NO163140B - SOLUTION MIXING. - Google Patents

Abstract

Detergent compositions which comprise base powder granules containing detergent active materials and amorphous aluminosilicate together with a post-dosed peroxygen bleach compound exhibit improved ion-exchange properties and bleach stability if the level of moisture in the granules lies between given limits which depend on the levels of aluminosilicate, detergent active and alkaline salt if any present in the granules. Exemplified moisture contents lie between 10.7% and 21.0% of the base powder granules.

Description

It is known to make spray-dried detergent mixtures that contain detergent-active materials, detergency builders and possibly other components including bleaching agents. In British patent document no. 1 4 73 202, it is proposed to use X-ray amorphous aluminosilicate materials as detergency builders, instead of the more common alkali metal phosphates that have been used up to now. However, detergent compositions containing amorphous aluminosilicate often suffer from the disadvantage of having poor ion exchange properties when first formed, and these ion exchange properties deteriorate even more during storage, and if the composition additionally contains bleaching materials, the stability of such bleaching materials during storage is often poor .

We have discovered that granular detergent compositions based on amorphous aluminosilicate having improved initial and long-term ion exchange properties can be obtained by controlling the level of moisture in such compositions. We have also discovered that if such mixtures additionally contain bleaching materials, the storage stability of such bleaching materials is also improved.

Granular detergent mixtures invariably contain water. Most or all of this water is relatively loosely bound and is lost when the mixture is heated to, for example, 135°C. This loosely bound water consists of water of crystallization from the components in the mixture, and further water that is more loosely bound to such ingredients as detergent-active materials.

As used herein, the term "moisture" is the water lost from the mixture when it is heated to 135°C.

However, in mixtures containing amorphous aluminosilicate and also in mixtures containing NTA (sodium nitrile triacetate), some water is not lost at 135°C. However, this more firmly bound water adds to the total water content of the mixture.

We have discovered that the properties of mixtures containing amorphous aluminosilicate are dependent on the moisture content of the mixture rather than the total water content.

If the mixture comprises a spray-dried base powder containing at least one washing active and an amorphous aluminosilicate building material, to which various additional components such as bleaching agents have been dosed, the critical factor in the ion exchange properties of the mixture is the moisture content of the base powder.

Therefore, according to the invention, a detergent mixture is provided which comprises spray-dried base powder granules, together with one or more post-dosed ingredients which include 5-50% of a peroxygen bleaching compound, the base powder granules containing at least 2-60% of a synthetic detergent-active material, 10-60% of an amorphous aluminosilicate building material, moisture, possibly soap, possibly crystalline aluminosilicate building material and possibly an alkaline salt selected from among alkali metal silicates, alkali metal carbonates, alkali metal phosphates and mixtures thereof, the aforementioned percentages being by weight based on the entire mixture, and the mixture is characterized by the moisture content in the granules is determined by the following formula:

where M is the moisture content of the granules in parts by weight, measured by the loss of water from the granules at 135°C, A is the amount of detergent active material including soap, if present, in the granules in parts by weight, S is the amount of the alkaline salt in the granules in parts by weight , X is the amount of aluminosilicate building material including crystalline aluminosilicate building material, if present, in the granules in parts by weight, and y is a number from 0.25 to 0.7, preferably 0.5-0.6.

If the base powder contains no sodium silicate and/or if it contains crystalline aluminosilicate (zeolite) in addition to the amorphous material, y is preferably between 0.25 and 0.5. Otherwise, the preferred level for y is from 0.5 to 0.6.

If the value of y is too low (which corresponds to a

relatively dry powder), it has been found that the ion exchange properties of the powder may be unsatisfactory. If the value of y is too high (which corresponds to a relatively high moisture content), the powder properties and bleaching stability may become unacceptable, and in extreme cases discoloration of the powder may occur.

THE SYNTHETIC DETERGENT MATERIAL

The mixtures according to the invention necessarily contain a synthetic detergent-active material otherwise known as a detergent-active surfactant, which is present at a total level of between 2 and 60% by weight, especially approx. between 5 and 40% of the mixture.

