SK105996A3 - Particulated detergent composition and method for producing same - Google Patents

Abstract

A particulate detergent composition comprising an organic surfactant system, a detergency builder system and optionally other detergent ingredients, characterized in that (a) the organic surfactant system comprises mobile ethoxylated nonionic surfactant in an amount of at least 10 wt.% based on the whole composition, and (b) the composition also comprises a graft copolymer of (i) polyethylene, polypropylene or polybutylene oxide with (ii) vinyl acetat e (optionally partially saponified), in a weight ratio of (i) to (ii) of from 1 : 0.2 to 1 : 10.

Description

Particulate detergent composition and process for its preparation

Technical field

The invention relates to particulate detergent compositions comprising a defined polymer that provides the benefits of soil release, for example, a graft polymer of vinyl acetate units on a polyethylene oxide backbone. The compositions of the present invention contain relatively high levels of liquid nonionic surfactants and have a high bulk density.

BACKGROUND OF THE INVENTION

EP 219 048A (BASF) discloses the use of grafted polyalkylene oxide / vinyl acetate copolymers as graying inhibitors of synthetic textile fabrics during laundering and post-laundering treatment.

EP 358 474A (Unilever) discloses detergent compositions comprising a graft copolymer of this type in conjunction with a low HLB surfactant system exhibiting surprisingly enhanced anti-redeposition properties for polyester / cotton fabrics.

EP 358 473A and EP 358 472A (Unilever) also relate to enhancing the anti-redeposition properties when a graft copolymer is used in conjunction with an aluminosilicate detergent component and an acrylic polymer, or with dipicolinic acid as a detergent component.

We have now unexpectedly found that incorporation of these graft copolymers into some particulate detergent compositions may additionally provide another rather different benefit that is not associated with anti-redeposition or contamination suspensions: when high levels of liquid nonionic surfactant are present in high bulk density powders. , the release of the nonionic surfactant can be substantially reduced. Laundry delivery can also be improved.

EP 358 474A (Unilever) mentioned above describes compositions

- 2 containing an ethoxylated nonionic surfactant. However, said benefit (increased antiredeposition) is obtained only with a nonionic surfactant having a low cloud point and a low HLB value. For example, no benefit was observed with a C12-15 alcohol ethoxylated with an average of 7 or more moles of ethylene oxide per mole of alcohol. Described as a preferred level of nonionic surfactant is from 3 to 10% by weight of the total composition, and the compositions specifically described in the Examples contain only 4% by weight of the nonionic surfactant. High bulk density is not described. Particular discoveries of EP 358 473A and EP 358 472A (Unilever are similar.

WO 92 06152A and WO 93 19145A (Procter & Gamble) disclose the use of soil release polymers which comprise a graft copolymer in compositions wherein the surfactant system comprises a polyhydroxy fatty acid amide. Powders of high bulk density are exemplified in WO 92 06152A, but contain only low levels of ethoxylated surfactant (less than 2.5% by weight).

EP 455 468A (Protein Technologies International) discloses novel protein contaminant releasing materials and compares them to the graft copolymers of the type discussed above. In particular, the powder compositions described contain 5% by weight of a nonionic surfactant (C 2-15 alcohol, 9 EO).

SUMMARY OF THE INVENTION

Accordingly, the invention provides a particulate detergent composition comprising an organic surfactant system, a detergent builder system, and optionally other ingredients, wherein (a) the organic surfactant system comprises a liquid ethoxylated nonionic surfactant in an amount of at least 10% by weight of the total composition; ) the composition also comprises a graft copolymer of (i) polyethylene oxide, polypropylene oxide or polybutylene oxide with

(Ii) vinyl acetate (optionally partially saponified, in a weight ratio of (i) to (ii) of from 1: 0.2 to 1:10, and (c) the mixture has a bulk density of at least 650 g / l.

The invention also provides a process for preparing a particulate detergent composition as defined above comprising preparing an almost homogeneous granular base by mixing and granulating, then optionally post-dosing the other ingredients, the graft copolymer being incorporated as an aqueous solution during the mixing and granulation process.

The invention further provides the use of a copolymer as defined above for reducing and preventing the release of a nonionic surfactant from a particulate detergent composition having a bulk density of at least 650 g / L and containing at least 10% by weight of a liquid ethoxylated nonionic surfactant.

