GB2199338A - Coloured detergent particles - Google Patents

Abstract

A process for the production of a coloured detergent powder comprises mixing a spray-dried detergent powder with a dyestuff and then treating the resulting mixture with a binder. Preferred dyestuffs are copper and nickel phthalocyanines and Red Carmin Microsol-FBS-X. Suitable binders are aqueous solutions of acrylic or acrylic/maleic polymers, water alone and aqueous sodium silicate, potassium or sodium triphosphate or sugar. The coloured powder may be used to provide "speckles" in a white detergent powder

Description

PROCESS FOR THE PRODUCTION OF COLOURED DETERGENT PARTICLES TECHNICAL FIELD OF INVENTION The present invention relates to the production of coloured detergent particles, and their incorporation as "speckles" in white or differently coloured detergent powders.

BACKGROUND AND PRIOR ART Detergent powders without added colourant are generally white or near-white in colour, but some ingredients, especially organic materials such as enzyme granules or bleach precursors, may be brown, yellow or grey. The incidence of such discoloured particles in a finished detergent powder can give the whole product an off-white, unattractive appearance. This problem can be overcome by incorporating relatively large amounts of white pigment (titanium dioxide) and/or.fluorescent brightening agent in the off-white particles, but this is expensive and not always possible or successful.It is therefore common practice to incorporate vividly coloured particles ("speckles") in detergent powders: the presence of some relatively large, strongly coloured particles in the powders renders the presence of slightly discoloured brownish, yellowish or greyish particles undetectable.

One method currently in use for the production of coloured particles or "speckles" is for a detergent slurry containing a dye but otherwise identical to that of the base powder to be spray-dried. A disadvantage of that method is that unless special measures are taken, the speckles produced have the same particle size distribution as the base powder itself, including a significant quantity of fine particles that would not show up as speckles in a product but would merely give an overall darkening. It is therefore necessary to remove the fine particles by sieving.Another disadvantage is that it is not normally necessary in view of the quantities involved for a spray-drying tower to be permanently dedicated to speckles production - and indeed one may not be permanently available - so the tower and slurry system used must periodically be shut down and thoroughly cleaned to remove all dyestuff. This is inconvenient, and the disposal of large amounts of discoloured waste water without detriment to the environment is also a problem.

GB 1 050 127 (Procter & Gamble) and GB 1 248 994 (Colgate-Palmolive) disclose a different approach whereby coloured speckles consisting mainly of an inorganic builder salt are prepared by non-spray-drying mixing processes and then admixed with a white base powder.

These processes have the disadvantage that the speckles are of substantia' different composition from the base powder, and their addition to the base powder changes the overall composition.

The present inventors have therefore investigated the possibility of colouring a spray-dried powder by mixing a dyestuff therewith to obtain a coloured powder, which could then be admixed as speckles with the bulk of the (white) spray-dried powder. The dyestuff must be easily dispersible or soluble in the detergent solution to avoid textile discolouration. The dyestuff chosen must also be stable against bleaches and other detergent ingredients and against light.

We have now found that speckles can successfully be prepared by admixing a dyestuff with a detergent powder, provided that the dyestuff is suitably chosen and that the mixture of base powder and dyestuff is subsequently treated with a binder.

DEFINITION OF THE INVENTION The present invention accordingly provides a process for the production of a coloured particulate detergent composition, which process comprises the steps of: (i) mixing a spray-dried detergent powder with a dyestuff and (ii) treating the powder with a binder The invention further provides a process for the production of a particulate detergent composition comprising particles of a first colour and particles of a second colour, wherein a spray-dried detergent powder of a first colour is admixed with a spray-dried detergent powder of a second colour prepared by a process as defined in the previous paragraph.

DESCRIPTION OF THE INVENTION The present invention is concerned first with a process for making coloured detergent particles, and secondly with a process for incorporating these as "speckles" in a detergent powder of a different colour (generally white). The speckles prepared in accordance with the invention may be mixed with a white or differently coloured base powder by any suitable conventional method: they will generally form a minor proportion of the final product, for example, 0.2 to 3% by weight, for maximum visual contrast. Preferably the speckles, apart from their colour, are of the same composition as the rest of the base powder, so that the composition as a whole does not vary with the proportion of speckles present.

