EP0700427B1

EP0700427B1 - Detergent compositions

Info

Publication number: EP0700427B1
Application number: EP94915116A
Authority: EP
Inventors: Jelles Vincent Boskamp; Helen Burgess; Mark Phillip Houghton; Christophe Joyeux
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1993-05-26
Filing date: 1994-04-26
Publication date: 1997-09-17
Anticipated expiration: 2014-04-26
Also published as: SK144695A3; DE69405735D1; JPH08511568A; DE69405735T3; ES2107218T3; CZ309995A3; EP0700427A1; ES2107218T5; HUT74019A; HU9503374D0; DE69405735T2; AU6648594A; EP0700427B2; PL311749A1; WO1994028098A1

Abstract

A particulate detergent composition which is not the direct product of a spray-drying process has a high bulk density (»650 g/l) and contains a surfactant system consisting essentially of ethoxylated nonionic surfactant and optional primary alcohol sulphate, zeolite builder, and a citrate salt. Delivery and dissolution in the wash are improved by the choice of ethoxylated nonionic surfactant having an average degree of ethoxylation of 5.2 to 8.0, preferably about 7.

Description

TECHNICAL FIELD

The present invention relates to particulate detergent compositions of high bulk density containing anionic and nonionic surfactants and zeolite builder.

BACKGROUND AND PRIOR ART

EP 544 492A (Unilever) discloses detergent powders of high bulk density comprising an organic surfactant system (ethoxylated nonionic surfactant plus primary alcohol sulphate), zeolite builder, and other optional ingredients. The ethoxylated nonionic surfactant, which is the predominant component (at least 60 wt%) of the surfactant system, has a degree of ethoxylation not exceeding 6.5, preferably from 3 to 6.5 and more preferably from 4 to 5.5. This high-performance surfactant system gives excellent detergency, and the use of relatively high levels of zeolite allows the formulation of free-flowing powders containing high levels of these mobile surfactants.
These compositions are representative of the recent trend towards powders of high bulk density, prepared by processes that eliminate, or do not introduce, the porosity typical of traditional spray-dried powders. These include post-tower densification of spray-dried powders, and, more preferably, wholly non-tower routes involving dry-mixing, agglomeration, granulation and similar processes.
With formulations of this type, however, some problems have been experienced in the delivery of the active ingredients of the powder to the wash in an automatic washing machine. Delivery is a two-step process: the first step is the dispensing of the powder into the wash liquor, either from the dispenser drawer of the washing machine or from a dispensing device (a wash ball or similar) supplied by the powder manufacturer; and the second is dissolution of the powder once it arrives in the wash water.
It has surprisingly been found that in high bulk density powder of the type mentioned above, delivery is greatly improved by the use of a nonionic surfactant having a higher degree of ethoxylation, provided that a citric acid salt is also present.
Citrates are well known as detergency builders used to supplement zeolites. Their use in zeolite-built powders is disclosed, for example, in EP 313 143A, EP 313 144A, EP 448 297A and EP 448 298A (Unilever); GB-A-1 408 678, EP 1310A, EP 1853B, EP 326 208A, EP 456 315A and WO 91 15566A (Procter & Gamble); DE 2 336 182C (Lion); and GB 2 095 274B (Colgate).
EP-A-0508034 discloses a granular detergent composition which is characterised by containing polyvinylpyrrolidone to give good dye transfer-inhibition effects without impairment of particulate soil removal. It is mentioned that citric acid may be used as a carboxylate chelating agent.
EP-A-0508358 relates to a laundry detergent composition characterised by containing an alkaline cellulase and polyvinylpyrrolidone. Citrates may be used as builder.
However, the use of citrate in the presence of specific nonionic surfactant to improve the dissolution of a high bulk density detergent powder has not been described in literature.

