EP0328190A2

EP0328190A2 - Particulate laundry detergent composition

Info

Publication number: EP0328190A2
Application number: EP19890200221
Authority: EP
Inventors: Hendrik Willem Brouwer; Machiel Goedhart; Marco Waas; Simon Willemse
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1988-02-12
Filing date: 1989-02-02
Publication date: 1989-08-16
Anticipated expiration: 2009-02-02
Also published as: JPH0668120B2; DE68915015T2; DE68915015D1; EP0328190A3; EP0328190B1; GB8803263D0; ES2051983T3; JPH01268799A

Abstract

A low or zero phosphate laundry detergent composition is based on a particulate partially neutralized (25-60 mole%) fatty acid mixture, of which up to 35% may be unsaturated. Preferably, the partially neutralized fatty acid base material is present as spray-cooled prills. A particulate solid base, for example sodium carbonate or sodium alkaline silicate, is also present. Non-soap surfactants and other conventional detergent ingredients may be included. The compositions are free-flowing and have excellent powder properties as well as good washing performance.

Description

Technical Field

The present invention relates to a novel, particulate laundry detergent composition which contains no, or reduced levels of inorganic phosphate compounds. Furthermore, it relates to a particulate base material suitable for use in such detergent compositions and to a method of manufacturing this particulate base material.

Background of the Invention

Conventional laundry detergent compositions contain phosphate compounds, especially sodium tripolyphosphate (STP), as building agents. Owing to the negative effects of phosphates on the environment, there has been an increasing interest in developing new laundry detergent compositions which have a low or zero phosphate content. However, it has proved to be difficult to match the excellent builder properties of the phosphate-containing compositions.
It is known to use zeolites as builder in zero-P laundry detergent formulations. However, the application of zeolites in laundry detergent formulations has a number of drawbacks. In the first place, zeolites have a tendency to cause a bad powder structure. Further more, they tend to interact with silicates which are usually present in the composition as anti-corrosion agents, and they can cause dispensing problems in the washing machine and incrustation on the washed fabrics.

Definition of the Invention

We have now found that in accordance with the present invention a new low- or zero-P particulate laundry detergent composition can be provided, without the need for zeolites. The compositions of the invention utilise acid soap both as a powder base and as a builder:
The composition according to the invention comprises as a first particulate material a fatty acid mixture in which up to 35 mole% may be unsaturated fatty acids, which mixture has been neutralised to an extent of 25-60 mole %, and as a second particulate material a base in an amount sufficient to render the pH of the composition at a 0.5 wt% concentration in water higher than 8.
Optionally conventional detergent additives may be present, such as a bleach system, proteolytic enzymes, anti-foaming agents, optical brighteners, perfumes, anti-corrosion additives, etc.
The composition according to the invention exhibits very satisfactory wash performance without the need for phosphate or zeolite builders, although the presence of low levels of these materials is not prohibited and may be beneficial. Powder properties such as flow and compressibility are also excellent. The particulate laundry detergent composition according to the invention preferably contains 30-80 wt.% of granular acid soap particles.
The acid soap is a mixture of free fatty acids and soap, or a partially neutralized mixture of fatty acids. In principle, a wide range of saturated and/or unsaturated fatty acids may be used, but it was found that the powder properties of the particulate composition become less favourable at a content of unsaturated fatty acids of more than 35 mole%. More specifically, such powders tend to be sticky and are barely free-flowing. The lower the proportion of saturated fatty acid of chain length <C14 present, the greater the proportion of unsaturated fatty acids that can be tolerated.
Preferably, the mixture of fatty acid consists essentially of 5 - 20 mole% C16-C18 unsaturated fatty acids, and 95 - 80 mole% of a mixture of C8-C14 saturated fatty acids and C16-C18 saturated fatty acids in a ratio of 3:1-1:2.
For the purpose of this invention, the following definitions will be used: C8-C14 saturated fatty acids will also be referred to as laurics, C14-C16 saturated fatty acids as stearics and C16-C18 unsaturated fatty acids as oleics.
In the mixture of fatty acids, the C16-C18 saturated fatty acids or stearics are mainly responsible for the builder properties, while they contribute little to detergency. The C16-C18 unsaturated fatty acids or oleics are important for their builder properties but especially for detergency. The C8-C14 saturated fatty acids or laurics contribute both to the building and to the detergency, but their main function is to facilitate processing of the soap/fatty acid mixture, and to ensure adequate dissolution properties.
The laundry detergent compositions according to the present invention can be prepared by dry-mixing the various ingredients into a suitable mixture.
According to the invention, the acid soap is used in the form of a particulate material, for example, prills or noodles. Particle size and shape may be chosen at will and are discussed in more detail below. These acid soap particles can be prepared by dissolving a suitable amount of soap in a mixture of fatty acid in the molten state, followed by solidification and processing of the solid mass. Alternatively, they can be prepared by partial in situ saponification or neutralization of a mixture of fatty acids. In this process, a solid base material is gradually admixed with the molten fatty acid mixture. Suitable basic compounds are, for example, soda ash (sodium carbonate), sodium disilicate or metasilicate, or sodium hydroxide. When soda ash is used, only C02 is formed as a by-product, which is easily removed from the reaction mixture. When using sodium alkaline silicates, the formation of insoluble silicates may lead to a higher viscosity of the molten soap/fatty acid mixture. On the other hand, incorporation of silicates directly in the soap/fatty acid matrix is advantageous for the powder structure, and problems associated with the dry mixing of silicates as such are avoided. The operating temperature required to process these mixtures increases with the fatty acid chain length and degree of neutralization, and is preferably within the range of 70-140 C.
Furthermore, the detergent composition of the present invention contains a particulate base in an amount sufficient to render the pH of the composition, at a 0.5 wt.% concentration in water, higher than 8. As a base material, in principle any base can be used which can be prepared in a particulate form and which readily dissolves in water without forming precipitates with the soap fatty acid particles. Preferably, the same base is used as for the partial neutralization of the fatty acid mixture.
The laundry detergent composition according to the invention may additionally contain other detergent compounds, such as anionic and/or nonionic non-soap detergent-active compounds. These may be incorporated in the particulate acid soap base, or present as a separate ingredient. The acid soap particles may contain up to 10% by weight of anionic and/or nonionic surfactant: higher levels can be detrimental to powder properties.
Alternatively or additionally, anionic or nonionic surfactants, but especially nonionic surfactants, may be carried on a porous inorganic material which is admixed with the acid soap particles. An example of such an adjunct is a liquid ethoxylated C13-C15 alcohol sprayed on to a Burkeite carrier. If the inorganic carrier is a basic material, the adjunct may serve as the basic component (second particulate material) of the composition.
A particularly preferred method of preparing acid soap particles was found to be spray-cooling. It was found thereby that particles or prills are obtained with excellent properties with regard to the dissolution rate, stability and to wash performance of the complete detergent composition.
Using the spray-cooling process, prills of any desired size and bulk density can be obtained by manipulation of the process conditions. Prills of average particle size 250-1000 m and buk density 400-750 g/e are preferred for compatibility with the other solid ingredients of the compsition, so that segregation in the pack is minimised.
When following the soap/fatty acid spray-cooling route, apart from the builder/active and solubility requirements, a number of additional factors should be considered:

