Process for stabilisation of coloured bleaching compositions

Details Process for stabilisation of coloured bleaching compositions Process for stabilisation of coloured bleaching compositions

2002-10-24

2003-09-23

Gupta, Yogendra N. (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Liquid composition

C510S380000

Reexamination Certificate

active

06624134

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to process of stabilising a pigment in a hypochlorite-containing bleaching composition. The present invention also relates to a hypochlorite-containing composition comprising an encapsulated pigment.
BACKGROUND OF THE INVENTION
Bleaching compositions are well-known in the art. Amongst the different bleaching compositions available, those relying on bleaching by hypohalite bleaches such as hypochlorite are often preferred, mainly for performance reasons.
An objective of the beach manufacturer is to achieve a bleach product that is stable, both chemically and physically over time, for example over periods of storage. This has been a constant challenge often owing to the aggressive nature of hypohalite bleaches.
Coloured bleaching compositions are particularly preferred often because the distinct appearance of the composition facilitates it's recognition by a consumer, thereby reducing potential misuse or consumption of a potentially irritant or even poisonous composition. However formulating a coloured bleaching composition can present a variety of stability related problems. The principal problems include, the settling of pigment to the bottom of the container and oxidation of dyes and pigments in the hypohalite bleach-containing bleaching composition.
It is the object of the present invention to provide a hypohalite-containing composition comprising a pigment and in which the pigment is chemically stable, even upon storage.
Thickened bleaching compositions are also preferred herein as the higher viscosity of the composition can aid suspension of the pigment. Thus, in a preferred embodiment of the invention, it is an objective to improve the physical stability of the pigment.
An advantage of the compositions according to the present invention is that in the pigment-containing bleaching compositions as described herein the pigment is chemically stable upon storage even in case said bleaching composition is formulated under alkaline conditions.
Another advantage of the compositions of the present invention is that they deliver effective bleaching performance, more particularly effective whiteness performance when used in any laundry application, as well as effective stain removal performance on various stains, even upon storage of the composition.
Advantageously the compositions of the invention are suitable for the bleaching of different types of surfaces including hard-surfaces like floors, walls, tills, glass, kitchen surfaces, bathrooms surfaces, toilet bowls and/or dishes and the like as well as fabrics. More particularly, the compositions of the present invention are suitable for bleaching any type of fabrics including natural fabrics (e.g., fabrics made of cotton, viscose, linen, silk and wool), synthetic fabrics such as those made of polymeric fibers of synthetic origin as well as those made of both natural and synthetic fibers.
A further advantage of the liquid bleaching compositions of the present invention is that said bleaching compositions are suitable for various laundry bleaching applications both when used in diluted conditions, e.g. as a detergent additive or a fully formulated laundry detergent composition, and when used in neat condition, e.g. as a liquid pretreater (spotter).
SUMMARY OF THE INVENTION
According to the present invention there is provided a process for stabilising an insoluble pigment in the presence of hypochlorite by combining the pigment with silica or a salt thereof. According to another aspect of the present invention the combination of pigment and silica or a salt thereof is present as a component of a hypochlorite-containing composition.
According to another aspect of the present invention there is provided a bleaching composition comprising hypochlorite and an insoluble pigment wherein the pigment is coated with silica.
DETAILED DESCRIPTION OF THE INVENTION
Process of Stabilisation
The present invention relates to a process of stabilising a pigment in the presence of hypochlorite and more preferably in a hypochlorite-containing bleaching composition. As is discussed above, bleaching compositions have from time to time in the past be designed to comprise a colouring agent, for example a pigment or dye. However selecting a colouring agent that could withstand the aggressive nature of the bleaching agent-containing bleaching composition and remain both chemically and physically stable over time has still proved problematic.
Colouring agents are available on the market that are specifically designed to be bleach and pH resistant. One of the most commonly used colouring agents having this characteristic is a pigment known as ultramarine blue. However the applicants have found that this pigment, although initially chemically stable to bleach, looses colour over time. The inability of the pigment to withstand chemical deterioration, for example via oxidation by the bleach and/or via chemical degradation due to the alkalinity, when present, of the bleaching composition, over time is believed to be due to the disruption of the structure of the pigment.
The Applicants have found that stabilisation is achieved by combining the pigment with silica or a salt thereof, and hence loss of colour through chemical instability can be decreased.
Furthermore, it has been observed that when a bleaching composition is formulated at an alkaline pH, the problem of the chemical instability of pigments is further increased due to the chemical degradation of the pigments by the alkalinity of the bleaching composition. The Applicants have now found that stabilisation is achieved by combining the pigment with silica or a salt thereof, in a bleaching composition preferably formulated at an alkaline pH, more preferably at a pH of from 10 to 14, and most preferably at a pH of from 12 to 14, and hence loss of colour through chemical instability can be decreased.
By “chemically stable”, it is meant that the hypochlorite in the compositions of the present invention does not undergo more than 25% loss of available chlorine after 5 days of storage at 50° C. ±0.5° C., preferably not more than 20%. The % loss of available chlorine may be measured using the method described, for instance, in “Analyses des Eaux et Extraits de Javel” by “La chambre syndicate nationale de L'eau de Javel et des produits connexes”, pages 9-10 (1984). Said method consists in measuring the available chlorine in the fresh compositions, i.e. just after they are made, and in the same compositions after 5 days at 50° C.
By “chemically stable”, it is also meant that the pigment is stable to hypohalite bleach as determined according to the following test method:
Given K is the % of pigment in the composition, prepare the following 6 standards, agitating continually until comparison.
0
Distilled water
1
0.2 × K % Pigment + Balance Water
2
0.4 × K % Pigment + Balance Water
3
0.6 × K % Pigment + Balance Water
4
0.8 × K % Pigment + Balance Water
5
K % Pigment + Balance Water
The hypochlorite composition comprising pigment and silica or salt thereof in study is prepared and stored for 10 days at 40° C. and then stirred. The composition is then compared with the 6 reference samples as described above. Four expert panelists will grade the color intensity of the hypochlorite composition by comparison of the colour intensity of the composition with the 6 reference samples (above) assigning to the composition a color intensity grade equal to the number of the standard sample which is most similar. If the average color intensity grade is equal or higher than 1 then the pigment is stable to hypohalite. More preferably, the average color intensity grade is higher than 2 and even more preferably higher than 3.
Hypohalite Bleach
An essential component of the invention is a hypohalite bleach. Hypohalite bleaches may be provided by a variety of sources, including bleaches that are oxidative bleaches and subsequently lead to the formation of positive halide ions as well as bleaches that are organic based sour

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