DEFINITION OF THE INVENTION

The present invention accordingly provides a particulate detergent composition which is not the direct product of a spray-drying process, the composition having a bulk density of at least 650 g/l and comprising:

(a) from 15 to 50 wt% of a surfactant system consisting essentially of
- (i) ethoxylated nonionic surfactant which is a primary C₈-C₁₈ alcohol having an average degree of ethoxylation within the range of from 5.2 to 8.0,
- (ii) optionally primary alcohol sulphate,
- (iii) optionally not more than 25 wt% (based on the surfactant system) of alkylbenzene sulphonate,
(b) from 20 to 70 wt% (anhydrous basis) of alkali metal aluminosilicate builder,
(c) from 5 to 40 wt% of a water-soluble salt of citric acid,
(d) optionally other detergent ingredients to 100 wt%.

The invention further provides the use of nonionic surfactant which is an ethoxylated primary C₈-C₁₈ alcohol having an average degree of ethoxylation within the range of from 5.2 to 8.0 to improve the delivery and dissolution characteristics of a particulate detergent composition having a bulk density of at least 650 g/l which is not the direct process of a spray-drying process and which comprises:

(a) from 15 to 50 wt% of a surfactant system consisting essentially of
- (i) ethoxylated nonionic surfactant,
- (ii) optionally primary alcohol sulphate,
- (iii) optionally not more than 25 wt% (based on the surfactant system) of alkylbenzene sulphonate,
(b) from 20 to 70 wt% (anhydrous basis) of alkali metal aluminosilicate builder,
(c) from 5 to 40 wt% of a water-soluble salt of citric acid,
(d) optionally other detergent ingredients to 100 wt%.

DETAILED DESCRIPTION OF THE INVENTION

The high bulk density particulate detergent compositions of the invention contain as essential ingredients:

(a) a defined surfactant system,
(b) an aluminosilicate builder,
(c) a citric acid salt.

Other optional ingredients may be present as necessary or desired.
The compositions are preferably made by mixing and granulation processes that do not involve spray-drying. However, the invention also encompasses compositions that have been prepared by spray-drying and subsequently subjected to a granulation, densification or similar treatment that removes or reduces the porosity typical of a spray-dried powder.
The compositions of the invention are characteristically of low particle porosity. Preferably the particles have a void volume not exceeding 10 wt%, more preferably not exceeding 5 wt%, and desirably as low as possible. Void volume may be measured by mercury porosimetry.

The surfactant system

The compositions of the invention contain from 15 to 50 wt%, preferably from 15 to 30 wt%, of a defined surfactant system.
The essential ingredient of the surfactant system is an ethoxylated alcohol nonionic surfactant having an average alkyl chain length of C₈-C₁₈ and an average degree of ethoxylation within the range of from 5.2 to 8.0.
The nonionic surfactant preferably has an alkyl chain length of C₁₂-C₁₆, more preferably from C₁₂-C₁₄.
Advantageously, the nonionic surfactant, whether of vegetable or petrochemical origin, is predominantly or wholly linear. Especially preferred are nonionic surfactants derived from coconut oil. However, synthetic materials containing some branched material are also within the scope of the invention.
The average degree of ethoxylation is preferably within the range of from 6 to 7.5, more preferably from 6.5 to 7.5, and most preferably is about 7.
The desired degree of ethoxylation may be achieved, for example, by using a single commercial material having a nominal degree of ethoxylation of 7; for example coconut alcohol 7EO (eg Kolb's Inbentin* or DAC's Lorodac*), average degree of ethoxylation 6.9; or Synperonic* A7 from ICI, degree of ethoxylation 6.9 (* indicates Trade Mark).
Similarly, commercial materials having a nominal degree of ethoxylation of 6.5 are available and are suitable for use in the present invention.
Advantageously, lower degrees of ethoxylation within the scope of the present invention may be achieved, as disclosed in EP 544 492A (Unilever) discussed above, by mixing a commercial 7EO (nominal) material with a commercial 3EO (nominal) material in suitable proportions, provided that at least 55 wt% of the mixture is constituted by the 7EO (nominal) material.
Thus the nonionic surfactant used in the compositions of the invention may comprise commercial nonionic surfactant having a nominal average degree of ethoxylation of 7 (55-100 wt%, preferably 60-100 wt%), optionally in combination with commercial nonionic surfactant having a nominal average degree of ethoxylation of 3 (0-45 wt%, preferably 0-40 wt%).
The calculated average degrees of ethoxylation of some 3EO/7EO nonionic mixes are shown in Table 1, together with the measured values for some commercial materials.
Of course, desired overall average degrees of ethoxylation between 5.2 and 7 may also be achieved by using a single commercial material, or alternatively by using a mixture of three or more commercial materials. Table 1

