Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Reexamination Certificate
2000-08-29
2002-09-17
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...
C510S283000, C510S284000, C510S303000, C510S367000, C510S370000, C510S375000, C510S376000
Reexamination Certificate
active
06451752
ABSTRACT:
FIELD OF INVENTION
This invention relates to a method for bleaching stained fabrics, more particularly by pretreating the stained fabric, before washing, with a pretreatment composition that comprises an organic ligand that forms a transition metal complex as bleach catalyst. The invention further relates to the use of the ligand or complex in a pretreatment composition for applying to stained fabrics prior to washing in an aqueous wash liquor.
BACKGROUND OF INVENTION
EP-A-0909809 discloses a class of iron coordination complexes useful as catalysts for the bleach activation of peroxy compounds, including iron complexes comprising the ligand N,N-bis(pyridin-2-yl-methyl)-1,1-bis(pyridin-2-yl)-1-aminoethane, also referred to as MeN4Py. These catalysts are said to be useful in bleaching systems comprising a peroxy compound or a precursor thereof, such as in the washing and bleaching of substrates including laundry, dishwashing and hard surface cleaning, or for bleaching in the textile, paper and woodpulp industries, and in waste water treatment.
In our co-pending application PCT/GB99/02876, we describe methods for catalytically bleaching substrates with atmospheric oxygen in aqueous medium, using metal ligand complexes as catalytic bleaching agents. These methods are said to be particularly applicable to bleaching of laundry fabrics, suitably in detergent formulations, but also may be used for hard surface cleaning, waste-water treatment, pulp bleaching in paper manufacture, leather manufacture, dye transfer inhibition, food processing, starch bleaching, sterilisation, whitening in oral hygiene preparations and/or contact lens disinfection.
However, there remains a need for improved methods of bleaching stained laundry fabrics. Thus, it would be desirable to be able to effect improved bleaching of particular stain types. It would also be desirable to be able to bleach a broader profile of stain types more effectively.
SUMMARY OF INVENTION
We have now found that improved or broader stain profile bleaching can be achieved in accordance with the present invention, by using a specified ligand or transition metal complex bleach catalyst to pretreat stained fabrics prior to washing.
Accordingly, in a first aspect, the present invention provides a method of bleaching fabric stains comprising applying a pretreatment composition to a stained fabric, and subsequently washing the pretreated fabric in an aqueous wash liquor, wherein:
the pretreatment composition comprises a ligand which forms a complex with a transition metal, the complex catalysing bleaching of stains by atmospheric oxygen; and
one or both of the pretreatment composition and the wash liquor are substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system.
In a second aspect, the present invention provides the use of a ligand which forms a complex with a transition metal, the complex catalysing bleaching of stains by atmospheric oxygen, in a pretreatment composition for applying to stained fabrics prior to stain bleaching by washing the pretreated fabric in an aqueous wash liquor.
Preferably, the ligand is N,N-bis(pyridin-2-yl-methyl)-1,1-bis(pyridin-2-yl)-1-aminoethane, and the complex is an iron complex.
We have found that certain stain types can be more effectively bleached on stained fabrics by the pretreatment. Thus, the bleaching of oily stains such as tomato stain can be improved by the pretreatment. For stains of this type, a peroxygen bleach such as hydrogen peroxide, or a peroxy-based or -generating bleach system, may be present or absent in the pretreatment composition, but preferably is absent. Bleaching of tea stains may also be improved by the pretreatment. For stains of this type, a peroxygen bleach such as hydrogen peroxide, or a peroxy-based or -generating bleach system, should be present in the pretreatment composition.
In order to provide a more effective bleaching performance over a range of different stain types, it is preferred that one of the pretreatment composition and the wash liquor comprises a peroxygen bleach such as hydrogen peroxide or a peroxy-based or -generating bleach system. Thus, the other of the pretreatment composition and the wash liquor is free of peroxygen bleach or a peroxy-based or -generating bleach system. Since the specificity of catalytic bleaching for particular stain types may be altered according to the presence or absence of peroxygen bleach or a peroxy-based or -generating bleach systems, a broader stain profile may be bleached more effectively by ensuring that either the pretreatment or the wash liquor, but not both, comprise peroxy bleach.
For example, it may be postulated that catalytic bleaching with atmospheric oxygen will predominate in the wash liquor during the wash cycle when the wash liquor is substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system, so as to favour bleaching of tomato stain types over tea stain types, whereas peroxy bleach catalysis will predominate during the pretreatment if the pretreatment composition comprises peroxygen bleach or a peroxy-based or -generating bleach system, so as to favour bleaching of tea stain types over tomato stain types.
Alternatively, the peroxygen bleach or peroxy-based or -generating bleach system could absent from the pretreatment composition and present only in the wash liquor so as to favour the bleaching of tomato stain types during the pretreatment and the bleaching of tea stain types during the main wash cycle. By altering the specificity of bleaching for particular stain types between the pretreatment step and the main wash step, a broad stain profile bleaching can be effected.
In a preferred embodiment, therefore, the pretreatment composition comprises peroxygen bleach or a peroxy-based or -generating bleach system and the wash liquor is substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system. In this embodiment, preferably the stained fabric comprises a tea stain.
In an alternative embodiment, the pretreatment composition is substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system and the wash liquor comprises peroxygen bleach or a peroxy-based or -generating bleach system. In this embodiment, preferably the stained fabric comprises a tomato, oil or tomato/oil stain.
We have also found that the bleaching effect on certain stain types, for example tomato/oil stain types, may be enhanced by the presence of unsaturated fatty acids, such as oleic acid, or esters thereof, preferably unsaturated fatty acid oils, in the pretreatment composition. Therefore, in a preferred embodiment, the pretreatment composition comprises an unsaturated fatty acid oil in combination with the ligand or complex. The unsaturated fatty oils are relatively inexpensive and it is postulated that similar materials will serve to provide a similar bleach enhancing activity. Enhancement of the bleaching process will likely be found in compounds having a hydrogen that is relatively prone to abstraction by a free radical. Other examples of compounds that are likely suitable as bleach enhancers are found in compounds containing an allylic hydrogen, a hydrogen alpha to an ether (anomeric effect), a hydrogen alpha to an amine, a benzylic hydrogen etc.
Any suitable fabric that is susceptible to stain bleaching or one that one might wish to subject to bleaching may be used. Preferably the fabric is a laundry fabric or garment. In a preferred embodiment, the method according to the present invention is carried out on a laundry fabric using an aqueous pretreatment composition. In particular, the treatment may be effected prior to a conventional wash cycle.
The pretreatment composition will comprise at least the ligand or complex in combination with a suitable medium, such as an aqueous or nonaqueous solvent, or an inert carrier such as a filler. It will be appreciated that the composition may take any suitable form, such as a solid, powder, paste, gel or liquid. Preferably, the pretreatment composition is in the form of a liquid.
The
Delroisse Michel Gilbert
Jones David Andrew
Smith Richard George
Wells John Francis
Gupta Yogendra N.
Honig Milton L.
Petruncio John M
Unilever Home & Personal Care USA , division of Conopco, Inc.
LandOfFree
Method of pretreating and bleaching stained fabrics does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of pretreating and bleaching stained fabrics, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of pretreating and bleaching stained fabrics will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2879226