DETAILED DESCRIPTION OF THE INVENTION

The particulate detergent compositions of the present invention comprise a graft copolymer as described and claimed in EP 219 048A (BASF).

The compositions also contain a relatively high level of liquid ethoxylated nonionic surfactant. These surfactants provide substantial efficacy gains, but for such compositions, the phenomenon known as bleeding-release of the nonionic surfactant may be a major problem. The liquid surfactant may migrate through the powder, becoming unevenly distributed, leading to loss of efficacy, loss of powder flow and sticking; when a porous (e.g., cardboard) package is used, the nonionic surfactant tends to move through the narrow capillaries of the packaging material, leading to penetration and external staining. Bleeding is a typical problem of powders of high bulk density and correspondingly low particle porosity.

According to the present invention, the presence of a graft copolymer as defined above and as discussed in more detail below may reduce or prevent the release of a nonionic surfactant. This effect is enhanced when the water-soluble citric acid salt present, preferably sodium citrate, is present.

Vaccine copolymer

The graft copolymers used in the compositions of this invention are described and claimed in EP 219 048A (BASF). They can be obtained by seeding a polyalkylene oxide having a molecular weight (number average) of 2000 to 100000 with vinyl acetate, which may be partially saponified, in a weight ratio of polyalkylene oxide to vinyl acetate of from 1: 0.2 to 1:10. The vinyl acetate can be saponified, for example, in the range up to 15% by weight.

The polyalkylene oxide may comprise ethylene oxide, propylene oxide and / or butylene oxide units; polyethylene oxide is preferred.

A preferred polyalkylene oxide has a number average molecular weight of from 4000 to 50,000, and a weight ratio of polyalkylene oxide to vinyl acetate of from 1: 0.5 to 1: 6. Especially preferred are polymers obtained from polyethylene oxide having a molecular weight of 2000 to 5000 and having a weight ratio of polyalkylene oxide to vinyl acetate of from 1: 0.5 to 1: 6.

A material within the scope of this definition, based on polyethylene oxide of molecular weight 6000 (equivalent to 136 ethylene oxide units), containing approximately 3 parts by weight of vinyl acetate units per 1 part by weight of polyethylene oxide, and having a molecular weight of 24000 itself, is commercially available from BASF as Sokolan. ) HP22.

The polymers are preferably present in the compositions of the invention in amounts of from 0.1 to 10% by weight, preferably from 0.2 to 5% by weight, and more preferably from 0.3 to 2% by weight.

The graft copolymer is available in the form of an aqueous solution suitable for use in preparing the detergent compositions of the present invention as described in detail below.

Surface active system

The compositions of the present invention contain at least 10% by weight of a liquid ethoxylated nonionic surfactant. Preferred compositions comprise at least 12% by weight of the liquid ethoxylated nonionic surfactant.

Preferably, the ethoxylated alcohol nonionic surfactant has an average alkyl chain length of C8-C18, preferably C12-C18 aliphatic alcohols ethoxylated with 2.5 to 8.0 moles of ethylene oxide per mole of alcohol are particularly preferred. The benefit associated with the invention is particularly marked with the CI2 ^- Ci5 alcohols having an average degree of ethoxylation of from 6.5 to 8.0.

A preferred surfactant system for use in the compositions of the present invention comprises an ethoxylated nonionic surfactant in conjunction with a primary alcohol sulfate (PAS).

In this embodiment, the ethoxylated nonionic surfactant preferably comprises from 30 to 90% by weight of the surfactant system, more preferably from 40 to 70% by weight; and the PAS preferably constitutes from 10 to 70% by weight, more preferably from 30 to 60% by weight of the surfactant system. Preferably, the entire composition comprises at least 5% PAS by weight.

The compositions of the invention may also preferably contain a fatty acid soap, suitably in an amount of from 1 to 5% by weight. The presence of soap is advantageous because it acts as a powder structurant, thereby providing a dry, free-flowing powder. However, the presence of soap in the compositions of the present invention is not essential.

Water-soluble salts

According to a preferred embodiment of the invention, the compositions comprise at least one water-soluble salt. The presence of a water-soluble salt appears to be very advantageous in terms of reducing the release of the non-ionic surfactant and can also perform other functions in the composition at the same time.