7EO (nominal) (wt%) 3EO (nominal) (wt%) Average EO of mixture

Calculated

45 55 4.8

50 50 5.0

55 45 5.2

60 40 5.4

70 30 5.8

80 20 6.2

90 10 6.6

100 - 7.0

Measured: ethoxylated coconut alcohol

45 55 4.78

60 40 5.20

100 - 6.90

Measured: Synperonic (Trade Mark) (ICI)

45 55 4.76

60 40 5.34

100 - 4.76
The ethoxylated nonionic surfactant may be the sole surfactant in the compositions of the invention.
Alternatively, according to a preferred embodiment of the invention, primary alcohol sulphate (PAS) may also be present.
In this embodiment, the ethoxylated nonionic surfactant preferably constitutes from 30 to 90 wt% of the surfactant system, more preferably from 40 to 70 wt%; and the PAS preferably constitutes from 10 to 70 wt%, more preferably from 30 to 60 wt%, of the surfactant system. Preferably the whole composition contains at least 5 wt% of PAS.
The PAS suitably has a chain length in the C₈-C₁₈ range, preferably C₁₂-C₁₆. If desired, mixtures of chain lengths may be used as described and claimed in EP 342 917A (Unilever).
Wholly or predominantly linear PAS is preferred. PAS of vegetable origin, and more especially PAS from coconut oil (cocoPAS), is especially preferred. However, it is also within the scope of the invention to use branched PAS as described and claimed in EP 439 316A (Unilever).
The PAS is preferably present in sodium salt form.
In principle minor amounts of other anionic surfactants may be present, provided that the surfactant system contains no more than 25 wt% of alkylbenzene sulphonates. These materials appear to have a detrimental effect on delivery and dissolution. Preferably the compositions of the invention contain no more than 5 wt% (based on the whole composition) of alkylbenzene sulphonates, and more preferably contain none.

The aluminosilicate builder

The detergent compositions of the invention contain an alkali metal, preferably sodium, aluminosilicate builder. Sodium aluminosilicates may generally be incorporated in amounts of from 20 to 70% by weight (anhydrous basis), preferably from 25 to 50 wt%.
The alkali metal aluminosilicate may be either crystalline or amorphous or mixtures thereof, having the general formula:

0.8-1.5 Na₂O. Al₂O₃. 0.8-6 SiO₂
These materials contain some bound water and are required to have a calcium ion exchange capacity of at least 50 mg CaO/g. The preferred sodium aluminosilicates contain 1.5-3.5 SiO₂ units (in the formula above). Both the amorphous and the crystalline materials can be prepared readily by reaction between sodium silicate and sodium aluminate, as amply described in the literature.
Suitable crystalline sodium aluminosilicate ion-exchange detergency builders are described, for example, in GB-A-1 429 143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well-known commercially available zeolites A and X, and mixtures thereof.
The zeolite may be the commercially available zeolite 4A now widely used in laundry detergent powders. However, according to a preferred embodiment of the invention, the zeolite builder incorporated in the compositions of the invention is maximum aluminium 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 having a silicon to aluminium ratio not exceeding 1.33, preferably within the range of from 0.90 to 1.33, and more preferably within the range of from 0.90 to 1.20.
Especially preferred is zeolite MAP having a silicon to aluminium 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 g of anhydrous material.

