GB2217340A - Preparation of a granular detergent composition - Google Patents

Abstract

Fluorescer is incorporated into a previously prepared granular detergent composition (for example a spray dried powder) by postdosing the fluorescer in the form of a premix containing a particulate diluent. Fluorescer which is added in this way serves to brighten the detergent powder and the release of powder into the equipment used to make the detergent composition is avoided.

Description

PROCESS FOR THE PREPARATION OF A GRANULAR DETERGENT COMPOSITION This invention relates to a process for the preparation of a granular detergent composition containing a fluorescer (optical brightener).

It is common practice to add a fluorescer (also termed an optical brightener) to a detergent composition at a low level. The purpose of adding a low level of fluorescer is to enhance the perceived whiteness of the washed laundry. Most fluorescers are themselves creamy off-white, or sometimes yellowish powders. It is normal practice to incorporate any fluorescer by dispersing it in the detergent slurry which is then spray-dried to form a powder. When fluorescer is incorporated in this conventional fashion it provides an additional benefit of changing the natural dull off-white appearance of the detergent powder to a bright white which users regard as desirable.If the detergent powder is made in this conventional manner, incorporating fluorescer into the slurry before spray-drying, examination of samples of the powder under ultra-violet light shows that the spray-dried granules contain uniformly distributed fluorescer.

This traditional method of incorporating fluorescer gives excellent results but it means that the crutcher, spray-drying tower and associated equipment are all contaminated with fluorescer. If it is desired to use the same plant to make a non-fluorescent product it is necessary to shut down the plant and clean it to remove fluorescer, which is both costly and inconvenient.

Some particulate ingredients of detergent compositions are conventionally added afterwards (postdosed) to the powder which has been spray-dried. This is normally done for components which cannot be added to the slurry before spray-drying either because they are unstable at the relatively high temperatures encountered in the spray-drying tower or because they are incompatible with other components of the slurry. Post-dosing does not appear to be an attractive route for adding fluorescers, because these are generally in the form of finely divided, very dusty powders which are not easy to handle. It could be expected that a uniform distribution of the fluorescer would be hard to achieve, so that the product powder would be only an off-white powder containing fluorescer particles which are also off-white.

However, GB-A-2179971 contains a final Example in which fluorescer is one of several ingredients including nonionic detergent added to previously spray-dried base beads. EP-A-220024 contains Examples in which fluorescer is one of several ingredients added to previously spray dried base beads. In neither case is the technique for addition fully disclosed, nor is the perceived whiteness of the product mentioned. The product of EP-A-220024 is packed in closed sachets.

We have found that addition of fluorescer to a previously-formed granular detergent composition, e.g.

spray-dried particles, can give a product which is not a dull off-white as predicted, but surprisingly has a greater apparent whiteness than the composition prior to admixture of fluorescer.

Broadly therefore, the present invention provides a process for incorporating fluorescer into a granular detergent composition, comprising admixing fluorescer in a particulate condition with an initial detergent composition which is, or includes, a spray-dried mixture containing one or more detergent-actives, which may be anionic, nonionic or a mixture of both.

We have also appreciated that such addition of fluorescer can be carried out very conveniently if the fluorescer is first admixed with a particulate diluent material to form a premix which is itself added to the spray-dried powder. The improved whiteness of the powder is obtained even when the fluorescer is added as a premix, in this way.

The diluent will generally be a fine or fairly fine inorganic salt, and sodium sulphate can conveniently be used for this purpose. Finely divided soaps can also be used.

It is very desirable that some nonionic detergent active is present since this has been found greatly to assist the improvement in whiteness of the powder when fluorescer is added. It may be incorporated in the initial detergent composition, preferably in the spray-dried mixture, or it may be sprayed on to the granular detergent composition. Preferably nonionic detergent active is sprayed on anyway, as it aids the distribution of postdosed fluorescer, and the obtaining of a product which is of uniform whiteness, and is a bright, white powder. It is desirable that the nonionic detergent active is one or more nonionic actives which are liquid or semi-solid at 20"C, and that the amount of nonionic active present in the final composition is at least % by weight, preferably at least 1% or better at least 1.5t.

In other respects the detergent composition can be conventional. The composition into which the fluorescer is incorporated will generally be spray-dried granules, containing anionic and/or nonionic detergent active and possibly containing detergent builder and filler.

The detergent composition may contain other postdosed materials in addition to the fluorescer, e.g.

builders, bleaches, anti-redeposition and lather control agents.

The overall composition will generally contain at least 5% by weight detergent active, and indeed detergent active in the initial composition will generally provide at least 5% of the final composition.

A detergent composition formed by the process of this invention, possibly including components post-dosed after the fluorescer, may typically contain, as weight percentages of the total composition, at least the following: Detergent active 2 - 90% Organic and/or inorganic detergency builder 2 - 80% Filler O - 50% Bleach and bleach activator 0 - 25 Fluorescer O - 5% Pigment and/or dye 0 - 5% Lather control agent 0 - 108 Enzymes O - 5% Buffers, anti-redeposition agents, perfume 0 - 10% Water balance Preparation of a premix of fluorescer and diluent can be carried out by any convenient technique for dry mixing solids. It is desirable to use a sealed mixer to prevent escape of dust. A rotary mixer or drum mixer would be suitable. The mixing process could use low or high amounts of energy, and apply low or high shear to the materials.

Fluorescers are sometimes supplied with some diluent already present, typically 5 to 108 of sodium chloride or sulphate. A premix for admixture with the initial composition will preferably contain more diluent than that (if any) included by the supplier of fluorescer.