Suitable detergent surfactants are well known and readily available, such as described in "Surface Active Agents and Detergents", vol. I and II by Schwartz, Perry and Berch.

Synthetic anionic washing compounds that can be used are usually water-soluble alkali metal salts of organic sulfates and sulfonates that have alkyl radicals containing from approx. 8 to 22 carbon atoms, the term alkyl being used to include the alkyl part in higher acyl radicals. Examples of suitable synthetic anionic detergent compounds are sodium and potassium alkyl sulfates, especially those obtained by sulfation of the higher (C 8 -C 8 ) alcohols produced by reducing the glycerides of tallow or coconut oil; sodium and potassium alkyl(C8-C20)-benzenesulfonates, especially linear sodium sec.-alkyl (C^q-C^j. )-benzenesulfonates, sodium alkyl glyceryl ether sulfates, especially such ethers of the higher alcohols derived from tallow or coconut oil and synthetic alcohols derived from petroleum; sodium coconut oil fatty acid monoglyceride sulfates and sulfonates; sodium and potassium salts of sulfuric acid esters of higher (Cg-Clg) fatty alcohol-alkylene oxide, especially -ethylene oxide, reaction products; the reaction between fatty acids, e.g. coconut fatty acids esterified with isethionic acid and neutralized with sodium hydroxide; sodium and potassium salts of fatty acid amides of methyl taurine; alkane monosulfonates, e.g. those originating from the reaction of α-olefins (CQ-C2Q) with sodium bisulphite and those originating from the reaction of paraffins with SO2 and CI2

and then hydrolyzing with a base to produce a randomized sulfonate; and olefin sulfonates, this term to describe the material made by reacting olefins, especially C1Q-C20-α-olefins, with SO3 and then neutralizing and hydrolyzing the reaction product.

Non-ionic detergent-active compounds can alternatively or additionally be used. Examples of nonionic detergent active compounds include the reaction products of alkylene oxides, usually ethylene oxide, with alkyl(cg~C22^^enols, generally 5-25 EO; i.e. 5-25 units of ethylene oxide per molecule; the condensation products of aliphatic (Cg- C-^g) primary or secondary linear or branched alcohols with ethylene oxide, generally 5-40 EO, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called non-ionic detergent-active compounds include long-chain tertiary -amine oxides, long-chain tertiary phosphine oxides and dialkyl sulphoxides.

Mixtures of detergent-active compounds, for example mixed anionic or mixed anionic and non-ionic compounds, can be used in the detergent mixtures, in particular to

give these regulated low-foaming properties. This is beneficial for mixtures intended for use in automatic washing machines which are foam intolerant.

Amounts of amphoteric or zwitterionic detergent compounds can also be used in the compositions according to the invention, but this is not normally desired due to their relatively high price. If any amphoteric or zwitterionic detersive compounds are used, especially sulfobetaines, e.g. hexadecyldimethylammoniopropanesulfonate, it is usually in small quantities in mixtures which are based on the much more commonly used anionic and/or nonionic detergent active preparations.

Some soap may also be present in the mixtures, esp

in low-foaming mixtures together with mixed synthetic and non-ionic washing compounds. Such soaps are the sodium salts, or less desired the potassium salts, of c±2~ C22~ fatty acids > especially natural fatty acids derived from nut oils, e.g. coconut oil or palm kernel oil, or preferably tallow-class fat, e.g. beef and sheep tallow, palm oil, lard, some

vegetable butter and castor oil, or mixtures thereof. Mixtures are preferred of tallow class soaps, which are soaps of predominantly C14_C2o (mainly C^g) fatty acids of which normally at least approx. 40% are saturated fatty acids, with soaps from nut oils, which are soaps of predominantly C^0_C14 (mainly9 C]_2* fatty acids, of which normally at least about 75% are saturated fatty acids. The amount

of soap can vary widely from 0.5 to 20% by weight based on the mixture, but is normally from 1 to 5% if present for suds control purposes. Larger amounts of soap can be used as an additional washing-active compound.

