EP0448298A1

EP0448298A1 - Detergent compositions

Info

Publication number: EP0448298A1
Application number: EP19910302218
Authority: EP
Inventors: Jelles Vincent Boskamp
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1990-03-19
Filing date: 1991-03-15
Publication date: 1991-09-25
Also published as: ZA912024B; CA2038491C; GB9104613D0; CA2038490A1; CA2038491A1; JPH04227692A; AU7296991A; BR9101074A; BR9101075A; GB9006171D0

Abstract

A fabric washing detergent composition, preferably particulate, comprises detergent-active compounds and a detergency builder system comprising an aluminosilicate (18-45 wt%) and a citrate (3-18 wt%) in a ratio of 2.5:1-6:1, and is free from solid peroxyacid compounds and peroxybenzoic acid precursors.

Description

TECHNICAL FIELD

The present invention relates to detergent compositions, especially particulate detergent compositions, suitable for the laundering of fabrics in domestic or commercial washing machines. The compositions contain a specific combination of aluminosilicate and citrate builder salts.

BACKGROUND AND PRIOR ART

Detergent compositions for heavy-duty fabric washing conventionally contain materials - detergency builders - to lower the concentration of calcium water hardness ions in the wash liquor and thus to give good detergency in hard water as well as in soft water.
Alkali metal aluminosilicate ion-exchangers, especially the crystalline sodium aluminosilicate zeolite 4A, are now well-known replacements for the inorganic phosphates traditionally used as detergency builders in fabric washing detergents. It is also well known that zeolites show certain deficiencies in detergency building, as compared with phosphates, and that supplementary building power is generally desirable. In many zero-phosphate premium detergent powders now on the European market, homo- or copolymers of acrylic acid are included for this purpose.
It is also known to include citric acid and/or its salts in detergent compositions, but these compounds are well-known to be poor sequestrants of calcium ions and to contribute little to detergency building.
Detergent compositions built with crystalline aluminosilicate (zeolite) and also containing citrates are specifically disclosed in GB 1 473 201 (Henkel), GB 1 429 143 (Procter & Gamble), GB 1 470 250 (Procter & Gamble), EP 1310A (Procter & Gamble), EP 1853A (Procter & Gamble), EP 75 796B (Procter & Gamble), GB 2 095 274B (Colgate-Palmolive), DE 2 336 182C (Lion), EP 234 867A (Clorox), and also in our copending European Patent Application No. 90 311 672.1 filed on 24 October 1990.
Water-softening or detergency building granules based on zeolites and citrates are disclosed in EP 243 908A (Henkel), DE 3 144 297A (Degussa), EP 22 023A (Union Carbide), and also in our copending European Patent Application No. 90 309 051.2 filed on 17 August 1990.
EP 313 143A (Unilever) discloses bleaching detergent compositions containing aluminosilicate (15-40 wt%), citric acid or alkali metal citrate (1-15 wt%), and a solid organic peroxyacid (1-15 wt%). EP 313 144A (Unilever) describes and claims bleaching detergent compositions containing aluminosilicate (15-40 wt%), citric acid or alkali metal citrate (1-15 wt%), an inorganic peroxy compound (5-35 wt%), and a peroxybenzoic acid bleach precursor (1-10 wt%). Both specifications claim improved cleaning and bleaching performance when a builder system based on zeolite and citrate is used in conjunction with these specific bleach systems.
The present inventor has now discovered that detergent compositions containing aluminosilicate and citrate together in particular amounts and particular proportions can give unexpectedly good detergency, better than that obtained in other amounts and proportions, in the absence of the specific bleach systems disclosed in EP 313 143A and EP 313 144A. Surprisingly, compositions of the invention can give detergency as good as that obtained from compositions built with aluminosilicate/acrylic polymer, despite the known inferiority of citrate to acrylic polymer as a binder of calcium ions.

