WO2001021757A1

WO2001021757A1 - Detergent compositions and process for their preparation

Info

Publication number: WO2001021757A1
Application number: PCT/EP2000/008170
Authority: WO
Inventors: Satishkumar Gopinat Nair; Winston Anthony Pereira
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 1999-09-20
Filing date: 2000-08-18
Publication date: 2001-03-29
Also published as: BR0007164B1; TR200101371T1; AU7411500A; BR0007164A; CN1336955A

Abstract

A particulate laundry detergent composition having a bulk density of at least 600 g/l comprises: (a) from 5 to 30 wt% of a mixed surfactant system wherein at least 25% of the surfactant is an alpha-olefin sulphonate having from 14 to 20 carbon atoms, (b) from 5 to 95 wt% of inorganic salts comprising inorganic detergency builders and/or other inorganic salts, and optionally other conventional detergent ingredients. The compositions may be prepared by: (i) mixing inorganic salts comprising detergency builders with alpha-olefin sulphonate forming at least 25 wt% of the total surfactant in a high shear kneading mixer; (ii) spraying the other surfactants; and (iii) optionally adding the conventional ingredients on to the mix, and blending the mixture.

Description

DETERGENT COMPOSITIONS AND PROCESS FOR THEIR PREPARATION

TECHNICAL FIELD

The invention relates to a particulate detergent composition with a bulk density of at least 600 g/litre having a mixed active system produced by a non-tower process.

BACKGROUND OF THE INVENTION

Fabric washing compositions contain, as an essential ingredient, a surfactant system whose role is to assist in removal of soil from the fabric and its suspension in the wash liquor. Other important components are the detergent builders together with optional components for example abrasives, fillers, perfumes, alkaline salts and bleaching agents.

There has been considerable interest in detergent industry for the production of granulated detergent powders exhibiting specific bulk densities. Powders exhibiting different bulk densities are available and specific processes are used to target specific range of bulk densities. Generally detergent powders with low bulk density (0.35-0.45 g/cc) are prepared by spray drying and the powders prepared by conventional dry-mix route have high bulk densities (0.6-1.2 g/cc). However, the capital cost for spray drying is very high and the process is capital intensive.

Conventional laundry detergent powders intended for the hand wash contain a substantial level of anionic surfactant, most usually alkylbenzene sulphonate. Anionic surfactants are ideally suited to the hand wash because they combine excellent defergency on a wide range of soils with high foaming. Alkylbenzene sulphonates are, however, highly calcium- intolerant and the formulations require substantial levels of defergency builder (calcium builder). The most commonly used water-soluble defergency builder is sodium tripolyphosphate but it is comparatively expensive. Apart from being expensive, phosphate builders have restrictions in use from the point of view of protection of the natural environment which is affected by use of phosphate builders in detergent compositions.

Attempts have been made to provide granular detergents avoiding the use of phosphate builders and zeolite (aluminosilicate) was found to be an effective substitute to phosphate builder.

US-A-4 350 619 discloses a zeolite-containing non-phosphate granular detergent composition comprising from 20 to 25% by weight of mixed surfactants of at least one alpha-olefin sulphonate having 14 to 20 carbon atoms and linear alkylbenzene sulphonate having 10 to 14 carbon atoms in the alkyl group thereof along with sodium silicate. Although this exploits the good defergency characteristics of zeolites as an alternative to phosphate builder, in order to obviate the problems of zeolite deposition on fabric or cloth, it proposes the use of sodium silicate. This process is also restricted to the spray drying tower route process of manufacture, which is also expensive and capital intensive.

Particulate detergent compositions of high bulk density prepared by non-tower processes are well known in the prior art and widely available in the market. However, the amount of water or other liquid ingredients to be incorporated into formulation becomes a problem while processing the powders by the non-tower route. The flow property of the formulations gets affected.

It is thus the basic objective of the present invention to provide a particulate laundry detergent composition with bulk density of at least 600 g/litre which would minimise/avoid the necessity of expensive phosphate/zeolite builder and the buffer salt sodium silicate and yet achieve improved flow properties and with good defergency benefits.

Another object of the present invention is directed to provide a process of manufacture of particulate laundry detergent composition utilising a selective mixed surfactant system which would be calcium tolerant and minimise/avoid the use of expensive phosphate/zeolite builders and buffer salts such as sodium silicate. Yet another object of the present invention is to provide a simple and cost effective dry mix (non-tower) process of manufacture of particulate laundry detergent composition with bulk density of at least 600 g/litre with improved flow properties and good defergency.