THE AMORPHOUS ALUMINOSILICATE BUILDING MATERIAL

The mixtures according to the invention necessarily contain an amorphous aluminosilicate building material, which is present at a level of from 10 to 60% by weight, especially 12.5-50% by weight calculated on the mixture.

Amorphous aluminosilicate building materials are described in detail in British Patent Document No. 1,473,202.

However, the amorphous aluminosilicates described there have one significant shortcoming, namely that they react with sodium silicate, which is a significant component in most detergent mixtures. The mechanism of the reaction between amorphous aluminosilicate and sodium silicate is not fully understood, but its effect is to reduce the effectiveness of the aluminosilicate as a detergency builder in that it reduces the removal of hardness ions and can also reduce the capacity of the aluminosilicate for such ions.

Efforts have been made to overcome this shortcoming of amorphous aluminosilicates by modifying the manufacturing process for detergent compositions containing these two materials. For example, British patent no. 2 013 707 proposes an alternative route for the production of detergent mixtures where the sodium silicate is added to the detergent mixture in such a way that the reaction between the sodium silicate and the sodium aluminosilicate is reduced to a minimum.

In the context of the present invention, we prefer to use an amorphous aluminosilicate which can be used in the production of detergent mixtures, where orthodox spray drying equipment is used and where no special techniques are required to prevent reaction between the sodium silicate and the amorphous sodium aluminosilicate. This amorphous aluminosilicate can be produced in a particle size such that it can be used in detergent mixtures without further size reduction and also with a sufficiently high solids content so that very large amounts of water do not have to be removed from the aluminosilicate and thus from a detergent slurry containing the aluminosilicate, which makes it commercially less attractive.

A stable slurry of the aluminosilicate can be produced

in the presence of suitable dispersants and size-reduced aluminosilicate by crushing or milling a slurry of aluminosilicate and dispersant.

The preferred amorphous hydrated sodium aluminosilicate is characterized by a chemical composition calculated on an anhydrous basis:

and has, calculated on a dry basis, a calcium ion exchange capacity greater than 100 mg CaO/g, a magnesium capacity greater than 50 mg MgO/g, an average particle size in the range of 2-20 pm, and the ability to form a filter cake having a solids content of range 35-50%, in a filter press with a closing pressure on

5.62 kg/cm', as this filter cake can be converted into a pumpable slurry in the aforementioned solids range, and has a silicate resistance (as defined below) so that the second-order rate constant k for the calcium exchange process is greater than 0.2 °H ^

-1 p

min and a residual water hardness after 10 minutes of less than 1.5 °H and which after drying at 50 °C to 80% solids has a rate constant k, (to be defined later) greater than 0.4 2 °H — 1 min —<1> and a residual water hardness after 10 minutes of less than 1 °H.

References to °H in this description and in the requirements are to French degrees of hardness defined as

1°H Ca = 10~<4> molar Ca<++>.

Preferably, the amorphous hydrated sodium aluminosilicate has the following chemical composition:

and may optionally contain an inert, soluble salt, e.g. sodium sulfate.

The calcium and magnesium ion exchange capacities are determined as follows.

Sodium aluminosilicate (equivalent to 1.00 g of anhydrous solid determined as the residue after heating to constant weight at 700°C) is added to 1 liter of 5.0 x 10~<3> M CaCl2" solution and stirred for 15 minutes at 20°C The aluminosilicate is then removed by Millipore membrane filtration, and the residual calcium concentration (Z x 10~<3> M) of the filtrate is determined by complexometric titration or atomic absorption spectrophotometry.

The calcium exchange capacity is calculated as 56{5.0-Z) mg CaO/g aluminosilicate.

The magnesium ion exchange capacity is measured in a similar way using a 5 x 10 -3 M MgCl2~ stock solution and a pH in the range 9.5-10.5.