DEFINITION OF THE INVENTION

The present invention provides a detergent composition for fabric washing, comprising:

(i) one or more detergent-active compounds selected from anionic, nonionic, cationic, amphoteric and zwitterionic detergent-active compounds and combinations thereof,
(ii) a detergency builder system comprising:
- (a) a crystalline or amorphous alkali metal aluminosilicate in an amount of from 18 to 45 wt% (anhydrous basis),
- (b) citric acid and/or a salt thereof, in an amount equivalent to from 3 to 18 wt% of sodium citrate dihydrate,

The invention also provides a method of washing fabrics, which includes the step of bringing the fabrics into contact with an aqueous wash liquor containing a detergent composition as defined in the previous paragraph.
The invention further provides the use of (x) citric acid or a salt thereof, in an amount equivalent to from 3 to 18 wt% of sodium citrate dihydrate, as a detergency builder in a detergent composition for fabric washing comprising:

(i) one or more detergent-active compounds selected from anionic, nonionic, cationic, amphoteric and zwitterionic detergent-active compounds and combinations thereof,
(ii) a detergency builder system comprising (y) a crystalline or amorphous alkali metal aluminosilicate, or mixture thereof, in an amount of from 18 to 45 wt% (anhydrous basis),

DETAILED DESCRIPTION OF THE INVENTION

The detergent composition of the invention contains, as essential components, a detergent-active compound, and a detergency builder system.

The detergent-active compound

The detergent compositions of the invention will contain, as essential ingredients, one or more detergent-active compounds (surfactants) which may be chosen from soap and non-soap anionic, cationic, nonionic, amphoteric and zwitterionic detergent-active compounds, and mixtures thereof. Many suitable detergent-active compounds are available and are fully described in the literature, for example, in "Surface-Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch.
The preferred detergent-active compounds that can be used are soaps and synthetic non-soap anionic and nonionic compounds.
Anionic surfactants are well-known to those skilled in the art. Examples include alkylbenzene sulphonates, particularly linear alkylbenzene sulphonates having an alkyl chain length of C₈-C₁₅; primary and secondary alkyl sulphates, particularly C₁₂-C₁₅ primary alkyl sulphates; alkyl ether sulphates; olefin sulphonates; alkyl xylene sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates. Sodium salts are generally preferred.
Nonionic surfactants that may be used include the primary and secondary alcohol ethoxylates, especially the aliphatic C₁₂-C₁₅ primary and secondary alcohols ethoxylated with an average of from 3 to 20 moles of ethylene oxide per mole of alcohol; and alkylpolyglycosides.
Preferred detergent-active systems, suitable for compositions intended for use in automatic fabric washing machines, comprises anionic non-soap surfactant, or nonionic surfactant, or combinations of the two in any ratio, optionally together with soap.
The total amount of detergent-active compounds present may suitably lie in the range of from 5 to 40 wt%.

The detergency builder system

In the compositions of the invention, the detergency builder system comprises, and preferably consists essentially of, two components (a) and (b). For convenience, the component (a) will be referred to hereinafter as the aluminosilicate, and the component (b) will be referred to as the citrate. All percentages of the aluminosilicate will be based on the anhydrous material, and all percentages of the citrate will be based on sodium citrate dihydrate equivalent.

The aluminosilicate (a)