1. To ensure adequate handling and storage properties, the soap/fatty acid-mixture should be sufficiently solid at temperatures below 35-40 C.
2. For processing reasons, complete liquefaction should preferably be possible below 100°C. In practice, this means a maximum mixing temperature <150 C. It was found that meeting this requirement means that the soap content of the mixture should be limited to 25-60 mole%, depending on the fatty acid composition.
3. The composition of the mixture, in terms of fatty acid types and degree of neutralization, should be such as to ensure adequate solubility at low wash peratures, i.e. in the 20-40° C region.

It will be clear to the man skilled in the art that these requirements are not easy to fulfil at the same time. A number of characteristics of soap/fatty acid mixtures have to be considered.
Firstly, soaps as well as fatty acids may form various eutectic complexes; such complexes may also be formed between soaps and fatty acids, resulting in highly' complicated phase diagrams for such mixtures. This aspect is particularly relevant to the question of meeting the 35-40 ° C target for the solidification temperature. In addition, it was found that preferably the relative amounts of laurics and stearics should not exceed a 1:1 ratio; nevertheless, some liquefaction at the eutectic temperature of about 33 C cannot be avoided. Although not ideal from a handling/stability point of view, the presence of some low melting laurics/stearics complex may be expected to have a favourable effect on the low temperature solubility.
Secondly, a further complication arises from the phenomenon of metathesis; addition of soap to a fatty acid mixture will lead to equilibration reactions, resulting in the presence of soap and free acids for all chain length homologues in a specific ratio, depending on the reactivity of the individual acids. Fortunately, the reactivities of unsaturated and saturated acids differ to such an extent that in a practical situation in these mixtures, the oleics will be preferentially converted into soap. Significant amounts of lauric soap and stearic soap can only present when the proportion of soap exceeds that of oleate.
The invention will now be illustrated by the following Examples.

EXAMPLES 1-3

A number of fatty acid mixtures were prepared, having the compositions shown in Table A. The mixtures were then heated and at approximately 65. C they began to melt. Heating was continued and after complete melting at a temperature of about 80 C soda ash (sodium carbonate) was gradually added in an amount of 0.1 kg/min to control the C02-evolution until the desired degree of neutralization had been reached. At the same time, the temperature was gradually raised to approximately 140` C.
Subsequently, the partially neutralized fatty acid mixture was allowed to cool until solidification had occurred. The solid mass was noodled, using a sodium press. Noodles having a diameter of 1 mm and a length of about 5 mm were obtained. The properties of the noodles and the handling properties are shown in Table A. The solubility was measured as follows: The rate of dissolution of the soap/fatty acid noodles was determined by monitoring the increase in conductivity resulting from dissolution of the soap part of the noodles. In this method, 3 g/I of the sample is added to 1 I demineralized water at 25^.C with continuous stirring, using a magnetic stirrer. The rate of dissolution is expressed as the time required to dissolve 50% of the soluble part of the soap/fatty acid blend (t½) . The maximum conductivity is measured after heating to above the melting temperature of the fatty acids, followed by cooling down to ambient temperature.
It follows from Table A that the handling properties of the noodles were good, while satisfactory solubility was observed.

