WO2004000988A1

WO2004000988A1 - Process for production of solid detergent compositions

Info

Publication number: WO2004000988A1
Application number: PCT/EP2003/005722
Authority: WO
Inventors: Satish Kumar Goel; Sujitkumar Suresh Hibare; Narayanan Subrahmaniam
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Lever Limited
Priority date: 2002-06-20
Filing date: 2003-05-27
Publication date: 2003-12-31
Also published as: ZA200409283B; AU2003245900A1; MY134365A; CN1662639A; BR0311527A

Abstract

A process is provided for preparing a non-granular solid detergent composition with entrapped gas bubbles, the composition comprising:5-80% by weight of detergent active;0.1-10% by weight of a chemical blowing agent that decomposes to generate a gas at a temperature range 50-90oC optionally in presence of water; 5-30% by weight of water; and0-30% by weight of detergency builder;which process comprises the steps of i. mixing the various ingredients of the formulation in a mixer; ii. mixing 0.1-10% of the chemical blowing agent to the said mix at a temperature below 50o C;iii. extruding the said mix at a temperature of 50-90oC wherein heat is provided to the said mix from the outside by heating the extruder barrel and from the inside by heating the screw shaft and/or the screw flights; and,iv. optionally, cooling the extruded bars, converting them into billets and forming tablets.

Description

PROCESS FOR PRODUCTION OF SOLID DETERGENT COMPOSITIONS

TECHNICAL FIELD

The invention relates to a process for the manufacture of detergent bars suitable for fabric washing or hard surface cleaning. The invention particularly relates to a process for the manufacture of "aerated" detergent bars wherein the chemical blowing agent in the formulation is decomposed during extrusion by providing heat from both the barrel and screw shaft, to release gas and the liberated gas is entrapped.

BACKGROUND AND PRIOR ART

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. Detergent bars require an acceptable physical strength so that they retain their structural integrity during handling, transport and use. The hardness of the bars, at the time of manufacture and subsequently, is an especially important property. Commercially available detergent bars contain detergent active components and detergent builders, fillers, structurants, hardeners together with optional components for example abrasives, perfumes, colourants and bleaching agents.

The water content in the detergent bars is generally maintained around 6%. The binders and fillers used in non-soap detergent (NSD) bars are typically minerals and the low moisture content coupled with the use of high proportion of minerals result in NSD bars with high density making them considerably smaller. If gases such as air, oxygen, nitrogen or carbon dioxide can be entrapped in the detergent bar the bulk density of the bar can be reduced and it enables the manufacture of larger bars . It is also possible to entrap sufficient air in order to make the bars float in the washing solution. The concept of entrapment of air or gas has been achieved more particularly for soap bars as it is an advantage to have the bars float in the bath tub.

Several patents (WO-A-9744434, WO-A-0017308) disclose the use of peroxygen bleaches, such as perborates and percarbonates, in detergent bar compositions. These are used as a source of active oxygen in the formulations. But in these cases care is taken to see that the compounds do not decompose during the process of manufacture but are available during use. Usually the product is conveyed to a two-stage vacuum plodder operating at high vacuum, so that entrapped air is removed.

Our co-pending application (1158/MUM/2000) discloses a process for preparing a non-granular solid detergent composition with entrapped gas bubbles comprising:

(a) 5-80%wt of detergent active;

(b) 0.1-10%wt of a chemical blowing agent that decomposes to generate a gas at a temperature range 50-90°C optionally in presence of water;

(c) 5-30%wt of water;

(d) 0-30%wt of detergent builders; which process comprises the steps of i . mixing the various ingredients of the formulation in a mixer ; ii. mixing 0.1-10% of the chemical blowing agent to the said mix at a temperature below 50 °C and maintaining a temperature not exceeding 50°C ; iii. extruding the said mix at a temperature of 50-90°C ;and iv. optionally, cooling the extruded bars, converting them into billets and forming tablets. US6153293 (Dahl et al . ) discloses an extruded composite structural artificial lumber product manufactured from wood fiber and polyethylene, wherein the blend is extruded through an extruder in which the flights and the extruder barrel are heated in order to obtain a product with higher density on the outside and lower on the inside. However, it does not teach that screw shaft heating in addition to barrel heating will reduce the overall density of detergent products.

There is a consumer felt need for preparing detergent bars with low bulk density and processes are available to manufacture such detergent bars. However there is a limitation on the extent of reduction in density. Aeration of detergent products enable production of larger sized bars and also improve the in- use benefits. The process described in our co-pending application involves a chemical blowing agent that decomposes to generate a gas at a temperature range 50-90 °C in the extruder. Raising the temperature to increase the extent of aeration is not desirable as this produces a soft bar which leads to problems in downstream processing like cutting, stamping and wrapping. It is also not desirable to increase the extent of aeration by increasing the extrusion time as this reduces the throughput and thereby the productivity of the machine .