WO-A-00/40682, not published before the priority date of the present invention, discloses detergent compositions of unspecified bulk density, containing alkyl olefin sulphonate surfactant. However, the total level of surfactant is very high, i.e. 45 wt % or more. The compositions also contain high levels of silicate.

GB-A-2 166 452 discloses an example of a composition comprising 38 wt % by weight of a mixed synthetic detergent composition and 1 wt % soap, 13.2% by weight of this composition being alkyl olefin sulphonate. The composition contains 20 wt % of zeolite. Such compositions are said preferably to have a bulk density of from 600 to 980 g/l.

Detergent compositions containing alkyl olefin sulphonate are also known from JP-A- 01132698, JP-A-61246300, JP-A-07054000 and JP-A-02103297.

However, there remains a need for detergent compositions having moderate surfactant levels, and little or no phosphate or aluminosilicate builder, which are suitable for hand wash regimes, and are calcium tolerant. This need is met by the present invention.

DEFINITION OF THE INVENTION

A first aspect of the present invention provides a particulate laundry detergent composition having a bulk density of at least 600 g/litre comprising:

(a) from 5 to 30 wt% of a mixed surfactant system wherein at least 25% of the surfactant is an alpha-olefin sulphonate having 14 to 20 carbon atoms,

(b) from 5 to 95 wt% of inorganic salts comprising inorganic defergency builders and/or other inorganic salts, and optionally other conventional detergent ingredients.

A second aspect of the present invention provides a particulate laundry detergent composition having a bulk density of at least 600 g/l and comprising:

(a) from 5 to 30 wt% of a mixed surfactant system wherein at least 5% of the surfactant is an alpha-olefin sulphonate having from 14 to 20 carbon atoms,

(b) from 5 to 95 wt% of inorganic salts comprising inorganic detergency builders and/or other inorganic salts,

and optionally other conventional detergent ingredients; said inorganic detergency builders being free of phosphates and zeolites and/or other inorganic salts.

A third aspect of the present invention provides a particulate laundry detergent composition having a bulk density of at least 600 g/l and comprising:

(b) from 5 to 95 wt % of inorganic salts comprising inorganic detergency builders and/or other inorganic salts,

and optionally other conventional detergent ingredients; wherein component (b) comprises sodium carbonate as inorganic detergency builder and optionally, a non- builder organic salt.

DETAILED DESCRIPTION OF THE INVENTION

The composition of the invention is based on a mixed surfactant system but essentially comprising at least 25% by weight of an alpha-olefin sulphonate having 14 to 20 carbon atoms, plus a high content of inorganic salts consisting detergency builders and other non-builder salts. The conventional optional ingredients may also be present. The mixed surfactant system

The mixed surfactant system (a) used in the composition according to the invention will preferably comprise in addition to an alpha-olefin sulphonate having 14 to 20 carbon atoms, surfactants which are generally chosen from both anionic, nonionic, cationic, zwitterionic detergent actives or mixtures thereof. The level of alpha-olefin sulphonate in the composition is preferably 25 to 75% of the total surfactant system.

Detergent compositions according to the present invention, preferably comprise from 5 to 20 wt%, more preferably from 8 to 15 wt% of the mixed surfactant system (a), or preferably they comprise from 20 to 30 wt% of the mixed surfactant system (a).

Component (a) is a mixed surfactant system. Therefore, in addition to the alpha olefin sulphonate, at least one other component must be present. Examples of suitable detergent-active compounds for this purpose are compounds commonly used as surface- active agents given in the well-known textbooks "Surface Active Agents", Volume I by Schwartz and Perry and "Surface Active Agents and Detergents", Volume II by Schwartz, Perry and Berch. These may be selected from anionic, nonionic, cationic, zwitterionic and amphoteric detergent active compounds and mixture thereof.

It is especially preferred that the at least one other component of mixed surfactant system (a) comprises a non-soap anionic detergent active

Suitable anionic detergent active compounds are water soluble salts of organic sulphuric reaction products having in the molecular structure an alkyl radical containing from 8 to 22 carbon atoms, and a radical chosen from sulphonic acid or sulphuric acid ester radicals and mixtures thereof.