The speckles of the present invention are prepared by a simple mixing process which is effective when the specific type of dyestuff defined above is used, but is ineffective with other dyestuffs. The base powder, sieved to remove very small ( < 200 ssm) and very large ( > 3000 m) particles, is thoroughly mixed, using any suitable apparatus, with the dry pulverulent dyestuff. The proportion of dyestuff in the mixed product (by weight) is within the range of from 100 to 5000 ppm, preferably fro 1000 to 2000 ppm.

The mixing step is followed by a binding step whereby the mixture of base powder and dyestuff is treated with a binder in an anount of from 0.5 to 5% by weight, preferably from 1 to 3% by weight, based on the mixture.

The binder is a liquid and preferred binders are aqueous solutions or dispersions of water-soluble polymers; nonionic surfactants (either alone or mixed with water);. or mixtures of the two. Any film-forming polymer may be used, but polymers that also fulfil another function in the detergent composition, for example, as a builder, antiredeposition agent or antiincrustation agent, are preferred. Suitable polymers include polymeric polycarboxylates, for example, polyacrylates and acrylic/maleic copolymers: polyacrylamides; polyvinyl alcohol and polyvinyl acetate; and cellulose derivatives, for example, sodium carboxymethylcellulose.

Another binder that may be used is aqueous sodium silicate solution. When the level of dye is low, water alone may be an adequate binder.

Suitable nonionic surfactants include ethoxylated alcohols, fatty acids and alkylphenols. Preferred nonionic surfactants are C12-Cl5 primary alcohol 3-30 EO ethoxylates. Especially preferred are longer-chain higher ethoxylates, for example, tallow alcohol 18EO and 25EO, which can be sprayed on in a molten state and allowed to solidify. If mixtures of nonionic surfactant and water are sprayedon, care should be taken, for example by spraying at elevated temperature, to avoid gelling.

When the binder level is relatively high, for example, above 3% by weight in the case of an aqueous binder, a subsequent drying step may be necessary. If the binder is a nonionic surfactant, the binder level at which a drying step becomes necessary will depend very much on the composition of the base powder.

The dyestuff may be a water insoluble pigment dyestuff. Especially preferred examples of such pigment dyestuffs are copper and nickel phthalocyanines, for example, Hostaperm (Trade Mark) Blue and Green ex Hoechst AG and Sicomet (Trade Mark) Blue and Green ex BASF AG (Colour Index 74 160, 74 260). Other pigment dyestuffs, for example, azo-dyestuffs, may also be used.

Water-soluble dyestuffs are also suitable for use in the process of the invention. Preferably the water-soluble dyestuff is Red Carmin Microsol FBS-X.

When water-soluble dyestuffs are used there are two other convenient processes for the production of a coloured detergent.

In the first the binder is sprayed onto the powder in a mixer so as to agglomerate the powder and then the dye, preferably in solution is sprayed on the agglomerate. If necessary the product is dried.

In the second process the binder and dye are sprayed on to the powder at the same time. The binder and dye may be sprayed separately or as a mixture.

The second of these processes is usually to be preferred because it involves fewer process steps. The process also tends to give rise to somewhat larger particles than the first process.

The base powder used in the process of the invention is prepared by spray-drying an aqueous slurry containing all desired ingredients that are sufficiently heat-insensitive to be processed by this method.

The base powder will generally contain one or more anionic and/or nonionic surfactants. Examples of anionic surfactants include alkylbenzene sulphonates, expecially sodium C8-C15 linear alkylbenzene sulphonates; primary and secondary alkyl sulphates, especially sodium C12-C15 primary alkyl sulphates; olefin sulphonates; alkane sulphonates; alkyl ether sulphates; and fatty acid ester sulphonates. Examples of nonionic surfactants include the primary and secondary alcohol ethoxylates, especially the C12-Cls primary and secondary alcohols ethoxylated with an average of from 3 to 20 moles of ethylene oxide per mole of alcohol.