To quantify the water softening performance of these sodium aluminosilicates and to compare them with known amorphous aluminosilicates and the known zeolites, the following test is used:

The test is intended to simulate some of those conditions

which is prevalent when sodium aluminosilicate is used in a washing system.

The response of a Radiometer calcium ion specific electrode is determined by the addition of aliquots (0-20 ml) of calcium--2

chloride (3 x 10 M) to a solution of 5 ml M NaCl in 175 ml water at 50°C. The resulting solution is 0.025 M in Na<+> and 3 x 10 3 M in Ca<++.> To this is added sufficient aluminosilicate to give 2.5 g/liter (anhydrous basis), and stirring is maintained throughout the water softening measurement. The electrode response is measured over the next 10 minutes and, using the calibration data, is calculated as Ca<++->concentration (°H) versus time. Water softening can be conveniently summarized by the hardness remaining after 1 and 10 minutes.

The electrode test is used on filter cake, dried powders and on the slurries produced by the silicate resistance test.

To test the resistance of the various aluminosilicates to sodium silicate, a sample of the aluminosilicate to be tested is mixed with sodium silicate, sodium sulphate and water so that a homogeneous slurry is formed which has the following composition:

A sample of this slurry is tested for water softening activity by the calcium ion specific electrode method, taking into account the fact that 4.0 grams of slurry contains 1.0 g of aluminosilicate (anhydrous basis). The slurry is heated at 80°C for 1 hour in a water bath, and the electrode measurement is repeated on the additional sample. Differences in the two water softening measurements indicate the adverse reaction between the components. For the sake of simplicity, this can be summarized on the basis of the calcium hardness values obtained within 1 and 10 minutes.

If the aluminosilicate sample has a very low solids content, e.g. less than 30%, or if additional water must be added to the mixture to enable the production of a fluid slurry, the test may still be carried out, provided that the ion exchange measurement is taken into account when weighing the samples.

The water softening kinetics involved in the determination of the rate constant k involves the application of the data which

'in

is achieved by using the calcium ion-specific electrode as described above.

The water softening curve, °H Ca, against time (minutes) is summarized by a second-order speed-velocity equation of the following form: which upon integration becomes:

where CaQ is the initial hardness, (30°H);

Cagg is the equilibrium hardness at t = °°;

k is the rate constant which has dimensions

minute "°H Ca ;

ks is the rate constant for yield after the silicate treatment;

k^ is the rate constant of the filter cake or it

stabilized slurry dried in the absence of silicate;

t is the time in minutes.

A convenient method of evaluating these constants in the case where yield is practically complete within 10 minutes is to choose the hardness remaining after 1 minute and .10 minutes and solve the equation.

This contains the approximation that Ca^-Ca^ = 30 (ie ^ aeq = 0), but in practice this does not affect the result significantly.

The equilibrium hardness is determined by:

In situations where it is obvious that significant yield is still occurring after 10 minutes, albeit slowly, the time period should be extended until practically no further yield occurs and a measured value for Ca equilibrium can be obtained, the k value can then be determined from the above equation weight hardness equation.

The most effective sodium aluminosilicates for use

1 according to the invention has a speed constant kg above

2 and an equilibrium calcium concentration (Ca^) less than 1 °H after silicate treatment.

Amorphous aluminosilicates, which economically will provide a filter cake with a relatively high solids content containing an aluminosilicate with a particle size suitable for incorporation in detergent mixtures according to the invention and which have the good properties for silicate resistance previously expressed, can be produced by a method where aqueous sodium silicate, with the composition Na2° 2-4 SiO2°g a concentration3°n in the range 1-4 mol/liter SiO2; an aqueous aluminate having a composition of 1-2 Na2O A^O-j and a concentration in the range of 0.5-2.0 mol/liter A^O^ is intimately mixed together at a temperature of up to 45°C in a mixing device to produce a sodium aluminosilicate mixture which is immediately subjected to high shear in a disintegrator to produce a particle size of aluminosilicate less than 20 nm, and then aged.

