FORM -2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See Section 10)
IMPROVED PROCESS OF EXTRUSION
HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

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, colour 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 di oxide 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 (WO9744434, WO WO0017308 Procter & Gamble) disclose the use of peroxygen bleaches such as perborate 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
2

conveyed to a two stage vacuum plodder operating a 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 :
5-80% detergent active;
0.1-10% 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% water;
0-30% 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 ; 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, where the blend is extruded through an extruder in which the flights and the extruder barrel is heated in order to obtain a product with higher density on the outside and lower on the inside.
There is a consumer felt continuing need for preparing detergent bars with low bulk density. Aeration of detergent products enable production of low bulk density 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 resulted in soft bars which lead 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.Thus while further aeration and consequential lower bulk density products is a continuing need in the art, there has been the above
3

limitations to improve upon the aeration of detergent products using such chemical
blowing agents.

OBJECTS OF THE INVENTION

It is the object of the invention to provide cost effective and jndustrially viable

process to further improve desired aeration of non-granular detergenr products to obtain low density products with superior in-use properties.
Another object of the present invention is to provide a selective improved process for the manufacture of low-density detergent products by entrapping gas, that is generated by the decomposition of the component of the detergent formulation during extrusion, without need for raising temperature of the blend so to affect the quality of the bar and/or in any manner affecting the desired productivity level in such manufacture.
It has been surprisingly found by way of the present invention that carrying out the step of extrusion of the mix involving chemical blowing agents maintaining a temperature of 50-90°C by heating of the said mix both from inside and outside the extruder provided for significant reduction in density of the bar as compared to that achieved by extruding the mix at the same temperature of 50-90°C by heating the same from outside by heating only the barrel of the extruder.
SUMMARY OF THE INVENTION
Thus, according to the basic aspect of the present invention there is provided a process for preparing a non-granular solid detergent composition with entrapped gas bubbles comprising
5-80% detergent active
0.1-10% 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% water
0-30% detergent builders
which process comprises the steps of
i. mixing the various ingredients of the formulation in a mixer
4

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 maintaining a temperature of 50-900C by selectively
heating said mix both from the outside and inside of the extruder.

iv. optionally cooling the extruded bars, converting them into billets and forming tablets.
According to a preferred aspect of the present invention there is provided a process for preparing a non-granular solid detergent composition with entrapped gas bubbles comprising
5-80% detergent active
0.1-10% 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% water
0-30% 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
iii. extruding the said mix maintaining a temperature of 50-90°C by selectively heating said mix from the outside of the extruder by heating the extruder barrel and from the inside of the extruder by heating the screw shaft and/or the screw flights.
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 rise in the temperature above the decomposition temperature of the chemical blowing agent in the extruder helps in releasing the gas which gets entrapped in the bar formulation during extrusion and enables the preparation of low density bars. However, as discussed hereinbefore it is not possible to raise the
5

temperature of the mix to higher than beyond 90°C to improve air entrapment as
that affected bar properties nor was it desirable to increase the extrusion time

which affected productivity. Keeping in view such limitations, the'present invention
achieves the desired further reduction in density by way of the above selective

heating of the mix from inside the extruder by heating of said screw shaft and/or the
screw flight and from outside by heating of the barrel without need for any increase of the temperature of the mix beyond 90°C and/or the increase in the extrusion time which affected productivity.
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 with or without 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.
The invention i§ 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, ?3jngle 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.
6

Chemical blowing agents:

Chemical blowing agents used in the formulation are thpse, 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 and several others listed in "Polymeric materials encyclopedia" vol. 1, CRC Press, edited by J.C. Salamone, bicarbonates which give CO2 on heating, or di-isocyanates which give CO2 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 0.1 to10% by weight but preferably in the range 1-5%.
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 which 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.

7

Inorganic participates:

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.
8

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 6 kg was prepared by taking 4.54 kg of a soap containing 20% 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. This 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
9

Table 1

Composition (% wt) Example 1 Example 2 Example 3 Example 4
TFM 59 59 59 59
Moisture 20.5 20.5 20.5 20.5
Alkaline silicate 2.0 2.0 2.0- 2.0
Aluminium sulphate 1.0 1.0 1.0 1.0
China Clay 15.0 15.0 15.0 15.0
Boric Acid 1.0 1.0 1.0 1.0
Sodium perborate 1.5 1.5 1.5 1.5
Property
Density (glee) 1.17 0.96 0.97 0.83
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

Example -1 Example-4
Bar loss to solution, gm 1.26 0.90
Total mush, gm 1.92 0.97
This shows aeration of the bars decrease the bulk density and thus increase the size and also improve the in-use properties to give better economy in use.
10

WE CLAIM :
1. A process for preparing a non-granular solid detergent compositon with
entrapped gas bubbles comprising
5-80% detergent active
0.1-10% 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% water 0-30% 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
iii. extruding the said mix maintaining a temperature of 50-90°C by selectively heating said mix both from the outside and inside of the extruder
iv. optionally cooling the extruded bars, converting them into billets and forming tablets.
2. A process as claimed in claim 1 comprising
5-80% detergent active
0.1-10% 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% water
0-30% 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
11

iii. extruding the said mix maintaining a temperature of 50-90°C by
selectively heating said mix from the outside of the extruder by heating
the extruder barrel and from the inside of the extruder.'.by heating the screw shaft anoYor the screw flights.
iv. optionally cooling the extruded bars, converting thenyjhtp billets and forming tablets.
3. A process as claimed in anyone of claims 1 to 2 wherein the temperature of
the extruder is raised by said selective heating both from inside and outside of
the extruder to 60-90°C so that the generation of the gas takes place only in
the extruder.
4. A process as claimed in anyone of claims 1 to 3 wherein the temperature of
the extruder is maintained by said selective heating both from inside and
outside of the extruder at a temperature range 60-75 °C.
5. A process as claimed in anyone of claims 1 to 4 wherein the temperature of
the bar coming out of the extruder is cooled down to - 45° C by way of either
cooling thQ die or by passing it through a cooling tunnel.
6. A process as claimed in anyone of claims 1 to 5 wherein the detergent
composition comprise alongwith said 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 any conventional detergent composition comprising
detergent active, builder, structurants .inorganic particulars and additives.
7. A process as claimed in anyone of claims 1 to 6 wherein the said chemical
blowing agents are selected from sodium perborate, hydrogen peroxide and
other per-oxy compounds, azo compounds which give out nitrogen on
decomposition preferably 1,1-azobis-isobutyronitrile, 2,2-azobis(2,4-dimethyl-
valenonitrile),2,2-azobis(4-methoxy-2,4-dimethylvalenonitrile)and
bicarbonates which give CO2 on heating, di-isocyanates which give CO2 by
reacting with water and boro-hydrides which give out hydrogen.
12

8. A process as claimed in anyone of claims 1 to 7 wherein the chemical blowing
agent is incorporated in the composition is in the range of 1-5%.

9. A process as claimed in anyone of claims 2 to 8 wherein the heating of the
mix is carried out by heating of the extruder from outside by passing hot water .

through the barrel of the extruder and from inside by passing hot water
through the screw shaft with or without the screw flights.
10. A process for preparing a non-granular solid detergent composition with
entrapped gas bubbles substantially as herein described and illustrated with
reference to the examples.
Dated this 19th day of June 2003.
13