Process for the bleaching of fabrics

Bleaching and dyeing; fluid treatment and chemical modification – Bleaching – Chemical

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Details

8107, 510302, 510303, 510309, 510312, 510336, 510337, 510372, 25218638, 25218641, D06L 302, D06L 316

Patent

active

057139628

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/US94/05817 filed May 24, 1994.


TECHNICAL FIELD

The present invention relates to the bleaching of fabrics and to pretreatment compositions for fabrics.


BACKGROUND

The bleaching of fabrics is extensively discussed in the art. Various bleaching compositions have been designed for this purpose, which can be classified in two classes: peroxide bleaching compositions and hypochlorite bleaching compositions. Peroxide bleaching has the advantage over hypochlorite bleaching that it is generally regarded as safer to the color of fabrics and as non-yellowing on white fabrics.
A major drawback of peroxygen bleaches is that they are less active than chlorine bleaches at low temperatures which are often encountered in modern laundering operations. Thus peroxygen bleach activators have been developed which have been extensively addressed in the art. A particular class of peroxygen bleach activators is constituted by peracid precursors which react with hydrogen peroxide to form peracids which are the activated bleaching species.
Treatments of fabrics before they are washed, often referred to as fabric pretreatments are also known in the art. In these pretreatments, an effective quantity of a given liquid or pasty composition is applied onto a portion of the fabrics, typically the heavily soiled portions, before the fabrics are washed in an aqueous wash liquor.
It has now been found that a particularly effective bleaching of fabrics can be achieved in connection with a pretreatment operation, provided a liquid or pasty composition is used which comprises acetyl triethyl citrate as a peracid precursor.
Acetyl triethyl citrate has been disclosed as a peracid precursor in the context of laundry bleaching in co-pending PCT application US 92-10445.


SUMMARY OF THE INVENTION

The present invention is a process of bleaching fabrics which comprises the steps of applying on at least a portion of said fabrics an effective amount of a liquid or pasty composition comprising acetyl triethyl citrate, then washing said fabrics in an aqueous wash liquor, wherein an effective amount of hydrogen peroxide is provided either in said liquid or pasty composition, or in said wash liquor.


DETAILED DESCRIPTION OF THE INVENTION

The present invention involves the use of a liquid or pasty composition comprising acetyl triethyl citrate. By liquid or pasty, it is meant herein a composition which can be conveniently applied on fabrics before the fabrics are washed. Ideally, the compositions for use in the process of the present invention should not be so thick as to be difficult to apply on fabrics, or so thin as to compromise on the accuracy of the application on the fabrics. Accordingly, suitable compositions for use herein range from thin liquids to gels. Preferred compositions for use herein have a viscosity of from 50 cps to 10000 cps at 50 rpm at 20.degree. C.
As an essential feature of the present invention, the compositions for use herein must comprise an effective amount of acetyl triethyl citrate. Acetyl triethyl citrate is a known chemical which is commercially available for instance under the trade name Citroflex.RTM., available from Morflex, but acetyl triethyl citrate Was only disclosed as a bleach activator for the first time in co-pending PCT application US 92-10445. As discussed therein, acetyl triethyl citrate provides a wide variety of benefits, especially in the context of a liquid bleaching composition where it displays excellent storage stability, compared to the peracid precursors in the art. Furthermore, acetyl triethyl citrate has the peculiarity that it is a substantially water-insoluble liquid peracid precursor which perhydrolyses into a substantially water-soluble peracid. We have now found that this peculiarity makes it particularly advantageous to use acetyl triethyl citrate in the context of the present invention.
Indeed, because it is a substantially water-insoluble liquid peracid precursor, acetyl triethyl citrate tends to affine onto the surface of fabrics and/or stains where i

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patent: 5409632 (1995-04-01), Showell et al.

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