The citric acid salt

The compositions of the invention also contain as an essential ingredient a water-soluble salt of citric acid, preferably sodium citrate.
The citrate salt is present in an amount of from 5 to 40 wt%, preferably from 10 to 35 wt%, more preferably from 15 to 30 wt%. Especially good results have been obtained from compositions containing from 20 to 25 wt%.
Where the citrate salt is sodium citrate, the percentages refer to the dihydrate.

Other builders

Other builders may also be included in the detergent compositions of the invention as necessary or desired. For example, polycarboxylate polymers, more especially polyacrylates and acrylic/maleic copolymers, may suitably be used in amounts of from 0.5 to 15 wt%, especially from 1 to 10 wt%.

Other ingredients

The compositions in accordance with the invention may contain sodium carbonate, to increase detergency and to ease processing. Sodium carbonate may generally be present in amounts ranging from 1 to 60 wt%, preferably from 2 to 40 wt%, and most suitably from 2 to 13 wt%. However, compositions free of alkali metal carbonate are also within the scope of the invention.
The compositions also advantageously contain fatty acid soap, as a powder structurant, suitably in an amount of from 1 to 5 wt%.
Other ingredients which may be present in the base powder include fluorescer; sodium silicate; and antiredeposition agents such as cellulosic polymers, for example, sodium carboxymethyl cellulose.
Optional ingredients that may generally be admixed (postdosed) to give a final product include bleach components such as sodium perborate or percarbonate, bleach activators and bleach stabilisers; sodium carbonate; proteolytic and lipolytic enzymes; dyes; foam control granules; coloured speckles; perfumes; and fabric softening compounds. This list is not intended to be exhaustive.

Preparation of the detergent compositions

As previously indicated, the compositions of the invention are of high bulk density and are preferably prepared by non-tower (non-spray-drying) processes in which solid and liquid ingredients are mixed and granulated together. Such powders have relatively non-porous particles and may be especially prone to delivery, dispersion and dissolution problems in use.
According to a preferred process, mixing and granulation are carried out in a high-speed mixer/granulator having both a stirring and a cutting action. The high-speed mixer/granulator, also known as a high-speed mixer/densifier, may be a batch machine such as the Fukae (Trade Mark) FS, or a continuous machine such as the Lödige (Trade Mark) Recycler CB30.
Suitable processes are described, for example, in EP 544 492A, EP 420 317A and EP 506 184A (Unilever).
Generally the inorganic builders and other inorganic materials (for example, zeolite, sodium carbonate) are granulated with the surfactants, which act as binders and granulating or agglomerating agents. Any optional ingredients as previously mentioned may be incorporated at any suitable stage in the process. Fatty acid soap may be prepared by in situ neutralisation with sodium hydroxide solution during the mixing and granulation process.
In these processes, any PAS present may be already neutralised, that is to say in salt form, when dosed into the high-speed mixer/granulation, or alternatively may be added in acid form and neutralised in situ. If desired, PAS and nonionic surfactant may be introduced in the form of a homogeneous liquid blend, as described in EP 265 203A and EP 507 402A (Unilever). EP 420 317A and EP 506 184A (Unilever) disclose a different process wherein PAS acid, which is a liquid, is mixed and reacted with a solid inorganic alkaline material, such as sodium carbonate, in a continuous high-speed mixer. The resulting granule or "adjunct" is then dosed into another high-speed mixer with the nonionic surfactants and solid ingredients. All these processes are suitable for the preparation of compositions of the invention.
In accordance with normal detergent powder manufacturing practice, bleach ingredients (bleaches, bleach precursor, bleach stabilisers), proteolytic and lipolytic enzymes, coloured speckles, perfumes and foam control granules are most suitably admixed (postdosed) to the dense homogeneous granular product - the base powder - after it has left the high-speed mixer/granulator.
The citrate salt may suitably be among the postdosed ingredients.

