Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Reexamination Certificate
2001-02-28
2003-10-28
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
C510S302000, C510S438000
Reexamination Certificate
active
06638901
ABSTRACT:
FIELD OF INVENTION
This invention relates to compositions and methods for catalytically bleaching substrates with atmospheric oxygen and a peroxyl species, using a metal-ligand complex as catalyst.
BACKGROUND OF INVENTION
Peroxygen bleaches are well known for their ability to remove stains from substrates. Traditionally, the substrate is subjected to hydrogen peroxide, or to substances which can generate peroxyl radicals, such as inorganic or organic peroxides. Generally, these systems must be activated. One method of activation is to employ wash temperatures of 60° C. or higher. However, these high temperatures often lead to inefficient cleaning, and can also cause premature damage to the substrate.
A preferred approach to generating peroxyl bleach species is the use of inorganic peroxides coupled with organic precursor compounds. These systems are employed for many commercial laundry powders. For example, various European systems are based on tetraacetyl ethylenediamine (TAED) as the organic precursor coupled with sodium perborate or sodium percarbonate, whereas in the United States laundry bleach products are typically based on sodium nonanoyloxybenzenesulphonate (SNOBS) as the organic precursor coupled with sodium perborate.
Precursor systems are generally effective but still exhibit several disadvantages. For example, organic precursors are moderately sophisticated molecules requiring multi-step manufacturing processes resulting in high capital costs. Also, precursor systems have large formulation space requirements so that a significant proportion of a laundry powder must be devoted to the bleach components, leaving less room for other active ingredients and complicating the development of concentrated powders. Moreover, precursor systems do not bleach very efficiently in countries where consumers have wash habits entailing low dosage, short wash times, cold temperatures and low wash liquor to substrate ratios.
Alternatively, or additionally, hydrogen peroxide and peroxy systems can be activated by bleach catalysts, such as by complexes of iron and the ligand MeN4Py (i.e. N,N-bis(pyridin-2-yl-methyl)-bis(pyridin-2-yl)methylamine) disclosed in WO95/34628, or the ligand Tpen (i.e. N,N,N′,N′-tetra(pyridin-2-yl-methyl)ethylenediamine) disclosed in WO97/48787.
As discussed by N. J. Milne in J. of Surfactants and Detergents, Vol 1, no 2, 253-261 (1998), it has long been thought desirable to be able to use atmospheric oxygen (air) as the source for a bleaching species. The use of atmospheric oxygen (air) as the source for a bleaching species would avoid the need for costly peroxyl generating systems. Unfortunately, air as such is kinetically inert towards bleaching substrates and exhibits no bleaching ability. Recently some progress has been made in this area. For example, WO 97/38074 reports the use of air for oxidising stains on fabrics by bubbling air through an aqueous solution containing an aldehyde and a radical initiator. A broad range of aliphatic, aromatic and heterocyclic aldehydes is reported to be useful, particularly para-substituted aldehydes such as 4-methyl-, 4-ethyl- and 4-isopropyl benzaldehyde, whereas the range of initiators disclosed includes N-hydroxysuccinimide, various peroxides and transition metal coordination complexes.
However, although this system employs molecular oxygen from the air, the aldehyde component and radical initiators such as peroxides are consumed during the bleaching process. These components must therefore be included in the composition in relatively high amounts so as not to become depleted before completion of the bleaching process in the wash cycle. Moreover, the spent components represent a waste of resources as they can no longer participate in the bleaching process.
The recent development of air bleaching using O2 bleaching catalysts has provided an effective bleach composition that does not rely on peroxygen bleach or a peroxy-based or peroxyl-generating bleach system. One significant advantage of these recent developments is that the oxygen in the air is provided free.
Presently, oxygen bleaching catalysts per se are more selective in bleaching oily stains, for example tomato stains than polar stains, for example tea. It would be advantageous to provide an air bleaching composition that is effective on both oily and polar stains. In addition, it would be advantageous to provide a bleaching composition that contains a reduced amount of peroxyl or peroxyl generating system per wash dose.
SUMMARY OF INVENTION
We have now found that it is possible to achieve a bleaching composition that has a broad stain bleaching ability, for example, bleaching of both oily tomato and tea type stains.
Catalysts of the present invention catalyse bleaching of stains with either oxygen or peroxy species. An object of the present invention is to provide a bleaching composition that allows bleaching in a single wash with both oxygen and a hydroperoxy species in the presence of a catalyst, i.e., dual bleaching. The dual bleaching is achieved by an aqueous solution of a bleaching composition in which oxygen competes with a peroxyl species for interaction with an oxygen bleaching catalyst. The concentration of peroxyl species that is provided by a unit dose allows oxygen bleaching to compete in an aqueous wash.
When a peroxyl species is present in a dominant concentration in an aqueous solution of an oxygen bleaching catalyst the reaction of oxygen with the oxygen bleaching catalyst is suppressed. One factor that is difficult to change in an aqueous solution is the low solubility of oxygen in water. The concentration of oxygen in water is relatively low when compared to organic solvents. The oxygen concentration in water is approximately 0.2 mM at 20° C. and the solubility of oxygen in water decreases about 15% per 10° C. increase in temperature of the water as detailed in The Handbook of Chemistry and Physics, 72
nd
Edition, CRC press. Hence, the oxygen concentration in water at 40° C. is approximately 0.15 mM. In order, for oxygen in an aqueous solution to compete with a peroxyl species, the concentration of the peroxyl species has to be substantially below conventional concentrations of between 5 and 10 mM that are found in aqueous wash mixtures. Throughout the disclosure and claims the description of oxygen concentration refers to the concentration of oxygen dissolved in an aqueous environment unless otherwise specified.
Alternatively, dual bleaching is achieved in a stepwise fashion by changing from oxygen bleaching to hydroperoxy bleaching during the course of an aqueous wash. The stepwise bleaching may be achieved in the following manner. 1) Initially bleaching with oxygen followed by raising the concentration of a peroxyl species present. 2) Reducing the concentration of peroxyl species in the wash such that oxygen bleaching is effective.
In contrast to having a limited amount of a hydroperoxy species present in a wash the bleaching composition may contain an agent for decomposing hydrogen peroxide during a wash cycle. Initially during a wash hydrogen peroxide acts as the main bleaching agent in conjunction with a catalyst but as the wash proceeds a hydrogen peroxide decomposing agent is released into the wash. The hydrogen peroxide decomposing agent decomposes hydrogen peroxide into water and oxygen thereby reducing the hydrogen peroxide concentration in the wash. A consequence of reducing the hydrogen peroxide concentration in the wash is that oxygen dissolved in the wash can compete for the catalyst. It is most likely that amounts of the oxygen generated from decomposition of hydrogen peroxide will end up in solution in the wash and participate in the oxygen catalysed bleaching process. A particular benefit of generating hydrogen peroxide in solution is that some gasses other than oxygen in solution, for example nitrogen, will be displaced by the oxygen generated in situ. A beneficial consequence is that the oxygen concentration in an aqueous wash mixture may well exceed 0.2 mM. Oxygen makes up approximately 20% of air and the m
Hage Ronald
Swarthoff Ton
Tetard David
Thornthwaite David William
Gupta Yogendra N.
Honig Milton L.
Petruncio John M
Unilever Home & Personal Care USA , division of Conopco, Inc.
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