The alkali metal (preferably sodium) aluminosilicate builder may be crystalline or amorphous or a mixture thereof, and has 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 about 50 mg CaO/g. The preferred aluminosilicates contain 1.5-3.5 SiO₂ units (in the formula above) and have a particle size of not more than about 100 µm, preferably not more than about 20 µm. Both amorphous and crystalline aluminosilicates can be made readily by reaction between sodium silicate and sodium aluminate, as amply described in the literature.
Crystalline aluminosilicates (zeolites) are preferred for use in the present invention. Suitable materials are described, for example, in GB 1 473 201 (Henkel) and GB 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.
Zeolite A, more especially Type 4A zeolite, is especially preferred for use in the present invention, as described in more detail below.
Also especially preferred for use in the present invention is the novel zeolite P (maximum aluminium zeolite P, hereinafter zeolite MAP) described and claimed in EP 384 070A (Unilever). Zeolite MAP is defined as zeolite P having a silicon to aluminium ratio not exceeding 1.33, preferably from 0.9 to 1.33, more preferably from 0.9 to 1.2. Preferred zeolite MAP has a silicon to aluminium ratio not exceeding 1.15 and has a tetragonally distorted cubic crystal structure. Especially preferred zeolite MAP has a silicon to aluminium ratio not exceeding 1.07.
Detergency builders and detergent compositions containing zeolite MAP and citrate are also the subject of our copending Application of even date (Case C3367/1) claiming the priority of British Patent Application No. 90 06171.4 filed on 19 March 1990.
Although zeolites contain water of hydration, as mentioned above, for the purposes of the present invention amounts and percentages of zeolites are expressed in terms of the anhydrous material.

The citrate

The second essential builder component of the compositions of the invention is citric acid or a salt thereof, preferably sodium citrate. This salt normally exists in the form of the dihydrate, and for the purposes of the present invention amounts and percentages of citrates are expressed in terms of sodium citrate dihydrate.
It should be understood, however, that the use of other wholly and partially neutralised citric acid salts, and the free acid itself, in equivalent amounts, is also within the scope of the invention.

Amounts and ratios

Both the amounts and the proportions of the two builder components are important. It has been found that, to obtain detergency similar to that of comparable compositions built with aluminosilicate and acrylic polymer, the aluminosilicate should be present in an amount of from 18 to 45 wt% and the citrate should be present in an amount of from 3 to 18 wt%
Also important is the proportion of aluminosilicate to citrate. The weight ratio of aluminosilicate to citrate should be within the range of from 2.5:1 to 6:1.

Preferred builder systems

In a first preferred embodiment of the invention, the detergency builder system comprises from 18 to 30 wt%, preferably from 20 to 30 wt%, more preferably from 22 to 28 wt% and most preferably from 24 to 28 wt%, of the alkali metal aluminosilicate; and from 3 to 18 wt%, preferably from 5 to 7 wt%, of the citrate. The aluminosilicate is preferably zeolite A or zeolite MAP.
The total amount of aluminosilicate plus citrate is preferably from 22 to 36 wt%, preferably from 28 to 36 wt%. The ratio of aluminosilicate to citrate is preferably from 3:1 to 6:1, more preferably from 4:1 to 5:1.
The first preferred embodiment of the invention is especially applicable to compositions containing a bleach system, as described below.
In a second preferred embodiment of the invention, the detergency builder system comprises from 35 to 45 wt%, preferably from 37 to 42 wt%, of the alkali metal aluminosilicate and from 9 to 18 wt%, preferably from 10 to 15 wt%, of the citrate. The aluminosilicate is preferably zeolite A.
The total amount of aluminosilicate plus citrate is preferably from 50 to 60 wt%, and the ratio of aluminosilicate to citrate is preferably form 2.5:1 to 4.5:1.
The second preferred embodiment of the invention is esepcially applicable to compositions that do not contain a bleach system.

Other builder components

The compositions of the invention may be formulated without homo- or copolymers of acrylic acid, for example, polyacrylates or acrylic/maleic copolymers. Preferred compositions are substantially free from such polymers, although compositions containing them are not excluded from the scope of the invention.
The amount of soluble silicates in the compositions of the invention is preferably kept to a relatively low level: preferably below 5 wt%, and more preferably below 1 wt%.
The compositions of the invention may advantageously contain alkali metal carbonate, to provide alkalinity rather than for detergency building. The amount of alkali metal, preferably sodium, carbonate may suitably range from 2 to 20 wt%, preferably from 5 to 15 wt%.