It may also be desirable to include one or more soaps of fatty acids. The soaps which can be used are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower oil or hardened rapeseed oil.

The total amount of detergent-active material (surfactant), excluding soap, in the base powder is generally within the range of from 10% to 60% by weight.

In a fully formulated product containing perhaps 30 to 70% by weight of base powder this amount will be correspondingly less. For low-sudsing powders intended for use in European drum-type washing machines the weight ratio of anionic surfactant to nonionic surfactant preferably does not exceed 10:1, and more preferably does not exceed 6:1.

The base powder will also contain one or more detergency builders. Detergency builders are very well known to those skilled in the art and include sodium tripolyphosphate, orthophosphate and pyrophosphate; crystalline and amorphous sodium aluminosilicate; sodium carbonate; and monomeric and polymeric polycarboxylates, for example, sodium citrate, nitrilotriacetate and polyacrylate, and acrylic copolymers. The amount of detergency builder in the base powder may perhaps range from 20 to 80% by weight, and will be correspondingly lower in a fully formulated product.

Other inorganic salts without a detergency building function, for example, sodium silicate or sodium sulphate, may also be present in the base powder, as may heat-insensitive minor ingredients such as fluorescers and antiredepositon agents.

A fully formulated detergent product will generally also include ingredients that cannot be spray-dried because of heat-sensitivity or incompatibility with other slurry ingredients. Examples of such materials are bleaches, bleach activators, bleach stabilisers, enzymes, lather suppressors and perfumes. These ingredients are generally postdosed to the base powder. To prepare speckled products in accordance with the invention, the speckles will generally be postdosed, together will the other ingredients just mentioned, to the bulk of the base powder.

Generally the base powder will be white and the speckles a contrasting colour such as blue, green, red or pink. It is of course also within the scope of the invention to postdose speckles of a contrasting or darker colour to a base powder that is itself coloured.

EXAMPLES The invention is further illustrated by the following non-limiting Examples in which parts and percentages are by weight unless otherwise stated.

Spray-dried base powders were prepared to the following composit;ons (in weight 5): Example 1 Example 2 Sodium linear alkylbenzene 10.0 9.0 sulphonate Nonionic surfactant 12EO 3.0 2.0 Sodium aluminosilicate 35.0 Sodium tripolyphosphate - 30.0 Sodium silicate 2.0 5.0 Sodium sulphate 20.0 40.0 Minor ingredients (fluorescer, antiredeposition agent, foam depressant etc), water to 100.0 to 100.0 Five samples of each powder were prepared by sieving to remove particles < 200 ssm and > 3000 ssm.

Each sample of base powder was thoroughly mixed, in a batch mixer, with a copper phthalocyanine pigment dyestuff, in dry powder form, five different amounts of dyestuff being used as shown below. The dyestuff was Hostaperm (Trade Mark) Blue B2G, C.I. 74 160, beta form (Pigment Blue 15:3), ex Hoechst AG. Into each mixture was then sprayed 3% by weight of a 40% aqueous solution of an acrylic/maleic copolymer (Sokalan (Trade Mark) CP5 ex BASF).

Uniformly coloured blue powders were obtained, the colour deepening with increasing dyestuff content. The appearances of the coloured samples of Example 1, expressed by the CIE colour co-ordinates x, y and Y measured for tablets formed from the powders, were as follows: Example Concentration of CIE co-ordinates dyestuff (ppm) x y Y la 312.5 0.225 0.259 56 lb 625 0.225 0.225 51 lc 1250 0.223 0.252 43 1d 2500 0.221 0.249 35 le 5000 0.217 0.246 28 For comparison, a coloured powder was prepared by including a 30% dispersion of the same dyestuff, at a level giving a dyestuff content of 1200 ppm, in a slurry corresponding to that of the base powder of Example 1, and spray-drying the slurry. The colour co-ordinates of the comparative powder were almost identical to those of Example lc containing 1250 ppm of dyestuff incorporated by the process of the invention.