The intimate mixture of the aluminate and the silicate solutions

can be conveniently achieved with such a mixer as that described in the Handbook of Chemical Engineering by Perry & Chilton, 5th ed., ch. 21, ref 21-4, under the heading "Jet Mixers".

The purpose of such mixers is to ensure rapid and intimate mixing of the two solutions.

This is achieved by applying a positive pressure, for example by pumping each of the solutions and forcing one of them through a small nozzle or nozzle into a stream of the other solution.

Suitable disintegrators for use in reducing the particle size of the sodium aluminosilicate include devices designed to provide high shear, such as Waring® mixers supplied by Warxng Products Division, Dynamics Corporation of America, New Hartford, Connecticut,

USA, and Greaves SM <®>mixers, supplied by Joshua Greaves & Sons Limited, Ramsbottom, Lancashire, England. Various other devices can be used, but it is believed that if the shearing force is provided by rotation of a stirrer blade in the reaction mixture, no such device will be satisfactory unless the top speed of the rotor exceeds 300 m/min. Preferably, the top speed is in the range of 1000-3000 m/min.

The processing after the high shear treatment may include an aging step for the free-flowing slurry which typically extends over a period of 1-2 hours, but may be longer. The precipitation formation and aging can take place in the presence of an inert salt, for example sodium sulfate. The aged slurry may also be treated with a dilute mineral acid, such as sulfuric acid, to reduce its pH to about 10.0 or 11.0 before washing and filtering.

THE PEROXYGEN BLEACHING COMPOUND

The products according to the invention necessarily contain a peroxygen bleaching compound, at a level of

between 5 and 50% by weight calculated on the mixture, in particular between 8 and 32% by weight. Suitable peroxygen bleaches include

sodium perborate (for example in the form of the tetrahydrate) and sodium percarbonate.

THE ALKALINE SALT

The products according to the invention can include an alkaline salt selected from alkali metal silicates, carbonates and phosphates.

The amount of sodium silicate used can vary widely depending on the type of product involved, ie from a minimum of 0.1 to 50% by weight of the resulting detergent mixture. Normally, however, amounts in the range from 0.5 to 20% are used, especially approx. 1 to 15%, for conventional purposes, ie for corrosion inhibition, pH buffer regulation and powder structuring properties. Amounts of sodium silicate in excess of this and up to approx. 40% is occasionally used for supplementary washability-building properties in laundry detergent mixtures. Even higher levels of sodium silicate may be present in other types of powdered detergent mixtures, for example for dishwashing or industrial purposes where high alkalinity is common.

Any normal type of sodium silicate can be used, preferably with a sodium oxide:silica ratio of from about 2:1 to approx. 1:4, for example alkaline sodium silicate (Na20.2Si02) neutral sodium silicate (Na20.3Si02), sodium metasilicate (Na2O.SiO2) or sodium orthosilicate (2Na2O.SiO2), or mixtures thereof, the less alkaline silicates (Na20.l -4Si02) is preferred.

Examples of other suitable alkaline materials include sodium carbonate, sodium tripolyphosphate, sodium orthophosphate and sodium pyrophosphate. These alkaline materials will also add to the building capacity of the mixes. The use of sodium pyrophosphate can lead to unacceptably high levels of inorganic deposition on the fabric, and it is therefore preferred to include less than 5% pyrophosphate in the compositions, preferably virtually no pyrophosphates.

OTHER INGREDIENTS

The detergent mixtures made according to the invention can contain any of the conventional additives in the quantities in which such additives are normally used in laundry detergent mixtures. • Examples of these additives include foam enhancers, e.g. alkanolamides, especially those monoethanolamides derived from palm kernel fatty acids and coconut fatty acids, powder flow aids, e.g. finely divided silicon dioxide and other aluminosilicates, antifoam agents, antigen deposition agents, e.g. sodium carboxymethyl cellulose, peracid bleach precursors, chlorine-releasing bleaches such as trichloroisocyanuric acid and alkali metal salts of dichloroisocyanuric acid, fabric softeners, e.g. clay species of smectite and illite types, anti-ash forming agents, starches, lime soap dispersants, inorganic salts, e.g. sodium sulfate, and usually present in very small amounts, fluorescent agents, perfume, such enzymes as proteases and amylases, germicides and coloring agents. In addition, particularly in the case of non-ionic detergent compositions, it may be desirable to add slurry stabilizers, for example copolyethylene/maleic anhydride and copolyvinyl methyl ether/maleic anhydride, usually in the salt form.