Examples of suitable anionic detergents are sodium and potassium alcohol sulphates, especially those obtained by sulphating the higher alcohols produced by reducing the glycerides of tallow or coconut oil; sodium and potassium alkyl benzene sulphonates such as those in which the alkyl group contains from 9 to 15 carbon atoms ; sodium alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow and coconut oil ; sodium coconut oil fatty acid monoglyceride sulphates ; sodium and potassium salts of sulphuric acid esters of the reaction product of one mole of a higher fatty alcohol and from 1 to 6 moles of ethylene oxide ; sodium and potassium salts of alkyl phenol ethylene oxide ether sulphate with from 1 to 8 units of ethylene oxide molecule and in which the alkyl radicals contain from 4 to 14 carbon atoms; the reaction product of fatty acids esterified with isothionic acid and neutralised with sodium hydroxide where, for example, the fatty acids are derived from coconut oil and mixtures thereof.

A preferred surfactant system comprises alpha-olefin sulphonate and linear alkylbenzene sulphonate used in a weight ratio of from 1 :10 to 10:1 , preferably from 1 :5 to 5:1.

Suitable nonionic detergent active compounds can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

Suitable amphoteric detergent-active compounds that optionally can be employed are derivatives of aliphatic secondary and tertiary amines containing an alkyl group of 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilizing group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyltaurate. Suitable cationic detergent- active compounds are quaternary ammonium salts having an aliphatic radical of from 8 to 18 carbon atoms, for instance cetyltrimethyl ammonium bromide.

Suitable zwitterionic detergent-active compounds that optionally can be employed are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having an aliphatic radical of from 8 to 18 carbon atoms and an aliphatic radical substituted by an anionic water-solubilising group, for instance 3-(N-N-dimethyl-N- hexadecylammonium) propane-1 -sulphonate betaine, 3-(dodecylmethyl sulphonium) propane-1 -sulphonate betaine and 3-(cetylmethylphosphonium) ethane sulphonate betaine.

Inorganic salts

The inorganic salts in the formulation may be detergency builders and/or other inorganic salts. The detergency builder used in the formulation is most preferably sodium carbonate (see further below). However, other commonly employed detergency builders such as sodium tripolyphosphate and aluminosilicat.es such as zeolites may be employed especially (except in the case of the second aspect of the present invention). The other inorganic salts may selected from water soluble sulphates, other water soluble carbonates, chlorides and water insoluble minerals. The builder component is preferably in the range from 5 to 50 wt% and the non-builder salts in total are preferably present from 5 to 50 wt% of the composition.

As mentioned above, the inorganic salts (b) preferably comprise sodium carbonate as detergency builder, optionally in admixture with a non-builder inorganic salt. Compositions of the invention may suitably comprise from 15 to 80 wt%, preferably from 20 to 70 wt%, of the sodium carbonate.

Preferably, the sodium carbonate builder is also accompanied in the composition by a seed crystal material, preferably calcite. Sodium carbonate as a component of a builder system also comprising a seed crystal material such as calcite is a true calcium-binding builder. However, the carbonate on its own (i.e. without the calcite) is seldom a strong calcium binder because it is usually poisoned by another component in the formulation such as crystal growth inhibitors (e.g. low-medium MW polyacrylat.es), or even materials within the water or coming from the wash load itself. Sodium carbonate can also be poisoned so as to be low or non-calcium binding by inclusion in the formulation of, for example, of sodium tripolyphosphate, even at relatively low levels of the tripolyphosphate, so that the carbonate will not behave as a builder. The same effect occurs if silicates are present. In that case, the carbonate will only be included for as an alkaline buffer. However, since sodium carbonate is a preferred inorganic detergency builder, compositions according to the present invention are preferably free from phosphates and/or silicates and/or other inorganic salts. Since sodium carbonate is a water soluble and less expensive detergency builder than aluminosilicate builders such as zeolites, compositions according to the present invention are also preferably free from aluminosilicates.

Thus, in summary, it is possible by way of the above composition of the invention having the mixed surfactant system to have products for the hand wash with significantly improved flow properties and good detergency. Importantly by way of the composition of the invention it is possible to eliminate the use of phosphate and zeolite builders especially when the detergent active level is above 20%. In order to reduce cost it is also possible to eliminate the buffer salt such as sodium silicate, which are used to provide the necessary alkalinity. Compositions according to the invention have been found to exhibit significantly better detergency than present formulations.

It has been found that when we have a mixed active system comprising of alpha-olefin sulphonate it is possible to produce a non-phosphate/zeolite detergent powder with good flow properties and with significantly superior detergency.

Other ingredients

The compositions of the invention may also optionally contain up to 10 wt % of other beneficial ingredients. Such ingredients are preferably selected from minerals, organic builders, enzymes, antiredeposition agents, fluorescers, and perfumes, also bleaches, bleach precursors, bleach stabilisers, sequestrants, soil release agents (usually polymers) and other polymers.