Bleach system

Detergent compositions according to the invention may also suitably contain a bleach system, provided that peroxybenzoic acid bleach precursors and solid organic peroxyacids are absent.
The bleach system preferably comprises one or more peroxy bleach compounds, for example, inorganic persalts, which may be employed in conjunction with precursors to improve bleaching action at low wash temperatures. More preferably the bleach system comprises an inorganic persalt optionally in conjunction with a precursor other than a peroxybenzoic acid precursor.
Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate.
Preferred bleach precursors are peracetic acid precursors, especially tetraacetylethylene diamine (TAED), and the novel quaternary ammonium and phosphonium bleach activators disclosed in US 4 751 015 and US 4 818 426 (Lever Brothers Company), more especially cholyl p-sulphophenyl carbonate (CSPC).
If desired, the bleach system may also include a bleach stabiliser (heavy metal sequestrant).
Compositions containing a bleach system are preferably in accordance with the first preferred embodiment of the invention, as described above.
The benefits of the present invention are, however, also observed with bleach-free compositions, and those are preferably in accordance with the second preferred embodiment of the invention described above.

Dicarboxylic acid structurant

The invention is especially, but not exclusively, concerned with detergent compositions in particulate form.
Particulate compositions of the invention may advantageously contain a dicarboxylic acid powder structurant. Suitable materials include succinic acid, adipic acid, glutaric acid and mixtures thereof. The acids may be employed in free acid or in salt (wholly or partially neutralised) form. The dicarboxylic acid is suitably employed in an amount within the range of from 0.5 to 5 wt%. A commercial mixture of adipic acid (maximum 33 wt%), glutaric acid (maximum 50 wt%) and succinic acid (maximum 31 wt%) is available from BASF, Ludwigshafen, Germany under the trade mark Sokalan DCS, and a similar mixture of sodium salts under the trade mark Sokalan DCN.
Particulate detergent compositions containing succinates as powder structurants are described and claimed in EP 61 295B (Unilever).

Other ingredients

Other materials that may be present in detergent compositions of the invention include fluorescers, antiredeposition agents, inorganic salts such as sodium sulphate, enzymes, lather control agents, fabric softening agents, pigments, coloured speckles, and perfumes. This list is not intended to be exhaustive.

Preparation of the detergent compositions

Detergent compositions of the invention may be prepared by any suitable method. The particulate detergent compositions which are the preferred embodiment of the invention are suitably prepared by spray-drying a slurry of compatible heat-insensitive ingredients, and then spraying on or postdosing those ingredients unsuitable for processing via the slurry. The skilled detergent formulator will have no difficulty in deciding which ingredients should be included in the slurry and which should not.
Both the aluminosilicate and the citrate builder components are suitable for inclusion in the slurry, although it may be advantageous for processing reasons for part of the aluminosilicate to be incorporated post-tower.
The particulate detergent compositions of the invention may be prepared to any suitable bulk density. Compositions having bulk densities of at least 400 g/l, more preferably at least 500 g/l, are of especial interest.
The invention is further illustrated by the following non-limiting Examples, in which parts and percentages are by weight unless otherwise stated.

EXAMPLES

Example 1, Comparative Examples A - D

Detergent powders containing a mixed anionic/nonionic detergent-active system, zeolite 4A, sodium citrate and a TAED/sodium perborate bleach system were prepared, by spray-drying and postdosing, in accordance with the following general formulation:
The formulations of Example 1 and Comparative Examples A, B and C contained zeolite/citrate builder systems as follows:
The detergency performance of each formulation was compared with that of the following control formulation, Comparative Example D, containing zeolite and acrylic/maleic copolymer (Sokalan (Trade Mark) CP5 ex BASF, Ludwigshafen, Germany):
Detergencies were assessed by washing five different test cloths in a Siemens Siwamat (Trade Mark) 660 front-loading automatic washing machine in 40° French hard water (Ca:Mg ratio 7:1) at 60°C.
The test cloths used were as follows:

(1) oil/silica/ink soil on cotton;
(2) oil/silica/ink soil on polyester/cotton;
(3) Indian ink/olive oil soil on polyester/cotton;
(4) proteinaceous (casein) soil on cotton;
(5) proteinaceous (casein) soil on polyester/cotton.