Powder properties

The particulate detergent compositions of the invention have bulk densities of at least 650 g/l, preferably at least 770 g/l, and more preferably at least 800 g/l.
As indicated previously, powder porosity is typically low: preferably, the void volume does not exceed 10 wt%, and more preferably it does not exceed 5 wt%. Such low values are not exhibited by powders which are the direct products of spray-drying processes.
Advantageously, the content of "fines", that is to say, particles smaller than 180 micrometres, does not exceed 10 wt%, and more preferably it does not exceed 5 wt%.

Examples

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

Test methods used in the Examples

Delivery into the wash, dispersion and dissolution characteristics were assessed by means of three different tests.

Test 1: cage test

Delivery characteristics of the powders were compared using a model system which simulates the delivery of a powder in an automatic washing machine, under more adverse conditions (low temperature, minimal agitation) than those normally encountered in a real wash situation.
For this test a cylindrical vessel having a diameter of 4 cm and a height of 7 cm, made of 600 micrometre pore size stainless steel mesh, and having a top closure made of Teflon and a bottom closure of the mesh just described, was used. The top closure had inserted therein a 30 cm metal rod to act as a handle, and this handle was attached to an agitator arm positioned above 1 litre of water at 20°C in an open container. By means of this agitator apparatus the cylindrical vessel, held at 45 degrees, could be rotated through a circle with a 10 cm radius over a period of 2 seconds and allowed to rest for 2 seconds, before the start of the next rotation/rest cycle.
A 50 g powder sample was introduced into the cylindrical vessel which was then closed. The vessel was attached to the agitator arm which was then moved down to a position such that the top of the cylindrical vessel was just below the surface of the water. After a 10 second delay, the apparatus was operated for 15 rotation/rest cycles.
The cylindrical vessel and handle were removed from the water and and the vessel detached from the handle. Surface water was carefully poured off, and any powder residues transferred to a preweighed container and dried for 24 hours at 100°C. The weight of dried residue as a percentage of the initial powder weight (50 g) was then calculated.

Test 2: delivery device test

Delivery characteristics of the powders were also compared using a model system which emulates the delivery of a powder in an automatic washing machine from a flexible delivery device of the type supplied with Lever's Persil (Trade Mark) Micro System powder in the UK: a spherical container of flexible plastics material having a diameter of approximately 4 cm and a top opening of diameter approximately 3 cm.
In this test the delivery device was attached in an upright position (opening uppermost) to an agitator arm positioned above water. By means of this apparatus the device could be moved vertically up and down through a distance of 30 cm, the lowest 5 cm of this travel being under water. 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° and allowed to rest in the resulting tilted orientation for 2 seconds before redescending. 5 litres of water at a temperature of 20°C were used.
A preweighed powder sample was introduced into the device in its highest position, and the apparatus then allowed to operate for six cycles and stopped when the device was again in its highest position. Surface water was carefully poured off, and any powder residues transferred to a preweighed container. The container was then dried at 100°C for 24 hours, and the weight of dried residue as a percentage of the initial powder weight calculated.

Test 3: black pillowcase test

A washing machine test was also used to determine the extent that insoluble residues were deposited on washed articles. The machine used was a Siemens Siwamat (Trade Mark) Plus 3700 front-loading automatic washer.
A 100 g dose of powder was placed in a flexible delivery device as described previously. The delivery device was placed inside a black cotton pillowcase having dimensions of 30 cm by 60 cm, taking care to keep it upright, and the pillowcase was then closed by means of a zip fastener. The pillowcase containing the (upright) delivery device was then placed on top of a 3.5 kg dry cotton washload in the drum of the washing machine.
The machine was operated on the "heavy duty cycle" at a wash temperature of 40°C, using water of 15° French hardness and an inlet temperature of 20°C. At the end of the wash cycle the pillowcase was removed, opened and turned inside out, and the level of powder residues on its inside surfaces determined by visual assessment using a scoring system of 1 to 5: a score of 5 corresponds to a residue of approximately 75 wt% of the powder, while 1 indicates no residue. A panel of five assessors was used to judge each pillowcase and allot a score. With each powder the wash process was carried out ten times and the scores were averaged over the ten repeats.

