Ligand and complex for catalytically bleaching a substrate

Details Ligand and complex for catalytically bleaching a substrate Ligand and complex for catalytically bleaching a substrate

2001-02-28

2003-11-11

Kifle, Bruck (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Unsubstituted hydrocarbyl chain between the ring and the -c-...

C540S474000

Reexamination Certificate

active

06646122

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a class of ligand or complex useful as catalysts for catalytically bleaching substrates with atmospheric oxygen, and as catalysts in the bleaching of textiles such as laundry fabrics whereby bleaching by atmospheric oxygen is catalysed after the treatment.
2. The Related Art
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 hydroperoxyl 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 hydroperoxyl bleach radicals 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 nonanoyloxybenzenesulfonate (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 N4Py (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. According to these publications, molecular oxygen may be used as the oxidant as an alternative to peroxide generating systems. However, no role in catalysing bleaching by atmospheric oxygen in an aqueous medium is reported.
It has long been thought desirable to be able to use atmospheric oxygen (air) as the source for a bleaching species, as this would avoid the need for costly hydroperoxyl 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.
Accordingly, it would be desirable to be able to provide a bleaching system based on atmospheric oxygen or air that does not rely primarily on hydrogen peroxide or a hydroperoxyl generating system, and that does not require the presence of organic components such as aldehydes that are consumed in the process. Moreover, it would be desirable to provide such a bleaching system that is effective in aqueous medium.
It may also be noted that the known art teaches a bleaching effect only as long as the substrate is being subjected to the bleaching treatment. Thus, there is no expectation that hydrogen peroxide or peroxy bleach systems could continue to provide a bleaching effect on a treated substrate, such as a laundry fabric after washing and drying, since the bleaching species themselves or any activators necessary for the bleaching systems would be assumed to be removed from the substrate, or consumed or deactivated, on completing the wash cycle and drying.
It would be therefore also be desirable to be able to treat a textile such that, after the treatment is completed, a bleaching effect is observed on the textile. Furthermore, it would be desirable to be able to provide a bleach treatment for textiles such as laundry fabrics whereby residual bleaching occurs when the treated fabric has been treated and is dry.
SUMMARY OF THE INVENTION
We have found a novel class of ligand or complex that is surprisingly effective in catalysing the bleaching of substrates using atmospheric oxygen or air.
Accordingly, in a first aspect, the present invention provides a ligand of the general formula (I):
wherein R
1
, R
2
, and R
3
independently represent a group selected from methyl, pyridin-2-yl, quinolin-2-yl, pyrazol-1-yl, 3,5-dimethylpyrazol-1-yl, N-methyl-amido, and N-isopropyl-amido; provided at least two of R
1
, R
2
and R
3
represent a coordinating group, the ligand being selected from:
1,4-bis(pyridin-2-ylmethyl)-7-ethyl-1,4,7-triazacyclononane;
1,4-bis(quinolin-2-ylmethyl)-7-ethyl-1,4,7-triazacyclononane;
1,4-bis(pyrazol-1-ylmethyl)-7-ethyl-1,4,7-triazacyclononane;
1,4-bis(3,5-dimethylpyrazol-1-ylmethyl)-7-ethyl-1,4,7-triazacyclononane;
1,4-bis(N-methylimidazol-2-ylmethyl)-7-ethyl-1,4,7-triazacyclononane;
1,4,7-tris(quinolin-2-ylmethyl)-1,4,7-triazacyclononane;
1,4-bis(N-isopropylacetamido)-7-ethyl-1,4,7-triazacyclononane; and
1,4-bis(N-methylacetamido)-7-ethyl-1,4,7-triazacyclononane.
In a second aspect, the present invention provides a complex of the ligand and a transition metal.
An advantage of the class of ligand and complex according to the present invention is that the complex can catalyse bleaching of a substrate by atmospheric oxygen, thus permitting its use in a medium such as an aqueous medium that is substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system. We have also found that complexes of this class are surprisingly effective in catalysing bleaching of the substrate by atmospheric oxygen after treatment of the substrate.
DETAILED DESCRIPTION OF THE INVENTION
Advantageously, the ligand or complex according to the present invention permits all or the majority of the bleaching species in the medium (on an equivalent weight basis) to be derived from atmospheric oxygen. Thus, the medium can be made wholly or substantially devoid of peroxygen bleach or a peroxy-based or -generating bleach system. Furthermore, the complex is a catalyst for the bleaching process and, as such, is not consumed but can continue to participate in the bleaching process. Thus, the ligand or complex can provide a catalytically activated bleaching system which is based on atmospheric oxygen, is therefore both cost-effective and environmentally friendly. Moreover, a bleaching system can be provided that is operable under unfavourable wash conditions which include low temperatures, short contact times and low dosage requirements. Furthermore, the catalyst is effective in an aqueous medium and is therefore particularly applicable to bleaching of laundry fabrics. Therefore, whilst the catalyst according to the present invention may be u

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