Alongside the essential aluminosilicate washability builders discussed above, other conventional washability builders may be present, e.g. sodium carboxymethyloxysuccinate, sodium nitrile triacetate and crystalline aluminosilicates (zeolites).

PROCESSING THE MIXTURES

The invention necessarily requires that the base powder granules be made by spray drying.

The slurrying and atomization drying steps in the method according to the invention can be carried out with conventional equipment for this purpose, for example in crutches, paddle or turbo mixers and atomization drying towers. Normal temperatures can be used for these operations, for example from 30

to 100°C, preferably 70 to 90°C for the slurry and 200 to 450°C for the drying gas inlet in the premist drying process, the higher temperatures within this range being generally preferred for economic reasons.

The base powder necessarily contains the detergent-active surfactant and the amorphous aluminosilicate. The peroxy bleach, together with any other heat-sensitive ingredients, can then be mixed with the base powder granules. The alkaline salt, if present, may be included in the granules, mixed with them afterwards, or both. If sodium silicate is the alkaline salt, it may be advantageous to add it afterwards to further reduce the risk of reaction with the sodium aluminosilicate in the slurry. It is preferred that any subsequently added materials be in their fully hydrated form.

In what follows, the invention will be illustrated by the following examples.

PRODUCTION OF AMORPHOUS ALUMINOSILICATE MATERIAL (NAS)

When using the mixer described below, the following preparation method was used: Batches of aluminate and silicate were prepared by adjusting commercial baths to suitable concentration and temperature. These were each pumped with

7 litres/min. to the mixing device (jet) and the resulting stream passed through a vessel of 30 liter capacity where it was subjected to intense agitation. The volume of the product in the stirred reactor was maintained at approx. 17 liters when adjusting the overflow speed. The reaction product was collected and allowed to

be aged, with gentle stirring, for 2 hours before the aluminosilicate was removed on a filter and washed free of the alkaline reaction bath.

The filter cake was prepared for the production of a stable, pumpable aqueous suspension by incorporating a suitable dispersant and reducing the particle size of the aluminosilicate to between 4.0 and 6.0 Mm by milling or crushing the aluminosilicate in an aqueous medium containing said dispersant, all in accordance with the teachings of British Patent No. 1,051,336.

It is noted that alternatively the filter cake, or the suspension prepared above, can be converted into dry powder form by a number of drying techniques. In order to preserve the ion-building properties, it is important that the remaining moisture content (loss on ignition) in the aluminosilicate is not less than approx. 20% by weight. Filter cakes can conveniently be dried in a drying cabinet at a temperature of 50°C for the purpose of testing the preservation of the ion exchange properties and determining the k^ value.

Of the following examples, the mixer used was a Greaves SM mixer, which had a high speed impeller rotating at approx. 3000 rpm with a top speed of 19 75 m/min.

Vigorous stirring is required to (a) prevent gelation which would lead to low solids filter cakes, and (b) control the particle size of the aluminosilicate.

For laboratory productions on a small scale, a Waring mixer (Model CB 6 "1 gallon capacity") which has a high-speed impeller, approx. 13,000 rpm, which produces a top speed of approx. 2800 m/min. Ion exchange performance - Ca electrode method ( °HCa)

EXAMPLES 1 TO 4

Using the amorphous aluminosilicate material prepared as indicated above, particulate detergent compositions were prepared by spray drying a base powder and adding thereto a number of post dosed ingredients. The base powders had the following composition, in parts by weight expressed as anhydrous material.