Preparation of the compositions

The compositions of the invention may be prepared by any suitable process. The choice of processing route may be in part dictated by the stability or heat-sensitivity of the surfactants involved, and the form in which they are available.

For example, alpha-olefin sulphonate is robust, and is available in powder, paste and solution form.

Alkyl ether sulphate is more sensitive to heat, is susceptible to hydrolysis, and is available as concentrated (e.g. about 70% active matter) aqueous paste, and as more dilute (e.g. 28.5 wt%) solution.

In all cases, ingredients such as enzymes, bleach ingredients, sequestrants, polymers and perfumes which are traditionally added separately (e.g. enzymes postdosed as granules, perfumes sprayed on) may be added after the processing steps outlined below.

Suitable processes include:

(1) drum drying of principal ingredients, optionally followed by granulation or postdosing of additional ingredients;

(2) non-tower granulation of all ingredients in a high-speed mixer/granulator, for example, a Fukae (Trade Mark) FS series mixer, preferably with at least one surfactant in paste form so that the water in the surfactant paste can act as a binder;

(3) preparation, by spray-drying or by non-tower granulation as in (2), of a base powder composed of structured particles comprising inorganic salts and part of the surfactant, followed by admixture of additional surfactant in suitable granular form.

In all process routes, sodium alkaline silicate can be admixed in the form of solution, or as powder, or as sodium carbonate/sodium silicate granules, for example, Nabion (Trade Mark) 15 ex Rhodia.

When the anionic surfactant consists of or comprises an alkylbenzenesulphonate surfactant, it is preferably made by a non-tower route (NTR) granulation process (i.e. not by spray-drying), e.g. using a VRV-type mixer and an aluminosilicate layering agent is incorporated together with sodium carbonate, preferably in light powder form.

Typically, 60-100 parts by weight of powder from the mixer are made up to 100 parts with a minors granule produced by any convenient NTR process (e.g. containing perfume, speckles, enzymes(s), bleach and diluents).

The main powder prior to addition of the minors granule is typically formulated with the anionic surfactant, e.g. alkylbenzene sulphonate (up to 65% by weight, preferably up to 50% by weight), from 2-5% to 40% by weight of the light powder sodium carbonate, from 0% to 20% of diluents such as clay and or other salts, in cases other than the second aspect of the invention, for example sodium tripolyphosphate and from 1% to 40% of the aluminosilicate. The sodium carbonate is granulated with the anionic surfactant, preferably in acid form, and then layered with the aluminosilicate. Further diluents can also be added prior to layering.

According to a fourth aspect of the invention there is provided a preferred process for manufacture of a detergent composition by the non-tower route comprising:

(i) mixing inorganic salts comprising detergency builders with alpha-olefin sulphonate forming at least 5 wt% of the surfactant in a high shear kneading mixer;

(ii) spraying the other surfactants; and

(iii) optionally adding the conventional ingredients on to the mix and blending the mixture.

The preferred mixers for this preferred process according to the present invention include mixers with kneading members of Sigma type, dispersion, multiwiping overlap, single curve or double naben. The double arm kneading mixers can be of overlapping or the tangential design. Others suitable are ribbon mixer and the ploughshear mixer & similar mixers like V- blenders or mixers. When the active content in the powder is high it is specifically preferred to use ploughshare mixer or V-blenders. Suitably, the kneading members of the high shear kneading mixer are rotated at a speed of 20-150 per minute and preferably 50-60 rpm. The residence time in the mixer is in the order of 10-50 minutes. The mixer being maintained at a temperature in the range of SOC to 95°C, preferably about 50-80°C by heating/cooling. The mixer can have a combination of a fast blade and a slow blade. Preferably the ratio of the speeds of the blades being in the range of 1 :1 to 1:7, preferably 1 :2 to 1:4.

The invention will now be illustrated with reference to the following non-limiting Examples.

EXAMPLES

Process for preparing the detergent formulation

A batch was prepared where the different ingredients in the proportion mentioned in Table 1 was employed. Inorganic salt, minerals and sodium carbonate was taken in a sigma mixer to which alpha-olefin sulphonate paste was added and homogenised. Linear alkyl benzene sulphonic acid, colour, and other conventional ingredients were sprayed on to the mix. The flow aid such as precipitated calcite was added and mixed.

Table 1

Evaluation of the composition

The compositions of examples 1 to 5 were evaluated for their flow property and detergency as per the following procedure.