For example, the compositions may contain sodium carbonate, which is in any case useful for increasing detergency and may facilitate processability. Sodium carbonate may generally be present in amounts ranging from 1 to 60% by weight, preferably from 2 to 40% by weight, and most preferably from 2 to 13% by weight. However, mixtures without alkali metal carbonate are also within the scope of this invention.

According to a highly preferred embodiment of the invention, the compositions comprise a water-soluble citric acid salt, more preferably sodium citrate. Citrate is of course valuable as a detergent component as well as for enhancing the anti-bleeding effect associated with the present invention.

Citrate is preferably present in an amount of from 0.5 to 40% by weight (as sodium citrate dihydrate, of the total composition).

Particularly preferably, the citrate has a Rosin-Rammler particle size of less than 800 µm, preferably from 100 to 500 gm, and is incorporated in the homogeneous base granules of the composition rather than added.

Other ingredients

The compositions of the present invention comprise a detergent builder system which preferably comprises an alkali metal aluminosilicate, preferably sodium. Sodium aluminosilicates may suitably be incorporated in amounts of from 10 to 60% by weight (anhydrous basis).

The alkali metal aluminosilicates may be either crystalline or amorphous or mixtures thereof, with the general formula 7 0.8-1.5 Na ₂ O. A1 ₂ O ₃ . 0.8-6 SiO ₂

These materials contain bound water and have a calcium exchange capacity of at least 50 mg CaO / g. Preferred sodium aluminosilicates contain 1.5 to 3.5 SiO ₂ units (in the above formula). Both amorphous and crystalline material can be prepared readily by reaction between sodium silicate and sodium aluminate, as is amply described in the literature.

Suitable crystalline sodium aluminosilicates as ion exchange detergent ingredients are described, for example, in GB 1 429 143 (Procter & Gamble). Preferred sodium aluminosilicates of this type are the well-known commercially available zeolites A and X, and mixtures thereof.

The zeolite may be a commercially available zeolite 4A, at the same time widely used in laundry detergent powders. However, according to a preferred embodiment of the invention, the zeolite component incorporated in the compositions of the invention is maximum aluminum zeolite P (zeolite MAP) as described and claimed in EP 384 070A (Unilever). Zeolite MAP is defined as an alkali metal aluminosilicate of the zeolite P type with a silicon to aluminum ratio not exceeding 1.33, more preferably not exceeding 1.07; preferably in the range from 0.90 to 1.33, and more preferably in the range from 0.90 to 1.20.

Particularly preferred is a zeolite MAP having a silicon to aluminum ratio not exceeding 1.07, more preferably about 1.00. The calcium binding capacity of zeolite MAP is generally at least 150 mg CaO per gram of anhydrous material.

If desired or desired, other detergent ingredients may also be present in the detergent compositions of the present invention. As mentioned above, citrates are particularly preferred.

Another class of detergent builders that may be incorporated are polycarboxylate polymers, more particularly polyacrylates and acrylate / maleate copolymers, which may suitably be used in amounts of from 0.5 to 15% by weight, especially from 1 to 10% by weight.

Other components that may be present include a fluorescent reagent; sodium silicate; bleaching ingredients such as sodium perborate or percarbonate, bleach activators and bleach stabilizers; sodium carbonate; proteolytic and lipolytic enzymes; coloring agents; foam control granules; colored grains; perfumes; fabric softening agents. This list is not intended to be exhaustive.

Bulk density and powder properties

The invention relates to detergent powders of high bulk density: at least 650 g / l, preferably at least 700 g / l, and more preferably at least 800 g / l. Preferred compositions of the invention have an void volume not exceeding 10%, more preferably not exceeding 5%; the void volume can be measured by a known mercury intrusion porosimetry technique.

Preferably the content of fine particles, i.e. particles smaller than 180 µπι, does not exceed 10% by weight and more preferably does not exceed 5% by weight.

Preparation of detergent compositions

The high bulk density powders to which this invention is applicable are generally not a direct product of the spray-drying process, although they can be prepared by concentrating the spray-dried base powder.

However, a preferred method of preparation involves preparing a dense, almost homogeneous granular base in a non-tower (not spray-drying) manner in which the liquid and solid components are mixed and granulated together. If desired, other components may be sequentially postdosed.

