Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1999-06-11
2001-01-23
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S294000, C510S298000, C510S441000, C510S446000
Reexamination Certificate
active
06177393
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for making detergent tablets suitable for use in either laundry or automatic dishwashing 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. It has however, been found that solubility of the tablet generally decreases with increasing compression/compaction force. Detergent manufacturers have directed tablet development efforts toward striking a balance between strength and solubility.
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. This process, although providing tablets of sufficient hardness, results in tablets that suffer from a reduction in rate of dissolution in water. Henkel EP-0170791 describes a process for making a tablet detergent composition comprising per compounds and tabletting aids. The detergent composition is compacted 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. Henkel WO93/00419 describes increasing tablet hardness by providing a detergent composition comprising polymer. Unilever EP-0466484 and EP-0522766 describe increasing tablet hardness by providing a tabletted detergent composition comprising liquid binder and particles of specific size ranges. Japanese patent application Kao J06207199 A describes a process for making a detergent composition in tablet form wherein the process consists of the 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. Henkel EP-0579659, 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 is thus the object of the present invention to provide a detergent composition in tablet form that is sufficiently hard to meet handling, transportation and storage needs, without negatively affecting the rate of dissolution of the tablet.
The present invention provides a process for making a detergent composition in tablet form, wherein the tablet produced has increased hardness. Detergent tablets comprise a particulate base detergent matrix and liquid components.
It has surprisingly been found that by selectively applying the low viscosity non-aqueous liquid components of a detergent composition onto a specifically selected high porosity fraction of the particulate base detergent matrix harder tablets are produced. It is believed that the non-aqueous liquid components of a tablet detergent composition act as lubricants at the surface of the components of the particulate base detergent matrix. These components, once provided with additional lubrication, slide over each other more easily reducing the potential for particulate fusion during the tabletting step. It is therefore, the aim of the present invention to reduce such lubrication and increase tablet hardness. It is believed that the non-aqueous liquid components are held within pores of the particulate base detergent matrix, increasing tablet hardness by providing liquid bridges which effectively bind particulate components together.
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, the process comprising the steps of
a) selecting a high porosity fraction of the total particulate base detergent matrix such that the average porosity of said high porosity fraction is at least 5% greater 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 high porosity fraction;
c) admixing the product of step (b) with remaining components of the detergent composition; and
d) 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 high porosity fraction.
High Porosity Fraction
The high porosity fraction of the particulate base detergent matrix comprises particulate matrix components, either raw materials or processed particles (eg produced by spray drying, agglomeration or any other conventional particle-producing method) that are selected from the total particulate base detergent matrix for their high porosity characteristics. The high porosity fraction is characterised in that the average porosity of this fraction is at least 5% greater, preferably 10% greater, most preferably 20% greater than the average porosity of the particulate base detergent matrix. Particularly preferred components of the high porosity fraction include builder compounds and alkalinity sources.
The high 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 high porosity fraction should be sufficient to substantially absorb the non-aqueous low viscosity liquids. Thus the weight ratio of high porosity fraction to non-aqueous low viscosity liquids is at least 1:1 preferably at least 1.5:1 and most preferably 2:1 or even at least 5:1 or 10:1.
Porosity
The porosity of the components of the particulate base detergent matrix and particularly the high porosity fraction, can be measured by any known method. Suitable 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-Agueous Liquid Component of Viscosity 1000 cp or Less
Essentially any liquid component that is substantially non-aqueous traditionally used as a component of a tablet detergent composition can be used. By substantially non-aqueous it is meant liquids comprising less than 10%, preferably less than 5%, most preferably less than 2% by weight water. Non-aqueous liquid components of viscosity 1000 cp or less measured at ambient temperature are applied to the high porosity fraction. Preferred examples of non-aqueous liquid components employed in the process of the present invention are surfactants, especially non-ionic surfactant, and hydrocarbon oils as described below. Visco
McGowan Steven Baldwin
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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