Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
1999-06-10
2001-01-23
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S224000, C510S294000, C510S298000
Reexamination Certificate
active
06177398
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for making detergent tablets suitable for use in automatic dishwashing or laundry washing methods.
BACKGROUND
Detergent compositions in tablet form are known in the art It is understood that tabletted detergent compositions hold several advantages over granular detergent compositions. Examples of such advantages include ease of handling, transportation and storage. Tablets are therefore required to be of sufficient hardness such that they do not crumble or disintegrate on handling, transportation or storage.
Detergent tablets are traditionally prepared by the compression or compaction of granular detergent compositions. The most common method used by detergent manufacturers for increasing tablet hardness is to increase the compaction pressure of the machinery employed to tablet the detergent composition. EP-0,170,791 Henkel describes a process for making a tablet detergent composition comprising per compounds and tabletting aids. The detergent composition is compressed at a pressure of 5×10
7
to 10
8
Pa resulting in tablets having a breaking strength of between 50 and 120 N.
Other methods of controlling tablet hardness and dissolution have been discussed in the prior art. Detergent manufacturers have for example, introduced alterations in the detergent formulation, thereby changing the characteristics of the tablet. WO93/00419 Henkel describes increasing tablet hardness by providing a detergent composition comprising polymer. EP-0,466,484 and EP-0,522,766 Unilever describe increasing tablet hardness by providing a tabletted detergent composition comprising liquid binder and specific particle size ranges. Japanese patent application J06,207,199 A Kao describes a process for making a deterrent composition in tablet form wherein the process consists of mixing nonionic surfactant and an oil absorbing material, granulating the mixture to provide particles of specific size and density, then compacting the resulting particles to form a tablet. EP-0,579,659 Henkel, describes a process for preparing a detergent tablet wherein the alkaline detergent additives are agglomerated with builder, water and nonionic surfactant resulting in a tablet having a high break strength.
It has however, been found that ease of ejection of the tablet from the tablet press decreases with increasing compression/compaction pressure. Furthermore, the tabletting machinery at high compression/compaction pressure tends to damage the outermost surface of the tablet, as well as potentially damaging the machinery itself. Damage to the outermost surface of the tablet, such as scoring or scratching is unacceptable to the consumer. It is thus the object of the present invention to provide a detergent composition in tablet form that is not only sufficiently hard to meet handling, transportation and storage needs, but which can also be readily ejected from the tablet press without damage to the outermost surface.
It has surprisingly been found that by selectively spraying non-aqueous low viscosity liquid components of a detergent composition onto a specially selected low porosity fraction of the solid components of a detergent composition tablets that are more readily removed from a tablet press without damage are produced.
SUMMARY OF THE INVENTION
According to the present invention there is provided a process for making a detergent tablet by tabletting a detergent composition comprising solid components which form a total particulate base detergent matrix and non-aqueous liquid components having viscosity of 1000 cp or less measured at ambient temperature, said process comprising the steps of
a) selecting a low porosity fraction of the total particulate base detergent matrix such that the average porosity of said low porosity fraction is at least 5% less than the average porosity of the total particulate base detergent matrix;
b) applying said non-aqueous liquid components of viscosity 1000 cp or less measured at ambient temperature to the low porosity fraction;
c) admixing the product of step (b) with remaining components of the detergent composition and tabletting the detergent composition.
DESCRIPTION OF THE INVENTION
Particulate Base Detergent Matrix
The particulate base detergent matrix may comprise essentially any particulate component traditionally used in detergent compositions. This includes for example builder compounds, bleaching agents, alkalinity sources, lime soap dispersants, organic polymeric compounds including polymeric dye transfer inhibiting agents, crystal growth inhibitors, heavy metal ion sequestrants, enzymes and enzyme stabilisers, corrosion inhibitors, suds suppressors, solvents, fabric softening agents, optical brighteners and hydrotropes. The particulate base detergent matrix essentially comprises a low porosity fraction.
Low Porosity Fraction
The low porosity fraction comprises particulate matrix components, either as raw materials or processed particles (i.e. produced by spray drying, agglomeration or any other conventional particle processing method) that are selected from the total particulate base detergent matrix for their low porosity characteristics. The low porosity fraction is characterised in that the average porosity of this fraction is 5% less, preferably at least 10% less, most preferably at least 14% less than the average porosity of the particulate base detergent matrix. Particularly preferred components of the low porosity fraction include builder compounds and alkalinity sources.
The low porosity fraction generally comprises at least 5% by weight, preferably at least 10%, or even at least 15% or 20% by weight of the total particulate base detergent matrix. The amount of low porosity fraction should be sufficient such that at least a proportion of the non-aqueous low viscosity liquid is not absorbed by the low porosity fraction. Thus the weight ratio of low porosity fraction to non-aqueous low viscosity liquids is 1:1 preferably at least 1:1.5 and most preferably 1:2.
Porosity
The porosity of the components of the particulate base detergent matrix and particularly the low porosity fraction, can be measured by any known methods. These methods may include, for example, image analysis, mercury porosimetry, determination and comparison of volume and mass, determination and comparison of surface area and diameter, gas chromatography, x-ray small angle scattering and displacement methods. A preferred method of measuring porosity is the mercury porosimetry method. However, for particles of less than 1 mm in diameter an alternative method may be preferred.
Non-aqueous Liquid components of viscosity 1000 cp or less
Non-aqueous liquid components of viscosity 1000 cp or less measured at ambient temperature for use herein may include any non-aqueous liquid component that is substantially non-aqueous traditionally used as a component of a tablet detergent composition and having the appropriate viscosity. By substantially non-aqueous it is meant liquids having less than 10%, preferably less than 5%, most preferably less than 2% by weight water. Preferred examples of non-aqueous liquid components employed in the process of the present invention are surfactants, especially non-ionic surfactants, and hydrocarbon oils as described below. Viscosity is measured as described below.
The non-aqueous low viscosity liquid can be applied to an agglomerate by any known application method. The preferred method of application is by spraying the non-aqueous low viscosity liquid on to the low porosity fraction.
Viscosity
The viscosity of the liquid components can be measured by any known method for determining viscosity. Viscosity for the purposes of the present invention is measured by a Brookfield Laboratory Viscometer, available from Brookfield Viscometer Ltd.
Agglomeration
In a preferred aspect of the present invention, the total particulate base detergent matrix and most preferably at least the low porosity fraction comprises particulates which are prepared by agglomeration. Agglomerates can be prepared using any conventional agglome
McGregor Alasdair Duncan
Warwick Jane Margaret
Douyon Lorna M.
Dressman Marianne
Miller Steven W.
The Procter & Gamble & Company
William Zerby Kim
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