EXAMPLE 1, COMPARATIVE EXAMPLES A to C

Four detergent powders of high bulk density were prepared to the formulations shown in Table 2. Base powders were prepared using a continuous high-speed mixer/granulator, and other ingredients were postdosed as shown. The sodium citrate, where present, was postdosed as particulate sodium citrate dihydrate having an average particle size of about 800 µm.
All powders contained PAS, nonionic surfactant, and zeolite builder. Comparative Example A and Example 1 contained sodium citrate; Comparative Example A contained 7EO and 3EO nonionic surfactants, while Example 1 was a similar formulation containing only 7EO nonionic surfactant to the same total level. Comparative Examples B and C were two similar compositions containing no sodium citrate.

Table 3 shows the powder properties and delivery characteristics of the powders. Comparison of Examples A and 1 shows that changing the nonionic surfactant to an all-7EO system in a citrate-containing formulation substantially improved delivery characteristics. Comparison of Examples B and C showed that no such improvement was observed when citrate was absent.

Table 2:

formulations
Example	A	1	B	C
Base
CocoPAS	6.37	6.37	5.81	5.81
Nonionic 7EO	6.37	14.42	5.81	13.17
Nonionic 3EO	8.05	-	7.35	-

Zeolite MAP	39.49	39.20	36.04	35.77
Sodium carbonate	1.05	1.05	0.96	0.96
Fatty acid soap	2.37	2.37	2.04	2.16
SCMC	0.98	0.98	0.89	0.89
Moisture	5.32	5.61	4.98	5.12

Total	70.00	70.00	63.88	63.88

Postdosed
Sodium citrate (2 aq)	23.47	23.47	-	-

Sodium percarbonate	-	-	20.50	20.50
TAED granules	-	-	4.75	4.75
Catalyst granules	-	-	2.40	2.40
Sodium silicate	-	-	2.90	2.90

Antifoam/ fluorescer	3.15	3.15	3.00	3.00
EDTMP (Dequest 2047)	1.43	1.43	0.37	0.37
Enzymes	1.50	1.50	1.75	1.75
Perfume	0.45	0.45	0.45	0.45
	$\bar{\underset{̲}{100.00}}$	$\bar{\underset{̲}{100.00}}$	$\bar{\underset{̲}{100.00}}$	$\bar{\underset{̲}{100.00}}$

Table 3:

properties
Example	A	1	B	C
Nonionic surfactants
wt% 7EO	44	100	44	100
wt% 3EO	56		56
average EO	4.77	7.0	4.77	7.0

Powder properties
Bulk density (g/l)	914	899	890	898

wt% fines	5.2	3.0	5.4	1.5

Delivery properties
Test 1 (wt% residue)	56	32	52	70

Test 2 (wt% residue)	31	0	15	12

Test 3 (score 1-5)	1.0	0.4	1.0	1.5

Insolubles at 20°C	5.5	2.2	3.4	4.2

Example 2

A composition was prepared having a formulation corresponding to that of Example 1 but containing the following surfactant system:

CocoPAS 6.37

Nonionic 7EO 8.65 (60%)

Nonionic 3EO 5.77 (40%)
The composition gave zero residues when dosed via the dispenser drawer of three different automatic washing machines (Phillips, Zanussi, Siemens).

Examples 3 to 6

Four further machine wash formulations in accordance with the present invention are shown below.