The results, expressed as reflectance differences at 460 nm (δδR₄₆₀) as compared with Comparative Example D, were as follows:
These results clearly show the superiority of Example 1 over the control Comparative Example D, while Comparative Examples A, B and C were inferior to the control on all test cloths.

Examples 2 and 3

Detergent powders containing a mixed anionic/nonionic detergent-active system, zeolite 4A, sodium citrate and a TAED/sodium perborate bleach system were prepared, by spray-drying and postdosing, in accordance with the following formulations:
Both compositions showed good detergency comparable to that of Comparative Example D.

Example 4

A detergent powder containing a mixed anionic/nonionic detergent-active system, zeolite 4A, sodium citrate and a TAED/sodium perborate bleach system and having good detergency and good powder properties was prepared, by spray-drying and postdosing, in accordance with the following formulation:

Examples 5 and 6, Comparative Examples E to H

Bleach-free detergent powders containing a higher level of zeolite 4A were prepared, by spray-drying and postdosing, in accordance with the following general formulation:
The formulations of Examples 5 and 6 and Comparative Examples E to G contained zeolite/citrate builder systems as follows:
The detergency performance of each formulation was compared with that of a control formulation, Comparative Example H, containing 42.00 wt% zeolite 4A and 2.00 wt% acrylic/maleic copolymer (Sokalan (Trade Mark) CP5 ex BASF, Ludwigshafen, Germany).
Detergency was measured in a tergotometer in 40° (French) hard water (Ca:Mg ratio 7:1) at 40°C and a product dosage of 3 g/l. Cotton test cloths with proteinaceous (casein) soil were washed together with a white ballast load. The results, expressed as reflectance differences at 460 nm (δδR₄₆₀) as compared with Comparative Example H, were as follows:

Examples 7 to 9

Detergent powders containing a mixed anionic/nonionic detergent-active system, zeolite MAP, sodium citrate and a TAED/sodium perborate bleach system were prepared to the following formulations (in parts by weight):
Example 9 was identical to Example 7 except that the zeolite MAP was replaced by 26.00 parts of zeolite 4A.
The zeolite MAP was prepared on a pilot scale by the method described in Examples 1 to 3 of EP 384 070A (Unilever). Its silicon to aluminium ratio was 1.10 and it had a tetragonally distorted cubic crystal structure.
Detergency was measured in a tergotometer in 26° (French) hard water (Ca:Mg ratio 4:1) at 60°C and a product dosage of 4 g/l. Test cloths as described below were washed together with a white ballast load. The results, expressed as reflectance differences at 460 nm (δR₄₆₀), were as follows:

Test cloths

(1) oil/silica/ink soil on cotton;
(3) Indian ink/olive oil soil on polyester/cotton;
(6) Indian ink/olive oil soil on cotton.

These results show that zeolite MAP/citrate compositions within the invention give even better results than zeolite 4A/citrate compositions.

Claims

1 A detergent composition for fabric washing, comprising:

(i) one or more detergent-active compounds selected from anionic, nonionic, cationic, amphoteric and zwitterionic detergent-active compounds and combinations thereof,

(ii) a detergency builder system comprising:

(a) a crystalline or amorphous alkali metal aluminosilicate, or mixture thereof,

(b) citric acid and/or a salt thereof,

characterised in that the aluminosilicate (a) is present in an amount of from 18 to 45 wt% (anhydrous basis), the citrate (b) is present in an amount equivalent to from 3 to 18 wt% of sodium citrate dihydrate, and the weight ratio of (a) (anhydrous basis) to (b) (as sodium citrate dihydrate equivalent) being within the range of from 2.5:1 to 6:1;
the composition being free from solid peroxyacid compounds and from peroxybenzoic acid precursors.

