Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-03-23
2002-08-13
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S443000, C510S446000, C510S452000
Reexamination Certificate
active
06432905
ABSTRACT:
TECHNICAL FIELD
The present invention relates to granular detergent products of low to medium bulk density having superior rates of dissolution, flowability and granulometry and their preparation by a dry neutralisation process.
BACKGROUND AND PRIOR ART
There has been considerable interest in the detergent industry for the production of granulated detergent powders exhibiting specific bulk densities.
Generally, detergent powders prepared by spray drying have a low bulk density, for example in the range 350-500 g/l, whilst powders prepared by conventional non-tower routes in which powders are dry-mixed and optionally agglomerated have high bulk densities, for example at least 700 g/l. Powders with an intermediate bulk density, for example in range 450-800 g/l are obtained by mixing powders prepared by spray drying and dry-mix routes in appropriate combinations. However, the capital cost for such a process is very high as spray drying process is capital intensive.
The process of dry neutralisation for preparing detergent powders is known in the art but such a process often results in powders having a high bulk density. WO 96/04359 (Unilever) discloses a process of dry neutralisation for preparing a detergent powder of required bulk density in which it is preferred to choose the particle size distribution of the raw material or add a flow aid. Indian Patent No. 166307 (Hindustan Lever) discloses the specific use of an internal recirculating fluidised bed and mentions that use of a conventional fluidised bed will lead to a lumpy and sticky product.
Hydrotropes have generally been used in liquid detergent compositions to aid phase stabilisation. U.S. Pat. No. 3,926,827 (Colgate-Palmolive) describes hydrotropes as components which can retain oxygen bubbles giving the detergent more volume.
WO95/23206 (Procter & Gamble) discloses a process for making a detergent composition by making a paste comprising a surfactant system and a specific hydrotrope or a mixture and a detergency builder and agglomerating the same. This formulation has a bulk density greater than 650 g/l.
WO 98/44084 (Procter & Gamble) discloses a detergent particle comprising an anionic surfactant and a hydrotrope for use in detergent compositions to provide improved dispensing of the composition. These particles are formed by spray drying a paste or slurry comprising the anionic sulphonate surfactant.
The principal object of the present invention is to provide a non-spray drying process for the preparation of granular detergent compositions with good powder properties and having a bulk density less than 800, preferably less than 700 g/l, more preferably less than 650 g/l. In particular, the detergent composition should have good rates of dissolution, flowability and granulometry.
A further object of the present invention is to provide a process for the preparation of detergent compositions having an intermediate bulk density that is cost effective in comparison to other conventional processes. The applicants have found that the aforesaid objects may be achieved by dry neutralisation of the acid precursor of an anionic surfactant with an alkaline solid in the presence of a hydrotrope such as p-toluene sulphonic acid.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a process for the preparation of a granular detergent product comprising contacting a liquid binder component comprising an acid precursor of an anionic surfactant and a hydrotrope with a solid particulate starting material comprising a neutralising agent in a low shear mixer and granulating the mixture, wherein the hydrotrope is present at a level of at least 1% by weight of the acid precursor of the anionic surfactant.
According to a second aspect, the present invention provides a granular detergent product of bulk density in the range 450 to 800 g/l obtained according to the process of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
Hereinafter, in the context of this invention, the term “granular detergent product” encompasses granular finished products for sale, as well as granular components or adjuncts for forming finished products, e.g. by post-dosing to or with any other form of admixture with further components or adjuncts.
A granular detergent product as herein defined contains at least 5 wt %, preferably at least 10 wt % of a synthetic anionic surfactant.
As used hereinafter, the term “powder” refers to materials substantially consisting of grains of individual materials and mixtures of such grains. As used hereinafter, the term “granule” refers to a small particle of agglomerated smaller particles, for example, agglomerated powder particles. The final product of the process according to the present invention consists of, or comprises a high percentage of granules. However, additional granular and or powder materials may optionally be post-dosed to such a product.
For the purposes of this invention, the flow properties of the granular product are defined in terms of the dynamic flow rate (DFR), in ml/s, measured by means of the following procedure. A cylindrical glass tube of internal diameter of 35 mm and length of 600 mm is securely clamped with its longitudinal axis in the vertical position. Its lower end is terminated by a cone of polyvinyl chloride having an internal angle of 15° and a lower outlet orifice of diameter 22.5 mm. A first beam sensor is positioned 150 mm above the outlet, and a second beam sensor is positioned 250 mm above the first sensor.
To determine the dynamic flow rate, the outlet orifice is temporarily closed and the cylinder filled with the granular detergent product to a point about 10 cm above the upper sensor. The outlet is opened and the flow time t (seconds) taken for the powder level to fall from the upper sensor to the lower sensor measured electronically. This is repeated 2 or 3 times and an average time taken. If V is the volume (ml) of the tube between the upper and lower sensors, the DFR is given by V/t.
Unless specified otherwise, values relating to powder properties such as bulk density, relate to the weathered granular detergent product.
The Process
The process involves dry neutralisation of the acid precursor of an anionic surfactant with a solid neutralising agent in the presence of a hydrotrope such as p-toluene sulphonic acid.
The Low Shear Mixer
The process of this invention is carried out in a low shear mixer. Suitable low shear mixers for use in the process include rotating bowl mixers, drum mixers or concrete mixers. A low shear mixer of the gas fluidisation type which comprises a fluidisation zone into which the liquid binder is sprayed onto the solid material may also be used.
The liquid binder components may simply be pumped into the low shear mixer or may be introduced as a spray. The liquid binder is preferably sprayed into the low shear mixer.
In a preferred embodiment, the acid precursor of the anionic surfactant and the hydrotrope are at a temperature greater that 50° C., preferably greater than 55° C. when fed to the mixer and contacted with the solid starting material. If other components are present in the liquid binder, it is also preferred that these components be at a temperature greater that 50° C., preferably greater than 55° C. when fed to the mixer.
In a highly preferred embodiment, the acid precursor of an anionic surfactant and the hydrotrope are heated together to a temperature above 50° C. and then sprayed onto the solid starting material, preferably through the same nozzle, using a pump into a low shear mixer.
It has been found that in order to achieve the benefit of the invention, the acid precursor of the anionic surfactant and the hydrotrope must be added substantially simultaneously to the low shear mixer. This may be done by adding the two components simultaneously but in separate streams to the mixer. However, it is highly preferred that the two components are brought together prior to being fed into the mixer and are fed as a single stream.
Another important process parameter is the addition of the acid precursor and
Gowrishankaran Chandrasekaran
Pereira Winston Anthony
Sengupta Rana
Mitelman Rimma
Ogden Necholus
Unilever Home & Personal Care USA , division of Conopco, Inc.
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