	3	4	5	6
CocoPAS	8.47	10.60	12.71	13.77
Nonionic 6.5EO	12.71	10.58	8.47	7.41
Soap	1.95	1.63	1.30	1.14
Zeolite MAP	34.34	26.29	18.33	14.35
Sodium carbonate	1.44	1.80	2.16	2.34
SCMC	0.89	0.74	0.59	0.52
Moisture, salts	1.80	2.26	2.71	2.93

Sodium citrate	7.08	14.80	22.42	26.23
Antifoam/fluorescer	3.00	3.00	3.00	3.00
Silicate	3.67	3.67	3.67	3.67
Percarbonate	16.85	16.85	16.85	16.85
TAED	3.75	3.75	3.75	3.75
Mn catalyst	1.27	1.27	1.27	1.27
EDTMP	0.37	0.37	0.37	0.37
Enzymes	1.75	1.75	1.75	1.75
Perfume	0.65	0.65	0.65	0.65
	$\bar{100.00}$	$\bar{100.00}$	$\bar{100.00}$	$\bar{100.00}$

Claims

A particulate detergent composition which is not the direct product of a spray-drying process, the composition having a bulk density of at least 650 g/l and comprising:
(a) from 15 to 50 wt% of a surfactant system consisting essentially of
(i) ethoxylated nonionic surfactant which is a primary C₈-C₁₈ alcohol having an average degree of ethoxylation within the range of from 5.2 to 8.0,

(ii) optionally primary alcohol sulphate,

(iii) optionally not more than 25 wt% (based on the surfactant system) of alkylbenzene sulphonate,

(b) from 20 to 70 wt% (anhydrous basis) of alkali metal aluminosilicate builder,

(c) from 5 to 40 wt% of a water-soluble salt of citric acid,

(d) optionally other detergent ingredients to 100 wt%.
A detergent composition as claimed in claim 1, wherein the ethoxylated nonionic surfactant comprises commercial nonionic surfactant having a nominal average degree of ethoxylation of 7 (55-100 wt%), optionally in combination with commercial nonionic surfactant having a nominal average degree of ethoxylation of 3 (0-45 wt%).
A detergent composition as claimed in claim 1, wherein the nonionic surfactant has an average degree of ethoxylation within the range of from 6 to 7.5.
A detergent composition as claimed in claim 1, wherein the surfactant system consists essentially of from 30 to 60 wt% of primary alcohol sulphate and from 40 to 70 wt% of ethoxylated nonionic surfactant.
A detergent composition as claimed in claim 1, which contains at least 10 wt% (in total, based on the whole composition) of ethoxylated nonionic surfactant.
A detergent composition as claimed in claim 1, which contains at least 5 wt% (based on the whole composition) of primary alcohol sulphate.
A detergent composition as claimed in claim 1, which comprises from 10 to 35 wt% of the citric acid salt.
A detergent composition as claimed in claim 1, wherein the citric acid salt is sodium citrate.
A detergent composition as claimed in claim 1, wherein the alkali metal aluminosilicate is zeolite P having a silicon to aluminium ratio not exceeding 1.33 (zeolite MAP).
Use of nonionic surfactant which is an ethoxylated C₈-C₁₈ alcohol having an average degree of ethoxylation within the range of from 5.2 to 8.0 to improve the delivery and dissolution characteristics of a particulate detergent composition having a bulk density of at least 650 g/l which is not the direct product of a spray-drying process and which comprises:
(a) from 15 to 50 wt% of a surfactant system consisting essentially of
(i) ethoxylated nonionic surfactant,

(ii) optionally primary alcohol sulphate,

(iii) optionally not more than 25 wt% (based on the surfactant system) of alkylbenzene sulphonate,

(b) from 20 to 70 wt% (anhydrous basis) of alkali metal aluminosilicate builder,

(c) from 5 to 40 wt% of a water-soluble salt of citric acid,

(d) optionally other detergent ingredients to 100 wt%.