The colour co-ordinates of the five samples (Examples 2a-2e) prepared with the base powder of Example 2 were very similar to those of the corresponding Example 1 samples.

Possible dye transfer to fabrics was tested by slurrying each sample with water (1:1 by weight) and rubbing the resulting slurries into cotton and synthetic fabrics. No discolouration was observed with Examples la-lc and Examples 2a-2c. Slight discolouration was observed with Examples 1d and 2d, and more pronounced discolouration with Example le and 2e. It will be appreciated, however, that this is a severe test which exposes the fabrics to dyestuff concentration very much higher than would ever be encountered with a real product.

Fully formulated detergent powders were prepared by mixing each base powder with the appropriate speckles and with other ingredients as follows: parts Base powder (Example 1 or Example 2) 71.4 Speckles (Example lc or Example 2c) 0.6 Bleach ingredients (sodium perborate, 25.0 TAED) Minor ingredients (enzyme, lather 3.0 suppresor, perfume) 100.0 Both products were white powders with vividly coloured blue speckles distributed through them.

Examples 3-7 A conventional spray-dried powder was prepared by known techniques. Fine and course particles were removed by sieving to give a mean particle diameter of 640 ssm.

Samples of the powder were separately treated with a binder or binder solution in a mixer. 7.5 wt% of an aqueous solution of a red dye, Red Carmin Microsol FBS-X, was then sprayed on to the particles which were thoroughly mixed. The particles were then recovered and the mean particle diameter measured. All of the samples were vividly coloured.

Example Binder Mean Particle No. size/microns 3 Water 6.6% 685 4 Water 3.3% and 42% silicate 730 solution* 5 Water 3.3% and 25% Narlex LD134 785 solution* 6 Water 3.3% and 3.3% Potassium 710 Tripolyphosphate 7 Water 3.3% and 3.3% Sugar 710 * The binder solutions were added in amount sufficient to give 3.3% (solids) binder in the product.

Examples 8-16 A conventional detergent powder prepared by conventional spray drying techniques and having a mean particle diameter was taken. Portions were taken and to each portion was added, with mixing in a batch mixer, simultaneously a solution of a binder and a solution of a dye. The powder was recovered and the mean particle size measured. All the powders were vividly coloured. Example Binder Amount of Amount of Mean Particle Binder (wt%) Dye Solution diameter ( m) (wt%) 8 42% sodium silicate 3.3 10.85 890-905 9 25% Narlex LD 34 3.3 10.85 730-940 10 Potassium 3.3 10.85 770-830 Tripolyphosphate 11 Sugar 3.8 10.35 780 12 Sodium 0.75 13.45 830-850 Tripolyphosphate 13 42% sodium silicate 3.4 9.3 790 14 25% Narlex 2D 34 3.4 9.3 795 15 Potassium 3.4 9.3 700 Tripolyphosphate 16 Sodium 0.8 9.3 770 Tripolyphosphate In Examples 8 to 12 the dye employed was Red Carmin Microsol FBS-X. In Examples 13 to 16 a blue dye eas employed.

Claims (5)

Claims

1. A process for the production of a coloured particulate detergent composition, which process comprises the steps of: (i) mixing a detergent powder with a dyestuff and (ii) treating the powder with a binder.

2. A process as claimed in claim 1, wherein the dyestuff is a copper or nickel phthalocyanine.

3. A process as claimed in claim 1 or claim 2 wherein the binder comprises a polymer in aqueous solution or dispersion and/or a nonionic surfactant.

4. A process as claimed in claim 3, wherein the binder comprises a polyacrylate or an acrylic/maleic copolymer.

5. A process for the production of a particulate detergent composition comprising particles of a first colour and particles of a second colour, wherein a spray-dried detergent powder of a first colour is admixed with a spray-dried detergent powder of a second colour prepared by a process as claimed in any preceding claim.