Of the ingredients listed above, surfactants, aluminosilicate, fluorescent, sodium carbonate, sodium silicate, and other salts may be suitably incorporated into the base, while whitening ingredients, enzymes, perfumes, colorants, suds control granules and fabric softening agents will generally be post-dose.

According to a preferred method, the preparation of the base powder is carried out in a high speed mixer / granulator which acts both by mixing and by chopping. The high-speed mixer / granulator, also known as a high-speed mixer / densifier, can be a dispensing machine, such as a Fukae (trademark) FS, or a continuously operating machine, such as the Lodige (trademark) Recycler CB30. Suitable methods are described, for example, in EP 544 492A, EP 420 317A and EP 506 184A (Unilever).

Incorporation of sodium citrate

As indicated above, according to a preferred embodiment of the invention, sodium citrate (or other alkali metal citrate) is incorporated in the granular basis as described and claimed in WO 95 14767A (Unilever).

Citrate. in the base powder, it desirably has an amount of at least 0.5% by weight, preferably from 0.5 to 40% by weight, of the total composition; and desirably at least 3% by weight, more preferably at least 5% by weight, and most preferably from 3 to 15% by weight of the total mixture.

The sodium citrate incorporated in the base powder preferably has a fine particle size, it should have a Rosin-Rammler particle size not exceeding 800 gm, preferably not exceeding 500 gm, and most preferably from 100 to 500 gm.

Generally, inorganic detergent ingredients and other inorganic materials (e.g., zeolite, sodium carbonate) are granulated with surfactants that act as binders and granulating and agglomerating reagents. The citric acid salt may be incorporated at this stage. The fatty acid soap may be prepared in situ by neutralization with sodium hydroxide solution during the mixing and granulation process.

Optionally, the citric acid salt may be incorporated in intimate admixture with a surfactant, more preferably a nonionic surfactant. Alternatively, it may be added in solid form. The fatty acid may also be added in the form of a masterbatch with a surfactant, again preferably a nonionic surfactant.

Any optional ingredients, as mentioned previously, may be incorporated at any suitable stage of the process.

In these processes, the PAS present may already be neutralized, i.e. in the form of a salt, when dosed into a high speed mixer / granulator, or alternatively it may be added in acid form and neutralized in situ. If desired, the PAS and the nonionic surfactant may be introduced in the form of a homogeneous liquid composition as described in EP 265 203A and EP 507 402A (Unilever). EP 420 317A and EP 506 184A (Unilever) disclose another process wherein the PAS acid, which is liquid, is mixed and reacted with a solid inorganic alkaline material such as sodium carbonate in a continuous high speed mixer. The resulting granules or addition is then metered into another high speed mixer with nonionic surfactants and solids.

All of these processes are suitable for preparing the composition of the invention.

In accordance with normal practice in the manufacture of detergent powders, bleach components (bleach, bleach precursor, bleach stabilizer), proteolytic and lipolytic enzymes; colored grains; perfumes; The suds control granules are most conveniently post-dosed to the base powder after it has left the high speed mixer / granulator.

If desired, additional citrate may be among the postdosing ingredients. This may not have fine particles and preferably has a comparable particle size to the rest of the composition.

Incorporation of a graft copolymer

As indicated above, in the general process outlined above, a preferred method for incorporating a graft copolymer comprises incorporating a solution (preferably aqueous) of the graft copolymer between the liquid components in the mixing and granulation process used to prepare the base powder.

Thus, a preferred process of the invention involves preparing an almost homogeneous granular base by mixing and granulating, then optionally post-dosing the other ingredients. The grafted copolymer may be incorporated as an aqueous solution during the mixing and granulation process.

Sokolan HP22 is commercially available as a 20% by weight solution, which is very suitable for incorporation by this route.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be further illustrated by the following non-limiting examples in which parts and percentages are by weight unless otherwise indicated. The components used in the Examples have the following abbreviations:

CocoPAS: coconut alcohol sulphate

Non-ionic PAL 3E0: coconut alcohol ethoxylated with 3 moles of ethylene oxide per mole of alcohol

Non-ionic PAL 7E0: coconut alcohol ethoxylated with 7 moles of ethylene oxide per mole of alcohol

Zeolir MAP: zeolite MAP powder as described and claimed in EP 384 070A (Unilever), Si: Al ratio 1.00

Percarbonate: sodium percarbonate with a protective coating of sodium metaborate and sodium metasilicate as described in GB 2 123 044B (Kao)

TAED: tetraacetylethylenediamine (granules)

EDTMP: ethylenediaminetetramethylene phosphonate, calcium salt: Dequest (Trade Mark) ex. Monsanto.