It is the object of the invention to produce aerated non- granular detergent products with superior in-use properties.

Another object of the present invention is to provide a novel process for the manufacture of low-density detergent products by entrapping gas, that is generated by the decomposition of the gas-generating component of the detergent formulation during extrusion, more effectively than just raising temperature to a particular level during extrusion.

DEFINITION OF THE INVENTION Thus, according to the present invention there is provided a process for preparing a non-granular solid detergent composition with entrapped gas bubbles, the composition comprising:

5-80% by weight of detergent active;

0.1-10% by weight of a chemical blowing agent that decomposes to generate a gas at a temperature range 50-90°C optionally in presence of water;

5-30% by weight of water; 0-30% by weight of detergency builder; which process comprises the steps of i . mixing the various ingredients of the formulation in a mixer; ii. mixing 0.1-10% of the chemical blowing agent to the said mix at a temperature below 50° C; iii. extruding the said mix at a temperature of 50-90°C wherein heat is provided to the said mix from the outside by heating the extruder barrel and from the inside by heating the screw shaft and/or the screw flights; and, iv. optionally, cooling the extruded bars, converting them into billets and forming tablets.

DETAILED DESCRIPTION OF THE INVENTION:

It is essential that the detergent composition containing the chemical blowing agent does not encounter a temperature greater than 50° C before the mass reaches the extruder. The raise in the temperature above the decomposition temperature of the chemical blowing agent helps in releasing the gas which gets entrapped in the bar formulation during extrusion and enables the preparation of low density bars.

It is possible that the temperature of the mass is raised to 60-90°C just before feeding into the extruder but it is preferred that the detergent composition does not encounter a temperature greater than 50° C until it is in the extruder. The heating of the detergent composition in the extruder is provided for from the outside by heating the extruder barrel and from the inside by heating the screw shaft and/or the screw flights. As a preferred aspect of the invention, the temperature of the extruder is raised to 60-90°C so that the generation of the gas takes place only in the extruder. It is particularly preferred that the temperature of the extruder is maintained at a temperature range 60-75°C. As a preferred aspect of the invention, the temperature of the bar coming out of the extruder should be cooled down to - 45° C by way of either cooling the die or by passing it through a cooling tunnel .

Processing

The invention is carried out in any mixer conventionally used in soap/detergent manufacture and is preferably a high shear kneading mixer. The preferred mixers include ploughshare mixer, mixers with kneading members of sigma type, multi wiping overlap, single curve or double arm. The double arm kneading mixers can be of overlapping or tangential in design. Alternatively the invention can be carried out in a helical screw agitator vessel or multi head dosing pump/high shear mixer and spray drier combinations as in conventional processing. The composition that can be processed by the above process to entrap the gas in order to reduce the density of the bar, is any conventional detergent composition comprising detergent active, builder, structurants etc but containing 0.1-10% a chemical blowing agent that decomposes to generate a gas at a temperature range 50-90°C optionally in presence of water.

Chemical blowing agents:

Chemical blowing agents used in the formulation are those that decompose at temperatures in the range 50-90°C and generate a gas. A few examples of such compounds are sodium perborate, hydrogen peroxide and other per-oxy compounds, certain azo compounds which give out nitrogen on decomposition for e.g. 1 , 1-azobis-isobutyronitrile, 2 , 2-azobis (2 , 4-dimethyl- valenonitrile) , 2 , 2-azobis (4-methoxy-2 , 4-dimethylvalenonitrile) and several others listed in "Polymeric materials encyclopedia" vol. 1, CRC Press, edited by J.C. Salamone, bicarbonates which give C0₂ on heating, or di-isocyanates which give C0₂ by reacting with water and boro-hydrides which give out hydrogen .

The level at which the chemical blowing agent is incorporated in the composition is in the range of from 0.1 to 10% by weight, but preferably in the range 1-5% by weight.

Detergent Active:

The detergent active used in the process may be soap or non- soap surfactants. The composition according to the invention will preferably comprise detergent actives that are generally chosen from both anionic and nonionic detergent actives. Other actives such as cationic, amphoteric and zwitterionic surfactants may also be used. Examples of suitable detergent- active species are given in the following well-known textbooks: (i) "Surface Active Agents", Volume I by Schwartz and Perry, (ii) "Surface Active Agents and Detergents", Volume II by Schwartz, Perry and Berch, (iii) "Handbook of Surfactants", M. R. Porter, Chapman and Hall, New York, 1991.

Builders :

The detergency builders used in the formulation are preferably inorganic and suitable builders include, for example, alkali metal aluminosilicates (zeolites) , alkali metal carbonate, sodium tripolyphosphate (STPP) , tetrasodium pyrophosphate (TSPP) , citrates, sodium nitrilotriacetate (NTA) and combinations of these. Builders are suitably used in an amount ranging from 1 to 30% by wt .