A premix will generally contain fluorescer and diluent in a weight ratio of 20:1 to 1:200, preferably 5:1 to 1:20 more preferably 1:1 to 1:10.

Suitable non-agglomerating granular diluents include zeolites, finely divided soaps, sodium, potassium, lithium, magnesium, and/or calcium, sulphates, carbonates, fluorides, borates, orthophosphates, pyrophosphates, tripolyphosphates, and mixtures thereof. Sodium sulphate is especially preferred. Calcium carbonate may be in the form of calcite.

The diluent may have a mean particle size of from about 50 microns to about 600 microns, preferably from about 200 microns to about 400 microns, be relatively nonhygroscopic and have essentially no tendency to agglomerate. We prefer sodium sulphate having a mean particle size of around 300 microns.

Admixing of fluorescer or the preferred premix to the initial detergent composition can be carried out with conventional equipment. A screw feeder would be suitable or, as we prefer, a weighbelt feeder.

This invention is particularly applicable to granular compositions which will be used as portions from a greater bulk, so that the user sees the loose powder. The invention may therefore include a final stage of packing the fluorescer-containing composition into containers for retail sale such as will give an end user access to loose granular powder to extract a portion thereof.

The invention will be further explained and illustrated by the following Examples.

Example 1 An initial detergent composition consisted of spray-dried granules whose formulation was: 8 by weight Sodium alkyl benzene sulphonate 9.0 Nonionic detergent active (Cl2-l5 fatty alcohol 7EO) 6.0 Sodium silicate 9.0 Sodium tripolyphosphate 37.5 Sodium sulphate 24.3 Ethylene diamine tetraacetic acid 0.2 Sodium carboxymethyl cellulose 0.7 Polyacryl ate 1.5 Water balance Fluorescer (Photine C.B.U.S. from Hickson Welch) was mixed with finely divided sodium sulphate in a weight ratio of 1:1, using a "V" mixer.

This premix was mixed with the initial detergent composition, in a weight ratio of 1:100 using the same mixer (after first cleaning it).

Example 2 Some of the admixture of Example 1 was sprayed with 4t by weight of nonionic detergent active (C1215 fatty alcohol 3 EO) and mixed again.

After 24 hours storage, small samples of the initial composition, the product of Example 1 and the product of Example 2 were tipped side by side on a sheet of white paper and viewed under normal daylight. The initial composition appeared distinctly off-white, the product of Example 1 appeared acceptably white and the product of Example 2 was a bright white.

Example 3 The procedure of Example 1 was repeated using three initial detergent compositions which were the same as that of Example 1, except for having 6% of sodium alkyl benzene sulphonate and 0%, 2%, and 4 of the 7EO nonionic detergent active.

After mixing the fluorescer premix with the initial compositions, and after varying periods of storage, small samples were viewed under normal daylight, and compared with the respective initial detergent composition.

For the composition without nonionic detergent active there was some whitening effect, while the compositions with nonionic detergent active present both displayed strong whitening due to the fluorescer and were bright white granules. The composition with 4% nonionic detergent active was whiter than that with 2%.

Example 4 The procedure of Example 1 was repeated using initial detergent compositions with 12.5% of sodium alkyl benzene sulphonate and 0%, 1% and 2% of the 7EO nonionic detergent active. Once again samples were viewed under normal daylight after storage and compared with the respective initial compositions. The composition without nonionic detergent active displayed some whitening effect while the compositions with 1% and 2% nonionic detergent active both displayed a marked whitening due to the fluorescer and were a bright white.

It was noted that when nonionic detergent active was absent or at a low (1%) level, the whitening effect of the fluorescer was slow to appear, requiring several days storage, while with higher levels of nonionic detergent active the whitening effect was both stronger, and quicker to appear.

If desired, nonionic detergent active could be sprayed onto the products of Examples 3 and 4, as in Example 2, with the same benefit of further enhancing the perceived whiteness of the granules.

The products of these Examples are intended to be packed in conventional cardboard cartons or closable containers of any convenient form, such that an end user will scoop out or tip out a portion of the loose powder from the container, and see the loose granular powder when placing it in a washing machine.

Claims (10)

1. A process for incorporating a fluorescer in a granular detergent composition, which comprises: admixing particulate fluorescer with an initial granular detergent composition which is, or which includes, a spray-dried mixture containing one or more detergentactives selected from anionic detergent actives, nonionic detergent actives and mixtures of anionic and nonionic detergent actives.

2. A process as claimed in claim 1 comprising admixing the particulate fluorescer with a particulate diluent to form a premix and then admixing the premix with the initial granular composition.

3. A process as claimed in claim 1, wherein the particulate diluent comprises an inorganic salt.

4. A process as claimed in claim 2, wherein the particulate diluent comprises sodium sulphate.

5. A process as claimed in any one of the preceding claims wherein the premix contains fluorescer and diluent in a weight ratio between 20:1 and 1:200.

6. A process as claimed in any one of the preceding claims wherein the premix contains fluorescer and diluent in a weight ratio between 1:1 and 1:10.

7. A process as claimed in any one of the preceding claims, wherein nonionic detergent active is included in the initial granular detergent composition and/or admixed before or after admixing fluorescer, so that the composition formed contains at least 0.5% by weight of nonionic detergent active.

8. A process as claimed in any one of the preceding claims wherein the initial detergent composition contains at least 0.5 by weight of nonionic detergent active.

9. A process as claimed in claim 7 wherein the spray-dried mixture contains at least 0.5t by weight of nonionic detergent active.

10. A process as claimed in any one of the preceding claims, wherein the spray-dried mixture contains at least 0.5* by weight of anionic detergent active, preferably at least 4%.