With CMC:

sodium carboxymethylcellulose

Catalyst: bleach catalyst granules as described and claimed in international patent application no. PCT / GB94 / 01904 filed September 2, 1994

PVP: polyvinylpyrrolidone

The following tests were used to compare the release of the nonionic surfactant and the dosing characteristics.

Bleeding nonionic surfactant release test

The assay used provides an estimate of the degree of release of the nonionic surfactant over a three week storage period at 37 ° C by measuring the amount of nonionic surfactant absorbed by the pre-weighed filter paper placed on top and bottom of the powder column.

A 800 g sample of powders was weighed. The powder was poured to a depth of 1 cm at the base of a 15 cm diameter cylindrical container and an accurately weighed filter paper (Schleicher and Chúli No. 589) was placed on top of the powder. Additional powder was added to an approximate depth of 5 cm above the paper and then covered with a second accurately weighed filter paper. The remaining powder sample was then used to cover the second filter paper. The container was tightly sealed and stored in a dry atmosphere at 37 ° C for 3 weeks. After this storage period, the filter papers were removed and weighed, the paper weight increase was calculated, and the values for the two increases were averaged.

Washing Test 1: Cage Test

Powder dosing characteristics were compared using a model system that simulated powder dosing in an automatic washing machine under more unfavorable conditions (low temperature, minimum agitation) than normal in a real washing situation.

For this test, a cylindrical vessel with a diameter of 4 cm and a height of 7 cm, made of a 600 μιη pore size steel sieve, with a top cap made of teflon and a bottom cap made of a sieve as described above, was used.

The top closure had a 30 cm metal wire attached as a hinge and this hinge was attached to a stirrer arm placed above 1 liter of water at 20 ° C in an open container. Using this agitator, the cylindrical vessel suspended at a 45 ° angle could be rotated in a circle of 10 cm diameter over a period of 2 seconds and left still for 2 seconds before the start of the next rotation / rest cycle.

g a sample of powder was placed in a cylindrical container which was then closed. The vessel was attached to a stirrer arm that moved down to a position where the top of the cylinder vessel was just below the surface of the water. After a 10-second pause, the device performed 15 rotation / rest cycles.

The cylindrical vessel and hinge were removed from the water and the vessel was detached from the hinge. The surface water was carefully discarded and the powdered residue transferred to a preweighed container and dried at 100 ° C for 24 hours. Then the percentage of the starting weight (50 g) was calculated from the weight of the dry residue.

Test 2: Test by the dosing device

Dosing characteristics for powders were also compared using a model system that emulated powder dosing in an automatic washing machine from a flexible dispensing device of the type supplied with Lever's Persil (trademark) Micro System Powder in the UK: a spherical container of flexible plastic material with a diameter approximately 4 cm and an aperture of approximately 3 cm in diameter.

In this test, the metering device was attached in the up position (the highest aperture) to an overhead stirrer arm. Using this device, the device could move vertically up and down in the range of 30 cm, the lowest cm of this track were underwater. Each up or down journey had a duration of 2 seconds, the device being allowed to rest 5 cm under water for 4 seconds at the lowest position and at the highest position being rotated through 100 ^e and retained in the resulting tilted orientation for 2 seconds before falling.

The weighed sample of powder was introduced into the machine at its uppermost position and the instrument was allowed to run for six cycles and stopped when the machine was again in the uppermost position. The surface water was carefully poured off and the remainder of the powder was transferred to a pre-weighed container. The container was dried at 100 ° C for 24 hours and the percentage by weight of dry residue from the initial weight of the powder was calculated.

Examples 1 and 2, Comparative Examples A to C

Bleaching detergent powders of high bulk density were prepared with the composition as shown in Table 1. Examples 1 and 2 were according to the present invention, while Examples A to C were comparative.