Inorganic particulates :

Inorganic particulate phase is not an essential ingredient of the formulation but may be incorporated especially for hard surface cleaning compositions. Preferably, the particulate phase comprises a particulate structurant and/or abrasive which is insoluble in water. In the alternative, the abrasive may be soluble and present in such excess to any water present in the composition that the solubility of the abrasive in the aqueous phase is exceeded and consequently solid abrasive exists in the composition.

Suitable inorganic particulates can be selected from, particulate zeolites, calcites, dolomites, feldspars, silicas, silicates, other carbonates, bicarbonates, sulphates and polymeric materials such as polyethylene.

The most preferred inorganic particulates are calcium carbonate (as Calcite) , mixtures of calcium and magnesium carbonates (as dolomite) , sodium hydrogen carbonate, borates, boric acid, sodium/potassium sulphate, zeolite, feldspars, talc, koalin and silica.

Calcite, talc, kaolin, feldspar and dolomite and mixtures thereof are particularly preferred due to their low cost and colour.

Other additives:

Other additives such as one or more water insoluble particulate materials such as polysaccharides such as starch or modified starches and cellulose may be incorporated.

Minor additives:

Conventional ingredients preferably selected from enzymes, antiredeposition agents, fluorescers, colour, preservatives and perfumes, also bleaches, bleach precursors, bleach stabilisers, sequestrants, soil release agents (usually polymers) and other polymers may optionally be incorporated up to 10 %wt .

The invention will now be illustrated by the following non- limiting examples.

Examples .

Process for preparation of the Detergent bars: Different formulations as described in Table 1 were prepared by the processes described below and analysed for bar density and in-use properties .

Soap bars : a. Conventional Process:

A batch of about 6kg was prepared by taking 4.54 kg of a soap containing 25% water in a sigma mixer at room temperature. To this was added 0.12 kg of aluminium sulphate, 0.06 kg of boric acid, 0.9 kg of washed china clay, 0.285 kg of alkaline silicate and 0.09 kg of sodium perborate and mixing them thoroughly at room temperature. The resulting mass was then extruded in the conventional manner at a temperature of about 45°C (Example 1) .

b. Process where only the barrel was heated:

A batch similar to the one mentioned above in example 1 was prepared in the mixer. However temperature in the extruder was maintained at 85°C by passing hot water through the barrel of the extruder (Example 2) .

c. Process where only the screw was heated:

A batch similar to the one mentioned above in example 1 was prepared in the mixer. However temperature in the extruder was maintained at 85°C by passing hot water through the screw shaft of the extruder (Example 3) .

d. Process according to the invention:

A batch similar to the one mentioned in example 1 was prepared in the mixer. Here, the temperature of the extruder was maintained at 85°C by passing hot water both through the barrel of the extruder as well as through the screw shaft. (Example 4) .

Analysis of the density of the bar:

The density of the bar is measured by the standard method and calculated using the formula :

Density (grams/cm³) = Weight of bar (grams)

Volume in cm³ Table 1 .

The data in Table-1 above show that there is reduction in bar density when only the barrel (Example 2) or the screw (Example 3) of the extruder is heated to 85°C. It is seen that the reduction in density is significantly higher when both the barrel and the screw of the extruder are heated as compared to heating the barrel or the screw alone.

Analysis of in-use properties:

Mush refers to the paste like layer formed on the surface of the bar during use. The paste like mush on the bar is weighed in grams. The economy in use is determined by bar loss to solution. The control (Example 1) and the bar according to the invention (Example 4) were assessed for the above properties and the data is presented in Table-2.

Table 2

This shows that aeration of the bars decreases the bulk density (thus increasing the size) and also improves the in-use properties to give better economy in use.

Claims

1. A process for preparing a non-granular solid detergent composition with entrapped gas bubbles, the composition comprising:

5-80% by weight of detergent active;

5-30% by weight of water; and

0-30% by weight of detergency builder; which process comprises the steps of i. mixing the various ingredients of the formulation in a mixer; ii. mixing 0.1-10% of the chemical blowing agent to the said mix at a temperature below 50° C; iii. extruding the said mix at a temperature of 50-90°C wherein heat is provided to the said mix from the outside by heating the extruder barrel and from the inside by heating the screw shaft and/or the screw flights; and, iv. optionally, cooling the extruded bars, converting them into billets and forming tablets.

2. A process according to claim 1, wherein the concentration of the chemical blowing agent used in said process is in the range of 1-5% by weight.

3. A process according to claim 1 or claim 2, wherein the blowing agent is selected from bicarbonates, di- isocyanates, boro-hydrides, 1 , 1-azobis-isobutyronitrile, 2, 2-azobis (2 , 4-dimethyl-valenonitrile) , 2 , 2-azobis (4- methoxy-2 , 4-dimethylvalenonitrile ) and mixtures thereof.

A process according to any of claims 1-3, wherein the temperature of the extruder is raised to 60°-90°C so that the generation of the gas takes place only in the extruder.