Bleaching and dyeing; fluid treatment and chemical modification – Bleaching – Chemical
Reexamination Certificate
2000-08-29
2001-10-16
Delcotto, Gregory (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Bleaching
Chemical
C510S303000, C510S311000, C510S372000, C510S376000, C252S186330
Reexamination Certificate
active
06302921
ABSTRACT:
FIELD OF INVENTION
This invention relates to a method for bleaching stained fabrics, more particularly by washing a stained fabric in an aqueous wash liquor in the presence of a wash additive 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 as a wash additive for addition to an aqueous wash liquor for bleaching stains on fabrics.
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 as a wash additive for addition to an aqueous wash liquor for bleaching stains on fabrics.
Accordingly, in a first aspect, the present invention provides a method of bleaching fabric stains comprising washing a stained fabric in an aqueous wash liquor in the presence of a wash additive, wherein:
the wash additive 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 wash additive 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, on a carrier as a wash additive for addition to an aqueous wash liquor for bleaching stains on fabrics.
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 adding the ligand or complex to a wash liquor as a wash additive. Thus, the bleaching of oily stains such as tomato stain can be improved by addition of the wash additive to the wash liquor. 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 wash additive, and may be present or absent in the wash liquor, but preferably is absent from the wash liquor. Bleaching of tea stains may also be improved by addition of the wash additive. For stains of this type, a peroxygen bleach such as hydrogen peroxide, or a peroxy-based or -generating bleach system, should be present in one or both of the wash additive and the wash liquor, and preferably is present in the wash additive.
In order to provide a more effective bleaching performance over a range of different stain types, it is preferred that a peroxygen bleach or a peroxy-based or -generating bleach system is present in the wash additive and is absent in the wash liquor. It will be appreciated that once the wash additive has been added to the wash liquor, additive materials such as the ligand or complex and, if present, peroxy bleach will migrate into the wash liquor medium.
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 laundry fabrics and the wash additive is added to the wash liquor in a conventional wash cycle.
The wash additive will comprise at least the ligand or complex in combination with any suitable carrier. The purpose of the carrier is simply to support or contain the additive active materials such as the ligand or complex and peroxy bleach, if present, and to allow delivery of the additive active materials into the wash liquor when the wash additive is added. It will be appreciated that any carrier suitable for this purpose may be used in accordance with the method of the invention.
The ligand or complex may conveniently be deposited on or impregnated into the carrier by any suitable means, for example as a liquid which is then optionally dried, or as a dry powder. Preferably, the ligand or complex is carried in or on the carrier in a composition that includes a solvent or carrier medium for the ligand or complex. The composition may take any suitable form, such as a solid, powder, paste, gel or liquid. Preferably, the composition is in the form of a liquid.
In a particularly preferred embodiment the method according to the present invention is carried out on a laundry fabric using aqueous wash liquor. In particular, the addition of the wash additive may be effected in, or as an adjunct to, an essentially conventional wash cycle for cleaning laundry. More preferably, the wash additive is added in an aqueous detergent wash liquor. The ligand or complex can be delivered into the wash liquor from a carrier, which can be particulate, sheet-like or comprise a three-dimensional object. The carrier can be dispersible or soluble in the wash liquor or may remain substantially intact.
The wash additive may, for example, be presented in the form of a body from which the complex is slowly released during the whole or part of the laundry process. Such release can occur over the course of a single wash or over the course of a plurality of washes. In the latter case it is envisaged that the complex can be released from a carrier substrate used in association with the wash process, e.g. from a body placed in the dispenser drawer of a washing machine, elsewhere in the delivery system or in the drum of the washing machine. When used in the drum of the washing machine the carrier can be freely moving or fixed relative to the drum. Such fixing can be achieved by mechanical means, for example by barbs that interact with the drum wall, or employ other forces, for example a magnetic force. The modification of a washing machine to provide for means to hold and retain such a carrier is envisaged similar means being known from the analogous art of toilet block manufacture. Freely moving carriers such as shuttles for dosage of surfactant materials and/or other detergent ingredients into the wash can comprise means for the release of the complex into the wash.
In the alternative, the wash additive can be presented in a form that is dispersed and preferably is soluble in the wash liquor. The additive can take any of the physical forms used for wash additives, including powder, granule, pellet, sheet, tablet, block, bar or other such solid form or take the form of a paste, gel or liquid. Dosage of the additive can be unitary or in a quantity determined by the user. While it is envisaged that such additives can be used in the main washing
Delroisse Michel Gilbert
Jones David Andrew
Smith Richard George
Wells John Francis
Delcotto Gregory
Honig Milton L.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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