EXAMPLES 4-6

Examples 1-3 were repeated, but instead the molten acid/soap mixtures were spray-cooled in a spray tower to form prills. The spray-cooling conditions are shown in Table B. The powder properties of the prills obtained are given in Table C.
From comparison of Examples 1-3 with 4-6 it follows that by spray-cooling the partially neutralized fatty acid mixtures, prills are obtained having particularly advantageous solubility and powder properties.

EXAMPLE 7

A mixture of fatty acids was prepared, having thefollowing composition :

20 wt.% oleics
45 wt.% C12-C14 fatty acids
35 wt.% stearics

High density prills were obtained, having highly satisfactory powder handling properties, as shown in Table D.

EXAMPLE 8

The procedure of Example 7 was repeated, using a fatty acid mixture of the following composition :

30 wt.% oleics
40 wt.% C12-C14 fatty acids
30 wt.% stearics

EXAMPLE 9

The acid soap prills obtained according to Example 7 were used to formulate a complete laundry detergent composition by dry-mixing various other ingredients to the prills, such as a nonionic detergent on a Burkeite carrier, a bleach system and an enzyme.
The composition of the complete detergent powder is given in Table E. Also shown are two commercially available laundry detergent compositions, composition B being a low-P and composition A a zero P composition, both based on zeolites.
The wash performance of these three compositions was established in a Zanussi ZF 822W top loading drum washing machine, using the normal 40* C cotton cycleprogramme "C". 2.5 kg clean mixed wash load of clean cotton pieces and standard soiled test cloths was processed at a liquor/cloth ratio of approximately 6. The water temperature was 20 ° C at a pressure of 2.0 kg/cm2. The water hardness was 9 or 25 GH. The wash powder was added in a dosage of 7.5 g/I. The differences in reflectance of the test clothes before and after the wash ( R^*460) were recorded.
The results of the tests at the two different degrees of water hardness using four different test cloths, including the standard EMPA-101 and WFK-10C cloths, are shown in Table F. From these results it is clear that, even at a high water hardness, a very satisfactory washing performance was observed, despite the fact that no phosphate or zeolite builder was present.

Claims

1. Particulate laundry detergent composition comprising as a first particulate material a fatty acid mixture in which up to 35 mole% may be unsaturated fatty acids, which mixture has been neutralised to an extent of 25-60 mole %, and as a second particulate material a base in an amount sufficient to render the pH of the composition at a 0.5 wt% concentration in water higher than 8.

2. Particulate laundry detergent composition according to claim 1, which contains 30-80% of the partially neutralised fatty acid mixture.

3. Particulate laundry detergent composition according to claim or claim 2, in which the mixture of fatty acids essentially consists of 5 - 20 mole% C16-C18 unsaturated fatty acids, and 95 - 80 mole% of a mixture of C8-C14 saturated fatty acids and C16-C18 saturated fatty acids in a ratio of 3:1-1:2.

4. Particulate laundry detergent composition according to any preceding claims, in which the base is sodium carbonate or sodium alkaline silicate.

5. Particulate laundry detergent composition according to any preceding claim, additionally comprising a non-soap detergent active material.

6. Particulate laundry detergent composition according to claim 5, comprising up to 10 wt% anionic and/or nonionic detergent material within the first granular material.

7. Particulate laundry detergent composition according to claim 5, comprising a liquid nonionic material on a porous inorganic carrier.

8. Particulate laundry detergent composition according to any preceding claim, additionally comprising a peroxy bleach system and/or sodium alkaline silicate and/or an antifoam compound and/or an enzyme.

9. Particulate acid soap material suitable as a base powder for manufacturing laundry detergent powders, consisting essentially of a fatty acid mixture in which up to 35 mole% may be unsaturated fatty acids, which mixture has been neutralised to an extent of 25-60 mole%.

10. Particulate acid soap material according to claim 9, in which the mixture of fatty acids essentially consists of 5 - 20 mole% C16-C18 unsaturated fatty acids, and 95 - 80 mole% of a mixture of C8-C14 saturated fatty acids and C16-C18 saturated fatty acids in a ratio of 3:1-1:2.

11. Particulate acid soap composition according to claim 9 or claim 10, in the form of prills or noodles.

12. Particulate acid soap material according to any one of claims 9-11 in which the degree of neutralisation is 30-40 mole%.

13. Process for manufacturing the particulate acid soap material according to claim 9, characterised by the steps of melting a mixture of fatty acids optionally containing one or more soaps, partially neutralising the mixture if necessary by adding a base, and converting it to a particulate solid form.

14. Process according to claim 13, characterised in that the particulate acid soap material is prepared by spray-cooling the partially neutralised molten mixture of fatty acids to form prills.

15. Process according to claim 13 or claim 14, characterised in that the mixture of fatty acids is partially neutralised by addition of sodium carbonate and/or sodium alkaline silicate.