Base powders were prepared using a continuous high speed mixer / granulator and the other ingredients were post-dosed as indicated. Sokolan HP22 was incorporated as a 20 wt% aqueous solution, but the amounts herein are for 100 wt% material. The sodium citrate dihydrate incorporated in the base had a Rosin-Rammler particle size of 415 μπι.

Table 2 lists the nonionic surfactant release and dosing characteristics for base powders prior to post-dosing the ingredients at the bottom of Table 1.

The detergency of all powders (solid blends) was very similar, but Sokolan HP22 provided significant enhancement of the removal of oily soiling from polyester and polyester / cotton fabrics.

Examples 1 and 2, Comparative Examples A to C Table 1: Composition

Example A B 1 C 2 basis CocoPAS 5.82 5.98 5.55 5.82 6.04 Non-ionic PAL 3E0 5.27 5.65 5.25 - - Non-ionic PAL 7E0 7.91 8.38 7.78 13.18 14.16 Sokolan HP22 - - 0.74 - 0.79 Soap 2.05 1.40 1.30 2.05 - Zeolite MAP 36,64 39,17 38.85 36.65 38.98 Sodium citrate - 4.25 4.18 - 4.85 Sodium carbonate 1.16 1.20 1.11 1.16 1.20 SCMC 0.90 - - 0.90 - Water / salt 5.49 0.47 0.43 5.49 0.47 Pretty 65.25 66.49 65.18 65.25 66,48 Post / Portion Sodium carbonate 2.23 - 2.30 2.23 - Antifoam / 3.00 4.00 3.00 3.00 4.00 fluorescent substance TAED granules 4.75 4.75 4.75 4.75 4.75 Mn catalyst 1.70 1.70 1.70 1.70 1.70 Sodium percarbonate 20.50 20.50 20.50 20.50 20.50 EDTMP 0.37 0.37 0.37 0.37 0.37 enzymes 1.75 1.75 1.75 1.75 1.75 perfume 0.45 0.45 0.45 0.45 0.45

PAL - surfactant

Examples 1 and 2, Comparative Examples A to C Table 2: properties and test results

Example A B 1 C 2 Citran in Basis / / / Sokolan HP22 solution / / basically Non-ionic PAL 3EO / 7EO / / / Only non-ionic PAL 7E0 / / Bleeding 36.0 35.0 0 45.0 11.0 Cage test 47.2 24.8 23.7 70.0 26.1 Dosing test 62.3 0 0 50.0 0 equipment

Examples 3 to 8

Table 3 shows some examples of non-bleaching compositions of the present invention.

These preparations also contained post-dosed sodium citrate dihydrate of larger particles than sodium citrate dihydrate incorporated in the base powders.

Table 3: Examples 3 to 8, non-bleaching preparations

Example 3 4 5 6 7 8 basis CocoPAS 6.16 5.84 10.66 9.44 6.46 6.46 Non-ionic PAL 3E0 5.78 - 4.24 3.83 5.86 - Non-ionic PAL 7E0 5.78 13.74 6.37 5.76 8.78 14.64 Sokolan HP22 0.68 0.65 0.62 0.65 0.51 0.51 Soap 1.84 2.03 1.85 1.64 2.25 2.25 Zeolite MAP 38.66 38.49 30,91 31.52 40,15 40,15 Sodium citrate 4.95 4.71 - 4.30 - - Sodium carbonate 1.31 1.31 2.18 1.83 1.26 1.26 SCMC - - - - 0.72 0.72 Water / salt 4.72 6.03 5.32 5.92 6.22 6.22

Pretty 72.80 72,8062,15 64,89 72,22 72,22 Post / Portion Sodium carbonate 20.62 20.62 30.47 27.73 21.53 21.53 antifoam 3.20 3.20 4.00 4.00 3.15 3.15 ingredient / PVP EDTMP 1.43 1.43 1.43 1.43 1.43 1.43 enzymes 1.50 1.50 1.50 1.50 1.50 1.50 perfume 0.45 0.45 0.45 0.45 0.45 0.45

Claims (22)