2 A detergent composition as claimed in claim 1, characterised in that it contains from 18 to 30 wt% (anhydrous basis) of the aluminosilicate (a) and from 3 to 9 wt% of the citrate (b).

3 A detergent composition as claimed in claim 2, characterised in that the aluminosilicate (a) is present in an amount within the range of from 22 to 28 wt% (anhydrous basis).

4 A detergent composition as claimed in claim 2 or claim 3, characterised in that the citrate (b) is present in an amount within the range of from 5 to 7 wt% (sodium citrate dihydrate basis).

5 A detergent composition as claimed in any one of claims 2 to 4, characterised in that the weight ratio of (a) to (b) is within the range of from 4:1 to 5:1.

6 A detergent composition as claimed in any one of claims 2 to 5, characterised in that the total amount of (a) (anhydrous basis) plus (b) (as sodium citrate dihydrate equivalent) is within the range of from 22 to 36 wt%.

7 A detergent composition as claimed in any one of claims 2 to 6, characterised in that the aluminosilicate component (a) is zeolite A or maximum aluminium zeolite P.

8 A detergent composition as claimed in any one of claims 2 to 7, characterised in that it comprises a bleach system comprising an inorganic persalt optionally in conjunction with a bleach precursor other than a peroxybenzoic acid precursor.

9 A detergent composition as claimed in claim 8, characterised in that the bleach system comprises sodium perborate tetrahydrate, sodium perborate monohydrate, or sodium percarbonate, optionally in conjunction with a bleach precursor selected from peracetic acid precursors and cationic bleach precursors.

10 A detergent composition as claimed in claim 9, characterised in that the bleach precursor comprises tetraacetylethylenediamine or cholyl p-sulphophenyl carbonate.

11 A detergent composition as claimed in claim 1, characterised in that it contains from 35 to 45 wt% (anhydrous basis) of the aluminosilicate component (a) and from 9 to 18 wt% of the citrate (b).

12 A detergent composition as claimed in claim 11, characterised in that the aluminosilicate component (a) is present in an amount within the range of from 37 to 42 wt% (anhydrous basis).

13 A detergent composition as claimed in claim 11 or claim 12, characterised in that the citrate (b) is present in an amount of from 10 to 15 wt% (sodium citrate dihydrate basis).

14 A detergent composition as claimed in any one of claims 11 to 13, characterised in that the weight ratio of (a) to (b) is within the range of from 2.5:1 to 4.5:1.

15 A detergent composition as claimed in any one of claims 11 to 14, characterised in that the total amount of (a) (anhydrous basis) and (b) (sodium citrate dihydrate basis) is within the range of from 50 to 60 wt%.

16 A detergent composition as claimed in one of claims 11 to 15, characterised in that the aluminosilicate (a) is zeolite A.

17 A detergent composition as claimed in any one of claims 11 to 16, characterised in that it does not contain a bleach system.

18 A detergent composition as claimed in any preceding claim, characterised in that it is in particulate form.

19 A method of washing fabrics, characterised by the step of bringing the fabrics into contact with an aqueous wash liquor containing a detergent composition as claimed in any preceding claim.

20 The use of (x) citric acid and/or a salt thereof as a detergency builder in a detergent composition for fabric washing comprising:

(ii) a detergency builder system comprising (y) a crystalline or amorphous alkali metal aluminosilicate or mixture thereof,

characterised that the citrate (x) is used in an amount equivalent to from 3 to 18 wt% of sodium citrate dihydrate, the aluminosilicate (y) is present in an amount of from 18 to 45 wt% (anhydrous basis), and the weight ratio of (y) (anhydrous basis) to (x) (as sodium citrate dihydrate equivalent) is within the range of from 2.5:1 to 6:1;
the composition being free from solid peroxyacid compounds and from peroxybenzoic acid precursors.