From the moisture content of the base powder stated above, measured by weight loss at 135°C, the values of "y" were calculated, with the following formula: where A is the total amount of anionic and non-ionic detergent active materials in parts by weight, including soap if any present, S is the amount of alkaline salt (sodium silicate) in parts by weight, and X is the amount of amorphous aluminosilicate in parts by weight. The calculated values for "y" were:

To these spray-dried base powders were added various post-dose ingredients as follows:

The ion exchange properties of these powders after storage were determined by washing the powders with deionized water on a filter cake to extract the insoluble aluminosilicate material and by drying. 0.5 g of the dried material was then added to 200 ml of water having a hardness of 30°FH (equivalent to a calcium ion concentration of 3 x 10 mol). The free calcium ion concentration was measured after 1 minute. The powders were stored for 6 weeks at 37°C and 70% relative humidity (Examples 4, 4A and 4B) or for 12 weeks at 28°C and 70% relative humidity (Examples 1, 2, 2A, 3 and 3A). In the same way, the ion exchange properties of the base powders were measured immediately after spray drying. The results were as follows:

A water hardness of 3°FH or less is considered a reasonable target. It therefore follows that all the powders tested were satisfactory with the exception of example 2A.

It is noted that, for example, 2A is y = 0.18, i.e. well below the limit of 0.25 set by the present invention.

The powders from examples 1 to 4 were stored under varying conditions after which the percent perborate that had been cleaved was measured. Similar powders were produced in which the amorphous aluminosilicate was replaced by Zeolite-4A, of similar particle size, to provide control samples. With the zeolite-containing powders, the moisture content was lower, namely between approx. 4.5 and 8% of the base powders. Moisture content identical to Examples 1 to 4 leads to poor powder properties and even more perborate decomposition during storage. The results were as follows:

These examples show the benefit of using amorphous aluminosilicate rather than zeolite.

EXAMPLES 5 AND 6

Two spray-dried base powders were produced with the following compositions:

The following ingredients were then dosed into this spray-dried base powder, as follows:

After storage at 37°C and 70% relative humidity for 4 weeks, 39% and 28% of the sodium perborate in Example 5 respectively

and 6 split. For comparison, where the amorphous aluminosilicate was replaced in Example 5 with zeolite 4A of similar particle size, more than 80% of the sodium perborate decomposed under the same conditions.

EXAMPLE 7

A base powder was spray-dried which had a composition identical to Example 4, but in which no sodium silicate was included. The water level was 9.7 parts, and the total basis powder weight was 53.4 parts. The moisture content was 7.1 parts (13.3%), which gave a value for y equal to 0.42.

The base powder was granulated with 5 parts sodium silicate (SiO2/Na2O=2.0), 18 parts sodium tripolyphosphate (measured as anhydrous), 4 parts water and 19.6 parts sodium perborate (measured as NaBo2•H2°2'3H20'' giving a total powder weight of 100 parts.

After storage at 37°C and 70% relative humidity for 6 weeks, 23% of the sodium perborate was decomposed.

For comparison, where the amorphous aluminosilicate was replaced with zeolite 4A, 82% of the sodium perborate decomposed under the same conditions.

This powder was then evaluated for its ion exchange properties in the same manner as described in connection with Examples 1 to 4, with the exception that the time was measured for the water hardness to drop to 3.3°FH. Immediately after production, this time was 0.4 min. After storing the powder for 6 weeks at 28°C and 70% relative humidity, this time was 0.7 min. These results indicated a satisfactory powder.

EXAMPLES 8 TO 10

A number of detergent compositions were prepared by spray-drying an aqueous slurry containing the following ingredients:

This slurry was spray dried to give detergent base powders with the following moisture contents:

The values for y can be calculated from these moisture contents using A=13.0, X=21.0 and S=5.0 as follows:

It will be seen that examples 9 and 10 have y-values within the present invention, while examples A, B and 8 are included for comparison purposes.

To these spray-dried base powders were added

22 parts by weight of partially hydrated sodium tripolyphosphate (18 parts calculated on an anhydrous basis) and 25 parts by weight of sodium perborate tetrahydrate.

