main aqueous detergent slurry in the same spray-drying tower equipment via a separate nozzle system comprising one or more nozzles situated in the spray-drying tower at about the same level as the main detergent nozzle system or lower.

2. A process according to Claim 1, characterized in that said separate nozzle system for the EDTMP-slurry is situated in and/or around the centre of the spray-drying tower.

3. A process according to Claim 1 or 2, characterized in that said EDTMP-slurry comprises ethylene diamine tetra-(methylene phosphonate) and calcium hydroxide in a mole ratio of from 1:1 to 1:3.

4. A process according to Claim 3, characterized in that said EDTMP-slurry has a pH-value of above 12.

5. A process according to Claim 3 or 4, characterized in that said EDTMP-slurry comprises EDTMP and Ca(OH)2 in a mole ratio of 1:3 and has a pH-value of above 1 3.