(i) Detergency Measurement

Soiling and washing protocols

Cotton fabric swatches were desized by washing in a detergent solution in the washing machine at 90°C for 1 hour. The swatches were rinsed thrice and dried. A standard composite soil comprising of a mixture of synthetic sebum and particulates was loaded on swatches using a spray method such that the reflectance of the fabric reached 55 ± units at 460 nm.

These swatches were soaked in detergent solution of a concentration of 5g/l and were agitated using a tergotometer for 10 minutes. The swatches were rinsed well with water and dried.

Measurement of Detergency

The initial reflectance of the soiled fabric was measured at 460 nm. using a Milton Roy Match Scan II. The fabric was washed following the protocol described above and the reflectance of the washed fabric was measured. The difference in the reflectance of the fabric before and after wash represented as ΔR460* gives the detergency benefit. % detergency was calculated. ΔR460^* = R460^* (washed) - R460^* (soiled)

(ii) Determination Of flow property

The flow property of the powder is measured by determining the time taken for the powder contained in a tube to flow between two fixed marks 25 cms apart out of a standard cone and is expressed as ml/sec. The value is directly related to the flowability of the powder.

Table 2

The data presented in Table 2 shows that when the mixed surfactant system including the alpha-olefin sulphonate is incorporated in the composition there was significant improvement in the flow property of the powder with good detergency characteristics.

Preparation of high active powders

A batch was prepared where the different ingredients in the proportion mentioned in Table 3 was employed. Inorganic salt, minerals and sodium carbonate was taken in a Plough share mixer to which alpha-olefin sulphonate paste was added and homogenised. Linear alkyl benzene sulphonic acid, colour, and other conventional ingredients were sprayed on to the mix. The flow aid such as precipitated calcite was added and mixed.

Table 3

The Examples 8 and 11 which are according to the invention had good flow properties and superior detergency as compared to the controls even in the absence of expensive phosphate and zeolite builders.

The powder prepared according to the invention also exhibits superior in-use properties such as good solubility, good and faster lathering, good detergency and therefore economy in use.

Claims

1. A particulate laundry detergent composition having a bulk density of at least 600 g/l and comprising:

(a) from 5 to 30 wt% of a mixed surfactant system wherein at least 25% of the surfactant is an alpha-olefin sulphonate having from 14 to 20 carbon atoms,

and optionally other conventional detergent ingredients.

2. A detergent composition according to claim 1 , wherein the alpha-olefin sulphonate constitutes from 25 to 75% of the total surfactant system.

3. A detergent composition according to either preceding claim, wherein the inorganic salts (b) comprise inorganic detergency builders free of phosphates and zeolites and/or other inorganic salts.

4. A composition according to any preceding claim, wherein component (b) comprises sodium carbonate as inorganic detergency builder and optionally, a non- builder inorganic salt.

5. A detergent composition according to claim 4, which comprises from 15 to 80 wt%, preferably from 20 to 70wt%, of the sodium carbonate.

6. A composition according to claim 4 or claim 5, further comprising a seed crystal material, preferably calcite, for the sodium carbonate inorganic detergency builder.

7. A detergent composition according to any preceding claim, comprising from 5 to 20 wt%, preferably from 8 to 15 wt% of the mixed surfactant system (a).

8. A detergent composition according to any of claims 1 to 6, comprising from 20 to 30 wt% of the mixed surfactant system (a).

9, A detergent composition according to any preceding claim, which is substantially free of sodium silicate.

10. A detergent composition according to any preceding claim, wherein the surfactant system (a) further comprises linear alkylbenzene sulphonate.

11. A detergent composition according to claim 10, wherein the surfactant system (a) comprises the alpha-olefin sulphonate and the linear alkylbenzene sulphonate in a weight ratio of 10:1 to 1 :10, preferably from 5:1 to 1:5.

12. A particulate laundry detergent composition having a bulk density of at least 600 g/l and comprising:

(b) from 5 to 95 wt % of inorganic salts comprising inorganic detergency builders and/or other inorganic salts, and optionally other conventional detergent ingredients; said inorganic detergency builders being free of phosphates and zeolites and/or other inorganic salts.

13. A particulate laundry detergent composition having a bulk density of at least 600 g/l and comprising:

14. A non-spray-drying process for manufacture of a detergent composition according to any of claims 1 , 12 and 13, the process comprising:

(i) mixing inorganic salts comprising detergency builders with alpha-olefin sulphonate forming at least 25 wt% of the total surfactant in a high shear kneading mixer;

(ii) spraying the other surfactants; and

(iii) optionally adding the conventional ingredients on to the mix, and blending the mixture.