The initial ion exchange rate for these mixtures was measured in the same manner as described in Example 7. The time taken for the water hardness to drop to 3.3°FH was as follows:

The powders from examples B and 10 were stored for 12 weeks at 28°C and 70% relative humidity. After this storage, the ion exchange rate was measured again. In the case of Example B, the time taken to reach 3.3° FH was longer than 10 minutes and in Example 10 0.9 minutes.

These results show the utility of the ion exchange properties in spray drying the base powder to a moisture content which gives a value for y according to the invention.

The powders, from Examples B and 10, were stored for 12 weeks under varying conditions, after which the bleach stability was determined by measuring the percent perborate that had been decomposed after that time. The results were:

These results show that the mixture according to the invention, example 10, shows improved bleaching stability compared to the comparative mixture, example B.

The mixture from example B is approximately the same as that described in example 1 in British Patent No. 2 013 707.

The detergent active material used in the preceding examples was approximately:

Claims (5)

1. Detergent composition comprising spray-dried base powder granules, together with one or more post-dosed ingredients including 5-50% of a peroxygen bleaching compound, wherein the base powder granules contain at least 2-60% of a synthetic detergent-active material, 10-60% of an amorphous aluminosilicate building material, moisture, optionally soap, optionally crystalline aluminosilicate building material and optionally a alkaline salt selected from among alkali metal silicates, alkali metal carbonates, alkali metal phosphates and mixtures thereof, the mentioned percentages being by weight based on the entire mixture, characterized in that the moisture content of the granules is determined by the formula where M is the moisture content of the granules in parts by weight, measured by the water loss from the granules at 135<*>C, A is the amount of the washed active material including soap, if present, in the granules i parts by weight, S is the amount of the alkaline salt in the granules i parts by weight, X is the amount of aluminosilicate builder including crystalline aluminosilicate builder, if present, i the granules in parts by weight, and y is a number from 0.25-0.7, below it condition that unless the base powder granules are free of alkali metal silicate and/or contains crystalline aluminosilicate building material, the value of y is in the range 0.5-0.7. 2. Detergent mixture as stated in claim 1, characterized in that the moisture content in the base powder granules corresponds to a value for y of between 0.5 and 0.6. 3. Mixture as specified in claim 1, characterized in that the base powder granules do not contain any sodium silicate and that the moisture content in them correspond to a value for y between 0.25 and 0.5. 4. Mixture as specified in claim 1, characterized in that at least the synthetic detergent active material, the soap, the amorphous aluminosilicate and sodium silicate are contained in the spray-dried base granules, the sodium perborate is a post-dosed ingredient and the moisture content in the base granules is 10.7-21% by weight, based on the weight of the base granules, the mixture comprising , based on the total composition: 5-40% by weight synthetic detergent active material; 1-5% by weight soap; 12.5-50% by weight amorphous aluminosilicate; 1-15% by weight sodium silicate; and 8-32% by weight sodium perborate. 5. Mixture as stated in any one of claims 1-4, characterized in that the amorphous aluminosilicate builder is an amorphous hydrated sodium aluminosilicate with a chemical composition calculated on an anhydrous basis: which has, calculated on a dry basis, a calcium ion exchange capacity greater than 100 mg CaO/g, a magnesium capacity greater than 50 mg MgO/g, an average particle size in the range of 2-2 0 µm, and the ability to form a filter cake having a solids content in the range 35-50%, in a filter press with a closing pressure of 5.62 kg/cm<2>, as the filter cake can be converted into a pumpable slurry in the aforementioned solids area, and has a silicate resistance (as defined here) which is such that the other order rate constant ks for the calcium exchange process is greater than 0.2°H-<1>min<-1> and a residual water hardness after 10 minutes of less than 1.5°H and which after drying at 50°C to 80% solids has a rate constant K<j (as defined here) of more than 0.42°H~<1>min^<1> and a residual water hardness after 10 minutes of less than 1°H.