PATENT CLAIMS A particulate detergent composition comprising an organic surfactant system, a detergent builder system, and optionally other ingredients, characterized in that (a) the organic surfactant system comprises a liquid ethoxylated nonionic surfactant in an amount of at least 10% by weight of the total composition, (b) the composition also comprises a graft copolymer of (i) polyethylene oxide, polypropylene oxide or polybutylene oxide with (ii) vinyl acetate (optionally partially saponified, in a weight ratio of (i) to (ii) of from 1: 0.2 to 1:10, and ( (c) the mixture has a bulk density of at least 650 g / l. 2. A detergent composition as claimed in claim 1 comprising at least 12% by weight of liquid ethoxylated nonionic surfactant. 3. A detergent composition according to claim 1, characterized in CA in that the nonionic surfactant comprises one or more of 12 ^ ^_ ^ 15 aliphatic alcohols ethoxylated with from 2.5 to 8.0 moles of ethylene oxide. The detergent composition of claim 3, wherein the nonionic surfactant comprises one or more ^C 12 ^C 15 aliphatic alcohols ethoxylated with 6.5 to 8.0 moles of ethylene oxide. Detergent composition according to any one of the preceding claims, characterized in that the organic surfactant system comprises essentially: (i) an ethoxylated nonionic surfactant (60 to And (ii) optionally a primary alcohol sulfate (0-40% by weight of the surfactant system). 6. A detergent composition according to claim 5 wherein the surfactant system consists essentially of from 30 to 90% by weight of the ethoxylated nonionic surfactant and from 10 to 70% by weight of the surfactant. of the primary alcohol sulfate). Detergent composition according to any one of the preceding claims, characterized in that the graft copolymer can be obtained by grafting a polyalkylene oxide having a molecular weight (number average) of 2000 to 100000 with vinyl acetate (optionally partially saponified) in a weight ratio of polyalkylene oxide to vinyl acetate of 1: 0. 2 to 1:10. Detergent composition according to any one of the preceding claims, characterized in that the graft copolymer can be obtained by grafting a polyalkylene oxide having a molecular weight (number average) of 2000 to 50,000 with vinyl acetate (optionally partially saponified) in a polyalkylene oxide to vinyl acetate weight ratio of 1: 0; 5 to 1: 6. Detergent composition according to any one of the preceding claims, characterized in that the graft copolymer is present in an amount of from 0.1 to 10% by weight. A detergent composition according to any preceding claim, further comprising a water-soluble citric acid salt. The detergent composition according to claim 10, wherein the composition comprises from 0.5 to 40% by weight of sodium citrate. A detergent composition according to claim 11, which comprises an almost homogeneous granular base and optionally post-dosed components, characterized in that the granular base comprises at least 0.5% by weight (of the total mixture) of sodium citrate. 13. A detergent composition according to claim 12 wherein the granular base comprises from 3 to 15% by weight (of the total composition) of sodium citrate. The detergent composition according to claim 12 or 13, wherein the citrate in an almost homogeneous granular base has a Rosin-Rammler particle size not exceeding 800 µm. Detergent composition according to any one of the preceding claims, characterized in that the detergent system comprises from 10 to 60% by weight (based on the total composition) of crystalline or amorphous alkali metal aluminosilicate. 16. A detergent composition according to claim 15 wherein the alkali metal aluminosilicate is zeolite P having a silicon to aluminum ratio not exceeding 1.33 (zeolite MAP). Detergent composition according to any one of the preceding claims, characterized in that the void volume does not exceed 10%. The detergent composition of claim 17, wherein the void volume does not exceed 5%. A process for preparing a particulate detergent composition according to any preceding claim, comprising preparing an almost homogeneous granular base by mixing and granulating, then optionally post-dosing the other ingredients, characterized in that an aqueous solution of graft copolymer (b) is included in the granulation process. 20. The method of claim 19 wherein the water-soluble citric acid salt is also incorporated into an almost homogeneous granular base. 21. The method of claim 20 wherein the water-soluble salt is sodium citrate and is incorporated in an amount of at least 0.5% by weight of the total composition. Use of a graft copolymer of (i) polyethylene oxide, polypropylene oxide or polybutylene oxide with (ii) vinyl acetate (optionally partially saponified, in a weight ratio of (i) to (ii) of from 1: 0.2 to 1:10, to prevent or reduce release The nonionic surfactant of the particulate detergent composition having a bulk density of at least 650 g / L comprises an organic surfactant system comprising a liquid ethoxylated nonionic surfactant in an amount of at least 10% by weight of the total composition, a detergent builder system, and optionally other detergent builders.